Convex Pressure Disc for Uniform Wafer Bonding
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Solution Overview
Problem
In the semiconductor industry, the bonding process of product wafers to carrier wafers often results in nonuniform bond forces due to the rheological and fluid-dynamic properties of the bonding adhesive, leading to inhomogeneous layer thickness and excess material displacement, particularly at the edge of the substrate.
Innovation Solution
A pressure disc with a convexly curved pressure transfer side is used to apply force in the center of the bond layer, where material flow is obstructed, preventing premature transfer of force to the edge bead and reducing excess material displacement, with the curvature allowing for uniform pressure distribution and minimal deviation from planarity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If flat pressure discs are used to apply uniform bond force, then the bond force distribution should be uniform, but inhomogeneous layer thickness occurs due to material flow differences between center and edge
Solution Approach 1:
The pressure disc is designed with a convexly curved pressure transfer side instead of a flat surface. This curvature allows the initial contact zone to be restricted to the center region, creating a defined initial zone A where bonding begins. The curved surface gradually distributes pressure from the center outward, controlling material flow and preventing edge bead formation while maintaining progressive bond force application.
Solution Approach 2:
The pressure disc creates different pressure conditions in different regions: the center region (initial zone A) experiences high pressure first to initiate bonding and obstruct material flow, while the edge regions experience pressure progressively later. This local differentiation of pressure application timing and intensity resolves the contradiction between uniform force distribution and homogeneous layer thickness.
2Strength
If high pressure is applied to bond wafers, then bonding strength is improved, but excess material is forced out at the edges forming edge beads
Solution Approach 1:
The convex curvature of the pressure disc performs a preliminary action by establishing the initial zone A in the center before edge contact occurs. This preliminary configuration of the pressure distribution prevents material from being forced to the edges before bonding is initiated, thereby preventing edge bead formation while still allowing high pressure to be applied for strong bonding.
3Area of stationary object
If the pressure disc contacts the entire wafer surface simultaneously, then bonding area is maximized, but material flow cannot be controlled leading to inhomogeneous thickness
Solution Approach 1:
The convex curvature geometry of the pressure disc naturally restricts the initial contact area to the center region (initial zone A) while allowing progressive contact expansion to the edges. This geometric design achieves controlled material flow restriction during the bonding process while ultimately achieving full surface bonding area, resolving the contradiction between bonding area and thickness uniformity.
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 ensures a uniform bond force application, reducing the formation of edge beads and achieving a more homogeneous bond layer thickness, thereby enhancing the bonding process by hindering material flow at the center and minimizing excess material displacement.
Implementation Method 1
the product substrate which has been deposited on the bond layer is bent by the action apparatus toward the center of the bond layer and thus due to its elastic deformation prevents the premature transfer of force from the action apparatus to the 'edge bead'
Data Source
AI summary
A device for bonding of a second substrate onto a first substrate, comprising a receiving apparatus for receiving the first substrate which has been coated with a bond layer and the second substrate which is held on the bond layer, and an action apparatus for applying a bond force to the second substrate on one action side of the second substrate, which side faces away from the bond layer proceeding from an initial zone A, which lies within an edge zone R of the action side as far as action on the entire action side.Furthermore, this invention relates to a corresponding method.