JP3878353B2 - Vertical MOS semiconductor device having current detection cell - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor device having a current detection function, and more particularly to a structure of a current detection cell portion.
[0002]
[Prior art]
Overcurrent protection is an important issue in MOSFETs. Conventionally, a detection resistor or current shunt has been inserted into the bus, but in recent years, current detection elements (cells) have become on-chip. The power loss for detection, the number of parts, and the detection circuit can be simplified. FIG. 9 is a cross-sectional view of a conventional vertical MOSFET in which such current detection cells are formed on the same chip as the main current cell, FIG. 10 is a cross-sectional perspective view thereof, and a plan view of a stripe-shaped polysilicon gate pattern portion. Are shown in FIG.
[0003]
As shown in these drawings, a vertical MOS structure has a plurality of stripe-shaped gate electrodes 6 provided on an N-type semiconductor substrate 1 with an insulating film 5 interposed therebetween, and a semiconductor substrate using these gate electrodes 6 as a mask. A plurality of base regions 3 of P conductivity type formed in one surface region, and two N conductivity types formed along the gate electrode 6 in each region of these base regions 3 Source region 4 is formed. A source electrode 7 that contacts both the base region 3 and the source region 4 is connected in common to the plurality of base regions 3 in which the source regions 4 are formed. A source electrode terminal S is derived. The source electrode terminal S, the source region 4 to which the source electrode 7 is commonly connected, the base region 3 including them, the gate electrode 6 disposed between the base regions 3, and the surface of the semiconductor substrate 1 A main current cell 101 is constituted by the back surface electrode 9 provided on the surface.
[0004]
Next, a gate electrode 8 is disposed on the semiconductor substrate 1 in parallel with the gate electrode 6 constituting the main current cell 101 via the insulating film 5. As shown in FIG. 11, the gate electrode 8 has an oblong window 9 formed at the center thereof, and a P-conductive base region 23 is formed through the window 9. In the surface region of the base region 23, two source regions 24 are formed along the elliptical window 9, and both the source region 24 and the base region 23 are formed. The sense electrode 27 to be contacted is formed independently of the source electrode 7. A source region 24 to which the sense electrode 27 is connected; a sense electrode terminal Se connected to the source region 24; a base region 23 including the source region 24; and gate electrodes 8 disposed on both sides thereof. A current detection cell 202 is constituted by the back electrode 9 provided on the surface of the semiconductor substrate 1.
[0005]
Note that gate electrodes 6 constituting the main current cell 101 are disposed on both sides of the gate electrode 8 (only one of them is shown in FIG. 11), and between these gate electrodes 6 as well. A base region 3 constituting the main current cell 101 is formed.
[0006]
[Problems to be solved by the invention]
As described above, in a conventional semiconductor device having a current detection function, a unit cell is formed by double diffusion using a polysilicon gate as a mask material, and a part of the cell is taken out as a current detection cell by another electrode. . In general, when the current detection cell region is formed with the same polysilicon gate width and opening width as the main current cell portion so that the current detection cell exhibits the same output characteristics as the main current cell, the end portion of the base region 23 of the current detection cell region is formed. In FIG. 11, a region (FIG. 11) is formed in which the distance dL between the base regions with the adjacent main current cells is larger than the distance d at the center of the base region 23.
[0007]
In the MOSFET having such a structure, when a high voltage in the reverse direction is applied between the source electrode terminal S and the back electrode 9, and between the sense electrode terminal Se and the back electrode 9, the current detection cell region and the main current cell region In the portion where the distance between the base regions is large, the depletion layer is not sufficiently spread compared to the portion where the distance is small, and the electric field is concentrated on this portion, so that the breakdown voltage is lowered and the breakdown voltage of the entire MOSFET is deteriorated. there were.
[0008]
The present invention has been made in view of the above problems, and an object thereof is to prevent a breakdown voltage from being lowered in a MOSFET having a current detection function.
[0009]
[Means for Solving the Problems]
A vertical MOS semiconductor device having a current detection cell according to the present invention includes a plurality of stripe-shaped gate electrodes arranged substantially in parallel via an insulating film on the surface of a first conductivity type semiconductor substrate, A plurality of second conductivity type base regions formed in the semiconductor substrate using the gate electrode as a mask, a first conductivity type source region formed in these base regions, and these source regions Of the plurality of base regions to be formed, a source electrode commonly connected to the source region in the base region excluding a part thereof, and a source electrode in the partial base region are connected A plurality of base regions including the source electrode and the source region to which the source electrode is connected in common, and a back electrode provided on a back surface of the first conductivity type semiconductor substrate. And the back electrode Ri principal current cell is configured, wherein the one of a plurality of stripe-shaped gate electrode are longitudinally extended oblong windows along the gate electrode is formed, the gate electrode, wherein In a vertical MOS structure semiconductor device in which a current detection cell is constituted by a sense electrode, a base region including the source region to which the sense electrode is connected, and the back electrode, a gate electrode constituting the current detection cell The oblong window formed in the window has a width at the end in the longitudinal direction larger than the width at the center in the longitudinal direction. The window of the second conductivity type formed on the semiconductor substrate using the gate electrode as a mask. The width of the end portion of the base region is larger than the width of the central portion in the longitudinal direction .
[0010]
Further, in the vertical MOS semiconductor device semiconductor device having the current detection cell according to the present invention, the elliptical window formed in the gate electrode constituting the current detection cell has its longitudinal end enlarged substantially in a fan shape. The base region formed using the gate electrode as a mask is shorter in length than the base region that constitutes the main current cell, and the base region that constitutes the current detection cell. The end portion has a current detecting cell according to claim 1, wherein the end portion is substantially fan-shaped.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of a semiconductor device having a current detection function according to the present invention will be described below with reference to the drawings. 1 is a plan view of a polysilicon gate pattern portion in a vertical MOSFET according to an embodiment of the present invention, FIG. 2 is a cross-sectional view of the vertical MOSFET, and FIG. 3 is a cross-sectional perspective view thereof. In the drawings, the same components as those of the conventional semiconductor device are designated by the same reference numerals, and the detailed description thereof will be omitted. The following mainly focuses on differences from the conventional device. explain.
[0012]
As shown in the figure, the structure of the MOSFET of the present invention includes a polysilicon gate electrode 6 formed in a stripe shape on an N-type semiconductor substrate 1 with an insulating film 5 interposed therebetween, and two gates using the gate electrode as a mask. A P-type base region 3 formed in the semiconductor substrate by heavy diffusion; an N-type source region 4 selectively formed at a predetermined depth on the surface of the base region; and the base region 3 and the source region 4, and a main current cell region 101 connected to the source electrode 7 is formed.
[0013]
Next, a gate electrode 8 is disposed on the semiconductor substrate 1 in parallel with the gate electrode 6 constituting the main current cell 101 via the insulating film 5. As shown in FIG. 1 , the gate electrode 8 is formed with an oblong window 11 whose end is enlarged in a fan shape at the center thereof, and a P-conductivity type base region is formed through the window 11. 13 is formed. In the surface region of the base region 13 , two source regions 14 are formed along the central portion of the stripe-shaped window 11 whose ends are enlarged in a fan shape. A sense electrode 17 that contacts both the base electrode 14 and the base region 13 is formed independently of the source electrode 7. A source region 14 to which the sense electrode 17 is connected, a base region 13 including the source region 14, a gate electrode 8 disposed on both sides thereof, and a back electrode 9 provided on the surface of the semiconductor substrate 1 Thus, the current detection cell 102 is configured.
[0014]
As described above, the MOSFET structure of the present invention is characterized in that the base region of the current detection cell 102 is formed by a striped mask pattern whose ends are expanded in a fan shape. With this structure, the withstand voltage of the current detection cell 102 can be increased as compared with the conventional device. The reason for this will be described with reference to FIGS. 4 to 7 in comparison with the conventional apparatus. 4 is a top view of the current detection cell portion of the present invention, FIG. 5 is a cross-sectional view taken along the line AA of FIG. 4, and FIGS. 6 and 7 are corresponding drawings in the conventional apparatus. As shown in FIGS. 4 and 5, the base region 13 of the current detection cell portion of the present invention has a distance from the base region 3 of the adjacent main current cell region 101 shorter than the other portions at the end portion. Since the depletion layers due to the reverse bias spread as shown by the broken lines in the figure, they overlap with each other, so that the electric field does not concentrate and the breakdown voltage is almost the same as that of the main current cell. On the other hand, in the conventional apparatus, as shown in FIGS. 6 and 7, the base region 23 of the current detection cell portion has a distance from the base region 3 of the adjacent main current cell region 101 at the end thereof. Since it becomes large, the depletion layer does not spread sufficiently, the electric field in this part becomes larger than in other parts, and the breakdown voltage in this part decreases, resulting in breakdown at a low voltage.
[0015]
The breakdown voltage characteristics of the MOSFET having the structure according to the present invention are shown in FIG. 8 in comparison with the breakdown voltage characteristics of the conventional structure (shown by broken lines in the figure).
[0016]
The above embodiment exemplifies an N-channel type MOSFET, but can be applied to a MOS type semiconductor device such as an IGBT (Insulated Gate Bipolar Transistor) or a reverse conductivity type semiconductor device depending on the structure of the semiconductor wafer.
[0017]
Furthermore, in the present invention, the shape of the end portion of the base region constituting the current detection cell is intended to shorten the distance between the base region constituting the adjacent main current cell, so that the shape is the above fan shape. It is not limited.
[0018]
【The invention's effect】
As described above, the present invention expands the area of the base region end of the current detection cell region formed in a part of the main current cell region with respect to the main body portion, thereby The breakdown voltage can be prevented from being lowered, and the breakdown voltage of the entire semiconductor device incorporating the current detection cell can be improved.
[Brief description of the drawings]
FIG. 1 is a plan view of a silicon gate pattern portion in a vertical MOSFET according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view of the vertical MOSFET of FIG.
3 is a cross-sectional perspective view of the vertical MOSFET of FIG.
4 is a top view of a current detection cell portion in the vertical MOSFET of FIG. 1. FIG.
5 is a cross-sectional view taken along line AA in FIG.
FIG. 6 is a top view of a current detection cell portion in a conventional vertical MOSFET.
7 is a cross-sectional view taken along line AA in FIG.
FIG. 8 is a diagram for explaining the breakdown voltage characteristics of a MOSFET having a structure according to the present invention.
FIG. 9 is a cross-sectional view of a conventional vertical MOSFET.
FIG. 10 is a cross-sectional perspective view of a conventional vertical MOSFET.
FIG. 11 is a plan view of a stripe-like polysilicon gate pattern portion in a conventional vertical MOSFET.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... N-type semiconductor substrate 3 ... P-type base region 4 ... N-type source region 5 ... Gate insulating film 6 ... Gate electrode 13 ... P-type base region 14 ... N-type source region 23 ... P-type base Region 24 ... N-type source region
101 ... Main current cell region
102 ... Current detection cell region
202 ... Current detection cell region

Claims (2)

A plurality of striped gate electrodes arranged substantially in parallel on the surface of the first conductivity type semiconductor substrate with an insulating film interposed therebetween, and a plurality of second gate electrodes formed on the semiconductor substrate using these gate electrodes as a mask. A base region of two conductivity types, a first conductivity type source region formed in these base regions, and a part of the plurality of base regions in which these source regions are formed A source electrode commonly connected to the source region in the base region excluding, a sense electrode connected to the source region in the part of the base region, and a back surface of the first conductivity type semiconductor substrate consists of a back surface electrode provided on the source electrode, the plurality of base to the source electrode includes a common connected the source regions - main current cell by a source region and said back electrode is formed, said plurality Striped One of the over gate electrode, longitudinally extended oblong windows along the gate electrodes are formed, the gate electrode, the sense electrode, the source region where the sense electrodes are connected In a vertical MOS structure semiconductor device in which a current detection cell is configured by a base region including the back electrode and the back electrode, an oblong window formed in the gate electrode forming the current detection cell The width of the end portion is larger than the width of the central portion in the longitudinal direction, and the width of the end portion of the second conductivity type base region formed on the semiconductor substrate using the gate electrode as a mask is also the center in the longitudinal direction. A vertical MOS semiconductor device having a current detection cell, wherein the vertical MOS semiconductor device is larger than the width of the portion . The oblong window formed in the gate electrode constituting the current detection cell has its longitudinal end portion enlarged in a substantially fan shape, and the base region formed using the gate electrode as a mask The length of the base region constituting the main current cell is shorter than that of the base region constituting the main current cell, and the end of the base region constituting the current detection cell is substantially fan-shaped. Vertical MOS semiconductor device having current detection cells.

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