Plasma processing method

Abstract

The invention provides a plasma processing method. The method comprises a first etching step (S01) for etching the ruthenium-containing film using plasma and a second etching step (S02) for etching the ruthenium-containing film using plasma after the first etching step, the second etching step comprising: a first step (S11) for forming a modified layer on the surface of the ruthenium-containing film using plasma generated from a halogen element-containing gas; and a second step (S12) in which the modified layer is separated using plasma generated from an oxygen element-containing gas, and the first step and the second step are alternately repeated.

Description

Technical Field

[0001] The invention relates to a plasma processing method for a semiconductor substrate. Background Art

[0002] As the microfabrication of semiconductor devices progresses, processing with fine line width and high aspect ratio is required. In the wiring process, Cu (copper) is widely used as a wiring material corresponding to the miniaturization, but as the miniaturization progresses, the resistivity of Cu becomes a problem. As a substitute material for Cu, Ru (ruthenium) is listed as a candidate material.

[0003] Patent document 1 discloses a high-precision metal film etching method for etching metals such as Ru and / or their metal oxide films little by little. The etching method of Patent document 1 comprises: a first step of exposing the metal film to ions or radicals of halogen atoms and adsorbing them without applying an electric field such as a high-frequency bias; and a second step of etching the metal film adsorbed with halogen atoms by applying an electric field such as a weak high-frequency bias and exposing it to ions or radicals of oxygen. In the first step, secondary products formed by the plasma reaction of metal and chlorine are formed on the surface of the metal film, so that etching can be performed in the second step even when the energy of oxygen plasma is low.

[0004] Prior Art Literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2007-305892 Summary of the invention

[0007] -Problems to be solved by the invention-

[0008] The finer the structure of a semiconductor device, the more important it is that the surface state of the structure formed by plasma processing has an influence on the performance of the semiconductor device. According to the inventor's research, the surface of the Ru film formed by the method disclosed in Patent Document 1 is considered to be rough and has residual damage caused by exposure to oxygen plasma, which reduces the performance of the semiconductor device. On the other hand, it is necessary to avoid a significant reduction in the productivity of the plasma etching process.

[0009] An object of the present invention is to provide a plasma processing method in which a Ru-containing film pattern formed by plasma etching has a good surface state while suppressing a decrease in the productivity of the plasma etching process.

[0010] -Methods for solving problems-

[0011] A plasma treatment method according to one embodiment of the present invention is a plasma treatment method for plasma etching a ruthenium-containing film of a processed substrate having the ruthenium-containing film, and the method comprises the following steps: a first etching step, in which the ruthenium-containing film is etched using plasma; and a second etching step, in which the ruthenium-containing film is etched using plasma after the first etching step, the second etching step comprising: a first step, in which a modified layer is formed on the surface of the ruthenium-containing film using plasma generated by a halogen-containing element gas; and a second step, in which the modified layer is detached using plasma generated by an oxygen-containing element gas, and the second etching step alternately repeats the first step and the second step.

[0012] -Effects of the Invention-

[0013] The present invention provides a plasma treatment method for obtaining a Ru-containing film pattern with a good surface condition. Other objects and novel features will become apparent from the description of this specification and the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a schematic diagram of the structure of a plasma processing device.

[0015] Figure 2 : is a flow chart of the plasma processing of this embodiment.

[0016] Figure 3 It is a diagram illustrating the device processing steps of the plasma treatment according to this embodiment.

[0017] Figure 4 It is a diagram showing the surface change of the Ru film during the over-etching process.

[0018] Figure 5 It is a figure which shows the effect of this Example.

[0019] Figure 6 It is a figure which shows the effect of this Example.

[0020] Figure 7 It is a figure which shows the effect of this Example.

[0021] Figure 8 It is a figure which shows the effect of this Example.

[0022] Fig. 9 3 is a top view of the Ru line wiring formed in Example 1.

[0023] Fig.10 This is a diagram illustrating the device processing steps in Example 2.

[0024] Fig.11 This is a diagram illustrating the device processing steps in Example 3.

[0025] Fig.12This is a top view of the mask pattern in Example 3.

[0026] -Description of Reference Numerals-

[0027] 100: vacuum container, 101: substrate to be processed, 102: shower plate, 103: sample stage, 104: microwave power supply, 105: mass flow controller, 106: gas pipeline, 107: exhaust pipe, 108: pressure control valve, 109: pump, 110: high frequency power supply for substrate bias, 111: control unit, 121: microwave generation source, 122: rectangular waveguide, 123: microwave matching device, 124 : Transducer, 125: Circular waveguide, 126: Cavity chamber, 127: Electromagnet, 128: Separator, 201, 202, 203, 501, 502, 503, 601, 602, 603: Sample, 211: Oxide film, 212, 301, 302, 303, 304: Ru film, 213: SiN film, 214: Hard mask, 311, 313: Surface, 312: Ru x Cl y Modified layer, 401: Ru wire wiring, 511: Si substrate, 512: fin, 513: Ru film, 514: oxide film, 515: hard mask, 611: Ru film, 612: insulating film (oxide film), 613: SiN film, 614: hard mask. DETAILED DESCRIPTION

[0028] Figure 1 An example of a plasma processing apparatus for performing the plasma processing of this embodiment is shown. Here, as an example of a plasma processing apparatus, an example of a plasma processing apparatus for generating electron cyclotron resonance (ECR) excited plasma is shown. In an ECR excited plasma processing apparatus, microwaves are used as an excitation source, and plasma is generated by applying an external magnetic field.

[0029] The plasma processing apparatus includes a sample stage 103 on which a substrate (wafer) 101 to be processed is placed in a vacuum container 100, and performs plasma processing on the substrate 101 to be processed using plasma generated in the vacuum container 100. A high-frequency power supply 110 for substrate bias is connected to the sample stage 103. By controlling the applied substrate bias (high-frequency power), the directionality and energy of ions incident on the substrate 101 to be processed can be controlled. An exhaust pipe 107 is connected to the vacuum container 100, and a pressure control valve 108 and a pump 109 for adjusting the pressure inside the vacuum container 100 are connected to the exhaust pipe 107. The pump 109 exhausts the inside of the vacuum container 100 via the exhaust pipe 107 and the pressure control valve 108, and maintains the vacuum container 100 in a low pressure state during plasma processing.

[0030] The microwave generating source 121 generates microwaves by receiving power from a microwave power source (plasma generating power source) 104. The microwave power generated by the microwave generating source 121 is adjusted by a microwave matching device 123, and propagates from a rectangular waveguide 122 to a circular waveguide 125 and a cavity chamber 126 via a converter 124, and the cavity chamber 126 causes the propagated microwave power to resonate.

[0031] The cavity chamber 126 is separated from the vacuum container 100 by a partition plate 128. The partition plate 128 is formed of a dielectric that transmits microwave power and maintains the vacuum state inside the vacuum container 100. An electromagnet 127 is provided outside the vacuum container 100 and the cavity chamber 126 to form a magnetic field inside the cavity chamber 126 and the vacuum container 100 to generate electron cyclotron resonance.

[0032] A shower plate 102 is provided with many holes for supplying gas to the interior of the vacuum container 100, and a gas pipeline 106 for supplying gas is provided between the partition plate 128 and the shower plate 102. The gas is supplied to the interior of the vacuum container 100 through the gas pipeline 106 after the flow rate is adjusted by a mass flow controller (Mass Flow Controller: MFC) 105. In order to obtain the desired film quality, the MFC 105 is preferably installed in the structure of each gas system. The gas supplied by each gas system is, for example, a gas containing an oxygen element (O), a gas containing a halogen element, and an inert gas. In the following embodiments, as a gas containing an oxygen element (O), O is shown. 2 For example, CO, CO 2 、SO 2 , COS, etc. In addition, as the halogen-containing gas, Cl 2 For example, HBr, CF 4 , SF 6 NF 3 , CHF 3 The inert gas can be used for switching the gas or improving uniformity, and for example, rare gases such as nitrogen, He, and Ar can be used.

[0033] The control unit 111 controls the microwave power source 104 , the electromagnet 127 , the MFC 105 , the pressure control valve 108 , the pump 109 , and the high-frequency power source 110 for substrate bias to perform plasma processing on the substrate 101 .

[0034] use Figure 2 as well as Figure 3 , the process flow of this embodiment is described. Figure 3The device cross-sectional structure of the wiring layer (1 layer) of the processed substrate 101 is extracted and shown. The sample 201 has a layer structure in which an oxide film 211, a Ru film 212, and a SiN film 213 are stacked in sequence, and a patterned hard mask 214 is formed thereon. The oxide film 211 is a silicon oxide film (SiO 2 ), Ru film 212 is a Ru film or an oxide thereof, etc. containing Ru elements. In the process flow of this embodiment, by plasma etching a substrate to be processed having a structure like sample 201, the pattern of the hard mask 214 is transferred to the SiN film 213 and the Ru film 212. First, the sample 201 is subjected to main etching (first etching) (S01). The main etching process is an anisotropic etching process, which is a continuous etching process in which the etching progresses according to the pattern of the hard mask 214 and ends when it is determined that the oxide film 211 has been reached. By setting it as continuous etching, the productivity of plasma etching can be improved. However, at the stage where step S01 ends, as in sample 202 (refer to Figure 3 ) as shown in FIG. 1 , after step S01 is completed, the Ru film 212 of the sample 202 becomes a state in which the surface roughness of the side wall etched by plasma is large and plasma damage remains on its surface.

[0035] Therefore, in the process flow of this embodiment, after the main etching, the sample 202 is subjected to over-etching (second etching) (S02) to remove the surface roughness of the side wall of the Ru film 212 and the plasma damage formed on the side wall surface. The over-etching process is to repeatedly perform Cl 2 Plasma treatment (S11) and O 2 The plasma treatment (S12) is a cyclic etching process.

[0036] Figure 4 Indicates the surface change of the Ru film during the over-etching process. Figure 4 In the figure, Figure 3 The side surface of the Ru film 212 is oriented upward. The Ru film 301 shows the Ru film after step S01 is completed. The surface 311 of the Ru film 301 has a large surface roughness and plasma damage remains.

[0037] In Cl 2 During the plasma treatment (S11), Cl is supplied as a halogen-containing gas from the gas line 106. 2 At this time, a weak high-frequency power (about 50W) may be applied to the substrate 101 from the substrate bias high-frequency power supply 110. Alternatively, the high-frequency power may not be applied. 2 The result of the plasma treatment (S11) is a Ru film 302. 2The plasma treatment adsorbs Cl on the surface of the Ru film, and the surface is modified. Specifically, Ru and Cl are combined on the surface of the Ru film 302 to form a non-volatile Ru x Cl y Modified layer 312.

[0038] In O 2 During the plasma treatment (S12), O is supplied from the gas line 106. 2 As oxygen-containing element gas, plasma is generated. At this time, in order to make the surface state of the Ru film as smooth as possible, high-frequency power is not applied to the substrate 101 to be processed. 2 The result of the plasma treatment (S12) is a Ru film 303. 2 Plasma treatment is to make the Ru on the surface of the Ru film x Cl y The modified layer 312 is separated from the surface. 2 During plasma treatment, the following reactions occur.

[0039] Ru x Cl y +O→RuO 2 +O x Cl y +Cl 2 →RuO 4 +O x Cl y +Cl 2

[0040] RuO 4 The volatile ions are separated from the Ru film, and etching progresses. The surface 313 of the Ru film 303 is smoother than the surface 311 of the Ru film 301 .

[0041] In this way, by repeatedly performing the Cl 2 Surface modification by plasma treatment (S11) and O 2 The plasma treatment ( S12 ) is released and etching progresses, so that the surface of the Ru film is smoothed. This state is the Ru film 304 .

[0042] The sample at the end of step S02 is Figure 3 Sample 203 is shown. The surface roughness of the Ru film pattern formed by plasma etching was suppressed, and plasma damage on the surface was also removed.

[0043] Figure 5 Indicates that Cl is carried out in 1 step 2 Plasma treatment, O 2The etching amount during plasma treatment and the etching amount during one cycle of overetching process are shown in Figure 2. It can be seen that the etching amount during one cycle of overetching process is greater than the simple sum of the etching amounts in each cycle. In the overetching process, it is believed that O is formed on the surface of the Ru film. x Cl y Helps promote etching.

[0044] Figure 6 The figure shows the change in the surface roughness (RMS) of the Ru film formed by the over-etching process after 20 cycles. It can be seen that the etching amount progressed by about 75nm (3.8nm / cycle, see Figure 5 ), during which the surface roughness is improved by about 50% compared with that before overetching (Initial).

[0045] Figure 7 Indicates that Cl is carried out in 1 step 2 Plasma treatment, O 2 Changes in the surface roughness of the Ru film during plasma treatment. 2 The surface roughness after plasma treatment is roughly the same as that before treatment (Initial). 2 The surface roughness after plasma treatment is significantly worse than that before treatment. 2 Plasma treatment starts, which can prevent O 2 Deterioration of surface condition due to plasma treatment.

[0046] Figure 8 FIG. 4 shows the change in the surface roughness of the Ru film when the over-etching process of this embodiment is performed for 20 cycles, and FIG. 4 shows the change in the surface roughness of the Ru film when the over-etching process is performed for 20 cycles as a comparative example. 2 Changes in the surface roughness of the Ru film when 20 cycles were performed while applying high-frequency power (50 W) to the substrate to be processed during plasma processing. It can be seen that in the comparative example, the surface roughness was significantly deteriorated. It is believed that this is because high-energy oxygen ions were incident on the Ru film by applying high-frequency power to the substrate to be processed, thereby deteriorating the surface roughness.

[0047] Next, a description will be given of an example of processing a semiconductor device using the plasma processing of this embodiment.

[0048] [Example 1]

[0049] Example 1 is a Ru wire wiring process. The process of Ru wire wiring process is as follows Figure 3 In the main etching process (S01), Cl mixed with halogen-containing gas is fed from the gas pipeline 106. 2 , O as oxygen-containing element gas2 The mixed gas is supplied while being diluted with Ar gas as an inert gas to generate plasma. In addition, in order to improve the productivity of plasma etching, it is preferable to set it as continuous etching in the main etching process, but it can also be set as Cl 2 Plasma treatment and O 2 In this case, in order to set it as an anisotropic etching process, 2 During the plasma processing, high frequency power is also applied to the substrate to be processed.

[0050] Fig. 9 3 is a top view of the Ru line wiring formed in Example 1. Figure 3 The cross-sectional view is equivalent to the cross-sectional view along Fig. 9 The cross-sectional view of the AA section is shown. The Ru wire wiring 401 is arranged at a pitch of about 20 nm. By applying the process of this embodiment, the Ru residue can be removed from the sidewalls and hem of the Ru wire wiring that has been plasma etched. As a result, the LER (Line Edge Roughness: Line Edge Roughness) / LWR (Line Width Roughness: Line Width Roughness) of the wiring can be improved.

[0051] [Example 2]

[0052] Example 2 is a Ru wiring process (Buried Power Rail), which shows an example of forming a Ru buried wiring on a Si substrate having a fin structure. Fig.10 In the sample 501, a Ru film 513 is formed on a Si substrate 511 on which a fin 512 is formed, and the fin 512 and the Ru film 513 are insulated from each other by an oxide film 514. In addition, a hard mask 515 remains on the fin 512.

[0053] First, the main etching (S01) is performed on the sample 501. The main etching process is an anisotropic etching process, and the etching of the portion other than the Ru film 513 does not progress due to the presence of the oxide film 514 and the hard mask 515, and only the plasma etching of the Ru film 513 progresses. At the stage where step S01 is completed, as shown in sample 502, the Ru film 513 of sample 502 after step S01 is completed has a large surface roughness on the upper surface subjected to plasma etching, and plasma damage remains on its surface.

[0054] Then, the main etching is performed on the sample 502 to over-etch (S02), and the surface roughness of the upper surface of the Ru film 513 and the plasma damage formed on the side wall surface are removed. The sample at the stage where step S02 is completed is the sample 503. The surface roughness of the upper surface of the Ru film 513 is suppressed, and the plasma damage on the surface is also removed. As a result, the Ru buried wiring with a smooth upper surface can be obtained.

[0055] In Example 2, similarly to Example 1, the main etching process is preferably continuous etching, but may also be cyclic etching.

[0056] [Example 3]

[0057] Example 3 is hole processing (Via processing), Fig.11 The sample 601 has a layer structure in which a Ru film 611 and a SiN film 613 are stacked, and a patterned hard mask 614 is formed thereon. In addition, an insulating film (oxide film) 612 is formed so as to bury the Ru film 611. Fig.12 A top view of the hard mask 614 is shown. Fig.11 The cross-sectional view is equivalent to the cross-sectional view along Fig.12 A cross-sectional view of section BB is shown.

[0058] First, the sample 601 is subjected to main etching (S01). The main etching process is the same as that of Example 1. In order to improve the productivity of plasma etching, it is preferred to set it as continuous etching in the main etching process, but it can also be set as cyclic etching. In this case, since it is set as an anisotropic etching process, 2 During the plasma treatment, high frequency power is also applied to the substrate to be processed. At the stage where step S01 is completed, as shown in sample 602, the Ru film 611 of sample 602 after step S01 is completed has a large surface roughness on the bottom and side surfaces of the via hole where plasma etching has been performed, and plasma damage remains on the surface.

[0059] Then, the main etching is performed on the sample 602 (S02), and the surface roughness of the etched surface of the Ru film 611 and the plasma damage formed on the surface are removed. The sample at the stage where step S02 is completed is the sample 603. The surface roughness of the Ru film 611 is suppressed, and the plasma damage on its surface is also removed. As a result, a via hole with a smooth bottom and side surfaces can be obtained.

[0060] The present invention is not limited to the above-mentioned embodiments, but includes various variations. For example, the above-mentioned embodiments and variations are described in detail for easy understanding of the present invention, and are not necessarily limited to having all the structures described. In addition, a part of the structure of a certain embodiment or variation can be replaced with the structure of other embodiments or variations, and the structure of other embodiments or variations can be added to the structure of a certain embodiment or variation. In addition, with respect to a part of the structure of each embodiment or variation, other structures can be added / deleted / replaced. For example, as a plasma processing device for implementing the plasma processing of this embodiment, an ECR excitation plasma processing device is illustrated, but it is not limited to this. For example, it can be an inductively coupled plasma (ICP) processing device or a capacitively coupled plasma (CCP) processing device. In addition, a radical etching chamber in which an ion shielding plate is provided in the vacuum container 100 can also be used.

Claims

1. A plasma processing method, comprising: performing plasma etching on a ruthenium-containing film of a substrate to be processed having the ruthenium-containing film; The plasma treatment method is characterized by comprising the following steps: A first etching step of etching the ruthenium-containing film using plasma; and a second etching step, after the first etching step, etching the ruthenium-containing film using plasma, The second etching process comprises: a first step of forming a modified layer on the surface of the ruthenium-containing film using plasma generated by a halogen-containing element gas; and a second step of detaching the modified layer using plasma generated by an oxygen-containing element gas, and the second etching process alternately repeats the first step and the second step.

2. The plasma processing method according to claim 1, wherein: In the second step, the high frequency power supplied to the sample stage on which the substrate to be processed is placed is 0 W.

3. The plasma processing method according to claim 1, wherein: The plasma in the first etching process is generated by a mixed gas of a halogen-containing gas and an oxygen-containing gas.

4. The plasma processing method according to claim 1, wherein: The first etching process comprises: a third step of forming a modified layer on the surface of the ruthenium-containing film using plasma generated from a halogen-containing gas; and a fourth step of removing the modified layer using plasma generated from an oxygen-containing element gas, wherein the first etching process alternately repeats the third step and the fourth step.

5. The plasma processing method according to claim 1, wherein: The second etching process starts from the first step.

6. The plasma processing method according to claim 1, wherein: The halogen-containing gas is chlorine, and the oxygen-containing gas is oxygen.

7. The plasma processing method according to claim 1, wherein: The ruthenium-containing film is a ruthenium film, The ruthenium film is formed on the silicon oxide film, and the silicon nitride film is formed on the ruthenium film.

8. The plasma processing method according to claim 1, wherein: The processed substrate has a Fin FET structure, The ruthenium-containing film is embedded between the fins.

Images