Material Properties and Applications of Silicon Dioxide (SiO2)
Silicon Dioxide (SiO2) is an oxide of silicon. Depending on the purity and crystalline form, there are several types of products available including Quartz, Fused Silica and Borosilicate Glass.
SiO2 has unique chemical and mechanical properties including excellent abrasion resistance, good electrical insulation and low thermal expansion and high thermal stability.
For device fabrication, this material has been used for several purposes, deposited by plasma enhanced chemical vapor deposition (PECVD) or atomic layer deposition (ALD).
• Insulation layer
• Etch stop of a silicon-on-insulator (SOI) substrate
• Hard mask for dry etching
• Substrate of microfluidics
SiO2 Etching for Hard Mask Patterning
SiO2 mask has some advantages over photoresist. The mask shows higher etch selectivity especially when etching metals and hard materials such as silicon carbide (SiC). Also, it does not cause burning in high stage temperature compared to the photoresist.
SAMCO has provided SiO2 etching solutions for hard mask patterning.
Mask patterning of SiO2 on InP substrate was performed using a reactive ion etching (RIE) system. The etched profile showed vertical and smooth surfaces.
Etch Rate : 21 nm/min
Etch Selectivity : 1.46 (over photoresist)
SiO2 (4 µm width L/S pattern) etching was performed using an ICP etch system.
Etch Depth : 6.5 µm
Etch Rate : 325 nm/min
Nanoscale patterning of SiO2 (L/S and dot pattern) was performed using an ICP etch system for photonic crystal fabrication.
Etch Rate : 79.7 nm/min
Etch Selectivity : 5.5 (over photoresist)
Profile Angle : 87°
High-rate SiO2 Etching
High-rate SiO2 etching is one of the process requirements of customers in wafer fabs.
SAMCO has developed high-rate SiO2 etching process by optimizing the process recipe.
Etch Depth : 30 µm
Etch Rate : 500 nm/min
Etch Mask : Cr
10 µm width L/S pattern
Etch Depth : 11.2 µm
Etch Rate : 560 nm/min
Etch Selectivity : 2.0 (over photoresist)
Etch Depth : 150 µm
Etch Rate : 400 nm/min
Etch Mask : Ni
SiO2 Microchannel Fabrication
SiO2 is widely used as a substrate of microfluidics devices as well as polymer materials such as cyclic-olefin-copolymer (COC) and polydimethylsiloxane (PDMS). SiO2 has some advantages over the polymer materials. For instance, SiO2 low absorption of molecules and mechanical stability to pressure.
Photo courtesy of Shikata Lab, Osaka University
SiO2 Microlens Fabrication
SiO2 microlens are key components of optical MEMS devices. SAMCO offers fabrication processes of SiO2 microlens, combining with SiO2 plasma-enhanced-chemical-vapor-deposition (PECVD) processes.
Height and profile angle can be adjusted by recipe optimization. Also, the etched profile shows smooth surface.
Photo courtesy of AIST Kansai
Etch Rate : 100 nm/min
Etch Selectivity : 1.2 (over photoresist)
SiO2 Nanoscale Etching
SiO2 nanoscale etching is required for fabrication of nano-electro-mechanical-system (NEMS) devices and nano photonic devices.
SiO2 anti-reflection film of moth-eye structure was created combining with PECVD, dry etching and subsequent wet etching. The SiO2 film was periodically patterned in less than 1 µm pitch.
Photo courtesy of AIST Kansai