HK1199329B - Semiconductor process sensor and method of characterizing semiconductor process - Google Patents

Description

Semiconductor processing technology sensor and method for representing semiconductor processing technology

The present application is a divisional application of an invention patent application having an application date of 2009, 9 and 22, an application number of 200980161604.1 (international application number of PCT/US2009/057823), and an invention name of "semiconductor processing process, voltage, and temperature sensor".

Cross Reference to Related Applications

This application is based on the priority of 35u.s.c.119(e) of U.S. provisional application No.61/229,056 entitled "process, voltage, and temperature sensor" filed on 7/28/2009, which is incorporated by reference herein in its entirety.

Technical Field

The present invention relates generally to semiconductor devices and, more particularly, to a sensor capable of monitoring an operating parameter of a semiconductor device.

Background

The performance of a semiconductor device may vary depending on the conditions (conditions) under which the device is used. For example, performance characteristics of a semiconductor device such as rise time, fall time, gain, bandwidth, linearity, frequency response, etc., typically vary with the supply voltage level at which the device is used and the temperature of the device. However, even if two devices of the same type are manufactured using the same manufacturing equipment and operated under identical conditions, one device may behave differently than the other. This difference in performance typically occurs because, despite the fact that the devices are formed using the same fabrication equipment and process steps, minor (minute) differences in the processes used to form each individual device still occur. Such differences in the processing techniques used to form each individual device are generally more pronounced between devices formed on different semiconductor wafers or between devices formed on different wafers and at different times (i.e., in different batches), but these differences can even occur between devices formed on the same wafer (e.g., if a first device is located at the edge of the wafer and another device is located at a more central location). Due to these slight differences in the processing techniques used to form the individual devices, the performance of one device may differ from the performance of another device.

In many applications, these slight variations in the processing techniques used to form the devices, as well as any resulting differences in performance, may be of little concern or can be tolerated by the design of the electronic circuit or device in which the device is used. However, in many applications, such differences in performance between devices of the same type may have an effect on the operation of the electronic circuit or device in which the device is used.

Disclosure of Invention

Applicants have recognized that certain semiconductor devices are very sensitive to temperature, supply voltage levels, and the processing techniques used to form the devices. This sensitivity can be a problem when semiconductor devices of the same design and manufacture are desired to perform consistently. Accordingly, applicants have developed a sensor that is capable of sensing both the voltage level and temperature at which the device is operating, and of sensing parameters indicative of the process by which the device is produced, in order to characterize the performance of the device. This information can then be used to compensate the device to ensure more consistent performance between different devices of the same design and manufacture, regardless of differences in performance between devices, differences in the temperature and supply voltage at which the devices operate, or all of the above.

According to one aspect of the invention, an integrated circuit is provided. The integrated circuit includes: the process sensor is configured to sense a process parameter indicative of a semiconductor process used to form the integrated circuit and provide a characterization of the semiconductor process to an output of the process sensor based on the process parameter. The temperature sensor is configured to provide an indication of a temperature of the integrated circuit to an output of the temperature sensor. The voltage sensor is configured to provide an indication of a supply voltage level of the integrated circuit to an output of the voltage sensor. The output of the process sensor is electrically connected to at least one of a temperature sensor and a voltage sensor to compensate at least one of the indication of the temperature and the indication of the power supply voltage level in response to the characterization of the semiconductor process.

According to one embodiment of the invention, the output of the process sensor is electrically connected to both a temperature sensor and a voltage sensor to compensate both the indication of the temperature and the indication of the supply voltage level in response to the characterization of the semiconductor process.

According to another embodiment of the present invention, the process sensor provides a characterization of the semiconductor process each time the process sensor is powered on. In a further embodiment, the temperature sensor is configured to dynamically provide an indication of the temperature of the integrated circuit to an output of the temperature sensor, and wherein the voltage sensor is configured to dynamically provide an indication of the supply voltage level of the integrated circuit to an output of the voltage sensor.

According to another embodiment of the present invention, the integrated circuit includes an associated semiconductor device collectively formed with a process sensor, a temperature sensor, and a voltage sensor using the same semiconductor process fabrication steps. According to one embodiment of the invention, the associated semiconductor device is programmable. In a further embodiment, the associated semiconductor device is compensated in response to the characterization of the semiconductor process provided by the process sensor, the indication of the temperature provided by the temperature sensor, and the indication of the power supply voltage level provided by the voltage sensor.

According to another embodiment of the present invention, the integrated circuit further comprises an algorithm state machine electrically connected to the output of the process sensor, the output of the temperature sensor, the output of the voltage sensor, and the programmable input of the associated semiconductor device. The algorithm state machine is configured to compensate the associated semiconductor device in response to the characterization of the semiconductor process provided by the process sensor, the indication of the temperature provided by the temperature sensor, and the indication of the power supply voltage level provided by the voltage sensor. In a further embodiment, the associated semiconductor device includes a programmable gain amplifier, wherein the algorithm state machine includes an input for receiving an operational setting indicative of at least one of a gain and a frequency response of the programmable gain amplifier. The algorithm state machine is configured to compensate the programmable gain amplifier in response to the characterization of the semiconductor process provided by the process sensor, the indication of the temperature provided by the temperature sensor, and the indication of the power supply voltage level provided by the voltage sensor in accordance with the operational setting.

According to another embodiment of the invention, the integrated circuit further comprises at least one interface electrically connected to the output of the process sensor, the output of the temperature sensor, the output of the voltage sensor, and the programmable input of the associated semiconductor device. The interface is configured to provide the characterization of the semiconductor process provided by the process sensor, the indication of the temperature provided by the temperature sensor, and the indication of the supply voltage level provided by the voltage sensor to an external device, and to receive the compensated operational setting from the external device for provision to the programmable input of the associated semiconductor device.

According to another embodiment of the invention, the associated semiconductor device has an output for providing an output signal. The integrated circuit further comprises: at least one interface electrically connected to an output of the process sensor, an output of the temperature sensor, and an output of the voltage sensor. The at least one interface is configured to provide the characterization of the semiconductor process provided by the process sensor, the indication of the temperature provided by the temperature sensor, and the indication of the power supply voltage level provided by the voltage sensor to an external device to cause the external device to compensate an output signal of the associated semiconductor device based on the characterization of the semiconductor process, the indication of the temperature, and the indication of the power supply voltage level.

In accordance with another aspect of the present invention, a method of monitoring the formation of a semiconductor device in accordance with a semiconductor processing process is provided. The method comprises the following operations: sensing a process parameter indicative of a semiconductor process used to form the semiconductor device; characterizing the semiconductor process based on the sensed process parameter. The method further comprises the following steps: sensing a temperature of the semiconductor device; sensing a power supply voltage level being supplied to the semiconductor device; and compensating for at least one of a sensed temperature of the semiconductor device and a sensed power supply voltage level being provided to the semiconductor device in response to the characterization operation.

According to one embodiment, the compensating operation comprises compensating both the sensed temperature of the semiconductor device and the sensed power supply voltage level being provided to the semiconductor device in response to the characterizing operation. According to another embodiment of the present invention, the operations of sensing a process parameter, sensing a temperature, sensing the power supply voltage level being provided to the semiconductor device, and compensating for both the sensed temperature and the sensed power supply voltage level being provided to the semiconductor device are performed dynamically in response to the characterization operation.

According to another embodiment of the present invention, the operation of characterizing the semiconductor process includes characterizing the semiconductor process as one of a fast, nominal, and slow operation.

According to another embodiment of the invention, the semiconductor device is a programmable semiconductor device, the method further comprising the operations of: adjusting at least one programmable parameter of the semiconductor device in response to the compensated sensed temperature, the compensated sensed supply voltage level, and the characterized semiconductor process. In a further embodiment, the operation of adjusting comprises the operations of: receiving an operational setting for the programmable semiconductor device; indexing the operational setting using the compensated sensed temperature, the compensated sensed power supply voltage level, and the characterized semiconductor process to determine a compensated operational setting; and providing the compensated operational setting to the programmable semiconductor device for adjusting the at least one programmable parameter. In a further embodiment, the receiving, indexing, and providing operations are performed on the same integrated circuit as the programmable semiconductor device. In an alternative embodiment, the receiving and indexing operations are performed by a processor located on an integrated circuit different from the programmable semiconductor device.

According to another aspect of the present invention, there is provided a semiconductor process sensor for characterizing an operating semiconductor process used to form the semiconductor process sensor, the semiconductor process sensor comprising: a constant reference voltage source, a process sensing resistor, a constant current source, and an analog-to-digital converter. The constant reference voltage source has an output for providing a constant reference voltage signal. The process sense resistor has a first terminal electrically connected to the output of the constant reference voltage source and a second terminal for providing a sensed voltage signal, the resistance of the process sense resistor being dependent upon at least one variable in a semiconductor process used to form the semiconductor process sensor. The constant current source is electrically connected to the second terminal of the process sense resistor. The analog-to-digital converter, coupled to the second terminal of the process sensing resistor, is configured to provide at least one output signal indicative of a semiconductor process used to form the semiconductor process sensor.

In accordance with another embodiment of the invention, the process sensor further includes a voltage divider having an input electrically connected to the output of the constant reference voltage source and an output, the voltage divider including a plurality of resistors connected in series between the input of the voltage divider and the output of the voltage divider. The analog-to-digital converter is also connected to the voltage divider, which provides at least one voltage to the analog-to-digital converter as a reference voltage signal in another aspect of this embodiment, each resistor of the voltage divider has substantially the same height, width, and length, and the process senses the height and width of the resistor. The height of the process sense resistor is approximately the same as the height of each resistor of the voltage divider, while the width of the process sense resistor is substantially smaller than the width of each resistor of the voltage divider.

According to another embodiment of the invention, the process sensor further comprises a voltage divider having an input electrically connected to the output of the constant reference voltage source and an output. The voltage divider provides a plurality of different reference voltage signals. The analog-to-digital converter includes at least one comparator having a first input electrically connected to the voltage divider for receiving a first one of the plurality of different reference voltage signals, a second input electrically connected to the voltage divider for receiving a second one of the plurality of different reference voltage signals, and a third input electrically connected to the second terminal of the process sense resistor for receiving the sensed voltage signal. The at least one comparator is configured to compare the sensed voltage signal to first and second voltage reference signals and provide at least one comparator output signal that is the at least one output signal characterizing the semiconductor process used to form the semiconductor process sensor.

According to another embodiment of the invention, the voltage divider comprises a plurality of resistors connected in series between the input and output terminals of the voltage divider. The plurality of series resistors includes a first resistor, a second resistor, a third resistor, and a fourth resistor. A first resistor has a first terminal and a second terminal, the first terminal of the first resistor being electrically connected to the input of the voltage divider and the first terminal of the process sense resistor, and the second terminal of the first resistor being electrically connected to the first input of the at least one comparator. A second resistor has a first terminal and a second terminal, the first terminal of the second resistor being electrically connected to the second terminal of the first resistor. A third resistor has a first terminal and a second terminal, the first terminal of the third resistor being electrically connected to the second terminal of the second resistor, and the second terminal of the third resistor being electrically connected to the second input of the at least one comparator. A fourth resistor has a first terminal and a second terminal, the first terminal of the fourth resistor being electrically connected to the second terminal of the third resistor, and the second terminal of the fourth resistor being electrically connected to the output of the voltage divider. In a further embodiment, a second terminal of the second resistor is electrically connected to an input of the constant reference voltage source.

According to another embodiment of the invention, the at least one comparator comprises a first comparator and a second comparator. The first comparator has a first input for receiving a first reference voltage signal and a second input for receiving a sensed voltage signal. The first comparator is configured to compare the sensed voltage signal to a first reference voltage signal and provide a first comparator output signal in response to the sensed voltage signal being greater than the first reference voltage signal and provide a second comparator output signal in response to the sensed voltage signal being less than the first reference voltage signal. The second comparator has a first input for receiving a second reference voltage signal and a second input for receiving the sensed voltage signal. The second comparator is configured to compare the sensed voltage signal to a second reference voltage signal and provide a third comparator output signal in response to the sensed voltage signal being greater than the second reference voltage signal and provide a fourth comparator output signal in response to the sensed voltage signal being less than the second reference voltage signal.

According to another embodiment of the invention, the process sensor further comprises an encoder. The encoder has a first input for receiving the first comparator output signal, a second input for receiving the second comparator output signal, a third input for receiving the third comparator output signal, and a fourth input for receiving the fourth comparator output signal. The encoder is configured to assert (assert) a first output signal in response to the sensed voltage signal being greater than a first reference voltage signal, assert a second output signal in response to the sensed voltage signal being less than the first reference voltage signal and greater than a second reference voltage signal, and assert a third output signal in response to the sensed voltage signal being less than the second reference voltage signal. According to another aspect of the invention, the semiconductor process is characterized as fast in response to the encoder asserting the first output signal, the semiconductor process is characterized as nominal in response to the encoder asserting the second output signal, and the semiconductor process is characterized as slow in response to the encoder asserting the third output signal.

In accordance with another aspect of the present invention, a method of characterizing a semiconductor process used to form a semiconductor process sensor is provided. The method comprises the following operations: providing a substantially constant reference voltage to the voltage divider and the process sense resistor; generating a plurality of different reference voltages in a voltage divider based on the substantially constant reference voltage; determining a sensed voltage dropped across a process sense resistor based on the substantially constant reference voltage, a resistance of the process sense resistor being dependent on at least one variable (variation) in a semiconductor process used to form the semiconductor process sensor. The method further comprises the following steps: comparing the plurality of different reference voltages to the sensed voltage; and characterizing the semiconductor process used to form the semiconductor process sensor based on the comparing operation.

According to an embodiment of the present invention, the generating operation includes an operation of generating a first reference voltage and a second reference voltage, and wherein the comparing operation includes an operation of comparing the sensed voltage with the first reference voltage and the second reference voltage. In a further embodiment, the characterization operation comprises the operations of: characterizing the semiconductor processing process as fast in response to the sensed voltage being greater than the first reference voltage; characterizing the semiconductor processing process as nominal in response to the sensed voltage being less than the first reference voltage and greater than the second reference voltage; and characterizing the semiconductor processing process as slow in response to the sensed voltage being less than the second reference voltage. In a further embodiment, the method further comprises: the first output signal is asserted in response to the semiconductor process being characterized as fast, the second output signal is asserted in response to the semiconductor process being characterized as nominal, and the third output signal is asserted in response to the semiconductor process being characterized as slow.

According to another aspect of the present invention, there is provided a semiconductor process sensor, comprising: a constant reference voltage source configured to generate a constant reference voltage signal; a process sensor element coupled to the constant reference voltage source and configured to receive the constant reference voltage signal, sense a process parameter indicative of a semiconductor process used to form the semiconductor process sensor, and generate a process measurement signal indicative of the semiconductor process used to form the semiconductor process sensor as one of rated, above rated, or below rated based on the sensed process parameter.

According to another aspect of the present invention, there is provided a method of characterizing a semiconductor process used to form a semiconductor process sensor, the method comprising the acts of: providing a substantially constant reference voltage to the process sensing element; sensing, with the process sensing element, a process parameter indicative of a semiconductor process used to form a semiconductor process sensor; and based on the sensing operation, generating a process measurement signal characterizing the semiconductor process used to form the semiconductor process sensor as one of nominal, above nominal, or below nominal.

According to another aspect of the present invention, there is provided a semiconductor process sensor, comprising: a constant reference voltage source configured to generate a constant reference voltage signal; a process sensing element coupled to the constant reference voltage source; and means for sensing a voltage drop across the process sensing element and for characterizing a semiconductor process used to form the semiconductor process sensor as one of nominal, above nominal, and below nominal based on the voltage drop.

Drawings

The drawings are not intended to be drawn to scale. In the drawings, each identical or nearly identical component that is illustrated in various figures is represented by a like numeral. For purposes of clarity, not every component may be labeled in every drawing. In these drawings:

FIG. 1 is a block diagram of a process, voltage and temperature (PVT) sensor according to an embodiment of the present invention;

FIG. 2 is a block diagram of an exemplary process sensor for use in the process sensor of the PVT of FIG. 1;

FIG. 3 is a more detailed schematic diagram of the process sensor of FIG. 2;

FIG. 4 is a block diagram of a temperature sensor used in the PVT sensor of FIG. 1;

FIG. 4A is a more detailed schematic diagram of a portion of the temperature sensor of FIG. 4;

FIG. 5 is a block diagram of a voltage sensor used in the PVT sensor of FIG. 1;

FIG. 5A is a more detailed schematic diagram of a portion of the voltage sensor of FIG. 5;

FIG. 6 is a flow chart of an exemplary method of operation of the process, voltage and temperature sensors of FIG. 1;

FIG. 7 is a block diagram of an exemplary programmable summing amplifier with an on-chip look-up table/state machine in accordance with the present invention;

FIG. 8 is a simplified schematic diagram of an amplifier or attenuator (attenuator) of the programmable gain amplifier of FIG. 7;

FIG. 9 illustrates a portion of a lookup table according to an embodiment of the invention;

FIG. 10 is a flow chart of an exemplary method of operation of the programmable gain amplifier of FIG. 6;

FIG. 11 is a block diagram of an exemplary programmable gain amplifier with an off-chip firmware look-up table and bus interface in accordance with another embodiment of the present invention;

FIG. 12 is a block diagram of an F programmable gain amplifier with an off-chip firmware lookup table according to another embodiment of the invention; and

fig. 13 is a flow chart of a method of operation of the programmable gain amplifier described in fig. 11 and 12.

Detailed Description

This invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of "including," "comprising," or "having," "containing," "involving," and variations thereof herein, is meant to encompass the items listed thereafter and equivalents thereof as well as additional items.

In many semiconductor device applications, it is beneficial for a semiconductor device to provide a consistent output signal. For example, in a cable television (CATV) system, an upstream Programmable Gain Amplifier (PGA) that provides and maintains a consistent output signal (in terms of, for example, DC gain, gain bandwidth, gain-plateau temperature, plateau compensation, linearity, etc.) is desirable to ensure that downstream components operate properly or efficiently. In such applications, it is also desirable to be able to provide a consistent output signal across different devices of the same design and manufacture. Although individual devices may be tested to determine performance characterizations (characteristics) and then classified to provide end users with different devices having similar performance characterizations, such testing and classification typically increases the cost of the devices. Moreover, such testing does not account for differences in the environment in which the devices are used, and such differences in the supply voltage levels and/or temperatures at which the devices operate can still result in one device behaving differently than another.

Embodiments of the present invention relate to a process, voltage and temperature (PVT) sensor configured to sense process parameters indicative of a process used to generate the PVT sensor, a supply voltage level at which the PVT sensor operates, and a temperature at which the PVT sensor operates. The PVT sensor is preferably implemented on the same integrated circuit as the associated device and formed by the same processing steps as the associated device, so that the parameters sensed (sense) by the PVT sensor accurately reflect (deflect) those parameters of the associated device. However, the PVT sensor and associated devices may be implemented on separate integrated circuits. If the PVT sensor and associated device are implemented on separate integrated circuits, the PVT sensor may also be used to sense parameters that accurately reflect those of the associated device. For example, if the PVT sensor is placed in close proximity to, or mounted on a common substrate (substrate) with, the associated device, and the same power supply is used to provide the power supply voltage for each, the voltage and temperature parameters sensed by the PVT sensor will accurately reflect those of the associated device.

According to embodiments in which the PVT sensor and the associated device are formed on the same integrated circuit and using the same steps, sensed process parameters indicative of the process used to produce the associated device are used to qualitatively (functionally) characterize the performance of the associated device and to provide a performance-related output signal of the associated device, a sensed operating supply voltage level of the associated device, and a sensed operating temperature of the associated device. These output signals may be used to configure the associated device to compensate for the associated device, thereby providing a more consistent output despite performance differences between different chips of the same design and manufacture, and despite differences in the conditions under which the devices operate. In one embodiment, at least a portion of the associated device is programmable and the portion is programmed in response to the output signal to compensate the associated device to provide a consistent output. In another embodiment, a device downstream from the associated device is configured in response to the output signal to compensate for performance differences in the associated device.

Referring to fig. 1, wherein a block diagram of a circuit 100 according to an embodiment of the present invention is shown, the circuit 100 is configured to be connected (e.g., physically, electrically, or both) to an associated semiconductor device (not shown), including a PVT sensor 102. The PVT sensor 102 is connected to a voltage reference circuit 104. As will be discussed in detail below, the voltage reference circuit 104 includes a bandgap (bandgap) voltage reference source 106 connected to a typical Low-Dropout (LDO) regulator 108. The PVT sensor 102 includes a temperature sensor 112, a voltage sensor 114, a process sensor 116, and a transformer circuit 103. The process sensor 116 has a plurality of inputs including an input 126a coupled to the output 111 of the bias circuit 103 and an input 126b coupled to the output 110 of the voltage reference circuit 104. The temperature sensor 112 has a plurality of inputs including an input 118a connected to the output 111 of the bias circuit 103, an input 118b connected to the output 110 of the voltage reference circuit 104, and an input 118c connected to the output 128 of the process sensor 116. The voltage sensor 114 has a plurality of inputs including an input 122a connected to the output 111 of the bias circuit 103, an input 122b connected to the output 110 of the voltage reference circuit 104, and an input 122c connected to the output 128 of the process sensor 116. As shown in fig. 1, the bias circuit 103 is included in the PVT sensor 102; however, in another embodiment, the bias circuit 103 is not included in the PVT sensor 102.

The voltage reference circuit 104 provides a plurality of stable reference voltages to the temperature sensor 112, the voltage sensor 114, and the process sensor 116. The conventional bandgap reference source 106 serves as a reference for the conventional LDO voltage regulator 108 so that the output from the voltage reference circuit 104 is stable in temperature and supply voltage, e.g., 3.3 volts. The bias circuit 103 provides a plurality of stable bias currents and voltages to the temperature sensor 112, the voltage sensor 114, and the process sensor 116 in response to the voltage reference circuit 104. It is understood that the voltage reference circuit and the bias circuit 103 may be integrated with or separate from the PVT sensor 102. For simplicity, some details of the connections between the bias circuit 103 and the sensors 112 and 116 are not shown in subsequent figures.

As explained in greater detail below in connection with figures 2 and 3, the process sensor 116 is configured to sense a process parameter representative of a process used to fabricate the PVT sensor (and the associated, co-formed semiconductor device) and provide a characterization of the process to the output 128. In one embodiment, the process characterization is a three-bit number, one of which three values is representative of a "speed" of the process, i.e., the relative performance of the transistor and other co-formed device in terms of its designed performance relative to a nominal performance for a given fabrication process (e.g., transistor gain, polysilicon conductivity, implant dose, etc.). For example, if the process speed is determined to be slow compared to a nominal amount (hereinafter referred to as a "slow" process), a first bit is set high and the other two bits are set low. If the process speed is determined to be nominal compared to the nominal amount (hereinafter referred to as a "nominal" process), a second bit is set high and the other two bits are set low. If the process speed is determined to be fast compared to the nominal amount (hereinafter referred to as a "fast" process), a third bit is set high and the other two bits are set low. It should be appreciated that in other embodiments, the process characterization may include any number of bits or values, may be encoded differently, and may be representative of process parameters other than speed, such as capacitance.

As explained in more detail below in conjunction with fig. 4 and 4A, the temperature sensor 112 is configured to sense a wafer (die) temperature of the PVT sensor (and associated co-formed semiconductor device) and provide an indication of the wafer temperature of the PVT sensor and the associated semiconductor device to the output 120. In one embodiment, the indication of temperature comprises 5 bits, representing a temperature range of-40 ℃ to 85 ℃. These 5 bits (ranging from 00000 to 11111) represent subdivisions of the 32 different temperature ranges on which indications of the wafer temperature of the PVT sensor (and associated co-formed semiconductor devices) can be run. It should be appreciated that the indication of the wafer temperature may include any number of bits, may represent any temperature range, and may be subdivided into any number of smaller (or larger) steps. For example, in another embodiment, the indication of temperature may include 6 bits, representing a temperature range of-20 ℃ to 65 ℃. These 6 bits (ranging from 000000 to 111111) represent subdivisions of 64 different temperature ranges. It is to be appreciated that these subdivisions may be, but need not be, identical.

As explained in more detail below in conjunction with fig. 5 and 5A, the voltage sensor 114 is configured to sense a voltage of a power supply (not shown) of the PVT sensor (and associated co-formed semiconductor device) and provide an indication of the power supply voltage level to the output 124. In one embodiment, the indication of the power supply voltage level includes 4 bits representing a voltage range of 4.5 volts to 5.5 volts. These 4 bits (ranging from 0000 to 1111) represent 16 different subdivisions of the voltage range over which indications of the supply voltage levels of the PVT sensors (and associated co-formed semiconductor devices) operate. It should be appreciated that the indication of the power supply voltage level may be any number of bits, may represent any voltage range, and may be subdivided into any number of smaller (or larger) equal or different steps (steps). For example, in another embodiment, the indication of the power supply voltage level may include 3 bits representing a voltage range of 4.7 volts to 5.2 volts. These 3 bits (ranging from 000 to 111) represent a sub-division of 8 different voltage ranges.

Referring now to FIG. 2, further details of the process sensor 116 according to an embodiment of the invention will be described. The process sensor 200 includes a constant reference voltage source 20 corresponding to the voltage reference circuit 104 (fig. 1), a process sensor element 204 coupled to the constant reference voltage source 202, an encoder 206 coupled to the process sensor element 204, and an optional digital buffer 208 coupled to the encoder 206, an output of the digital buffer 208 forming an output 210 of the process sensor 200.

The constant reference voltage source 202 provides a constant reference voltage signal to the process sensor element 204. In one embodiment, the constant reference voltage source 202 is provided by the voltage reference circuit 104 of fig. 1, but it is to be appreciated that the constant voltage source 202 may be a separate (separate) stable voltage reference source. The process sensor element 204 senses one or more parameters indicative of the process used to produce the sensor element (and associated co-formed semiconductor device), characterizes the process, and outputs a digital signal indicative of the characterization. In the embodiments described below, the process sensor element 204 characterizes speed as one of three levels, slow, nominal, or fast.

It will be appreciated that the speed of PVT sensors and associated co-formed semiconductor devices can vary with the process used to fabricate these devices. For example, in a 90 nanometer (nm) CMOS fabrication process, variability in the fabrication process typically results in certain devices being fabricated using that process exhibiting better (e.g., faster) design-nominal values and certain devices exhibiting worse (e.g., slower) design-nominal values. These differences in performance typically result from variations in one or more process parameters, such as feature transistor dimensions, dopant dose variations, and even substrate wafer orientation and variations in dopants therein. Moreover, such variations in process parameters can have more or less impact on certain components of the device (e.g., PMOS transistors) than other components of the device (e.g., NMOS transistors). Thus, it should be appreciated that the process sensor element 204 can be designed to divide speed into less than or more than three levels depending on potential process variables. For example, operating one type of transistor (e.g., PMOS transistor) as opposed to another type of transistor (e.g., NMOS transistor), the performance can be transistor type characteristics and characterized as fast/fast, fast/nominal, fast/slow, slow/fast, etc. As described in detail below with respect to FIG. 3, the process sensor element 204 provides process measurement output (fast, nominal, slow) based on polysilicon resistor resistance variables, although other process sensing methods and output characterization are possible.

The encoder 206 encodes the signal from the process sensor element 204 into a digital signal, in this example, only one of the three bits is assigned a value (assert) at a given time. The digital buffer 208 provides the digital signal to an output 210. For example, in one embodiment, if the process speed is determined to be slow, the first bit is set high and the other two bits are set low. If the process speed is determined to be nominal, the second bit is set high and the other two bits are set low. If the process speed is determined to be fast, the third bit is set high and the other two bits are set low. It should be appreciated that in other embodiments, the fab characterization may include any number of bits depending on the underlying fab variable, and may employ different encodings.

FIG. 3 illustrates a more detailed exemplary embodiment of the process sensor 200 of FIG. 2 according to one embodiment of the invention. The process sensor 300 includes a constant reference voltage source 202, a voltage divider 311, a process sense resistor Rs304, a process sense transistor 307, a plurality of comparators 306/encoders 312, and a plurality of buffered outputs 314, 316, 318. An input 302 connected to the output of the constant reference voltage source 202 (which may be the voltage reference circuit 104 in fig. 1) receives a stable voltage therefrom and drives a voltage divider 311. The process sense resistor Rs304 and the process sense transistor 307 are connected to a voltage divider 311. The plurality of comparators 306 are connected to the voltage divider 311, the process sense resistor Rs304, and the process sense transistor 307. The encoder 312 is coupled to the comparator 306 and a plurality of outputs 314, 316, 318.

In the example shown, process sense resistor Rs304 receives a constant voltage from input 302 via voltage divider 311. The gate of process sense transistor 307 receives a constant bias from bias source 103 (not shown in FIG. 3, but shown in FIG. 1) and acts as a constant current source. As will be explained in detail below, the resistance of process sense resistor Rs304 is more sensitive to variations in the manufacturing process used to fabricate process sensor 300 than the resistors of voltage divider 311. Accordingly, voltage Vs305 produced by process sense resistor Rs304 is dependent on the process used to produce the process sensor element. Comparator 306 monitors voltages VI 308 and V2310 from voltage divider 311, as well as voltage Vs305, and provides a digital signal characterizing the process used to produce the process sensor element. The process used to produce the process sensor element is characterized in response to whether voltage Vs305 is found to be greater than VI 308, between VI 308 and V2310, or less than V2310. In one embodiment, characterization of the process represents a speed of the process used to form the process sensor element and a speed of the process used to form the associated semiconductor device. The speed is characterized as slow when Vs305 is less than voltage V2310, rated when voltage Vs305 is between VI 308 and V2310, and fast when voltage Vs305 is greater than VI 308. Encoder 312 receives the digital signal from comparator 306 and produces three bit signals representing the speed of the process used to form the sensor element (and the associated co-formed semiconductor device), including slow bit 314, rated bit 316, and fast bit 318 as described above. It should be appreciated that in other embodiments, the process characterization may include any number of bits and may be encoded differently. It should also be appreciated that characterization of the speed may be performed differently, such as using an oscillator or a clock.

As is well known, the resistance of an integrated circuit resistor relates to the resistivity of the material from which the resistor is made and the physical dimensions of the resistor. Also, the resistance of the resistor is proportional to the ratio of the length of the resistor to the cross-sectional area of the resistor. Although the speed of the device is not directly measured, the difference in the resistance of the process sense resistor Rs304 is a strong indicator of the overall device performance. To make the resistor 304 more process sensitive to process variations than the resistors in the voltage divider, the cross-sectional area of the process sense resistor Rs304 is significantly smaller than the cross-sectional area of the resistors in the voltage divider 311. In this example, the process sense resistor Rs304 and the resistors of the voltage divider 311 are conventional polysilicon resistors, and the heights of all the resistors are substantially the same. The resistances of all of the electrical resistors in the voltage divider 311 and the process sense resistor Rs304 are substantially the same (e.g., the process sense resistor Rs304 is almost 25 kohms and the resistor in the voltage divider 311 is almost 27 kohms), the width of the resistor in the voltage divider 311 is approximately twice the width of the resistor in the process sense resistor Rs304, and the length of each resistor in the voltage divider 311 is almost equal to twice the length of the process sense resistor Rs 304. It should be appreciated that the cross-sectional area of the resistor may be other than 2: 1 (e.g., 3: 1), the height of the resistors may be different from each other, and the resistance of the voltage divider resistor and the resistance of the process sense resistor Rs304 may be different from each other. It should also be appreciated that techniques other than resistance transformation may be used to detect a change in the process (e.g., ring oscillator frequency).

It should be appreciated that the process sensor 300 is substantially unaffected by changes in the power supply voltage level and changes in temperature. This is a result of the stable reference voltage provided by the constant reference voltage source 202 and also because of the nature (nature) of the process characterization provided by the comparator 306. The comparator monitors the relationship between the voltage Vs305 and the voltages Vl308 and V2310 (e.g., whether Vs305 is greater than Vl308, between Vl308 and V2310, or less than V2310). Thus, any effect from temperature changes will have substantially equal effect on all voltages Vl, V2, and V3, and the relationship between Vs305 and Vl308 and V2310 will remain substantially the same. Process sensor 300 will remain unaffected by variations in the power supply voltage level and temperature.

Further details of the temperature sensor 112 of FIG. 1 will now be described with reference to FIG. 4, in accordance with an embodiment of the present invention. Temperature sensor 400 includes a process-induced error correction circuit 402, a temperature sensor element 404, a buffer 406, a constant reference voltage source 408, an analog-to-digital (a/D) converter 410, a thermometer-to-binary code converter 412, an optional digital buffer 414, an output of which digital buffer 414 forms an output 416 of temperature sensor 400. The temperature sensor element 404 is connected to the process-induced error correction circuit 402. The buffer 406 is connected to the temperature sensor element 404. An analog-to-digital converter 410 is connected to the buffer 406 and the constant reference voltage source 408. Thermometer-to-binary transcoder 412 is coupled to analog-to-digital converter 410. The digital buffer 414 is connected to the thermometer-to-binary transcoder 412.

Process sensing error correction circuit 402 receives 3-bit process characterization data from process sensor 300 (fig. 3) and operates to at least partially compensate temperature sensor element 404 in response to the process characterization data to reduce the effect of process variations on the temperature sensor. As explained in more detail below, temperature sensor element 404 detects the wafer temperature of the temperature sensor, and thus of the associated semiconductor device, and provides a voltage signal representative of the temperature of the wafer to buffer 406. The buffer 406 is configured to buffer the temperature sensor element 404 from the analog-to-digital converter 410 to prevent the load of the analog-to-digital converter 410 from affecting the temperature sensor element 404. In one embodiment, buffer 406 is an optional component of an optional temperature sensor 400. A constant reference voltage source 408, such as voltage reference circuit 104 (fig. 1), provides a constant reference voltage signal to an analog-to-digital converter 410. Alternatively, the constant reference voltage source 408 may comprise an LDO regulator that is independent of the LDO regulator 108 in fig. 1. Analog-to-digital converter 410 compares the voltage signal from buffer 406 to a constant reference voltage signal and, based on the comparison, provides a coded thermometer digital signal representative of the wafer temperature to thermometer-to-binary code converter 412. The conventional thermometer-to-binary code converter 412 converts the coded thermometer digital signal into a binary code digital signal, which has a small number of bits. Finally, the digital buffer 414 provides a binary code digital signal representative of the wafer temperature of the associated semiconductor device to an output 416. As described above, the digitization of the wafer temperature is 5 bits.

Further details of the process-induced error correction circuit 402 and the temperature sensor element 404 according to an embodiment of the invention are now described with reference to fig. 4A. The process-induced error correction circuit 402 includes a logic circuit 402A, a plurality of switches 410A, 412A, and a plurality of resistors 414A, 416A. The logic circuit 402A is coupled to a plurality of outputs 314, 316, 318 from the process sensor 300 (fig. 3). Each of the plurality of switches 410A, 412A is controlled by an output of the logic circuit 402A. Each of the plurality of resistors 414A, 416A is connected to an output of the plurality of switches 410A, 412A.

The temperature sensor element 404 includes a thermally-stable temperature sensing resistor 408A and a temperature-dependent current source transistor 420. The temperature sensing resistor 408A is in series with a plurality of thermally stable resistors 414A, 416A of the process-induced error correction circuit 402.

The logic circuit 402A receives the three-bit process characterization from the process sensor 300 (FIG. 3). In response to the process characterization received from the process sensor, the logic circuit 402A operates the plurality of switches 41 OA, 412A. By opening or closing the respective switches 41 OA, 412A, the respective resistors 414A, 416A are either energized or bypassed. Accordingly, the current flowing in the resistors 414A, 416A, and thus the current flowing in the temperature sensing resistor 408A, may be adjusted to at least partially compensate for variations in the process used to produce the temperature sensor element 404. For example, in one embodiment, in response to the process characterization representing a slow process, as described above, the logic circuit 402A operates to turn on the switch 41 OA and turn off the switch 412A. The resistors 414A and 416A are thus bypassed to adjust the current through the temperature sensing resistor 408A to at least partially compensate for the slow process. In another embodiment, in response to the process characterization representing a fast process, as described above, the logic circuit 402A operates to turn off the switch 41 OA and the switch 412A. The resistors 414A and 416A are thus energized to adjust the current through the temperature sensing resistor 408A to at least partially compensate for the fast process. Accordingly, the temperature sensor element 404 remains relatively unaffected by variations in the process used to produce the sensor element. It is to be appreciated that the logic circuit 402A, the plurality of switches 41 OA, 412A, and the resistors 414A, 416A may be variously configured to provide a desired compensation for the sensor element 404.

To generate a voltage signal to be digitized by the analog-to-digital converter 410 (fig. 4), a temperature-dependent current source transistor 420 is connected to the bandgap circuit 106 (fig. 1) to provide a current Proportional To Absolute Temperature (PTAT) to the temperature sense resistor 408A. Depending on the temperature and the resulting (quenching) resistance of the temperature sense resistor 408A, the constant current from the transistor 420 creates a voltage signal across the sense resistor 408A and, if energized, the resistors 414A, 416A. Thus, the voltage signal at node 418A generated by temperature sensor element 404 varies with temperature.

Further details of voltage sensor 114 (FIG. 1) according to an embodiment of the present invention are now described with reference to FIG. 5. Voltage sensor 500 includes a process-induced error correction circuit 502, a voltage sensor element 504, a buffer 506, a constant reference voltage source 508, an analog-to-digital converter 510, a thermometer-to-binary code converter 512, and an optional digital buffer 514, an output of digital buffer 514 forming an output 516 of voltage sensor 500.

Voltage sensor element 504 is coupled to an output of process induced error correction circuit 502. A buffer 506 is connected to the output 504 of the voltage sensor element. An analog-to-digital converter 510 is connected to the output of the buffer 506 and to the constant reference voltage source 508. Thermometer-to-binary code converter 512 is connected to the output of analog-to-digital converter 510. A digital buffer 514 is connected to the output of the thermometer-to-binary transcoder 512.

Process-induced error correction circuit 502 receives a three-bit process characterization from process sensor 300 (fig. 3) and operates in response to the process characterization to compensate voltage sensor element 504 to reduce the effect of process variations on the voltage sensor. As will be explained in greater detail below, the voltage sensor element 504 detects a supply voltage level applied to the voltage sensor and associated co-formed semiconductor devices (not shown) and provides a voltage signal representative of the supply voltage level to the buffer 506. The buffer 506 is configured to buffer the voltage sensor element 504 from the analog-to-digital converter 510 to prevent the load of the analog-to-digital converter 510 from affecting the voltage sensor element 504. In one embodiment, buffer 506 is an optional component of voltage sensor 500. A constant reference voltage source 508, such as voltage reference circuit 104 (fig. 1), provides a constant reference voltage signal to an analog-to-digital converter 510. Alternatively, the constant reference voltage source 508 may comprise an LDO voltage regulator separate from the voltage regulator of the voltage reference circuit 104. Analog-to-digital converter 510 compares the voltage signal to a constant reference voltage signal and, in response to the comparison, provides a thermometer-coded digital signal representative of the power supply voltage level to thermometer-binary code converter 512. The thermometer-to-binary code converter 512 converts the thermometer-coded digital signal into a binary-coded digital signal having a smaller number of bits. Finally, digital buffer 514 provides a binary coded digital signal representative of the supply voltage level of the associated semiconductor device to output 516. The indication of the supply voltage level may comprise 4 bits as described above.

Further details of process-induced error correction circuit 502 and voltage sensor element 504 according to an embodiment of the present invention are now described with reference to fig. 5A. The process-induced error correction circuit 502 includes a first plurality of switches 512A, 514A, 516A and a second plurality of switches 506A, 508A, 510A. Each of the first plurality of switches 512A, 514A, 516A is connected to the output 110 of the voltage reference circuit 104. The individual switches 506A, 508A, 510A are each connected to one of the individual outputs 314, 316, 318 from the process sensor 300 (FIG. 3). For example, in one embodiment, the first switch 506A is connected to the slow bit 314 of the process sensor 300. The second switch 508A is connected to the nominal bit 316 of the process sensor 300 and the third switch 510A is connected to the fast bit 318 of the process sensor 300. The first plurality of switches 512A, 514A, 516A are also connected to the second plurality of switches 506A, 508A, 510A to form three circuit legs (leg). For example, a first circuit leg may include switches 512A and 506A, a second circuit leg may include switches 514A and 508A, and a third circuit leg may include switches 516A and 510A. The voltage sensor element 504 includes a resistor 518A connected to each of the first plurality of switches 512A, 514A, 516A and a node 520A.

The output 110 of the voltage reference circuit 104 (fig. 1) provides a stable reference voltage to each of the first plurality of switches 512A, 514A, 516A. The second plurality of switches 506A, 508A, 510A are controlled to operate three legs of the process-sensitive error correction circuit 502 and to compensate the voltage sensor member 504 for variations in the process used to generate the voltage sensor member. However, in one embodiment, only one of the three legs may be energized at any one time. For example, in one embodiment, in response to a process characterization indicating a slow process, the first leg is activated by turning on the first switch 506A via the slow bit 314, turning off the second switch 508A via the nominal bit 316, and turning off the third switch 510A via the fast bit 318. In another embodiment, in response to a process characterization indicating a fast process, the third leg is activated by turning off the first switch 506A via the slow bit 314, turning off the second switch 508A via the nominal bit 316, and turning on the third switch 510A via the fast bit 318. In a final example, the second leg is activated by turning off the first switch 506A via the slow bit 314, turning on the second switch 508A via the nominal bit 316, and turning off the third switch 510A via the fast bit 318 in response to the process characterization indicating a nominal process.

The current flowing in the voltage sensor element 504 varies depending on which leg is energized. In one embodiment, the current flowing in the energized leg, and thus the current flowing in the pressure sensor element 504, may depend on parameters of the device within the energized leg. In one embodiment, the current flowing in the energized leg is dependent on the dimensional characteristics of the switches in the energized leg such that the current flowing in the energized leg is proportional to the width to length ratio of the switches in the energized leg.

As an example, in one embodiment, each switch of the second plurality of switches 506A, 508A, 510A has substantially the same dimensional parameters (e.g., length of 0.6 microns, width of 10 microns, and including three finger gates (gatefinger), while each switch of the first plurality of switches 512A, 514A, 516A has different dimensional parameters. for example, each of the first, second, and third switches 512A, 514A, and 516A includes four finger gates and a length of 2 microns, but the width of the first switch 512A is 4.8 microns, the width of the second switch 514A is 5 microns, and the width of the third switch 516A is 5.2 microns. thus, since the drain current of the first plurality of switches 512A, 514A, 516A is proportional to the width to length ratio, the current through each leg will also change. The current in the voltage sensor element 504 can be adjusted to compensate for any variations in the manufacturing process used to produce the voltage sensor element. It is to be appreciated that the operational and dimensional parameters of the switch may be configured differently.

As shown in FIG. 5A, the voltage sensor element 504 includes a transistor 522A in series with a thermally stable resistor 518A the transistor 522A essentially acts as a saturated switch and the current flowing through the resistor 518A will vary depending on which of the three legs is activated. The voltage dropped across resistor 518A, determined by the resistance of resistor 518A and the current supplied by process-induced error correction circuit 502, is offset (Vcc) by the supply voltage to produce a process-compensated voltage signal at node 520A that is representative of the supply voltage level. Thus, in response to the slow process characterization, the first circuit leg (including switches 512A and 506A) is energized, a smaller voltage is dropped across resistor 518A, and the voltage signal provided at node 520A is biased less than when the third circuit leg (including switches 516A and 510A) is energized based on the fast process characterization. The compensated process voltage signal generated at node 520A is provided to buffer 506 (FIG. 5). Thus, the voltage sensor element 504 remains substantially unaffected by variations in the processing used to produce the sensor element and temperature variations.

Figure 6 is a flow chart illustrating a method of operating a PVT sensor in accordance with an embodiment of the present invention. The method begins at block 602. At block 604, a semiconductor device including associated PVT sensors formed together in accordance with an embodiment of the present invention is powered on (power on). In response to being powered up, the PVT sensor characterizes the process sensor elements used to produce the PVT sensor and, thus, the associated semiconductor device, at block 606. As described above, in embodiments of the present invention, the PVT sensor may characterize the speed of the process sensor element (and associated co-formed semiconductor device). In response to the characterization of the process, the PVT sensor provides a process control signal to an output of the PVT sensor indicative of the process used to produce the PVT sensor (and associated semiconductor device). At block 608, the PVT sensor compensates the voltage sensor in response to the process control signal and determines the supply voltage level. In response to determining the supply voltage level, the PVT sensor provides a voltage control signal representative of the supply voltage level of the PVT sensor and the associated semiconductor device. At block 610, the PVT sensor compensates the temperature sensor in response to the process characterization and determines a wafer temperature of the PVT sensor and the temperature sensor of the associated semiconductor device. In response to determining the wafer temperature, the temperature sensor provides a temperature control signal indicative of the wafer temperature of the PVT sensor and associated semiconductor devices. Blocks 606, 608, and 610 may be repeated in one or more passes to continuously and dynamically characterize the process used to produce the PVT sensor and the associated semiconductor device, sense the supply voltage levels of the PVT sensor and the associated semiconductor device, and sense the wafer temperatures of the PVT sensor and the associated semiconductor device, in accordance with embodiments of the present invention. It will be appreciated that the order of execution of blocks 608 and 610 may vary. It will also be appreciated that the process may be dynamically characterized in order to account for (accountfor) (e.g., due to aging of the device) any process characterization variations over the lifetime of the associated semiconductor device. In one embodiment, the characterization of the process is performed each time the associated semiconductor device is powered up.

In accordance with embodiments of the present invention, the PVT sensor provides control signals that may be used to configure an associated semiconductor device based on the sensed process technology, supply voltage level, and wafer temperature level, thereby providing a more consistent output signal. As mentioned above, one example of a semiconductor device that may significantly benefit from a consistent output signal is the upstream PGA of a CATV system.

Figure 7 is a block schematic diagram of a semiconductor device 700 including an integrated PVT sensor in accordance with the present invention. As shown, the semiconductor device includes a PGA701 and a PVT sensor 702 according to an embodiment of the present invention. PGA701 includes a two-stage amplifier 714, a two-stage attenuator 712, drivers 716a, 716b, and a switch 718. Driver 716a is connected to the output of amplifier 714. Driver 716b is connected to the output of amplifier 712. The switch 718 is connected to the outputs of both drivers 716a, 716 b.

Semiconductor device 700 also includes bandgap voltage reference circuit 710, LDO voltage regulator 708, at least one bias circuit 706, at least one bias controller 704, an on-chip look-up table/state machine 720, and a Serial Peripheral Interface (SPI) 722. The LDO voltage regulator 708 is connected to the output of a bandgap voltage reference circuit 710. The at least one bias circuit 706 is coupled to an output of the LDO voltage regulator 708 and to inputs of an amplifier 714 and an attenuator 712. The at least one bias controller 704 is coupled to an input of the at least one bias circuit 706. The on-chip look-up table/state machine 720 is connected to the amplifier 714, the gain input of the attenuator 712, and the output of the PVT sensor 702, and a Serial Peripheral Interface (SPI)722 is connected to the on-chip look-up table/state machine 720.

As described above, the bandgap voltage reference circuit 710 and the LDO voltage regulator 708 provide a constant reference voltage to the at least one biasing circuit 706 and the PVT sensor 702 (connections not shown). As also described above, the PVT sensor 702 characterizes the process used to produce the PVT sensor (and associated co-formed semiconductor devices), senses the supply voltage level of the associated semiconductor device, senses the wafer temperature of the associated semiconductor device, and provides corresponding control signals.

The control signal is provided to the at least one bias controller 704, which is configured to control the at least one bias circuit 706 in response to the control signal. In one embodiment, the control signals provided by the PVT sensor 702 are also provided to the on-chip look-up table/state machine 720.

The gain and frequency response of the PGA700 may be controlled using an amplifier 714, an attenuator 712, a driver 716, the at least one bias circuit 706, and a switch 718. In one example, the amplifier has a DC gain of-1 to 32dB and the attenuator has a DC gain of-2 to-27 dB.

Shown in fig. 8 is one embodiment of the first or second stage of amplifier/attenuator 712/714 and the bias circuit 806. Each stage (stage)800 of the amplifier/attenuator is a common emitter based amplifier/attenuator with a selectable degeneration resistor 804 and a selectable frequency compensation capacitor 802. In one embodiment, the first stage has a 0.1dB good gain step (gain step) and the second stage has a 1dB gain step. It should be appreciated that the amplifier/attenuator may be configured with more or less than two stages, and the gain step may be defined differently. The bias circuit 806 includes a plurality of selectable current sources.

Referring to fig. 7 and 8, in response to the control signals provided by the PVT sensor 702, the bias controller 704 operates a plurality of selectable current sources of the bias circuit 806 in order to provide the desired bias current to the amplifier/attenuator stage 800. In one embodiment, only one current source may be selected at any one time.

In addition to receiving control signals from the PVT sensor 702, the on-chip look-up table/state machine 720 may also receive a signal including the desired DC gain of the PGA. In one embodiment, the desired DC gain is input to the look-up table/state machine through SPI 722. However, it should be appreciated that the desired DC gain may be communicated to the look-up table/state machine by other methods (e.g., parallel input).

The on-chip look-up table/state machine 720 controls the frequency response and DC gain of the amplifier 714 and attenuator 712 in response to the control signal provided by the PVT sensor 702 and the desired DC gain provided to the look-up table/state machine 720. The look-up table/state machine 720 controls the selectable degeneration resistor 804, the selectable frequency compensation capacitor 802, and the switch 718 to adjust the desired DC gain at the output of the PGA 700. In an embodiment of the present invention, the look-up table/state machine 720 comprises an Algorithmic State Machine (ASM) capable of controlling the operation of the amplifier 714, attenuator 712, and switch 718 in response to the PVT sensor and the desired gain input.

Shown in fig. 9 is an embodiment of a portion of an on-chip look-up table/state machine. The on-chip lookup table 900 includes a DC gain level index (index)902, a temperature sensor input level index 904, and a process sensor input level index 906. The on-chip lookup table 900 may also include a voltage sensor input level index (not shown). It should be appreciated that the table shown in FIG. 9 shows the inputs and outputs of the on-chip look-up table/state machine. Depending on the desired DC gain and PVT control signals input to the lookup table, the lookup table 900 identifies which resistors of the first and second stages should be switchably set to produce the desired DC gain, and the state machine of the lookup table/state machine operates to set the identified resistors. For example, referring to fig. 9, if the temperature sensor control signal from the PVT is 10001, the process from the PVT is characterized as 010 and the desired gain is 111011, the on-chip look-up table/state machine maps the control signal and desired gain to the corresponding index and operates to close the switches corresponding to the first stage resistor 12 and the second stage resistor 17 in order to maintain the desired 111011 gain. The index used to determine which selectable frequency compensation capacitor 802 to select based on the output of the PVT sensor and the desired frequency response of the PGA can be provided in the same energy-efficient manner.

Fig. 10 is a flow chart illustrating a method of PGA operation with an on-chip look-up table/state machine and PVT sensors in accordance with an embodiment of the present invention. The method begins at block 1002. At block 1004, an on-chip look-up table/state machine receives a desired DC gain provided by a user. At block 1006, an on-chip lookup table/state machine receives sensor data from the PVT sensor. At block 1008, the on-chip lookup table/state machine configures the PGA in response to sensor data from the PVT sensor and the desired DC gain as described above to produce the desired DC gain at the output of the PGA. At block 1010, a determination is made whether a parameter of the PGA (such as a desired gain, process characterization, wafer temperature, and/or supply voltage) has changed. If no parameter change is determined, block 1010 is repeated. If it is determined that at least one PGA parameter has changed, at block 1012, the look-up table/state machine modifies the configuration of the PGA as described above in order to maintain the desired DC gain. The PGA is modified at block 1012 and block 1010 is repeated. It should be appreciated that the modification of the frequency response of the PGA may be made in a similar manner.

Shown in fig. 11 is a semiconductor device 1100 comprising a PGA1101 and a PVT sensor 1106 in accordance with an embodiment of the present invention. PGA1101 shown in fig. 11 is similar to PGA701 shown in fig. 7, except for the integration of a look-up table/state machine. Unlike PGA701 of fig. 1, PGA1101 does not include an on-chip look-up table/state machine. Alternatively, the PGA1101 communicates with the off-chip processor 1002 that has downloaded the firmware lookup table 1104. The firmware lookup table 1104 may include control signals and desired gain indices as described above with reference to fig. 9. In one example, the firmware lookup table is programmed with a circuit description of the PGA (e.g., written in C + +) to receive the output of the PVT sensor and the desired gain setting value and provide a compensated gain setting value back to the PGA based thereon. It should be appreciated that the circuit description storage look-up table may be written in any other programming language. In another example, the firmware lookup table is stored in one of an SRAM, EEPROM, or flash memory of the microprocessor; however, it should be appreciated that the firmware lookup table may be stored in any type of computer memory. The microprocessor 1102 may be located on the same Printed Circuit Board (PCB) (not shown) as the PGA 1101.

The microprocessor 1102 is programmed to control the gain and frequency response of the PGA 1101. The PVT sensor 1106 characterizes the process used to produce the PVT sensor (and the associated semiconductor device), senses the supply voltage level of the associated semiconductor device, senses the wafer temperature of the associated semiconductor device, and provides a corresponding P, V, T sensor signal to the microprocessor 1002 via bus 1112. The microprocessor 1102 receives P, V, T the sensor signal from the PVT sensor 1106 and maps the sensor signal and the user-provided desired gain to corresponding indices in the downloaded firmware lookup table 1104 to provide a compensated gain signal to the PGA1101 to compensate the sensed parameter. In one embodiment, the compensated gain signal is sent to the PGA1101 via the SPI1108 and is configured to control the operation of the amplifier 1111 and the attenuator as described above. By storing the firmware lookup table on a separate microprocessor 1102, the die area (die area) of the PGA1101 is reduced and the firmware lookup table 1104 can be easily updated by downloading an updated version of the firmware lookup table.

Shown in fig. 12 is a semiconductor device 1200 including a PGA1202 and a PVT sensor 1206 according to another embodiment of the present invention. The PGA1202 of fig. 12 is similar to the PGA1101 of fig. 11, except for the configuration of the connections between the PVT sensors 1206 and the microprocessor 1208. Unlike the PGA1101 of fig. 11, the PGA1202 of fig. 12 does not include a separate bus connecting the PVT sensor 1206 to the microprocessor 1208. Alternatively, the PVT sensor 1206 provides P, V, T a sensor signal to the SPI1210, and the SPI1210 sends sensor signal communications from the PVT sensor 1206 to the microprocessor 1208.

The microprocessor 1208 is programmed to control the gain and frequency response of the PGA 1202. PVT sensor 1206 characterizes a process used to produce the PVT sensor (and the associated semiconductor device), senses the supply voltage level of the associated semiconductor device, senses a wafer temperature of the associated semiconductor device, and provides a corresponding P, V, T sensor signal to SPI 1210. The microprocessor 1208 receives P, V, T the sensor signal from the SPI1210 and maps the sensor signal and the user-provided desired gain to corresponding indices in the downloaded firmware lookup table 1212 in order to provide a compensated gain signal to the PGA1202 to compensate for the sensed parameter. In one embodiment, the compensated gain signal is sent to PGA1200 via SPI1210 and is configured to control the operation of amplifier 1214 and attenuator 1216 as described above. When interfacing the PVT sensor 1206 and the microprocessor 1208 using the SPI1210, a reduced PCB area or a simplified PCB wiring diagram (routing scheme) may be used. It should be appreciated that even though the connection between the PVT sensor 1206 and the microprocessor 1208 is different from that in fig. 7 and 11, the format of the control signal and the desired gain index may be the same as that described with reference to fig. 9.

Fig. 13 is a flow chart illustrating a method of operation of a PGA with an off-chip firmware query and PVT sensor in accordance with an embodiment of the present invention. The method begins at block 1302. At block 1304, the off-chip firmware lookup table receives a desired DC gain provided by the user. At block 1306, an off-chip firmware lookup table receives sensor data from the PVT sensors. At block 1308, the microprocessor configures the PGA in response to the sensor data from the PVT sensor and the user-provided desired DC gain as described above to produce the desired DC gain at the output of the PGA. At block 1310, a determination is made as to whether any parameter of the PGA (such as desired gain, process characterization, wafer temperature, and/or supply voltage) has changed. In response to a determination that there is no parameter change, then block 1310 is repeated. Alternatively, in response to a determination that there is at least one PGA parameter change, at block 1312 the microprocessor queries the firmware lookup table for a corresponding modification, and at block 1314, in response to a corresponding modification found in the firmware lookup table, the microprocessor configures the PGA1202 by providing a corresponding gain setting to the PGA as described above to offset the (counteract) changed parameter, and maintain the desired DC gain. It should be appreciated that the modification of the frequency response of the PGA may be performed in a similar manner.

It should be appreciated that although the PVT sensor of the present invention has been described with respect to the PGA of a CATV system, the PVT sensor may be used in any other device that is sensitive to temperature, voltage or process variations and in which stable output is desired. For example, PVT sensors may be used in digital logic circuits to adjust input or output buffer impedance, or to improve stability of the integrated oscillator and to improve integrated circuit oscillator performance uniformity from oscillator chip to oscillator chip.

In accordance with the present invention, disadvantages associated with sensitive semiconductor devices, such as inconsistencies, are reduced by providing a sensor that is capable of sensing the voltage level and temperature at which the device operates, sensing parameters indicative of the process by which the device is produced in order to characterize the performance of the device, and providing a sensor signal that can be used to compensate the device in order to ensure more consistent performance.

As described above, embodiments of the present invention contemplate a process, voltage, and temperature (PVT) sensor configured to sense a process parameter indicative of a process used to produce an associated co-formed device, a supply voltage level at which the associated device is operated, and a temperature at which the associated device is operated. It should be appreciated that in one embodiment, the PVT sensor is implemented on the same integrated circuit and formed from the same process steps as the associated device, such that the parameters sensed by the PVT sensor accurately reflect the parameters of the associated device. However, in another embodiment, the PVT sensor and associated devices may also be implemented on separate integrated circuits that are in close proximity to each other (e.g., attached to the same substrate). Where the PVT sensors are implemented on separate integrated circuits relative to the associated device but are in close physical proximity to each other (e.g., on the same substrate) and are powered by the same power supply, the PVT sensors can be used to provide compensated process temperature signals and power supply voltage signals that accurately reflect the temperature and power supply voltage of the associated semiconductor device

According to one embodiment, sensed process parameters indicative of a process used to produce the PVT sensor and associated co-formed semiconductor device are used to qualitatively characterize the performance of the associated device, and an output signal indicative of the performance of the PVT sensor and associated device, a sensed operating supply voltage level of the PVT sensor and associated device, and a sensed operating temperature of the PVT sensor and associated device are provided. These output signals may be used to configure the associated device to compensate for the associated device to provide a more consistent output regardless of performance differences between different chips of the same design and manufacture, and regardless of differences in the conditions under which the devices operate. In one embodiment, at least a portion of the associated device is programmable and the portion is programmed in response to the output signal to compensate the associated device to provide a consistent output. In another embodiment, a device operatively located downstream from the associated device can be configured in response to the output signal to compensate for performance differences in the associated device.

Having thus described several aspects of at least one embodiment of this invention, it is to be appreciated various alterations, modifications, and improvements will readily occur to those skilled in the art. Such alterations, modifications, and improvements are intended to be part of this disclosure, and are intended to be within the scope of the invention. Accordingly, the foregoing description and drawings are by way of example only.

Claims (20)

1. A semiconductor process sensor, comprising:

a constant reference voltage source configured to generate a constant reference voltage signal;

a process sensor element coupled to the constant reference voltage source and configured to receive the constant reference voltage signal, sense a process parameter indicative of a semiconductor process used to form the semiconductor process sensor, and generate a process measurement signal characterizing the semiconductor process used to form the semiconductor process sensor as one of nominal, above nominal, or below nominal based on the sensed process parameter.

2. The semiconductor process sensor of claim 1, wherein the process measurement signal characterizes the semiconductor process as one of slow, nominal, and fast.

3. The semiconductor process sensor of claim 2, wherein the semiconductor process is characterized as one of slow, nominal, and fast, which is transistor type specific.

4. The semiconductor process sensor of claim 1, further comprising an encoder coupled to the process sensor element and configured to receive the process measurement signal and encode the process measurement signal into a digital process measurement signal.

5. The semiconductor process sensor of claim 1, wherein the process sensor element comprises:

a process sense resistor having a first terminal electrically coupled to the constant reference voltage source and a second terminal providing a sensed voltage signal, the process sense resistor having a resistance that is dependent on at least one variable in a semiconductor process used to form the semiconductor process sensor;

a constant current source electrically coupled to the second terminal of the process sense resistor; and

an analog-to-digital converter coupled to the second terminal of the process sense resistor and configured to provide a process measurement signal indicative of a semiconductor process used to form the semiconductor process sensor.

6. The semiconductor process sensor of claim 5, further comprising a voltage divider having an input electrically coupled to the output of the constant reference voltage source and a plurality of outputs, each of the outputs providing one of a plurality of different reference voltage signals, the voltage divider comprising a plurality of resistors connected in series between the input and reference terminals of the voltage divider, the voltage divider providing at least one of the plurality of voltage signals to the analog-to-digital converter.

7. The semiconductor process sensor of claim 6, wherein each of the plurality of resistors of the voltage divider and the process sense resistor have a height, a width, and a length, the height, the width, and the length of each of the plurality of resistors of the voltage divider are the same, the height of the process sense resistor is approximately the same as the height of each of the plurality of resistors of the voltage divider, and the width of the process sense resistor is less than the width of each of the plurality of resistors of the voltage divider.

8. The semiconductor process sensor of claim 6, wherein the analog-to-digital converter comprises at least one comparator, the at least one comparator has a first input electrically coupled to the first of the plurality of outputs of the voltage divider to receive a first reference voltage signal, a second input electrically coupled to the second of the plurality of outputs of the voltage divider to receive a second reference voltage signal, and a third input electrically coupled to the second terminal of the process sense resistor to receive the sensed voltage signal, the at least one comparator is configured to compare the sensed voltage signal with first and second voltage reference signals, and providing at least one comparator output signal, the at least one comparator output signal being a process measurement signal indicative of a semiconductor process used to form the semiconductor process sensor.

9. The semiconductor process sensor of claim 8, wherein the plurality of resistors comprises:

a first resistor having a first terminal and a second terminal, the first terminal of the first resistor being electrically coupled to the input of the voltage divider and the first terminal of the process sense resistor, and the second terminal of the first resistor being electrically coupled to the first input of the at least one comparator;

a second resistor having a first terminal and a second terminal, the first terminal of the second resistor being electrically coupled to the second terminal of the first resistor and the second terminal of the second resistor being electrically coupled to the input of the constant reference voltage source;

a third resistor having a first terminal and a second terminal, the first terminal of the third resistor being electrically coupled to the second terminal of the second resistor and the second terminal of the third resistor being electrically coupled to the second input of the at least one comparator; and

a fourth resistor having a first terminal and a second terminal, the first terminal of the fourth resistor being electrically coupled to the second terminal of the third resistor and the second terminal of the fourth resistor being electrically coupled to the reference terminal.

10. The semiconductor process sensor of claim 8, wherein the at least one comparator comprises:

a first comparator having a first input for receiving a first reference voltage signal and a second input for receiving a sensed voltage signal, the first comparator configured to compare the sensed voltage signal to the first reference voltage signal and provide a first comparator output signal in response to the sensed voltage signal being greater than the first reference voltage signal and provide a second comparator output signal in response to the sensed voltage signal being less than the first reference voltage signal; and

a second comparator having a first input for receiving a second reference voltage signal and a second input for receiving a sensed voltage signal, the second comparator configured to compare the sensed voltage signal to the second reference voltage signal and provide a third comparator output signal in response to the sensed voltage signal being greater than the second reference voltage signal and provide a fourth comparator output signal in response to the sensed voltage signal being less than the second reference voltage signal.

11. The semiconductor process sensor of claim 10, further comprising an encoder having a first input for receiving the first comparator output signal, a second input for receiving the second comparator output signal, a third input for receiving the third comparator output signal, and a fourth input for receiving the fourth comparator output signal, the encoder configured to assert the first output signal in response to the sensed voltage signal being greater than the first reference voltage signal, to assert the second output signal in response to the sensed voltage signal being less than the first reference voltage signal and greater than the second reference voltage signal, and to assert the third output signal in response to the sensed voltage signal being less than the second reference voltage signal.

12. The semiconductor process sensor of claim 11, wherein the first output signal characterizes the semiconductor process as fast, the second output signal characterizes the semiconductor process as nominal, and the third output signal characterizes the semiconductor process as slow.

13. The semiconductor process sensor of claim 12, further comprising a digital buffer coupled to the encoder and configured to provide the first, second, and third output signals to an output of the semiconductor process sensor.

14. The semiconductor process sensor of claim 1, wherein the process sensor element generates the process measurement signal each time the semiconductor process sensor is powered up.

15. A method of characterizing a semiconductor process used to form a semiconductor process sensor, the method comprising acts of:

providing a constant reference voltage to the process sensing element;

sensing, with the process sensing element, a process parameter indicative of a semiconductor process used to form a semiconductor process sensor; and

based on the sensing operation, a process measurement signal is generated that characterizes the semiconductor process used to form the semiconductor process sensor as one of nominal, above nominal, or below nominal.

16. The method of claim 15, wherein generating a process measurement signal comprises performing a characterization specific to a type of transistor in which the semiconductor process is performed.

17. The method of claim 15, wherein sensing a process parameter comprises determining a sensed voltage drop across a process sensing element, and generating a process measurement signal comprises generating a process measurement signal characterizing the semiconductor process as one of nominal, above nominal, or below nominal based on the sensed voltage.

18. The method of claim 17, wherein said generating a process measurement signal comprises the operations of:

generating a plurality of different reference voltages based on a constant reference voltage;

comparing a plurality of different reference voltages to the sensed voltage; and

the semiconductor processing process is characterized based on the comparison operation.

19. The method of claim 18, wherein the characterizing operation comprises operations of:

characterizing the semiconductor processing process as fast in response to the sensed voltage being greater than the first reference voltage;

characterizing the semiconductor processing process as nominal in response to the sensed voltage being less than the first reference voltage and greater than the second reference voltage;

in response to the sensed voltage being less than the second reference voltage, characterizing the semiconductor processing process as slow.

20. A semiconductor process sensor, comprising:

a constant reference voltage source configured to generate a constant reference voltage signal;

a process sensing element coupled to the constant reference voltage source; and

for sensing a voltage drop across a process sensing element and for characterizing a semiconductor process used to form a semiconductor process sensor as one of nominal, above nominal and below nominal based on the voltage drop.