PECVD Nitride and Oxide Deposition for Front-Side-Only Wafer Processing
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Solution Overview
Problem
Existing semiconductor fabrication processes for forming silicon nitride and silicon oxide layers in integrated circuits often require high temperatures and long heat cycles, leading to unwanted layer formation on the wafer backside, increased process complexity, and additional costs for removal.
Innovation Solution
A method using plasma-enhanced chemical vapor deposition (PECVD) to form high-quality nitride and oxide layers on the front side of a semiconductor wafer, involving the use of differential surfaces in a processing chamber coupled with a plasma-igniting external radio frequency source, and post-treatment with helium and nitrogen to enhance film properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If furnace-based batch processing is used to form nitride and oxide layers, then satisfactory film attributes are achieved, but unwanted layers form on the wafer back side requiring additional removal steps
Solution Approach 1:
The patent applies local quality by making the wafer front side and back side experience different processing conditions. The front side is exposed to plasma and precursor gases for nitride and oxide layer formation, while the back side is shielded or exposed to different conditions, preventing unwanted layer formation. This selective processing eliminates the need for back side layer removal steps.
Solution Approach 2:
The patent segments the processing into distinct stages: front side processing for nitride and oxide layer formation, and back side processing for different purposes. This segmentation allows independent optimization of each side's processing conditions, achieving high film quality on the front side without creating unwanted layers on the back side.
2Manufacturing precision
If furnace-based batch processing is used to form nitride and oxide layers, then satisfactory film attributes are achieved, but long heat cycles and high temperatures increase processing time
Solution Approach 1:
The patent replaces the thermal field (furnace heating) with a plasma field for nitride and oxide layer formation. Plasma-enhanced chemical vapor deposition (PECVD) allows film formation at lower temperatures and shorter times compared to traditional thermal processing, significantly reducing processing time while maintaining or improving film quality.
Solution Approach 2:
The patent changes the processing parameters from high temperature (700°C and above) and long duration to lower temperature and shorter duration by using plasma enhancement. This parameter change enables faster processing while achieving satisfactory or superior film attributes.
3Manufacturing precision
If furnace-based batch processing is used to form nitride and oxide layers, then layers are formed on both wafer sides, but additional chemicals and costs are required to remove back side layers
Solution Approach 1:
The patent applies local quality by making the wafer front side and back side experience different processing conditions. The front side is exposed to plasma and precursor gases for nitride and oxide layer formation, while the back side is shielded or exposed to different conditions, preventing unwanted layer formation. This selective processing eliminates the need for back side layer removal steps.
Solution Approach 2:
The patent extracts or removes the problematic back side layer formation by modifying the processing setup. This could involve using a wafer holder that shields the back side, or processing conditions that only affect the front side, thereby eliminating the need for subsequent removal operations and associated chemical consumption.
4Productivity
If plasma-enhanced chemical vapor deposition is used to form nitride and oxide layers, then layers are deposited only on the wafer front side, but process control and uniformity become more challenging
Solution Approach 1:
The patent uses a plasma processing system that can perform multiple functions: nitride layer deposition, oxide layer deposition, and selective front-side processing. This multi-functional approach consolidates several operations into one system, improving productivity while managing complexity through integrated control.
Solution Approach 2:
The patent implements feedback control in the plasma processing system to maintain uniformity and control film properties. Sensors and control algorithms monitor processing conditions in real-time and adjust parameters to ensure consistent film quality across the wafer front side, addressing the control challenges of selective processing.
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
The PECVD method allows for the formation of nitride and oxide layers with improved properties, such as increased breakdown strength and density, reduced hydrogen content, and lower leakage, while selectively depositing layers only on the wafer front side, thus reducing process complexity and costs.
Implementation Method 1
a plasma-igniting external radio frequency source
Implementation Method 2
depositing one of a nitride or oxide on at least an exposed portion of either the semiconductor wafer or a layer affixed relative to the wafer front side by reacting at least two precursor gases for a selected one of the nitride or oxide layer in the chamber while the plasma igniting external radio frequency source is enabled
Implementation Method 3
post-treating the one of a nitride or oxide with the plasma igniting external radio frequency source enabled and with exposure to helium and nitrogen in the absence of at least one of the at least two precursor gases
Data Source
AI summary
A method of forming at least one of a nitride or oxide layer for an integrated circuit, the method comprising: (i) positioning a semiconductor wafer in a processing chamber, the semiconductor wafer including a wafer front side and the processing chamber including differential surfaces adapted to be coupled to a plasma-igniting external radio frequency source; (ii) depositing one of a nitride or oxide on at least an exposed portion of either the semiconductor wafer or a layer affixed relative to the wafer front side by reacting at least two precursor gases for a selected one of the nitride or oxide layer in the chamber while the plasma igniting external radio frequency source is enabled; and (iii) post-treating the one of a nitride or oxide with the plasma igniting external radio frequency source enabled and with exposure to helium and nitrogen in the absence of at least one of the at least two precursor gases.