Semiconductor Die Packaging Two-Step Molding Compound Removal
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Solution Overview
Problem
The existing grinding technologies in semiconductor packaging are inaccurate, leading to yield loss due to the inability to precisely stop the grinding process when copper posts are fully exposed, resulting in over-grinding and incomplete exposure.
Innovation Solution
A method involving a two-step process for removing the molding compound layer, where the first step uses grinding or CMP to partially expose the copper posts, followed by an etching process to fully expose the contact pads, allowing for more precise control and avoiding damage to the semiconductor dies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a single-step grinding process is used to remove molding compound, then the process is simple and fast, but the precision of copper post exposure is poor leading to over-grinding or incomplete exposure
Solution Approach 1:
The grinding process is divided into multiple steps: a first grinding step that removes a first portion of the molding compound, followed by a second grinding step that removes a second portion to fully expose the copper posts. This segmentation allows each step to be optimized for specific precision requirements, resolving the contradiction between precision and process simplicity.
Solution Approach 2:
The first grinding step performs a preliminary removal of the molding compound to bring the copper posts close to exposure without fully exposing them. This preliminary action prevents over-grinding in the subsequent step while ensuring complete exposure is achieved, thereby improving precision without excessive complexity.
2Manufacturing precision
If grinding is continued until copper posts are fully exposed, then complete exposure is achieved, but over-grinding occurs damaging the semiconductor dies
Solution Approach 1:
The multi-step grinding process provides a cushioning effect by removing molding compound in controlled portions. The first step removes a safe amount of material, and the second step completes the exposure, preventing direct contact between the grinding tool and the semiconductor die. This beforehand cushioning protects the die from damage while ensuring complete copper post exposure.
Solution Approach 2:
The process uses partial action by removing only the necessary portions of molding compound in two separate steps rather than attempting to remove all material in one step. This controlled partial removal ensures complete copper post exposure while avoiding excessive removal that would damage the die.
3Productivity
If the molding compound layer is removed completely in one step, then the process is efficient, but the thin layers make it difficult to stop at the right time
Solution Approach 1:
The molding compound removal is segmented into two distinct grinding steps, each removing a specific portion of the compound. This segmentation improves measurement precision by allowing intermediate inspection and control between steps, while maintaining overall productivity through efficient material removal in each step.
Solution Approach 2:
The multi-step process incorporates feedback mechanisms where the result of the first grinding step is evaluated before proceeding to the second step. This feedback loop allows for precise control of the grinding depth and ensures the process stops at the correct point to fully expose copper posts without damage.
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 enhances the precision of the grinding process, reducing yield loss by ensuring complete exposure of copper posts without damaging the semiconductor dies, thereby improving the overall packaging process efficiency.
Implementation Method 1
a first process is performed to remove a first portion of the molding compound layer
Implementation Method 2
the first step uses grinding or CMP to partially expose the copper posts
Implementation Method 3
followed by an etching process to fully expose the contact pads
Data Source
AI summary
A method of packaging a semiconductor device, comprising: attaching a plurality of dies to a carrier wafer, wherein each of the dies includes a top surface; forming a molding compound layer over the dies, wherein the top surface of the dies are covered by the molding compound layer; removing a first portion of the molding compound layer; removing a second portion of the molding compound layer such that the top surface of the dies is not covered by the molding compound layer; forming a redistribution layer (RDL) over the top surface of the dies; forming a plurality of solder balls over at least a portion of the RDL; and singulating the dies.