Semiconductor Wafer Charge Reduction Using TMAH Rinse
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Solution Overview
Problem
During the fabrication of integrated circuits, electrostatic charges accumulate on semiconductor wafers during the spin-rinse-drying process, leading to interference with processing equipment and potential defects in semiconductor devices.
Innovation Solution
The method involves using a tetramethylammonium hydroxide (TMAH) solution to reduce electrostatic charges on silicon-on-insulator wafers by applying it after the development operation and subsequent rinsing with deionized water, followed by a spin-drying process to minimize charge accumulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If spin-rinse-drying process is used to clean semiconductor wafers, then cleaning efficiency is improved, but electrostatic charge accumulation increases
Solution Approach 1:
A conductive solution is introduced as an intermediary substance between the wafer and the spin-rinse-drying process. The conductive solution is applied to the wafer surface before drying, serving as a mediator that provides a charge dissipation pathway during the mechanical spinning process, thereby reducing electrostatic accumulation while maintaining cleaning efficiency
Solution Approach 2:
The electrical conductivity parameter of the processing environment is changed by introducing a conductive solution with specific ionic composition. This parameter change transforms the electrical properties of the wafer surface, enabling charge dissipation during the spin-drying process while maintaining the mechanical cleaning function
2Object-generated harmful factors
If electrostatic charges are reduced using conductive solutions, then charge accumulation is minimized, but additional process steps are required
Solution Approach 1:
The conductive solution application step is merged with the existing rinse step in the spin-rinse-drying process. Instead of adding a separate conductive solution application step, the conductive solution is applied during the rinse phase, combining two functions into one process stage and minimizing additional process complexity
Solution Approach 2:
The conductive solution serves multiple functions simultaneously: it acts as a cleaning agent during rinsing, provides charge dissipation during spinning, and leaves a conductive residue that continues to dissipate charges after drying. This multi-functionality reduces the need for separate process steps
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 significantly reduces electrostatic charges on the wafers, preventing interference with photolithographic and other fabrication processes and minimizing defects in semiconductor devices, as illustrated by a substantial drop in charge levels from -50V to less than -5V.
Implementation Method 1
A tetramethylammonium hydroxide (TMAH) solution is applied to the semiconductor substrate to reduce charges accumulated in the semiconductor substrate
Implementation Method 2
the wafer is then subjected to a spin-drying operation
Data Source
AI summary
Embodiments are directed to a method for minimizing electrostatic charges in a semiconductor substrate. The method includes depositing photoresist on a semiconductor substrate to form a photoresist layer on the semiconductor substrate. The photoresist layer is exposed to radiation. The photoresist layer is developed using a developer solution. The semiconductor substrate is cleaned with a first cleaning liquid to wash the developer solution from the photoresist layer. A tetramethylammonium hydroxide (TMAH) solution is applied to the semiconductor substrate to reduce charges accumulated in the semiconductor substrate.