Polysilicon Recess Etching With Bubble Removal in High-Aspect Structures
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Solution Overview
Problem
Etching failure occurs in recess portions of high aspect ratio on semiconductor substrates due to bubble formation and clogging, preventing fresh processing liquid from reaching the polysilicon layer.
Innovation Solution
A substrate processing method and apparatus that includes an immersion step and an etching step, where bubbles generated inside the recess portion are removed through methods such as adjusting silicon concentration, draining processing liquid, generating bubbles in the liquid, or applying ultrasonic vibration to prevent clogging and facilitate etching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a polysilicon layer is etched with an alkaline processing liquid in a recess portion of high aspect ratio, then etching of the polysilicon layer is performed, but bubbles generated by the reaction clog the recess portion and prevent fresh processing liquid from reaching the polysilicon layer, causing etching failure
Solution Approach 1:
The patent converts the harmful effect of bubbles into a beneficial one by intentionally generating bubbles through a gas supply unit. These controlled bubbles rise through the processing liquid, creating upward flow that carries away reaction bubbles from the recess portions, thereby preventing clogging and ensuring continuous etching.
Solution Approach 2:
The patent uses pneumatic principles by supplying gas to generate bubbles in the processing liquid. The gas bubbles create hydraulic flow that circulates the processing liquid through the recess portions, enabling continuous removal of reaction bubbles and maintenance of etching efficiency.
2Productivity
If the recess portion has high aspect ratio to accommodate miniaturized elements, then element density is increased, but bubble removal becomes difficult and etching failure occurs
Solution Approach 1:
The patent converts the difficulty of bubble removal in high aspect ratio recesses into an advantage by using gas-supplied bubbles to create upward flow. This flow actively carries reaction bubbles out of the deep recess portions, making bubble removal easy even in high aspect ratio structures that enable high element density.
Solution Approach 2:
The patent changes the physical state and flow parameters of the processing liquid by introducing gas bubbles. This creates dynamic flow conditions that enhance bubble removal capability without altering the geometric parameters of the high aspect ratio recess portions, thereby maintaining element density while improving operability.
3Duration of action of stationary object
If processing liquid is continuously supplied to maintain etching, then etching progress is maintained, but reaction bubbles accumulate and clog the recess portion
Solution Approach 1:
The patent converts the accumulated bubbles, which would normally clog the recess portion, into a useful flow mechanism. By continuously supplying gas to generate bubbles, the system creates sustained upward flow that continuously removes reaction bubbles, allowing continuous processing liquid supply to maintain etching without bubble accumulation.
Solution Approach 2:
The patent ensures continuous etching action by continuously supplying gas to maintain bubble generation and flow. This continuous flow action prevents bubble accumulation while maintaining processing liquid circulation, thereby achieving both continuous etching and bubble removal simultaneously.
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 and apparatus effectively suppress etching failure by ensuring the processing liquid reaches the polysilicon layer, maintaining etching progress and preventing bubble clogging in recess portions.
Implementation Method 1
by reaction of the polysilicon layer and the processing liquid, bubbles of hydrogen are generated
Implementation Method 2
the bubbles generated inside the recess portion are removed by applying an ultrasonic vibration to the processing liquid
Implementation Method 3
the bubbles generated inside the recess portion are removed by supplying a gas below the substrate and generating bubbles inside the processing liquid
Data Source
AI summary
A substrate processing method includes immersing a substrate in an alkaline processing liquid and etching, by the processing liquid, a polysilicon layer filled in a recess portion of columnar shape extending substantially perpendicular to a principal surface of the substrate, and in etching the polysilicon layer, bubbles generated inside the recess portion are removed.