Backside Stress Deposition for Wafer Bow Correction
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Solution Overview
Problem
Semiconductor fabrication processes lead to substrate bowing due to stress from multiple layers of film, causing distortion and reducing feature size uniformity, which results in overlay errors and challenges in achieving a flat wafer surface.
Innovation Solution
A system and method for modifying wafer bow by measuring the initial wafer bow using a metrology module and applying a correction film on the backside surface of the substrate, using a backside deposition module, to adjust internal stresses and achieve a predetermined wafer bow value.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple layers of film are deposited on the working surface of the substrate during semiconductor fabrication, then the device functionality is improved, but the substrate bowing increases causing wafer shape distortion
Solution Approach 1:
The patent applies asymmetry by depositing the correction film only on the backside surface of the substrate rather than symmetrically on both surfaces. This asymmetric deposition creates a stress gradient that specifically counteracts the bowing induced by front-side film layers, effectively correcting the wafer shape distortion while preserving the device functionality achieved through multiple film layers.
Solution Approach 2:
The correction film deposited on the backside surface acts as a counterweight to the stress accumulated from multiple front-side film layers. By carefully controlling the thickness and material properties of this correction film, the patent generates an opposing stress that neutralizes the bowing effect, thereby correcting the wafer shape without removing the functional film layers.
2Shape
If a correction film is deposited on the backside surface to correct wafer bow, then the wafer shape is improved, but the process complexity increases
Solution Approach 1:
The patent implements preliminary action by measuring the wafer bow after front-side film deposition and calculating the required correction film parameters before actual deposition. This pre-planning approach optimizes the correction process by determining the exact thickness and material composition needed, avoiding trial-and-error iterations and reducing overall process complexity despite adding a deposition step.
Solution Approach 2:
The correction film serves as an intermediary element between the stressed front-side film layers and the substrate. This intermediary layer absorbs and redistributes the internal stresses, mediating the mechanical interaction between the functional films and the substrate to achieve shape correction without requiring complex restructuring of the existing 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
The solution effectively corrects substrate bow, improves overlay accuracy, and enhances the uniformity of critical features on the wafer surface by physically modifying internal stresses through backside film deposition.
Implementation Method 1
The correction film can physically modify internal stresses on the substrate and causes the substrate to have the modified wafer bow with the predetermined wafer bow value
Data Source
AI summary
A method of microfabrication is provided. A substrate having a working surface and having a backside surface opposite to the working surface is received. The substrate has an initial wafer bow resulting from one or more micro fabrication processing steps executed on the working surface of the substrate. The initial wafer bow of the substrate is measured and the initial wafer bow is used to generate an initial wafer bow value that identifies a degree of first order wafer bowing of the substrate. A correction film recipe based on the initial wafer bow value is identified. The correction film recipe specifies parameters of a correction film to be deposited on the backside surface of the substrate to change wafer bow of the substrate from the initial wafer bow to a modified wafer bow. The correction film on the backside surface of the substrate according to the correction film recipe is deposited. The correction film physically modifies internal stresses on the substrate and causes the substrate to have a modified bow with the predetermined wafer bow value.