Buried Circuit Layer Transfer via Selective Barrier
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Solution Overview
Problem
Existing methods for transferring buried circuit layers are problematic due to aggressive chemical etching solutions that damage the circuits, particularly in the case of Backside Illumination sensors, where lateral etching occurs, rendering the sensors unusable.
Innovation Solution
A method involving a donor substrate with an etching stop zone and a peripheral trench or trimming, where a selective barrier material is deposited on the exposed circuit layer, allowing for chemical etching without damaging the circuits, and subsequent bonding to a receiver substrate for safe transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If chemical etching is used to thin the donor substrate, then the substrate can be thinned effectively, but the aggressive chemical solutions damage the buried circuit layer through lateral etching
Solution Approach 1:
A peripheral barrier layer is deposited as an intermediary protective structure between the aggressive chemical etching solution and the buried circuit layer. This barrier layer acts as a mediator that allows the etching process to proceed while preventing direct contact between the chemical solution and the circuits, thus resolving the contradiction between etching efficiency and circuit integrity
Solution Approach 2:
The peripheral barrier layer is deposited in advance before the chemical etching process begins. This preliminary protective action ensures that when the aggressive etching solution is applied, the circuit layer is already protected, preventing lateral etching damage while allowing the thinning process to proceed
2Reliability
If a peripheral barrier layer is deposited to protect the circuit layer, then lateral etching is prevented, but the process complexity increases
Solution Approach 1:
Instead of protecting the entire substrate uniformly, the barrier layer is applied locally only to the peripheral region where the circuit layer exists. This localized approach provides necessary protection while minimizing the addition of process steps and material complexity
3Ease of manufacture
If the donor substrate is thinned uniformly, then the transfer process is simplified, but the peripheral region with circuits is damaged by lateral etching
Solution Approach 1:
The substrate thinning process is segmented into two distinct zones: a central region that is thinned uniformly for easy processing, and a peripheral region protected by the barrier layer where circuits are preserved. This segmentation allows both simplified manufacturing and high precision circuit preservation to coexist
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 method effectively transfers buried circuit layers without damaging them, enabling the production of functional Backside Illumination sensors by preventing lateral etching and ensuring the integrity of the circuit layer during the transfer process.
Implementation Method 1
depositing on the exposed face of said circuit layer and on the contoured face or on the walls of said trench, a layer of a selective barrier material with respect to etching said layer of circuits
Implementation Method 2
thinning the donor substrate (1) by chemical etching of its rear face
Implementation Method 3
the bonding of the donor and recipient substrates takes place by molecular adhesion
Data Source
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AI summary
The invention relates to a method for transferring a buried layer of circuits (2). Said method is characterised in that it includes the following steps which involve: taking a donor substrate (1, 1') including on the inside an area (7, 7') for halting the etching and covered on one of the surfaces (12) thereof, referred to as "front", with a layer of circuits (2); providing either a peripheral groove (3) that extends away from the side edge (13) of said donor substrate (1, 1') or a peripheral clipping (3') on the entire circumference of said substrate, on the side of the surface thereof covered with the layer of circuits (2), said clipping (3') or said groove (3) being provided deep enough to pass entirely through the layer of circuits (2) and extending into the donor substrate (1, 1'); depositing, on the exposed surface (21) of said layer of circuits (2) and on the clipped surface (13') or on the walls of said groove (3), a layer of a material (4) for selectively halting the etching of said layer of circuits (2), referred to as the "second halting layer", without blocking said groove (3); adhering a receiving substrate (5) to said donor substrate (1, 1') on the side covered by said second halting layer (4); reducing the thickness of the donor substrate (1) by chemical etching of the rear surface thereof (11), until reaching said area (7, 7') for halting the etching, such as to obtain the transfer of said buried layer of circuits (2) to said receiving substrate (5).