Conformal Oxide Dry Etch Trench Uniformity
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Solution Overview
Problem
Existing dry etch processes for silicon oxide in integrated circuits often result in non-uniform trench width variations due to heterogeneous deposition methods, leading to inconsistent etch rates and potential electrical issues in contact formation.
Innovation Solution
A method involving sequential introduction of hydrogen-containing and fluorine-containing precursors into a substrate processing region, followed by sublimation to remove solid by-products, ensuring consistent etch rates across different silicon oxide layers regardless of deposition methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional dry etch processes are used on heterogeneously deposited silicon oxide layers, then the etch process can proceed, but trench width variations occur due to non-uniform etch rates
Solution Approach 1:
The etch process is divided into multiple sequential steps with different gas chemistries (e.g., CF4 step followed by NF3 step). Each step targets specific aspects of the etching process, allowing independent optimization of etch rate and selectivity for different silicon oxide deposition types, thereby achieving uniform trench width across heterogeneous layers
Solution Approach 2:
The patent varies process parameters including gas flow rates, pressure, temperature, and precursor composition between different etch steps. By adjusting these parameters, the etch rate is optimized for each specific silicon oxide layer type (e.g., PECVD vs. CVD), ensuring consistent trench width uniformity across heterogeneous deposits
2Productivity
If high etch rate is achieved to improve productivity, then material removal is faster, but uniformity of etch rate across trench sides is compromised
Solution Approach 1:
The patent employs periodic alternation between different gas precursors (e.g., CF4 and NF3) in sequential steps. This periodic action allows the process to alternate between high etch rate phases and uniformity control phases, achieving both high overall productivity and consistent trench width uniformity across heterogeneous silicon oxide layers
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 achieves homogeneous etch rates up and down trench sides, maintaining uniformity and preventing electrical issues by consistently removing a few monolayers per etch cycle, even with heterogeneously deposited silicon oxide layers.
Implementation Method 1
exposing the patterned substrate to hydrogen by flowing a hydrogen-containing precursor into the substrate processing region
Implementation Method 2
exposing the patterned substrate to fluorine by flowing a fluorine-containing precursor into the substrate processing region to form solid by-products
Implementation Method 3
raising a temperature of the substrate above a sublimation temperature to remove the solid by-products
Data Source
AI summary
A method of etching silicon oxide from a trench is described which allows more homogeneous etch rates up and down the sides of the trench. One disclosed method includes a sequential introduction of (1) a hydrogen-containing precursor and then (2) a fluorine-containing precursor into a substrate processing region. The temperature of the substrate is low during each of the two steps in order to allow the reaction to proceed and form solid residue by-product. A second disclosed method reverses the order of steps (1) and (2) but still forms solid residue by-product. The solid residue by-product is removed by raising the temperature in a subsequent sublimation step regardless of the order of the two steps.