Trisilane Silicon Layer Formation at Low Temperatures
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Solution Overview
Problem
The challenge is to form smooth n-type doped silicon films at an acceptable deposition rate, as reducing deposition temperatures to achieve smoother films leads to unacceptably low deposition rates due to dopant poisoning of the substrate surface, making it difficult to balance smoothness and throughput in semiconductor processing.
Innovation Solution
A method involving the use of trisilane as a silicon precursor and an n-type dopant precursor, such as phosphine, in a batch process chamber, where the deposition conditions are set to operate in the kinetic regime, allowing for the formation of very smooth and conformal n-type doped silicon layers with high deposition rates, independent of the dopant precursor flow rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If deposition temperature is reduced to achieve smoother films, then film smoothness is improved, but deposition rate decreases to unacceptably low levels
Solution Approach 1:
The patent changes the chemical parameters of the deposition system by switching from silane to trisilane as the silicon precursor gas. This parameter change enables the deposition process to operate at lower temperatures (reducing thermal budget) while maintaining high deposition rates, thereby achieving smooth films without the typical trade-off of reduced productivity
Solution Approach 2:
The patent introduces a specific dopant precursor that acts as an intermediary substance. This dopant precursor enables n-type doping during deposition without causing the surface poisoning effect that normally occurs with conventional dopants, thus maintaining high deposition rates even at lower temperatures where smooth films are formed
2Quantity of substance
If n-type dopant is introduced during deposition to form doped films, then doping is achieved, but deposition surface is poisoned causing strong reduction in deposition rate
Solution Approach 1:
The patent uses a specially selected dopant precursor as an intermediary that delivers dopant atoms to the growing film without causing surface poisoning. This intermediary approach allows n-type doping to occur during deposition while maintaining high deposition rates, avoiding the harmful side effects of conventional dopant introduction methods
Solution Approach 2:
The patent changes the chemical form and delivery mechanism of the dopant by using a dopant precursor instead of conventional dopant sources. This parameter change in dopant delivery enables dopant incorporation without the adverse surface poisoning effect, thus maintaining high productivity
3Manufacturing precision
If deposition temperature is reduced to deposit smoother n-type doped films, then film smoothness is improved, but deposition rate falls to unacceptably low levels due to combined effects of temperature reduction and dopant poisoning
Solution Approach 1:
The patent simultaneously changes two critical parameters: the silicon precursor (from silane to trisilane) and the dopant delivery method (using dopant precursor). These combined parameter changes enable the deposition of smooth n-type doped films at lower temperatures without the deposition rate penalty that would normally result from temperature reduction and dopant poisoning
Solution Approach 2:
The dopant precursor serves as an intermediary that enables n-type doping during low-temperature deposition without causing surface poisoning. This intermediary approach resolves the combined problem of temperature reduction and dopant poisoning, allowing smooth film formation at acceptable deposition rates
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 enables the production of uniformly thin, continuous doped silicon films with high smoothness and high throughput, facilitating the production of semiconductor devices with smaller circuit dimensions and higher reliability, while reducing thermal budgets and maintaining acceptable deposition rates at lower temperatures.
Implementation Method 1
depositing a silicon layer on a plurality of substrates in a batch process chamber by exposing the substrates to trisilane
Implementation Method 2
The silicon layer is doped by exposing the substrates to an n-type dopant precursor during at least part of the deposition of the silicon layer
Data Source
AI summary
A doped silicon layer is formed in a batch process chamber at low temperatures. The silicon precursor for the silicon layer formation is a polysilane, such as trisilane, and the dopant precursor is an n-type dopant, such as phosphine. The silicon precursor can be flowed into the process chamber with the flow of the dopant precursor or separately from the flow of the dopant precursor. Surprisingly, deposition rate is independent of dopant precursor flow, while dopant incorporation linearly increases with the dopant precursor flow.