JPH07183347A - Method for evaluating semiconductor tool material - Google Patents

Abstract

PURPOSE:To detect a metal impurity released from a tool material by performing heat treatment by erecting a wafer for monitoring and the forming body of a semiconductor tool material machined in a wafer shape on a wafer board consisting of a high-purity crystal, etc., provided inside a process tube and then measuring the characteristics of the wafer for monitor. CONSTITUTION:Two forming bodies 13 of a semiconductor jig material are erected on a wafer board 12 with a fixed spacing while retaining a wafer 14 for monitor in-between, the wafer board 12 is placed inside a process tube 11 made of crystal, and then the wafer board 12 is heat-treated for a specific amount of time at a specific temperature within a certain gas atmosphere. The metal impurity released from the forming body 13 of semiconductor tool material is adhered to the wafer 14 for monitor by heat treatment. Then, various kinds of characteristics of the wafer 14 for monitor containing the metal impurity are measured, thus determining the type, amount, and distribution of the metal impurity which easily travels due to the heating of the forming body 13 of semiconductor jig material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for evaluating a semiconductor jig material, and more particularly, to evaluate the contamination of a semiconductor jig material such as a wafer boat or a process tube used for heat treatment of a semiconductor with a semiconductor. A method for evaluating a semiconductor jig material.

[0002]

2. Description of the Related Art In recent years, with the development of the semiconductor industry, various semiconductor manufacturing processes have been adopted when forming various elements and the like on a semiconductor substrate such as a silicon wafer.

In these semiconductor manufacturing processes,
Various heat treatments such as thermal oxidation are performed, but if the container used for performing this kind of heat treatment or the semiconductor jig that holds the semiconductor substrate is not of sufficiently high purity, the semiconductor jig is used to remove the semiconductor substrate. There is a problem that the metal is contaminated with the metal and the contamination causes a malfunction of the semiconductor device.

Therefore, it is necessary to rigorously check the purity and the like of these semiconductor jigs to see if they adversely affect the semiconductor substrate. Also, under the actual heat treatment conditions, the semiconductor jigs should be used for semiconductor inspection. It is also necessary to investigate in detail how much the substrate is contaminated.

As a conventional method for evaluating a semiconductor jig material used for a wafer boat, a process tube, etc., a semiconductor jig material is pressurized and melted, and an atomic absorption analysis method,
A method for analyzing the amount of impurities contained in a semiconductor jig material by quantifying metal impurities in a solution using an ICP analysis method or the like, and a semiconductor wafer for examining the degree of contamination of a semiconductor wafer by the semiconductor jig material. By actually using a semiconductor jig such as a process tube or a wafer boat manufactured by using a jig material, by heat-treating a metal collecting object having a metal diffusion coefficient equal to or less than that of silicon, A method for measuring the degree of contamination of a collected object (Japanese Patent Laid-Open No. 4-267)
No. 327), a method of quantifying the metal collected in the metal collecting object by heat-treating the metal collecting object and the like with the metal collecting object and the semiconductor jig being in contact with each other. Month Semiconduc
tor World June issue, 1992, pp. 58-65), and the like.

[0006]

However, in the method of dissolving the semiconductor jig material described above and quantifying it by chemical analysis or the like, the amount of impurities is known, but the semiconductor treatment of quartz, silicon carbide, carbon, etc. It is not clear to what extent the degree of contamination differs depending on the conditions in which impurities contained in ingredients are used, such as differences in atmosphere and temperature, and 0.1 ppm
There is a problem that the following ultra-trace analysis cannot be performed easily.

Further, in the method of heat-treating an object for collecting metal by actually using the process tube, the wafer boat, etc. made of the semiconductor jig material described above, a jig having a complicated shape must be manufactured as a prototype. Since it has to be done, there are problems that the cost for evaluation is high and it takes time. Further, since the distance between the metal collecting object and the jig is long, there is a problem that the contamination from the semiconductor jig material is small and highly accurate evaluation cannot be performed.

Further, in the so-called sandwich annealing method in which the metal collecting object described above is sandwiched between semiconductor jig materials and heat-treated, the surface of the metal collecting object is mechanically damaged by physical contact. Therefore, there is a problem that the method of evaluating contamination by OSF or the like cannot be used. Further, there is a problem that the cost becomes high because a special object for collecting metal is required.

The evaluation using the OSF characteristics is
This is a method of evaluating the number, distribution, etc. of impurities by utilizing the fact that impurities diffused on a Si wafer form large stacking faults by heat treatment for a long time and observing the stacking faults with a microscope or the like.

The present invention has been made in view of the above problems, and it does not damage the monitor wafer for evaluation by directly contacting the metal wafer with the metal impurities released from the jig material during the high temperature heat treatment. It is an object of the present invention to provide a method for evaluating a semiconductor jig material which can be easily and highly sensitively detected and whose influence on semiconductor characteristics can be clarified.

[0011]

In order to achieve the above object, a method for evaluating a semiconductor jig material according to the present invention comprises: a wafer boat made of high-purity quartz or high-purity silicon carbide provided in a process tube; A characteristic is that the characteristics of the monitor wafer are measured by arranging a monitor wafer and a molded body of a semiconductor jig material processed into a wafer in parallel and performing heat treatment.

A method for evaluating a semiconductor jig material according to the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view schematically showing an apparatus for carrying out the method for evaluating a semiconductor jig material according to the present invention. In the figure, reference numeral 11 denotes a quartz process tube.

As shown in FIG. 1, two molded bodies 13 of semiconductor jig material are erected on the wafer boat 12 in parallel with monitor wafers 14 at regular intervals. 12 is placed inside the process tube 11 made of quartz. When the molded body 13 of the semiconductor jig material and the monitor wafer 14 are placed on the wafer boat 12,
It is necessary to keep a predetermined interval so that the molded body 13 of the semiconductor jig material and the monitor wafer 14 do not come into direct contact with each other.

After mounting the wafer boat 12 on which the molded body 13 of the semiconductor jig material is placed on the process tube 11 made of quartz, heat treatment is performed at a predetermined temperature and time in a constant gas atmosphere.

It is preferable that the processing temperature is the temperature at which the silicon wafer is actually heat-treated for accurate evaluation, but higher temperature can be used for shortening the processing time. It is preferable for the accurate evaluation of the semiconductor jig material that the processing time and the atmosphere are the same as the conditions for actually heat-treating the silicon wafer. By processing the jig material, it is possible to make a relative evaluation of the semiconductor jig material.

By the heat treatment, the metal impurities released from the molded body 13 of the semiconductor jig material adhere on the monitor wafer 14. Therefore, various characteristics of the monitor wafer 14 containing the metal impurities are measured.
Here, the measurement of physical properties of the monitor wafer 14 refers to measurement of various physical and chemical characteristics of the monitor wafer 14, which will be described in detail later, but analysis of impurity content, impurity distribution, etc. Is also included in the measurement of properties in this case. From this, it is possible to know the type, amount, and distribution of the metal impurities that are easily moved by heating the molded body 13 of the semiconductor jig material, and to evaluate the influence of the movement (contamination) of these metals on the semiconductor. it can.

The monitor wafer 14 used in the present invention
Is manufactured so that the characteristics of the monitor wafer 14 can be satisfactorily measured when impurities are attached to the wafer 14, for example, a so-called BD (back damage) having a gettering function on the back surface. ) It is an N-type semiconductor wafer which has not been subjected to a treatment and has a resistance value of about 5 to 30 Ω · cm and a crystal orientation of (100). Further, the monitor wafer 14 is not usually subjected to heat treatment or the like.

Since the molded body 13 of the semiconductor jig material to be evaluated in the present invention needs to be set on the wafer boat 12, it has the same shape as the monitor wafer 14 or a shape having a slightly larger diameter. It is preferred that If the shape or size of the monitor wafer 14 is significantly different from that of the monitor wafer 14, the evaluation area is reduced or a special treatment is required to set the wafer boat 12 by preventing normal gas flow in the diffusion furnace. It is not preferable because tools are required.

When the measurement is carried out using the wafer boat 12 or the like made of the semiconductor jig material which is the object of evaluation, the amount of contamination is small and the distribution can be made in the contaminated region, making accurate evaluation difficult.

Needless to say, the wafer boat 12 required to set the molded body 13 of the semiconductor jig material and the monitor wafer 14 needs to be of high purity, and generally quartz glass, particularly high purity. It is preferable that the content of metal impurities contained in the synthetic quartz glass is 0.1 ppm or less. Further, when the required treatment temperature is higher than 1100 ° C., it is preferable to use high-purity silicon carbide having higher heat resistance than quartz glass. This high-purity silicon carbide also contains 0.1 pp of metal impurities.
It is preferably m or less. Further, it is necessary to set the molded body 13 of the semiconductor jig material and the monitor wafer 14 so as not to come into direct contact with each other. Physical contact between the molded body 13 of semiconductor jig material and the monitor wafer 14 causes defects such as scratches, which makes it impossible to accurately evaluate the formation of the OSF and the like. The distance between the molded body 13 of the semiconductor jig material and the monitor wafer 14 is 0.5 to
It is preferably 20 mm, more preferably 2 to 4 mm.

The process tube 11 made of quartz is also preferably of the highest purity possible in order to prevent the monitor wafer 14 from being contaminated, and the metal impurity content is 0.1.
ppm or less is preferable.

The impurities in the heat-treated monitor wafer 14 are analyzed by evaluating the characteristics of the monitor wafer 14, and the methods include the lifetime measurement method (μ-PCD method), the OSF method, and the surface. An oxide film analysis method and the like can be mentioned. It should be noted that other characteristics may be evaluated as necessary.

In the lifetime measuring method, a resistance value of a monitor wafer is obtained by irradiating a laser beam and reflecting intensity of microwaves. Then, the lifetime of the carrier in the monitor wafer 14 is calculated from this value. Further, the OSF method is the same as the above-described monitor wafer 1
4 is a method of forming an OSF on the surface of the monitor wafer 14. In the surface oxide film analysis method, the oxide film of the monitor wafer 14 generated when heat-treated in an oxidizing atmosphere is dissolved in an acid such as hydrofluoric acid, and then the atomic absorption method is used. This is a method for quantifying impurities contained in a solution.

In the lifetime measuring method, it is possible to evaluate how much impurities are involved in deterioration of semiconductor characteristics such as deterioration of carrier lifetime. In the OSF method, heavy metals which are likely to cause defects are generated. It is possible to know specifically where and how much pollution is occurring. Further, in the surface oxide film analysis method, it is possible to know the degree of contamination by the type of metal regarding which metal is contained and to what extent, and the contamination source is clarified.

[0026]

According to the method for evaluating a semiconductor jig material having the above structure, a wafer for monitoring and a semiconductor jig processed into a wafer shape are mounted on a wafer boat made of high-purity quartz or high-purity silicon carbide provided in a process tube. Heat treatment is performed in parallel with the molded body of the material, and the semiconductor characteristics of the monitor wafer are measured, so there is no risk of damaging the evaluation monitor wafer by direct contact, and the semiconductor jig material during high temperature heat treatment. The metal impurities released from the can be detected easily and with high sensitivity. Further, the measurement of these characteristics makes it possible to clarify the influence of impurities on the semiconductor characteristics.

[0027]

Embodiments of the method for evaluating a semiconductor jig material according to the present invention will be described below with reference to the drawings.

[Embodiment 1] As shown in FIG. 1, a molded product 13 of a semiconductor jig material for evaluation made of silicon carbide processed into the same shape and size as a 4-inch wafer was monitored by a 4-inch monitor. A wafer boat 12 made of quartz (metal impurity content: about 0.2 ppm) is set together with the wafer 14 for use, and these are placed in the process tube 11 made of quartz, and the temperature is set to 1200 ° C. in a dry oxygen stream. Heat treatment is performed for 2 hours. The above treatment was performed three times for each of the molded bodies 13 of the semiconductor jig material composed of three types (A, B, C) of silicon carbide having different purities.

Using the monitor wafer 14 that has been subjected to the above-mentioned treatment, the lifetime is measured by the lifetime measurement method, the OSF in the monitor wafer 14 is observed by the OSF method, and the impurities are analyzed by the surface oxide film analysis method. I went.

In the lifetime measuring method, LTA-330A manufactured by Leo Giken was used as a measuring instrument, laser light was irradiated at a laser wavelength of 904 nm and a laser current value of 20 A, and it was used for monitoring by the reflection intensity of microwaves. The carrier lifetime was calculated by obtaining the resistance value of the wafer 14, and the average value thereof was calculated.

In the OSF method, the monitor wafer 14 that has been subjected to the above-mentioned treatment is washed with HF and then at 1000 ° C. for 1 hour.
After heat treatment for 6 hours and further etching, the OSFs grown were observed with a microscope and the number thereof was counted.

In the surface oxide film analysis method, the heat treatment is applied to the monitor wafer 14 whose surface has been oxidized.
The SiO ₂ film was decomposed by bringing it into contact with F vapor, the HF vapor was diluted with pure water and collected, and the impurities in the obtained hydrofluoric acid solution were analyzed by an atomic absorption method.

The results of the above analysis are shown in Table 1. 2 and 3 are plan views of the lifetime value distribution on the monitor wafer 14 showing the analysis results of the lifetime value. 2 is a plan view showing the lifetime value distribution of the material A, and FIG. 3 is a plan view showing the lifetime value distribution of the material C. 2 and 3, the larger the black dot, the longer the lifetime.

As is clear from Table 1, the contamination of the semiconductor jig material can be evaluated with high accuracy. Further, as shown in FIGS. 2 and 3, the lifetime value on the monitor wafer 14 was almost uniform over the entire surface.

[Embodiment 2] Molded body 13 of semiconductor jig material and monitor wafer 14 similar to those used in Embodiment 1
Were heat-treated under the same conditions as in Example 1 except that was set on the wafer boat 14 made of high-purity silicon carbide (metal impurity content: about 0.2 ppm), and the same measurement as in Example 1 was performed. . The results are shown in Table 1 below.

Due to the wafer boat 12 made of silicon carbide,
Although the lifetime value was lowered in the lower part of the monitor wafer 14, the other values were in good agreement with the results of Example 1 as shown in Table 1.

Comparative Example 1 The semiconductor jig material for evaluation used in Example 1 was melted under pressure, and the amount of impurity metal was determined by atomic absorption spectrometry. The results are shown in Table 2 below.

As is clear from Table 2, in the method of applying pressure and dissolving a sample and then analyzing by atomic absorption spectrometry, 1 p
Since the value below pm cannot be analyzed accurately,
Unlike the result of Example 1, a clear value could not be obtained, and the analysis result did not clearly explain the difference in impurity content.

[Comparative Example 2] Example 1 except that the molded body 13 of the semiconductor jig material and the monitor wafer 14 used in Example 1 were set in contact with the groove on the wafer boat 12 made of quartz. Heat treatment was performed under the same conditions, and the same measurement as in Example 1 was performed. The results are shown in Table 1 below.

As is clear from Table 1, the observation result of OSF is significantly different from the results of Examples 1 and 2, and the evaluation is not reliable.

[Comparative Example 3] The wafer used in Example 1 was prepared by using three kinds of semiconductor jig materials (A, B, C) made of silicon carbide having different purities similar to those used in Example 1. A wafer boat having the same shape as the boat 12 was manufactured. next,
Only the monitor wafer 14 was set in the wafer boat 12 made of silicon carbide, heat-treated in the same manner as in Example 1, and the same measurement as in Example 1 was performed. The results are shown in Table 1 below. The distribution of lifetime values on the monitor wafer 12 obtained when the material A was used as a wafer boat is shown in FIG.

As is clear from Table 1, the wafer boat 12 and the monitor wafer 14 made of the semiconductor jig material.
Since there is a large distance from, the contamination by the impurity metal is small, and the difference in the metal impurity content between the materials is almost unknown. Further, as shown in FIG. 4, contamination by the semiconductor jig material is limited to the lower portion of the monitor wafer 14, and contamination by the atmosphere in the furnace is limited to the peripheral portion of the monitor wafer. Could not be evaluated clearly.

[0043]

[Table 1]

[0044]

[Table 2]

As described above, by using the lifetime measuring method, the OSF method and the surface oxide film analyzing method used in the above-mentioned embodiment, the metal impurities released from the semiconductor jig material during the high temperature heat treatment can be easily and increased. The sensitivity can be detected and the influence on the semiconductor characteristics can be clarified.

[0046]

As described above in detail, in the method for evaluating a semiconductor jig material according to the present invention, a wafer boat made of high-purity quartz or high-purity silicon carbide provided in a process tube is used for monitoring. Since the wafer and the molded body of the semiconductor jig material processed into a wafer shape are subjected to heat treatment in parallel to measure the semiconductor characteristics of the monitor wafer, it is possible to damage the monitor wafer for evaluation by direct contact. In addition, it is possible to easily and highly sensitively detect metal impurities emitted from semiconductor jig materials during high-temperature heat treatment, and to clarify the effect on semiconductor characteristics. It greatly contributes to the improvement.

[Brief description of drawings]

FIG. 1 is a sectional view schematically showing a method for evaluating a semiconductor jig material according to the present invention.

2 is a plan view showing a lifetime value distribution of a monitor wafer obtained by heat treatment of the semiconductor jig material A of Example 1. FIG.

FIG. 3 is a plan view showing a lifetime value distribution of a monitor wafer obtained by heat treatment for the semiconductor jig material C of Example 1.

FIG. 4 is a plan view showing a lifetime value distribution of a monitor wafer obtained by heat treatment of the semiconductor jig material A of Comparative Example 3.

[Explanation of symbols]

 11 Quartz Process Tube 12 Wafer Boat 13 Semiconductor Jig Material Molded Body 14 Monitor Wafer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuo Koike 2201 Kamioda, Kamikita-cho, Kijima-gun, Saga Sumitomo Sitix Co., Ltd. Kyushu Office

Claims (1)

[Claims] 1. A wafer boat made of high-purity quartz or high-purity silicon carbide provided in a process tube, a monitor wafer and a molded product of a semiconductor jig material processed into a wafer are placed side by side for heat treatment. A method for evaluating a semiconductor jig material, which comprises measuring the characteristics of a monitor wafer.