Varian Associates

About: Varian Associates is a based out in . It is known for research contribution in the topics: Beam (structure) & Wafer. The organization has 2160 authors who have published 2591 publications receiving 46002 citations.

Envelope apparatus for localized vacuum processing

Abstract: @ An envelope apparatus is provided for facilitating the production of a vacuum at a localized region on the surface (30) of an article such as a semiconductor wafer. The vacuum permits vacuum processing in the localized region. The envelope apparatus includes an internal processing zone (32) in which the requisite processing level vacuum is maintained. The envelope apparatus also includes intermediate vacuum zones (34) surrounding the internal processing zone. The internal processing zone and surrounding intermediate vacuum zones are exposed at an external surface so that when the external surface is placed in spaced apart, close coupled opposition to the article being processed a graded vacuum seal is formed. The graded seal extends from the internal processing zone, past the intermediate vacuum zones and out to ambient. The envelope apparatus is held either in a fixed position with respect to the surface of the article or actively tracks the topography of the surface of the article so that the gap between the external surface and the surface of the article lies within an acceptable range. For semiconductor processing applications, it has been found that a graded seal formed by two-stage differential pumping and having a gap in the range of 20 micrometers to 40 micrometers will permit vacuums on the order of 10.5 Torr to be maintained within the interior processing zone of the envelope apparatus.

The specification of oscillator characteristics from measurements made in the frequency domain

Abstract: A cross-correlation technique for measuring the very short-term (milliseconds to seconds) properties of stable oscillators is described. Time-dependent functions representing signals from two separate oscillators are led to a function multiplier where the instantaneous product of the functions is made. The oscillators are either set to a given phase relation or allowed a small relative drift so that a slow beat frequency is observed. Short-term fluctuations superimposed upon the slow beat signal from the multiplier output will represent the instantaneous phase difference between the oscillators when the inputs are in quadrature. When the inputs are in and out of phase, the fluctuations represent amplitude fluctuations. The time averaging function is determined by a filter having a rectangular pass band from nearly zero frequency to a cutoff frequency v c . The mean square frequency deviation measured in a bandwidth ω c is obtained by differentiating, filtering, squaring, and averaging the signal from the function multiplier data being taken when the input signals are in quadrature. Mean square averages of amplitude and phase averaged over various bandwidths ω c may be obtained by bypassing the differentiator. Sample data from measurements on hydrogen masers are presented, and the effect of thermal noise is seen to be the major factor limiting the short-term frequency stability of the signals.

Variable field coupled cavity resonator circuit

Abstract: In a resonant chain of coupled cavities such as used in a standing-wave linear particle accelerator it is often desirable to change the field strength in some cavities relative to some others. For example, if the output particle energy of an accelerator is changed by varying the fields of all cavities, the distribution of energies of output particles is disturbed. This distribution is largely controlled by the fields in the first group of cavities traversed by the particle beam. According to the invention, the fields can remain constant in the first group and be varied in following cavities. This is done by varying the distribution of electromagnetic field in one cavity asymmetrically with respect to the preceding and the following cavity. The asymmetric coupling produces different acceleration fields in one part of acceleration structure relative to another part. In an accelerator whose accelerating cavities are coupled via non-interacting side cavities, the different coupling may be produced by making the standing-wave field in one side-cavity asymmetric with respect to its coupling irises.

Signal processor for ultrasonic imaging

Abstract: A signal processor for an ultrasonic imaging system permits the selection of scan angles and focusing distances. The system includes an ultrasonic receiver comprising an array of electromechanical transducers, with the individual transducers being coupled to phase selection circuitry whereby non-continuous delay values can be introduced between adjacent transducers. Proper selection of the delay values between adjacent transducers can accomplish preferential ultrasonic reception or transmission in particular directions. An optimized switching arrangement minimizes the number of electronic components required to provide the desired delay values.

Apparatus for controlling thermal transfer in a cyclic vacuum processing system

Abstract: Apparatus for providing thermal transfer between a semiconductor wafer and a heat sink or source in a vacuum processing chamber includes a platen against which the wafer is sealed to define a thermal transfer region therebetween. The platen includes a passage for gas flow between the chamber and the thermal transfer region and a conduit for circulation of a cooling fluid. The platen further includes a fluid-actuated valve responsive to the pressure of the cooling fluid for closing the passage. When the pressure in the chamber reaches a predetermined value, the cooling fluid is turned on and closes the valve. Gas at the predetermined pressure, typically in the range of 0.5 to 100 Torr, is trapped in the thermal transfer region and conducts thermal energy. In a preferred embodiment, a plurality of platens are positioned on a rotating disc in an ion implantation system.