Dual Etch Stop Layer Protects Semiconductor Device Layers
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Solution Overview
Problem
Existing flip-chip bonding processes face challenges in preventing damage to semiconductor device layers during substrate removal, as wet chemical etchants can penetrate and cause cracking or chemical reactions, despite the use of etch stop layers.
Innovation Solution
The implementation of a dual etch stop layer system, comprising a wet etch stop layer and a sacrificial semiconductor layer, followed by a dry etch stop layer, which protects the semiconductor device layers by preventing wet etchant penetration and facilitating efficient dry etching for substrate removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single etch stop layer is used to protect semiconductor device layers during substrate removal, then the protection against wet chemical etchants is insufficient, but adding multiple etch stop layers increases process complexity
Solution Approach 1:
The patent divides the protective barrier into multiple specialized layers: a wet etch stop layer (first etch stop layer) that resists wet chemical etchants, and a dry etch stop layer (second etch stop layer) that protects during dry etching processes. Each layer is optimized for specific etching conditions, providing comprehensive protection without requiring excessive thickness in any single layer.
Solution Approach 2:
The patent introduces a sacrificial layer positioned between the wet etch stop layer and the semiconductor device layers. This intermediary sacrificial layer serves as a buffer that can be selectively removed after wet etching, allowing the wet etch stop layer to be removed subsequently without damaging the semiconductor device layers.
2Productivity
If wet chemical etching is used to remove the substrate, then etching speed is improved, but penetration and damage to semiconductor device layers occurs
Solution Approach 1:
The patent applies preliminary protective measures by forming the wet etch stop layer and sacrificial layer before the wet etching process. These layers create a chemical barrier that prevents the wet etchant from penetrating into and damaging the semiconductor device layers, allowing fast wet etching to proceed safely.
Solution Approach 2:
The patent uses a sacrificial layer that is intentionally designed to be temporary and removable. This sacrificial layer is placed between the wet etch stop layer and the semiconductor device layers, serving its protective function during wet etching, then being completely removed in a subsequent dry etching step, leaving no permanent residue.
3Productivity
If etch stop layers are removed using wet chemical etching, then removal speed is improved, but delamination and chemical reactions occur
Solution Approach 1:
The patent replaces the wet chemical etching process with a dry etching process for removing the etch stop layers. This substitution eliminates the harmful chemical reactions and delamination issues associated with wet etchants, while still achieving effective removal through controlled dry plasma etching.
Solution Approach 2:
The patent changes the etching parameters by switching from liquid-based wet etching to gas-based dry etching. This parameter change fundamentally alters the removal mechanism, avoiding the chemical compatibility issues that cause delamination and unwanted reactions with the semiconductor device layers.
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 effectively mitigates damage to semiconductor device layers by using a wet etching process to remove the substrate and a dry etching process to remove the etch stop layers, ensuring reliable bonding of semiconductor devices to an integrated circuit die without delamination or chemical reactions.
Implementation Method 1
the wet chemical etchant may penetrate into the stack of semiconductor device layers via the interface between the sidewall protection structure and the etch stop layer
Implementation Method 2
performing a dry etching process to remove the wet etch stop layer and the sacrificial semiconductor layer
Implementation Method 3
bonding a frontside of the bonding structure to an integrated circuit (IC) die via, for example, solder bumps
Data Source
AI summary
In some embodiments, the present disclosure relates to a method of forming a package assembly. A wet etch stop layer is formed over a frontside of a semiconductor substrate. A sacrificial semiconductor layer is formed over the wet etch stop layer, and a dry etch stop layer is formed over the sacrificial semiconductor layer. A stack of semiconductor device layers may be formed over the dry etch stop layer. A bonding process is performed to bond the stack of semiconductor device layers to a frontside of an integrated circuit die, wherein the frontside of the semiconductor substrate faces the frontside of the integrated circuit die. A wet etching process is performed to remove the semiconductor substrate, and a dry etching process is performed to remove the wet etch stop layer and the sacrificial semiconductor layer.