Alternating Semiconductor-Dielectric Phase Shift Mask
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
As semiconductor device feature sizes decrease, photolithography processes face challenges with optical fringing and diffraction effects, leading to distortion and increased critical dimension errors due to defects like crystal haze and particles in phase shift masks, particularly in molybdenum silicide-based masks.
Innovation Solution
A phase shift mask is developed using alternating semiconductor and dielectric layers, such as silicon and silicon dioxide, with controlled etch selectivities to reduce crystal haze and enhance physical damage resistance, along with a shading layer to improve light absorption and resolution, replacing traditional molybdenum silicide materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If molybdenum silicide-based phase shift masks are used, then phase shifting capability is achieved, but crystal haze and particle defects increase
Solution Approach 1:
The patent replaces single-material molybdenum silicide phase shifters with composite structures consisting of multiple semiconductor layers (e.g., silicon, germanium, silicon germanium) and dielectric layers (e.g., silicon dioxide, silicon nitride) stacked in alternating fashion. This composite structure achieves the required phase shifting capability while eliminating crystal haze and particle defects associated with molybdenum silicide.
Solution Approach 2:
The patent changes the material composition parameters by transitioning from metallic molybdenum silicide to semiconductor-dielectric composites. This parameter change modifies the optical and physical properties of the phase shifter, achieving phase shifting through refractive index differences rather than metallic absorption, thereby eliminating harmful crystal haze effects.
2Productivity
If feature sizes decrease to increase density, then IC chip capacity increases, but optical fringing and diffraction effects worsen
Solution Approach 1:
The patent segments the phase shifter into multiple thin alternating layers of semiconductor and dielectric materials. This segmentation creates a distributed phase shifting effect that better controls optical wavefronts, reducing fringing and diffraction effects at reduced feature sizes while maintaining pattern transfer accuracy.
Solution Approach 2:
The patent changes the optical parameters of the phase shifter by using multi-layer semiconductor-dielectric structures with controlled thicknesses and refractive indices. This enables precise control of phase shifts and amplitude modulation, improving resolution and reducing optical artifacts at smaller feature dimensions.
3Ease of manufacture
If traditional single-layer phase shifters are used, then manufacturing process is simple, but etch selectivity control and profile quality are poor
Solution Approach 1:
The patent segments the phase shifter into multiple alternating layers with different etch selectivities. This segmentation enables selective etching processes to create vertical sidewalls and precise profiles by exploiting the contrasting etch rates between semiconductor and dielectric layers, significantly improving profile quality despite increased structural complexity.
Solution Approach 2:
The patent uses composite semiconductor-dielectric layers with deliberately chosen different etch selectivities. This composite structure allows sequential or selective removal of layers during fabrication, enabling precise control of phase shifter profiles and reducing defects while maintaining manufacturability through established multi-layer deposition and etching techniques.
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 enhances the precision and accuracy of pattern transfer during photolithography by reducing critical dimension errors and manufacturing defects, improving the yield and cost-effectiveness of semiconductor production.
Implementation Method 1
phase shift mask (PSM)... shift a phase of selected light passing through the photomask or the reticle by π (180 degrees)
Implementation Method 2
The phase shifter includes a plurality of semiconductor layers and a plurality of dielectric layers arranged in an alternating fashion
Implementation Method 3
a shading layer to improve light absorption and resolution
Implementation Method 4
the undesired light is scattered or offset by the destructive interference
Data Source
AI summary
A phase shift mask (PSM) includes a light transmitting substrate. The PSM further includes a phase shifter over the light transmitting substrate, wherein the phase shifter includes a plurality of semiconductor layers and a plurality of dielectric layers stacked in an alternating fashion.