Method for improving selectivity in selective etching process

Abstract

The processing method includes etching the metal nitride layer with an etchant. The etchant may be, for example, WCl5, WOCl4 or TaCl5. A method for improving the selectivity of the etching process is also disclosed.

Description

Technical Field

[0001] The present disclosure relates to methods of etching thin films. In particular, the present disclosure relates to processes for selectively etching metal nitride films for metal gate applications. Background Art

[0002] The semiconductor industry is rapidly developing chips with smaller and smaller transistor sizes to achieve more functionality per unit area. As device sizes continue to shrink, the gaps / spaces between devices also continue to shrink, increasing the difficulty of physically isolating a device from another device. Filling high aspect ratio trenches / spaces / gaps between devices with high quality dielectric materials, which are often formed into irregular shapes, becomes extremely challenging for existing methods including gap filling, hard mask and spacer application.

[0003] Integrated circuits are fabricated by processes that create complex patterned layers of material on a substrate surface. Creating patterned material on a substrate requires a controlled method for removing exposed material. It is often useful to have an etch process that etches one material faster than another. This etch process is said to be selective for the first material. Due to the diversity of materials, circuits, and processes, etch processes have been developed that selectively remove one or more materials from a wide range of materials.

[0004] Metal nitrides (e.g., TaN and TiN) are widely used in metal gates as high-k and n-type metal capping, p-type metal, or etch stop layers. In advanced integration schemes (10nm and beyond 10nm), both TaN and TiN are often exposed on the surface before subsequent metal deposition. To achieve tunable work function, it would be useful to control the thickness of the substrate TaN or TiN before metal deposition.

[0005] Existing methods for selectively etching one metal nitride over another do not exhibit high levels of etch selectivity. Therefore, processes seeking to utilize existing methods must deposit a larger amount of nitride film, so that a longer etch is performed in order to establish a sufficient thickness difference between the two metal nitride films. The deposition of thicker layers and longer etch processes require additional processing time and material sources, thereby reducing yield and increasing manufacturing costs.

[0006] Therefore, there is a need in the art for new methods of selectively etching metal nitride films with increased selectivity. Summary of the invention

[0007] One or more embodiments of the present disclosure relate to an etching method that includes providing a substrate having a metal nitride film thereon. The metal nitride film includes atoms of a first metal and nitrogen atoms. The metal nitride film is exposed to a co-flow of an etchant and hydrogen gas to etch the metal nitride film. The etchant has an empirical formula that includes one or more atoms of a second metal, one or more atoms of oxygen, and one or more atoms of a halogen.

[0008] Additional embodiments of the present disclosure relate to a selective etching method that includes providing a substrate that includes a TaN material and a TiN material. The substrate is exposed to a co-flow of a metal oxyhalide etchant and hydrogen gas to remove a first thickness of the TaN material and a second thickness of the TiN material. The first thickness is greater than the second thickness.

[0009] Further embodiments of the present disclosure relate to methods for improving etch selectivity. The method includes providing a substrate including a TaN material and a TiN material. The substrate is exposed to a co-flow of a metal halide etchant and hydrogen gas to remove a first thickness of the TaN material and a second thickness of the TiN material, the first thickness being greater than the second thickness, and the ratio of the first thickness to the second thickness being greater than a similar etching process performed without the hydrogen gas. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The above briefly summarizes the manner in which the above-described features of the present disclosure can be understood in detail, as well as a more specific description of the present disclosure, which can be obtained by referring to the embodiments, some of which are illustrated in the accompanying drawings. However, it should be noted that the accompanying drawings only illustrate typical embodiments of the present disclosure and therefore should not be considered as limiting the scope of the present disclosure, as the present disclosure may admit to other equally effective embodiments.

[0011] Figure 1 A schematic diagram illustrating a processing method according to one or more embodiments of the present disclosure. DETAILED DESCRIPTION

[0012] Before describing several exemplary embodiments of the present disclosure, it will be understood that the present disclosure is not limited to the details of construction or process steps set forth in the following description. The present disclosure can be incorporated into other embodiments and can be implemented or carried out in various ways.

[0013] As used herein, "substrate," "substrate surface," and the like refer to any substrate upon which a process is performed or to the surface of any material formed on a substrate, process. For example, depending on the application, substrate surfaces upon which processes may be performed include, but are not limited to: a material such as silicon, silicon oxide, strained silicon, silicon on insulator (SOI), carbon-doped silicon oxide, silicon nitride, doped silicon, germanium, gallium arsenide, glass, sapphire; and any other material such as metals, metal nitrides, metal alloys, and other conductive materials. Substrates include, but are not limited to, semiconductor wafers. Substrates may be exposed to pretreatment processes to polish, etch, reduce, oxidize, hydroxylate (or otherwise create or graft target chemical moieties to impart chemical functionality), anneal, and / or bake the substrate surface. In addition to processing directly on the surface of the substrate itself, in the present disclosure, any film processing steps disclosed may also be performed on underlying layers formed on the substrate, as disclosed in more detail below, and the term "substrate surface" is intended to include such underlying layers as indicated in the context. Thus, for example, where a film / layer or portion of a film / layer has been deposited onto a substrate surface, the exposed surface of the newly deposited film / layer becomes the substrate surface. What a given substrate surface contains will depend on the material to be deposited and the specific chemistry used.

[0014] Some embodiments of the present disclosure advantageously provide methods of etching metal nitride films from metal oxyhalides without using an oxygenating process. Some embodiments advantageously provide methods of selectively etching TaN over TiN without using an oxygenating process. Some embodiments of the present disclosure advantageously provide methods of increasing the selectivity of a metal nitride etching process using a metal-halogen containing etchant.

[0015] Figure 1 A schematic diagram of an etching method 100 according to one or more embodiments of the present disclosure is shown. A substrate 110 is provided having at least one metal nitride film 120 thereon. When used in this regard, the term "provided" means that the substrate is positioned in a suitable location or environment for processing. In some embodiments, as shown, the substrate 110 further includes a metal nitride film 130. Those skilled in the art will recognize that the metal nitride film 130 is optional in some embodiments.

[0016] The metal nitride film 120 can be any suitable metal nitride. In some embodiments, the metal nitride film 120 includes atoms of a first metal and atoms of nitrogen. The ratio of the first metal atoms to the nitrogen atoms can be any suitable ratio. The first metal can be any suitable metal. In some embodiments, the first metal is titanium or tantalum. In some embodiments, the metal nitride film 120 includes TaN or TiN.

[0017] The metal nitride film 130 may be any suitable metal nitride film different from the metal nitride film 120. In some embodiments, the metal nitride layer 120 includes TaN and the metal nitride film 130 includes TiN.

[0018] After providing the substrate 110, the metal nitride film 120 is exposed to a co-flow of an etchant 131 and hydrogen gas to etch the metal nitride film 120. In some embodiments, the etchant 131 has an empirical formula including one or more atoms of a second metal, one or more atoms of oxygen, and one or more atoms of a halogen. In some embodiments, the etchant 131 does not substantially contain a plasma.

[0019] The second metal can be any suitable metal. In some embodiments, the second metal is tungsten, niobium, or tantalum. In some embodiments, the first metal of the metal nitride film 120 and the second metal of the etchant 131 are the same. In some embodiments, the first metal of the metal nitride film 120 and the second metal of the etchant 131 are different.

[0020] In some embodiments, one or more atoms of the halogen in the etchant 131 consist essentially of chlorine. As used in this regard, the term "consisting essentially of chlorine" means that the halogen atoms contained in the etchant 131 are greater than 95%, 98%, 99%, or 99.5% chlorine on an atomic basis.

[0021] In some embodiments, the etchant 131 is a metal oxyhalide. In some embodiments, the etchant 131 consists essentially of WOCl4. As used in this regard, the term "consisting essentially of" means that the composition of the stated species on a molar basis is greater than or equal to about 95%, 98%, 99%, or 99.5% of the etchant.

[0022] In some embodiments, the etchant 131 is a solid reactant contained in an ampoule 132. The ampoule 132 can be any suitable ampoule for semiconductor processing and can include a heater (not shown), an inlet, and an outlet. The ampoule 132 can be configured to perform vapor draw using a carrier gas 133. The temperature of the ampoule 132 can be controlled to sublime the solid reactant so that the carrier gas 133 can extract the reactant from the ampoule 132. In some embodiments, the etchant 131 includes WOCl4 and the temperature of the ampoule 132 is in a range of about 50°C to about 90°C.

[0023] Suitable carrier gas 133 may include one or more of helium, nitrogen, argon, hydrogen, krypton, or xenon. In some embodiments, carrier gas 133 includes or consists essentially of hydrogen (H2). As used in this context, the term "consisting essentially of hydrogen" means that carrier gas 133 is greater than or equal to about 95%, 98%, 99%, or 99.5% hydrogen on a molar basis. In some embodiments, a carrier gas other than hydrogen is used to extract reactants from ampoule 132.

[0024] For embodiments in which a carrier gas other than hydrogen is used to extract the etchant from the ampoule, the carrier gas after the etchant is extracted may be referred to as an etching gas. In some embodiments, the flow rate of the etching gas may be controlled. In some embodiments, the flow rate of the etching gas is in a range of 10 to 2,000 sccm. In some embodiments, the flow rate of the hydrogen gas may be controlled. In some embodiments, the flow rate of the hydrogen gas is in a range of 50 to 10,000 sccm. In some embodiments, the ratio between the flow rate of the etching gas and the flow rate of the hydrogen gas is in a range of about 4 to about 6 or is about equal to 5.

[0025] In some embodiments, the etching gas and the hydrogen gas are mixed before entering the processing chamber. In some embodiments, the etching gas and the hydrogen gas are provided separately to the chamber.

[0026] In some embodiments, the hydrogen gas is delivered to the processing chamber in a continuous flow, while the etching gas is intermittently flowed. In some embodiments, the etching gas is delivered to the processing chamber in a continuous flow, while the hydrogen gas is intermittently flowed. In some embodiments, the etching gas and the hydrogen gas are flowed alternately.

[0027] In some embodiments, the temperature of the substrate 110 is maintained throughout the method 100. Without being bound by theory, it is believed that an etching process performed at a higher temperature provides faster etch material removal. Therefore, in some embodiments, the substrate is maintained at a temperature ranging from about 50°C to about 500°C, or about 100°C to about 500°C, or about 300°C to about 500°C, or about 400°C to about 500°C, or about 450°C to about 500°C, or about 400°C to about 475°C, or about 400°C to about 460°C. In some embodiments, the substrate is maintained at a temperature greater than or equal to about 400°C, greater than or equal to about 450°C, or greater than or equal to about 460°C. In some embodiments, the substrate is maintained at a temperature of about 460°C.

[0028] Some embodiments of the present disclosure advantageously provide methods utilizing metal oxyhalide etchants rather than metal halide etchants. Without being bound by theory, it is believed that metal oxyhalide etchants decompose at higher temperatures. Therefore, etching processes performed at temperatures below the decomposition temperature of these etchants deposit a minimal amount of metal of the metal oxyhalide etchant. In some embodiments, substantially no second metal is deposited on the substrate. As used in this regard, "substantially no" second metal means that the average thickness of the second metal film is less than 10% for every 60 seconds of exposure of the substrate to the co-flow of the etchant and hydrogen. Less than Less than or less than

[0029] Exposing the metal nitride film 120 to a co-flow of the etchant 131 and the hydrogen gas removes a thickness T1 of the metal nitride film 120. As shown, in some embodiments, when the metal nitride film 130 is present, exposing the metal nitride film 130 to a co-flow of the etchant and the hydrogen gas removes a thickness T2 of the metal nitride film 130. In some embodiments, where the metal nitride film 120 comprises TaN and the substrate further comprises a TiN film, etching the metal nitride film 120 removes a greater thickness of the metal nitride film 120 than the metal nitride film 130. In other words, T1 is greater than T2.

[0030] Some embodiments of the present disclosure provide a selective etching process in which the removal of TaN is favored over the removal of TiN. In some embodiments, the etchant 131 has an etching rate for the metal nitride film 120 that is greater than about 3 times, 4 times, or 4.5 times the etching rate for the metal nitride film 130. In other words, the ratio of the first thickness to the second thickness is greater than or equal to about 3, greater than or equal to about 4, or greater than or equal to about 4.5.

[0031] Some embodiments of the present disclosure advantageously provide methods for enhancing or increasing the selectivity of an etching process by co-flowing hydrogen gas with an etchant.

[0032] A substrate 110 including TaN material and TiN material is provided. The substrate is exposed to a co-flow of a metal halide etchant and hydrogen gas to remove a first thickness of the TaN material and a second thickness of the TiN material. The first thickness is greater than the second thickness.

[0033] The metal halide etchant can be any suitable species comprising metal atoms and halogen atoms. In some embodiments, the metal halide etchant comprises WCl5, NbCl5, or WOCl5 or consists essentially of WCl5, NbCl5, or WOCl5.

[0034] The ratio of the first thickness to the second thickness with the co-flow of hydrogen is greater than for a similar etching process performed without hydrogen. As used in this regard, a "similar etching process" is one in which all other process parameters (substrate temperature, etchant, ampoule temperature, carrier gas flow rate, processing chamber pressure, etc.) are held constant.

[0035] A standard process is a process that is improved without the addition of hydrogen. Thus, the carrier gas of the standard process includes a carrier gas other than hydrogen. In some embodiments, the carrier gas other than hydrogen is completely or partially replaced by hydrogen such that the total flow rate (in sccm) of the carrier gas provided to the processing chamber is the same.

[0036] According to one or more embodiments, the substrate 110 is subjected to processing after etching the metal nitride film. This processing can be performed in the same chamber or in one or more separate processing chambers. In some embodiments, the substrate is moved from a first chamber to a separate second chamber for further processing. The substrate can be moved directly from the first chamber to the separate processing chamber, or it can be moved from the first chamber to one or more transfer chambers and then to the separate processing chamber. Thus, the processing equipment can include multiple chambers connected by a transfer station. Such equipment can be called a "cluster tool" or a "cluster system", and similar names.

[0037] Typically, a cluster tool is a modular system comprising multiple chambers that perform various functions including substrate centering and orientation, degassing, annealing, deposition and / or etching. According to one or more embodiments, the cluster tool includes at least a first chamber and a central transfer chamber. The central transfer chamber can accommodate a robot that can transport substrates between and within the processing chambers and the load lock chamber. The transfer chamber is typically maintained under vacuum conditions and provides an intermediate stage for transporting substrates from one chamber to another and / or to a load lock chamber positioned at the front end of the cluster tool. Two well-known cluster tools that may be adapted for use in the present invention are and Both are available from Applied Materials, Inc., Santa Clara, California. However, the exact arrangement and combination of chambers may be varied for performing specific steps of the processes described herein. Other processing chambers that may be used include, but are not limited to, cyclic layer deposition (CLD), atomic layer deposition (ALD), chemical vapor deposition (CVD), physical vapor deposition (PVD), etching, pre-cleaning, chemical cleaning, thermal treatments such as RTP, plasma nitridation, degassing, orientation, hydroxylation, and other substrate processes. By performing the processes in chambers on a cluster tool, surface contamination of the substrate with atmospheric impurities may be avoided without having to oxidize prior to deposition of subsequent films.

[0038] According to one or more embodiments, the substrate is continuously under vacuum or "load lock" conditions and is not exposed to ambient air when moving from one chamber to the next. The transfer chamber is thus under vacuum and is "pumped down" at vacuum pressure. An inert gas may be present in the processing chamber or the transfer chamber. In some embodiments, the inert gas is used as a purge gas to remove some or all of the reactants. According to one or more embodiments, a purge gas is injected at the outlet of the deposition chamber to prevent reactants from moving from the deposition chamber to the transfer chamber and / or additional processing chambers. Thus, the flow of the inert gas forms a curtain at the outlet of the chamber.

[0039] Substrates may be processed in a single substrate deposition chamber, where a single substrate is loaded, processed, and unloaded prior to processing another substrate. Substrates may also be processed in a continuous manner, similar to a conveyor belt system, where multiple substrates are individually loaded into a first portion of the chamber, moved through the chamber, and unloaded from a second portion of the chamber. The shape of the chamber and associated conveyor belt system may form a straight path or a curved path. Additionally, the processing chamber may be a carousel, where multiple substrates move about a central axis and are exposed to deposition, etching, annealing, cleaning, etc. processes in a carousel path.

[0040] During processing, the substrate may be heated or cooled. Such heating or cooling may be accomplished by any suitable means, including, but not limited to, changing the temperature of the substrate support, and flowing heated or cooled gas to the substrate surface. In some embodiments, the substrate support includes a heater / cooler that can be controlled to change the substrate temperature conductively. In one or more embodiments, the gas used (reactive gas or inert gas) is heated or cooled to locally change the substrate temperature. In some embodiments, the heater / cooler is positioned within the chamber adjacent to the substrate surface to convectively change the substrate temperature.

[0041] The substrate may also be stationary or rotated during processing. A rotating substrate may be rotated continuously or in intermittent steps. For example, the substrate may be rotated during the entire process, or the substrate may be rotated a small amount between exposures to different reactant gases or purge gases. Rotating the substrate (continuously or stepwise) during processing may help produce a more uniform deposition or etching by minimizing the effects of local variations, such as in gas flow geometry.

[0042] References throughout the specification of this application to "one embodiment," "certain embodiments," "one or more embodiments," or "an embodiment" mean that the particular features, structures, materials, or characteristics described in conjunction with the embodiment are included in at least one embodiment of the present invention. Thus, phrases such as "in one or more embodiments," "certain embodiments," "in one embodiment," or "in an embodiment" that appear throughout the specification of this application 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.

[0043] Although the present invention is described herein with reference to specific embodiments, it will be understood that these embodiments are merely illustrative of the principles and applications of the present invention. Various modifications and variations can be made to the methods and apparatus of the present invention without departing from the spirit and scope of the present invention, as will be apparent to those skilled in the art. Therefore, it is intended that the present invention include modifications and variations within the scope of the appended claims and their equivalents.

Claims

1. An etching method comprising: A metal nitride film is exposed to a co-flow of an etchant and hydrogen gas to etch the metal nitride film, the metal nitride film comprising a first metal, the etchant having an empirical formula comprising one or more atoms of a second metal, one or more atoms of oxygen, and one or more atoms of a halogen, the second metal being tungsten, niobium, or tantalum, wherein the metal nitride film comprises TaN and TiN.

2. The method of claim 1, wherein the first metal and the second metal are the same metal.

3. The method of claim 1, wherein the first metal and the second metal are different metals.

4. The method of claim 1, wherein the etchant is substantially free of plasma.

5. The method of claim 1, wherein the one or more atoms of halogen in the etchant consist of chlorine.

6. An etching method comprising: A metal nitride film is exposed to a co-flow of a metal oxyhalide etchant and hydrogen gas to etch the metal nitride film, the metal nitride film comprising a first metal, wherein the metal nitride film comprises TaN and TiN, the metal oxyhalide etchant comprising a second metal and the second metal is tungsten, niobium or tantalum.

7. The method of claim 6, wherein the metal oxyhalide etchant consists of WOCl4. The method of claim 6 , wherein substantially no second metal is deposited.

9. The method of claim 6, wherein the metal nitride and the metal oxyhalide comprise the same metal.

10. The method of claim 6, wherein the metal nitride and the metal oxyhalide comprise different metals.

11. An etching method comprising: The metal nitride film is exposed to a flow of hydrogen gas and a flow of an etching gas including an etchant to etch the metal nitride film, the metal nitride film including a first metal, the etchant having an empirical formula including one or more atoms of a second metal, one or more atoms of oxygen, and one or more atoms of a halogen, wherein the metal nitride film includes TaN and TiN, and the second metal is tungsten, niobium, or tantalum. The method of claim 11 , wherein the etching gas comprises hydrogen.

13. The method of claim 11, wherein the etching gas comprises one or more of helium, nitrogen, argon, krypton, or xenon.

14. The method of claim 11, wherein the flow of hydrogen gas flows continuously and the flow of the etching gas flows intermittently.

15. The method of claim 11, wherein the flow of the etching gas flows continuously and the flow of hydrogen gas flows intermittently.

16. The method of claim 11, wherein the flow of hydrogen gas and the flow of the etching gas are flowed alternately.

17. The method of claim 11, wherein the flow of hydrogen gas is provided separately from the flow of the etching gas.

18. The method of claim 11, wherein the flow of hydrogen gas is mixed with the flow of the etching gas prior to exposure to the metal nitride film. 19 . The method of claim 11 , wherein a ratio between a flow rate of the flow of the etching gas and a flow rate of the hydrogen gas flow is in a range of 4 to 6.

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