Etching Silicon Oxide Films on Multi-Layer Substrates
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Solution Overview
Problem
Existing etching methods for silicon oxide films on substrates with multiple underlying films at different heights face challenges in etching holes of varying depths without damaging the underlying films, particularly due to high ion irradiation rates and difficulties in depositing by-products at the bottom of deeper holes.
Innovation Solution
An etching method using a substrate processing apparatus that employs a sequence of gases to etch silicon oxide films at different depths, with a first gas exposing the underlying films, a second gas depositing by-products on the first underlying film, and a third gas removing these by-products, repeated multiple times to prevent damage and achieve precise etching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional etching methods are used to etch silicon oxide films on substrates with multiple underlying films at different heights, then holes of varying depths can be etched, but the underlying films in the lower and intermediate layers suffer from high ion irradiation damage
Solution Approach 1:
The etching process is segmented into multiple steps using different gases: first gas for initial etching to expose underlying films, second gas for depositing by-products on lower/intermediate underlying films, third gas for removing by-products. This segmentation allows different regions to receive different treatments, protecting underlying films from excessive ion irradiation damage while achieving the required etching depth.
Solution Approach 2:
The etching process employs periodic alternation between deposition mode (second gas) and removal mode (third gas) multiple times. This periodic action allows by-products to be deposited on underlying films during deposition phases, protecting them from ion damage, and then removed during removal phases to maintain etching progress, thereby reducing cumulative ion irradiation damage.
2Manufacturing precision
If etching is performed to expose underlying films in the lower and intermediate layers, then holes of different depths are formed, but by-products accumulate at the bottom of deeper holes
Solution Approach 1:
The process periodically alternates between deposition mode (second gas) where by-products accumulate at the bottom of deeper holes protecting underlying films, and removal mode (third gas) where by-products are removed. This periodic cycle prevents permanent by-product accumulation while allowing temporary protection of underlying films during etching.
Solution Approach 2:
The etching process changes gas composition parameters between steps: first gas for initial etching, second gas with higher deposition tendency for by-product formation, and third gas with higher removal capability for by-product elimination. These parameter changes enable dynamic control of by-product accumulation and removal to achieve precise hole depth variation.
3Device complexity
If a single gas is used for etching silicon oxide films, then the process is simple, but selectivity and damage suppression to underlying films are insufficient
Solution Approach 1:
The etching process is divided into multiple segments using different gases: first gas for initial etching to expose underlying films, second gas for depositing protective by-products, and third gas for removing by-products. This segmentation enhances selectivity and damage suppression capabilities while maintaining reasonable process complexity through systematic gas sequence 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 method allows for the etching of silicon oxide films at different depths on each underlying film without damaging the multiple underlying films, improving selectivity and reducing damage to the lower and intermediate layers while promoting etching in the upper layer.
Implementation Method 1
the silicon oxide film above the first underlying film and the second underlying film is etched by using a first gas, to expose the first underlying film
Implementation Method 2
the silicon oxide film above the second underlying film is etched by using a second gas while depositing deposits on the first underlying film
Implementation Method 3
the silicon oxide film above the second underlying film is further etched by using a third gas while removing the deposits on the first underlying film
Data Source
AI summary
There is provision of a method for etching a substrate above which a first underlying film, a second underlying film positioned deeper than the first underlying film, a silicon oxide film formed on the first and second underlying films, and a mask on the silicon oxide film are provided. In the mask, first and second openings are formed above the first and second underlying films respectively. After the first underlying film is exposed by etching the silicon oxide film using a first gas, the silicon oxide film is etched by using a second gas while depositing deposits on the first underlying film, and the silicon oxide film is etched by using a third gas while removing the deposits on the first underlying film. The etching using the second gas and the etching using the third gas are repeated multiple times.