JPH0891993A - Production of silicon single crystal substrate and method for quality control - Google Patents

Abstract

PURPOSE: To provide methods both for producing a silicon substrate capable of manifesting stable resistivity even by any heat treatments during a production process for semiconductor elements and for quality control. CONSTITUTION: This method for producing a silicon substrate is to keep the silicon single crystal substrate containing nitrogen added thereto during the growth thereof at any temperature of 900-1250 deg.C at least before a production process for semiconductor elements, heat the substrate at the temperature for about 10min to 1hr and recover the resistivity to the value just after growing the single crystal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a manufacturing method and a quality control method for a silicon single crystal substrate containing nitrogen.

[0002]

2. Description of the Related Art In the production of a silicon single crystal substrate (hereinafter referred to as a silicon substrate) or the production of a semiconductor device using the same, a silicon substrate is subjected to a heat treatment in a wide temperature range of 600 to 1250 ° C. For example, in the former case, about 650 ° C. and 30
There is a heat treatment for a minute, and the latter includes an oxidation step, a heat treatment at about 1200 ° C. for intrinsic gettering or diffusion.

On the other hand, in the heat treatment especially in the high temperature region, for the purpose of preventing the generation of crystal defects due to the thermal stress generated in the silicon substrate at that time, for example, JP-A-57-11.
As shown in No. 7497, it has been proposed to add nitrogen into a silicon single crystal.

[0004]

However, when a heat treatment is applied to a silicon substrate to which nitrogen is added, the resistivity thereof is 10% or more before and after the heat treatment in the measured value, unlike the silicon substrate to which nitrogen is not added. It may change, and it has been difficult to guarantee the resistivity of the silicon substrate to which nitrogen is added.

The present invention has been made in view of the above circumstances, and provides a method for manufacturing a silicon substrate to which nitrogen is added and a quality control method which show stable resistivity by any heat treatment during the semiconductor element manufacturing process. The purpose is to do.

[0006]

According to a first aspect of the present invention, there is provided a method of manufacturing a silicon single crystal substrate, wherein a step of adding nitrogen during the growth of the silicon single crystal, a step of cutting the silicon single crystal, and a cutting step. The silicon single crystal substrate is held at any temperature between 900 ° C. and 1250 ° C. at least before the semiconductor element manufacturing process and heated for about 10 minutes to 1 hour to recover the resistivity to the value immediately after the single crystal growth. And a process.

A method for manufacturing a silicon single crystal substrate according to a second aspect is the method for manufacturing a silicon single crystal substrate according to the first aspect, wherein the concentration of the added nitrogen is 3 × 10 ¹⁴ at.
It is characterized by being oms / cm ³ or more.

A method for manufacturing a silicon single crystal substrate according to claim 3 is the method for manufacturing a silicon single crystal substrate according to claim 1 or 2, wherein the growing of the silicon single crystal comprises:
It is characterized in that it is performed by the FZ method.

A method for manufacturing a silicon single crystal substrate according to claim 4 is the method for manufacturing a silicon single crystal substrate according to any one of claims 1 to 3, wherein the heat treatment is performed in a wet oxygen atmosphere, a dry oxygen atmosphere or a nitrogen atmosphere. It is characterized in that any one is performed.

According to a fifth aspect of the quality control method for a silicon substrate, a silicon single crystal substrate to which nitrogen is added during the growth of the single crystal is at least 9 times before the semiconductor element manufacturing process.
It is characterized by holding at any temperature between 00 ° C. and 1250 ° C. and heating for about 10 minutes to 1 hour to recover the resistivity to the value just after the single crystal growth.

[0011]

According to the present invention, the resistivity of the nitrogen-added silicon substrate can be made substantially equal to the value immediately after the growth of the single crystal, and the resistivity is not changed by the subsequent heat treatment. Furthermore, when the heat treatment according to the present invention is performed in a wet oxygen atmosphere, the resistivity easily recovers to the value immediately after the single crystal growth. Therefore, according to the manufacturing method and the resistivity measuring method of the present invention, a semiconductor element can be manufactured with high yield from a silicon substrate to which nitrogen is added. Particularly, when the concentration of nitrogen added during the growth of the silicon single crystal is 3 × 10 ¹⁴ atoms / cm ³ or more, the effect is high.

When the heat treatment temperature is 900 ° C. or lower,
Since the heat treatment time is 1 hour or more in order to match the resistivity after cooling to the value immediately after the growth of the single crystal, it cannot be said to be industrial. On the other hand, when the temperature of the heat treatment is 1250 ° C. or higher, there is a high possibility that crystal defects will occur due to thermal stress during heating and cooling even though nitrogen is added to the silicon substrate. Further, the rate of temperature rise is, for example, 1 per minute.
C. to 10.degree. C. is used, but it can be freely selected as long as the silicon substrate subjected to the heat treatment is not destroyed or the crystallinity is deteriorated.

[0013]

EXAMPLES A method for manufacturing a silicon single crystal substrate and a quality control method according to the present invention will be described below.

First, an example of a method for manufacturing a silicon substrate will be described with reference to FIG. A silicon single crystal is grown while adding nitrogen to the single crystal in an atmosphere gas in which nitrogen gas or a compound containing nitrogen is added to argon gas or a rarely used mixed gas of argon and hydrogen. The growth of the silicon single crystal at this time is performed by, for example, the floating zone melting method (FZ method).
Done by Next, the silicon substrate obtained by slicing the silicon single crystal to a predetermined thickness and further mechanically polishing the chamfered peripheral portion is subjected to an etching treatment to remove the crushed layer on the surface. Subsequently, the back surface side of the silicon substrate is subjected to sandblasting to provide a work strain layer. After this step, the heat treatment according to the present invention is performed to cool to room temperature. Finally, the main surface side of the silicon substrate is mirror-polished. Next, the heat treatment according to the present invention was performed under different conditions to find the most suitable condition for the purpose of the present invention.

[Experiment 1] First, a silicon substrate obtained by adding nitrogen during the growth of a single crystal was heated at 650 ° C. for 20 minutes.
Heat treatment was performed for 1 minute. Also, in this heat treatment,
I tried changing the heat treatment atmosphere. The specific conditions and results are as follows.

1. Conditions For the sample substrate, an n-type {111} single crystal with a diameter of 76 mm to which nitrogen was added during the single crystal growth by the FZ method was used. In addition, eight types of substrates shown in Table 3 were prepared in order to investigate the effects of the substrate resistivity and the nitrogen concentration in the substrate. Further, as another sample substrate, a substrate shown in Table 2 prepared in the same classification as in Table 1 except that it was p-type was used.

[0017]

[Table 1]

[0018]

[Table 2]

As shown in Tables 1 and 2, different kinds of silicon substrates are heat-treated in three atmospheres: nitrogen (N2), wet oxygen (wet O2) and argon (Ar). Then, after cooling the silicon substrate to room temperature, the resistivity before the heat treatment was compared with the resistivity after the heat treatment.

2. Results The results are shown in FIG. 2 (A), (B) and FIG. 3 (A), (B).
Is shown in. Here, FIG. 2A shows the change in resistivity with respect to the n-type silicon substrate, and FIG. 3A shows the change in resistivity with respect to the p-type silicon substrate. Figure 2
From (A) and FIG. 3 (A), it is understood that the resistivity changes remarkably before and after the heat treatment at 650 ° C. Further, it can be seen that in the heat treatment at 650 ° C., even if the heat treatment atmosphere is changed, there is not much influence on the change in the resistivity. further,
When comparing a p-type silicon substrate and an n-type silicon substrate,
It can be seen that the p-type has a larger rate of change in resistivity. Note that when the p-type silicon substrate having a resistivity of 500 Ω · cm is heat-treated in a wet oxygen atmosphere, the change in resistivity is smaller than that in other heat-treatment atmospheres.

Further, FIG. 2B and FIG. 3B show AST.
Using the M conversion formula (F723-82), the above-mentioned resistivity change is corrected to carrier concentration change. When converted into the carrier concentration change in this way, with some exceptions, it can be said that the higher the nitrogen concentration is, the larger the carrier concentration change is. When the ratio of change in resistivity is compared between the p-type silicon substrate and the n-type silicon substrate, it can be seen that the p-type is larger by one digit.

[Experiment 2] In this experiment, a silicon substrate obtained by adding nitrogen during single crystal growth was heat-treated in a nitrogen atmosphere, and the temperature and time were changed while changing the experiment. The conditions and results of this experiment are as follows.

1. Conditions The heat treatment temperature is 700 ° C, 900 ° C and 1 in a nitrogen atmosphere.
Set to 000 ℃, 1 minute, 4 minutes for each
Heat treatment was performed for 8, 20, 60, and 120 minutes, and then cooled to room temperature, and the resistivity was examined. Further 1200
A heat treatment experiment of only 8 ° C. for 8 minutes was added. In this experiment, a p-type silicon substrate having a diameter of 76 mm, a plane orientation of {100}, and a resistivity of 150 Ω · cm immediately after single crystal growth was used. Also, the cooling time, that is, room temperature (24 to 2
The time for cooling to (5 ° C.) was 15 seconds.

2. Results The results are shown in Figure 4. From this figure, it can be seen that the resistivity increases greatly at the beginning of the heat treatment, but if the heat treatment is further continued, the resistivity gradually decreases to the value immediately after the single crystal growth. For example, 100
When the heat treatment is performed at 0 ° C., the resistivity is almost recovered to 150 Ω · cm immediately after the single crystal growth in about 10 minutes. Further, it is understood that when the temperature is higher than 1000 ° C., it takes less time to recover the resistivity in the state immediately after the single crystal growth. On the other hand, it can be seen that when the temperature is lower than 1000 ° C., it takes a long time to recover the resistivity immediately after the growth of the single crystal.

[Experiment 3] In the next experiment, when a silicon substrate obtained by adding nitrogen during single crystal growth was heat-treated, the heat treatment was performed in various atmospheres and the change in resistivity before and after the heat treatment was performed. The proportions were compared. The specific conditions and results are as follows.

1. Conditions As the sample substrate, a p-type {111} single crystal with a diameter of 76 mm to which nitrogen was added during single crystal growth by the FZ method was used. In addition, eight types of substrates shown in Table 3 were prepared in order to investigate the effects of the substrate resistivity and the nitrogen concentration in the substrate.

[0027]

[Table 3]

The various samples as described above were heat-treated in three atmospheres of wet oxygen (wet O ₂ ), dry oxygen (dry O ₂ ), and nitrogen (N ₂ ). The heat treatment temperature is 1000 ° C. and the heat treatment time is 20.
Set to minutes. The heat treatment with wet oxygen was performed in a steam oxidation furnace.

2. Results The results are shown in FIGS. 5 (A) and 5 (B). Here, in FIG. 5A, the vertical axis represents the resistivity change, and FIG.
FIG. 5B shows the change in resistivity shown in FIG.
3-82) shows that converted into carrier concentration change. Here, the small change rate of the resistivity or the carrier concentration means that the once-increased resistivity has recovered to the vicinity of the value immediately after the single crystal growth.
On the other hand, a large rate of change means that the resistivity is still recovering. From these drawings, in the wet oxygen atmosphere, the error (± 0.3 to ± 0.5
%, It is understood that the resistivity has recovered to a value almost immediately after the single crystal growth. The dry oxygen atmosphere is
Although the change in resistivity is larger than in a wet oxygen atmosphere, if the heat treatment time is set slightly longer than in a wet oxygen atmosphere,
It was confirmed in subsequent experiments that the resistivity was restored to the value immediately after the single crystal growth.

Next, a theoretical consideration will be added to the above experimental results. FIG. 6 outlines the recovery process of the resistivity. In the silicon single crystal obtained by adding nitrogen during single crystal growth,
A complex of vacancies and nitrogen molecules is formed. When the crystal having the composite is subjected to heat treatment, a deep level is formed and carriers are easily trapped, and as a result, the resistivity is increased. However, when heat treatment is further applied, the deep level once formed disappears due to the outward diffusion of vacancies and / or the inward diffusion of Si between the lattices, and the resistivity is restored to the value just after the single crystal growth. Of.

When heat-treated in an oxygen atmosphere, a SiO ₂ film is formed on the surface of the silicon substrate and excess Si is diffused inward, so that the vacancies disappear and the deep levels disappear at the same time.

When the wet oxygen atmosphere is compared with the dry oxygen, the resistivity change in the wet oxygen atmosphere is small. The reason why the SiO ₂ film formation rate is faster in the wet O ₂ atmosphere is that the inward diffusion of Si is faster. This is because the rate of recovery of the resistivity increases at the same heat treatment temperature and heat treatment time.

In the case of N ₂ atmosphere, the interstitial S
It is presumed that not only the inward diffusion of i but also the outward diffusion of vacancies has a great influence.

In Experiment 3, the resistivity change in the nitrogen atmosphere was larger than that in the oxygen atmosphere.
This is probably due to the long cooling time. In other words, in Experiment 3, since the cooling time was set to about 15 minutes, N ₂ was diffused inward during cooling, although the deep level once disappeared, thereby causing a change in resistivity again. . Therefore, in the case of a nitrogen atmosphere, it is necessary to cool immediately after the deep level disappears.

[Experiment 4] In the next experiment, the silicon substrate that had been subjected to the first heat treatment under the conditions according to the present invention was further subjected to the second heat treatment under various conditions to examine the degree of change in resistivity before and after the heat treatment. .

1. Conditions As the sample substrate, n-type and p-type silicon substrates having a surface orientation {100} to which the concentration of nitrogen shown in Table 4 was added during the growth by the FZ method and having a resistivity of 150 Ω · cm immediately after the single crystal growth were prepared. Then, heat treatment of Sample 1 and Sample 2 was performed.

[0037]

[Table 4]

The first heat treatment was carried out in wet oxygen for sample 1 at 1200 ° C. for 60 minutes and for sample 2 at 1000 ° C. 60
I went for a minute. Subsequently, a second heat treatment is performed under three conditions of 700 ° C. for 20 minutes, 800 ° C. for 60 minutes, and 1100 ° C. for 60 minutes,
The resistivities before and after that were compared.

2. As a result, the change in resistivity due to the second heat treatment was 1% or less, which was within a negligible range. That is, the first heat treatment according to the present invention, when applied to a silicon substrate to which nitrogen is added, restores the resistivity of the silicon substrate to the value immediately after single crystal growth, and further makes the value substantially constant. Therefore, it is effective when measuring the resistivity of the silicon substrate.

Although the invention made by the present inventor has been specifically described based on the embodiments, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the scope of the invention. Needless to say.

In the above examples, the p-type silicon substrate having a large change in resistivity was evaluated in Experiments 2 and 3.
The n-type silicon substrate having a small change in resistivity is of course effective.

In the above embodiment, the silicon substrate obtained by the FZ method has been described, but it goes without saying that the silicon substrate obtained by the Czochralski method (CZ method) is also applicable.

Further, in the above-mentioned embodiment, the silicon substrate which has been subjected to the sandblast treatment has been described. However, since it is considered that the stabilization of the resistivity is based on the above-mentioned principle, the present invention can be applied to the silicon substrate which is not subjected to the sandblast treatment. Of course, can be applied.

[0044]

The effects obtained by the representative one of the inventions disclosed in the present application will be briefly described as follows. When heat treatment is applied to a silicon substrate to which nitrogen is added during single crystal growth, the holes that cause the generation of deep levels are eliminated, and the resistivity immediately after single crystal growth can be recovered. Easy to manage.

[Brief description of drawings]

FIG. 1 is a process drawing showing a method for manufacturing a silicon single crystal substrate according to the present invention.

2A and 2B are charts showing a change in resistivity and a change in carrier concentration of an n-type silicon substrate when heat treatment is performed under conventional heat treatment conditions (temperature and time).

3 (A) and 3 (B) are charts respectively showing a change in resistivity and a change in carrier concentration of a p-type silicon substrate when heat treatment is performed under conventional heat treatment conditions (temperature and time).

FIG. 4 is a chart showing changes in resistivity when heat treatment conditions (temperature and time) are changed.

5A and 5B are tables showing a change in resistivity and a change in carrier concentration of a p-type silicon substrate when heat treatment is performed under the heat treatment conditions (temperature and time) of this example.

FIG. 6 is a diagram for explaining the mechanism of the change in resistivity.

Claims (5)

[Claims] 1. A step of adding nitrogen during the growth of a silicon single crystal, a step of cutting the silicon single crystal, and a cut silicon single crystal substrate at least 900 ° C. to 1250 ° C. before a semiconductor element manufacturing step. And a temperature of about 10 minutes to 1 hour to recover the resistivity to a value immediately after the single crystal growth, the method for producing a silicon single crystal substrate. 2. The concentration of the added nitrogen is 3 × 10 5.
^{14. The} method for manufacturing a silicon single crystal substrate according to claim 1, wherein the concentration is ¹⁴ atoms / cm ³ or more. 3. The method for manufacturing a silicon single crystal substrate according to claim 1, wherein the growth of the silicon single crystal is performed by an FZ method. 4. The method for manufacturing a silicon single crystal substrate according to claim 1, wherein the heat treatment is performed in any one of a wet oxygen atmosphere, a dry oxygen atmosphere and a nitrogen atmosphere. 5. A silicon single crystal substrate to which nitrogen is added during the growth of a single crystal is held at any temperature between 900 ° C. and 1250 ° C. at least before the semiconductor element manufacturing process, and the silicon single crystal substrate is maintained for about 10 minutes to 1 minute. A method for quality control of a silicon substrate, which comprises heating for a period of time to recover the resistivity to a value immediately after growing a single crystal.