IN
SITU HOSTä APPLICATION NOTE
The Justification for an Automation Product for In Situ Applications
Introduction
For more than two decades, the widespread adoption of in situ and in line metrology has appeared to be on the horizon. Residual gas analyzers (RGA) and in situ particle counters (ISPM) are but two of many promising applications that have yet to fulfill their potential.
The promise of in situ and in line metrology still exists. The right automation product will make a significant impact on the industry. The primary justification for in situ metrology is that it is real-time. If a batch of contaminated wafers comes to a PVD cluster, unless the contamination is very gross, the batch will probably be processed, subsequent batches will also be processed, until finally, the next set of ex situ qualification tests are performed. The jeopardy is significant.
Status Quo
The RGA hardware manufacturers have two major classes of software product. The first class is designed for human interaction. The automation capability, especially the automated analysis capability, is extremely limited. This class is generally intended for maintenance functions like helium leakchecking or troubleshooting and assumes a technician will be present. The value of this aspect is sometimes overlooked. The choice to automate the instrument can sometimes result in a compromise of the maintenance function, since the human interface changes dramatically, making it difficult for the routine user.
The second class is designed for complete automation. The capability can be substantial, but market acceptance has been very limited. The reasons for the lack of success include:
- The human interface is more complex than necessary. The suppliers assumed at the outset that the customer would not be competent to maintain the product, so the user-friendly issue was never a priority. In some cases, the human interface complexity was intentional in order to encourage dependency on the supplier.
- The system is expensive, especially if one considers the cost of perpetual support.
Dynamic Data Exchange (DDE)ä
A third party host application would not be possible except for the fact that most of the supplier’s standard RGA software, the class of software intended for human interaction, supports a technology called “Dynamic Data Exchange” or DDE. DDE is a Microsoft standard for applications sharing data. This makes it possible for a host system to have access to response data in real-time. The suppliers whose software supports DDE includes Inficon TWare32ä, MKS RGA for Windowsä, and Onix Gasworksä.
Application
The transfer chamber on a cluster tool is an example of in situ application that requires an intelligent host. If we monitor the instrument, we will clearly see obvious sources of chemistry change. However, unless the system knows which reactor has been exposed to the transfer chamber at the time of the chemistry change, it has no chance of making use of the data. If we know the state of the operation, from a single instrument we can qualify multiple reactors.
A second case study is the degas reactor on a PVD cluster. The IR20, an infrared sensor that measures the output of the lamps, is used to synchronize the analysis to the degas process. On the standard lamp degas reactor design, the output of the lamps is not a closed loop control, only the setpoint is controlled. In addition to providing the synchronization for the in situ analysis, a process control is added.
From the start, the design principle for in situ hostä was a product that the customer could support. The Microsoft Office Developer’s environment was selected. The Excel module was chosen as the logic engine for the project. Microsoft Visual Basic 6 (VB6) was chosen as the “glue” application. These choices have resulted in a product that is very familiar.
If an engineer decides a change to the analysis is required, if the engineer can use the formula bar in Excel, the engineer is competent to make the change in this product.
In addition, the software that was designed for human interaction is still running in the background, and easily accessible with in situ hostä. In this way we do not compromise our maintenance operation by installing an automation module.
Conclusion
A system to enable in situ and in line metrology that is capable, but also supportable by the fab population is justified. In situ hostä has the features that will enable it to fill the requirement of a user friendly, technically capable, and affordable solution for this valuable role.
Bradshaw
Vacuum Technology 3417
Steven Drive Plano,
Texas 75023, USA (972)
618-7014
