Sidewall Deposit Removal via Oxygen Plasma Dehydration
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Solution Overview
Problem
In semiconductor device manufacturing, the existing methods for removing silicon oxide deposits from sidewall patterns during the STI process suffer from low selectivity, leading to damage of silicon dioxide structures and worsened selectivity due to moisture absorption, especially when using etching gases containing carbon, which results in incomplete removal and potential damage to gate oxide films.
Innovation Solution
A method involving a plasma processing apparatus and gas processing apparatus sequence, where a substrate is exposed to hydrogen fluoride gas, followed by oxygen plasma to dehydrate the surface, and then to a mixed hydrogen fluoride and methanol gas atmosphere in a cyclical process to effectively remove silicon oxide deposits while preventing damage to silicon dioxide layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If hydrogen fluoride gas is used to remove silicon oxide deposits, then deposit removal is achieved, but selectivity is low and silicon dioxide structures are damaged
Solution Approach 1:
The deposit removal process is divided into multiple sequential steps: first exposing to hydrogen fluoride gas to remove silicon oxide deposits, then exposing to oxygen plasma to dehydrate the surface, and finally exposing to mixed hydrogen fluoride and alcohol gas. This segmentation allows each step to perform a specific function, improving overall selectivity and preventing damage to silicon dioxide structures.
Solution Approach 2:
Oxygen plasma exposure is performed as a preliminary action between the hydrogen fluoride gas exposure and the final deposit removal step. This preliminary dehydration step removes moisture from the surface, preventing water-induced chain reactions that would otherwise damage silicon dioxide structures during subsequent hydrogen fluoride exposure.
2Productivity
If etching gas containing carbon is used, then etching process is completed, but organic matter remains in deposit and cannot be completely removed
Solution Approach 1:
Alcohol gas is introduced as an intermediary substance in the final exposure step. The alcohol molecules interact with both the organic matter in the deposit and the hydrogen fluoride gas, facilitating complete removal of carbon-containing deposits while the oxygen plasma-prepared surface ensures clean reaction products are formed.
Solution Approach 2:
The invention uses a composite gas atmosphere combining hydrogen fluoride and alcohol in specific proportions. This composite approach leverages the etching capability of hydrogen fluoride while the alcohol component addresses organic matter removal, achieving complete deposit removal that neither gas could accomplish alone.
3Loss of time
If queuing time after etching process is long, then production flow is maintained, but moisture absorption worsens selectivity ratio
Solution Approach 1:
Oxygen plasma exposure is performed as a preliminary dehydration step that removes moisture from the surface regardless of queuing time duration. This preliminary action ensures that even after long waiting periods, the surface remains dry and selective to hydrogen fluoride, maintaining high selectivity ratio for deposit removal.
Solution Approach 2:
The process employs periodic exposure to oxygen plasma at controlled intervals, creating a cyclic dehydration treatment. This periodic action ensures moisture is consistently removed from the surface, counteracting the moisture absorption that occurs during queuing time and maintaining stable selectivity ratio.
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 ensures complete removal of silicon oxide deposits and organic matter from sidewall patterns without damaging the silicon dioxide structures, maintaining selectivity and preventing excessive moisture-induced reactions, even with varying queuing times after the etching process.
Implementation Method 1
a reaction between the deposit and hydrogen fluoride (SiO2+4HF→SiF4+2H2O)
Implementation Method 2
exposing the substrate to oxygen plasma while heating
Implementation Method 3
exposing the substrate to oxygen plasma while heating after the step of exposing the substrate to the first atmosphere
Implementation Method 4
exposing the substrate to a second atmosphere containing hydrogen fluoride gas to remove the deposit on the substrate after the step of exposing the substrate to the oxygen plasma
Data Source
AI summary
One embodiment of the deposit removal method includes: preparing a substrate having a pattern on which a deposit is deposited, the pattern being formed by etching; exposing the substrate to a first atmosphere containing hydrogen fluoride gas; exposing the substrate to oxygen plasma while heating after the step of exposing the substrate to the first atmosphere; and exposing the substrate to a second atmosphere containing hydrogen fluoride gas to remove the deposit on the substrate after the step of exposing the substrate to the oxygen plasma.