Semiconductor device

• US 20070007537A1
• Filed: 07/03/2006
• Published: 01/11/2007
• Est. Priority Date: 07/04/2005
• Status: Active Grant

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Omura, Ichiro, Ogura, Tsuneo
• Granted Patent: US 7,915,617 B2
• Time in Patent Office: Days
• US Class Current: 257/77
• CPC Class Codes: H01L 21/26586 characterised by the angle between the ion beam and the crystal planes or the main crystal surface
• CPC Class Codes: H01L 29/0619 with a supplementary region doped oppositely to or in rectifying contact with the semiconductor containing or contacting region, e.g. guard rings with PN or Schottky junction
• CPC Class Codes: H01L 29/0696 of cellular field-effect devices, e.g. multicellular DMOS transistors or IGBTs
• CPC Class Codes: H01L 29/086 Impurity concentration or distribution
• CPC Class Codes: H01L 29/0869 Shape cell layout H01L29/0696
• CPC Class Codes: H01L 29/0878 Impurity concentration or distribution
• CPC Class Codes: H01L 29/1033 with insulated gate, e.g. characterised by the length, the width, the geometric contour or the doping structure with channel and gate aligned in the lengthwise direction H01L29/42376; with buried channel H01L29/7838
• CPC Class Codes: H01L 29/1045 the doping structure being parallel to the channel length, e.g. DMOS like
• CPC Class Codes: H01L 29/105 with vertical doping variation H01L29/7827 takes precedence
• CPC Class Codes: H01L 29/1095 Body region, i.e. base region, of DMOS transistors or IGBTs cell layout H01L29/0696
• CPC Class Codes: H01L 29/1608 Silicon carbide
• CPC Class Codes: H01L 29/41766 with at least part of the source or drain electrode having contact below the semiconductor surface, e.g. the source or drain electrode formed at least partially in a groove or with inclusions of conductor inside the semiconductor H01L29/41733 - H01L29/41758 take precedence
• CPC Class Codes: H01L 29/42368 the thickness being non-uniform
• CPC Class Codes: H01L 29/66068 the devices being controllable only by the electric current supplied or the electric potential applied, to an electrode which does not carry the current to be rectified, amplified or switched, e.g. three-terminal devices
• CPC Class Codes: H01L 29/7397 and a gate structure lying on a slanted or vertical surface or formed in a groove, e.g. trench gate IGBT
• CPC Class Codes: H01L 29/7802 Vertical DMOS transistors, i.e. VDMOS transistors
• CPC Class Codes: H01L 29/7813 with trench gate electrode, e.g. UMOS transistors trench gate electrodes per se H01L29/4236
• CPC Class Codes: H01L 29/7828 without inversion channel, e.g. vertical ACCUFETs, normally-on vertical MISFETs

Abstract

A semiconductor device comprises: a first semiconductor layer of silicon carbide of a first conductivity type; a second semiconductor layer of silicon carbide of a second conductivity type selectively provided on the first semiconductor layer; a main electrode layer of silicon carbide of the first conductivity type selectively provided on the second semiconductor layer; a gate insulating film provided on the second semiconductor layer; a gate electrode formed on the gate insulating film; and a third semiconductor layer of the first conductivity type intervening a current path which is formed between the main electrode layer and the first semiconductor layer when an ON voltage is applied to the gate electrode. The third semiconductor layer is selectively provided on the first semiconductor layer and is adjacent to the second semiconductor layer. A doping density of the third semiconductor layer is higher than a doping density of the first semiconductor layer.

Claims

1. A continuous web of self-supporting adhesive sheet material useful for making a transparent adhesive interlayer comprising:

(a) an area of uniform thickness profile across at least 20% of its width starting the center of the web and continuing in both directions toward the outer edges of the web, and (b) two areas of variable thickness profile increasing in thickness from the outer edges of the web to the area of uniform thickness at the center of the web, such that by splitting the web in the region of uniform thickness, two pieces of sheet can be obtained each having an area of at least 20% uniform thickness.

2. The continuous web of self-supporting adhesive sheet material of claim 1 wherein said material is polyvinyl butyral.

3. The continuous web of self-supporting adhesive sheet material of claim 2 wherein said variable thickness profile has a wedge angle from 0.1 to 1.0 milliradians.

4. The continuous web of self-supporting adhesive sheet material of claim 2 wherein said uniform thickness is from 380 to 2286 micrometers.

9. The process of claim 21 wherein the wedge-shaped thickness profile has a wedge angle from 0.1 to 1.0 milliradian.

10. The process of claim 21 wherein said uniform thickness is from 380 to 2286 micrometers.

15. The continuous web of self-supporting adhesive sheet material of claim 4 wherein the sheeting has a gradated shade band in the area of uniform thickness.

16. The continuous web of self-supporting adhesive sheet material of claim 1 wherein said variable thickness profile has a wedge angle from 0.1 to 1.0 milliradians.

17. The continuous web of self-supporting adhesive sheet material of claim 1 wherein said uniform thickness is from 380 to 2286 micrometers.

18. The continuous web of self-supporting adhesive sheet material of claim 3 wherein said uniform thickness is from 380 to 2286 micrometers.

19. The continuous web of self-supporting adhesive sheet material of claim 18 wherein the sheeting has a gradated shade band in the area of uniform thickness.

20. The continuous web of self-supporting adhesive sheet material of claim 18 wherein the two areas of variable thickness profile are wedge shaped.

21. The continuous web of self-supporting adhesive sheet material of claim 18 wherein the two areas of variable thickness profile increase symmetrically relative to the web centerline.

22. The continuous web of self-supporting adhesive sheet material of claim 18 wherein the two areas of variable thickness profile increase asymmetrically relative to the web centerline.

23. The continuous web of self-supporting adhesive sheet material of claim 18 wherein the two areas of variable thickness profile increase in thickness in a linear fashion.

24. The continuous web of self-supporting adhesive sheet material of claim 18 wherein the two areas of variable thickness profile increase in thickness in a continuous but non-linear fashion.

25. The continuous web of self-supporting adhesive sheet material of claim 18 wherein the two areas of variable thickness profile include regions where the slope is increasing according to the equation of a curved line.

28. A process for preparing transparent adhesive interlayer, the process comprising:

a. providing a continuous web of self-supporting adhesive sheet material as claimed in claim 1;

b. slitting said web at or near its mid-point to form two slit webs; and

c. winding the slit webs onto separate rolls.

5. (canceled)

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26. A continuous web of self-supporting adhesive sheet material useful for making a transparent adhesive interlayer comprising:

(a) an area of uniform thickness profile across at least 20% of its width stating the center of the web and continuing in both directions toward the outer edges of the web, (b) two areas of uniform minimum thickness along the outer portions of the web, and (c) two areas of variable thickness profile increasing in thickness from the two areas of uniform thickness to the area of uniform thickness at the center of the web, such that by splitting the web in the region of uniform thickness, two pieces of sheet can be obtained each having an area of at least 20% uniform thickness.

27. The continuous web of self-supporting adhesive sheet material of claim 26 wherein said material is polyvinyl butyral, the variable thickness profile has a wedge angle from 0.1 to 1.0 milliradians, and the uniform thickness is from 380 to 2286 micrometers.