Method for reducing microscopic scallop-like undulations and macro scallop-like undulations on semiconductor devices

Abstract

Embodiments of the present disclosure relate to methods for patterning a layer of material on a substrate. The method includes forming a hard mask layer on a material layer disposed on a substrate. The material layer includes a plurality of first layers and a plurality of second layers alternately formed over the substrate. The method further includes performing a first etching process to form features through the hard mask layer in the material layer by supplying a first etching gas; performing an oxidation process to oxidize sidewalls of the features by supplying an oxidizing gas; and performing a second etching process to etch the sidewalls of the features formed in the material layer by supplying a second etching gas.

Description

Background Art

[0001] field

[0002] Embodiments of the present disclosure generally relate to etching processes for structures in semiconductor applications. In particular, embodiments of the present disclosure provide methods for etching a multi-material layer to form features in the multi-material layer with sidewalls having reduced sidewall thickness variation.

[0003] Related technical description

[0004] In smaller and lighter electronic devices with higher performance and increased features, three-dimensional (3D) integrated circuits (ICs) designed with through-holes and trenches have been adopted. Through-holes and trenches are used for electrical connections and pass through multiple material layers formed on a semiconductor substrate. The adoption of through-holes and trenches faces high costs and challenges associated with high-volume manufacturing. One such challenge includes producing through-holes and trenches with sidewalls that have reduced sidewall thickness variation. Through-holes and trenches with reduced sidewall thickness variation are generally more robust and can be effectively filled with materials such as dielectrics and metals. In contrast, through-holes and trenches with large sidewall thickness variation (e.g., scalloped sidewalls) can result in ineffective filling, resulting in reduced yield and long-term component reliability issues. Unfortunately, existing etching methods produce through-holes and trenches with large sidewall thickness variation and / or are impractical for high-volume manufacturing. Another factor affecting the adoption of through-holes and trenches includes the cost of performing plasma etching, which is affected by, for example, the overall etch rate.

[0005] Therefore, there is a need for a method for an etch process to form features with reduced sidewall thickness variation in multiple material layers at a fast etch rate. Summary of the Invention

[0006] Embodiments of the present disclosure provide a method for patterning a material layer on a substrate. The method includes forming a hard mask layer on a material layer disposed on the substrate. The material layer includes a plurality of first layers and a plurality of second layers alternately formed above the substrate. The method further includes performing a first etching process to form features in the material layer through the hard mask layer by supplying a first etching gas; performing an oxidation process to oxidize sidewalls of the features by supplying an oxidizing gas; and performing a second etching process to etch the sidewalls of the features formed in the material layer by supplying a second etching gas.

[0007] Embodiments of the present disclosure also provide a method for etching a material layer on a substrate through a hard mask in a processing chamber. The method includes supplying a first etching gas to a material layer having a hard mask formed thereon in the processing chamber to form a feature in the material layer. The material layer includes a plurality of first layers and a plurality of second layers alternately formed above the substrate. The method further includes supplying an oxidizing gas after supplying the first etching gas to oxidize sidewalls of the feature; and, after supplying the oxidizing gas, exposing the feature to a second etching gas.

[0008] Embodiments of the present disclosure also provide a method for reducing sidewall thickness variation of a feature etched in a material layer. The method includes flowing an oxidizing gas to the material layer in a processing chamber, the material layer including a plurality of first layers and a plurality of second layers alternately formed above a substrate; and forming an oxide layer on the sidewall of the feature, wherein the oxide layer has a first side and a second side, the first side of the oxide layer being disposed on and conforming to the contour of the feature, and the second side of the oxide layer having a second side variation of about 1 nm to about 2 nm, the second side variation being a difference between a maximum point on the second side and a minimum point on the second side. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] In order that the manner in which the above-recited features of the present disclosure are obtained and can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to the embodiments of the disclosure illustrated in the appended drawings.

[0010] Figure 1 is a flow chart of a method for patterning a material layer on a substrate according to one or more embodiments of the present disclosure.

[0011] Figure 2A is a schematic cross-sectional view of a structure before a main etching process according to one or more embodiments of the present disclosure.

[0012] Figure 2B is a schematic cross-sectional view of a structure having a hard mask layer and an adhesion layer disposed thereon prior to a main etch process according to one or more embodiments of the present disclosure.

[0013] Figure 2C is a schematic cross-section of a feature formed in a multi-material layer prior to an oxidation process according to one or more embodiments of the present disclosure.

[0014] Figure 2D is a schematic cross-section of a feature formed in the multi-material layer 204 after a post-etch process in operation according to one or more embodiments of the present disclosure.

[0015] Figure 3Ais a schematic cross-section of a portion of a structure before oxidation according to one or more embodiments of the present disclosure.

[0016] Figure 3B is a schematic cross-section of a portion of an oxidized structure according to one or more embodiments of the present disclosure.

[0017] To facilitate understanding, identical reference numerals have been used, where possible, to designate common elements in the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.

[0018] It is to be noted, however, that the appended drawings illustrate only exemplary embodiments of this disclosure and are therefore not to be considered limiting of its scope, for the disclosure may admit to other equally effective embodiments. DETAILED DESCRIPTION

[0019] A method for patterning features with reduced sidewall thickness variation in multiple material layers is provided. The method utilizes a first etching process to form a feature in a material layer through a hard mask layer by supplying a first etching gas, an oxidation process to oxidize the sidewalls of the feature by supplying an oxidizing gas, and a second etching process to etch the sidewalls of the feature formed in the material layer by supplying a second etching gas. By doing so, features with reduced sidewall thickness variation can be formed at a high overall etch rate.

[0020] Processing chambers that may be suitable for benefiting from the present disclosure are SYM 3 TM A process chamber is available from Applied Materials, Inc., located in Santa Clara, Calif. It is contemplated that other process chambers, including those from other manufacturers, may be suitable for practicing embodiments of the present disclosure.

[0021] Figure 1 is a flow chart of a method 100 for patterning a layer of material disposed on a substrate. Figures 2A to 2D 1 is a cross-sectional view of a structure 200 formed on a substrate 202, corresponding to various stages of method 100. Method 100 can be used to etch high aspect ratio features, such as ratios greater than 10:1, in a material layer.

[0022] Depending on the desired implementation, the substrate 202 may be a silicon-based material, a suitable insulating material, or a conductive material. The substrate 202 may include a silicon-based material such as crystalline silicon (e.g., Si <100> or Si <111> ), silicon oxide, strained silicon, silicon germanium, doped or undoped polysilicon, doped or undoped silicon wafers and patterned or non-patterned wafers, silicon on insulator (SOI), carbon-doped silicon oxide, silicon nitride, doped silicon, germanium, gallium arsenide, glass or sapphire. The substrate 202 can have various diameters, such as 200 mm, 300 mm, 450 mm or other diameters, and rectangular or square substrates. Unless otherwise stated, the embodiments and examples described herein are performed on substrates with a diameter of 200 mm, 300 mm or 450 mm. In embodiments where an SOI structure is used for the substrate 202, the substrate 202 can include a buried dielectric layer disposed on a silicon crystalline substrate. In the examples described herein, the substrate 202 is a crystalline silicon substrate.

[0023] like Figure 2A As shown, the structure 200 may include a multi-material layer 204 formed of a conductive material and used as a part of an integrated circuit, such as a gate electrode, an interconnection machine, and a contact plug. In some embodiments, the multi-material layer 204 includes a plurality of stacked layers formed on a substrate 202. The multi-material layer 204 may include a first layer 206 and a second layer 208 alternately formed above the substrate 202. Although Figure 2A Six repeating layers of the first layer 206 and the second layer 208 are shown alternately formed over the substrate 202 , but any desired number of repeating pairs of the first layer 206 and the second layer 208 may be utilized.

[0024] In some examples, the multi-material layer 204 can be formed of a refractory metal, such as tungsten (W), molybdenum (Mo), tantalum (Ta), titanium (Ti), hafnium (Hf), vanadium (V), chromium (Cr), manganese (Mn), ruthenium (Ru), their alloys, their silicides, their nitrides, or combinations thereof. In other examples, the first layer 206 and the second layer 208 can be other metals, such as copper (Cu), nickel (Ni), cobalt (Co), iron (Fe), aluminum (Al), palladium (Pd), gold (Au), silver (Au), platinum (Pt), their alloys, their nitrides, or combinations thereof. In one embodiment, the first layer 206 is formed of silicon germanium (SiGe) and the second layer 208 is formed of silicon (Si). The multi-material layer 204 can have a total thickness of approximately 0.2 μm to approximately 25 μm. The first layers 206 can each have a thickness of approximately 10 nanometers to approximately 100 nanometers. The second layers 208 can each have a thickness of approximately 10 nm to approximately 100 nm.

[0025] In operation 101, an etch resist hard mask layer 210 is formed on a multi-material layer 204 disposed on a substrate in a processing chamber prior to an etching process. Figure 2B As shown, structure 200 includes a hard mask layer 210 formed in a desired pattern on a multi-material layer 204. The pattern on the hard mask layer 210 can have openings 214 with a size ranging from about 1.0 μm to about 1.3 μm to form features with a high aspect ratio (e.g., greater than about 5:1) and a spacing between adjacent openings 214 of between about 50 nm and about 180 nm. Structure 200 can include an adhesion layer 212 formed between the multi-material layer 204 and the hard mask layer 210. The adhesion layer 212 can serve as a barrier layer between the multi-material layer 204 and the hard mask layer 210. The adhesion layer 212 can also serve as a polish stop layer for a subsequent chemical mechanical polishing (CMP) operation.

[0026] The hard mask layer 210 can be formed of tetraethyl orthosilicate (TEOS) or silicon oxynitride (SiON) and has a thickness of about 0.5 μm and about 2 μm. The adhesion layer 212 can be formed of any dielectric material, such as silicon nitride (Si3N4), and has a thickness of less than about 100 nm. The hard mask layer 210 and the adhesion layer 212 can be deposited by any suitable deposition process, such as a chemical vapor deposition (CVD) process, a physical vapor deposition (PVD) process, an atomic layer deposition (ALD) process, or a spin coating process. Subsequently, the hard mask layer 210 and / or the adhesion layer 212 are patterned by a photolithography process using a patterned photoresist layer (not shown) covering the hard mask layer 210.

[0027] In some embodiments, additional layers may be disposed above the hard mask layer 210, such as an advanced patterning film (APF), a dielectric anti-reflective coating (DARC), a bottom anti-reflective coating (BARC), a top anti-reflective coating (TARC), a photoresist (PR) layer, a carbon layer, or other suitable layers. The APF may include a carbon film, an amorphous carbon film, or other suitable APF. The APF layer has a thickness of approximately 250 nm to approximately 750 nm, for example, approximately 500 nm. The DARC has a thickness of approximately 25 nm to approximately 100 nm, for example, approximately 80 nm. The BARC has a thickness of approximately 10 nm to approximately 50 nm, for example, approximately 25 nm. The TARC has a thickness of approximately 10 nm to approximately 50 nm, for example, approximately 25 nm. The PR layer may include a photosensitive material, such as a polymer, a sensitizer, or a baking solvent. The PR layer has a thickness of approximately 50 nm to approximately 500 nm, for example, approximately 150 nm.

[0028] In operation 102, as Figure 2C As shown, a first etching process (also referred to as a "main etching" process) is performed to form features 218 (e.g., trenches or through-holes) in the multi-material layer 204 through the hard mask layer 210. The features 218 can be formed in a plasma processing chamber using plasma-excited species or radicals. In the main etching process of operation 104, the multi-material layer 204 is etched to a predetermined depth using an etching gas. In some embodiments, the process gas can flow along with the etching gas. In one embodiment, an HBr process gas / Cl2 etching gas mixture can be used because chlorine-containing etching gases provide a fast etching rate for the multi-material layer 204. In some embodiments, the fast etching rate is between about 100 nm / min and about 200 nm / min. In other embodiments, the fast etching rate is greater than about 200 nm / min. The main etching process can continue until the depth of the features 218 in the multi-material layer 204 reaches a predetermined depth. In some embodiments, the determined depth of the features 218 in the multi-material layer 204 is from about 0.2 μm to about 4.5 μm. In other embodiments, the depth of the main etching process may be the depth of one first layer 206 and one second layer 208 , for example, from about 20 nm to about 60 nm, and repeated until the depth of the feature 218 reaches a predetermined depth.

[0029] During the main etching process of operation 102, due to the difference between the etching rate of the first layer 206 and the etching rate of the second layer 208, the etched features 218 (e.g., trenches or through-holes) in the multi-material layer 204 may have a profile consisting of rough sidewalls having scallop-like shaped protrusions and depressions (referred to as "scallops") or other rough features. Figure 2C In the example shown, during the main etching process using the etching gas mixture at operation 104 , the first layer 206 has a slower etch rate than the second layer 208 .

[0030] Figure 3A is a schematic cross section of a portion of structure 200 before the oxidation process. As a result of the etch rate variation, e.g. Figure 3A As shown, the first layer 206 includes a concave portion 340 that is recessed compared to the second layer 208, and the second layer 208 includes a convex portion 350 that is protruding compared to the first layer 206. The combination of the concave portion 340 and the convex portion 350 is collectively referred to as "scalloping." In some embodiments, the convex portion 350 and the concave portion 340 may not be directly aligned with the first layer 206 and the second layer 208, respectively. For example, the concave portion 340 may appear on a portion of the first layer 206 and a portion of the second layer 208, or the convex portion 350 may appear on a portion of the first layer 206 and a portion of the second layer 208. The convex portion 350 and the concave portion 340 have an increased surface area compared to the desired flat surface of the groove or through-hole.

[0031] Suitable examples of process gases include, but are not limited to, hydrocarbon-containing gases such as methane (CH4), sulfur hexafluoride (SF6), silicon chloride (SiCl), carbon tetrafluoride (CF4), hydrogen bromide (HBr), argon (Ar), chlorine (Cl2), nitrogen (N2), helium (He), and oxygen (O2). In addition, the process gas may include gases containing nitrogen, chlorine, fluorine, oxygen, and hydrogen, such as BCl3, C2F4, C4F8, C4F6, CHF3, CH2F2, CH3F, NF3, NH3, CO2, SO2, CO, N2, NO2, N2O, and H2. Suitable examples of etching gases include SF6 or chlorine-containing gases, such as Cl2, SiCl4, BCl3, SiHCl3, SiH2Cl2, SiH3Cl, Si2Cl6, or combinations thereof. In one embodiment, the chlorine-containing etching gas includes SiCl4, Cl2, and BCl3.

[0032] During the main etch process in operation 104, several process parameters may also be adjusted. In one embodiment, an etching gas, such as chlorine, is supplied at a flow rate of about 10 sccm to about 1000 sccm, such as about 30 sccm to about 800 sccm, or about 100 sccm to about 500 sccm. A process gas, such as HBr, may be supplied at a flow rate of about 50 sccm to about 1000 sccm (e.g., about 300 sccm). In one embodiment, the ratio of process gas to etching gas (P:E ratio), such as HBr:Cl2, may be about 1:10 to about 10:1, such as about 3:2 (e.g., about 300 sccm HBr to about 200 sccm Cl2). By increasing the process gas in the P:E ratio, the scalloping may be pushed deeper into the trench or through-hole. Too little process gas may exhibit less curvature in the scalloping, but may also result in higher lateral losses due to the high amount of etching gas. Too much process gas may reduce the etch rate due to insufficient etching gas and exhibit more curvature.

[0033] In one embodiment, the process pressure in the plasma processing chamber is adjusted to about 3 mTorr to about 100 mTorr, such as about 10 mTorr to about 50 mTorr, such as about 15 mTorr. Lowering the chamber pressure can achieve more directional etching and minimize lateral etching, thereby producing less bowing.

[0034] In one embodiment, a second etching gas can flow into the chamber together with the process gas and the etching gas. The second etching gas can include a silicon-containing etching gas. Suitable examples of silicon-containing etching gases include SiCl4, SiHCl3, SiH2Cl2, SiH3Cl and Si2Cl6. The silicon-containing etching gas can help passivate the silicon oxide on the sidewalls, thereby reducing scalloping. The silicon-containing etching gas can flow into the chamber at a rate of about 0 sccm to about 100 sccm, such as about 5 sccm to about 50 sccm, such as about 20 sccm. However, a higher amount of silicon-containing etching gas may result in a slower etching rate.

[0035] When performing the main etching process in operation 104, an RF source and / or bias power may be utilized. The RF bias power applied when supplying the etching gas helps form a reactive etchant with desired directionality so that it travels downward to the surface of the multi-material layer 204 exposed from the hard mask layer 210 to primarily etch the multi-material layer 204. Conversely, eliminating the RF bias power can help distribute active species in the plasma more evenly across the hard mask layer 210. For example, an RF source power of approximately 500 watts to approximately 2000 watts may be applied to maintain the plasma within the processing chamber. An RF bias power of approximately 500 watts to approximately 6000 watts, for example approximately 1500 watts, may be applied.

[0036] During the main etching process of operation 104 , the substrate support pedestal for supporting the substrate 202 is maintained at a temperature of about 50° C. to about 290° C., for example, about 110° C.

[0037] In operation 103, an oxidation process is performed to reduce the sidewall thickness variation of the features 218 etched in the main etching process in operation 104. The oxidation process includes flowing an oxidizing gas into the chamber to form an oxide layer 360, such as Figure 3B As shown. In one embodiment, an oxidizing gas of between about 50 sccm and about 250 sccm, for example, about 180 sccm, is delivered to the chamber. The oxidizing gas may include O2, H2O, O3 (ozone), or a combination thereof. In some embodiments, the chamber pressure during the oxidation process is about 10 mTorr to about 50 mTorr, for example, about 20 mTorr. An RF bias power may be applied to maintain the plasma in the processing chamber. The RF bias power may be applied from about 500 to about 600 watts, for example, about 2500 watts. In an embodiment using O2, a dry oxidation process is performed. In an embodiment using H2O, a wet oxidation process is performed. In one embodiment, the first layer 206 is formed of silicon germanium (SiGe), and the second layer 208 is formed of silicon (Si). The oxidation process forms a silicon oxide material (e.g., SiO2) on the surfaces of the first layer 206 and the second layer 208.

[0038] Figure 3B is a schematic cross-section of a portion of structure 200 after an oxidation process. The increased surface area of the scalloped concave portion 340 and convex portion 350 promotes the growth of an oxide layer 360. Oxide layer 360 also includes a first side 362 and a second side 364. First side 362 of oxide layer 360 is disposed on the sidewall of feature 218. In some embodiments, oxide layer 360 is disposed on and conforms to the sidewall profile of feature 218. Second side 364 of oxide layer 360 is substantially linear, for example, having a second side variation of between about 0 nm and about 5 nm (e.g., about 1 nm to about 2 nm). The second side variation is defined as the difference between the maximum point on second side 364 and the minimum point on second side 362. The growth of oxide layer 360 on the sidewall of feature 218 results in reduced sidewall variation within the trench or through-hole. The sidewall variation is defined as the difference between the maximum point on convex portion 350 and the minimum point on concave portion 340. The sidewall variation due to the oxidation process is between about 0 nm and about 5 nm, for example, about 1 nm and about 2 nm.

[0039] At operation 104 , a second etch process (also referred to as a “post-etch” process) is performed to further reduce sidewall thickness variations of the features 218 etched in the main etch process at operation 104 . Figure 2DFIG1 is a schematic cross-section of feature 218 formed in multi-material layer 204 after the post-etch process of operation 104. Using a fluorine-containing etching gas, the sidewall variations remaining from the oxidation process can be removed by removing byproducts of the oxidation process. As a result, the protrusions 350 and recesses 340 formed on the sidewalls of feature 218 are removed or reduced to a scalloped undulation having a magnitude of less than about 1.5 nm. Suitable examples of fluorine-containing etching gases include SF6, CH2F4, C4F8, CF4, CHF3, C2F6, C3F8, NF3, HF, or combinations thereof.

[0040] In some embodiments, the post-etching process is performed by simultaneously supplying a fluorine-containing etching gas, a passivation gas, and an inert gas such as argon (Ar) in a plasma processing chamber.

[0041] The passivation gas selectively passivates the sidewalls of feature 218 to reduce the curved profile of the sidewalls of feature 218. Suitable examples of passivation gases include HBr, BCl3, SF6, or H2S. In one embodiment, the fluorine-containing etch gas includes SF6 and the passivation gas includes HBr.

[0042] An inert gas, such as argon (Ar), is delivered at a high flow rate to create a low pressure at or near the bottom of the feature 218 in the multi-material layer 204, so that the second etching gas reaches the bottom of the feature 218 in the multi-material layer 204. As a result, the sidewall thickness variation of the feature 218 can be reduced.

[0043] During the post-etch process of operation 104, certain process parameters may also be adjusted. In one example, SF6 and HBr gases may be supplied at flow rates of approximately 25 sccm to approximately 150 sccm (e.g., approximately 50 sccm) and approximately 10 sccm to approximately 1000 sccm (e.g., approximately 50 sccm), respectively. An inert gas, such as argon (Ar), may be supplied at a flow rate of 100 sccm to approximately 1000 sccm (e.g., approximately 900 sccm). The fluorine-containing etching gas may be supplied in pulses with a pulse duration of approximately 1 second to approximately 10 seconds (e.g., approximately 5 seconds). The duty cycle (i.e., the ratio of the "on" period during which the fluorine-containing etching gas is supplied to the "off" period during which the fluorine-containing etching gas is not supplied) may be approximately 1:3 to approximately 3:1, e.g., approximately 1:1. Depending on the total thickness of the multi-material layer 304, the post-etch process at operation 104 may be repeated for from approximately 6 seconds to approximately 1800 seconds, e.g., approximately 40 seconds, corresponding to approximately 4 pulse cycles. In one embodiment, the process pressure in the plasma processing chamber is adjusted to about 10 mTorr to about 5000 mTorr, such as about 20 mTorr to about 500 mTorr.

[0044] An RF source and / or bias power supply may be utilized when performing the etching process. For example, an RF source power of less than about 2000 watts may be applied to maintain the plasma within the processing chamber. When a fluorine-containing etching gas is supplied, an RF bias power of less than about 6000 watts may be applied, and an RF bias power of about 1000 watts to about 6000 watts may be applied.

[0045] During the post-etch process of operation 104 , the plasma processing chamber is maintained at a temperature of about 75° C. to about 150° C., for example, about 110° C.

[0046] In some embodiments, the flow rate of SF 6 , the number of SF 6 pulse cycles, and the temperature in the plasma processing chamber are adjusted to adjust the thickness variation (eg, the amount of scalloping) of the sidewalls of feature 118 .

[0047] In some embodiments, the trenches or through-holes are formed by main etching the multi-material layer 204, oxidizing the multi-material layer 204, and post-etching the multi-material layer 204. In other embodiments, the trenches or through-holes are formed by main etching a single first layer 206 and a single second layer 208, oxidizing the first layer 206 and the second layer 208, post-etching the first layer 206 and the second layer 208, and repeating the main etching, oxidation, and post-etching of each subsequent first layer 206 and the second layer 208. In other embodiments, the trenches or through-holes are formed by main etching one or more first layers 206 and one or more second layers 208, oxidizing the one or more first layers 206 and one or more second layers 208, post-etching the one or more first layers 206 and one or more second layers 208, and repeating the main etching, oxidation, and post-etching of each subsequent one or more first layers 206 and one or more second layers 208.

[0048] Benefits of the present disclosure include improved patterning of features with precise and uniform profiles in three-dimensional (3D) semiconductor device structures. The method according to the embodiments disclosed herein utilizes a three-operation etching process that includes a main etching process that forms features through multiple material layers by continuously supplying etching gas, an oxidation process that oxidizes and reduces the thickness variation of the sidewalls of the features, and a post-etching process that reduces the sidewall thickness variation of the features through the multiple material layers by pulsing the etching gas. The main etching process provides a fast etching rate through the multiple material layers, while the oxidation process and the post-etching process are adjusted to reduce the sidewall thickness variation of the features to a desired sidewall thickness variation. By doing so, features with reduced sidewall thickness variation can be formed at a high overall etch rate.

[0049] While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, and the scope of the disclosure is determined by the claims that follow.

Claims

1. A method for patterning a material layer on a substrate, the method comprising: forming a hard mask layer on a material layer disposed on a substrate, the material layer including a plurality of first layers and a plurality of second layers alternately formed over the substrate; performing a first etching process to form features in the material layer through the hard mask layer by supplying a first etching gas; performing an oxidation process to oxidize sidewalls of the feature by supplying an oxidizing gas; as well as A second etching process is performed to etch the sidewalls of the features formed in the material layer by supplying a second etching gas.

2. The method of claim 1 , wherein the plurality of first layers and the plurality of second layers comprise tungsten (W), molybdenum (Mo), tantalum (Ta), titanium (Ti), hafnium (Hf), vanadium (V), chromium (Cr), manganese (Mn), ruthenium (Ru), alloys thereof, silicides thereof, nitrides thereof, copper (Cu), nickel (Ni), cobalt (Co), iron (Fe), aluminum (Al), palladium (Pd), gold (Au), silver (Au), platinum (Pt), alloys thereof, nitrides thereof, silicon germanium (SiGe), silicon (Si), or combinations thereof.

3. The method of claim 1, wherein: The material layer has a thickness between 0.2 μm and 25 μm; and Each of the plurality of first layers and the plurality of second layers each has a thickness between 10 nm and 30 nm.

4. The method of claim 1, wherein the sidewall variation is from about 1 nm to about 2 nm, and wherein the sidewall variation is a difference between a maximum point on a convex portion of the sidewall and a minimum point on a concave portion of the sidewall.

5. The method of claim 1, wherein: The first etching gas comprises Cl2, SiCl4, BCl3, SiHCl3, SiH2Cl2, SiH3Cl, Si2Cl6 or a combination thereof; and The second etching gas includes SF6, CH2F4, C4F8, CF4, CHF3, C2F6, C3F8, NF3, HF or a combination thereof. The method of claim 1 , wherein the oxidizing gas comprises O 2 , H 2 O, O 3 , or a combination thereof. 7 . The method of claim 1 , wherein during the oxidation process, the oxidizing gas flows at a rate of about 50 sccm to about 250 sccm.

8. The method of claim 1, wherein a chamber pressure during the oxidation process is about 10 mTorr to about 50 mTorr, and an RF power bias of about 500 W to about 600 W is applied.

9. A method for etching a material layer on a substrate through a hard mask in a processing chamber, the method comprising: supplying a first etching gas to a material layer having a hard mask formed thereon in a processing chamber to form features in the material layer, the material layer including a plurality of first layers and a plurality of second layers alternately formed over a substrate; After supplying the first etching gas, supplying an oxidizing gas to oxidize the sidewalls of the feature; as well as After supplying the oxidizing gas, the feature is exposed to a second etching gas.

10. The method of claim 9, wherein the plurality of first layers and the plurality of second layers comprise tungsten (W), molybdenum (Mo), tantalum (Ta), titanium (Ti), hafnium (Hf), vanadium (V), chromium (Cr), manganese (Mn), ruthenium (Ru), alloys thereof, silicides thereof, nitrides thereof, copper (Cu), nickel (Ni), cobalt (Co), iron (Fe), aluminum (Al), palladium (Pd), gold (Au), silver (Au), platinum (Pt), alloys thereof, nitrides thereof, silicon germanium (SiGe), silicon (Si), or combinations thereof.

11. The method of claim 9, wherein: The material layer has a thickness between 0.2 μm and 25 μm; and Each of the plurality of first layers and the plurality of second layers has a thickness between 10 nm and 30 nm.

12. The method of claim 9, wherein the sidewall variation is from about 1 nm to about 2 nm, and wherein the sidewall variation is a difference between a maximum point on a convex portion of the sidewall and a minimum point on a concave portion of the sidewall.

13. The method of claim 9, wherein: The first etching gas comprises Cl2, SiCl4, BCl3, SiHCl3, SiH2Cl2, SiH3Cl, Si2Cl6 or a combination thereof; and The second etching gas includes SF6, CH2F4, C4F8, CF4, CHF3, C2F6, C3F8, NF3, HF or a combination thereof.

14. The method of claim 9, wherein the oxidizing gas comprises O2, H2O, O3, or a combination thereof.

15. The method of claim 9, wherein the oxidizing gas is supplied at a rate of about 50 sccm to about 250 sccm.

16. A method for reducing sidewall thickness variation of a feature etched in a material layer, the method comprising: flowing an oxidizing gas to a material layer in a processing chamber, the material layer including a plurality of first layers and a plurality of second layers alternately formed over a substrate; as well as An oxide layer is formed on the sidewalls of the feature, wherein the oxide layer has a first side and a second side, the first side of the oxide layer being disposed on and conformal to the contour of the feature, and the second side of the oxide layer having a second side variation of about 1 nm to about 2 nm, the second side variation being a difference between a maximum point of the second side and a minimum point of the second side.

17. The method of claim 16, wherein the plurality of first layers and the plurality of second layers comprise tungsten (W), molybdenum (Mo), tantalum (Ta), titanium (Ti), hafnium (Hf), vanadium (V), chromium (Cr), manganese (Mn), ruthenium (Ru), alloys thereof, silicides thereof, nitrides thereof, copper (Cu), nickel (Ni), cobalt (Co), iron (Fe), aluminum (Al), palladium (Pd), gold (Au), silver (Au), platinum (Pt), alloys thereof, nitrides thereof, silicon germanium (SiGe), silicon (Si), or combinations thereof.

18. The method of claim 16, wherein the oxidizing gas comprises O2, H2O, O3, or a combination thereof.

19. The method of claim 16, wherein the oxidizing gas flows at a rate of about 50 seem to about 250 seem.

20. The method of claim 16, wherein: The material layer has a thickness between 0.2 μm and 25 μm; and Each of the plurality of first layers and the plurality of second layers has a thickness between 10 nm and 30 nm.

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