STI Etch Critical Dimension Control via BARC Mapping
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Solution Overview
Problem
Current shallow trench isolation (STI) etch processes face challenges in accurately controlling critical dimensions due to limitations in measuring the thickness of the bottom anti-reflective coating (BARC) layer and variations during lithography and etching, leading to inefficiencies and product losses.
Innovation Solution
The method employs optical critical dimension measurement equipment to measure BARC layer thickness and establish a mapping relation between pre- and post-etch critical dimensions, allowing for precise adjustment of the hard mask layer trimming time to control STI critical dimensions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional measurement methods are used to measure photoresist linewidth, then measurement simplicity is maintained, but measurement precision is insufficient because BARC layer thickness cannot be measured
Solution Approach 1:
The patent introduces an optical critical dimension measurement equipment as an intermediary device between the lithography process and etching process. This equipment measures both the photoresist pattern linewidth and the BARC layer thickness, providing comprehensive measurement data that serves as a mediator to establish the mapping relationship between pre-etch and post-etch critical dimensions, thereby improving measurement precision without excessive complexity
Solution Approach 2:
The patent replaces conventional mechanical or simple optical measurement methods with advanced optical critical dimension measurement equipment that uses optical principles to non-contactively measure both photoresist linewidth and BARC layer thickness simultaneously, achieving higher precision measurement while maintaining operational simplicity
2Manufacturing precision
If only photoresist pattern dimensions are monitored, then monitoring simplicity is maintained, but manufacturing precision deteriorates because BARC layer thickness variations are not accounted for
Solution Approach 1:
The patent performs preliminary measurement of both photoresist pattern linewidth and BARC layer thickness before the etching process using optical critical dimension measurement equipment. This preliminary action establishes a mapping relationship between pre-etch and post-etch critical dimensions, allowing the system to predict and compensate for etching variations, thereby improving manufacturing precision without significantly impacting productivity
Solution Approach 2:
The patent implements a feedback mechanism where the measured photoresist linewidth and BARC layer thickness data are used to determine the trimming time for the hard mask layer. This feedback loop ensures that the STI critical dimensions are precisely controlled by adjusting the etching process parameters based on actual measurements, rather than relying solely on fixed process parameters
3Reliability
If exposure offset and etching variations are not compensated, then process simplicity is maintained, but reliability deteriorates due to dimension shifts
Solution Approach 1:
The patent establishes a feedback-based process control system where optical critical dimension measurement equipment measures the photoresist pattern and BARC layer, and the measured data is used to determine the hard mask layer trimming time. This feedback mechanism compensates for exposure offsets and etching chamber variations, ensuring reliable STI critical dimension control while managing process complexity through systematic data utilization
Solution Approach 2:
The patent performs preliminary measurements of photoresist linewidth and BARC layer thickness before etching to establish a mapping relationship that accounts for potential variations. This preliminary action enables the system to pre-determine appropriate trimming parameters, thereby improving reliability by anticipating and compensating for dimension shifts before they occur
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 enables precise control of STI critical dimensions, improving process efficiency and product yield by considering BARC layer thickness variations, unlike conventional methods that rely solely on photoresist pattern dimensions.
Implementation Method 1
utilizes optical critical dimension (OCD) measurement equipment to measure the BARC layer thickness
Implementation Method 2
etching the substrate by using the hard mask pattern as a mask to form the shallow trenches
Data Source
AI summary
The present invention provides a method for controlling a critical dimension of shallow trench isolations in a STI etch process, comprises the following steps: before the STI etch process, pre-establishing a mapping relation between a post-etch and pre-etch critical dimension difference of a BARC layer and a thickness of the BARC layer; and during the STI etch process after coating the BARC layer, measuring the thickness of the BARC layer and determining a trimming time for a hard mask layer according to a critical dimension difference corresponding to the measured thickness in the mapping relation and a critical dimension of a photoresist pattern, then performing a trimming process for the hard mask layer lasting the trimming time to make a critical dimension of the hard mask layer equal to a required critical dimension of an active area, and etching a substrate to form shallow trenches with a predetermined critical dimension.