Ultra Thin Wafer Handling via Rigid Carrier and Melted Support Layer
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Solution Overview
Problem
Ultra thin semiconductor wafers are fragile and prone to cracking and warpage during handling and processing, leading to decreased yield and quality in chip packages due to conventional encapsulation methods, which also accumulate heat and cause performance issues.
Innovation Solution
A method involving a rigid wafer carrier attached to the front surface of the wafer with an adhesive layer, and a support layer coated on the back surface to encapsulate and support the wafer during processing, using adhesion tapes for dicing, and removing the support layer by heating it above its melting temperature for efficient separation into individual parts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If ultra thin wafer thickness is reduced to decrease package thickness and increase chip speed, then package thickness is reduced and chip speed is increased, but wafer strength is insufficient leading to cracking and deformation during handling
Solution Approach 1:
The support structure is divided into multiple components: a rigid carrier substrate that provides overall mechanical support, and discrete support elements (such as beads or pillars) that are positioned at specific locations on the wafer backside. This segmented approach provides distributed support to prevent deformation while maintaining the ultra-thin wafer structure.
Solution Approach 2:
A carrier substrate acts as an intermediary between the ultra-thin wafer and the handling equipment. The carrier provides mechanical strength and rigidity during handling, transport, and processing, while the wafer itself remains ultra-thin. The support elements on the wafer backside further mediate between the wafer's fragility and the mechanical stresses of processing.
2Reliability
If molding compound is used to encapsulate ultra thin wafer for handling protection, then wafer handling reliability is improved, but heat accumulation occurs impacting device performance
Solution Approach 1:
The support elements (beads or pillars) are selectively removed from the wafer backside after the carrier is no longer needed. This extraction of unnecessary support structures allows for subsequent packaging without the interference of molding compounds over the support elements, enabling better thermal management in the final device.
Solution Approach 2:
The support elements are designed with specific material properties and geometric parameters (size, spacing, height) that can be optimized to provide adequate mechanical support during handling while minimizing interference with thermal dissipation in the final packaged device.
3Ease of manufacture
If molding compound delaminates from wafer during handling, then wafer is subject to warpage decreasing process yield, but conventional encapsulation methods are used
Solution Approach 1:
Support elements are applied to the wafer backside before the wafer is mounted on the carrier. This preliminary action ensures that the wafer has adequate support during carrier attachment and subsequent handling, preventing warpage and delamination issues that would occur with conventional encapsulation methods.
Solution Approach 2:
The support elements serve a temporary function during handling and processing, then can be removed or left in place depending on the application. This disposable approach to support structures avoids the long-term thermal management issues of permanent molding compound encapsulation while providing adequate protection during the critical handling phase.
4Productivity
If wafer edges are exposed during dicing process without proper support, then dicing can proceed, but edges are susceptible to cracking and chipping
Solution Approach 1:
The rigid carrier substrate and backside support elements provide cushioning and mechanical support to the wafer edges before the dicing process begins. This prior protection prevents cracking and chipping during handling and the dicing operation itself, ensuring high edge integrity without compromising dicing efficiency.
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 reduces wafer breakage and warpage, maintaining high throughput with low breakage rates and improving the reliability of chip packages by stabilizing the wafer during handling and processing.
Implementation Method 1
a rigid wafer carrier attached to the front surface of the wafer with an adhesive layer
Implementation Method 2
removing the support layer by heating it above its melting temperature for efficient separation into individual parts
Data Source
AI summary
A method for thin wafer handling and processing is provided. In one embodiment, the method comprises providing a wafer having a plurality of semiconductor chips, the wafer having a first side and a second side. A plurality of dies are attached to the first side of the wafer, at least one of the dies are bonded to at least one of the plurality of semiconductor chips. A wafer carrier is provided, wherein the wafer carrier is attached to the second side of the wafer. The first side of the wafer and the plurality of dies are encapsulated with a planar support layer. A first adhesion tape is attached to the planar support layer. The wafer carrier is then removed from the wafer and the wafer is diced into individual semiconductor packages.