RF Sputtering Darkspace Gap Control via Segmented Shield
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Solution Overview
Problem
In semiconductor fabrication, the lack of control over the darkspace gap in physical vapor deposition (PVD) chambers leads to plasma penetration and contamination, particularly in RF PVD processes, where manufacturing tolerances make it difficult to maintain a small gap size and prevent sputtering of the backing plate and darkspace shield materials.
Innovation Solution
A target assembly design with a recessed backing plate and a target that are coplanar with the darkspace shield, where the vertical darkspace gap is defined during manufacturing, ensuring a constant and reduced gap size, and the horizontal gap is maintained to inhibit plasma ignition and material deposition on the target edge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the darkspace gap is kept large, then electrical arcing between target and darkspace shield is inhibited, but plasma ignition within the gap occurs and sputtered material deposits on target edge causing contamination
Solution Approach 1:
The darkspace shield is divided into multiple segments around the target periphery, with each segment independently adjustable. This segmentation allows optimization of gap dimensions in different regions to simultaneously prevent arcing and minimize plasma contamination.
Solution Approach 2:
The darkspace shield segments are made adjustable rather than fixed, allowing dynamic optimization of the gap size between target and shield. This enables the system to adapt to different operating conditions and maintain optimal contamination prevention while preventing arcing.
2Object-affected harmful factors
If the darkspace gap is kept small, then plasma ignition is prevented and material deposition is reduced, but electrical arcing between target and darkspace shield occurs
Solution Approach 1:
Different regions of the darkspace shield are positioned at different distances from the target, creating locally optimized gap configurations. This allows the gap to be small in regions where contamination prevention is critical while maintaining larger gaps in regions where arcing prevention is the priority.
3Ease of manufacture
If target and darkspace shield are aligned to chamber body, then alignment is simplified, but manufacturing tolerances make it difficult to control darkspace gap size consistently
Solution Approach 1:
The darkspace shield segments are designed to self-align with the target using mechanical features such as tapered surfaces or positioning pins. This self-alignment mechanism eliminates the need for complex external alignment procedures while ensuring consistent gap dimensions within tight tolerances.
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 design improves control over the darkspace gap, reducing contamination and allowing for precise control of material deposition, thereby enhancing the uniformity and quality of films deposited on semiconductor wafers.
Implementation Method 1
Sputtering is a physical vapor deposition (PVD) process in which high-energy ions impact and erode a solid target and deposit the target material on the surface of a substrate
Implementation Method 2
A plasma is generated within the PVD chamber by a RF power source coupled to the target assembly
Data Source
AI summary
Improved designs of target assemblies and darkspace shields are disclosed. Methods of improving darkspace gap in sputtering chambers and sputtering chambers having an improved darkspace gap are also disclosed. Disclosed is a target assembly having a substantially coplanar backing plate and a target are vertically spaced from the darkspace shield.