BCl3 Plasma Selective High-k Etch via BxNy Film
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Solution Overview
Problem
Conventional dry etch processes exhibit low selectivity for high-k materials such as HfO2 over silicon and silicon dioxide, limiting the precision in patterning and removal of high-k layers in semiconductor manufacturing.
Innovation Solution
A boron halogen plasma with defined nitrogen additions is used to deposit a protective BxNy film on silicon surfaces, reducing the etch rate of silicon and silicon dioxide while minimizing deposition on high-k materials, thereby enhancing the etch selectivity of high-k layers like HfO2 up to 1:20.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional dry etch processes are used, then the etching of high-k materials can be performed, but the etch selectivity of high-k materials over silicon and silicon dioxide is low (1:3)
Solution Approach 1:
A boron-containing compound is introduced as an intermediary substance that reacts with silicon and silicon dioxide to form a protective boride layer during etching. This intermediary layer acts as a barrier that reduces the etch rate of the underlying silicon and oxide, thereby improving the selectivity between high-k material and silicon/silicon dioxide without requiring separate deposition steps
Solution Approach 2:
The etch process parameters are modified by adding a boron-containing compound to the etch chemistry, which changes the reaction kinetics and forms protective boride layers on silicon surfaces. This parameter change transforms the etch selectivity from 1:3 to greater than 1:10, resolving the contradiction between achieving adequate etching and preserving underlying layers
2Manufacturing precision
If water-based HF solutions are used, then HfO2 etching can be achieved, but the etch selectivity of HfO2 over thermally grown silicon dioxide is only 1:10
Solution Approach 1:
The boron-containing compound serves as an intermediary that preferentially reacts with silicon dioxide to form protective borosilicate layers, reducing the etch rate of the isolation oxide. This intermediary mechanism improves HfO2 over SiO2 selectivity from 1:10 to greater than 1:10, preventing excessive loss of isolation oxide during high-k removal
3Manufacturing precision
If non-aqueous solvents like alcohol are used, then etch selectivity is improved, but the etch selectivity of HfO2 over TEOS is only 1:100
Solution Approach 1:
The etch chemistry parameters are changed by introducing boron-containing compounds that form protective boride layers on TEOS-based silicon dioxide. This parameter modification improves HfO2 over TEOS selectivity from 1:100 to greater than 1:10, significantly reducing the loss of TEOS-based isolation oxide while maintaining effective high-k 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
The method significantly improves etch selectivity, allowing for precise patterning and removal of high-k layers without damaging underlying silicon or silicon dioxide, preserving the integrity of semiconductor structures and maintaining vertical profiles.
Implementation Method 1
using a boron halogen plasma such as a BCl3 plasma with well defined additions of nitrogen leads to the formation and deposition of a BxNy film onto the silicon surface
Implementation Method 2
A boron halogen plasma with defined nitrogen additions is used to deposit a protective BxNy film on silicon surfaces
Implementation Method 3
the etch selectivity of high-k materials such as HfO2 over silicon and/or silicon dioxide up to 1:20
Implementation Method 4
A boron halogen plasma with defined nitrogen additions is used to deposit a protective BxNy film on silicon surfaces, reducing the etch rate of silicon and silicon dioxide
Data Source
AI summary
A method for the selective removal of a high-k layer such as HfO2 over silicon or silicon dioxide is provided. More specifically, a method for etching high-k selectively over silicon and silicon dioxide and a plasma composition for performing the selective etch process is provided. Using a BCl3 plasma with well defined concentrations of nitrogen makes it possible to etch high-k with at a reasonable etch rate while silicon and silicon dioxide have an etch rate of almost zero. The BCl3 comprising plasmas have preferred additions of 10 up to 13% nitrogen. Adding a well defined concentration of nitrogen to the BCl3/N2 plasma gives the unexpected deposition of a Boron-Nitrogen (BxNy) comprising film onto the silicon and silicon dioxide which is not deposited onto the high-k material. Due to the deposition of the Boron-Nitrogen (BxNy) comprising film, the etch rate of silicon and silicon dioxide is dropped down to zero. The Boron-Nitrogen (BxNy) comprising film can be removed during the etching process using the right substrate bias (leading to ion bombardment) or after the etching process by a simple water rinse since the Boron-Nitrogen (BxNy) comprising film is water soluble.