Wafer Shape Stress Control for Precise W2W Bonding Alignment
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Solution Overview
Problem
Current semiconductor fabrication processes face challenges in accurately bonding wafers due to non-linear physical wafer distortions induced by processing, leading to alignment failures and significant yield loss, especially with the advent of 3D packaging and shrinking alignment tolerances.
Innovation Solution
A method involving generating modification maps based on wafer shape data to adjust internal stresses, forming stressor films on wafers, and aligning them to correct distortions, using modules for metrology, deposition, coating, and bonding processes to enhance wafer handling and bonding yield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional bonding processes are used without wafer shape correction, then the process is simple and fast, but alignment accuracy deteriorates due to non-linear wafer distortions
Solution Approach 1:
The patent applies preliminary action by measuring wafer shape before bonding and pre-correcting distortions through stressor film formation. The modification map is generated in advance based on measured wafer shape data, and stressor films are formed on wafers before the bonding process to pre-compensate for expected distortions, thereby improving alignment accuracy without adding complexity to the bonding operation itself.
Solution Approach 2:
The patent changes physical parameters of the wafer by forming stressor films with controlled stress characteristics. The stressor films modify the internal stress state of wafers, changing parameters such as wafer curvature and shape. This allows dynamic adjustment of wafer geometry to achieve flatness requirements for accurate alignment, resolving the contradiction between maintaining simple processes and achieving high precision.
2Manufacturing precision
If wafer shape correction through stressor film formation is implemented, then bonding accuracy improves, but manufacturing time and process steps increase
Solution Approach 1:
The stressor film formation and wafer shape correction are performed as preliminary steps before bonding. By measuring wafer shape in advance and pre-forming stressor films, the patent eliminates the need for time-consuming adjustments and rework during the bonding process itself. This preliminary correction approach reduces overall manufacturing cycle time while maintaining high bonding accuracy.
Solution Approach 2:
The patent implements feedback by measuring actual wafer shape data and using this information to generate customized modification maps. The measured wafer shape feeds into the modification map generation, which then guides stressor film formation. This closed-loop feedback approach ensures accurate correction without excessive processing time, as only the necessary corrections are applied based on actual measurements.
3Measurement precision
If stressor films are formed and modified to correct wafer shape, then alignment precision improves, but process complexity and equipment requirements increase
Solution Approach 1:
The patent applies universality by using a modification map that serves multiple functions: it guides stressor film formation, controls heating patterns, and directs ion implantation. This single data structure integrates multiple correction approaches, reducing the need for separate complex equipment systems. The same modification map can be used across different correction methods, simplifying equipment requirements while maintaining high alignment precision.
Solution Approach 2:
The modification map acts as an intermediary between wafer measurement data and the various correction processes. Instead of requiring direct complex interactions between measurement systems and multiple correction equipment, the modification map serves as a mediator that translates measurements into actionable parameters for stressor film formation, heating, and ion implantation. This intermediary approach reduces equipment complexity while achieving precise alignment correction.
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 improves wafer alignment and bonding accuracy, reducing overlay errors and increasing yield by manipulating wafer shape through stress control layers, enhancing bonding performance and reducing voiding.
Implementation Method 1
generating a first modification map based on wafer shape data of the first wafer and the second wafer. The first modification map defines adjustments to internal stresses of the first wafer. A first wafer shape of the first wafer is modified by forming a first stressor film on the first wafer based on the first modification map
Implementation Method 2
the heat is applied to the first stressor film using a laser system that is configured to heat at least one of the first wafer or a wafer chuck that is configured to hold the first wafer
Implementation Method 3
applying heat to the first stressor film
Implementation Method 4
a photoresist layer of the first stressor film is developed to form a relief pattern
Implementation Method 5
a shape control layer of the first stressor film is etched using the relief pattern as an etching mask
Implementation Method 6
the modifying the first stressor film includes implanting ions into the first stressor film
Data Source
AI summary
A method, for bonding a first wafer to a second wafer, includes generating a first modification map based on wafer shape data of the first wafer and the second wafer. The first modification map defines adjustments to internal stresses of the first wafer. A first wafer shape of the first wafer is modified by forming a first stressor film on the first wafer based on the first modification map. The first wafer is aligned with the second wafer after the modifying. The first wafer is bonded to the second wafer.