Recessed Source Contact for High Density Lateral DMOS
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Solution Overview
Problem
The traditional process of forming lateral double diffused metal oxide semiconductor transistors (DMOS) is complex and costly due to the need for multiple photoresist and mask layers, resulting in a larger device size and increased base resistance of parasitic bipolar transistors.
Innovation Solution
The introduction of a recessed source contact that extends vertically through the source region to reach the body region, allowing for reduced source opening width and eliminating the need for multiple photoresist and mask layers, thereby simplifying the fabrication process and reducing device size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple photoresist and mask layers are used to form the source region, body contact region, and source contact, then the fabrication process can achieve proper doping and contact formation, but the device size increases and fabrication complexity and cost increase
Solution Approach 1:
The patent merges the formation of the source region, body contact region, and source contact into a single photolithography step using one photoresist layer and one mask layer. The source opening is designed to simultaneously define all three regions, eliminating the need for multiple sequential patterning steps and reducing fabrication complexity while maintaining manufacturing precision
Solution Approach 2:
The single source opening structure serves multiple functions: it defines the source region for doping, creates the body contact region, and forms the source contact opening. This multi-functional design reduces the number of required photolithography layers and simplifies the overall fabrication process
2Manufacturing precision
If multiple photoresist and mask layers are used to form the source region, body contact region, and source contact, then proper doping and contact formation can be achieved, but fabrication cost increases
Solution Approach 1:
The patent combines multiple fabrication steps into a single photolithography operation, reducing material consumption (photoresist, masks) and process time. This merging of steps directly reduces fabrication cost while maintaining the precision needed for proper doping and contact formation
Solution Approach 2:
The single source opening pattern serves as a master template that simultaneously creates multiple functional regions through subsequent processing steps, eliminating the need to create separate patterns for each region and reducing overall fabrication cost
3Reliability
If the source contact covers both the P+ body contact region and the N+ source region, then proper electrical contact is achieved, but the source opening width increases device size
Solution Approach 1:
The patent transitions from a purely lateral contact geometry to a vertical contact geometry by extending the source contact downward through the source region to reach the body contact region. This vertical dimension allows the contact to access multiple conductive regions without requiring a large lateral opening width, thus reducing device size while maintaining electrical contact reliability
Solution Approach 2:
The source contact structure is designed to nest within the source opening and extend vertically to contact the body contact region, creating a nested configuration where the contact traverses through the source region to reach the underlying body contact, achieving reliable electrical connection with minimal lateral space
Data Source
AI summary
The present disclosure discloses a lateral DMOS with recessed source contact and method for making the same. The lateral DMOS comprises a recessed source contact which has a portion recessed into a source region to reach a body region of the lateral DMOS. The lateral DMOS according to various embodiments of the present invention may have greatly reduced size and may be cost saving for fabrication.