Reticle damage due to ESD is a well-known phenomenon.. A defective reticle prints defective dies1. Unfortunately, ESD damage to reticles is a common problem and becoming more common as time goes on. We have developed a diagnostic tool called the Canary Reticle for the purpose oflocating the sources of ESD damage within a photo bay. Over the past year, we have used it to study the effects of ESD on reticles. In this article, we summarize the findings ofthe study2. Extremely high levels of electrostatic charge develops in cleanrooms in general and particularly so for semiconductor cleanrooms. The absence of surface contamination, the action ofihe HEPA filters in sweeping ions out ofthe room and low humidity results in much higher voltage levels on objects as compared to conventional rooms. Many ofthe objects used must be excellent insulators or are insulators, but have been selected for other physical properties. Examples are quartz reticles and Teflon wafer cassettes and plastic reticle pods. The chrome structures on reticles have sharp corners, which concentrate the electric fields, making breakdown ofthe air between them easy to occur. The voltage on a conductor is the same at all points. Thus, in the presence of a voltage gradient (Electric field), the potential differences are focused into the gaps between the chrome structures, again making discharge easy. It is hoped that by understanding the mechanisms for ESD damage photo engineers will better be able to avoid it.
Electrostatic discharge (ESD) effects on reticles are a well known and dreaded phenomenon in the semiconductor industry. Isolated chrome structures in the scribe lane but also in the device content are susceptible to ESD damage during reticle handling or storage. So far electrical field measurements document the risk by numbers, but what is behind this number? Is it dangerous or just unpleasant? What is about cumulative effects? CANARY is the answer on this. An ESD test reticle with such a high sensitivity that several hundreds of handling cycles, representing reticle lifetimes of several months, can be simulated within a few hours. Customized versions can easily be designed in order to reflect customer specific design and technology requirements.
Integration and automation have gained more and more ground in modern IC-manufacturing.
It is difficult to make a direct calculation of the profit these
investments yield. On the other hand, the demands to man, machine and technology
have increased enormously of late; it is not difficult to see that only by means of
integration and automation can these demands be coped with. Here are some salient
U the complexity and costs incurred by the equipment and processes have got
. owing to the reduction of all dimensions, the tolerances within which the
various process steps have to be carried out have got smaller and smaller and
the adherence to these tolerances more and more difficult
U the cycle time has become more and more important both for the development and
control of new processes and, to a great extent, for a rapid and reliable
supply to the customer.
In order that the products be competitive under these conditions, all sort of costs
have to be reduced and the yield has to be maximized.
Therefore, the computer-aided control of the equipment and the process combined with
an automatic data collection and a real-time SPC (statistical process control) has
become absolutely necessary for successful IC-manufacturing.
Human errors must be eliminated from the execution of the various process steps by
automation. The work time set free in this way makes it possible for the human
creativity to be employed on a larger scale in stabilizing the processes. Besides, a
computer-aided equipment control can ensure the optimal utilization of the equipment
round the clock.