US20140262028A1

US20140262028A1 - Non-Contact Wet-Process Cell Confining Liquid to a Region of a Solid Surface by Differential Pressure

Info

Publication number: US20140262028A1
Application number: US14/013,281
Authority: US
Inventors: Rajesh Kelekar
Original assignee: Intermolecular Inc
Current assignee: Intermolecular Inc
Priority date: 2013-03-13
Filing date: 2013-08-29
Publication date: 2014-09-18
Also published as: US20140273314A1; US20140272112A1; US9305791B2; US20140273309A1; US9466499B2; US20140273497A1

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.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Prov. Pat. App. No. 61/780,128, filed 13 Mar. 2013, which is entirely incorporated by reference herein for all purposes.

BACKGROUND

Related fields include combinatorial methods for device process development; in particular, combinatorial methods of developing and optimizing wet processes and the formulations used in those processes.
A variety of electronic, optical, or micro-mechanical devices are fabricated by forming many small components on a common larger substrate (e.g., a semiconductor wafer or a sheet of glass, polymer, or carbon). “Wet” processes, involving the application of liquid to the substrate, may be used in many phases of fabrication: cleaning, etching, polishing, texturing, passivation and other surface reactions, and film-deposition methods such as plating, dip-coating, and spin-coating.
Often the fabrication of a particular device involves both wet processes and “dry” (no-liquid) processes such as treatments with gas, plasma, solid particulates, or electrical and magnetic fields. The performance of these devices is often highly sensitive to contamination. Performing as many of the processes as possible in the same controlled environment (e.g., the same process chamber or sealed group of chambers) minimizes the risk of exposure. The risk of contamination exposure is also reduced by reducing the need for chamber-cleaning operations that admit ambient atmosphere to the chamber; confining both dry and wet process substances to the substrate surface, where possible, is helpful.
Since most substrates are flat, the confinement of liquid can be challenging. Often the liquid is dispensed from a cell, or reactor, inside the chamber. An open end of the cell may seal to the substrate by touching it. However, unwanted particle deposition, abrasion, and other forms of damage may result from the contact. This may be tolerable if the affected area does not include any device features; for example, the extreme outer periphery of a substrate may be left unprocessed to facilitate robotic handling or for other reasons. However, some fabrication methods call for isolated processing of one or more regions of the substrate that may be adjacent to other regions where devices are fabricated.
One example of a requirement for isolated processing of regions on a substrate is high-productivity combinatorial (HPC) processing. As part of the discovery, optimization and qualification of each unit process, it is desirable to rapidly and efficiently test different i) materials, ii) unit-process conditions, iii) sequences and integrations of unit-process modules in a processing tool, iv) sequences of processing tools in different process-integration flows, and (v) combinations thereof. Results can be acquired faster and at lower cost if each set of variables tested does not consume an entire substrate; i.e., if multiple materials, process conditions, sequences, integration flows, or combinations can be tested on isolated sites of the same substrate. HPC processing techniques have been successfully adapted to both dry and wet chemical processing.
Known non-contact approaches to site-isolated or substrate-confined wet processing include suspending the substrate with the process surface facing downward and sending the liquid upward to the surface with atomizers or impellers. Other non-contact approaches include dispensing a barrier liquid or gas around the periphery of the cell; the pressure of the barrier liquid or gas acts to confine the process liquid to the desired area of the substrate. The mechanisms for these approaches are complex and costly. Some require high-quality consumables that also add cost. Some approaches also leave undesired gaps between processed sites, or may require moving the reactor cell or the substrate to produce contiguous or overlapping processed sites.
Therefore, the industry would benefit from simple, robust non-contact techniques for confining wet-process liquids to isolated sites on a substrate. Additional benefits would result from an ability to process contiguous or overlapping sites without needing to translate the reactor cell(s) or the substrate.

SUMMARY

The following summary presents some concepts in a simplified form as an introduction to the detailed description that follows. It does not necessarily identify key or critical elements and is not intended to reflect a scope of invention.
The body of a reactor cell for processing an isolated site on a substrate has a peripheral channel around its main cavity. At least four cavity ports (CP1, CP2, CP3, CP4) connect the outside of the body to the main cavity, and at least one peripheral port (PP) connects the outside of the body to the peripheral channel. The manipulation of fluid (meaning either liquid or gas) communication through the ports allows process liquid to be confined to either (1) an area of the substrate inside a circle defined by the outer border of the peripheral channel (the “internal site”), or (2) an area of the substrate outside a circle defined by the inner border of the peripheral channel (the “external site”). If both areas are processed in sequence, there is an overlap region, defined by the inner and outer borders of the peripheral channel, which is processed twice. For example, if the opening of the peripheral channel facing the substrate is circular, the twice-processed overlap region is annular. In operation, the reactor cell is placed just slightly above the substrate surface, never touching. The gap height is chosen in a range where surface tension dominates the process liquid's wetting behavior (e.g., about 0.25 mm).
To process the internal site, CP1 is connected to PP; CP2 is connected to a process-liquid source; CP3 is connected to a controllable exhaust (e.g., a vacuum pump configured to evacuate the main cavity); and CP4 is connected to a controllable gas source. As liquid is introduced through CP2, gas inflow through CP4 and gas outflow through CP3 are balanced to maintain a constant underpressure, compared to the ambient chamber pressure outside the reactor cell, of about −25 mm H₂O. For example, CP3 may be connected to an exhaust via a mass flow controller and CP4 may have an orifice connected to the chamber ambient atmosphere. The orifice controls the flow impedance, the mass flow controller controls the flow rate and the two controls together maintain the desired underpressure in the reactor cell. The liquid is allowed to fill the cavity and channel above the gap; e.g., to a height of about 6 mm above the substrate. Meniscus effects, coupled with the pressure differential, cause the process liquid to wet up the peripheral channel rather than spreading across the substrate outside the cell.
To process the external site, PP is opened to the chamber ambient; CP1 and CP2 are sealed; gas flows controllably in through CP3 and out through CP4. For example, CP3 may be connected to a pressure source (e.g., a container of pressurized gas or a gas compressor) and CP4 may have an orifice connected to the chamber ambient atmosphere. The control of flow impedance by the orifice and the control of flow by the mass flow controller together maintain the desired overpressure in the reactor cell. Process liquid is introduced outside the cell while the gas inflow and outflow inside the main cavity is controlled to produce a slight overpressure (˜+25 mm H₂O) compared to the chamber ambient. The liquid is allowed to fill the peripheral channel above the gap; e.g., to a height of about 6 mm above the substrate. Meniscus effects, coupled with the pressure differential, cause the process liquid to wet up the peripheral channel rather than spreading across the substrate into the area under the main cavity.
In both cases, the process liquid wetting up into the peripheral channel covers the area of substrate directly under the peripheral channel. Thus this area is common to the external site and the internal site, and will be processed twice as a result of sequential processing of the external and internal sites.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings may illustrate examples of concepts, embodiments, or results. They do not define or limit the scope of invention. They are not drawn to any absolute or relative scale. In some cases, identical or similar reference numbers may be used for identical or similar features in multiple drawings.

FIG. 1 is a schematic diagram of device development using primary, secondary, and tertiary screening methods that include HPC processing and may also include conventional processing.

FIG. 2 is a simplified schematic diagram illustrating a general methodology for combinatorial process sequence integration that includes site-isolated processing, conventional processing, or both.

FIGS. 3A and 3B are two conceptual views of a combinatorially-processed substrate.

FIG. 4 is a schematic diagram of one type of generic combinatorial wet processing system used to investigate processes involving liquids.

FIGS. 5A, 5B, and 5C are various schematic views of an example of a no-contact reactor cell body.

FIGS. 6A and 6B are schematic cross-sections of a no-contact reactor cell with a controllable orifice processing an internal site and an external site of a substrate.

FIGS. 7A and 7B are schematic cross-sections of a no-contact reactor cell with controllable gas inlet and exhaust processing an internal site and an external site of a substrate.

FIG. 8 is a flowchart of a method for processing an internal site on a substrate.

FIG. 9 is a flowchart of a method for processing an external site on a substrate.

FIGS. 10A-10D are conceptual views of substrates with sequentially processed internal and external sites.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

In the following description, methods for evaluating processing conditions and wet chemicals are illustrated using a simple planar structure. The description and teachings can be readily applied to any simple or complex testing methodology.
Unless the text or context clearly dictates otherwise: (1) By default, singular articles “a,” “an,” and “the” (or the absence of an article) may encompass plural variations; for example, “a layer” may mean “one or more layers.” (2) “Or” in a list of multiple items means that any, all, or any combination of less than all the items in the list may be used in the invention. (3) Where a range of values is provided, each intervening value is encompassed within the invention. (4) “About” or “approximately” contemplates up to 10% variation; “substantially” contemplates up to 5% variation. (5) “Fluid” may be either liquid or gas. (6) A “port” is an opening for fluid communication between otherwise separate spaces. (7) “Wet” and “wick” describe spreading of liquid on a surface due to adhesion. (8) “Process liquid” may include colloids or suspensions containing solid particles and capable of flowing (e.g., slurries).
HPC generally varies materials, unit processes, or process sequences (collectively, “candidates”) across multiple regions on a substrate. The results of the variations can be characterized to determine which candidates merit further evaluation or may be the most suitable for production or high-volume manufacturing. Systems and methods for HPC processing are described in U.S. Pat. Nos. 7,544,574, 7,824,935, 7,871,928, 7,902,063, 7,947,531, and 8,084,400, and also in US Published Pat. Apps. 2007/0267631, 2007/0202614, and 2007/0202610. All of these are incorporated by reference herein for all purposes.
FIG. 1 is a schematic diagram of device development using primary, secondary, and tertiary screening methods that include HPC processing and may also include conventional processing. The diagram 100 illustrates how the selection of a subset of the most promising candidates at each stage decreases the relative number of combinatorial processes that need to be run in the next stage. Generally, a large number of processes are performed during a primary screening stage. Based on the primary-screening results, a subset of promising candidates is selected and subjected to a secondary screening stage. Based on the secondary-screening results, a smaller subset of promising candidates is selected and subjected to a tertiary screening stage, and so on. In addition, feedback from later stages to earlier stages can be used to refine the success criteria and provide better screening results.
For example, thousands of materials may be evaluated during a materials discovery stage 102, a primary screening stage. Techniques for this stage may include, e.g., dividing substrates into coupons and depositing materials on each of the coupons. Materials, deposition processes, or both may vary from coupon to coupon. The processed coupons are then evaluated using various metrology tools, such as electronic testers and imagers. A subset of promising candidates is advanced to the secondary screening stage, materials and process development stage 104.
Hundreds of materials (i.e., a magnitude smaller than the primary stage) may be evaluated during the materials and process development stage 104, which may focus on finding the best process for depositing each of the candidate materials. A subset of promising candidates is selected to advance to the tertiary screening stage, process integration stage 106.
Tens of material/process pairs may be evaluated during the process integration stage 106, which may focus on integrating the selected processes and materials with other processes and materials. A subset of promising candidates is selected to advance to device qualification stage 108.
A few candidate combinations may be evaluated during the device qualification stage 108, which may focus on the suitability of the candidate combinations for high volume manufacturing. These evaluations may or may not be carries out on full-size substrates and production tools. Successful candidate combinations proceed to pilot manufacturing stage 110.
The schematic diagram 100 is an example. The descriptions of the various stages are arbitrary. In other embodiments of HPC, the stages may overlap, occur out of sequence, or be described or performed in other ways.
HPC techniques may arrive at a globally optimal process sequence by considering the interactions between the unit manufacturing processes, the process conditions, the process hardware details, and material characteristics of components. Rather than only considering a series of local optima for each unit operation considered in isolation, these methods consider interaction effects between the multitude of processing operations, influenced by the order in which they are performed, to derive a global optimum sequence order.
HPC may alternatively analyze a subset of the overall process sequence used to manufacture a device; the combinatorial approach may optimize the materials, unit processes, hardware details, and process sequence used to build a specific portion of the device. Structures similar to parts of the subject device structures (e.g., electrodes, resistors, transistors, capacitors, waveguides, or reflectors) may be formed on the processed substrate as part of the evaluation.
While certain materials, unit processes, hardware details, or process sequences are varied, other parameters (e.g., composition or thickness of the layers or structures, or the unit process action such as cleaning, surface preparation, deposition, surface treatment, or the like) are kept substantially uniform across each discrete region of the substrate. Furthermore, while different materials or unit processes may be used for corresponding layers or steps in the formation of a structure in different regions of the substrate, the application of each layer or the use of a given unit process may be substantially consistent among the different regions. Thus, aspects of the processing may be uniform within a region (inter-region uniformity) or between regions (intra-region uniformity), as desired.
The result is a series of regions on the substrate that contain structures or unit process sequences that have been uniformly applied within that region or, as applicable, across different regions. This process uniformity allows comparison of the properties within and across the different regions so that the variations in test results are due to the intentionally varied parameter (e.g., material, unit process, unit process parameter, hardware detail, or process sequence) and not a lack of process uniformity. The positions of the discrete regions can be defined as needed, but are preferably systematized for ease of tooling and design of experiments. The number, location, and variants of structures in each region preferably enable valid statistical analysis of test results within and between regions.
FIG. 2 is a simplified schematic diagram illustrating a general methodology for combinatorial process sequence integration that includes site-isolated processing, conventional processing, or both. In one embodiment, the substrate is initially processed using conventional process N, then processed using site isolated process N+1. During site isolated processing, an HPC module may be used, such as the HPC module described in U.S. Pat. No. 8,084,400. The substrate can then be processed using site isolated process N+2, and thereafter processed using conventional process N+3. Testing is performed and the results are evaluated. The testing can include physical, chemical, acoustic, magnetic, electrical, optical, etc. tests. From this evaluation, a particular process from the various site isolated processes (e.g. from steps N+1 and N+2) may be selected and fixed so that additional combinatorial process sequence integration may be performed using site isolated processing for either process N or N+3. For example, a next process sequence can include processing the substrate using site isolated process N, conventional processing for processes N+1, N+2, and N+3, with testing performed thereafter.
Various other combinations of conventional and combinatorial processes can be included in the processing sequence. The combinatorial process sequence integration can be applied to any desired segments and/or portions of an overall process flow. Characterization can be performed after each process operation and/or series of process operations within the process flow as desired. Furthermore, the flows can be applied to entire monolithic substrates, or portions such as coupons.
Parameters which can be varied between site-isolated regions include, but are not limited to, process material amounts, reactant species, process temperatures, process times, process pressures, process flow rates, process powers, reagent compositions, the rates at which the reactions are quenched, atmospheres in which the processes are conducted, order in which materials are deposited, hardware details including gas or liquid distribution assemblies, etc. These process parameter examples are not an exhaustive list; numerous other process parameters used in device manufacturing may also be varied.
Within a region, the process conditions may be kept substantially uniform, in contrast to gradient processing techniques which rely on the inherent non-uniformity of the material deposition. That is, each site-isolated region may be processed in a substantially consistent and substantially uniform way, even though the materials, processes, and process sequences may vary from region to region over the substrate. Thus, the testing will find optima without interference from process variation differences between processes that are meant to be the same. Regions may be contiguous, or may overlap, or may be surrounded by unprocessed margins. Where regions are contiguous or overlapping, the materials or process interactions in the overlap may be uncertain. However in some embodiments at least 50% of the area within a region is uniformly processed and all testing can be done in that uniform area. Experiments may be designed to allow potential overlap only between materials or processes that will not adversely affect the result of the tests.
Combinatorial processing can be used to determine optimal processing parameters (e.g., time, concentration, temperature, stirring rate, etc.) of wet processing techniques such as wet etching, wet cleaning, rinsing, and wet deposition techniques (e.g., electroplating, electroless deposition, chemical bath deposition, dip coating, spin coating, and the like).
FIGS. 3A and 3B are two conceptual views of a combinatorially-processed substrate. FIG. 3A is a top view of substrate 300 showing 6 site-isolated regions 302, 312, 322, 332, 342, and 352. Although substrate 300 is rectangular in the illustration, any suitable substrate shape such as circular, square, or polygonal may also be used in some embodiments. Although the site-isolated regions 302, 312, 322, 332, 342, and 352 are shown as separated from each other by unprocessed areas of substrate 300, in some embodiments the site-isolated regions may be contiguous or partially overlapping. Some of the site-isolated regions may be chosen to be processed identically (as regions 302 and 352 are shown here with identical shading) to test the consistency of the results on different regions of the same substrate.
FIG. 3B is a sectional view through section line A-A of FIG. 3A showing different films formed on site-isolated regions 332, 342, and 352. The regions could alternatively have identical (or no) films formed, and the variation could instead be in the cleaning, etching, polishing, or some other treatment of the different regions.
FIG. 4 is a schematic diagram of one type of generic combinatorial wet processing system used to investigate processes involving liquids. Substrate 300 and site-isolated regions 332, 342, and 352 are shown in cross-section similarly to FIG. 3B. Each site-isolated region is covered by one of the individual reactor cells 402, 412, and 422. The reactor cells confine different liquids 406, 416, and 426 to their main cavities 401, 411, and 421 and thus to the underlying regions 332, 342, and 352 of the substrate. Conduits 404, 414, and 424 are connected to the cells. Some types of conduits deliver process liquid to the reactor cells, while other conduits may remove the process liquids, inject or remove gases or buffer liquids, or maintain pressure equilibrium with the chamber ambient. The illustrated conduits 404, 414, and 424 are in fluid communication with main cavities 401, 411, and 421 of reactor cells 402, 412, and 422 through ports 405, 415, and 425 respectively. Wet processes such as cleaning, etching, surface treatment, surface functionalization, etc. may be investigated by HPC by varying liquid parameters (e.g., composition, temperature, exposure time) between different site-isolated regions.
FIGS. 5A, 5B, and 5C are various schematic views of an example of a no-contact reactor cell body. FIG. 5A is a bottom perspective view, FIG. 5B is a top perspective view, and FIG. 5C is a cross-section through section A-A of FIG. 5B. A main cavity 501 is defined by an inner ceiling 511 and an inner sidewall 521 extending to the cell bottom surface 533. A peripheral channel 502 extends around the periphery of main cavity 501 between the inner sidewall 521 and the outer sidewall 523. Peripheral channel 502 is also open at the cell bottom surface 533. At least one peripheral port 512 extends between peripheral channel 502 and the outer surface of the cell body. At least four cavity ports 541, 551, 561, and 571 extend between main cavity 501 and the outer surface of the cell body. The outer surface of the cell body includes outer top 513 and outer sidewall 523.
Optionally, a spout 531 may extend into main cavity 501 to extend the second cavity port 551 that delivers liquid to main cavity 501. Spout 531 may prevent incoming liquid from being drawn into any nearby gas exhausts operated through, for example, third cavity port 561. For example, a spout longer than 10 mm may effectively prevent liquid from being drawn into a nearby gas exhaust. Depending on its length, spout 531 may also be used to withdraw a liquid from main cavity 501 if coupled to a pump by appropriate controllable valves. For example, the spout may extend to within 2 mm of the bottom surface. In some embodiments, an orifice 543 may be included on fourth cavity port 571 to control inflow or outflow of gas to and from main cavity 501.
Numerous variations on the illustrated example are possible. For example, outer sidewall 523, inner sidewall 521, and peripheral channel 502 need not have annular cross-sections parallel to cell bottom surface 533. Rectangular, rounded-rectangular, polygonal, or ovoid cross-sections may be used. Peripheral port 512 and cavity ports 541, 551, 561, and 571 need not penetrate through outer top 513 as shown, but may alternatively penetrate through outer sidewall 523. The ports need not be arranged in a straight line as illustrated, but may be arranged in any convenient configuration. Peripheral channel 502 need not have the same depth as main-cavity 501 as shown; either one may extend further into the cell body than the other.
FIGS. 6A and 6B are schematic cross-sections of a no-contact reactor cell with a controllable orifice processing an internal site and an external site of a substrate. In FIG. 6A, a reactor cell with an orifice 643 processes an interior site on substrate 600. The reactor cell bottom surface 633 does not touch the substrate 600, but hovers over it at a gap height 610. Gap height 610 may be between about 0.2 mm and about 0.3 mm. Gap height 610 may be controlled by a height (or proximity) sensor 647 in communication with a controller 608, such as a computer. Height sensor 647 may be on the reactor cell, or may be part of a substrate holder, or may be part of a machine vision system. Some embodiments of machine-vision-based height sensors may operate from outside the chamber, viewing the cells and substrates through windows.
The outer end of peripheral port 612 and the outer end of first cavity port 641 are connected to each other by gas conduit 604 to maintain pressure equilibrium between main cavity 601 and peripheral channel 602. A liquid source 605 is connected by liquid conduit 614 to second cavity port 651, delivering liquid 606 to the substrate through spout 631. Liquid delivery may also be controlled by controller 608. Gas is drawn out of main cavity 601 through the third cavity port 661, for example by a vacuum pump 615. The pressure inside main cavity 601 and peripheral channel 602 is maintained slightly lower than ambient by a control loop including a pressure sensor 607, pressure monitor 617, orifice control 612, and orifice valve 637. The control loop components 607, 617, 627, and 637, as well as vacuum pump 615, may also be controlled by controller 608.
Pressure sensor 607 measures the pressure inside the reactor cell or the pressure differential between the cell interior and the chamber ambient. Pressure monitor 617 monitors the pressure differential between the cell interior and the chamber ambient. In some embodiments, pressure monitor 617 monitors the signals from two or more pressure sensors, and one of the sensors may be in the chamber outside the reactor cell. If the pressure inside main cavity 601 drops below a predetermined minimum value, controller 608 causes orifice valve 637 to open, admitting ambient gas from the surrounding chamber, and optionally may decrease or stop the pumping function a vacuum pump 615, until the pressure is within a desired range. If the pressure inside main cavity 601 rises above a predetermined maximum value, controller 608 causes orifice valve 637 to close, and optionally may increase the pumping function of vacuum pump 615, until the pressure is within a desired range.
The desired range and the minimum and maximum pressure values are calculated to keep liquid 606 confined to main cavity 601 and peripheral channel 602. Liquid 606 wets up the walls of main cavity 601 and peripheral channel 602, and is confined in gap 610 by meniscus 616. The pressure range inside the cell within which this condition can be maintained can be calculated from factors such as the viscosity of liquid 606, the height of gap 610, and the adhesion of liquid 606 to the materials of the top surface of substrate 600 and the walls of the main cavity and peripheral channel (for example, the hydrophilic or hydrophobic properties of those surfaces if a liquid 606 is an aqueous solution). For example, for many process liquids 606, a pressure range between −0.9 and −1.1″ (−23 to −28 mm) H₂O will confine the process liquid to the interior site.
In FIG. 6B, a reactor cell with an orifice 643 processes an exterior site on substrate 600. The reactor cell bottom surface 633 does not touch the substrate 600, but hovers over it at a gap height 610. Gap height 610 may be controlled by a height sensor 647 in communication with a controller 608.
In this configuration, peripheral port 612 is open to maintain pressure equilibrium between peripheral channel 602 and the chamber ambient. First cavity port 641 and second cavity port 651 are sealed, as schematically symbolized by stoppers 624. A gas source 625 is connected by gas conduit 634 to third cavity port 661, delivering gas to the main cavity. The pressure inside main cavity 601 is maintained slightly higher than ambient by the control loop including pressure sensor 607, pressure monitor 617, orifice control 612, and orifice valve 637. Orifice valve 637 may be controllable to open and close, thus permitting or restricting gas flow between the main cavity and the chamber ambient. In some embodiments, valve 637 may be continuously variable between a full-open position and a fully-closed position. The control loop components 607, 617, 627, and 637, as well as gas source 625, may also be controlled by controller 608.
If the pressure inside main cavity 601, as measured by pressure sensor 607 and monitored by pressure monitor 617, drops below a predetermined minimum value, controller 608 causes orifice valve 637 to close and gas source 625 to deliver more gas to raise the pressure to a value within the desired range. If the pressure inside main cavity 601 rises above a predetermined maximum value, controller 608 causes orifice valve 637 to open, and optionally may decrease or stop delivery of gas from source 625, until the pressure is within the desired range. The minimum and maximum pressure values are calculated to keep liquid 626 excluded from main cavity 601 and confined to peripheral channel 602 and an area outside the reactor cell. Liquid 626 wets up the walls of peripheral channel 602 and the outer cell body wall 613, and is confined in gap 610 by meniscus 636. The pressure range inside the cell within which this condition can be maintained can be calculated from factors such as the viscosity of liquid 626, the height of gap 610, and the adhesion of liquid 626 to the materials of the top surface of substrate 600 and the walls of the reactor cell (for example, the hydrophilic or hydrophobic properties of those surfaces if a liquid 626 is an aqueous solution). For many process liquids 626, a pressure range between +0.9 and +1.1″ (+23 to +28 mm) H₂O will confine the process liquid to the exterior site.
Processing the common exterior site of multiple reactor cells can be useful in HPC to map, and remove from the individual SIR results, any process non-uniformity varying spatially across the substrate due to the hardware or some underlying non-uniformity of the substrate itself.
FIGS. 7A and 7B are schematic cross-sections of a no-contact reactor cell with controllable gas inlet and exhaust processing an internal site and an external site of a substrate. In FIG. 7A, a reactor cell with an orifice 733 processes an interior site on substrate 700. The reactor cell bottom surface 733 does not touch the substrate 700, but hovers over it at a gap height 710. Gap height 710 may be between about 0.2 mm and about 0.3 mm. Gap height 710 may be controlled by a height sensor 747 in communication with a controller 708, such as a computer, similarly to the embodiment illustrated in FIG. 6A.
Peripheral port 712 and first cavity port 741 are connected to each other by gas conduit 704 to maintain pressure equilibrium between main cavity 701 and peripheral channel 702. A liquid source 705 is connected by liquid conduit 714 to second cavity port 751, delivering liquid 706 to the substrate through spout 731. Liquid delivery may also be controlled by controller 708. Gas is drawn out of main cavity 701 through the fourth cavity port 771, for example by a vacuum pump 715. Gas from gas source 725 may be let into the main cavity through conduit 734 and port 761. In some embodiments, the connections and roles of port 761 and port 771 may be reversed. The pressure inside main cavity 701 and peripheral channel 702 is maintained slightly lower than ambient by a control loop including a pressure sensor 707, pressure monitor 717, and flow control 757. Flow control 757 may be configured to control both the inflow through port 761 and the outflow through port 771. The control loop components 707, 717, 757, 725, and 715 may also be controlled by controller 708.
If the pressure inside main cavity 701, as measured by pressure sensor 707 and monitored by pressure monitor 717, drops below a predetermined minimum value, controller 708 causes more gas delivery from gas source 725, and optionally may decrease or stop the pumping function a vacuum pump 715, until the pressure is within a desired range. If the pressure inside main cavity 701 rises above a predetermined maximum value, controller 708 increases the pumping function of vacuum pump 715, and optionally may decrease or stop the gas delivery from gas source 725, until the pressure is within a desired range. As in FIG. 6A, the desired range and the minimum and maximum pressure values are calculated to keep liquid 706 confined to main cavity 701 and peripheral channel 702. Liquid 706 wets up the walls of main cavity 701 and peripheral channel 702, and is confined in gap 710 by meniscus 716.
In FIG. 7B, a reactor cell with an orifice 733 processes an exterior site on substrate 700. The reactor cell bottom surface 733 does not touch the substrate 700, but hovers over it at a gap height 710. Gap height 710 may be controlled by a height sensor 747 in communication with a controller 708.
In this configuration, peripheral port 712 is open to maintain pressure equilibrium between peripheral channel 702 and the chamber ambient. First cavity port 741 and second cavity port 751 are sealed, as schematically symbolized by stoppers 724. Gas source 725 remains connected by gas conduit 734 to third cavity port 761 and vacuum pump 715 remains connected to fourth cavity port 771. The pressure inside main cavity 701 is maintained slightly higher than the chamber ambient by the control loop including pressure sensor 707, pressure monitor 717, and flow control 757 that may control both inflow through third cavity port 761 and outflow through fourth cavity port 771. The control loop components may also be controlled by controller 708.
If the pressure inside main cavity 701, or the pressure differential between main cavity 701 and the chamber ambient, drops below a predetermined minimum value, controller 708 causes more gas delivery from gas source 725, and optionally may decrease or stop the pumping function a vacuum pump 715, until the pressure is within a desired range. If the pressure inside main cavity 701 rises above a predetermined maximum value, controller 708 increases the pumping function of vacuum pump 715, and optionally may decrease or stop the gas delivery from gas source 725, until the pressure is within a desired range.
Thus the functions and connections of ports 761 and 771 are the same when processing an external site in FIG. 7B as when processing an internal site in FIG. 7A; only the minimum, maximum, and desired range of differential pressures have changed to provide an overpressure in the main cavity instead of an underpressure. As in FIG. 6B, the minimum and maximum pressure values are calculated to keep liquid 726 excluded from main cavity 701 and confined to peripheral channel 702 and an area outside the reactor cell. Liquid 726 wets up the walls of peripheral channel 702 and the outer cell body wall 713, and is confined in gap 710 by meniscus 736.
The examples in FIGS. 6A-7B demonstrate that any suitable known method of regulating pressure inside the reactor cell to be slightly under or slightly over chamber ambient can be used in some variant of this type of reactor cell.
FIG. 8 is a flowchart of a method for processing an internal site on a substrate. Initially, the connections to the cavity and peripheral ports are configured 801. A peripheral port is connected to a first cavity port, a liquid source is connected to a second cavity port, and connections to a third cavity port and a fourth cavity port operate to provide a slight gas underpressure compared to chamber ambient. If the fourth cavity port has an orifice with a controllable valve as in FIGS. 6A and 6B, a vacuum pump may be connected to the third cavity port. Without a controllable orifice, a gas source may be connected to the third cavity port and a vacuum pump may be connected to the fourth cavity port, or vice versa.
The reactor cell is positioned 802 over the substrate without touching it, leaving a narrow gap (e.g., between about 0.2 mm and about 0.3 mm) between the top surface of the substrate and the bottom surface of the cell. A below-ambient pressure is created 803 in the main cavity by controlling the inflow and outflow of gas through the third and fourth cavity ports.
Process liquid is introduced 804 into the main cavity through the second cavity port. The process liquid may be a deposition layer material, an etchant, a cleaning solution, a polishing mixture, or any other liquid used for any other process. Due to the underpressure, the process-liquid forms a meniscus in the gap and wets up the walls of the main cavity and the peripheral channel above the cell bottom. The liquid may be introduced 804 to a depth of, for example, between 4 mm and 10 mm.
As the liquid is introduced 804 and the substrate is processed 805, the pressure inside the main cavity is maintained within a desired range below chamber ambient pressure by controlling the inflow and outflow of gas through the third and fourth cavity ports. Keeping the pressure within the desired range confines the process liquid to an area of the substrate underneath this cell, within the outer periphery of a projection of the peripheral channel onto the substrate surface. For example, the desired range may be between −23 mm and −28 mm H₂O.
When the process using the process liquid is complete, the process liquid is removed 806 from the substrate. This may be done in any manner used for known substrate-contacting reactor cells; for example, by pumping it out of the cell through a liquid-exhaust conduit, or by raising the cell higher above the substrate and rinsing the entire substrate with a rinsing solution. In processes where it is critical that the process liquid must not touch any part of the substrate other than the interior site, the underpressure may be maintained while the liquid is pumped out to keep it confined to the interior site. If a brief contact with the process liquid would not adversely affect part of the substrate outside the interior site, the underpressure may be released while the liquid is being removed 806. Afterward, the next process 809 may begin.
FIG. 9 is a flowchart of a method for processing an external site on a substrate. Initially, the connections to the cavity and peripheral ports are configured 901. A peripheral port is opened to vent the peripheral channel to the ambient atmosphere in the chamber, the first and second cavity ports are sealed, and connections to a third cavity port and a fourth cavity port operate to provide a slight gas overpressure compared to chamber ambient. If the fourth cavity port has an orifice with a controllable valve as in FIGS. 6A and 6B, a gas source may be connected to the third cavity port. Without a controllable orifice, a gas source may be connected to the third cavity port and a vacuum pump may be connected to the fourth cavity port, or vice versa.
The reactor cell is positioned 902 over the substrate without touching it, leaving a narrow gap (e.g., between about 0.2 mm and about 0.3 mm) between the top surface of the substrate and the bottom surface of the cell. An above-ambient pressure is created 903 in the main cavity by controlling the inflow and outflow of gas through the third and fourth cavity ports.
Process liquid is introduced 904 onto the substrate outside the main cavity. The process liquid may be a deposition layer material, an etchant, a cleaning solution, a polishing mixture, or any other liquid used for any other process. Due to the overpressure, the process-liquid forms a meniscus in the gap and wets up the walls of the peripheral channel and the outer sidewall of the cell above the cell bottom. The liquid may be introduced 904 to a depth of, for example, between 4 mm and 10 mm.
As the liquid is introduced 904 and the substrate is processed 905, the pressure inside the main cavity is maintained within a desired range above chamber ambient pressure by controlling the inflow and outflow of gas through the third and fourth cavity ports. Keeping the pressure within the desired range confines the process liquid to an area of the substrate outside the inner periphery of a projection of the peripheral channel onto the substrate surface, and excludes the liquid from the area under the main cavity. For example, the desired range may be between +23 mm and +28 mm H₂O.
When the process using the process liquid is complete, the process liquid is removed 906 from the substrate. This may be done in any manner used for known substrate-contacting reactor cells. In processes where it is critical that the process liquid must not touch an inner part of an interior site (i.e., the area under the main cavity), the overpressure may be maintained while the liquid is removed so that no liquid flows into that area. If a brief contact with the process liquid would not adversely affect that area, the overpressure may be released while the liquid is being removed 906. Afterward, the next process 909 may begin.
FIGS. 10A-10D are conceptual views of substrates with sequentially processed internal and external sites. FIG. 10A is a top view of a section of a substrate 1000 where both an interior site and an exterior site have been processed using one of the described no-contact reactor cells. Circular area 1001 is the area that was located under the main cavity of the reactor cell. Annular area 1003 surrounding circular area 1001 is the area that was located under the peripheral channel of the reactor cell. Rectangular area 1002 outside annular area 1003 is the area that was located outside the outer boundary of the peripheral channel.
As shown in FIGS. 6A-7B, both an interior site and an exterior site of a reactor cell may include annular area 1003 under the peripheral channel, causing area 1003 to be processed twice. FIGS. 10B-10D are sectional views through section B-B of FIG. 10A, showing some of the possible results of the overlap of the two processed areas.
In FIG. 10B, sequential processes with a no-contact cell deposited new layer 1010 on substrate 1000. A raised ring, appearing in the sectional view as a pair of bumps 1003B, resulted from the double processing of overlap zone 1003.
In FIG. 10C, sequential processes with a no-contact cell etched uniform layer 1020 on substrate 1000 down from its previous height 1004. An indented ring, appearing in the sectional view as a pair of troughs 1003C, resulted from the double processing of overlap zone 1003.
Often, in the HPC context, the doubly-processed overlap regions can be ignored by doing all the characterizations in other parts of the substrate. However, there are situations where the overlap regions may share the characteristics of the non-overlap regions.
In FIG. 10D, sequential processes with a no-contact cell processed layer 1030 on substrate 1000 without creating any non-uniformity in the overlap zone. A number of approaches can produce this result. For example, a layer formed like 1010 with double deposition in the overlap zone might, in some circumstances, be etched like 1020 such that two etch steps in the overlap zone level the raised area to the same plane as its surroundings. As another example, layer 1030 may have been buried under an overlayer 1040, which was wholly etched away using a wet etchant that does not etch layer 1030. The second exposure therefore did not affect layer 1030. As a further example, layer 1030 could be a coating or other surface treatment that chemically reacts with unprocessed substrate 1000 but not with an already-reacted area 1001 or 1002. Other processes can also result in a uniformly processed interior site and exterior site with no non-uniformity in the overlap zone.
Although the foregoing examples have been described in some detail to aid understanding, the invention is not limited to the details in the description and drawings. The examples are illustrative, not restrictive. There are many alternative ways of implementing the invention. Various aspects or components of the described embodiments may be used singly or in any combination. The scope is limited only by the claims, which encompass numerous alternatives, modifications, and equivalents.

Claims

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 H₂O.

18. The reactor cell of claim 1, further comprising:

an orifice on an outer end of the fourth cavity port;

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 H₂O.

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.