Backside Metallization Using Patterned Nanosilver Ink
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Solution Overview
Problem
Existing backside metallization methods for semiconductor wafers inhibit stealth dicing, making it difficult to separate dies along scribe lines due to blanket metal coverage, which increases manufacturing costs and material waste.
Innovation Solution
Inkjet printing of a patterned nanosilver conductive ink on the backside of silicon wafers, leaving clearance areas along scribe lines to facilitate stealth dicing, reducing material waste and eliminating the need for expensive metal deposition equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If blanket metal deposition is applied on the backside of the wafer, then electrical and thermal conductivity is improved, but stealth dicing is inhibited and die separation becomes difficult
Solution Approach 1:
The continuous metal layer is segmented into discrete metal regions that are confined within die boundaries by scribe line clearances. This segmentation allows the metal to provide conductivity where needed while leaving gaps at scribe lines that enable laser-based stealth dicing to separate dies without interference from continuous metal coverage.
Solution Approach 2:
The metal deposition is applied locally only within die areas rather than uniformly across the entire wafer backside. The patterned metal regions are positioned to provide electrical and thermal conductivity for each die while deliberately excluding the scribe line regions, creating local quality variations that satisfy both conductivity requirements and dicing needs.
2Reliability
If blanket metal deposition is applied on the backside of the wafer, then conductivity is improved, but manufacturing cost increases due to expensive metal deposition equipment
Solution Approach 1:
The patent replaces complex physical vapor deposition or chemical vapor deposition equipment with a simpler inkjet printing system. The conductive ink containing metal particles is deposited using inkjet technology, which is a more accessible and less expensive manufacturing approach while achieving the same thermal and electrical conductivity functions.
Solution Approach 2:
The patent changes the state of metal from requiring deposition as a thin film through complex vacuum or chemical processes to being applied as a particulate suspension in ink form. This parameter change from film deposition to particulate printing simplifies the manufacturing equipment requirements while maintaining the conductivity function.
3Reliability
If blanket metal deposition is applied on the backside of the wafer, then conductivity coverage is maximized, but material waste increases
Solution Approach 1:
The patent extracts or removes metal material from the scribe line regions while retaining it within die boundaries. By taking out the metal from areas where it is not needed for conductivity (scribe lines) and concentrating it only where required (die regions), the solution reduces overall material usage while maintaining adequate conductivity coverage for functional areas.
Solution Approach 2:
Instead of applying metal uniformly across the entire wafer surface (excessive action), the patent applies metal only to the extent necessary within die regions (partial action). This partial coverage approach provides sufficient conductivity for each die while avoiding unnecessary material deposition in inter-die scribe line areas, thereby reducing material waste.
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
Enables efficient separation of dies while providing electrical and thermal conductivity, reducing manufacturing costs and maintaining conductivity across the wafer surface.
Implementation Method 1
a layer of metal may be deposited on the backside of the wafer... Backside metallization provides an electrically conductive contact
Implementation Method 2
Backside metallization provides an electrically conductive contact and/or a heat conductive contact for the dies. Backside metallization is often employed in power devices to provide improved heat dissipation.
Implementation Method 3
A laser is focused, through a second surface of the wafer, at a point between the first surface of the silicon wafer and the second surface of the silicon wafer
Data Source
AI summary
A method for backside metallization includes inkjet printing a pattern of nanosilver conductive ink on a first surface of a silicon wafer. The silicon wafer includes a plurality of dies. The pattern includes a clearance area along a scribe line between the dies. A laser is focused, through a second surface of the wafer, at a point between the first surface of the silicon wafer and the second surface of the silicon wafer. The second surface is opposite the first surface. The dies are separated along the scribe line.