JPS5947738A - Measurement of diffusion layer - Google Patents

Abstract

PURPOSE:To accurately and easily measure diffusion layer of wafer in the manufacturing line and suppress increase of cost for quality control by measuring P-N junction generated through conversion of the area other than the P type diffusion layer to the N type by processing a substrate forming the P type diffusion layer at a lower temperature. CONSTITUTION:An alcohol saturated solution of B2O2 is applied to a single side of P type silicon substrate having resistivity of 15-20OMEGAcm and thickness of 210mum obtained by doping boron with the CZ method. The silicon substrate is heated for 140hr at 1,290 deg.C and a diffusion layer is formed on the P type silicon substrate in the depth of 160mum with the surface concentration of boron of 10<20>pcs/cm<3>. An element thus obtained is used as a sample for measurement. This sample is heated for 12hr at 460 deg.C under a gas of H2, O2, N2 or a mixed gas of them. Thereby the area other the diffused layer of sample is converted into an N type conductive region layer. This sample is then cut into segments having adequate sizes and are polished until a angle of 5 deg.43' can be obtained. After applying the hydrofluoric acid solution to the polishing surface of segment 1, the polishing surface is heated by an infrared lamp for about one minute in order to form a staining film. Depth (h) of diffused layer is obtained from thickness of film using known equation by observing such staining film with a microscope.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention provides 4. a measurement force fl [of a diffusion layer of a silicon wafer].
In particular, the new diffusion layer measuring force 6+3H is used to easily and accurately measure the diffusion layer of a silicon wafer on an actual production line.

[Technical background of the invention]

Formed by impurity diffusion layer of silicon sea urchin, thermal diffusion and ion implantation! 7 L, it is extremely important to accurately determine the diffusion depth of the diffusion layer and the width of the non-diffused region layer in the quality control of semiconductor manufacturing. Resistivity 0.
5~5000ΩC7) J low concentration P type 7 recon ueno・
Conventionally, it is difficult to measure the depth of the diffusion layer for a silicon substrate in which a highly concentrated P-type diffusion layer containing acceptor impurities is formed. In this way, σ)′I+/, ti
Quality control force for measuring the depth of the t-layer〃-1Left 1-
5τ, the following two methods are viable, but these methods have drawbacks as described below, so they are more difficult to implement.
[Background technology problems] Conventionally, a high concentration P-type diffusion layer was formed on a low concentration P-type silicon substrate. 1- Method for measuring the depth of the diffusion layer of a silicon wafer formed with
．． The following two methods have been implemented.

The first method is an indirect method, and in this first method, a VcN type sea urchin, which is different from the P type silicon sea urchin manufactured on the annual production line, is used as a measurement sample.
-1 Under the same conditions as the N-type Ueno and the P-type Tsuni...
After diffusing type impurities to form a PN junction, the depth of the diffusion layer of the N-type wafer is measured by a well-known staining method or gold plating method, and the measured value is the depth of the diffusion layer of the P-type silicon wafer. Convert to measured value.

In order to obtain accurate measurement values using this indirect measurement method, the substrate concentration of the N-type wafer, which is the measurement data, must match the substrate concentration of the P-type wafer, but in the actual production line, It is difficult to achieve this, and in addition to this discrepancy in substrate concentration between the two substrates, there is also the phenomenon of increased concentration difference during the formation of the diffusion layer, as described below. The error between the apparent measured value and the true value of P-type Tuni... is even larger, and it is impossible to accurately determine the measured value fql by this first method. Diffusion layer type /j'y, II'' as described above
The phenomenon of increasing concentration difference between both j and c in 1- is the difference between the behavior of σ) N-type impurities and the behavior of P-type impurities in an oxidizing atmosphere. That is, oxidation r1: Although the concentration of N-type impurities increases in the atmosphere (7
7! The dullness tends to decrease, and therefore,
After forming the diffusion layer, the concentration difference between both wafers increases further.1. This will further increase the error between the measured value and the true value.
The second method is the ``Redding Resistance'' method, which measures the spreading resistance based on the concentration gradient between the impurity ffd fu in the substrate and the impurity concentration in the diffusion layer. Nine measuring machines are commercially available.

In this seventh method, unlike the first method, there is no need to prepare an N-type wafer, and there is no need to prepare a P-type wafer to be measured. This method is more accurate than the first method; however, even with this method, if the concentration gradient between the diffusion layer and the substrate is small, the error is about 4 to 8 μ. In addition, there is a problem in that the cost required for quality control increases significantly because the measuring machine is expensive.

[Purpose of the invention]

This invention σ solves the problems existing in the conventional method as described above, makes it possible to more accurately and easily measure the diffusion layer of a silicon wafer in an actual production line, and significantly increases the cost required for quality control. The purpose of this invention is to provide a novel method for measuring a diffused layer.

[Summary of the invention]

The present invention was developed by focusing on the phenomenon in which some of the oxygen present in a single crystal silicon wafer becomes a donor when the wafer is subjected to low-temperature heat treatment. After forming the substrate, the parts other than the P-type diffusion layer are converted to the rN type by subjecting the substrate to low-temperature heat treatment, and the resulting PN junction is formed using a known staining method, gold plating method, etc. It is characterized by making it possible to measure the diffused layer with high precision by measuring.Various values can be selected for the heat treatment conditions depending on the impurity concentration of the silicon substrate and the impurity concentration of the diffused layer, but in general, 550
C. or less within 50 hours is effective. In addition, the impurity degree of the silicon substrate is 05 to 5000Ωα in terms of resistivity.
You can choose within the range.

[Embodiments of the invention]

Resistivity 15-200 obtained by boron doping by CZ method
cm% thickness 210 pm (D After coating one side of the P type silicon substrate with an alcohol saturated solution of VcB203,
The silicon substrate was heated at 1290°C for 140 hours with p, +y
1. ,, boron surface concentration is 160 at 1020 pieces/n4
A diffusion layer with a depth of μm was formed on a P-type silicon substrate, and this was used as a measurement sample (see FIG. 1).

The sample in Figure 1 was heated at 460°C IF in a mixed gas atmosphere of 2,0°8N2 or VJ, Konoshira.
Heat treatment was performed for 2 hours to convert the portion of the sample other than the diffusion layer into an N-type conductive region layer as shown in FIG.

After heat treatment as described above, the sample was cut into small pieces.

After polishing the small piece 1 at an angle of 5°43' as shown in FIG. 6, measurements were made as follows using a known staining method.

That is, hydrogen fluoride 500 CC:, nitric acid (cc.
After applying a hydrofluoric acid solution consisting of 500 cc of pure water to the angle-polished surface of the small moon 1, the angle-polished surface was heated with an infrared lamp for about 1 minute to form a staining film. Then, this staining film is observed under a microscope and the depth h of the diffusion layer is calculated from the thickness of the staining film using a known formula.
'l asked for it. As a result, the error according to the measuring method of the present invention was 1 μm or less.

In addition, when we measured the diffusion layer thickness using the same method by varying the impurity concentration and heat treatment time of the P-type silicon substrate used as a sample, we were able to obtain similar results. Impurity doping method for P-type silicon substrate: A sample was formed using the FZ method instead of the frCZ method, and the diffusion layer was measured on this sample under the same conditions as above, but the same results could not be obtained. did it.

〔Effect of the invention〕

As a result of the above, in the present invention, t:r+, [□:1
, well-known scrubbing register 57 probe i'j
= Accurate and low-cost measurement of the diffused layer) is provided by the method of the present invention.
This makes it possible to improve the quality of semiconductor chains without increasing the manufacturing cost.

In the above embodiments, only examples using the staining method have been shown, but it is also possible to use the staining method 1 (instead of C, a known gold plating method or the spreading resistance side 511 method may be used).

[Brief explanation of drawings]

FIGS. 1 to 6 are cross-sectional views of measurement samples during each step VC of the method of the present invention. 1...A small piece that has been cut. 1st 2nd 3rd 77th edition' 179- /1

Claims (1)

[Claims] 41 When a silicon substrate containing an acceptor impurity is diffused or ion-implanted with an acceptor impurity at a higher concentration than that of the silicon substrate, the depth of the diffusion layer or ion implantation layer of the silicon substrate or the non-diffusion region layer or 7 In a method for measuring the width of a non-ion implanted region layer, the silicon sea urchin is heat treated at 430 to 520° C. for 1 to 50 hours, and the valve diffusion region layer or the non-ion implanted region layer is made into an N-conducting layer. A diffusion layer measuring method characterized by forming a PN junction by inverting it to a b-type, and then measuring the depth or the width.