Non-Flat PVD Collimator for Wafer Thickness Uniformity
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Solution Overview
Problem
Traditional PVD systems result in uneven deposition of target material on semiconductor wafers due to the finite size of the target, leading to thicker layers on sidewalls and thinner layers at the bottom of etchings, causing non-uniform thickness distribution.
Innovation Solution
The use of a collimator with non-uniform passage dimensions and orientations to filter target material, allowing only material perpendicular to the wafer to pass through, thereby improving thickness uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a traditional PVD system deposits target material onto a semiconductor wafer, then material is deposited on the wafer surface, but the deposition is uneven with thicker layers on sidewalls and thinner layers at the bottom of etchings
Solution Approach 1:
The collimator is divided into multiple passages of different lengths and orientations. Each passage is segmented to control material flow from specific angular directions, with central passages being shorter and peripheral passages being longer, creating zone-specific deposition control
Solution Approach 2:
Different regions of the collimator are designed with different passage characteristics. Central passages have different lengths compared to peripheral passages, creating local variations in material flow control. This allows each zone to address specific deposition uniformity issues in corresponding wafer regions
2Manufacturing precision
If the target material is deposited without a collimator, then the deposition process is simple, but the thickness distribution is non-uniform
Solution Approach 1:
The collimator acts as an intermediary component between the target and the semiconductor wafer. It mediates the material flow by filtering angles and directing deposition patterns, achieving uniform thickness distribution without requiring changes to the target or wafer themselves
Solution Approach 2:
The solution moves from a simple point-source deposition model to a three-dimensional angular control system. By introducing the collimator with its multi-passage structure, the system controls material deposition from multiple angular dimensions simultaneously, achieving uniformity through spatial differentiation
3Manufacturing precision
If a collimator with uniform passages is used, then the structure is simple to manufacture, but it cannot achieve the required 67% improvement in thickness uniformity
Solution Approach 1:
The collimator employs asymmetric passage design where central passages differ in length from peripheral passages. This asymmetry is deliberately introduced to compensate for the natural non-uniformity in deposition patterns, with longer peripheral passages reducing material flow to outer regions and shorter central passages allowing greater flow to the center
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
Achieves a 67% or greater improvement in thickness uniformity of the deposited layer, particularly beneficial for copper seed layers in semiconductor fabrication.
Implementation Method 1
Physical vapor deposition (PVD) is commonly used within the semiconductor industry, as well as within solar, glass coating, and other industries. A PVD system is used, for example, to deposit metal layers onto substrates such as semiconductor wafers that are positioned in a vacuum plasma chamber.
Data Source
AI summary
A physical vapor deposition (PVD) system includes: a pedestal configured to accommodate a semiconductor wafer; a cover plate above the pedestal configured to hold a target; and a collimator disposed above the pedestal and below the cover plate. The collimator has an upper surface and a lower surface. The lower surface is flat, and the upper surface is non-flat. A first thickness, in a vertical direction, of the collimator at a central portion is smaller than a second thickness, in the vertical direction, of the collimator at a peripheral portion.