High-Aspect-Ratio Plasma Etching With Heated Electrode Selectivity
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Solution Overview
Problem
As semiconductor device sizes shrink, existing etching technologies face challenges in creating high aspect ratio features with high density and selectivity, particularly in dielectric layers, leading to issues like mask erosion and etch stop during the production of memory cell arrays for DRAM.
Innovation Solution
A method involving a plasma processing chamber where an etch gas is formed into a high density plasma with a top outer electrode maintained at a temperature of at least 150° C, using a specific RF power configuration and gas flow control to etch features, reducing mask erosion and etch stop while increasing selectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional etching is used to etch higher aspect ratio features, then device density increases, but mask selectivity deteriorates leading to mask erosion and etch stop
Solution Approach 1:
The patent changes the temperature parameter of the plasma processing chamber to at least 150°C, which fundamentally alters the etching chemistry and physics to achieve high mask selectivity while etching high aspect ratio features. This temperature parameter change enables the process to overcome the conventional trade-off between aspect ratio and mask selectivity.
2Productivity
If etching depth increases to achieve high aspect ratio, then feature density improves, but mask erosion increases reducing selectivity
Solution Approach 1:
By maintaining the plasma chamber at elevated temperature (at least 150°C), the patent modifies the etching process to be more selective to the dielectric layer while preserving the mask material. This temperature control enables deep etching without proportional mask erosion, achieving high productivity with minimal substance loss from the mask.
3Speed
If conventional plasma etching is used, then etch rate is maintained, but etch stop occurs during high aspect ratio feature formation
Solution Approach 1:
The patent maintains stable plasma conditions through controlled temperature (at least 150°C) and pressure parameters, preventing the formation of protective layers that would cause etch stop. This stable parameter control ensures continuous etching through high aspect ratio features without interruption, maintaining both high speed and etch continuity.
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 the etching of high aspect ratio features with improved selectivity and reduced mask erosion, achieving high throughput and stability, even at aspect ratios of 50:1 and potentially up to 100:1, with less than 1% under-etched features and maintaining steady-state etch rates.
Implementation Method 1
The etch gas is formed into a plasma, which etches the etch layer
Data Source
AI summary
A method for etching features in an etch layer in a plasma processing chamber is provided. An etch gas is flowed into the plasma processing chamber. A top outer electrode is maintained at a temperature of at least 150° C. during the etching of the features. The etch gas is formed into a plasma, which etches the etch layer.