Advanced Process Control
Though Advanced Process Control (APC) is well established in Si-technology, the concepts are not yet widely used in compound semiconductor industries. At LayTec, however, we already equip all of our in-situ tools with APC capabilities, as these features are mandatory for improving yield and cutting costs. Traditionally, APC is divided into two different parts:
- Fault detection and classification (FDC)
- Run-to-run control
In response to the requirements of the MOCVD process in the compound semiconductor industry, we have also added a third part: Real time feedback control
A vital part of the LayTec solution for APC is the EpiGuard® feature of LayTec's EpiNet software. EpiGuard® allows for the running of multiple, user-configurable pre-defined analysis tasks on the in-situ measured data in real-time, while also comparing the results with pre-defined specification values and control limits.
Please visit our EpiNet product page to learn more.
At Jenoptik Diode Lab (Germany), LayTec EpiTTs monitor MOCVD growth of edge emitting laser bars. The tools are routinely used to calibrate growth rate and composition during calibration runs as well as to control production runs (Fig. 1). Specific key values, such as temperature or growth rate of specific layers on specific wafers, are extracted from the in-situ data and transferred into the MES (manufacturing execution system) for SPC (statistical process control). So, process stability can be monitored run-to-run and potential deviations can be detected immediately, paving the way for run-to-run control.
Fig. 1: In-situ growth rate data of one wafer and one specific layer, extracted from the MES system, showing all growth runs within 1.5 years as used for SPC in production.
The data in Fig. 1 (red circle) shows slight trends from run to run within one session. The deviations are based on conditioning effects of the reactor caused by an increasing coating. Jenoptik's experience proves that EpiTT is a valuable part of process control.