DRIE Substrate Cleaning via TMAH and Acidic Solutions
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Solution Overview
Problem
Micro-fluid ejection heads experience decreased droplet placement accuracy and fluid misdirection due to residual AlFx species left after the deep reactive ion etching (DRIE) process, which accumulate in nozzles and flow features, causing misdirection of ejected fluid.
Innovation Solution
A method involving the use of an aqueous tetramethyl ammonium hydroxide (TMAH) solution, possibly with a surfactant, and a mixture of glacial acetic acid and ammonium fluoride in dimethylacetamide (NE-14) to remove the AlFx residue from the substrate, followed by rinsing and drying, effectively dissolving and removing the residue without affecting the micro-fluid ejection head's performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If DRIE process is used to etch fluid supply slots, then manufacturing precision and wall profile control are improved, but AlFx residue accumulates in nozzles causing droplet placement inaccuracy
Solution Approach 1:
The patent applies preliminary action by performing residue removal treatments (contacting with aqueous TMAH solution, stripping photoresist, dissolving passivating coating) immediately after the DRIE process and before final assembly. This prevents AlFx residue from accumulating in nozzles and causing droplet misdirection, while preserving the manufacturing precision benefits of DRIE.
2Manufacturing precision
If nozzle size is reduced to improve fluid flow control, then manufacturing precision is improved, but droplet placement accuracy decreases due to residue accumulation
Solution Approach 1:
The patent extracts the harmful AlFx residue from the system by applying chemical treatments (aqueous TMAH solution, acidic solution) that selectively remove the residue from nozzle surfaces and fluid supply slots. This extraction process eliminates the source of droplet misdirection while preserving the precisely controlled small nozzle dimensions.
3Manufacturing precision
If sequential etching and passivation steps are performed to achieve high aspect ratio, then manufacturing precision is improved, but AlFx residue is generated and causes fluid misdirection
Solution Approach 1:
The patent converts the harmful effect of AlFx residue into a beneficial process by using the residue's chemical reactivity. The aqueous TMAH solution and acidic treatments specifically react with AlFx to dissolve and remove it, transforming the problematic byproduct of high aspect ratio etching into a target for selective chemical removal.
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
The removal of AlFx residue significantly improves droplet placement accuracy by preventing residue accumulation in nozzles and flow features, reducing misdirection and enhancing print quality, as demonstrated by reduced capability radius and increased accuracy in fluid droplet placement.
Implementation Method 1
contacting the substrate with an aqueous tetramethyl ammonium hydroxide solution (TMAH)... dissolving a passivating coating from the substrate
Implementation Method 2
The substrate may then be contacted with an acidic solution then rinsing and drying the substrate
Data Source
AI summary
The present disclosure provides a method of cleaning a semiconductor substrate after a DRIE etch process, wherein residue from the DRIE process is removed without damaging the substrate. The process may include contacting the micro-fluid ejection head with an aqueous solution of TMAH, stripping a photoresist etch mask from the micro-fluid ejection head, and dissolving a passivating coating from the substrate. Then the substrate may be contacted with an acidic solution. The method may further include rinsing and drying the substrate.