Degas processes typically employ inert gases such as Argon or Nitrogen. The use of these gases can be challenging as they generate an elevated baseline in RGAs due to large amounts of chemical background noise caused by metastable decay. This results in reduced sensitivity which can be problematic for manufacturers who want to identify changes in trace gases (which are indicative of issues during the manufacturing process) quickly and easily.

V-lens technology, a unique enabling solution, helps to overcome this issue by providing a consistently low mass independent baseline and detection levels in the low ppb range. This is achieved with unique ion optics that utilize a patented double-focusing and deflection mechanism that significantly reduces background and enhances sensitivity (see figure).

The result is a gas analyzer with limits of detection in the low ppb range without compromise to any other aspect of instrument performance.

This state-of-the-art RGA technology is integrated with Process Eye Professional control platform, a recipe based, user-configurable software program. The combination of V-lens, a closed ion source, and automated inlet allows for sensitive and reproducible monitoring of the complete ALD, CVD, or Etch process cycle.

By maximizing the ratio between ALD, CVD, or Etch chamber gas signals and the gas background in the differentially pumped analyzer housing, the V-lens and closed ion source enables low ppm-level detection for trace contaminants in the process gas.

A real life example where degas monitoring of a signature mass could only be achieved when utilizing V-lens technology is shown in the figure. The baseline is significantly reduced allowing for unequivocal identification of the target mass. This allows for faster and easier identification of trace gases which is critical in many manufacturing processes.

When the system is utilized with the powerful features of the Process Eye™ and TOOLweb® RGA sensor control software package, the result is completely automated operation and highly reliable and sensitive photoresist detection. Unscheduled downtimes are reduced and device yields are improved.

The 300mm Resist-Torr XD considers many different parameters of the degas step and combines that data to provide information in the form of a meaningful number, without the need for user-interpretation. This measurement, termed the PR Index, is a normalized measure of wafer borne photoresist contamination that can be presented in various forms to compare data over time.

The 300mm Resist-Torr XD can interrupt the processing of any wafer automatically, without operator intervention, if a wafer enters the vacuum system with detrimental levels of residual photoresist, as determined by the PR Index. The example (Figure 4) shows a PR index trace for a series of test wafers and provides the user a selective way to detect patterns that indicate contamination. The PR index is shown as a black trend in the top line and the alarm level as a yellow line. The black PR line can be seen to elevate indicating that it has identified contaminated wafers. The PR Index allows a more sensitive and reliable method for detecting photoresist contamination.

Using TOOLweb RGA sensor integration option for process tools, the 300mm Resist-Torr XD can be used as a degas chamber sensor in a completely automated process environment (Figure 5). TOOLweb RGA maintains a constant monitor of tool activities with all sensor data being framed by wafer logistics before alarm models are applied. Full alarm and data reporting to the FAB host and FDC are available so real time monitoring of chamber conditions and flagging of any process excursions from ideal conditions is possible.