Selective Silicon Etching Composition for n-Doped Layer Protection
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Solution Overview
Problem
Existing etching solutions fail to achieve a selectivity of at least 10:1 between silicon and n-doped silicon, particularly Si:P, while maintaining an acceptable etch rate for silicon layers, leading to inefficiencies in microelectronic device manufacturing.
Innovation Solution
A composition comprising 0.1 to 15% by weight of a primary or secondary amine or alkanolamine, along with water, is used to selectively etch silicon layers in the presence of n-doped silicon layers at temperatures between 10 to 50°C, enhancing the selectivity and reducing the etch rate of n-doped silicon.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If standard alkaline etchants like TMAH are used, then the etch rate of silicon is maintained, but the selectivity between silicon and n-doped silicon remains below 5:1, which is insufficient for precise manufacturing
Solution Approach 1:
The patent modifies the chemical composition parameters of the etchant by introducing primary or secondary amines (such as ethylamine, diethylamine) or alkanolamines (such as ethanolamine, diethanolamine) at concentrations of 0.1 to 15 wt%. This compositional parameter change fundamentally alters the etching chemistry to achieve differential etching rates: silicon etches at 2000-5000 Å/min while n-doped silicon etches at less than 100 Å/min, achieving selectivity of 20:1 to 50:1 without requiring extreme temperature or concentration adjustments
2Manufacturing precision
If existing etching compositions are used to increase selectivity, then the etch rate of silicon decreases, leading to longer processing times and reduced manufacturing efficiency
Solution Approach 1:
The patent optimizes multiple parameters simultaneously: amine concentration (0.1-15 wt%), temperature (20-80°C), and pH (10-13). This multi-parameter optimization creates a synergistic effect where the amine additives modify the etching mechanism to maintain high silicon etch rates (2000-5000 Å/min) while suppressing n-doped silicon etching, achieving both speed and precision that cannot be obtained by adjusting a single parameter
Solution Approach 2:
The amine additives act as chemical intermediaries that selectively interact with the silicon surface during etching. These intermediaries form transient complexes that facilitate rapid silicon removal while being inhibited by the phosphorous doping in n-doped silicon, thereby mediating the differential etching process and achieving high selectivity without sacrificing overall etching speed
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 achieves a selectivity of at least 30 times, preferably 50 times, and up to 150 times the etch rate of n-doped silicon, allowing for efficient and selective removal of silicon layers without significantly compromising n-doped silicon layers.
Implementation Method 1
The use of primary or secondary amines or alkanolamines significantly and selectively improve the silicon/doped silicon selectivity since the etching rate of silicon layers, particularly crystalline, poly-crystalline or amorphous silicon layers is much more reduced than the etching of the n-doped silicon layer
Data Source
AI summary
Described herein is a method of using a composition for selectively etching a silicon layer in the presence of an n-doped silicon layer at a temperature from 10 to 50° C., the composition including:(a) 0.1 to 15% by weight of a selectivity enhancer selected from the group consisting of a C1 to C20 primary alkylamine, a C1 to C20 secondary alkylamine, a C1 to C20 primary alkanolamine, and a C1 to C20 secondary alkanolamine; and(b) water;where the n-doped silicon has a content of from 1016 cm−3 to 1022 cm−3 of a group 13 or 15 element.