Phase-Shifting Contact Hole Unit Cell for Lithography
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Solution Overview
Problem
Current photolithographic techniques, particularly phase-shifting masks, are inadequate for forming contact hole patterns due to different design requirements for isolated, semi-dense, dense array, and randomly distributed contact configurations, leading to inefficiencies and variability in contact hole formation.
Innovation Solution
A contact hole unit cell structure is introduced, comprising a contact hole region, phase-shifting orthogonal regions, and a border region, with chrome pads, where the contact hole and border regions have the same phase, and the phase-shifting regions are out of phase, allowing for consistent phase shifting across various contact arrangements and reducing diffraction effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional phase-shifting masks are used for contact hole formation, then different mask designs are required for isolated, semi-dense, dense array, and randomly distributed contact configurations, but this increases device complexity and reduces manufacturing efficiency
Solution Approach 1:
The patent applies universality by designing a single phase-shifting mask structure that can be used for all contact hole configurations (isolated, semi-dense, dense array, and randomly distributed). The mask includes a phase-shifting region with alternating transparent and opaque regions arranged in a specific pattern that universally produces the desired light interference effects regardless of the contact configuration, eliminating the need for multiple different mask designs.
2Adaptability or versatility
If conventional phase-shifting masks are used, then contact hole formation requires multiple different mask designs for various configurations, but this increases production time and reduces productivity
Solution Approach 1:
The universal mask design allows a single mask to process all contact configurations in one photolithography step, eliminating the need for multiple sequential processing steps or mask changes. This significantly improves productivity by forming all types of contact holes simultaneously using the same mask structure.
3Manufacturing precision
If phase-shifting regions are placed adjacent to contact holes, then light interference patterns are created, but this produces side-lobe patterns that reduce manufacturing precision
Solution Approach 1:
The patent converts the harmful side-lobe diffraction patterns into beneficial effects by strategically placing opaque regions within the phase-shifting structure. These opaque regions block the unwanted diffracted light that would create side lobes, while the alternating transparent and opaque regions continue to produce the desired constructive interference at the contact hole locations. The harmful diffraction is transformed into a controlled light-blocking mechanism that enhances precision.
4Manufacturing precision
If attenuated phase-shifting mask techniques are used, then contact holes can be formed, but the intensity contrast is insufficient reducing process margins
Solution Approach 1:
The patent applies local quality by creating regions of different light transmission characteristics within the phase-shifting mask. The alternating transparent and opaque regions provide locally optimized light interference: transparent regions allow light transmission for constructive interference at contact holes, while opaque regions block light to create high contrast and prevent side lobes. This local variation in optical properties achieves both high intensity contrast and precise contact hole formation.
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 solution enables the use of a single unit cell for all contact arrangements, improving the intensity contrast and reducing side-lobe patterns, thereby enhancing the precision and consistency of contact hole formation, even in densely packed configurations.
Implementation Method 1
Phase-shifting material is situated on the mask substrate to provide a phase shift to light radiation as it passes through the mask
Implementation Method 2
Two shifters can be used on a mask to shine light on the same region of a photoresist. In a region where the light passing through one of the shifters is in phase with the light passing through the other shifter, a feature can be created on the photoresist that is narrower than the distance between the two shifters
Implementation Method 3
While such a technique may be appropriate for making IC line and space structures, it is generally unsatisfactory for forming contact hole patterns
Data Source
AI summary
A method for forming a contact hole unit cell is provided. A light transparent contact hole region of a first phase is positioned at a first plane. A light transparent phase-shifting region of a second phase is positioned at the first plane, the second phase being substantially out of phase with the first phase. The phase-shifting region substantially surrounds the contact hole region. A light transparent border region is positioned at the first plane outside the phase-shifting region. The border region has a phase substantially the same as that of the contact hole region. A chrome pad is positioned at the first plane outside and contacting at least a portion of the border region. The contact hole region, the phase-shifting region, the border region, and the chrome pad are positioned to cause light from the first plane to be reinforcing in a target contact hole configuration on a second plane and to be substantially neutralizing outside the target contact hole configuration on the second plane.