Plasma Etching Tool and System

Abstract

A method of processing a substrate, comprising: loading the substrate into a plasma etching chamber, the substrate including a patterned hard mask layer and an underlying layer, the plasma etching chamber having a chamber portion with a surface containing a high melting point 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 portion to the plasma to sputter the high melting point metal from the surface of the chamber portion; exposing the substrate to the plasma to deposit the high melting point metal on a portion of the patterned hard mask layer and selectively etch the underlying layer with respect to the patterned hard mask layer.

Description

Technical Field

[0001] Cross - Reference to Related Applications This application claims the benefit of U.S. Non - Provisional Patent Application No. 17 / 832,897, filed on June 6, 2022, which is incorporated herein by reference.

[0002] The present invention generally relates to systems and methods for processing substrates, and in particular embodiments, to plasma etching tools and systems.

Background Art

[0003] Generally, semiconductor devices such as integrated circuits (ICs) are fabricated by sequentially depositing and patterning layers of dielectric, conductive, and semiconductor materials on a substrate to form a network of electronic components and interconnecting elements (e.g., transistors, resistors, capacitors, metal lines, contacts, and vias) integrated in a monolithic structure. Many of the processing steps used to form the constituent structures of semiconductor devices are implemented using plasma processes.

Summary of the Invention

Problems to be Solved by the Invention

[0004] The semiconductor industry has repeatedly reduced the minimum feature size of semiconductor devices down to a few nanometers in order to increase the integration density of components. Accordingly, the semiconductor industry increasingly demands plasma processing technologies for providing processes that pattern features, often at atomic - scale dimensions, with accuracy, precision, and profile control. Addressing this challenge, along with the uniformity and reproducibility required for high - volume production of ICs, requires further innovation in plasma processing technologies.

Means for Solving the Problems

[0005] According to an embodiment of the present invention, a method for processing a substrate, comprising: loading the substrate into a plasma etching chamber, the substrate including a patterned hard mask layer and an underlying layer, the plasma etching chamber having a chamber portion with a surface containing a high melting point 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 portion to the plasma to sputter the high melting point metal from the surface of the chamber portion; and exposing the substrate to the plasma to deposit the high melting point metal on a portion of the patterned hard mask layer and selectively etch the underlying layer with respect to the patterned hard mask layer.

[0006] According to an embodiment of the present invention, a plasma etching system for a substrate, comprising: an etching chamber; a substrate holder disposed in the etching chamber; an upper electrode disposed in the etching chamber, the upper electrode having a surface containing a high melting point 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 high melting point metal from the surface of the upper electrode; and a focus ring disposed on the substrate holder and configured to surround the substrate.

[0007] According to one embodiment of the present invention, a plasma etching system for a substrate, comprising: an etching chamber, wherein an upper wall inside the etching chamber contains a high melting point metal; a substrate holder disposed in the etching chamber; an upper electrode including a helical coil disposed outside the etching chamber, the upper electrode surrounding the upper part of the etching chamber; a bottom electrode connected to the substrate holder; a radio frequency (RF) power source connected to the upper 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 focus ring disposed on the substrate holder and configured to surround the substrate.

[0008] For a more complete understanding of the present invention and its advantages, reference is now made to the following description taken in conjunction with the accompanying drawings.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5A

Figure 5B

Figure 6

DETAILED DESCRIPTION OF THE INVENTION

[0010] This application relates to systems and methods for processing substrates by plasma etching and metal sputtering, which can be useful for fabrication processes for high-capacity three-dimensional (3D) memory devices such as 3D-NAND (or vertical NAND), 3D-NOR, or dynamic random access memory (DRAM) devices. Fabrication of such devices often requires 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 having an aspect ratio (the ratio of the height of the feature to the width of the feature) higher than 20:1 are generally considered high aspect ratio features, and in some cases, it may be desirable to fabricate even higher aspect ratios such as 100:1 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 layer (ACL) and amorphous silicon. New materials such as metals, metal nitrides, metal carbides, and metal silicides may provide better etching selectivity, but the deposition of thick films suitable for the HAR etching process and their patterning tend to be challenging. Therefore, a simple yet effective HAR process may be desired. Embodiments of this application disclose systems and methods for fabricating HAR features by a plasma etching process incorporating metal sputtering. Specifically, such a plasma etching system is characterized by at least one chamber portion containing a metal element, such as a high melting point metal like tungsten (W). The metal-containing chamber portion may be the upper electrode, focus ring, chamber wall, or other parts of the plasma processing system, which may be configured to be sputtered in the presence of plasma to supply the metal element to the plasma. The sputtered metal may then be deposited on a hard mask on the substrate to form a passivation layer, which may conveniently improve the etching selectivity.

[0011] First, an exemplary plasma etching system having a metal-containing chamber portion will be described with reference to FIGS. 1 and 2 for a capacitively coupled plasma (CCP) processing system and an inductively coupled plasma (ICP) processing system, respectively. Next, the expected interactions of reactive species during plasma etching in the plasma etching chamber will be described with reference to FIGS. 3 and 4 for cases with and without metal sputtering from the chamber portion. Subsequently, FIGS. 5A and 5B show the steps of a plasma etching process for patterning a high aspect ratio (HAR) feature that utilizes metal sputtering to enhance etching selectivity. An exemplary process flow diagram is shown in FIG. 6. All figures in the present disclosure are drawn for illustrative purposes only and are not to scale, including the aspect ratio of the features.

[0012] FIG. 1 shows an exemplary capacitively coupled plasma (CCP) processing system 10 according to various embodiments.

[0013] As shown in FIG. 1, the CCP processing system 10 includes a plasma etching chamber 110, and a substrate 100 can be disposed on a substrate holder 105. In various embodiments, the substrate 100 may be part of a semiconductor device or may include a semiconductor device and may have undergone several processing steps (e.g., following a conventional process). Thus, the substrate 100 may include semiconductor layers useful in various microelectronics. For example, the semiconductor structure may include a substrate 100 in which various device regions are formed.

[0014] In one or more embodiments, substrate 100 can be a silicon wafer or a silicon-on-insulator (SOI) wafer. In certain embodiments, substrate 100 can include a silicon germanium wafer, a silicon carbide wafer, a gallium arsenide wafer, a gallium nitride wafer, or other compound semiconductors. In other embodiments, substrate 100 includes heterogenous layers such as silicon germanium on silicon, gallium nitride on silicon, silicon carbon on silicon, as well as silicon on silicon layers or SOI substrates. In various embodiments, substrate 100 is patterned or embedded into other components of the semiconductor device.

[0015] One or more process gases can be introduced into plasma etching chamber 110 by gas delivery system 115. Gas delivery system 115 can include a plurality of gas flow controllers for controlling the flow of multiple gases into plasma etching chamber 110. In some embodiments, an optional center / edge splitter can be used to independently adjust the gas flow rates at the center and edges of substrate 100. Further, in one embodiment, gas delivery system 115 can have a special showerhead configuration disposed on top of plasma etching chamber 110. For example, gas delivery system 115 can be integrated with upper electrode 150 and have a showerhead configuration on top of upper electrode 150, and the showerhead configuration can cover the entire substrate 100 and include a plurality of gas inlets spaced appropriately. Alternatively, gas can be introduced through a dedicated gas inlet of any other suitable configuration. Plasma etching chamber 110 can further be equipped with one or more sensors such as a pressure monitor, a gas flow monitor, and / or a gas species density monitor. The sensors can be integrated as part of gas delivery system 115 in various embodiments.

[0016] In FIG. 1, 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 combination of a mechanical roughing pump and one or more turbo molecular pumps). To facilitate a uniform gas flow during plasma processing, the gas may be removed from a plurality of gas outlets or locations within the plasma etching chamber 110 (e.g., on the opposite side of the substrate 100).

[0017] In various embodiments, the substrate holder 105 may be integrated with a chuck (e.g., a circular electrostatic chuck (ESC)) disposed near the bottom of the plasma etching chamber 110 and connected to the bottom electrode 120, or may be part of the chuck. The surface of the chuck or substrate holder 105 may be coated with a conductive material (e.g., a carbon-based or metal nitride-based coating). The substrate 100 may optionally be maintained at a desired temperature using a temperature sensor and a heating element connected to a first temperature controller 140. In certain embodiments, the temperature sensor may comprise a thermocouple, a resistance temperature detector (RTD), a thermistor, or a semiconductor-based integrated circuit. In one embodiment, the heating element may comprise, for example, a resistive heater. Additionally, there may be a cooling element, such as a liquid cooling system, coupled to the first temperature controller 140. The bottom electrode 120 may be connected to one or more RF power supplies 130 to generate a plasma 160 within the plasma etching chamber 110. As illustrated in FIG. 1, for example, multiple RF power supplies may be used to simultaneously provide high-frequency RF power (HF) and low-frequency RF power (LF). In various embodiments, HF can be used for plasma and radical generation, and LF can be used for ion acceleration within the sheath of the plasma 160 on the substrate 100, which enables plasma etching on the substrate 100. In certain embodiments for a CCP processing system, the frequency of HF may be in the range of 27 MHz to 150 MHz, and the frequency of LF may be in the range of 400 kHz to 13 MHz. The RF power supply 130 may be used to supply continuous wave (CW), and pulsed RF power may be used to maintain the plasma 160. The plasma 160 shown between the upper electrode 150 and the bottom electrode 120 exemplifies a direct plasma generated near the substrate 100 within the plasma etching chamber 110.

[0018] In various embodiments, RF pulsing in the kHz range may be used to power the plasma 160. Using RF pulsing can help generate 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 where electrons deposit charges on the insulating material, forming a local electric field that can guide positive ions to the sidewalls and cause lateral etching. Therefore, it may also be important to finely tune the power conditions of the plasma etching process to minimize the broadening of the critical dimension (CD) of high aspect ratio (HAR) features. In certain embodiments, a moderate duty cycle of 10% to 100% may be used. In one embodiment, 18 kW of bias power may be pulsed at a frequency of 5 kHz with a 60% duty cycle.

[0019] As further shown in FIG. 1, the upper electrode 150 may be a conductive circular plate near the upper part inside the plasma etching chamber 110. In various embodiments, the upper electrode 150 may be connected to the direct current (DC) voltage source 165 of the CCP processing system 10. The DC voltage is used in combination with the RF power from the RF power source 130 to generate a DC superimposed RF plasma inside the plasma etching chamber 110. In FIG. 1, the DC voltage may be supplied to the upper electrode 150. In another embodiment, the DC voltage may be supplied to the bottom electrode 120. In various embodiments, the DC voltage may be advantageously adjusted to tune the degree of metal sputtering and thus the concentration of metal elements in the plasma 160.

[0020] The DC voltage supplied by the DC voltage source 165 can be in the range from positive to negative. A negative DC voltage at the upper electrode 150 can advantageously adjust (e.g., increase) the average ion energy of the plasma species 160. In various embodiments, the DC voltage V coupled to the upper electrode 150 DC may be in the range of 0 V to about 3000 V. In one embodiment, the DC voltage V coupled to the upper electrode 150 DCIt may be about -200V. In a further embodiment, instead of the DC voltage source 165, other RF power sources may be used and configured to supply RF power to the upper electrode 150. In one or more embodiments, the frequency of the RF power to the upper electrode 150 may be in the range of 400 kHz to 13 MHz.

[0021] In various embodiments, the CCP processing system 10 is characterized in particular by an upper electrode 150 that includes a metal, for example having a metal-containing coating 152. During plasma processing such as reactive ion etching (RIE) using the CCP processing system 10, the metal of the metal-containing coating 152 may advantageously be sputtered by ion bombardment, and as a result, the plasma 160 will contain the metal. Then, this metal sputtered into the plasma 160 may be deposited on a hard mask present on the substrate 100 to form a passivation layer, which may enhance the etching selectivity as further described with reference to FIGS. 3 to 5B. In various embodiments, the metal can be a transition metal. In a particular embodiment, the metal can be tungsten (W). Examples of metals useful for the metal-containing coating 152 further include titanium (Ti) and tantalum (Ta), although other metals can also be used. Generally, elements that exhibit better etching resistance than the etching mask used in the process are useful and preferred when deposited from the plasma 160. In a particular embodiment, the metal-containing coating 152 may be in the form of a pure metal, although in other embodiments, it may be a metal carbide (e.g., WC), a metal nitride (e.g., WN), a metal silicide (WSi x )), or other metal compounds. Further, the metal-containing coating 152 may also have a thin layer of oxide on its surface.

[0022] In one or more embodiments, the upper electrode 150 may be connected to a second temperature controller 155 configured to control the temperature of the upper 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 include, for example, a resistive heater. Additionally, there may be a cooling element, such as a liquid cooling system, coupled to the second temperature controller 155. Since metal sputtering is dependent on the temperature of the target, controlling the temperature of the upper electrode 150 can be useful for adjusting the degree of metal sputtering. For example, increasing the temperature of the metal-containing coating 152 can enhance metal sputtering by the plasma 160.

[0023] In FIG. 1, the metal-containing coating 152 covers the bottom surface of the upper electrode 150, but in alternative embodiments, as long as metal sputtering is possible, metal may be incorporated into the chamber portion of the plasma etching chamber 110 in any reasonable form. Accordingly, the metal may be incorporated, for example, by the upper electrode 150 that is made entirely of metal, a metal carbide, a metal nitride, a metal silicide, or other metal compound, plated, brazed, or deposited.

[0024] In various embodiments, the CCP processing system 10 may further include a focus ring 154 disposed on the bottom electrode 120 so as to surround the substrate 100. The focus ring 154 can advantageously maintain and extend the uniformity of the plasma 160 in order to achieve process consistency at the edge of the substrate 100. In various embodiments, the focus ring 154 can have a width of several centimeters. In various embodiments, there can be a gap for mechanical clearance between the circumference of the substrate 100 and the focus ring 154. In certain embodiments, the gap can be from several hundred micrometers to several millimeters. 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.

[0025] In certain embodiments, similar to the upper electrode 150 described above, the focus ring 154 may include a focus ring metal-containing coating 156 on its surface. The metal of the focus ring metal-containing coating 156 may be utilized as an additional source of metal 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 certain embodiments, the metal of the focus ring metal-containing coating 156 may be in the form of a pure metal, but in other embodiments, metal carbides (e.g., WC), metal nitrides (e.g., WN), metal silicides (WSi x) or other metal compounds. In one or more embodiments, instead of having a focus ring metal-containing coating 156, the focus ring 154 can be made entirely of metal, metal carbide, metal nitride, metal silicide, or other metal compounds, and can be plated, brazed, or deposited.

[0026] As shown in FIG. 1, in one embodiment, the focus ring 154 may be connected to an RF power source 170 configured to apply an RF bias to the focus ring 154. In another embodiment, a DC voltage source may be used instead of the RF power source. By applying a bias to the focus ring 154, the uniformity of the plasma 160 in the plasma etching chamber 110 can be advantageously improved, and further, in particular, the degree of metal sputtering from the surface of the focus ring metal-containing coating 156 and / or the focus ring 154 can be adjusted. In certain embodiments, the first temperature controller 140 may also be configured to control the temperature of the focus ring 154. Similar to the upper electrode 150, controlling the temperature of the focus ring metal-containing coating 156 can be useful for adjusting the degree of metal sputtering.

[0027] Although the incorporation of metal into the upper electrode 150 and the focus ring 154 has been described above, any suitable chamber portion, including but not limited to the chamber walls, can be fabricated to include metal on or near the surface for use as a metal source for metal sputtering.

[0028] FIG. 2 shows an exemplary inductively coupled plasma (ICP) processing system 20 according to an alternative embodiment. For illustrative purposes, some parts of the ICP processing system 20 common to the CCP processing system 10 shown in FIG. 1 are omitted (e.g., the first temperature controller 140 and the RF power source 170) and will not be repeated below.

[0029] In FIG. 2, the ICP processing system 20 includes a plasma etching chamber 210 configured to maintain a plasma 260 directly above a substrate 200 loaded on a substrate holder 205. A focus ring 254 may be arranged to surround the substrate 200. A process gas may be introduced into the plasma etching chamber 210 through a gas inlet connected to a gas flow control system 215, and may 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 may include various components such as a high-pressure gas canister, valves (e.g., throttle valves), pressure sensors, gas flow sensors, vacuum pumps, pipes, and an electronically programmable controller. The bottom electrode 220 may be connected to an RF bias power supply 230. For an ICP configuration, the top electrode 250 may be located outside the plasma etching chamber 210 and may be a conductive helical coil electrode wound around a dielectric sidewall 216. The top electrode 250 may be connected to an RF source power supply 265. As further shown in FIG. 2, the gas inlet is an opening in the upper plate 212, and the gas outlet is an opening in the bottom plate 214. The upper plate 212 and the bottom plate 214 may be conductive and may be electrically connected to a system ground (reference potential).

[0030] In various embodiments, the ICP processing system 20 is characterized, in particular, by an upper plate 212 within the plasma etching chamber 210 that includes a metal having, for example, a metal-containing coating 252. Unlike previous embodiments of the CCP processing system 10, the upper electrode 250 is located outside the plasma etching chamber 210. Thus, the metal-containing chamber portion for metal sputtering can be, for example, the upper plate 212 rather than the upper electrode 250. The metal-containing coating 252 can function as a metal source for metal sputtering during plasma processing, for example, during 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 certain embodiments, the metal-containing coating 252 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 (WSi x ), or other metal compounds.

[0031] Similar to previous embodiments, the focus ring 254 may also include a focus ring metal-containing coating 256 that can function as an additional metal source for metal sputtering.

[0032] Although not specifically shown in FIG. 2, the ICP processing system 20 may further include any additional components useful for plasma processing, such as a temperature controller for the substrate 200, a bottom electrode 220, and / or an RF power source for the focus ring 254 and 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 supply a DC voltage or RF power to a chamber portion (e.g., the upper plate 212) separated from the primary RF system to generate the plasma 260. Such additional voltage or power can advantageously tune the degree of metal sputtering and thus the concentration of metal elements in the plasma 260.

[0033] The configurations of the plasma etching systems described above (e.g., CCP processing system 10 and ICP processing system 20) are merely exemplary. In alternative embodiments, various alternative configurations incorporating metal-containing chamber portions for metal sputtering can be used for the plasma processing system. In an alternative embodiment for the ICP processing system, the conductive helical coil electrode (e.g., upper electrode 250 in FIG. 2) may be located on the upper plate 212 rather than on the sidewall 216. In this configuration, the upper plate 212 may be made of a dielectric material so that an electromagnetic field can be coupled to the plasma 260 within the plasma etching chamber 210. Accordingly, unlike FIG. 2, the focus ring metal-containing coating 256 may be applied to the sidewall 216 rather than to the upper plate 212. In another example, the plasma processing system can be a resonator such as a helical resonator. Further, a microwave plasma (MW) or other suitable system can be used. In some embodiments, a pulsed RF power source and a pulsed DC voltage source (as opposed to a continuous wave RF power source) may be used. In various embodiments, the RF power, chamber pressure, substrate temperature, gas flow rate, and other plasma process parameters may be selected according to respective process recipes.

[0034] In various embodiments, as further described with reference to FIGS. 3 and 4, a plasma etching process such as reactive ion etching (RIE) may include controlling the plasma state to enable / disable metal sputtering from the metal-containing chamber portion.

[0035] FIG. 3 shows a cross-sectional view of an upper electrode 150 of a CCP processing system and a substrate 100 disposed within an etching chamber, according to various embodiments, where the plasma 160 within the etching chamber causes sputtering on the upper electrode 150 and reactive ion etching (RIE) on the substrate 100.

[0036] In FIG. 3, a material layer 310 can be formed on the substrate 100. In various embodiments, the material layer 310 is a target layer that will be patterned into one or more high aspect ratio (HAR) features. In certain embodiments, the HAR features etched in the material layer 310 can be contact holes, slits, or other suitable structures including recesses. In one embodiment, the material layer 310 can be a silicon oxide layer. The material layer 310 can be deposited using suitable techniques such as chemical vapor deposition (CVD), physical vapor deposition (PVD), vapor deposition methods including atomic layer deposition (ALD), and 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.

[0037] Still referring to FIG. 3, a patterned layer 320 is formed on the material layer 310. In various embodiments, the patterned layer 320 can include any material useful for enabling patterning of the material layer 310 by subsequent patterning processes. In various embodiments, the patterned layer 320 can include a photoresist, an organic dielectric layer (ODL), or an amorphous carbon layer (ACL). The patterned layer 320 can 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 can be a layer stack including multiple layers, such as a three-layer stack commonly used for photolithography processes. The patterned layer 320 can be formed first, for example, by depositing a hard mask layer using suitable spin coating techniques, or vapor growth techniques 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 can then be patterned using lithography processes and anisotropic etching processes. The relative thicknesses of the patterned layer 320 and the material layer 310 can have any suitable relationship. For example, the patterned layer 320 can be thicker than the material layer 310, thinner than the material layer 310, or the same thickness as the material layer 310. In one embodiment, the patterned layer 320 has a thickness of 0.1 μm to 10 μm.

[0038] The patterned layer 320 and / or the material layer 310 can be collectively regarded as part of the substrate 100. Further, the substrate 100 can include other layers. For example, for the purpose of patterning layers, there can be a three-layer structure including a photoresist layer, a SiON layer, and an optical planarization layer (OPL).

[0039] Fabricating the HAR feature in the material layer 310 can be performed by a plasma etching process that generates the plasma 160 using a combination of process gases. In various embodiments, the process gas can include any suitable gas that provides an etchant for the plasma etching process, such as a halogen. In certain embodiments, the process gas can include a fluorocarbon or a hydrofluorocarbon. Examples of such process gases include tetrafluoromethane (CF4), fluoromethane (CHF3), difluoromethane (CH2F2), octafluoropropane (C3F8), hexafluoropropylene (C3F6), perfluorobutane (C4F 10 ), octafluorocyclobutane (C4F8), octafluoro-2-butene (C4F8), perfluoropentane (C5F 12 ), hexafluorobutadiene (C4F6), hexafluoro-2-butyne (C4F6), and hexafluorocyclobutene (C4F6). In certain embodiments, other gases can be added, such as noble gases and / or moderators. For example, in certain embodiments, argon (Ar) and diatomic oxygen (O2) can be included as a noble gas and a moderator, respectively.

[0040] Accordingly, in certain embodiments, the plasma 160 can include positively charged species 302 (e.g., Ar + ), carbon species 306, and fluorine species 308, as shown in FIG. 3. Here, when sufficient ion impact energy is supplied to the positively charged species 302, sputtering of the metal from the metal-containing coating 152 of the upper electrode 150 becomes possible. As indicated by the arrows in FIG. 3, the positively charged species 302 collide with the metal-containing coating 152, and metal species 304 can be sputtered into the plasma.

[0041] To enable and control metal sputtering, various process parameters can be utilized. For example, increasing the DC voltage applied to the upper electrode 150 can increase the ion bombardment energy of the positively charged species 302 and, thus, their sputtering ability. Additionally, the degree of metal sputtering may depend on the temperature of the metal-containing coating 152, and a higher temperature may result in a greater amount of sputtering. Thus, local temperature control can be utilized 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 affect metal sputtering and, thus, may be selected in the process recipe as appropriate.

[0042] Still referring to FIG. 3, since the plasma 160 enables reactive ion etching (RIE), recesses are formed in the material layer 310 according to the pattern of the patterned layer 320. In various embodiments, fluorine species 308 can function as the main etchant. During this etching, a passivation layer 330 may be formed on the surface of the patterned layer 320, and beneficially, etching of the hard mask is prevented, thereby improving the etching selectivity. In various embodiments, the passivation layer 330 can be formed by the deposition of metal species 304 and carbon species 306, although in other embodiments, other chemical species may be involved. In one or more embodiments, the passivation layer 330 can include a metal carbide having high mechanical and chemical stability, such as tungsten carbide (WC). In various embodiments, the passivation layer 330 can include carbon species 306, the hard mask material, or carbon derived from both. If the hard mask is a silicon-based material, only the carbon species 306 can be a source for the carbon in the passivation layer 330.

[0043] Figure 4 shows a cross-sectional view of the upper electrode 150 of the CCP processing system and the substrate 100 disposed within the etching chamber according to an alternative embodiment, where the plasma 160 within the etching chamber causes deposition on the upper 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 the same as those shown in FIG. 3 and thus will not be repeated.

[0044] In FIG. 4, in order to deactivate metal sputtering while maintaining etching ability, the conditions of the plasma 160 can be changed from those of FIG. 3. As illustrated in FIG. 4, metal sputtering by ion bombardment can be deactivated, for example, by the formation of a deposited layer 410 containing carbon. In various embodiments, the deposited layer 410 can include a carbon material formed by the deposition of carbon species 306 of the plasma 160. The deposited layer 410 passivates the metal-containing coating 152 and can protect it from being sputtered by ions such as positively charged species 302 (e.g., Ar + ). In one or more embodiments, this sputter-free state can be achieved by turning off or reducing the DC voltage V dc applied to the upper electrode 150, thereby reducing the ion bombardment energy of the species of the plasma 160. Additionally, other process parameters may be controlled to deactivate metal sputtering. In one embodiment, the metal-containing coating 152 may be cooled. In certain embodiments, the process conditions can deactivate metal sputtering without forming the deposited layer 410.

[0045] As described above with reference to FIGS. 3 and 4, the plasma process conditions used to etch the material layer 310 may or may not enable metal sputtering from a metal-containing chamber portion (e.g., the upper electrode 150 having the metal-containing coating 152), mainly depending on the ion impact energy supplied to the plasma 160. Generally, higher ion impact energy is desirable for a faster etching rate and may enable metal sputtering, but may impair etching selectivity and the formation of the passivation layer 330. Thus, to address this trade-off, the plasma etching process in various embodiments can be a multi-step process using multiple plasma conditions, e.g., a periodic process that repeats sputtering conditions and non-sputtering conditions. Thus, embodiments can advantageously balance the etching rate and the etching selectivity.

[0046] Furthermore, in various embodiments, the process conditions and process recipes may be selected to achieve the desired thickness of the passivation layer 330. The presence of the passivation layer 330 is beneficial in improving the etching selectivity to the hard mask, while excessive deposition of the passivation layer 330 may cause undesirable critical dimension (CD) shrinkage and / or clogging issues. Thus, 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 and metal sputtering for forming the passivation layer 330.

[0047] FIGS. 5A and 5B show cross-sectional views of an exemplary substrate during an exemplary high aspect ratio (HAR) patterning process using a plasma processing system according to various embodiments.

[0048] FIG. 5A shows a cross-sectional view of an incoming substrate 100 having a patterned layer 320 and a material layer 310, which is similar to that shown in FIGS. 3 and 4 and thus details are not repeated. The material layer 310 is to be patterned to form HAR features, which may 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 forming conformal high aspect ratio contact holes (HARC) or trenches (HART). In certain embodiments, the material layer 310 is a layer stack comprising multiple layers, such as an alternating oxide layer and nitride layer. As shown in FIG. 5, the patterned layer 320 is characterized by having recesses 510.

[0049] FIG. 5B shows a cross-sectional view of the substrate 100 after reactive ion etching (RIE).

[0050] The plasma etching process may be a single-step process or a multi-step process including a cyclic process, and as described above, may be a fluorocarbon or hydrofluorocarbon-based process. In FIG. 5B, the HAR features are formed by extending the recesses 510 into the material layer 310 by a plasma etching process. As described with reference to FIGS. 3 and 4, the plasma processing system enables high anisotropic plasma etching since metal sputtering from the metal-containing chamber portion is possible. This is due to metal sputtering and metal deposition onto the hard mask to form a passivation layer 330 containing a metal (e.g., metal carbide). In certain embodiments, some other polymer deposition (e.g., sidewall deposition onto the material layer 310) may occur.

[0051] The passivation layer 330 may include metal from sputtered metal and carbon, a hard mask, or both from chemical species in the plasma. In various embodiments, the passivation layer 330 may include a metal, a metal nitride, a metal carbide, or a metal silicide. In one embodiment, the passivation layer 330 may include a metal carbide (e.g., WC). Using these metal-containing materials, particularly for the passivation layer 330, on a conventional hard mask material can be beneficial in an efficient HAR patterning process. While these metal-containing materials can, in some cases, be used as the hard mask (e.g., the patterned layer 320) itself to provide excellent etch selectivity, depositing a sufficiently thick film and patterning these metal-containing materials as a hard mask can be challenging. In this approach, in addition to new materials, it may be necessary to develop completely new technologies for deposition and patterning. In contrast, various embodiments of the present disclosure integrate a thin film of a metal-containing material (e.g., as the passivation layer 330) with a conventional hard mask material (e.g., amorphous carbon and / or amorphous silicon), which is significantly easier to process and pattern as a hard mask. As a result, the etch resistance of the conventional hard mask material can be substantially improved with minimal additional steps. Thus, the improved etch selectivity for the hard mask during the plasma etching process can reduce the consumption of the hard mask. Further, this method does not require any metal elements to be included in the process gas by providing a metal-containing chamber portion to the plasma processing system. In various embodiments, conventional process gases such as fluorocarbons for the HAR patterning process can be utilized with little or no change.

[0052] Further, as shown in FIG. 5B, the recess 510 may reach the upper surface of the substrate 100. Plasma etching processes according to various embodiments may provide good selectivity to the material of the substrate 100 (e.g., silicon) in addition to the hard mask. Accordingly, the formation of the recess 125 may advantageously stop at the upper surface of the substrate 100. Once the plasma etching process for forming the HAR features is completed, appropriate subsequent fabrication steps may follow, for example, according to a conventional process recipe. Such steps may include, but are not limited to, removal of the remaining hard mask, metallization, removal of the staircase etch, and staircase etching to form a staircase structure in the material layer 310 when fabricating a 3D NAND device.

[0053] FIG. 6 shows a process flow diagram of a reactive ion etching (RIE) process according to one embodiment.

[0054] In FIG. 6, the process flow 60 begins with providing a substrate in a plasma etching chamber (block 610, FIG. 5A), the substrate comprising a patterned hard mask layer and an underlying layer, and the plasma etching chamber comprising an upper electrode having a surface containing a transition metal (e.g., W). Next, a process gas for the RIE process may be flowed into the plasma etching chamber (block 620). Then, while flowing the process gas, source power is applied to the bottom electrode of the plasma etching chamber to generate plasma in the plasma etching chamber (block 630). Thereafter, the surface of the upper electrode is exposed to the plasma and the transition metal may be sputtered from the surface of the upper electrode (block 640). Simultaneously or thereafter, the substrate is exposed to the plasma and the transition metal is deposited on a portion of the patterned hard mask layer, and the underlying layer may be etched selectively with respect to the patterned hard mask layer (block 650, FIG. 5B)

[0055] Here, exemplary embodiments of the present invention are summarized. Other embodiments may be understood throughout this specification as well as from the patent claims appended hereto.

Examples

[0056] Example 1. A method for processing a substrate, comprising loading the substrate into a plasma etching chamber, wherein the substrate includes a patterned hard mask layer and an underlying layer, and the plasma etching chamber has a chamber portion having a surface containing a high melting point 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 portion to the plasma to sputter the high melting point metal from the surface of the chamber portion; exposing the substrate to the plasma to deposit the high melting point metal on a portion of the patterned hard mask layer and selectively etch the underlying layer with respect to the patterned hard mask layer.

[0057] Example 2. The method according to Example 1, wherein the high melting point metal is tungsten, molybdenum, niobium, tantalum, or ruthenium.

[0058] Example 3. The method according to Example 1 or 2, wherein the plasma is an inductively coupled plasma (ICP), and the chamber portion is an upper plate disposed on the upper wall of the plasma etching chamber.

[0059] Example 4. The method according to Example 1 or 2, wherein the plasma is a capacitively coupled plasma (CCP), and the chamber portion is a second electrode disposed above the plasma etching chamber.

[0060] Example 5. The method according to any one of Examples 1 to 4, further comprising controlling the temperature of the second electrode to tune the degree of sputtering from the second electrode.

[0061] Example 6. The plasma etching chamber further includes a focus ring, the focus ring surrounds the substrate and has a surface containing another high melting point metal, and the method further includes exposing the surface of the focus ring to the plasma to perform sputtering of another high melting point metal from the surface of the focus ring, the method according to any one of Examples 1 to 5.

[0062] Example 7. The method according to any one of Examples 1 to 6, further including controlling the temperature of the focus ring to tune the degree of sputtering from the focus ring.

[0063] Example 8. The method according to any one of Examples 1 to 7, further including applying a direct current (DC) voltage or radio frequency (RF) power to the second electrode to tune the degree of sputtering from the second electrode.

[0064] Example 9. The high melting point metal deposited on a portion of the patterned hard mask layer forms a metal carbide that maintains the portion of the patterned hard mask layer from being etched by the plasma, the method according to any one of Examples 1 to 8.

[0065] Example 10. The process gas includes fluorine and carbon, the method according to any one of Examples 1 to 9.

[0066] Example 11. A plasma etching system for a substrate, including an etching chamber, a substrate holder disposed in the etching chamber, an upper electrode disposed in the etching chamber, the upper electrode having a surface containing a high melting point metal, the upper electrode, 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 etching chamber and sputter a high melting point metal from the surface of the upper electrode, the first RF power source, and a focus ring disposed on the substrate holder and configured to surround the substrate.

[0067] Example 12. The plasma etching system according to Example 11, further comprising a second radio frequency (RF) power source connected to the bottom electrode, the second RF power source being configured to supply a bias to the plasma.

[0068] Example 13. The plasma etching system according to Example 11 or 12, further comprising a direct current (DC) voltage source connected to the upper electrode, the DC voltage source being configured to supply a DC voltage to the upper electrode.

[0069] Example 14. The plasma etching system according to any one of Examples 11 to 13, further comprising a third RF power source connected to the upper electrode, the third RF power source being configured to supply RF power to the upper electrode.

[0070] Example 15. The plasma etching system according to any one of Examples 11 to 14, further comprising a fourth radio frequency (RF) power source connected to the focus ring.

[0071] Example 16. The plasma etching system according to any one of Examples 11 to 15, further comprising a first sensor coupled to the upper electrode to measure the temperature of the upper electrode, a first heating element configured to heat the upper electrode, and a first temperature controller 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 upper electrode.

[0072] Example 17. A plasma etching system according to any one of Examples 11 to 16, further comprising: a second sensor coupled to the bottom electrode or the focus ring to measure the temperature of the bottom electrode or the focus ring; a second heating element configured to heat each of the bottom electrode or the focus ring; and a second temperature controller coupled to the second sensor and the second heating element, wherein the second temperature controller is configured to control the second heating element based on the measured temperature of each of the bottom electrode or the focus ring.

[0073] Example 18. A plasma etching system according to any one of Examples 11 to 17, wherein the focus ring has an upper surface containing another high melting point metal.

[0074] Example 19. A plasma etching system for a substrate, comprising: an etching chamber, wherein an upper wall inside the etching chamber contains a high melting point metal; a substrate holder disposed in the etching chamber; an upper electrode including a helical coil disposed outside the etching chamber, the upper electrode surrounding the upper part of the etching chamber; a bottom electrode connected to the substrate holder; a radio frequency (RF) power source connected to the upper electrode, the first RF power source being configured to generate plasma in the etching chamber, and the plasma being configured to sputter metal from the upper wall; and a focus ring disposed on the substrate holder and configured to surround the substrate.

[0075] Example 20. A plasma etching system according to Example 19, wherein the focus ring contains another high melting point metal.

[0076] Although the present invention has been described with reference to exemplary embodiments, the present specification is not intended to be construed in a limiting sense. Various modifications and combinations of the exemplary embodiments, as well as other embodiments of the present invention, will be apparent to those skilled in the art by reference to this specification. Accordingly, the appended claims are intended to embrace any such modifications or embodiments.

Claims

1. A method for processing a substrate, comprising: loading the substrate into a plasma etching chamber, wherein the substrate comprises a patterned hard mask layer and an underlying layer, and the plasma etching chamber comprises: a chamber portion having a surface containing a high melting point metal; a first electrode; and; 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 portion to the plasma to sputter the high melting point metal from the surface of the chamber portion; exposing the substrate to the plasma to deposit the high melting point metal on a portion of the patterned hard mask layer and selectively etch the underlying layer with respect to the patterned hard mask layer; A method comprising.

2. The method according to claim 1, wherein the high melting point metal is tungsten, molybdenum, niobium, tantalum, or ruthenium.

3. The method according to claim 1, wherein the plasma is an inductively coupled plasma (ICP), and the chamber portion is an upper plate disposed on an upper wall of the plasma etching chamber.

4. The method according to claim 1, wherein the plasma is a capacitively coupled plasma (CCP), and the chamber portion is a second electrode disposed above the plasma etching chamber.

5. The method according to claim 4, further comprising controlling a temperature of the second electrode to tune an extent of the sputtering from the second electrode.

6. The plasma etching chamber further comprises a focus ring, the focus ring surrounds the substrate and has a surface containing another high melting point metal, and the method further comprises exposing the surface of the focus ring to the plasma to perform sputtering of the another high melting point metal from the surface of the focus ring. The method according to claim 4.

7. The method according to claim 4, further comprising controlling a temperature of the focus ring to tune an extent of the sputtering from the focus ring.

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

9. The high melting point metal deposited on the portion of the patterned hard mask layer forms a metal carbide that maintains the portion of the patterned hard mask layer from being etched by the plasma, according to the method of claim 1.

10. The process gas contains fluorine and carbon, according to the method of claim 1.

11. A plasma etching system for a substrate, an etching chamber, a substrate holder disposed in the etching chamber, an upper electrode disposed in the etching chamber, the upper electrode having a surface containing a high melting point metal, a bottom electrode connected to the substrate holder, a first radio frequency power source (first RF power source) connected to the bottom electrode, the first RF power source configured to generate plasma in the etching chamber and sputter the high melting point metal from the surface of the upper electrode, a focus ring disposed on the substrate holder and configured to surround the substrate, A plasma etching system comprising.

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

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

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

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

16. A first sensor coupled to the upper electrode to measure the temperature of the upper electrode, a first heating element configured to heat the upper electrode, A first temperature controller 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 upper electrode. The plasma etching system according to claim 11, further comprising.

17. A second sensor coupled to the bottom electrode or the focus ring to measure the temperature of the bottom electrode or the focus ring. A second heating element configured to heat each of the bottom electrode or the focus ring. A second temperature controller 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 measured temperature of each of the bottom electrode or the focus ring. The plasma etching system according to claim 11, further comprising.

18. The plasma etching system according to claim 11, wherein the focus ring has an upper surface containing another high melting point metal.

19. A plasma etching system for a substrate, An etching chamber, wherein an upper wall inside the etching chamber contains a high melting point metal. A substrate holder disposed in the etching chamber. An upper electrode including a helical coil disposed outside the etching chamber, the upper electrode surrounding the upper portion of the etching chamber. A bottom electrode connected to the substrate holder. A radio frequency power source (RF power source) connected to the upper electrode, the RF power source being configured to generate plasma in the etching chamber, the plasma being configured to sputter the high melting point metal from the upper wall. A focus ring disposed on the substrate holder and configured to surround the substrate. A plasma etching system comprising.

20. The plasma etching system according to claim 19, wherein the focus ring contains another high melting point metal.

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