Maintaining a consistent wafer processing environment is critical in today’s manufacturing processes. As device feature sizes and film thicknesses approach Angstrom levels, yield and tool productivity are highly susceptible to micro-variations in the wafer processing environment.
The Traditional Approach
Most fabs today combat wafer process inconsistencies with available tool information and delayed feed forward / backward control loops. Due to the ease of accurate measurements, a chamber’s temperature, process pressure, and RF power are well characterized and tightly controlled for each and every wafer processed. The other key parameters – gas flow and chamber condition, however are more difficult and
often impossible to measure in real-time.
For gas flow, most fabs rely on the feedback from the mass flow controller (MFC) system subcomponent,
which can often be erroneous at low flows; the only means for calibrating MFCs are off-line approaches (e.g., Gas Box Rate-Of-Rise by MKS Instruments) which are time consuming and labor intensive. Coarse control loops and costly metrology steps are also put in place to check wafer parameters post or pre-processing (e.g., CD measurements, etch rate monitors) and then make gas flow set point adjustments on the fly. A very common example is a post poly-etch CD measurement taken through scatterometry that then feeds back changes to the recipe’s O2 gas flow set point so that CDs sit within a tighter distribution.
For chamber condition measurements, most fabs rely on off-line wafer monitors or leak check systems to ensure key parameters like etch rate, particles and leak rates are in spec. The few fabs that adopt real-time monitoring systems like residual gas analyzers (RGA) and optical emission spectrometers (OES) struggle to use the information quickly and effectively since their clarity and sensitivity to the species that exist inside the wafer processing environment is poor. Fabs spend large amounts of time and labor troubleshooting the chamber condition for which they have little to no understanding of the underlying species causing the issue.
The Pivotal Approach
Pivotal’s technology is aimed at providing real-time, easy-to-understand, high accuracy / sensitivity measurements of these two critical parameters that are cannot be properly measured today: Gas Flow
and Chamber Condition.
Gas Flow Monitor (GFM) technology
- Real-time:Measurement taken during wafer processing for each gas of each recipe step for each wafer processed
- Easy-to-understand:Primary standard measurement using pressure, temperature and volume. No complex heat transfer or pressure / fixed orifice proxies
- High accuracy: NIST traceable offering an accuracy of ±0.5% of set point
Sensor X technology
- Real-time: Chamber gas diffuses instantaneously into micro-cavity with ultra-high density plasma created for OES analysis; no moving parts
- Easy-to-understand:Molecular species are ripped apart and emit light at atomic wavelengths making species identification very easy
- High sensitivity: Sub parts-per-million (PPM) sensitivity due to atomic vision
Pivotal’s core GFM and Sensor X technologies provide the first commercial means of measuring key parameters of the wafer processing environment, thereby enabling an order of magnitude improvement in tool productivity