The demand for high frequency and high bit rates is increasing to meet the requirement for broadband, mobile, and handheld communications systems. A SAW filter is a layered structure and consists of CVD thin film of metal, such as Aluminum on either a crystaline quartz, lithium niobate, lithium or tantalate substrate. The high SAW velocity and the demanding thermal conductivity requires optimum materials that can perform reliably under extreme high frequency.With the shrinkage of SAW devices, an ARC® layer has become a necessary component to the formation of the SAW filter, in that critical dimension control of this structure determines the performance of the SAW. The function of the ARC layer is to control reflectivity, standing waves and reflective notching. This addtional layer assures the structure's dimensions are uniform.

Diagram of a SAW device fabrication:

1. A substrate is coated with a precise thichness of Aluminum by evaporation. Then a layer of ARC material and photoresist are applied and baked.

2. The photosensitive material is patterned during exposure to a UV light source. Developed photoresist areas reveal patterns of Aluminum. (A dry etch ARC layer can also be used, but the ARC layer will have to be etched, not developed to expose the substrate.)

3. The photoresist patterned wafer is then etched by the use of reactive ion etching. This removes the exposed Aluminum.

4. The photoresist and ARC material are then stripped off, leaving the patterned wafter containing the SAW device.

Depending on your wavelength and photoresist compatibility, here is a list of possible BARC products that can aid your process:

Would you like more information about thess products? Please click here to access our request form or call +573.364.0300 (U.S.A.) and request an ARC® products technical expert.

365nm	436nm
ARC® i-CON	XLT-B
XHRiC
WiDE®B

SAW Devices

SAW Device Applications

Diagram of a SAW device fabrication:

Diagram of a completed SAW device.