Deep Hole Etching Using SiF4 and SF6 Gas Mixtures
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Solution Overview
Problem
The Bosch process for forming deep holes in substrates results in scalloping on the sidewalls due to alternating etching and polymerization steps, leading to reduced sidewall coverage and a low average etching rate, with insufficient photoresist selectivity causing substrate surface roughness and hole shape irregularities.
Innovation Solution
A method involving multiple plasma etching steps using specific gas mixtures, including SiF4, O2, and HBr, with controlled self-bias voltage to form a hole with a high selectivity ratio and etching rate, using a photoresist film as a mask to prevent polymer deposition and maintain a satisfactory hole shape.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the Bosch process is used with alternating etching and polymerization steps, then deep holes can be formed in substrate, but fine concavities and convexities (scalloping) are formed on the sidewall, reducing coverage rate and degrading covering property
Solution Approach 1:
The etching process is divided into multiple sequential steps with different gas compositions rather than alternating etching and polymerization steps. The first etching step uses a mixed gas containing SF6, O2, and HBr to form the hole, followed by a second etching step using a different mixed gas composition to smooth the sidewall and remove scalloping, thereby segmenting the process to achieve both deep hole formation and smooth sidewalls
Solution Approach 2:
The gas composition parameters are changed between etching steps. The first etching step uses a mixed gas containing SF6, O2, and HBr, while the second etching step uses a mixed gas with different composition ratios. By changing the gas parameters, the etching characteristics are modified to first create the deep hole and then smooth the sidewall, eliminating scalloping while maintaining high etching rate
2Manufacturing precision
If other processes are used to avoid scalloping, then sidewall coverage may improve, but photoresist film selectivity ratio becomes insufficient, causing photoresist elimination and substrate surface roughness
Solution Approach 1:
The gas composition parameters are optimized to achieve high photoresist selectivity. The mixed gas containing SF6, O2, and HBr is used with specific flow rate ratios and pressure conditions that enhance the etching selectivity between the substrate and photoresist film. This prevents photoresist elimination while maintaining smooth sidewalls and good coverage
Solution Approach 2:
A composite mixed gas consisting of SF6, O2, and HBr is used instead of single gases or simple binary mixtures. The combination of these three gases creates synergistic effects that provide both high etching rate and high photoresist selectivity, preventing photoresist damage while achieving the desired hole shape and sidewall quality
3Productivity
If etching and polymerization steps are alternately repeated with equal time length, then deep holes can be formed, but average etching rate becomes low because almost half the time is spent on polymerization
Solution Approach 1:
The polymerization step is completely removed from the process. Instead of alternating etching and polymerization steps, the invention uses continuous etching with optimized gas compositions. The first etching step forms the deep hole, and the second etching step smooths the sidewall, eliminating the time-consuming polymerization step while maintaining process effectiveness
Solution Approach 2:
The etching action continues continuously without interruption by polymerization steps. The process uses sequential etching steps with different gas compositions rather than alternating etching and polymerization. This continuous useful action maintains high average etching rate while achieving both deep hole formation and smooth sidewalls
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 the formation of deep holes with a high etching rate and selectivity ratio, preventing scalloping and maintaining a smooth sidewall, thus improving the coverage and shape of the deep hole.
Implementation Method 1
performing plasma etching on the substrate by using a mixed gas including SF6, O2, and HBr
Implementation Method 2
a second etching step of forming a hole in the substrate by performing plasma etching on the substrate by using a second mixed gas including at least SF6, O2, and HBr
Data Source
AI summary
A method for manufacturing a semiconductor device for forming a deep hole in a substrate by using a photoresist film formed on the substrate includes a positioning step of positioning a substrate inside an etching chamber, the substrate having a photoresist film including an opening part formed thereon, a first etching step of performing plasma etching on the substrate positioned inside the etching chamber by using a first mixed gas including at least SiF4 and O2 with the photoresist film as a mask, and a second etching step of forming a hole in the substrate by performing plasma etching on the substrate by using a second mixed gas including at least SF6, O2, and HBr after the first etching step.