TRENCH MOSFET WITH TRENCHED FLOATING GATES HAVING THICK TRENCH BOTTOM OXIDE AS TERMINATION
First Claim
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1. A semiconductor power device comprising:
- a plurality of power transistor cells disposed in an active area near a top surface of an epitaxial layer of first conductivity type grown on a semiconductor substrate of said first conductivity type wherein each of said transistor cells is surrounded by trenched gates;
multiple trenched floating gates disposed in a termination area surrounding said active area and each of said trenched floating gates having a floating voltage wherein said trenched floating gates further penetrating through a body region and extending into said epitaxial layer;
said trenched gates and said multiple trenched floating gates comprising a conductive material padded by a gate insulation layer filled in trenches, wherein said gate insulation layer having a thick bottom oxide on bottom surface of said trenches with a thickness greater than sidewall oxide along sidewall of said trenches;
said body region of a second conductivity type formed in both said active cell area and said termination area disposed immediately adjacent to said trenched floating gates;
said trenched gates further extended to wider trenched gates in a gate contact area having a greater trench width than said trench gates in said active cell area for electrically connecting to a gate metal; and
a source region of said first conductivity type disposed only in said power transistor cells in said active area but not in said termination area comprising said multiple trenched floating gates and no source regions disposed in said epitaxial layer regions adjacent to said wider trenched gate in said gate contact area
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Abstract
A power semiconductor power device having composite trench bottom oxide and multiple trench floating gates is disclosed. The gate charge is reduced by forming a pad oxide surrounding a HDP oxide on trench bottom. The multiple trenched floating gates are applied in termination for saving body mask.
21 Citations
25 Claims
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1. A semiconductor power device comprising:
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a plurality of power transistor cells disposed in an active area near a top surface of an epitaxial layer of first conductivity type grown on a semiconductor substrate of said first conductivity type wherein each of said transistor cells is surrounded by trenched gates; multiple trenched floating gates disposed in a termination area surrounding said active area and each of said trenched floating gates having a floating voltage wherein said trenched floating gates further penetrating through a body region and extending into said epitaxial layer; said trenched gates and said multiple trenched floating gates comprising a conductive material padded by a gate insulation layer filled in trenches, wherein said gate insulation layer having a thick bottom oxide on bottom surface of said trenches with a thickness greater than sidewall oxide along sidewall of said trenches; said body region of a second conductivity type formed in both said active cell area and said termination area disposed immediately adjacent to said trenched floating gates; said trenched gates further extended to wider trenched gates in a gate contact area having a greater trench width than said trench gates in said active cell area for electrically connecting to a gate metal; and a source region of said first conductivity type disposed only in said power transistor cells in said active area but not in said termination area comprising said multiple trenched floating gates and no source regions disposed in said epitaxial layer regions adjacent to said wider trenched gate in said gate contact area - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. A semiconductor power device comprising:
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a plurality of N-channel or P-channel MOSFET cells surrounded by trenched gates in an active area near a top surface of an epitaxial layer of first conductivity grown on a substrate of first conductivity type; said trenched gates further extended to wider trenched gates in a gate contact area having greater trench width than said trench gates in said active cell area for electrically connecting a gate metal; at least three trenched floating gates disposed in a termination area surrounding said active cell area having a floating voltage wherein said trenched floating gates penetrating through a body region and extending into said epitaxial layer; said trenched gates and said trenched floating gates comprising a conductive material padded by a gate insulation layer filled in trenches, wherein said gate insulation layer having a thick bottom oxide on bottom surface of said trenches with a thickness greater than sidewall oxide along sidewall of said trenches; said body region formed in both said active cell area and said termination area disposed immediately adjacent to said trenched floating gates; a source region of said first conductivity type disposed only in said active area but not in said termination area having said multiple trenched floating gates and no source regions disposed in said epitaxial layer adjacent to said wider trenched gate in said gate contact area an insulation layer overlying said semiconductor device and a plurality of source-body contact trenches opened through said insulation layer and said source region and extending into said body region for filling with a source-body contact metal plug therein for electrically contacting said source region and said body region; a patterned source metal layer disposed on top of said insulating layer for electrically contacting said source-body contact plug; and a drain electrode disposed on a bottom surface of a semiconductor substrate supporting said semiconductor power device. - View Dependent Claims (19)
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20. A method of manufacturing a semiconductor power device comprising:
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(a) forming a plurality of trenches in an epitaxial layer of first conductivity type; (b) depositing a HDP oxide on trench sidewall, and bottom, and top surface of said mesa area wherein said trench sidewall has thinner oxide than said trench bottom and said mesa area; (d) removing, using wet etching, the oxide on trench sidewall completely, and the oxide on trench bottom and said mesa area partially wherein a remaining oxide and said pad oxide on trench bottom defined as bottom oxide layer; (e) depositing a photo resist filled into said trenches and top surface of said mesa area; (f) removing a portion of said photo resist from top surface of said mesa area to expose said portion of surface area of said oxide on said mesa area where said oxide layer can be removed; (g) removing said oxide on said top surface of said mesa area completely; (h) forming a gate oxide on trench sidewall; and (i) forming trenched gates, trenched floating gates, body regions, source regions and trenched source-body contact in said epitaxial layer. - View Dependent Claims (21, 22, 23, 24, 25)
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Specification