Wafer Dicing via Backside Cutting and Trench Etching
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Solution Overview
Problem
Existing semiconductor wafer dicing methods using saw blades result in reduced usable wafer area and microcrack formation near the edges, leading to potential device failure and limitations in testing circuit placement.
Innovation Solution
The method involves etching trenches on the semiconductor wafer to reduce street widths between electronic devices, forming a passivation layer on the trench walls, and cutting the wafer from the backside aligned with these trenches to minimize contact with electronic devices and prevent microcrack propagation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a rotating saw blade is used to cut through the semiconductor wafer from the front side, then the wafer can be separated into individual devices, but the width of the saw blade reduces the overall usable area of the semiconductor wafer
Solution Approach 1:
The patent inverts the conventional dicing approach by cutting the wafer from the backside instead of the front side. The saw blade enters through the backside and cuts along the trenches that were formed on the front side, allowing the blade width to be excluded from the usable device area while maximizing the front surface area available for electronic devices.
Solution Approach 2:
The patent applies preliminary action by forming trenches on the front side of the wafer before the actual cutting process. These trenches define the boundaries of the devices and guide the saw blade during backside cutting, ensuring precise separation while minimizing the impact of blade width on usable area.
2Productivity
If a rotating saw blade is used to cut through the semiconductor wafer, then the wafer can be diced, but microcracks are caused near the edge of the saw street which may propagate and cause device failure
Solution Approach 1:
The patent eliminates microcrack formation by inverting the cutting direction. By cutting from the backside along pre-formed trenches rather than cutting through the front side near device edges, the mechanical stress that causes microcracks is avoided, preventing crack propagation into the electronic devices.
Solution Approach 2:
The trenches formed on the front side serve as an intermediary structure that guides the saw blade during backside cutting. These trenches act as a mediator between the cutting process and the devices, providing a safe pathway for the blade that prevents direct contact and potential damage to the electronic devices.
3Reliability
If test circuits are formed in areas of the wafer that will be used as saw streets, then device functionality can be tested, but the width required for test circuits increases the overall street width
Solution Approach 1:
The patent resolves the conflict between testing and street width by inverting the cutting approach. Test circuits can be formed in the trenches on the front side, and since the saw blade cuts from the backside, the full width of the trenches is available for testing without increasing the effective street width that impacts device area.
Data Source
AI summary
Methods for processing semiconductor wafers are described herein. One embodiment includes removing portions of a first side of the semiconductor wafer to form a number of trenches of a particular depth in rows and columns. The method further includes forming a passivation layer on side walls of the number of trenches. The method also includes cutting a second side of the semiconductor wafer in rows and columns aligned with the number of trenches such that the semiconductor wafer singulates into a number of dice.