Cryogenic Plasma Etching with RF Cycling to Prevent Etch Stop
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Solution Overview
Problem
Existing etching methods face challenges in controlling substrate surface temperature during plasma etching, leading to non-uniform etching rates and 'etch stop' issues, particularly when processing silicon oxide films at extremely low temperatures.
Innovation Solution
An etching method that alternates between two conditions: one with continuous RF power and another without, using hydrogen-containing and fluorine-containing gases, to maintain the substrate surface temperature below −35°C, thereby preventing 'etch stop' and enhancing etching rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If continuous RF power is applied during plasma etching, then plasma heating temperature increases, but substrate surface temperature becomes difficult to control and etch stop occurs
Solution Approach 1:
The patent applies periodic action by alternately switching between first RF power (for plasma generation) and second RF power (for heating) in a cyclic manner. This allows the substrate surface temperature to be periodically heated and then cooled, preventing continuous temperature rise and etch stop while still achieving the desired plasma heating temperature for efficient etching.
2Manufacturing precision
If substrate surface temperature is maintained at process temperature, then etching uniformity improves, but etching rate decreases due to heat input from plasma
Solution Approach 1:
The patent uses periodic switching between first RF power (which provides plasma heating for high etching rate) and second RF power (which controls substrate surface temperature for etching uniformity). During the first RF power period, the substrate receives plasma heating that increases etching rate. During the second RF power period, temperature control maintains etching uniformity. This periodic alternation resolves the contradiction by achieving both high etching rate and good uniformity.
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 effectively prevents 'etch stop' and increases etching rates by controlling the substrate temperature, improving the uniformity and efficiency of silicon oxide film etching.
Implementation Method 1
the plasma is generated from a hydrogen-containing gas and a fluorine-containing gas by using first radio frequency power output from a first radio frequency power source
Implementation Method 2
the output of the second radio frequency power from the second radio frequency power source is stopped
Data Source
AI summary
A plasma processing apparatus includes a pedestal to receive a substrate thereon; a temperature control mechanism provided in the pedestal; a heat transfer gas supply mechanism configured to supply a heat transfer gas to a back surface of the substrate; a first radio frequency power source configured to output first high frequency power having a first frequency; a second radio frequency power source configured to output second high frequency power having a second frequency that is lower than the first frequency; and a temperature measurement unit configured to control a surface temperature of the substrate to have a temperature lower than −35 degrees C. by using the temperature control mechanism provided in the pedestal and to perform feedback control of stopping the output of the second radio frequency power from the second radio frequency power source.