Semiconductor Device Impurity Density Profile for Electron Inflow Control
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Solution Overview
Problem
In semiconductor devices, the separation of high density impurity regions and intermediate density impurity regions is challenging, leading to difficulties in controlling electron inflow efficiency and stabilizing device properties, especially when p-type impurities diffuse into n-type regions during melting, causing unintended conductivity type changes at boundaries.
Innovation Solution
A semiconductor device with a specific impurity density distribution, characterized by local maximum and minimum values, is created by implanting first conductivity type impurities at different depths and activating them through heat treatment and melting, ensuring a 'box profile' that separates high and intermediate density regions effectively, reducing the influence of intermediate density regions on electron inflow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the n-type impurity density at the boundary between high density impurity region and intermediate density impurity region is increased to prevent p-type impurity diffusion, then the separation between high density impurity region and intermediate density impurity region deteriorates
Solution Approach 1:
The patent applies parameter changes by establishing specific quantitative relationships between impurity densities at different locations. The condition N2 ≥ N3/10 ensures that the minimum impurity density in the high density region maintains sufficient carrier concentration to prevent p-type impurity diffusion, while the condition N2 < N3 ensures adequate separation between regions. This quantitative parameter control resolves the contradiction by finding the optimal balance point.
Solution Approach 2:
The patent implements local quality by creating distinct impurity density characteristics in different regions. The high density impurity region has locally high impurity concentration (N1 > N3) to ensure low contact resistance, while the intermediate density impurity region has lower concentration to maintain separation. The boundary region specifically maintains N2 ≥ N3/10 to prevent conductivity type changes, applying different quality requirements to different locations.
2Device complexity
If the intermediate density impurity region is positioned closer to the high density impurity region to reduce device complexity, then the control precision of electron inflow efficiency deteriorates
Solution Approach 1:
The patent uses parameter changes to define the spatial relationship between regions through the condition a > 2b, where a is the distance from the surface to the peak of the high density region and b is the distance from the peak to the valley. This quantitative constraint ensures that while regions are positioned close together to minimize device complexity, the electron inflow efficiency remains controllable through the maintained separation distance.
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 stabilizes semiconductor device properties by ensuring the high density region is isolated from the intermediate density region, maintaining high electron inflow efficiency and preventing unintended conductivity type changes, thus enhancing device performance during mass production.
Implementation Method 1
first conductivity type impurities are implanted into a surface of a semiconductor substrate
Implementation Method 2
a region in the vicinity of the surface is melted, and thereafter solidified again
Implementation Method 3
the impurities are diffused over an entirety of the melted region
Implementation Method 4
after which a region in the vicinity of the surface is melted
Data Source
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Figure 5~6
AI summary
A semiconductor device, in which, in a density distribution of first conductivity type impurities in the first conductivity type region 38 measured along a thickness direction of the semiconductor substrate 12, a local maximum value N1, a local minimum value N2, a local maximum value N3, and a density N4 are formed in this order from front surface side, a relationship of N1>N3>N2>N4 is satisfied, a relationship of N3/10>N2 is satisfied, and a distance "a" from the surface to the depth having the local maximum value N1 is larger than twice a distance "b" from the depth having the local maximum value N1 to the depth having the local minimum N2.