Wafer Wet Etching with Variable Rotation for Flatness Control
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Solution Overview
Problem
The existing monolithic wafer wet etching process struggles to achieve the required flatness and prevent corrosion pits, especially when dealing with materials like cobalt, aluminum, and copper, due to uneven chemical solution distribution and oxidation issues.
Innovation Solution
A method involving multiple etching treatments with varying rotation speeds and chemical solution flow rates to ensure uniform distribution and thick liquid film coverage, minimizing oxidation and etching defects, including a first etching process at a high rotation speed, a second process at a reduced speed to maintain solution thickness, and a third process at an even lower speed for uniform etching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional wet etching process is used, then the etching can be completed, but the surface flatness is poor and corrosion pits occur
Solution Approach 1:
The etching process is divided into multiple sequential etching treatments, where each treatment consists of three distinct etching processes with different rotation speeds. This segmentation allows each stage to address specific aspects of the etching challenge, progressively improving surface flatness while preventing corrosion pit formation through controlled chemical solution distribution.
Solution Approach 2:
The rotation speed of the substrate is dynamically adjusted during the etching process. The first etching process uses a first rotation speed, the second etching process uses a second rotation speed different from the first, and the third etching process uses a third rotation speed. This dynamic adjustment optimizes chemical solution distribution at different stages, ensuring uniform etching and preventing corrosion pits.
2Productivity
If the rotation speed is high, then the etching efficiency is improved, but the chemical solution distribution becomes uneven
Solution Approach 1:
The rotation speed is dynamically varied across three distinct etching processes. The first process uses a first rotation speed optimized for initial etching, the second process uses a second rotation speed to improve solution distribution uniformity, and the third process uses a third rotation speed to complete the etching. This dynamic speed adjustment resolves the contradiction between etching efficiency and solution distribution uniformity.
Solution Approach 2:
The etching process employs periodic variation in rotation speeds through three sequential etching processes. Each process uses a different rotation speed regime, creating a periodic pattern of high-speed etching followed by uniformity-focused stages. This periodic action ensures both high productivity and uniform chemical solution distribution throughout the overall etching treatment.
3Manufacturing precision
If the chemical solution film is thin, then the etching precision is improved, but the oxidation of the layer to-be-etched increases
Solution Approach 1:
The first and second etching processes serve as preliminary treatments that establish optimal chemical solution distribution and prevent oxidation before the final third etching process. By pre-conditioning the surface with controlled rotation speeds and solution films, the subsequent etching can achieve high precision without oxidation damage to the layer to-be-etched.
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 enhances surface flatness and reduces the likelihood of corrosion pit defects by maintaining a thick, uniform chemical solution film, effectively addressing the challenges of surface uniformity and material oxidation in semiconductor manufacturing.
Implementation Method 1
The wet etching process uses an etching solution to etch a wafer
Implementation Method 2
the substrate is at a first rotation speed; after the first etching process, performing a second etching process, where in the second etching process, a rotation speed of the substrate is reduced from the first rotation speed to a second rotation speed
Data Source
AI summary
A wet etching method is provided in the present disclosure. The method includes providing a substrate, where a layer to-be-etched is on a surface of the substrate; and performing etching treatments on the layer to-be-etched till a thickness of the layer to-be-etched reaches a target thickness. Each etching treatment includes performing a first etching process, where the substrate is at a first rotation speed; after the first etching process, performing a second etching process, where a rotation speed of the substrate is reduced from the first rotation speed to a second rotation speed, and a liquid film of a chemical solution on the surface of the substrate is increased to a first thickness; and after the second etching process, performing a third etching process, where the substrate is at a third rotation speed, and the third rotation speed is lower than or equal to the first rotation speed.