Substrate Rotation Speed Control for Electrostatic Charge Removal
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Solution Overview
Problem
Substrate treatment processes for semiconductor and liquid crystal display devices often result in electrostatic charging due to friction during rinsing, which can lead to device malfunctions, and existing methods using CO2-containing deionized water are insufficient in reducing charge levels.
Innovation Solution
A substrate treatment method involving a water-containing liquid supply followed by a puddle process at a reduced rotation speed or cessation of rotation, using either deionized water or organic solvents to form a liquid film on the substrate, which enhances charge removal by minimizing friction-induced charging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If deionized water is supplied to the substrate while rotating at high speed during rinsing, then rinsing effectiveness is improved, but electrostatic charge accumulation on the substrate increases
Solution Approach 1:
The substrate rotation is performed in two distinct phases: a first rotation phase at high speed for water supply and rinsing, followed by a second rotation phase at low speed or stationary state for charge removal. This periodic alternation between different rotation speeds allows the system to achieve both effective rinsing and charge reduction without continuous high-speed rotation
Solution Approach 2:
The rotation speed parameter is changed between two distinct states: a first rotation speed during water supply for effective rinsing, and a second rotation speed (lower than the first) or non-rotating state for charge removal. This parameter change enables the system to optimize for different functions at different times, reducing electrostatic charge accumulation while maintaining rinsing effectiveness
2Object-affected harmful factors
If CO2-containing deionized water is used in the rinsing process, then substrate charge amount is reduced, but further charge reduction demanded by the market cannot be met
Solution Approach 1:
The charge removal action is performed as a preliminary or subsequent step after the rinsing process. By introducing a dedicated charge removal phase with reduced rotation speed or stationary state, the system proactively addresses charge accumulation before the substrate leaves the treatment apparatus, ensuring market demand for lower charge levels is met
Solution Approach 2:
The useful action of charge removal is continued through the second rotation phase or stationary puddle process, maintaining the liquid film contact with the substrate surface for a predetermined period. This continuous charge removal action ensures thorough charge reduction that satisfies market demands beyond what single-phase CO2-containing water could achieve
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
Effectively reduces substrate charge levels by allowing greater charge release than accumulation, with organic solvents offering improved charge removal efficiency due to increased contact area with ambient air.
Implementation Method 1
the substrate is liable to be electrostatically charged mainly due to friction between the water and the substrate
Implementation Method 2
the charges are released from the substrate surface into the air via the liquid film
Data Source
AI summary
A substrate treatment method is disclosed, which can effectively reduce the amount of charges accumulated on a substrate due to treatment of the substrate with a water-containing liquid. The method comprises the steps of: supplying a water-containing liquid to a substrate held generally horizontally by a substrate holding/rotating mechanism while rotating the substrate at a first rotation speed; and removing charges from the substrate after the water supplying step by performing a puddle process for a predetermined period by retaining a liquid film of a predetermined liquid on a surface of the substrate held generally horizontally by the substrate holding/rotating mechanism with the substrate being rotated at a second rotation speed lower than the first rotation speed or kept in a non-rotating state without further supplying the predetermined liquid to the liquid film.