Semiconductor Substrate Etching After Tungsten Oxide Pretreatment

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Solution Overview

Problem

Conventional etching agents fail to effectively produce semiconductor substrates for memory elements using metallic tungsten due to the formation of a tungsten oxide film that prevents contact with titanium or titanium alloys, leading to reduced production efficiency.

Innovation Solution

A method involving a pretreatment agent with tungsten oxide etchants like acids or ammonium salts to remove the tungsten oxide film, followed by an etching agent containing oxidizing agents, fluorine compounds, and metallic tungsten corrosion inhibitors to selectively etch titanium or titanium alloys, ensuring high Ti/W etching selectivity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional etching agents are used to selectively etch titanium or titanium alloy, then the etching process should proceed effectively, but the tungsten oxide film formed on the metallic tungsten surface prevents the etching agent from contacting titanium, causing etching failure

Engineering Contradiction:

Improveetching effectivenessVSAvoidtungsten oxide film interference

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies preliminary action by introducing a pretreatment step before the main etching process. The pretreatment agent (containing HF, HNO3, or CH3COOH) is applied first to remove the tungsten oxide film from the metallic tungsten surface, exposing the underlying titanium or titanium alloy. This preliminary removal of the oxide barrier enables the subsequent etching agent to effectively contact and etch the titanium layer without interference.

Inventive Principle:

Principle #10Preliminary action

2Reliability

If a pretreatment agent is used to remove tungsten oxide film, then the etching agent can contact titanium effectively, but the production time increases due to the additional pretreatment step

Engineering Contradiction:

Improveetching effectivenessVSAvoidproduction time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent applies parameter changes by optimizing the composition and concentration of the pretreatment agent to achieve rapid tungsten oxide removal. The pretreatment agent contains specific concentrations of HF (0.1-10%), HNO3 (0.1-10%), or CH3COOH (1-50%), which are tuned to maximize etching speed while minimizing processing time. This optimization ensures that the pretreatment step, while necessary, does not excessively extend the overall production cycle.

Inventive Principle:

Principle #35Parameter changes

3Productivity

If the removal rate of tungsten oxide with pretreatment agent is increased, then production efficiency improves, but the selectivity between tungsten oxide removal and titanium preservation may be compromised

Engineering Contradiction:

Improveproduction efficiencyVSAvoidselective etching precision

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The patent applies the intermediary principle by using a specifically designed pretreatment agent composition that acts as a selective mediator. The pretreatment agent contains HF, HNO3, or CH3COOH in optimized concentrations that preferentially react with tungsten oxide while having minimal effect on titanium or titanium alloy. This selective chemistry allows rapid removal of the oxide barrier without significantly etching the underlying titanium layer, thus maintaining manufacturing precision while improving productivity.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 enables the rapid removal of tungsten oxide, allowing for high-performance semiconductor substrate production with improved production efficiency by ensuring effective etching of titanium-containing films without damaging metallic tungsten.

Implementation Method 1

a step (1) of bringing a semiconductor substrate including a titanium-containing film that contains at least one of titanium and a titanium alloy, a metallic tungsten film, and a tungsten oxide film into contact with a pretreatment agent to remove at least a part of the tungsten oxide film

Methodology Applied

Scientific EffectChemical etching:

Implementation Method 2

a step (2) of bringing the semiconductor substrate after being subjected to the step (1) into contact with an etching agent to remove at least a part of the titanium-containing film

Methodology Applied

Scientific EffectSelective chemical etching:

Data Source

PatentUS20240170278A1Method for producing semiconductor substrate for memory elements

Publication Date: 2024.05.23 MITSUBISHI GAS CHEM CO INC

AI summary

Provided is a method for producing a semiconductor substrate for high-performance memory elements with high production efficiency.The method for producing a semiconductor substrate for memory elements, comprising a step (1) of bringing a semiconductor substrate including a titanium-containing film that includes at least one of titanium and a titanium alloy, a metallic tungsten film, and a tungsten oxide film into contact with a pretreatment agent to remove at least a part of the tungsten oxide film; and a step (2) of bringing the semiconductor substrate after being subjected to the step (1) into contact with an etching agent to remove at least a part of the titanium-containing film, wherein the pretreatment agent includes at least one tungsten oxide etchant that is selected from the group consisting of acids, ammonia, and ammonium salts.