Etching Composition for Semiconductor Substrates
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Solution Overview
Problem
Current etching processes for semiconductor substrates face challenges such as isotropic etching's non-directional nature, high defect levels, and hazardous chemicals, while anisotropic etching is orientation-dependent and requires specific silicon wafer orientations, necessitating the need for a non-toxic, environmentally friendly etching composition that can provide a wider processing window and selectively etch certain crystal planes to achieve a sigma-shaped recess.
Innovation Solution
A composition comprising water, a quaternary ammonium compound, an amine compound, and optional buffering agents and corrosion inhibitors, which can be used to etch semiconductor substrates, providing a sigma-shaped etch profile with controlled (110)/(100) selectivity ratios, thus overcoming the limitations of conventional etchants like TMAH-based solutions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If isotropic etching is used, then the substrate is etched uniformly in all directions, but undercutting occurs and mask protection is compromised
Solution Approach 1:
The patent modifies the chemical composition parameters of conventional TMAH etchant by adding quaternary ammonium compounds (such as tetraethylammonium hydroxide or tetramethylammonium hydroxide) and adjusting the concentration ratios. This parameter change transforms the etching characteristics to achieve both uniformity and directional control, resolving the contradiction between isotropic uniformity and anisotropic precision.
2Manufacturing precision
If conventional TMAH-based etchants are used, then anisotropic etching with directional control is achieved, but the chemicals present handling and safety problems
Solution Approach 1:
The patent changes the chemical composition parameters by incorporating quaternary ammonium compounds as alternative or supplementary etching agents to conventional TMAH. These quaternary ammonium compounds offer comparable anisotropic etching performance with improved safety profiles, reducing the harmful factors while maintaining manufacturing precision.
Solution Approach 2:
The patent creates a composite etching solution by combining quaternary ammonium compounds with conventional TMAH or other base materials. This composite approach leverages the directional etching capability of TMAH while the quaternary ammonium compounds provide enhanced safety and reduced corrosiveness, simultaneously addressing both precision and safety requirements.
3Manufacturing precision
If silicon wafers with specific Miller index orientations are used for anisotropic etching, then controlled etch patterns are achieved, but the process becomes orientation-dependent and less versatile
Solution Approach 1:
The patent develops a multi-functional etching composition that can effectively etch multiple crystal orientations (including <100>, <110>, and <111> planes) with controlled selectivity. The quaternary ammonium compound formulation provides universal applicability across different wafer orientations, reducing the strict orientation dependency while maintaining precise etch pattern control through chemical composition rather than physical orientation constraints.
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 composition enables effective anisotropic etching with improved selectivity and reduced undercutting, providing a safer, more environmentally friendly alternative for semiconductor manufacturing by achieving a sigma-shaped recess with controlled etch rates and reduced corrosive effects.
Implementation Method 1
Present methods for etching such a film require that the film be exposed to a chemical etching agent to remove portions of the film
Implementation Method 2
Anisotropic etching, unlike isotropic etching, provides a directional etching of the substrate surface. In this regard, undercutting under the mask is sharpened to well-defined corners because the typical etchant chemicals used in this process such as potassium hydroxide (KOH), tetramethylammonium hydroxide (TMAH), and tetraethylammonium hydroxide (TEAH), which etch at different rates for different crystal orientations such as Si(110), Si (100), and Si (111) crystal plans
Data Source
AI summary
A composition and method using same useful for etching a semiconductor substrate comprising: from about 25 to 86% by weight of water; from about 0 to about 60% by weight of a water-miscible organic solvent; from about 1 to about 30% by weight of a base comprising a quartenary ammonium compound; from about 1 to about 50% by weight of an amine compound wherein the amine compound is selected from the group consisting of a secondary amine, a tertiary amine, and mixtures thereof; from about 0 to about 5% by weight of a buffering agent; from about 0 to about 15% by weight of a corrosion inhibitor.