Carbon Hardmask Deposition with Pulsed LF RF for Low-Stress Selectivity
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Solution Overview
Problem
Current methods for forming ashable hard masks (AHMs) using plasma enhanced chemical vapor deposition (PECVD) result in films with high stress, limiting their usefulness due to low etch selectivity and increased line-bending, which affects the precision of semiconductor processing.
Innovation Solution
The method involves exposing a substrate to a hydrocarbon precursor and helium gas using a dual radio frequency (RF) plasma source with pulsed low frequency (LF) power, high power, and a high frequency (HF) component, achieving high etch selectivity and low stress by adjusting the duty cycle and power levels to reduce internal stress and increase the modulus of the AHM film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PECVD process is used to form AHM films, then etch selectivity is improved, but internal stress increases
Solution Approach 1:
The patent applies periodic action by pulsing the low frequency RF power during the PECVD process. The LF power is pulsed at a duty cycle between 10% and 75%, creating periodic plasma conditions that allow controlled deposition while reducing internal stress accumulation in the AHM film, thereby resolving the contradiction between achieving high etch selectivity and minimizing internal stress.
Solution Approach 2:
The patent changes key process parameters including using high power LF pulsing (at least 3000 W per 300 mm wafer), specific duty cycles (10%-75%), and high frequency constant power to optimize the deposition conditions. These parameter changes enable the formation of AHM films with both high etch selectivity and reduced internal stress by controlling the plasma chemistry and film growth dynamics.
2Reliability
If high power LF pulsing is applied, then modulus and selectivity are increased, but process complexity increases
Solution Approach 1:
The patent employs a dual RF plasma source that can deliver both high frequency and low frequency power to the substrate. This multi-functional plasma source allows the same equipment to achieve enhanced film properties through LF pulsing without requiring additional processing steps or equipment, thereby increasing selectivity while managing process complexity through universal tool capability.
3Reliability
If helium carrier gas is used, then sputtering is reduced, but deposition rate may be affected
Solution Approach 1:
The patent uses helium as the carrier gas instead of traditional gases like argon or nitrogen. Helium's unique properties reduce sputtering of the AHM film during deposition, improving film integrity and reducing internal stress. The deposition rate is maintained through optimization of other parameters including high power LF pulsing and appropriate process conditions, balancing film quality with productivity.
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 produces AHM films with improved etch selectivity and reduced stress, minimizing line-bending and enhancing the performance of AHMs in semiconductor processing by maintaining high selectivity while reducing internal stress.
Implementation Method 1
generating a plasma using a dual radio frequency (RF) source
Implementation Method 2
depositing on the substrate an AHM film by a plasma enhanced chemical vapor deposition (PECVD) process
Implementation Method 3
Pulsing the LF power at a high power, high frequency, and low duty cycle (DC) may increase the modulus, and thus the selectivity, of the AHM film
Implementation Method 4
A carrier gas of substantially helium may also reduce sputtering of the AHM film
Data Source
AI summary
Methods and related apparatus for depositing an ashable hard mask (AHM) on a substrate include pulsing a low frequency radio frequency component at a high power. Pulsing low frequency power may be used to increase the selectivity or reduce the stress of an AHM. The AHM may then be used to etch features into underlying layers of the substrate.