JP2009071044A - Semiconductor device, and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor device capable of restraining variation of the semiconductor device thickness in the semiconductor device having a convex part formed around and on the inner side of the outer periphery of the surface. <P>SOLUTION: The semiconductor device 100 includes a semiconductor layer 2, an emitter electrode 6 formed on the surface of the semiconductor layer 2, a first convex part 4 with the insulation property at least on the surface, formed around and on the inner side of the outer periphery of the surface of the semiconductor device 100, and a second convex part 8 formed in the inner side range of the first convex part 4. The first convex part 4 and the second convex part 8 have flat surfaces in the same plane. Since the second convex part 8 is disposed in the inner side range of the first convex part 4, distortion to the surface side of the inner side range of the first convex part 4 is restrained at the time of polishing the rear side of the semiconductor wafer. Thereby, a semiconductor device 100 having a small thickness variation after polishing the rear side is achieved. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a semiconductor device having a convex portion on the surface and a manufacturing method thereof. In particular, the present invention relates to a semiconductor device that includes a convex portion that goes around the outer periphery along the outer periphery and is thinned by polishing the back surface, and a manufacturing method thereof.

Semiconductor devices are being made thinner. For example, in a vertical FET (Field Effect Transistor) and a vertical IGBT (Insulated Gate Bipolar Transistor), it is necessary to polish and thin the semiconductor wafer in order to reduce loss.
In the step of polishing and thinning the semiconductor wafer, the back surface of the semiconductor wafer on which the surface structure of the semiconductor device is formed is polished.
Some semiconductor devices include a convex portion that goes around the inside of the outer periphery along the outer periphery of the surface of the semiconductor device. For example, in the case of an IGBT, a guard ring for securing a withstand voltage is formed in a range inside the outer periphery of the surface of the semiconductor device, and the surface is covered with an insulating film. The insulating film is formed thick to prevent charging. The thick insulating film forms a convex portion that goes around the inside of the outer periphery along the outer periphery of the surface of the semiconductor device.

  In the step of polishing the back surface of the semiconductor wafer, the back surface of the semiconductor wafer is polished with a grindstone while the surface of the semiconductor wafer is pressed against the support plate after the surface of the semiconductor wafer is protected with a protective tape. When the back surface of the semiconductor wafer is polished with a grindstone, the semiconductor wafer may be bent toward the front surface side.

  There has been proposed a back surface polishing method for suppressing polishing of the back surface in a state where the vicinity of the outer periphery of the semiconductor wafer is bent to the front surface side. In this method, an electrode group protruding from the surface of the semiconductor wafer is formed in the formation range of the semiconductor device group in the semiconductor wafer, whereas no electrode group is formed in the vicinity of the outer periphery of the semiconductor wafer. The dummy electrode is formed in the vicinity of the outer periphery of the semiconductor wafer, paying attention to the fact that polishing is performed in a state where the vicinity of the outer periphery of the semiconductor wafer is bent to the surface side. When backside polishing is performed by forming a dummy electrode in the vicinity of the outer periphery of the semiconductor wafer, it is possible to suppress polishing in a state where the vicinity of the outer periphery of the semiconductor wafer is bent to the front surface side. This backside polishing method is disclosed in Patent Document 1. By the back surface polishing method of Patent Document 1, it is possible to prevent the semiconductor wafer after polishing from becoming uneven in the vicinity of the outer periphery of the semiconductor wafer.

JP 2005-314002 A

  Compared to the size of a semiconductor wafer, the size of each semiconductor device is much smaller. Considering the unit of a semiconductor wafer having a large size, since the influence of the bending that occurs during polishing of the semiconductor wafer significantly affects the thickness of the semiconductor wafer after polishing, research for suppressing the occurrence of bending has been conducted. Technology has been developed. On the other hand, the size of each semiconductor device is remarkably small, and the influence of bending in each semiconductor device is ignored and has not been studied.

  As described above, the back surface of the semiconductor wafer on which the surface structure of the semiconductor device is formed is polished and thinned. Irregularities exist on the surface of the semiconductor wafer on which the surface structure is formed. For this reason, although the size of each semiconductor device is small, when observed accurately, when polishing the back surface of the region where the surface of the semiconductor wafer is a recess, the semiconductor wafer is bent to the surface side. Polish the back side. On the other hand, when the back surface of the region where the front surface is a convex portion is polished, the semiconductor wafer is polished without being bent. As a result, the thickness of the semiconductor wafer after polishing varies within the semiconductor device even though the influence of bending is small. The semiconductor wafer is thick in the region where the surface of the semiconductor wafer is concave, and the semiconductor wafer is thin in the region where the surface of the semiconductor wafer is convex.

The thinning of the semiconductor device is progressing, and the semiconductor wafer is easily bent to the front side when the back surface of the semiconductor wafer is polished. For this reason, it has been found that the thickness of the semiconductor wafer after polishing becomes uneven in the semiconductor device, which adversely affects the characteristics of the semiconductor device. For example, in the case of an IGBT, if there is a region where the thickness of the semiconductor wear is locally thin in the semiconductor device, a large current is concentrated there, and heat is likely to be generated. In the case of an IGBT, when heated, the gate threshold voltage decreases and an increasingly large current tends to flow. A positive feedback phenomenon that a large current flows and generates heat, which also causes a large current to flow, appears, and there is a possibility that the IGBT may be damaged by the large local heat generation. Since individual semiconductor devices are small in size, it has been found that there are cases where this is a problem, although it is not easily affected by the bending of the semiconductor wafer during polishing of the semiconductor wafer.
The present invention was created in order to recognize and solve the above-described problems.

The semiconductor device created by the present invention has a structure in which the semiconductor wafer is not easily bent during back surface polishing. The semiconductor device includes a first convex portion that makes a round along the outer periphery of the surface of the semiconductor device, and a second convex portion that is disposed in an inner range of the first convex portion of the surface of the semiconductor device. I have. The first and second protrusions have a flat surface and the surfaces are in the same plane.
Although this semiconductor device is small compared to a semiconductor wafer, it is difficult to bend at the time of back surface polishing. When polishing the back surface in the inner range, the semiconductor wafer bends to the front surface side. In order to cope with this semiconductor device, the second convex portion is arranged in a range inside the convex portion that goes around the outer peripheral portion of the surface of the semiconductor device. Since the 2nd convex part is arranged, it can polish in the state where the inner side range of the convex part which makes a round of an outer peripheral part bent to the surface side was controlled at the time of back surface grinding of a semiconductor wafer. A semiconductor device in which the variation of the thickness of the semiconductor wafer in the semiconductor device is small can be realized.

The present invention is particularly suitable for a semiconductor device in which the surface of the termination region of the semiconductor device is covered with a thick insulating film. In this case, the first convex portion is formed by an insulating material covering the surface of the termination region of the semiconductor device. In this type of semiconductor device, the surface electrode often extends in the inner area of the first protrusion on the surface of the semiconductor device. In this case, it is preferable that the second convex portion is formed of a conductive material and is electrically connected to the surface electrode.
In this case, the second convex portion not only suppresses the inner area of the first convex portion from being bent toward the front surface when polishing the back surface of the semiconductor wafer, but also functions as a part of the electrode. When the semiconductor device is fixed with solder or the like, the contact area with the solder can be increased, which contributes to lowering the contact resistance. It also contributes to improving the mechanical joint strength. Furthermore, the heat dissipation capability of the semiconductor device is also improved.

The present invention also provides a method of manufacturing a semiconductor device. The method of manufacturing a semiconductor device created in the present invention includes a first convex portion that goes around the inside of the outer periphery along the outer periphery of each section (a semiconductor device is manufactured in each section) obtained by dividing the wafer surface into a plurality of sections. A step of forming the second convex portion in the inner range of the first convex portion on the surface of the wafer, and affixing a protective tape to the surface of the semiconductor wafer on which the first convex portion and the second convex portion are formed And a step of polishing the back surface of the semiconductor wafer having a protective tape attached to the front surface. In the above, the first convex portion and the second convex portion are formed so that the surfaces are flat and the surfaces are in the same plane. The order of forming the first convex portion and the second convex portion is not particularly limited. The first convex portion may be formed after the second convex portion is formed, or vice versa.
According to the above method, in order to polish the back surface of the semiconductor wafer in a state where the second convex portion is disposed in the inner range of the first convex portion that makes a round along the outer periphery, the inner range of the first convex portion is It can grind | polish in the state which suppressed bending to the surface side. A semiconductor device having a small variation in the thickness of the semiconductor wafer in the semiconductor device can be manufactured.

In this manufacturing method, the back surface structure of the semiconductor device may be formed after the back surface polishing. For example, when manufacturing an IGBT, an impurity may be injected from the back surface after the back surface polishing, followed by heat treatment to form a diffusion region, or a collector electrode or the like may be formed.
In this manufacturing method, after the back surface structure is formed, the semiconductor wafer may be diced into individual semiconductor devices.
These steps are not directly related to manufacturing a semiconductor device in which the variation in the thickness of the semiconductor wafer in the semiconductor device is small.

In the step of forming the second convex portion, it is preferable to form the second convex portion so that the interval between the convex portion and the convex portion is smaller than the width of the grindstone used for back surface polishing.
In this case, the phenomenon that the semiconductor wafer bends to the front side when the back surface of the semiconductor wafer is polished is significantly suppressed. A semiconductor device in which the variation of the thickness of the semiconductor wafer in the semiconductor device is extremely small can be manufactured.

According to the present invention, it is possible to suppress the fluctuation of the thickness of the semiconductor device in the semiconductor device including the convex portion that goes around the outer periphery along the outer periphery of the surface. A semiconductor device having uniform characteristics in the semiconductor device can be realized. If the characteristics change non-uniformly in the semiconductor device, a local characteristic degradation portion exists, which degrades the overall quality of the semiconductor device. According to the present invention, a semiconductor device with high overall quality can be realized.
In particular, when the second convex portion is formed of a conductive material, the surface area of the electrode can be increased, and the heat dissipation capability of the semiconductor device can be improved.

Preferred features of the embodiments described below are listed.
(First Feature) The semiconductor device is a rectangular parallelepiped IGBT. A guard ring for securing a withstand voltage is formed in a range inside the outer periphery of the surface, and the surface of the termination region where the guard ring is formed is covered with an insulating film. A metal electrode film is formed on the surface of the semiconductor device in a range inside the insulating film that circulates along the outer periphery of the surface. At least the outermost surface of the metal electrode film is made of aluminum, and the second convex portion is also made of aluminum.
(2nd characteristic) The several 2nd convex part is disperse | distributed and arrange | positioned in the inner side range of the convex part which goes around the outer peripheral part.
(3rd characteristic) The 2nd convex part extended long is arrange | positioned in the inner side range of the convex part which goes around the outer peripheral part.

(First embodiment)
FIG. 1 is a sectional view showing the vicinity of the surface of a semiconductor device 100 according to the first embodiment of the present invention. The semiconductor device 100 is an IGBT. The semiconductor device 100 circulates inside the outer periphery along the outer periphery of the surface of the semiconductor device 100 and the emitter electrode 6 formed on the surface of the semiconductor layer 2, and at least the surface is insulative. The first convex portion 4 and the metal second convex portion 8 formed in the inner range of the first convex portion 4 are provided. The surface of the 1st convex part 4 and the 2nd convex part 8 is flat, and the surface exists in the same plane. Although not shown, a back surface structure such as a collector electrode is formed on the back surface of the semiconductor device 100. In addition, although not shown, an internal structure of an IGBT composed of an emitter region, a body region, a drift region, a collector region, and the like is formed in the semiconductor layer 2, and is along the outer periphery of the surface of the semiconductor layer 2. A guard ring that makes a round of the inner periphery is formed. The 1st convex part 4 has covered the surface of the termination | terminus area | region in which the guard ring is formed. The 1st convex part 4 functions also as an antistatic film.

FIG. 2 is a perspective view of the semiconductor device 100. FIG. 1 is a cross-sectional view taken along the line II of FIG. A gate wiring extends inside reference numeral 10. The gate wiring is covered with an insulating protective film 10, and the protective film 10 is continuous with the first convex portion 4. In the semiconductor device 100, four blocks of IGBT are arranged. It can be said that the semiconductor device is completed for each block.
The surfaces of the protective film 10 and the first convex portion 4 are flat and are aligned in the same plane. The protective film 10 and the first convex part 4 make a round of the inner periphery along the outer periphery of each of the IGBTs divided into four blocks. It can also be said that the protective film 10 is a part of a convex portion that goes around the inside of the outer periphery along the outer periphery of each block.
If the second convex portion 8 does not exist, the semiconductor wafer bends to the front surface side every four regions surrounded by the convex portions 4 and 10 that make a round during back surface polishing. Since the 2nd convex part 8 is arrange | positioned, it is preventing that the semiconductor layer 2 bends to the surface side at the time of back surface grinding | polishing.
Reference numeral L1 indicates the maximum distance between the first convex part 4 and the second convex part 8, and reference numeral L2 indicates the distance between the second convex part 8 and the second convex part 8.

FIG. 3 shows a cross-sectional view of the semiconductor device 100 of the present invention in the back surface polishing step. As shown in FIG. 3, the semiconductor device 100 is manufactured in each section obtained by dividing the surface of the semiconductor wafer 50 into a plurality of parts. That is, the 1st convex part 4 which makes a round of the inner periphery of the outer periphery along the outer periphery of each division which divided | segmented the surface of the semiconductor wafer 50 into several divisions is formed. Further, the second convex portion 8 is also formed in the inner range of the first convex portion 4 on the surface of the semiconductor wafer 50.
In the back surface polishing step, the semiconductor wafer 50 on which the plurality of semiconductor devices 100 are formed is turned upside down, and the surface of the semiconductor wafer 50 is fixed on the support plate 14. Although not shown, a protective tape for protecting the surface structure of the semiconductor device 100 is attached to the surface of the semiconductor wafer 50. Next, the back surface of the semiconductor wafer 50 fixed on the support plate 14 is polished using the grindstone 12. When the back surface of the semiconductor wafer 50 is polished using the grindstone 12, a force that presses the semiconductor wafer 50 against the support plate 14 acts on the semiconductor wafer 50.
The distance L1 between the first convex part 4 and the second convex part 8 and the distance L2 between the second convex part 8 and the second convex part 8 are all equal to or smaller than the width L3 of the grindstone 12. Therefore, even when the back surface of the region where the surface of the semiconductor device 100 is a concave portion is polished, the semiconductor device wafer 50 does not bend to the front surface side. The semiconductor device wafer 50 is polished to a uniform thickness.

4 (1) to 4 (4) show an example of a method for manufacturing the semiconductor device 100. FIG.
As shown in FIG. 4A, a semiconductor wafer 50 in which the surface structure of the semiconductor device 100 is completed is prepared in each section obtained by dividing the surface of the semiconductor wafer 50 into a plurality of parts. At this stage, an emitter electrode (surface electrode) 6 is formed on the surface of the semiconductor layer 2 in each section. Moreover, the 1st convex part 4 which goes around the inner periphery of the outer periphery along the outer periphery of the surface of the semiconductor layer 2 is also formed. The 1st convex part 4 should just be the insulating surface, may be insulated to the inside, and the inside may be electroconductive. The 1st convex part 4 is formed so that the surface may become flat.
Next, as shown in FIG. 4 (2), the metal second convex portion 8 is formed in the inner range of the first convex portion 4. The second convex portions 8 can be formed with an arbitrary width and number in the inner range of the first convex portion 4. The second convex portion 8 is formed so that the surface is flat and the surface is in the same plane as the first convex portion 4.
Here, the term “in the same plane” includes that the second convex portion 8 is compressed during polishing and the surface of the first convex portion 4 and the surface of the second convex portion 8 are in the same plane. This is because, depending on the material of the second protrusion 8 and the force with which the semiconductor wafer 50 is pressed during polishing, the second protrusion 8 may be compressed during polishing and the height of the surface may be lowered. Therefore, the height of the second convex portion 8 may be slightly higher than the height of the first convex portion 4 in anticipation of the compression of the second convex portion 8 during polishing.
Next, as shown in FIG. 4 (3), the protective tape 16 is affixed to the surface of the semiconductor wafer 50 on which the first protrusions 4 and the second protrusions 8 are formed. The protective tape 16 protects the surface structure so as not to be damaged when the back surface is polished.
Next, as shown in FIG. 4 (4), the back surface of the semiconductor wafer 50 is polished and thinned. The back surface polishing step is performed by the method shown in FIG. After the back surface polishing, the back surface structure of the semiconductor device 100 is formed. Thereafter, the semiconductor wafer 50 is diced and cut into individual semiconductor devices 100 to manufacture the semiconductor device 100.

(Second embodiment)
FIG. 5 shows a top view of the semiconductor device 200 according to the second embodiment of the present invention. FIG. 6 is a cross-sectional view of the vicinity of the surface in the VI-VI cross section of FIG.
In the semiconductor device 200, the second convex portion 8 is formed continuously in the VI-VI cross-sectional direction. When the second convex portion 8 is formed in this manner, the width of the concave portion is smaller than that of the semiconductor device 100, so that the effect of suppressing the bending during back surface polishing is great.
5, the vertical width L5 of the semiconductor device 200 is 9.4 mm, the horizontal width L7 is 13 mm, the vertical width L4 of the concave portion is 6.3 mm, the horizontal width L6 of the concave portion is 1.5 mm, and the horizontal width of the second convex portion. L8 is formed to be 1 mm.

(Third embodiment)
FIG. 7 shows a top view of a semiconductor device 300 according to the third embodiment of the present invention. FIG. 8 is a cross-sectional view of the vicinity of the surface in the VIII-VIII cross section of FIG.
In the semiconductor device 300, a plurality of second convex portions 8 are formed in the VIII-VIII cross-sectional direction. When the second convex portion 8 is formed in this way, the surface area of the second convex portion 8 is larger than that of the semiconductor device 100, so that the contact resistance can be further reduced. Further, the mechanical bonding strength can be improved. The heat dissipation capability of the semiconductor device 300 can be further improved.

(Fourth embodiment)
FIG. 9 shows a top view of a semiconductor device 400 according to the fourth embodiment of the present invention. FIG. 10 is a cross-sectional view of the vicinity of the surface in the XX cross section of FIG.
In the semiconductor device 400, the second convex portion 8 is formed in the entire concave portion inside the first convex portion 4. When the second convex portion 8 is formed in this way, there is no concave portion on the surface, so that bending during back surface polishing is less likely to occur. Fluctuations in the thickness of the semiconductor device 400 after the back surface polishing can be greatly suppressed.

  In the semiconductor device of the present invention, it is preferable that at least the outermost surface of the metal electrode film formed on the surface of the semiconductor device is formed of aluminum, and the second convex portion 8 is also formed of aluminum. Aluminum is a soft metal and has high shock absorption. The 2nd convex part 8 can also be utilized as a buffer material at the time of wire bonding.

As mentioned above, although the Example of this invention was described in detail, these are only illustrations and do not limit a claim. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.
For example, although IGBT was described in the embodiment, other semiconductor devices may be used.
The technical elements described in this specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology exemplified in this specification or the drawings can achieve a plurality of objects at the same time, and has technical usefulness by achieving one of the objects.

1 is a cross-sectional view of the vicinity of a surface of a semiconductor device 100 according to a first embodiment of the present invention. 1 is a perspective view of a semiconductor device 100. FIG. FIG. 3 shows a cross-sectional view of a back surface polishing process of the semiconductor device 100. (1) to (4) show a method for manufacturing the semiconductor device 100. The top view of the semiconductor device 200 which is 2nd Example of this invention is shown. A cross-sectional view of the vicinity of the surface of the semiconductor device 200 is shown. The top view of the semiconductor device 300 which is 3rd Example of this invention is shown. A cross-sectional view of the vicinity of the surface of the semiconductor device 300 is shown. The top view of the semiconductor device 400 which is 4th Example of this invention is shown. A cross-sectional view of the vicinity of the surface of the semiconductor device 400 is shown.

Explanation of symbols

2: Semiconductor layer 4: First convex portion 6: Emitter electrode 8: Second convex portion 10: Protective film 12: Grinding wheel 14: Support plate 16: Protective tape 50: Semiconductor wafers 100, 200, 300, 400: Semiconductor device L1 : Distance L2 between the first and second protrusions of the semiconductor device 100: Distance L3 between the second and second protrusions of the semiconductor device 100: Wheel width L4: Vertical width L5 of the semiconductor device 200: Semiconductor device 200 width L6: vertical width L7 of the concave portion of the semiconductor device 200: horizontal width L8 of the concave portion of the semiconductor device 200: horizontal width of the second convex portion of the semiconductor device 200

Claims (4)

A first convex portion that makes a circuit around the inside of the outer periphery along the outer periphery of the surface of the semiconductor device;
A second convex portion disposed in an inner range of the first convex portion on the surface of the semiconductor device;
The semiconductor device, wherein the first and second protrusions have flat surfaces and the surfaces are in the same plane. The first protrusion is formed of an insulating material covering the surface of the termination region of the semiconductor device;
The surface electrode extends in the inner area of the first convex portion on the surface of the semiconductor device,
2. The semiconductor device according to claim 1, wherein the second convex portion is formed of a conductive material and is electrically connected to the surface electrode. A method of manufacturing the semiconductor device according to claim 1,
Forming a first protrusion that circulates around the inside of the outer circumference along the outer circumference of each section obtained by dividing the surface of the semiconductor wafer into a plurality of sections;
Forming a second protrusion in the inner area of the first protrusion on the surface of the semiconductor wafer;
Applying a protective tape to the surface of the semiconductor wafer on which the first and second protrusions are formed;
It comprises a step of polishing the back surface of a semiconductor wafer with a protective tape attached to the surface,
The method of manufacturing a semiconductor device, wherein the first protrusion and the second protrusion are formed so that the surfaces are flat and the surfaces are in the same plane.   4. The semiconductor device according to claim 3, wherein, in the step of forming the second convex portion, the second convex portion is formed so that the interval between the convex portion and the convex portion is smaller than the width of the grindstone used for back surface polishing. Manufacturing method.

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