JPH05319989A - Production of single crystal - Google Patents

Abstract

PURPOSE:To minimize surface fine unevennesses of a wafer in a method for producing a single crystal while continuously feeding a granular polysilicon raw material. CONSTITUTION:The method for producing a single crystal is characterized by using granular polysilicon having <=1000(cm<2>/g) specific surface area, further washing the granular polysilicon with an aqueous solution of hydrofluoric acid and employing the washed granular polysilicon in a method for pulling up the silicon single crystal while continuously feeding the granular polysilicon raw material. Surface fine unevennesses can be minimized in a silicon wafer prepared by working the single crystal obtained according the method for producing the single crystal and the silicon wafer worked from the silicon single crystal according to this invention is capable of maintaining good surface cleanness and expected as a substrate for highly integrated devices.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a silicon single crystal while continuously supplying a granular polysilicon raw material into a silicon melt.

[0002]

2. Description of the Related Art In recent years, demands for higher quality and larger diameter silicon single crystals have increased with the high integration of devices. As a method for producing a single crystal that meets these requirements, a continuous Czochralski method (hereinafter referred to as a continuous CZ method, in which a single crystal is pulled while continuously supplying a raw material, is referred to, for example, Japanese Patent Publication No.
0-10184) is advantageous. The reason is that there is little change in the resistance value and oxygen concentration in the ingot longitudinal direction as well as in the silicon wafer surface, it is almost uniform in the ingot, and it is long without being restricted by the initial charge amount of the crucible. And a single crystal having a large diameter can be pulled up.

Further, as the feed material, it is possible to use granular polysilicon produced by thermally decomposing monosilane or trichlorosilane, for example, Japanese Patent Laid-Open No. 61-361797.
Japanese Patent Application Laid-Open No. 62-241889. The use of this granular polysilicon raw material has an advantage that the raw material supply amount can be easily controlled.

Further, in addition, as a continuous CZ method, Japanese Patent Application Laid-Open No. 1-282194 sets forth the residual hydrogen amount or residual chlorine amount in the granular silicon raw material to reduce the rupture phenomenon occurring when the raw material is melted. A method for producing a single crystal is disclosed, and Japanese Patent Application Laid-Open No. 2-18376 discloses a method of pulling up a silicon melt by providing a shielding portion at the tip of a guide tube for feeding a granular raw material to reduce ripples in the silicon melt. A method of reducing the dislocation generation rate of a single crystal is disclosed.

These studies are being carried out to meet the high quality demands of silicon wafers accompanying the recent higher integration and higher speed of devices. However, these continuous CZ method patents are only related to the stability of single crystal production, and do not satisfy the demand for quality associated with the increase in diameter of silicon wafers.

[0006]

With respect to the quality of silicon wafers, and particularly the surface quality of silicon wafers, the cleanliness of the wafer surface is often a problem. As a measure of surface cleanliness, there are the number of small dust called particles, the number of minute surface irregularities, and the amount of metal surface contaminants, and various studies have been conducted to improve the cleanliness of the silicon wafer surface. ..

Here, the above-mentioned particles are foreign materials derived from the polishing and cleaning steps of the wafer, and are scattered in the form of dust on the surface of the smooth silicon wafer.

Is a surface irregularity of about 10 μm or less scattered on the surface of the wafer, which is a foreign substance different from the silicon wafer, whereas this is a variation of the geometrical shape of the surface of the silicon wafer. ..

, Is quantitatively measured by a surface inspection meter, but it may be included in the number of particles and counted.

A silicon wafer obtained by processing a silicon single crystal produced by the continuous CZ method using the above-mentioned granular polysilicon as a raw material may have many fine irregularities on its surface. As described above, the surface fine irregularities are also counted as particles by the silicon wafer surface inspection instrument. This means that the high surface cleanliness required for a 16M class silicon wafer or the like, for example, the target of 10 or less particles on the surface of an 8-inch silicon wafer, must be 10 or less on the entire surface of the silicon wafer. In addition, other surface defects must be reduced as much as possible.

Next, according to ASTM F154-84, the surface irregularities of the polished silicon wafer are dimples,
It shows that there are orange peels and scratches.
As a cause, dimples lack polishing amount,
Orange peel is said to be too fast polishing speed or non-uniformity of polishing liquid flow, and scratch is said to be contamination of foreign matter into the polishing liquid.

However, these are surface irregularities that are generated exogenously during processing, and even if a solution to the cause described there is taken, it has not been solved.

Further, the morphology of the foreign surface irregularities is as follows: dimples are dents whose contours are not clearly defined and have a size of about 10 μm;
The scratches are so-called scratches with a narrow width relative to the length,
It is reported that these surface irregularities are randomly distributed in the surface of the silicon wafer regardless of the center and the edge, and the surface fine irregularities known by the present inventors to be described later are those extraneous surface irregularities. Is clearly different in that it is not counted as a particle.

In addition, reports other than foreign surface irregularities are as follows:
The small pits detected as particles after SC1 (ammonia / hydrogen peroxide) cleaning by the study of Furihata et al. Are disclosed in Preliminary Lectures 29p-R-15 and 16 of the 37th Applied Physics Association Joint Lecture Meeting.

However, this also relates to crystals pulled by the batch CZ method, which is different from the continuous CZ method. Further, the fine pits gradually become larger as the SC1 cleaning is repeated, but the surface fine unevenness which is a problem of the present invention is different in that it is not changed by the repeated SC1 cleaning.

Further, in terms of distribution and morphology, these minute pits are generated in the surface of the silicon wafer like surface roughness, and even a large pit has a depth of 0.5 μm and a depth of 0.06 μm, the present invention has a problem. There are many surface fine irregularities in the central portion of the silicon wafer, and their size and depth are on the order of microns.

The object of the present invention is, in a method for producing a silicon single crystal while continuously supplying a granular polysilicon raw material, the fine unevenness which is inherently introduced into the surface of a silicon wafer obtained from the single crystal as much as possible. To reduce.

[0018]

The present inventors have invented the following as a result of further examination of a method for reducing surface fine irregularities which are fine defects based on the above-mentioned findings.

According to the present invention, the interior of a quartz crucible is divided into a single crystal growth portion and a raw material melting portion, and a small hole is provided in the partition so that a silicon melt can flow, and a granular polysilicon raw material is continuously fed into the raw material melting portion. And the atmosphere gas in the chamber is argon and the atmosphere is in a reduced pressure, and the seed crystal is brought into contact with the central melt surface of the single crystal growth portion, and then the seed crystal is pulled up by a rotating means to produce a silicon single crystal. In the method, a granular raw material having a specific surface area of 1000 cm ² / g or less is used.
In the method for producing a silicon single crystal described above, a granular raw material washed with a hydrofluoric acid-based aqueous solution is used, which is a method for producing a single crystal.

[0020]

In the method for producing a single crystal according to the present invention, by using the above-mentioned granular polysilicon raw material, it becomes possible to finally produce a single crystal which becomes a silicon wafer with extremely few fine irregularities as fine surface defects. It is a thing.

In order to eliminate the fine irregularities on the surface of the silicon wafer, the present inventors have completed various aspects of the surface fine irregularities and have completed the present invention.

Next, the analysis of minute surface irregularities will be described. Analysis of surface micro-irregularities FIGS. 3 and 4 are scanning electron micrographs (magnification × 1000 of each) of the surface micro-irregularities appearing on the silicon wafer.
0, × 7000). These photographs show that the surface fine irregularities are polyhedrons such as octagons.

Further, FIG. 5 is a scanning electron micrograph (magnification × 7000) of observing the inside of the fine surface irregularities when the silicon wafer is tilted. It can be seen from FIG. 5 that the inside of the fine surface irregularities is a concave defect.

The inner surface of this defect is smooth,
It is hollow. No trace of foreign particles is found in the cavity. In addition, EDS (Energy D
The results of ispersive spectroscopy analysis also showed that the inner surface of the cavity had the same composition as the bulk.

From these facts, the defects recognized as surface fine irregularities on the silicon wafer seem to be pores filled with some gas in the crystal in the single crystal state. Further, its shape is a polyhedron close to a sphere, and its diameter is relatively large at about 10 μm, which confirms that this defect is a pore.

Distribution of surface fine irregularities Next, in order to investigate the distribution of surface fine irregularities, as a result of two-dimensional investigation in the state of the silicon wafer, the surface fine irregularities were found to be large in the central portion of the silicon wafer. It's been found. The central portion of the silicon wafer is where solidification is most delayed when pulling a single crystal, and is a portion where porosity is most likely to appear from a metallurgical point of view. From this, it can be inferred that the surface fine irregularities in question are pores.

Pursuit of Gas Invasion Route From the above and above, it was speculated that the cause of this defect is the bubbles generated during solidification. It is not clear whether the bubbles are based on the difference in solubility between the solid and the melt at the solid-liquid interface or whether the bubbles floating in the melt happen to be trapped at the solid-liquid interface. However,
This is because the amount of gas in the melt is larger than the critical value. Therefore, the cause of gas invasion was sought.

It is considered that the dissolution of the gas component in the melt is caused by (1) gas absorption at the gas-liquid interface when the feedstock comes into contact with the melt, and (2) the feedstock. The latter is the cause of the bubbles in the case of concern. This is because, when supplying the polysilicon raw material to the silicon melt surface of the crucible, the silicon obtained by heating the polysilicon rod and the case of using granular polysilicon produced by thermal decomposition from the vapor phase of silane etc. This is because, when compared with the case of using the melt, the surface fine irregularities were found specifically in the former and not found in the latter at all.

Relationship between Granular Material and Defects When granular polysilicon is used as a material, a large amount of surface fine irregularities do not always occur, and there is a difference in surface fine irregularities depending on the properties of the granular polysilicon. I understood. Therefore, the surface condition of the granular polysilicon with many surface fine irregularities
The cross-section and constituent elements were investigated in detail.

1) Surface State FIGS. 6 and 7 are scanning electron microscope enlarged photographs (magnification × 10000) of the surface of the granular polysilicon.

FIG. 6 shows the surface of granular polysilicon in which many fine surface irregularities are generated on a silicon wafer. There are many fine particles on the surface and the surface irregularities are large, and it seems that the gap is connected to the inside of the grain. Looks like. On the other hand, FIG.
Is the surface of the granular polysilicon in the case where the silicon wafer has few surface fine irregularities, and the surface is often covered with a film-like substance, and the surface has few irregularities.

2) Cross-section FIGS. 8 and 9 are enlarged photographs of a scanning electron microscope (magnification × 300) showing the voids in the fracture surface of the granular polysilicon raw material.
0). FIG. 8 is a fracture surface of granular polysilicon in which many fine surface irregularities are generated on the silicon wafer, and shows that there is a gap in the grain. Moreover, the gap has a state like a void generated when the fine particles are filled,
This suggests that the voids are connected to the surface of the grain. That is, the granular raw material is a sintered body of silicon fine particles, each void in the raw material particles passes through the gaps between the fine particles,
It is connected to the surface of the raw material particles. On the other hand, FIG. 9 is a fracture surface of the granular polysilicon in the case where the silicon wafer has few surface irregularities, and shows that there are few gaps in the particles.

3) Hydrogen / Chlorine Analysis From the manufacturing principle of granular polysilicon raw material, hydrogen / chlorine is naturally contained in the grains. When hydrogen / chlorine analysis of granular polysilicon was performed, no difference was found in the hydrogen / chlorine content regardless of the appearance of surface micro-irregularities on the wafer. In particular, the range of hydrogen content is 0.5 to 5
It was ppm, and there was no correlation between the hydrogen content of the granular polysilicon raw material and the number of appearance of surface fine irregularities.

Therefore, a specific surface area, which represents the surface roughness of the granular polysilicon and the internal voids as the total surface area per unit mass, is adopted as the amount of the surface roughness and the internal pores.

As described above, the inventors of the present invention conducted various analyzes and experiments on the fine surface irregularities on the surface of the silicon wafer. First, as a result of various tests as shown in Example 1 described later, between the specific surface area (cm ² / g) represented by the total area per unit mass of the granular polysilicon raw material and the surface fine irregularities (pieces / wafer). , As shown in FIG. 1, the specific surface area is 1000
It was found that the surface fine irregularities are 2 (pieces / wafer) or less when it is cm ² / g or less.

In this case, the surface fine irregularities are defined to be 2 (pieces / wafer) or less because the device is highly integrated.
Demand for surface cleanliness of silicon wafer is 6-8
In the case of an inch silicon wafer, the number of particles in the surface of the silicon wafer is 10 or less, and the surface irregularities are several or less. Since the minute defects in the present invention are counted in both the particles and the surface irregularities, the number (pieces /
This is because the number of wafers or less, or 2 (pieces / wafer) or less, must be quantitatively set.

Next, when the specific surface area of the granular polysilicon raw material is small, the reason for the small amount of surface fine irregularities at the silicon wafer stage is considered as follows.

For example, in the single crystal manufacturing apparatus of FIG. 2, the granular polysilicon raw material 9 is charged into the outside of the partition member 10 and melted, and the molten silicon passes through the small holes 11 and continues to the silicon single crystal 5. To solidify. In the granular polysilicon raw material having a large specific surface area, gas exists in the grains.

When the granular polysilicon raw material 9 enters the silicon melt and dissolves, a part of the gas in the particles dissolves in the silicon melt, but most of it dissolves in the silicon melt. It remains without. The gas in the granular polysilicon particles at that time gathers through the fine pores in the particles and exists as bubbles in the silicon melt. The bubbles expand in volume due to the pressure and temperature of the silicon melt. A considerable amount of bubbles are discharged into the atmosphere by forced and natural convection in the silicon melt, but the bubbles that reach the solidification interface are taken into the ingot and become voids. Becomes

That is, the atmospheric gas in the furnace penetrates the gaps between the fine-grained silicon particles constituting the granular polysilicon and enters the voids in the particles, which are mixed in the silicon melt when the raw materials are melted. Bubbles in the furnace atmosphere mixed in the silicon melt are trapped in the crystal, and become cavities in the crystal that are the source of the surface fine irregularities. Further, if the granular polysilicon has a small specific surface area, the inclusion of bubbles is reduced, and as a result, the fine surface irregularities are reduced.

Further, the inventors of the present invention can obtain a granular material having a predetermined specific surface area by washing and etching with a hydrofluoric acid-based aqueous solution, even if the granular material has a large specific surface area.
It was found that a single crystal having few surface irregularities can be obtained by using these granular raw materials having a smooth surface, as shown in Example 2 described later. As a result of the above, the silicon single crystal obtained by the present invention is expected as a substrate for highly integrated devices because the resistance value and oxygen concentration as the quality are uniform in the ingot length in the hand direction and in the in-plane direction of the silicon wafer, Therefore, the silicon wafer processed from the silicon single crystal of continuous raw material supply has better surface cleanliness than ever before. Next, examples of the present invention will be described.

[0042]

【Example】

[Example 1] (1) A method for producing a granular polysilicon raw material. The granular polysilicon raw material used in the method of the present invention is manufactured as follows. The manufacturing method of granular polysilicon raw material is
Monosilane or trichlorosilane is introduced into the fluidized bed and pyrolyzed to form granular polysilicon.

The quality of the granular polysilicon is strongly influenced by the operating conditions of the fluidized bed, in particular, the time change of the flow rate of the raw material gas such as monosilane and the temperature distribution in the fluidized bed.

The quality of the raw material of granular polysilicon is as follows.
Specific surface area is important. This is due to the operating conditions described below.

The granular polysilicon is formed by thermally decomposing monosilane or trichlorosilane in the fluidized bed. The reaction at this time is as follows: 1) The source gas is decomposed near the upper electrode of the seed and silicon is deposited to grow. 2) There are those that grow repeatedly by repeating the process in which the fine powder generated by the reaction in the gas phase adheres to the silicon particles and sinters. In the former case, the surface irregularities are small and the internal pores are few, resulting in a dense structure. In the latter case, the surface irregularities are large and the internal pores are large and the specific surface area is large.

Needless to say, the granular polysilicon raw material of the present invention can be achieved by using dense particles as a raw material. Even in the latter case, if the fine powder is sufficiently sintered and grown, dense particles having a small specific surface area can be produced, and the object of the present invention can be achieved. These are possible, for example, by reducing the flow rate of the raw material gas such as monosilane or trichlorosilane described above and lowering the temperature in the fluidized bed.

(2) Raw material supply and single crystal manufacturing method. A single crystal ingot is manufactured by the single crystal manufacturing apparatus shown in FIG. 2 using the granular polysilicon raw material manufactured as described above. In FIG. 2, 1 is a quartz crucible, and 2 is a graphite crucible.
The graphite crucible 2 is set inside the pedestal 4
It is supported so that it can move up and down and rotate. Reference numeral 5 is a silicon single crystal, 7 is a raw material silicon melt contained in the quartz crucible 1, and the silicon single crystal 5 grown in a columnar shape is pulled from the silicon melt 7. 3 is an electric resistance heating body (heater) surrounding the graphite crucible 2, 6 is a hot zone heat insulating material surrounding the electric resistance heating body 3,
These are housed in the chamber 8, and the apparatus for producing these single crystals is basically the same as the apparatus for producing silicon single crystals by the ordinary CZ method.

Reference numeral 10 denotes a ring-shaped partition member which is made of high-purity quartz and is concentrically arranged in the quartz crucible 1. One or more ring-shaped partition members are provided in a region below the center in the height direction. Several small holes 11 are provided therethrough. This partition member 10
Are set in the quartz crucible 1 together when the granular polysilicon raw material 9 is charged, and are arranged in the silicon melt 7 so as to surround the silicon single crystal 5 after the raw material is melted. It is exposed from the silicon melt surface.
Further, the lower edge is almost fused to the quartz crucible 1 and does not rise. Therefore, the silicon melt in the raw material supply part 12 outside the partition member 10 can be gently moved to the inner single crystal growth part 13 only through the small holes 11, so that the raw material supply part 12 and the single crystal growth part 13 can be moved. And can be fully separated.

The reference numeral 15 designates an opening provided in the chamber 8 corresponding to the melt surface of the raw material supply section 12, and a granular or massive polysilicon raw material supply apparatus 14 is inserted and fixed in the opening 15. The front end of the supply device 14 faces the silicon melt liquid surface of the raw material supply part 12. The supply device 14 is connected to a raw material supply chamber (not shown) provided outside the chamber 8 as shown in the drawing, and the granular raw material polysilicon 9 is provided on the silicon melt surface of the raw material supply unit 12. Supply continuously.

In the upper part of the chamber-8, temperature detectors 16 and 17 for measuring the temperature of the melt surface of the raw material supply part 12 and the temperature of the melt surface of the other single crystal growing part 13 are provided. It is arranged. 18 is a heat insulating plate, which is made of a high strength graphite plate. The outer periphery of the heat insulating plate 18 is supported by the hot zone heat insulating material 6, and the partition member 10 and the raw material supply unit 1
It is set to surround 2. This heat retaining plate 18
In order to prevent the solidification of the melt generated from the part of the partition member 10 exposed from the melt and to enhance the heat retention effect of the melt of the raw material supply part 12, the bottom part (inner peripheral part) is brought close to the silicon melt surface ( In this embodiment, they are arranged at about 10 mm). Reference numeral 19 is a hole provided corresponding to the field of view of the temperature detector, and 20 is a hole provided in the supply path of the granular polysilicon.

In the single crystal manufacturing apparatus of FIG. 2,
Although not shown, it goes without saying that a control means for surely controlling the temperatures of the raw material supply part 12 and the single crystal growth part 13, a single crystal pulling and rotating means, a crucible rotating means, an inert gas supplying and discharging means are provided.

Next, in the single crystal production apparatus constructed as shown in FIG. 2, a fluidized bed of monosilane or trichlorosilane is provided inside and outside the partition member 10 arranged in the quartz crucible 1 as described above. The granular polysilicon 9 obtained by thermal decomposition and precipitation in
The crucibles 1 and 2 are heated on the electric resistance heating body 3 to melt the granular polysilicon 9 in the raw material supply section 12. In this case, the melting surfaces of both are kept at the same level.

Now, after the seed crystal is brought into contact with the melt surface of the single crystal growing portion 13, it is rotated at a predetermined speed (1 mm / min) by rotating means (not shown) and pulling means (not shown). When gradually pulled up, crystal growth occurs with solidification of the contact liquid surface, and a cylindrical silicon single crystal 5 having a diameter of 6 inches is obtained. During this period, the granular polysilicon 9 is continuously supplied from the raw material supply device 14 onto the surface of the silicon melt of the raw material supply unit 12, and the granular polysilicon 9 is supplied.
Is melted by the silicon melt of the raw material supply unit 12, passes through the small holes 11 of the partition member 10, and the single crystal growth unit 1
Gently move to No. 3 and use raw granular polysilicon 9 of molten raw material.
Keep the liquid level at a constant level. At this time, the turbulence or ripple of the silicon melt caused by the supply of the granular polysilicon 9 onto the surface of the melt of the raw material supply unit 12 is prevented by the partition member 10.
And is not propagated to the single crystal growth portion 13.

From the beginning of melting of the granular polysilicon raw material to the completion of pulling the single crystal, an atmosphere gas is introduced by means of an inert gas supply and discharge means (not shown). The atmosphere gas is argon gas and the pressure is 20 Torr.
Is.

In producing a single crystal using the above-described single crystal production apparatus, a silicon single crystal ingot was produced in advance using granular polysilicon raw materials having different specific surface areas of the granular silicon raw material, and the obtained single crystal was obtained. The crystal was processed into a silicon wafer by a normal wafer processing process to evaluate the quality.

In order to evaluate the quality of the silicon wafer, a surface inspector was used to measure fine irregularities on the surface of the silicon wafer. At this time, the minute irregularities generated from the bulk crystal quality and the silicon wafer processing step were identified. As an identification method, the particles were separated into a large diameter and a small diameter at the time of measuring the particles of the surface inspection meter, and the particles having the large diameter were counted. This is based on the fact that the above-mentioned count number by the surface inspector showed an extremely strong correlation with the surface fine unevenness derived from the polyhedron-shaped bulk crystallinity observed by the optical microscope.

The relationship between the above-identified results and the specific surface area (cm ² / g), which represents the unevenness of the surface of the granular polysilicon raw material and the number of pores inside by the total area per unit mass, was investigated.

FIG. 1 is a graph showing the experimental results with the specific surface area (cm ² / g) of the granular polysilicon raw material given to the surface fine irregularities (pieces / wafer), and the horizontal axis shows the granular polysilicon raw material by the BET method. The specific surface area (cm ² / g) is shown by taking the fine surface irregularities (pieces / wafer) on the vertical axis.

The specific surface area (cm ² / g) is measured by the BET method, which is a kind of adsorption method and is calculated from the adsorption amount of a gas adsorbed on the surface of particles in a monolayer (for example, the Chemical Engineering Handbook, Revised 5th Edition p. .230 Maruzen)

As is apparent from FIG. 1, the specific surface area is 100.
When it was 0 (cm ² / g) or less, the number of surface fine irregularities was 2 (pieces / wafer) or less, and when the specific surface area of the granular polysilicon raw material was small, the number of surface fine irregularities at the silicon wafer stage was small.

Here, the lower limit of measurement of this measuring device is 100 (cm
² / g), the measurement value of 0 or less was shown as the measured value.

FIG. 6 and FIG. 7 show enlarged scanning electron microscope photographs (magnification × 10000) showing the appearance of the surface state of granular polysilicon which causes some defects due to fine irregularities on the surface when a silicon wafer is processed. FIG. 6 shows the surface when a large number of fine surface irregularities are generated on the silicon wafer. There are many fine particles on the surface, and the surface irregularities are large.
In addition, the gap seems to be connected to the inside of the grain. On the other hand, FIG. 7 shows the surface in the case where the silicon wafer has few surface minute irregularities, and the surface is covered with a film-like substance in a large proportion and the surface irregularities are small.

8 and 9 are enlarged scanning electron microscope photographs (magnification × 3000) of a fracture surface of granular polysilicon which causes some defects due to fine irregularities on the surface when a silicon wafer is processed. FIG. 8 is a fracture surface in the case where many fine surface irregularities are generated on the silicon wafer, and there is a gap in the grain, and the gap has a state like a void (shadow portion) generated when the fine particles are filled. This suggests that the voids are connected to the surface of the grain. on the other hand,
FIG. 9 is a fracture surface of the granular polysilicon in the case where the silicon wafer has few surface fine irregularities, and shows that there are few gaps in the grain.

[Example 2] As described above, the granular raw material having a small specific surface area can be achieved by changing the conditions of the fluidized bed. However, even the granular raw material having a large specific surface area can be washed and etched to obtain the granular raw material having a small specific surface area. Can be obtained. Specifically, a granular polysilicon raw material having an average specific surface area of 15,000 cm ² / g was washed in an aqueous solution of 5% hydrofluoric acid for 15 minutes and surface-etched. The average specific surface area of the washed and surface-etched granular polysilicon raw material was measured and found to be 700 cm ² / g. Using this raw material, a single crystal was pulled up under the same conditions as in Example 1 to form a silicon wafer, and then the surface fine irregularities of the silicon wafer were measured. As a result, the number of fine surface irregularities was one on the entire surface of the silicon wafer. The method of the present invention has the effect of not only reducing the specific surface area but also reducing the surface contamination.

As the granular polysilicon raw material used in the present invention, any one of monosilane and trichlorosilane can be applied.

[0066]

According to the method of the present invention, the specific surface area is 1000.
A silicon wafer obtained by processing a single crystal obtained by continuously supplying a granular polysilicon raw material having a surface area of (cm ² / g) or less or having its surface washed can have extremely small surface fine irregularities. It becomes possible, and since the resistance value and oxygen concentration as quality are uniform in the ingot length in the hand direction and in the in-plane direction of the silicon wafer, it is expected as a substrate for highly integrated devices. The processed silicon wafer can maintain better surface cleanliness than ever before.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the specific surface area (cm ² / g) of a granular silicon raw material and surface fine irregularities (pieces / wafer).

FIG. 2 is a schematic cross-sectional explanatory diagram of a single crystal manufacturing apparatus used in an example of the present invention.

FIG. 3 is a scanning electron micrograph (magnification: 10000) of surface fine irregularities appearing on a silicon wafer.

FIG. 4 is a scanning electron micrograph (magnification × 7000) of surface fine irregularities appearing on a silicon wafer.

FIG. 5 is a scanning electron micrograph of surface fine irregularities when a silicon wafer is tilted.

FIG. 6 is a scanning electron micrograph showing the appearance of the surface state of the granular polysilicon raw material in the case where many surface fine irregularities are generated.

FIG. 7 is a scanning electron micrograph showing the appearance of the surface state of the granular polysilicon raw material when the number of fine surface irregularities is small.

FIG. 8 is a scanning electron micrograph showing voids present in a fractured surface of a granular polysilicon raw material when many surface fine irregularities are generated.

FIG. 9 is a scanning electron micrograph showing voids present in the fracture surface of the granular polysilicon raw material when the number of surface fine irregularities is small.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 quartz crucible, 2 graphite crucible, 3 electric resistance heating body (heater), 4 pedestal, 5 silicon single crystal, 6 heat insulating material, 7 silicon melt, 8 chamber, 9 granular polysilicon raw material, 10 partitioning member, 11 small holes, 12 raw material supply part, 13 single crystal growth part, 14 raw material supply device, 15 opening part, 16 temperature detector, 17 temperature detector, 18 heat insulating plate, 19 hole, 20 hole.

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[Procedure amendment]

[Submission date] April 20, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Brief explanation of the drawing

[Correction method] Change

[Correction content]

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the specific surface area (cm ² / g) of a granular silicon raw material and surface fine irregularities (pieces / wafer).

FIG. 2 is a schematic cross-sectional explanatory diagram of a single crystal manufacturing apparatus used in an example of the present invention.

FIG. 3 is a scanning electron micrograph (magnification × 10000) showing the crystal structure of the surface of a silicon wafer.

FIG. 4 is a scanning electron micrograph (magnification × 7000) showing the crystal structure of the surface of a silicon wafer.

FIG. 5 is a scanning electron micrograph (magnification × 7000) showing a crystal structure of a surface when a silicon wafer is tilted.

FIG. 6 is a scanning electron micrograph (magnification × 10000) showing the metal structure of the surface of the granular polysilicon raw material.

FIG. 7 is a scanning electron micrograph (magnification × 10000) showing the metal structure of the surface of the granular polysilicon raw material.

FIG. 8 is a scanning electron micrograph (magnification: 3000) showing a metal structure of a fracture surface of a granular polysilicon raw material.

FIG. 9 is a scanning electron micrograph (magnification × 3000) showing a metal structure of a fracture surface of a granular polysilicon raw material.

[Explanation of Codes] 1 quartz crucible, 2 graphite crucible, 3 electric resistance heating element (heater), 4 pedestal, 5 silicon single crystal, 6 heat insulating material, 7 silicon melt, 8 chamber, 9 granular polysilicon raw material , 10 partition members, 11 small holes, 12 raw material supply part, 13 single crystal growing part, 14 raw material supply device, 15 opening part, 16 temperature detector, 17 temperature detector, 18 heat insulating plate, 19 hole, 20 hole.

Claims (5)

[Claims] 1. A quartz crucible is divided into a single crystal growing portion and a raw material melting portion, small holes are provided in the partition so that a silicon melt can flow, and a granular polysilicon raw material is continuously fed into the raw material melting portion. After the supply, the atmosphere gas in the chamber is argon and the atmosphere is in a reduced pressure, and the seed crystal is brought into contact with the central melt surface of the single crystal growth portion, and then the seed crystal is pulled up by the rotating means to produce a silicon single crystal. A method for producing a single crystal, characterized in that a granular raw material having a specific surface area of 1000 cm ² / g or less is used. 2. A quartz crucible is divided into a single crystal growing portion and a raw material melting portion, small holes are provided in the partition so that a silicon melt can flow, and the raw material melting portion is continuously filled with a granular polysilicon raw material. After the supply, the atmosphere gas in the chamber is argon and the atmosphere is in a reduced pressure, and the seed crystal is brought into contact with the central melt surface of the single crystal growth portion, and then the seed crystal is pulled up by the rotating means to produce a silicon single crystal. A method for producing a single crystal, characterized in that a washed granular material is used. 3. A quartz crucible is divided into a single-crystal growing portion and a raw material melting portion, small holes are provided in the partition so that a silicon melt can flow, and the raw material melting portion is continuously filled with a granular polysilicon raw material. After the supply, the atmosphere gas in the chamber is argon and the atmosphere is in a reduced pressure, and the seed crystal is brought into contact with the central melt surface of the single crystal growth portion, and then the seed crystal is pulled up by the rotating means to produce a silicon single crystal. A method for producing a single crystal, characterized in that a granular raw material washed with a hydrofluoric acid-based aqueous solution is used. 4. The method for producing a single crystal according to claim 1, wherein a washed granular raw material is used in the method for producing the silicon single crystal. 5. The method for producing a silicon single crystal, wherein a granular raw material washed with a hydrofluoric acid-based aqueous solution is used.