Method for reducing roughness of materials using irradiated etchants - Patent Application 20070122997

Abstract

A method is disclosed for irradiating an etching solution to provide controlled etching of a material. An etching solution (e.g., gas, liquid, or a combination thereof) having a first level of reactants is applied to the surface of the material to be etched. The etching solution is irradiated so that the etching solution has a second level of reactants greater than the first level. The surface of the material is modified (e.g., oxidized) by the irradiated etching solution, and the modified layer of the material is removed. The exposure and removal can be repeated or cycled to etch the material. Furthermore, in oxidation / dissolution embodiments, oxidation and dissolution can occur simultaneously, and the oxidation rate can be greater than the dissolution rate. The material can be a polycrystalline material, polycrystalline metal, and / or other material. One etching solution can include hydrogen peroxide, which is irradiated to form hydroxyl radicals.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to the following applications: U.S. Provisional Patent Application No. 62 / 779,604, filed December 14, 2018, and entitled "ROUGHNESS REDUCTION METHODS FOR WET ETCH OF POLYCRYSTALLINE MATERIALS," and U.S. Patent Application No. 16 / 287,669, filed February 27, 2019, and entitled "ROUGHNESS REDUCTION METHODS FOR MATERIALS USING ILLUMINATED ETCH SOLUTIONS," the entire contents of which are incorporated herein by reference. [Background technology]

[0002] SUMMARY The present disclosure relates to methods for the fabrication of microelectronic workpieces that involve etching layers of material on the microelectronic workpieces.

[0003] Device formation within a microelectronic workpiece typically involves a series of manufacturing techniques involving the formation, patterning, and removal of many layers of material on a substrate for the microelectronic workpiece. Etch processes are often used to remove layers of material from the surface of the substrate. As feature sizes of materials to be etched for electronic devices formed on the microelectronic workpiece continue to shrink, it becomes increasingly difficult to control etch uniformity on the macroscale and microscale. Liquid Etching agent Traditional wet etch processes using etchants often lack precise nanoscale control over etching behavior. This lack of control is problematic where small amounts of material are to be removed and / or where a smooth surface finish is desired.

[0004] Roughness control during etch processing, especially for polycrystalline materials, is a challenging task. Polycrystalline materials exhibit variable reactivity to etchants depending on the surface crystal orientation of the polycrystalline material. Polycrystalline materials also exhibit variable reactivity to etchants at the grain boundaries and defect sites of the polycrystalline material. This variable reactivity leads to undesirable etching variability and surface roughness in traditional wet etch processes.

[0005] 1A-1B (Prior Art) provide diagrams associated with such prior etching solutions and related problems involving variable reactivity and undesirable etching variability.

[0006] Looking first at Figure 1A (Prior Art), an exemplary embodiment 100 is provided for traditional etching techniques. Etching agent 106 is applied to a material 104 on the surface of a substrate 108 for a microelectronic workpiece. In the exemplary embodiment 100, the material 104 to be etched is cobalt (Co), which is pre-formed on the surface of the substrate 108. In the exemplary embodiment 100, a liquid Etching agent 106 provides an oxidative dissolution etching mechanism in which the material 104 is etched by a liquid Etching agent oxidized by 106, then liquid Etching agent Dissolved by 106.

[0007] The traditional oxidative dissolution etching mechanism for cobalt leads to significant surface roughening and pitting. In this traditional approach, cobalt etching is driven by an oxidation / dissolution mechanism, where an oxidizing agent (e.g., hydrogen peroxide) oxidizes the cobalt as represented by arrow 110. ox The oxidation rate constant of CoO x Oxidize cobalt (Co) to form CoO x is then transferred to k as represented by arrow 112. d It is dissolved in solution through complexation with etchant molecules (e.g., citrate anions) with a dissolution rate constant of k ox is k dsmaller than (k ox <k d ), this condition results in uneven etching at the grain boundaries of the polycrystalline cobalt, leading to pitting and roughening of the surface.

[0008] 1B (Prior Art) provides a representative surface image 150 of this pitting and roughening of the surface due to the undesirable etching variability associated with traditional oxidative dissolution techniques. In contrast, an ideal wet etch process would provide a constant etch rate that is independent of the surface chemistry (e.g., grain boundaries) of the material being etched. Summary of the Invention [Means for solving the problem]

[0009] Etching agent Embodiments are described herein that provide controlled etching of materials using irradiation of Etching agent (e.g., gas Etching agent ,liquid Etching agent or a combination thereof) onto the material, Etching agent The radiation contains reactants that react with the surface of the material, ultimately leading to etching of the material. The material to be etched can be, for example, a polycrystalline material, a polycrystalline metal, and / or other material to be etched or polished. The disclosed embodiments utilize radiation as an external tool to contact the material. In etching agent The present invention provides a method for controlling the reactivity of an etchant at a material surface, thereby enabling modification of the etching behavior. Chemical composition and other parameters can also be used, in part, to control the etching behavior and the morphology and chemistry of the surface after etching. The disclosed embodiments thereby control and / or reduce surface roughness during etching of materials, such as polycrystalline materials, at both the microscopic and macroscopic levels. These results demonstrate the use of a etchant applied to a material surface to provide point-of-use generation of a highly reactive etchant that etches the material regardless of the surface chemistry of the material. Etching agentIn one exemplary embodiment, the liquid Etching agent is an aqueous solution containing hydrogen peroxide, where hydroxyl radicals are generated by irradiation (e.g., using ultraviolet light) to form a highly reactive etchant. Different or additional features, variations, and embodiments may be implemented, and related systems and methods may be utilized.

[0010] In one embodiment, the method includes receiving a substrate for a microelectronic workpiece having a material to be etched from a surface of the substrate; Etching agent Applying Etching agent having a first level of reactant for the material; Etching agent and exposing the surface of the material to radiation to form a modified layer of material on the surface of the material, wherein the exposure Etching agent A method of processing a substrate for a microelectronic workpiece is disclosed that includes causing a layer of material to have a second level of reactant to the material that is greater than the first level, and removing the modified layer of material.

[0011] In an additional embodiment, Etching agent is a gas Etching agent ,liquid Etching agent or a combination thereof. In a further embodiment, the method further comprises cyclically repeating the exposing and removing to etch the material. In a further embodiment, the exposing and removing occur in a single processing step. In yet a further embodiment, the exposing and removing occur in different processing steps.

[0012] In an additional embodiment, Etching agent is a liquid Etching agent wherein the exposure oxidizes the surface of the material to form an oxide as the modified layer. In a further embodiment, a uniform layer of oxide is formed and the removal is performed by applying a liquid to dissolve the oxide in a separate process step. Etching agent In a further embodiment, Etching agentcomprises an aqueous solution comprising hydrogen peroxide, and removing comprises using an aqueous solution comprising a complexing agent. In still further embodiments, the complexing agent comprises at least one of citrate, ethylenediamine, ethylenediaminetetraacetate (EDTA), malic acid, oxalic acid, glycine, alanine, or iminodiacetic acid.

[0013] In additional embodiments, the removal is performed by simultaneously oxidizing and removing the liquid. Etching agent In a further embodiment, the method comprises dissolving the oxide using a liquid Etching agent comprises an aqueous solution containing hydrogen peroxide and citrate.

[0014] In additional embodiments, the material to be etched comprises a polycrystalline metal. In further embodiments, the polycrystalline metal comprises cobalt.

[0015] In additional embodiments, the liquid Etching agent In a further embodiment, the liquid In etching agent In yet a further embodiment, the irradiation comprises irradiating the liquid with light having a wavelength of less than 560 nm. Etching agent In still further embodiments, the irradiation comprises irradiating the liquid with ultraviolet (UV) light having a wavelength between 10 nm and 400 nm. Etching agent In a further embodiment, the hydroxyl radicals oxidize the material.

[0016] In additional embodiments, the exposure comprises: Etching agent In a further embodiment, selectively irradiating includes irradiating with ultraviolet (UV) light in one or more on / off patterns. In a further embodiment, selectively irradiating includes using two or more different colors of light. In yet a further embodiment, removing also includes irradiating the modified layer of material using two or more different colors of light. In a further embodiment, selectively irradiating includes irradiating the modified layer where desired. Etching agentirradiating one or more areas of Etching agent This includes not irradiating other areas of the

[0017] In an additional embodiment, the method also includes controlling the exposure to compensate for non-uniform layer thickness within the surface. Etching agent comprises an aqueous solution containing at least one of ozone or hypochlorous acid.

[0018] In an additional embodiment, the method comprises: Etching agent and adjusting the exposure so that different areas of the material are exposed differently to provide different amounts of etching in the different areas. In a further embodiment, the method also includes measuring the material and controlling the adjustment based on the measurement to provide feedforward control. In yet a further embodiment, the measuring includes measuring at least one of a topology of a surface of the material or a thickness of the material.

[0019] In one embodiment, the method includes receiving a substrate for a microelectronic workpiece having polycrystalline metal to be etched from a surface of the substrate, applying a liquid containing hydrogen peroxide to the surface of the substrate, and Etching agent Apply the liquid Etching agent having a first level of reactant for the polycrystalline metal and a liquid Etching agent to cause the formation of hydroxyl radicals from hydrogen peroxide, wherein the formation of hydroxyl radicals at least partially Etching agent having a second level of reactant to the polycrystalline metal, the second level of reactant being greater than the first level of reactant; Etching agent A method of processing a substrate for a microelectronic workpiece is disclosed that includes oxidizing a polycrystalline metal with a fluorine atom to form a metal oxide and removing the metal oxide.

[0020] In an additional embodiment, the method also includes repeating the irradiation, oxidation, and removal to etch the polycrystalline metal. Etching agentwherein the oxidation has an oxidation rate constant greater than the dissolution rate constant of the dissolution.

[0021] In one embodiment, a method for polishing includes receiving a material to be polished and polishing a surface of the material. Etching agent Apply the Etching agent having a first level of reactant for the material; Etching agent and exposing the surface of the material to radiation to form a modified layer of material on the surface of the material, wherein the exposure Etching agent has a second level of reactant with the material that is greater than the first level; and removing the modified layer of the material so that the material has a polished surface, where the polished surface has a surface variation that is less than the surface of the material prior to the exposure and removal.

[0022] In an additional embodiment, Etching agent is a gas Etching agent ,liquid Etching agent or a combination thereof. In a further embodiment, the method also includes cyclically repeating the exposing and removing to polish the material.

[0023] Different or additional features, variations and embodiments may also be implemented and related systems and methods may be utilized.

[0024] A more complete understanding of the present invention and its advantages may be obtained by reference to the following description in conjunction with the accompanying drawings, in which like reference numerals indicate like features. It should be noted, however, that the accompanying drawings illustrate only exemplary embodiments of the disclosed concepts and therefore should not be considered limiting in scope, as other equally effective embodiments of the disclosed concepts may be recognized. [Brief explanation of the drawings]

[0025] [Figure 1A](PRIOR ART) Provides charts associated with prior etching solutions that suffer from problems associated with variable reactivity and undesirable etching variability. [Figure 1B] (PRIOR ART) FIG. 1A (PRIOR ART) provides a representative surface image of surface pitting and roughening due to undesirable etching variability associated with traditional oxidative dissolution techniques. [Figure 2A] An exemplary embodiment is provided in which irradiation of a liquid etchant is used to facilitate control, preferably real-time control, of the etch rate and uniformity of etching of material on the surface of a substrate for a microelectronic workpiece. [Figure 2B] 2B provides a representative surface image of the smooth surface achieved due to the improved etch uniformity associated with the irradiation approach of FIG. 2A. [Figure 3A] 1 provides a representative surface image of the roughness before the cyclic processing mode in which the oxidation and dissolution reactions are decoupled. [Figure 3B] 3A provides representative surface images of roughness reduction compared to FIG. 3A after etching using a cyclic processing mode. [Figure 3C] 3A and 3B provide representative diagrams of AFM (atomic force microscopy) surface roughness profiles before and after etching treatment as represented by the surface images of FIGS. 3A and 3B. [Figure 4A] An exemplary embodiment 400 of a scanner solution is provided in which a light emitting diode (LED) array is used to illuminate a liquid etchant applied to the surface of a substrate for a microelectronic workpiece. [Figure 4B] An exemplary embodiment is provided in which irradiation of a liquid etchant dispensed onto a surface of a substrate for a microelectronic workpiece is supplied by one or more laser sources. [Figure 5A] 1 is a process flow diagram of an exemplary embodiment of using radiation to adjust reactants in a liquid etchant to thereby improve etch uniformity in etching of material on a surface of a substrate for a microelectronic workpiece. [Figure 5B]1 is a process flow diagram of an exemplary embodiment that uses irradiation to form hydroxyl radicals in a liquid etchant with hydrogen peroxide, thereby improving etch uniformity in etching polycrystalline metal on the surface of a substrate for a microelectronic workpiece. [Figure 6] 1 is a process flow diagram of an exemplary embodiment in which irradiation is used to adjust reactants within an etchant (e.g., at least one of a gas etchant, a liquid etchant, or a combination thereof) to thereby improve etch uniformity in etching of material on a surface of a substrate for a microelectronic workpiece. [Figure 7] 1 is a process flow diagram of an exemplary embodiment of polishing a material using irradiation of an etchant (e.g., at least one of a gas etchant, a liquid etchant, or a combination thereof). DETAILED DESCRIPTION OF THE INVENTION

[0026] As described herein, methods are disclosed that provide controlled etching of materials, such as polycrystalline materials or metals, using irradiation to modulate the reactivity of an etchant to facilitate etching independent of the surface chemistry of the material. Other advantages and implementations can be achieved while still utilizing the processing techniques described herein.

[0027] Controlling nanoscale etch uniformity helps minimize device failure in microelectronic devices and circuits formed on microelectronic workpieces. Traditional wet etching chemistries often fail to provide precise etch control for materials such as polycrystalline materials and metals. For example, variable etch rates at grain boundaries and / or on different crystal facets of polycrystalline materials can lead to surface roughening during etching. The disclosed embodiments provide a method for achieving etch uniformity at both the microscale and macroscale by generating highly reactive etchants at the point of use through controlled irradiation. In one embodiment, the disclosed embodiments provide these beneficial results when used to etch metal polycrystalline structures, such as polycrystalline metallic cobalt. Other polycrystalline materials and polycrystalline metals, as well as other materials, can also be etched using the irradiation techniques described herein.

[0028] In one embodiment, the highly reactive hydroxyl radical (HO * ) is applied to the surface of a polycrystalline material Etching agent Hydroxyl radicals are generated as etchants for polycrystalline materials through irradiation with ultraviolet (UV) light. Hydroxyl radicals are strong oxidizers and will etch polycrystalline materials at room temperature. In one embodiment, hydroxyl radicals are generated using ultraviolet (UV) light irradiation of an aqueous solution of hydrogen peroxide (H2O2) in contact with the material to be etched. Irradiation can also be selectively provided at the point of use to better control the etch process and rate.

[0029] This point-of-use solution uses liquid Etching agentOne or more areas of a solution (e.g., an aqueous solution of hydrogen peroxide) are selectively irradiated where etching of the surface is desired, while other areas where etching is not desired are not irradiated. For example, irradiation of hydrogen peroxide results in the formation of hydroxyl radicals, which lead to increased levels of the reactant. However, once irradiation is removed, the hydroxyl radicals are short-lived and are rapidly reabsorbed into the aqueous solution. For example, the lifetime of hydroxyl radicals after removal of irradiation is less than 2-5 microseconds. As such, selective UV irradiation can be used to tailor the reactivity of the etchant and, therefore, the liquid. Etching agent The thermodynamics and kinetics of the etching reaction can be modified for selective areas of hydroxyl radicals. The high reactivity coupled with the microsecond lifetime of hydroxyl radicals allows for rapid and / or near-instantaneous oxidation of the material surface layer, regardless of local surface reactivity. Subsequent removal of the oxide layer provides a smooth etched surface. Additionally, large-scale etch uniformity can be achieved by spatially adjusting the UV light intensity in a feedforward process during the irradiation process. Other variations can also be implemented while still utilizing the techniques described herein.

[0030] One key advantage of the disclosed embodiments is the ability to nearly instantaneously tune the reactivity of an etchant in situ using controlled irradiation. This tunability allows access to a wider parameter space on the potential-pH diagram (i.e., Pourbaix diagram) of a photosensitive etchant without the need to mix additional reactants and chemicals. This simplifies the process chemistry and reduces the cost of wet etch processing.

[0031] As described herein, the disclosed embodiments provide one or more of the following: (1) real-time, point-of-use adjustment of etchant reactivity, allowing for tuning of etching behavior without the need for additional chemical mixtures or aggressive conditions; (2) taking advantage of the short lifetime of reactive, transient excited states by creating reactive, transient excited states at the surface of a microelectronic workpiece (e.g., a semiconductor wafer) and then using them to etch the surface; (3) controlling surface roughness during etching of polycrystalline materials; (4) enabling temporal and spatial control of etch rates on the surface of a microelectronic workpiece; and / or (5) providing feedforward control to compensate for non-uniform layer thicknesses across a microelectronic workpiece. Additional and / or different advantages and features may also be provided in accordance with the techniques described herein.

[0032] 2A-2B and 3A-3C illustrate a liquid applied to a polycrystalline material to be etched on the surface of a microelectronic workpiece. Etching agent 10 provides diagrams associated with disclosed embodiments in which irradiation is used to adjust the etch rate of a . Additional and / or different embodiments can be implemented utilizing the techniques described herein.

[0033] It should be noted that the illumination described herein can be selective illumination applied in real time to provide point-of-use control. Etching agent Typically, for a given material, a solution has a set reactivity and etch rate based on the solution's composition and temperature. The disclosed embodiments provide a method for analyzing a liquid having a given composition at a given temperature in real time. Etching agent Additionally, the disclosed embodiments allow for adjustment of the etch rate with respect to the position and / or location of the material on the surface of the microelectronic workpiece, and feed-forward control can be utilized to achieve greater uniformity across the microelectronic workpiece.

[0034] traditional Etching agent It is further noted that the solution potential and pH of the solution place the solution at a single point on the Pourbaix diagram. The parameters are set by the composition of the solution, which uniquely sets the thermodynamic equilibrium species that will exist when the solution is placed in contact with the surface to be etched, and also sets the solubility of the etch products. As such, the etching behavior of the system is determined.

[0035] In contrast, the disclosed embodiments use irradiation to enhance the reactivity and / or Etching agent In an embodiment herein, a wet etch process is provided in which the potential of the electrode is adjusted to achieve a desired etching behavior. Etching agent The liquid contains a photosensitive compound that undergoes a photochemical reaction upon irradiation to produce a reactive etchant (e.g., radicals or radical ions). Etching agent may also contain additional components to solubilize or volatilize the etching products.

[0036] In one embodiment, the hydroxyl radical (HO * ) is used as a transient excited state species, generated from the photolysis of hydrogen peroxide. Other examples include, but are not limited to, singlet oxygen, excited state molecules, radicals, dimers, complexes, and / or other materials with properties that allow reactive etchants to be generated and / or tuned through irradiation. For example, similar reactive species can be generated from the photolysis of aqueous solutions of ozone or hypochlorous acid. Other variations can also be implemented.

[0037] In one exemplary implementation, the disclosed embodiments are used to reduce surface roughening in etching of polycrystalline metallic materials. In a further exemplary embodiment, the polycrystalline metallic material is cobalt.

[0038] Wet etching of polycrystalline materials is often achieved through an oxidative dissolution mechanism. Etchant solutions contain oxidizers and reactants that promote the dissolution of etch products. The etching behavior (e.g., etch rate, etch uniformity) and therefore the final surface morphology are a function of the chemical reactions at given locations on the surface of the material to be etched. Variable etch rates on polycrystalline materials are a common problem with traditional wet etch processes, and this variability often leads to undesirable surface morphologies such as roughening and pitting. As described herein, adjusting the oxidation and dissolution reaction rates through irradiation, preferably in real time, makes it possible to modify the etching behavior and achieve uniform etching.

[0039] Hydrogen peroxide is a commonly used etchant in wet etch processes. As recognized in the present embodiment, irradiation of hydrogen peroxide with light having a wavelength (λ) less than 560 nanometers (nm) (i.e., λ<560 nm) results in quantitative photolysis to form hydroxyl radicals. For example, UV light having a wavelength between 10 nm and 400 nm can be used for this irradiation (e.g., 10 nm≦λ≦400 nm). Hydroxyl radicals have a very high oxidation potential (e.g., 2.8 volts) and a microsecond lifetime (e.g., lifetime ≦2-5 microseconds). The combination of high reactivity and short lifetime allows for the near-instant oxidation of a uniform surface layer, which can then be removed.

[0040] Cobalt can be considered an exemplary polycrystalline material that can be etched using the disclosed embodiments.

[0041] Looking first at FIG. 2A, an exemplary embodiment 200, as described herein, utilizes a liquid etchant to facilitate control, preferably real-time control, of etch rate and uniformity. Etching agent is used, provided in accordance with the disclosed technique. Etching agent206 is applied to a material 204 on the surface of a substrate 208 for a microelectronic workpiece. In the exemplary embodiment 200, the material 204 to be etched is cobalt (Co), which is pre-formed on the surface of the substrate 208. In the exemplary embodiment 200, a liquid Etching agent 206 provides an oxidative dissolution etching mechanism in which the material 204 is dissolved in a liquid Etching agent oxidized by 206, then liquid Etching agent In contrast to the previous solution, in accordance with the techniques described herein, the liquid Etching agent Irradiation 205 is used to transition 206 from a first level of reactant with material 204 on the surface of substrate 208 to a second level of reactant with material 204. Furthermore, the second level of reactant is greater than the first level of reactant.

[0042] In one embodiment, a liquid containing hydrogen peroxide (H2O2) Etching agent When irradiated with UV light, hydrogen peroxide is split into two hydroxyl radicals (OH * ) is formed. This formation of hydroxyl radicals raises the oxidation potential of the solution from about 1.8 volts (V) to about 2.8 V. The reactive hydroxyl radicals speed up the oxidation reaction, increasing the oxidation rate constant k represented by arrow 210. ox is the dissolution rate constant k d This dissolution rate is significantly increased by the oxidation rate (k ox >>k d ) facilitates the formation of a thin, uniform layer of oxide 214 on the material surface at a constant rate. This oxide 214 is then slowly removed to provide a smooth surface. When cobalt is the material 108, cobalt oxide (CoOx) is the oxide 214.

[0043] 2B provides a representative surface image 250 of this smooth surface resulting from the improved etch uniformity associated with the irradiation approach of the disclosed embodiments described herein. In the representative surface image 250, scale is provided by a bar 252 representing a length of 500 nm.

[0044] It should be noted that the rapid formation of the surface oxide layer additionally blocks etchant diffusion through grain boundaries and defect sites in polycrystalline materials, thereby reducing or minimizing pitting. From surface morphology analysis, pitting-related corrosion also did not occur under or was reduced using the irradiation techniques described herein. In addition, surface roughness was significantly reduced from its initial value. Additional and / or different benefits may also be achieved.

[0045] Exemplary process modes were also tested using the UV-enhanced peroxide (UVP) wet etching method described herein for etching polycrystalline materials. To these exemplary process modes, two exemplary process modes in which the UVP wet etching method was applied were used to etch polycrystalline cobalt: a continuous UVP process and a cyclical oxidative dissolution process.

[0046] As an example of a sequential UVP treatment, a mixture of hydrogen peroxide (H2O2) and citric acid (e.g., in the form of citrate) adjusted to a pH of 10 (pH=10) was used. In this mode, the oxidation and dissolution reactions are simultaneous. The results of this treatment, with irradiation, are shown in Figure 2B with a representative image 250. The results of this treatment, without irradiation, are shown in Figure 1B (Prior Art) with a representative surface image 150.

[0047] As noted above, Figure 1A (Prior Art) provides an exemplary embodiment 100 of the oxidation and dissolution kinetics of cobalt in contact with an aqueous solution of hydrogen peroxide (HO) and citrate in the absence of UV irradiation. Figure 1B (Prior Art) corresponds to an exemplary surface image 150 of the post-etch morphology of the treatment without UV irradiation as represented by Figure 1A (Prior Art).

[0048] In contrast, as noted above, Figure 2A provides an exemplary embodiment 200 of the oxidation and dissolution kinetics of cobalt in contact with an aqueous solution of HO and citrate in the presence of UV irradiation. Figure 2B corresponds to an exemplary surface image 250 of the post-etch morphology of the treatment with UV irradiation as represented by Figure 2A. UV irradiation generates transient hydroxyl radicals, enabling higher oxidation rates that lead to reduced surface roughness even for very low etch amounts.

[0049] In one embodiment, a cyclic processing mode is used. In this example cyclic processing mode, the oxidation and dissolution reactions are separated. In a first step, the cobalt is oxidized using an irradiation process (e.g., a UVP process) in the absence of citrate (e.g., dissolved away) for a given time. Then, an aqueous solution of citric acid (e.g., in the form of citrate) is used to remove the oxide (e.g., oxidized cobalt) layer. Careful control of the UVP oxidation and dissolution times allows for uniform etching of the cobalt.

[0050] It should be noted that the complexing agent is not limited to citrate, and different complexing agents can be used for this purpose. For example, the complexing agent can include ligands from the families of carboxylic acids, amines, amino acids, alcohols, etc. Examples include, but are not limited to, ethylenediamine, ethylenediaminetetraacetic acid (EDTA), malic acid, oxalic acid, glycine, alanine, and iminodiacetic acid. It should further be noted that the removal rate depends on the type of complexing agent.

[0051] Figures 3A-3C provide representative results of this cyclic processing mode.

[0052] Figure 3A provides a representative surface image 300 of roughness before cycling. This diagram represents the material on the surface of the substrate as received. In this example, the material layer is 30 nm thick and has an RMS (root mean square) roughness of 1.76 nm.

[0053] FIG. 3B provides a representative surface image 350 of the roughness reduction compared to FIG. 3A after etching polycrystalline cobalt using a cyclic UVP process. The material layer is now 26 nm thick, as 4 nm was removed by etching. The RMS roughness has improved to 0.86 nm, and the roughness reduction is visible in the surface image. In the representative surface image 350, a scale is provided by the bar 352, which represents a length of 200 nm.

[0054] FIG. 3C provides a representative diagram 370 of AFM (atomic force microscopy) surface roughness profiles 374 / 376 before and after the etching process represented by the surface images of FIGS. 3A and 3B. The roughness profiles 374 / 376 show the smoothing effect of the etching process, for example, after etching 4 nm from the surface of polycrystalline cobalt. The vertical axis represents the normalized height of the surface in nanometers, and the horizontal axis represents the length in micrometers (μm) in one direction along the surface of the material. The top line is roughness profile 374, which represents the surface of the material as received, and the as-received surface variation is represented by bar 378. The bottom line is roughness profile 376, which represents the surface of the material after etching 4 nm, and the post-etched surface variation is represented by bar 380. In the representative diagram 370 and roughness profiles 374 / 376, the scale is provided by bar 372, which represents a length of 4 nm. As can be seen, the surface roughness is significantly reduced by the cycling process.

[0055] In additional embodiments, the liquid Etching agent Through spatial and / or temporal control of the UV light intensity delivered to the liquid, the etch rate can be controlled over a relatively large surface area of ​​the substrate of the microelectronic workpiece. Etching agent the liquid while leaving other areas unexposed to UV light. Etching agent Different areas of the surface can be irradiated with UV light. For temporal control, the UV light can be applied to different areas of the surface for different amounts of time. As such, by adjusting the spatial and / or temporal irradiation of the surface of the microelectronic workpiece, different etching rates are achieved.

[0056] Liquids applied to the surface of substrates for microelectronic workpieces, including spinner solutions and laser / scanner solutions Etching agent A variety of illumination systems can be used to illuminate the wafer. When implemented in a spinner, the illumination source can optionally be synchronized with the substrate motion to illuminate individual areas of the wafer with a time-invariant intensity. Spatially resolved illumination can be achieved, for example, using a light-emitting diode (LED) array. LED arrays work well when low spatial resolution is acceptable. The LED array can be rotated synchronously with the substrate in the spin chamber, or the spatial intensity of the array can be synchronized with the wafer motion. If higher spatial resolution is desired, a laser source and scanner can be used to provide illumination. The laser source can be moved / scanned across the wafer surface in a motion that provides greater light intensity to areas of the wafer requiring a higher etch rate. Both of these exemplary implementations can be used to illuminate the wafer with a single wavelength or multiple wavelengths to illuminate the wafer. In etching agent The reactants can be adjusted. Note that other light sources can also be used. Furthermore, light sources can be combined, for example, zone flood exposure extended with precision laser scanning can be used as the illumination system. Other variations and implementations can also be used while still utilizing the techniques described herein.

[0057] 4A-4B provide exemplary embodiments of scanner and laser / scanner solutions for illuminating the surface of a microelectronic workpiece.

[0058] Looking first at FIG. 4A, an exemplary embodiment 400 illustrates a liquid applied to a surface of a substrate for a microelectronic workpiece, such as a semiconductor wafer 404. Etching agent Prior to irradiation, a liquid is applied onto the surface of the wafer 404 in the spin chamber using a delivery system 406. Etching agent is dispensed. In the exemplary embodiment 400, the LED array 402 can be a single wavelength or multiple wavelengths by interspersing different emitters within the array. The power of the individual emitters can be adjusted in real time to control the illumination intensity across the surface of the wafer. In one embodiment, the LED array 402 is mechanically synchronized to the movement of the wafer 404, as indicated by arrows 403 and 405. In another embodiment, the LED array 402 remains stationary while the intensity of the individual emitters is synchronized to the movement of the wafer 404. Additional variations can also be implemented.

[0059] FIG. 4B illustrates a liquid dispensed onto the surface of a substrate for a microelectronic workpiece, such as a semiconductor wafer 404. Etching agent 450 is provided in an exemplary embodiment in which the irradiation is provided by one or more laser sources 452 / 456. Prior to irradiation, a liquid is applied onto the surface of the wafer 404 in the spin chamber using a delivery system 406. Etching agent is dispensed. A single laser or multiple laser sources 452 / 456 are then used for irradiation. For example, if it is desired to irradiate the wafer 404 with multiple wavelengths, multiple laser sources 452 / 456 can be used. Steering optics 454 / 458 are used to raster the laser beams from the laser sources 452 / 456 over the wafer surface. The dwell time of the laser spot over each point on the surface of the wafer 404 controls the etch enhancement at that point. The movement of the laser beam can be synchronized with the movement of the wafer 404, as represented by arrows 405, 455, and 459.

[0060] In yet additional embodiments, etch uniformity can be improved across a relatively large surface area of ​​a substrate of a microelectronic workpiece through feedforward techniques. For example, the surface topology and / or layer thickness of the substrate can be measured across a selected surface area, and the amount of etching of different regions within this surface area can be determined based on the measurements and the desired results. For example, if a resulting smooth surface is desired, spatial and / or temporal control of UV light exposure can be used to adjust local etch rates to even out peaks and valleys in the topology to achieve the desired target surface parameters. As such, feedforward control provides a technique for compensating for non-uniform layer thicknesses and / or other variations across a microelectronic workpiece.

[0061] Figure 5A shows the liquid Etching agent 5 is a process flow diagram of an exemplary embodiment 500 for adjusting reactants in a liquid to thereby improve etch uniformity of etching of material on a surface of a substrate for a microelectronic workpiece. At block 502, a substrate for a microelectronic workpiece is received, the substrate having material to be etched from the surface of the substrate. At block 504, a liquid Etching agent is applied to the surface of the substrate, and the liquid Etching agent At block 506, the liquid Etching agent is irradiated and the liquid Etching agent At block 508, the material is mixed with a liquid having a second level of reactant for the material, the second level being greater than the first level. Etching agent to form an oxide. The oxide is removed at block 510. Note that additional and / or different processes may be used while still utilizing the irradiation techniques described herein.

[0062] FIG. 5B shows the use of irradiation to convert a liquid containing hydrogen peroxide into Etching agent5 is a process flow diagram of an exemplary embodiment 550 for forming hydroxyl radicals in a solution to thereby improve etch uniformity in etching a polycrystalline metal on a surface of a substrate for a microelectronic workpiece. At block 552, a substrate for a microelectronic workpiece is received, the substrate having a polycrystalline metal to be etched from the surface of the substrate. At block 554, a liquid containing hydrogen peroxide is added to the solution. Etching agent is applied to the surface of the substrate, and the liquid Etching agent At block 556, the liquid Etching agent is irradiated to cause the formation of hydroxyl radicals from hydrogen peroxide, and the formation of hydroxyl radicals causes, at least in part, the formation of liquid Etching agent At block 558, the polycrystalline metal is dissolved in a liquid Etching agent to form a metal oxide. The metal oxide is removed at block 560. Note that additional and / or different processes may be used while still utilizing the irradiation techniques described herein.

[0063] Figure 6 shows the use of irradiation Etching agent (e.g., gas Etching agent ,liquid Etching agent 6 is a process flow diagram of an example embodiment 600 for adjusting reactants in a substrate (at least one of a substrate, a substrate layer, a substrate surface, a substrate layer ... Etching agent is applied to the surface of the substrate, Etching agent has a first level of reactants for the material. Etching agent and the surface of the material is exposed to radiation to form a modified layer of material on the surface of the material, the exposure causing Etching agentThe modified layer of material is then removed at block 608. Note that additional and / or different processes may be used while still utilizing the irradiation techniques described herein.

[0064] Figure 7 shows Etching agent (e.g., gas Etching agent ,liquid Etching agent 7 is a process flow diagram of an exemplary embodiment 700 for polishing a material using radiation of at least one of: irradiating a material with a laser beam; irradiating a material with a laser beam; and irradiating a material with a laser beam. At block 702, a material to be polished is received. At block 704, Etching agent is applied to the surface of the material, Etching agent has a first level of reactants for the material. Etching agent and the surface of the material is exposed to radiation to form a modified layer of material on the surface of the material, the exposure causing Etching agent The modified layer of material has a second level of reactant to the material that is greater than the first level. At block 708, the modified layer of material is removed, leaving the material with a polished surface. The polished surface is polished in that it has less surface variation than the surface of the original material being etched. It should be noted that additional and / or different processes may be used while still utilizing the irradiation techniques described herein.

[0065] It should be noted that one or more deposition processes may be used to form the material layers described herein. For example, one or more deposition processes may be performed using a chemical vapor deposition (CVD) process, a plasma-enhanced CVD (PECVD) process, a physical vapor deposition (PVD) process, an atomic layer deposition (ALD) process, and / or other deposition processes. For plasma deposition processes, precursor gas mixtures may be used, including, but not limited to, hydrocarbons, fluorocarbons, or hydrocarbon-containing nitrogen in combination with one or more diluent gases (e.g., argon, nitrogen, etc.) at various pressure, power, flow, and temperature conditions. Lithography processes for photoresist (PR) layers may be performed using optical lithography, extreme ultraviolet (EUV) lithography, and / or other lithography processes. Etch processes may be performed using plasma etch processes, discharge etch processes, and / or other desired etch processes. For example, plasma etch processes may be performed using plasmas containing fluorocarbons, oxygen, nitrogen, hydrogen, argon, and / or other gases. Additionally, operating variables of the process can be controlled to ensure that CD (critical dimension) target parameters of the via are achieved during via formation. Operating variables can include, for example, chamber temperature, chamber pressure, gas flow rate, frequency and / or power applied to the electrode assembly in generating the plasma, and / or other operating variables for the process. Variations can also be implemented while still utilizing the techniques described herein.

[0066] It should be noted that references throughout this specification to "one embodiment" or "an embodiment" mean that a particular feature, structure, material, or characteristic described in connection with that embodiment is included in at least one embodiment of the present invention, but do not indicate that it is present in every embodiment. Thus, the appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification do not necessarily refer to the same embodiment of the present invention. Furthermore, particular features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments. In other embodiments, various additional layers and / or structures may be included and / or described features may be omitted.

[0067] As used herein, "microelectronic workpiece" refers generally to an object processed in accordance with the present invention. A microelectronic workpiece may include any material portion or structure of a device, particularly a semiconductor device, or other electronic device, and may be a base substrate structure, such as a semiconductor substrate, or a layer on or overlying the base substrate structure, such as a thin film. Thus, it is not intended to limit the workpiece to any particular base structure, underlying layer, or overlying layer, patterned or unpatterned, but rather is intended to include any such layer or base structure and any combination of layers and / or base structures. While the following description may refer to a particular type of substrate, this is for illustrative purposes only and not limitation.

[0068] As used herein, the term "substrate" refers to and includes a base material or structure upon which a material is formed. It will be understood that a substrate can include a single material, multiple layers of different materials, one or more layers having regions of different materials or structures therein, etc. These materials can include semiconductors, insulators, conductors, or combinations thereof. For example, a substrate can be a semiconductor substrate, a base semiconductor layer on a supporting structure, a metal electrode, or a semiconductor substrate having one or more layers, structures, or regions formed thereon. A substrate can be a conventional silicon substrate or other bulk substrate including a layer of semiconductor material. As used herein, the term "bulk substrate" refers to and includes not only silicon wafers, but also silicon-on-insulator ("SOI") substrates such as silicon-on-sapphire ("SOS") substrates and silicon-on-glass ("SOG") substrates, epitaxial layers of silicon on a base semiconductor substrate, and other semiconductor or optoelectronic materials, such as silicon germanium, germanium, gallium arsenide, gallium nitride, and indium phosphide. The substrate may be doped or undoped.

[0069] Systems and methods for processing microelectronic workpieces have been described in various embodiments. Those skilled in the art will recognize that the various embodiments may be practiced without one or more of the specific details, or with other substitutions and / or additional methods, materials, or components. In other instances, well-known structures, materials, or operations have not been shown or described in detail to avoid obscuring aspects of the various embodiments of the invention. Similarly, specific numbers, materials, and configurations are set forth for purposes of explanation to provide a thorough understanding of the invention. However, the invention may be practiced without the specific details. Furthermore, it is understood that the various embodiments shown in the figures are illustrative representations and are not necessarily drawn to scale.

[0070] Further modifications and alternative embodiments of the described systems and methods will be apparent to those skilled in the art in light of this specification. Accordingly, it will be appreciated that the described systems and methods are not limited by these exemplary configurations. It should be understood that the forms of the systems and methods shown and described herein should be taken as exemplary embodiments. Various changes in implementation may be made. Accordingly, although the invention is described herein with reference to specific embodiments, various modifications and changes may be made without departing from the scope of the invention. Accordingly, the specification and accompanying drawings should be regarded in an illustrative rather than a restrictive sense, and such modifications are intended to be included within the scope of the invention. Furthermore, any benefits, advantages, or solutions to problems described herein with reference to specific embodiments are not intended to be construed as critical, required, or essential features or elements of any or all claims.

Claims

1. 1. A method for processing a substrate for a microelectronic workpiece, comprising: receiving a substrate for a microelectronic workpiece having polycrystalline material to be etched from a surface of the substrate; applying an etchant to the surface of the substrate, the etchant having a first level of reactant with the polycrystalline material; exposing the etchant and the surface of the polycrystalline material to radiation to form an oxidized layer of material on the surface of the polycrystalline material, wherein the exposure causes the etchant to have a second level of reactants with the polycrystalline material, the second level of reactants having an oxidation rate constant greater than the oxidation rate constant of the first level of reactants; removing the oxide layer of material by dissolution, wherein an oxidation rate constant of the second level reactant is greater than a dissolution rate constant of the dissolution; the etching agent comprises an aqueous solution containing hydrogen peroxide, and the removing comprises using an aqueous solution containing a complexing agent. method.

2. The method of claim 1 , wherein the etching agent comprises at least one of a gaseous etching agent, a liquid etching agent, or a combination thereof.

3. The method of claim 1 , further comprising cyclically repeating said exposing and removing to etch said material.

4. The method of claim 1 , wherein the exposing and removing are performed in at least one of a single process step or multiple process steps.

5. The method of claim 1 , wherein the etchant comprises a liquid etchant.

6. The method of claim 5 , wherein the removing comprises using the liquid etchant in multiple process steps to dissolve the oxide layer.

7. 10. The method of claim 1, wherein the complexing agent comprises at least one of citrate, ethylenediamine, ethylenediaminetetraacetate (EDTA), malic acid, oxalic acid, glycine, alanine, or iminodiacetic acid.

8. The method of claim 5 , wherein the removing comprises dissolving the oxide layer using the liquid etchant simultaneously with oxidation.

9. 1. A method for processing a substrate for a microelectronic workpiece, comprising: receiving a substrate for a microelectronic workpiece having polycrystalline material to be etched from a surface of the substrate; applying an etchant to the surface of the substrate, the etchant having a first level of reactant with the polycrystalline material; exposing the etchant and the surface of the polycrystalline material to radiation to form an oxidized layer of material on the surface of the polycrystalline material, wherein the exposure causes the etchant to have a second level of reactants with the polycrystalline material, the second level of reactants having an oxidation rate constant greater than the oxidation rate constant of the first level of reactants; removing the oxide layer of material by dissolution, wherein an oxidation rate constant of the second level reactant is greater than a dissolution rate constant of the dissolution; the removing includes dissolving the oxide layer using a liquid etchant simultaneously with oxidation; the liquid etchant comprises an aqueous solution containing hydrogen peroxide and citrate; method.

10. 6. The method of claim 5, wherein the polycrystalline material to be etched comprises a polycrystalline elemental metal, the polycrystalline elemental metal comprising cobalt.

11. The method of claim 5 , wherein the liquid etchant comprises hydrogen peroxide.

12. 12. The method of claim 11 , wherein the irradiation of the hydrogen peroxide results in the formation of hydroxyl radicals in the liquid etchant, and the second level of reactants results at least in part from the formation of the hydroxyl radicals, which oxidize the material.

13. 13. The method of claim 12, wherein the irradiating comprises irradiating the liquid etchant with light having at least one of a wavelength less than 560 nm or a wavelength between 10 nm and 400 nm.

14. The method of claim 1 , wherein the exposing comprises selectively irradiating the etchant.

15. 15. The method of claim 14, wherein the selectively irradiating comprises irradiating with ultraviolet (UV) light in one or more on / off patterns.

16. 15. The method of claim 14, wherein the selectively irradiating comprises irradiating with two or more different colors of light, and the removing comprises irradiating the oxidized layer of material using two or more different colors of light.

17. 15. The method of claim 14, wherein the selectively irradiating comprises irradiating one or more areas of the etchant where an oxide layer is desired and not irradiating other areas of the etchant.

18. 1. A method for processing a substrate for a microelectronic workpiece, comprising: receiving a substrate for a microelectronic workpiece having polycrystalline material to be etched from a surface of the substrate; applying an etchant to the surface of the substrate, the etchant having a first level of reactant with the polycrystalline material; exposing the etchant and the surface of the polycrystalline material to radiation to form an oxidized layer of material on the surface of the polycrystalline material, wherein the exposure causes the etchant to have a second level of reactants with the polycrystalline material, the second level of reactants having an oxidation rate constant greater than the oxidation rate constant of the first level of reactants; removing the oxide layer of material by dissolution, wherein an oxidation rate constant of the second level reactant is greater than a dissolution rate constant of the dissolution; the etching agent comprises an aqueous solution containing at least one of ozone or hypochlorous acid; method.

19. 1. A method for processing a substrate for a microelectronic workpiece, comprising: receiving a substrate for a microelectronic workpiece having polycrystalline material to be etched from a surface of the substrate; applying an etchant to the surface of the substrate, the etchant having a first level of reactant with the polycrystalline material; exposing the etchant and the surface of the polycrystalline material to radiation to form an oxidized layer of material on the surface of the polycrystalline material, wherein the exposure causes the etchant to have a second level of reactants with the polycrystalline material, the second level of reactants having an oxidation rate constant greater than the oxidation rate constant of the first level of reactants; removing the oxide layer of material by dissolution, wherein an oxidation rate constant of the second level reactant is greater than a dissolution rate constant of the dissolution; adjusting the exposure so that different areas of the etchant are exposed in different ways to provide different amounts of etching in the different areas; The method further includes measuring the polycrystalline material to provide feedforward control and controlling the adjusting based on the measuring, the measuring including measuring at least one of a topology of a surface of the polycrystalline material or a thickness of the polycrystalline material. method.

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