JP2007019226A - Measuring method of semiconductor substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a simple measuring method which can directly express defective information in the vicinity of a surface of a substrate used mainly for a device. <P>SOLUTION: In a method for measuring defects on the surface of a semiconductor silicon substrate manufactured by the Czochralski method, under an atmospheric gas having an etching action for the semiconductor silicon substrate; the semiconductor silicon substrate is heated at a temperature which is equal to or more than 1,100°C and less than a melting point, for 10 minutes to 4 hours. Defects on the surface of the semiconductor silicon substrate are etched to form a pit. Thereafter, in the measuring method of the semiconductor silicon substrate, the pit is measured, thereby measuring defects on the surface of the semiconductor silicon substrate. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for measuring defects in a semiconductor silicon substrate manufactured by the Czochralski method, and more particularly to a method for measuring defects present on the surface of a substrate.

  In silicon crystals produced by the Czochralski method, there are agglomerates of point defects and oxygen-related defects introduced from a quartz crucible. Up to now, silicon crystals having a relatively high crystal growth rate and having dominant vacancies have been widely used in terms of productivity.

  However, due to the recent demand for higher integration and higher reliability of devices, silicon crystals having a crystal growth rate lower than that of conventional devices have been used. In this case, since the formation of void agglomerates (voids) during crystal growth is suppressed, the behavior of the oxygen-related defects (sometimes referred to as Grown-in oxygen precipitation nuclei) will receive more attention. Became.

  Here, since the size of the oxygen precipitation nuclei in the silicon substrate that is cut out from the grown silicon crystal and not subjected to the heat treatment is extremely small, it is easy to evaluate the oxygen-related defects in the substrate of this as-grown. In general, there is no effective method. For example, oxygen precipitation nuclei (precipitates) are grown by some kind of heat treatment such as a two-step heat treatment, and then evaluated by a selective etching method or an optical method. Further, Patent Document 1 discloses a method in which one end surface of a wafer is mirror-finished, immersed in a basic aqueous solution, selectively etched, and evaluated.

  However, there has been a problem that even if a silicon substrate that has been cut out in the same manner as described above is cut out in the same manner, it is not necessarily a good product after the device is manufactured. Further, since a plurality of heat treatment steps are required, there is a problem that it takes time. Furthermore, these conventional methods generally have only a problem of expressing defect information in the inside (bulk) of a silicon substrate and hardly expressing defect information in the vicinity of the substrate surface mainly used in devices.

Japanese Patent No. 2680482

  It is an object of the present invention to provide a simple measurement method capable of directly expressing defect information near the surface of a substrate mainly used in a device.

  In order to solve the above-mentioned problems, the present invention is a method for measuring defects on the surface of a semiconductor silicon substrate manufactured by the Czochralski method, wherein the semiconductor silicon substrate is etched under an atmospheric gas having an etching action. The semiconductor silicon substrate is subjected to a heat treatment at a temperature of 1100 ° C. or higher and lower than the melting point for 10 minutes to 4 hours to etch the defects on the surface of the semiconductor silicon substrate, thereby forming pits. A method for measuring a semiconductor substrate is provided, wherein defects on the surface of the semiconductor silicon substrate are measured.

By such a measurement method, the semiconductor silicon substrate is heat-treated in the above temperature and time range, and the defects existing on the surface of the substrate are etched, so that pits are formed to reveal the defect information and not disappear. Thus, it is possible to measure the defect by allowing it to remain and then measuring the pit. Since the pits are marks of etched defects, the defects on the surface of the silicon substrate can be accurately measured and grasped.
Further, it is very simple because defect information that has not been seen in the past can be made obvious by simply performing the heat treatment.

At this time, it is desirable that the temperature of the heat treatment be 1200 ° C. or lower (claim 2).
Thus, if the temperature of the heat treatment is set to 1200 ° C. or lower, the temperature in the heat treatment is not excessively increased, and therefore, the pits formed during the heat treatment, that is, the traces of defects existing on the surface of the substrate are eliminated. It is possible to suppress the occurrence of defects and to more accurately measure defects by leaving pits more reliably.

At this time, it is desirable that the atmospheric gas is argon, hydrogen, or a mixed gas thereof.
In this way, if the atmosphere gas is argon, hydrogen, or a mixed gas thereof, the surface of the silicon substrate can be etched in a small amount under high-temperature heat treatment, and minute defects can be accurately etched and revealed. be able to. Moreover, it is also a gas frequently used in heat treatment or the like and is easy to prepare.

Preferably, the pit is measured by a particle counter.
Thus, if measurement is performed using a particle counter, it is possible to easily and accurately measure pits formed on the substrate surface. Therefore, accurate data can be obtained about the defects present on the surface of the silicon substrate.

  By the method for measuring a semiconductor substrate of the present invention, minute defects such as oxygen precipitates present on the surface of the semiconductor silicon substrate that were not visible in the past have been revealed by etching to form pits. It can be left without being completely extinguished, and then by measuring the pits, it is possible to accurately and easily measure the micro defects on the substrate surface.

Hereinafter, embodiments of the present invention will be described, but the present invention is not limited thereto.
As described above, the behavior of defects such as oxygen precipitates has become more important as silicon crystals with a low crystal growth rate have been used due to the recent demand for higher integration and higher reliability of devices. It became so. The above-mentioned defects in the silicon substrate cut out from this crystal and not subjected to heat treatment are extremely minute. For the detection of these minute defects, for example, after growing oxygen precipitation nuclei by heat treatment such as two-step heat treatment, it is selected. A method for detecting and measuring defects by an etching method or an optical technique is disclosed.

  However, even if the substrate is the same as that determined to be defect-free on the substrate surface by the above-mentioned conventional method, there is a problem that it is not necessarily a non-defective product after device manufacture, and a plurality of steps are required. There was a problem that it took time and effort. Moreover, the defects measured by the conventional method are actually present inside the substrate, or the defects near the surface are eliminated by the two-stage heat treatment, and are mainly used in the device. There was a problem that correct information about defects existing near the substrate surface could not be grasped.

  Therefore, the present inventors have conducted intensive investigations on minute defects existing near the surface of the substrate. Specifically, the silicon substrate was heat-treated in an atmospheric gas having an etching action, and the surface of the silicon substrate and changes in minute defects were investigated.

  When the silicon substrate is put into a heat treatment furnace, for example, an extremely thin oxide film or nitride film is formed on the surface of the silicon substrate due to air entrainment or the like. The oxide film or the like begins to be etched at a temperature range of 1000 ° C. or higher, and is removed in a shorter time as the furnace temperature becomes higher. When this oxide film or the like is removed and the silicon surface is exposed, silicon migration occurs so as to fill the recesses due to the etching of silicon.

  Here, when there is a foreign substance other than silicon, that is, for example, a defect such as oxygen precipitate near the surface of the silicon substrate, and it is exposed on the surface of the substrate, the etching of the component constituting the foreign substance is performed in the same manner as the oxide film etc. First occurs. By this etching, pits are formed on the surface of the silicon substrate as the remnants of the defects. This pit changes to a very gentle recess shape by subsequent silicon migration. If the heat treatment is further continued, the dent shape becomes gentler due to migration, and the pit disappears.

  Therefore, the present inventors investigated the optimum conditions of heat treatment that generates pits based on defects on the wafer surface and does not disappear, and performs heat treatment for 10 minutes to 4 hours at a temperature of 1100 ° C. or higher and lower than the melting point. A simple method can be used to etch the defects on the surface of the silicon substrate to form the above-mentioned pits and leave them without annihilation, thereby revealing and measuring the defect information existing on the surface of the silicon substrate. The headline and the present invention were completed.

Hereinafter, embodiments of the present invention will be described in detail.
First, a silicon crystal is pulled up by the Czochralski method, cut out from the crystal, and an as-grown semiconductor silicon substrate not subjected to heat treatment is prepared.
This semiconductor silicon substrate is placed on, for example, a heat treatment boat and carried into a heat treatment furnace. Then, the silicon substrate is heat treated in an atmosphere of argon, hydrogen, or a mixed gas thereof in a heat treatment furnace. The heat treatment furnace used when carrying out the measurement method of the present invention is not particularly limited with respect to a so-called vertical type, horizontal type, batch type or single wafer type, or even a heating type. Any material can be used as long as it can perform heat treatment in the above-described temperature and time range.

  Specifically, for this heat treatment, the furnace temperature when the silicon substrate is charged is, for example, 700 ° C., and the temperature in the furnace is increased until a temperature range of 1100 ° C. or higher and lower than the melting point of silicon is reached. The furnace temperature is kept at a certain temperature within the temperature range for 10 minutes to 4 hours. By this heat treatment in the above temperature range / holding time, defects such as oxygen precipitates that exist on the surface of the silicon substrate are exposed to form pits, and further, the pits are completely eliminated without causing the pits to completely disappear. The pit remains as a trace of existence. The furnace temperature during the heat treatment is not necessarily kept constant as long as it is in the range of 1100 ° C. or higher and lower than the melting point, but the pits are easier to control if the temperature is kept constant.

  Thereafter, the temperature in the furnace is lowered, the heat treatment boat is taken out, the silicon substrate is taken out, and pits which are traces of defects formed on the surface thereof are measured by, for example, a particle counter. By measuring the pits, the defects present on the substrate surface are measured. The measurement of surface defects is not limited to the particle counter, and any method capable of detecting surface pits may be used. For example, OPP, AFM, SEM, or the like may be used.

  By such a measuring method of the present invention, defect information such as oxygen precipitates manifested on the surface of the silicon substrate, that is, the pits are left without disappearing, and by measuring the pits, the device is not inside the substrate, It is possible to accurately measure defects that are latent on the surface of the substrate to be fabricated. Therefore, highly reliable data regarding defects on the surface of the substrate can be easily obtained, and effective data can be provided in manufacturing a device. In consideration of the influence of silicon migration, it is preferable that the time for performing the heat treatment on the silicon substrate is 10 minutes to 1 hour because more accurate data can be obtained.

  In the measurement method of the present invention, it is desirable that the temperature of the heat treatment is 1200 ° C. or lower. During the heat treatment, the higher the furnace temperature, the faster the progress of defect etching such as oxygen precipitates existing on the silicon substrate surface, and the greater the influence of silicon migration. By setting the in-furnace temperature to 1200 ° C. or less, it is possible to more reliably prevent pits from disappearing completely and to remain. Thereby, the defect of the substrate surface can be measured more accurately. In addition, if the temperature is 1200 ° C. or lower, the burden on the furnace is reduced, and there is no concern about contamination of the wafer.

  If the atmosphere gas in the heat treatment is argon, hydrogen, or a mixed gas thereof, the silicon substrate surface can be etched in a small amount as described above, and these gases are frequently used in the heat treatment step and the like. Therefore, there is an advantage that it is easy to prepare. However, the gas that can be used is not limited to this, and any gas that can form pits by etching defects on the wafer surface by heat treatment may be used.

  If a particle counter is used when measuring pits formed on the substrate surface after the heat treatment, it is possible to accurately and easily measure pits. Therefore, highly accurate data can be easily obtained for defects present on the surface of the silicon substrate.

EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further in detail, this invention is not limited to this.
(Examples 1-7, Comparative Examples 1-4)
A silicon crystal having a crystal growth rate of 0.6 mm / min was pulled by the Czochralski method, and cut out from this crystal to prepare a silicon substrate having a low density of void defects <100> and a diameter of 200 mm. This sample was heat-treated in a vertical heat treatment furnace (DD-813V manufactured by Hitachi Kokusai Electric Co., Ltd.) while changing the furnace temperature and holding time, and then the particle size was set to 0.12 μm or more using a particle counter (SP1 manufactured by KLA Tencor). The pits on the silicon substrate surface were measured.

  As heat treatment conditions, the temperature in the heat treatment furnace at the time of loading the substrate was set to 700 ° C., and the temperature was raised to X ° C. (X = 900 to 1220 ° C.) after loading the silicon substrate (6 ° C./min to 700 to 1000 ° C., 1000 ° C. From the above, the temperature was increased at 3 ° C./min). Then, the temperature is maintained at X ° C. for t hours (t = 0 min to 8 hours), and then the temperature is decreased to 700 ° C. at 3 ° C./min. When the furnace temperature reaches 700 ° C., the silicon substrate is taken out of the furnace. It was.

More specifically, X = 900 ° C. (Comparative Example 1), 1050 ° C. (Comparative Example 2), 1100 ° C. (Example 1), 1150 ° C. (Example 2), 1200 ° C. (Example 3), 1220 The temperature was set to 0 ° C. (Example 4), and in each case, the silicon substrate was subjected to a heat treatment with a holding time t = 1 hour, and defects were measured.
Further, X is fixed at 1150 ° C., t = 0 (Comparative Example 3), 10 minutes (Example 5), 1 hour (Example 6), 4 hours (Example 7), and 8 hours (Comparative Example 4). Defects were measured when the heat treatment was applied.

The atmosphere gas was argon (20 L / min).
When the pits were measured with a particle counter on the silicon substrate before the heat treatment, the maximum was 10 pieces / wafer, and there was no specific distribution.

  A graph showing the relationship between the number of pits per wafer after a series of heat treatments (ie, defect density) and the heat treatment temperature X when the holding time t is fixed at 60 minutes is shown in FIG. A graph showing the relationship with the holding time t when X is fixed at 1150 ° C. is shown in FIG. FIG. 3 shows an observation view of the wafer surface before heat treatment and the wafer surface after heat treatment in Examples 1 to 3 and 5-7.

  From FIG. 1, it can be seen that in the heat treatment temperature range of the present invention, the peak is around 1100 ° C., and the defect density tends to decrease as the temperature increases. For example, at 900 ° C. outside the above range, the value is not so different from the defect density (10 / wafer) in a state where heat treatment is not performed. Further, at 1000 to 1100 ° C., the surface roughness of the substrate surface was large due to insufficient etching of the oxide film or nitride film on the silicon substrate surface, and proper evaluation could not be performed. In this range, a predicted value is indicated by a dotted line.

  Thus, at a temperature outside the temperature range of the heat treatment in the measurement method of the present invention (˜1100 ° C.), the progress of the etching is slow, and the oxide film and the defect on the substrate surface are hardly etched, and the defect Even if pits due to etching are not formed, or even if the oxide film is relatively etched, it is insufficient, the surface is rough, due to the presence of a concave shape other than pits due to minute etching of defects, etc. The defect density cannot be measured accurately.

  Therefore, the oxide film is sufficiently etched away, the defect etching is sufficiently advanced, and if the measured value is in the temperature range from 1100 ° C. or higher, where the defect density tends to decrease due to silicon migration, the surface is surely This indicates a pit formed by etching a nearby defect, and accurate defect density data can be obtained. As can be seen from FIG. 1, the defect density decreases as the heat treatment temperature increases. This is considered to be an influence due to the progress of migration, and it is preferable to set the heat treatment temperature to 1100 to 1200 ° C. in order to capture and quantify the existence of defects more reliably. When heat treatment is performed at a temperature exceeding 1200 ° C., it is preferable to shorten the heat treatment time.

  Further, it can be seen from FIG. 2 that when the heat treatment time range of the present invention has a peak around 10 minutes and the heat treatment is further performed for a long time, the defect density decreases. Further, at 0 to 10 minutes, the defect density rapidly increases toward a peak around 10 minutes. In the range of 0 to 10 minutes, it is considered that the influence of etching of an oxide film or the like formed on the substrate surface is included. When the time exceeds 4 hours, the pit disappears due to migration, and the defect density further decreases.

  Therefore, in order to obtain accurate data of defects existing on the substrate surface, it is desirable to employ data obtained by performing a heat treatment for 10 minutes to 4 hours. Similarly, in the case of FIG. 2, if the heat treatment is continued for a long time, the migration proceeds correspondingly. Therefore, if more reliable data on the surface of the substrate is obtained, the heat treatment time is set to about 10 minutes to 1 hour. It is more preferable to prevent the pits from disappearing.

  Thus, by the measurement method of the present invention, defects such as oxygen precipitates latent on the surface of the substrate not subjected to the heat treatment immediately after being cut out from the silicon crystal, which could not be obtained by the conventional measurement method, It is possible to measure accurately and extremely easily as compared with the prior art.

  The present invention is not limited to the above embodiment. The above embodiment is an example, and has substantially the same configuration as the technical idea described in the claims of the present invention. Are included in the technical scope.

  In this example, as shown in FIGS. 1 and 2, the heat treatment time is fixed to 1 hour or the heat treatment temperature is fixed to 1150 ° C., but the present invention is not limited to this example. In an atmospheric gas with an etching action, heat treatment is performed at a temperature of 1100 ° C. or higher and lower than the melting point for a time range of 10 minutes or longer and 4 hours or shorter to etch defects, form and remain pits, and measure this Thus, any method for measuring defects on the substrate surface may be used.

It is the graph which showed the relationship between the defect density in the wafer after heat processing, and the heat processing temperature when heat processing time is fixed to 60 minutes. It is the graph which showed the relationship between the defect density in the wafer after heat processing, and the heat processing time when heat processing temperature was fixed to 1150 degreeC. It is an observation figure of the wafer surface before performing heat processing, and the wafer surface after heat processing in Examples 1-3, and 5-7.

Claims (4)

  A method for measuring defects on the surface of a semiconductor silicon substrate manufactured by the Czochralski method, wherein the semiconductor silicon substrate is etched for 10 minutes at a temperature of 1100 ° C. or higher and lower than the melting point in an atmospheric gas having an etching action. The semiconductor silicon substrate is subjected to heat treatment for 4 hours or less to etch the defects on the surface of the semiconductor silicon substrate to form pits, and then measure the pits to obtain the surface of the semiconductor silicon substrate. A method for measuring a semiconductor substrate, comprising: measuring defects in the semiconductor substrate.   The method for measuring a semiconductor substrate according to claim 1, wherein a temperature of the heat treatment is 1200 ° C. or less.   The method for measuring a semiconductor substrate according to claim 1, wherein the atmospheric gas is argon, hydrogen, or a mixed gas thereof.   The semiconductor substrate measurement method according to claim 1, wherein the pit is measured by a particle counter.

Images