EUV Lithography Resist Healing via EMR Absorbing Molecules
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Solution Overview
Problem
Current photolithography techniques face challenges with missing contact holes and scummed contact holes due to photon shot noise and chemical noise, leading to defects in substrate patterning, particularly with EUV lithography where low power levels and high energy photons result in uneven acid concentration and stochastic noise.
Innovation Solution
The use of EMR absorbing processes with multiple exposures of different energy levels, such as EUV and UV, where a first exposure generates photosensitizer molecules that are then activated by a second exposure to increase acid concentration, allowing for the formation of complete contact holes and minimizing scumming through a two-step develop process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a single patterned exposure is used in traditional CAR, then the process is simple, but acid concentration is insufficient and patterning contrast is low
Solution Approach 1:
The exposure process is segmented into two distinct steps: first a patterned exposure to generate photosensitizer molecules, then a flood exposure to activate those molecules and generate acid. This segmentation allows each step to be optimized independently, achieving high acid concentration while maintaining process control
Solution Approach 2:
The photosensitizer molecules are generated in advance during the first patterned exposure, before the actual acid generation occurs. This preliminary action ensures that when the flood exposure occurs, the photosensitizer is already in position to amplify acid generation locally, achieving high contrast without requiring high overall exposure energy
2Object-affected harmful factors
If EUV lithography is used with low power levels, then substrate damage is reduced, but photon shot noise increases causing missing contact holes
Solution Approach 1:
The photosensitizer molecules serve a dual function: they are generated by the low-power EUV exposure and then self-activate during the flood exposure to generate the acid needed for patterning. This self-service mechanism allows the system to overcome the low photon flux limitation of EUV sources without increasing substrate damage
Solution Approach 2:
The system changes the wavelength parameter from EUV (first exposure) to UV (flood exposure). The UV wavelength is absorbed by the photosensitizer molecules generated during EUV exposure, enabling acid generation amplification. This parameter change allows the system to leverage the low damage of EUV while achieving sufficient acid concentration through UV activation
3Quantity of substance
If photosensitizer molecules are generated throughout the resist, then acid amplification is maximized, but scumming occurs at the bottom of contact holes
Solution Approach 1:
The photosensitizer generation is made local to the patterned regions through the first patterned exposure. Only areas receiving EUV photons generate photosensitizer molecules, ensuring that subsequent UV-induced acid generation occurs only where needed. This local quality control prevents scumming in non-patterned areas while maintaining acid amplification where required
Solution Approach 2:
The process uses periodic action with two distinct exposure phases: first a patterned exposure that creates a spatially selective distribution of photosensitizer, then a flood exposure that activates those molecules. This periodic approach separates the functions of pattern definition and acid generation, preventing unwanted scumming while achieving sufficient acid concentration in patterned regions
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 addresses missing contact holes and scumming by amplifying acid generation in incomplete holes and removing scummed areas, maintaining critical dimensions and profiles of already formed features without significant impact.
Implementation Method 1
a first wavelength of EMR is exposed through a patterned mask onto the radiation sensitive material to generate the EMR absorbing molecules within the radiation sensitive material
Implementation Method 2
a second wavelength of EMR... can excite the photosensitizer molecules in the radiation sensitive material that results in the acid comprising a second acid concentration that is greater than the first acid concentration
Implementation Method 3
utilizes acid generated within the resist feature for deprotection
Data Source
AI summary
Substrate processing techniques to alleviate missing contact holes, scummed contact holes and scummed caused bridging are disclosed. In one embodiment, electromagnetic radiation (EMR) absorbing molecules are utilized in a process that uses an initial patterned exposure followed by a flood exposure. In one embodiment, a Photo-Sensitized Chemically-Amplified Resist (PSCAR) resist process is utilized to form contact holes in which an initial exposure and develop process is performed followed by a flood exposure and a second develop process. In another embodiment, a process is utilized in which precursors of EMR absorbing molecules are incorporated into a layer underlying the resist layer. Thus, enhanced formation of EMR absorbing molecules will result at the interface of the resist layer and the underlying layer.