JPH04105046A - Measuring method for inter-lattice oxygen concentration of drawup silicon wafer - Google Patents

Abstract

PURPOSE:To calculate the inter-lattice oxygen concentration of pullup Si wafer through a simple measuring process by sensing the photo-penetrativenesses of a pullup Si wafer unground chemically and a floating band Si wafer whose both surfaces are ground into mirror face. CONSTITUTION:In a measuring device 10 a Michelson interferometer 12 prepares an interferential beam of light using a beam of light given from a light source 11, and a polarizer 13 makes the interferential beams of light into parallel beams of polarized light. As No. 1 process this parallel polarized light is projected to a specimen M (pullup Si wafer unground chemically) at a Brustar angle, and the photo-penetrativeness of the specimen M is measured by a sensor 14. As No. 2 process the parallel polarized light is put incident to an object R (floating band Si wafer with both surfaces ground into mirror face) at the Brustar angle, and the photo-penetrativeness of the object R is measured by the sensor 14. As No. 3 process, a calculating device 15 calculates the photo- absorptiveness from the sensing results of the sensor 14, and then the inter- lattice oxygen concentration of the specimen M can be calculated.

Description

Detailed Description of the Invention (1) Purpose of the Invention [Field of Industrial Application] The present invention relates to a method for measuring interstitial oxygen concentration in pulled wrinkled wafers, and in particular, to a method for measuring interstitial oxygen concentration in pulled wrinkled silicon wafers that have not been chemically polished. The results are derived from the light transmission characteristics measured with parallel polarized light incident at Brewster's angle and the light transmission characteristics measured with parallel polarized light incident at Brewster's angle on a floating band silicon wafer as a control whose front and back surfaces are mirror-polished. The present invention relates to a method for measuring interstitial oxygen concentration of a pulled silicon wafer by calculating the interstitial oxygen concentration of the upper silicon wafer.

[Prior Art] Conventionally, this type of method for measuring the interstitial oxygen concentration of pulled silicon wafers has been carried out using a pulled silicon wafer that has not been chemically polished and which has been extracted from a production line, and a pulled silicon wafer whose front and back surfaces are both the front and back sides of the pulled silicon wafer. By simultaneously injecting infrared light into a pair of floating zone silicon wafers that have been processed to ensure the same optical behavior as the floating zone silicon wafer, the optical transmission characteristics of the pulled silicon wafer and the floating zone silicon wafer can be evaluated. A method has been proposed in which the interstitial oxygen concentration of a pulled silicon wafer is determined by measuring the light transmission characteristics.

[Problems to be solved] However, in the conventional method for measuring the interstitial oxygen concentration of pulled silicon wafers, since both the front and back surfaces of the pulled silicon wafers have not yet been mirror-polished, (1) it is difficult to ensure that the optical behavior is the same; This has the disadvantage that both the front and back sides of a floating zone silicon wafer as a control must be processed in the same way as both the front and back sides of a pulled silicon wafer, which also has the disadvantage of making the measurement work complicated. (iii) There was also the drawback that measurement accuracy could not be improved.

Therefore, in order to eliminate these drawbacks, the present invention simplifies the measurement work and improves measurement accuracy by making it possible to use a floating band diagonal with mirror-polished surfaces on both sides as a control. The present invention aims to provide a method for measuring interstitial oxygen concentration in pulled silicon wafers.

(2) Structure of the invention [Means for solving the problems] The means for solving the problems provided by the present invention are [(a)
A first step for measuring the light transmission characteristics of a pulled wrinkled silicon wafer by making parallel polarized light incident at the Brewster angle on an unchemically polished pulled silicon wafer; (C) measuring the light transmission properties of the floating band silicon wafer by making parallel polarized light incident on the floating band silicon wafer at Brewster's angle; a third step for calculating the interstitial oxygen concentration of the pulled silicon wafer from the light transmission characteristics of the silicon wafer and the light transmission characteristics of the floating zone silicon wafer measured in the second step; ``Method for measuring interstitial oxygen concentration in silicon wafers.''

[Function] The method for measuring the interstitial oxygen concentration of a pulled silicon wafer according to the present invention is based on the light transmission characteristics of a pulled silicon wafer that has not been chemically polished and Since the interstitial oxygen concentration of the pulled silicon wafer is calculated from the light transmission characteristics of the floating zone silicon wafer with mirror polishing on both sides, (i1) without processing the floating zone silicon wafer with mirror polishing on both the front and back sides. It has the effect of making it usable as a mirror surface, which in turn has the effect of (11) simplifying the measurement work, and fiii) improving the measurement accuracy.

[Example] Next, a preferred example of the method for measuring interstitial oxygen concentration of a pulled silicon wafer according to the present invention will be given.
This will be explained in detail with reference to the accompanying drawings.

Figure 1 is a simplified configuration diagram showing a measuring device for carrying out an embodiment of the method for measuring the interstitial oxygen concentration of pulled silicon wafers according to the present invention.

FIGS. 2 to 4 are explanatory diagrams for explaining one embodiment of the method for measuring interstitial oxygen concentration in a pulled silicon wafer according to the present invention.

Examples - First, the structure and operation of an embodiment of the method for measuring the interstitial oxygen concentration of a pulled silicon wafer according to the present invention will be described in detail.

The method for measuring the interstitial oxygen concentration of a pulled silicon wafer according to the present invention involves making parallel polarized light incident on a pulled silicon wafer that has not been chemically polished (referred to as an "unchemically polished pulled silicon wafer") at the Brewster angle. The first step is to measure the light transmission characteristics (here, the transmitted light intensity ■; the same applies below for ssi) of the upper silicon wafer (i.e., a non-chemically polished pulled silicon wafer), and the first step is to measure the light transmission characteristics (here, the transmitted light intensity ■) of the upper silicon wafer (i.e., the pulled silicon wafer that has not been chemically polished). Floating zone silicon wafer (°“
By making parallel polarized light incident on a mirror-polished floating-band silicon wafer (herein referred to as a mirror-polished floating-band silicon wafer) at a Brewster angle φ8, the light transmission characteristics (here, transmitted light intensity ■) of a floating-band silicon wafer (namely, a mirror-polished floating-band silicon wafer) are determined. a second step for measuring the same);
The optical transmission properties of pulled silicon wafers (i.e. non-chemically polished pulled silicon wafers) measured by the process of
Here, the transmitted light intensity ■. 6. ) and the light transmission characteristics (here, the transmitted light intensity ■) of the floating zone silicon wafer (i.e., the mirror-polished floating zone silicon wafer) measured in the second step, and the interstitial oxygen concentration [01c] of the pulled silicon wafer. and a third step for calculating.

1st. In the second step, the Brewster angle φ
The reason for making parallel polarized light incident in step 8 is that reflection occurs when parallel polarized light enters and exits a pulled silicon wafer (i.e., a non-chemically polished pulled silicon wafer) and a floating band silicon wafer (i.e., a mirror-polished floating band silicon wafer). The objective is to substantially prevent the occurrence of multiple reflections within pulled silicon wafers (i.e., non-chemically polished pulled silicon wafers) and floating band silicon wafers (i.e., mirror-polished floating band silicon wafers). . Here, parallel polarized light refers to polarized light that has only components parallel to the plane of incidence on the incident objects (here, unchemically polished pulled silicon wafers and mirror-polished floating zone silicon wafers). In addition, a pulled silicon wafer refers to a silicon wafer created from a silicon single crystal manufactured by a pulling method (so-called "Czochralski method"), and usually has both front and back surfaces generated by the cutting process of the silicon single crystal. The floating zone silicon wafer is mechanically polished to ensure flatness on both the front and back surfaces prior to chemical polishing to remove the fractured layer of the silicon wafer. A manufactured silicon wafer.

The reason why the floating zone silicon wafer is used as a control in the second step is that its interstitial oxygen concentration [0i1 is extremely small compared to the interstitial oxygen concentration [0,c] of the pulled silicon wafer. It is in. Further, the reason why both the front and back surfaces of the floating zone silicon wafer are mirror-polished is to prevent incident light (here, parallel polarized light) from being scattered on both the front and back surfaces.

In the third step, the light transmission properties of the pulled silicon wafer (i.e., non-chemically polished pulled silicon wafers) measured by the first step (here, the transmitted light intensity I.ssl and the The procedure for calculating the interstitial oxygen concentration [0+.1 of the pulled silicon wafer from the light transmission characteristics (here, the transmitted light intensity I0) of the floating zone silicon wafer (that is, the mirror-polished floating zone silicon wafer) is as follows. be.

First, the interstitial oxygen concentration [0, C
I is the optical absorption coefficient (also referred to as the optical absorption coefficient of the pulled silicon wafer) aE caused by the vibration of interstitial oxygen in the pulled silicon wafer and the conversion coefficient k (currently 3.03XlO
It can be expressed as [0+c] = kat using the following formula: [0+c] = kat.Here, the optical absorption coefficient α of the pulled silicon wafer is the wave number 1
Absorbance A of a pulled silicon wafer with thickness d at 106 cm-' and optical path length ff of parallel polarized light incident at Brewster angle φ8 = 1. []42d can be expressed as follows from the Lambert-Beer modulus w.

The absorbance A of a pulled silicon wafer is the light transmission characteristic (here, the transmitted light intensity
) and the light transmission characteristics (in this case, transmitted light intensity) of a floating zone silicon wafer (i.e., a mirror-polished floating zone silicon wafer), so the light transmission characteristics of an unchemically polished pulled-up silicon wafer ( Here, the transmitted light intensity is calculated.Isl and the light transmission characteristics of the mirror-polished floating zone silicon wafer (here, the transmitted light intensity ■) and the light scattering characteristics on the surface of the unchemically polished pulled-up silicon wafer (here, the scattered light intensity Is')
) and the light scattering characteristics on the back surface of the unchemically polished pulled silicon wafer (here, the scattered light intensity is 1.□), A=symbol. (■°”s + I s++ I 92)■.

It can be expressed as follows.

Therefore, the interstitial oxygen concentration of the pulled silicon wafer [
0,c] is U○"" 1.042d ×,,,I Q! 1! l + I"+Is5 engineering.

is required.

Here, (1°"+1"'+1"') is the light transmission property of the unchemically polished pulled silicon wafer (here, the transmitted light intensity Ioss) and the light scattering property on both the front and back surfaces (here, the scattered light It is calculated from the absorbance characteristic, which is the natural logarithm of the reciprocal of the ratio of the sum of the intensities 1., 1.21 and the light transmission characteristic of the mirror-polished floating zone silicon wafer (here, the transmitted light intensity I.). is the interstitial oxygen concentration [0
:c] is not O (indicated by a solid line) at a wave number of 1106 cm-' (i.e. peak value) and interstitial oxygen concentration [0,c] is O (indicated by a broken line) The value at a wave number of 11.06 cm'' is obtained as shown in FIG.

Example '-5 Also, with reference to FIG. 1, the configuration and operation of a measuring device for carrying out an embodiment of the method for measuring the interstitial oxygen concentration of a silicon wafer according to the present invention will be explained in detail. explain.

This is a measuring device for carrying out the method for measuring the interstitial oxygen concentration of pulled silicon wafers according to the present invention, and includes a light source 1 such as a crowbar lamp, and a translucent 112A that transmits light from a light source 11. The movable mirror 12B is divided into two parts by
and a Michelson interferometer 12 that forms interference light by reflecting it by a fixed 5ttzc and superimposing it, and a parallel polarized light obtained by polarizing the light given from the Michelson interferometer 12 (i.e., interference light) to the sample. The trowel is a non-chemically polished pulled-up silicon wafer (M) and the control trowel is a mirror-polished floating zone silicon wafer (R). Strength I. A detector 14 is connected to the detector 14 for detecting the light transmission characteristics of the ssl and the reference R (in this case, transmitted light intensity of parallel polarized light), and a sample M is connected to the detector 4.
A calculation device for calculating the interstitial oxygen concentration of the sample M after calculating the absorbance characteristics from the light transmission characteristics (i.e., transmitted light intensity r.) of the control R (i.e., the transmitted light intensity r.) It is equipped with I5. If necessary, there is a reflection tR1 between the sample M and the pair R and the detection strike 4.
6A16B is inserted. Incidentally, a reflecting mirror (not shown) may be inserted between the Michelson interferometer 12 and the polarizer 13, if necessary.

Therefore, in the measuring device, the interference light created by the Michelson interferometer 12 from the light given from the light source 11 is converted into parallel polarized light by the polarizer 13, and then the interference light is transmitted to the sample M.
and control R.

Since the sample IIM and the control R undergo absorption and scattering according to their optical properties, the absorbance characteristics calculated by the calculation device 15 from the detection results by the detector 14 have a shape as shown in FIG.

The calculation device 15 calculates the optical absorption coefficient α of the sample M shown in FIG. Calculate the interstitial oxygen concentration [0, el of chemically polished pulled silicon wafer) M.

In addition, for the purpose of promoting understanding of the method for measuring the interstitial oxygen concentration of a pulled silicon wafer according to the present invention, specific numerical values will be given and explained.

! First, the pulled-up silicon wafer is placed on a placing plate in a state where both the front and back surfaces have been mechanically polished (that is, the state of a non-chemically polished pulled-up silicon wafer), and the interstitial oxygen concentration is measured according to the interstitial oxygen concentration measuring method according to the present invention. [0, CI was measured (first
(see table).

After that, the pulled silicon wafer is subjected to chemical polishing and mirror polishing on both the front and back surfaces, and in this state (that is, the state of the mirror polished pulled silicon wafer), the interstitial oxygen concentration is measured according to the method of measuring interstitial oxygen concentration according to the present invention. Concentration [01e
(see Table 1).

The interstitial oxygen concentration [0,cl'' measured for unchemically polished pulled silicon wafers and the interstitial oxygen concentration [0,cl'' measured for mirror polished pulled silicon wafers are expressed by the vertical axis Y and the horizontal axis, respectively. When plotted on a graph defined as X, as shown in FIG. 3, they were on the straight line Y=X and were in good agreement.

Therefore, according to the present invention, by directly adopting unchemically polished pulled silicon wafers and double-sided polished floating zone silicon wafers as samples and controls, the interstitial oxygen concentration [0, cl of pulled silicon wafers can be directly determined. It turns out that it can be measured.

1. Takumi Takumi ■ Pulled silicon wafers are prepared by cutting silicon single crystals in a cutting process (i.e., unchemically polished pulled silicon wafers) according to the method for measuring interstitial oxygen concentration according to the present invention. The interstitial oxygen concentration [0, cl was measured (see Table 2).

After that, the pulled silicon wafer was subjected to chemical polishing and mirror polishing on both the front and back sides, and in this state (that is, the state of the mirror polished pulled silicon wafer), it was subjected to the method for measuring interstitial oxygen concentration according to the present invention. Therefore, the interstitial oxygen concentration [0, c
(see Table 2).

The interstitial oxygen concentration measured for unchemically polished pulled silicon wafers [0 haze and the interstitial oxygen concentration measured for mirror polished pulled silicon wafers [0, cIo] are the vertical axis Y and the horizontal axis X, respectively. When plotted on the graph shown in FIG. 4, it was found that they were on the straight line Y=X and were in good agreement.

Therefore, according to the present invention, the interstitial oxygen concentration EO,c) of the pulled wrinkled wafer can be determined by directly adopting the non-chemically polished pulled silicon wafer and the double-sided polished floating zone silicon wafer as samples and controls. It turns out that it can be measured directly.

”! Note that although the above explanation has been made only for the case where the Michelson interferometer 12 is used, the present invention is not limited to this, and may also be applied to the case where a spectrometer is used instead of the Michelson interferometer. Inclusive.

(3) Effects of the Invention As is clear from the above, the method for measuring interstitial oxygen concentration of pulled silicon wafers according to the present invention, as disclosed in the above-mentioned [Means for solving problems], Since the interstitial oxygen concentration of the pulled silicon wafer is calculated from the light transmission characteristics of the pulled silicon wafer and the light transmission characteristics of the floating zone silicon wafer whose front and back surfaces are mirror-polished, (i) both the front and back surfaces are mirror-polished; This has the effect of making it possible to use the floating zone silicon wafer as it is without any processing, which in turn has the effect of (11) simplifying the measurement work, and (iii) the effect of improving measurement accuracy. has.

[Brief explanation of drawings]

FIG. 1 is a simplified configuration diagram showing an apparatus for carrying out an embodiment of the method for measuring the interstitial oxygen concentration of pulled silicon wafers according to the present invention, and FIGS. 2 to 4 show pulled silicon wafers according to the present invention. FIG. 2 is an explanatory diagram for explaining one embodiment of a method for measuring interstitial oxygen concentration in a wafer. 10・・・・・・・・・・・・Interstitial oxygen concentration measuring device・・・・・・・・・・Light source 12・・・・・・・・・・Michelson interferometer 1
2A...Semi-transparent mirror 12B...Movable mirror 12G...Fixed mirror 13...Polarizer 14 .........Detector 15......Calculating devices 16A, 16B
・・・・・・Reflector M・・・・・・・・・・・・・・・
・Sample R・・・・・・・・・・・・・・・Contrast

Claims (1)

[Scope of Claims] (a) A first step for measuring the light transmission characteristics of a pulled silicon wafer by making parallel polarized light incident on the pulled silicon wafer at the Brewster angle, which has not been chemically polished; b) a second step for measuring the light transmission properties of the floating zone silicon wafer by making parallel polarized light incident at the Brewster angle on a floating zone silicon wafer as a control whose front and back surfaces are mirror-polished; ) Calculating the interstitial oxygen concentration of the pulled silicon wafer from the light transmission characteristics of the pulled silicon wafer measured in the first step and the light transmission characteristics of the floating zone silicon wafer measured in the second step. A method for measuring interstitial oxygen concentration in a pulled silicon wafer, comprising: a third step.