AVS2013 Session VT+EN+TF-TuA: Vacuum for Industrial Processing

For countless decades we have relied on Mil-Std 883 Method 1014 to insure not only military, but medical, telecommunication, aerospace, aviation, automotive, and hi-rel commercial devices were hermetic. The Howl-Mann equation, based on the ideal gas law, provided the fundamental theory necessary to relate air-equivalent leak rate measurements to tracer gas bombing pressures, times, and Pass/Fail points. Over the past three decades we have tried to find a relationship between moisture ingress and measured leak rate, and only in the last decade have we made fundamental progress toward that goal by using a highly sensitive leak detector and a specially designed mass spectrometer. Moisture ingress departs from ideal gas behavior because of it’s polar nature and the “three monolayer theory” proposed by Aaron DerMarderosian suggests that there is a surface migration component which is often overlooked. This paper will review leak test and IGA data taken over the past 40 years on commercially manufactured hermetic devices with the hope of identifying both dependent and independent variables which will help us predict moisture ingress, and as a result, reliability.

Nowadays a broad range of applications exists using PVD hard coatings produced under vacuum condition. For instance thin diamond-like carbon films and other carbon containing coatings are widely used in car engines and are mandatory for modern fuel saving high pressure Diesel injection systems. Coated cutting tools allow for more severe cutting conditions and/or increased life time which results in lower costs per work piece for the component manufacturer. In applications like steel sheet forming and blanking or plastic injection moulding the coated tools show less adhesive and abrasive wear so that cleaning cycles of the tool can be extended and life time is increased. In some applications the tribological advantages of hard coatings are combined with a desired decorative appearance.

This presentation will give an overview of typical applications of PVD coatings as well as the vacuum coating systems and processes used to manufacture those coatings. Typical failure mechanisms and approaches to overcome limitations and strategies to increase the performance of the coatings and to cope with new requirements in future applications will be presented. Coating performance and failure mechanisms will be reported using techniques like Rockwell indentation, calo test, pin-on-disc test, scanning electron microscopy, energy dispersive x-ray spectroscopy, micro indentation or x-ray diffraction.

Over the past decade the semiconductor industry has relied upon increasingly complex optical and processing techniques to reduce the feature size of microelectronic devices from 100 nm to 22 nm without reducing the wavelength of the lithographic light (193 nm). Since the cost to continue this trend is rapidly becoming prohibitive, the industry is poised to undergo a dramatic shift to Extreme-Ultraviolet Lithography (EUVL) using 13.5 nm (92 eV) radiation. One of the many technical challenges to this transition has been the degradation of throughput and optical resolution caused by the buildup of carbonaceous deposits on optic surfaces resulting from EUV-induced decomposition of organic species which are continuously outgassed during EUV irradiation of the chemically complex photoresists. The National Institute of Standards and Technology (NIST) is uniquely positioned to address this problem using our Synchrotron Ultraviolet Radiation Facility (SURF III) which has a peak output near 13.5 nm. We have directly measured EUV-induced contamination rates of various species over a wide range of partial pressures as a function of EUV intensity, dose and wavelength. Among other findings, these investigations revealed two regimes of contamination. For intensities high enough that the EUV-induced reaction rate far exceeds the thermal desorption rate, the contamination rate is independent of intensity and scales linearly with partial pressure since every adsorbed molecule photoreacts. In the opposite limit, the surface coverage of adsorbed precursor molecules in thermal equilibrium with the gas phase is only slightly perturbed by EUV irradiation. The contamination rate in this case scales linearly with intensity, as expected, but also displays a quasi-logarithmic dependence on partial pressure over many decades. Although initially surprising, this sub-linear pressure scaling was found to be consistent with temperature-programmed desorption measurements (in collaboration with Rutgers University) and with models of desorption kinetics on non-ideal surfaces. I will summarize these results and discuss how fundamental investigations such as these enabled the development of practical methods to systematically measure the contamination produced by outgassing of EUV resists. Together with additional measurements and models, this allowed the makers of EUVL tools to define the maximum allowable level of resist outgas contamination that could be managed by in situ mitigation and cleaning techniques. I will outline the resulting outgas testing protocols first fully implemented at NIST in 2011 to which all resists must be subjected before use in EUVL tools.

In lithography processes handling of reticles and reticle blanks is a very critical step. Defects (particles, scratches, pits and bumps) in a reticle will lead to printed defects on the wafer which is a very important cost and throughput driver. Particles on reticle blanks that are processed in a deposition are also critical. With decreasing node values particle size requirements are going down to values less than 50 nm and the requirements on allowed added particles per reticle pass (PRP) are going down to PRP<0.1 for reticle handlers. These values must be met for both atmospheric handlers and vacuum handlers. Currently there are no qualified atmospheric or vacuum robots and handlers that can meet this requirement.

Therefore TNO is initiating a Shared Research Development program on contamination control of ultra-clean electronics manufacturing to increase productivity, performance and lifetime of manufacturing equipment for the high tech electronics industry. One of the ongoing projects is the development of an ultraclean modular EUV reticle handling system consisting of a robot with a dual end effector, a DualPod opener and a reticle flip unit that will meet the industry requirements with respect to particle free handling.

In this talk we will show the design of the reticle handler, the design rules for meeting the PRP requirements both for an atmospheric handler and a vacuum handler and the issues involved with the qualification of such a machine. Given the total time needed for performing a full reticle pass (opening of DualPod, atmospheric transport of InnerPod, Evacuating LoadLock, Opening InnerPod inside vacuum, Transport of reticle in vacuum, flipping the reticle etc.) , the low number of particles that is allowed to be added per pass and the qualification time needed to measure the added particles, system qualification is a complicated process. The system is currently being built and qualified at TNO with our own in-house built particle scanner. After qualification the system can be added to any reticle processing system that meets SEMI standards and can also be used to qualify sub-modules, such as load locks, robots, flipping unit, etc.