CN1328758C - Manufacturing method of multifunction integrated sensor chip - Google Patents

Abstract

The invention discloses a method for manufacturing a multifunctional integrated sensor chip, which uses micro-mechanical electronic system technology and integrated circuit micro-machining technology to manufacture three sensors that can be sensitive to pressure, temperature and humidity respectively on a tube core with an area of 5mm×5mm The three units are based on different effects. The pressure unit is based on the piezoresistive effect and is mainly used to detect changes in environmental pressure; the temperature unit is based on the thermal resistance effect and is used to detect changes in ambient temperature; the humidity unit is based on the capacitance principle and is used to Detect changes in ambient humidity. The multifunctional integrated sensor chip produced by the present invention can be used to detect parameters related to human comfort such as environmental pressure, temperature, humidity, etc., and provide a small environment with satisfactory comfort for environmental control equipment, and can be integrated on portable instruments, such as watches, Mobile phones, etc., portable and easy to use.

Description

Method for making multifunctional integrated sensor chip

technical field

The invention belongs to the technical fields of micro-mechanical electronic system (MEMS) technology and integrated circuit micro-processing technology, and in particular relates to a method for producing a multifunctional integrated sensor chip using the micro-mechanical electronic system (MEMS) technology and integrated circuit micro-processing technology.

Background technique

At present, various single-function sensor manufacturing technologies based on MEMS technology have become more and more mature, and sensor technology is developing in the direction of integration and intelligence. There are three ways to integrate sensors: one is to integrate multiple sensors with the same function or similar functions into a one-dimensional or two-dimensional sensor array; the second is to integrate sensors and integrated circuits on the same chip; the third One refers to the integration of different types of sensors, such as sensors that integrate sensitive units such as pressure, temperature, humidity, flow, and acceleration.

At present, domestic research on sensor integration focuses on the second type mentioned above. Through a unified CMOS process or flip-chip technology, the sensor and processing circuit are integrated on one chip to improve the detection accuracy of the sensor. Realize intelligence and expand its application range. However, there are relatively few studies on the integration of various functional sensors on a die, mainly integrating two devices of temperature and humidity.

There are many studies abroad on the third integration method, such as NASA-JPL (National Aeronautics and Space Administration-Jet Propulsion Laboratory) has studied the mini-weather stations (Mini-weather stations), which integrates pressure, temperature, micro-humidity, radiation sensor, hydrometer and laser Doppler anemometer, etc.; the ST-3000 smart sensor chip size of American Honywell Company is 3×4×2mm ³ , which integrates CPU, EPROM and three sensors of static pressure, differential pressure and temperature ; The composite mechanical sensor developed by EG&G IC Sensors in the United States can simultaneously measure the three-dimensional vibration acceleration, velocity, and displacement of a certain point of an object; NEC has developed an integrated FET sensor that detects the four components of glucose, urea, vitamin K, and albumin .

The main advantages of the multifunctional integrated sensor are: it can make the sensor detect from point to surface or even to the body, so as to realize multi-dimensional information, and change single parameter detection into multi-parameter detection. Integration will enable sensor technology to gain benefits in the following aspects: (1) Small size, light weight, and low cost; (2) Good fault tolerance, high confidence, and stable performance; (3) Increased measurement dimensions and improved spatial resolution , expanding the coverage of space and time; (4) improving the detection performance, increasing the effectiveness of the response, and improving the reliability and maintainability of the system. Integration will also reduce the performance requirements for a single sensor, but when integrating multiple sensing elements, it is necessary to fully consider the performance complementarity, electromagnetic compatibility, and resource sharing of sensing elements.

However, there are the following difficulties in integrating multiple sensors on one chip: first, the processing technology of various types of sensors may not be compatible; second, if a certain sensor on the same die needs to be in direct contact with the external environment , while other sensors must be sealed, which will cause difficulties in integrated packaging. Even so, the above-mentioned problems can be completely resolved if the integrated sensor type is carefully selected, and the packaging structure and processing technology are arranged reasonably.

With the improvement of human living standards and higher requirements for the living environment, it is necessary to detect the environmental quality of living places, such as pressure, temperature, humidity and other indicators closely related to human comfort, and it is required to be portable, Easy to use.

Contents of the invention

The purpose of the present invention is to provide a method for making a multifunctional integrated sensor chip, using micro-electromechanical systems (MEMS) technology and integrated circuit micro-machining technology, to make on a single tube core for detecting indicators related to human comfort such as pressure, Multifunctional integrated sensor for temperature and humidity.

The technical solution adopted to achieve the above object is a method for manufacturing a multi-functional integrated sensor chip, which is characterized in that, using micro-mechanical electronic system technology and integrated circuit micro-machining technology to produce energy Three sensor units sensitive to pressure, temperature and humidity respectively; the manufacturing method thereof comprises the following steps:

1) Oxidizing the cleaned n-type single crystal silicon wafer to form a silicon dioxide layer of 800±50nm;

2) Then coat photoresist on the silicon dioxide layer, add a resistive strip mask plate, and photocut the shape of the resistive strip structure of the pressure unit and temperature sensor unit on the front side, and diffuse the boron at a concentration of 2×10 ¹⁹ /cm ³ ions to form a p-type resistance strip with a junction depth of 2-2.5 μm;

3) forming silicon nitride with a thickness of 120nm±20nm as a stress matching layer on the silicon dioxide layer by low-pressure vapor deposition;

4) Add a back cavity mask plate, photolithography on the back, remove part of the silicon dioxide, and use a mixture of ethylenediamine, catechol and water (EPW) to anisotropically etch the n-type silicon substrate to form a film C-cup pressure chamber with a thickness of 25 μm;

5) Add a resistance hole mask plate, and form resistance holes by photolithography on the front side;

6) Then sputter the silicon-aluminum material with a ratio of Si:Al=1:99 on the front side, with a thickness of 2.5 μm to 3.0 μm;

7) Add electrode mask plate, etch electrode shape, form electrode leads of pressure, temperature, humidity sensor unit, and form interdigitated electrode of humidity sensor unit;

8) Carry out metallization treatment for 30 minutes in a _N2 environment at a temperature of 480°C to form an ohmic contact;

9) Carrying out vacuum electrostatic bonding, encapsulating the n-type monocrystalline silicon wafer on borosilicate glass with a thickness of 2 mm, and forming a vacuum chamber with a vacuum degree of 10 ^-5 millitorr in the cavity area for detecting the ambient pressure;

10) Evenly coat the moisture-sensitive film on the humidity unit;

11) Finally perform dicing into individual dies.

The chip produced by the method of the invention has small volume and low energy consumption, and is easy to be packaged on popular portable instruments such as watches and mobile phones, and is convenient to use.

Description of drawings

Fig. 1 is a schematic diagram of the structure of the present invention.

Fig. 2 is a schematic diagram of the resistance strip structure of the pressure unit in the present invention.

Fig. 3 is a working principle diagram of the pressure unit of the present invention.

Fig. 4 is a schematic diagram of the resistance strip structure of the temperature unit in the present invention.

Fig. 5 is a schematic diagram of the electrode structure of the humidity unit in the present invention.

Fig. 6 is a physical photo of the present invention.

The structural principle and working principle of the present invention will be described in detail below in conjunction with the accompanying drawings.

Detailed ways

With reference to Fig. 1, the present invention makes three sensitive units: pressure I, temperature II and humidity unit III on (100) crystal plane, 5mm * 5mm tube core by MEMS technology and integrated circuit micromachining technology, the back side of pressure unit I is C-type silicon cup, temperature II and humidity unit III are arranged in the fixed support area of the die to eliminate the influence of pressure on the temperature and humidity unit, the chip is packaged on borosilicate glass 1 by vacuum bonding process, the key technology of which It lies in the process compatibility during the production process. The three units are based on different effects. The pressure unit is based on the piezoresistive effect and is mainly used to detect environmental pressure changes; the temperature unit is based on the thermal resistance effect and is used to detect changes in ambient temperature; the humidity unit is based on the capacitance principle and is used to detect environmental changes. changes in humidity.

The basic manufacturing process is as follows: the cleaned n-type (001) single crystal silicon wafer 2 is oxidized to form a silicon dioxide layer 4 of 800±50nm; the photoresist is coated, a resistive strip mask is added, and the pressure is etched on the front side. The resistance strip shape of unit I and temperature unit II, the diffusion concentration of boron ions is 2×10 ¹⁹ /cm ³ , forming a p-type resistance strip layer 3 with a junction depth of 2-2.5 μm, including four resistance strips of pressure unit I Line 7 and resistance strip 10 of temperature unit II; form a silicon nitride layer 5 with a thickness of 120nm±20nm as a stress matching layer by low-pressure vapor deposition (LPCVD); add a back cavity mask plate, backside photolithography, and remove part of silicon dioxide Layer 4, using EPW (a mixture of ethylenediamine, catechol and water) etching solution to anisotropically etch the n-type monocrystalline silicon substrate 2 to form a C-shaped cup pressure chamber with a film thickness of 25 μm; add resistance holes For the mask plate, resist holes are formed by photolithography on the front side; then the silicon aluminum material with a ratio of Si:Al=1:99 is sputtered on the front side, and the thickness is 2.5-3.0 μm; an electrode mask plate is added to etch out the pressure unit I Electrode leads 8 and pressure welding block series 9, electrode leads 11 and pressure welding block series 12 of temperature unit II and electrode leads 14 and pressure welding block series 15 of humidity unit III, and form interdigitated electrodes 13 of humidity unit III; 30 minutes of metallization in a _N2 environment at a temperature of 480 ° C is conducive to the formation of ohmic contacts; vacuum electrostatic bonding is performed to package the silicon chip on a 2mm thick borosilicate glass 1 and form a vacuum in the cavity area A vacuum chamber with a temperature of 10 ^-5 millitorr is used to detect the ambient pressure; the moisture-sensitive film 6 is evenly coated on the humidity unit; and finally, dicing is performed into a single die.

The working principles of the three sensitive units are introduced below.

The pressure sheet I mainly includes four p-type piezoresistive resistance strips 7, electrode leads 8 and pressure soldering block series 9. The function of the pressure soldering block series 9 is to realize the internal and external leads of the chip through gold wire ball bonding. The four resistance strips 7 are all along the silicon film The crystal orientation is arranged at the place of stress concentration, and the shape and structure are shown in schematic diagram 2. A cavity is formed on the back of the pressure unit I through an anisotropic etching technique, and a vacuum is formed after the tube core is vacuum-bonded with the borosilicate glass 1 . When the external environment pressure P acts on the silicon membrane, the silicon membrane is deformed and the disturbance W _P is generated, as shown in Figure 3. Based on the piezoresistive effect, the resistance of two of the resistance strips becomes larger, and the resistance of the other two becomes smaller. The Wheatstone full bridge composed of four resistance strips is excited by a constant power supply, and the output and the external environment pressure P is proportional to the electrical signal to realize the detection of external pressure.

The temperature unit II includes a p-type resistance strip 10 formed by a diffusion process as shown in FIG. The p-type resistance strips 10 are arranged in the [100] crystal orientation of the silicon wafer, and since the piezoresistive coefficient of the [100] crystal orientation is small, the influence of pressure on the temperature unit can be reduced. The resistivity of the resistor strip is as follows:

$\mathrm{<span\; class="notranslate">\; \&rho;</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; Q</span>}{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; Q</span>}{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}}$

In the formula, μ _n and μ _p are the mobilities of n-type and p-type carriers, respectively, q is the electron charge, and N and P are doped with n-type and p-type carrier concentrations in Si, respectively.

For p-type silicon, there is p>>N, so

$\mathrm{<span\; class="notranslate">\; \&rho;</span>}<span\; class="notranslate">\; \&ap;</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; Q</span>}{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}}$

Among them, μ _p is inversely proportional to the temperature T, so as the temperature changes, the resistivity ρ changes proportionally. According to the following formula,

$\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; \&rho;</span>}\frac{\mathrm{<span\; class="notranslate">\; L</span>}}{\mathrm{<span\; class="notranslate">\; S</span>}}$

In the formula, R is the resistance value of the resistance strip, ρ is the resistivity, L is the length of the resistance strip, and S is the cross-sectional area of the resistance strip.

Through the pressure welding block series 12, the outer leads are drawn out through gold wire ball welding, and the proportional relationship between the ambient temperature T and the resistance value R of the resistance bar can be obtained, so that T can be measured.

Humidity unit III forms an aluminum layer with a thickness of 2.5 to 3.0 μm on the silicon chip through a sputtering process, and then forms interdigitated electrodes 13, electrode leads 14 and a series of pads 15 through an etching process, as shown in Figure 5. Wherein the interdigitated electrode 13 includes an electrode 51 plate and an electrode 52 plate. A moisture-sensitive material with strong moisture absorption and dehumidification ability is selected and evenly coated in the gaps of the interdigital electrodes to form a moisture-sensitive film 6 with a thickness of 3 μm. When the humidity of the environment changes, the dielectric constant ε of the moisture-sensitive film 6 changes proportionally,

according to $C=\frac{\mathrm{\&epsiv;S}}{d}$ , where S and d are respectively the cross-sectional area of the electrode and the distance between the two electrodes, and S and d are constant. Therefore, through the pressure soldering block series 15, the outer lead is drawn out through gold wire ball bonding, and the change with the ambient humidity can be measured. proportional to the capacitance C value.

Shown in Fig. 6 is the multifunctional integrated sensor chip prepared by the method of the present invention, which has the advantages of small size, high integration, multifunctionality, and low cost, and can be widely used to detect environmental pressure, temperature, humidity, etc. and human comfort The parameters related to the degree of comfort are provided to the environmental control equipment to achieve a small environment with satisfactory comfort, and can be packaged with portable instruments, such as watches and mobile phones, which are easy to use.

Claims (4)

1. the manufacture method of a multifunction integrated sensor chip, it is characterized in that, adopt micromechanics electronic system technology and integrated circuit micro-processing technology on the tube core of a 5mm * 5mm area, to produce and to distinguish responsive pressure, temperature, three sensor units of humidity; Its manufacture method comprises the following steps:

1) will form the silicon dioxide layer of 800 ± 50nm through the n type monocrystalline silicon piece that cleans through peroxidating;

2) apply photoresist then on silicon dioxide layer, add the resistor stripe mask plate, front lighting carves the resistor stripe planform of pressure unit and temperature sensor unit, and diffusion concentration is 2 * 10 ¹⁹/ cm ³The boron ion, forming junction depth is the p type resistor stripe of 2～2.5 μ m;

3) forming thickness by low pressure gas phase deposition again on silicon dioxide layer is that 120nm ± 20nm silicon nitride is as the stress matching layer;

4) add back of the body chamber mask plate, part silicon dioxide is removed in back side photoetching, and adopting the mixture corrosive liquid of ethylenediamine, catechol and water is that EPW carries out anisotropic etch to n type silicon base, and forming thickness is the C type cup pressure chamber of 25 μ m;

5) add resistance hole mask plate, positive photoetching forms the resistance hole;

6) to carry out the sputter ratio be Si: Al=1 in the front then: 99 silica-alumina material, thickness are 2.5 μ m～3.0 μ m;

7) add the electrode mask plate, the etching electrode shape forms the contact conductor of pressure, temperature, humidity sensor unit, and forms the interdigital electrode of humidity sensor unit;

8) in temperature be 480 ℃ N ₂Carry out 30 minutes metalized in the environment, form ohmic contact;

9) carry out the vacuum static electricity bonding, n type monocrystalline silicon piece is encapsulated on the thick Pyrex of 2mm, and to form vacuum degree in cavity area be 10 ^-5The vacuum chamber of millitorr is used for testing environment pressure;

10) evenly apply humidity-sensitive film in the humidity unit;

11) be diced into singulated dies at last.

2. the method for claim 1 is characterized in that, described pressure unit comprises four p type pressure drag resistor stripes, contact conductor and press welding block series, four Hui Sideng full-bridges that p type pressure drag resistor stripe constitutes; Press welding block series is used for realizing in the chip and the outer lead-in wire of chip by gold ball bonding; Four resistor stripes are all along silicon fiml

The crystal orientation is arranged in stress raiser, and the back side of pressure unit forms pressure chamber by anisotropic corrosion technique, forms vacuum behind tube core and the Pyrex vacuum bonding.

3. the method for claim 1 is characterized in that, described temperature unit comprises contact conductor and the press welding block series that p type resistor stripe and sputter, etching technics form, and p type resistor stripe is arranged in [100] crystal orientation of silicon chip.

4. the method for claim 1, it is characterized in that, described humidity unit forms the aluminium lamination that thickness is 2.5～3.0 μ m by sputtering technology on silicon, form interdigitation electrode, contact conductor and press welding block series by etching technics again, wherein the interdigitation electrode comprises two electrode pads; Select for use the stronger wet sensory material of moisture absorption and dehumidification ability evenly to be coated in the space of interdigital electrode, forming thickness is the humidity-sensitive film of 3 μ m; When the humidity of environment changes, the proportional variation of the DIELECTRIC CONSTANT of humidity-sensitive film,

According to formula $C=\frac{\mathrm{\&epsiv;S}}{d},$ Wherein S, d are sectional area and two electrode spacings that are respectively electrode, and S, d are constant, therefore by press welding block series, draw outer lead through gold ball bonding, just can record and the proportional capacitor C value of the variation of ambient humidity.