Non-Contact Wet-Process Cell Confining Liquid to a Region of a Solid Surface by Differential Pressure

Abstract

An open-bottomed reactor cell for wet processing of substrates can be configured to confine a process liquid to an area under the cell (processing the “internal site”), or alternatively to exclude the process liquid from most of the area under the cell (processing the “external site”) without physical contact between the cell and substrate. A slight underpressure or overpressure maintained inside the main cavity of the cell causes the liquid to form a meniscus in the narrow gap between the cell and substrate rather than flowing outside the desired process area. An area under a peripheral channel outside the main cavity of the cell is shared by both the internal site and the external side, allowing the entire substrate to be processed.

What is claimed is: 
     
         1 . A reactor cell, comprising:
 a cell body having an outer sidewall;   a main cavity in the cell body;   first, second, third, and fourth cavity ports extending from the main cavity to an outer surface of the cell body;   a peripheral channel in the cell body; and   a peripheral port extending from the peripheral channel to the outer surface of the cell body;   wherein the main cavity and the peripheral channel are open at a bottom surface of the cell;   wherein an inner sidewall surrounds the main cavity; and   wherein the peripheral channel extends around the periphery of the main cavity between the inner sidewall and the outer sidewall.   
     
     
         2 . The reactor cell of  claim 1 , further comprising a spout extending into the main cavity from the second cavity port. 
     
     
         3 . The reactor cell of  claim 2 , wherein the spout is longer than about 10 mm. 
     
     
         4 . The reactor cell of  claim 2 , wherein the spout extends to within 2 mm of the bottom surface. 
     
     
         5 . The reactor cell of  claim 1 , wherein the outer sidewall, the inner sidewall, and the peripheral channel have annular cross-sections parallel to the bottom surface. 
     
     
         6 . The reactor cell of  claim 1 , wherein the outer sidewall, the inner sidewall, and the peripheral channel have circular, rectangular, rounded-rectangular, ovoid, or polygonal cross-sections parallel to the bottom surface. 
     
     
         7 . The reactor cell of  claim 1 , wherein at least one of the first cavity port, the second cavity port, the third cavity port the fourth cavity port, or the peripheral port penetrates an outer top of the cell body. 
     
     
         8 . The reactor cell of  claim 1 , wherein the main cavity and the peripheral channel have equal depth. 
     
     
         9 . The reactor cell of  claim 1 , further comprising a height sensor configured to measure a gap height of the bottom surface above a substrate. 
     
     
         10 . The reactor cell of  claim 9 , wherein the gap height is calculated to support a stable meniscus of process liquid across the gap, given a viscosity for the process liquid and a pressure differential between the main cavity and an ambient atmosphere. 
     
     
         11 . The reactor cell of  claim 9 , wherein the gap height is between about 0.2 mm and 0.3 mm. 
     
     
         12 . The reactor cell of  claim 1 , further comprising a pressure sensor configured to measure a pressure inside the main cavity or a pressure differential between the main cavity and an ambient atmosphere outside the cell body. 
     
     
         13 . The reactor cell of  claim 12 , further comprising:
 a pressure monitor configured to monitor the pressure differential between the main cavity and an ambient atmosphere outside the cell body; and   a controller configured to regulate gas flow into and out of the main cavity to keep the pressure differential between a predetermined minimum value and a predetermined maximum value.   
     
     
         14 . The reactor cell of  claim 1 , further comprising:
 a gas conduit connecting an outer end of the peripheral port to an outer end of the first cavity port; and   a liquid source connected to deliver liquid to the main cavity through the second cavity port.   
     
     
         15 . The reactor cell of  claim 1 , further comprising:
 a first seal preventing gas flow through the first cavity port between the main cavity and the outer surface of the cell body; and   a second seal preventing gas flow through the second cavity port between the main cavity and the outer surface of the cell body.   
     
     
         16 . The reactor cell of  claim 1 , further comprising:
 an orifice on an outer end of the fourth cavity port;   a controllable orifice valve connected to the orifice to permit or restrict gas flow between the main cavity and an ambient atmosphere; and   a vacuum pump connected to the third cavity port;   wherein the vacuum pump withdraws gas from the main cavity, or the orifice valve admits ambient gas to the main cavity, as needed to maintain an underpressure in the main cavity compared to the ambient pressure when a process liquid fills the cell to a height above a gap between the bottom surface of the cell and a top surface of a substrate; and   wherein the underpressure causes the process liquid to form a meniscus in the gap below an outer periphery of the peripheral channel.   
     
     
         17 . The reactor cell of  claim 16 , wherein the underpressure is between about −23 and −28 mm H 2 O. 
     
     
         18 . The reactor cell of  claim 1 , further comprising:
 an orifice on an outer end of the fourth cavity port;   a controllable orifice valve connected to the orifice to permit or restrict gas flow between the main cavity and an ambient atmosphere; and   a gas source connected to the third cavity port;   wherein the gas source delivers gas to the main cavity, or the orifice valve allows gas to leave the main cavity, as needed to maintain an overpressure in the main cavity compared to the ambient pressure when a process liquid surrounds the cell to a height above a gap between the bottom surface of the cell and a top surface of a substrate; and   wherein the overpressure causes the process liquid to form a meniscus in the gap below an inner periphery of the peripheral channel.   
     
     
         19 . The reactor cell of  claim 16 , wherein the overpressure is between about +23 and +28 mm H 2 O. 
     
     
         20 . The reactor cell of  claim 1 , further comprising:
 a gas source connected to the third cavity port; and   a vacuum pump connected to the fourth cavity port;   wherein the gas source delivers gas to the main cavity, or the vacuum pump draws gas from the main cavity, as needed to maintain a pressure differential between the main cavity and the ambient atmosphere when a process liquid is present inside or outside the cell to a height above a gap between the bottom surface of the cell and a top surface of a substrate;   wherein the pressure differential causes the process liquid to form a meniscus in the gap below a periphery of the peripheral channel;   wherein the pressure differential is negative if the process liquid is inside the cell; and   wherein the pressure differential is positive if the process liquid is outside the cell.