Semiconductor Field Stop Layer Segmentation
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Solution Overview
Problem
The existing semiconductor devices with vertical semiconductor elements face challenges in reducing manufacturing costs while maintaining breakdown voltage and preventing switching surges, particularly due to the limitations of proton irradiation times and the need for special equipment for selenium handling.
Innovation Solution
A semiconductor device with a field stop (FS) layer comprising a phosphorus/arsenic layer and a proton layer, where the proton layer is deeper and has a gradually decreasing impurity concentration, reducing electric field concentration and manufacturing costs by optimizing the depth and concentration ratio of the proton layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If proton irradiation is used to form a deep FS layer, then the activation ratio significantly decreases with increased dose amount, requiring long irradiation time, but this reduces productivity and increases manufacturing cost
Solution Approach 1:
The FS layer is segmented into multiple layers: a first FS layer formed by phosphorus ion implantation at a shallow depth, and a second FS layer formed by proton irradiation at a deeper depth. This segmentation allows each layer to be optimized independently, with the first layer providing high concentration near the surface and the second layer providing deep penetration, thereby reducing the total proton dose required and shortening irradiation time while maintaining manufacturing precision
Solution Approach 2:
The invention changes the parameters of the FS layer formation process by using two different doping methods with different characteristics. Phosphorus ion implantation is used for shallow, high-concentration doping, while proton irradiation is used for deeper, lower-concentration doping. This parameter change allows the FS layer to achieve the required depth and concentration profile without requiring excessively high proton doses, thus reducing irradiation time and improving productivity
2Productivity
If selenium is used for ion implantation to form a deep FS layer, then fabrication yield is improved, but special equipment for handling selenium is required
Solution Approach 1:
The invention replaces selenium, which requires special handling equipment and infrastructure, with proton irradiation using a conventional particle accelerator. The proton source is a standard piece of equipment in semiconductor manufacturing, eliminating the need for special selenium handling facilities. Although proton irradiation has lower activation ratio, the combination with phosphorus implantation achieves the desired FS layer formation without requiring expensive and complex selenium handling equipment
3Manufacturing precision
If phosphorus ion implantation is used to form FS layer, then it is formed at shallow depth, but this makes it sensitive to damage on the back side and causes collector leakage
Solution Approach 1:
The FS layer is segmented into two distinct layers: a first FS layer formed by phosphorus ion implantation at shallow depth (0.5-2.0 μm) and a second FS layer formed by proton irradiation at deeper depth (5-15 μm). This segmentation protects the shallow phosphorus layer from back-side damage while the deeper proton layer provides the necessary depth to prevent collector leakage, thus maintaining both manufacturing precision and device reliability
4Loss of time
If proton concentration peaks at deep position, then the problem of long proton irradiation time is not solved, but an electric field concentration occurs at the boundary between FS layer and drift layer, reducing breakdown voltage
Solution Approach 1:
The invention applies local quality by creating different concentration profiles in different regions of the FS layer. The first FS layer (phosphorus) has high concentration near the back surface, while the second FS layer (proton) has lower concentration at deeper positions. This local quality distribution prevents electric field concentration at the FS layer-drift layer boundary, maintaining breakdown voltage, while the combined structure reduces the total proton dose required, addressing both time loss and reliability concerns
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 configuration improves productivity, reduces manufacturing costs, ensures higher breakdown voltage, and minimizes switching surges by effectively managing the impurity concentration and depth of the proton layer within the FS layer.
Implementation Method 1
a proton layer doped with proton... The impurity concentration of the proton layer peaks inside the phosphorus/arsenic layer and gradually, continuously decreases at a depth greater than the phosphorus/arsenic layer
Implementation Method 2
a phosphorus/arsenic layer doped with phosphorus or arsenic... The phosphorus/arsenic layer is formed from a back side of a semiconductor substrate to a predetermined depth
Data Source
AI summary
In a semiconductor device having a vertical semiconductor element configured to pass an electric current between an upper electrode and a lower electrode, a field stop layer includes a phosphorus/arsenic layer doped with phosphorus or arsenic and a proton layer doped with proton. The phosphorus/arsenic layer is formed from a back side of a semiconductor substrate to a predetermined depth. The proton layer is deeper than the phosphorus/arsenic layer. An impurity concentration of the proton layer peaks inside the phosphorus/arsenic layer and gradually, continuously decreases at a depth greater than the phosphorus/arsenic layer.