BOE Etchant pH Feedback for Stable Wet Etching Rates
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The etching rate in wet etching processes increases rapidly with wafer throughput due to recycling of buffered oxide etchant (BOE) solutions, leading to uncontrollable etching rates, high chemical consumption, and reduced production efficiency, as hydrogen and fluoride ion concentrations rise, causing excessive corrosion and thicker oxide film etching.
Innovation Solution
A method involving a purified water supply mechanism connected to the etchant supply system, which injects water based on pH changes to stabilize hydrogen and fluoride ion concentrations, and using long-wavelength light to inhibit NH4F decomposition, ensuring controlled etching rates without frequent BOE replacement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If buffered oxide etchant (BOE) solution is recycled to reduce chemical consumption and cost, then chemical consumption decreases, but hydrogen and fluoride ion concentrations rise causing etching rate to increase uncontrollably
Solution Approach 1:
The patent implements a feedback control system where pH sensors continuously monitor the etchant solution in the etching tank. When the pH value changes indicating ion concentration drift, the system automatically adjusts by injecting purified water or replacing etchant solution, thereby maintaining stable etching rate while still recycling the solution to reduce chemical consumption
Solution Approach 2:
The patent changes the physical-chemical parameters of the etchant solution by controlling pH values and ion concentrations through automated water injection and solution replacement. This allows the system to maintain optimal etching conditions (stable hydrogen and fluoride ion concentrations) while recycling the etchant, thus resolving the contradiction between chemical consumption reduction and etching rate control
2Manufacturing precision
If BOE solution is replaced frequently to maintain stable etching rate, then etching rate control improves, but production efficiency decreases due to frequent shutdowns
Solution Approach 1:
The automated feedback control system continuously monitors pH and ion concentrations, allowing the etching process to run continuously with automatic adjustments. This eliminates the need for frequent manual shutdowns and replacements, thereby maintaining stable etching rate control while improving production efficiency through uninterrupted processing
Solution Approach 2:
The patent enables continuous etching operation by automatically managing etchant solution quality through pH monitoring and controlled water injection. The etching process continues without interruption, and the system maintains stable etching rates by dynamically adjusting solution composition, thus achieving both precision control and high productivity
3Reliability
If NH4F decomposition is allowed to proceed naturally to maintain etchant composition, then chemical effectiveness is maintained, but excessive corrosion occurs and oxide film thickness increases
Solution Approach 1:
The patent controls the decomposition of NH4F by monitoring and adjusting pH values and ion concentrations. By maintaining pH within specific ranges and controlling fluoride ion concentrations, the system prevents excessive corrosion and oxide film thickening while still allowing sufficient NH4F decomposition to maintain etchant effectiveness
Solution Approach 2:
The system uses pH sensors and ion concentration monitoring to detect when NH4F decomposition is progressing too far. The feedback control automatically injects purified water or replaces solution to reverse the harmful effects, thereby preventing excessive corrosion while maintaining necessary chemical effectiveness for etching
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 maintains a stable etching rate, reduces chemical consumption, and enhances production efficiency by controlling ion concentrations and minimizing corrosion, allowing for consistent wafer throughput without frequent shutdowns.
Implementation Method 1
The purified water supply mechanism injects purified water into the etchant supply mechanism according to a change range of pH of the etchant in the etchant supply mechanism to ensure that a hydrogen ion concentration and a fluoride ion concentration of the etchant in the etchant supply mechanism are stable
Implementation Method 2
using long-wavelength light to inhibit NH4F decomposition
Data Source
AI summary
A method for improving an etching rate of wet etching involves an etching reaction chamber used for etching work. The etching reaction chamber is connected with an etchant supply mechanism. The etchant supply mechanism is connected with a purified water supply mechanism. The purified water supply mechanism injects purified water into the etchant supply mechanism according to a change range of pH of the etchant in the etchant supply mechanism to ensure that a hydrogen ion concentration and a fluoride ion concentration of the etchant in the etchant supply mechanism are stable.