Semiconductor Package Structure Using a Sacrificial Layer for Backgrinding
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Solution Overview
Problem
The backgrinding process for semiconductor wafers, particularly for next-generation materials like Silicon Carbide (SiC) and Gallium Nitride (GaN), faces a significant risk of die cracking due to their increased hardness and brittleness, which existing methods fail to adequately address.
Innovation Solution
A semiconductor packaging structure is developed that includes a sacrificial layer on the die back surface, a protective layer on the active surface, and a molding layer that forms a cavity contour, along with a conductive layer conformally following this contour, to prevent die cracking during the thinning process. This structure also includes filled vias for electrical coupling and a heat sink for thermal management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If backgrinding process is applied to reduce wafer thickness, then wafer thickness is reduced, but die cracking occurs due to hardness and brittleness of next-generation materials
Solution Approach 1:
A sacrificial layer is deposited on the die back surface before the backgrinding process. This preliminary action provides mechanical support during thinning, preventing die cracking. After grinding, the sacrificial layer is removed to expose the thinned die back surface, achieving both thickness reduction and crack prevention.
Solution Approach 2:
The sacrificial layer acts as an intermediary between the grinding wheel and the die back surface. It absorbs the mechanical stress during grinding, protecting the brittle die material from cracking while allowing the desired thinning to occur.
2Reliability
If sacrificial layer is added to prevent die cracking, then die cracking is prevented, but process complexity increases
Solution Approach 1:
The sacrificial layer is designed to be temporary - deposited before grinding to prevent cracks, then completely removed afterward. This approach adds minimal permanent complexity while solving the cracking problem during the critical thinning process.
Solution Approach 2:
The sacrificial layer uses a simple, easily deposited material that serves its protective function temporarily and is then removed. This disposable approach prevents cracking without requiring permanent structural modifications to the packaging.
3Length of moving object
If conventional backgrinding is used on SiC and GaN materials, then thickness reduction is achieved, but manufacturing yield decreases due to die cracking
Solution Approach 1:
The sacrificial layer is deposited on all dies before backgrinding begins. This preliminary protective measure ensures that even brittle SiC and GaN materials can be thinned without cracking, maintaining high manufacturing yield while achieving the required thickness reduction.
Solution Approach 2:
The sacrificial layer mediates between the aggressive grinding process and the fragile die material, enabling high-yield production of thinned SiC and GaN devices by preventing stress-induced cracking during manufacturing.
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 effectively prevents die cracking during the backgrinding process, enhances electrical connectivity, and improves thermal dissipation, making it suitable for handling brittle semiconductor materials while maintaining package stability and efficiency.
Implementation Method 1
A method is disclosed to solve the issue of die cracking during the backgrinding process
Implementation Method 2
a conductive layer conformally to the cavity contour for forming a concave contour of the conductive layer
Implementation Method 3
filled vias in the protective layer by filling the pre-vias with a conductive medium, and the filled vias are electrically coupled to the die pad
Implementation Method 4
a heat sink disposed on the conductive layer
Data Source
AI summary
The present application discloses a semiconductor structure including one or more dies, a protective layer formed on a die active surface, pre-vias formed in the protective layer, and a molding layer encapsulating the die(s) and the protective layer. The die has a die back surface exposed from the molding layer, and the molding layer has a molding thickness larger than a die thickness and a thickness of the protective layer combined for forming a cavity contour. The semiconductor structure also includes a conductive layer formed conformally to the cavity contour for forming a concave contour of the conductive layer. The present application also discloses methods of making the semiconductor structure having a sacrificial layer for solving an issue of die cracking during a thinning process such as backgrinding to a reconstituted panel with the dies embedded within the molding layer.