JP2010192544A - 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 can be eliminated. <P>SOLUTION: After the surface of a silicon wafer made of single crystal is ground and a processing altered layer is formed on a wafer surface layer, the altered layer is irradiated with high-energy light to be fused, and solidified. The altered layer has a higher coefficient of light absorption than single-crystal silicon and is thereby fused by light heating before the wafer is fused to be changed into an epitaxial film. Consequently, the slip due to the epitaxial growth heating is not caused and the decrease in surface roughness of the epitaxial film due to the void defect on the wafer surface can be eliminated. <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 earnest research, the inventor paid attention to a work-affected layer, amorphous silicon, and polycrystalline silicon, which are made of processing damage having a higher extinction coefficient than single crystal silicon. That is, only a work-affected layer obtained by grinding is formed on the surface layer of a silicon wafer made of single crystal silicon, or an amorphous silicon film or a polycrystalline silicon film is formed on the surface of the work-affected layer. Next, high energy light such as laser light is used. (1) Although the single crystal silicon does not melt, the work-affected layer having a higher extinction coefficient than the silicon single crystal melts the liquid phase epitaxy heat treatment condition or solid phase without melting Heating under the heat treatment conditions of epitaxy, or (2) Liquid that does not melt single crystal silicon, but melts the work-affected layer having a higher absorption coefficient than silicon single crystal and the deposited amorphous silicon film or polycrystalline silicon film The above-mentioned problems can be solved if the epitaxial film is made of single crystal silicon by heating under the heat treatment conditions of phase epitaxy or the heat treatment conditions of solid phase epitaxy without melting, and then cooling and solidifying it. As a result, the present invention was 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 modified layer forming step of grinding a surface of a silicon wafer made of single crystal silicon and forming a work-affected layer due to work damage on a surface layer of the silicon wafer, Heating is performed under the liquid phase epitaxy heat treatment conditions involving melting by irradiation with energy light or the solid phase epitaxy heat treatment conditions without melting due to irradiation with high energy light, and then cooled, and then epitaxially formed of single crystal silicon. An epitaxial silicon wafer manufacturing method including a heat treatment step for forming a film.

  According to the first aspect of the present invention, the surface of a silicon wafer made of single crystal silicon is ground to form a work-affected layer due to processing damage on the surface layer of the silicon wafer (a deteriorated layer forming step). Thereafter, the work-affected layer is heated under liquid phase epitaxy heat treatment conditions involving melting by irradiation with high energy light or solid phase epitaxy heat treatment conditions without melting due to irradiation with high energy light, and then cooled and solidified. When the heat-processed damaged layer is solidified by cooling, the crystallinity of the solid region (single crystal silicon) of the silicon wafer is inherited at the solid-liquid interface of the processed damaged layer, and the processed damaged layer (silicon) is single crystal silicon. An epitaxial film made of The work-affected layer has a higher extinction coefficient than single crystal silicon. Therefore, if a light heating type annealing furnace is used, before the silicon wafer made of single crystal silicon reaches the melting point (1412 ° C.), the work-affected layer is epitaxially made of single crystal silicon by liquid phase epitaxy or solid phase epitaxy. It can be modified into a membrane. Here, “inheriting crystallinity” means inheriting the crystal plane and crystal orientation of the solid region of the silicon wafer.

  That is, it is possible to perform epitaxial growth in a pseudo manner, and to eliminate the occurrence of slip of the silicon wafer due to heating of conventional epitaxial growth. Moreover, even if void defects exist on the wafer surface, an epitaxial film having a high surface flatness can be obtained by melting the work-affected layer after grinding the wafer surface. As a result, a 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.
The grinding is performed, for example, by pressing a rotating grinding wheel at a predetermined rotation speed against the surface of the silicon wafer using a surface grinding apparatus. Thereby, a work-affected layer that is a work damage layer is formed on the wafer surface layer. Specifically, when the wafer surface is ground using a grinding wheel of # 170 to # 800, a work-affected layer having a thickness (depth) of 11 to 34 μm is formed. The thickness of the work-affected layer may be designed (changed) according to the device active layer.
The work-affected layer has a higher extinction coefficient than single crystal silicon, as with amorphous silicon.

  In the heat treatment process, the work-affected layer heated to the melting point or higher or heated to near the melting point on the surface of the silicon wafer is subjected to liquid phase epitaxial growth or solid-phase epitaxial growth reflected in the single crystal silicon structure. Becomes an epitaxial film of single crystal silicon.

The heat treatment method may be heating under conditions that melt the work-affected layer. At this time, the work-affected layer becomes a single crystal by taking over the crystallinity including the interface with the work-affected layer of the silicon wafer, which is a solid region, based on the interface with the work-affected layer of the silicon wafer made of single crystal silicon. (Liquid phase epitaxy).
On the other hand, in the case of solid phase epitaxy, the work-affected layer is not melted, and heating is stopped to near the melting point. As a result, the work-affected layer becomes a single crystal by taking over the crystallinity including the crystal plane of the support substrate wafer, which is a solid region, with reference to the interface with the work-affected layer of the silicon wafer.
Moreover, the adjustment of the specific resistance of the epitaxial film grown by liquid phase epitaxial growth or solid phase epitaxial growth can be adjusted by introducing a specified amount of dopant into the work-affected layer in advance.

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, when the work-affected layer is melted, the laser energy density is 1 to 20 J / cm ² depending on the laser wavelength. If it is less than 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 ² to 5 J / cm ² . If it is this range, a commercially available laser annealing apparatus can be used. In addition, for example, the laser energy density without melting the work-affected layer is set to a value that is about 10% lower than the condition with melting.
As the laser type, an excimer laser, a solid-state laser, a semiconductor laser, or the like having a wavelength that can enter the silicon is used. Further, laser light having two or more types of wavelengths may be irradiated from the silicon surface. When lamp light is used as the high energy light, for example, the temperature may be set to 500 ° C. to 1350 ° C. and heated for several milliseconds to several minutes.

  According to the second aspect of the present invention, a dopant is ion-implanted into the work-affected layer between the deteriorated layer forming step and the heat treatment step, and in the heat treatment step, the dopant is added to the melted work-affected layer. It is a manufacturing method of the epitaxial silicon wafer of Claim 1 diffused.

According to the invention described in claim 2, the ion implantation amount of the dopant may be set so 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 (depth) of the target work-affected layer. Preferably, when the dopant is implanted in the vicinity of the surface layer of the work-affected layer, a load is not applied to the ion implantation apparatus, a medium current ion implantation apparatus or the like can be used, and the ionic current is increased to increase productivity.

  The invention according to claim 3 is a modified layer forming step of grinding a surface of a silicon wafer made of single crystal silicon and forming a work damaged layer due to processing damage on a surface layer of the silicon wafer, and after the deteriorated layer forming step, A deposition step of depositing an amorphous silicon film or a polycrystalline silicon film on a surface of the work-affected layer; and after the deposition step, the amorphous silicon film or polycrystalline silicon film deposited on the work-affected layer and the work-affected layer. Is heated under conditions of heat treatment for liquid phase epitaxy accompanied by melting by irradiation with high energy light or under conditions for heat treatment of solid phase epitaxy without melting due to irradiation of high energy light, and then cooled, from single crystal silicon. An epitaxial silicon wafer manufacturing method including a heat treatment step for forming an epitaxial film.

  According to the third aspect of the present invention, the surface of the silicon wafer made of single crystal silicon is ground to form a work-affected layer due to processing damage on the surface layer of the silicon wafer (a deteriorated layer forming step). Thereafter, an amorphous silicon film or a polycrystalline silicon film is deposited on the surface of the work-affected layer by a thin film growth method such as a CVD (chemical vapor deposition) method (deposition step). Next, the deposited amorphous silicon film or polycrystalline silicon film and the work-affected layer are subjected to a liquid phase epitaxy heat treatment condition involving melting by irradiation with high-energy light, or solidified without melting due to irradiation with high-energy light. Heating is performed under the heat treatment conditions of phase epitaxy, and then it is cooled and solidified (heat treatment step). When the heat-treated silicon solidifies, the crystallinity of the solid region (single crystal silicon) is inherited at the solid-liquid interface of the heat-treated silicon, and the heat-treated silicon becomes an epitaxial film made of single crystal silicon. Compared to single crystal silicon, the work-affected layer, amorphous silicon, and polycrystalline silicon have a higher extinction coefficient. In particular, amorphous silicon is said to be about an order of magnitude higher. Therefore, if an optical heating type annealing furnace is used, the amorphous silicon film or polycrystalline silicon film on the work-affected layer and the work-affected layer are melted before the single crystal silicon wafer reaches the melting point, This can be cooled and solidified to be transformed into an epitaxial film.

Moreover, even if a void defect exists on the wafer surface, it can be removed by forming a work-affected layer by grinding the wafer surface. In addition, immediately after the deposition of the silicon film on the subsequent work-affected layer, even if micro unevenness due to the surface unevenness of the work-affected layer is transferred to the surface of the silicon film, the heat treatment conditions for the liquid phase epitaxy in the subsequent heat treatment process Alternatively, it can be melted away by heat treatment under the heat treatment conditions of solid phase epitaxy. As a result, an epitaxial film having a high surface flatness can be obtained.
Further, the specific resistance of the silicon film grown by liquid phase epitaxial after melting can be adjusted 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.

  The invention according to claim 4 is the method for producing an epitaxial silicon wafer according to claim 3, 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 generally determined because the specifications differ depending on the customer's 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 fifth aspect of the present invention, a dopant is ion-implanted into the amorphous silicon film or the polycrystalline silicon film between the deposition step and the heat treatment step. 5. The method for producing an epitaxial silicon wafer according to claim 3, wherein the dopant is diffused into the crystalline 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 dopant ion implantation energy may be set so that the implantation depth is shallower than the thickness of the target amorphous silicon film or polycrystalline silicon film. Preferably, when the dopant is implanted near the surface layer of the amorphous silicon film or 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, resulting in a large ion current. Productivity increases.

The invention according to claim 6 is the method for producing an epitaxial silicon wafer according to any one of claims 1 to 5, wherein the high-energy light is laser light or lamp light.
In particular, when laser light is employed, the laser scan speed and irradiation time can be arbitrarily changed, so that the solidification speed and the like can be changed, and the quality of the obtained epitaxial film can be improved.

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.
As the lamp light, for example, an RTA (rapid thermal annealing) apparatus or an FLA apparatus (flash lamp annealing) can be used. In the case of solid layer epitaxial growth, a normal resistance heating furnace may be used.

  The invention according to claim 7 is the method for producing an epitaxial silicon wafer according to any one of claims 1 to 6, wherein the surface of the epitaxial film is polished after the heat treatment step.

  According to the seventh aspect of the invention, since the surface of the epitaxial film is polished after the heat treatment 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 less than the thickness of the epitaxial film, but is reduced as much as possible to prevent deterioration of flatness 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 1000 nm. If the thickness is less than 5 nm, it is difficult to uniformly polish the surface with the current CMP (Crystal Originated Particle) apparatus. Conversely, if the polishing allowance is large, the flatness may be deteriorated.

According to the first aspect of the present invention, after the surface of a single crystal silicon wafer is ground and a work-affected layer is formed on the surface layer of the wafer, the work-affected layer is irradiated with high-energy light to cause liquid phase epitaxy with melting. Heating is performed under heat treatment conditions or heat treatment conditions for solid phase epitaxy without melting, and then cooled to solidify. Since the work-affected layer has a higher extinction coefficient than single crystal silicon, if the optically heated, the work-affected layer melts and solidifies before the single crystal silicon wafer reaches the melting point, and is transformed into an epitaxial film. Can do. As a result, liquid phase epitaxial growth or solid phase epitaxial growth can be performed, and slip generated during heating associated with conventional vapor phase epitaxial growth can be eliminated.
Moreover, even if void defects are present on the wafer surface, an epitaxial film having a high surface flatness can be obtained by grinding the wafer surface and melting the work-affected layer thereafter. As a result, a reduction in the surface roughness of the epitaxial film due to void defects on the wafer surface can be eliminated.

According to the invention described in claim 3, after the surface of the single crystal silicon wafer is ground and a work-affected layer is formed on the surface of the wafer, an amorphous silicon film or a polycrystalline silicon film is deposited on the surface of the work-affected layer. Let Thereafter, the deposited silicon film and the work-affected layer are heated under a liquid phase epitaxy heat treatment condition involving melting by irradiation with high energy light or a solid phase epitaxy heat treatment condition without melting. Next, by cooling and solidifying this, the heat-treated silicon can be modified into an epitaxial film. As a result, it is possible to perform liquid phase epitaxial growth or solid phase epitaxy of the epitaxial film, and to eliminate the slip that has occurred during heating accompanying conventional vapor phase epitaxial growth.
Moreover, even if a void defect exists on the wafer surface, it can be removed by forming a work-affected layer by grinding the wafer surface. In addition, immediately after the deposition of the silicon film on the subsequent work-affected layer, even if minute unevenness due to the surface unevenness of the work-affected layer is transferred to the surface of the silicon film, this is achieved by melting the silicon film in the subsequent heat treatment process. Can be dissolved. As a result, an epitaxial film having a high surface flatness can be obtained.

  In particular, according to the invention described in claim 7, since the surface of the epitaxial film is polished after the heat treatment step, even if minute irregularities exist on the surface of the epitaxial film, it is equivalent to a commercially available epitaxial silicon wafer. The surface flatness can be obtained.

It is a longitudinal cross-sectional view of the silicon wafer used for the manufacturing method of the epitaxial silicon wafer which concerns on Example 1 of this invention. It is a longitudinal cross-sectional view of the silicon wafer which shows the deteriorated layer formation process of the manufacturing method of the epitaxial silicon wafer which concerns on Example 1 of this invention. It is a longitudinal cross-sectional view of the silicon wafer which shows the heat processing process of the manufacturing method of the epitaxial silicon wafer which concerns on Example 1 of this invention. It is a longitudinal cross-sectional view of the silicon wafer which shows the film-forming state of the epitaxial film of the manufacturing method of the epitaxial silicon wafer which concerns on Example 1 of this invention. It is a longitudinal cross-sectional view of the silicon wafer which shows the grinding | polishing process of the epitaxial film of the manufacturing method of the epitaxial silicon wafer which concerns on Example 1 of this invention. It is a longitudinal cross-sectional view of the silicon wafer used for the manufacturing method of the epitaxial silicon wafer which concerns on Example 2 of this invention. It is a longitudinal cross-sectional view of the silicon wafer which shows the altered layer formation process of the silicon wafer of the manufacturing method of the epitaxial silicon wafer which concerns on Example 2 of this invention. It is a longitudinal cross-sectional view of the silicon wafer which shows the deposition process of the manufacturing method of the epitaxial silicon wafer which concerns on Example 2 of this invention. It is a longitudinal cross-sectional view of the silicon wafer which shows the heat treatment process of the manufacturing method of the epitaxial silicon wafer which concerns on Example 2 of this invention. It is a longitudinal cross-sectional view of the silicon wafer which shows the film-forming state of the epitaxial film of the manufacturing method of the epitaxial silicon wafer which concerns on Example 2 of this invention. It is a longitudinal cross-sectional view of the silicon wafer which shows the grinding | polishing process of the manufacturing method of the epitaxial silicon wafer which concerns on Example 2 of this invention. It is a longitudinal cross-sectional view of the silicon wafer used for the manufacturing method of the epitaxial silicon wafer which concerns on Example 3 of this invention. It is a longitudinal cross-sectional view of the silicon wafer which shows the deteriorated layer formation process of the manufacturing method of the epitaxial silicon wafer which concerns on Example 3 of this invention. It is a longitudinal cross-sectional view of the silicon wafer which shows the heat processing process of the manufacturing method of the epitaxial silicon wafer which concerns on Example 3 of this invention. It is a longitudinal cross-sectional view of the silicon wafer which shows the film-forming state of the epitaxial film of the manufacturing method of the epitaxial silicon wafer which concerns on Example 3 of this invention. It is a longitudinal cross-sectional view of the silicon wafer which shows the grinding | polishing process of the manufacturing method of the epitaxial silicon wafer which concerns on Example 3 of this invention.

  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 1.3 × 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 2 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 the silicon wafer will be described with reference to the flow sheets of FIGS.
As shown in FIG. 1a, a silicon wafer 10 is first prepared by the manufacturing method described above.
Next, the silicon wafer 10 is adsorbed to the wafer holding plate of the single-wafer single-side grinding apparatus 20, and the surface of the silicon wafer 10 is ground with a # 800 cup-type resinoid grinding wheel 20a (FIG. 1b, grinding process). The grinding amount of the wafer surface layer at this time is 80 μm. As a result, a work-affected layer 10a having a processing damage of 11 μm in thickness is formed on the wafer surface layer.

Then, the ground silicon wafer 10 is inserted into a laser annealing furnace (pulse system) in a vacuum or in a helium gas atmosphere or an argon gas atmosphere. Here, the work-affected layer 10a is irradiated with Nd: YLY laser light (wavelength 527 nm) at an energy density of 4.5 J / cm ² (FIG. 1c, heat treatment step). As a result, the work-affected layer 10a is melted to form the molten silicon layer 11.
As described above, the work-affected layer 10a is a work damage layer having a light absorption coefficient that is one digit higher than that of single crystal silicon. Therefore, when a laser annealing furnace is used and excimer laser light (high energy light) is irradiated under the above-described conditions, the single crystal silicon wafer 10 having a lower absorption coefficient than the work-affected layer 10a does not melt, and only the work-affected layer 10a is melted. Melts.

  Thereafter, the molten silicon layer 11 is cooled and solidified, whereby only the work-affected layer 10a is transformed into a single crystal epitaxial film 12 (FIG. 1d). If the laser annealing furnace is used in this way, the work-affected layer 10a is melted before the single crystal silicon wafer 10 reaches the melting point. Thereafter, the molten silicon layer 11 is cooled and solidified. At the solid-liquid interface of the melted silicon (processed layer 10a), the crystallinity of the silicon wafer 10 that is a solid region is taken over, and an epitaxial film of single crystal silicon is obtained. 12 is grown.

That is, it is possible to perform epitaxial growth in a pseudo manner, and to eliminate the occurrence of slip of the silicon wafer accompanying the heating of the conventional (vapor phase) epitaxial growth. Moreover, even if void defects exist on the surface of the silicon wafer 11, the work-affected layer 10a is melted after grinding the wafer surface, so that the epitaxial film 12 having a high surface flatness can be obtained. As a result, it is possible to eliminate the decrease in the surface roughness of the epitaxial film 12 due to the void defect on the wafer surface.
Actually, in the grinding process, the surface of the silicon wafer was ground with three types of resinoid grinding wheels of # 170, # 325, and # 800. As a result of measurement using a scanning electron microscope, the thickness of the work-affected layer 10a obtained was 34 μm in the case of # 170, 26 μm in the case of # 325, and 11 μm in the case of # 800.

Next, the silicon wafer 10 is bonded to the lower surface of the polishing head of the single wafer type polishing apparatus via the carrier plate with the melted portion facing downward, and the wafer surface layer has a polishing amount of about 0.05 μm, for example. With chemical mechanical polishing. As a result, an epitaxial silicon wafer 30 is produced (FIG. 1e).
As a result, even if unevenness occurs on the silicon surface after laser irradiation, void defects and dislocation clusters can be eliminated at a lower temperature than in the case of single crystal silicon during melting, and the surface roughness of the wafer can be reduced. In addition, such an effect can be obtained in a low-power optical heating type annealing furnace as compared with a high-power optical heating type annealing furnace capable of melting single crystal silicon (melting point: 1412 ° C.). Therefore, the cost of the annealing furnace can be reduced and the life of the optical heating source can be extended.

Next, an epitaxial silicon wafer manufacturing method according to Embodiment 2 of the present invention will be described with reference to the flow sheets of FIGS.
The manufacturing method of the epitaxial silicon wafer of Example 2 is characterized by the following points. That is, a work-affected layer 10a is formed on the surface layer of the silicon wafer 10 (FIG. 2a) (FIG. 2b), and an amorphous silicon film 13 is deposited on the surface of the work-affected layer 10a by a CVD (chemical vapor deposition) method. (FIG. 2c, deposition process). Thereafter, the excimer laser light is irradiated to the amorphous silicon film 13 and the work-affected layer 10a, and these are melted to form a thick molten silicon layer 11A as compared with the case of Example 1 (FIG. 2d, heat treatment step). Next, the molten silicon layer 11A is cooled and solidified to transform the molten silicon layer 11A into a thick epitaxial film 12A (FIG. 2e). Then, the surface of the altered epitaxial film 12A is chemically and mechanically polished to produce an epitaxial silicon wafer 30A (FIG. 2f).

The amorphous silicon film 13 is deposited by placing the silicon wafer 10 on which the work-affected layer 10a is formed in a CVD furnace set to 200 to 400 ° C., using hydrogen gas as a base, silane gas, and if necessary. Diborolane gas is introduced to deposit an amorphous silicon film 13 of 2 μm.
A polycrystalline silicon film may be deposited instead of the amorphous silicon film 13. 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, a dopant may be added to the amorphous silicon film 13 in the deposition process, or the dopant may not be added, but the amorphous silicon film 13 may be added between the deposition process and the heat treatment process. The dopant may be ion-implanted from the surface. In this case, the following ion implantation process is performed.
First, the silicon wafer 10 with the amorphous silicon film 13 is inserted into a furnace of a medium current ion implantation apparatus, and a 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 13 in the heat treatment step.

Nd: irradiation conditions YLY laser light, wavelength 527 nm, at an energy density of 4.5 J / cm ^2, irradiating the entire surface of the silicon wafer 10. As a result, not only the amorphous silicon film 13 but also the work-affected layer 10a is melted at the same time, resulting in a thick molten silicon 11A. Thereafter, this is cooled and solidified to obtain a thick epitaxial film 12A.
Since it comprised in this way, even when the micro unevenness | corrugation resulting from the surface unevenness | corrugation of the work-affected layer 10a is transferred to the surface of the amorphous silicon film 13 just after deposition, the subsequent amorphous silicon film 13 and the work-affected layer 10a By melting, an epitaxial film 12A having a high surface flatness is obtained. In this way, the epitaxial silicon wafer 30A is manufactured.
Other configurations, operations, and effects are in a range that can be estimated from the first embodiment, and thus description thereof is omitted.

Next, with reference to the flow sheet of FIG. 3, the manufacturing method of the epitaxial silicon wafer which concerns on Example 3 of this invention is demonstrated.
The manufacturing method of the epitaxial silicon wafer according to the third embodiment is characterized by the following points. That is, a work-affected layer 10a is formed on the surface layer of the silicon wafer 10 (FIG. 3a) (FIG. 3b), and then the silicon wafer 10 is inserted into a flash lamp furnace. Next, the furnace temperature is raised to 1250 ° C., and heating is performed for a time on the millisecond level.

Thereby, the work-affected layer 10a becomes silicon 11B without melting (FIG. 3c). As a result, the silicon layer 11B without melting is single-crystallized by taking over the crystallinity including the crystal plane of the solid region with reference to the interface between the silicon wafer 10 and the silicon layer 11B without melting. Thereafter, the silicon wafer 10 is taken out of the furnace. Thereby, the silicon layer 11B without melting is transformed into the epitaxial film 12B (FIG. 3d). Then, the surface of the altered epitaxial film 12B is chemically mechanically polished to produce an epitaxial silicon wafer 30B (FIG. 3e).
Other configurations, operations, and effects are in a range that can be estimated from the first embodiment, and thus description thereof is omitted.

10 Silicon wafer,
10a Processed layer,
12, 12A, 12B epitaxial film,
13 Amorphous silicon film,
30, 30A, 30B Epitaxial silicon wafer.

Claims (7)

A modified layer forming step of grinding a surface of a silicon wafer made of single crystal silicon and forming a work-affected layer due to processing damage on a surface layer of the silicon wafer;
The work-affected layer is heated under a liquid phase epitaxy heat treatment condition involving melting by irradiation with high energy light or a solid phase epitaxy heat treatment condition without melting due to irradiation with high energy light, and then cooled. And a method of manufacturing an epitaxial silicon wafer comprising a heat treatment step for forming an epitaxial film made of single crystal silicon. Between the deteriorated layer forming step and the heat treatment step, dopant is ion-implanted into the processed damaged layer,
The method for manufacturing an epitaxial silicon wafer according to claim 1, wherein in the heat treatment step, the dopant is diffused into the melted work-affected layer. A modified layer forming step of grinding a surface of a silicon wafer made of single crystal silicon and forming a work-affected layer due to processing damage on a surface layer of the silicon wafer;
A deposition step of depositing an amorphous silicon film or a polycrystalline silicon film on the surface of the altered layer after the altered layer formation step;
After the deposition step, the amorphous silicon film or polycrystalline silicon film deposited on the work-affected layer and the work-affected layer are subjected to a heat treatment condition of liquid phase epitaxy accompanied by melting by irradiation with high energy light or high energy light. A method for producing an epitaxial silicon wafer, comprising: a heat treatment step of heating to an epitaxial film made of single crystal silicon by heating under a heat treatment condition of solid phase epitaxy without melting due to irradiation, and then cooling.   The method for producing an epitaxial silicon wafer according to claim 3, wherein a vapor phase growth method using a dopant gas is employed in the deposition step. During the period from the deposition step to the heat treatment step, dopant is ion-implanted into the amorphous silicon film or the polycrystalline silicon film,
5. The method of manufacturing an epitaxial silicon wafer according to claim 3, wherein, in the heat treatment step, the dopant is diffused into the melted amorphous silicon film or polycrystalline silicon film.   The method for manufacturing an epitaxial silicon wafer according to any one of claims 1 to 5, wherein the high energy light is laser light or lamp light.   The method for manufacturing an epitaxial silicon wafer according to claim 1, wherein the surface of the epitaxial film is polished after the heat treatment step.

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