JPS5933972B2 - Silicon substrate manufacturing method - Google Patents

Description

[Detailed Description of the Invention] The present invention provides a mirrored wafer for use in semiconductor devices.
Relating to a method of manufacturing.

Usually, mirrored wafers are used for silicon substrates for ICs and VLSIs.

Mirror wafers include silicon substrates that have been sliced, lapped, chamfered, and etched from silicon single crystal rods and then polished, and silicon substrates that have been sliced, lapped, chamfered, and etched from silicon single crystal rods. Recently, silicon substrates are often subjected to gettering treatment.

Gettering processing can be roughly divided into extrinsic gettering and intrinsic gettering (hereinafter referred to as IG). One type of extrinsic getttering is backside damage (hereinafter referred to as BSD), and it is common practice to inject abrasive particles onto the back side of a silicon substrate using liquid honing, sandblasting, etc. to cause damage. . This damage can be done by controlling the particle size of the abrasive grains and the jetting pressure of the abrasive grains to create a crack layer of 5 to 10 microns on the back surface of the silicon substrate.
There are two types of stacking faults that occur on the backside of the silicon substrate during the subsequent semiconductor device process.

While the type that provides a crack layer does not easily eliminate the gettering effect during the semiconductor device manufacturing process, there are problems such as deformation of the silicon substrate, typified by warpage, and the residual effects of contamination adhered to the crack layer.

In addition, the type that generates stacking faults does not cause problems with substrate deformation or contamination during the semiconductor device manufacturing process, but the gettering effect disappears, making it difficult to improve IC hold time and yield rate as expected. There is a problem that it cannot be obtained.

As explained in detail in Japanese Patent Application No. 56-142334, the present applicant conducted an experiment on the IG-applied mirror surface wafer.
After the two-step heat treatment at high and low temperatures, the surface layer of the mirror wafer was removed, thereby reducing the hold time failure of the MOS memory.

Subsequently, the present inventors conducted various continuous experiments to improve the hold time and non-defective rate after semiconductor device fabrication, and found that after applying BSD to the mirrored wafer, the mirrored wafer was exposed to 3 to 10% oxygen. 2-step heat treatment at high temperature and low temperature in an atmosphere containing oxygen, or 2-step heat treatment at high temperature and low temperature in an atmosphere containing 3 to 10% oxygen, followed by low temperature in an atmosphere containing no oxygen. It has been found that significant effects can be obtained by removing the surface layer of

That is, in a method of manufacturing a silicon substrate from a semiconductor silicon rod by a pulling method using a quartz crucible, after the semiconductor silicon rod is made into a wax material, a processing step such as an etching step, a polishing step, or an intermediate step thereof is performed. In the process, after imparting BSD of the type that causes stacking faults during the semiconductor device process to the mirror-finished wafer,
Two-step heat treatment at high temperature and low temperature in an atmosphere containing 10% oxygen, or two-step heat treatment at high temperature and then low temperature in an atmosphere containing 3 to 10% oxygen. By applying this method and then removing the silicon surface layer, a great effect was obtained.

The feature of the present invention is that after BSD processing on the mirror surface wafer, 3~
After performing a two-step heat treatment at high and low temperatures in an atmosphere containing 10% oxygen, or a two-step heat treatment at a high temperature and then at a low temperature in an oxygen-free atmosphere in an atmosphere containing 3 to 10% oxygen, The purpose is to remove the surface layer.

Each example will be described below.

Example 1 Oxygen concentration 14-18×1017at0ms/Cc (AS
P-type (100) 7-10Ω {, 100ψ, 525μ, which has been subjected to slicing, chamfering, wrapping and etching processes from CZ dislocation-free single crystal containing 'RM display)
1.5kg of abrasive grains with an average particle size of 10μ are applied to the mirror surface wafer.
/(BSD processing was performed by injecting with air pressure of 1-J mo Vf.

After cleaning the specular wafer, it was subjected to a two-step heat treatment of 8 hours at 1150°C and then 8 hours at 700°C in an atmosphere containing 5% oxygen (F6) to Ar to remove the diluted wafer. The oxide film was removed with acid, and 10 to 20μ of the surface layer, which is the opposite side to the BSD processed surface, was removed by mirror polishing.First
The figure shows the case where a MOS type memory 1C device is manufactured using the mirror-finished wafer according to this embodiment (curve A), and the case where the BS
After applying D, the surface layer was removed after 2-step heat treatment in an atmosphere of Ar only (curve B), and when BSD was applied and the surface layer was removed without performing 2-step heat treatment (curve C). A comparison of the hold times of curves) is shown.

In FIG. 1, the horizontal axis shows the hold time (unit: MS) and the vertical axis shows the number of samples. As shown in Figure 1, the hold time is A
The curve was longer than curves B and C, and the hold time failure could be significantly reduced. Due to this,
11 in an atmosphere containing 5(f) oxygen with BSD.
This shows that performing a two-step heat treatment of 8 hours at 50°C and 8 hours at 7000C to remove a 10-20μ surface layer is important for improving the hold time. Example 2 A mirror surface wafer similar to that of Example 1 was subjected to the same BSD processing, and after cleaning, it was heated at 1150°C for 8 hours in an atmosphere containing 3% oxygen in Ar and then at 700 atmosphere C for 8 hours. 2
Step heat treatment is performed, the oxide film is removed with dilute hydrofluoric acid, and B
The surface layer, which is the opposite side to the SD processed surface, is polished to a 10%
~20μ removed.

After processing these wafers into MOS memory C, the hold time was measured. As a result, the improvement was the same as in Example 1, and the hold time defects were significantly reduced. Example 3 An experiment exactly the same as in Example 1 was conducted using an atmosphere of Ar with 10% oxygen added.

After processing the obtained wafer into MOS memory 1C, the hold time was measured, and the improvement was found to be the same as in Example 1.
The result was similar to that of the previous example, and the hold time failure was significantly reduced.
Example 4 An experiment exactly the same as in Example 1 was conducted using an atmosphere of Ar with 2% oxygen added.

After processing the obtained wafer into MOS memory 1C, the hold time was measured, and the results are shown in Figure 1B.
It was almost the same as the curve, and there was almost no discernible improvement. Example 5 An experiment completely similar to Example 1 was conducted using an atmosphere containing 15% Arf1C oxygen.

The obtained wafer was processed into MOS memory 1C, and the hold time was measured, and the results are shown in Figure 1C.
It was almost the same as the curve, and there was almost no discernible improvement. Example 6 In Example 1, a mirror polishing step was added after the etching step, and similar BSD processing and similar heat treatment were performed, and 0.5 to 5 μm of the surface layer was removed by mirror polishing.

After processing the obtained way into MOS memory 1C, the hold time was measured, and the improvement was found in Example 1.
The result was similar to that of the previous example, and the hold time failure was significantly reduced.
Example 7 In Example 1, a mirror polishing step was added after the etching step, and the same heat treatment was performed without BSD processing, and 0.5 to 5 μm of the surface layer was removed by mirror polishing.

After processing the obtained wafer into a MOS memory IC, its hold time was measured, and the result was almost the same as the curve B in FIG. 1, with almost no improvement observed. Example 8 In Examples 1 to 7, high-temperature heat treatment was performed in an atmosphere containing an amount of oxygen in each example, low-temperature heat treatment was performed in an atmosphere without oxygen, and other conditions were the same as those in each example. I conducted an experiment.

After processing the obtained wafer into a MOS memory 1C, the hold time was measured and the results were almost the same as those in each example. Example 9 In Example 1, the high-temperature heat treatment was conducted in an atmosphere containing only Ar, and the low-temperature heat treatment was conducted in an Ar atmosphere containing 5 (F6) oxygen.

After processing the obtained way into a MOS memory 1C, the hold time was measured, and almost no improvement was observed. Although abrasive grains with an average grain size of 10 μm were used for the BSD processing in each of the above examples, similar results were obtained with abrasive grains with an average grain size of 3 μm.

Furthermore, similar results were obtained when N2 gas was used instead of Ar gas as the atmospheric gas during the heat treatment. As described in each of the above embodiments and FIG. 1, when the mirror surface wafer fabricated by the method of the present invention is processed into MOS memory 1C, the hold time is significantly improved, and defects due to hold time are significantly reduced. The effect of reducing
The rate of non-defective products has improved.

[Brief explanation of the drawing]

FIG. 1 shows the hold time characteristics of a MOS type memory 1C device. The horizontal axis shows the hold time (unit: MS), and the vertical axis shows the number of samples.

Claims (1)

[Claims] 1. A method for manufacturing a mirror-finished wafer for use in semiconductor devices, in which BSD (backside damage) is applied to a mirror-finished wafer and the mirror-finished wafer is damaged by 3 to 10%.
A method for manufacturing a silicon substrate for a semiconductor device, which comprises performing two-step heat treatment at high and low temperatures in an atmosphere containing oxygen to remove a surface layer of the mirror-finished wafer, which is the surface opposite to the BSD processed surface. 2. In a method for manufacturing a mirrored wafer used in semiconductor devices, BSD (backside damage) is applied to a mirrored wafer, and the mirrored wafer is
% of oxygen, followed by low-temperature heat treatment in an oxygen-free atmosphere to remove the surface layer of the mirror-finished wafer, which is the surface opposite to the BSD processed surface. A method for manufacturing a silicon substrate for semiconductor devices. 3 Heat treatment in an atmosphere containing 3 to 10% oxygen,
3. The method of manufacturing a silicon substrate for a semiconductor device according to claim 1, wherein 0.5 to 20 μm of the surface layer of the mirror-finished wafer is removed.