Behavior and Detection of Particles in Vacuum Processes

Abstract

This paper will describe theoretical calculations of the gravitational fall of particles in vacuum as a function of pressure and particle size, and will give confirming experimental observations of particle deposition on silicon wafers in a test vacuum system. Also, using silicon wafers as test vehicles, observations will be described about the effects of wafer orientation, pumpdown and venting rates, and moving parts on the generation and behavior of particles in a vacuum system. Further confirmation of these results will be presented through the use of a modified laser particle counter in vacuum to directly measure particles in the vacuum chamber.

Ablation debris control by means of closed thick film filtered water immersion

“…Six sites were machined on all samples, each produced using an increasing number of pulses (3,6,12,60, 120 and 480 pulses) to produce an ablation rate matrix. The feature of interest for debris analysis in this study was the feature machined using six pulses.…”

“…They are all limited in two ways: possible damage of a wafer that has already had significant manufacturing effort expended upon it [12] and post process cleaning can only remove debris left behind after machining has finished -it cannot prevent the effects of debris during machining. Because of this, an in-line technique is preferential.…”

Particle Transport in Parallel-Plate Reactors

“…In the present geometry, however, approximating the net deposition as a linear combination of these two terms has not proven as successfid. One complicating issue is that there are two expressions for the pure diffi.wion case, Equation (5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15) for the small-Pe limit, and Equation (5.16) for the large-Pe limit, opposed to the single expression from the Levich-Smoluchowski analysis. Physically, the Levich-Smoluchowski allows deposition to increase without bound as the particles become more difi%sive (because of the infinite domain), while in the present geometry there is an upper bound to diffusive deposition which is imposed by the finite domain.…”

“…A major cause of semiconductor yield degradation is contaminant particles that deposit on wafers while they reside in the many processing tools required to manufacture integrated circuits (Cooper, 1986;Bowling and Larrabee, 1989). Particle deposition on a wafer can occur during wafer handling (e.g., robot arm manipulations or door openings), process setup (e.g., establishing flows, pressures, or temperatures), or during the actual process step (e.g., chemical vapor deposition, plasma etch, or sputtering).…”

“…Bowling and Larrabee (1989) recognized the increasing number of processes being carried out at low pressure, and reported analytic and experimental results for the gravitational deposition of particles in a vacuum chamber. Periasamy et al (1993) looked at low-pressure particle deposition mechanisms including sedimentation, convective-diffision, thermophoresis, and other phoretic forces.…”