Dual Backside Stress Layers for Wafer Bow Shift Control
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Solution Overview
Problem
Wafer bow during semiconductor processing causes issues such as improper clamping, handling problems, and pattern transfer defects, and existing backside film compensations lead to significant bow shifts and potential cracking during thermal cycles.
Innovation Solution
Depositing a first backside layer with internal stress matching that of the frontside layers to counteract bow, followed by a second backside layer with opposite internal stress to minimize bow shift and reduce cracking during thermal cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a single backside layer is deposited to counteract wafer bow, then wafer flatness is improved, but bow shift and cracking occur during thermal cycles
Solution Approach 1:
The backside compensation layer is divided into two separate layers: a first backside layer with internal stress matching the frontside layers to counteract bow, and a second backside layer with opposite or neutral internal stress to minimize bow shift during thermal cycles. This segmentation allows each layer to perform its specific function independently, resolving the contradiction between achieving flatness and maintaining thermal stability.
Solution Approach 2:
The invention changes the internal stress parameter of the backside compensation layers by using two layers with different stress characteristics. The first layer has internal stress of the same type as frontside layers (tensile or compressive), while the second layer has opposite or neutral stress, creating a balanced system that maintains wafer flatness while reducing thermal-induced bow shift.
2Manufacturing precision
If additional backside material is deposited to maintain wafer flatness, then pattern transfer accuracy is improved, but wafer handling problems and damage risk increase
Solution Approach 1:
The compensation structure is segmented into two functional layers on the backside, where the first layer provides the necessary stress compensation for pattern transfer accuracy, while the second layer with opposite or neutral stress prevents excessive bow shift that would cause handling problems during subsequent processing.
Solution Approach 2:
The second backside layer is deposited in advance to counteract the potential bow shift that would occur during thermal cycles, preventing wafer handling problems before they occur during subsequent processing operations.
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
The method maintains wafer integrity by minimizing bow shift and reducing the likelihood of cracking, ensuring stable processing through thermal cycles.
Implementation Method 1
depositing a first backside layer on a backside of the substrate, wherein the first backside layer reduces the bow in the substrate, wherein the first backside layer and the one or more frontside layers have internal stresses of a first type; depositing a second backside layer over the first backside layer, wherein the second backside layer has an internal stress of a second type, which is opposite the first type or is neutral
Implementation Method 2
exposing the substrate to a thermal process that increases the substrate's temperature to at least about 600° C.
Data Source
AI summary
Provided are methods and structures for keeping the integrity of layers deposited on a semiconductor wafer through a thermal cycle. Deposition of a second backside layer, or a cap, with an internal stress opposite to a first backside layer may be used to reduce bow shift of a wafer during a thermal cycle. The first backside layer may have a tensile internal stress or a compressive internal stress. The second backside layer has an internal stress opposite to the first backside layer. Each of the backside layers may be deposited by a backside deposition apparatus.