Dynamic Temperature Control in Wet Etch Processes
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Solution Overview
Problem
Existing wet etching processes for semiconductor surfaces using phosphoric and sulfuric acid require long over-etch times to ensure complete film removal, leading to reduced throughput and selectivity issues due to variations in film thickness across the wafer surface.
Innovation Solution
Dynamic control of sulfuric acid dispensing to create a customized temperature profile across the semiconductor surface, allowing independent adjustment of phosphoric acid concentration and temperature, enabling localized etch rate control to compensate for thickness variations without over-etching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If long over-etch times are used to guarantee complete film removal, then film removal completeness is improved, but throughput is reduced
Solution Approach 1:
The patent applies local quality by creating a non-uniform temperature profile across the wafer surface through radial dispensing of sulfuric acid. Different regions of the wafer receive different temperatures, allowing the etch rate to be locally optimized. Thicker regions receive higher temperatures for faster etching, while thinner regions receive lower temperatures to prevent over-etching, thereby completing film removal across the entire wafer without requiring excessive over-etch time that would reduce throughput.
Solution Approach 2:
The patent implements dynamics by dynamically adjusting the temperature profile during the etch process. The sulfuric acid dispensing system continuously modifies the temperature distribution across the wafer surface in real-time, allowing the etch rate to adapt to the local film thickness profile. This dynamic control enables complete film removal while minimizing over-etch time, thus maintaining high throughput.
2Manufacturing precision
If high selectivity to nitride is required to compensate for thickness variations, then film removal accuracy is improved, but over-etch time increases
Solution Approach 1:
The patent uses local quality to achieve precise film removal by tailoring the temperature profile to match the film thickness distribution. Each region of the wafer is etched at a temperature optimized for its local film thickness, allowing accurate removal of thick regions without requiring prolonged processing that would over-etch thin regions. This localized optimization improves manufacturing precision while reducing overall over-etch time.
3Reliability
If stable operating conditions at acid boiling points are used, then etch selectivity is improved, but temperature control flexibility is reduced
Solution Approach 1:
The patent applies local quality by maintaining the bulk phosphoric acid at its boiling point for high selectivity, while locally modulating the temperature at different wafer regions through sulfuric acid dispensing. This allows the system to enjoy the benefits of stable boiling conditions for overall process control while achieving flexible local temperature adjustment to match film thickness variations across the wafer surface.
Solution Approach 2:
The patent merges two approaches: using phosphoric acid at boiling point for high selectivity and adding sulfuric acid for local temperature modulation. The combination allows the system to maintain the advantages of stable operating conditions while gaining temperature control flexibility through the superimposed sulfuric acid heating effect in different radial zones.
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 reduces over-etch time, improves throughput, and enhances selectivity by customizing the etch rate profile to match the film thickness profile, ensuring efficient film removal without damaging thinner regions.
Implementation Method 1
The dynamic control of this invention is performed by co-dispensing sulfuric acid to significantly control the process temperature profile and consequently the etch rate profile is controlled by the variation of local temperature induced by the local sulfuric acid dispense
Implementation Method 2
Phosphoric acid etching is a well-established process (e.g., treating wafers on wet benches). Known processes employ stable operating conditions such as acid boiling points. These processes provide good selectivity of nitride to oxide (35:1 at 165 Centigrade)
Data Source
AI summary
A method for controlling the temperature profile of phosphoric acid process over a wafer surface through the dynamic control of radial dispensing of sulfuric acid at a selected temperature, which includes providing a substrate with a layer formed thereupon; dispensing a first chemical and second chemicals onto the layer while adjusting at least one parameter of the second chemical dispense to vary the etch rate across a region of the substrate.