Phase Shift Mask Alkaline Cleaning Haze Prevention
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Solution Overview
Problem
Conventional phase shift masks suffer from haze defects due to residual sulfuric acid and damage from alkaline cleaning solutions, which hinder the formation of high-resolution patterns in semiconductor devices.
Innovation Solution
A phase shift mask design incorporating a transparent layer, a transmittance control layer, and a shading layer, with a hard mask layer, that utilizes an alkaline cleaning solution to completely remove sulfuric acid ions without damaging the phase shift pattern, ensuring effective light transmittance and phase control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sulfuric acid cleaning solution is used to remove contaminants, then cleaning effectiveness is improved, but haze defects are generated due to residual sulfuric acid
Solution Approach 1:
An alkaline substance (ammonium hydroxide or other alkaline cleaning agent) is introduced as an intermediary to neutralize the sulfuric acid residue on the phase shift mask. The alkaline substance reacts with the acidic contaminants to form soluble salts that can be easily rinsed away, thereby eliminating the harmful haze defects while maintaining effective cleaning.
2Object-affected harmful factors
If alkaline cleaning solution is used to remove sulfuric acid residue, then haze defects are prevented, but phase shift layer is damaged by hydroxyl group
Solution Approach 1:
The concentration of the alkaline cleaning solution is optimized to a specific range (typically 0.1-5% ammonium hydroxide) to achieve effective neutralization of sulfuric acid while minimizing damage to the phase shift layer. Additionally, the cleaning time and temperature parameters are controlled to prevent excessive exposure that could harm the phase shift layer.
Solution Approach 2:
The cleaning process is applied selectively to specific regions of the phase shift mask, focusing the alkaline treatment only on areas with sulfuric acid residue while minimizing exposure of the phase shift layer to alkaline conditions. This may involve targeted application methods or localized cleaning zones.
3Ease of manufacture
If conventional cleaning process is used, then manufacturing simplicity is maintained, but complete removal of sulfuric acid is not achieved
Solution Approach 1:
The cleaning process is designed as a continuous multi-step sequence: sulfuric acid cleaning → alkaline neutralization → thorough rinsing. Each step builds on the previous one to ensure complete removal of sulfuric acid residues. The continuous flow of cleaning solutions and systematic progression through different chemical treatments ensures no acid residue remains while maintaining process efficiency.
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
The solution effectively prevents haze defects and maintains the integrity of the phase shift pattern, enabling the formation of high-resolution, precise patterns in semiconductor devices by ensuring complete removal of sulfuric acid ions and resistance to alkaline cleaning.
Implementation Method 1
the phase shift mask is rinsed using a solution including diluted ammonium hydroxide reacting with sulfuric acid
Implementation Method 2
the light transmitted through one passage may have a phase difference of about 180° from light passing through adjacent openings of the phase shift mask. The light having the phase difference of about 180° may cause destructive interference
Data Source
AI summary
A phase shift mask having a first region and a second region in a transverse direction includes a transparent layer, a phase shift pattern disposed in the first region, a transmittance control layer pattern disposed in the second region, and a shading layer pattern disposed on the transmittance control layer pattern. The phase shift pattern has a first pattern including a transparent material and a second pattern including metal. The phase shift mask may prevent haze effects through a cleaning process using an alkaline cleaning solution.