Vacuum Chuck Polymeric Embossments Wafer Flatness
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Solution Overview
Problem
Existing vacuum chucks fail to maintain a sufficiently flat substrate surface during wafer bonding processes, leading to misalignment issues due to variations in embossment height, which are not adequately addressed by conventional lapping techniques as semiconductor device sizes continue to decrease.
Innovation Solution
A vacuum chuck with polymeric embossments of specific material properties and arrangements, including a base substrate with high elastic modulus and metal barrier layers, is used to achieve a peak-to-valley flatness of 2.5 microns or less across the wafer surface, ensuring improved alignment and adhesion shear strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional lapping techniques are used to flatten the base substrate surface, then the surface flatness is improved, but the alignment precision is insufficient for decreasing semiconductor device sizes
Solution Approach 1:
The patent changes the material parameter of the embossments from traditional rigid materials to polymeric materials with specific mechanical properties (Young's modulus between 1.5-3.5 GPa, tensile strength between 70-120 MPa). This parameter change allows the embossments to deform and conform to the wafer surface, achieving superior flatness (peak-to-valley variation of 2.5 microns or less) that enables precise alignment for decreasing device sizes.
Solution Approach 2:
The patent employs composite material structures including polymeric embossments overlying a base substrate, with the polymeric layer providing both structural support and compliant surface contact. The combination of rigid base substrate and compliant polymeric embossments creates a hybrid structure that achieves both mechanical stability and surface flatness required for high-precision alignment.
2Strength
If the embossment height varies on the vacuum chuck surface, then the substrate clamping is achieved, but the wafer surface flatness deteriorates leading to misalignment
Solution Approach 1:
The patent specifies precise parameter ranges for the polymeric embossments including Young's modulus between 1.5-3.5 GPa and tensile strength between 70-120 MPa. These parameter controls ensure the embossments provide sufficient clamping force while maintaining uniform height and compliance, achieving wafer surface flatness with peak-to-valley variation of 2.5 microns or less.
Solution Approach 2:
The patent applies polymeric material specifically to the embossment structures that contact the wafer surface, creating a localized compliant region. This local quality change allows the embossment tops to conform to the wafer surface while the base substrate maintains structural integrity, ensuring both effective clamping and uniform wafer flatness across the entire surface.
3Stability of the object's composition
If a rigid suction substrate is used, then the structural stability is maintained, but the ability to compensate for surface irregularities and foreign matter is reduced
Solution Approach 1:
The patent creates a composite structure with a rigid base substrate providing structural stability and polymeric embossments providing surface compliance. The base substrate maintains overall chuck stability while the polymeric embossment layer compensates for surface irregularities and foreign matter, achieving both structural stability and reliable surface planarization.
Solution Approach 2:
The patent uses polymeric material as a flexible thin film layer on the embossment surfaces. This flexible layer can deform to accommodate surface irregularities and embed foreign matter, maintaining reliable wafer contact and planarization while the underlying rigid base substrate provides necessary structural stability.
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 solution provides a vacuum chuck that maintains a flat substrate surface with improved alignment and reduced wafer sag, enhancing the precision and yield of wafer bonding processes by ensuring a peak-to-valley measurement of 1 micron or less across the clamped wafer surface.
Implementation Method 1
a vacuum chuck with polymeric embossments... when the wafer is suctioned... a pressure delta of between 50 torr and 750 torr between the vacuum chuck and the backside of the prime wafer
Implementation Method 2
An elastic coating layer is coated by way of an undercoat layer on the tip-end faces of the protrusions. When the wafer is suctioned, even if a foreign matter is interposed between the wafer and the suction surface, because the foreign matter embeds itself into the coating layer, the planarization of the wafer is improved.
Implementation Method 3
the second peak to valley flatness may be a flatness as measured by interferometry with a peak to valley variation of 2.5 microns or less
Data Source
Figure 1~3
Figure 4A~4C
Figure 5
AI summary
A vacuum chuck with polymeric embossments is disclosed. The polymeric embossments are formed on the surface of a base substrate and are lapped to a flatness such that a wafer substrate clamped by the vacuum chuck has a peak to valley flatness that is less than a peak to valley flatness across the base substrate. Lapping of the polymeric embossments accommodates for variations in the flatness of the base substrate so long as the embossments are tall enough to stand over the peak to valley height variations in the base substrate.