Ultraviolet Photodiode Visible Light Sensitivity Reduction
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Solution Overview
Problem
Existing ultraviolet light receiving elements have difficulty in reducing spectral sensitivity in the visible light range, as the peak concentration position of the photodiode insensitive to ultraviolet light is not accurately determined, leading to increased sensitivity in the visible light range.
Innovation Solution
The ultraviolet light receiving element is designed with a first photodiode sensitive to ultraviolet light and a second photodiode insensitive to ultraviolet light, where the second well implantation layer has a peak concentration position deeper than the first by a calculated depth, using the expression d_p ≈ d_s * exp(α * x_p), to equalize visible light sensitivities and reduce spectral sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the peak concentration position of the well implantation layer in the photodiode insensitive to ultraviolet light is set deeper than in the photodiode sensitive to ultraviolet light, then ultraviolet light sensitivity differentiation is achieved, but spectral sensitivity in the visible light range increases
Solution Approach 1:
The patent applies parameter changes by precisely controlling the peak concentration position parameter of the well implantation layer. The second well implantation layer's peak concentration position is set to be deeper than the first by a specific depth dp, which is calculated based on the depth ds from the surface to the peak concentration position of the surface implantation layer and the light absorption coefficient α. This quantitative parameter adjustment achieves ultraviolet sensitivity differentiation while controlling visible light spectral sensitivity.
Solution Approach 2:
The patent implements preliminary action by pre-calculating and pre-setting the peak concentration position depth dp of the second well implantation layer before manufacturing. The depth is determined using the formula dp = ds - (1/α) * ln(2), where ds and α are known parameters. This preliminary determination prevents excessive visible light spectral sensitivity from occurring during device operation.
2Ease of manufacture
If the peak concentration position of the second well implantation layer is simply set deeper, then manufacturing is simplified, but visible light sensitivity increases
Solution Approach 1:
The patent transforms the manufacturing process from simple depth setting to precise parameter control. Instead of merely setting the second well implantation layer deeper, the patent specifies that the peak concentration position difference dp must equal ds - (1/α) * ln(2). This parameter-based approach maintains manufacturing feasibility while achieving precise spectral sensitivity control.
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 effectively reduces spectral sensitivity in the visible light range by ensuring both photodiodes have equal sensitivity, thereby enhancing the element's ability to detect ultraviolet light while minimizing sensitivity to visible light.
Implementation Method 1
The peak concentration position from the surface of the semiconductor substrate is made different between the impurity implantation layers of the two photodiodes, to thereby make one of the two photodiodes sensitive to the ultraviolet light and the other photodiode insensitive to the ultraviolet light
Data Source
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AI summary
Provided is an ultraviolet light receiving element capable of reducing visible light sensitivity. The ultraviolet light receiving element includes: a first photodiode sensitive to an ultraviolet light provided in a first region of a semiconductor substrate; and a second photodiode insensitive to the ultraviolet light provided in a second region of the semiconductor substrate. A second well implantation layer in the second photodiode has a peak concentration position deeper than a peak concentration position of a well implantation layer in the first photodiode by a depth equal to a depth from a surface of the semiconductor substrate to a peak concentration position of a surface implantation layer in the second photodiode.