JP2011103354A - Evaluation method and evaluation device of rear surface roughness of semiconductor wafer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an evaluation method of rear surface roughness of a semiconductor wafer for evaluating rear surface roughness easily. <P>SOLUTION: The evaluation method includes: glossiness acquiring processes (A10-A30) for acquiring glossiness measured at a specific incident angle which reflects power spectrum density of an irregular component belonging to a specific wavelength region out of irregular components of a rear surface of the etched semiconductor wafer; and an evaluation process (A40) for evaluating roughness of a wafer rear surface by determining whether the glossiness is in an allowable range or not. At that time, power spectrum density of the irregular component belonging to the specific wavelength region is power spectrum density correlating to a leak amount of inert gas supplied as a heat exchange medium between the wafer rear surface and an attraction surface of an electrostatic chuck plate. The allowable range correlates with a range of the leak amount. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a back surface roughness evaluation method and an evaluation apparatus for a semiconductor wafer or the like.

  Conventionally, in manufacturing a device (semiconductor element) from a semiconductor wafer in which only the front surface is mirror-polished (hereinafter, a silicon wafer which is a representative example thereof) is manufactured, the silicon wafer is subjected to chemical vapor deposition (CVD). It is known that a thin film is deposited on the front surface of the wafer by processing, or a thin film is partially removed by dry etching.

In these processes, the wafer front surface is generally processed by electrostatic chucking the back surface of the wafer to the chucking surface of the chuck plate, and the thin film deposition thickness by the CVD process and the etching rate of the dry etching process are set. In order to make the front surface uniform, it is necessary to keep the temperature of the silicon wafer uniform in the front surface.
The temperature of the silicon wafer is adjusted by heat exchange between the chuck plate and the silicon wafer. This heat exchange is affected by the contact between the wafer back surface and the chuck suction surface, and this contact property depends on the roughness of the wafer back surface and the shape of the chuck suction surface. In other words, the chuck suction surface is grooved so as not to bite dust between the wafer back surface and the chuck suction surface, and the wafer back surface has irregularities (roughness). Is not completely in contact with the chuck suction surface over the entire surface, and a contact portion and a non-contact portion are generated.

  Therefore, helium gas is supplied as a heat exchange medium from the supply port formed in the chuck suction surface to the gap formed in the non-contact portion between the chuck suction surface and the wafer back surface, and the uniformity within the heat exchange surface Is being promoted. In this case, the amount of helium gas set according to not only the set temperature on the wafer front surface but also the groove shape of the chuck suction surface and the roughness of the back surface of the wafer (supply amount per unit time (flow rate)) It is supplied so as to fill a gap between the wafer and the electrostatic chuck. If the supply amount of helium gas is small, the heat exchange action becomes insufficient, and as a result, the temperature distribution on the front surface of the wafer becomes non-uniform. On the other hand, if the supply amount of helium gas is large, the heat exchange operation is sufficiently performed, and as a result, the temperature distribution on the front surface of the wafer becomes uniform, but the temperature on the front surface of the wafer becomes lower than the set temperature. Things happen. For this reason, it is necessary to set the supply amount of helium gas according to the groove shape of the chuck suction surface and the roughness of the back surface of the wafer so that the temperature on the front surface of the wafer becomes the set temperature.

  By the way, in recent years, with the high integration of devices, in order to further improve the flatness of a silicon wafer, the technique has shifted from acid etching to alkaline etching in an etching process which is one manufacturing process of a silicon wafer. Therefore, silicon wafers provided to device manufacturers are in a state where both those having an acid etching surface and those having an alkali etching surface are mixed.

  Under such circumstances, glossiness measured according to a conventionally used index of wafer roughness, for example, Ra (arithmetic average roughness) or an incident angle of 20 degrees or 60 degrees defined by JIS. It has been confirmed that when the supply amount of the helium gas is set according to the above and the helium gas is supplied at the set supply amount, the heat exchange performance varies even with the same Ra and glossiness.

  This is because the acid-etched surface and the alkali-etched surface have different roughness properties, but according to the Ra and the glossiness, even if the roughness properties are different, they have the same value. There is a case where helium gas partially leaks from the gap between the wafer back surface and the chuck adsorption surface, even if the Ra and the glossiness are the same value, due to the difference in the roughness characteristics of the wafer back surface. This is thought to be due to variations.

For this reason, for example, the supply amount of helium gas is set for an acid etching surface having a certain Ra value (for example, x), and then the above supply amount is set for an alkali etching surface having the same Ra value x. When helium gas is supplied, there may be a case where the supply amount of helium gas is insufficient.
That is, in setting the amount of helium gas supplied in the device manufacturing process, there are cases where the conventional roughness index cannot be used, and therefore, a new index that replaces the conventional index has been desired.

  In response to such a request, as disclosed in Patent Document 1, there is a technique for evaluating the contact between the wafer back surface and the chuck suction surface, and consequently the roughness of the wafer back surface, using the leak amount of helium gas as an index. Proposed and implemented.

JP 2004-247404 A

  As described above, when the etching surface of the wafer is manufactured so that the leakage amount is within a predetermined range (for example, 0.1 ml / min or less) using the leakage amount as an index, any surface of the alkali etching surface and the acid etching surface can be obtained. Even so, the supply amount of helium gas and other conditions can be made common during the CVD process and the dry etching process in the device manufacturing process. However, there is a problem that it takes a long time to measure the leak amount.

  The present invention has been devised in view of such problems, and provides a backside roughness evaluation method and an evaluation apparatus for a semiconductor wafer that can easily evaluate the roughness of the backside of a semiconductor wafer. With the goal.

  In order to achieve the above object, the semiconductor wafer back surface roughness evaluation method according to claim 1 of the present invention is to calculate the power spectral density of the concavo-convex component belonging to a specific wavelength region among the concavo-convex components of the back surface of the etched semiconductor wafer. A glossiness acquisition step for obtaining a glossiness measured at a specific incident angle to be reflected, and determining whether or not the glossiness obtained in the glossiness acquisition step is within an allowable range. An evaluation step for evaluating the roughness of the semiconductor wafer, and the power spectral density of the concavo-convex component belonging to the specific wavelength region is measured between a back surface of the semiconductor wafer and a suction surface of a chuck plate that electrostatically chucks the back surface of the semiconductor wafer. The power spectral density correlates with the leak amount of the inert gas supplied as the exchange medium, and the allowable range is a range of the leak amount. Characterized in that it is a tolerance correlated with.

The semiconductor wafer back surface roughness evaluation method according to claim 2 is the semiconductor wafer back surface roughness evaluation method according to claim 1, wherein the specific wavelength region is a region of 80 to 120 μm, The specific incident angle is in the range of 80 to 90 degrees.
According to a third aspect of the present invention, there is provided a semiconductor wafer back surface roughness evaluation apparatus, comprising: a light source for irradiating light at a specific incident angle on the back surface of an etched semiconductor wafer; and reflecting in a specular reflection direction from the back surface of the semiconductor wafer. A light receiver for receiving the reflected light, calculation means for obtaining the glossiness of the reflected light, and determining whether the calculated glossiness is within a preset allowable range, thereby determining the semiconductor wafer. Evaluation means for evaluating the roughness of the back surface of the semiconductor wafer, wherein the specific incident angle is an angle for capturing a concavo-convex component belonging to a specific wavelength region among the concavo-convex components on the back surface of the semiconductor wafer, and belongs to the specific wavelength region The uneven component has a power spectral density between the back surface of the semiconductor wafer and the adsorption surface of the chuck plate that electrostatically chucks the back surface of the semiconductor wafer. A profile-component which correlates with the amount of leakage of the inert gas supplied as the allowable range, characterized in that it is a tolerance correlated with the range of the leakage amount.

  The backside roughness evaluation apparatus for a semiconductor wafer according to a fourth aspect of the present invention is the backside roughness evaluation apparatus for a semiconductor wafer according to the third aspect, wherein the specific wavelength region is an area of 80 to 120 μm, The specific incident angle is in the range of 80 to 90 degrees.

According to the semiconductor wafer back surface roughness evaluation method and evaluation apparatus of the present invention, the gloss measurement time is short and sufficient, and therefore the back surface (etching) of the silicon wafer W whose surface is mirror-polished only. In the surface roughness setting, the roughness of the back surface of the semiconductor wafer can be easily evaluated.
Then, the amount of inert gas leakage during device manufacture correlates with the power spectral density of the concavo-convex component belonging to the specific wavelength region, and the glossiness of the specific incident angle indicates the power spectral density of the concavo-convex component belonging to the specific wavelength region. Therefore, by manufacturing the back surface so that the glossiness at the specific incident angle is within the allowable range, the leakage amount can also be within the allowable range, and the back surface that does not affect the device manufacturing is removed from the wafer. It can be satisfactorily manufactured at the manufacturing stage.

  Further, if the specific wavelength region is a region of 80 to 120 μm, and the concave and convex component belonging to the specific wavelength region is captured at an incident angle of 80 to 90 degrees, the concave and convex component corresponding to the wavelength of 80 to 120 μm is particularly an inert gas. Since the correlation with the leak amount is high, the wafer back surface that does not affect the device manufacturing can be manufactured more favorably at the wafer manufacturing stage.

It is a flowchart which shows the back surface roughness evaluation method of the semiconductor wafer which concerns on one Embodiment of this invention. It is a schematic diagram which shows the back surface roughness evaluation apparatus of the semiconductor wafer which concerns on one Embodiment of this invention. It is a graph which shows the power spectrum density according to wavelength of the roughness of the back surface of 11 types of sample wafers considered in the process of creating the back surface roughness evaluation method and evaluation apparatus of the semiconductor wafer which concerns on one Embodiment of this invention. It is the graph which plotted the power spectral density and helium gas flow rate in wavelength 5-15 micrometers considered in the process of creating the back surface roughness evaluation method and evaluation apparatus of the semiconductor wafer concerning one embodiment of the present invention. It is the graph which plotted the power spectrum density and helium gas flow rate in wavelength 45-55 micrometers considered in the process of creating the back surface roughness evaluation method and evaluation apparatus of the semiconductor wafer concerning one embodiment of the present invention. It is the graph which plotted the power spectrum density and the helium gas flow rate in wavelength 80-120 micrometers considered in the process of creating the back surface roughness evaluation method and evaluation apparatus of the semiconductor wafer concerning one Embodiment of this invention. It is the graph which plotted the power spectral density and helium gas flow rate in wavelength 500-600 micrometers considered in the process of creating the back surface roughness evaluation method and evaluation apparatus of the semiconductor wafer concerning one embodiment of the present invention. It is the graph which plotted the power spectrum density and helium gas flow rate in wavelength 1050-1150 micrometers considered in the process of creating the back surface roughness evaluation method and evaluation apparatus of the semiconductor wafer concerning one embodiment of the present invention. 1 is a schematic diagram of a leak amount measuring apparatus for measuring a leak amount, which is a prerequisite technique for a semiconductor wafer back surface roughness evaluation method and an evaluation apparatus according to an embodiment of the present invention. It is a flowchart which shows the helium gas flow rate measuring method used as the premise technique of the back surface roughness evaluation method and evaluation apparatus of the semiconductor wafer which concerns on one Embodiment of this invention. The helium gas flow rate and the glossiness of the back surface of the semiconductor wafer in the case where the incident angle is 15 to 25 degrees, considered in the process of creating the semiconductor wafer back surface roughness evaluation method and evaluation apparatus according to an embodiment of the present invention, It is a graph which shows correlation of these. Considered in the process of creating a semiconductor wafer back surface roughness evaluation method and evaluation apparatus according to an embodiment of the present invention, the helium gas flow rate and the glossiness of the back surface of the semiconductor wafer when the incident angle is 55 to 65 degrees It is a graph which shows correlation of these. Considered in the process of creating a semiconductor wafer back surface roughness evaluation method and evaluation apparatus according to an embodiment of the present invention, the helium gas flow rate and the glossiness of the back surface of the semiconductor wafer when the incident angle is 80 to 90 degrees It is a graph which shows correlation of these.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[One Embodiment]
With reference to FIGS. 1-13, the back surface roughness evaluation method and evaluation apparatus of the semiconductor wafer of one Embodiment of this invention are demonstrated.
<Configuration>
The semiconductor wafer back surface roughness evaluation method of the present invention is applied to a silicon wafer (semiconductor wafer) whose wafer back surface roughness is evaluated by a leak amount of an inert gas (for example, helium gas) in a device manufacturing stage (for example, in a device manufacturer). On the other hand, it is suitable for implementation at the wafer manufacturing stage (for example, at a wafer maker).

Before describing the method for evaluating the roughness of the back surface of a semiconductor wafer according to the present invention, a method for measuring a leakage amount, a wafer manufacturing method, and a device manufacturing method will be described.
<Measurement method of leak amount>
A method for measuring the leak amount will be described. As a method for measuring the leak amount, a leak amount measuring apparatus 1 as shown in FIG. 9 is used, and helium gas is used as an inert gas.

The leak amount measuring device 1 includes a chamber 2, an electrostatic chuck device 10, a vacuuming device 20, an air release device 30, a helium gas supply device 40, and a heating mechanism (not shown).
The electrostatic chuck apparatus 10 includes a chuck plate 11, a dielectric layer 12 formed on the chuck plate 11, and a power source (not shown) that applies a voltage to the dielectric layer 12. The dielectric layer 12 is charged by applying a voltage to the dielectric layer 12 from the power source, and the silicon wafer W is also charged along with this, and the Coulomb acting between the dielectric layer 12 and the silicon wafer W is actuated. By force, the back surface of the silicon wafer W can be attracted and fixed (electrostatic chuck) to the upper surface (chuck attracting surface) of the chuck plate 11. In addition, the chucking surface is grooved so that dust can be prevented from being bitten between the silicon wafer W and the chuck plate 11.

  The vacuuming device 20 is a device that evacuates the chamber 2, and includes a vacuum gauge 21 that measures the degree of vacuum in the chamber 2, a rotary pump 22 that evacuates the chamber 2 at a general speed, and the chamber 2 at a high speed. It has two vacuum pumps, a turbo molecular pump 23 that evacuates the inside. First, the inside of the chamber 2 is evacuated to some extent while removing dust by the rotary pump 22, and then the vacuum degree of the chamber 2 is reached to an absolute vacuum by the turbo molecular pump 23.

The atmosphere release device 30 is a device that supplies nitrogen into the chamber 2 to release the chamber 2 to the atmosphere, and includes a nitrogen tank 31, a nitrogen flow meter 32, and a nitrogen flow rate controller 33. The nitrogen flow rate controller 32 controls the flow rate of the nitrogen flowing into the chamber 2 from the nitrogen tank 31 while the nitrogen flow rate controller 33 controls the flow rate.
The helium gas supply device 40 is a device that supplies helium gas between the chuck plate 11 and the silicon wafer W, and includes a helium tank 41 that stores helium gas, a helium gas flow rate per unit time (helium gas supply amount). ), A timer (not shown) built in the flow meter 42, and a constant pressure controller 43 for controlling the helium gas flow rate per unit time so that the pressure in the chamber 2 is constant. have.

  Here, the amount of helium gas leak is not directly measured, but the amount of helium gas leak is determined using the flow rate of helium gas as an index. That is, since the helium gas flow rate controlled by the flow meter 42 and the amount of helium gas leakage are proportional so that the pressure in the chamber 2 is constant, the helium gas leakage amount is large when the helium gas flow rate is large. In addition, when the flow rate of helium gas is small, it is determined that the amount of leak of helium gas is small.

  With such a leak amount measuring apparatus 1, the leak amount is measured in the procedure as shown in FIG. As described above, here, the amount of helium gas leakage is not directly measured, but the amount of helium gas leakage is determined using the helium gas flow rate as an index. The pressure (kPa) of helium gas, the applied voltage (V), the chuck temperature (° C.), and the degree of vacuum (Pa) are appropriately set according to the groove shape of the chuck plate 11.

First, in step S <b> 10, the silicon wafer W is attached to the chuck plate 11.
Subsequently, in step S20, the chamber 2 is evacuated by the evacuation device 20. The degree of vacuum at this time is, for example, 5.0 × 10 ^{−5 to} 5.0 × 10 ⁻⁴ (kPa).
Subsequently, in step S30, the chuck plate 11 is heated by a heating mechanism (not shown), and the chuck plate 11 is held in a temperature range of, for example, 149.5 ° C. to 150.5 ° C. This is because if the temperature fluctuates during the measurement of the helium gas flow rate, the chuck plate 11 and the silicon wafer W are thermally expanded or contracted, so that the contact state between the back surface of the wafer and the chuck suction surface changes, resulting in a leak amount of helium gas. This is because the flow of helium gas varies as a result.

Subsequently, in step S40, counting of a timer (not shown) built in the flow meter 42 is started, and measurement of the helium gas flow rate is started by the flow meter 42 (timer count time t = 0).
Subsequently, in step S50, a voltage is applied to the dielectric layer 12 of the chuck plate 11 at the time point 10 seconds after the start of measurement (t = 10), and the wafer back surface is electrostatically chucked to the chuck attracting surface. In addition, the voltage application time of step S50 is not limited to the time of 10 seconds after the start of measurement as described above, and may be a time within the range of 1 to 20 seconds after the start of measurement.

Subsequently, in step S60, helium gas is supplied between the wafer back surface and the chuck suction surface by the helium gas supply device 40 at a time point (t = 30) 30 seconds after the start of measurement. Note that the time point of supplying the helium gas in step S60 is not limited to the time point of 30 seconds after the start of measurement as described above, and may be a time point within a range of 1 to 50 seconds after the start of measurement.
Subsequently, in step S70, the measurement of the helium gas flow rate is finished at 330 seconds (t = 330) after the start of measurement. Note that the end point of the helium gas flow rate measurement in step S70 is not limited to the point of time of 330 seconds after the start of measurement as described above, and may be a point in the range of 100 to 500 seconds after the start of measurement.

Subsequently, in step S80, nitrogen is supplied into the chamber 2 by the atmosphere release device 30 to release the inside of the chamber 2 into the atmosphere.
By such a method, with the wafer back surface electrostatically chucked to the chuck suction surface, the contact occurrence characteristics (in other words, heat exchange characteristics) between the wafer back surface and the chuck suction surface are measured. can do.
<Wafer manufacturing method>
Next, the silicon wafer W to be evaluated in the present invention will be described.

The silicon wafer W is manufactured by a manufacturing method including at least an etching process. For example, the silicon wafer W is manufactured through various processes such as a slicing process, a grinding process (or lapping process), an etching process, and a mirror polishing process in this order. It has come to be.
In the slicing step, the silicon wafer W is cut out by slicing the single crystal ingot with a slicing apparatus such as an inner peripheral blade or a wire saw.

In the grinding process, the front surface and the back surface of the silicon wafer W are ground one by one with fixed abrasive grains. In the lapping process, both surfaces of the plurality of wafers W are simultaneously lapped by the free abrasive grains.
In the etching process, both surfaces of the silicon wafer W are acid-etched with an acid-based etchant, or both surfaces of the silicon wafer W are alkali-etched with an alkali-based etchant.
In the mirror polishing step, only the front surface of the silicon wafer W is polished until it becomes a mirror surface.

<Device manufacturing method>
A method for manufacturing a device in the device manufacturing stage from the silicon wafer W manufactured as described above will be described. The device manufacturing method includes a step of depositing a thin film on the front surface of the wafer by a CVD process and a step of partially removing the thin film by a dry etching process.

  In the CVD process and the dry etching process, the silicon wafer W is electrostatically chucked and a predetermined process is performed. At this time, heat exchange between the silicon wafer W and the electrostatic chuck needs to be performed uniformly within the wafer surface. Therefore, helium gas is supplied between the two as a heat exchange medium. However, since the roughness of the back surface of the wafer varies between wafers, a difference occurs in the adhesion between the back surface of the wafer and the chuck suction surface. Therefore, there is a difference in the amount of helium gas leakage between the silicon wafers W. Variations in temperature occur.

  In the device manufacturing stage, an allowable range in which the variation in the leak amount can be allowed is set, and the helium gas flow rate is measured by the above-described leak amount measuring apparatus 1 before the CVD process and the dry etching process. If it is within the allowable range, the silicon wafer W is evaluated as a non-defective product having a desired back surface, assuming that the leak amount of helium gas is within the allowable range, and the above processing is performed.

<< This evaluation method and evaluation apparatus >>
In the wafer manufacturing stage, the roughness of the wafer back surface is evaluated in the following manner so that a silicon wafer W having a desired back surface, that is, a silicon wafer W having a desired leak amount can be input to the device manufacturing stage. Evaluate with an evaluation device.
As shown in FIG. 2, the gloss evaluation device 60 as a semiconductor wafer back surface roughness evaluation device is a specular gloss meter that conforms to the JISZ 8741 standard, and includes a light source 61, a light receiver 62, a calculator 63, And an evaluator 64. The light source 61, the light receiver 62, and the arithmetic unit 63 constitute a glossiness acquisition unit.
The light source 61 is a daylight D ₆₅ light source having a color temperature of about 6504K as defined in JIS Z 8741, and has an incident angle of, for example, 85 degrees (specific incident angle) on the back surface of the silicon wafer W as a sample. It is comprised so that light may be irradiated.

The light receiver 62 is configured to receive reflected light in which the incident light is reflected in the specular reflection direction (regular reflection direction).
The computing unit (calculating means) 63 is built in the light receiver 62 and is configured to calculate the glossiness of the received reflected light. As specified in JIS Z 8741, the glossiness is a specular gloss at a specified incident angle of the reference surface with a glass surface having a constant refractive index of 1.567 over the entire visible wavelength range. The degree is expressed as 100 (%).

The evaluator (evaluation means) 64 includes a memory in which an allowable glossiness range is stored in advance, and a processing unit (processing circuit) that determines whether the glossiness calculated by the calculator 63 is within the allowable range. By this, it is comprised so that the roughness of the back surface of the silicon wafer W may be evaluated.
Then, the roughness of the back surface of the silicon wafer W is evaluated using such a gloss evaluation device 60 in the procedure as shown in FIG.

First, in step A10 (irradiation process; glossiness acquisition process), the light source 61 irradiates the back surface of the silicon wafer W placed on a flat surface with a light beam having an incident angle of, for example, 85 degrees and a specified opening angle. .
Subsequently, in step A20 (light receiving step; glossiness obtaining step), a light beam (reflected light) having a specified opening angle reflected in the specular reflection direction is received by the light receiver 62.

Subsequently, in step A30 (gloss degree calculation step; gloss level acquisition step), the calculation unit 63 calculates the gloss level of the reflected light received by the light receiver 62.
Finally, in step A40 (back surface roughness evaluation process), it is determined whether or not the glossiness calculated by the evaluator 64 is within this allowable range (for example, a range of 50 to 100%). The roughness of the back surface of the wafer W is evaluated.

The evaluation method and the evaluation apparatus as shown in FIG. 1 and FIG. 2 show that the inventor has the power spectrum density of the roughness component having a wavelength of 80 to 120 μm among the roughness components of the silicon wafer W as helium gas. This is based on the discovery that it correlates with the amount of leakage.
Prior to the present invention, the inventor first drawn a power spectral density function for each wavelength of the surface shape of the back surface of 11 types of sample silicon wafers as shown in FIG. According to FIG. 3, it is confirmed that each sample silicon wafer has roughness components of various wavelengths and various intensities.

  Next, the helium gas flow rate (sccm) was measured for each sample silicon wafer with the leak amount measuring apparatus 1 described above. Then, data relating to several wavelengths such as wavelengths of 5 to 15 μm, 45 to 55 μm, 80 to 120 μm, 500 to 600 μm, and 1050 to 1150 μm are extracted from the entire wavelength region shown in FIG. 3 and shown in FIGS. 4 to 8. Thus, for each wavelength, a graph was drawn with the helium gas flow rate on the horizontal axis and the power spectral density on the vertical axis. In each of FIGS. 4 to 8, the numerals in the drawings indicate the sample numbers of the wafers.

  Then, for example, there was no correlation between the helium gas flow rate and the power spectral density at wavelengths of 5 to 15 μm, 45 to 55 μm, 500 to 600 μm, and 1050 to 1150 μm, but there was a constant correlation between the two at wavelengths of 80 to 120 μm. It was confirmed that there was. And this inventor has reflected the roughness component of this wavelength 80-120 micrometers in the glossiness of incident angle 80-90 degree | times, and the roughness component of wavelength 80-120 micrometers by the glossiness of incident angle 80-90 degree | times. Investigated that it is possible to grasp. That is, it was investigated that there is a correlation between the helium gas flow rate and the glossiness at an incident angle of 80 to 90 degrees.

  11 to 13 are diagrams showing the correlation between the helium gas flow rate and the glossiness of the back surface of the silicon wafer W when the incident angles are 15 to 25 degrees, 55 to 65 degrees, and 80 to 90 degrees, respectively. is there. Generally, the helium gas flow rate is large when the back surface gloss is small (the back surface roughness is large), and conversely, the helium gas flow rate when the back surface gloss is large (the back surface roughness is small). However, it was found that when the incident angle is 80 to 90 degrees, a higher correlation is obtained than when the incident angles are 15 to 25 degrees and 55 to 65 degrees.

  Therefore, the silicon wafer W and the chuck are electrostatically chucked by the chuck plate 11 in the chamber 2 in the device manufacturing process and the helium gas is supplied between the back surface and the chuck suction surface. As an index for evaluating the back surface in which no difference occurs between the wafers in heat exchange with the plate 11, in this embodiment, a glossiness with an incident angle of 80 to 90 degrees is newly adopted.

  In the etching process of the semiconductor wafer manufacturing method described above, the power of the concavo-convex component having a wavelength of 80 to 120 μm among the concavo-convex component on the etched surface, regardless of whether acid etching or alkali etching is performed. The etched surface is managed so that the spectral density is within the allowable range, that is, the glossiness with an incident angle of 80 to 90 degrees is within the allowable range.

At this time, for example, when the glossiness at an incident angle of 80 to 90 degrees on the alkali-etched surface is out of the allowable range, a new process (adjustment process) for polishing the alkali-etched surface in the above-described semiconductor wafer manufacturing method is etched. It is preferable to carry out after the process so that the alkali-etched surface is within an allowable range.
The allowable range for the glossiness at an incident angle of 80 to 90 degrees correlates with the range of variation in the amount of leak of helium gas that is allowed as no difference in heat exchange between wafers in the device manufacturing stage. It is.

<Action and effect>
Since the semiconductor wafer back surface roughness evaluation method and evaluation apparatus according to an embodiment of the present invention are configured as described above, the following operations and effects are achieved.
In setting the roughness of the back surface (etched surface) of the silicon wafer W with only the front surface mirror-polished, helium gas leaks at the device manufacturing stage in order to set the back surface processing conditions that do not affect device manufacturing. In consideration of the introduction of the evaluation method based on the amount, the incident angle that can capture the concave-convex component having a wavelength of 80-120 μm among the concave-convex component on the back surface that correlates with the leak amount of helium gas is 80- Since the glossiness of 90 degrees is used as a new index, the glossiness measurement time is sufficient in a short time, and therefore the roughness of the back surface can be easily evaluated.

[Others]
As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment, A various change is possible in the range which does not deviate from the main point of this invention.
For example, in the above embodiment, the acquisition of the concavo-convex component in the wavelength region of 80 to 120 μm with the glossiness of the incident angle of 80 to 90 degrees is aimed, but the correlation of the leak amount of helium gas has a certain range. Since the power spectral density of the concavo-convex component of the wavelength belonging to the inside is allowed, it is aimed at a specific wavelength region having a predetermined width centered on another wavelength (for example, 150 μm), and is glossed at another incident angle (for example, 70 to 75 degrees) The degree may be measured.

  Moreover, in the said embodiment, helium gas is used for evaluation of the amount of leaks, However, You may replace with other inert gas (for example, argon gas). However, helium gas is suitable because it has a low molecular weight and easily leaks from the gap between the wafer back surface and the chuck adsorption surface.

  The present invention can be used in the semiconductor manufacturing industry, and is particularly suitable for use when a wafer manufacturer evaluates a semiconductor wafer to be provided to a device manufacturer.

DESCRIPTION OF SYMBOLS 1 Leak amount measuring apparatus 2 Chamber 10 Electrostatic chuck apparatus 20 Vacuum drawing apparatus 30 Atmospheric release apparatus 40 Helium gas supply apparatus 60 Gloss evaluation apparatus 61 Light source 62 Light receiver 63 Calculator (calculation means)
64 Evaluator (Evaluation means)
W Silicon wafer (semiconductor wafer)

Claims (4)

A glossiness obtaining step for obtaining a glossiness measured at a specific incident angle reflecting a power spectrum density of a concavo-convex component belonging to a specific wavelength region of the concavo-convex component on the back surface of the etched semiconductor wafer;
An evaluation step of evaluating the roughness of the back surface of the semiconductor wafer by determining whether or not the glossiness obtained in the glossiness acquisition step is within an allowable range,
The power spectral density of the concavo-convex component belonging to the specific wavelength region is a leak amount of an inert gas supplied as a heat exchange medium between the back surface of the semiconductor wafer and an adsorption surface of a chuck plate that electrostatically chucks the back surface of the semiconductor wafer. Power spectral density correlating with
The method for evaluating the roughness of a back surface of a semiconductor wafer, wherein the allowable range is an allowable range correlated with the range of the leak amount. 2. The semiconductor wafer back surface roughness evaluation method according to claim 1, wherein the specific wavelength region is a region of 80 to 120 [mu] m, and the specific incident angle is in a range of 80 to 90 degrees. A light source that irradiates light at a specific incident angle to the back surface of the etched semiconductor wafer;
A light receiver for receiving reflected light reflected from the back surface of the semiconductor wafer in the specular reflection direction;
A computing means for obtaining a glossiness of the reflected light;
An evaluation means for evaluating the roughness of the back surface of the semiconductor wafer by determining whether or not the calculated glossiness is within a preset allowable range; and
The specific incident angle is an angle that captures an uneven component belonging to a specific wavelength region among the uneven components on the back surface of the semiconductor wafer,
The concavo-convex component belonging to the specific wavelength region has a power spectral density of an inert gas supplied as a heat exchange medium between the back surface of the semiconductor wafer and a suction surface of a chuck plate that electrostatically chucks the back surface of the semiconductor wafer. It is an uneven component that correlates with the amount of leakage,
The backside roughness evaluation apparatus for a semiconductor wafer, wherein the permissible range is a permissible range that correlates with the leak amount range. 4. The semiconductor wafer back surface roughness evaluation apparatus according to claim 3, wherein the specific wavelength region is a region of 80 to 120 [mu] m, and the specific incident angle is in a range of 80 to 90 degrees.

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