Research Disclosure

摘要

According to an aspect of the present invention, there is provided a clamp assembly, the clamp assembly comprising a clamp configurable to clamp a support member to a lower base surface of the clamp by electrostatic adhesiun. and an arrangement configurable to direct a gas to the lower base surface of the clamp, wherein the arrangement is configurable to humidify the gas by exposing the gas to a liquid. Advantageously, a humidified gas may more effectively discharge the lower base surface of the clamp than a non-humidified gas. The clamp may be configurable to clamp an article to an upper base surface of the clamp by electrostatic adhesion. Advantageously, this electrostatic clamping may enable clamping a substrate in vacuum. The arrangement may be configurable to condense at least a part of the liquid on the lower base surface of the clamp and to remove the at least a part of the liquid from the lower base surface of the clamp. The arrangement may be configurable to maintain a pressure of the gas at or above a first threshold, wherein the first threshold corresponds to a pressure that equals 80% of a vapor pressure of the liquid at a temperature of the lower base surface of the clamp. Alternatively the first threshold may correspond to a pressure that equals 90% or 100% of a vapor pressure of the liquid at a temperature of the lower base surface of the clamp. The percentage may depend on the lower base surface condition to condense at least part of the liquid on the lower base surface of the clamp. Advantageously, maintaining a pressure of the gas at or above this threshold may result in condensation of the liquid forming on the lower base surface of the clamp, which may accelerate discharging of the lower base surface. The arrangement may be configurable to maintain a pressure of the gas at or below a second threshold, wherein the second threshold corresponds to a pressure sufficient to move or lift the clamp with respect to the assembly. The arrangement may be configurable to remove the humidified gas from the lower base surface of the clamp. Advantageously, this may remove a residual charge from the lower base surface of the clamp. The lower base surface of the clamp may be provided with an opening configured to direct the humidified gas out of the opening. The arrangement may comprise a pump. The arrangement may comprise at least one pressure sensor. The arrangement may comprise a controller. The controller may be communicably coupled in the pump and the pressure sensor. The arrangement may comprise a reservoir for the liquid. The arrangement may he configurable to expose the gas to the liquid by directing the gas through the reservoir. The lower base surface of the clamp may comprise at least one burl. The at least one burl may define at least one channel between the clamp and a support member. An upper surface of the support member may be provided with an opening configured to direct the humidified gas out of the opening. The clamp assembly may comprise one or more fluid conduits. The arrangement may be configurable to direct the gas into the at least one channel via the one or more fluid conduits. The clamp may be configurable to be coupled to the support member by electrostatic adhesion. According to a further aspect of the present invention, there is provided a method of discharging a lower base surface of a clamp. wherein the clamp is configurable to clamp a support member to the lower base surface of the clamp by eleclroslalic adhesion, and wherein the method comprises the steps of: humidifying the gas by exposing the gas to a liquid; and directing the humidified gas to the lower base surface of the clamp. The method may further comprises a step of pressurizing the gas to between a first and a second threshold, wherein the first threshold is 80% or 90% or 100% of a vapor pressure of the gas at a temperature of the lower base surface of the clamp, and the second threshold is a pressure sufficient to move or lift the clamp with respect to the support member or the assembly. The method may further comprise a step, e.g. a subsequent step, of removing the humidified gas from the lower base surface of the clamp. The step of exposing the gas to a liquid may comprise directing the gas through a reservoir of the liquid. The liquid may comprises at least one of water and/or isopropanol alcohol. The lower base surface of the clamp may be discharged after the article has been removed from the upper base surface of the clamp.