JP4675749B2 - Epitaxial wafer manufacturing method - Google Patents

Description

  The present invention relates to a method for manufacturing an epitaxial wafer, and more particularly to a method for manufacturing an epitaxial wafer having a thick epitaxial layer excellent in flatness and resistivity uniformity.

  When manufacturing a semiconductor device, an epitaxial wafer in which a layer made of a silicon single crystal is formed on a silicon substrate (silicon wafer) may be used. When manufacturing such an epitaxial wafer, an epitaxial growth apparatus is used, for example, a chlorosilane-based source gas is supplied to grow a layer (epitaxial layer) made of a silicon single crystal on a silicon substrate. There are various types of epitaxial growth apparatuses such as a vertical type, a single wafer type, and a cylinder type. For example, when manufacturing a thick film epitaxial wafer for PMOS or IGBT, it is necessary to form a thick epitaxial layer, and therefore, a vertical epitaxial apparatus having relatively high productivity is mainly used.

When epitaxial growth is performed using a vertical epitaxial apparatus, the substrate is placed on a susceptor and an epitaxial layer is grown on the surface. However, the temperature on the back side of the substrate becomes high, the substrate is deformed into a concave shape, the outer peripheral part is lifted from the susceptor, and a monocrystalline or polycrystalline silicon layer grows on the outer peripheral part on the back side of the substrate. . In particular, when thick epitaxial growth is performed, a local bulge in the outer peripheral portion called a back surface crown occurs.
In the epitaxial wafer, the back surface of the substrate becomes the reference surface, such as when the wafer is ground or polished in addition to the stepper chuck in the device process, but the back surface crown deteriorates the flatness of the epitaxial wafer. In the lithography process, it causes a resolution failure near the outer periphery. In recent years, the miniaturization of elements has been advanced with the improvement in performance of devices. When microfabrication is performed using a stepper in a device process, the depth of focus becomes shallow, so that there is an increasing demand for improvement in flatness even for thick film epitaxial wafers.

Further, when manufacturing an epitaxial wafer for PMOS, IGBT or the like, a silicon substrate doped with boron or arsenic at a high concentration is used. When epitaxial growth is performed using a highly doped substrate, a dopant in the substrate once jumps out into the gas phase and is taken into the epitaxial layer again, so-called auto-doping (auto-doping) occurs. When autodoping occurs, the resistivity distribution of the epitaxial layer deteriorates. Therefore, it is common to form a SiO ₂ film as a film for preventing autodoping on the back surface of the silicon substrate before epitaxial growth. .
However, the silicon layer tends to grow thick in the vicinity of the boundary of the SiO ₂ film for preventing auto-doping on the back surface. Therefore, although it is disadvantageous for auto-doping, a method of widely removing a SiO ₂ film in a region from 2 mm to 5 mm from the outermost peripheral portion to suppress generation of a back crown is widely adopted.

As a method for reducing the adhesion of silicon on the back surface or chamfered portion of the substrate, a method of performing epitaxial growth at a low speed has been proposed (see Patent Document 1). By making the growth conditions diffusion-limited by slow growth so that the source gas is consumed on the surface side, formation of the back crown or the like can be suppressed.
However, even if the formation of the back crown can be suppressed to some extent by the slow growth, the reduction in productivity is inevitable. In addition, when the growth is performed at a low speed, there is a problem that a crown is easily generated on the outer peripheral portion on the surface side (epitaxial layer) of the substrate.
Although there is a method of suppressing the generation of the back surface crown to some extent by devising the shape of the susceptor, it is impossible to completely prevent the silicon from adhering to the back surface or chamfered portion of the substrate.

  On the other hand, as a method for improving flatness after epitaxial growth, after the epitaxial growth, the crown is temporarily removed by polishing the back surface of the substrate with the surface of the epitaxial layer as a reference surface, and then the epitaxial layer is ground or ground with the back surface as a reference surface. There is a method of improving flatness by polishing. However, after the epitaxial growth, in particular, when the crown is also formed in the epitaxial layer, there is a problem that an accurate reference plane cannot be obtained by the above method and high flatness cannot be obtained. Moreover, since the front and back surfaces are polished and time-consuming, there is a problem in terms of cost.

Further, in a thick film epitaxial wafer for IGBT and PMOS, strict management is required not only for the thickness of the epitaxial layer but also for the uniformity of resistivity.
As described above, the resistivity distribution is generally improved by preventing the dopant from diffusing outwardly with the SiO ₂ film formed on the back surface of the substrate. However, particularly when growing a thick epitaxial layer for IGBT or PMOS in a vertical epitaxial apparatus, in order to suppress the formation of the back surface crown, as described above, the SiO ₂ on the back surface in the outer region of about 2 mm to 5 mm from the outermost peripheral portion. It is necessary to remove the film. As a result, autodoping increases and the resistivity distribution in the wafer surface of the epitaxial layer deteriorates, resulting in a problem that strict standards cannot be satisfied.

JP-A-8-279470

  In view of the above problems, the present invention makes it possible to easily and inexpensively manufacture an epitaxial wafer having an epitaxial layer that is excellent in flatness and uniformity in resistivity even when a thick epitaxial layer is formed. It aims to provide a possible method.

According to the present invention, in a method of manufacturing an epitaxial wafer by growing an epitaxial layer on a silicon substrate, at least a silicon substrate having a silicon oxide film formed on the back surface is used, and an epitaxial layer made of silicon is formed on the surface of the substrate. A step of growing a layer, and rotating the silicon substrate using a spin etcher and supplying an etchant having a higher etching rate for silicon than the silicon oxide film to the back surface of the substrate, thereby growing the epitaxial layer method for manufacturing an epitaxial wafer which comprises a step of removing by etching a silicon layer formed on the back surface and the chamfered portion of the substrate during the Ru is provided.

  During the growth of the epitaxial layer, silicon adheres to the back surface and the chamfered portion of the silicon substrate to form a silicon layer. Using a spin etcher, etching is performed by supplying the above etching solution to the back surface of the substrate (see FIG. By performing spin etching, the silicon layer formed on the back surface and the chamfered portion of the substrate can be easily removed. The silicon oxide film formed in advance on the back surface of the substrate functions as an etch stop film, and also has an effect of preventing autodoping. Therefore, an epitaxial wafer having an epitaxial layer having excellent flatness and excellent uniformity of resistivity can be manufactured easily and at low cost.

In this case, the surface of the silicon substrate, but it may also be grown the epitaxial layer in the above 50μm thick.
When an epitaxial layer having a thickness of 50 μm or more is grown, the back surface crown tends to be large, but the back surface crown can be easily removed by using the spin etcher and the etching solution as described above. Therefore, a thick film epitaxial wafer having excellent flatness can be easily manufactured at low cost.

It said epitaxial layer, a vertical-type epitaxial device or single with-wafer epitaxial device has preferably be grown.
These epitaxial devices are excellent in productivity and can form an epitaxial layer with relatively high film thickness uniformity. On the other hand, even if a backside crown or the like is formed on the substrate, it can be easily removed by using a spin etcher and an etching solution as described above. Therefore, a thick film epitaxial wafer having excellent flatness can be manufactured with higher productivity.

Examples silicon substrate, the silicon oxide film is Ru can be used those which are formed in the inner region of from the outermost periphery portion of the substrate to 1 to 2 mm.
As described above, if the silicon oxide film is formed near the outermost periphery of the silicon substrate to be used, autodoping can be extremely effectively prevented even when a highly doped substrate is used. On the other hand, although the back surface crown becomes larger, there is no problem in the present invention because the back surface crown is removed by spin etching after epitaxial growth. Therefore, it is possible to easily and reliably manufacture a high quality epitaxial wafer having both resistivity distribution and flatness.

As the silicon oxide film on the back surface of the silicon substrate, Ru can be used film for preventing auto-doping when growing the epitaxial layer on the substrate.
When a highly doped silicon substrate is used, a silicon oxide film is formed on the back surface as a film for preventing autodoping, and this oxide film can be used as it is as a film for etching stop at the time of spin etching. Therefore, a high-quality thick film epitaxial wafer for PMOS or IGBT can be easily manufactured without causing an increase in cost.

As the silicon substrate, the silicon oxide film is Ru may be used those which are formed in a thickness of less than 2 [mu] m.
A silicon oxide film having a thickness of 2 μm or less can be easily formed. For example, if it has a thickness of 1 to 2 μm, it functions sufficiently as an etch stop film and an auto-dope film. .

Wherein the etching solution, Ru can be used as a main component hydrofluoric acid and nitric acid.
If the etching solution is mainly composed of hydrofluoric acid and nitric acid, the etching rate ratio with respect to silicon can be reliably higher than that of the silicon oxide film, and the back surface crown and the like can be reliably removed, while the silicon oxide film Etching of the formed part can be prevented.

Wherein the etching solution, have preferably be those ratio of the etch rate of silicon to the silicon oxide film in the temperature range of 20 ° C. to 40 ° C. has a more than 30-etching properties.
If spin etching is performed using an etching solution having such etching characteristics, the back crown and the like can be reliably removed in a short time. Further, since the selection ratio is high, the silicon oxide film as a mask is not completely etched.

After growing the epitaxial layer, prior to said etching, a step of covering the surface side of the silicon substrate with a resist, after the etching, Ru can also include a step of removing the resist.
If the front surface side (epitaxial layer) of the substrate is masked with a resist before etching, contamination of the epitaxial layer and generation of scratches can be reliably prevented when etching the back surface side using a spin etcher.

After the etching, as a reference surface to the back surface of the substrate, a step of polishing the epitaxial layer, or the Ru can also include the step of polishing the epitaxial layer after grinding.
Since the back surface crown is removed by etching using a spin etcher, the flatness of the epitaxial layer can be further enhanced by grinding or polishing the epitaxial layer with the back surface as a reference surface. Further, even if the epitaxial layer is contaminated or scratched during the etching by the spin etcher, the contamination or the like can be surely removed by grinding or polishing the epitaxial layer.

  According to the present invention, epitaxial growth is performed using a silicon substrate having a silicon oxide film formed on the back surface, and the silicon layer formed on the back surface and the chamfered portion of the substrate is more suitable for silicon than the silicon oxide film by using a spin etcher. Etching is removed by supplying an etching solution having a high etching rate. Since the silicon oxide film on the back side of the substrate can also be used as a silicon oxide film for preventing auto-doping, it prevents auto-doping during epitaxial growth and etch-stop film when etching away the back crown, etc. Also works.

  Therefore, when manufacturing a thick film epitaxial wafer for PMOS, IGBT, etc., for example, even when an epitaxial layer having a thickness exceeding 100 μm is grown, a thick film epitaxial wafer with excellent flatness and resistivity uniformity can be easily obtained. Can be manufactured. If such an epitaxial wafer is used, it is possible to prevent occurrence of poor resolution in the subsequent photolithography process.

Hereinafter, a case where an epitaxial wafer is manufactured using a silicon substrate (silicon wafer) by the method of the present invention will be specifically described with reference to the accompanying drawings.
FIG. 1 is a flowchart showing an example of a process for manufacturing an epitaxial wafer according to the present invention.

  First, as a substrate on which an epitaxial layer is grown, a silicon substrate having a silicon oxide film formed on the back surface is prepared (FIG. 1A). In order to obtain such a silicon substrate, as in the case of manufacturing a normal silicon wafer, for example, a silicon single crystal grown by the Czochralski method is sliced and then subjected to processing such as lapping, chamfering and etching. It should be noted that an ordinary polished wafer having one or both surfaces polished, or an etching wafer in which neither front or back surfaces are polished may be used. What kind of silicon substrate is used may be determined according to the standard.

Then, a silicon oxide film (SiO ₂ ) may be formed on the surface (back surface) opposite to the side on which the epitaxial layer of the silicon wafer is formed.
A method for forming the oxide film is not particularly limited, and a CVD method, a thermal oxidation method, or the like can be used. However, the CVD method is preferable because it can be formed at a low temperature and is simple and low cost.

  FIG. 2A schematically shows a silicon substrate having an oxide film formed on the back surface. The silicon oxide film 2 on the back surface of the substrate 1 functions as an etch stop when etching is performed by supplying an etchant to the back surface side using a spin etcher described later. However, when it is necessary to prevent autodoping during epitaxial growth, an autodope preventing film can also be used. For example, when epitaxial growth is performed using a heavily doped silicon substrate, a CVD oxide film is formed on the back surface of the substrate as an auto-dope prevention film. This CVD oxide film prevents auto-doping during epitaxial growth, and further functions as an etch stop film in etching using a spin etcher.

  In the case of a normal auto-doping-preventing oxide film, the oxide film is removed in advance in the region from 2 mm to 5 mm from the outermost peripheral portion in order to suppress the formation of the back surface crown during epitaxial growth. When the substrate 1 is particularly highly doped, it is preferable that a silicon oxide film is formed in an inner region from the outermost peripheral portion to 1 to 2 mm. Thus, if the silicon oxide film 2 is formed on the back surface of the substrate 1 up to the vicinity of the outermost periphery, autodoping can be more effectively prevented. On the other hand, even if the back crown grows large, there is no problem in the present invention because it can be easily removed by the spin etcher.

  Further, the thickness of the silicon oxide film on the back surface is not particularly limited, but can be easily formed if it is 2 μm or less. For example, if a silicon oxide film having a thickness of 0.2 to 2 μm is formed, it is used for etching stop. The film can be sufficiently functioned as an autodoping film, and further, it does not become thicker than necessary.

After preparing a silicon substrate with a silicon oxide film formed on the back surface, an epitaxial layer made of silicon is grown on the surface of the substrate (FIG. 1B).
Although the epitaxial growth apparatus used here is not specifically limited, For example, a vertical epitaxial apparatus can be used conveniently. The vertical epitaxial apparatus is excellent in productivity and can form an epitaxial layer with relatively high film thickness uniformity.
On the other hand, a single wafer type epitaxial apparatus may be used. The single wafer type apparatus can grow an epitaxial layer excellent in film thickness uniformity at high speed, and can easily cope with the case where epitaxial growth is performed on a large silicon substrate having a diameter of 200 mm or more (more preferably 300 mm or more). .
Of course, a cylinder type epitaxial growth apparatus can also be used.

  The thickness of the epitaxial layer to be grown is not particularly limited, but the present invention is particularly effective when growing a thick epitaxial layer of 50 μm or more. FIG. 2B schematically shows the substrate 1 after a thick epitaxial layer (for example, 50 μm or more) is grown using a vertical epitaxial apparatus. When the thick epitaxial layer 5 is grown on the surface of the substrate 1, silicon adheres to the back surface and the chamfered portion of the substrate 1, and the back surface crown 4 is easily formed particularly at the boundary with the oxide film 2 on the back surface. The height of the back surface crown 4 may reach about 2 μm to 20 μm although it depends on the growth conditions. In particular, when the growth is performed under diffusion-controlled conditions, the crown 3 is likely to be formed on the outer peripheral portion of the surface. Such crowns 3 and 4 on the front and back surfaces cause deterioration in flatness.

Therefore, in the present invention, in order to remove the silicon layer formed on the back surface and the chamfered portion of the substrate during the growth of the epitaxial layer after the epitaxial growth, etching using a spin etcher is performed (FIG. 1D).
FIG. 3 schematically shows etching using a spin etcher. The spin etcher 7 includes a nozzle 8 for supplying an etching solution 9, a vacuum suction table 10 that can rotate an axis, a cup 11 for collecting the etching solution after use, and the like.

  After the epitaxial growth, the spin etcher 7 is used to suck and hold the epitaxial layer side of the epitaxial wafer so that the center position of the wafer is aligned with the axis of the suction table 10. Then, the suction table 10 is rotated at a rotational speed of about 500 to 1000 rpm, and an etching solution (etchant) 9 is supplied from a nozzle 8 positioned substantially at the center of wafer rotation. Of course, the etching solution may be supplied directly to the periphery of the wafer.

  As the etchant 9, an etchant having a higher etching rate for silicon than the silicon oxide film is supplied. It is preferable that the etching rate ratio of silicon to the silicon oxide film is as large as possible, and that having an etching characteristic of 20 or more, in particular, the etching rate ratio of silicon to the silicon oxide film in the temperature range of 20 ° C. to 40 ° C. is 30 or more It is preferable. By having such a selection ratio, the back surface crown can be surely removed, and the oxide film serving as a mask is completely removed during etching, so that the back surface of the wafer is not etched.

  Specifically, an etchant mainly containing hydrofluoric acid and nitric acid can be preferably used. In particular, when the ratio of (backside silicon growth layer height) / (silicon oxide film thickness) ratio is less than 100, it is used in a state heated to 30 ° C. or higher in order to increase reaction efficiency and productivity. Is preferred. On the other hand, when the ratio is 100 or more, it is advantageous to use a hydrofluoric acid / nitric acid-based etchant at 30 ° C. or lower because the selectivity of the etching rate of silicon to the silicon oxide film is increased.

For example, the back crown can be easily removed by allowing an etching solution mainly composed of hydrofluoric acid and nitric acid to flow down at a flow rate of about 2 liters / minute. The etching solution 9 flows from the center toward the outer periphery on the back surface of the wafer, and is accelerated by the centrifugal force accompanying the rotation of the wafer as it goes toward the outer periphery. Therefore, even if the etching solution reaches the silicon layer formed in the chamfered portion on the outermost periphery of the wafer, it is recovered in the recovery cup 11 without going around the wafer surface. If air is supplied from the air supply means 12 provided on the suction table 10 to the outer peripheral portion of the wafer, it is possible to more reliably prevent the etching solution from flowing into the epitaxial layer.
By performing such spin etching, the back surface crown (back surface silicon growth layer) is removed by etching.

  After etching of the backside silicon growth layer proceeds and disappears, the lower silicon oxide film acts as an etch stop layer. Therefore, the etching stops or is greatly reduced, so that the silicon substrate itself can be prevented from being etched. By removing the backside crown in this way and preventing the original substrate itself from being etched by the backside silicon oxide film, a reference surface for performing polishing or the like to increase the flatness of the epitaxial layer as will be described later after etching. Can be secured.

In addition, as a method for removing the back surface crown and the like, for example, there is a method of immersing the wafer after epitaxial growth in an etching solution, but in this case, the surface side (epitaxial layer) is strictly masked with a wax or the like that can withstand high temperatures, and after etching The process becomes complicated, such as the need to remove wax and the like.
On the other hand, in the etching using the spin etcher 7, the back surface crown and the like can be easily and inexpensively removed by supplying the etching solution to the back surface side while rotating the wafer.

Note that before the etching using the spin etcher as described above, a step of covering the surface side of the substrate with a resist may be included (FIG. 1C).
After the epitaxial growth, the surface side (epitaxial layer side) of the substrate is covered with, for example, a photoresist. If the surface side of the substrate is coated with a resist, the epitaxial layer does not come into direct contact with the adsorption table 10 during spin etching, so that contamination of the epitaxial layer and generation of scratches can be reliably prevented. Further, even when a part of the etching solution circulates to the surface side during the etching by the spin etcher, the epitaxial layer can be prevented from being etched.

After the spin etching, pure water (rinse solution) is allowed to flow down from the nozzle 8 onto the wafer while the rotation of the suction table 10 is maintained. Note that cleaning may be performed by separately providing a nozzle for supplying pure water or the like. Next, the rinse liquid is shaken off and dried by the centrifugal force of air blow and wafer rotation.
When the epitaxial layer is covered with a resist before spin etching, the resist may be removed after etching using, for example, a suitable solvent (FIG. 1E).
Through the steps as described above, the flatness of the thick film epitaxial wafer can be improved by removing the silicon layer on the back surface and the chamfered portion such as the back surface crown generated during the epitaxial growth and regenerating the original reference surface.

Since the epitaxial wafer manufactured as described above has a high flatness on the back surface, the epitaxial layer is ground using the back surface as a reference surface (FIG. 1 (F)), and then further polished to further improve the flatness. (FIG. 1 (G)).
Depending on the thickness of the epitaxial layer that has been grown and the final thickness and flatness of the target epitaxial layer, the epitaxial layer side of the epitaxial wafer treated with the spin etcher is used, for example, with a # 2000 mesh wheel. By using surface grinding, the in-plane thickness of the epitaxial layer is made uniform by grinding with an allowance of 5 to 25 μm. After grinding, for example, polishing is performed with a machining allowance of 5 to 10 μm using a plate adhesion polishing apparatus. The flatness may be improved by polishing only the epitaxial layer without performing surface grinding.

  Epitaxial layer is ground and polished as necessary with the back surface of the epitaxial substrate masked with a silicon oxide film as a reference surface by removing the back surface crown by spin etching as described above, so that the thickness of the epitaxial layer is uniform. Property can be further improved. In this case, the crown on the surface side can also be removed. Further, in the present invention, the crown on the back surface is removed by etching, and the surface can be ground and polished on the basis of the original flat back surface, so that the surface can be finished with very high flatness. In the conventional method of grinding or polishing both the front and back surfaces, the first flat surface cannot be obtained due to the influence of the crown on the opposite side, and then the opposite surface is ground and polished. Even if the influence cannot be removed, the present invention can also solve such a problem.

In addition, when polishing an epitaxial layer, it is not necessary to mask the resist of the epitaxial layer before spin etching as described above. This is because even if the epitaxial layer is contaminated or scratched when adsorbed and held by the spin etcher, the contamination or the like can be removed by polishing the epitaxial layer thereafter.
After polishing, finish cleaning can provide an epitaxial wafer with a higher flatness having an epitaxial layer with a predetermined thickness.

Examples of the present invention will be described below.
(Example)
As a substrate for epitaxial growth, a boron-doped low-resistance silicon mirror wafer (diameter 200 mm) grown by the CZ method was prepared. A CVD silicon oxide film having a thickness of 0.5 μm was formed on the back surface of the substrate. However, the CVD silicon oxide film was removed in an outer region of 2 mm from the outermost peripheral portion of the substrate. Using this substrate, a 127 μm epitaxial layer was grown at a growth rate of 1.2 μm / min using SiHCl ₃ as a source gas in a vertical epitaxial apparatus (DC8600 manufactured by Hitachi Kokusai Electric). The temperature during growth was 1150 ° C.

  After the epitaxial growth, the shape of the outer periphery of the back surface was measured using a stylus type shape measuring instrument (SV-600 manufactured by Mitutoyo). FIG. 4A shows the step data of the outer periphery of the back surface. A step (back crown) of about 3 μm to 8 μm grew on the outer periphery of the back surface. The figure shows data at the orientation flat (orientation flat) position and the non-orientation position.

  A 30 ° C. hydrofluoric acid etchant (hydrofluoric acid: nitric acid: acetic acid: water = 15: 43: 5: 33) at a flow rate of 2 liters / minute while rotating the wafer at 700 rpm with a spin etcher on the back side of this epitaxial wafer Etching was performed for about 30 seconds. Thereby, silicon having a thickness of about 30 μm is etched in the exposed portion of silicon. In this etchant, the etching selectivity between silicon and the oxide film was 200 or more, and the silicon oxide film on the back surface remained after the etching.

FIG. 4B shows step data on the outer periphery of the back surface of the epitaxial wafer after the spin etching. It can be seen that the crown of the outer peripheral portion of the back surface is removed at both the orientation flat position and the non-orientation position, and the initial shape of the back surface of the substrate is substantially maintained in the portion masked with SiO ₂ .

  Next, the back side of the epitaxial wafer was affixed to a ceramic plate with wax, and the allowance was about 7 μm so that the epitaxial layer had a target thickness of 120 μm, and mechanochemical polishing was performed with a single-side polishing apparatus.

  The flatness (SFQRMax22 mm × 22 mm) of the epitaxial wafer immediately after epitaxial growth and after polishing through spin etching was measured using a capacitance type thickness measuring device ADE9500, and the change in flatness is shown in FIG. FIG. 5 shows that the flatness is greatly improved before and after polishing.

  The present invention is not limited to the above embodiment. The above embodiment is merely an example, and the present invention has the same configuration as that of the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.

  In the above embodiment, the case where epitaxial growth is mainly performed using a vertical epitaxial growth apparatus has been described. However, the size of the epitaxial growth apparatus and the silicon substrate to be used is not particularly limited, and for example, a silicon substrate having a diameter of 300 mm or more is used. The present invention can be applied even when epitaxial growth is performed using a single wafer epitaxial growth apparatus.

It is a flowchart which shows an example of the manufacturing process of the epitaxial wafer which concerns on this invention. It is the schematic which shows the silicon substrate before and behind the epitaxial growth used in this invention. (A) Before epitaxial growth (B) After epitaxial growth It is the schematic which shows the state etched using a spin etcher. It is a graph which shows the level | step difference of a back surface outer peripheral part. (A) After epitaxial growth (before spin etching) (b) After spin etching It is a graph which shows the change of the flatness of the epitaxial wafer immediately after epitaxial growth and after polishing through spin etching.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Silicon substrate, 2 ... Silicon oxide film, 3 ... Surface crown, 4 ... Back surface crown, 5 ... Epitaxial layer, 7 ... Spin etcher, 8 ... Nozzle, 9 ... Chemical solution (etchant), 10 ... Adsorption table, 11 ... Chemical solution Recovery cup, 12 ... air supply means.

Claims (9)

In a method of manufacturing an epitaxial wafer by growing an epitaxial layer on a silicon substrate, at least a step of using a silicon substrate having a silicon oxide film formed on the back surface and growing an epitaxial layer made of silicon on the surface of the substrate; The silicon substrate is rotated using a spin etcher, and an etching solution having a higher etching rate with respect to silicon than the silicon oxide film is supplied to the back surface of the substrate, whereby the epitaxial layer is grown. Etching and removing the silicon layer formed on the back surface and the chamfered portion, and after etching, polishing the epitaxial layer with the back surface of the substrate as a reference surface, or grinding the epitaxial layer including the step of polishing after Method for producing an epitaxial wafer characterized.   2. The method of manufacturing an epitaxial wafer according to claim 1, wherein the epitaxial layer is grown on the surface of the silicon substrate to a thickness of 50 [mu] m or more.   3. The method for manufacturing an epitaxial wafer according to claim 1, wherein the epitaxial layer is grown using a vertical epitaxial apparatus or a single wafer epitaxial apparatus.   4. The silicon substrate according to any one of claims 1 to 3, wherein the silicon oxide film is formed in an inner region of 1 to 2 mm from the outermost peripheral portion of the substrate. The manufacturing method of the epitaxial wafer of description.   5. The film according to claim 1, wherein a film for preventing autodoping when the epitaxial layer is grown on the substrate is used as the silicon oxide film on the back surface of the silicon substrate. The manufacturing method of the epitaxial wafer of description.   6. The method for producing an epitaxial wafer according to claim 1, wherein the silicon substrate has a thickness of 2 [mu] m or less.   The method for producing an epitaxial wafer according to any one of claims 1 to 6, wherein the etching solution is mainly composed of hydrofluoric acid and nitric acid.   8. The etching solution according to claim 1, wherein the etching solution has an etching characteristic in which a ratio of etching rate of silicon to the silicon oxide film in a temperature range of 20 ° C. to 40 ° C. is 30 or more. The method for producing an epitaxial wafer according to claim 1.   2. The method according to claim 1, further comprising: covering the surface side of the silicon substrate with a resist after growing the epitaxial layer and before performing the etching; and removing the resist after the etching. The manufacturing method of the epitaxial wafer as described in any one of thru | or 8.

Images