Amorphous Silicon Gap-Fill Deposition With Cyclic Hydrogen Degassing
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Solution Overview
Problem
Conventional methods for depositing amorphous silicon films face challenges in achieving good conformality and throughput, particularly in high aspect-ratio features, due to issues like hydrogen bubble formation and limited step coverage.
Innovation Solution
The method involves exposing a substrate to a silicon precursor to form an amorphous silicon film with outgassable hydrogen species, followed by an inert degas environment to remove these species, and repeating this process to achieve a predetermined film thickness with high conformality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional LPCVD process is used to deposit amorphous silicon, then low hydrogen content is achieved, but step coverage and gap-fill performance are poor
Solution Approach 1:
The patent employs periodic pulsed deposition cycles where the substrate alternates between exposure to silicon precursor (disilane) and inert degas environment. Each cycle deposits a thin amorphous silicon layer followed by hydrogen removal, repeating this sequence to build up the film to desired thickness while maintaining low hydrogen content and good step coverage throughout the deposition process
2Productivity
If high deposition rate is used, then throughput is improved, but hydrogen entrapment and bubble formation occur
Solution Approach 1:
The pulsed deposition process uses periodic cycles of precursor exposure followed by inert environment degas steps. During each inert environment phase, hydrogen outgasses from the deposited film before subsequent layers are deposited, preventing hydrogen accumulation and bubble formation even when operating at higher deposition rates
Solution Approach 2:
The inert environment exposure is applied preliminarily between deposition steps to remove hydrogen from the film before additional material is deposited. This preliminary hydrogen removal prevents entrapment of hydrogen that would otherwise lead to bubble formation during high-rate deposition
3Temperature
If PECVD process is used, then lower temperature operation is enabled, but step coverage and gap-fill performance deteriorate
Solution Approach 1:
The patent uses periodic pulsed deposition with alternating precursor and inert environment exposure. This allows conformal film deposition at lower temperatures by removing hydrogen during inert phases, preventing the need for high-temperature LPCVD processes while achieving good gap-fill performance through multiple thin-layer deposition cycles
Solution Approach 2:
The process changes the deposition parameters by using pulsed precursor exposure with inert environment intervals, enabling lower temperature operation while maintaining good step coverage and gap-fill performance that would otherwise require high-temperature LPCVD processes
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 allows for the deposition of amorphous silicon films with high conformality (>90%) and defect-free, bubble-free films, while also enabling lower temperature processing and improved throughput.
Implementation Method 1
exposing a substrate surface to a silicon precursor to form an amorphous silicon film having an outgassable species comprising hydrogen
Implementation Method 2
The amorphous silicon film is exposed to an inert degas environment to remove the outgassable species from the amorphous silicon film
Data Source
AI summary
Methods for depositing film comprising cyclical exposure of a substrate surface to a precursor and a degas environment to remove gas evolved from the film. Some embodiments further comprise the incorporation poisoning the top of a feature to inhibit film growth at the top of the feature. Some embodiments further comprising etching a portion of the film deposited at the top of a feature between cycles to increase gap-fill uniformity.