JP2001044206A - Method of heat-treating silicon wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent deterioration in the device performance of a semiconductor device due to metal impurities and hence prevent reduction in its product yield by increasing gettering effect, independently of the concentration and kinds of the metal impurities and surely and sufficiently capturing the metal impurities in a polysilicon layer. SOLUTION: A PBS(polysilicon back side) wafer is placed in a furnace having an atmosphere of nitrogen, hydrogen or argon gas and held therein for 0.5-2 hours at a first temperature of 950-1,100 deg.C. Successively, the wafer is cooled to a second temperature of 700-800 deg.C at a rate of 2-4 deg.C/minute. After being held in the furnace for 1-5 hours at the second temperature, the wafer is taken out of the furnace for cooling down to the room temperature. Alternatively, the wafer is held for 0.5-2 hours at the first temperature and successively cooled to the second temperature of 700-800 deg.C at a rate of 5-2 deg.C/minute, after which the wafer is removed from the furnace for cooling to the room temperature, without being held at the second temperature or while being held for 5 hours at the second temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for heat-treating a silicon wafer having a polysilicon layer on the back surface.
More specifically, the present invention relates to a method for heat-treating a silicon wafer capable of removing metal impurities from a device formation region on a wafer surface.

[0002]

2. Description of the Related Art Generally, in the manufacture of semiconductor device elements, a silicon wafer cut at a predetermined thickness from a silicon single crystal ingot grown by the Czochralski method (hereinafter referred to as CZ method) as a substrate. Is used. 2. Description of the Related Art In recent years, in semiconductor device elements, the degree of integration of devices has been remarkably increased, and accordingly, higher quality silicon wafers have been required. For this reason, in the device manufacturing process, efforts are being made to clean the manufacturing process, and efforts are being made to increase the integrity of the vicinity of the surface of the silicon wafer, which is an electrically active region of the device, that is, to make the vicinity of the wafer surface defect-free. ing.
To make the vicinity of the surface of this silicon wafer defect-free,
Oxygen precipitates near the surface of silicon wafers (Bulk Micro
Defect, hereinafter referred to as BMD. It is important to reduce the density of ()) as much as possible. This BMD becomes apparent in the silicon wafer by the heat treatment. If this BMD exists near the wafer surface, it adversely affects device reliability and yield.

In the device manufacturing process, Fe, C
There are several manufacturing steps in which metal impurities such as u and Ni are mixed. If these metal impurities are present near the wafer surface, device characteristics will be degraded or the product yield will be reduced. There is a need to. For this reason, the importance of a technique (a gettering technique) for controlling the BMD density and removing metal impurity contamination from the device formation region is increasing. Usually, the gettering technique includes an internal gettering method (hereinafter, referred to as an IG method),
Extrinsic Gettering (hereinafter E)
It is called the G method. ).

The IG method reduces the oxygen concentration near the wafer surface by high-temperature heat treatment to form a layer without BMD (hereinafter, referred to as a DZ layer) near the wafer surface, and a high-density layer deeper than the DZ layer. In this method, BMD having a high density is generated, and the BMD defect is used as a trapping source of metal impurities. In the EG method, abrasive grains of SiO ₂ are artificially jetted from the jet nozzle to the back surface of the wafer by air pressure,
A method in which mechanical damage is applied to the rear surface of the wafer, and crystal defects generated from the mechanical damage are used as a source for capturing metal impurities (Back Side Damage, hereinafter referred to as BSD method).
Alternatively, a method of growing a polysilicon layer of about 0.5 to 1.5 μm on the back side of a silicon wafer and using this polysilicon layer as a source for capturing metal impurities (PolySilicon Back Sid)
e, hereinafter referred to as PBS method. )and so on.

Among the above gettering techniques, the IG method requires a complicated and long-time heat treatment in order to create a gettering source, and is not necessarily required for gettering of a metal element such as Ni that is rapidly diffused in silicon. Not effective. Also, in the BSD method, it is difficult to completely remove silicon dust generated in the process of causing mechanical damage from a wafer,
There is a problem that can be a source of a new defect, and there is also a problem that it is difficult to quantitatively control back surface damage with good reproducibility. For this reason, the PBS method without these drawbacks has been reviewed. Semiconductor device manufacturers use this PB
By heat-treating a silicon wafer (hereinafter referred to as a PBS wafer) having a polysilicon layer formed on the back surface by the S method, metal impurities generated in the device manufacturing process can be captured by the polysilicon layer. This heat treatment reduces the cost of the heat treatment and reduces the risk of contamination resulting from the manufacturing process (heat treatment) at high temperatures.
The wafer is placed in a furnace, the maximum temperature is kept at a low temperature of less than 1000 ° C., kept for 1 to 2 hours, cooled down to about 800 ° C. at a rate of 4 ° C./min or more, immediately taken out of the furnace and allowed to cool to room temperature It has been done.

[0006]

SUMMARY OF THE INVENTION However, PBS
In the above-described conventional heat treatment method of a wafer, when a metal which is an impurity contaminates the wafer surface at a high concentration or a diffusion coefficient in a wafer is small even if the concentration is not high, an attempt is made to capture a metal element such as Fe. In this case, there is a problem that it is difficult to reliably and sufficiently capture this metal impurity in the polysilicon layer. An object of the present invention is to provide a heat treatment method for a silicon wafer that enhances the gettering effect irrespective of the concentration and type of metal impurities in a device manufacturing process, and reliably and sufficiently captures the metal impurities in a polysilicon layer. is there. Another object of the present invention is to provide a heat treatment method for a silicon wafer that prevents device characteristics deterioration due to metal impurities and does not reduce the product yield of semiconductor devices.

[0007]

The invention according to claim 1 is
In the method for heat-treating a silicon wafer having a polysilicon layer on the back surface, the silicon wafer is placed in a furnace in a nitrogen, hydrogen, or argon gas atmosphere, and is subjected to 950 to 950.
Hold at a first temperature of 1100 ° C. for 0.5 to 2 hours and subsequently cool the wafer at a rate of 2 to 4 ° C./min for 700 to 800
This is a method for heat-treating a silicon wafer, wherein the temperature is lowered to a second temperature of 1 ° C., the temperature is maintained at the second temperature for 1 to 5 hours, and then taken out of the furnace and allowed to cool to room temperature. The invention according to claim 3 is a method for heat-treating a silicon wafer having a polysilicon layer on the back surface, wherein the silicon wafer is placed in a furnace in a nitrogen, hydrogen or argon gas atmosphere, and the first temperature is 950 to 1100 ° C. And then the wafer is cooled at a rate of 0.5 to 2 ° C./min to a second temperature of 700 to 800 ° C., without holding at the second temperature, or This is a method for heat treating a silicon wafer, wherein the silicon wafer is taken out of a furnace and allowed to cool to room temperature after holding for less than 5 hours.

According to the first and third aspects of the present invention, the maximum temperature (first temperature) of the heat treatment is set higher and the holding time is set longer than before. Accordingly, the impurity metal is Fe, which has a small diffusion coefficient in the wafer, and is 10 ¹² to 1
Even if the wafer is contaminated at a high concentration of 0 ¹³ atoms / cm ² , the impurity metal sufficiently diffuses into the wafer bulk without forming silicide near the wafer surface. In the invention according to the first aspect, after maintaining at the first temperature, it is cooled at the same speed as that of the related art, and is maintained at the second temperature of 700 to 800 ° C. for a predetermined time. This allows the metal diffused in the wafer bulk to be captured in the polysilicon layer without remaining in the wafer bulk. On the other hand, in the invention according to the third aspect, after the temperature is maintained at the first temperature, the cooling is performed at a lower speed than the conventional one.
During this slow cooling, the metal diffused in the wafer bulk is captured in the polysilicon layer without remaining in the wafer bulk.

The invention according to claims 2 and 4 is a heat treatment method in which a first temperature in a furnace of a silicon wafer having a polysilicon layer on a back surface is in a range of 1050 to 1100 ° C. According to the second and fourth aspects of the present invention, by setting the first temperature of the highest temperature to 1050 ° C., the impurity metal is Fe and the wafer is contaminated at a higher concentration of 10 ¹³ atoms / cm ² or more. Even so, the metal impurities can be captured in the polysilicon layer on the back surface of the wafer.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The PBS wafer of the present invention is CZ
After lapping a silicon wafer cut to a predetermined thickness from single crystal silicon grown by the method, chamfering it, removing the damage on the wafer surface by chemical etching and turning it into a mirror-finished silicon wafer, On the back side of the CVD (Chemical Vapor Depositio)
Fabricated by forming a polysilicon layer having a thickness of 0.5 to 1.5 μm at a temperature of 600 to 700 ° C. using, for example, SiH ₄ by the method n). If the thickness of the polysilicon layer is less than 0.5 μm, the gettering effect is poor, and if it exceeds 1.5 μm, the productivity is reduced. The oxygen concentration in the silicon wafer of the present invention is 1 × 10 ^{18 to} 1.4 × 10 ¹⁸
Adjusted to atoms / cm ³ (former ASTM).

The role of the PBS wafer is to diffuse the metal impurities arriving at the wafer surface in the active region into the bulk of the wafer by heat-treating the PBS wafer, and to leave the metal impurities on the back surface of the wafer without remaining in the bulk of the wafer. Capturing metal impurities in the polysilicon layer. The degree of diffusion of this metal impurity into the wafer bulk and capture in the polysilicon layer is determined by the concentration of the metal impurity and the diffusion coefficient of the metal as the impurity in the wafer bulk,
It is determined by the heat treatment conditions of the PBS wafer. That is, when the wafer surface is contaminated with metal impurities at a high concentration, when heat treatment is performed at a low temperature, the metal is not sufficiently diffused into the wafer bulk, and a part of the wafer surface forms silicide which is a silicide. If the surface of the wafer is contaminated with impurities of a metal having a low diffusion coefficient, the cooling rate of the PBS wafer held at the first temperature, which is the highest temperature, is increased, and the metal diffuses toward the rear surface of the wafer in the wafer bulk. The speed is reduced and some metals tend to remain in the wafer bulk. Therefore, in these cases, a high gettering effect by the polysilicon layer cannot be expected.
As a metal with a small diffusion coefficient in the wafer bulk,
Fe.

[0012] Explaining this Fe as an example of a metal impurity, the concentration of Fe on the wafer surface is 10 ¹⁰ to 10.
If it is about ¹¹ atoms / cm ² , heat treatment of the PBS wafer at 950 ° C. for 1 hour allows the Fe element to sufficiently diffuse into the wafer bulk. However, when the concentration of Fe is higher, 10 ¹¹ to 10 ¹² at
At oms / cm ² , the heat treatment at 950 ° C. cannot sufficiently diffuse into the wafer bulk, and forms Fe silicide on the silicon surface. At this concentration, it is necessary to perform a heat treatment at a temperature of 950 ° C. or more in order to diffuse all the Fe elements from the silicon surface into the wafer bulk. At a higher concentration of 10 ¹³ atoms / cm ² or more, it is necessary to perform a heat treatment at 1050 ° C. in order to diffuse all Fe elements into the wafer bulk.

In the present invention, for the above reasons, in the heat treatment of the PBS wafer, the maximum temperature and the holding time are determined according to the concentration of contaminating metal impurities. In the first heat treatment method for the PBS wafer (the method according to claim 1), the PBS wafer is placed in a furnace in an atmosphere of nitrogen, hydrogen, or argon gas, and is heated at a first temperature of 950 to 1100 ° C. for 0.5 to 2 hours. The wafer is then cooled at a rate of 2 to 4 ° C./min to a second temperature of 700 to 800 ° C., kept at the second temperature for 1 to 5 hours, taken out of the furnace and released to room temperature. Let cool. In the second heat treatment method (the method according to claim 3), the PBS wafer is placed in a furnace in an atmosphere of nitrogen, hydrogen, or argon gas and held at a first temperature of 950 to 1100 ° C. for 0.5 to 2 hours. Then, the wafer is
After lowering the temperature to a second temperature of 700 to 800 ° C. at a rate of ２2 ° C./min, without holding at the second temperature or after holding for less than 5 hours, it is taken out of the furnace and allowed to cool to room temperature.

A preferred maximum temperature (first temperature) in this heat treatment is 1050 to 1100 ° C. If the maximum temperature is lower than 950 ° C., metal impurities cannot be sufficiently diffused into the wafer bulk. If the maximum temperature exceeds 1100 ° C., the diffusion effect is good, but there is a concern that the safety and reliability of the device may be deteriorated. . The preferred holding time of the maximum temperature is 1 to
2 hours. If the holding time is less than 0.5 hour, sufficient diffusion of metal impurities cannot be obtained, and improvement in the diffusion effect cannot be expected even if heat treatment is performed for more than 2 hours. Further, the preferable cooling rate after holding at the highest temperature is 2-3 ° C./min in the first heat treatment method, and 0.5 to 3 ° C./min in the second heat treatment method.
1 ° C./min. If the cooling rate is less than the lower limit, a sufficient gettering effect can be obtained, but it is not industrially suitable.
If the upper limit is exceeded, metal impurities remain in the wafer bulk, and a sufficient gettering effect cannot be obtained.

[0015]

Next, examples of the present invention will be described together with comparative examples. <Example 1> First, a silicon wafer cut from a silicon single crystal ingot grown by doping with boron (B) by the CZ method was wrapped, chamfered, and the wafer surface was damaged by chemical etching. After removal, a mirror-finished silicon wafer having a thickness of 625 μm, a diameter of 150 mm, and an oxygen concentration of 1.3 × 10 ¹⁸ atoms / cm ³ (former ASTM) was obtained. On the back side of this wafer, CV
D. Method 1. Using SiH ₄ at a temperature of 650 ° C. and a thickness of 1.
A 5 μm polysilicon layer was formed to obtain a PBS wafer. Next, the wafer surface is fed with a Fe concentration of 5 × 10 ^{11 to} 5 × 10 ¹² atoms / cm by spin coating.
^It was forcibly contaminated so that it was about ² . The back surface of the wafer before gettering of Fe was cleaned by a one-drop etching (DE) method using a mixed solution of 5% HF and 5% H ₂ O ₂ . In this DE method, one droplet of the mixed liquid is dropped on the end of the PBS wafer on which the orientation flat is formed, and after the droplet spreads over the entire back surface of the wafer by surface tension, the droplet is applied to the end opposed to the orientation flat. This is a method of cleaning the back surface of the wafer by collecting again in the form of droplets. In this example, a PBS wafer whose front surface was forcibly contaminated with Fe and whose back surface was cleaned was placed in a furnace, and the temperature was raised to 1000 ° C. of the first temperature (T ₁ ) at a rate of 5 ° C./min in a nitrogen gas atmosphere. Then, after holding for 2 hours, the temperature was lowered to 700 ° C. of the second temperature (T ₂ ) at a rate of 5 ° C./min. After holding for 5 hours, the wafer was taken out of the furnace and allowed to cool to room temperature.

<Embodiment 2> Similar to Embodiment 1, the surface was made of Fe.
Prepare a PBS wafer whose back surface has been cleaned by forcibly contaminating it, put this PBS wafer into a furnace, and raise the temperature to 1000 ° C. of the first temperature (T ₁ ) at a rate of 5 ° C./min in a nitrogen gas atmosphere. Then, after holding for 2 hours, the temperature was lowered to the second temperature (T ₂ ) of 700 ° C. at a rate of 0.5 ° C./min, immediately taken out of the furnace and allowed to cool to room temperature.

<Comparative Example 1> As in Example 1, the surface was made of Fe.
Prepare a PBS wafer whose back surface has been cleaned by forcibly contaminating it, put this PBS wafer into a furnace, and raise the temperature to 1000 ° C. of the first temperature (T ₁ ) at a rate of 5 ° C./min in a nitrogen gas atmosphere. Then, after holding for 2 hours, the temperature was lowered to the second temperature (T ₂ ) of 700 ° C. at a rate of 5 ° C./min, immediately taken out of the furnace and allowed to cool to room temperature.

<Comparative Example 2> The surface was made of Fe as in Example 1.
Prepare a PBS wafer whose back surface has been cleaned by forcibly contaminating it, put this PBS wafer into a furnace, and raise the temperature to 1000 ° C. of the first temperature (T ₁ ) at a rate of 5 ° C./min in a nitrogen gas atmosphere. Then, after holding for 2 hours, the temperature was lowered to 700 ° C. of the second temperature (T ₂ ) at a rate of 5 ° C./min. After holding for 5 hours, the wafer was taken out of the furnace and allowed to cool to room temperature. Then, the PBS wafer is put into the furnace again, and
The temperature was raised to 00 ° C., maintained for 2 hours, immediately taken out of the furnace, and reheated to cool to room temperature.

<Comparative Example 3> As in Example 1, the surface was made of Fe.
Prepare a PBS wafer whose back surface has been cleaned by forcibly contaminating it, put this PBS wafer into a furnace, and raise the temperature to 900 ° C. of the first temperature (T ₁ ) at a rate of 5 ° C./min in a nitrogen gas atmosphere. Then, after holding for 2 hours, the temperature was lowered to the second temperature (T ₂ ) of 700 ° C. at a rate of 5 ° C./min, immediately taken out of the furnace and allowed to cool to room temperature. Thereafter, the PBS wafer was placed again in the furnace, heated to 800 ° C. and maintained for 2 hours, immediately taken out of the furnace, and subjected to a reheat treatment for cooling to room temperature.

<Comparative Example 4> As in Example 1, the surface was made of Fe.
Prepare a PBS wafer whose back surface has been cleaned by forcibly contaminating it, put this PBS wafer into a furnace, and raise the temperature to 900 ° C. of the first temperature (T ₁ ) at a rate of 5 ° C./min in a nitrogen gas atmosphere. Then, after holding for 2 hours, the temperature was lowered to 700 ° C. of the second temperature (T ₂ ) at a rate of 5 ° C./min. After holding for 5 hours, the wafer was taken out of the furnace and allowed to cool to room temperature. Then, the PBS wafer is put into the furnace again, and
The temperature was raised to 00 ° C., maintained for 2 hours, immediately taken out of the furnace, and reheated to cool to room temperature.

<Comparative Example 5> As in Example 1, the surface was made of Fe.
Prepare a PBS wafer whose back surface has been cleaned by forcibly contaminating it, put this PBS wafer into a furnace, and raise the temperature to 900 ° C. of the first temperature (T ₁ ) at a rate of 5 ° C./min in a nitrogen gas atmosphere. Then, after holding for 2 hours, the temperature was lowered to 700 ° C. of the second temperature (T ₂ ) at a rate of 5 ° C./min. After holding for 5 hours, the wafer was taken out of the furnace and allowed to cool to room temperature.

<Comparative Example 6> As in Example 1, the surface was made of Fe.
Prepare a PBS wafer whose back surface has been cleaned by forcibly contaminating it, put this PBS wafer into a furnace, and raise the temperature to 900 ° C. of the first temperature (T ₁ ) at a rate of 5 ° C./min in a nitrogen gas atmosphere. Then, after holding for 2 hours, the temperature was lowered to the second temperature (T ₂ ) of 700 ° C. at a rate of 0.5 ° C./min, immediately taken out of the furnace and allowed to cool to room temperature.

<Embodiment 3> An Fe concentration of 2 × 10 ¹² to 2 × 10 ¹³ atoms / c was applied to the surface of a PBS wafer obtained in the same manner as in Embodiment 1 by spin coating.
is forcibly contaminated so that the order of m ^2. Then Example 1
After cleaning the back surface of the wafer before gettering in the same manner as described above, the PBS wafer whose back surface has been cleaned is placed in a furnace, and the first temperature (T ₁ ) is 1050 ° C. at a rate of 5 ° C./min in a nitrogen gas atmosphere. Temperature, and hold it there for 2 hours.
At a rate of / min to a second temperature (T ₂ ) of 800 ° C.,
Then, after holding for 5 hours, the wafer was taken out of the furnace and allowed to cool to room temperature.

<Embodiment 4> Similar to Embodiment 3, the surface was made of Fe.
Prepare a PBS wafer whose back surface has been cleaned by forcibly contaminating it, put this PBS wafer into a furnace, and raise the temperature to 1050 ° C. of the first temperature (T ₁ ) at a rate of 5 ° C./min in a nitrogen gas atmosphere. Then, after holding for 2 hours, the temperature was decreased to a second temperature (T ₂ ) of 800 ° C. at a rate of 0.5 ° C./min, immediately taken out of the furnace and allowed to cool to room temperature.

<Comparative Example 7> As in Example 3, the surface was made of Fe.
Prepare a PBS wafer whose back surface has been cleaned by forcibly contaminating it, put this PBS wafer into a furnace, and raise the temperature to 1050 ° C. of the first temperature (T ₁ ) at a rate of 5 ° C./min in a nitrogen gas atmosphere. Then, after holding for 2 hours, the temperature was lowered at a rate of 5 ° C./min to a second temperature (T ₂ ) of 800 ° C., immediately taken out of the furnace and allowed to cool to room temperature. Thereafter, the PBS wafer was placed again in the furnace, heated to 800 ° C. and maintained for 2 hours, immediately taken out of the furnace, and subjected to a reheat treatment for cooling to room temperature.

<Comparative Example 8> The surface was made of Fe as in Example 3.
Prepare a PBS wafer whose back surface has been cleaned by forcibly contaminating it, put this PBS wafer into a furnace, and raise the temperature to 1050 ° C. of the first temperature (T ₁ ) at a rate of 5 ° C./min in a nitrogen gas atmosphere. Then, after holding for 2 hours, the temperature was lowered to 800 ° C. of the second temperature (T ₂ ) at a rate of 5 ° C./min. After holding for 5 hours, the wafer was taken out of the furnace and allowed to cool to room temperature. Then, the PBS wafer is put into the furnace again, and
The temperature was raised to 00 ° C., maintained for 2 hours, immediately taken out of the furnace, and reheated to cool to room temperature.

<Comparative Evaluation> Examples 1 to 4 and Comparative Examples 1 to
The Fe concentration before and after the heat treatment of the PBS wafer No. 8 was measured in the vicinity of the wafer surface (in a range of 6 μm in depth from the surface), the back surface of the wafer, and the wafer bulk sandwiched between these two surfaces. The concentration of Fe near the front surface and the back surface of the wafer is determined by the DSE method (Drop Sandwich Ething method).
BD method (Bulk Decomposition method) during bulk
Was measured with a graphite furnace atomic absorption spectrometer. The ratio of the measured value to the total Fe concentration mixed in the silicon wafer was shown as a residual%. Table 1 shows the results.

[0028]

[Table 1]

As is clear from Table 1, in Comparative Examples 1 to 8, Fe remained at a high ratio on the wafer surface and the wafer bulk as the device formation region after the heat treatment.
It can be seen that e is not sufficiently captured by the polysilicon layer on the back surface of the wafer. On the other hand, in Examples 1 to 4, the residual ratio of Fe on the wafer surface, which is the device formation region, shows a low value, and the residual ratio of Fe is low even in the wafer bulk, and Fe is contained in the polysilicon layer on the back surface of the wafer. The high ratio indicates that Fe is effectively captured in the polysilicon layer. Comparative Examples 2 to
In 4, 7, and 8, the re-heat treatment was performed, but it was found that Fe was not sufficiently captured by the polysilicon layer when cooled to room temperature.

[0030]

As described above, according to the present invention, P
The BS wafer is placed in a furnace in an atmosphere of nitrogen, hydrogen, or argon gas, and at a first temperature of 1000 to 1100 ° C.
Hold for 5 to 2 hours, then keep the wafer at 2-4 ° C /
The temperature is lowered to a second temperature of 700 to 800 ° C. at a rate of 1 minute and kept at the second temperature for 1 to 5 hours, and then taken out of the furnace and allowed to cool to room temperature, or 0 to 900 ° C. Hold for 0.5 to 2 hours, then remove the wafer for 0.5
After cooling down to a second temperature of 700 to 800 ° C. at a rate of ２2 ° C./min, without holding at the second temperature or after holding for less than 5 hours, it is taken out of the furnace and allowed to cool to room temperature, After sufficiently diffusing metal impurities such as Fe having a low diffusion rate into the silicon wafer bulk, the metal impurities can be reliably captured in the polysilicon layer without remaining in the wafer bulk.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Shigeru Okuchi 1-297 Kitabukurocho, Omiya-shi, Saitama Mitsubishi Materials Silicon Research Center F-term (reference) 4G077 AA02 BA04 CF10 DB01 FE05 FE12

Claims (4)

[Claims] 1. A method for heat-treating a silicon wafer having a polysilicon layer on its back surface, comprising: placing the silicon wafer in a furnace in a nitrogen, hydrogen or argon gas atmosphere at a first temperature of 950 to 1100 ° C. Hold for 5 to 2 hours, and then remove the wafer for 2 to 2 hours.
Cooling the silicon wafer at a rate of 4 ° C./min to a second temperature of 700 to 800 ° C., maintaining the temperature at the second temperature for 1 to 5 hours, and taking out from the furnace and allowing it to cool to room temperature; Heat treatment method. 2. The method according to claim 1, wherein the first temperature of the silicon wafer having the polysilicon layer on the back surface is in the range of 1050 to 1100 in the furnace.
2. The heat treatment method according to claim 1, wherein the temperature is ° C. 3. A method for heat-treating a silicon wafer having a polysilicon layer on the back side, comprising: placing the silicon wafer in a furnace in an atmosphere of nitrogen, hydrogen or argon gas at a first temperature of 950 to 1100 ° C. Hold for 5 to 2 hours and then place the wafers in 0.
After cooling to a second temperature of 700 to 800 ° C. at a rate of 5 to 2 ° C./min, without holding at the second temperature, or
A method for heat-treating a silicon wafer, comprising taking out the furnace from the furnace and allowing it to cool to room temperature after holding for less than an hour. 4. A first temperature of a silicon wafer having a polysilicon layer on a back surface in a furnace is from 1050 to 1100.
The heat treatment method according to claim 3, wherein the temperature is ° C.