Dry Etching Gas Flow Ratio for Semiconductor Trench Formation
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Solution Overview
Problem
Conventional plasma etching processes using mixed gases like chlorine and hydrogen bromide generate silicon chloride and silicon bromide reaction products with high freezing points, which accumulate and adhere to the inner walls of dry etching devices, causing operational issues and reducing the yield of semiconductor devices.
Innovation Solution
A method involving a dry etching process using a mixed gas containing a fluorine-based gas, hydrogen bromide, and chlorine, with a specific flow rate ratio of more than 0 and less than 0.04, to reduce the accumulation of reaction products and minimize sidewall etching in semiconductor substrates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a mixed gas of chlorine and hydrogen bromide is used for plasma etching, then the etching process can be performed effectively, but silicon chloride and silicon bromide reaction products accumulate and adhere to the inner wall surface of the chamber
Solution Approach 1:
The patent changes the chemical composition parameters of the etching gas by introducing a fluorine-based gas (such as SF6, CF4, or CHF3) into the mixed gas system. This parameter change transforms the reaction products from high-freezing-point silicon chloride and silicon bromide into lower-freezing-point silicon fluoride, thereby reducing accumulation on chamber walls while maintaining effective etching performance
2Productivity
If a mixed gas of chlorine and hydrogen bromide is used for plasma etching, then etching can proceed, but cleaning time increases due to reaction product accumulation
Solution Approach 1:
By modifying the gas composition to include fluorine-based gas, the patent changes the physical properties of reaction products (lower freezing point), which directly reduces the time required for chamber cleaning between batches while maintaining productive etching operation
3Object-generated harmful factors
If fluorine-based gas is added to the etching gas mixture, then reaction product accumulation is reduced, but sidewall etching may increase
Solution Approach 1:
The patent precisely controls the flow rate ratio of fluorine-based gas to total gas (maintained at 0.01 or less) to achieve a balance: this parameter setting is sufficient to reduce reaction product accumulation while limiting excessive fluorine activity that would cause significant sidewall etching
Solution Approach 2:
The patent applies a small but sufficient amount of fluorine-based gas (flow rate ratio ≤ 0.01) - this partial action is enough to achieve the desired reduction in reaction product accumulation without overdoing it, which would cause excessive sidewall 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
This approach effectively reduces the amount of reaction products adhering to the etching device, shortens cleaning times, and minimizes sidewall etching, thereby improving the manufacturing efficiency and yield of semiconductor devices.
Implementation Method 1
a plasma etching process using a halogen family gas has been widely used conventionally
Implementation Method 2
a mixed gas of chlorine (Cl2) and hydrogen bromide (HBr) has been used as an etching gas
Implementation Method 3
A silicon chloride and a silicon bromide, which have relatively high freezing points, easily remain in a dry etching device and adhere to and accumulate on the inner wall surface
Data Source
AI summary
A trench is formed at an exposed portion of a semiconductor substrate by performing a dry etching process with a hard mask of silicon oxide film serving as an etching mask in a dry etching device. At this time, a mixed gas of tetrafluoromethane (CF4), a hydrogen bromide gas (HBr), and a chlorine gas (Cl2) is used as an etching gas. The dry etching process is performed under the condition that a flow rate ratio is more than 0 and less than 0.04, the flow rate ratio being a value obtained by dividing a flow rate NF by a flow rate TF, the flow rate NF being a flow rate obtained by dividing a flow rate of the tetrafluoromethane by the number of fluorine atoms bonded to one molecule of the tetrafluoromethane, the flow rate TF being a total flow rate of the hydrogen bromide gas and the chlorine gas.