Reverse-conducting IGBT Contact Formation via Cover Layer Protection
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Solution Overview
Problem
Conventional reverse-conducting insulated gate bipolar transistors face challenges in forming body contact regions due to differing depths of first and second contacts, leading to difficulties in simultaneous processing and potential deterioration of diode characteristics.
Innovation Solution
The solution involves separately forming first and second contacts with the first contact having a larger thickness extending to the body contact region, and applying a cover layer to protect the uppermost surface of the first contact during subsequent processing, while ensuring the body region in the second cell region is covered with an insulating film to prevent direct contact with conductive films.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the first contact and second contact are formed simultaneously by etching the interlayer insulating film, then the manufacturing process is simplified, but the manufacturing precision deteriorates because the contacts have different depths and cannot be properly formed
Solution Approach 1:
The patent divides the contact formation process into separate steps: the second contact is formed first by etching the interlayer insulating film, then the first contact is formed in a subsequent step. This segmentation allows each contact to be optimized independently - the second contact reaches the appropriate depth in the interlayer insulating film, while the first contact can extend deeper to reach the body contact region without affecting the second contact's formation precision
Solution Approach 2:
The second contact is formed in advance before the first contact. This preliminary action establishes the correct depth and position of the second contact in the interlayer insulating film, and then the first contact is formed in a subsequent step that can independently control its own depth to reach the body contact region
2Reliability
If a conductive film is formed on the body region to create ohmic contact, then the diode characteristics improve, but the switching speed deteriorates due to contamination on the exposed uppermost surface of the first contact
Solution Approach 1:
The patent introduces a cover layer as an intermediary protective element that covers the uppermost surface of the first contact during subsequent processing steps. This cover layer prevents contamination of the first contact surface when conductive films are formed, allowing the conductive film to be properly formed on the body region for ohmic contact without introducing contaminants that would degrade switching speed
Solution Approach 2:
The cover layer is formed in advance before the conductive film deposition process. This preliminary protective action ensures that the uppermost surface of the first contact is shielded from contamination during the subsequent formation of conductive films on the body region, maintaining both diode characteristics and switching speed
3Manufacturing precision
If the first contact is formed with large thickness to reach the body contact region, then the body contact region formation is improved, but the device complexity increases due to the need for separate processing steps and cover layer
Solution Approach 1:
The cover layer serves multiple functions: it protects the uppermost surface of the first contact from contamination during subsequent processing, provides a planar surface for subsequent film deposition, and can be removed selectively to expose the first contact surface if needed. This multi-functionality justifies the additional processing step by providing benefits beyond simple protection
Data Source
AI summary
A reverse-conducting insulated gate bipolar transistor and a method of manufacturing the same are disclosed. More particularly, the insulated gate bipolar transistor and the method of manufacturing the same are configured to form a cover layer so as to prevent external exposure of an uppermost surface of a first contact in a first cell region, thereby maximally reducing occurrences of contamination during subsequent processing.