Ammonia-DI Water Contactor Control for Stable Conductivity

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Solution Overview

Problem

Existing systems face challenges in maintaining precise control over the concentration of ammonia (NH3) in deionized water during semiconductor fabrication processes, particularly at dynamically changing flow rates, leading to issues with charge buildup on wafers and etching of acid-sensitive materials.

Innovation Solution

A system that dissolves ammonia gas in deionized water using a gas mixing device and a contactor, with sensors and a controller to adjust the ammonia flow rate based on the water flow rate and conductivity set points, ensuring stable conductivity and preventing etching of materials.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If NH3 gas is supplied at low flow rate to DI-water, then total absorption of NH3 is achieved, but liquid backflow into gas supply line occurs causing control instability

Engineering Contradiction:

ImproveNH3 concentration controlVSAvoidflow control stability

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent introduces a carrier gas (nitrogen or dry air) as an intermediary medium to transport NH3 gas to the contactor. This carrier gas system prevents direct low-flow NH3 supply to water, eliminating backflow into the NH3 supply line while maintaining precise concentration control through controlled carrier gas flow rates

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces direct mechanical flow control of NH3 gas with a two-stage system: first controlling carrier gas flow mechanically, then using feedback control based on conductivity measurements to adjust NH3 flow. This substitution stabilizes the system by using electrical conductivity as an intermediate control parameter

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If hollow-fiber membrane system is used to dissolve gas at constant flow rate, then stable conductivity is achieved, but 90%+ saturation requires excess gas supply increasing cost and contamination risk

Engineering Contradiction:

Improveconductivity stabilityVSAvoidexcess NH3 gas

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The patent transitions from static constant-flow membrane systems to a dynamic system where NH3 gas flow rate is continuously adjusted based on real-time conductivity measurements and water flow rate variations. This dynamic adaptation eliminates the need for excessive gas supply while maintaining stable conductivity

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent implements feedback control by measuring the conductivity of the generated liquid and using this information to adjust the NH3 gas flow rate. This closed-loop system ensures precise NH3 concentration control without requiring 90%+ saturation, reducing both cost and contamination risk

Inventive Principle:

Principle #23Feedback

3Quantity of substance

If concentrated NH3 solution is diluted into DI-water, then high dilution rate (1000x) is required, but accurate mixing is challenging due to limited mixing time

Engineering Contradiction:

ImproveNH3 concentration controlVSAvoidmixing accuracy

Core Design Contradiction:

Quantity of substanceVSEase of manufacture

Solution Approach 1:

The patent uses gas-liquid contactor technology where NH3 gas is introduced into the water stream, utilizing fluid dynamics and gas-liquid mass transfer principles. This approach replaces the challenging liquid-liquid dilution process with a more controllable gas-liquid absorption process, achieving accurate concentration control through gas flow regulation rather than precise liquid mixing

Inventive Principle:

Principle #29Pneumatics and hydraulics

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 system achieves precise control over NH3 concentration, preventing charge buildup and etching, while maintaining compatibility with advanced semiconductor processes, reducing waste and operational costs.

Implementation Method 1

dissolving ammonia gas in deionized water

Methodology Applied

Scientific EffectGas dissolution: Absorption (physical)

Implementation Method 2

a sensor in fluid communication with the at least one inlet of the contactor for measuring a flow rate of the deionized water

Methodology Applied

Scientific EffectFlow rate measurement:

Implementation Method 3

The controller is configured to set a flow rate of the ammonia gas supplied from the first gas source based on the flow rate of the deionized water measured by the sensor, and a predetermined conductivity set point

Methodology Applied

Scientific EffectConductivity control:

Data Source

PatentUS11826713B2Systems and methods for generating a conductive liquid comprising deionized water with ammonia gas dissolved therein

Publication Date: 2023.11.28 MKS INSTR INC

AI summary

Systems and methods are described for dissolving ammonia gas in deionized water. The system includes a deionized water source and a gas mixing device including a first inlet for receiving ammonia gas, a second inlet for receiving a transfer gas, and a mixed gas outlet for outputting a gas mixture including the ammonia gas and the transfer gas. The system includes a contactor that receives the deionized water and the gas mixture and generates deionized water having ammonia gas dissolved therein. The system includes a sensor in fluid communication with at least one inlet of the contactor for measuring a flow rate of the deionized water, and a controller in communication with the sensor. The controller sets a flow rate of the ammonia gas based on the flow rate of the deionized water measured by the sensor, and a predetermined conductivity set point.