Silicon mandrel etch after native oxide punch-through

Abstract

Apparatus, systems and methods for performing a silicon-containing material removal process on a workpiece are provided. In one example implementation, the method may include generating a substance from a process gas in a first chamber using an inductive coupling element. The method may include introducing a fluorine-containing gas and the substance to form a mixture. The mixture may include exposing a silicon structure of the workpiece to the mixture to remove at least a portion of the silicon structure.

Description

[0001] Priority declaration

[0002] This application claims the benefit of priority to U.S. Provisional Application Serial No. 62 / 782,653, filed on December 20, 2018, entitled “Silicon Mandrel Etch after Native Oxide Punch-Through,” which is incorporated herein by reference. This application claims the benefit of priority to U.S. Provisional Application Serial No. 62 / 790,661, filed on January 10, 2019, entitled “Silicon Mandrel Etch after Native Oxide Punch-Through,” which is incorporated herein by reference. Technical Field

[0003] The present disclosure generally relates to surface processing of workpieces, such as semiconductor workpieces. Background Art

[0004] Processing of semiconductor workpieces may involve deposition and removal of different material layers on a substrate. In semiconductor processing, device size and material thickness continue to decrease as critical dimensions in semiconductor devices decrease. In advanced device nodes, material removal with high selectivity to other materials becomes increasingly important to semiconductor device performance. For example, in some structures, silicon mandrel and silicon replacement gate removal may be of particular importance because such removal may damage spacers and / or leave residues on sublayers. Summary of the invention

[0005] Aspects and advantages of embodiments of the present disclosure will be set forth in part in the following description, or may be learned from the description, or may be learned through practice of the embodiments.

[0006] One example aspect of the present disclosure relates to a method for removing a silicon structure disposed on a workpiece. The method may include generating a species from a process gas in a first chamber using an inductive coupling element. The method may include introducing a fluorine-containing gas and the species to form a mixture. The mixture may include exposing a silicon structure of the workpiece to the mixture to remove at least a portion of the silicon structure.

[0007] Other example aspects of the present disclosure relate to systems, methods, and apparatus for chamber seasoning for hydrogen radical processing of workpieces.

[0008] These and other features, aspects and advantages of various embodiments will become better understood with reference to the following description and appended claims.The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the present disclosure and, together with the description, serve to explain the relevant principles. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] A detailed discussion of embodiments that will guide those skilled in the art is set forth in the specification with reference to the accompanying drawings, in which:

[0011] Figure 1 depicts an example silicon mandrel removal process on a structure according to an example embodiment of the present disclosure;

[0012] Figure 2 depicts an example silicon mandrel removal process on a structure according to an example embodiment of the present disclosure;

[0013] Figure 3 depicts an example plasma processing apparatus according to an example embodiment of the present disclosure;

[0014] Figure 4 depicts an example processing platform according to an example implementation of the present disclosure;

[0015] Figure 5 depicts a flow chart of an example process according to an example implementation of the present disclosure;

[0016] Figure 6 depicts a flow chart of an example process according to an example implementation of the present disclosure;

[0017] Figure 7 depicts an example implantation of a fluorine-containing gas using a plasma post-implantation according to an example embodiment of the present disclosure; and

[0018] Figure 8 An example plasma processing apparatus is depicted according to an example implementation of the present disclosure. DETAILED DESCRIPTION

[0019] Reference will now be made in detail to the embodiments of which one or more examples are illustrated in the accompanying drawings. Each example is provided by way of explanation of the embodiments, rather than by way of limitation of the present disclosure. Indeed, it will be apparent to those skilled in the art that various modifications and variations may be made to the embodiments without departing from the scope or spirit of the present disclosure. For example, a feature illustrated or described as a part of one embodiment may be used together with another embodiment to produce still further embodiments. Therefore, it is expected that aspects of the present disclosure cover such modifications and variations.

[0020] An example aspect of the present disclosure relates to a process for removing a silicon mandrel disposed on a workpiece. As critical dimensions in semiconductor devices decrease, the size and material thickness of the devices continue to decrease. In the manufacture of advanced logic and storage (e.g., dynamic random access memory DRAM) devices, the so-called self-aligned double patterning (SADP) technique can be an economical way to significantly reduce feature sizes with conventional lithography tool resolution. In an example SADP process flow, a spacer (e.g., SiN) pair structure is first formed in the mandrel (e.g., silicon) material. Subsequently, the mandrel material is selectively removed while the spacer structure remains intact. The spacer structure is further used as a hard mask in the following anisotropic ion etching process to transfer its pattern to the underlying material. In another example of a process flow, the self-aligned double patterning (SADP) scheme can be repeated in a so-called self-aligned quadruple patterning (SAQP) scheme.

[0021] In an example SADP / SAQP scheme, the size of the silicon (Si) mandrels is about 10-50 nm, with a height to width ratio (i.e., aspect ratio) of 4-8: 1. The silicon feature size and selective removal requirements are similar between the silicon mandrels in the SADP / SAQP process and the silicon replacement gates used in advanced field effect transistor (FET) device fabrication.

[0022] For semiconductor manufacturing systems and related processes, it is important to remove silicon mandrels and / or silicon replacement gates with high selectivity to spacer materials and other materials (e.g., oxides, TiN). Conventional methods can remove silicon mandrels and / or silicon replacement gates inside a plasma chamber with chlorine (Cl2), hydrogen bromide (HBr), etc. These conventional methods may have some disadvantages. There is concern about etching the material with chlorine (Cl2) and hydrogen bromide (HBr) gases. In addition, this method may result in lower selectivity or silicon residues. It may be necessary to follow a wet process to remove silicon residues or improve sublayer damage.

[0023] According to example aspects of the present disclosure, an inductively coupled plasma source (ICP) with very high selectivity can be used to remove silicon mandrels. More specifically, according to example aspects of the present disclosure, a fluorine-containing gas (e.g., nitrogen trifluoride (NF3) or tetrafluoromethane (CF4) or other fluorine-containing hydrocarbons such as CH2F2 (difluoromethane), CHF3 (fluoroform), CH3F (fluoromethane) can be used to form a highly selective species associated with a remote ICP plasma source for removing silicon mandrels while reducing damage to spacers and sublayers.

[0024] For example, an example aspect of the present disclosure relates to a method for removing a silicon structure disposed on a workpiece. The method may include generating a substance from a process gas using an inductive coupling element in a first chamber (e.g., a plasma chamber). The method may include introducing a fluorine-containing gas (e.g., nitrogen trifluoride (NF3) or tetrafluoromethane (CF4) or other fluorine-containing hydrocarbons such as CH2F2, CHF3, CH3F) or other fluorine-containing hydrocarbons such as CH2F2 (difluoromethane), CHF3 (fluoroform), CH3F (fluoromethane) with the substance to form a mixture. The method may include exposing a silicon structure of the workpiece to the mixture to remove at least a portion of the silicon structure. Examples of silicon structures may include silicon mandrels, silicon replacement gates, or any other suitable silicon-containing material. In some embodiments, the process gas may further include hydrogen (H2). In some other embodiments, the process gas may also include an inert gas, such as helium (He) or argon (Ar).

[0025] In some embodiments, a fluorine-containing gas (e.g., nitrogen trifluoride (NF3) or tetrafluoromethane (CF4) or other fluorine-containing hydrocarbons such as CH2F2, CHF3, CH3F) may be introduced as part of the process gas. The process gas may be allowed to enter the plasma chamber and a plasma may be induced using an inductively coupled plasma source to generate a mixture. Silicon structures on the workpiece (e.g., silicon mandrels or silicon replacement gates) may be exposed to the mixture (e.g., after filtering through a barrier) to be selectively removed.

[0026] In some embodiments, the process gas may include an inert gas. The inert gas may be allowed to enter the plasma chamber. A fluorine-containing gas (e.g., NF3 or CF4 or other fluorine-containing hydrocarbons such as CH2F2, CHF3, CH3F) may be injected outside the plasma chamber and at a downstream flow position of the plasma chamber. For example, a fluorine-containing gas (e.g., NF3 or CF4 or other fluorine-containing hydrocarbons such as CH2F2, CHF3, CH3F) may be injected via a post-plasma gas injection gas source. As an example, the post-plasma gas injection gas source may be located between a first grid plate and a second grid plate of a grid that separates the plasma chamber from the processing chamber. In some embodiments, the post-plasma gas injection gas source may be located below the grid in the processing chamber.

[0027] In some cases, it may be desirable to remove native oxide on the silicon mandrel or silicon replacement gate prior to removing the silicon mandrel or silicon replacement gate (e.g., native oxide punch-through process). According to example aspects of the present disclosure, the method may further include generating a capacitively coupled plasma using a plasma source. The method may include exposing a silicon mandrel or silicon replacement gate structure on a workpiece to the capacitively coupled plasma to remove a native oxide layer on top of at least a portion of the silicon mandrel or silicon replacement gate.

[0028] In some embodiments, a capacitively coupled plasma may be generated in a processing chamber of a separate plasma processing apparatus relative to an inductively coupled plasma source for performing a silicon mandrel or silicon replacement gate removal process. For example, a native oxide punch-through process and a silicon mandrel or silicon replacement gate removal process may be performed in a processing platform with a vacuum transfer (or near-vacuum transfer) between processing chambers of separate processing apparatuses. A workpiece may be placed into a first processing chamber of a first plasma processing apparatus to perform a native oxide punch-through process using a capacitively coupled plasma source. Using a workpiece handling robot in the transfer chamber, the workpiece may be transferred to a second processing chamber of a second plasma processing apparatus. After the native oxide punch-through process, according to an exemplary aspect of the present disclosure, the second plasma processing apparatus may generate an inductively coupled plasma to remove the silicon mandrel or silicon replacement gate.

[0029] In some embodiments, a capacitively coupled plasma may be generated in a processing chamber using the same plasma processing apparatus as that used to perform silicon mandrel or silicon replacement gate removal. For example, a workpiece may include a silicon mandrel or silicon replacement gate at least partially covered by a native oxide layer. The workpiece may be placed into a processing chamber for a silicon mandrel or silicon replacement gate removal process. Prior to the silicon mandrel or silicon replacement gate removal process, a native oxide punch-through process may be performed by a capacitively coupled plasma induced in the processing chamber to remove the native oxide layer on top of the silicon mandrel or silicon replacement gate. After the native oxide punch-through process, an indirect or remote inductively coupled plasma may be used for the silicon mandrel or silicon replacement gate removal process.

[0030] Example aspects of the present disclosure provide many technical effects and benefits. For example, an inductively coupled plasma source (ICP) with very high selectivity can be used to etch silicon mandrels or silicon replacement gates, and a capacitively coupled plasma source (CCP) can be used to etch through a thin layer of native oxide on top of the silicon mandrels or silicon replacement gates. As such, the silicon mandrels or silicon replacement gates can be completely removed while reducing damage on the spacer (e.g., SiN spacer) and sublayer (e.g., oxide sublayer, TiN sublayer) materials.

[0031] Example process parameters for removing silicon mandrels or silicon replacement gates using an inductively coupled plasma source according to example embodiments of the present disclosure are provided below:

[0032] Example 1

[0033] Process gas: CF4, NF3, H2

[0034] Dilution gas: He / Ar

[0035] Process pressure: about 200 mTorr to about 1000 mTorr (e.g., about 600 mTorr)

[0036] Inductively coupled plasma source power: about 600 W to about 2500 W (e.g., about 1500 W)

[0037] Capacitively coupled plasma source power: about 0 W to about 150 W (e.g., about 50 W)

[0038] Workpiece temperature: (20°C) about 5°C to 90°C (e.g., about 20°C)

[0039] Process cycle: about 10 seconds to 200 seconds (for example, 40 seconds)

[0040] Gas flow rate for process gas: about 50 sccm to about 500 sccm (e.g., 310 sccm)

[0041] For purposes of illustration and discussion, aspects of the present disclosure are discussed with reference to a "wafer" or semiconductor wafer. Using the disclosure provided herein, one of ordinary skill in the art will understand that the exemplary aspects of the present disclosure can be used in conjunction with any semiconductor substrate or other suitable substrate. Additionally, the term "about" used in conjunction with a numerical value is intended to mean within twenty percent (20%) of the recited numerical value. "Base" refers to any structure that can be used to support a workpiece.

[0042] Figure 1 An example silicon mandrel removal process on a structure 50 according to an example embodiment of the present disclosure is depicted. The structure 50 includes a spacer layer 52 (e.g., a SiN spacer layer), a silicon mandrel 54, a sublayer 56 (e.g., an oxide layer), and a substrate 58 (e.g., a silicon substrate). In some embodiments ( Figure 1 ), the structure 50 may include various sub-layers (eg, a silicon nitride layer, an oxide layer, etc.) disposed on a substrate 58.

[0043] A spacer opening process 60 according to example aspects of the present disclosure may be performed on the structure 50 to remove one or more portions of the spacer layer 52 covering the silicon mandrels 54 so that the silicon mandrels 54 may be exposed. After removing the spacer layer 52 on top of the silicon mandrels 54, a silicon mandrel removal process 70 may be performed on the structure 50 to remove the silicon mandrels 54. In some embodiments, the silicon mandrel removal process 70 exposes the silicon mandrels 54 to an inductively coupled plasma induced in a process gas (e.g., H2 / He / NF3, H2 / Ar / NF3, H2 / He / CF4, or H2 / Ar / CF4).

[0044] In some embodiments, the spacer opening process 60 and the silicon mandrel removal process 70 may be performed in the same processing apparatus. As an example, an inductively coupled plasma induced in a plasma chamber may be used to first remove the spacer layer 52, and then remove the exposed silicon mandrels 54. After removing the spacer layer 52 on top of the silicon mandrels 54, the inductively coupled plasma induced in the plasma chamber may be used to remove the silicon mandrels 54.

[0045] In some embodiments, the septum opening process 60 and the silicon mandrel removal process 70 may be performed in separate plasma processing apparatuses. For example, the septum opening process 60 and the silicon mandrel removal process 70 may be performed in one processing platform using vacuum transfer (or near vacuum transfer) between processing chambers of separate plasma processing apparatuses. Using a workpiece handling robot in the transfer chamber, the structure 50 may be transferred to a first processing chamber of a first plasma processing apparatus. The septum layer 52 may be removed using an inductively coupled plasma or a capacitively coupled plasma of the first plasma processing apparatus. Using a workpiece handling robot in the transfer chamber, the structure 50 may be transferred to a second processing chamber of a second processing apparatus. The silicon mandrel 54 may be removed using an inductively coupled plasma of a second plasma processing apparatus in a process gas (e.g., H2 / He / NF3, H2 / Ar / NF3, H2 / He / CF4, or H2 / Ar / CF4).

[0046] Figure 2 An example silicon mandrel removal process on a structure 80 according to an example embodiment of the present disclosure is depicted. The structure 80 includes a native oxide layer 82, a spacer layer 52, silicon mandrels 54, a sublayer 56 (e.g., an oxide layer), and a substrate 58 (e.g., a silicon substrate). In some embodiments ( Figure 2 ), the structure 80 may include various sub-layers (eg, silicon nitride layers, oxide layers, etc.) disposed on the substrate 58. As the silicon mandrels 54 are exposed to an oxygen-containing environment, a native oxide layer 82 may be formed on the silicon mandrels 54.

[0047] The native oxide punch-through process 90 may be performed using a capacitively coupled plasma source to remove the native oxide layer 82. The native oxide punch-through process 90 exposes the native oxide layer 82 to a plasma generated using a capacitively coupled plasma source to remove at least a portion of the native oxide layer 82 on top of the silicon mandrel layer 54. After removing the native oxide layer 82, the silicon mandrel removal process 70 may be performed according to example aspects of the present disclosure to expose the silicon mandrels 54 to species generated in an inductively coupled plasma to remove the silicon mandrels 54.

[0048] In some embodiments, the native oxide punch-through process 90 and the silicon mandrel removal process 70 may be performed in the same processing apparatus. For example, a capacitively coupled plasma using a capacitive coupling element in a processing chamber of the same processing apparatus may be used to remove the native oxide layer 82. After removing the native oxide layer 82 on top of the silicon mandrels 54, an inductively coupled plasma induced in the plasma chamber may be used to remove the silicon mandrels 54.

[0049] In some embodiments, the native oxide punch-through process 90 and the silicon mandrel removal process 70 may be performed in separate plasma processing apparatuses. For example, the native oxide punch-through process 90 and the silicon mandrel removal process 70 may be performed in one processing platform using vacuum transfer (or near vacuum transfer) between processing chambers of separate plasma processing apparatuses. Using a workpiece handling robot in the transfer chamber, the structure 80 may be transferred to a first processing chamber of a first plasma processing apparatus. The native oxide layer 82 may be removed using a capacitively coupled plasma of the first plasma processing apparatus. Using a workpiece handling robot in the transfer chamber, the structure 80 may be transferred to a second processing chamber of a second processing apparatus. The silicon mandrel 54 may be removed using an inductively coupled plasma of a second plasma processing apparatus in a process gas (e.g., H2 / He / NF3, H2 / Ar / NF3, H2 / He / CF4, or H2 / Ar / CF4).

[0050] Figure 3 An example plasma processing apparatus 100 is depicted in accordance with an example embodiment of the present disclosure. As illustrated, the plasma processing apparatus 100 includes a processing chamber 110 and a plasma chamber 120 separate from the processing chamber 110. The processing chamber 110 includes a workpiece support or susceptor 112 that operably supports a workpiece 114 to be processed, such as a semiconductor wafer. In this example illustration, plasma is generated in the plasma chamber 120 (i.e., a plasma generation region) by an inductively coupled plasma source 135, and desired species are directed from the plasma chamber 120 to a surface of the workpiece 114 through a barrier assembly 200.

[0051] The plasma chamber 120 includes a dielectric sidewall 122 and a ceiling 124. The dielectric sidewall 122, the ceiling 124, and the barrier 200 define a plasma chamber interior 125. The dielectric sidewall 122 may be formed of a dielectric material, such as quartz and / or alumina. An inductively coupled plasma source 135 may include an induction coil 130 disposed around the plasma chamber 120 adjacent to the dielectric sidewall 122. The induction coil 130 is coupled to an RF power generator 134 through a suitable matching grid 132. Process gases (e.g., hydrogen and carrier gas) may be provided to the chamber interior from a gas supply 150 and an annular gas distribution channel 151 or other suitable gas introduction mechanism. When the induction coil 130 is powered with RF power from the RF power generator 134, plasma may be generated in the plasma chamber 120. In particular embodiments, the plasma processing apparatus 100 may include an optional grounded Faraday shield 128 to reduce capacitive coupling of the induction coil 130 to the plasma.

[0052] like Figure 3 2, a barrier 200 separates the plasma chamber 120 from the processing chamber 110. The barrier 200 can be used to filter ions from a mixture generated by the plasma in the plasma chamber 120 to generate a filtered mixture. Neutral radicals generated by the plasma can pass through the barrier for exposure to a workpiece. In the processing chamber 110, the filtered mixture can be exposed to the workpiece 114.

[0053] In some embodiments, the grid 200 may be a multi-plate grid. For example, the grid 200 may include a first grid plate 210 and a second grid plate 220 spaced apart in parallel relation to each other. The first grid plate 210 and the second grid plate 220 may be separated by a certain distance.

[0054] The first grid plate 210 may have a first grid pattern with a plurality of holes. The second grid plate 220 may have a second grid pattern with a plurality of holes. The first grid pattern may be the same as or different from the second grid pattern. The charged particles may recombine on the walls in their path through the holes of each grid plate 210, 220 in the spacer. Neutral species (e.g., free radicals) may flow relatively freely through the holes in the first grid plate 210 and the second grid plate 220. The size and thickness of the holes of each grid plate 210 and 220 may affect the permeability of both charged particles and neutral particles.

[0055] In some embodiments, the first grid plate 210 may be made of metal (e.g., aluminum) or other conductive materials and / or the second grid plate 220 may be made of conductive materials or dielectric materials (e.g., quartz, ceramic, etc.). In some embodiments, the first grid plate 210 and / or the second grid plate 220 may be made of other materials, such as silicon or silicon carbide. If the grid plate is made of metal or other conductive materials, the grid plate may be grounded. In some embodiments, the grid assembly may include a single grid having one grid plate.

[0056] like Figure 3 , according to example aspects of the present disclosure, the apparatus 100 may include a gas delivery system 150 configured to deliver process gas to the plasma chamber 120, for example, via a gas distribution channel 151 or other distribution system (e.g., a showerhead). The gas delivery system may include a plurality of raw gas pipelines 159 as a gas source. The raw gas pipelines 159 may be controlled using valves and / or mass flow controllers to deliver a desired amount of gas into the plasma chamber as a process gas. Figure 3 , the gas delivery system 150 may include a raw gas line for delivering NF3 gas from NF3; a raw gas line for delivering CF4 gas; a raw gas line for delivering other fluorinated hydrocarbons such as CH2F2, CHF3, CH3F; a raw gas line for delivering a first hydrogen-containing gas (e.g., H2 / He, or hydrogen mixed with other inert gases); and / or a raw gas line for delivering a second hydrogen-containing gas (e.g., H2 / Ar, hydrogen mixed with other inert gases). Control valves and / or mass flow controllers 158 may be used to control the flow rate of each raw gas line to allow the process gas (e.g., H2 / He / NF3, H2 / Ar / NF3, H2 / He / CF4, or H2 / Ar / CF4) to flow into the plasma chamber 120.

[0057] Figure 4 An example processing platform 400 is depicted according to an example embodiment of the present disclosure. The processing platform 400 may include a front end portion 412, a load lock chamber 414, a transfer chamber 415, and a plurality of processing chambers including a first processing chamber 420 and a second processing chamber 430. In some embodiments, the processing platform 400 may include more than two processing chambers.

[0058] The front end portion 412 can be configured to maintain, for example, atmospheric pressure and can be configured to engage a workpiece input device 418. The workpiece input device 418 can include, for example, a box, a front opening unified pod, or other devices for supporting multiple workpieces. The workpiece input device 418 can be used to provide pre-processed workpieces to the processing platform 400 or receive processed workpieces from the processing platform 400.

[0059] The front end portion 412 may include one or more workpiece handling robots (not illustrated) for transferring workpieces from a workpiece input device 418 to, for example, the load-hold chamber 414, such as to and from a workpiece column 410 located in the load-hold chamber 414. In one example, the workpiece handling robots in the front end portion 412 may transfer pre-processed workpieces to the load-hold chamber 414 and may transfer processed workpieces from the load-hold chamber 414 to the one or more workpiece input devices 418. Any suitable robot for transferring workpieces may be used in the front end portion 412 without departing from the scope of the present disclosure. The workpiece may be transferred to and / or from the load-hold chamber 414 through a suitable slot, opening, or hole.

[0060] The load lock chamber 414 may include a transfer position having a workpiece column 410 configured to support a plurality of workpieces in a stacked arrangement. The workpiece column 410 may include, for example, a plurality of racks. Each rack may be configured to support one or more workpieces. In one example implementation, the workpiece column 410 may include one or more racks for supporting pre-processed workpieces and one or more racks for supporting processed workpieces.

[0061] The load lock chamber 414 may be used to adjust the pressure around the workpiece from the pressure associated with the front end portion 412 to a process pressure, such as a vacuum pressure or near vacuum pressure or other process pressure, and then transfer the workpiece to a processing chamber, such as the first processing chamber 420 and / or the second processing chamber 430. In some embodiments, suitable valves may be provided in conjunction with the load lock chamber 414 and other chambers to appropriately adjust the process pressure for processing the workpiece.

[0062] According to example aspects of the present disclosure, the first processing chamber 420 may include one or more capacitively coupled plasma sources to perform a native-oxide punch-through process. The second processing chamber 430 may include a chamber similar to Figure 3 A plasma source is provided to perform a silicon mandrel removal process according to an example embodiment of the present disclosure.

[0063] As explained, the first processing chamber 420 and the second processing chamber 430 can each be a dual workpiece processing chamber. The first processing chamber 420 and the second processing chamber 430 can each include a pair of processing stations arranged side by side so that a pair of workpieces can be exposed to the same process at the same time. Without departing from the scope of the present disclosure, the first processing chamber 420 and or the second processing chamber 430 can include a single processing station.

[0064] Each processing station may include a workpiece support (e.g., a pedestal) for supporting the workpiece during processing. In some embodiments, each processing station may share a common pedestal having two parts for supporting the workpiece. The first processing chamber 420 and / or the second processing chamber 430 may be selectively sealed from the transfer chamber 415 for processing.

[0065] The transfer chamber 415 may include a workpiece handling robot 450. The workpiece handling robot 450 may be configured to transfer a workpiece from the workpiece column 410 in the load-holding chamber 414 to a processing station in the first processing chamber 420 and / or the second processing chamber 430. The workpiece handling robot 450 may also transfer a workpiece between the first processing chamber 420 and the second processing chamber 430. For example, the workpiece handling robot 450 may transfer a workpiece from the workpiece column 410 in the load-holding chamber 414 to two side-by-side processing stations 422 and 424 in the first processing chamber 420. Similarly, the workpiece handling robot 450 may transfer a workpiece from the workpiece column 410 in the load-holding chamber 414 to two side-by-side processing stations 432 and 434 in the second processing chamber 430.

[0066] Figure 5 A flowchart of an example method (500) according to an example implementation of the present disclosure is depicted. Figure 3 The plasma processing apparatus 100 and Figure 4 The method (500) will be discussed with reference to a processing platform of FIG. The method (500) may be implemented in any suitable plasma processing apparatus. Figure 5 The steps are depicted as being performed in a particular order for purposes of illustration and discussion. Using the disclosure provided herein, one of ordinary skill in the art will appreciate that the individual steps of any method described herein may be omitted, expanded, performed simultaneously, rearranged, and / or modified in various ways without departing from the scope of the present disclosure. Additionally, various steps (not illustrated) may be performed without departing from the scope of the present disclosure.

[0067] At (510), the method may include generating a capacitively coupled plasma using a capacitive coupling element in a first chamber. At (520), the method may include exposing a silicon mandrel or a silicon replacement gate on a workpiece to the capacitively coupled plasma to remove at least a portion of a native oxide layer on top of the silicon mandrel or the silicon replacement gate.

[0068] For example, the native oxide punch-through process can be performed in the processing platform 400 using vacuum transfer (or near vacuum transfer) between the processing chambers 420 and 430. The workpiece can be placed in the first processing chamber 420 of the first plasma processing apparatus (e.g., the first plasma processing apparatus 100) to perform the native oxide punch-through process using capacitively coupled plasma. Using the workpiece handling robot 450 in the transfer chamber 415, the workpiece can be transferred to the second processing chamber 430 of the second plasma processing apparatus (e.g., the second plasma processing apparatus 100). After the native oxide punch-through process, the second plasma processing apparatus can generate an inductively coupled plasma to remove the silicon mandrel or the silicon replacement gate, as further described with respect to (530), (540), and (550).

[0069] At (530), the method may include generating a species from a process gas in the second chamber using an inductive coupling element. For example, the gas delivery system 150 of the second plasma processing apparatus 100 may use a raw gas line 159 to deliver a process gas (e.g., H2 / He, H2 / Ar) or an inert gas without hydrogen into the plasma chamber 120 to generate the species.

[0070] At (540), the method may include introducing nitrogen trifluoride (NF3) or tetrafluoromethane (CF4) or other fluorinated hydrocarbons such as CH2F2, CHF3, CH3F with the substance to form a mixture. In some embodiments, nitrogen trifluoride (NF3) or tetrafluoromethane (CF4) or other fluorinated hydrocarbons such as CH2F2, CHF3, CH3F may be introduced with the substance as part of the process gas. For example, the gas delivery system 150 may use the raw gas pipeline 159 to deliver the process gas (e.g., H2 / He / NF3, H2 / Ar / NF3, H2 / He / CF4, or H2 / Ar / CF4) into the plasma chamber 120 to form a mixture (e.g., free radicals). In some embodiments, nitrogen trifluoride (NF3) or tetrafluoromethane (CF4) or other fluorinated hydrocarbons such as CH2F2, CHF3, CH3F may be introduced via post-plasma gas injection, such as Figure 7 Further described in .

[0071] At (550), the method may include exposing silicon mandrels or silicon replacement gates on the workpiece to the mixture (e.g., after filtering through the barrier) to remove at least a portion of the silicon mandrels or silicon replacement gates. For example, the workpiece 114 may be exposed to species generated in an inductively coupled plasma (e.g., neutral species that pass through the barrier) to remove the silicon mandrels or silicon replacement gates.

[0072] Figure 6 A flow chart of an example process (600) is depicted according to an example implementation of the present disclosure. Figure 3The plasma processing apparatus 100 and Figure 4 The method (600) will be discussed with reference to the processing platform 400 of FIG. The method (600) can be implemented in any suitable plasma processing apparatus. For the purpose of illustration and discussion, Figure 6 The steps are depicted to be performed in a particular order. Using the disclosure provided herein, one of ordinary skill in the art will appreciate that the individual steps of any method described herein may be omitted, expanded, performed simultaneously, rearranged, and / or modified in various ways without departing from the scope of the present disclosure. Additionally, various steps (not illustrated) may be performed without departing from the scope of the present disclosure.

[0073] At (610), the method may include heating the workpiece in the processing chamber. For example, the workpiece 114 may be heated to a process temperature in the processing chamber 110. For example, the workpiece 114 may be heated using one or more heating systems associated with the susceptor 112. In some embodiments, the workpiece may be heated to a process temperature in a range of about 90° C. to about 400° C.

[0074] At (620), the method may include allowing a process gas to enter the plasma chamber. For example, the process gas may be allowed to enter the plasma chamber interior 125 from the gas source 150 through the annular gas distribution channel 151 or other suitable gas introduction mechanism. In some embodiments, the process gas may be an inert gas, such as helium, argon, etc. Other process gases may be used without departing from the scope of the present disclosure. For example, the process gas may include a mixture of an inert gas and hydrogen.

[0075] At (630), the method may include energizing the inductively coupled plasma source to generate plasma in the plasma chamber. For example, the induction coil 130 may be energized with RF energy from the RF power generator 134 to generate plasma within the plasma chamber interior 125.

[0076] At (640), the method may include filtering one or more ions generated by the plasma using a barrier to form a filtered mixture. The filtered mixture may include neutral species (e.g., excited noble gas molecules). In some embodiments, the one or more ions may be filtered using a barrier assembly that separates a plasma chamber from a processing chamber where a workpiece is located. For example, barrier assembly 200 may be used to filter ions generated by the plasma. Barrier 200 may have a plurality of holes. Charged particles (e.g., ions) may recombine on walls in their path through the plurality of holes. Neutral species (e.g., free radicals) may pass through the holes.

[0077] In some embodiments, the barrier 200 can be configured to filter ions with an efficiency greater than or equal to about 90%, such as greater than or equal to about 95%. The efficiency percentage for ion filtration refers to the amount of ions removed from the mixture relative to the total number of ions in the mixture. For example, an efficiency of about 90% indicates that about 90% of the ions are removed during filtration. An efficiency of about 95% indicates that about 95% of the ions are removed during filtration.

[0078] In some embodiments, the grid 200 may be a multi-plate grid. The multi-plate grid may have multiple grid plates in parallel. The arrangement and arrangement of the holes in the grid plates may be selected to provide a desired efficiency for ion filtration, such as greater than or equal to about 95%.

[0079] For example, the grid 200 may have a first grid plate 210 and a second grid plate 220 in parallel relation to each other. The first grid plate 210 may have a first grid pattern with a plurality of holes. The second grid plate 220 may have a second grid pattern with a plurality of holes. The first grid pattern may be the same as or different from the second grid pattern. Charged particles (e.g., ions) may recombine on the walls in their path through the holes of each grid plate 210, 220 in the grid 200. Neutral species (e.g., free radicals) may flow relatively freely through the holes in the first grid plate 210 and the second grid plate 220.

[0080] At (650), the method may include injecting NF3 or CF4 or other fluorine-containing hydrocarbons such as CH2F2, CHF3, CH3F into the filtered mixture to generate highly selective free radicals for removing silicon mandrels or silicon replacement gates. For example, NF3 or CF4 or other fluorine-containing hydrocarbons such as CH2F2, CHF3, CH3F may be injected via a post-plasma gas injection system that may be located between the first grid plate 210 and the second grid plate 220 of the spacer 200. NF3 or CF4 or other fluorine-containing hydrocarbons such as CH2F2, CHF3, CH3F may be injected via a post-plasma gas injection system at a location below the spacer. Figure 7 An example post-plasma gas injection is illustrated in .

[0081] At (660), the method may include exposing the workpiece to the filtered mixture in the processing chamber. More specifically, the workpiece 114 may be exposed to free radicals generated in the plasma and passing through the barrier assembly 200. For example, the workpiece 114 may be exposed to free radicals generated using post-plasma gas injection to remove silicon mandrels or silicon replacement gates.

[0082] According to an exemplary aspect of the present disclosure, the method may further include a native oxide punch-through process for removing a native oxide layer on a silicon mandrel or a silicon replacement gate. The native oxide punch-through process may include generating a capacitively coupled plasma from a process gas in a second chamber using a capacitive coupling element, and exposing a silicon mandrel or a silicon replacement gate on a workpiece to the capacitively coupled plasma to remove at least a portion of the native oxide layer on top of the silicon mandrel or the silicon replacement gate.

[0083] Figure 7 An example implantation of a fluorine-containing gas using post-plasma gas implantation according to an example embodiment of the present disclosure is depicted. The spacer 200 includes a first grid plate 210 and a second grid plate 220 disposed in a parallel relationship. The first grid plate 210 and the second grid plate 220 may be provided for ion / UV filtering.

[0084] The first grid plate 210 may have a first grid pattern with a plurality of holes. The second grid plate 220 may have a second grid pattern with a plurality of holes. The first grid pattern may be the same as or different from the second grid pattern. Species 215 from the plasma may be exposed to the barrier grid 200. Charged particles (e.g., ions) may recombine on the walls in their path through the holes of each grid plate 210, 220 in the barrier grid 200. Neutral species may flow relatively freely through the holes in the first grid plate 210 and the second grid plate 220.

[0085] After the second grid 220, a gas injection source 230 may be configured to introduce NF3 gas or CH4 gas or other fluorine-containing hydrocarbons such as CH2F2, CHF3, CH3F to the material passing through the grid 200. The mixture 225 may pass through a third grid 235 for exposure to a workpiece in a processing chamber.

[0086] For illustrative purposes, this example is discussed with reference to a grid having three grids. Without departing from the scope of the present disclosure, using the disclosure provided herein, one of ordinary skill in the art will understand that more or fewer grids may be used. Additionally, NF3 gas or CH4 gas or other fluorinated hydrocarbons such as CH2F2, CHF3, CH3F may be mixed with the material in the grid and / or anywhere behind the grid in the processing chamber. For example, the gas source 230 may be located between the first grid 210 and the second grid 220.

[0087] The plasma etching processes according to example aspects of the present disclosure (eg, native oxide punch-through process, silicon mandrel or silicon replacement gate removal process, and spacer opening process) may be performed using other plasma processing apparatuses without departing from the scope of the present disclosure.

[0088] The silicon mandrel or silicon replacement gate removal process and the native oxide punch-through process according to example aspects of the present disclosure may be implemented in the same plasma processing apparatus. In some embodiments, a capacitively coupled plasma may be generated in a processing chamber using the same plasma processing apparatus as the plasma processing apparatus used to perform silicon mandrel or silicon replacement gate etching. For example, a workpiece may include a silicon mandrel or silicon replacement gate at least partially covered by a native oxide layer. The workpiece may be placed into a processing chamber for a silicon mandrel or silicon replacement gate removal process. Prior to the silicon mandrel or silicon replacement gate removal process, the native oxide punch-through process may be performed by a capacitively coupled plasma induced in the processing chamber to remove the native oxide layer on top of the silicon mandrel or silicon replacement gate. After the native oxide punch-through process, an inductively coupled plasma may be used for a silicon mandrel or silicon replacement gate removal process. An example of such a processing chamber is further described below.

[0089] Figure 8 An example plasma processing apparatus 800 that can be used to perform processes according to example embodiments of the present disclosure is depicted. The plasma processing apparatus 800 is similar to Figure 3 A plasma processing apparatus 100 is provided.

[0090] More specifically, the plasma processing apparatus 800 includes a processing chamber 110 and a plasma chamber 120 separate from the processing chamber 110. The processing chamber 110 includes a substrate support or susceptor 112 that operably supports a workpiece 114 to be processed, such as a semiconductor wafer. In this exemplary illustration, plasma is generated in the plasma chamber 120 (i.e., a plasma generation region) by an inductively coupled plasma source 135, and desired species are directed from the plasma chamber 120 to the surface of the substrate 114 through the barrier assembly 200.

[0091] The plasma chamber 120 includes a dielectric sidewall 122 and a ceiling 124. The dielectric sidewall 122, the ceiling 124, and the barrier 200 define a plasma chamber interior 125. The dielectric sidewall 122 may be formed of a dielectric material, such as quartz and / or alumina. An inductively coupled plasma source 135 may include an induction coil 130 disposed around the plasma chamber 120 adjacent to the dielectric sidewall 122. The induction coil 130 is coupled to an RF power generator 134 through a suitable matching grid 132. A process gas (e.g., an inert gas) may be provided to the chamber interior from a gas supply 150 and an annular gas distribution channel 151 or other suitable gas introduction mechanism. When the induction coil 130 is powered with RF power from the RF power generator 134, plasma may be generated in the plasma chamber 120. In a particular embodiment, the plasma processing apparatus 100 may include an optional grounded Faraday cage 128 to reduce capacitive coupling of the induction coil 130 with the plasma.

[0092] like Figure 8 2, a barrier 200 separates the plasma chamber 120 from the processing chamber 110. The barrier 200 can be used to filter ions from a mixture generated by the plasma in the plasma chamber 120 to generate a filtered mixture. In the processing chamber, the filtered mixture can be exposed to the workpiece 114.

[0093] In some embodiments, the grid 200 may be a multi-plate grid. For example, the grid 200 may include a first grid plate 210 and a second grid plate 220 spaced apart in parallel relation to each other. The first grid plate 210 and the second grid plate 220 may be separated by a certain distance.

[0094] The first grid plate 210 may have a first grid pattern with a plurality of holes. The second grid plate 220 may have a second grid pattern with a plurality of holes. The first grid pattern may be the same as or different from the second grid pattern. The charged particles may recombine on the walls in their path through the holes of each grid plate 210, 220 in the spacer. Neutral species (e.g., free radicals) may flow relatively freely through the holes in the first grid plate 210 and the second grid plate 220. The size and thickness of the holes of each grid plate 210 and 220 may affect the permeability of both charged particles and neutral particles.

[0095] In some embodiments, the first grid plate 210 may be made of metal (e.g., aluminum) or other conductive materials and / or the second grid plate 220 may be made of conductive materials or dielectric materials (e.g., quartz, ceramic, etc.). In some embodiments, the first grid plate 210 and / or the second grid plate 220 may be made of other materials, such as silicon or silicon carbide. If the grid plate is made of metal or other conductive materials, the grid plate may be grounded.

[0096] Figure 8 The example plasma processing apparatus 800 is operable to generate a first plasma 802 (e.g., remote plasma) in the plasma chamber 120 and a second plasma 804 (e.g., direct plasma) in the processing chamber 110. The first plasma 802 may be generated by an inductively coupled plasma source. The second plasma 804 may be generated by, for example, a capacitively coupled plasma source (e.g., bias). As used herein, "remote plasma" refers to plasma generated away from a workpiece, such as in a plasma chamber separated from the workpiece by a barrier. As used herein, "direct plasma" refers to plasma directly exposed to a workpiece, such as plasma generated in a processing chamber having a pedestal that is operably supported by the workpiece.

[0097] More specifically, Figure 8The plasma processing apparatus 800 includes a bias source having a bias electrode 810 in a pedestal 112. The bias electrode 810 may be coupled to an RF power generator 814 via a suitable matching grid 812. When the bias electrode 810 is powered with RF energy, a second plasma 804 may be generated from the mixture in the processing chamber 110 for direct exposure to the workpiece 114. The processing chamber 110 may include an exhaust port 816 for exhausting gas from the processing chamber 110.

[0098] like Figure 8 , according to example aspects of the present disclosure, the apparatus 100 may include a gas delivery system 150 configured to deliver process gas to the plasma chamber 120, for example, via a gas distribution channel 151 or other distribution system (e.g., a showerhead). The gas delivery system may include a plurality of raw gas lines 159. The raw gas lines 159 may be controlled using valves and / or mass flow controllers to deliver a desired amount of gas into the plasma chamber as a process gas. Figure 8 As shown in FIG. 1 , the gas delivery system 150 may include a raw gas line for delivering NF3 gas; a raw gas line for delivering CF4 gas; a raw gas line for delivering other fluorinated hydrocarbons such as CH2F2, CHF3, CH3F; a raw gas line for delivering a first hydrogen-containing gas (e.g., H2 / He or hydrogen mixed with other inert gases) and / or a raw gas line for delivering a second hydrogen-containing gas (e.g., H2 / Ar, hydrogen mixed with other inert gases). A control valve and / or a mass flow controller 158 may be used to control the flow rate of each raw gas line to allow the process gas (e.g., H2 / He / NF3, H2 / Ar / NF3, H2 / He / CF4, or H2 / Ar / CF4) to flow into the plasma chamber 120.

[0099] According to example aspects of the present disclosure, the workpiece 114 may include a silicon mandrel or a silicon replacement gate at least partially covered by a native oxide layer. The workpiece 114 may be placed into the processing chamber 110 for a silicon mandrel or silicon replacement gate removal process. Prior to the silicon mandrel or silicon replacement gate removal process, a native oxide punch-through process may be performed by a capacitively coupled plasma 804 induced by a bias electrode 810 in the processing chamber 110 to remove the native oxide layer on top of the silicon mandrel or silicon replacement gate. After the native oxide punch-through process, an inductively coupled plasma 802 in the plasma chamber 120 may be used to etch the silicon mandrel or silicon replacement gate of the workpiece 114.

[0100] Although the subject matter has been described in detail in conjunction with its specific example embodiments, it should be understood that those skilled in the art, after obtaining the foregoing understanding, can easily produce changes, modifications and equivalents for these embodiments. Therefore, the scope of the present disclosure is illustrated rather than limited, and the present disclosure does not exclude the inclusion of such modifications, modifications and / or additions to the subject matter that are obvious to those skilled in the art.

Claims

1. A method for removing a silicon structure provided on a workpiece, the method comprising: generating a species from a process gas in a first chamber using an inductive coupling element; introducing a fluorine-containing gas and the substance to form a mixture; exposing the silicon structure of the workpiece to the mixture to remove at least a portion of the silicon structure; generating a plasma in the second chamber using a capacitively coupled plasma source; exposing the silicon structure of the workpiece to a capacitively coupled plasma to remove at least a portion of a native oxide layer on top of the silicon structure; wherein the first chamber is part of an independent first processing device, and the second chamber is part of an independent second processing device; The workpiece is transferred from the second chamber to the first chamber via vacuum transfer. 2 . The method of claim 1 , wherein the silicon structure comprises a silicon mandrel or a silicon replacement gate. 3 . The method according to claim 1 , wherein the process gas comprises hydrogen (H 2 ), helium (He) or argon (Ar).

4. The method according to claim 1, wherein the fluorine-containing gas comprises one or more of nitrogen trifluoride (NF3), tetrafluoromethane (CF4), fluoroform (CHF3), difluoromethane (CH2F2) or fluoromethane (CH3F).

5. The method of claim 1, wherein the fluorine-containing gas is introduced as part of the process gas. 6 . The method according to claim 1 , wherein the workpiece is transferred from the second chamber to the first chamber via a workpiece handling robot in a transfer chamber.

7. The method of claim 1, wherein the capacitively coupled plasma source is a bias electrode in the second chamber. 8 . The method of claim 1 , further comprising performing a spacer opening process before exposing the silicon structure of the workpiece to the mixture.

9. A plasma processing apparatus for removing a silicon structure provided on a workpiece, the plasma processing apparatus comprising a first processing chamber and a second processing chamber independent of the first processing chamber; The first processing chamber has a workpiece support configured to support the workpiece during plasma processing; a first plasma chamber separated from the first processing chamber by a first barrier; an inductive coupling element configured to induce a plasma in the first plasma chamber using a process gas; at least one gas source including a fluorine-containing gas source; wherein free radicals generated in the inductively coupled plasma pass through the first barrier for exposure to the silicon structure of the workpiece; a second plasma chamber separated from the second processing chamber by a second barrier; in, The second processing chamber has a capacitive coupling element configured to induce a capacitively coupled plasma in the second processing chamber, wherein the capacitively coupled plasma generates one or more species to remove at least a portion of a native oxide layer on top of the silicon structure.

10. The plasma processing apparatus of claim 9, wherein the silicon structure comprises a silicon mandrel or a silicon replacement gate.

11. The plasma processing apparatus of claim 9, wherein the at least one gas source further comprises a hydrogen (H2) gas source, a helium (He) gas source, or an argon (Ar) gas source.

12. The plasma processing apparatus of claim 9, wherein the at least one gas source is located outside of the first plasma chamber and at a downstream flow location of the first plasma chamber.

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