JP2010093140A - Method of manufacturing epitaxial silicon wafer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing an epitaxial silicon wafer in which a slip accompanying heating during epitaxial growth is not caused and a decrease in surface roughness of an epitaxial film due to a void defect on a wafer surface is eliminated. <P>SOLUTION: After an amorphous silicon film or polycrystalline silicon film is deposited on the surface of a silicon wafer made of single-crystal silicon, the film is irradiated with high-energy light to be fused, and is solidified to be modified into single crystal silicon. Consequently, liquid layer epitaxial growth of the epitaxial film is performed to eliminate the slip accompanying heating during epitaxial growth. Further, even when there is the void defect on the wafer surface, the epitaxial film having high surface flatness is obtained by fusing. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an epitaxial silicon wafer manufacturing method, and more particularly to an epitaxial silicon wafer manufacturing method capable of improving the quality of the surface layer of a silicon wafer.

When the silicon single crystal ingot is pulled up by the Czochralski method, excessive voids are introduced into the ingot and void defects are generated.
With the recent high integration and miniaturization of devices, there is a demand for a crystal defect-free wafer in which void defects and the like are completely eliminated from the surface layer of the silicon wafer on which the device is formed. This is because crystal defects cause a decrease in yield during device formation.

Therefore, a technique for controlling the temperature gradient and pulling speed of a single crystal ingot at the time of crystal pulling and suppressing the generation of point defects to reduce or eliminate void defects and dislocation clusters has been implemented in the wafer mass production process. However, at present, only a part of the ingot has achieved a crystal defect-free silicon single crystal only by controlling the crystal pulling. In addition, if the sensitivity of the surface inspection apparatus is increased, there is a possibility that even a region called void-free today is determined to be a region where minute void defects exist.
In particular, when a large-diameter wafer having a diameter exceeding 300 mm is used, it becomes more difficult to pull up an ingot that does not contain void defects and the like.

As a conventional technique for solving such a problem, a method of growing an epitaxial film on the surface of a silicon wafer is known.
Generally, in an epitaxial growth process, hydrogen baking is performed on a silicon wafer at a high temperature of 1100 ° C. or higher as the first step. This removes the surface oxide film and fills in the void defects existing on the wafer surface. However, in the case of a large-diameter wafer having a diameter exceeding 300 mm, there is a concern about the occurrence of slip during high-temperature heat treatment accompanying epitaxial growth. Therefore, it is expected that the temperature of the epitaxial process will be lowered in the future.

JP-A-8-181076

  However, when a silicon wafer having a void defect on the surface is adopted as a silicon wafer for low temperature epitaxial growth, the heating temperature at the time of hydrogen baking is low, and the filling of the void defect on the wafer surface becomes insufficient. As a result, minute irregularities on the surface of the wafer are transferred to the surface of the epitaxial film, or a defect is generated in the epitaxial film starting from a void defect, which ultimately degrades the device characteristics.

  Therefore, as a result of intensive studies, the inventor has focused on amorphous silicon and polycrystalline silicon, which have a higher extinction coefficient than single crystal silicon. That is, an amorphous silicon film or a polycrystalline silicon film is formed on the surface layer of a silicon wafer made of single crystal silicon. Next, high-energy light such as laser light is irradiated under conditions that do not melt the single crystal silicon, but melt the amorphous silicon film or polycrystalline silicon having a higher absorption coefficient than the silicon single crystal, and melt and solidify the film. . Thus, the inventors have found that the above problem can be solved if an amorphous silicon film or polycrystalline silicon is transformed (epitaxy) into single crystal silicon to form an epitaxial film, and the present invention has been completed.

  It is an object of the present invention to provide an epitaxial silicon wafer manufacturing method that eliminates the occurrence of slip caused by heating during epitaxial growth and eliminates the reduction in surface roughness of the epitaxial film due to void defects on the wafer surface. It is aimed.

  The invention according to claim 1 is a deposition step of depositing an amorphous silicon film or a polycrystalline silicon film on the surface of a silicon wafer made of single crystal silicon, and at least the amorphous silicon film or the polycrystalline silicon film after the deposition step. Is melted by irradiation with high energy light, and is cooled to be cooled to a single crystal silicon to be a single crystal silicon, and a method for producing an epitaxial film of the single crystal silicon is provided.

  According to the first aspect of the present invention, an amorphous silicon film or a polycrystalline silicon film is deposited on the surface of a silicon wafer made of single crystal silicon by a thin film growth method such as a CVD (chemical vapor deposition) method. Thereafter, the amorphous silicon film or the polycrystalline silicon film is melted and solidified by irradiation with high energy light, and this is transformed into single crystal silicon (liquid phase epitaxy). The liquid layer epitaxy is a phenomenon in which single crystallization takes over the crystallinity of the solid region at the melted solid-liquid interface. It is said that amorphous silicon and polycrystalline silicon have a higher extinction coefficient than single crystal silicon, and in particular, amorphous silicon is about one digit higher. Therefore, if an optical heating type annealing furnace is used, the amorphous silicon film or polycrystalline silicon film is melted before the single crystal silicon wafer reaches the melting point, and then cooled and solidified to be transformed into an epitaxial film. can do.

  That is, it is possible to perform epitaxial growth in a pseudo manner, and to eliminate generation of slip of the silicon wafer due to heating at this time. Moreover, even if void defects exist on the surface of the silicon wafer, and even if micro irregularities are transferred to the surface of the amorphous silicon film or the surface of the polycrystalline silicon film immediately after the deposition process, the film is then melted, An epitaxial film having a high surface flatness can be grown. That is, the reduction in the surface roughness of the epitaxial film due to void defects on the wafer surface can be eliminated.

As the silicon wafer, a single crystal silicon wafer or an SOI wafer can be employed.
The “surface of the silicon wafer” refers to a surface on which a device is formed.
It is said that amorphous silicon and polycrystalline silicon have a higher extinction coefficient than single crystal silicon, and in particular, amorphous silicon is about one digit higher.

In the melting step, the amorphous silicon film or the polycrystalline silicon film undergoes liquid layer epitaxial growth in which the amorphous silicon film melted on the single crystal substrate is reflected in the single crystal silicon structure, and becomes single crystal silicon.
The thickness of the amorphous silicon film and the polycrystalline silicon film may be designed according to the device active layer.
Moreover, the adjustment of the specific resistance of the silicon film which has been liquid-layer-epitaxial after melting can be dealt with by introducing a specified amount of dopant in advance into the amorphous silicon film or the polycrystalline silicon film.
“Deposition” here refers to growth of an amorphous silicon film or polycrystalline silicon that does not include epitaxial growth.

As a method for depositing the amorphous silicon film or the polycrystalline silicon film, for example, a vapor phase growth method may be employed. In addition, sputtering may be used.
As the vapor phase growth method, for example, an atmospheric pressure vapor phase growth method, a reduced pressure vapor phase growth method, a metal organic vapor phase growth method, or the like can be employed.
The vapor phase growth apparatus may be a single wafer type that processes silicon wafers one by one, a pancake type that can process a plurality of silicon wafers simultaneously, a barrel type, a hot wall type, or a cluster type.
For example, SiH ₄ can be used as a component of the reaction gas (source gas) used in the vapor phase growth method. Further, hydrogen can be employed as a component of the carrier gas.

As the light heating method, for example, various lamp annealing methods (spike clamp annealing method, flash lamp annealing method, etc.) and laser annealing methods (laser spike annealing method, etc.) can be employed.
As the high energy light, for example, lamp light, laser light or the like can be employed.
Although the irradiation energy of high-energy light varies greatly depending on the specifications of the apparatus, it is preferable that the energy is as high as possible because the processing time can be shortened. For example, the laser energy density is 0.1-20 J / cm ² . If it is less than 0.1 J / cm ² , the melting time becomes too long and the productivity is lowered. On the other hand, if it exceeds 20 J / cm ² , productivity is increased, but there is a problem of apparatus cost. A preferable irradiation energy of the high energy light is 0.5 to 5 J / cm ² . If it is this range, a commercially available laser apparatus can be used.
As the laser type, a laser having a wavelength that can penetrate into silicon, such as an excimer laser, a solid-state laser, or a semiconductor laser, is applied. Further, laser light having two or more types of wavelengths may be irradiated from the silicon surface.

The invention according to claim 2 is the method for producing an epitaxial silicon wafer according to claim 1, wherein the high-energy light is laser light or lamp light.
In particular, when laser light is employed, the laser scan speed can be arbitrarily changed, so that the solidification speed can be changed, and the quality of the obtained epitaxial growth film can be improved. In the case of lamp heating, the entire surface of the wafer is heated at a high temperature, which may cause slip.

As the laser light, for example, a third harmonic (wavelength 355 nm) pulse laser light of an excimer laser or YAG laser, Nd: YAG laser, Nd: YLF laser, Nd: glass fiber laser, Nd: YV04 laser, Yb: YAG A second harmonic, a third harmonic, a fourth harmonic, or the like such as a laser can be used. Further, the laser beam may be either pulsed irradiation or continuous irradiation, and it is preferable that the beam width be equal to or larger than the diameter of the silicon wafer because melting can be performed uniformly.
The irradiation energy of the laser beam, the number of irradiation pulses of the laser beam, and the pulse width of the laser beam are selected according to the type of the laser beam.

  A third aspect of the present invention is the method for producing an epitaxial silicon wafer according to the first or second aspect, wherein a vapor phase growth method using a dopant gas is employed in the deposition step.

As a component of the dopant gas, for example, PH ₃ (phosphine), AsH ₃ (arsine) or the like can be employed as the n-type. Further, for example, boron (B) can be employed as the p-type.
The dopant concentration cannot be determined unconditionally because the specifications differ depending on the device. In general, in the case of the p-type, 1.33 × 10 ^{14 to} 1.46 × 10 ¹⁶ atoms / cm ³ so as to be 1 Ω · cm or more and 100 Ω · cm or less.

  According to a fourth aspect of the present invention, dopant is ion-implanted into the amorphous silicon film or the polycrystalline silicon film between the deposition step and the melting step, and in the melting step, the molten amorphous silicon film or The method for manufacturing an epitaxial silicon wafer according to claim 1, wherein the dopant is diffused into the polycrystalline silicon film.

As described above, the dopant ion implantation amount may be set such that, for example, boron is 1.33 × 10 ^{14 to} 1.46 × 10 ¹⁶ atoms / cm ³ .
The ion implantation energy of the dopant may be set so that the implantation depth is smaller than the thickness of the target amorphous film or the polycrystalline silicon film. Preferably, when the dopant is implanted near the surface of the amorphous film or near the surface of the polycrystalline silicon film, a load is not applied to the ion implantation apparatus, and a medium current ion implantation apparatus or the like can be used. Productivity increases.

  Invention of Claim 5 is a manufacturing method of the epitaxial silicon wafer of any one of Claims 1-4 which grind | polish the surface of the said epitaxial film after the said fusion | melting process.

  According to the invention described in claim 5, since the surface of the epitaxial film is polished after the melting step, even if there are minute irregularities on the surface of the epitaxial film, the surface flatness equivalent to a commercially available epitaxial silicon wafer is obtained. You can get a degree.

  The amount of polishing of the surface of the epitaxial film is naturally made smaller than the thickness of the deposited amorphous film or the thickness of the polycrystalline silicon film, but is made as small as possible to prevent flatness deterioration due to polishing. That is, the polishing allowance is large enough to polish and remove the irregular defect height. For example, it is 5 to 100 nm. If the thickness is less than 5 nm, it is difficult to uniformly polish the surface with the current CMP (Chemical & Mechanical Polishing) apparatus, and the flatness may be deteriorated.

According to the first aspect of the present invention, after depositing an amorphous film or a polycrystalline silicon film on the surface of a silicon wafer made of single crystal silicon, the film is solidified by melting and cooling by irradiation with high energy light. , Change to single crystal silicon. Amorphous silicon or polycrystalline silicon has a higher extinction coefficient than single crystal silicon. Therefore, before the silicon wafer is melted, only this film can be melted and reformed to an epitaxial film. As a result, liquid layer epitaxial growth is possible, and slip that has occurred during the conventional epitaxial growth can be eliminated.
In addition, even if void defects exist on the wafer surface and minute irregularities are transferred to the film surface immediately after deposition, an epitaxial film with high surface flatness can be obtained by subsequent melting of the film. As a result, a reduction in the surface roughness of the epitaxial film due to void defects on the wafer surface can be eliminated.

  In addition, according to the invention described in claim 5, since the surface of the epitaxial film is polished after the melting step, even if a minute irregularity defect exists on the surface of the epitaxial film, it is equivalent to a commercially available epitaxial silicon wafer. Surface flatness can be obtained.

  Examples of the present invention will be specifically described below.

A method for manufacturing an epitaxial silicon wafer according to Embodiment 1 of the present invention will be described.
A silicon single crystal ingot having a void-rich void defect having a diameter of 200 mm and an initial oxygen concentration of 1.0 × 10 ¹⁸ atoms / cm ³ is pulled up by the Czochralski method. At that time, boron is added as a dopant until the specific resistance of the silicon single crystal ingot becomes 10 mΩ · cm. The resulting silicon single crystal ingot is sequentially subjected to block cutting, outer diameter grinding, and slicing steps. Thereby, a silicon wafer having a large number of void defects on the surface is produced.

Next, an epitaxial silicon wafer manufacturing method using this silicon wafer will be described with reference to the flow sheet of FIG.
As shown in FIG. 1A, first, a silicon wafer 10 is prepared by the manufacturing method described above.
Next, an amorphous silicon film 11 is deposited on the surface of the silicon wafer 10 (FIG. 1B, deposition step). Specifically, a silicon wafer is put into a furnace set at 200 to 400 ° C., silane gas and diborolane gas as needed are introduced based on hydrogen gas, and an amorphous film is deposited to 400 nm.
A polycrystalline silicon film may be deposited instead of the amorphous silicon film 11.
As a method for depositing polycrystalline silicon, a method of depositing polycrystalline silicon by introducing a monosilane gas into the CVD apparatus in a temperature range of about 500 ° C. to 750 ° C., for example, by reducing the pressure can be employed.

If necessary, in this deposition step, a dopant may be added to the amorphous silicon film 11 at the time of amorphous silicon film formation, or instead of adding a dopant, between the deposition step and the melting step, A dopant may be ion-implanted into the amorphous silicon film 11 from its surface. In this case, the following ion implantation process is performed.
First, the silicon wafer 10 with the amorphous silicon film 11 is inserted into a furnace of a medium current ion implantation apparatus, and dopant is ion-implanted so as to have a predetermined concentration at an acceleration voltage of 70 keV. Thereby, an ion implantation region having an implantation peak region at a position near a depth of 300 nm from the wafer surface is formed. When dopant ion implantation is employed, the dopant is uniformly diffused throughout the amorphous silicon film 11 in the melting step.

Next, the silicon wafer 10 with the amorphous silicon film 11 to which the dopant is added is inserted into a laser annealing furnace maintained in a nitrogen gas atmosphere. Here, excimer laser light (KrF laser, wavelength 248 nm) is irradiated to the entire wafer surface (FIG. 1C, melting step).
As described above, the amorphous silicon film 11 having a higher extinction coefficient than the single crystal silicon is grown on the surface of the silicon wafer 10. Therefore, using a laser annealing furnace, single crystal silicon does not melt, but amorphous silicon melts. Thereby, the amorphous silicon film 11 is transformed into single crystal silicon, and this is cooled and solidified to form the epitaxial film 12 (FIG. 1D).
Thereafter, the silicon wafer 10 is attached to the lower surface of the polishing head of the single wafer type polishing apparatus through the carrier plate with the epitaxial layer 12 facing down, and the surface of the epitaxial layer is subjected to chemical mechanical polishing (CMP) by about 50 nm. ) Thereby, the epitaxial silicon wafer 20 whose surface is processed and polished is manufactured.

As a result, the liquid layer epitaxial growth of the epitaxial film 12 reflecting the crystal structure from the underlying single crystal silicon due to the melting of the amorphous silicon film 11 is possible, and the occurrence of slip of the silicon wafer 10 due to heating during the conventional epitaxial growth is eliminated. Can do. Furthermore, since the amorphous silicon film 11 is once melted, void defects on the wafer surface and thus the surface of the epitaxial film 12 are eliminated. As a result, the reduction in the surface roughness of the epitaxial film 12 caused by void defects on the wafer surface can also be eliminated.
Furthermore, since the surface of the epitaxial film 12 is polished after the melting step, even if minute irregularities appear on the surface of the epitaxial film 12 after melting, the surface flatness equivalent to that of a commercially available epitaxial silicon wafer is obtained. Can be obtained.

Hereinafter, a result of actually manufacturing an epitaxial wafer by applying the epitaxial silicon wafer manufacturing method of the present invention will be described.
A silicon ingot having a hole-rich void defect having a diameter of 200 mm, an initial oxygen concentration of 1.0 × 10 ¹⁸ atoms / cm ³ and a specific resistance of 10 Ω · cm obtained under the growth conditions of Example 1 was processed into a wafer. Thereby, a large number of silicon wafers having void defects on the surface were obtained.
With respect to the wafer surface, particles of 0.09 μm or more were measured by a surface inspection apparatus (SP-1) manufactured by KEL Tencor. As a result, hundreds of particles were counted. When this particle was observed with an atomic force microscope (AFM), it was found to be a void defect.

Next, about 400 nm of an amorphous silicon film was deposited on the surface of the silicon wafer under the deposition conditions of Example 1. Thereafter, the amorphous silicon film was melted and solidified by laser light under the melting conditions of Example 1. As a result, the amorphous silicon film was transformed into an epitaxial film made of single crystal silicon. Subsequently, the surface of the epitaxial film was chemically and mechanically polished with the aim of 0.05 μm under the polishing conditions of Example 1. As a result, an epitaxial silicon wafer was obtained.
Thereafter, particles on the surface of the epitaxial film of the epitaxial silicon wafer were measured by the surface inspection apparatus. As a result, it was found that no particles exist in the portion of the surface of the epitaxial film corresponding to the void generation position on the surface of the silicon wafer.
Similarly, a polycrystalline silicon film was deposited to a thickness of about 500 nm on the surface of the silicon wafer under the deposition conditions of Example 1. Thereafter, polycrystalline silicon was melted and solidified under the melting conditions of Example 1. Similarly, the surface of the epitaxial film was polished with the aim of 0.05 μm by chemical polishing, and then the particles were measured. It was found that no particles exist in the portion corresponding to the void generation position on the surface.
Moreover, crystallinity evaluation by electron diffraction using a transmission electron microscope was performed on the obtained epitaxial silicon wafer. As a result, the silicon was completely crystalline in the melted and solidified region.

It is a flow sheet of the manufacturing method of the epitaxial silicon wafer concerning Example 1 of this invention.

Explanation of symbols

10 Silicon wafer,
11 Amorphous silicon film,
12 Epitaxial film,
20 Epitaxial silicon wafer.

Claims (5)

A deposition step of depositing an amorphous silicon film or a polycrystalline silicon film on the surface of a silicon wafer made of single crystal silicon;
After the deposition step, at least the amorphous silicon film or the polycrystalline silicon film is melted by irradiation with high energy light and cooled to be modified to single crystal silicon to form an epitaxial film of the single crystal silicon. An epitaxial silicon wafer manufacturing method comprising:   The method for producing an epitaxial silicon wafer according to claim 1, wherein the high-energy light is laser light or lamp light.   The method for producing an epitaxial silicon wafer according to claim 1, wherein a vapor phase growth method using a dopant gas is employed in the deposition step. Between the deposition step and the melting step, dopant is ion-implanted into the amorphous silicon film or the polycrystalline silicon film,
3. The method of manufacturing an epitaxial silicon wafer according to claim 1, wherein in the melting step, the dopant is diffused into the melted amorphous silicon film or polycrystalline silicon film.   The method for producing an epitaxial silicon wafer according to claim 1, wherein the surface of the epitaxial film is polished after the melting step.

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