Plasma etching tool and system

Abstract

A method of processing a substrate, comprising: loading a substrate into a plasma etch chamber, the substrate comprising a patterned hard mask layer and an underlying layer, the plasma etch chamber comprising: a chamber component having a surface comprising a refractory metal; and a first electrode; flowing a process gas into the plasma etching chamber; applying a source power to a first electrode of the plasma etch chamber while flowing the process gas to generate a plasma in the plasma etch chamber; exposing the surface of the chamber component to a plasma to sputter refractory metal from the surface of the chamber component; and exposing the substrate to a plasma to deposit a refractory metal onto a portion of the patterned hard mask layer and selectively etch the underlying layer to the patterned hard mask layer.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of U.S. Non-Provisional Application No. 17 / 832,897, filed on June 6, 2022, which is incorporated herein by reference. Technical Field

[0003] The present invention generally relates to a system and method for processing a substrate, and in particular embodiments, to a plasma etch tool and system. Background Art

[0004] Typically, semiconductor devices such as integrated circuits (ICs) are manufactured by sequentially depositing and patterning dielectric material layers, conductive material layers, and semiconductor material layers on a substrate to form a network of electronic components and interconnecting elements (e.g., transistors, resistors, capacitors, metal lines, contacts, and vias) integrated into a monolithic structure. Many of the processing steps used to form the component structures of semiconductor devices are performed using plasma processes.

[0005] The semiconductor industry has repeatedly reduced the minimum feature size in semiconductor devices to a few nanometers to increase the packing density of components. As a result, the semiconductor industry increasingly requires plasma processing technology to provide processes for patterning features with accuracy, precision and profile control, often at atomic-level dimensions. Meeting this challenge and the consistency and repeatability required for high-volume IC manufacturing requires further innovation in plasma processing technology. Summary of the invention

[0006] According to an embodiment of the present invention, a method for processing a substrate includes: loading the substrate into a plasma etching chamber, the substrate including a patterned hard mask layer and an underlying layer, the plasma etching chamber including: a chamber component having a surface containing a refractory metal; and a first electrode; flowing a process gas into the plasma etching chamber; applying source power to the first electrode of the plasma etching chamber while flowing the process gas to generate plasma in the plasma etching chamber; exposing the surface of the chamber component to the plasma to sputter the refractory metal from the surface of the chamber component; and exposing the substrate to the plasma to deposit the refractory metal onto a portion of the patterned hard mask layer and selectively etching the underlying layer to the patterned hard mask layer.

[0007] According to an embodiment of the present invention, a plasma etching system for a substrate includes: an etching chamber; a substrate holder disposed in the etching chamber; a top electrode disposed in the etching chamber, the top electrode having a surface containing a refractory metal; a bottom electrode connected to the substrate holder; a first radio frequency (RF) power source connected to the bottom electrode, the first RF power source being configured to generate plasma in the etching chamber and sputter the refractory metal from the surface of the top electrode; and a focusing ring disposed on the substrate holder and configured to surround the substrate.

[0008] According to an embodiment of the present invention, a plasma etching system for a substrate includes: an etching chamber, wherein an upper wall inside the etching chamber contains a refractory metal; a substrate holder disposed in the etching chamber; a top electrode including a spiral coil disposed outside the etching chamber, the top electrode surrounding an upper half of the etching chamber; a bottom electrode connected to the substrate holder; a radio frequency (RF) power source connected to the top electrode, the first RF power source being configured to generate plasma in the etching chamber, the plasma being configured to sputter metal from the upper wall; and a focusing ring disposed on the substrate holder and configured to surround the substrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] For a more complete understanding of the present invention and its advantages, reference will now be made to the following description taken in conjunction with the accompanying drawings, in which:

[0010] Figure 1 An exemplary capacitively coupled plasma (CCP) processing system having a top electrode with a metal coating according to various embodiments is shown;

[0011] Figure 2 An exemplary inductively coupled plasma (ICP) processing system having a top plate with a metal coating according to an alternative embodiment is shown;

[0012] Figure 3 shows a cross-sectional view of a top electrode of a CCP processing system and a substrate positioned in an etch chamber, wherein a plasma in the etch chamber causes sputtering on the top electrode and reactive ion etching (RIE) on the substrate, according to various embodiments;

[0013] Figure 4 shows a cross-sectional view of a top electrode of a CCP processing system and a substrate positioned in an etch chamber according to an alternative embodiment, wherein a plasma in the etch chamber causes deposition on the top electrode and reactive ion etching (RIE) on the substrate;

[0014] Figure 5A and 5BA cross-sectional view of an exemplary substrate during an exemplary high aspect ratio (HAR) patterning process using a plasma processing system according to various embodiments is shown, wherein Figure 5A An incoming substrate having a patterned hard mask and a material layer is shown, and Figure 5B shows a substrate after reactive ion etching (RIE) accompanied by transition metal deposition; and

[0015] Figure 6 A process flow diagram of a reactive ion etching (RIE) process using a plasma processing system according to one embodiment is shown. DETAILED DESCRIPTION

[0016] The present application relates to a system and method for processing a substrate by plasma etching and metal sputtering, which can be used in the manufacturing process of high-capacity three-dimensional (3D) memory devices (such as 3D-NAND (or vertical NAND), 3D-NOR) or dynamic random access memory (DRAM) devices. The manufacture of such devices may generally require the formation of conformal, high aspect ratio (HAR) features of circuit elements, such as high aspect ratio contacts (HARC) and high aspect ratio trenches (HART). Features with aspect ratios (ratios of feature height to feature width) higher than 20:1 are generally considered to be high aspect ratio features, and in some cases, manufacturing higher aspect ratios such as 100:1 may be desired for advanced 3D semiconductor devices. This complexity is mainly caused by the limited mask height and etching selectivity of conventional mask materials (such as amorphous carbon layers (ACLs) and amorphous silicon). Although new materials (such as metals, metal nitrides, metal carbides, and metal silicides) can provide better etching selectivity, the deposition of thick films and patterning them to be suitable for HAR etching processes are often challenging. Therefore, a simple and effective HAR process may be desired. Embodiments of the present application disclose systems and methods for manufacturing HAR features by a plasma etching process combined with metal sputtering. Specifically, such plasma etching systems are characterized by at least one chamber component containing a metal element (e.g., a refractory metal such as tungsten (W)). The metal-containing chamber component can be a top electrode, a focusing ring, a chamber wall, or other components of a plasma processing system, and they can be configured to be sputtered in the presence of plasma to provide the metal element to the plasma. The sputtered metal can then be deposited on a hard mask on a substrate to form a passivation layer, which can advantageously improve etching selectivity.

[0017] In the following, we first refer to Figure 1 and Figure 2 An exemplary plasma etching system having metal-containing chamber components is described for a capacitively coupled plasma (CCP) processing system and an inductively coupled plasma (ICP) processing system, respectively. Figure 3 and Figure 4 The possible interactions of reactive species in a plasma etch chamber during plasma etching with and without metal sputtering from chamber components are described. Figure 5A and 5B The steps of a plasma etching process for patterning high aspect ratio (HAR) features using metal sputtering for enhanced etch selectivity are shown. Figure 6 An exemplary process flow diagram is shown in . All drawings in this disclosure are for illustration purposes only and are not drawn to scale, including the aspect ratios of features.

[0018] Figure 1 An exemplary capacitively coupled plasma (CCP) processing system 10 is shown in accordance with various embodiments.

[0019] like Figure 1 As shown in , CCP processing system 10 includes plasma etching chamber 110, and substrate 100 can be placed on substrate holder 105. In various embodiments, substrate 100 can be part of or include a semiconductor device, and may undergo multiple processing steps such as conventional processes. Thus, substrate 100 can include semiconductor layers useful in various microelectronics. For example, a semiconductor structure can include substrate 100, in which various device regions are formed.

[0020] In one or more embodiments, the substrate 100 may be a silicon wafer or a silicon on insulator (SOI) wafer. In some embodiments, the substrate 100 may include a silicon germanium wafer, a silicon carbide wafer, a gallium arsenide wafer, a gallium nitride wafer, and other compound semiconductors. In other embodiments, the substrate 100 includes a heterogeneous layer, such as silicon germanium on silicon, gallium nitride on silicon, silicon carbon on silicon, and a layer of silicon on silicon or SOI substrate. In various embodiments, the substrate 100 is patterned or embedded in other components of a semiconductor device.

[0021] One or more process gases may be introduced into the plasma etching chamber 110 through a gas delivery system 115. The gas delivery system 115 may include a plurality of gas flow controllers to control the flow of a plurality of gases into the plasma etching chamber 110. In some embodiments, an optional center / edge distributor may be used to independently adjust the gas flow rate at the center and edge of the substrate 100. In addition, in one embodiment, the gas delivery system 115 may have a special nozzle configuration positioned at the top of the plasma etching chamber 110. For example, the gas delivery system 115 may be integrated with a top electrode 150, with a nozzle configuration on the top electrode 150, covering the entire substrate 100, including a plurality of appropriately spaced gas inlets. Alternatively, the gas may be introduced through a dedicated gas inlet of any other suitable configuration. The plasma etching chamber 110 may be further equipped with one or more sensors, such as a pressure monitor, a gas flow monitor, and / or a gas material density monitor. In various embodiments, the sensor may be integrated as part of the gas delivery system 115.

[0022] exist Figure 1 In the present invention, the plasma etching chamber 110 is a vacuum chamber and can be evacuated using one or more vacuum pumps 135, such as a single-stage pumping system or a multi-stage pumping system (e.g., a mechanical roughing pump combined with one or more turbomolecular pumps). To promote uniform gas flow during plasma processing, gas can be removed from more than one gas outlet or location in the plasma etching chamber 110 (e.g., on opposite sides of the substrate 100).

[0023] In various embodiments, the substrate holder 105 can be integrated with a chuck (e.g., a circular electrostatic chuck (ESC)) or a portion thereof located near the bottom of the plasma etching chamber 110 and connected to the bottom electrode 120. The surface of the chuck or substrate holder 105 can be coated with a conductive material (e.g., a carbon-based or metal nitride-based coating). The substrate 100 can be optionally maintained at a desired temperature using a temperature sensor and a heating element connected to the first temperature controller 140. In some embodiments, the temperature sensor may include a thermocouple, a resistance temperature detector (RTD), a thermistor, or a semiconductor-based integrated circuit. In one embodiment, the heating element may, for example, include a resistive heater. In addition, there may be a cooling element (e.g., a liquid cooling system) coupled to the first temperature controller 140. The bottom electrode 120 can be connected to one or more RF power sources 130 to generate a plasma 160 in the plasma etching chamber 110. As Figure 1As shown in , for example, more than one RF power source can be used to provide high frequency RF power (HF) and low frequency RF power (LF) simultaneously. In various embodiments, HF can be used for plasma and radical generation, and LF can be used for ion acceleration in the sheath of plasma 160 on substrate 100, which enables plasma etching on substrate 100. In certain embodiments of the CCP processing system, the frequency range of HF can be 27 MHz to 150 MHz, and the frequency range of LF can be 400 kHz to 13 MHz. RF power source 130 can be used to supply continuous wave (CW) or pulsed RF power to maintain plasma 160. The plasma 160 shown between the top electrode 150 and the bottom electrode 120 illustrates a direct plasma generated near substrate 100 in the plasma etching chamber 110.

[0024] In various embodiments, RF pulses in the kHz range may be used to power the plasma 160. Using RF pulses can help produce high energy ions (>keV) in the plasma 160 for the plasma etching process while reducing charging effects. The charging effect during the process is a phenomenon in which electrons accumulate charge on the insulating material, generating a local electric field that may direct positive ions to the sidewalls and cause lateral etching. Therefore, fine-tuning the power conditions of the plasma etching process may also be important for minimizing the widening of the critical dimension (CD) of high aspect ratio (HAR) features. In some embodiments, a moderate duty cycle of 10% to 100% may be used. In one embodiment, a bias power of 18kW may be pulsed at a frequency of 5kHz with a duty cycle of 60%.

[0025] exist Figure 1 As further shown in FIG. 1 , the top electrode 150 can be a conductive circular plate near the top of the plasma etching chamber 110. In various embodiments, the top electrode 150 can be connected to a direct current (DC) voltage source 165 of the CCP processing system 10. Combined with the RF power from the RF power source 130, the DC voltage is used to generate a DC-superimposed RF plasma in the plasma etching chamber 110. Figure 1 In one embodiment, a DC voltage may be supplied to the top electrode 150. In another embodiment, a DC voltage may be supplied to the bottom electrode 120. In various embodiments, the DC voltage may be advantageously adjusted to adjust the degree of metal sputtering, and thereby adjust the concentration of the metal element in the plasma 160.

[0026] The DC voltage supplied by the DC voltage source 165 can range from positive to negative. The negative DC voltage at the top electrode 150 can advantageously adjust (e.g., increase) the average ion energy of the species of the plasma 160. In various embodiments, the DC voltage VDC coupled to the top electrode 150 can be in the range of 0V to about 3000V. In one embodiment, the DC voltage VDC coupled to the top electrode 150 can be about -200V. In other embodiments, instead of the DC voltage source 165, another RF power source can be used and configured to provide RF power to the top electrode 150. In one or more embodiments, the frequency of the RF power reaching the top electrode 150 can range from 400kHz to 13MHz.

[0027] In various embodiments, the CCP processing system 10 is particularly characterized in that the top electrode 150 includes a metal, for example, having a metal-containing coating 152. During a plasma process (such as reactive ion etching (RIE)) using the CCP processing system 10, the metal of the metal-containing coating 152 can be advantageously sputtered by ion bombardment, generating a metal-containing plasma 160. The metal sputtered into the plasma 160 can then be deposited on a hard mask present on the substrate 100 to form a passivation layer, which can enhance the etch selectivity, as shown in reference Figure 3-5B Further described. In various embodiments, the metal can be a transition metal. In certain embodiments, the metal can be tungsten (W). Examples of metals that can be used for the metal-containing coating 152 further include titanium (Ti) and tantalum (Ta), but other metals can also be used. Generally, when deposited from the plasma 160, elements that exhibit better etching resistance than the etching mask used in the process are available and preferred. In certain embodiments, the metal-containing coating 152 can be in the form of a pure metal, but in other embodiments, it can be a metal carbide (e.g., WC), a metal nitride (e.g., WN), a metal silicide (WSix), or other metal compounds. In addition, the metal-containing coating 152 can also include a thin layer of oxide on the surface.

[0028] In one or more embodiments, the top electrode 150 may be connected to a second temperature controller 155, which is configured to control the temperature of the top electrode 150 and the metal-containing coating 152. The second temperature controller 155 may further include or be coupled to a temperature sensor and a heating element. In certain embodiments, the temperature sensor may include a thermocouple, a resistance temperature detector (RTD), a thermistor, or a semiconductor-based integrated circuit. In one embodiment, the heating element may, for example, include a resistive heater. In addition, there may be a cooling element (such as a liquid cooling system) coupled to the second temperature controller 155. Since metal sputtering may depend on the temperature of the target material, controlling the temperature of the top electrode 150 may help to regulate the degree of metal sputtering. For example, increasing the temperature of the metal-containing coating 152 may enhance metal sputtering by the plasma 160.

[0029] Despite Figure 1 In the embodiment, the metal-containing coating 152 covers the bottom surface of the top electrode 150, but in alternative embodiments, the metal can be incorporated into the chamber components of the plasma etch chamber 110 in any reasonable manner as long as metal sputtering can be achieved. Thus, the metal can be incorporated by, for example, the top electrode 150 is made entirely of, plated with, brazed with, or deposited with metal, metal carbides, metal nitrides, metal silicides, or other metal compounds.

[0030] In various embodiments, the CCP processing system 10 may further include a focus ring 154 positioned above the bottom electrode 120 to surround the substrate 100. The focus ring 154 may advantageously maintain and expand the uniformity of the plasma 160 to achieve process consistency at the edge of the substrate 100. In various embodiments, the focus ring 154 may have a width of several cm. In various embodiments, there may be a gap for mechanical clearance between the circumference of the substrate 100 and the focus ring 154. In certain embodiments, the gap may be several hundred microns to several mm. In various embodiments, the focus ring 154 may include a dielectric material having a desired dielectric constant. In certain embodiments, the focus ring 154 may include silicon. Some examples of silicon-based focus rings may include silicon, silicon oxide, doped silicon (e.g., boron-doped, nitrogen-doped, and phosphorus-doped), or silicon carbide. Alternatively, in some embodiments, the focus ring may include a carbon-based material.

[0031] In some embodiments, similar to the top electrode 150 as described above, the focus ring 154 may also include a focus ring metal-containing coating 156 on the surface. The metal of the focus ring metal-containing coating 156 may be used as an additional metal source for metal sputtering during the plasma process. The metal used in the focus ring metal-containing coating 156 may be tungsten (W), titanium (Ti), tantalum (Ta), or other metals. In one embodiment, the metal of the focus ring metal-containing coating 156 and the metal of the metal-containing coating 152 may be the same, but in another embodiment, they may be different. In some embodiments, the metal of the focus ring metal-containing coating 156 may be in the form of a pure metal, but in other embodiments, it may be a metal carbide (e.g., WC), a metal nitride (e.g., WN), a metal silicide (WSix), or other metal compounds. In one or more embodiments, the focus ring 154 (rather than having the focus ring metal-containing coating 156) may be completely made of, plated with, brazed with, or deposited with metal, metal carbides, metal nitrides, metal silicides, or other metal compounds.

[0032] like Figure 1 As shown in , in one embodiment, the focus ring 154 can be connected to an RF power source 170, which is configured to apply RF bias power to the focus ring 154. In another embodiment, a DC voltage source can be used instead of the RF power source. Applying bias power to the focus ring 154 can advantageously improve the uniformity of the plasma 160 in the plasma etching chamber 110, and also adjust the degree of metal sputtering, especially the degree of metal sputtering from the focus ring metal-containing coating 156 and / or the surface of the focus ring 154. In some embodiments, the first temperature controller 140 can also be configured to control the temperature of the focus ring 154. Similar to the top electrode 150, controlling the temperature of the focus ring metal-containing coating 156 can be used to adjust the degree of metal sputtering.

[0033] Although the above describes the incorporation of metal into the top electrode 150 and the focus ring 154, any suitable chamber component, including but not limited to the chamber wall, may be fabricated to contain metal on or near its surface and serve as a metal source for metal sputtering.

[0034] Figure 2 An exemplary inductively coupled plasma (ICP) processing system 20 according to an alternative embodiment is shown. For purposes of illustration, possible differences between the ICP processing system 20 and the ICP processing system 20 are omitted. Figure 1 Some parts (eg, first temperature controller 140 and RF power source 170) are common to the CCP processing system 10 shown in FIG. 1 and are not repeated below.

[0035] exist Figure 2In, the ICP processing system 20 includes a plasma etching chamber 210, which is configured to maintain a plasma 260 directly above a substrate 200 loaded on a substrate holder 205. A focusing ring 254 can be positioned to surround the substrate 200. Process gas can be introduced into the plasma etching chamber 210 through a gas inlet connected to a gas flow control system 215 and can be pumped out of the plasma etching chamber 210 through a gas outlet connected to a vacuum pump 235. The gas flow control system 215 can include various components, such as a high-pressure gas tank, a valve (e.g., a throttle valve), a pressure sensor, a gas flow sensor, a vacuum pump, piping, and an electronic programmable controller. The bottom electrode 220 can be connected to an RF bias power source 230. For the ICP configuration, the top electrode 250 can be a conductive spiral coil electrode located outside the plasma etching chamber 210 and coiled around a dielectric sidewall 216. The top electrode 250 can be connected to an RF source power source 265. As shown in FIG. Figure 2 As further shown in FIG. 2 , the gas inlet is an opening in the top plate 212, and the gas outlet is an opening in the bottom plate 214. The top plate 212 and the bottom plate 214 may be conductive and electrically connected to the system ground (reference potential).

[0036] In various embodiments, the ICP processing system 20 is characterized in that the top plate 212 contains metal, for example, there is a metal-containing coating 252 inside the plasma etching chamber 210. Unlike the previous embodiment of the CCP processing system 10, the top electrode 250 is located outside the plasma etching chamber 210. Therefore, the metal-containing chamber component for metal sputtering can be, for example, the top plate 212 instead of the top electrode 250. The metal-containing coating 252 can be used as a metal source for metal sputtering during plasma processing (such as reactive ion etching (RIE)) using the ICP processing system 20. In various embodiments, the metal can be tungsten (W), titanium (Ti), tantalum (Ta), or other metals. In some embodiments, the metal-containing coating 252 can be in the form of pure metal, but in other embodiments, it can be a metal carbide (e.g., WC), a metal nitride (e.g., WN), a metal silicide (WSix), or other metal compounds.

[0037] Similar to the previous embodiments, the focus ring 254 may also include a focus ring metal-containing coating 256, which may serve as an additional metal source for metal sputtering.

[0038] Although not in Figure 22, but the ICP processing system 20 may further include any additional components that may be used for plasma processing, such as temperature controllers for the substrate 200, the bottom electrode 220, and / or the focus ring 254, and an RF power source for the focus ring 254. In one or more embodiments, the ICP processing system 20 may further include a direct current (DC) voltage source or an RF power source configured to provide a DC voltage or RF power to chamber components (e.g., the top plate 212) that are separate from the main RF system to generate the plasma 260. Such additional voltage or power sources may advantageously adjust the degree of metal sputtering, and thereby adjust the concentration of the metal element in the plasma 260.

[0039] The configurations of the plasma etching systems (e.g., CCP processing system 10 and ICP processing system 20) described above are for example purposes only. In alternative embodiments, various alternative configurations may be used for plasma processing systems in conjunction with metal-containing chamber components for metal sputtering. In alternative embodiments of the ICP processing system, the conductive spiral coil electrode (e.g., Figure 2 The top electrode 250 in the embodiment of the present invention can be located above the top plate 212 instead of above the sidewall 216. In this configuration, the top plate 212 can be made of a dielectric material to allow the electromagnetic field to couple to the plasma 260 in the plasma etching chamber 210. Figure 2 Differently, the focus ring metal-containing coating 256 can be applied to the sidewall 216 instead of the top plate 212. In another example, the plasma processing system can be a resonator such as a spiral resonator. In addition, microwave plasma (MW) or other suitable systems can be used. In some embodiments, pulsed RF power sources and pulsed DC voltage sources (as opposed to continuous wave RF power sources) can also be used. In various embodiments, RF power, chamber pressure, substrate temperature, gas flow rate and other plasma process parameters can be selected according to the corresponding process recipe.

[0040] In various embodiments, a plasma etching process (such as reactive ion etching (RIE)) may include controlling plasma conditions to enable / disable metal sputtering from metal-containing chamber components, as described in reference to Figure 3 and 4 Further described.

[0041] Figure 3 A cross-sectional view of a top electrode 150 of a CCP processing system and a substrate 100 positioned in an etch chamber is shown, wherein a plasma 160 in the etch chamber causes sputtering on the top electrode 150 and reactive ion etching (RIE) on the substrate 100 , according to various embodiments.

[0042] exist Figure 3In the embodiment, the material layer 310 can be formed on the substrate 100. In various embodiments, the material layer 310 is a target layer to be patterned into one or more high aspect ratio (HAR) features. In some embodiments, the HAR features etched into the material layer 310 can be contact holes, slits, or other suitable structures including grooves. In one embodiment, the material layer 310 can be a silicon oxide layer. The material layer 310 can be deposited using appropriate techniques such as vapor deposition (including chemical vapor deposition (CVD), physical vapor deposition (PVD)), atomic layer deposition (ALD), and other plasma processes (such as plasma enhanced CVD (PECVD)) and other processes. In one embodiment, the material layer 310 has a thickness of 0.1 μm to 100 μm.

[0043] Still reference Figure 3 , the patterned layer 320 is formed on the material layer 310. In various embodiments, the patterned layer 320 may include any material that can be used to pattern the material layer 310 through a subsequent patterning process. In various embodiments, the patterned layer 320 may include a photoresist, an organic dielectric layer (ODL), or an amorphous carbon layer (ACL). The patterned layer 320 may include a hard mask, including but not limited to amorphous silicon, silicon oxide, silicon nitride, or a metal-based hard mask. In one or more embodiments, the patterned layer 320 may be a layer stack including a plurality of layers, for example, a three-layer stack commonly used in a photolithography process. The patterned layer 320 may be formed in the following manner: first, a hard mask layer is deposited using, for example, an appropriate spin coating technique or a vapor deposition technique (such as chemical vapor deposition (CVD), physical vapor deposition (PVD)), atomic layer deposition (ALD), and other plasma processes (such as plasma enhanced CVD (PECVD)) and other processes. The deposited hard mask layer may then be patterned using a photolithography process and an anisotropic etching process. The relative thicknesses of patterned layer 320 and material layer 310 may have any suitable relationship. For example, patterned layer 320 may be thicker, thinner, or the same thickness as material layer 310. In one embodiment, patterned layer 320 has a thickness of 0.1 μm to 10 μm.

[0044] The patterned layer 320 and / or the material layer 310 may be considered together as part of the substrate 100. In addition, the substrate 100 may also include other layers. For example, for the purpose of patterning the layers, there may be a three-layer structure including a photoresist layer, a SiON layer, and an optical planarization layer (OPL).

[0045] The HAR features can be manufactured in the material layer 310 by a plasma etching process using a combination of process gases to generate plasma 160. In various embodiments, the process gas may include any reasonable gas that can provide an etchant for the plasma etching process, such as a halogen. In some embodiments, the process gas may include a fluorocarbon or a hydrofluorocarbon. Examples of such process gases include tetrafluoromethane (CF4), trifluoromethane (CHF3), difluoromethane (CH2F2), octafluoropropane (C3F8), hexafluoropropylene (C3F6), perfluorobutane (C4F10), octafluorocyclobutane (C4F8), octafluoro-2-butene (C4F8), perfluoropentane (C5F12), hexafluorobutadiene (C4F6), hexafluoro-2-butyne (C4F6) and hexafluorocyclobutene (C4F6). In some embodiments, other gases such as rare gases and / or balance agents may also be added. For example, in certain embodiments, argon (Ar) and molecular oxygen (O 2 ) may be included as a noble gas and a balance agent, respectively.

[0046] Thus, in some embodiments, the plasma 160 may include positively charged species 302 (eg, Ar+), carbon species 306, and fluorine species 308, such as Figure 3 Here, when sufficient ion bombardment energy is provided to the positively charged species 302, sputtering of metal from the metal-containing coating 152 of the top electrode 150 can be achieved. Figure 3 As indicated by the middle arrows, positively charged species 302 impinge on the metal-containing coating 152 and metal species 304 may be sputtered into the plasma.

[0047] Various process parameters can be used to achieve and control metal sputtering. For example, increasing the DC voltage applied to the top electrode 150 can increase the ion bombardment energy of the positively charged species 302, and thereby increase their sputtering ability. In addition, the extent of metal sputtering can also depend on the temperature of the metal-containing coating 152, wherein higher temperatures result in a greater amount of sputtering. Therefore, precise local temperature control can be used to control metal sputtering. Other parameters, such as process time, gas composition (e.g., inert gas concentration), chamber pressure, RF source power, and RF bias power may also affect metal sputtering, and therefore can be selected accordingly in the process recipe.

[0048] Still reference Figure 3, in the case where the plasma 160 is capable of reactive ion etching (RIE), a groove is formed in the material layer 310 according to the pattern of the patterned layer 320. In various embodiments, the fluorine substance 308 can be used as a main etchant. During this etching, a passivation layer 330 can be formed on the surface of the patterned layer 320, which advantageously prevents the hard mask from being etched and thereby improves the etching selectivity. In various embodiments, the passivation layer 330 can be formed by depositing a metal substance 304 and a carbon substance 306, but in other embodiments, other substances may be involved. In one or more embodiments, the passivation layer 330 may include a metal carbide (e.g., tungsten carbide (WC)) that exhibits high mechanical and chemical stability. In various embodiments, the passivation layer 330 may include carbon derived from the carbon substance 306, the hard mask material, or both. If the hard mask is a silicon-based material, only the carbon substance 306 can be the carbon source in the passivation layer 330.

[0049] Figure 4 A cross-sectional view of a top electrode 150 and a substrate 100 positioned in an etching chamber of a CCP processing system according to an alternative embodiment is shown, wherein a plasma 160 in the etching chamber causes deposition on the top electrode 150 and reactive ion etching (RIE) on the substrate 100. The structure of the substrate 100 and the species of the plasma 160 are similar to Figure 3 The same as those shown in , and therefore will not be repeated.

[0050] exist Figure 4 The conditions of the plasma 160 can be determined from Figure 3 The conditions are changed to disable metal sputtering while maintaining etching capability. Figure 4 As shown in , metal sputtering by ion bombardment can be disabled by forming, for example, a deposition layer 410 containing carbon. In various embodiments, the deposition layer 410 can contain a carbon material formed by depositing carbon species 306 of the plasma 160. The deposition layer 410 can passivate and protect the metal-containing coating 152 from being sputtered by ions such as positively charged species 302 (e.g., Ar+). In one or more embodiments, the no-sputtering condition can be achieved by turning off or reducing the DC voltage Vdc applied to the top electrode 150, which reduces the ion bombardment energy of the species of the plasma 160. In addition, other process parameters can be controlled to disable metal sputtering. In one embodiment, the metal-containing coating 152 can be cooled. In some embodiments, the process conditions can disable metal sputtering without forming the deposition layer 410.

[0051] As mentioned above Figure 3 and 4As described, the plasma process conditions for etching the material layer 310 may or may not achieve metal sputtering from the metal-containing chamber components (e.g., the top electrode 150 having the metal-containing coating 152), which depends primarily on the ion bombardment energy provided to the plasma 160. Generally, higher ion bombardment energy may be desired for faster etching rates and to achieve metal sputtering, but this may compromise etching selectivity and the formation of the passivation layer 330. Therefore, to address this trade-off, in various embodiments, the plasma etching process may be a multi-step process employing multiple plasma conditions, for example, a cyclic process that repeats sputtering and non-sputtering conditions. Therefore, embodiments may advantageously allow for balancing etching rate and etching selectivity.

[0052] Furthermore, in various embodiments, process conditions and process recipes may be selected to obtain a desired thickness of the passivation layer 330. Although the presence of the passivation layer 330 is beneficial for improving the etch selectivity to the hard mask, excessive deposition of the passivation layer 330 may lead to undesirable critical dimension (CD) shrinkage and / or clogging issues. Therefore, process parameters such as process time, gas composition (e.g., inert gas concentration), chamber pressure, RF source power, and RF bias power may be selected to balance the extent of metal deposition to form the passivation layer 330 and metal sputtering.

[0053] Figure 5A and 5B A cross-sectional view of an exemplary substrate during an exemplary high aspect ratio (HAR) patterning process using a plasma processing system according to various embodiments is shown.

[0054] Figure 5A A cross-sectional view of an incoming substrate 100 having a patterned layer 320 and a material layer 310 is shown, similar to FIG. Figure 3 and 4 5 and will not be repeated in detail. The material layer 310 will be patterned to form HAR features, which can be useful in high-capacity three-dimensional (3D) memory devices such as 3D-NAND (or vertical NAND), 3D-NOR, or dynamic random access memory (DRAM) devices. These devices typically require the formation of conformal, high-aspect ratio contact holes (HARC) or trenches (HART). In some embodiments, the material layer 310 is a layer stack including multiple layers (e.g., alternating oxide layers and nitride layers). As shown in FIG. 5, the patterned layer 320 is characterized by having a groove 510.

[0055] Figure 5B A cross-sectional view of substrate 100 is shown after reactive ion etching (RIE).

[0056] The plasma etching process may be a single step process or a multi-step process including a cyclic process, and may be a fluorocarbon or hydrofluorocarbon based process as described above. Figure 5B In the embodiment, the HAR feature is formed by extending the recess 510 into the material layer 310 by a plasma etching process. Figure 3 and 4 As described, since the plasma processing system is capable of metal sputtering from metal-containing chamber components, highly anisotropic plasma etching can be achieved. This is due to metal sputtering and metal deposition on the hard mask to form a passivation layer 330 containing metal (e.g., metal carbide). In some embodiments, some other polymer deposition may also occur (e.g., sidewall deposition on material layer 310).

[0057] The passivation layer 330 may contain metal from the sputtered metal and carbon from substances in the plasma, hard mask, or both. In various embodiments, the passivation layer 330 may contain metal, metal nitride, metal carbide, or metal silicide. In one embodiment, the passivation layer 330 may contain metal carbide (e.g., WC). The use of these metal-containing materials specifically for the passivation layer 330 on conventional hard mask materials may be beneficial to efficient HAR patterning processes. Although these metal-containing materials themselves can potentially be used as hard masks (e.g., patterned layer 320) to provide excellent etching selectivity, it may be challenging to deposit a sufficiently thick film and pattern these metal-containing materials as hard masks. In this method, in addition to new materials, it may be necessary to develop completely new deposition and patterning techniques. In contrast, various embodiments of the present disclosure integrate thin films of metal-containing materials (e.g., as a passivation layer 330) with conventional hard mask materials (e.g., amorphous carbon and / or amorphous silicon), which are significantly easier to process and pattern as hard masks. Thus, the etch resistance of conventional hard mask materials can be greatly improved with minimal additional steps. Thus, during the plasma etching process, the improved etch selectivity to the hard mask can reduce the consumption of the hard mask. In addition, by providing metal-containing chamber components for plasma processing systems, these methods may not require any metal elements to be included in the process gas. In various embodiments, conventional process gases (such as fluorocarbons) used for HAR patterning processes can be utilized with little to no modification.

[0058] exist Figure 5BIt is further shown in Figure 5 that the groove 510 can reach the top surface of the substrate 100. In addition to the hard mask, the plasma etching process according to various embodiments can provide good selectivity to the material (e.g., silicon) of the substrate 100. Therefore, the formation of the groove 125 can advantageously stop at the top surface of the substrate 100. Once the plasma etching process for forming the HAR feature is completed, appropriate subsequent manufacturing steps can be followed according to, for example, conventional process recipes. In the case of manufacturing a 3D NAND device, such steps may include, but are not limited to, removing the remaining hard mask, metallization, and step etching to form a step structure in the material layer 310.

[0059] Figure 6 A process flow diagram of a reactive ion etching (RIE) process according to one embodiment is shown.

[0060] exist Figure 6 In the process flow 60, a substrate is provided in a plasma etching chamber (block 610, Figure 5A ), wherein the substrate includes a patterned hard mask layer and an underlying layer, and the plasma etching chamber includes a top electrode having a surface including a transition metal (e.g., W). Next, a process gas for an RIE process may be flowed into the plasma etching chamber (block 620). While the process gas is flowing, source power is then applied to the bottom electrode of the plasma etching chamber to generate a plasma in the plasma etching chamber (block 630). Subsequently, the surface of the top electrode may be exposed to the plasma to sputter the transition metal from the surface of the top electrode (block 640). Simultaneously or subsequently, the substrate may be exposed to the plasma to deposit the transition metal onto a portion of the patterned hard mask layer, and the underlying layer may be selectively etched to the patterned hard mask layer (block 650, Figure 5B ).

[0061] Exemplary embodiments of the present invention are summarized here. Other embodiments are also apparent from the overall description and claims presented herein.

[0062] Embodiment 1. A method for processing a substrate, comprising: loading the substrate into a plasma etching chamber, the substrate comprising a patterned hard mask layer and an underlying layer, the plasma etching chamber comprising: a chamber component having a surface comprising a refractory metal; and a first electrode; flowing a process gas into the plasma etching chamber; applying source power to the first electrode of the plasma etching chamber while flowing the process gas to generate plasma in the plasma etching chamber; exposing the surface of the chamber component to the plasma to sputter the refractory metal from the surface of the chamber component; and exposing the substrate to the plasma to deposit the refractory metal onto a portion of the patterned hard mask layer and selectively etching the underlying layer to the patterned hard mask layer.

[0063] Embodiment 2. The method of embodiment 1, wherein the refractory metal is tungsten, molybdenum, niobium, tantalum, or ruthenium.

[0064] Embodiment 3. The method of one of Embodiments 1 or 2, wherein the plasma is an inductively coupled plasma (ICP), and wherein the chamber component is a top plate disposed at an upper wall of the plasma etching chamber.

[0065] Embodiment 4. The method of one of Embodiments 1 or 2, wherein the plasma is a capacitively coupled plasma (CCP), and wherein the chamber component is a second electrode disposed in an upper half of the plasma etching chamber.

[0066] Embodiment 5. The method of any one of embodiments 1 to 4 further comprises controlling the temperature of the second electrode to adjust the extent of sputtering from the second electrode.

[0067] Embodiment 6. A method as described in any one of Embodiments 1 to 5, wherein the plasma etching chamber further includes a focusing ring, which surrounds the substrate and has a surface containing another refractory metal, and the method further includes exposing the surface of the focusing ring to the plasma to sputter the other refractory metal from the surface of the focusing ring.

[0068] Embodiment 7. The method of any one of embodiments 1 to 6, further comprising controlling the temperature of the focus ring to adjust the degree of sputtering from the focus ring.

[0069] Embodiment 8. The method of any one of embodiments 1 to 7, further comprising applying a direct current (DC) voltage or radio frequency (RF) power to the second electrode to adjust the extent of sputtering from the second electrode.

[0070] Embodiment 9. The method of any one of Embodiments 1 to 8, wherein the refractory metal deposited on the portion of the patterned hard mask layer forms a metal carbide that prevents the portion of the patterned hard mask layer from being etched by the plasma.

[0071] Embodiment 10. The method of any one of embodiments 1 to 9, wherein the process gas comprises fluorine and carbon.

[0072] Embodiment 11. A plasma etching system for a substrate, comprising: an etching chamber; a substrate holder disposed in the etching chamber; a top electrode disposed in the etching chamber, the top electrode having a surface comprising a refractory metal; a bottom electrode connected to the substrate holder; a first radio frequency (RF) power source connected to the bottom electrode, the first RF power source being configured to generate plasma in the etching chamber and sputter the refractory metal from the surface of the top electrode; and a focusing ring disposed on the substrate holder and configured to surround the substrate.

[0073] Embodiment 12. The plasma etching system of embodiment 11, further comprising a second radio frequency (RF) power source connected to the bottom electrode, the second RF power source being configured to supply bias power to the plasma.

[0074] Embodiment 13. The plasma etching system of one of Embodiments 11 or 12, further comprising a direct current (DC) voltage source connected to the top electrode, the DC voltage source being configured to supply a DC voltage to the top electrode.

[0075] Embodiment 14. The plasma etching system of any one of embodiments 11 to 13, further comprising a third RF power source connected to the top electrode, the third RF power source being configured to supply RF power to the top electrode.

[0076] Embodiment 15. The plasma etching system of any one of embodiments 11 to 14, further comprising a fourth radio frequency (RF) power source connected to the focus ring.

[0077] Embodiment 16. A plasma etching system as described in any one of Embodiments 11 to 15, further comprising: a first sensor coupled to the top electrode to measure the temperature of the top electrode; a first heating element configured to heat the top electrode; and a first temperature controller coupled to the first sensor and the first heating element, the first temperature controller configured to control the heating element based on the measured temperature of the top electrode.

[0078] Embodiment 17. A plasma etching system as described in any one of Embodiments 11 to 16, further comprising: a second sensor coupled to the bottom electrode or the focusing ring to measure the temperature of the bottom electrode or the focusing ring; a second heating element configured to heat the corresponding bottom electrode or the focusing ring; and a second temperature controller coupled to the second sensor and the second heating element, the second temperature controller configured to control the second heating element based on the corresponding measured temperature of the bottom electrode or the focusing ring.

[0079] Embodiment 18. The plasma etching system of any one of Embodiments 11 to 17, wherein the focus ring has a top surface comprising another refractory metal.

[0080] Embodiment 19. A plasma etching system for a substrate, comprising: an etching chamber, wherein an upper wall inside the etching chamber comprises a refractory metal; a substrate holder disposed in the etching chamber; a top electrode comprising a spiral coil disposed outside the etching chamber, the top electrode surrounding an upper half of the etching chamber; a bottom electrode connected to the substrate holder; a radio frequency (RF) power source connected to the top electrode, the first RF power source being configured to generate plasma in the etching chamber, the plasma being configured to sputter the metal from the upper wall; and a focusing ring disposed on the substrate holder and configured to surround the substrate.

[0081] Embodiment 20. The plasma etching system of Embodiment 19, wherein the focus ring comprises another refractory metal.

[0082] Although the present invention has been described with reference to illustrative embodiments, this description is not intended to be interpreted in a limiting sense. Various modifications and combinations of the illustrative embodiments and other embodiments of the present invention will be apparent to those skilled in the art with reference to the description. Therefore, the appended claims are intended to cover any such modifications or embodiments.

Claims

1. A method for processing a substrate, the method comprising: The substrate is loaded into a plasma etching chamber, the substrate comprising a patterned hard mask layer and an underlying layer, the plasma etching chamber comprising: a chamber component having a surface comprising a refractory metal; and a first electrode; flowing a process gas into the plasma etching chamber; applying source power to the first electrode of the plasma etch chamber to generate plasma in the plasma etch chamber while flowing the process gas; exposing a surface of the chamber component to the plasma to sputter the refractory metal from the surface of the chamber component; and The substrate is exposed to the plasma to deposit the refractory metal onto a portion of the patterned hard mask layer and selectively etch the underlying layer to the patterned hard mask layer.

2. The method of claim 1, wherein: The refractory metal is tungsten, molybdenum, niobium, tantalum, or ruthenium.

3. The method of claim 1, wherein: The plasma is an inductively coupled plasma (ICP), and wherein the chamber component is a ceiling disposed at an upper wall of the plasma etching chamber.

4. The method of claim 1, wherein: The plasma is a capacitively coupled plasma (CCP), and wherein the chamber component is a second electrode disposed in an upper half of the plasma etching chamber.

5. The method of claim 4, further comprising controlling a temperature of the second electrode to adjust a degree of sputtering from the second electrode.

6. The method of claim 4, wherein: The plasma etch chamber further includes a focus ring surrounding the substrate and having a surface including another refractory metal, the method further including exposing the surface of the focus ring to the plasma to sputter the other refractory metal from the surface of the focus ring.

7. The method of claim 4, further comprising controlling a temperature of the focus ring to adjust a degree of sputtering from the focus ring.

8. The method of claim 4, further comprising applying a direct current (DC) voltage or radio frequency (RF) power to the second electrode to adjust the extent of sputtering from the second electrode.

9. The method of claim 1, wherein: The refractory metal deposited on the portion of the patterned hard mask layer forms a metal carbide that prevents the portion of the patterned hard mask layer from being etched by the plasma.

10. The method of claim 1, wherein: The process gas contains fluorine and carbon.

11. A plasma etching system for a substrate, comprising: Etching chamber; a substrate holder disposed in the etching chamber; a top electrode disposed in the etching chamber, the top electrode having a surface comprising a refractory metal; a bottom electrode connected to the substrate holder; a first radio frequency (RF) power source connected to the bottom electrode, the first RF power source configured to generate a plasma in the etch chamber and sputter the refractory metal from a surface of the top electrode; as well as A focus ring is disposed on the substrate holder and configured to surround the substrate.

12. The plasma etching system of claim 11, further comprising a second radio frequency (RF) power source connected to the bottom electrode, the second RF power source configured to supply bias power to the plasma.

13. The plasma etching system of claim 11, further comprising a direct current (DC) voltage source connected to the top electrode, the DC voltage source configured to supply a DC voltage to the top electrode.

14. The plasma etching system of claim 11, further comprising a third RF power source connected to the top electrode, the third RF power source configured to supply RF power to the top electrode.

15. The plasma etching system of claim 11, further comprising a fourth radio frequency (RF) power source connected to the focus ring.

16. The plasma etching system of claim 11, further comprising: a first sensor coupled to the top electrode to measure a temperature of the top electrode; a first heating element configured to heat the top electrode; as well as A first temperature controller is coupled to the first sensor and the first heating element, the first temperature controller being configured to control the heating element based on the measured temperature of the top electrode.

17. The plasma etching system of claim 11, further comprising: a second sensor coupled to the bottom electrode or the focus ring to measure a temperature of the bottom electrode or the focus ring; a second heating element configured to heat the corresponding bottom electrode or the focus ring; as well as A second temperature controller is coupled to the second sensor and the second heating element, the second temperature controller being configured to control the second heating element based on the respective measured temperatures of the bottom electrode or the focus ring.

18. The plasma etching system of claim 11, wherein: The focus ring has a top surface comprising another refractory metal.

19. A plasma etching system for a substrate, comprising: an etching chamber, wherein an upper wall of the interior of the etching chamber comprises a refractory metal; a substrate holder disposed in the etching chamber; A top electrode including a spiral coil disposed outside the etching chamber, the top electrode surrounding an upper half of the etching chamber; a bottom electrode connected to the substrate holder; a radio frequency (RF) power source connected to the top electrode, the first RF power source configured to generate a plasma in the etching chamber, the plasma configured to sputter the metal from the upper wall; as well as A focus ring is disposed on the substrate holder and configured to surround the substrate.

20. The plasma etching system of claim 19, wherein: The focusing ring comprises another refractory metal.

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