Inverse Mask Pattern Reversal for Semiconductor Lithography
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Solution Overview
Problem
In advanced semiconductor lithography, mask defects, particularly in reflective and transmissive regions, lead to printable defects on semiconductor wafers, which are exacerbated by the increasing complexity and miniaturization of integrated circuits, necessitating improved lithography techniques to enhance pattern accuracy and reduce defect transfer.
Innovation Solution
The method involves using an inverse mask with a reversed area ratio of reflective and absorptive regions, combined with a sacrificial layer and hard mask layer processing, to transfer patterns onto wafers, thereby shifting defects from reflective regions to opaque regions, reducing printable defects during lithography.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional lithography with standard masks is used, then manufacturing process is simple, but mask defects transfer to wafers causing printing errors
Solution Approach 1:
The patent applies inversion by creating an inverse mask where the pattern is reversed compared to conventional masks. The inverse mask has transparent regions where conventional masks have opaque regions and vice versa. This inversion causes defects in the reflective region of the inverse mask to be transferred to the opaque region of the final pattern, where they are not printed on the wafer, thereby reducing defect transfer while maintaining process feasibility
Solution Approach 2:
The patent converts the harmful effect of mask defects into a beneficial outcome by utilizing etch selectivity between different mask layers. Defects that would normally print on the wafer are instead transferred to regions that serve as sacrificial layers and are subsequently removed. The harmful defect presence is thus converted into a process feature that eliminates defect printing while maintaining manufacturing feasibility
2Manufacturing precision
If inverse mask with reversed area ratio is used, then printable defects are reduced, but mask fabrication complexity increases
Solution Approach 1:
The patent segments the mask structure into multiple functional layers: an inverse mask layer with the reversed pattern, a sacrificial layer, and a hard mask layer. This segmentation allows each layer to serve a specific purpose - the inverse mask defines the pattern, the sacrificial layer captures defects, and the hard mask layer provides structural integrity. The segmentation makes the complex fabrication process manageable by dividing it into discrete, controllable steps
Solution Approach 2:
The patent introduces a sacrificial layer as an intermediary between the inverse mask and the final pattern transfer. This sacrificial layer acts as a mediator that receives defect transfers from the inverse mask during lithography, preventing defects from reaching the wafer. The intermediary layer thus protects the final product while enabling the use of the complex inverse mask structure
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 effectively minimizes the transfer of defects from the mask to the wafer by reversing the pattern and utilizing etch selectivity, enhancing the accuracy and reliability of lithography processes in semiconductor manufacturing.
Implementation Method 1
forming a patterned photoresist layer over the sacrificial layer using an inverse mask, wherein the inverse mask has a first pattern
Implementation Method 2
a lithography tool forms the patterned photoresist layer over the sacrificial layer by projecting a UV radiation through a inverse mask
Data Source
AI summary
A method of fabricating a semiconductor integrated circuit (IC) is disclosed. An inverse mask is provided. A sacrificial layer is deposited over a substrate. A patterned photoresist layer is formed over the sacrificial layer using the inverse mask. The sacrificial layer is then etched through the patterned photoresist layer to form a patterned sacrificial layer. A hard mask layer is deposited over the patterned sacrificial layer. The patterned sacrificial layer is then removed to form a second pattern on the hard mask layer.