Single phase proximity head having a controlled meniscus for treating a substrate

A system for processing a substrate is described. The system includes a proximity head, a mechanism, and a liquid supply. The proximity head is configured to generate a controlled meniscus. Specifically, the proximity head has a plurality of dispensing nozzles formed on a face of the proximity head. The dispensing nozzles are configured to supply a liquid to the meniscus and the suction holes are added to remove a used liquid from the meniscus. The mechanism moves the proximity head or the substrate with respect to each other while maintaining contact between the meniscus and a surface of the substrate. The movement causes a thin layer of the liquid to remain on the surface after being contacted by the meniscus. The liquid supply is in fluid communication with the dispensing nozzles, and is configured to balance an amount of the liquid delivered to the meniscus with an amount of liquid removed from the meniscus, the amount of liquid removed from the meniscus including at least the thin layer of the liquid remaining on the surface of the substrate.

CROSS REFERENCE TO RELATED APPLICATIONS

The present Application is related to the following U.S. Patents and U.S. Patent Applications, all of which are incorporated herein by reference in their entirety: U.S. patent application Ser. No. 11/173,729, filed Jun. 30, 2005 and entitled “A Method And Apparatus For Atomic Layer Deposition (ALD) In A Proximity System;” and U.S. patent application Ser. No. 11/539,611, filed Oct. 6, 2006 and entitled “Proximity Processing Using Controlled Batch Volume With An Integrated Proximity Head.

BACKGROUND

In the manufacture of integrated circuit (IC) devices, a semiconductor substrate, such as a silicon wafer, is processed by placing the substrate through any number of process steps. Such steps include deposition steps, removal steps, patterning steps (e.g., photolithography), and doping. In many instances, material is removed, added, or modified by exposing the substrate to a chemical for a period of time. In addition, there may be cleaning and rinsing steps to remove residue of the chemical left on the substrate, which could damage the device if allowed to remain.

As IC device features continue to decrease in size, existing methods for processing wafers by exposing the wafers to liquid chemicals have become inadequate. For example, a traditional immersion method, whereby a substrate is submerged in a liquid chemical, such as an organic solvent chemical or wet etching chemical, does not provide sufficient control over contact time between the substrate and the chemical. For example, the upper portion of the substrate may be the last to be lowered into the chemical and the first to be lifted out from the chemical. Furthermore, after being raised out of the chemical, the substrate may still have a layer of chemical adhered to the surface of the substrate for some time until the substrate can be moved to a rinsing and drying station. It would be desirable to more precisely control the contact time and the time to rinse.

In addition, substrate immersion does not provide an efficient use of the chemicals. For example, immersion requires significantly more chemical liquid than necessary to carry out the desired chemical reaction or process. In some instances, this liquid cannot be reused, or can only be reused a limited number of times. It would therefore be desirable to reduce the amount of chemical usage for a given process.

Finally, immersion techniques are amenable to batch processing, wherein a number of substrates are lowered into the chemical at the same time. While this improves the efficiency of the immersion technique, it requires additional handling of the substrate to load a number of substrates into a tray and then unload them. Each time a substrate is handled, i.e., moved from one process station to the next, it delays the time to the next process step. In addition, a time delay between removal of a substrate from a chemical and washing, rinsing, and drying operations can vary when a number of substrates are removed at once, but then are further processed only one at a time. It would be desirable to handle a substrate fewer times, and to provide for more consistent handling of substrates from one substrate to the next.

To overcome the advantages noted above, there is a need for improved mechanisms for treatment of a substrate with a liquid chemical.

SUMMARY

Broadly speaking, the present invention fills these needs by providing various techniques for wet treatment of substrates including etching, cleaning, wetting, washing, rinsing and drying resulting in a removal of unwanted layers, residuals, contaminants, watermarks, etc. left on the surface during previous processing steps.

It should be appreciated that the present invention can be implemented in numerous ways, including as a process, an apparatus, a system, a device, or a method, Several inventive embodiments of the present invention are described below.

In one embodiment, a system for processing a substrate is provided. The system includes a proximity head, a mechanism to move the proximity head with respect to a substrate (or a substrate with respect to proximity head, or both), and a liquid management system providing fluid communication with the proximity head. The proximity head is configured to generate on a surface of a substrate a controlled meniscus. Specifically, the proximity head has a plurality of distinct dispensing nozzles formed on a face of the proximity head, the dispensing nozzles being configured to supply a liquid to the meniscus, and plurality of distinct retrieving nozzles formed to remove a liquid from a meniscus after contacting with substrate. The mechanism to move the proximity head, or a substrate, or both with respect one to another, maintains controllable contact between the meniscus and a surface of the substrate and causes a thin layer of the liquid to remain on the surface after being contacted by the meniscus. The liquid supply is configured to balance an amount of the liquid delivered to the meniscus with an amount of liquid removed from the meniscus, the liquid removed including at least the thin layer of the liquid remaining on the substrate.

In another embodiment, a method for processing a substrate is provided. The method includes generating a controlled meniscus using a proximity head, the proximity head having a face in close proximity to a surface of the substrate. The controlled meniscus is generated by delivering a chemical to the meniscus through discrete nozzles formed in the face of the proximity head. The proximity head is moved over the substrate so that an area of contact between the meniscus and the substrate moves from one location to another location on the substrate. The moving of the proximity head causes a chemical remainder to be left behind the surface of the substrate at the first location, the chemical remainder being a layer of the chemical from the meniscus that adheres to the surface of the substrate. An amount of chemical being delivered to the proximity head is balanced with an amount of chemical removed from the meniscus back to the head (static mode), or with an amount of chemical removed from the meniscus back to the head and the chemical remainder (dynamic mode), so that the meniscus maintains a substantially constant volume of the chemical.

DETAILED DESCRIPTION

In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be apparent to one skilled in the art that the present invention may be practiced without some of these specific details. In other instances, well known process operations and implementation details have not been described in detail in order to avoid unnecessarily obscuring the invention. The term, “meniscus,” as used herein, refers to a volume of liquid bounded and contained in part by surface tension of the liquid. The meniscus is also controllable and can be moved over a surface in the contained shape. In specific embodiments, the meniscus is maintained by the delivery of fluids to a surface while also removing the fluids so that the meniscus remains controllable. Furthermore, the meniscus shape can be controlled by precision fluid delivery and removal systems that are in part interfaced with a controller a computing system, which may be networked. In some embodiments, a fluid delivery system is provided and no fluid removal system is provided, as described in more detail below.

FIG. 1is a perspective view of an exemplary implementation of a substrate processing system100. In this example, substrate160is positioned within a carrier150which passes between upper proximity head110and lower proximity head120in the direction of arrow166. In one embodiment, substrate160comprises a semiconductor wafer, such as a single crystal silicon wafer. Upper and lower proximity heads110,120, form a meniscus of fluid between them. Carrier150may be connected to track mechanism152, represented schematically as two double-headed arrows on either side of carrier150. In one embodiment, track mechanism152comprises two slotted rails on either side of carrier with a device that engages carrier150and causes carrier150to move between upper and lower proximity heads110,120in the direction of arrow166. In one embodiment, a substrate160is deposited on carrier150at a first location on one side of proximity heads110,120, and removed when carrier150arrives at a second location on an opposite side of proximity heads110,120. Carrier150may then pass back through proximity heads110,120, or over, under, or around proximity heads110,120, back to the first location, where a next substrate is deposited, and the process is repeated.

Although only pair of upper and lower proximity heads110,120is shown, any number of proximity heads, generating a plurality of menisci side-by-side, with carrier150passing through each in series. A plurality of menisci can be used, for example, to perform a plurality of treatment steps, such as etch, clean, and then rinse and dry. Furthermore, it is not required to have both an upper and lower proximity head, since a controlled meniscus can be generated on one side of a substrate with a single proximity head.

It should further be noted that, while in the example shown inFIG. 1, the substrate moves through proximity heads110,120in the direction of arrow152, it is also possible for the substrate to remain stationary while the proximity heads110,120, pass over and under the substrate. Furthermore, the orientation of the substrate as it passes between the proximity heads is arbitrary. That is, the substrate is not required to be oriented horizontally, but can instead be vertically oriented or at any angle.

In certain embodiments, a controller130, which may be a general purpose or specific purpose computer system whose functionality is determined by logic circuits or software, or both, controls the movement of carrier150and the flow of fluids to upper and lower proximity heads110,120. The flow of fluids to and from proximity heads110,120is controlled to maintain the meniscus in a stable state.

FIG. 2shows by way of example, a schematic representation of a system for supplying a chemical to a substrate using a controlled meniscus. As shown inFIG. 2, proximity head110moves to the left and/or substrate160moves to the right as shown by arrows105so that there is relative movement between proximity head110and substrate160. As a result of the relative movement, the controlled meniscus200, and the hydrophilicity of the substrate and/or surfactant content of the chemical, a thin layer or film of chemical remainder202adheres to substrate160so that substrate160is effectively wetted by proximity head110. It should be noted thatFIG. 2, being a schematic representation, is not intended to accurately represent relative dimensions of the various features shown.

Proximity head110includes at least one dispensing nozzle116(two are shown inFIG. 2) formed in a face111of proximity head110through which a liquid is supplied to form a meniscus200. The face111includes at least one flat region disposed proximate to and substantially parallel to surface of a substrate160, although multiple flat regions could be implemented having varying elevations and/or shapes. The liquid may be deionized water, RCA Clean chemicals, or other liquid designed to process substrate160. In addition, proximity head110includes one or more suction ports114(only one shown) applying a controlled suction to meniscus200. In one embodiment, suction ports114aspirate, substantially only liquid from meniscus200, and not surrounding gases. The lower proximity head120, not shown inFIG. 2, may be provided as a mirror image to the upper proximity head, and may operate in a similar manner. More details relating to proximity head structure and operation are incorporated by reference in the Cross Reference to Related Art section above. In particular, U.S. patent applications Ser. No. 10/261,839, 10/330,843, and 10/330,897 are referenced for additional details relating to proximity head structure and operation.

Substrate processing system100also includes a chemical supply system180and a chemical removal system190. Chemical supply system180and chemical removal system190may be connected to one another to allow recycling of chemicals. For example, a tertiary recycling system (not shown) may receive used chemical from chemical removal system190and treat the used chemical, e.g., by filtering, distilling, or other operations, before returning the used chemical to chemical supply system180. Chemical supply system180may include heating means (not shown) for heating the chemical, e.g., to enhance the reacting power of the chemical. Control unit130regulates the operation of chemical supply and retrieval systems180,190to ensure that the chemical flows to and from meniscus200are at controlled rates so that meniscus200remains in a stable state. By “a stable state,” it is meant that the meniscus has a substantially constant volume, spillage from the meniscus, which may be expected at the edges of the substrate, is controlled and compensated for. Thus, the fluid flowing to and from meniscus200is substantially balanced, with only sufficient additional fluid flowing to the meniscus to compensate for fluid202remaining on the meniscus and the expected amount, if any, of spillage.

In one embodiment, proximity head110includes a plurality of dispensing nozzles116surrounding a plurality of suction ports114as shown and described in more detail below with reference toFIG. 4. However, other configurations of nozzles are possible. For example, dispensing nozzles116may be provided along a leading edge112of proximity head110and suction ports114may be provided along a trailing edge118of proximity head110. In other embodiments, described in more detail below with reference toFIG. 7, only dispensing nozzles116are provided and no suction nozzles are needed. Although various configurations of nozzles are possible, in one embodiment, each configuration includes dispensing nozzles116formed as independent and discrete through-holes extending from a face111of proximity head110to an internal manifold (not shown) which equalizes fluid pressure among the nozzles, thereby ensuring each nozzle receives fluid or a vacuum at a pressure consistent with other nozzles.

FIG. 3shows by way of example a schematic representation of a proximity head110′. Proximity head110′ includes dispensing nozzles116that are angled to promote a flow of the chemical along arrows119. Depending on the flow rate and viscosity of the chemical, as well as other factors such as the hydrophobicity of substrate160, angled dispensing nozzles116′ may improve fluid dynamics within meniscus200.

FIG. 4shows a bottom view of an exemplary proximity head10with wafer160and carrier150shown in phantom. Face111of proximity head110includes a substantially flat surface disposed substantially parallel to substrate160. Face111also includes a plurality of distinct dispensing ports116surrounding a plurality of distinct suction ports114. This configuration is presented for exemplary purposes only and other configurations are possible. For example, in one embodiment, suction ports114are not provided or are replaced with additional dispensing nozzles116. In another embodiment, the dispensing nozzles116are surrounded by suction ports114. In another embodiment, a row of dispensing nozzles116are disposed at a leading edge of proximity head110and a row of suction ports114are disposed along a trailing edge of proximity head110. By “leading edge” it is meant the forward edge of proximity head that is first to encounter a substrate when moving in relation to the substrate. In yet another embodiment, dispensing nozzles116are interspersed with suction ports114, e.g., in a checker-board pattern.

FIG. 5shows exemplary meniscus control system250with chemical recycling. Chemical255, such as a chemical composition for processing or cleaning substrate160, is held by chemical supply tanks260,260′. When valves V2and V2′ are opened by control unit270, chemical255is allowed to flow under the influence of gravity through fluid lines264,264′ to dispensing nozzles116to form meniscus200. Chemical retrieval tank280is held under a vacuum by vacuum pump282and control unit270in response to pressure sensor284and flow meter286. Since chemical retrieval tank280is in fluid communication with suction port114via fluid line266, some of chemical255in meniscus200is drawn up to chemical retrieval tank280. In one embodiment, the vacuum in chemical retrieval tank280is adjusted until a predetermined fluid flow is registered by flow meter286.

Sensors262,262′ signal control unit270when the liquid level in chemical supply tanks260,260′ becomes too high or too low. In response to a signal indicating that liquid is too low, control unit270operates pump275to recycle used chemical257from chemical retrieval tank280to chemical supply tanks255,255′ via fluid lines268,276, and276′. Valves V1, V1′ are operated by control unit270to ensure that recycled chemical is supplied to the correct chemical supply tank.

FIG. 6shows exemplary meniscus control system300wherein metering pumps308,310, are used to control meniscus200. Specifically, control unit302operates metering pump310to draw chemical from chemical supply306and supply it in a controlled volumetric flow rate to meniscus200by way of dispensing nozzle116. Metering pump308is likewise driven to remove chemical from meniscus200and pass the used chemical to chemical removal system304. Metering pumps310,308are each capable of transferring chemicals from their respective inputs to their respective outputs at precise volumetric flow rates over a wide range of pressure differentials between their inlets and outlets. Although schematically represented with lobe-style impellers, any type of metering pump can be used. In one embodiment, control unit302drives metering pump310to deliver chemical to meniscus200at a higher flow rate when forming meniscus200, and then a lower rate of flow once meniscus200is formed. In another embodiment, not mutually exclusive with other embodiments described herein, control unit302drives metering pump308to remove chemical from meniscus200at a slightly lower flow rate than metering pump310is driven to supply chemical to the meniscus. In this manner, slightly more fluid is dispensed than removed by proximity head110, allowing a small amount of fluid to remain on substrate160as chemical remainder202.

FIG. 7shows exemplary meniscus control system350wherein proximity head110includes dispensing nozzles116and no suction ports114, Hence, in this embodiment, the chemical is not actively removed from the meniscus by the proximity head. Control unit352drives metering pump354to draw a chemical from chemical supply356and supply the chemical to meniscus200via dispensing nozzles116. Once meniscus200is formed, control unit352supplies only sufficient chemical to meniscus200to compensate for chemical remainder202adhering to substrate160, and potentially also to carrier150(FIGS. 1,4). It should be understood that a negligible amount of the chemical may additionally be removed by evaporation and/or lost to carrier150(FIGS. 1,4).

FIG. 8shows a substrate processing system400having a first proximity head110and a second proximity head410. Proximity head110is substantially as described above with reference toFIG. 2and generates a meniscus200leaving a chemical remainder202adhering to substrate160. Proximity head410includes centrally disposed dispensing nozzles116surrounded by suction ports that aspirate a mixture of liquid from meniscus412and surround gas. Proximity head may be constructed and operated as described in U.S. patent application Ser. No. 10/261,839 filed on Sep. 30, 2002, or U.S. patent application Ser. No. 10/404,692, filed Mar. 31, 2003, which are incorporated herein by reference. In one embodiment, gas nozzles113surround suction ports114and supply a mixture of nitrogen and isopropyl alcohol gas, which act to improve the integrity of liquid-vapor barrier of the meniscus. In one embodiment, meniscus412is formed from de-ionized water and effectively rinses and removes chemical remainder202, and leaves substrate160dry and spot-free behind meniscus412, e.g., at location414.

FIG. 9shows by way of example a multiple menisci proximity head450generating menisci200,452,454, and456. It should be noted that any number of menisci can be generated. Multiple menisci proximity head450can be used carry out multi-step processes on substrates. For example, the standard RCA cleaning process for silicon wafers requires first removing organic contaminants, a second step for removing oxides, and a final step to remove metallic traces (ions).

FIG. 10shows a flowchart500illustrating by way of example a procedure carried out with the substrate processing system herein described. The procedure begins as indicated by start block502and proceeds to operation504wherein a controlled meniscus is generated by delivering a chemical to the meniscus using dispensing nozzles in the proximity head. The flow can be controlled by gravity feeding the chemical to the proximity head as described above with reference toFIG. 5or using metering pumps or other means to control the delivery of liquid chemical to the meniscus.

In operation506, the proximity head is moved over the substrate, leaving a chemical remainder on the substrate surface. The chemical remainder may be, for example, a film of chemical adhering to the substrate surface. In one embodiment, a surfactant is added to the chemical to ensure adhesion with the substrate surface, which may or may not be hydrophilic.

In operation508, used chemical is optionally removed from the meniscus using suction ports formed in the proximity head. It should be noted that, depending on the chemical processes, the chemical may degrade and need to be refreshed by removing used chemicals and supplying new chemicals. For example, if the chemical is used for oxide removal and the chemical comprises a solution of sulfuric acid, the acidity of the solution may reduce as it reacts with the substrate surface. In one embodiment, therefore, the chemical is constantly being replaced with unused chemical for the purpose of maintaining desired properties thereof. The flow rate of chemical removal may depend on the chemical and process involved. In another embodiment, chemical replacement is not required so that removal is unnecessary.

In operation510, the meniscus is controlled by balancing the amount of chemical delivered to the meniscus with the amount of chemical removed and the amount of chemical remainder. The procedure then ends as indicated by operation512. It should be noted that, although the operations presented inFIG. 10are presented as being serial, they operations may be performed concurrently so that all operations take place simultaneously.