Plasma Enhanced Chemical Vapor Deposition (PECVD) is one of the most fundamental processes in microelectronics fabrication. While most of the PECVD equipment manufacturers provide anode-driven PECVD processes, SAMCO also offers a unique Cathode PECVD system which provides high-rate deposition with good step coverage.
What is Anode PECVD?
In the Anode PECVD configuration, the RF power is applied to the upper electrode (Anode) and the substrate electrode (Cathode) is grounded. The PECVD uses this electrical energy to generate a plasma in which the energy is transferred into a gas mixture. This transforms the gas mixture into radicals, ions, neutral atoms and molecules.
The result is that fewer ions are attracted to the substrate, and it is useful for devices which are sensitive to Ion Damage.
Schematic image of anode PECVD chamber
SAMCO offers anode PECVD processes for R&D and production of various devices.
SAMCO’s process capabilities of anode PECVD are as follows.
1. Superior deposition uniformity
2. Excellent stress control
RF Power vs. Film Stress
3. Good step coverage
Step coverage of SiNx by anode PECVD
One of the disadvantages of anode PECVD processes is a low deposition rate (typically around 50 nm/min) due to lower ion energy.
What is Cathode PECVD?
An RF-driven cathode makes maximum use of a self bias voltage by placing the sample on the cathode electrode. Ions are accelerated by the negative electric field of the cathode.
Compared to traditional anode PECVD technologies, SAMCO’s proprietary cathode coupled PECVD technologies show various advantages.
Schematic image of Cathode PECVD chamber
High-speed and Thick Film Deposition
High-speed deposition processes are achieved by utilizing cathode-driven high-energy ions. Compared to traditional anode PECVD processes (typically around 50 nm/min), cathode PECVD processes show higher oxide deposition rate of 167 nm/min.
Deposition Time vs. Oxide Thickness
The cathode coupled high-speed PECVD processes show significant advantages over anode PECVD in the case of thick film deposition. Oxide overclad layer is deposited faster without cracking. The layer also has superior step coverage. These processes are applicable to lightwave circuits fabrication and gap-filling of metal lines.
25 µm Thick Over-clad Formation
7.6 µm Thick Gap-filling
Safe Deposition Without Using SiH4
Silane (SiH4) is widely used for PECVD processes to obtain high quality films. One of the drawbacks of a SiH4-based PECVD process is the safety issue. SiH4 is a flammable gas and easily ignite on contact with air. Also, the gas has toxicity to the human body. Therefore, device manufacturers need to take care of the gas use in production lines in the aspect of environment, health and safety (EHS).
For more than 20 years, SAMCO has been working on taking advantage of safer PECVD processes using liquid source Tetraethyl Orthosilicate (TEOS). TEOS is safer and easier to handle compared to SiH4, and it can create as good a film as SiH4.
The synergy of TEOS and cathode coupling enables a high quality Silicon Oxide (SiO2) films with excellent step coverage on high aspect ratio which is particularly suited to via holes in a TSV process.
Oxide Step Coverage of TSV
Low Temperature Deposition
Traditionally, PECVD processes have required high temperature over 250°C to meet film quality demands. However, a variety of materials such as polymers and adhesives used for MEMS devices fabrication do not have enough heat durability. Therefore, our customers using these materials required low-temperature deposition processes.
SAMCO offers a unique low-temperature deposition process utilizing the cathode PECVD technologies. The self-bias collects ions efficiently, and the high electric field on the cathode does not require high temperature for film deposition. The deposition process at low temperature of 80°C shows higher deposition rate than a typical Anode PECVD process at 300°C.
Oxide Deposition Rate at 80°C vs. at 300°C
Controllable Film Properties
SAMCO’s cathode PECVD processes show highly controllable film properties.
These are some examples. For more specific data, please feel free to contact us.
1. Wet Etch Rate
Bias RF Power vs. Wet Etch Rate
Wet Etch Condition: 1% HF
Solution Temperature of 25°C
2. Film Hardness
Self Bias Voltage vs. Film Hardness
3. Film Stress
Bias RF Power vs. Film Stress
The Value of SAMCO’s PECVD Processes
Throughput enhancement with high-rate deposition
SAMCO’s cahode PECVD processes enable high-volume manufacturing with high deposition rates.
Satisfying various demands on film properties
SAMCO’s controllable PECVD processes are suitable for R&D to achieve process goals.
A wide range of systems
SAMCO offers anode and cathode PECVD solutions for R&D and production. SAMCO covers multiple wafer sizes from batch processing of small wafers to 450 mm.
SAMCO Cathode PECVD Systems
SAMCO offers Cathode PECVD systems for both R&D and production.
– for R&D
– Open-load System
– Processing up to ø8”wafers
– for R&D and pilot production
– Loadlock System
– Batch processing of small wafers or processing up to ø8”wafers
– for production
– Cassette-to-cassette System
– Batch processing of small wafers or processing up to ø12”wafers
More detail on SAMCO’s Cathode PECVD technologies can be found on “Chapter 3 TSV Processes” of the book below.
Three-Dimensional Integration of Semiconductors Processing, Materials, and Applications
Editors: Kazuo Kondo, Morihiro Kada, Kenji Takahashi
ISBN: 978-3-319-18674-0 (Print) 978-3-319-18675-7 (Online)