Temporary Wafer Bonding for Precision Via Thinning
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Solution Overview
Problem
Conventional single-sided wet etching processes for forming vias in thin inorganic substrates result in large undercutting, limited via density, and poor control over opening diameter, which can lead to substrate breakage and inefficient manufacturing due to thickness-dependent via size and lateral etching issues.
Innovation Solution
A method involving temporary bonding of inorganic wafers to handle wafers using a thin carbonaceous adhesion layer, followed by a double-sided abrasive process to thin the substrates and form vias with improved shape and reduced undercutting, allowing for precise control over via formation and increased substrate handling security.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If single-sided wet etching is used to form vias in thin inorganic substrates, then the process is simple to implement, but large undercutting occurs and via density is limited
Solution Approach 1:
The patent divides the via formation process into two distinct sides: a first surface with a via opening and a second surface with a sealed opening. This segmentation allows independent control of etching parameters on each side, enabling precise via diameter control while reducing undercutting. The first surface undergoes etching to create the via opening, while the second surface is sealed to prevent lateral etching, thus resolving the contradiction between process simplicity and via formation precision.
Solution Approach 2:
The patent introduces a sealant material layer as an intermediary on the second surface of the substrate. This sealant prevents etchant from accessing the back side, thereby eliminating lateral etching and undercutting that would otherwise occur in single-sided etching. The sealant material layer acts as a mediator that enables precise via formation while maintaining process feasibility, resolving the contradiction between ease of manufacture and manufacturing precision.
2Ease of operation
If single-sided wet etching is used, then the process is easier to operate, but control over opening diameter is poor and substrate breakage occurs
Solution Approach 1:
The patent segments the substrate processing into two surfaces with different treatments: the first surface is etched to form the via opening, while the second surface is sealed. This segmentation allows precise control of opening diameter by independently optimizing etching parameters on the first surface without compromising the second surface, thereby improving manufacturing precision while maintaining ease of operation.
Solution Approach 2:
The sealant material layer serves as an intermediary that prevents etchant from causing lateral etching and substrate breakage. By blocking the etchant on the second surface, the sealant enables precise opening diameter control on the first surface while maintaining process operability, thus resolving the contradiction between ease of operation and manufacturing precision.
3Ease of manufacture
If conventional via formation methods are used, then the process is straightforward, but via density is limited and manufacturing efficiency is low
Solution Approach 1:
The patent applies segmentation by treating the two surfaces of the substrate differently during via formation. The first surface is etched to create vias, while the second surface is sealed to prevent defects. This approach enables higher via density by allowing closer spacing of vias without compromising substrate integrity, thereby improving manufacturing efficiency while maintaining process straightforwardness.
Solution Approach 2:
The sealant material layer acts as an intermediary that enables higher via density by preventing lateral etching and substrate breakage. This allows more vias to be formed per unit area with improved reliability, increasing manufacturing efficiency while keeping the process straightforward and manageable.
4Ease of operation
If thin substrates are processed without support, then the substrate is easier to handle, but substrate breakage occurs during processing
Solution Approach 1:
The patent introduces a handle wafer as an intermediary substrate that provides mechanical support during processing. The handle wafer enables safe handling and processing of thin inorganic substrates without causing breakage, while allowing the thin substrate to maintain its desired thinness for the final application. This resolves the contradiction between ease of operation and substrate integrity.
Solution Approach 2:
The patent segments the substrate system into a thin inorganic substrate layer and a separate handle wafer layer. The handle wafer provides structural support and ease of handling, while the thin substrate maintains its functional properties. This segmentation allows the thin substrate to be processed safely without breakage, resolving the contradiction between handleability and integrity.
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 via formation by reducing undercutting, increasing via density, and improving control over via diameter, while ensuring secure handling and efficient processing of thin substrates, leading to more reliable and efficient manufacturing of thin inorganic substrates with precise via formation.
Implementation Method 1
forming a wafer stack at least by performing a temporary bonding process to temporarily bond at least a first inorganic wafer to a first surface of a handle wafer. The temporary bonding process may include formation of an adhesion layer between the first inorganic wafer and the first surface of the handle wafer.
Implementation Method 2
applying an abrasive process to at least part of the wafer stack. The abrasive process may reduce a thickness of the first inorganic wafer of the wafer stack.
Data Source
AI summary
Processed inorganic wafers and processing a wafer stack including an abrasive process are disclosed. A wafer stack may be formed at least by performing a temporary bonding process to temporarily bond at least a first inorganic wafer to a first surface of a handle wafer. The handle wafer may include at least one inorganic wafer, and the temporary bonding process may include formation of an adhesion layer between the first inorganic wafer and the first surface of the handle wafer. The adhesion layer may include a vacuum deposited carbonaceous film with a thickness between 1 nm and 100 nm, inclusive. An abrasive process may be applied to at least part of the wafer stack, and the abrasive process may reduce a thickness of the first inorganic wafer of the wafer stack. The first inorganic wafer may be debonded from the handle wafer after applying the abrasive process.