Reservoir-Based SiOx Etching for Uniform Plasma-Free Selectivity
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Solution Overview
Problem
Existing etching methods for semiconductor wafers face challenges in achieving selective and uniform etching of silicon oxide (SiOx) and silicon nitride (SiN) films without plasma, often resulting in non-uniform etching and potential etching of both films simultaneously.
Innovation Solution
An etching apparatus and method that utilizes a halogen-containing gas (HF) and a basic gas (NH3 or TMA) with controlled valve timing to selectively etch SiOx film by exploiting differences in incubation times, using separate tanks and synchronized valve operations to minimize gas reaction and ensure uniform diffusion, thereby achieving selective etching of SiOx over SiN.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If gases are supplied directly from tanks to the processing container without storage, then the etching process can start quickly, but the gas flow becomes unstable and etching uniformity deteriorates
Solution Approach 1:
The patent applies preliminary action by storing etching gases in advance in a reservoir at high pressure before the etching process begins. This pre-stored gas is then supplied to the processing container, ensuring stable and uniform gas flow throughout the etching process, thereby resolving the contradiction between quick process start and etching uniformity.
2Productivity
If both SiOx and SiN films are etched simultaneously using conventional methods, then the processing throughput increases, but selective etching capability is lost and film integrity deteriorates
Solution Approach 1:
The patent applies local quality by creating different gas environments for different film types. By controlling the supply of halogen-containing gas and basic gas separately and simultaneously, the method achieves selective etching: SiOx films are etched where halogen gas predominates, while SiN films remain intact where basic gas predominates or where the incubation time prevents etching. This resolves the contradiction between throughput and selective etching accuracy.
Solution Approach 2:
The patent utilizes periodic action through the incubation time mechanism. The basic gas requires a specific incubation period before it can etch SiN films, while halogen-containing gas etches SiOx films immediately. By controlling the timing and sequence of gas supply, the method achieves selective etching of SiOx before SiN, maintaining film integrity while enabling multi-film processing.
3Productivity
If gas flow rate is increased to improve etching speed, then productivity increases, but gas distribution uniformity across the wafer surface deteriorates
Solution Approach 1:
The patent applies pneumatics by using a reservoir to store etching gases at high pressure. This pressurized storage system enables controlled release of gas at optimal flow rates, ensuring uniform distribution across the wafer surface while maintaining high etching speed. The reservoir acts as a pressure buffer that stabilizes gas flow, resolving the contradiction between etching speed and gas distribution uniformity.
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 achieves high uniformity and selective etching of SiOx film while inhibiting SiN etching, improving throughput and minimizing gas variations across the wafer surface.
Implementation Method 1
supplying the first etching gas and the second etching gas, stored in the reservoir, to a processing container in which a substrate is accommodated by opening a valve provided downstream of the reservoir in the gas supply path, thus etching a first film formed on the substrate
Implementation Method 2
storing the first etching gas and the second etching gas in a reservoir provided in the gas supply path to increase an internal pressure of the reservoir
Data Source
AI summary
An etching method includes: supplying each of a first etching gas and a second etching gas that includes at least one selected from the group of an ammonia gas and an amine gas from a gas supply source to a gas supply path; storing the first etching gas and the second etching gas in a reservoir provided in the gas supply path to increase an internal pressure of the reservoir; and supplying the first etching gas and the second etching gas, stored in the reservoir, to a processing container in which a substrate is accommodated by opening a valve provided downstream of the reservoir in the gas supply path, thus etching a first film formed on the substrate.