JP2015141920A - Semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an art to reduce resistance generated when carriers pass a channel.SOLUTION: A semiconductor device 1 comprises: a gate electrode 22; a gate insulation film 23 which covers the gate electrode 22; a base layer 12 which contacts the gate insulation film 23 and in which a channel 30 where carriers pass is formed; a source layer 11 which contacts the gate insulation film 23 and is arranged adjacent to one side of the base layer 12; and a drift layer 13 which contacts the gate insulation film 23 and is arranged adjacent to the other side of the base layer 12. The base layer 12 includes in a part contacting the gate insulation film 23, a first source-side salient 10 which extends along the gate insulation film 23 to the source layer 11 side. In addition, the base layer 12 includes in a part contacting the gate insulation film 23, a first drift-side salient 20 which extends along the gate insulation film 23 to the drift layer 13 side.

Description

  The technology disclosed in this specification relates to a semiconductor device including a gate electrode.

  Patent Document 1 discloses a semiconductor device including a gate electrode. This semiconductor device is a MOSFET including a gate electrode and a trench that accommodates the gate electrode. In addition, the semiconductor device includes a source layer, a base layer, and a drift layer that are formed side by side in contact with the side surface of the trench. A source electrode is disposed on the surface of the source layer. A drain layer is disposed on the back surface of the drift layer, and a drain electrode is disposed on the back surface of the drain layer.

  In this semiconductor device, a channel is formed in the surface portion of the base layer located on the side surface of the trench by controlling the voltage applied to the gate electrode, and between the source electrode and the drain electrode via the source layer and the drift layer. Apply current.

JP 2009-259896 A

  In the semiconductor device disclosed in Patent Document 1, carriers (electrons) flow from the source layer to the channel formed in the base layer, and flow from the channel to the drift layer. In this semiconductor device, the region through which carriers (electrons) pass in the portion where carriers (electrons) flow from the source layer to the channel and the portion where the carriers (electrons) flow from the channel to the drift layer is narrow, so the resistance is high. Therefore, a technique for reducing the resistance is required.

  Therefore, an object of the present specification is to provide a semiconductor device capable of reducing resistance when carriers pass through a channel.

  A semiconductor device disclosed in this specification includes a gate electrode and a gate insulating film that covers the gate electrode. The semiconductor device includes a semiconductor layer in contact with the gate insulating film and in which a channel through which carriers pass is formed, and a source layer in contact with the gate insulating film and disposed adjacent to one side of the semiconductor layer And a drift layer disposed in contact with the gate insulating film and adjacent to the other side of the semiconductor layer. In addition, the semiconductor layer includes a first source-side protrusion that extends toward the source layer along the gate insulating film at a portion in contact with the gate insulating film.

  According to such a configuration, since the semiconductor layer includes the first source-side convex portion, a region where the source layer and the semiconductor layer are in surface contact is formed in a portion where the channel of the semiconductor layer is formed. Carriers (electrons) that flow into the channel from the source layer pass through the above-mentioned surface-contact region. Thus, since carriers (electrons) flow through the surface region when flowing from the source layer to the channel, the region through which carriers pass can be widened, and the resistance can be reduced.

  In the above embodiment, the semiconductor layer may further include a first drift side convex portion extending toward the drift layer along the gate insulating film at a portion in contact with the gate insulating film.

  According to such a configuration, since the semiconductor layer includes the first drift side convex portion, a region where the drift layer and the semiconductor layer are in surface contact is formed in a portion where the channel of the semiconductor layer is formed. Carriers (electrons) flowing from the channel to the drift layer pass through the region in contact with the surface. As a result, as in the case of the first source-side convex portion, when carriers (electrons) flow from the channel to the drift layer, a region through which carriers pass due to surface contact can be widened, and resistance can be reduced. .

  In the embodiment, the first source-side convex portion may have a width of 50 to 100 mm.

  The first drift side convex portion may have a width of 50 to 1000 mm.

  An inversion layer may extend from the gate insulating film to the entire width direction of the first source-side convex portion.

  An inversion layer may extend from the gate insulating film to the entire width direction of the first drift-side convex portion.

  Further, the width of the first drift side convex portion is wider than the width of the inversion layer extending from the gate insulating film, and the first drift side is within a range where the inversion layer does not extend when the inversion layer is formed. The convex part may be depleted.

  The semiconductor layer may further include a second source-side convex portion extending toward the source layer at a position spaced from the first source-side convex portion.

  In addition, a distance from the first source side convex portion to the second source side convex portion may be longer than a length of the first source side convex portion.

  The semiconductor layer may further include a second drift side convex portion extending toward the drift layer at a position spaced from the first drift side convex portion.

  The distance from the first drift side convex portion to the second drift side convex portion may be longer than the length of the second drift side convex portion.

It is sectional drawing of the semiconductor device which concerns on embodiment. It is sectional drawing which expands and shows the principal part of the semiconductor device which concerns on embodiment. It is sectional drawing of the semiconductor device which concerns on other embodiment. It is sectional drawing which expands and shows the principal part of the semiconductor device which concerns on other embodiment.

  Hereinafter, embodiments will be described with reference to the accompanying drawings. As shown in FIG. 1, the semiconductor device 1 according to the embodiment is a trench gate type semiconductor device including a semiconductor substrate 3 and a trench gate 2. In the present embodiment, a vertical MOSFET (Metal Oxide Semiconductor Field Effect Transistor) is illustrated as the semiconductor device 1. The MOSFET is used for a switching element for power control of various electric devices such as an automobile motor. FIG. 1 shows a unit structure of a MOSFET, but actually this unit structure is repeatedly formed in the horizontal direction.

  Examples of the semiconductor substrate 3 include silicon (Si) or silicon carbide (SiC) in which impurities are implanted. The semiconductor substrate 3 includes an n-type drain layer 14, an n-type drift layer 13 formed on the drain layer 14, a p-type base layer 12 formed on the drift layer 13, and a base layer 12. An n-type source layer 11 formed on the base layer 12 and a p-type contact layer 15 formed on the base layer 12 are provided. A back electrode 6 is disposed on the back surface of the semiconductor substrate 3, and a front electrode 5 is disposed on the surface of the semiconductor substrate 3.

A trench 21 is formed in the semiconductor substrate 3. The trench 21 extends in the depth direction (z direction) from the surface of the semiconductor substrate 3 and extends through the source layer 11 and the base layer 12 to the inside of the drift layer 13. A gate electrode 22 is disposed inside the trench 21 via a gate insulating film 23. The inner surface (side surface and bottom surface) of the trench 21 is covered with a gate insulating film 23. A gate electrode 22 is filled inside the gate insulating film 23. An interlayer insulating film 24 is disposed on the surface of the gate electrode 22. The interlayer insulating film 24 is formed between the gate electrode 22 and the surface electrode 5. A trench gate 2 is constituted by the trench 21, the gate insulating film 23 and the gate electrode 22. The gate insulating film 23 and the interlayer insulating film 24 are made of, for example, SiO ₂ . The gate electrode 22 is made of, for example, aluminum or polysilicon. The gate insulating film 23 is in contact with the surface (side surface and bottom surface) of the gate electrode 22 and covers the gate electrode 22. The gate insulating film 23 extends in the depth direction (z direction) along the gate electrode 22.

  The drain layer 14 is exposed on the back surface of the semiconductor substrate 3 and is in contact with the back electrode 6. The impurity concentration of the drain layer 14 is higher than the impurity concentration of the drift layer 13. The contact layer 15 is exposed on the surface of the semiconductor substrate 3 and is in contact with the surface electrode 5. The impurity concentration of the contact layer 15 is higher than the impurity concentration of the base layer 12.

  The source layer 11, the base layer 12, and the drift layer 13 are formed side by side in the vertical direction (z direction) along the gate insulating film 23.

  The source layer 11 is exposed on the surface of the semiconductor substrate 3 and is in contact with the surface electrode 5. Carriers (electrons) flow from the source layer 11. The source layer 11 is disposed adjacent to one side (upper side) of the base layer 12 and is in contact with the base layer 12. The source layer 11 is in contact with the gate insulating film 23.

  The drift layer 13 is formed around the trench gate 2. The drift layer 13 is disposed adjacent to the other side (lower side) of the base layer 12 and is in contact with the base layer 12. The drift layer 13 is in contact with the gate insulating film 23.

  The base layer 12 separates the source layer 11 and the drift layer 13. The base layer 12 is formed around the trench gate 2. The base layer 12 is in contact with the gate insulating film 23. As shown in FIG. 2, the base layer 12 extends along the gate insulating film 23 and the first source-side convex portion 10 extending toward the source layer 11 along the gate insulating film 23 in a portion in contact with the gate insulating film 23. And a first drift side convex portion 20 extending to the drift layer 13 side. When an on potential is applied to the gate electrode 22, an inversion layer is formed along the trench 21 in a portion of the base layer 12 that contacts the gate insulating film 23, and a channel 30 through which carriers pass is formed. The channel 30 is formed between the source layer 11 and the drift layer 13. According to research, the width of the inversion layer extending from the gate insulating film 23 toward the base layer 12 is about 50 to 100 mm. That is, the inversion layer is formed in the range of about 50 to 100 mm from the gate insulating film 23. Further, when the inversion layer is formed, a depletion layer is formed in a range adjacent to the inversion layer. According to research, the width of the depletion layer extending into the base layer 12 is about 100 to 200 mm from the gate insulating film 23. That is, the depletion layer is formed in the range of about 100 to 200 mm from the gate insulating film 23.

  The first source-side protrusion 10 protrudes from the base layer 12 toward the source layer 11 along the trench 21. The first source-side convex portion 10 is in contact with the gate insulating film 23. The first source-side convex portion 10 protrudes upward from the base layer 12 and extends into the source layer 11. The first source side convex portion 10 extends linearly along the gate insulating film 23 in the depth direction (y direction) of FIG. The first source-side convex portion 10 is in contact with the source layer 11, and a source contact surface 91 is formed at a portion in contact with the source layer 11. The source contact surface 91 faces the source layer 11 in the x direction. A height Ls of the source contact surface 91 in the vertical direction (z direction) (the length Ls of the first source side convex portion 10) is larger than a width Hs of the first source side convex portion 10 in the horizontal direction (x direction). . When the MOSFET is turned on, carriers (electrons) emitted from the source layer 11 pass through the source contact surface 91 and flow into the first source-side convex portion 10. The carriers (electrons) that have flowed into the first source side convex portion 10 pass through the channel 30 formed in the first source side convex portion 10.

  The width Hs in the horizontal direction (x direction) of the first source-side convex portion 10 is preferably set in relation to the width of the inversion layer formed in the base layer 12. In other words, when the inversion layer is formed on the base layer 12, the width Hs of the first source type convex portion 10 extends from the gate insulating film 23 to the entire area in the width direction of the first source type convex portion 10. It is preferable that they are set as follows. As described above, the width of the inversion layer extending from the gate insulating film 23 toward the base layer 12 is about 50 to 100 mm. Therefore, the width Hs of the first source side convex portion 10 is preferably 50 to 100 mm.

  The first drift side protrusion 20 protrudes from the base layer 12 toward the drift layer 13 along the trench 21. The first drift side convex portion 20 is in contact with the gate insulating film 23. The first drift side convex portion 20 protrudes downward from the base layer 12 and extends into the drift layer 13. The first drift side convex portion 20 extends linearly along the gate insulating film 23 in the depth direction (y direction) of FIG. The first drift side convex portion 20 is in contact with the drift layer 13, and a drift contact surface 92 is formed at a portion in contact with the drift layer 13. The drift contact surface 92 faces the drift layer 13 in the x direction. The height Ld in the vertical direction (z direction) of the drift contact surface 92 (the length Ld of the first drift side convex portion 20) is larger than the width Hd in the lateral direction (x direction) of the first drift side convex portion 20. . When the MOSFET is turned on, carriers (electrons) that have passed through the channel 30 in the base layer 12 pass through the drift contact surface 92 and flow into the drift layer 13.

  The width Hd in the lateral direction (x direction) of the first drift side convex portion 20 is preferably set in relation to the width of the inversion layer formed in the base layer 12. In other words, when the inversion layer is formed on the base layer 12, the width Hd of the first drift side protrusion 20 extends from the gate insulating film 23 to the entire region in the width direction of the first drift side protrusion 20. It is preferable that they are set as follows. As described above, the width of the inversion layer extending from the gate insulating film 23 toward the base layer 12 is about 50 to 100 mm. Therefore, the width Hd of the first drift side convex portion 20 is preferably 50 to 100 mm.

  Alternatively, the width Hd in the lateral direction (x direction) of the first drift-side convex portion 20 is wider than the width in which the inversion layer extends from the gate insulating film 23, and the range in which the inversion layer does not extend when the inversion layer is formed. The width | variety by which the 1st drift side convex part 20 of this is depleted may be sufficient. That is, when the inversion layer is formed on the first drift side convex portion 20, the width Hd may be set so that the depletion layer extends over the entire portion where the inversion layer is not formed. As described above, the width of the inversion layer is about 50 to 100 mm, and the range in which the depletion layer extends is from 100 to 1000 mm from the gate insulating film 23. Therefore, the width Hd of the first drift side convex portion 20 may be 50 to 1000 mm. Due to the difference in potential between the source layer 11 and the drift layer 13, the width of the first source side convex portion 10 and the width of the first drift side convex portion 20 may be different.

  The back electrode 6 and the front electrode 5 are made of a metal such as copper or aluminum, and a voltage can be applied between the drain layer 14 and the source layer 11.

  Next, the operation of the semiconductor device 1 having the above configuration will be described. In the semiconductor device 1, a forward voltage is applied between the back electrode 6 and the front electrode 5, and a gate voltage is applied to the gate electrode 22. Then, an inversion layer is formed in a portion of the base layer 12 that contacts the gate insulating film 23 by the gate voltage, and a channel 30 through which carriers (electrons) pass is formed. The channel 30 is formed between the source layer 11 and the drift layer 13 and extends along the side surface of the trench 21. Further, carriers (electrons) supplied from the source layer 11 by the forward voltage flow through the channel 30 formed in the base layer 12 and flow to the drift layer 13. Carriers (electrons) that have flowed to the drift layer 13 flow in the drift layer 13 in the vertical direction (depth direction) and flow toward the drain layer 14. Thereby, a current flows from the drain layer 14 to the source layer 11 when the semiconductor device 1 is turned on.

  According to the semiconductor device 1 according to the above embodiment, since the base layer 12 includes the first source side convex portion 10, the side surface (source contact surface 91) of the first source side convex portion 10 is in contact with the source layer 11. Therefore, carriers (electrons) flowing from the source layer 11 to the channel 30 pass through the source contact surface 91. Thereby, a region through which carriers (electrons) can pass when flowing from the source layer 11 to the channel 30 is widened. Furthermore, in the above-described embodiment, the width Hs of the first source side convex portion 10 is set so that the inversion layer spreads over the entire first source side convex portion 10. Therefore, as shown in FIG. 2, the inversion layer extends to the source contact surface 91, and it is easier for carriers (electrons) to flow into the channel 30 through the source contact surface 91. Therefore, it has been realized to reduce the resistance in this region. Further, since the base layer 12 includes the first drift side convex portion 20, the side surface (drift contact surface 92) of the first drift side convex portion 20 is in contact with the drift layer 13. Therefore, carriers (electrons) flowing from the channel 30 to the drift layer 13 pass through the drift contact surface 92. As a result, since the region through which carriers (electrons) can pass when flowing from the channel 30 to the drift layer 13 is wide, the resistance can be reduced. Even if the first drift side convex portion 20 in the range where the inversion layer does not extend when the inversion layer is formed on the first drift side convex portion 20, the first drift side convex portion 20 and the drift layer are depleted. 13 is relatively high, carriers (electrons) flow from the first drift side convex portion 20 to the drift layer 13. Further, since the channel 30 formed in the base layer 12 is shortened, the voltage for punch-through in the channel portion does not decrease. Therefore, the breakdown voltage of the channel portion is not reduced.

  As mentioned above, although one embodiment was described, a specific mode is not limited to the above-mentioned embodiment. For example, in the semiconductor device 1 according to another embodiment, as illustrated in FIGS. 3 and 4, the base layer 12 has the second source-side protrusion 60 extending toward the source layer 11 and the second layer extending toward the drift layer 13. The drift side convex part 70 may be further provided. In FIG. 3 or FIG. 4, the same components as those in FIG. 1 or FIG.

  As shown in FIGS. 3 and 4, the second source-side convex portion 60 protrudes upward from the base layer 12 and extends into the source layer 11. The second source-side convex portion 60 is in contact with the source layer 11. The second source side convex portion 60 is formed at a position separated from the first source side convex portion 10. A gap 96 is formed between the first source side convex portion 10 and the second source side convex portion 60. The source layer 11 is formed in the gap 96.

  The distance Ws from the first source side convex portion 10 to the second source side convex portion 60 is longer than the length Ls of the first source side convex portion 10 (Ws> Ls). The length Ls of the first source side convex portion 10 corresponds to the height of the source contact surface 91, and the first source side convex portion from the upper end of the base layer 12 in the portion where the first source side convex portion 10 is not formed. Up to the upper end of 10 is measured in the depth direction (z direction). The distance Ws from the first source side convex portion 10 to the second source side convex portion 60 corresponds to the length of the gap 96, and the end of the first source side convex portion 10 to the end of the second source side convex portion 60. Up to the part is measured in the horizontal direction (x direction).

  The second drift side convex portion 70 protrudes downward from the base layer 12 and extends into the drift layer 13. The second drift side convex portion 70 is in contact with the drift layer 13. The second drift side convex portion 70 is formed at a position separated from the first drift side convex portion 20. A gap 97 is formed between the first drift side convex portion 20 and the second drift side convex portion 70. The drift layer 13 is formed in the gap 97.

  The distance Wd from the first drift side convex portion 20 to the second drift side convex portion 70 is longer than the length Ld of the first drift side convex portion 20 (Wd> Ld). The length Ld of the first drift side convex portion 20 corresponds to the height of the drift contact surface 92, and the first drift side convex portion from the lower end of the base layer 12 in the portion where the first drift side convex portion 20 is not formed. Up to the lower end of 20 is measured in the depth direction (z direction). The distance Wd from the first drift side convex portion 20 to the second drift side convex portion 70 corresponds to the length of the gap 97, and the end of the first drift side convex portion 20 to the end of the second drift side convex portion 70. Up to the part is measured in the horizontal direction (x direction).

  According to such a configuration, the gap 96 to the second source side convex portion 60 can be widened with respect to the height of the source contact surface 91 of the first source side convex portion 10. As a result, carriers (electrons) easily flow to the source contact surface 91, and carriers (electrons) easily flow to the channel 30 through the source contact surface 91. Therefore, the resistance can be reduced. Similarly, the gap 97 to the second drift side convex portion 70 can be widened with respect to the height of the drift contact surface 92 of the first drift side convex portion 20. Thereby, carriers (electrons) can easily flow through the drift contact surface 92 to the drift layer 13, and the resistance can be reduced. In addition, with the second source side convex portion 60 and the second drift side convex portion 70, the breakdown voltage can be increased.

  Moreover, in the said embodiment, although the 1st drift side convex part 20 was provided, this can also be abbreviate | omitted.

  In the above embodiment, the MOSFET has been described as an example of the semiconductor device. However, the present invention is not limited to this configuration, and another example of the semiconductor device may be an IGBT (Insulated Gate Bipolar Transistor). Also in the IGBT, the same configuration as that of the MOSFET described above is used for the first source side convex portion 10, the first drift side convex portion 20, the second source side convex portion 60, the second drift side convex portion 70, and the like. it can.

  In the above embodiment, the trench gate type semiconductor device is used. However, the present invention is not limited to this configuration, and a planar gate type semiconductor device may be used.

  Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. 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.

DESCRIPTION OF SYMBOLS 1; Semiconductor device 2; Trench gate 3; Semiconductor substrate 5; Front surface electrode 6; Back surface electrode 10: 1st source side convex part 11; Source layer 12; Base layer 13; Drift layer 14; First drift side convex portion 21; trench 22; gate electrode 23; gate insulating film 24; interlayer insulating film 30; channel 60; second source side convex portion 70; second drift side convex portion 91; Contact surface 96; gap 97; gap

Claims (11)

A gate electrode;
A gate insulating film covering the gate electrode;
A semiconductor layer in contact with the gate insulating film and having a channel through which carriers pass; and
A source layer in contact with the gate insulating film and disposed adjacent to one side of the semiconductor layer;
A drift layer disposed in contact with the gate insulating film and adjacent to the other side of the semiconductor layer,
The semiconductor layer includes a first source-side protrusion that extends toward the source layer along the gate insulating film at a portion in contact with the gate insulating film.   The semiconductor device further includes a first drift side convex portion that extends toward the drift layer along the gate insulating film at a portion in contact with the gate insulating film.   The semiconductor device according to claim 1, wherein a width of the first source-side convex portion is 50 to 100 mm.   4. The semiconductor device according to claim 2, wherein a width of the first drift side convex portion is 50 to 1000 mm. 5.   5. The semiconductor device according to claim 1, wherein an inversion layer extends from the gate insulating film to the entire width direction of the first source-side convex portion.   6. The semiconductor device according to claim 1, wherein an inversion layer extends from the gate insulating film to the entire width direction of the first drift side convex portion.   The width of the first drift side convex portion is wider than the width of the inversion layer extending from the gate insulating film, and the first drift side convex portion is in a range where the inversion layer does not extend when the inversion layer is formed. The semiconductor device according to claim 2, wherein is depleted.   8. The semiconductor device according to claim 1, wherein the semiconductor layer further includes a second source-side convex portion extending toward the source layer at a position spaced from the first source-side convex portion.   The semiconductor device according to claim 8, wherein a distance from the first source side convex portion to the second source side convex portion is longer than a length of the first source side convex portion.   10. The semiconductor device according to claim 2, wherein the semiconductor layer further includes a second drift side convex portion extending toward the drift layer at a position spaced apart from the first drift side convex portion.   The semiconductor device according to claim 10, wherein a distance from the first drift side convex portion to the second drift side convex portion is longer than a length of the second drift side convex portion.

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