TiN Hard Mask Etching Uniformity via pH Control
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Solution Overview
Problem
Current etching methods for semiconductor substrates, particularly those using titanium nitride (TiN) as a hard mask, face challenges in achieving uniformity and efficient removal, leading to surface non-uniformity and residue issues during the etching process.
Innovation Solution
An etching method involving a substrate with a TiN layer and a transition metal layer, using an etching liquid with an ammonia compound, an oxidizing agent, and a surface uniformizing agent, specifically formulated to maintain a pH of 7 to 14 and containing components like nitric acid or hydrogen peroxide, to achieve uniform etching and efficient removal of the TiN layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If an etching liquid containing ammonia compound and hydrogen peroxide is used to etch TiN layer, then the TiN layer can be removed, but the surface of the TiN-containing layer becomes non-uniform causing partial residue after etching
Solution Approach 1:
The patent optimizes the pH value of the etching liquid to specifically 7, which is the key parameter change that enables uniform etching of the TiN layer while preventing surface non-uniformity and residue. This specific pH value balances the etching effectiveness with surface quality maintenance.
Solution Approach 2:
The etching liquid is formulated as a composite solution containing multiple components: ammonia compound (0.1-15% by mass), hydrogen peroxide (0.5-50% by mass), and water, with the pH precisely controlled at 7. This composite formulation synergistically achieves both high etching rate and uniform surface finish.
2Loss of substance
If conventional etching liquids are used to remove hard mask, then material removal can be achieved, but uniformization after etching of metal surface cannot be achieved
Solution Approach 1:
The patent sets the pH value of the etching liquid to exactly 7, which is the critical parameter change that enables simultaneous achievement of complete hard mask removal and uniform metal surface finish. This neutral pH value prevents excessive etching that would cause surface non-uniformity.
Solution Approach 2:
The etching liquid contains hydrogen peroxide (0.5-50% by mass) as a strong oxidizing agent that accelerates the removal of the TiN hard mask while the controlled pH ensures uniform etching. The oxidizing action efficiently breaks down the hard mask material without compromising surface uniformity.
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 method ensures uniformization of the TiN-containing layer and the metal layer, reducing etching unevenness and achieving a high etching rate while maintaining the quality of the semiconductor device production process.
Implementation Method 1
the etching liquid comprises an ammonia compound and an oxidizing agent, and has a pH of from 7 to 14
Implementation Method 2
processing a substrate having a first layer containing titanium nitride (TiN) and a second layer containing a transition metal by bringing an etching liquid into contact with the substrate and thereby removing the first layer
Data Source
AI summary
An etching method containing the step of processing a substrate having a first layer containing titanium nitride (TiN) and a second layer containing a transition metal by bringing an etching liquid into contact with the substrate and thereby removing the first layer, wherein the first layer has a surface oxygen content from 0.1 to 10% by mole, and wherein the etching liquid comprises an ammonia compound and an oxidizing agent, and has a pH of from 7 to 14.