Transparent Wafer Alignment Markers for Blur-Free Bonding
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Solution Overview
Problem
The existing wafer-to-wafer bonding process in semiconductor manufacturing faces challenges due to the blurriness of infrared images, which limits the accuracy of alignment, especially as critical features continue to shrink.
Innovation Solution
The implementation of optically visible alignment markers formed from generally transparent materials extending from the front surface to the back surface of the wafers, allowing for precise optical alignment rather than relying on infrared imaging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If infrared imaging is used for wafer alignment, then alignment can be performed through the wafer, but the image blurriness limits alignment accuracy
Solution Approach 1:
The patent introduces an optical marker as an intermediary element that facilitates alignment. The marker consists of a first portion on the front surface and a second portion on the back surface of the wafer, connected by a connecting portion that extends through the wafer thickness. This intermediary structure enables precise optical alignment by providing distinct visual references on both surfaces, solving the image blurriness problem of direct infrared imaging through the wafer.
Solution Approach 2:
The alignment marker is segmented into multiple distinct portions: a first portion on the front surface, a second portion on the back surface, and a connecting portion extending through the wafer. This segmentation allows each portion to serve specific alignment functions, with the front and back portions providing reference points for optical alignment while the connecting portion ensures structural integrity and proper positioning.
2Reliability
If conventional alignment marks are used, then the bonding process can proceed, but realignment errors lead to wasted wafers and increased costs
Solution Approach 1:
The optical alignment markers provide visual feedback during the bonding process, allowing operators to verify alignment accuracy before final bonding. The distinct front and back portions of the marker create visible alignment patterns that indicate whether the wafers are properly aligned, enabling corrective adjustments before irreversible bonding occurs, thus reducing wasted wafers.
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 the accuracy of wafer alignment to the nanometer scale, reducing errors and costs associated with realignment and wasted wafers, while improving the overall efficiency of the semiconductor manufacturing process.
Implementation Method 1
optically visible alignment markers formed from generally transparent materials extending from the front surface to the back surface of the wafers
Data Source
AI summary
Semiconductor devices, and related systems and methods, are disclosed herein. In some embodiments, the semiconductor device includes a first wafer having a front surface and a back surface opposite the front surface, and a second wafer having upper surface coupled to the back surface of the first wafer. The first wafer can also include one or more first alignment features. Each of the first alignment feature(s) can include a transparent material extending from the front surface to the back surface, thereby forming a window through the first wafer, allowing the location of conductive features on the front surface to be determined from the back surface using optical measurements. The second wafer can include one or more second alignment features that are positioned within a longitudinal footprint of a corresponding one of the first alignment features.