JP2013131569A - Semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inhibit characteristic variation of a semiconductor device having a field plate.SOLUTION: A semiconductor device comprises a field plate including: a first insulation film formed on a surface of a semiconductor substrate; a plurality of first electrodes formed on the first insulation film and arranged at intervals from an inner side to an outer side of the semiconductor substrate in a planar direction; a second insulation film covering lateral faces and surfaces of the plurality of first electrodes and having groove-like parts among the plurality of first electrodes; and second electrodes contacting internal surfaces of the groove-like parts of the second insulation film. An electrode width of the first electrode varies in a depth direction of the semiconductor substrate and a part of the first electrode overlaps at least a part of the neighboring second electrodes via the second insulation film.

Description

  The present invention relates to a semiconductor device.

  In order to improve the breakdown voltage of the semiconductor device, a field plate may be formed on the surface of the non-cell region at the periphery of the semiconductor substrate. As in Patent Document 1 or Patent Document 2, the field plate is provided with a plurality of floating electrodes that are insulated from each other. The plurality of electrodes are stacked via an insulating film in the thickness direction of the semiconductor substrate, and are arranged such that a part thereof overlaps with the insulating film when the semiconductor substrate is viewed in plan.

Japanese Patent Laid-Open No. 10-341018 JP 2005-209983 A

  In order to arrange the plurality of electrodes constituting the field plate so as to overlap each other, conventionally, a plurality of electrodes are formed by an etching method or a lift-off method using a patterning mask. For this reason, the positions of the plurality of electrodes may be shifted. In particular, during mass production, the overlapping area of the plurality of electrodes varies, and the characteristics of the semiconductor device may vary.

  A semiconductor device disclosed in this specification is formed in a floating state on a surface of a non-cell region, a semiconductor substrate having a cell region in which a semiconductor element is formed, and a non-cell region provided around the cell region. Field plate. The field plate is formed on the surface of the first insulating film formed on the surface of the semiconductor substrate and on the surface of the first insulating film, and the field plate is spaced apart from the inside toward the outside in the planar direction of the semiconductor substrate. The first electrode, the second insulating film that covers the side surfaces and surfaces of the plurality of first electrodes and has a groove-shaped portion between the plurality of first electrodes, and the inner wall surface of the groove-shaped portion of the second insulating film A second electrode. The electrode width of the first electrode changes in the depth direction of the semiconductor substrate, and a part of the first electrode overlaps at least a part of the adjacent second electrode via the second insulating film.

  According to the semiconductor device described above, the second electrode is formed so as to be in contact with the inner wall surface of the groove-shaped portion of the second insulating film between the plurality of first electrodes. Therefore, the second electrode can be used without using a pattern mask or the like. An electrode can be disposed between the first electrodes. Furthermore, the electrode width of the first electrode changes in the depth direction of the semiconductor substrate. Therefore, by forming the second electrode in contact with the inner wall surface of the groove-shaped portion of the second insulating film, a part of the first electrode is interposed between at least a part of the adjacent second electrode and the second insulating film. Can be placed in a state of overlapping. Since the first electrode and the second electrode can be arranged so as to overlap without using a pattern mask, the characteristics of the semiconductor device are less likely to vary.

  The electrode width of the first electrode may be the widest on the first insulating film side and may become narrower as the distance from the semiconductor substrate increases.

1 is a plan view of a semiconductor device of Example 1. FIG. It is the II-II sectional view taken on the line of FIG. 6 is a diagram illustrating a method for manufacturing the semiconductor device of Example 1. FIG. 6 is a diagram illustrating a method for manufacturing the semiconductor device of Example 1. FIG. 6 is a diagram illustrating a method for manufacturing the semiconductor device of Example 1. FIG. 6 is a diagram illustrating a method for manufacturing the semiconductor device of Example 1. FIG. It is sectional drawing of the semiconductor device which concerns on a modification. It is sectional drawing of the semiconductor device which concerns on a modification. It is sectional drawing of the semiconductor device which concerns on a modification. It is sectional drawing of the semiconductor device which concerns on a modification.

  A semiconductor device disclosed in this specification is formed in a floating state on a surface of a non-cell region, a semiconductor substrate having a cell region in which a semiconductor element is formed, and a non-cell region provided around the cell region. Field plate. The semiconductor element formed on the semiconductor substrate is not particularly limited, and examples thereof include an IGBT, a MOSFET, and a diode. These semiconductor elements may be a vertical type or a horizontal type. Good. Furthermore, a protective film (for example, a polyimide film, a silicon nitride film, etc.) may be provided on the surfaces of the semiconductor substrate and the field plate.

  The field plate is formed on the surface of the first insulating film formed on the surface of the semiconductor substrate and on the surface of the first insulating film, and the field plate is spaced apart from the inside toward the outside in the planar direction of the semiconductor substrate. The first electrode, the second insulating film that covers the side surfaces and surfaces of the plurality of first electrodes and has a groove-shaped portion between the plurality of first electrodes, and the inner wall surface of the groove-shaped portion of the second insulating film And a second electrode. As materials for the first electrode and the second electrode, conventionally known electrode materials can be used. Although not limited, when a specific example is given, conductive materials, such as metal materials, such as aluminum and copper, and semiconductor materials, such as polysilicon which injected the impurity, can be used.

  The plurality of first electrodes are spaced from the inner side to the outer side in the planar direction of the semiconductor substrate, and the second insulating film is formed along the side surface and the surface thereof. A groove shape is formed between the plurality of first electrodes. A second electrode is formed along the inner wall surface of the groove-shaped portion of the second insulating film.

  The electrode width of the first electrode changes in the depth direction of the semiconductor substrate. For example, the portion with the widest electrode width of the first electrode may be a portion in contact with the first insulating film, and further, the width of the first electrode may become narrower as the distance from the semiconductor substrate increases. In this case, since the interval between the adjacent first electrodes gradually increases from the side closer to the semiconductor substrate toward the side farther from the semiconductor substrate, the second insulating film and the second electrode are formed without a gap between the adjacent first electrodes. It becomes easy. Conversely, the portion with the widest electrode width of the first electrode may be the portion farthest from the first insulating film, and the width of the first electrode may become narrower as it approaches the semiconductor substrate. The shape of the side surface of the first electrode is not particularly limited, and may be, for example, a step shape, an inclined surface shape, a curved surface shape, or a combination thereof.

  Along the shape of the side surface of the first electrode, the shape of the inner wall surface of the groove of the second insulating film is, for example, stepped, inclined, curved, and a combination thereof. Since the second electrode is formed along the inner wall surface, the shape of the side surface of the second electrode is similarly a stepped shape, an inclined surface shape, a curved surface shape, or a combination thereof. Since the portion where the electrode width of the first electrode is wide extends in the plane direction of the semiconductor substrate toward the second electrode than the portion where the electrode width is narrow, when the semiconductor device is viewed in plan, a part of the first electrode However, it can be arranged so as to overlap with at least a part of the second electrode through the second insulating film.

  In the semiconductor device disclosed in this specification, alignment with a pattern mask is not necessary when forming the second electrode. Since the position of the second electrode is determined by the position of the first electrode and the thickness of the second insulating film, the first electrode and the second electrode can be easily aligned without using a pattern mask. is there. When forming the second electrode, a process of forming a pattern mask and performing etching or lift-off can be omitted, so that the manufacturing process of the semiconductor device can be simplified.

(Semiconductor device)
As shown in FIGS. 1 and 2, the semiconductor device 10 includes a semiconductor substrate 100 and a field plate 11. The semiconductor substrate 100 includes cell regions 1 a and 1 b and a non-cell region 2. The field plate 11 is formed on the surface of the non-cell region 2 so as to surround the cell regions 1 a and 1 b along the periphery of the semiconductor substrate 100. The semiconductor device 10 further includes a gate wiring (not shown), a front surface electrode 134, a back surface electrode 135, a gate pad 3, current detection region electrode pads 4 and 5, a temperature detection region 8, and a temperature detection electrode pad. 6 and 7 and a protective film 141. In FIG. 1, illustration of the protective film 141 is omitted. The semiconductor substrate 100 is a silicon substrate.

As shown in FIG. 2, the cell region 1 b includes a p ⁺ -type collector layer 105 exposed on the back surface of the semiconductor substrate 100, an n-type drift layer 101 formed on the surface of the collector layer 105, and a drift layer 101. A p-type body layer 106 formed on the surface of the semiconductor substrate 100, an n ⁺ -type emitter layer 107 and a p ⁺ -type body contact layer 108 formed on the surface of the body layer 106 and exposed on the surface of the semiconductor substrate 100. Is formed. In the cell region 1b, a trench gate 136 that penetrates the body layer 106 and the emitter layer 107 and reaches the drift layer 101 is formed from the surface side of the semiconductor substrate 100. In non-cell region 2, p ⁺ -type collector layer 105 exposed on the back surface of semiconductor substrate 100, n-type drift layer 101 formed on the surface of collector layer 105, and formed on the surface of drift layer 101 A p ⁺ -type first peripheral layer 102, a p-type second peripheral layer 103, and an n ⁺ -type third peripheral layer 104 are formed. The first peripheral layer 102 is formed between the second peripheral layer 103 and the body layer 106, and extends to a deeper position of the semiconductor substrate 100 than the second peripheral layer 103 and the body layer 106. The second peripheral layer 103 and the body layer 106 have substantially the same depth. The third peripheral layer 104 is shallower than the second peripheral layer 103 and the body layer 106.

  A back electrode 135 is formed in contact with the back surfaces of the cell region 1 b and the non-cell region 2. A surface electrode 134 is formed on the surface of the cell region 1b. A field plate 11 is formed on the surface of the non-cell region 2.

  The field plate 11 includes a first insulating film 121, a second insulating film 122, a plurality of first electrodes 131, and a plurality of second electrodes 132. The first insulating film 121 is formed in contact with the surface of the semiconductor substrate 100. The material of the first electrode 131 and the second electrode 132 is aluminum.

  As shown in FIG. 2, the plurality of first electrodes 131 are formed so as to be in contact with the surface of the first insulating film 121, and are each in the plane direction of the semiconductor substrate 100 (XY plane direction shown in FIGS. 1 and 2). They are spaced apart from each other. The cross-sectional shape of the first electrode 131 is trapezoidal, and the length of the lower base near the semiconductor substrate 100 is longer than the length of the upper base far from the semiconductor substrate 100. The first electrode 131 a having the widest electrode width is the lower base surface of the trapezoid shown in FIG. 2 and is in contact with the first insulating film 121. The first electrode 131 has the narrowest electrode width in the second portion 131b, and the second portion 131b is a surface on the upper bottom side of the trapezoid shown in FIG. The first portion 131a and the second portion 131b are surfaces parallel to the planar direction of the semiconductor substrate 100, and are directed from the first portion toward the second portion (that is, from the negative direction of the Z axis shown in FIG. 2 to the positive direction). The electrode width is decreasing at a constant rate. For this reason, the side surface of the first electrode 131 is inclined.

  The second insulating film 122 is formed so as to cover the first electrode 131 with a substantially constant thickness along the side surfaces and surfaces of the plurality of first electrodes 131. In FIG. 2, since the plurality of first electrodes 122 are separated from each other, the second insulating film 122 is also formed on the surface of the first insulating film 121 that is not covered by the first electrode 122. As shown in FIG. 2, the relationship between the thickness d1 of the first electrode 131 and the thickness d2 of the second insulating film 122 is d1> d2. Therefore, the space between the adjacent first electrodes 131 is not filled with the second insulating film 122, and the second insulating film 122 has a groove-shaped portion 122 a between the plurality of first electrodes 131. The cross section of the groove-like portion 122a of the second insulating film 122 is substantially V-shaped, and the width (in the X direction in FIG. 2) is wider toward the side farther from the semiconductor substrate 100.

  As shown in FIG. 2, the second electrode 132 is formed with a substantially constant thickness so as to be in contact with the inner wall surface of the groove-like portion 122 a between the plurality of first electrodes 131. The second electrode 132 is substantially V-shaped, and its electrode width is the narrowest on the side closest to the semiconductor substrate and the widest on the side farthest from the semiconductor substrate, contrary to the electrode width of the first electrode 131. The first electrode 131 and the second electrode 132 are separated from each other by a certain distance according to the thickness of the second insulating film 122, and a portion where the electrode width of the first electrode 131 is wide is directed to the adjacent second electrode 132. A portion where the electrode width of the second electrode 132 is wide extends toward the adjacent first electrode 131. Therefore, as shown in FIG. 2, when the semiconductor device 10 is viewed in plan, a part of the first electrode 131 overlaps a part of the second electrode 132 with the second insulating film 122 interposed therebetween. More specifically, for example, the first electrode 131 and the second electrode 132 included in the region indicated by reference numeral 150 overlap with each other with the second insulating film 122 interposed therebetween. Regarding the overlapping area of the first electrode 131 and the second electrode 132, the difference between the electrode width of the first portion 131a and the electrode width of the second portion 131b of the first electrode 131 is large, and the thickness d2 of the second insulating film 122 is The thinner it is, the bigger it will be. By adjusting the shape and thickness d1 of the first electrode 131 and the thickness d2 of the second insulating film 122, the size of the overlap between the first electrode 131 and the second electrode 132 (for example, the size of the region 150). Can be adjusted.

(Method for manufacturing semiconductor device)
A method for manufacturing the field plate 11 of the semiconductor device 10 will be described. The structure of the cell region and the like of the semiconductor device 10 can be manufactured using a conventionally known method for manufacturing a semiconductor device, and thus description thereof is omitted. For this reason, in FIGS. 3-6, illustration of the cell area | region in which the field plate is not formed is abbreviate | omitted.

  As shown in FIG. 3, an n-type semiconductor substrate made of silicon is prepared as the drift layer 101. The first peripheral layer 102, the second peripheral layer 103, and the third peripheral layer 104 are formed on the surface of the n-type semiconductor substrate by ion implantation or the like, and the semiconductor substrate 900 is manufactured.

  Next, as shown in FIG. 4, a first insulating film 121 is formed on the surface of the semiconductor substrate 900, and a plurality of first electrodes 131 are further formed on the surface of the first insulating film 121. The first insulating film 121 can be formed by, for example, CVD. The first electrode 131 is formed by forming an aluminum layer on the surface of the semiconductor substrate 900 and then isotropically etching the aluminum layer using a pattern mask in which a portion where the first electrode 131 is not formed is opened. A plurality of electrodes having a trapezoidal cross section as shown in FIG. 5 can be formed.

  Next, as shown in FIG. 5, a second insulating film 122 is formed on the surface of the first insulating film 121 and the surface and side surfaces of the first electrode 131 by CVD or the like. Since the thickness of the second insulating film 122 (d2 shown in FIG. 2) is thinner than the thickness of the first electrode 131 (d1 shown in FIG. 2), the groove-like portion 122a is formed between the adjacent first electrodes 131. A second insulating film 122 is formed.

  Next, as illustrated in FIG. 5, an aluminum layer 932 is formed on the surface of the second insulating film 122. Next, as shown in FIG. 6, the aluminum layer 932 formed on the surface of the second insulating film 122 is removed by planarization (for example, CMP (Chemical Mechanical Polishing) or cutting). As a result, only a portion of the aluminum layer 932 formed on the inner wall surface of the groove-shaped portion 122 a of the second insulating film 122 can be left, and this can be used as the plurality of second electrodes 132. Thereby, the field plate 11 can be formed.

  As described above, in the semiconductor device 10, the second electrode 132 is formed using the groove-like portion 122 a like a mold, and the position of the second electrode 132 is determined by the position and shape of the first electrode 131. Therefore, it is possible to easily align the first electrode 131 and the second electrode 132 without using a pattern mask. Further, when the second electrode 132 is formed, a process of forming a pattern mask and performing etching or lift-off can be omitted.

(Modification)
A modification of the shape of the first electrode, the second electrode of the field plate, and the second insulating film interposed therebetween will be described with reference to FIGS. In FIGS. 7 to 10, the cell region where the field plate is not formed is not shown. For example, as shown in FIG. 7, the side surface has a first electrode 231 having an arcuate shape, a second insulating film 222 having an arcuate groove-shaped portion 222a formed along this, and a semicircular arc-shaped cross section. The semiconductor device 12 including the second electrode 232 may be used. For example, as shown in a region 250, when the semiconductor device 12 is viewed in plan, a part of the first electrode 231 overlaps a part of the adjacent second electrode 232 with the second insulating film 222 interposed therebetween.

  Further, for example, as shown in FIG. 8, the first electrode 331 having a stepped side surface, a second insulating film 322 having a stepped groove-shaped portion 322a formed along the first electrode 331, and a stepped second electrode. The semiconductor device 13 including the electrode 232 may be used. For example, as shown in a region 350, when the semiconductor device 13 is viewed in plan, a part of the first electrode 331 overlaps a part of the adjacent second electrode 332 with the second insulating film 322 interposed therebetween.

  Further, for example, as illustrated in FIG. 9, the semiconductor device 14 may include a second electrode 432 having a substantially constant width in the depth direction of the semiconductor substrate 100. The first electrode 431 having a stepped side surface has the same shape as the first electrode 331 illustrated in FIG. 8. For example, the interval between the adjacent first electrodes 431 is twice the thickness of the second insulating film 422. In some cases, as shown in FIG. 9, the second insulating film 422 may fill the gap between the side surfaces of the adjacent first electrode 431 on the side close to the first insulating film 121. In this case, a portion between the adjacent first electrodes 431 of the second insulating film 422 becomes a groove-like portion 422 a having a constant width in the depth direction of the semiconductor substrate 100. As a result, the width of the second electrode 432 is also constant in the depth direction of the semiconductor substrate 100. Also in this case, since the first electrode 431 extends to the second electrode 432 side, as shown in a region 450, for example, when the semiconductor device 14 is viewed in plan, a part of the first electrode 431 is adjacent to the second electrode 431. A part of the two electrodes 432 overlaps with the second insulating film 422.

  For example, as shown in FIG. 10, the first portion 531 a having the widest electrode width is the surface farthest from the semiconductor substrate 100, and the second portion 531 b having the narrowest electrode width is the surface closest to the semiconductor substrate 100. May be. In the semiconductor device 15, the electrode width of the first electrode 531 gradually increases at a substantially constant rate from the side closer to the semiconductor substrate 100 to the side farther from the side, and the side surface of the first electrode 531 has an inclined surface shape. It has become. The interval between the adjacent first electrodes 531 of the second insulating film 522 formed along the first electrode 531 gradually decreases at a substantially constant rate from the side closer to the semiconductor substrate 100 to the side farther from the side. . The electrode width of the second electrode 532 gradually decreases at a substantially constant rate from the side closer to the semiconductor substrate 100 toward the side farther from the side. For example, as shown in a region 550, when the semiconductor device 15 is viewed in plan, a part of the first electrode 531 overlaps a part of the adjacent second electrode 532 with the second insulating film 522 interposed therebetween.

  As shown in the above embodiments and modifications, the shape of the side surface of the first electrode is not particularly limited as long as the electrode width of the first electrode can be changed in the depth direction of the semiconductor substrate. A stepped shape, an inclined surface shape, a curved surface shape, and a shape in which these are combined may be used. The second electrode may have a substantially constant electrode width, or the electrode width may change in the depth direction of the semiconductor substrate. In either case, the first electrode and the second electrode can be designed to overlap with each other with the second insulating film interposed therebetween.

  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.

  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.

Reference Signs List 1a, 1b Cell region 1b Cell region 2 Non-cell region 3 Gate pad 4, 5, 6, 7 Electrode pad 8 Temperature detection region 10, 12, 13, 14, 15 Semiconductor device 11 Field plate 100, 900 Semiconductor substrate 101 Drift layer 102 first peripheral layer 103 second peripheral layer 104 third peripheral layer 105 collector layer 106 body layer 107 emitter layer 108 body contact layer 121 first insulating films 122, 222, 322, 422, 522 second insulating films 122a, 222a, 322a, 422a Groove-shaped portions 131, 231, 331, 431, 531 First electrode 131a First portion 131b Second portion 132, 232, 332, 432, 532 Second electrode 134 Surface electrode 135 Back electrode 136 Trench gate 141 Protective film 150, 250, 350, 450, 550

Claims (2)

A semiconductor substrate having a cell region in which a semiconductor element is formed and a non-cell region provided around the cell region;
A semiconductor device comprising a field plate formed in a floating state on the surface of a non-cell region,
The field plate
A first insulating film formed on the surface of the semiconductor substrate;
A plurality of first electrodes formed on the surface of the first insulating film and spaced apart from the inner side to the outer side in the planar direction of the semiconductor substrate;
A second insulating film that covers the side surfaces and surfaces of the plurality of first electrodes and has a groove-shaped portion between the plurality of first electrodes;
A second electrode in contact with the inner wall surface of the groove-shaped portion of the second insulating film,
The electrode width of the first electrode changes in the depth direction of the semiconductor substrate, and a part of the first electrode overlaps at least a part of the adjacent second electrode via the second insulating film. apparatus.   2. The semiconductor device according to claim 1, wherein an electrode width of the first electrode is widest on the first insulating film side and narrows as the distance from the semiconductor substrate increases.

Images