Selective Etching with Hydroxyl Protective Film for Polysilicon
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Solution Overview
Problem
In semiconductor device construction, existing etching methods fail to selectively etch films like polysilicon without etching adjacent films, such as silicon germanium, due to the similar reactivity of etching gases with both materials, leading to unintended damage and process inefficiencies.
Innovation Solution
An etching method involving the formation of a protective film using a gas like methanol or water vapor, which selectively adsorbs on porous interlayer insulating films like SiOCN, preventing etching gases from reaching adjacent films like silicon germanium by sealing their pores, while allowing the etching of polysilicon films by dissolving the thinner protective film formed on them.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional etching gas is supplied to etch polysilicon film, then polysilicon etching is achieved, but adjacent silicon germanium film is also unintentionally etched due to similar reactivity
Solution Approach 1:
A protective film is introduced as an intermediary substance between the etching gas and the films to be protected. This protective film selectively adsorbs the etching gas, preventing it from reaching and damaging the silicon germanium film while allowing polysilicon etching to proceed. The protective film acts as a mediator that controls the interaction between etching gas and different film materials.
Solution Approach 2:
The protective film is formed in advance before the etching process begins. This preliminary action prepares the substrate surface with a protective layer that will prevent unintended etching during the subsequent etching step, ensuring that the silicon germanium film is protected before any harmful etching can occur.
2Object-generated harmful factors
If protective film is formed using compound with hydroxyl group or water, then adjacent films are protected from etching, but the protective film must be selectively dissolved to allow etching of target film
Solution Approach 1:
The protective film exhibits different properties at different locations or on different surfaces. It forms a thicker protective layer on films that need protection (like silicon germanium) while forming a thinner or no protective layer on films that need to be etched (like polysilicon). This local variation in protective film quality enables selective etching without requiring complex additional process steps.
Solution Approach 2:
The etching gas parameters (such as composition, flow rate, or energy) are changed during the process to achieve different effects. Initially, the etching gas conditions are set to allow etching of polysilicon through the protective film, and then parameters are adjusted to remove the protective film from areas where etching is desired, enabling selective etching through parameter control rather than additional 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 method enables selective etching of polysilicon films while protecting adjacent films like silicon germanium, ensuring precise control over the etching process and preventing unwanted etching, thus improving the efficiency and accuracy of semiconductor device fabrication.
Implementation Method 1
forming a protective film by supplying a protective film forming gas including at least one of a compound including a hydroxyl group and water to a substrate including a surface on which a first film and a second film are formed
Implementation Method 2
selectively etching the second film by supplying the etching gas to the substrate in a state in which the protective film is formed
Data Source
AI summary
An etching method includes: forming a protective film by supplying a protective film forming gas including at least one of a compound including a hydroxyl group and water to a substrate including a surface on which a first film and a second film are formed, each of which has a property of being etched by an etching gas, wherein the protective film covers the first film such that the first film is selectively protected from among the first film and the second film when the etching gas is supplied; and selectively etching the second film by supplying the etching gas to the substrate in a state in which the protective film is formed.