JP2006278523A - Wafer and its manufacturing method, and semiconductor substrate and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a wafer by which the characteristic of an epitaxial film formed on the surface of the wafer can be made uniform and appropriate. <P>SOLUTION: The method is used to manufacture a wafer 10 so that an epitaxial film is formed on its surface 11A. It includes a preparation step to prepare a wafer 15 whose front surface 15A and rear surface 15B are made flat; a convex-part formation step wherein a central convex 19 with a projecting central area is formed on the surface of the wafer prepared in the preparation step, and a peripheral convex 20 with a projecting peripheral area is formed on the rear surface thereof; and a grinding step wherein a pressure F is given to the front surface 18A and the rear surface 18B of the wafer 18 processed in the convex formation step, so as to cause any distortion in the wafer 18 and the front and rear surfaces are ground flat. The side of the front surface 11A has a convex bending shape, and when the wafer 10 is heated to form an epitaxial film on the front surface 11A, it is deformed and becomes flat. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a wafer for manufacturing a semiconductor substrate by forming a film on the surface, a manufacturing method thereof, and a semiconductor substrate and a manufacturing method thereof.

  Semiconductor elements such as LEDs (light emitting diodes) are manufactured by processing a semiconductor substrate, and the semiconductor substrate is manufactured by forming a film on the surface of a wafer. For example, a semiconductor substrate is manufactured by epitaxially growing gallium nitride on the surface of a GaAs wafer to form an epitaxial film, and the semiconductor substrate is processed to produce various light emitting elements such as LD (laser diode) and LED. A semiconductor element is manufactured (Patent Document 1).

When the epitaxial growth is performed, first, the front and back surfaces of the wafer are ground, and grinding marks on the front and back surfaces are removed to prepare a wafer having a flat shape and a mirror-finished surface. Next, the wafer 1 (shown by a broken line in FIG. 6) is placed on the susceptor 2 of the heating device, and the wafer 1 is heated from the back surface 1B side using the coil 3 of the heating device to bring the wafer 1 to a predetermined temperature. In this state, an epitaxial film is formed on the surface 1A of the wafer 1.
JP 2004-356609 A

  However, during the above heat treatment, the wafer 1 is heated on the back surface 1B side first, so that the thermal expansion of the back surface 1B is larger than that of the front surface 1A. Therefore, as shown by the solid line in FIG. It will warp in shape. For this reason, the temperature of the surface 1A of the wafer 1 becomes lower at the peripheral portion and becomes non-uniform, variation in epitaxial growth occurs, and the characteristics of the epitaxial film formed on the surface 1A become non-uniform.

  For example, when a semiconductor substrate is manufactured by performing epitaxial growth on the surface 1A of the wafer 1 using MOCVD technology and forming an epitaxial film having an LD structure, fogging occurs on the outer periphery of the surface of the semiconductor substrate, and the epitaxial film is formed. The characteristics are deteriorated, and the laser oscillation wavelength also shows a concentric distribution on the surface of the semiconductor substrate and becomes non-uniform in the plane.

SUMMARY OF THE INVENTION An object of the present invention is to provide a wafer and a method for manufacturing the same that can improve the characteristics of a film formed on the surface in a uniform and favorable manner.
Another object of the present invention is to provide a semiconductor substrate having uniform and good characteristics of a film formed on the surface of a wafer and a method for manufacturing the same.

  In a first configuration for solving the above-described problem, in a wafer having a surface on which a film is formed, the surface side opposite to the shape warped during the heat treatment for forming the film on the surface is convex. The wafer is characterized by being formed into a curved shape.

  A second configuration is the wafer according to the first configuration, wherein the film formed on the surface is a film formed by epitaxial growth.

  The third configuration is a wafer manufacturing method for manufacturing a wafer for forming a film on the front surface, and a preparation step for preparing a wafer having the front surface and the back surface formed on a flat surface, and the preparation step A convex portion forming step of forming a central convex portion protruding from the central region on the front surface of the prepared wafer and forming a peripheral convex portion protruding from the peripheral region on the back surface, and the above of the wafer having undergone the convex portion forming step, are described above. A wafer having a convex curved shape on the front surface side, wherein pressure is applied to the front surface and the back surface to cause distortion in the wafer, and in this state, the front surface and the back surface are ground. A method for manufacturing a wafer.

  A fourth configuration is a method for manufacturing a wafer according to the third configuration, wherein after the grinding step, a removal step of removing grinding traces on the front and back surfaces of the wafer is performed. It is a manufacturing method.

  A fifth configuration is the method for manufacturing a wafer according to the third or fourth configuration, wherein the sum of the protruding amount of the central convex portion on the front surface and the protruding amount of the peripheral convex portion on the back surface is formed. The method of manufacturing a wafer is characterized in that it is set to be approximately equal to the amount of warping of the curved shape.

  A sixth configuration is the method for manufacturing a wafer according to any one of the third to fifth configurations, wherein an outer diameter of the central convex portion on the front surface is smaller than an inner diameter of a peripheral convex portion on the rear surface, or The wafer manufacturing method is characterized by being set equal.

  A seventh configuration is a method for manufacturing a wafer according to any one of the third to sixth configurations, wherein the central convex portion and the peripheral convex portion are formed by an etching process. Is the method.

  The eighth configuration is a semiconductor substrate characterized in that a film is formed on the surface of the wafer described in the first or second configuration.

  A ninth configuration is the semiconductor substrate according to the eighth configuration, wherein the film is a film formed by epitaxial growth.

  According to a tenth configuration, a semiconductor substrate is manufactured by forming a film on a surface of a wafer obtained by the wafer manufacturing method according to any one of the third to seventh configurations. It is a manufacturing method.

  An eleventh configuration is the method for manufacturing a semiconductor substrate according to the tenth configuration, wherein the film formed on the surface of the wafer is a film formed by epitaxial growth. It is.

  According to the invention described in the first or second configuration, the wafer is configured in a curved shape convex to the surface side opposite to the shape warped during the heat treatment for forming a film on the surface, The wafer can be flattened during heat treatment for forming a film on the surface of the wafer. As a result, since the surface of the wafer becomes a uniform temperature during the heat treatment, the characteristics of the film formed on this surface can be made uniform and favorable on the surface.

  According to the invention described in any one of the third to seventh configurations, the central convex portion is formed on the front surface of the wafer and the peripheral convex portion is formed on the rear surface, and the wafer is distorted by applying pressure from the front surface and the rear surface. Since the surface and the back surface are subjected to surface grinding in the state where the above is generated, a curved wafer having a convex shape on the front surface side can be manufactured satisfactorily.

  According to the invention described in the eighth or ninth configuration, the wafer becomes flat during the heat treatment for forming the film, and the temperature of the surface of the wafer becomes uniform. The characteristics are uniform, and a semiconductor substrate with uniform quality can be manufactured over the entire surface.

  According to the invention described in the tenth or eleventh configuration, since the wafer becomes flat during the heat treatment for forming the film, the temperature of the surface of the wafer becomes uniform, and the film formed on the surface These characteristics can be made uniform and satisfactory, and as a result, a semiconductor substrate having uniform quality over the entire surface can be manufactured.

The best mode for carrying out the present invention will be described below with reference to the drawings.
FIG. 1 is a side view showing an embodiment of a wafer according to the present invention. FIG. 2 shows the wafer of FIG. 1, where (A) is a front view and (B) is a back view. 2A and 2B are contour lines indicating the curved structure of the wafer.

  As shown in FIGS. 1 and 2, a wafer 10 for manufacturing a semiconductor substrate (not shown) has a front surface 11A mirror-finished and a back surface 11B processed rough. A film is formed on the surface 11A of the wafer 10, for example, an epitaxial film is formed by epitaxial growth, and a semiconductor substrate is manufactured.

  Further, the wafer 10 is subjected to heat treatment to form an epitaxial film on the surface 11A. The wafer 10 has a shape opposite to the shape warped during the heat treatment, that is, a curved shape convex to the surface 11A side, as shown in FIG. As shown, the front surface 11A is formed as a convex curved surface, and the back surface 11B is formed as a concave curved surface. The warpage amount H of the wafer 10 is set corresponding to the warpage amount H0 (FIG. 6) when the flat wafer is subjected to the heat treatment. For example, the warpage amount H is set substantially equal to the warpage amount H0. The wafer 10 is configured to be flat during the heat treatment. Here, the warpage amount H of the wafer 10 is a distance between the apex P of the convex curved surface 11A and the bottom surface N of the concave curved back surface 11B. The warp amount H is set to a value of 5 to 20 μm, for example. The warpage amount H may be selected as appropriate so as to cancel the warpage of the wafer caused by the heating of the wafer in the film forming process described later.

  Therefore, when the wafer 10 is placed on the susceptor 13 of the heating device 12 shown in FIG. 3 to form an epitaxial film on the front surface 11A of the wafer 10, and the wafer 10 is heated from the back surface 11B side by the coil 14, The wafer 10 is deformed from the curved shape shown by the broken line in FIG. 3 to the flat shape shown by the solid line, and the entire surface of the surface 11A of the wafer 10 is heated to a uniform temperature. Therefore, when a semiconductor substrate having an LD structure is manufactured by forming an epitaxial film on the surface 11A of the wafer 10 using, for example, the MOCVD technique under the above heating condition, the characteristics of the epitaxial film are as follows. It becomes uniform over the entire surface. That is, no fogging occurs on the outer periphery of the epitaxial film in the semiconductor substrate, and the laser oscillation wavelength is uniform and good over the entire surface of the semiconductor substrate.

  Next, a manufacturing procedure for forming the wafer 10 in a curved shape convex toward the surface 11A as described above will be described with reference to FIG. This manufacturing procedure includes a preparation step shown in FIG. 4 (A), a protrusion forming step shown in FIGS. 4 (B) to 4 (D), a grinding step shown in FIG. 4 (E), and FIGS. (G) and the removal process. A wafer having a convex curved shape on the surface 11A side is then subjected to a polishing (or polishing) process, and a predetermined film is formed in the film forming process.

  First, in the preparation step, as shown in FIG. 4A, a wafer 15 is prepared by forming a front surface 15A and a back surface 15B on a flat surface of a thick wafer original plate sliced from an ingot.

  Next, in the convex portion forming step, first, as shown in FIGS. 4B and 5, a circular resist film 16 is applied to the central region of the front surface 15A of the wafer 15, and a ring shape is formed in the peripheral region of the back surface 15B. The resist film 17 is applied. Here, the present invention can be applied if the wafer 15 is 2 inches or more. For example, if the wafer 15 is a 3-inch wafer, the outer diameter D0 is D0 = 76 mm. The diameter d1 is set to 40 mm, for example, and the inner diameter d2 of the resist film 17 is set to 50 mm, for example. Then, the wafer 15 is etched using the resist films 16 and 17 as a mask (FIG. 4C), and then the resist films 16 and 17 are removed to form a central convex portion 19 on the surface 18A. The wafer 18 having the peripheral protrusion 20 formed on the back surface 18B is formed (FIG. 4D). The mask is not limited to a resist film, and a masking tape can also be used.

  In the wafer 18, the central protrusion 19 has a circular shape, and the outer diameter D <b> 1 is the same as the outer diameter d <b> 1 of the resist film 16. The peripheral convex portion 20 has a ring shape, and its inner diameter D2 is the same as the inner diameter d2 of the resist film 17. At this time, the outer diameter D1 of the central protrusion 19 is set to be smaller or equal to the inner diameter D2 of the peripheral protrusion 20. This is because the wafer 18 is easily deformed when a pressing force F acts on the wafer 18 from the front surface 18A and the back surface 18B in a grinding process described later.

  Further, the sum of the protrusion amount H1 of the central protrusion 19 and the protrusion amount H2 of the peripheral protrusion 20 is set to be approximately equal to the curvature amount H (FIG. 1) of the convex curve on the surface 11A side of the wafer 10 to be formed. Is done. Therefore, the sum of the protrusion amounts H1 and H2 is set to 5 to 20 μm. As described above, the front surface 18A and the back surface 18B of the wafer 18 are formed in a stepped shape by forming the central convex portion 19 and the peripheral convex portion 20, respectively.

  Next, in the grinding step, the wafer 18 on which the central convex portion 19 and the peripheral convex portion 20 are formed through the convex portion forming step is sandwiched between the upper and lower surface plates of the grinding apparatus, and the surface 18A of the wafer 18 is formed by these surface plates. And the pressing force F in the direction approaching each other acts on the back surface 18B. Since the front surface 18A and the back surface 18B of the wafer 18 are formed in a stepped shape, the wafer 18 is deformed and distorted by the action of the pressing force F. In this grinding step, the wafer 18 is subjected to surface grinding so that the front surface 18A and the back surface 18B become flat with the injected grinding liquid in a state in which the wafer 18 is distorted as described above. By this grinding process, the front surface 18A and the back surface 18B of the wafer 18 are ground for a total of 40 μm or more to form a thin and flat wafer 21 and the front surface 21A and the back surface 21B are roughened. This is because, if 20 μm is ground on one side, the thickness unevenness caused by slicing in the above-described preparation step and the slice damage layer can be removed.

  However, this grinding amount is appropriately changed and set according to the type of the wafer 10 to be formed. Further, in the grinding process, the front surface 18A and the back surface 18B are ground simultaneously by the grinding device. Note that a one-dot chain line in FIG. 4E shows an example of a grinding surface when the wafer 18 is surface ground.

  After the grinding step, a removal step is performed to remove grinding marks on the front surface 21A and the back surface 21B of the wafer 21 by, for example, an etching process. By carrying out this removal step, the flat wafer 21 is freed from distortion in the grinding step and transformed into a convex curved shape on the surface 11A side to become the wafer 10.

  After the removal process is completed, the surface 11A side is mirror-polished by mechanochemical polishing or the like in a polishing (or polishing) process, and then washed with an organic solvent, an alkaline aqueous solution, pure water, or the like, and further an etching solution After a very small amount of etching, etc., rinse with pure water and finish. In the finishing step, the above-described curved structure is maintained as it is.

  In the film formation process, the finished wafer 10 is carried into a heating device and heated, and a predetermined material is epitaxially grown on the surface 11A of the wafer 10 to form a film (epitaxial film), which becomes a semiconductor substrate. .

With the above configuration, the following effects (1) and (2) are achieved according to the above embodiment.
(1) Since the wafer 10 is formed in a curved shape that is convex to the surface 11A side, opposite to the shape that warps during heat treatment for forming an epitaxial film on the surface 11A, the surface 10A of the wafer 10 The wafer 10 can be planarized during the heat treatment for forming the epitaxial film. As a result, since the surface of the flat wafer 10 has a uniform temperature during the heat treatment, the characteristics of the epitaxial film formed on the surface 11A can be uniform and favorable on the surface 11A. Therefore, a semiconductor substrate with uniform quality can be manufactured over the entire surface.

  (2) A state in which the central convex portion 19 is formed on the front surface 18A of the wafer 18 and the peripheral convex portion 20 is formed on the back surface 18B, and the wafer 18 is distorted by applying the pressing force F from the front surface 18A and the back surface 18B. Thus, the front surface 18A and the back surface 18B are surface ground to form the wafer 21, and the wafer 10 is manufactured by removing the grinding marks on the front surface 21A and the back surface 21B of the wafer 21. The curved wafer 10 can be manufactured satisfactorily.

  As mentioned above, although this invention was demonstrated based on the said embodiment, this invention is not limited to this. For example, in the present embodiment, the case where the epitaxial film is formed on the surface 11A of the wafer 10 has been described. However, the present invention can be applied even when another film is formed.

Example 1
(Preparation process)
A GaAs ingot having an outer diameter of about 80 mm was used as a slice plate using a wire saw, and the slice plate was washed with a hydrocarbon-based organic solvent to obtain a crude GaAs wafer having a thickness of about 0.6 mm. A resist film was provided on the outside of the front surface of the rough GaAs wafer with a diameter of 40 mm and a back surface of 50 mm. Note that a photoresist made by Tokyo Ohka Co., Ltd. was used as the resist film, and was cured by heating on a hot plate for 1 minute.

(Projection forming process)
The rough GaAs wafer provided with the resist film was immersed in an etching solution to etch both the front and back surfaces. Etching of 8 μm was performed for both the front and back surfaces by etching for about 1 minute using 25 ° C. ammonia + hydrogen peroxide + pure water (1: 2: 4) as an etchant. After completion of the etching, cleaning was performed for 5 minutes in an ultrasonic cleaning tank filled with acetone to obtain a GaAs wafer having a central convex portion with a protrusion amount of 4 μm on the front surface and a peripheral convex portion with a protrusion amount of 4 μm on the back surface.

(Grinding process)
The GaAs wafer having the central convex portion and the peripheral convex portion was subjected to bevel grinding with an outer peripheral end surface grinder to obtain a GaAs wafer having an outer peripheral length of 76.0 mm. The GaAs wafer was placed on a glass surface plate of a double-side grinding machine, and an upper surface plate pressure of 2.0 kg / cm ² was applied while supplying an alumina grindstone and pure water to perform lapping on both sides. The grinding amount was 40 μm on both the front and back sides.

(Removal process)
The ground GaAs wafer was again immersed in the etching solution, and both the front and back surfaces were etched. Etching of about 10 μm is performed on both the front and back surfaces by etching for about 2 minutes using 17 ° C. ammonia + hydrogen peroxide + pure water (1: 8: 11) as an etching solution. Was removed.

(Polish (or polishing) process)
Adhesive (liquid wax) is provided on the backside of the GaAs wafer after re-etching, attached to an alumina ceramic plate with a flat ground surface, and then a hypochlorous acid aqueous solution and a porous polishing cloth are used with a single-side polishing machine After performing mechanochemical polishing with the above, it was washed with pure water for 1 minute and then blown with nitrogen. After this drying, the GaAs wafer was peeled off from the alumina ceramic plate. The peeled GaAs wafer was first dissolved and removed by washing with an organic solvent, washed with an alkaline aqueous solution, rinsed with pure water, and dried with IPA vapor.
The dried GaAs wafer is etched using a trace amount of ammonia + hydrogen peroxide + pure water (1: 1: 20) at 20 ° C., rinsed with pure water, spin-dried, and GaAs wafer. Got.
FIG. 7 (A) shows a photograph of the warped shape of the obtained GaAs wafer and a schematic diagram thereof. Shown in (B).
FIG. 7 (A). From (B), it was confirmed that the GaAs wafer according to Example 1 was a wafer having a convex curved structure on the surface side. In FIG. 7B, which is a schematic diagram of a warp shape of a GaAs wafer, OF. Is an orientation flat, IF is an index flat, and the described lines are contour lines every 2 μm.

(Film formation process)
When the wafer is placed on a susceptor of a heating device and heated from the back side in order to form an epitaxial film on the surface of the obtained GaAs, the wafer is deformed from a curved shape to a flat shape, and the wafer surface Is heated to a uniform temperature. For this reason, when an epitaxial film was formed using the MOCVD technique under the above heating condition and a semiconductor substrate having an LD structure was manufactured, the characteristics of the epitaxial film became uniform over the entire surface. Further, no fogging occurred on the outer periphery of the epitaxial film in the semiconductor substrate, and the laser oscillation wavelength was uniform and good over the entire surface of the semiconductor substrate.

(Example 2)
In the “projection forming step” described in Example 1, the same process as in Example 1 was performed, except that etching was performed for 2 minutes, and both the front and back surfaces were etched to 14 μm. A GaAs wafer was obtained. A warp shape photograph and a schematic diagram of the obtained GaAs wafer are shown in FIG. Shown in (B). FIG. From (B), it was confirmed that the GaAs wafer according to Example 2 was a wafer having a convex curved structure on the surface side. In FIG. 8B, which is a schematic view of the warp shape of a GaAs wafer, OF. , IF, and the indicated contour lines are the same as in Example 1.

(Comparative Example 1)
A GaAs wafer according to the related art is performed by performing the same process as in Example 1 except that masking, warp shape correction etching, and masking removal, which are the “convex part forming step” described in Example 1, are not performed. Got. A warp shape photograph and a schematic diagram of the obtained GaAs wafer are shown in FIG. Shown in (B). FIG. 9 (A). From (B), it was confirmed that the GaAs wafer which concerns on the comparative example 1 is a wafer which has a bowl-shaped curved structure. In FIG. 9B, which is a schematic diagram of a warp shape of a GaAs wafer, OF. , IF, and the indicated contour lines are the same as in Example 1.

  In the “film formation process”, when the wafer is placed on the susceptor of the heating device and heated from the back side to form an epitaxial film on the surface of the obtained GaAs, the wafer has a bowl-shaped curved structure. As a result, the outer periphery was deformed into a concave curved shape on the surface side rising from the center, and the surface of the wafer was heated to a non-uniform temperature. For this reason, when an epitaxial film is formed using the MOCVD technique under the above heating condition and a semiconductor substrate having an LD structure is manufactured, the characteristics of the epitaxial film are not uniform over the entire surface. Clouding occurred on the outer periphery of the epitaxial film on the substrate, and the laser oscillation wavelength was also different between the central portion and the peripheral portion of the semiconductor substrate.

1 is a side view showing an embodiment of a wafer according to the present invention. The wafer of FIG. 1 is shown, (A) is a front view, (B) is a back view. It is a side view which shows the condition when heat-processing in order to form an epitaxial film in the wafer of FIG. It is an operation | movement diagram which shows the manufacturing process which manufactures the wafer of FIG. FIG. 4B shows a coating state of the resist film, where FIG. 4A is a front view and FIG. 4B is a back view. It is a side view which shows the condition when heat-processing in order to form an epitaxial film in the conventional wafer. It is the curvature shape photograph (A) of the wafer which concerns on Example 1, and its schematic diagram (B). It is the curvature shape photograph (A) of the wafer which concerns on Example 2, and its schematic diagram (B). It is the curvature shape photograph (A) of the wafer which concerns on the comparative example 1, and its schematic diagram (B).

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Wafer 11A Front surface 11B Back surface 12 Heating device 19 Center convex part 20 Peripheral convex part H, H0 Warpage amount H1, H2 Protrusion amount D1 Outer diameter D2 Inner diameter

Claims (11)

In a wafer with a surface on which a film is formed,
A wafer characterized in that the surface side opposite to the shape warped during the heat treatment for forming the film on the surface is formed in a convex curved shape.   The wafer according to claim 1, wherein the film formed on the surface is a film formed by epitaxial growth. A wafer manufacturing method for manufacturing a wafer for forming a film on a surface,
A preparatory step of preparing a wafer in which the front and back surfaces are formed on a flat surface;
A convex portion forming step of forming a central convex portion protruding from the central region on the front surface of the wafer prepared in this preparation step, and forming a peripheral convex portion protruding from the peripheral region on the back surface;
A pressure step is applied to the front surface and the back surface of the wafer that has undergone the convex portion forming step to cause distortion in the wafer, and in this state, the surface and the back surface are ground to have a grinding step,
A method for producing a wafer, comprising producing a wafer having a convex curved shape on the surface side.   4. The method for manufacturing a wafer according to claim 3, wherein after the grinding step, a removing step for removing grinding marks on the front surface and the back surface of the wafer is performed.   The sum of the protruding amount of the central convex portion on the front surface and the protruding amount of the peripheral convex portion on the back surface is set to be approximately equal to the warped amount of the curved shape of the wafer to be formed. Wafer manufacturing method.   6. The wafer manufacturing method according to claim 3, wherein an outer diameter of the central convex portion on the front surface is set smaller than or equal to an inner diameter of a peripheral convex portion on the rear surface.   7. The wafer manufacturing method according to claim 3, wherein the central convex portion and the peripheral convex portion are formed by an etching process.   A semiconductor substrate comprising a film formed on the surface of the wafer according to claim 1.   The semiconductor substrate according to claim 8, wherein the film is a film formed by epitaxial growth.   A method for manufacturing a semiconductor substrate, comprising: forming a film on a surface of a wafer obtained by the method for manufacturing a wafer according to claim 3 to manufacture a semiconductor substrate.   The method of manufacturing a semiconductor substrate according to claim 10, wherein the film formed on the surface of the wafer is a film formed by epitaxial growth.