JPH0524968A - Production of single crystal - Google Patents

Abstract

PURPOSE:To reduce surface fine recessed and projected products inevitably introduced into a wafer of single crystals obtd. from a method for manufacturing single crystals while a granular polysilicon raw material is contiously fed. CONSTITUTION:A method for manufacturing silicon single crystals while a granular polysilicon raw material is continuously fed and in a single crystal manufacturing method characterized in that, in the method for manufacturing silicon single crystals while a granular polysilicon raw material is continuously fed to the inside of a silicon molten soln., the granular polysilicon raw material having >0 to 3% void areal rate is used. In a silicon wafer obtd. by working the single crystals obtd. by the subject method, the number of fine surface recessed and projected products can extremely be reduced, the surface cleanliness of the wafer can be held in a good condition and it is expected as a substrate for a highly integrated device.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art A continuous production technique for a silicon single crystal based on the Czochralski method (hereinafter referred to as CZ method) has been known for a long time (for example, Japanese Examined Patent Publication No. 40-10184). Along with the possibility of manufacturing, a technique for continuously supplying a granular silicon raw material to an apparatus system and continuously pulling a single crystal has been developed (for example, Japanese Patent Laid-Open Nos. 61-361797 and 62-62). −
No. 2,418,89), and more recently, a single crystal production method has been disclosed for the purpose of limiting the amount of residual hydrogen or the amount of residual chlorine in a granular silicon raw material so as to reduce the rupture phenomenon that occurs when the raw material is melted (Japanese Patent Laid-Open No. Hei 1 (1998) -1980 (1999)). -282194).

These studies are being carried out in order to meet the high quality demands of silicon wafers associated with the recent high integration and high speed of devices. However, the demand for quality is increasing with the increase in diameter of wafers. It is getting tougher.

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

The particles here are foreign particles derived from the steps of polishing and cleaning the wafer, and are scattered in the form of dust on the surface of the smooth wafer. Are minute irregularities of about 10 μm or less scattered on the wafer surface, and are foreign substances different from the wafer, whereas this is a change in the geometrical shape of the wafer surface. ..
, Is quantitatively measured by a surface inspection meter, but may be included in the number of particles and counted in some cases.

[0006]

DISCLOSURE OF THE INVENTION The inventors of the present invention have investigated the surface cleanliness of a wafer obtained from a single crystal and the origin of its influencing factors in a single crystal manufacturing technique for continuously supplying a granular silicon raw material. As a result of detailed research, the following was found.

A wafer produced from a single crystal produced by continuously supplying a granular silicon raw material has much more fine surface irregularities than a wafer produced from an ordinary CZ single crystal.

There are extrinsic and natural surface fine irregularities, and many wafers made from single crystals produced by continuous supply have natural ones. This is the usual CZ.
This is a difference from a wafer manufactured from a single crystal.

Intrinsic surface micro-reliefs have a close relationship with the feedstock. That is, it was newly found that a wafer having a high surface cleanliness can be produced if there are surface fine irregularities derived from the feed material and the feed material has a specific property.

The present invention was made on the basis of such a new finding, and relates to a single crystal manufacturing technique for continuously supplying a granular polysilicon raw material, and a wafer obtained from the single crystal.
The purpose is to reduce surface fine irregularities that are inherently introduced into the c.

[0011]

The method according to the present invention is a continuous production method of a single crystal in which a granular silicon raw material is continuously fed into a silicon melt, and the raw material has a void area ratio of 0%. It is characterized by exceeding 3% or less.

[0012]

The single crystal manufacturing method of the present invention has a void area ratio of 0%.
It is possible to finally produce a single crystal which becomes a silicon wafer with extremely few fine surface irregularities by continuously supplying a granular polysilicon raw material of more than 3% and less than 3%.

The inventors of the present invention conducted various tests on minute surface irregularities on the surface of the wafer as shown in Examples to be described later. As a result, the void area ratio (%) of the granular polysilicon raw material and the minute surface irregularities were obtained. As shown in FIG. 7, when the void area ratio is 3% or less, the number of minute surface irregularities becomes 2 or less, and when the void area ratio exceeds 3%, the number of minute surface irregularities becomes 2.
I knew that I would exceed the number of pieces.

In the present invention, the void area ratio is
It is the ratio of the void area to the entire wafer area.

Further, the reason why the number of fine surface irregularities is specified to be 2 or less is that the current 6 to 8 inch wafer for high integration has a record of 2 or less.

Next, when the porosity of the granular polysilicon raw material is small, the reason why the minute surface irregularities at the wafer stage are small is considered as follows.

For example, in the single crystal manufacturing apparatus of FIG. 1, raw material granular polysilicon 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. Solidify. At that time, since the gas in the voids of the granular polysilicon has a small volume, it remains without being solid-solved in the silicon melt except for the one evaporated immediately after dissolution, and the volume expands due to pressure and temperature. Although considerable bubbles are discharged into the atmosphere by forced and natural convection in the silicon melt, the bubbles that reach the solidification interface directly are taken into the silicon ingot and become voids. It becomes a fine surface irregularity.

As a result of the above, the silicon single crystal obtained by the present invention is used as a substrate for a highly integrated device because the resistance and oxygen concentration are uniform in the ingot length in the hand direction and in the wafer in-plane direction. As expected, therefore, wafers processed from this silicon single crystal must retain better surface cleanliness than ever before.

Next, examples of the present invention will be described.

[0020]

【Example】

 (1) A method for manufacturing a granular polysilicon raw material.

The granular polysilicon raw material used in the method of the present invention is manufactured as follows. The method for producing the granular polysilicon raw material is to introduce monosilane or trichlorosilane into the fluidized bed and thermally decompose it to form granular polysilicon.

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

It will be clarified later that the difference in the amount of voids in the granular raw material affects the quality of the granular polysilicon, but
This is due to the operating conditions described below.

The granular polysilicon is formed by thermally decomposing trichlorosilane or monosilane in a fluidized bed. The reaction at this time is as follows: 1) Raw material gas is decomposed near the upper electrode of the seed and silicon is deposited to grow. What is done 2) There is one that grows repeatedly by repeating the process in which fine powder generated by reaction in the gas phase adheres to silicon particles and sinters.

In the former case, the structure is dense, and in the latter case, the porosity is large. It goes without saying that the granular polysilicon raw material having a small amount of voids used in the present invention can be achieved by using dense particles as the raw material. Even in the latter case, if the fine powder is sufficiently sintered and grown, dense particles having a small amount of voids can be produced, and the object of the present invention can be achieved.

These can be achieved by reducing the flow rate of the raw material gas such as monosilane or trichlorosilane and lowering the temperature in the fluidized bed. (2) Raw material supply and single crystal manufacturing method.

Next, the method for producing a single crystal of the present invention will be described. FIG. 1 is a schematic sectional view of an example of a single crystal manufacturing apparatus used in an example of the present invention. In the figure, reference numeral 1 denotes a quartz crucible, which is set in a graphite crucible 2. The graphite crucible 2 is supported on a pedestal 4 so as to be vertically movable and rotatable. 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, and these are housed in a chamber 8. It is basically the same as the silicon single crystal manufacturing apparatus by the 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, and one or more ring-shaped partition members are provided in the 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, and the upper edge portion is melted. It is exposed from the liquid 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.

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 device 14 is inserted and fixed in the opening 15. The front end of the supply device 14 faces the melt surface of the raw material supply part 12. This supply device 14 is
As shown in the figure, the raw material supply chamber 1 (not shown) provided outside the chamber 8 is connected to the raw material supply unit 1.
The granular raw material polysilicon 9 is continuously supplied onto the molten liquid surface of No. 2.

In the upper part of the chamber-8, temperature detectors 16 and 1 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, respectively.
7 are provided.

A heat insulating plate 18 is made of a high-strength graphite plate. The heat insulating plate 18 has an outer periphery supported by the hot zone heat insulating material 6 and is set so as to surround the partition member 10 and the raw material supply unit 12. The heat insulating plate 18 prevents the solidification of the molten liquid generated from the portion of the partition member 10 exposed from the molten liquid, and melts the bottom (inner peripheral portion) of the raw material supply unit 12 in order to enhance the heat insulating effect. It is arranged close to the liquid surface (about 10 mm in this embodiment). 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 production apparatus of FIG. 1 described above, although not shown, the raw material supply section 12 and the single crystal growth section 1
It is needless to say that a control means for surely controlling the temperature of 3, a single crystal pulling and rotating means, a crucible rotating means, and an inert gas supply and discharge means are provided.

Next, in the single crystal manufacturing apparatus configured as shown in FIG. 1, trichlorosilane or monosilane is placed in the fluidized bed inside and outside the partition member 10 arranged in the quartz crucible 1 as described above. The granular polysilicon 9 obtained by thermally decomposing and depositing is heated as a melting raw material, and the crucibles 1 and 2 are heated in the electric resistance heating body 3 to melt the granular polysilicon 9 in the raw material supply unit 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 gradually rotated at a predetermined speed (1 mm / min) by rotating means (not shown) and pulling means (not shown). When the liquid crystal is pulled up, the contact liquid surface is solidified and the crystal is grown to obtain a cylindrical silicon single crystal 5 having a diameter of 6 inches. During this period, the granular polysilicon 9 is continuously supplied from the raw material supply device 14 onto the surface of the molten liquid of the raw material supply unit 12,
The granular polysilicon 9 is melted by the molten liquid of the raw material supply unit 12 and gently moves to the single crystal growth unit 13 through the small holes 11 of the partition member 10, and the liquid level of the raw material granular polysilicon 9 of the molten raw material is leveled. Hold constant. At this time,
The ripples generated by the supply of the granular polysilicon 9 onto the melt surface of the raw material supply unit 12 are blocked by the partition member 10 and are not propagated to the single crystal growth unit 13.

From the beginning of melting of the raw material granular polysilicon 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). Using the above-described single crystal manufacturing apparatus, silicon single crystal ingots are manufactured using granular polysilicon raw materials having different void area ratios, and the obtained single crystals are processed by a normal wafer processing process. And evaluated the quality. (3) Observation and evaluation of the wafer surface with a microscope.

On the other hand, the present inventors have conducted detailed research and study on the wafer surface produced by continuously supplying the granular polysilicon raw material as described above.

2 to 6 are photographs for explaining the appearance of surface defects on the wafer surface. That is, FIGS. 2 and 3 show the wafer A, respectively.
4 and an optical micrograph (magnification: 700) of the surface B and FIG.
And FIG. 5 are scanning electron micrographs (magnification × 10,000 and × 7,000) of the surfaces of A and B wafers, respectively.
Further, FIG. 6 is a scanning electron micrograph (magnification × 7,000) taken by inclining the wafer B of FIG. 5 by 55 °.

As shown in the photographs of FIGS. 2 to 6, the shaded portion indicates the hole portion in the wafer surface, and the glossy portion indicates the smooth wafer surface.

The appearance of the fine surface irregularities of the present invention is shown in FIGS.
As shown in the photograph of FIG. 6, the shape is a polyhedral concave shape, and many are distributed in the central portion of the wafer.
Therefore, it is clear that when a device is manufactured, it causes a defect. (4) Relationship with the void area ratio of the granular polysilicon raw material that affects the fine surface irregularities on the wafer surface. FIG. 7 shows the result of identifying the wafer surface and the void area ratio (%) of the granular polysilicon raw material. Shows the relationship with.

FIG. 7 is a graph showing the experimental results with the void area ratio (%) of the granular polysilicon raw material given to the minute surface irregularities (pieces). The horizontal axis shows the void area ratio (%) of the granular polysilicon raw material. Is shown by taking the number of minute surface irregularities (pieces) on the vertical axis. The void area ratio (%) was measured by sampling a granular polysilicon raw material, polishing the cross section, and measuring with an optical microscope.

As shown in FIG. 7, when the void area ratio is 3% or less, the number of fine surface irregularities becomes 2 or less. When the void area ratio exceeds 3%, the fine surface irregularities exceed 2, and the wafer (C) In order to secure the surface cleanliness, it is clear that the void area ratio of the granular polysilicon raw material needs to be 3% or less. The amount of residual hydrogen in the granular polysilicon used here was 1 to 10 ppm, and there was no relationship between the amount of residual hydrogen and the number of fine surface irregularities.

Further, granular polysilicon raw materials A, B and C
The void state inside was examined by scanning electron micrograph. Figure 8
10 is a scanning electron micrograph (magnification × 10,000) showing the void region in the granular polysilicon A, B, C raw material.
0).

As shown in FIGS. 8 to 10, it can be seen that polysilicon is not dense and has many voids. The dark portion of the photograph shows the void state.

Here, the void area ratio was obtained by the following equation.

Void area ratio (%) = area of dark portion / total area × 100 Further, the variation in the void area ratio within the production lot was small.

As the granular polysilicon used in the present invention, any one of monosilane and trichlorosilane can be applied as long as the void area ratio is more than 0% and 3% or less. Furthermore, the apparatus for producing a single crystal is not limited to the apparatus of this embodiment, and any other apparatus by the CZ method can be applied.

[0046]

The silicon wafer processed by the continuous supply single crystal manufacturing method using the granular polysilicon raw material according to the method of the present invention is capable of extremely reducing the number of innate minute surface irregularities, and has a resistance as a quality. The value and oxygen concentration are expected to be a substrate for highly integrated devices because the ingot length is uniform in the hand direction and the in-plane direction of the wafer. Therefore, a wafer processed from a silicon single crystal of continuous raw material supply is more excellent than before. It is possible to maintain good surface cleanliness.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional explanatory view of a single crystal manufacturing apparatus used in an example of the present invention.

FIG. 2 is an optical microscope photograph (magnification × 700) showing the appearance of surface defects of silicon wafer A.

3 is an optical micrograph (magnification: 700) showing the appearance of surface defects of silicon wafer B. FIG.

4 is a scanning electron micrograph (magnification: 10,000) showing the appearance of surface defects of silicon wafer A. FIG.

5 is a scanning electron micrograph (magnification × 7,000) showing the appearance of surface defects of silicon wafer B. FIG.

FIG. 6 is a scanning electron micrograph (magnification × 7,000) showing the appearance of surface defects on the silicon wafer B.

FIG. 7: Void area ratio (%) of granular silicon raw material and wafer
It is a relationship graph of the number (pieces) of minute surface irregularities on the c surface.

FIG. 8 is a scanning electron micrograph (magnification × 10,000) showing the state of voids in the granular polysilicon A raw material.

FIG. 9 is a scanning electron micrograph (magnification × 10,000) showing the state of voids in the granular polysilicon B raw material.

FIG. 10 is a scanning electron micrograph (magnification × 10,000) showing the state of voids in the granular polysilicon C raw material.

[Explanation of symbols]

 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 raw material granular polysilicon, 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] July 22, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

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

[Correction method] Change

[Correction content]

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional explanatory view of a single crystal manufacturing apparatus used in an example of the present invention.

FIG. 2 is an optical microscope photograph (magnification × 700) showing the crystal structure of the surface of silicon wafer A.

FIG. 3 is an optical micrograph (magnification × 700) showing the crystal structure of the surface of the silicon wafer B.

FIG. 4 is a scanning electron micrograph (magnification: 10,000) showing the crystal structure of the surface of silicon wafer A.

5 is a scanning electron micrograph (magnification × 7,000) showing the crystal structure of the surface of the silicon wafer B. FIG.

6 is a scanning electron micrograph (magnification × 7,000) showing the crystal structure of the surface of the silicon wafer B. FIG.

FIG. 7: Void area ratio (%) of granular silicon raw material and wafer
It is a relationship graph of the number (pieces) of minute surface irregularities on the c surface.

FIG. 8 is a scanning electron micrograph (magnification × 10,000) showing the grain structure in the granular polysilicon A raw material.

FIG. 9 is a scanning electron micrograph (magnification × 10,000) showing the grain structure in the granular polysilicon B raw material.

FIG. 10 is a scanning electron micrograph (magnification × 10,000) showing a grain structure in a granular polysilicon C raw material.

[Explanation of Codes] 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 raw material granular polysilicon , 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.

[Procedure Amendment 2]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 2

[Correction method] Change

[Correction content]

[Fig. 2]

[Procedure 3]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 3

[Correction method] Change

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[Figure 3]

Claims (1)

Claim: What is claimed is: 1. A method of producing a silicon single crystal while continuously supplying a granular polysilicon raw material into a silicon melt, wherein the void area ratio is more than 0% and not more than 3%. A method for producing a single crystal, which comprises using silicon.