Silicon Etch via Biased Plasma Amorphization
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Solution Overview
Problem
Current silicon selective dry etch processes lack sufficient flexibility and selectivity, particularly for patterned heterogeneous structures, where higher selectivity and directional etching are required without causing physical disturbance to miniature structures.
Innovation Solution
A method involving a biased plasma process to amorphize crystalline silicon, followed by a remote plasma etch using hydrogen-containing precursors, which transforms the etch process from isotropic to anisotropic, allowing for high selectivity and increased etch rates of amorphous silicon over crystalline silicon, with an ion suppressor reducing ionic species and minimizing plasma damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If remote plasma etching is used to selectively remove silicon, then material removal is achieved with minimal physical disturbance, but etch rate selectivity between amorphous and crystalline silicon is insufficient
Solution Approach 1:
A plasma treatment step is performed before the remote plasma etch to amorphize the silicon surface. This preliminary action transforms the crystalline silicon into amorphous silicon, which then etches at a much higher rate during the subsequent remote plasma etch step, achieving both minimal physical disturbance and high etch rate selectivity
Solution Approach 2:
The invention changes the physical state of silicon from crystalline to amorphous through plasma treatment. This parameter change in the material structure enables differential etching rates, where amorphous silicon etches significantly faster than crystalline silicon in the remote plasma etch process
2Productivity
If isotropic etching is performed, then material removal is achieved, but directional control and selectivity are lost
Solution Approach 1:
The plasma treatment step performed before etching modifies the silicon surface to be more reactive. This preliminary action enables the subsequent remote plasma etch to proceed directionally with high selectivity, transforming the normally isotropic etch into a directional (anisotropic) etch
Solution Approach 2:
By changing the physical state of silicon from crystalline to amorphous, the invention alters the etching characteristics from isotropic to anisotropic. The amorphous silicon structure allows for directional etching control that is not achievable with crystalline silicon in remote plasma processes
3Adaptability or versatility
If process flexibility is increased for silicon selective etch, then adaptability to different applications is improved, but process complexity increases
Solution Approach 1:
The plasma treatment step is a relatively simple preliminary action that can be easily integrated into existing process flows. It provides a versatile platform for achieving high selectivity across different applications without requiring complex equipment or multiple process steps
Solution Approach 2:
The invention achieves process flexibility through parameter changes in the plasma treatment and etch conditions rather than through complex process architectures. This allows adaptation to different applications while maintaining relatively simple process implementation
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 achieves a significant increase in etch rate selectivity, with amorphous silicon being removed at a rate greater than crystalline silicon by a multiplicative factor of over 200, and provides directional etching capabilities, reducing plasma damage and maintaining process flexibility.
Implementation Method 1
treating the patterned substrate with a local plasma formed from an inert gas. Treating the patterned substrate includes transitioning a crystalline silicon portion of the patterned substrate into an amorphous silicon portion of the patterned substrate
Implementation Method 2
flowing a hydrogen-containing precursor into a remote plasma region fluidly coupled to the substrate processing region while forming a remote plasma in the remote plasma region to produce the plasma effluents
Implementation Method 3
The plasma effluents are passed into the substrate processing region to etch the amorphous silicon from the patterned substrate
Data Source
AI summary
A method of selectively dry etching silicon from patterned heterogeneous structures is described. The method optionally includes a plasma process prior to a remote plasma etch. The plasma process may use a biased plasma to treat some crystalline silicon (e.g. polysilicon or single crystal silicon) to form amorphous silicon. Subsequently, a remote plasma is formed using a hydrogen-containing precursor to form plasma effluents. The plasma effluents are passed into the substrate processing region to etch the amorphous silicon from the patterned substrate. By implementing biased plasma processes, the normally isotropic etch may be transformed into a directional (anisotropic) etch despite the remote nature of the plasma excitation during the etch process.