Specific Process Knowledge/Thin film deposition/Deposition of Silicon Oxide

Deposition of Silicon Oxide can be done with either LPCVD, PECVD or by sputter technic. You can also make a silicon oxide layer by growing a thermal oxide in a hot furnace but that requires a silicon surface as a starting point.

Deposition of Silicon Oxide using LPCVD

The LPCVD oxide you can deposit at DANCHIP is called TEOS oxide. It can be made in the LPCVD TEOS furnace. It is a batch process meaning you can run a batch of 25 wafers at a time. The deposition takes place at temperatures of 700? degrees Celsius. The TEOS oxide has good step coverage and hole filing/covering properties and the film thickness is very uniform over the wafer?. We have two? standard TEOS processes: One for depositing ? and one for deposition ?. The TEOS oxide has a dielectric constant very close to the one for thermal oxide.

Deposition of Silicon Oxide using PECVD

PECVD oxide can be deposited in one of the PECVD systems. You can run 1-3 wafers at a time depending on which one of the PECVD's you use. The deposition takes place at 300 degrees Celcius. This can be of importance for some applications but it gives a less dense film and the oxide is expected to have some hydrogen incorporated. The step coverage and thickness uniformity of the film is not as good as for the LPCVD TEOS oxide. PECVD oxide has excellent floating properties when doped with boron and/or phosphorus. Then it can be used ex. as top cladding for waveguides or encapsulation of various structures/components. In one of our PECVD systems (PECVD3) we allow small amounts of metal on the wafers entering the system, this is not allowed in the LPCVD and in the other PECVD (PECVD1). It is also a possibility to dope the silicon oxide with Germanium for altering the refractive index of the oxide.

Deposition of Silicon Oxide using sputter deposition technic

At DANCHIP you can also deposit silicon oxide using Lesker sputter system. One of the advantages here is that you can deposite on any material you like.

Compare the methodes

	LPCVD	PECVD	Sputter technic
Stoichiometry	Si₃N₄ SRN SRN: Silicon Rich Nitride	Si_xN_yH_z Si_xO_yN_zH_v Can be doped with boron, phosphorus or germanium	?
Film thickness	Si₃N₄:~50Å - ~3000Å SRN: ~50Å - ~10000Å	~40nm - 10µm
Process Temperature	800-835 ^oC	300 ^oC
Step coverage	Good	Less good
Film quality	Dense film Few defects	Less dense film Incorporation of hydrogen in the film
Process volume	1-25 4" wafer per run deposition on both sides of the substrate	1-3 4" wafers or 1 6" wafer or many smaller chips per run deposition on one side of the substrate
Substrate material allowed	Silicon wafers with layers of silicon oxide or silicon (oxy)nitride Quartz wafers	Silicon with layers of silicon oxide or silicon (oxy)nitride Quartz Small amount of metal (in PECVD3)