Plasma Etching Pulse Timing for Stable Silicon Film Selectivity
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Solution Overview
Problem
Existing plasma processing methods struggle to achieve high etching selectivity and rate for silicon-containing films, particularly when using silicon oxide films and polysilicon masks, due to instability in plasma generation and potential peeling of the mask during etching.
Innovation Solution
A plasma processing method involving periodic supply of a negative pulse voltage to the substrate support and RF power, where the pulse voltage is initiated before the onset of RF power, stabilizing plasma generation and enhancing the etching process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional plasma processing methods are used for silicon-containing films, then etching can be performed, but etching selectivity is insufficient and mask peeling occurs
Solution Approach 1:
The patent applies periodic action by alternating between RF power supply (plasma generation period) and no RF power supply (non-plasma period) in a cyclic manner. During the plasma generation period, etching is performed with high ion bombardment energy. During the non-plasma period, the substrate surface is restored without ion bombardment. This periodic alternation achieves high etching selectivity while preventing mask peeling by providing restoration time for the mask and substrate surface.
Solution Approach 2:
The patent applies preliminary action by performing substrate surface restoration during the non-plasma period before the next etching cycle begins. This preliminary restoration action removes damaged layers and prepares the surface for the next etching cycle, ensuring high selectivity and preventing mask adhesion issues before they occur.
2Productivity
If continuous RF power is supplied for high etching rate, then productivity increases, but plasma stability deteriorates and mask peeling occurs
Solution Approach 1:
The patent uses periodic action to alternate between high-power plasma generation (for high etching rate) and zero-power restoration (for plasma stability). This periodic modulation allows the system to achieve high average etching rates while maintaining plasma stability through regular restoration cycles, preventing the degradation that would occur with continuous high-power operation.
3Productivity
If high ion bombardment energy is used for fast etching, then etching rate increases, but mask damage and peeling worsen
Solution Approach 1:
The patent applies periodic action by cycling between high ion bombardment energy periods (for high etching rate) and zero ion bombardment periods (for mask restoration). During the high-energy periods, rapid etching occurs. During the restoration periods, the mask and substrate surface are healed without ion damage. This periodic alternation achieves high productivity while minimizing cumulative mask damage and preventing peeling.
Solution Approach 2:
The patent applies beforehand cushioning by providing restoration periods between etching cycles. These restoration periods act as a cushioning mechanism that prevents cumulative mask damage by removing damaged layers and reinforcing the mask-substrate interface before the next high-energy etching cycle begins, thereby preventing peeling.
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 improves etching selectivity by 40% or more and etching rate by 30% or more, stabilizing plasma and reducing mask peeling, thereby enhancing the efficiency of silicon-containing film etching.
Implementation Method 1
ions generated in the plasma are accelerated and bombard the substrate
Implementation Method 2
periodically supplying RF power and generating plasma from the process gas by the RF power
Data Source
AI summary
A plasma processing method includes:a) providing a substrate on a substrate support;b) supplying a process gas;c) periodically supplying a pulse voltage to the substrate support; andd) periodically supplying RF power and generating plasma from the process gas to etch a silicon-containing film included in the substrate. The pulse voltage is negative. A first period in which a first pulse voltage is supplied and a second period in which the pulse voltage is not supplied or a second pulse voltage whose absolute value is less than that of the first pulse voltage is supplied are repeated in c). A third period in which first RF power is supplied and a fourth period in which the RF power is not supplied or second RF power less than the first RF power is supplied are repeated in d). The first period starts before a start of the third period.