VQ oxide monitoring
Printer-friendly version
Metallic contamination in semiconductors adversely affects device performance. As linewidths decrease the allowable levels of metal contamination get smaller and smaller. The most commonly occuring forms of metal contamination are either in the middle of the periodic table, called heavy metals, or are in the alkaline metal column, at the left of the periodic table.
Heavy metals diffuse into the bulk silicon. This type of contamination is discussed in the contamination section of this website. Alkaline metal contamination, such as sodium, usually occurs during processing and does not diffuse into the bulk silicon. Alkaline metal contamination affects oxides. The charge of ionized alkaline metals in oxides affects the oxide charge, measured as flat band voltage or equivalent.
Often, it is desirable to separate charge due to mobile ions from charge due to other things in the oxide. Sodium is the most commonly occurring alkaline metal contaminant, and its small diameter, ionized atoms migrate through the oxide in response to bias voltage. This variation in embedded charge in an oxide changes device performance, and the specs become unstable. Thus, it is desirable to limit the mobile charge contamination in an oxide.. Mobile charge can be detected via bias temperature stress tests.
The WT-2000 and WT-25000 tools monitor oxides via VQ measurement technology.
FEATURES:
- High throughput: complete analysis within 15 min
- High speed, high resolution mapping of a number of parameters
- Mobile charge measurement capability
- Combination with bulk contamination measurement such as Laser-SPV/m-PCD
- Real non-destructive characteristic by neutralizing the wafer after measurements
APPLICATION
MEASURED PARAMETERS
- Tox Electrical oxide thickness
- Vfb Flatband voltage
- Dit Interface state density
- Qm Mobile charge
- Vox Oxide voltage
- Qeff Effective charge
- Etunnel Tunneling electric field
- Vs Surface potential
- Vsurf Surface voltage
- Vtunnel Tunnel voltage
