Semiconductor UV Light Receiving Element Shallow Junction Formation
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Solution Overview
Problem
Existing methods for manufacturing semiconductor devices with both ultraviolet light receiving elements and MOS transistors on a silicon substrate face issues such as etching damage to the insulating film, low reliability due to charge traps, and difficulty in achieving a shallow junction for high sensitivity, leading to low throughput and incomplete ion implantation.
Innovation Solution
A method involving the formation of a first thermal oxide film as a gate oxide, followed by a second thermal oxide film for ion implantation in the light receiving element region, allowing for a low-dose impurity concentration and a shallow junction without etching damage, with the second oxide film being newly formed after removing the gate oxide film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a first thermal oxide film is formed as a gate oxide film and then patterned to form a gate electrode, then the MOS transistor can be formed, but the insulating film in the light receiving element region suffers etching damage and contains charge traps, reducing reliability
Solution Approach 1:
The oxide film formation process is segmented into two distinct stages: first forming a gate oxide film for the MOS transistor region, then removing it and forming a second oxide film for the light receiving element region. This segmentation allows each region to have an oxide film optimized for its specific function, preventing etching damage to the light receiving element's insulating film.
Solution Approach 2:
Different regions of the semiconductor device are given different oxide film qualities: the MOS transistor region receives a gate oxide film with specific thickness and properties, while the light receiving element region receives a second oxide film formed without etching damage. This local differentiation ensures each region has the optimal insulating film characteristics for its intended function.
2Quantity of substance
If ion implantation is performed through a thick insulating film to form an impurity region, then the impurity concentration can be increased, but the junction depth increases and the light receiving sensitivity decreases
Solution Approach 1:
The gate oxide film is removed before forming the second oxide film and performing ion implantation. This preliminary removal creates a condition where ion implantation can be performed through a thinner oxide film, enabling precise control of junction depth while achieving the required impurity concentration for the light receiving element.
3Manufacturing precision
If the insulating film is made thin to achieve shallow junction, then ion implantation dose can be reduced, but the film may not provide sufficient insulation and protection
Solution Approach 1:
The second oxide film acts as an intermediary layer that is optimized specifically for the light receiving element region. It provides the necessary insulation and protection while being thin enough to allow effective ion implantation for forming the shallow junction, resolving the conflict between insulation quality and junction depth 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 approach results in a semiconductor device with high reliability and a shallow junction, enabling effective detection of ultraviolet light with improved sensitivity and reduced manufacturing failures, while maintaining the quality of the insulating film in contact with the silicon surface.
Implementation Method 1
a first thermal oxide film, which serves as a gate oxide film of a MOS transistor, is formed on a surface of a silicon substrate
Implementation Method 2
ion implantation of an impurity is performed on the light receiving element forming region through the second thermal oxide film, to thereby form an impurity region
Implementation Method 3
a light receiving element configured to detect short-wavelength light, for example, an ultraviolet light
Implementation Method 4
A penetration depth of light in silicon (a depth at which an intensity of the incident light to the silicon is attenuated to 1/e due to absorption) has a wavelength dependence
Data Source
AI summary
In order to form a light receiving element having high reliability and a MOS transistor together on the same silicon substrate, after forming a gate electrode of the MOS transistor, a gate oxide film in a light receiving element forming region is removed. Then, a thermal oxide film is newly formed in the light receiving element forming region, and ion implantation is performed in the light receiving element forming region through the thermal oxide film such that a shallow pn junction is formed.