JP2000252336A - Method for sorting acceptable and rejective silicon wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the breakthrough of detection limit concerning to the size and density of an oxygen deposit to be measured by sorting an acceptable silicon wafer when a specific ESR signal obtained through ESR measurement of a micro oxygen deposit in silicon crystal is 0. SOLUTION: Surface part of a just grown silicon crystal wafer, inside of a DZ-IG silicon wafer, and the surface part of a silicon wafer having an epitaxially grown silicon crystal layer are measure by means of an ESR measuring instrument and an acceptable silicon wafer having an ESR signal of 0 when the g value of micro oxygen deposit equal to 2.006 is detected at high sensitivity and sorted. Since an oxygen deposit can be discriminated from other defects based on a g value obtained from the ESR signal, only the oxygen deposit can be identified and the breakthrough of detection limit can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for producing a silicon wafer near the surface of an as-grown silicon crystal or a silicon wafer having a silicon epitaxial growth layer on the surface. The present invention relates to an improvement in a method for detecting the presence of minute oxygen precipitates that are generated and cause device failure and for determining the quality of a silicon wafer.

[0002]

2. Description of the Related Art Generally, a silicon wafer serving as a substrate for forming a silicon device is required to have no defect near a surface serving as a device active region.

However, in practice, DZ (denuded) is used in a wafer made of as-grown silicon crystal.
zone) -IG (intrinsic gette)
ring) a silicon wafer, that is, a silicon wafer having an epitaxially grown silicon crystal layer in the DZ of a silicon wafer having a high temperature interstitial oxygen out-diffusion heat treatment and a two-step oxygen precipitation heat treatment to produce a DZ and an IG layer In the epitaxially grown silicon crystal layer and the like, minute oxygen precipitates are present, which has an adverse effect on device characteristics, that is, withstand voltage and leak current when an oxide film is formed.

In general, to detect minute oxygen precipitates formed near the surface of a wafer made of as-grown silicon crystal or near the surface of a silicon wafer having an epitaxially grown silicon crystal layer, Means such as observation using an optical microscope after chemical etching, detection using an infrared scattering tomograph, and observation using an electron microscope are known.

[0005] Among the above-mentioned conventional means, in observation by an optical microscope and in infrared scattering tomography, the detectable minute oxygen precipitates are limited to large ones. Even when a tomograph is used, the size of a defect that can be detected is 20 nm or more.

[0008] Atomic level defects can be detected by observation with an electron microscope. However, in the vicinity of the surface of a wafer made of as-grown silicon crystal, DZ-IG
If the density of defects existing in the DZ of the silicon wafer or in the vicinity of the surface of the silicon wafer having the epitaxially grown silicon crystal layer is low, it is difficult to detect such defects.

[0007]

SUMMARY OF THE INVENTION In the present invention, a breakthrough of the detection limit relating to the size and density of the oxygen precipitate to be measured is realized, so that a smaller minute oxygen precipitate can be detected. Low oxygen precipitates can be detected.

[0008]

SUMMARY OF THE INVENTION The present inventor has proposed a method for measuring the vicinity of the surface of a wafer made of as-grown silicon crystal, DZ-
In the DZ of an IG silicon wafer, near the surface of a silicon wafer having an epitaxially grown silicon crystal layer, etc., an ESR (electron spin resonance) is used.
ce) As a result of measurement with a measuring instrument, it was surprisingly found that minute oxygen precipitates could be detected with high sensitivity based on an ESR signal having a g value of 2.006.

The process in which the method of the present invention is obtained is as follows: First, a DLTS (deep level transitivity) is applied to a wafer made of as-grown silicon crystal.
An experiment was conducted to detect minute oxygen precipitates by applying the ent spectroscopy method, and the result is an experimental result based on the same DLTS method that is being carried out to judge the quality of the oxide film in the MOS device. It turned out to be very similar to the above, so when we tried to measure with an ESR measuring instrument, the above result was obtained.
Experiments were successively conducted on a DZ-IG silicon wafer and a silicon wafer having an epitaxially grown silicon crystal layer, and the same result was obtained.

It has been reported that an ESR signal having a g value of 2.006 is detected at a silicon / oxide film interface in a MOS device (if necessary,
"Y. Nisi, Jpn. J. Appl. Phys. 1
0, 52 (1971) ").

When ESR measurement is performed on the silicon / oxide film interface in the MOS device, an E value of 2.006 is obtained.
The exact reason for the appearance of the SR signal is unclear at this time, and according to one theory, in the case of silicon / amorphous SiO ₂ , it appears when the dangling bond between Si and O ₂ is broken.

However, at present, the present inventors have been able to elucidate whether the same phenomenon as the silicon / amorphous SiO ₂ interface occurs in the case of minute oxygen precipitates in the silicon crystal targeted by the present invention. However, in any case, by conducting the experiments disclosed in the present invention, it can be easily confirmed that minute oxygen precipitates in silicon crystals can be detected easily and with high sensitivity,
Its power is perceived to be superior to any conventional method.

From the above description, in the method for screening the quality of a silicon wafer according to the present invention, (1) a fine oxygen precipitate in a silicon crystal constituting a silicon wafer is obtained by ESR measurement. g value =
Selecting a silicon wafer having an ESR signal of 2.006 equal to 0 as a non-defective product, or

(2) In the above (1), the silicon wafer to be subjected to the ESR measurement is made of a silicon crystal as grown, a DZ-IG silicon wafer, or an epitaxially grown silicon crystal. Or a silicon wafer having a layer.

By employing the above-mentioned means, the oxygen precipitate to be measured can be detected irrespective of the size, unlike the case where an optical microscope or an infrared scattering tomograph is used.
Unlike the case of the electron microscope, the lower detection limit of the density can be sufficiently reduced by increasing the size of the object, unlike the case of the electron microscope, and furthermore, depends on the g value obtained from the ESR signal. Since it is possible to distinguish oxygen precipitates from other defects, it is possible to identify only oxygen precipitates, and therefore, an ES having a g value of 2.006
Silicon wafer with R signal of 0 or DZ
If an active semiconductor device is manufactured by selecting an IG silicon wafer or a silicon wafer having an epitaxially grown silicon crystal layer, and a defective product is generated, the cause is oxygen precipitates on the wafer. It is almost certain that it is in a place other than.

[0016]

FIG. 1 is an optical microscope photograph showing the appearance of oxygen precipitation inside a silicon crystal as a sample.

The silicon crystal used in this case is a p-type CZ (Czochralski) -Si crystal. Temperature: 500 [° C.] Time: time 10 [hours] and Temperature: 700 [° C.] Time: time 60 [hours] The oxygen precipitate heat treatment is continuously applied to generate oxygen precipitates in the silicon crystal.

Referring to the scale attached to FIG. 1, if the oxygen precipitates (white portions) are counted, the density is as follows:
It turns out that it is 3.9 × 10 ¹⁰ [cm ⁻³ ].

From this silicon crystal, the plane index (10
0) A rod-shaped sample having a size of 2 [mm] x 2 [mm] x 20 [mm] is cut out, cooled to a temperature of 10 (K), and then measured using an ESR measuring device. .

In the ESR measurement, a sample is set between two coils in an ESR measuring instrument, and a magnetic field is applied perpendicularly to the long axis of the sample, and the value of the magnetic field is set to 331.0 [m
T] to 341.0 [mT], and the measurement was performed by irradiating a 9.43 [GHz] microwave to the measured portion of the sample.

FIG. 2 is a diagram showing the relationship between the magnetic field and the value obtained by differentiating the magnetic susceptibility with the magnetic field. The horizontal axis represents the magnetic field, and the vertical axis represents the value obtained by differentiating the magnetic susceptibility with the magnetic field. is there.

According to the figure, g value = 3360 G!
The appearance of an ESR signal of 2.006 can be clearly seen, and this ESR signal is due to oxygen precipitates. When the interface state density is determined from the signal intensity, 1.3 × 10 ¹² [cm] ^-3 ].

The size of the oxygen precipitate in the sample shown in FIG. 1 is determined by a TEM (transmission element).
It has been found from observation by tron microscopy that the diameter is about 10 [nm].

Then, the number of interface states of one oxygen precipitate is determined by the following equation: the surface density of dangling bonds at the interface × the boundary area of the precipitate = 1 × 10 ¹⁶ [cm ⁻² ] × 4π ( 10 × 10 ^-9 ) ² [c
m ² ] ≒ 10 [pieces].

Therefore, from the ESR signal, the oxygen precipitate density was 1.3 × 10 ¹¹ [cm ^-3 ], which is larger than the value obtained from the optical micrograph of FIG. This is because observation by a microscope cannot detect small oxygen precipitates.

FIG. 3 is a diagram showing an optical microscope observation result and an ESR measurement result for explaining another embodiment of the present invention, and the horizontal axis represents the oxygen precipitate density obtained from the optical microscope observation. [Cm ^-3 ] is plotted on the vertical axis, and the oxygen precipitate density [cm ^-3 ] obtained from ESR measurement is plotted on the vertical axis.

The silicon crystal used in this case is a p-type CZ-Si crystal, which is obtained by depositing oxygen at a temperature of 500 ° C. for a time of 1 hour and a temperature of 700 ° C. for a time of 60 hours. The heat treatment and the temperature: 500 [° C] time: time 5 [hours] and the temperature: 700 [° C] time: time 60 [hours] were added to generate oxygen precipitates in the silicon crystal. Things.

In FIG. 3, the dashed line shows the result of observation with an optical microscope, and the plot shows the result of ESR measurement. It can be seen that there is a close correlation between them.

As shown in the figure, when the result of optical microscope observation and the result of ESR detection are compared, the result of ESR detection is higher than the result of optical microscope observation.
From this, it is clear that the oxygen precipitate can be detected better by ESR than by optical microscope observation.

FIG. 4 is a diagram showing the relationship between the magnetic field and the value obtained by differentiating the magnetic susceptibility with respect to the sample different from the samples described with reference to FIGS. 1 to 3, wherein the horizontal axis represents the magnetic field, and the vertical axis represents the magnetic field. Represents the value obtained by differentiating the magnetic susceptibility with the magnetic field.

The sample used in this case was a p-type CZ-S
An oxygen precipitate is generated in the silicon crystal by adding an oxygen precipitation heat treatment at a temperature of 700 [° C.] time: 10 [hours] to the i crystal.

According to the figure, g value = 3360 [G]
It was observed that an ESR signal of 2.006 appeared, and it was confirmed that this ESR signal was due to oxygen precipitates. When the same sample was observed with an optical microscope, no defect was found.

In the present invention, the present invention is not limited to the above-described embodiment, and many other modifications can be realized.
During the manufacturing process of the semiconductor device including the heat treatment process,
Perform SR measurement, judge pass / fail of silicon wafer,
Management for preventing the occurrence of defective products can be implemented.

[0034]

According to the method for screening the quality of a silicon wafer according to the present invention, a g-value = 2.0006 obtained by ESR measurement of minute oxygen precipitates in a silicon crystal constituting the silicon wafer. Are selected as non-defective silicon wafers whose ESR signal is zero.

By adopting the above configuration, unlike the case of using an optical microscope or an infrared scattering tomograph, the oxygen precipitate to be measured can be detected regardless of its size.
Unlike the case of the electron microscope, the lower detection limit of the density can be sufficiently reduced by increasing the size of the object, unlike the case of the electron microscope, and furthermore, depends on the g value obtained from the ESR signal. Since it is possible to distinguish oxygen precipitates from other defects, it is possible to identify only oxygen precipitates, and therefore, an ES having a g value of 2.006
Silicon wafer with R signal of 0 or DZ
If an active semiconductor device is manufactured by selecting an IG silicon wafer or a silicon wafer having an epitaxially grown silicon crystal layer, and a defective product is generated, the cause is oxygen precipitates on the wafer. It is almost certain that it is in a place other than.

[Brief description of the drawings]

FIG. 1 is an optical microscope photograph showing a state of oxygen precipitation inside a silicon crystal serving as a sample.

FIG. 2 is a diagram showing a relationship between a magnetic field and a value obtained by differentiating magnetic susceptibility with a magnetic field.

FIG. 3 is a diagram showing an optical microscope observation result and an ESR measurement result for explaining another embodiment of the present invention.

FIG. 4 is a diagram showing a relationship between a magnetic field and a value obtained by differentiating magnetic susceptibility with respect to a sample different from the samples described with reference to FIGS. 1 to 3;

Claims (2)

[Claims] A micro oxygen precipitate in a silicon crystal constituting a silicon wafer is removed by ESR (electron).
g obtained by spin resonance) measurement
Silicon whose value is 2.006 and whose ESR signal is 0
A method for selecting quality of a silicon wafer, the method comprising selecting a wafer as a non-defective product. 2. The method according to claim 1, wherein the silicon wafer to be subjected to the ESR measurement is made of as-grown silicon crystal or DZ
(Denuded zone) -IG (intrins)
2. The method as claimed in claim 1, wherein the method comprises one of a silicon wafer and a silicon wafer having an epitaxially grown silicon crystal layer.