JPH07142299A - Semiconductor silicon wafer - Google Patents

Abstract

PURPOSE:To enable stable supply of high quality silicon wafers, by specifying infrared scattering body density observed by applying an infrared scattering tomography using infrared rays having a specified wavelength, to a heat-treated semiconductor silicon wafer. CONSTITUTION:A silicon wafer manufactured by the Czochralski method is heat-treated at 1000-1200 deg.C for 30-60min. By applying an infrared scattering tomography using infrared rays in the wavelength range of 0.8-1.35mum to the semiconductor silicon wafer, density of infrared scattering body is observed. In this case, the infrared scattering body density in an arbitrary region of the silicon wafer is set lower than or equal to 1X10<5>cm<-3>. The non-defective ratio of oxide film withstand voltage is set higher than or equal to than 80%. The OSF (oxidation-induced Stacking Fault) density is set lower than or equal to 10cm<-2>.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a single crystal silicon wafer manufactured by the Czochralski method (CZ method),
By setting the infrared scatterer density of the silicon wafer to be observed after heat treatment at a specific temperature and time to a predetermined value or less, the yield rate of the oxide film is 80% or more and the OSF density is 10 cm ^-2 or less. The present invention relates to a semiconductor silicon wafer which is guaranteed to be a high quality silicon wafer.

[0002]

2. Description of the Related Art Since the quality of a silicon wafer used for manufacturing a semiconductor device affects the yield and reliability of the semiconductor device, various standards have been established for the quality. In particular, since crystal defects have a great influence on semiconductor device characteristics, various inspections are performed on silicon wafers before shipping. A commonly used inspection method is BMD (Bulk Micro De
OSF (Oxidation-induc)
ed Stacking Fault) etc. 1000
After performing a heat treatment on the wafer at 16 ° C. for about 16 hours, selective etching is performed, and the defect density is measured as an etch pit with an optical microscope.

The demands on the quality of silicon wafers used in the manufacture of highly integrated semiconductor devices are becoming more and more stringent year by year, and oxide film withstand voltage characteristics, which have not been much problem until now, other than the items of BMD / OSF. Is becoming an important item. In recent studies, it has been revealed that the crystal defects existing in as-grown also affect the oxide film breakdown voltage characteristic. However, in the inspection of BMD / OSF which has been performed as a crystal defect inspection until now, it is difficult to evaluate the oxide film withstand voltage characteristics, and the conventional inspection method and standard for crystal defects are insufficient.

The yield rate of the initial breakdown voltage of a silicon wafer is determined by preparing a large number of MOS capacitors each having an oxide film having a predetermined thickness and an electrode having a predetermined area on the silicon wafer, and applying a predetermined method to each MOS capacitor. The ratio of the number of MOS capacitors that did not cause dielectric breakdown to the total number of MOS capacitors when a voltage was applied is defined as a good initial oxide film breakdown voltage product. In a MOS capacitor, generally, a step of forming a polycrystalline silicon film by an LP-CVD method on an oxide film formed by thermal oxidation, then diffusing phosphorus, and patterning the polycrystalline silicon film by a photo-etching method. It is produced through. as mentioned above,
It takes a lot of time and effort to manufacture a MOS capacitor. Further, the conventional method of manufacturing a MOS capacitor is a destructive inspection involving thermal oxidation and the like.

[0005]

As described above, the demands on the quality of the silicon wafer are strict, the rate of non-defective oxide film breakdown voltage is high, and the OSF density is required to be a predetermined value or less. The characteristics and the OSF density can be easily measured by a destructive inspection, and there is no means for guaranteeing that the inspected silicon wafer holds the predetermined characteristics, and it is difficult to stably supply a high-quality silicon wafer.

The present invention aims to stably supply a high-quality silicon wafer, and to easily measure the oxide film withstand voltage characteristic and the OSF density by a destructive inspection and to maintain a predetermined high characteristic. The purpose is to provide a guaranteed semiconductor silicon wafer.

[0007]

DISCLOSURE OF THE INVENTION The inventors of the present invention, as shown in FIG.
It was found that the density of infrared scatterers observed by a defect observation method using infrared rays in a s-grown silicon wafer, that is, the infrared scattering tomography method, and the non-defective rate of the oxide film withstand voltage characteristic of the wafer are much more correlated. (Japanese Patent Application No. 4-266747). Also, this as-grow
The infrared scatterers observed at n are thermally very stable and
It was confirmed that there was no change even by heat treatment at 0 ° C. On the other hand, as shown in FIG.
It was also found that there is a very good correlation between the density of the infrared scatterer and the density of the OSF observed after heat treatment for 30 to 60 minutes at a temperature of 0 ° C. (Japanese Patent Application No. 55106/1993).
No.)

Therefore, when the infrared scatterer observed after the heat treatment for 30 minutes to 60 minutes at the temperature of 1100 ° C. to 1200 ° C. is measured, it is present as-grown and has a red color which correlates well with the oxide film withstand voltage characteristic. It was found that both the outer scatterer and the infrared scatterer newly generated by heat treatment and having a good correlation with OSF can be measured at one time. That is,
If the density of the infrared scatterer measured by this method is equal to or lower than a predetermined value at an arbitrary position on the wafer, it is clear from the relationship between the density of the infrared scatterer of FIGS. 1 and 2 and the oxide film breakdown voltage characteristic and the OSF density. Thus, it can be guaranteed that the silicon wafer has a good oxide film withstand voltage characteristic and a low OSF density.

The present invention has a time of 30 to 60 minutes and a temperature of 1
The infrared scatterer density observed by an infrared scattering tomography method using infrared rays in the wavelength range of 0.8 to 1.35 μm was measured for a semiconductor silicon wafer that had been subjected to heat treatment under the conditions of 100 ° C. to 1200 ° C. A semiconductor silicon wafer characterized in that it is 1 × 10 ⁵ cm ⁻³ or less in any area of the silicon wafer, the yield rate of the oxide film is 80% or more, and the OSF density is 10 cm ⁻² or less. .

In the present invention, the infrared scattering tomography method is to observe the infrared light from a vertical direction because when the infrared light is finely squeezed and made incident from the side surface of the sample, the light is scattered by defects contained in the crystal. The infrared scatterer density distribution can be obtained by synthesizing the slit-shaped scattered images and creating a cross-sectional image of the cross section scanned by the beam. Also,
In the above 90 ° scattering method, the wafer needs to be cleaved at the time of measurement, but if the measurement is performed by the Brewster's angle incidence (illumination) method, the cleaving is also unnecessary.

In the present invention, the short-time heat treatment applied to the wafer to be measured may be any atmosphere such as air, an oxidizing atmosphere such as O ₂ atmosphere, an inert gas atmosphere such as N ₂ or Ar, and the temperature is lower than 1100 ° C. Then, the correlation with the OSF density distribution is not sufficiently manifested in the defect distribution observed by the infrared scattering tomography method, and when the temperature exceeds 1200 ° C., the correlation is not sufficiently manifested.
A temperature condition of 0 ° C to 1200 ° C is required. Further, the heat treatment time is required to be 30 minutes or longer to sufficiently manifest the correlation between the infrared scatterer density and the OSF density distribution, but if it exceeds 60 minutes, the manifestation effect is saturated and the heat treatment is performed. It takes 30 to 60 minutes because it only takes time.

In the present invention, the wavelength of infrared rays in the infrared scattering tomography method is adjusted to 0.8 μm in consideration of the decrease in the transmittance to the Si crystal, and the infrared scattering ability is decreased due to defects and the absorption by free electrons is increased. Also, considering the sensitivity of the image tube to infrared rays, the upper limit is 1.35 μm.

In the present invention, the infrared scatterer density in any region of the silicon wafer is set to 1 × 10 ⁵ cm ^-3.
The reason for the following is 3 at a temperature of 1100 ° C to 1200 ° C.
The infrared scatterer observed after the heat treatment for 0 to 60 minutes was a
This infrared scatterer density includes both an infrared scatterer that exists in s-grown and has a good correlation with the oxide film withstand voltage characteristic, and an infrared scatterer that is newly generated by heat treatment and has a good correlation with OSF. Is 1 × 10 ⁵ cm ⁻³ or less, the oxide film withstand voltage characteristic is 80% or more and O
This is because it can be guaranteed that the SF is a silicon wafer of 10 pieces / cm ² .

[0014]

The present invention has a temperature of 30 to 60 minutes and a temperature of 110.
The infrared scatterer density observed by an infrared scattering tomography method using infrared rays having a wavelength in the range of 0.8 to 1.35 μm is as − for a semiconductor silicon wafer that has been heat-treated under the conditions of 0 ° C. to 1200 ° C. Focusing on the inclusion of both an infrared scatterer that is present in a grown state and has a good correlation with the oxide film withstand voltage characteristic, and an infrared scatterer that is newly generated by heat treatment and has a good correlation with OSF, the infrared scatterer density is By performing the measurement, it is possible to measure defects of both the oxide film withstand voltage characteristic and the OSF at the same time. By suppressing these defects to a low density, the silicon oxide film has a high oxide film withstand voltage characteristic and a low OSF density. Wafers can be manufactured. That is, if the density of the infrared scatterer measured by the above method is 1 × 10 ⁵ cm ⁻³ or less at any place on the silicon wafer,
2 and the density of the infrared scatterer of FIG. 2 and oxide film withstand voltage characteristics and OS
As is clear from the relationship of F density, the oxide film withstand voltage characteristic is 8
It can be ensured that the OSF density is 0% or more and the OSF density is 10 cells / cm ² or less.

[0015]

[Examples] 23 CZ-silicon wafers, which are expected to have different initial oxide film withstand rate, are prepared, and the oxide film thickness is 2
A MOS capacitor having a surface area of 50 mm and an electrode area of 8 mm ² was produced in the wafer surface. A voltage was applied to this MOS capacitor by the SV method, and the MOS capacitor that had a dielectric breakdown (12.5 μA / cm ² or more) at an electric field of 8 MV / cm or less was defective.
The ratio of the number of S capacitors to the initial oxide film withstand voltage non-defective rate. Next, the infrared scatterer density of the cleaved wafer after removing the MOS capacitor by etching was measured by the infrared scatter tomography method. FIG. 1 shows the relationship between the infrared scatterer density and the initial oxide film withstand voltage non-defective rate measured as described above. It is clear from FIG. 1 that the rate of non-defective initial oxide film breakdown voltage can be estimated by measuring the density of the infrared scatterers, and the density of the infrared scatterers is 1 × 10 ⁵
It can be seen that a yield rate of the oxide film withstand voltage of 80% or more can be obtained if the ^density is cm ⁻³ or less.

The wafer was cut out from the almost same place of the CZ-silicon ingot where the OSF is expected to occur, and after the heat treatment at 1150 ° C. for 60 minutes, the defect density of the defects observed by the infrared scattering tomography method in the wafer surface. That is, the infrared scatterer density was measured. The lower limit of defect detection is up to 9 × 10 ⁴ defects / cm ³ . Further, according to the conventional method, the silicon wafer is subjected to an oxidation treatment at 1150 ° C. for 8 hours, and after 5 minutes of selective etching (Wright etching),
The etch pits due to OSF were measured with an optical microscope. Infrared scatterer density and OSF measured as described above
FIG. 2 shows the relationship with the density. It is clear from FIG. 1 that the OSF density can be estimated by measuring the density of the infrared scatterers, and if the density of the infrared scatterers observed after the heat treatment is 10 ⁵ cm ⁻³ or less, the density of the OSF is It can be 10 or less per square cm.

The infrared scatterers observed after a short heat treatment at a temperature of 1100 ° C. to 1200 ° C. are as-grown.
In addition, we have measured the sum of those that are present in the above, which influence the breakdown voltage of the oxide film and those which are newly revealed by the heat treatment and are related to the OSF. A silicon wafer having a body density of 1 × 10 ⁵ cm ^-3 or less satisfies both conditions that the yield rate of the oxide film is 80% or more and the OSF is 10 cm ^-2 or less, and the crystal quality is very good. A wafer is obtained.

[0018]

According to the present invention, for the quality evaluation of a silicon wafer required for high integration, OSF and the defect affecting oxide film withstand voltage characteristics, which has been highlighted in recent years with high integration, have been investigated. Both items can be inspected simultaneously in a shorter time than before, and by setting the defect density within a predetermined range, a high-quality silicon wafer with high oxide film breakdown voltage characteristics and low OSF density can be obtained. It can be guaranteed that there is a stable supply of high-quality silicon wafers.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the density of infrared scatterers observed by as-grown and the yield rate of oxide film withstand voltage.

FIG. 2 is a graph showing the relationship between the infrared scatterer density observed after heat treatment at 1150 ° C. for 1 hour and the OSF density observed after heat treatment in an oxygen atmosphere at 1150 ° C. for 8 hours.

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[Procedure amendment]

[Submission date] December 6, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0005

[Correction method] Change

[Correction content]

[0005]

As described above, the demands on the quality of the silicon wafer are strict, the rate of non-defective oxide film breakdown voltage is high, and the OSF density is required to be a predetermined value or less. the characteristics and OSF density can be easily measured in a non-destructive inspection, yet there is no means which can ensure that the silicon wafers were examined holds the predetermined characteristic, it is difficult to stable supply of high quality silicon wafers.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0012

[Correction method] Change

[Correction content]

In the present invention, the lower limit of the wavelength of infrared rays in the infrared scattering tomography method is 0.8 μm in consideration of the decrease in the ability to penetrate into Si crystals, and the infrared ray scattering ability is reduced by defects and the absorption by free electrons is increased. Also, considering the sensitivity of the image tube to infrared rays, the upper limit is 1.35 μm.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0016

[Correction method] Change

[Correction content]

The wafer was cut out from the almost same place of the CZ-silicon ingot where the OSF is expected to occur, and after the heat treatment at 1150 ° C. for 60 minutes, the defect density of the defects observed by the infrared scattering tomography method in the wafer surface. That is, the infrared scatterer density was measured. The lower limit of defect detection is up to 9 × 10 ⁴ defects / cm ³ . Further, according to the conventional method, the silicon wafer is subjected to an oxidation treatment at 1150 ° C. for 8 hours, and after 5 minutes of selective etching (Wright etching),
The etch pits due to OSF were measured with an optical microscope. Infrared scatterer density and OSF measured as described above
FIG. 2 shows the relationship with the density. It is clear from FIG. 2 that the OSF density can be estimated by measuring the infrared scatterer density. If the density of the infrared scatterer observed after the heat treatment is 10 ⁵ cm ⁻³ or less, the OSF density is It can be 10 or less per square cm.

Continuation of the front page (72) Inventor Tatsuhiko Shigematsu 2201 Kamioda, Kohoku-cho, Kishima-gun, Saga Sumitomo Sitix Kyushu Office

Claims (2)

[Claims] 1. A time of 30 to 60 minutes and a temperature of 1100 ° C.
The infrared scatterer density observed by the infrared scattering tomography method using infrared rays in the wavelength range of 0.8 to 1.35 μm was measured for the semiconductor silicon wafer that had been subjected to the heat treatment under the condition of 1200 ° C. 1 in any area
A semiconductor silicon wafer having a size of × 10 ⁵ cm ^-3 or less. 2. The silicon wafer manufactured by the Czochralski method, wherein the yield rate of the oxide film is 80% or more and the OSF density is 10 cm ⁻² or less. Semiconductor silicon wafer.