Silicon Selective Etching via Remote Plasma Segmentation
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Solution Overview
Problem
Current dry etch processes struggle to achieve high selectivity in removing silicon relative to silicon oxide and silicon nitride, necessitating improved methods for precise and controlled etching in semiconductor manufacturing.
Innovation Solution
A method involving a remote plasma region with a fluorine-containing precursor and a hydrogen-containing precursor introduced separately, using a dual-channel showerhead to generate plasma effluents that selectively etch silicon at a higher rate than silicon oxide and silicon nitride, with an atomic flow ratio of hydrogen to fluorine between 4:3 and 10:1, ensuring controlled and selective removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional dry etch processes are used to remove silicon, then etching can be performed, but etch selectivity of silicon relative to silicon oxide and silicon nitride is insufficient
Solution Approach 1:
The etching process is segmented into two distinct regions: a remote plasma generation region and a substrate processing region. The plasma is generated remotely and then transported to the substrate region, allowing separate optimization of plasma generation and selective etching conditions. This segmentation enables the use of specific gas compositions and flow ratios that achieve high silicon selectivity without compromising process control.
Solution Approach 2:
The invention changes the chemical parameters of the etching process by using a hydrogen-containing precursor combined with a fluorine-containing precursor in specific atomic flow ratios (H:F between 4:3 and 10:1). This parameter change transforms the etching chemistry to achieve unprecedented silicon selectivity exceeding 100:1 relative to silicon oxide and silicon nitride, directly resolving the selectivity problem.
2Manufacturing precision
If higher etch selectivity is achieved through process optimization, then silicon removal precision improves, but process complexity increases
Solution Approach 1:
Hydrogen-containing precursor is introduced as an intermediary substance that modifies the etching chemistry. The hydrogen acts as a mediator that enhances the selectivity of silicon etching by interfering with the etching of silicon oxide and silicon nitride, achieving high precision without requiring complex process equipment or multiple process steps.
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 achieves high etch selectivity, allowing for precise and controlled removal of silicon, resulting in a smoother surface and improved performance of integrated circuits by selectively etching silicon at a rate greater than silicon oxide and silicon nitride, with etch selectivity ratios exceeding 100:1.
Implementation Method 1
RF power may be applied to generate plasma effluents in the remote plasma region
Implementation Method 2
Chemical etching is used for a variety of purposes including transferring a pattern in photoresist into underlying layers
Implementation Method 3
The atomic flow ratio of hydrogen to fluorine may be between about 4:3 and about 10:1 and the plasma effluents may etch the first exposed portion at a rate greater than an etch rate of the second exposed portion
Data Source
AI summary
A method of etching exposed silicon on patterned heterogeneous structures is described and includes a gas phase etch using plasma effluents formed in a remote plasma. The remote plasma excites a fluorine-containing precursor. Plasma effluents within the remote plasma are flowed into a substrate processing region where the plasma effluents combine with a hydrogen-containing precursor. The combination reacts with the patterned heterogeneous structures to remove an exposed silicon portion faster than a second exposed portion. The silicon selectivity results from the presence of an ion suppressor positioned between the remote plasma and the substrate processing region. The methods may be used to selectively remove silicon faster than silicon oxide, silicon nitride and a variety of metal-containing materials. The methods may be used to remove small etch amounts in a controlled manner and may result in an extremely smooth silicon surface.