Substrate Heating for Phosphoric Acid Etching Rate
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Solution Overview
Problem
The phosphoric acid etching process for semiconductor wafers and other substrates is hindered by temperature fluctuations in the etching solution, leading to reduced etching rates and increased processing time, especially in single-substrate treatment systems where the solution temperature drops before application.
Innovation Solution
Maintaining the substrate at a higher temperature (not lower than 250°C) and using a silicon suspension liquid with high heat conductivity to prevent temperature reduction of the phosphoric acid solution, promoting etching reactions and reducing the time required for the process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the phosphoric acid aqueous solution is supplied at about its boiling point to the substrate, then the etching rate is maximized, but the temperature of the phosphoric acid aqueous solution is reduced before supply in single substrate treatment type, reducing the etching rate
Solution Approach 1:
A heat exchange unit is introduced as an intermediary component between the phosphoric acid aqueous solution tank and the substrate. This heat exchange unit transfers heat from the heated substrate to the phosphoric acid aqueous solution, maintaining the solution temperature without direct heating of the solution tank, thus resolving the temperature reduction issue before supply
Solution Approach 2:
The invention changes the temperature parameter of the phosphoric acid aqueous solution by implementing a heating unit that heats the substrate to a temperature higher than the boiling point of the phosphoric acid aqueous solution. This temperature parameter change ensures the solution maintains its high temperature during the etching process, maximizing the etching rate
2Loss of time
If the substrate is maintained at higher temperature to increase etching rate, then the time required for etching is reduced, but energy consumption increases
Solution Approach 1:
The substrate serves a dual function: it is both the object being etched and the heat source for maintaining the phosphoric acid aqueous solution temperature. The substrate is heated to a temperature higher than the boiling point of the phosphoric acid aqueous solution, and this heat is then transferred to the solution through the heat exchange unit. This self-service approach allows the substrate to contribute to its own processing conditions, reducing external energy requirements
Solution Approach 2:
The heating function and the etching process are merged into a single integrated system. The heating unit heats the substrate, and the heat exchange unit simultaneously uses this heat to maintain the phosphoric acid aqueous solution temperature. This merging of functions eliminates the need for separate heating systems for both the substrate and the solution, reducing overall energy consumption while maintaining high etching rates
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 the etching rate by maintaining the phosphoric acid solution at a higher temperature, reducing the deposition of orthosilicic acid and promoting reactions, thereby shortening the etching process time and improving throughput.
Implementation Method 1
a higher temperature maintaining step of maintaining a substrate held by a substrate holding unit at a higher temperature that is not lower than 250° C.
Implementation Method 2
The silicon suspension liquid, which contains a great amount of highly heat-conductive silicon (Si) particles, has a heat absorptive property. The heat absorptive property of the silicon suspension liquid prevents the reduction in the temperature of the phosphoric acid aqueous solution
Implementation Method 3
a phosphoric acid etching process is performed on a substrate having a silicon nitride film and a silicon oxide film formed in a front surface thereof, as required, to selectively remove the silicon nitride film by supplying a higher temperature phosphoric acid aqueous solution as an etching liquid
Data Source
AI summary
The inventive substrate treatment apparatus includes a spin chuck which horizontally holds and rotates a wafer; a heater which is disposed in opposed relation to a lower surface of the wafer held by the spin chuck and heats the wafer from a lower side; a phosphoric acid nozzle which spouts a phosphoric acid aqueous solution to a front surface (upper surface) of the wafer held by the spin chuck; and a suspension liquid nozzle which spouts a silicon suspension liquid to the front surface of the wafer held by the spin chuck. The wafer is maintained at a higher temperature on the order of 300° C. and, in this state, a liquid mixture of the phosphoric acid aqueous solution and the silicon suspension liquid is supplied to the front surface of the wafer.