Silicon Micromachining Alignment Accuracy via Intermediary Marks
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Solution Overview
Problem
The existing micromachining process for bulk silicon has a relatively low alignment accuracy of 4-6 micrometers due to the use of double-sided lithography machines, which is inadequate for precise pattern alignment in applications like acceleration sensors and gyroscopes.
Innovation Solution
A positioning method that combines double-sided lithography with stepper lithography, using multiple alignment marks to enhance alignment accuracy, where the stepper lithography machine alignment mark is found by the double-sided lithography machine, allowing direct alignment of the second substrate by the stepper lithography machine, achieving an alignment accuracy of less than 0.5 micrometers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If double-sided lithography machine is used for pattern alignment, then the process can be implemented, but the alignment accuracy is poor (4-6 micrometers)
Solution Approach 1:
The alignment process is segmented into multiple stages: first using double-sided lithography machine alignment marks for initial positioning, then using stepper lithography machine alignment marks for precise pattern alignment. This segmentation allows each machine to perform its specialized function optimally, achieving overall high precision despite the complexity of using multiple systems.
Solution Approach 2:
The patent introduces intermediary alignment marks that serve as bridges between the double-sided lithography machine and the stepper lithography machine. These intermediary marks enable the transfer of positioning information between the two systems, allowing the less precise double-sided machine to still contribute to the final high-precision alignment through the stepper machine's superior accuracy.
2Ease of manufacture
If double-sided lithography machine is used twice for alignment, then the process can be completed, but the alignment accuracy deteriorates to 4-6 micrometers
Solution Approach 1:
The patent performs preliminary alignment using the double-sided lithography machine to position the alignment marks before the actual pattern fabrication. This preliminary action establishes a reference framework that enables the subsequent stepper lithography machine to achieve high-precision pattern alignment, thereby maintaining ease of manufacture while improving precision.
Solution Approach 2:
The patent uses alignment marks as copies or references that transfer positioning information between different lithography machines. The double-sided lithography machine creates alignment marks that serve as templates for the stepper lithography machine to follow, enabling the less precise machine to contribute to the final high-precision result through this copying mechanism.
Data Source
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AI summary
A positioning method in a microprocessing process of bulk silicon comprises the steps of: fabricating, on a first surface of a first substrate (10), a first pattern (100), a stepper photo-etching machine alignment mark (200) for positioning the first pattern, and a double-sided photo-etching machine first alignment mark (300) for positioning the stepper photo-etching machine alignment mark; fabricating, on a second surface, opposite to the first surface, of the first substrate, a double-sided photo-etching machine second alignment mark (400) corresponding to the double-sided photo-etching machine first alignment mark; bonding a second substrate (20) on the first surface of the first substrate; performing thinning on a first surface of the second substrate; fabricating, on the first surface of the second substrate, a double-sided photo-etching machine third alignment mark (500) corresponding to the double-sided photo-etching machine second alignment mark; and finding, on the first surface of the second substrate by using the double-sided photo-etching machine third alignment mark, a corresponding position of the stepper photo-etching machine alignment mark.