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Positively Pressurized Fluid to Assist Single-Stage Pumping and Prevent Pump Cavitations

IP.com Disclosure Number: IPCOM000124184D
Publication Date: 2005-Apr-11
Document File: 2 page(s) / 32K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method that positively pressurizes a container of fluid before it is pulled into the pumping cavity by a single-stage fluid pump. Benefits include eliminating pump cavitations and improving the dispense uniformity.

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Positively Pressurized Fluid to Assist Single-Stage Pumping and Prevent Pump Cavitations

Disclosed is a method that positively pressurizes a container of fluid before it is pulled into the pumping cavity by a single-stage fluid pump. Benefits include eliminating pump cavitations and improving the dispense uniformity.

Background

Single-stage pumps pull fluid from the container in the re-charge step. Expanding a pump’s bellows creates a low pressure vacuum in the cavity, and this can cause cavitations in the liquid medium which leads to air pockets in the pumping cavity. Air is usually dissolved in the fluid (photo-resist), and de-gasses under low pressure. This air is then trapped in the pump cavity and causes fluid pumping issues to occur. The air is highly expandable/contactable, and causes poor pumping performance that leads to poor uniformity of the deposited/spun on film.  In addition, air bubbles can also lead to film defect issues from poor dispenses, due to drips and the poor cut-off of the dispensing stream.

Air in the pump cavity continues to be a problem, and has not been addressed. Single-stage pumps are still in use on many pieces of processing equipment, and trapped air often leads to non-uniformity in the deposited film.  Pressurized fluid dispenses are also used, but not in conjunction with a pump. The pump is required to deliver a very consistent volume of fluid at a very consistent rate of dispense, which pressurized dispense systems are incapable of doing.

General Description

The disclosed method positively pressurizes a container of fluid before it is pulled into the pumping cavity by a single-stage fluid pump (see Figure 1). A dynamic feedback controller senses internal pump cavity pressure during the re-charge step, and a pressure sensor is connected to the fluid container. The pressure of the fluid container is kept positive to that of the pum...