RF Generator Binning for Uniform Plasma Etch Rate Control
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Solution Overview
Problem
The challenge of achieving uniformity in substrate processing during low frequency cycles in plasma etching is exacerbated by the increased influence of high frequency RF generator voltage on low frequency RF generator voltage, leading to non-uniform etch rates and deposition rates due to the formation of plasma sheaths and standing waves.
Innovation Solution
The method involves dividing the voltage cycle into predetermined bins and adjusting the frequency of the high frequency RF generator within these bins to control power delivery, thereby maintaining uniformity in etch rates and deposition rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high frequency RF generator voltage is used to generate plasma sheath, then plasma generation is improved, but uniformity of substrate processing deteriorates due to increased influence on low frequency RF generator voltage
Solution Approach 1:
The voltage cycle is divided into multiple bins (e.g., 8 bins) based on the plasma sheath voltage level. By segmenting the cycle, the system can apply different HF RF power levels during specific bins where the plasma sheath is at low levels, thereby preventing the harmful influence on LF RF generator while maintaining plasma generation during other bins.
Solution Approach 2:
The system applies periodic modulation to the HF RF generator power delivery, increasing power during specific bins when plasma sheath voltage is low and reducing or eliminating power during bins when plasma sheath voltage is high. This periodic action maintains plasma generation while preventing uniformity issues caused by excessive HF influence during critical phases.
2Power
If power delivery is increased during low frequency cycle, then plasma generation is improved, but uniformity of etch rate and deposition rate deteriorates
Solution Approach 1:
The system dynamically adjusts the HF RF generator power delivery in real-time based on the instantaneous plasma sheath voltage level during each bin. By making the power delivery dynamic rather than static, the system can increase power when it benefits plasma generation (during low plasma sheath voltage) while reducing power when it would harm uniformity, thus resolving the contradiction between power delivery and processing 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 enhances the uniformity of substrate processing by controlling power delivery during critical phases of the voltage cycle, improving etch rate and deposition rate consistency.
Implementation Method 1
A low frequency (LF) radio frequency (RF) generator and a high frequency (HF) RF generator are used to process a substrate. The LF RF generator and the HF RF generators generate RF signals that are used to generate plasma and a plasma sheath within a plasma chamber.
Implementation Method 2
The LF RF generator and the HF RF generators generate RF signals that are used to generate plasma and a plasma sheath within a plasma chamber.
Implementation Method 3
For each bin, a frequency of the HF RF generator is controlled to control power delivered by the HF RF generator. For example, the frequency of the HF RF generator is increased or decreased to increase the delivered power.
Implementation Method 4
A voltage of the plasma sheath cycles between a low level and a high level. During a time period at which the plasma sheath is at the low level, a first voltage of the plasma sheath generated based on the HF RF generator has a greater amount of influence on a second voltage of the plasma sheath generated based on the LF RF generator.
Data Source
AI summary
A method for achieving uniformity in an etch rate is described. The method includes receiving a voltage signal from an output of a match, and determining a positive crossing and a negative crossing of the voltage signal for each cycle of the voltage signal. The negative crossing of each cycle is consecutive to the positive crossing of the cycle. The method further includes dividing a time interval of each cycle of the voltage signal into a plurality of bins. For one or more of the plurality of bins associated with the positive crossing and one or more of the plurality of bins associated with the negative crossing, the method includes adjusting a frequency of a radio frequency generator to achieve the uniformity in the etch rate.