阅读说明：本技术 单晶硅晶圆的热处理方法 (Heat treatment method for single crystal silicon wafer ) 是由 曲伟峰 砂川健 中杉直 于 2018-12-25 设计创作，主要内容包括：本发明为一种单晶硅晶圆的热处理方法,其为在氮化性气氛下对Nv区域的单晶硅晶圆进行RTA热处理后,进行第二热处理而将BMD密度控制至规定的BMD密度的热处理方法,所述单晶硅晶圆的热处理方法中,预先求出BMD密度与RTA温度的关系的关系式,根据所述关系式,确定用于得到所述规定的BMD密度的RTA温度。由此,提供一种单晶硅晶圆的热处理方法,其用于制造表面无缺陷且在块体部分具有规定的BMD密度的退火晶圆及外延晶圆。(The present invention is a heat treatment method for a single crystal silicon wafer, which is a heat treatment method for performing RTA heat treatment on a single crystal silicon wafer in an Nv region in a nitriding atmosphere and then performing a second heat treatment to control a BMD density to a predetermined BMD density, wherein a relational expression of a relationship between the BMD density and the RTA temperature is obtained in advance, and the RTA temperature for obtaining the predetermined BMD density is determined based on the relational expression. Thus, a method of heat-treating a single crystal silicon wafer for manufacturing an annealed wafer and an epitaxial wafer having no defects on the surface and a predetermined BMD density in the bulk portion is provided.)

1. A heat treatment method for a single crystal silicon wafer, which comprises subjecting a single crystal silicon wafer in an Nv region to an RTA heat treatment in a nitriding atmosphere and then performing a second heat treatment to control a BMD density to a predetermined BMD density,

a relational expression of the relationship between the BMD density and the RTA temperature is obtained in advance,

and determining the RTA temperature for obtaining the specified BMD density according to the relational expression.

2. The method of heat-treating a single crystal silicon wafer according to claim 1, wherein the second heat treatment is performed at 850 to 950 ℃ for 2 hours or more and less than 32 hours.

3. The method for heat-treating a single crystal silicon wafer according to claim 1 or 2, wherein the nitriding atmosphere is an atmosphere containing ammonia gas.

4. The method of heat-treating a single crystal silicon wafer according to claim 3,

setting the control range of the predetermined BMD density to 1 × 10⁹～1×10¹¹/cm³，

The BMD density (/ cm)³)＝3×10⁴⁰exp (-8.86eV/kT) was used as the relation to become a gaugeThe RTA temperature is determined by way of the BMD density.

5. The method for heat-treating a single crystal silicon wafer according to any one of claims 1 to 4, wherein a heat treatment time of the RTA heat treatment is set to 1 second or more and less than 10 seconds.

6. The method for heat-treating a single crystal silicon wafer according to any one of claims 1 to 5, wherein an oxygen concentration of the single crystal silicon wafer is set to 13ppma (JEIDA) or more and less than 17ppma (JEIDA).

Technical Field

The present invention relates to a heat treatment method of a single crystal silicon wafer.

Background

In a conventional method for producing an annealed wafer or an epitaxial wafer, a defect-free wafer is subjected to RTA treatment in a nitriding atmosphere, vacancies are injected into the wafer, and then heat treatment is performed, whereby a DZ layer is formed on the surface and a BMD is formed inside, thereby imparting gettering capability to the bulk portion.

For example, patent document 1 discloses that a wafer of an ideal region (perfect region) containing no nitrogen-doped OSF region is subjected to RTA at a temperature of 1150 to 1250 ℃, and then a silicon wafer is subjected to a heat treatment at a temperature lower than the RTA heat treatment temperature to form a defect-free layer on a surface layer and simultaneously to a precipitation treatment for precipitating oxygen into internal vacancies.

Patent document 2 discloses that after new vacancies are formed in the wafer by RTA in an ammonia gas atmosphere, heat treatment is performed to form oxygen precipitates in the wafer.

Patent document 3 discloses that after RTA is performed at 1000 to 1250 ℃ in a gas atmosphere having a vacancy injection effect, vacancy density distribution in the thickness direction of the wafer is controlled by heat treatment at 600 to 1150 ℃ for 0.25 to 24 hours.

However, these heat treatment methods aim to control the BMD distribution in the thickness direction of the wafer so as to be a desired BMD distribution, and control of the BMD density is not considered.

Disclosure of Invention

Technical problem to be solved by the invention

The present invention has been made in view of the above circumstances, and an object thereof is to provide a heat treatment method for a single crystal silicon wafer for manufacturing an annealed wafer and an epitaxial wafer having no defects on the surface and a predetermined BMD density in the bulk portion.

Means for solving the problems

In order to solve the above-described problems, the present invention provides a heat treatment method for a single crystal silicon wafer, which comprises subjecting a single crystal silicon wafer in an Nv region to RTA heat treatment in a nitriding atmosphere, and then performing a second heat treatment to control a BMD density to a predetermined BMD density, wherein a relational expression of a relationship between the BMD density and the RTA temperature is obtained in advance, and the RTA temperature for obtaining the predetermined BMD density is determined from the relational expression.

In this way, when the RTA heat treatment is performed on the Nv region single crystal silicon in the nitriding atmosphere, the DZ layer is formed on the surface, and vacancies can be efficiently injected into the wafer in addition to vacancies originally present in the single crystal silicon wafer.

The solid solubility of RTA heat treated vacancies is affected by temperature and atmosphere. In this case, when the heat treatment atmosphere is a nitriding atmosphere, the solid solubility of vacancies is increased even at the same RTA temperature, and precipitation can be promoted.

In the present invention, a sample having a predetermined RTA temperature in a range (for example, 1150 to 1250 ℃) capable of injecting vacancies into a single crystal silicon wafer is prepared in advance, and then a second heat treatment is performed under predetermined conditions to form BMDs in the single crystal silicon wafer, whereby the relationship between the RTA temperature and the BMD density is determined in advance.

In the present invention, it was found that when the vacancy injection is carried out by the RTA treatment in a nitriding atmosphere, the vacancy injection is followed by the second heat treatment to cause the vacancy (V) to be associated with the silicon single crystalOxygen precipitation nuclei formed by reaction of oxygen (Oi) (V + Oi → VO, VO + Oi → VO)₂Etc.) to form stable BMD, a predetermined relational expression between BMD density and RTA temperature can be obtained. Then, by using this relational expression, it is possible to predict the BMD density from the RTA temperature or to determine the RTA temperature for controlling the BMD density to a predetermined BMD density.

The second heat treatment of the present invention is preferably performed at 850 to 950 ℃ for 2 hours or more and less than 32 hours.

When the second heat treatment is in the temperature range, the precipitation nuclei can be efficiently grown, and therefore, when the heat treatment time is 2 hours or more, stable BMD can be formed. In this case, considering the heat treatment cost, the upper limit of the heat treatment time is preferably less than 32 hours.

Moreover, when the heat treatment temperature is 850 ℃ or higher, precipitation nuclei can be efficiently grown, and when the heat treatment temperature is 950 ℃ or lower, the precipitation nuclei do not disappear, and therefore the precipitation nuclei can be efficiently grown.

The heat treatment atmosphere in this case may be, for example, an argon or oxygen atmosphere.

The nitriding atmosphere in the RTA heat treatment is preferably an atmosphere containing ammonia gas, for example, a mixed atmosphere of ammonia gas and argon gas.

Such an atmosphere enables efficient injection of vacancies into the single-crystal silicon wafer.

It was found that if the second heat treatment for growing and stabilizing precipitation nuclei is carried out after the RTA is carried out in such an ammonia gas-containing atmosphere, the BMD density (/ cm)³)＝3×10⁴⁰exp (-8.86eV/kT) (where K: Boltzmann constant, T: RTA temperature (K)) at a BMD density of 1 × 10⁹～1×10¹¹/cm³The range of (1) is true.

Therefore, using this relational expression, it is possible to estimate the BMD density from the RTA temperature or determine the RTA temperature for making the BMD density a desired BMD density.

The above-described relational expression is a relational expression between the RTA temperature and the BMD density, which is obtained by preparing a sample having a predetermined RTA temperature in advance, forming a stable BMD by the second heat treatment after the sample is subjected to the RTA heat treatment in a different nitriding atmosphere, for example, in a nitrogen atmosphere.

The heat treatment time of the RTA heat treatment of the present invention is preferably 1 second or more and less than 10 seconds.

When the RTA heat treatment is performed, a large number of vacancies are generated, which react with oxygen in the single crystal silicon substrate to form VO₂And the complex, and oxygen precipitation is promoted by the subsequent second heat treatment.

In this case, the generation amount of vacancies depends on the RTA temperature and not on the RTA time. Therefore, the relational expression of the present invention can be obtained as long as the RTA temperature is stable and the heat treatment time is 1 second or more.

The upper limit of the heat treatment time is not particularly limited, but is preferably less than 10 seconds in view of the heat treatment cost.

Further, it is preferable that the oxygen concentration of the single crystal silicon wafer of the present invention is set to 13ppma (jeida) or more and less than 17ppma (jeida).

When the oxygen concentration is in the above range, oxygen precipitation nuclei can be reliably formed by RTA heat treatment, and the relationship between the BMD density and the RTA temperature can be reliably obtained.

At this time, if the oxygen concentration is 13ppma or more, the size of the precipitation nuclei is easily grown to the critical size by RTA heat treatment.

Although the relational expression between the BMD density and the RTA temperature of the present invention is established even when the oxygen concentration is 17ppma or more, it is preferable to set the oxygen concentration to less than 17ppma in order to prevent problems in device characteristics such as electrical characteristics.

Effects of the invention

As described above, according to the method for heat-treating a single crystal silicon wafer of the present invention, an annealed wafer and an epitaxial wafer having no surface defects and a predetermined BMD density in a bulk portion can be easily and accurately produced from a relational expression between a BMD density and an RTA temperature obtained in advance.

Drawings

Fig. 1 is a graph showing a relational expression between BMD density and RTA temperature obtained in the present invention.

Fig. 2 is a graph showing establishment of the relational expression of the present invention.

Detailed Description

As described above, conventionally, a DZ layer is formed on the surface, the RTA heat treatment is performed on the wafer so as to give a desired BMD distribution to the bulk portion, and then, the second heat treatment, which is a heat treatment for growing the precipitation nuclei, is further performed.

As a result of earnest studies for solving the above-mentioned problems, the inventors of the present application have found that a predetermined relational expression between the BMD density and the RTA temperature can be obtained when the stable BMD is formed by performing RTA treatment in a nitriding atmosphere to inject vacancies and then growing oxygen precipitation nuclei formed by reacting the vacancies with oxygen in the single crystal silicon by subsequent heat treatment. Further, it has been found that, by using this relational expression, it is possible to predict the BMD density from the RTA temperature or determine the RTA temperature for controlling the BMD density to a predetermined BMD density, and the present invention has been completed.

That is, the present invention is a heat treatment method for a single crystal silicon wafer, which is a heat treatment method for performing RTA heat treatment on a single crystal silicon wafer in the Nv region in a nitriding atmosphere and then performing a second heat treatment to control the BMD density to a predetermined BMD density, the heat treatment method being characterized in that,

a relational expression of the relationship between the BMD density and the RTA temperature is obtained in advance,

and determining the RTA temperature for obtaining the specified BMD density according to the relational expression.

The present invention will be described in detail below, but the present invention is not limited thereto.

The "RTA heat treatment" of the present invention is a rapid thermal annealing and can be carried out in a commercially available RTA heat treatment furnace, in which vacancies are injected into the wafer and reacted with oxygen in the single-crystal silicon to form oxygen precipitation nuclei. Further, the "second heat treatment" is a heat treatment performed after the RTA heat treatment, and is a heat treatment for growing and stabilizing the formed oxygen precipitation nuclei.

In the present invention, a plurality of Nv-region single crystal silicon wafers (CW wafers: chemically etched wafers) are prepared first, and after the RTA temperature is determined in a nitriding atmosphere, the wafers are processed into PW wafers (mirror polished wafers), and then a second heat treatment for growing and stabilizing oxygen precipitation nuclei is performed, and the BMD density in the bulk of the single crystal silicon wafers is measured. The Nv region is a region in which vacancies (vacancies) are dominant among neutral (N) regions where atoms are suitable, and is a region in which oxygen precipitation easily occurs because vacancies are dominant.

Then, a relational expression between the BMD density and the RTA temperature is obtained from the correlation between the BMD density and the RTA temperature.

Preferably, the oxygen concentration of the silicon single crystal wafer at this time is set to 13ppma (JEIDA) or more and less than 17ppma (JEIDA), the heat treatment time of the RTA heat treatment is set to 1 second or more and less than 10 seconds, and the second heat treatment is performed under conditions of 850 to 950 ℃ and 2 hours or more and less than 32 hours.

Within such a range of conditions, a relational expression between the BMD density and the RTA temperature can be obtained.

For example, when the nitriding atmosphere is an ammonia gas-containing atmosphere (mixed atmosphere of ammonia and argon gas), the following relational expression is such that the RTA temperature is 1150 to 1250 ℃ and the BMD density is 1 × 10⁹～1×10¹¹/cm³Is true in the range of:

BMD Density (/ cm)³)＝3×10⁴⁰exp(-8.86eV/kT)。

Since this relational expression depends on the heat treatment atmosphere of RTA, it is necessary to obtain a relational expression between the BMD density and the RTA temperature in advance in the actually performed RTA atmosphere.

In the range of the RTA temperature of 1150 to 1250 ℃, the BMD density is increased along with the increase of the RTA temperature. When the RTA temperature is higher than 1250 ℃, the BMD density has a constant value or shows a slight decrease.

This is considered to be caused by the following reasons: even if the equilibrium concentration of vacancies V is high, in the high temperature region, the vacancy V is generated by the RTA heat treatment processThe form of the precipitation nucleus in (A) will be composed of VO₂Conversion to 4VO₂Therefore, a large amount of V is consumed for the formation of the precipitation nuclei.

In addition, in the heat treatment of the present invention, two forms of BMDs, plate-like and polyhedral, are formed, and when the BMDs are plate-like, the dimensions are 40 to 300nm (diagonal length); the size of the polyhedron is about 10 to 50nm (the length of the diagonal).

Although the CW wafer is used to perform the RTA heat treatment in the nitriding atmosphere and the second heat treatment is performed after the PW wafer is processed, the RTA heat treatment may be performed using the PW wafer and the second heat treatment may be performed after the RTA heat treatment if the relationship between the BMD density and the RTA temperature is simply obtained.

Then, the RTA temperature is determined so as to obtain a predetermined BMD density, or the BMD density is estimated from the RTA temperature, using a relational expression between the RTA temperature and the BMD density obtained in advance.

For example, when RTA is performed in an ammonia-containing atmosphere, the BMD density of the control is set, and the RTA temperature is determined using the following relationship:

BMD Density (/ cm)³)＝3×10⁴⁰exp(-8.86eV/kT)。

Then, when an annealed wafer having a predetermined BMD density is produced, CW processing is performed on the single crystal silicon wafer in the Nv region, and RTA heat treatment is performed for 1 second or more and less than 10 seconds at a temperature determined by the above relational expression in an atmosphere containing ammonia, thereby forming oxygen precipitation nuclei.

Then, the nitride film formed on the surface is PW processed to remove it, and then a second heat treatment is performed at 850 to 950 ℃ for 2 to 32 hours to grow and stabilize oxygen precipitation nuclei.

The atmosphere for the second heat treatment may be an argon atmosphere or an oxygen atmosphere.

When the atmosphere of the second heat treatment is an oxygen atmosphere, cleaning with hydrofluoric acid is necessary to remove the oxide film formed on the surface.

Further, an epitaxial layer may be formed on the surface of the annealed wafer obtained in this manner to produce an epitaxial wafer.