JP2007208145A - Semiconductor device manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor device manufacturing method which can effectively prevent breakage of a semiconductor wafer, and can favorably perform a semiconductor device manufacturing process. <P>SOLUTION: A circular notch is formed in an manner such that a blade 21 is abutted vertical to one main surface of a semiconductor wafer 11, and the blade 21 is rotated. Then the blade 21 is moved in the circumferential direction of the semiconductor wafer 11. The process for forming the circular notch is carried out several times, whereby, a reinforcement portion 11a having the thickness of semiconductor wafer 11 before grinding is formed on the semiconductor wafer 11. The reinforcement portion 11a functions as a reinforcement member when a semiconductor manufacturing process, such as process for transferring the semiconductor wafer 11, diffusion process, metal film forming process etc. is carried out. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a semiconductor device.

  Conventionally, a power semiconductor element such as a power transistor includes a semiconductor substrate on which a plurality of semiconductor regions are formed, and electrodes formed on both sides of the semiconductor substrate. With the improvement of the heat dissipation characteristics of the semiconductor element, in other words, with the further increase in power of the semiconductor element, an attempt has been made to form a semiconductor substrate thin also in the power semiconductor element.

  Conventionally, a power semiconductor device including a thin semiconductor substrate is manufactured by the following procedure (for example, Patent Document 1).

  First, a semiconductor wafer is prepared, and impurities are diffused on one main surface of the semiconductor wafer to form a plurality of semiconductor regions. Next, an annular wafer reinforcing member to which an adhesive tape is attached is prepared, and the wafer reinforcing member is attached to one main surface of the semiconductor wafer.

  Subsequently, with the wafer reinforcing member attached, the other main surface of the semiconductor wafer is ground to process the semiconductor wafer thinly. In the grinding process, the grinding wheel is brought into contact with the other main surface of the semiconductor wafer, and the grinding wheel is rotated at a high speed.

  Next, a metal film is vapor-deposited on the other main surface of the semiconductor wafer subjected to grinding to form a back electrode. Thereafter, the semiconductor wafer is divided to obtain a semiconductor element (semiconductor chip) having a thin semiconductor substrate.

According to this manufacturing method, since the thinned semiconductor wafer is supported by the reinforcing member, it is possible to prevent the semiconductor wafer from being damaged during various processes and substrate transport.
JP 2002-100589 A

  By the way, in the manufacturing method described above, an adhesive such as an adhesive tape is used to fix the reinforcing member to the semiconductor wafer. However, since the heat-resistant temperature of the adhesive is about 200 ° C., when the metal film is formed on the other main surface of the semiconductor wafer, components such as the adhesive volatilize, which may adversely affect the formation of the metal film. .

  Further, when impurity diffusion is performed on the other main surface of the thinned semiconductor wafer, the diffusion temperature of the impurity is as high as, for example, 800 ° C. to 1000 ° C. Therefore, such a diffusion step is performed with the reinforcing member attached. There is a problem that can not be.

  The present invention has been made in view of the above circumstances, and provides a method for manufacturing a semiconductor device that can satisfactorily prevent a semiconductor wafer from being damaged and that can be more satisfactorily subjected to a semiconductor manufacturing process such as an impurity diffusion process. The purpose is to provide.

In order to achieve the above object, a method of manufacturing a semiconductor device according to the first aspect of the present invention includes:
A grinding step of grinding the semiconductor wafer by bringing the blade perpendicularly into contact with one main surface of the semiconductor wafer and rotating the blade;
A grinding position adjusting step of adjusting a position where the blade is brought into contact with the semiconductor wafer and adjusting a grinding position;
In the grinding position adjusting step, the position of the blade is adjusted so that an outer peripheral edge portion of the semiconductor wafer is formed thicker than a central region of the semiconductor wafer.

  In the grinding position adjusting step, the blade may be moved in the circumferential direction of the semiconductor wafer, and the blade may be further moved in the radial direction of the semiconductor wafer.

  In the grinding position adjusting step, a wafer table on which the semiconductor wafer is placed may be rotated, and the blade may be moved in the radial direction of the semiconductor wafer.

  In the grinding position adjusting step, a wafer table on which the semiconductor wafer is placed may be rotated, and the wafer table may be moved in the radial direction of the semiconductor wafer.

  In the grinding position adjusting step, since the circular groove is formed, the position of the blade may be adjusted so that a plurality of grooves that are concentric with the semiconductor wafer are continuously formed.

  According to the present invention, by rotating the blade in the circumferential direction of the semiconductor wafer and further moving inward in the radial direction to grind the semiconductor wafer, the outer peripheral edge of the semiconductor wafer can be obtained without using an adhesive or the like. Since the reinforcing portion can be formed satisfactorily, it is possible to provide a method for manufacturing a semiconductor device that can prevent damage to the semiconductor wafer and can perform a semiconductor manufacturing process more satisfactorily.

  A method of manufacturing a semiconductor device according to each embodiment of the present invention will be described with reference to the drawings.

  First, a semiconductor wafer 11 having an area capable of obtaining a plurality of semiconductor devices and made of, for example, a silicon single crystal is prepared. As shown in FIG. 1A, the semiconductor wafer 11 includes an oriental flat, and the planar shape of the semiconductor wafer 11 is substantially circular. For example, the semiconductor wafer 11 has a thickness of 800 μm and a diameter of 200 mm (8 inches).

  A predetermined semiconductor region is formed by diffusing P-type impurities or N-type impurities on one main surface (the upper surface shown in FIG. 1B) of the semiconductor wafer 11 by a thermal diffusion method, an ion implantation method, or the like. Further, the metal film 12 is formed on one main surface of the semiconductor wafer 11 by using sputtering, vacuum deposition or the like. For example, taking a power transistor as an example, an emitter region, a base region, and the like are formed on one main surface of the semiconductor wafer 11, and the metal film 12 formed on one main surface of the wafer 11 includes, for example, an emitter electrode, A base electrode is configured.

  From these steps, a semiconductor wafer 11 having a plurality of semiconductor regions and an electrode film 12 formed on one main surface side is obtained as shown in FIG. In FIG. 1, the semiconductor region is not shown.

  Next, in order to grind the other main surface of the semiconductor wafer 11, for example, a dicer 40 shown in FIG. 2 is prepared. The dicer 40 shown in FIG. 2 includes a wafer table 30 that holds the semiconductor wafer 11 and a grinding mechanism 20 that is disposed at a predetermined interval with respect to the wafer table 30.

  The wafer table 30 has a disk-like planar shape, and is configured to hold the semiconductor wafer 11 by vacuum suction. The wafer table 30 is connected to a rotation drive mechanism (not shown) and is rotatable in the circumferential direction about the central axis (θ axis).

  The grinding mechanism 20 includes a blade (grinding blade) 21 connected to the spindle spindle 22, a spindle motor 23 that rotates the spindle spindle 22, a motor bracket 24 to which the spindle spindle 22 and the spindle motor 23 are fixed, and a motor bracket 24. A rotation mechanism (not shown) that rotates about the center axis (θ axis), the motor bracket 24 in the Z-axis direction (the Z1 axis direction separating from the main surface of the wafer table 30), and the main surface of the wafer table 30. A Z-axis moving carriage 25 that moves in the Z2 direction), a Z-axis moving mechanism 26 that moves the Z-axis moving carriage 25 in the Z-axis direction, and a Z-axis moving mechanism 26 that is fixed and moves on a rail (not shown). A Y-axis moving carriage 27 that moves in the Y-axis direction (Y1 direction parallel to the main surface of the wafer table 30 and Y2 direction); The has. The Y-axis moving carriage 27 moves in the Y1 direction and the Y2 direction by a Y-axis moving mechanism (not shown).

  Subsequently, the semiconductor wafer 11 is fixed on the wafer table 30 so that the center thereof is located on the central axis (θ axis), and the Z-axis moving carriage 25 is lowered, that is, moved in the Z2 direction to be close to the wafer table 30. Then, the blade 21 is brought into perpendicular contact with the upper surface of the semiconductor wafer 11 fixed on the wafer table 30. The blade 21 rotates at high speed around the central axis of the spindle spindle 22 by rotating the spindle spindle 22 by the spindle motor 23. Thus, for example, if the lower surface of the blade 21 is lowered from the surface of the semiconductor wafer 11 to about 3/4 of the thickness (in this embodiment, the thickness of the semiconductor wafer 11 is about 800 μm, and thus about 600 μm) and is ground, A groove having a depth of 600 μm can be formed on the main surface of the wafer 11. That is, the semiconductor wafer 11 that remains after grinding has a thickness of 200 μm.

  In the present embodiment, when the semiconductor wafer 11 is ground by the blade 21, the motor bracket 24 is rotated about the central axis (θ axis). As a result, as shown in FIG. 3A, the blade 21 moves concentrically with the semiconductor wafer 11 along the outer peripheral edge of the semiconductor wafer 11 along the dotted line in the arrow R direction. An annular groove (first annular groove) is formed on the main surface.

  Further, in the present embodiment, as shown in FIGS. 3A to 3C, since the grinding proceeds from the outer peripheral side of the semiconductor wafer 11 to the center side of the wafer, the outer region from the groove formed first is It remains as the reinforcing part 11a. Accordingly, the position at which the blade 21 is first brought into contact with the semiconductor wafer 11 is determined according to how wide the reinforcing portion 11a is formed. As will be described later, the reinforcing portion 11a functions as a reinforcing member in the diffusion process, the metal film forming process, and the like when the semiconductor wafer 11 is transferred.

  Next, the blade 21 is not moved in the Z-axis direction, and the Y-axis moving carriage 27 is moved to the center side of the semiconductor wafer 11 by the thickness of the blade 21 or a distance slightly smaller than the thickness, in the Y1 direction shown in FIG. Move. As a result, the blade 21 comes into contact with the main surface area of the semiconductor wafer 11 inside the first annular groove, and this area is ground in an annular shape. As a result, as shown in FIG. 3C, a second annular groove 50b continuous with the first annular groove 50a is formed.

  By repeating such a grinding process, a third annular groove continuous with the second annular groove, a fourth annular groove continuous with the third annular groove, and the like are sequentially formed on the main surface of the semiconductor wafer 11. An annular groove is formed, and a wide annular groove as shown in FIGS. 4A and 4B is formed.

  Finally, by moving the blade 21 to the center of the semiconductor wafer 11, the central side of the semiconductor wafer 11 becomes thinner than the peripheral region as shown in FIGS. 5A and 5B, and a circular groove is formed. The In this way, the reinforcing portion 11a and the element forming region 11b are formed on the semiconductor wafer 11.

  The element formation region 11b has a circular planar shape as shown in FIGS. 5A and 5B, and its thickness Tb is 200 μm. The element formation region 11b has a diameter of about 19 cm. Further, the reinforcing portion 11 a having the thickness of the semiconductor wafer 11 before being ground remains on the outer peripheral edge of the semiconductor wafer 11. The reinforcing portion 11a is formed in an annular shape as shown in FIG. The reinforcing portion 11a has a thickness Ta of, for example, 800 μm, and the reinforcing portion 11a has a width of about 5 mm. The reinforcing portion 11a functions so that the element forming region 11b is not damaged by various impacts applied to the semiconductor wafer 11 when the semiconductor wafer 11 is transferred, the impurity is diffused into the element forming region 11b, and the electrode forming step.

  Next, in order to form a semiconductor diffusion region on the other main surface of the semiconductor wafer 11, the semiconductor wafer 11 is transferred to an apparatus for performing a diffusion process. Subsequently, an impurity diffusion process is performed on the semiconductor wafer 11 in a state where the element forming region 11b of the semiconductor wafer 11 is reinforced by the reinforcing portion 11a. Thereby, a semiconductor region (for example, a collector region) is formed on the other main surface of the semiconductor wafer. Since impurity diffusion or the like is performed while being reinforced by the reinforcing portion 11a as described above, it is possible to prevent the element formation region 11b from being damaged.

  Subsequently, a metal electrode (for example, a collector electrode) is formed on the other main surface of the semiconductor wafer 11 by carrying it to an apparatus for forming an electrode and performing sputtering, vacuum deposition, or the like. Even when the electrodes are formed, the semiconductor wafer 11 is processed in a state in which the reinforcing portion 11a is formed. Therefore, it is possible to prevent the element formation region 11b from being damaged.

  As described above, a thin (200 μm) semiconductor wafer 11 in which a semiconductor region and an electrode are formed on both one main surface and the other main surface is obtained.

  Next, in order to divide the semiconductor wafer 11 to obtain a large number of semiconductor chips, the semiconductor wafer 11 is transferred to a known dicing apparatus.

When dicing the semiconductor wafer 11, a tape member is attached to one main surface of the semiconductor wafer 11, and the blade 21 is operated in a mesh pattern on the other main surface of the semiconductor wafer 11. Thus, the semiconductor wafer 11 is divided into a large number of semiconductor chips each having a square planar shape and having a semiconductor region and electrodes formed on one main surface and the other main surface.
A semiconductor device is manufactured from the above steps.

  As described above, according to the manufacturing method of the semiconductor device of the present embodiment, since the element forming region 11b is supported by the reinforcing portion 11a, the semiconductor wafer 11 is damaged in the transport, impurity diffusion process, electrode forming process, and the like. This can be prevented well.

  Further, since the reinforcing portion 11a is formed integrally with the semiconductor wafer 11, the reinforcing portion 11a has the same heat resistance as the element forming region 11b, and various semiconductor processes (impurity diffusion process, metal film forming process, etc.). It has heat resistance exceeding the processing temperature. Therefore, various semiconductor processes can be performed on the semiconductor wafer 11 in a state where the semiconductor wafer 11 is reinforced by the reinforcing portion 11a. Further, since the reinforcing portion 11 a is formed integrally with the semiconductor wafer 11, no adhesive or the like is required to attach the reinforcing member to the semiconductor wafer 11. For this reason, even if a high temperature heat treatment is performed, the components of the adhesive and the like are not volatilized and the metal film formation or the like is not adversely affected.

  Further, since the reinforcing portion 11a and the element formation region 11b are formed by grinding the semiconductor wafer 11 using the blade 21, for example, the thickness of the element formation region 11b is uniformly formed as compared with the case where etching is used. can do. For example, when forming an element formation region, a reinforcing portion, or the like using etching or the like, it is difficult to form the thickness of the element formation region uniformly in the surface direction. Further, in order to selectively etch a specific region, it is necessary to form a mask on the semiconductor wafer. However, when the mask is removed after forming the element formation region, the semiconductor wafer may be damaged. There is a problem.

  In the present embodiment, since the blade 21 is brought into contact with the main surface of the semiconductor wafer 11 perpendicularly and moved in an annular manner along the outer peripheral edge of the semiconductor wafer 11, the element formation region 11b is formed. The reinforcing portion 11a having a desired width can be formed satisfactorily, and the strength of the semiconductor wafer 11 can be obtained stably. On the other hand, for example, as shown in FIG. 6, the grinding wheel is brought into contact with the other main surface (surface to be ground) of the semiconductor wafer, and the grinding wheel is rotated at a high speed in the direction of arrow M1 shown in FIG. A method of rotating in the circumferential direction as indicated by arrow M2 along the periphery of the semiconductor wafer is also conceivable. However, in this method, since the reinforcing portion is formed when rotating in the direction of the arrow M2, the width of the reinforcing portion cannot be formed stably. If the width of the reinforcing portion cannot be stably formed, the strength of the semiconductor wafer 11 may be reduced.

The present invention is not limited to the above-described embodiments, and various modifications and applications are possible.
For example, in the above-described embodiment, the configuration in which the blade 21 is continuously moved in the Y1 direction without moving in the Z-axis direction has been described as an example. However, the present invention is not limited to this, and when the blade 21 is moved in the Y1 direction, the blade 21 is moved in the Z1 direction by the Z-axis moving carriage 25, the blade 21 is once separated from the main surface of the semiconductor wafer 11, and then again Z Grinding may be performed by moving the blade 21 in the Z2 direction by the axial movement carriage 25 and bringing the blade 21 into contact with the main surface of the semiconductor wafer.

  In the above-described embodiment, the case where grinding is performed from the outer peripheral edge side of the semiconductor wafer 11 toward the center has been described as an example. However, the present invention is not limited to this, and grinding may be performed from the center toward the outer peripheral edge side. .

  Further, in the above-described embodiment, the motor bracket 24 is rotated around the central axis (θ axis), the blade 21 is moved in the circumferential direction of the semiconductor wafer 11, grinding is performed to form an annular groove, and further the Y axis is moved. Although the configuration in which the blade 21 is moved in the radial direction of the semiconductor wafer 11 by the carriage 27 has been described as an example, the configuration is not limited thereto. For example, the configuration is such that the blade 21 is rotated without moving the blade 21 about the θ axis, the blade 21 is moved in the radial direction by the Y-axis moving carriage 24, the wafer table 30 is rotated, and the wafer table 30 is further moved. It is also possible to adopt a configuration that moves in the radial direction.

  In the embodiment described above, the semiconductor region and the electrode film are formed on one main surface of the semiconductor wafer 11, and then the reinforcing portion 11a is formed. However, after the reinforcing portion 11a is formed, the semiconductor region is formed on one main surface. An electrode film may be formed. Further, after forming the reinforcing portion 11 a, a semiconductor region may be formed on the other main surface of the semiconductor wafer 11, and a semiconductor region may be further formed on one main surface of the semiconductor wafer 11. Note that it is possible to arbitrarily set whether the semiconductor region and the electrode are formed on one or both of the main surface and the other main surface of the semiconductor wafer 11, and at which stage the reinforcing portion 11a is formed. It is possible to set arbitrarily.

  The present invention is particularly suitable for a method of manufacturing a power semiconductor device in which electrodes are formed on one main surface and the other main surface of a semiconductor substrate, but manufacturing a thin semiconductor device in which electrodes are formed only on one main surface of a semiconductor substrate. It can also be applied to the method.

  In the above-described embodiment, the case where 3/4 of the thickness of the semiconductor wafer is ground is taken as an example, but what depth is ground can be arbitrarily set. Moreover, although the case where the semiconductor wafer 11 consists of a silicon single crystal was mentioned as an example, it is not restricted to this.

(A) is a perspective view which shows the semiconductor wafer used with the manufacturing method of the semiconductor device which concerns on embodiment of this invention, (b) is sectional drawing. It is a figure which shows the grinding device used with the manufacturing method of the semiconductor device which concerns on embodiment of this invention. (A) is a perspective view which shows the manufacturing method of the semiconductor device which concerns on embodiment of this invention, (b) is sectional drawing. (C) is sectional drawing which shows the manufacturing method of the semiconductor device which concerns on embodiment of this invention. (A) is a perspective view which shows the manufacturing method of the semiconductor device which concerns on embodiment of this invention, (b) is sectional drawing. (A) is a perspective view which shows the manufacturing method of the semiconductor device which concerns on embodiment of this invention, (b) is sectional drawing. It is a figure which shows the other grinding method typically.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Semiconductor wafer 11a Reinforcement part 11b Element formation area 20 Grinding mechanism 21 Blade 22 Spindle spindle 23 Spindle motor 24 Motor bracket 25 Z axis moving carriage 26 Z axis moving mechanism 27 Y axis moving carriage 30 Wafer table 40 Dicer

Claims (5)

A grinding step of grinding the semiconductor wafer by bringing the blade perpendicularly into contact with one main surface of the semiconductor wafer and rotating the blade;
A grinding position adjusting step of adjusting a position where the blade is brought into contact with the semiconductor wafer and adjusting a grinding position;
In the grinding position adjusting step, the position of the blade is adjusted so that the outer peripheral edge portion of the semiconductor wafer is formed thicker than the central region of the semiconductor wafer. .   2. The method of manufacturing a semiconductor device according to claim 1, wherein in the grinding position adjusting step, the blade is moved in a circumferential direction of the semiconductor wafer, and further, the blade is moved in a radial direction of the semiconductor wafer.   2. The method of manufacturing a semiconductor device according to claim 1, wherein in the grinding position adjusting step, a wafer table on which the semiconductor wafer is placed is rotated, and the blade is further moved in the radial direction of the semiconductor wafer.   2. The method of manufacturing a semiconductor device according to claim 1, wherein, in the grinding position adjusting step, a wafer table on which the semiconductor wafer is placed is rotated, and the wafer table is further moved in a radial direction of the semiconductor wafer. .   5. The grinding position adjusting step includes adjusting the position of the blade so that a plurality of grooves concentric with the semiconductor wafer are continuously formed in order to form a circular groove. The method for manufacturing a semiconductor device according to any one of the above.

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