High-Aspect-Ratio Stack Etching With Layer-Switched Plasma Chemistry
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Solution Overview
Problem
Existing etching methods for high aspect ratio structures, particularly in semiconductor wafer processing, fail to achieve a desirable etch rate, especially when using metal-containing chemistry for nitrogen-containing layers, leading to under etching or etch stop issues.
Innovation Solution
A method involving the alternating use of non-metal and metal-containing gases, controlled by a processor, to etch nitrogen-containing and oxide layers respectively, with specific RF signal pulsing to optimize etch rates and prevent under etching, ensuring a predetermined etch rate is achieved.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If metal-containing chemistry is used for etching nitrogen-containing layers, then mask remaining budget is improved, but under etching or etch stop occurs at the nitrogen-containing layer
Solution Approach 1:
The patent applies periodic switching between metal-containing chemistry and non-metal gas chemistry during the etching process. The controller alternates between these chemistries in timed intervals, allowing the metal-containing chemistry to etch oxide layers (improving mask remaining budget) while switching to non-metal gas chemistry when etching nitrogen-containing layers (preventing under etching). This periodic action resolves the contradiction by applying the right chemistry at the right time based on the layer being etched.
2Productivity
If metal-containing gas is used to etch oxide layers, then pre-determined etch rate is achieved, but under etching occurs in nitrogen-containing layers
Solution Approach 1:
The patent implements local quality by applying different etching chemistries to different layers within the stack structure. Metal-containing gas is specifically applied when etching oxide layers to achieve high etch rates, while non-metal gas is applied when etching nitrogen-containing layers to ensure uniform etching and prevent under etching. The controller determines which layer is being etched and switches chemistry accordingly, providing locally optimized etching conditions for each material type.
3Productivity
If non-metal gas is used for etching nitrogen-containing layers, then pre-determined etch rate is achieved, but mask remaining budget deteriorates
Solution Approach 1:
The patent uses periodic switching between chemistry types to resolve this contradiction. Non-metal gas is applied during nitrogen-containing layer etching to achieve pre-determined etch rates, while metal-containing chemistry is applied during oxide layer etching to maintain mask remaining budget. The controller alternates between these chemistries based on real-time detection of layer boundaries, ensuring both high etch rate and good mask remaining budget are achieved through time-based chemistry switching.
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 allows for precise control of etching processes, achieving the desired etch rate and reducing the chances of under etching in high aspect ratio structures by using non-metal gases for nitrogen-containing layers and metal-containing gases for oxide layers, with RF signal pulsing optimizing deposition across feature top and bottom portions.
Implementation Method 1
A radiofrequency (RF) generator generates an RF signal and supplies the RF signal via a match to a plasma reactor. The plasma reactor has a semiconductor wafer that is etched when the RF signal is supplied and an etchant gas is supplied to the plasma reactor.
Implementation Method 2
The semiconductor wafer is etched when the RF signal is supplied and an etchant gas is supplied to the plasma reactor
Data Source
AI summary
A method for etching a stack is described. The method includes etching a first nitrogen-containing layer of the stack by applying a non-metal gas and discontinuing the application of the non-metal gas upon determining that a first oxide layer is reached. The first oxide layer is under the first nitrogen-containing layer. The method further includes etching the first oxide layer by applying a metal-containing gas. The application of the metal-containing gas is discontinued upon determining that a second nitrogen-containing layer will be reached. The second nitrogen-containing layer is situated under the first oxide layer. The method includes etching the second nitrogen-containing layer by applying the non-metal gas.