SiC Semiconductor Ion Implantation Mask Alignment
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Solution Overview
Problem
The existing methods for manufacturing silicon carbide semiconductor devices face challenges in forming ion implanted regions in a self-alignment manner due to difficulties in achieving perpendicular side surfaces of ion implantation masks and the need for multiple steps, leading to inaccuracies and increased complexity.
Innovation Solution
A method involving the formation of a first and second ion implantation mask using photolithography, where the first mask defines the source region and the second mask, in contact with the first, forms the base region, allowing for self-aligned ion implantation with reduced steps and high accuracy by using a resist as the ion implantation mask, eliminating the need for inorganic masks and additional etching steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If LPCVD method is used to deposit material for second ion implantation mask and entire surface is etched back, then second ion implantation mask is formed on side surface of first ion implantation mask, but corner part of upper part of second ion implantation mask is also etched, making it difficult to form perpendicular side surface
Solution Approach 1:
The patent divides the ion implantation mask formation into two separate masks (first and second ion implantation masks) formed by photolithography, where each mask is independently patterned. This segmentation allows the first mask to define the source region with precise perpendicular sides, while the second mask defines the base region, eliminating the need for etching back that causes corner rounding and boundary blurring.
Solution Approach 2:
The first ion implantation mask is formed and used to define the source region before the second ion implantation mask is formed. This preliminary action establishes a precise reference structure that guides the subsequent formation of the base region, ensuring accurate spatial relationship and boundary definition without compromising perpendicularity.
2Reliability
If inorganic mask is used as ion implantation mask with film forming step, pattern transfer step and etching step, then ion implanted region can be formed, but step number increases and it becomes difficult to reduce step number
Solution Approach 1:
The patent extracts and eliminates the inorganic mask formation steps (LPCVD deposition, pattern transfer, and etching) from the process by using organic photoresist masks instead. This extraction removes the complex multi-step inorganic mask formation sequence while maintaining the essential function of defining ion implanted regions through photolithography alone.
Solution Approach 2:
The patent uses disposable organic photoresist masks that can be directly patterned and removed after use, replacing durable but complex inorganic masks. These photoresist masks are applied, patterned by photolithography, used for ion implantation, and then removed, eliminating the need for complex inorganic mask formation and removal steps.
3Ease of manufacture
If pattern of ion implantation mask is formed by combination of pattern transfer step and etching step, then ion implantation mask pattern dimension accuracy is reduced
Solution Approach 1:
The patent uses photoresist masks that are directly patterned by photolithography without requiring separate pattern transfer and etching steps. The photoresist is applied, exposed, developed, and used directly as the ion implantation mask, preserving the high dimensional accuracy achieved during photolithography while simplifying the overall process.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables the formation of silicon carbide semiconductor devices with high accuracy in channel dimension control and reduced step complexity, improving the controllability and precision of ion implanted regions without the use of inorganic masks, thereby enhancing the manufacturing process.
Implementation Method 1
implanting impurities of the first conductivity type from the first opening with an ion beam using the third ion implantation mask to form the source region
Implementation Method 2
implanting impurities of the second conductivity type with an ion beam from a second opening formed in the second ion implantation mask after the removal of the first ion implantation mask to form the base region
Data Source
AI summary
The present invention includes steps below: (a) forming, on a drift layer, a first ion implantation mask and a second ion implantation mask individually by photolithography to form a third ion implantation mask, the first ion implantation mask having a mask region corresponding to a channel region and having a first opening corresponding to a source region, the second ion implantation mask being positioned in contact with an outer edge of the first ion implantation mask and configured to form a base region; (b) implanting impurities of a first conductivity type from the first opening with an ion beam using the third ion implantation mask to form a source region in an upper layer part of the silicon carbide drift layer; (c) removing the first ion implantation mask after the formation of the source region; and (d) implanting impurities of a second conductivity type with an ion beam from a second opening formed in the second ion implantation mask after the removal of the first ion implantation mask to form a base region deeper than the source region in the upper layer part of the drift layer.