Selective Tungsten Etching via Chlorine-Methane Plasma
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Solution Overview
Problem
Current etching processes for tungsten-containing materials face challenges such as low etch rates, high temperatures, and difficulty in removing tungsten oxide and tungsten metal from high aspect ratio trenches without damaging inter-layer dielectric materials, leading to prolonged processing times and potential thermal budget exceedance.
Innovation Solution
The method involves flowing chlorine-containing and hydrocarbon precursors into a semiconductor processing chamber to form a plasma, which selectively etches tungsten-containing materials at low temperatures, achieving high etch rates and selectivity over silicon-containing materials, while maintaining minimal residue and preserving substrate features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If wet HF etch is used to remove tungsten-containing materials, then the etching process is simple and cost-effective, but the etch rate is slow and it cannot penetrate constrained trenches effectively
Solution Approach 1:
The patent replaces wet chemical etching with a plasma-based etching process that uses reactive ion bombardment and chemical reactions to remove tungsten-containing materials. The plasma process provides both chemical reactivity and physical sputtering effects, achieving high etch rates while maintaining anisotropic etching profiles that can penetrate constrained trenches effectively.
Solution Approach 2:
The patent employs specific plasma process parameters including chlorine-containing precursors (Cl2, BCl3), hydrocarbon precursors (CH4, C2H6), radio frequency power (10-1000W), and pressure control (1-100 mTorr) to optimize the etching reaction. These parameter changes enable selective removal of tungsten oxide and tungsten metal at controlled rates while protecting underlying structures.
2Productivity
If high power plasma is used to increase etch rate, then productivity improves, but substrate damage from electric arcs increases
Solution Approach 1:
The patent optimizes plasma process parameters by using moderate power levels (10-1000W radio frequency power) combined with specific precursor ratios and pressure conditions (1-100 mTorr). This parameter optimization maintains high etch rates while preventing electric arc formation that would cause substrate damage. The use of chlorine-containing and hydrocarbon precursors at controlled flow rates further stabilizes the plasma process.
Solution Approach 2:
The patent uses chlorine-containing precursors (Cl2, BCl3) and hydrocarbon precursors (CH4, C2H6) as intermediary substances that facilitate the etching reaction through controlled chemical pathways. These intermediaries react with tungsten-containing materials to form volatile products that can be removed, providing high etch rates without requiring high power plasma that would cause substrate damage.
3Productivity
If high temperature processing is used to remove tungsten oxide, then etching efficiency improves, but thermal budget constraints are exceeded and inter-layer dielectric materials are damaged
Solution Approach 1:
The patent replaces thermal-based removal processes with plasma-based etching that operates at lower temperatures. The plasma process uses reactive species and ion bombardment to chemically react with and physically remove tungsten-containing materials, achieving high etching efficiency without the high temperatures that would damage inter-layer dielectric materials or exceed thermal budget constraints.
Solution Approach 2:
The patent employs specific plasma process parameters including radio frequency power (10-1000W), pressure (1-100 mTorr), and precursor flow rates to enable efficient tungsten oxide and tungsten metal removal at low temperatures. The use of chlorine-containing and hydrocarbon precursors creates highly reactive plasma species that enhance etching efficiency without requiring thermal activation.
4Manufacturing precision
If selective etching of tungsten over silicon is required, then pattern transfer precision improves, but process complexity increases
Solution Approach 1:
The patent achieves high selectivity for tungsten-containing materials over silicon-containing materials through optimized plasma process parameters. By controlling precursor composition (chlorine-containing and hydrocarbon precursors), power levels (10-1000W), and pressure (1-100 mTorr), the process selectively removes tungsten oxide and tungsten metal while leaving silicon-based inter-layer dielectric materials intact. The selectivity ratio of tungsten to silicon etching exceeds 100:1, enabling precise pattern transfer without complex process steps.
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 enables efficient removal of tungsten-containing materials at lower temperatures with high selectivity, reducing processing time and thermal budget constraints, and ensuring complete removal with minimal residue, thus improving semiconductor device fabrication.
Implementation Method 1
forming a plasma from the chlorine-containing precursor and the methane to produce plasma effluents
Implementation Method 2
The plasma effluents may produce an oxychloride of tungsten
Data Source
AI summary
Exemplary methods for removing tungsten-containing material may include flowing a chlorine-containing precursor into a processing region of a semiconductor processing chamber. The methods may also include flowing methane into the processing region of the semiconductor processing chamber. The methods may include forming a plasma from the chlorine-containing precursor and the methane to produce plasma effluents. The methods may also include contacting a substrate with the plasma effluents. The substrate may include an exposed region of a tungsten-containing material. The plasma effluents may produce an oxychloride of tungsten. The methods may also include recessing the exposed region of the tungsten-containing material.