Classifications

• • H10P50/287—
• • H10P52/00—
• • H10P50/00—
• • H10P72/0424—

Definitions

• the present invention relates generally to cleaning a semiconductor substrate, and more particularly, to methods and systems for applying an oxidizing solution to a surface of a semiconductor substrate.
• the fabrication of semiconductor devices involves numerous processing operations. These operations include, for example, impurity implants, gate oxide generation, inter-metal oxide depositions, metallization depositions, photolithography patterning, etching operations, chemical mechanical polishing (CMP), etc. As these operations generate particles and residue, there is a need to clean wafer surfaces, thus removing the contaminants such as adhered particles and adsorbed compounds (e.g., organic and metallic) from the surfaces of the wafer. Contaminants should be removed from wafer surfaces, as the presence of such contaminants has a detrimental effect on the performance of the integrated circuit devices.
• impurity implants include, for example, impurity implants, gate oxide generation, inter-metal oxide depositions, metallization depositions, photolithography patterning, etching operations, chemical mechanical polishing (CMP), etc.
• CMP chemical mechanical polishing
• Figures IA and IB illustrate two types of prior art, two sided wafer scrubbers.
• Figure IA shows a horizontally orientated, conventional wafer scrubber 100.
• Figure IB shows a vertically oriented, conventional wafer scrubber 100'.
• Both Figures IA and IB include a pair of brush cores 102a and 102b each having been mounted by a corresponding brush 104a and 104b. As shown, the outer surface of each of the brushes 104a and 104b is covered with numerous nodules 105a and 105b, respectively.
• brushes 104a, 104b can also have a substantially smooth surface (i.e., without significant nodules 105a, 105b). In both orientations, a wafer 106 is scrubbed as the symmetrical brushes 104a and 104b rotate in a corresponding rotation direction of 108a and 108b.
• the physical makeup of the brush cores 102a and 102b are identical.
• the outer surfaces of the brushes 104a and 104b are constructed from the same material, thus having the same density and compressibility as well as surface contact areas with the wafer. Therefore, in both configurations of prior art wafer scrubbers, an identical amount of pressure is applied to each of the contact areas as the brushes 104a and 104b are respectively applied to the front and the back side of the wafer 106 with identical forces. Consequently, in prior art wafer scrubbers, the front side and the back side of the wafers are treated identically, even though only the front side of the wafer includes active components.
• a cleaning chemistry 110 is also added as the brushes 104a and 104b are rotated.
• the cleaning chemistry 110 can be provided through a nozzle or drip outlet 112 or from inside the brushes 104a and 104b.
• the cleaning chemistry 110 assists in dislodging and diluting the contaminates on the surface of the wafer W.
• the cleaning chemistry 110 can also carry the dislodged and diluted contaminates away from the wafer.
• the cleaning chemistry 110 can be DI water or more reactive chemistries such as chlorinated and fluorinated chemistries, one or more acidic solutions, or one or more alkali solutions.
• the selected cleaning chemistry is dependent on the contaminate targeted for removal.
• a sulfuric acid and hydrogen peroxide mixture (hereafter "SPM”) cleaning chemistry is typically used.
• SPM sulfuric acid and hydrogen peroxide mixture
• the cleaning chemistry 110 and/or the wafer can also be heated to aid in the cleaning.
• the present invention fills these needs by providing a method and system for applying an oxidizing solution to a surface of a semiconductor substrate. It should be appreciated that the present invention can be implemented in numerous ways, including as a process, an apparatus, a system, computer readable media, or a device. Several inventive embodiments of the present invention are described below.
• One embodiment provides a method of processing a substrate.
• the method includes applying a solution to a surface of a substrate. At least one reacting species can be produced by dissociation of the solution. A first material on the substrate is reacted and the reacted first material can be removed.
• the solution can include at least one of a group consisting of H 2 O 2 or H 2 O.
• the oxidizing radical can include at least one of a group consisting of O 3 , O 2 , OH, O or OOH.
• the reacting species can be produced by dissociation of the solution by applying a light to the solution.
• the light can be an ultraviolet light.
• the light can be applied to the solution before the solution contacts the surface of the substrate.
• the light can be applied to the solution for at least a portion of a time the solution contacts the surface of the substrate.
• the light can have a wavelength of less than or equal to about 300 nm.
• the light can have a wavelength of between about 180 nm and about 220 nm.
• the light can be collimated.
• the light can be pulsed. Substantially only a portion of the first material that is exposed to the light is oxidized.
• Applying the solution to the surface of the substrate can include forming a layer of the solution on the surface of the substrate having a thickness less than a recombination length of the reacting species.
• the solution can include at least a ten percent concentration OfH 2 O 2 .
• the first material can be an organic material.
• the first material can be exposed through a pattern in a mask layer.
• Applying the solution to the surface of a substrate can include applying the solution through a dynamic liquid meniscus.
• the method can also include rinsing the surface of the substrate.
• Another embodiment provides a system for processing a substrate.
• the system includes a substrate support, a substrate supported thereon and a layer of a solution supported on a surface of the substrate.
• the system also includes an energy source capable of dissociating the solution to produce a reacting species.
• the energy source can be a light source.
• the energy source can be a UV light source.
• the energy source can be included in an enclosure.
• the energy source can be included in a proximity head and the layer of the solution can be supported on the surface of the substrate within a dynamic liquid meniscus.
• Figure IA shows a horizontally orientated, conventional wafer scrubber.
• Figure IB shows a vertically oriented, conventional wafer scrubber.
• Figure 2 shows a side view of a system for cleaning a substrate, in accordance with one embodiment of the present invention.
• Figure 3 is a graph of a concentration of the oxidizing radicals as compared to a depth of the solution from which the oxidizing radicals are generated, in accordance with one embodiment of the present invention.
• Figure 4A shows a portion of the substrate that has been etched exposure to hydrogen peroxide and UV light, in accordance with one embodiment of the present invention.
• Figure 4B is a graph, of a scan across the region, in accordance with one embodiment of the present invention.
• Figure 5 shows a substrate, in accordance with one embodiment of the present invention.
• Figure 6 is a detailed view of a system for generating oxidizing radicals upstream of the surface of the substrate, in accordance with one embodiment of the present invention.
• Figure 7 is a diagram of a system for generating oxidizing radicals upstream of the surface of the substrate, in accordance with one embodiment of the present invention.
• FIG. 8 is a diagram of a proximity head for supporting a dynamic liquid meniscus, in accordance with one embodiment of the present invention.
• FIG. 9 flowchart of the method operations of generating oxidizing radicals for processing a substrate, in accordance with one embodiment of the present invention.
• SPM i.e., sulfuric acid and hydrogen peroxide mixture
• SPM cleans organic contaminants from a surface of a substrate by oxidizing the organic contaminants.
• SPM can also be used to remove a layer of organic materials by oxidizing the organic material.
• One embodiment of the present invention provides a system and method for reacting materials (e.g., oxidizing or otherwise reacting the materials) on the surface of the substrate using a combination of hydrogen peroxide (H 2 O 2 ) and a selected wavelength and intensity of light.
• hydrogen peroxide and the selected wavelength and intensity of light can be used to remove organic residues or polymer films (e.g., photoresist).
• the selected wavelength and intensity of light dissociates the hydrogen peroxide into two hydroxyl radicals.
• the hydroxyl radicals can also form hydrogen peroxide byproducts (e.g., hydroperoxy radicals, atomic oxygen and ozone).
• the hydroxyl radicals and hydrogen peroxide byproducts are hereafter referred to as oxidizing radicals.
• the oxidizing radicals are very reactive with organic materials and can readily oxidize organic material to form CO and other organic by-products (e.g., CO 2 and HHCO, etc.). The CO and the other organic by- products can then be more easily removed such as rinsed away from the surface of the substrate.
• the selected wavelength of light can be within an ultraviolet (UV) light spectrum (i.e., between wavelengths of about 180nm and about 300nm).
• UV light passes through the hydrogen peroxide, the hydrogen peroxide absorbs the UV light to form the oxidizing radicals.
• the UV light is only able to pass through a relatively small depth (e.g., about 3 mm) of the hydrogen peroxide before being fully absorbed by the hydrogen peroxide. Therefore, if a relatively thin film (i.e., less than about 2 mm) of hydrogen peroxide is formed on the surface of the substrate, then the oxidizing radicals can be formed on the surface of the substrate so as to react with any organic materials on the surface of the substrate.
• the relatively thin film of hydrogen peroxide can be formed on the surface of the substrate by spinning the substrate.
• the substrate can be spun greater than about 200 rpm. As the rotational speed of the substrate is increased, the depth of the film of hydrogen peroxide formed on the surface of the substrate is reduced.
• a UV light source e.g., laser, pulsed lamp, blanket, collimated light source, etc.
• the oxidizing radicals are formed on the surface of the substrate and react with any organic material that may be present.
• the combination of hydrogen peroxide and UV light can be used to perform a near-anisotropic, wet etch process.
• Typical wet etch processes are isotropic in nature.
• a polymer layer to be etched includes an opaque mask layer (e.g., hard mask or other opaque mask layer suitable to sufficiently block the type of energy applied) covering an organic layer (e.g., photoresist).
• the opaque mask layer is pattered in a conventional patterning process. Once the opaque mask layer is patterned, the desired film of peroxide can be formed.
• the thickness of the peroxide film can be between 1 micron and about 100 micron in depth.
• the light e.g., a UV light
• the UV light causes the oxidizing radicals to be formed on the surface of the exposed substrate and react with the organic material in the organic layer that is not protected by the patterned opaque mask layer.
• the oxidizing radicals are formed by the reaction of the UV light and the hydrogen peroxide, then the etching is generally formed only in the areas that the UV light impinges upon due to the fast radical recombination rate and diffusion path length of reactants to the surface of the substrate.
• FIG. 2 shows a side view of a system 200 for cleaning a substrate, in accordance with one embodiment of the present invention.
• the system 200 includes a substrate support 202 that supports the substrate 208.
• the substrate support actuator 203 can move the substrate support 202 and the substrate 208 in a vertical direction 204 and can also rotate the substrate 208, such as in direction 206.
• the substrate 208 includes several layers 210, 212.
• a puddle of processing solution 222 e.g., water and/or hydrogen peroxide or combinations thereof
• a dispensing nozzle 224 can dispense the solution 222 from a source 226 onto the top surface 208A.
• An energy source 230 is oriented toward the top surface 208A of the substrate 208.
• the energy source 230 can include a light source or other source of energy source sufficient to dissociate the solution 222 to produce at least one reactive species (e.g., at least one species of oxygen radical).
• the energy source 230 is oriented such that the energy 232 (i.e., light) emitted therefrom and is emitted in direction 234 that is substantially perpendicular to the top surface 208A.
• the light source 230 can be a continuous D2 lamp (i.e., about 180 nm to about 220 nm), a Xenon lamp (i.e., about 240 to about 300 nm wavelength) that is pulsed (e.g., about 5 microsecond pulse at a pulse rate of about 80 Hz).
• the selected light source is dependent on the reactivity desired.
• a first organic material may react more oxidizing radicals generated by UV in the 180 nm range.
• a second organic material may react more readily with oxidizing radicals generated by UV in the 300 nm range.
• the precise intensity of the light source 230 used is dependent upon the desired results.
• the intensity of the of the light source 230 is increased, the reactivity of the generated oxidizing radicals is also increased. Therefore to quickly remove some relatively minor organic residue, then a low intensity may be selected. Conversely, to etch through a layer of organic material, then the intensity may be significantly increased. Further, some organic materials may react in a more desirable manner with a pulsed light source that is pulsed at a relatively high, peak intensity (i.e., power) but with an average intensity over time that is relatively low.
• a first organic material may react in a desirable manner (e.g., timely reaction rate, predictable, controllable, etc.) with oxidizing radicals that are generated by a light source 230 that is pulsed in 5 microsecond pulses, at 20-40 mJ per pulse, at a pulse rate of 80Hz.
• the first organic material may not react as desirably (e.g., reaction rate is reduced as compared to pulsed light source) if the light source 230 is operated at a continuous intensity of 3 watts.
• the system 200 for cleaning the substrate 208 can also be enclosed within an enclosure 240.
• the enclosure 240 can be any type of suitable enclosure.
• variables such as the temperature, pressure or other environmental factors (e.g., atmosphere, purging gas or liquid flow rates, etc.) that may be controlled during the cleaning process.
• the enclosure 242 can be any type of enclosure suitable to provide the control of the desired factors.
• a control system 242 is also included.
• the control system 242 is coupled to the hydrogen peroxide source 226, substrate support actuator 203 and the light source 230 so as to control the operating parameters of the hydrogen peroxide source, substrate support actuator and the light source.
• the control system 242 can also control variables such as the temperature, pressure or other environmental factors (e.g., atmosphere, purging gas or liquid flow rates, etc.) that may be desired to be controlled during the cleaning process.
• Figure 3 is a graph 300 of a concentration of the reacting species as compared to a depth of the solution 222 from which the reacting species (e.g., oxidizing radicals) are generated, in accordance with one embodiment of the present invention.
• the intensity of the light is reduced in accordance with the absorption rate of the solution 222.
• the concentration of reacting species correspondingly reduced.
• the intensity of the light is at its greatest and therefore the corresponding concentration of the reacting species is also at its greatest.
• the concentration of the reacting species at least in part determines the reactivity or oxidizing rate of the organic material on the surface 208A of the substrate. Therefore, if a selected concentration of A is required to achieve a desired reactivity at the surface 208 A of the substrate, then the solution 222 can have a depth no greater than about depth d to the surface 208A of the substrate.
• solution 222 contains a 70% concentration of peroxide that is diluted in a substantially UV transparent liquid (e.g., water), then the UV absorption rate is 100 cm '1 and therefore the UV light can penetrate about 0.01 cm.
• a substantially UV transparent liquid e.g., water
• the concentration of the solution can also be selected to select a corresponding reactivity.
• the solution 222 can be between 1 and 70% dilution of hydrogen peroxide in a liquid, such as water, that is substantially transparent to UV light or other applicable energy type.
• Reacting specie can also be generated from H 2 O (i.e. a 0% hydrogen peroxide concentration) in a deep UV light having a wavelength shorter than about 180 nm with a sufficient intensity.
• the gaseous environment of the enclosure 240 can also be other than ambient air.
• a substantially pure nitrogen atmosphere can be used to minimize dissipation of UV light intensity.
• gases could include any inert gases such as Argon or other noble gases.
• the temperature of the solution 222 can also be manipulated to select a corresponding reactivity.
• the temperature can be between about 0 and about 180 degrees C.
• Figure 4A shows a portion 402 of the substrate 208 that has been etched by exposure to hydrogen peroxide and UV light, in accordance with one embodiment of the present invention.
• the portion 402 is approximately 40 mm across.
• the substrate 208 has a surface layer that is about 3200 angstroms thick.
• Figure 4B is a graph 450, of a scan across the region 402, in accordance with one embodiment of the present invention. As shown in the graph 450, the surface layer has a thickness of about 3200 angstroms. Toward the center of the portion, the surface layer has been etched to a thickness of about 1900 angstroms. On average, the thickness of the surface layer has been reduced (e.g., etched) by about 800 angstroms.
• FIG. 5 shows a substrate 208, in accordance with one embodiment of the present invention.
• the substrate 208 includes an organic layer 504 formed on top of the substrate.
• a patterned mask layer 502 is formed on the organic layer 504.
• the mask layer 502 can be of a material that blocks the transmission of the light or at least those wavelengths of light that may be used to produce the reactive species.
• the patterned mask layer 502 is also substantially less reactive to the reactive species than the underlying organic layer 504 (e.g., the reacting species can be selective to the mask layer 502).
• a solution 222 is supported on the surface of the patterned mask layer 502.
• the patterned mask layer 502 includes an opening 508, through which the underlying organic layer 504 is exposed.
• the light source 230 directs light 232 through the solution 222 and onto the surface of the mask layer 502.
• Reactive species 512 are represented as star-shapes.
• the reactive species 512 are generated within the solution 222, only where the light 232 contacts the solution.
• the concentration of the reactive species 512 is very high near the surface of the solution 222.
• the concentration of the reactive species 512 is reduced as the depth of the solution 222 increases (e.g., near the bottom of the feature 514 that is being etched into the organic layer 504).
• the etching of the organic layer 504 is generally limited to the portion of the organic layer that is in a direct "line of sight" with the light source 230. While the reactive species 512 are not being generated in regions 510, a relatively low concentration of the reactive species does still exist outside of the direct light until the low concentration of reactive species undergo recombination. This distance is referred to a recombination length and is further defined as the distance the reactive species persist away from direct interaction with the light 232. As a result, the etching of the organic layer is substantially anisotropic. This can provide significant benefits in reduced undercutting that may occur in prior art, isotropic wet etching processes.
• FIG. 6 is a detailed view of a system 600 for generating reactive species upstream of the surface of the substrate, in accordance with one embodiment of the present invention.
• the system 600 includes a light source 230 that is enclosed within a light source enclosure 610.
• the light source enclosure 610 includes baffles 612 that block the UV from impinging on the surface 208 A.
• the light 232 In operation, the light 232 generates reactive species 614 (e.g., oxidizing radicals) in the solution 222 at a first concentration while exposed to the light 232.
• reactive species 614 e.g., oxidizing radicals
• the concentration of oxidizing radicals quickly dissipates.
• the first concentration is sufficiently high concentrated enough, then when the oxidizing radicals 614 pass through the baffles 612 and reach the surface 208A at second concentration of the oxidizing radicals.
• the second concentration of the oxidizing radicals is sufficient to oxidize the organic materials on the surface 208A.
• FIG. 7 is a diagram of a system 700 for generating reactive species upstream of the surface 208 A of the substrate, in accordance with one embodiment of the present invention.
• the system 700 includes a light source enclosure 610 wherein the light source 230' is oriented substantially parallel to the surface 208 A. The light 232' is therefore applied substantially parallel to the surface 208A. Baffles 612' ensure that the light 232' is blocked from reaching the surface 208A.
• FIG 8 is a diagram of a proximity head 810 for supporting a dynamic liquid meniscus, in accordance with one embodiment of the present invention.
• the proximity head 810 can include the light source enclosure 610.
• the reactive species 614 are generated in the light source enclosure 610.
• the solution, including the reactive species 614 is transported to the surface via a dynamic liquid meniscus 812.
• the proximity head 810 supports the dynamic liquid meniscus 812.
• the solution is provided to the proximity head 810 by a solution source 820.
• a second solution e.g., IPA
• One or both of the solution and the second solution can be transported to the proximity head at least in part by a substantially inert gas (e.g., nitrogen, argon, etc.).
• a substantially inert gas e.g., nitrogen, argon, etc.
• a vacuum source 232 is applied to the proximity head 810 from a vacuum source 822.
• the light source enclosure 610 included in the proximity head 810 may or may not include the baffles 612. In the light source enclosure 610 does not include the baffles, then the reactive species can be generated at the surface of the substrate as described above.
• FIG. 9 flowchart of the method operations 900 of generating oxidizing radicals for processing a substrate, in accordance with one embodiment of the present invention.
• a substrate is received for processing.
• a solution is applied to the surface of the substrate.
• the solution can be water, hydrogen peroxide or a mixture of water and hydrogen peroxide or other solutions from which reactive species can be generated as described herein.
• reactive species are generated in the solution. Illuminating the solution with a light of the desired wavelength and intensity can generate the reactive species.
• one or more oxidizing radicals can be generated from a solution containing water, hydrogen peroxide or a combination thereof.
• the reactive species are applied to the surface of the substrate until a desired quantity of organic material is reacted.
• the reactive species can be generated at the surface of the substrate (e.g., as described in Figures 2-5) or "up stream" of the surface of the substrate (e.g., as described in Figures 6-8).
• the reactive species readily react at least a portion of the organic material (e.g., an organic layer or an organic residue).
• the generation of the reactive species can be stopped and the surface rinsed to remove any reacted organic material.
• the method operations can then end.
• the invention may employ various computer-implemented operations involving data stored in computer systems. These operations are those requiring physical manipulation of physical quantities. Usually, though not necessarily, these quantities take the form of electrical or magnetic signals capable of being stored, transferred, combined, compared, and otherwise manipulated. Further, the manipulations performed are often referred to in terms, such as producing, identifying, determining, or comparing.
• any of the operations described herein that form part of the invention are useful machine operations.
• the invention also relates to a device or an apparatus for performing these operations.
• the apparatus may be specially constructed for the required purposes, or it may be a general-purpose computer selectively activated or configured by a computer program stored in the computer.
• various general-purpose machines may be used with computer programs written in accordance with the teachings herein, or it may be more convenient to construct a more specialized apparatus to perform the required operations.
• the invention can also be embodied as computer readable code on a computer readable medium.
• the computer readable medium is any data storage device that can store data that can thereafter be read by a computer system. Examples of the computer readable medium include hard drives, network attached storage (NAS), read-only memory, random- access memory, CD-ROMs, CD-Rs, CD-RWs, magnetic tapes, and other optical and non- optical data storage devices.
• the computer readable medium can also be distributed over a network coupled computer systems so that the computer readable code is stored and executed in a distributed fashion.

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• Cleaning Or Drying Semiconductors (AREA)
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• 2005
  • 2005-06-23 WO PCT/US2005/022172 patent/WO2006012174A2/en not_active Ceased
  • 2005-06-23 JP JP2007519288A patent/JP2008504714A/ja not_active Withdrawn
  • 2005-06-23 KR KR1020067027743A patent/KR20070026687A/ko not_active Withdrawn
  • 2005-06-23 EP EP05762857A patent/EP1782461A4/en not_active Withdrawn
  • 2005-06-23 CN CNA2005800285221A patent/CN101006571A/zh active Pending
  • 2005-06-28 TW TW094121622A patent/TWI271793B/zh not_active IP Right Cessation

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