JP2742247B2 - Manufacturing method and quality control method for silicon single crystal substrate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

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

On the other hand, in order to prevent generation of crystal defects due to thermal stress generated in a silicon substrate at the time of heat treatment especially in a high temperature region, Japanese Patent Application Laid-Open No.
No. 7,497, it has been proposed to add nitrogen to a silicon single crystal.

[0004]

However, when heat treatment is performed on a silicon substrate to which nitrogen is added, unlike a silicon substrate to which nitrogen is not added, the measured resistivity is 10% or more before and after the heat treatment. In some cases, it has been difficult to guarantee the resistivity of the silicon substrate to which nitrogen has been added.

The present invention has been made in view of the above points, and provides a method of manufacturing a nitrogen-doped silicon substrate and a method of controlling the quality thereof, which exhibit a stable resistivity by any heat treatment during a semiconductor device manufacturing process. It is intended to be.

[0006]

A method for manufacturing a silicon single crystal substrate according to claim 1 includes a step of adding nitrogen during the growth of the silicon single crystal, a step of cutting the silicon single crystal, and a step of cutting the silicon single crystal. By heating the silicon single crystal substrate at least at any temperature between 900 ° C. and 1250 ° C. for at least 10 minutes to 1 hour before the semiconductor device manufacturing process, the silicon single crystal substrate can be manufactured before the semiconductor device manufacturing process. Recovering the resistivity of the substrate to a value immediately after growing the single crystal.

According to a second aspect of the present invention, in the method of manufacturing a silicon single crystal substrate according to the first aspect, the concentration of the nitrogen added is 3 × 10 ¹⁴ at.
oms / cm ³ or more.

According to a third aspect of the present invention, there is provided a method of manufacturing a silicon single crystal substrate according to the first or second aspect, wherein the growing of the silicon single crystal comprises:
It is characterized by performing by the FZ method.

According to a fourth aspect of the present invention, in the method of manufacturing a silicon single crystal substrate according to any one of the first to third aspects, the heat treatment is performed in a wet oxygen atmosphere, a dry oxygen atmosphere, or a nitrogen atmosphere. It is characterized by being performed in any one of them.

According to a fifth aspect of the present invention, there is provided a method for controlling the quality of a silicon substrate, the method comprising the steps of:
Hold at any temperature between 250 ° C for about 10 minutes to 1
It is characterized by measuring the resistivity of the substrate whose resistivity has been restored to a value immediately after the single crystal growth by heating for a time.

[0011]

According to the present invention, the resistivity of the silicon substrate to which nitrogen has been added can be made substantially equal to the value immediately after the single crystal is grown, and the resistivity does not change during 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 is grown. Therefore, according to the manufacturing method and the resistivity measuring method according to the present invention, a semiconductor element can be manufactured with high yield from a silicon substrate to which nitrogen is added. In particular, 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 temperature of the heat treatment is 900 ° C. or less,
In order to make the resistivity after cooling equal to the value immediately after the growth of the single crystal, a heat treatment time of one hour or more is required, so it is not 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 due to thermal stress will occur during heating and cooling, even though nitrogen is added to the silicon substrate. Further, the heating rate is, for example, 1
C. to 10.degree. C. is used, but can be freely selected as long as the silicon substrate subjected to the heat treatment is not broken or crystallinity is deteriorated.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS 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. At this time, the silicon single crystal is grown, for example, by a floating zone melting method (FZ method).
Done by Next, the silicon substrate obtained by slicing the silicon single crystal into a predetermined thickness and further mechanically polishing the silicon substrate is chamfered at its peripheral portion and then subjected to an etching treatment to remove a crushed layer on the surface. Subsequently, sandblasting is performed on the back surface side of the silicon substrate to provide a work strain layer. After this step, the heat treatment according to the present invention is performed and the temperature is cooled 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, and conditions most suitable for the purpose of the present invention were searched for.

[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 for a minute. In this heat treatment,
I changed the heat treatment atmosphere. The specific conditions and results are as follows.

1. Conditions For a sample substrate, an n-type, {111} single crystal having 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. Further, as another sample substrate, a substrate shown in Table 2 prepared in the same classification as Table 1 except that it was of p-type was used.

[0017]

[Table 1]

[0018]

[Table 2]

As shown in Tables 1 and 2, for the silicon substrates of different types, the heat treatment is performed under three conditions of 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 FIGS. 2 (A) and 2 (B) and FIGS. 3 (A) and 3 (B).
Is shown in Here, FIG. 2A shows a change in resistivity for an n-type silicon substrate, and FIG. 3A shows a change in resistivity for a p-type silicon substrate. FIG.
From FIG. 3A and FIG. 3A, it can be seen that the resistivity changes significantly 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, the change in the resistivity is not so affected. further,
When comparing a p-type silicon substrate and an n-type silicon substrate,
It can be seen that the p-type has a higher rate of change in resistivity. Note that when a 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 in other heat treatment atmospheres.

FIGS. 2B and 3B show AST.
The change in the resistivity is converted into a change in the carrier concentration using the M conversion formula (F723-82). When converted into a change in carrier concentration in this way, with some exceptions, it can be said that the higher the nitrogen concentration, the greater the change in carrier concentration. It should be noted that when the p-type silicon substrate and the n-type silicon substrate are compared with respect to the rate of change in resistivity, it is found that the p-type silicon substrate is one digit larger.

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

1. Conditions Heat treatment temperature in nitrogen atmosphere at 700 ° C, 900 ° C and 1
Set at 000 ° C. for 1 minute, 4 minutes,
Heat treatment was performed for 8 minutes, 20 minutes, 60 minutes, and 120 minutes, and then, the temperature was lowered to room temperature, and the resistivity was examined. Further 1200
A heat treatment experiment at 8 ° C. for only 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 immediately after growing a single crystal was 150 Ω · cm was used. The cooling time, that is, the room temperature after the heat treatment (24 to 2
(5 ° C.) for 15 seconds.

2. Results The results are shown in FIG. From this figure, it can be seen that the resistivity once increases significantly at the beginning of the heat treatment, but when the heat treatment is further continued, the resistivity tends to gradually decrease 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, which is the resistivity immediately after growing the single crystal, in about 10 minutes. Also, it can be seen that when the temperature is higher than 1000 ° C., the time required to recover to the resistivity immediately after the single crystal growth is reduced. On the other hand, when the temperature is lower than 1000 ° C., it can be seen that the time required to recover to the resistivity immediately after the growth of the single crystal becomes longer.

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

1. Conditions As a 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 above samples were heat-treated in three kinds of 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 (B). Here, FIG. 5A shows the resistivity change on the vertical axis, and FIG.
FIG. 5B shows the change in resistivity in FIG.
3-82) shows the result of conversion into carrier concentration change. Here, that the rate of change of the resistivity or the carrier concentration is small means that the resistivity once increased has recovered to a value close to the value immediately after the growth of the single crystal.
On the other hand, a large change rate means that the resistivity is still recovering. From these figures, it can be seen that 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 greater than in a wet oxygen atmosphere, if the heat treatment time is 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 was grown.

Next, a theoretical consideration for the above experimental results will be added. FIG. 6 outlines the recovery process of the resistivity. In a 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, so that the carrier is easily trapped, and as a result, the resistivity increases. 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 lattices, and the resistivity recovers to the value immediately after the single crystal growth. It is.

When heat treatment is performed 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 vacancies disappear and deep levels disappear.

The reason why the change in resistivity in the wet oxygen atmosphere is small when wet oxygen and dry oxygen are compared is that the inward diffusion of Si is performed quickly because the formation rate of the SiO ₂ film is higher in the wet O ₂ atmosphere. This is because, as a result, the rate of recovery of the resistivity at the same heat treatment temperature and heat treatment time increases.

In the case of an N ₂ atmosphere, S
It is presumed that the influence of not only the inward diffusion of i but also the outward diffusion of holes is large.

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

[Experiment 4] In the next experiment, the silicon substrate 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, and the degree of change in resistivity before and after the heat treatment was examined. .

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

[0037]

[Table 4]

In the first heat treatment, sample 1 was heated at 1200 ° C. for 60 minutes in wet oxygen and sample 2 was heated at 1000 ° C. for 60 minutes.
Minutes went. 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 resistivity before and after that was compared.

2. Results As a result, the change in resistivity due to the second heat treatment was 1% or less and was within a negligible range. That is, when the first heat treatment according to the present invention is performed on a silicon substrate to which nitrogen is added, the resistivity of the silicon substrate is restored to a value immediately after the single crystal is grown, and the value is made 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-described embodiments, and may be variously modified without departing from the gist thereof. Needless to say.

In the above embodiment, the p-type silicon substrate having a large change in resistivity was evaluated in Experiments 2 and 3.
It is needless to say that the present invention is also effective for an n-type silicon substrate having a small change in resistivity.

In the above embodiment, the silicon substrate obtained by the FZ method has been described. However, it is needless to say that the present invention can be applied to a silicon substrate obtained by the Czochralski method (CZ method).

Further, in the above embodiment, the silicon substrate 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 is applied to the silicon substrate which is not subjected to the sandblast treatment. Can of course be applied.

[0044]

The effects obtained by typical ones of the inventions disclosed in the present application will be briefly described as follows. When a silicon substrate to which nitrogen is added is subjected to a heat treatment during the growth of a single crystal, the vacancies that cause the generation of a deep level disappear, and the resistivity can be restored to the resistivity immediately after the growth of the single crystal. Management becomes easy.

[Brief description of the drawings]

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

FIGS. 2A and 2B are tables respectively 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).

FIGS. 3A and 3B are tables 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 a change in resistivity when heat treatment conditions (temperature and time) are changed.

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

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

Claims (5)

(57) [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 step of subjecting the cut silicon single crystal substrate to 900 ° C. to 1250 ° C. at least before a semiconductor element manufacturing step. Recovering the resistivity of the silicon single crystal substrate to a value immediately after the single crystal growth before heating the semiconductor single crystal by holding at any temperature between about 10 minutes and 1 hour. A method for manufacturing a silicon single crystal substrate, characterized in that: 2. The nitrogen concentration to be added is 3 × 10
^{2. The} method for producing a silicon single crystal substrate according to claim 1, wherein the concentration is ¹⁴ atoms / cm ³ or more. 3. The method according to claim 1, wherein the growing 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 one of a wet oxygen atmosphere, a dry oxygen atmosphere, and a nitrogen atmosphere. 5. A method for manufacturing a silicon single crystal substrate to which nitrogen is added during the growth of a single crystal, before manufacturing a semiconductor element.
Hold at any temperature between 0 ° C and 1250 ° C for about 1
A quality control method for a silicon single crystal substrate, comprising: measuring a resistivity of a substrate whose resistivity has been restored to a value immediately after growing a single crystal by heating for 0 minute to 1 hour.