Semiconductor Impurity Control via Laser Annealing
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Solution Overview
Problem
In semiconductor device manufacturing, the melting and solidification process can lead to unintentional formation of regions with unintended conductivity types due to surface impurities diffusing into the melted region, causing instability and performance issues in devices like diodes and MOSFETs.
Innovation Solution
A method involving two implantation steps followed by melting and solidification, where the first implantation increases impurity concentration near the surface, and the second implantation focuses on shallower regions, ensuring that the impurities diffuse within controlled depths to prevent unintended conductivity type formation, and the use of laser annealing to activate and distribute impurities effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the surface of the semiconductor substrate is melted and then solidified to eliminate crystal defects and form high impurity concentration regions, then crystal defect density is reduced and impurity concentration is increased, but impurities of other conductivity types adhering to the surface diffuse into the melted region and cause unintentional formation of regions with unintended conductivity types
Solution Approach 1:
The patent applies preliminary action by performing a first ion implantation to increase the concentration of first conductivity type impurities in a first increased region before the melting process. This pre-positioning of impurities ensures that when the surface is melted and impurities of other conductivity types diffuse into the melted region, the first conductivity type impurity concentration remains sufficiently high to prevent unintentional formation of regions with unintended conductivity types.
Solution Approach 2:
The patent applies local quality by creating different impurity concentration distributions in different depth regions. The first increased region has a higher concentration of first conductivity type impurities compared to other regions. This localized high concentration ensures that even after melting and diffusion of opposite polarity impurities, the first conductivity type characteristics are maintained in specific regions while allowing flexibility in other areas.
2Manufacturing precision
If ion implantation is performed to increase impurity concentration in a target region, then the impurity concentration in that region is increased, but crystal defects are formed in the implanted region
Solution Approach 1:
The patent applies phase transitions by melting the surface region containing the ion-implanted impurities and then allowing it to solidify. This phase transition process eliminates crystal defects formed during ion implantation while redistributing the impurities throughout the melted region. The melting and solidification cycle restores crystal structure integrity while maintaining the desired impurity concentration distribution.
Solution Approach 2:
The patent combines multiple processes - ion implantation to introduce impurities and melting/solidification to eliminate defects. By merging these processes in sequence, the patent achieves both high impurity concentration and low crystal defect density in the same region, resolving the contradiction between impurity concentration enhancement and crystal structure preservation.
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 prevents unintentional formation of regions with unintended conductivity types, enhances impurity concentration control, reduces crystal defects, and stabilizes semiconductor device performance, particularly in diodes, by ensuring high impurity concentrations and minimizing noise during reverse recovery operations.
Implementation Method 1
melting and then solidifying a first semiconductor region between a specific depth and the surface
Implementation Method 2
the impurities diffuse in an entirety of the melted region
Implementation Method 3
a first implantation of implanting first conductivity type impurities into a semiconductor substrate of a first conductivity type from a surface of the semiconductor substrate
Implementation Method 4
the use of laser annealing to activate and distribute impurities effectively
Data Source
AI summary
A structure having high, middle, and low impurity concentration regions disposed from a surface side of a substrate is more suitably manufactured. A method of manufacturing a semiconductor device includes: a first implantation of first conductivity type impurities into a first conductivity type semiconductor substrate from a surface; melting and solidifying a first semiconductor region between a depth and the surface, wherein the depth is deeper than a depth having a peak impurity concentration in an increased region where the impurity concentration was increased in the first implantation, and shallower than a deeper end of the increased region; a second implantation of the impurities from the surface into a region shallower than the depth; and melting and solidifying a region in which the impurity concentration was increased in the second implantation.