Polysilicon Dummy Layer for Accurate Dry-Etch Endpoint Detection
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Solution Overview
Problem
Existing methods for detecting the end point of dry-etching in semiconductor manufacturing are inaccurate when dealing with small active regions or multiple insulation films of different thicknesses, leading to potential over-etching and degradation of transistor characteristics.
Innovation Solution
A dummy layer made of polysilicon is formed on the element isolation film to enhance the detection of the end point during dry-etching, specifically by increasing the emission intensity difference of a specific spectral line, allowing for more accurate detection even when etching films of varying thicknesses simultaneously.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the area of the semiconductor substrate (active region) to be exposed under the insulation film is small, then the etching process can be completed, but the emission intensity of the specific spectral line of plasma is too small to distinguish the levels of the emission intensity for accurate end point detection
Solution Approach 1:
A dummy layer is introduced as an intermediary structure formed on the element isolation film surrounding the active region. This dummy layer has the same material composition and etching characteristics as the gate insulation film, allowing plasma emission signals to be generated from this auxiliary structure. The emission intensity from the dummy layer provides a sufficient signal for accurate end point detection even when the active region area is small, thereby solving the contradiction between measurement precision and active region area.
2Measurement precision
If insulation films having different thicknesses are dry-etched simultaneously, then the etching process can be completed for all regions, but it is difficult to perform end point detection accurately when the semiconductor substrate under the thicker insulation film is exposed
Solution Approach 1:
The detection function is segmented from the active region and assigned to a separate dummy layer structure. The dummy layer is formed only in specific regions (surrounding the active region) and has the same etching characteristics as the gate insulation film. During simultaneous etching of insulation films with different thicknesses, the dummy layer provides a dedicated signal source that clearly indicates when the substrate under the thicker insulation film is exposed, enabling accurate end point detection without interference from the complexity of varying insulation film thicknesses.
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
The polysilicon dummy layer improves the accuracy of end point detection by increasing the emission intensity difference, ensuring minimal over-etching and maintaining transistor quality, particularly when etching films of different thicknesses.
Implementation Method 1
there is a method of detecting an end point based on a change of emission intensity (an emission amount) of a specific spectral line of plasma that is observed during dry-etching
Data Source
AI summary
The invention enhances the accuracy of an end point detection when an insulation film formed on a semiconductor substrate is dry-etched. Gate layers made of polysilicon are formed, and an end point detection dummy layer made of polysilicon is formed on a LOCOS. After the gate layers and the dummy layer are formed, a TEOS film is formed on a silicon substrate so as to cover the gate layers and the dummy layer. The TEOS film, a thin gate oxide film and a thick gate oxide film are then dry-etched to form sidewalls on the sidewalls of the gate layers and also expose the front surface of the P well of the silicon substrate in a region surrounded by the LOCOS. The end point detection dummy layer helps the end point detection by being exposed during this dry-etching to enhance the accuracy of the end point detection.