Plasma treatment method

Abstract

The present disclosure provides a plasma treatment method for etching back to a prescribed depth a conductive material surrounded by an insulating film and with a seam present, the plasma treatment method enabling the formulation of a process with excellent etching depth uniformity and a high selectivity ratio with respect to a surrounding material. This plasma treatment method is for etching back a conductive material surrounded by an insulating film and with a seam formed, and includes a step for generating plasma using a gas containing a sedimentary element and a halogen element, and etching the conductive material by means of radicals of the generated plasma while forming a deposition film containing the sedimentary element on top of the conductive material.

Description

Plasma treatment method

[0001] The present disclosure relates to a plasma processing method, and more particularly to a plasma processing method relating to a dry etching method applied in the field of manufacturing semiconductor manufacturing equipment and the like.

[0002] Due to demands for lower power consumption and increased memory capacity, semiconductor devices are becoming increasingly miniaturized and three-dimensional in their structure. Accordingly, the wiring process for connecting transistors, which are switching elements, is also becoming increasingly miniaturized and complex. One wiring process involves an etch-back process in which a conductive material, such as W, TiN, or polysilicon, deposited in a trench using chemical vapor deposition (CVD) to a predetermined depth. Known methods for this process include depositing a conductive material in the trench and then directly etching it back to the predetermined depth using dry etching, or depositing a conductive material, planarizing it using chemical mechanical polishing (CMP), and then etching it back to the predetermined depth using dry etching. These etch-back processes require techniques for flattening the conductive material in the trench to a consistent thickness to reduce variations in the resistance of the wiring pattern. As the wiring process becomes more complex, techniques for selectively processing the conductive material relative to the surrounding materials are also required. Furthermore, with the miniaturization of wiring processes, there is a demand for technology that can process conductive materials with high aspect ratios at high throughput.

[0003] FIG. 1(a) shows a cross-sectional view of a trench portion after forming a film of conductive material 101 and performing CMP. In this schematic view, hafnium oxide (HfO ２ The figure shows a structure in which a conductive material 101 is surrounded by a first insulating film 103 made of a high-k material such as silicon dioxide (SiON) and a second insulating film 104 made of a low-k material such as silicon oxycarbonitride (SiOCN), with a seam 102 formed within the conductive material 101. This seam is a void that occurs when a conductive film is formed by the CVD method, and the problem is that this seam expands during the subsequent etch-back process, causing the thickness of the conductive material to become uneven.

[0004] As a method for suppressing seam expansion during dry etching, Patent Document 1 reports a method of using a sulfur-based compound gas to utilize the competitive reaction between sulfur deposition and etching, and performing anisotropic etching by applying a wafer bias to actively attract ions. Patent Document 2 reports a method of depositing a sulfur-based material layer using a gas that can release free sulfur into plasma, while performing anisotropic etching by applying a wafer bias to actively attract ions. Patent Document 3 reports a method of performing reactive ion etching using a gas mixture of chlorine gas and oxygen gas, to which a predetermined amount of gas containing at least one element selected from carbon, fluorine, and nitrogen has been added. Furthermore, Patent Document 4 reports a radical-based chemical dry etching method that includes a seam filling step using a passivating gas and a high-selectivity etching method that utilizes the difference in incubation time between the mask material and the material to be etched.

[0005] JP 7-226393 JP 11-214354 JP 9-232285 JP 2022-19660

[0006] In the methods described in Patent Documents 1, 2, and 3, in which a deposited film is formed in the seam area and then dry-etched while irradiating ions, the deposited film fills the seam, thereby suppressing the expansion of the seam during etching. However, as shown in Figure 2, ion irradiation 201 causes etching of the first insulating film 103 or the second insulating film 104. As device materials become more complex, it has become difficult to process conductive materials selectively relative to surrounding materials. Furthermore, as shown in Patent Document 4, radical-based etching can suppress ion irradiation and process conductive materials with a high selectivity relative to surrounding materials. However, in methods that utilize the incubation time between the etched material and the mask material, processing of the etched material must be stopped within the incubation time of the mask material. Therefore, to process high-aspect-ratio patterns, it is necessary to return to the passivation gas step within a time shorter than the incubation time of the mask material. Repeating the passivation gas step and processing the etched material reduces throughput, which has been an issue.

[0007] The present disclosure provides a plasma processing method for etching back a conductive material surrounded by an insulating film and having a seam to a predetermined depth, which can establish a process with excellent uniformity in etching depth and a high selectivity with respect to surrounding materials.

[0008] Other objects and novel features will become apparent from the description of this specification and the accompanying drawings.

[0009] A brief summary of representative aspects of this disclosure is as follows.

[0010] A plasma processing method according to one embodiment of the present disclosure is a plasma processing method for etching back a conductive material that is surrounded by an insulating film and has a seam, the method comprising the steps of generating plasma using a gas containing a depositing element and a halogen element, and etching the conductive material with radicals from the generated plasma while forming a deposition film containing the depositing element on the conductive material.

[0011] Furthermore, a plasma processing method according to one embodiment of the present disclosure is a plasma processing method for etching back a conductive material that is surrounded by an insulating film and has a seam, the method comprising: a first step of generating plasma using a gas containing a depositing element and a halogen element, and etching the conductive material with radicals of the generated plasma while forming a deposition film containing the depositing element on the conductive material; and a second step of etching the conductive material with plasma generated using a gas containing a halogen element, wherein the gas containing the halogen element does not contain the depositing element.

[0012] In addition, in a plasma processing method for processing a conductive material formed inside a trench surrounded by an insulating film to a predetermined depth, plasma is generated using a gas containing a deposition element and a halogen element, and radicals formed by the plasma are used to mainly etch the conductive material, forming a deposited film with a thickness equal to or greater than half the width of a seam formed inside the conductive material, while processing the conductive material to the predetermined depth.

[0013] According to the plasma processing method according to one embodiment of the present disclosure, a high selectivity to an insulating film can be achieved and variations in etching depth can be reduced.

[0014] Furthermore, by using radicals produced by plasmatizing a gas containing a deposition element to form a deposited film that is at least half the width of the seam, it is possible to suppress the expansion of the seam during dry etching. Furthermore, by plasmatizing a gas containing a deposition element and a halogen element and etching a conductive material using a process mainly driven by radicals in the plasma, it is possible to suppress ion irradiation and process the conductive material with a high selectivity relative to surrounding materials. Furthermore, radicals generated by plasmatizing a halogen element can penetrate a deposited film formed using radicals produced by plasmatizing a deposition element, and the radicals generated by plasmatizing a halogen element can penetrate the deposited film and reach the conductive material, thereby achieving a high-throughput process in which the conductive material is continuously processed while a deposited film is being formed.

[0015] 1 is a cross-sectional view of a conductive material having a seam in a wafer processing method according to an embodiment of the present disclosure, and a diagram showing a mechanism for etching while forming a deposited film; FIG. 2 is a cross-sectional view showing etching actively using ions, which is a conventional method, in a wafer processing method according to an embodiment of the present disclosure; FIG. 3 is a cross-sectional view showing a schematic configuration of a wafer processing apparatus according to an embodiment of the present disclosure; FIG. 4 is a graph showing changes in the amount of etching of a TiN film and the thickness of a deposited film with respect to process time when etching is performed while forming a deposited film in a wafer processing method according to an embodiment of the present disclosure; ４ and Cl ２ 1 is a graph showing the etching amount when plasma is generated using a mixed gas in which the Cl element ratio is changed by controlling the flow rate of SiCl in the wafer processing method according to the embodiment of the present disclosure. ４ and Cl ２ From the process by Cl ２ 10 is a graph showing the change in etching amount and deposition film thickness with respect to process time when the process is switched to the SiCl process in the wafer processing method according to the embodiment of the present disclosure. ４ and Cl ２ and Cl ２ 10 is a table comparing the etching depth variation and the selectivity with respect to the surrounding material when ion-based etching and radical-based etching are performed using a single gas to generate plasma.

[0016] Hereinafter, examples will be described with reference to the drawings. However, in the following description, the same components will be assigned the same reference numerals, and repeated explanations may be omitted. Note that the drawings may be more schematic than the actual embodiment to make the description clearer, but they are merely examples and do not limit the interpretation of the present disclosure.

[0017] The present disclosure relates to a plasma processing method as a wafer processing method in which a conductive material (101) is continuously etched while a deposition film (106) is formed on the wafer (3005) to be etched by converting a gas containing a deposition property element and a halogen element into plasma in the space above the separation plate (3002), in a plasma processing apparatus (1) which is a dry etching apparatus including a vacuum vessel (3001) into which a processing gas is supplied under reduced pressure, a wafer stage (3006) on the upper surface of which a processing wafer (3005) is placed, and one or more separation plates (3002) which divide the space above the wafer stage (3006) inside the vacuum vessel (3001) into two or more upper and lower spaces.

[0018] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0019] 3 is a cross-sectional view showing the structure of a typical wafer processing apparatus for implementing this embodiment, which uses an electron cyclotron resonance plasma source. While this embodiment describes a plasma source using the electron cyclotron resonance method, this method is not limited to plasma sources using the electron cyclotron resonance method, and can be applied to other plasma sources. In other words, other plasma sources using high-frequency power, such as inductively coupled or capacitively coupled plasma sources, may also be used.

[0020] As shown in FIG. 3 , the plasma processing apparatus 1 includes a processing chamber 3101 inside a vacuum vessel 3001. A dielectric plate 3102 for airtight sealing is disposed above the processing chamber 3101. A separation plate 3002 is installed in the processing chamber 3101 inside the vacuum vessel 3001, and the separation plate 3002 separates the processing chamber 3101 inside the vacuum vessel 3001 into an upper first space 3003 and a lower second space 3004. The second space 3004 is equipped with a wafer stage 3006, which serves as a sample stage for placing or placing a wafer 3005 to be etched as a sample. The wafer 3005 can be processed by irradiating it with plasma or radicals generated in the plasma. The separation plate 3002 functions as a shielding plate to prevent ions from entering the sample stage. A conductive material is formed on the wafer 3005 to be etched, and the conductive material is etched inside the processing chamber 3101.

[0021] High frequency power 3007 generated from a high frequency power supply 3107 for generating plasma is introduced into the vacuum vessel 3001 from above the device via a waveguide 3008 and a cavity resonator 3009. Here, microwaves with a frequency of 300 MHz to 300 GHz are used as the microwave high frequency power 3007 for generating plasma.

[0022] Furthermore, a process gas 3010 is introduced into the vacuum vessel 3001 by a predetermined method, and is exhausted from the bottom of the vacuum vessel 3001 by a vacuum pump or the like in an exhaust direction 3011. At this time, the flow rate and exhaust speed of the process gas 3010 are appropriately monitored, and by controlling the flow rate of the process gas and the exhaust speed of the vacuum pump in accordance with the monitored values, it is possible to maintain the inside of the vacuum vessel 3001 at a desired pressure.

[0023] The process gas introduced into the vacuum vessel 3001 generates and maintains plasma at a position where electron cyclotron resonance occurs due to the high frequency power 3007 and the static magnetic field generated by the static magnetic field coil 3012, which serves as a magnetic field generating mechanism for forming a magnetic field within the processing chamber 3101. In this device configuration, the generation position of the plasma that generates electron cyclotron resonance can be changed by the coil current value of the static magnetic field coil 3012, and when the generation position is set within the first space 3003, neutral radicals formed in the plasma are preferentially supplied to the wafer 3005 to be etched.

[0024] On the other hand, when the generation position is set in the second space 3004, the plasma is directly irradiated onto the wafer to be etched 3005, making it possible to perform processing using ions and radicals in the plasma. In other words, the separation plate 3002 can separate the plasma generation chamber into an upper plasma generation chamber formed by the first space 3003 and a lower plasma generation chamber formed by the second space 3004.

[0025] The wafer stage 3006 has a temperature control function and can be controlled to any temperature. The wafer stage 3006 also has a function of fixing the wafer 3005 to be etched thereon, and a function of supplying a thermally conductive gas between the wafer 3005 to be etched and the wafer stage 3006, thereby maintaining a pressure between the two (3005, 3006) of, for example, 0.1 kPa to 10 kPa. This thermally conductive gas improves the thermal conductivity between the wafer stage 3006 and the wafer 3005 to be etched, enabling the temperature of the wafer 3005 to be etched to be efficiently controlled even within the vacuum chamber 3001.

[0026] The function of fixing the wafer 3005 to be etched to the wafer stage 3006 may be a mechanical chuck that mechanically holds down the edge of the wafer 3005 to fix it, but when the wafer 3005 is fixed, foreign matter generated by wear of the holding mechanism and the wafer 3005 becomes an issue during mass production. Therefore, as shown in Figure 3, it is desirable to install a first electrode 3013 and a second electrode 3014 to which a DC voltage is applied within the wafer stage 3006, and apply opposite positive and negative voltages to each electrode to generate Johnsen-Rahbek force or Coulomb force to electrically fix the sample 3005. In other words, it is preferable to electrostatically attract the sample 3005 to the sample stage 3006 using an electrostatic chuck.

[0027] 3, a high frequency bias power supply 3108 that applies a high frequency bias potential having a frequency of, for example, 10 kHz to 100 MHz may be connected to the wafer stage 3006 in order to actively attract ions formed in the plasma to the wafer to be etched 3005. In this way, when plasma is generated in the second space 3004, a wafer bias, which is high frequency power, can be supplied from the high frequency bias power supply 3108 to the wafer stage 3006, thereby realizing reactive ion etching using the ions and radicals in the plasma.

[0028] 3, separation plate 3002 is installed to preferentially supply radicals to wafer 3005 to be etched. As for the structure of separation plate 3002, a method may be used in which separation plate 3002 is made of a metal material such as aluminum, titanium, or stainless steel (SUS), and separation plate 3002 is electrically connected to earth (ground potential), a DC power supply, or an AC power supply, thereby electrically blocking positively charged ions and negatively charged electrons generated in the plasma and supplying only radicals generated in the plasma to wafer 3005. In this case, however, the surface of the metal material is exposed to the plasma, causing the metal material to scatter, and metal contamination can deteriorate the electrical characteristics of processed wafer 3005, which poses a problem during mass production.

[0029] One possible method for suppressing metal contamination is to coat the conductive material with a silicon (Si)-containing oxide film, an yttrium (Y)-containing oxide film, or an aluminum (Al)-containing oxide film, thereby preventing the metal from coming into direct contact with the plasma. However, coating increases production costs, and if part of the coating film disappears due to long-term processing, metal contamination may occur.

[0030] Therefore, it is desirable that the structure of the separation plate 3002 be made only of a dielectric material such as a Si-containing oxide film, a Y-containing oxide film, or an Al-containing oxide film. In particular, quartz, which is a Si-containing oxide film, does not contain metals such as Y or Al inside, and is therefore a desirable dielectric material for suppressing metal contamination.

[0031] 3 uses only one separation plate 3002, but a structure combining a plurality of separation plates 3002 may also be used. However, it is desirable that one of the plurality of separation plates 3002 has a hole on the outer periphery of the separation plate 3002, that is, outside half the radius of the separation plate 3002. In addition, as long as there is a gap between the outside of the separation plate 3002 and the wall of the vacuum vessel 3001, the structure and area of ​​the hole are not particularly important.

[0032] Although this embodiment describes a discharge method utilizing electron cyclotron resonance using microwaves of 300 MHz to 300 GHz as the high frequency power 3007 for generating plasma in Fig. 3, the plasma source is not particularly limited as long as it is an apparatus in which a separation plate 3002 is installed in a vacuum vessel 3001 and plasma can be generated in a first space 3003 above the separation plate 3002. In other words, a plasma source using other high frequency power utilizing an inductive coupling method or a capacitive coupling method may also be used.

[0033] Next, a first example will be described in which a wafer 3005 to be etched is processed using the above-described plasma processing apparatus 1. Here, as shown in the cross-sectional view of FIG. 1(a), the wafer 3005 to be etched is made of a conductive material 101 having a seam 102 and a surrounding area made of hafnium oxide (HfO ２The wafer 3005 to be etched has a pattern formed thereon, surrounded by a first insulating film 103 made of a high-k material such as silicon oxycarbonitride (SiOCN) and a second insulating film 104 made of a low-k material such as silicon oxycarbonitride (SiOCN). Note that, although this embodiment describes a method using titanium nitride (TiN) as the conductive material 101, similar embodiments can also be realized when processing other conductive materials 101 such as tungsten (W), polysilicon (Poly-Si), ruthenium (Ru), cobalt (Co), and iridium (Ir).

[0034] This Example 1 describes a plasma processing method for etching back a conductive material (101) that is surrounded by insulating films (103, 104) and has a seam (102). This plasma processing method includes the steps of generating plasma using a gas containing a depositing element and a halogen element, and etching the conductive material (101) with radicals from the generated plasma while forming a deposition film (106) containing the depositing element on the conductive material (101).

[0035] First, the wafer 3005 to be etched is loaded onto the stage 3006 in the processing chamber 3101. When the wafer 3005 is loaded, for example, the wafer 3005 to be etched is loaded onto a transfer arm from a transfer chamber maintained under vacuum onto the wafer stage 3006, and three or more pusher pins provided in the wafer stage 3006 are raised to lift the wafer 3005 to be etched from the transfer arm by the pusher pins.

[0036] Thereafter, the transfer arm is retracted into the transfer chamber, and the pusher pins holding the wafer 3005 to be etched are lowered into the wafer stage 3006, thereby placing the wafer 3005 to be etched on the wafer stage 3006.

[0037] In this method, in order to prevent the generation of foreign matter due to wear between the back surface of the wafer 3005 and the pusher pin, it is desirable to select the optimum operating speed, tip shape and material of the pusher pin.

[0038] Alternatively, the transport arm may be brought in with the pusher pins raised in advance, and then the height of the transport arm may be lowered and then retracted into the transport chamber, thereby holding the wafer to be etched 3005 with the pusher pins, and then the pusher pins holding the wafer to be etched 3005 may be lowered into the wafer stage 3006, thereby placing the wafer to be etched 3005 on the wafer stage 3006.

[0039] Next, opposite positive and negative DC voltages are applied to a first electrode 3013 and a second electrode 3014 installed in the wafer stage 3006, respectively, to generate a Johnson-Rahbek force or a Coulomb force, and the wafer to be etched 3005 is electrically fixed on the wafer stage 3006. It is desirable to apply the same positive and negative voltages, but it is also possible to apply a positive voltage or a negative voltage to the first electrode 3013.

[0040] This means that the wafer to be etched 3005 will remain fixed on the wafer stage 3006 until the electrical fixation is released, and the generation of foreign matter due to wear of the wafer to be etched 3005 and the wafer stage 3006 caused by movement of the wafer to be etched due to pressure fluctuations during the process, etc., can be suppressed.

[0041] Next, a thermally conductive gas is introduced between the wafer 3005 to be etched and the wafer stage 3006. This thermally conductive gas improves the thermal conductivity between the wafer stage 3006 and the wafer 3005 to be etched, and even within the vacuum chamber 3001, the temperature of the wafer 3005 to be etched can be efficiently controlled at a set temperature by using the temperature control function of the wafer stage 3006.

[0042] It is desirable to use helium (He) gas as the thermal conduction gas because it has good thermal conductivity and is stable. However, argon (Ar) gas and nitrogen (N ２It is also preferable to maintain a pressure of 0.1 kPa to 10 kPa between the wafer 3005 to be etched and the wafer stage 3006 in the processing chamber 3101, and it is also preferable that the wafer 3005 to be etched is firmly fixed electrically by a DC voltage applied to the first electrode 3013 and the second electrode 3014 so that the wafer 3005 does not move even under this pressure.

[0043] Next, a gas containing a deposition element (hereinafter simply referred to as deposition element) and a halogen element is introduced at a predetermined flow rate, high-frequency power 3007 is supplied from a waveguide 3008, and the coil current value of a static magnetic field coil 3012 is set so as to cause electron cyclotron resonance in the upper first space 3003. This generates plasma in the upper first space 3003, and the conductive material 101 is etched back to a predetermined etching depth. In this process, it is desirable to control the gas exhaust speed in an exhaust direction 3011 at the bottom of the vacuum vessel 3001 so that the inside of the vacuum vessel 3001 is maintained at a set pressure.

[0044] Furthermore, by setting the static magnetic field coil 3012 so that plasma is generated in the first space 3003, radicals formed in the plasma using a gas containing a deposition element and a halogen element preferentially reach the wafer to be etched 3005. Therefore, etching mainly caused by radicals in the plasma generated by the gas containing a deposition element and a halogen element can be achieved.

[0045] Here, radical-based etching is performed using a gas containing silicon (Si) or carbon (C) as the deposition element and chlorine (Cl), fluorine (F), or bromine (Br) as the halogen element. In this case, as shown in FIG. 1( b), radicals 107 generated by the gas containing the deposition element are used to form a deposition film 106 on the conductive material 101, first insulating film 103, and second insulating film 104. It has been newly discovered that the radicals 107 generated by the gas containing the halogen element pass through the deposition film 106 and further etch the conductive material 101 below the deposition film 106. Because the deposition film formed in the seam 102 is formed from the conductive material 101 on both sides of the seam 102, forming a deposition film 106 with a thickness equal to or greater than half the seam width 105 allows etching to proceed while completely covering the void portion of the seam 102. The expansion of the seam 102 during dry etching is due to the fact that the diffusion rate of radicals in a gas phase is faster than the diffusion rate of radicals in a solid, such as the conductive material 101, and therefore the radicals reach the seam 102 at a high rate. In other words, if the entire seam 102 can be covered with a solid deposition film 106, the diffusion rate of radicals in the deposition film 106 is slowed, thereby suppressing the expansion of the seam 102 during dry etching. Even when using a radical etch with a high selectivity to the surrounding material, the expansion of the seam 102 during dry etching can be suppressed by using radicals produced by plasmatizing a gas containing a deposition element to form a deposition film 106 that is at least half the seam width 105. Furthermore, the radicals produced by plasmatizing a halogen element can penetrate the deposition film 106 formed using radicals produced by plasmatizing a deposition element, thereby achieving a high-throughput process in which the conductive material 101 is continuously processed while the deposition film 106 is being formed.

[0046] The gas containing the deposition element consisting of Si element or C element and the halogen element consisting of Cl element, F element or Br element includes silicon tetrachloride (SiCl ４ ) gas and silicon tetrafluoride (SiF ４ ) gas and carbon tetrafluoride (CF ４ ) gas and fluoroform (CHF３ ) gas and fluoromethane (CH ３ F) gas and hexafluorobutadiene (C ４ F ６ ) gas and octafluorocyclopentene (C ５ F ８ It is preferable to use a gas such as silane (SiH ４ ) gas and methane (CH ４ ) gas containing Si element or C element, boron trichloride (BCl ３ ) gas and chlorine (Cl ２ ) gas and sulfur hexafluoride (SF ６ ) gas and nitrogen trifluoride (NF ３ Alternatively, a gas containing a halogen element gas such as fluorine (HF) gas, hydrogen bromide (HBr) gas, or the like may be used. In order to achieve a uniform plasma distribution, these gases may be replaced with Ar gas, He gas, xenon (Xe) gas, or N ２ Gas and hydrogen (H ２ ) It may be diluted with gas such as gas before use.

[0047] Furthermore, if a gas containing a deposition element and a halogen element is introduced, and plasma is generated in the lower second space 3004 and the wafer 3005 to be etched is directly irradiated with the plasma, a self-bias is generated between the plasma and the wafer 3005 to be etched. As a result, ions generated in the plasma are accelerated by the self-bias and incident on the wafer 3005 to be etched. This makes it difficult to obtain a sufficient selectivity with respect to the surrounding material. Furthermore, if a wafer bias is applied to the wafer 3005 to be etched, the ion energy increases, further worsening the selectivity. Therefore, it is desirable to perform etching while forming the deposition film 106 using a radical-based process. Specifically, it is desirable to develop a process in which the wafer 3005 to be etched is irradiated with radicals at a dose 10 times or more the dose of ions irradiated thereto, thereby forming the deposition film 106 while etching.

[0048] Furthermore, if excessive dissociation occurs in the plasma when radicals are generated using a gas containing a deposition element, the deposition film 106 will be formed excessively, making it difficult to etch the conductive material 101. In order to suppress excessive dissociation, it is desirable to select an arbitrary pressure within the processing chamber 3101, for example, from a range of 0.05 Pa to 100 Pa (0.05 Pa to 100 Pa). In other words, the pressure within the processing chamber 3101 in which the conductive material 101 is etched is set to, for example, a pressure within the range of 0.05 Pa to 100 Pa.

[0049] Next, after the conductive material 101 has been processed to a predetermined processing depth, the introduction of the thermal conduction gas between the wafer 3005 to be etched and the wafer stage 3006 is stopped, and then plasma is generated in the second space 3004 below to release the electrical fixation between the wafer 3005 to be etched and the wafer stage 3006. That is, after the conductive material 101 has been etched to a predetermined depth, the application of the DC voltage for electrostatically attracting the sample 3005 to the sample stage 3006 is stopped while maintaining the plasma generated in the second space 3004 between the shielding plate 3002 and the sample stage 3006. Here, if the first electrode 3013 and the second electrode 3014 have the same area and the applied voltage is turned off at the same time, the electrical fixation can, in principle, be released even without plasma.

[0050] However, due to differences in the plasma processing apparatus 1, the areas of the two (3013, 3014) may differ slightly, or there may be a slight discrepancy in the timing of turning off the applied voltage, which may cause charges to accumulate on the wafer to be etched 3005 and the wafer stage 3006. In this case, the electrical fixation may not be completely released, and the wafer 3005 may occasionally be damaged when being unloaded, which becomes an issue during mass production.

[0051] Therefore, it is desirable to generate plasma in the second space 3004 directly above the wafer 3005 to be etched and form an electrical path with electrons and ions in the plasma to release the electric charges accumulated in the wafer 3005 to be etched and the wafer stage 3006. In other words, it is desirable to turn off the DC voltage applied to the first electrode 3013 and the second electrode 3014 while the plasma is generated in the second space 3004. With this configuration, damage to the wafer 3005 when the wafer 3005 is unloaded can be suppressed, and a process suitable for mass production can be realized.

[0052] When the DC voltage applied to the first electrode 3013 and the second electrode 3014 is turned off, in order to more easily remove the accumulated charge, the voltage value applied to both electrodes (3013, 3014) may be changed or the pusher pin may be moved up and down while plasma is still being generated in the second space 3004.

[0053] It is desirable to select a gas for generating plasma in this process that does not significantly affect the shape of the wafer 3005 to be etched, such as a rare gas.

[0054] However, if generating plasma in the second space 3004 changes the etching shape, the DC voltage applied to the first electrode 3013 and the second electrode 3014 may be turned off without generating plasma in the second space 3004. In this case, however, in order to prevent damage to the wafer 3005, it is necessary to give particular consideration to the speed at which the pusher pins are raised and lowered, and to select materials for the pusher pins and wafer stage 3006 that are less likely to accumulate electric charge.

[0055] Next, the plasma is extinguished, and all gases are stopped from being introduced into the vacuum vessel 3001. Thereafter, the wafer 3005 to be etched is carried out from the wafer stage 3006.

[0056] When the wafer 3005 is unloaded, for example, three or more pusher pins provided in the wafer stage 3006 are raised to lift the wafer 3005 to be etched, and the wafer 3005 is then loaded from the transfer chamber by a transfer arm. At this time, in order to prevent contact between the wafer 3005 to be etched and the transfer arm, the wafer 3005 to be etched needs to be lifted to a position higher than the transferred transfer arm. Thereafter, the pusher pins are lowered into the wafer stage 3006, so that the wafer 3005 to be etched can be held by the transfer arm. Thereafter, the transfer arm is retracted into the transfer chamber, so that the wafer 3005 to be etched can be unloaded from the vacuum chamber 3001.

[0057] In this method, in order to prevent the generation of foreign matter due to wear between the back surface of the wafer 3005 and the pusher pin, it is desirable to select the optimum operating speed, tip shape and material of the pusher pin.

[0058] In this process, the temperature may be changed to another temperature during etching. However, since changing the temperature of the wafer stage 3006 increases the process time, it is desirable not to change the temperature of the wafer stage 3006. Specifically, it is desirable to set and maintain the temperature of the wafer stage 3006 at any temperature within the range of -50°C to +150°C. In other words, the temperature of the sample stage 3006 on which the sample 3005 on which the conductive material 101 is formed is set to a temperature within the range of -50°C to 150°C.

[0059] In this method, the wafer 3005 to be etched is carried out from the vacuum chamber 3001 with the deposition film 106 deposited on the pattern. However, this deposition film 106 can be removed by wet etching such as SC1 cleaning using a mixed solution of ammonia water and hydrogen peroxide solution or hydrofluoric acid (HF) cleaning, and it has been confirmed that this does not cause any problems in subsequent processes. The SC1 cleaning process is carried out using, for example, H ２ O / Ammonium hydroxide (NH ４ OH) / hydrogen peroxide (H ２ O ２ ) mixed acid to remove organic matter and particles from the wafer surface.

[0060] Moreover, this deposition film 106 may be removed inside the vacuum chamber 3001. For example, before the wafer 3005 to be etched is carried out, a gas containing a halogen element is introduced into the vacuum chamber 3001 in the case of a Si-based deposition film, i.e., a deposition film 106 containing silicon elements, and a gas containing an oxygen element is introduced into the vacuum chamber 3001 in the case of a C-based deposition film, i.e., a deposition film 106 containing carbon elements, to generate plasma and perform dry etching (plasma etching) to remove the film.

[0061] In this case, the space in which the plasma is generated may be either above (first space 3003) or below (second space 3004) the separation plate 3002. However, if plasma is generated below (second space 3004) the separation plate 3002 and the wafer 3005 to be etched is directly irradiated with the plasma, a self-bias is generated between the plasma and the wafer 3005 to be etched. As a result, ions generated in the plasma are accelerated by the self-bias and enter the wafer 3005 to be etched. This may damage the conductive material 101 and insulating films 103 and 104 of the wafer 3005 to be etched. For this reason, it is desirable to use dry etching in which plasma is generated above (first space 3003) the separation plate 3002.

[0062] Alternatively, the deposition film 106 may be removed by dry etching using only gas without using plasma.

[0063] The process of removing this deposition film 106 does not necessarily have to be performed inside the same vacuum vessel 3001; as long as the deposition film 106 can be removed, the wafer to be etched 3005 may be moved to the vacuum vessel 3001 of another plasma processing apparatus 1 and then the deposition film 106 may be removed.

[0064] Furthermore, when processing a plurality of wafers 3005 to be etched repeatedly, it is also possible to periodically perform a cleaning sequence using plasma between the first wafer 3005 to be etched and the next wafer 3005 to be etched. In this cleaning sequence, it is desirable to use a sequence for removing reaction products from the material to be etched that have adhered to the inner wall of the vacuum vessel 3001 during etching, or a sequence for forming a protective film on the inner wall of the vacuum vessel 3001 in order to maintain the inner wall in a constant state.

[0065] In the cleaning sequence, plasma is preferably generated in the second space 3004 below the separation plate 3002, where reaction products from the wafer 3005 to be etched are likely to adhere. However, because reaction products from the wafer 3005 to be etched may also adhere to the first space 3003 above the separation plate 3002, a cleaning sequence in which plasma is generated in both the first space 3003 and the second space 3004 is preferably performed. Here, either the first space 3003 or the second space 3004 may be performed first, and the first space 3003 and the second space 3004 may be alternated during the cleaning sequence. In other words, after the conductive material 101 is etched to a predetermined depth, it is preferable to clean the processing chamber 3101 using plasma generated in the first space 3003 between the dielectric plate 3102 and the shielding plate 3002, or plasma generated in the second space 3004 between the shielding plate 3002 and the sample stage 3006.

[0066] When performing this cleaning sequence, a wafer for cleaning may be placed on the wafer stage 3006. However, in order to reduce the cost of the wafer for cleaning, it is desirable to perform the cleaning sequence without placing the wafer for cleaning on the wafer stage 3006. In other words, when cleaning the processing chamber 3101, it is desirable not to place the sample 3005 on the sample stage 3006.

[0067] The gas used in this cleaning is BCl 2 to remove deposits formed in the vacuum vessel 3001. ３ and Cl ２and science fiction ６ and NF ３ It is desirable to use a plurality of halogen element gases such as HF and HBr. ２ ) and carbon dioxide (CO ２ When forming a protective film, an oxygen-containing gas such as SiCl ４ and SiH ４ and CH ４ It is desirable to use a gas containing Si element or C element such as the above.

[0068] As an example of using the wafer processing method (plasma processing method) according to the first embodiment of the present disclosure, a TiN film is used as the conductive material 101 to be etched, and SiCl is used as the gas containing a deposition element and a halogen element. ４ and Cl ２ The results of an experiment in which a mixed gas of the above was introduced to generate plasma, and the conductive material 101 was etched while a deposition film 106 was formed will be described.

[0069] First, a wafer 3005 on which a TiN film, which is the conductive material 101, is formed is placed on a wafer stage 3006 inside the vacuum chamber 3001 using a transfer arm and pusher pins, and the wafer 3005 is electrically fixed on the wafer stage 3006. Next, the stage temperature is set to −5° C. using the temperature control function provided in the wafer stage 3006.

[0070] Next, SiCl ４ and Cl ２Gas was introduced, microwave power of 500 W was supplied from the waveguide 3008, and plasma was generated above the separation plate 3002 by electron cyclotron resonance. At this time, the pressure inside the vacuum vessel 3001 was maintained at 0.8 Pa. Furthermore, by generating plasma above the separation plate 3002 inside the vacuum vessel 3001 (first space 3003), only neutral radicals formed in the plasma were preferentially supplied to the wafer 3005. After that, etching of the conductive material 101 was performed for a predetermined time, and then Ar gas was introduced, plasma was generated below the separation plate 3002 (second space 3004), and the wafer 3005 to be etched was released from its electrical fixation, and then the wafer 3005 to be etched was carried out.

[0071] FIG. 4 shows the change in the amount of etching (FIG. 4(a)) and the change in the thickness of the deposited film (FIG. 4(b)) with respect to the TiN processing time when the TiN film was processed for different processing times. From FIG. 4(a), it can be seen that the amount of etching increases as the processing time increases. Also, from FIG. 4(b), it can be seen that the thickness of the deposited film 106 also increases as the processing time increases. This is because the halogen element passes through the deposited film 106 and reaches the conductive material 101, causing etching of the conductive material 101 to proceed. In other words, SiCl containing the deposition element Si and the halogen element Cl ４ and Cl ２ By using the mixed gas, a high-throughput wafer processing method can be realized in which etching of the conductive material 101 proceeds continuously while the deposition film 106 is being formed.

[0072] Here, in order to suppress the expansion of the seam 102 during etching, it is desirable to form a deposited film 106 that is at least half the seam width 105 in order to fill and flatten the seam 102. Furthermore, a comparison of Figures 4(a) and (b) reveals that when the deposited film 106 is 60 nm or thicker, the amount of TiN etched per unit time slows. Therefore, it is desirable for the thickness of the deposited film 106 formed during etching to be at least half the seam width 105 but not greater than 60 nm. In other words, the thickness of the deposited film 106 when the conductive material 101 is etched to a predetermined depth should be within the range of half the width 105 of the seam 102 to 60 nm.

[0073] Figure 5 shows the SiCl ４ and Cl ２ 5 shows the results of comparing the change in the amount of TiN etched over the same processing time by changing the flow rate ratio of the introduced gas and the ratio of Cl to the total amount of Si and Cl in the introduced gas. As shown in FIG. 5, when the Cl ratio was 80% or more and less than 100%, etching of TiN progressed, and TiN could be continuously etched while the deposited film 106 was formed. On the other hand, when the Cl ratio was 100%, the deposited film 106 was not formed, and TiN etching did not progress at all. Therefore, in order to continuously etch the conductive material while forming the deposited film 106, it is desirable to set the ratio of Cl to the total amount of Si and Cl to 80% or more and less than 100%.

[0074] Next, in order to confirm the effectiveness of the first embodiment, as shown in the cross-sectional view of FIG. 1(a), TiN was used as the conductive material 101 having the seam 102, and HfO was used as the first insulating film 103. ２ The patterns using SiOCN as the second insulating film 104 were compared using the following three methods.

[0075] The first method is to introduce Cl, a gas containing halogen elements, into the vacuum vessel 3001. ２ Gas was introduced, plasma was generated below the separation plate 3002 inside the vacuum vessel 3001 (second space 3004), and a wafer bias was applied so that ions were preferentially supplied to the wafer 3005, thereby performing etching.

[0076] The second method is to deposit SiCl containing a deposition element and a halogen element in a vacuum vessel 3001. ４ and Cl ２ A mixed gas of the above was introduced, plasma was generated below the separation plate 3002 inside the vacuum vessel 3001 (second space 3004), and a wafer bias was applied so that ions were preferentially supplied to the wafer 3005, thereby performing etching.

[0077] The third method is to deposit SiCl containing a deposition element and a halogen element in a vacuum vessel 3001. ４ and Cl ２A mixed gas of the above gases was introduced, and plasma was generated above the separation plate 3002 inside the vacuum vessel 3001 (first space 3003), so that only neutral radicals formed in the plasma were preferentially supplied to the wafer 3005, thereby performing etching.

[0078] 8 shows the results of evaluating the variation in etching depth of the conductive material 101 in the trench when etching is performed by the above three techniques, and the selectivity of the conductive material 101 to the first insulating film 103 or the second insulating film 104. Note that the selectivity to the first and second insulating films (103, 104) is the smaller of the values ​​calculated by the following (Equation 1) and (Equation 2).

[0079] 8 shows that when the process gas does not contain a deposition element, the seam 102 expands during etching, resulting in a large etching depth variation of 24.2 nm. On the other hand, as shown in the second method, when the process gas contains a deposition element, the expansion of the seam 102 during etching can be suppressed, and the etching depth variation can be reduced to 4.0 nm. This shows that, in an etching method in which plasma is generated below the separation plate 302 (second space 3004) and ions preferentially supply the wafer 3005 to be etched, the addition of a deposition element improves the etching depth variation. On the other hand, the selectivity ratio with respect to the first and second insulating films (103, 104) is a low value of less than 2, and it is clear that in a process in which ions are preferentially irradiated, it is difficult to process the conductive material 101 selectively with respect to the surrounding materials (103, 104) as shown in FIG. 2.

[0080] Next, from the results of the third method, it was found that radical-based etching, in which a deposition element is contained in the process gas and plasma is generated above the separation plate 3002 (first space 3003), can achieve a process with a high selectivity of 50 or more for the first and second insulating films (103, 104) by eliminating ion irradiation. Furthermore, in this process, as shown in FIG. 1(b), the halogen element diffuses through the solid deposition film 106, thereby achieving continuous etching with a reduced diffusion rate of the halogen element. This suppresses the expansion of the seam 102 due to the diffusion of the halogen element in the gas phase, thereby achieving a process with an etching depth variation of 1.0 nm.

[0081] In addition, in this experimental result, SiCl ４ and Cl ２ The mixed gas used was SiCl ４ and SiF ４ and CF ４ and CHF ３ and CH ３ F and C ４ F ６ Or C ５ F ８ Such gases may be used alone or in combination with other gases. ４ and CH ４ In a gas containing Si or C elements such as BCl ３ and Cl ２ and science fiction ６ and NF ３ Alternatively, a gas containing a halogen element gas such as HF or HBr may be used.

[0082] As described above, in a dry etching method (plasma processing method) for processing to a predetermined depth the conductive material 101 formed inside a trench surrounded by insulating films 103 and 104, plasma is generated using a gas containing a deposition element and a halogen element, and etching is performed mainly using radicals formed by the plasma. This makes it possible to suppress the expansion of the seam 102 during dry etching, achieve a high selectivity to the surrounding materials 103 and 104, and achieve high-throughput continuous etching.

[0083] A second embodiment using the present disclosure will be described below. This embodiment is a plasma processing method having a two-step etching method for processing a conductive material to a predetermined depth using a first step of radical-based etching using a gas containing a deposition element and a halogen element, and a second step of radical-based etching using a gas containing a halogen element but not a deposition element.

[0084] More specifically, the plasma processing method for etching back a conductive material (101) that is surrounded by insulating films (103, 104) and has a seam (102) includes a first step and a second step. In the first step, plasma is generated using a gas containing a deposition element and a halogen element, and the conductive material (101) is etched with radicals from the generated plasma while a deposition film (106) containing the deposition element is formed on the conductive material (101). In the second step, the conductive material (101) is etched with plasma generated using a gas containing a halogen element. Here, the halogen element-containing gas does not contain a deposition element. Furthermore, the plasma in the first step is generated in a first space 3003 between a dielectric plate 3102 and a shielding plate 3002. The plasma in the second step is generated in a second space 3004 between the shielding plate 3002 and the sample stage 3006.

[0085] The following description will be given with reference to the drawings.

[0086] Using the plasma processing apparatus 1, which is a wafer processing apparatus shown in FIG. 3, as shown in the cross-sectional view of FIG. 1(a), the conductive material 101 having the seam 102 and the surrounding area are treated with HfO ２ This embodiment describes a second example in which a wafer to be etched 3005 is processed, on which a pattern is formed, surrounded by a first insulating film 103 made of a high-k material such as TiN and a second insulating film 104 made of a low-k material such as SiOCN. Note that, although this embodiment describes a method using TiN as the conductive material, a similar embodiment can also be realized in processing other conductive materials such as W, polysilicon, Ru, Co, and Ir.

[0087] First, the wafer 3005 to be etched is loaded onto the stage 3006 in the processing chamber 3101. When the wafer 3005 is loaded, for example, the wafer 3005 to be etched is loaded onto a transfer arm from a transfer chamber maintained under vacuum onto the wafer stage 3006, and three or more pusher pins provided in the wafer stage 3006 are raised to lift the wafer 3005 to be etched from the transfer arm by the pusher pins.

[0088] Thereafter, the transfer arm is retracted into the transfer chamber, and the pusher pins holding the wafer 3005 to be etched are lowered into the wafer stage 3006, thereby placing the wafer 3005 to be etched on the wafer stage 3006.

[0089] In this method, in order to prevent the generation of foreign matter due to wear between the back surface of the wafer 3005 and the pusher pin, it is desirable to select the optimum operating speed, tip shape and material of the pusher pin.

[0090] Alternatively, the transport arm may be brought in with the pusher pins raised in advance, and then the height of the transport arm may be lowered and then retracted into the transport chamber, thereby holding the wafer to be etched 3005 with the pusher pins, and then the pusher pins holding the wafer to be etched 3005 may be lowered into the wafer stage 3006, thereby placing the wafer to be etched 3005 on the wafer stage 3006.

[0091] Next, opposite positive and negative DC voltages are applied to the first electrode 3013 and the second electrode 3014 installed in the wafer stage 3006, respectively, to generate a Johnson-Rahbek force or a Coulomb force, and the wafer 3005 to be etched is electrically fixed on the wafer stage 3006. In other words, it is preferable to electrostatically attract the sample 3005 to the sample stage 3006 using an electrostatic chuck. It is desirable to apply the same positive and negative voltages, but it is also possible to apply either a positive voltage or a negative voltage to the first electrode 3013.

[0092] This means that the wafer to be etched 3005 will remain fixed on the wafer stage 3006 until the electrical fixation is released, and the generation of foreign matter due to wear of the wafer to be etched 3005 and the wafer stage 3006 caused by movement of the wafer to be etched 3005 due to pressure fluctuations during the process, etc., can be suppressed.

[0093] Next, a thermally conductive gas is introduced between the wafer 3005 to be etched and the wafer stage 3006. This thermally conductive gas improves the thermal conductivity between the wafer stage 3006 and the wafer 3005 to be etched, and even within the vacuum chamber 3001, the temperature of the wafer 3005 to be etched can be efficiently controlled at a set temperature by using the temperature control function of the wafer stage 3006.

[0094] It is desirable to use He as the thermal conduction gas because it has good thermal conductivity and is stable. However, Ar and N ２ It is also preferable to maintain a pressure of 0.1 kPa to 10 kPa between the wafer 3005 to be etched and the wafer stage 3006, and it is preferable that the wafer 3005 to be etched is firmly fixed electrically by a DC voltage applied to the first electrode 3013 and the second electrode 3014 so that the wafer 3005 does not move even under this pressure.

[0095] Next, as shown in step 601 of FIG. 6, the conductive material 101 is etched by radical-based etching using a gas containing a deposition element and a halogen element, while forming a deposition film 106 of a predetermined thickness on the conductive material 101.

[0096] In this step 601, a gas containing a deposition element and a halogen element is introduced at a predetermined flow rate, high-frequency power 3007 is supplied from a waveguide 3008, and the coil current value of a static magnetic field coil 3012 is set so as to cause electron cyclotron resonance in the upper first space 3003. This generates plasma in the upper first space 3003, etching the conductive material 101 and forming a deposition film 106 of a predetermined thickness on the conductive material 101. In this step 601, it is desirable to control the gas exhaust speed in the exhaust direction 3011 so that the pressure inside the vacuum vessel 3001 is maintained at a set value. The pressure inside the processing chamber 3101 is desirably selected from a range of 0.05 Pa to 100 Pa (0.05 Pa to 100 Pa), for example. That is, the pressure inside the processing chamber 3101 in which the conductive material 101 is etched is set to, for example, a pressure within the range of 0.05 Pa to 100 Pa.

[0097] Furthermore, by setting the static magnetic field coil 3012 so that plasma is generated in the first space 3003, radicals formed in the plasma using a gas containing a deposition element and a halogen element preferentially reach the wafer to be etched 3005. Therefore, etching mainly caused by radicals in the plasma generated by the gas containing a deposition element and a halogen element can be achieved.

[0098] Here, radical-based etching is performed using a gas containing Si or C as the deposition element and Cl, F, or Br as the halogen element. In this case, as shown in FIG. 1B, radicals generated by the gas containing the deposition element are used to form a deposition film 106 on the conductive material 101, the first insulating film 103, and the second insulating film 104, while radicals generated by the gas containing the halogen element pass through the deposition film 106 and further etch the conductive material 101 below the deposition film 106. Because the deposition film 106 formed in the seam 102 is formed from the conductive material 101 on both sides of the seam 102, forming the deposition film 106 with a thickness equal to or greater than half the seam width 105 allows etching to proceed while completely covering the void seam portion 102. The expansion of the seam 102 during dry etching is due to the fact that the diffusion rate of radicals diffusing in a gas phase is faster than the diffusion rate of radicals in a solid, such as the conductive material 101, and therefore the radicals reach the seam 102 at a high speed. In other words, if the entire seam 102 can be covered with a solid deposition film 106, the diffusion rate of radicals in the deposition film 106 is slowed, thereby suppressing the expansion of the seam 102 during dry etching. Even when using a radical etch with a high selectivity to the surrounding materials (103, 104), the deposition film 106 is formed to a width equal to or greater than half of the seam width 105 using radicals formed by plasmatizing a gas containing a deposition element. This suppresses the expansion of the seam 102 during dry etching, and allows the radicals generated by plasmatizing a halogen element to penetrate the deposition film 106 formed using radicals formed by plasmatizing a deposition element, thereby enabling the conductive material 101 to be continuously etched while forming the deposition film 106 to a predetermined thickness.

[0099] The gas containing the deposition element consisting of Si element or C element and the halogen element consisting of Cl element, F element or Br element includes SiCl ４ and SiF ４ and CF ４ and CHF ３ and CH ３ F and C ４ F ６ Or C５ F ８ It is desirable to use such gases alone or in combination with other gases. ４ and CH ４ In a gas containing Si or C elements such as BCl ３ and Cl ２ and science fiction ６ and NF ３ It is also possible to use a gas containing a halogen element gas such as HF or HBr. In order to make the plasma distribution uniform, these gases may be mixed with Ar, He, Xe, or N. ２ and H ２ It may be diluted with a gas such as

[0100] Next, a deposited film 106 of a predetermined thickness is formed on the conductive material 101, and then, as shown in step 602 of FIG. 6 , radical-based etching using a gas containing a halogen element is performed, and the halogen element penetrates the deposited film 106, and the conductive material 101 is etched to a predetermined depth in a state in which the deposited film 106 is formed.

[0101] In this step 602, a gas containing a halogen element is introduced at a predetermined flow rate, high-frequency power 3007 is supplied from a waveguide 3008, and the coil current value of a static magnetic field coil 3012 is set so as to cause electron cyclotron resonance in the upper first space 3003. This generates plasma in the upper first space 3003, and the conductive material 101 is etched to a predetermined depth while maintaining the thickness of the deposited film 106 formed in step 601. In this step 602, it is desirable to control the gas exhaust speed in the exhaust direction 3011 so that the inside of the vacuum chamber 3001 is maintained at a set pressure.

[0102] Furthermore, by setting the static magnetic field coil 3012 so that plasma is generated in the first space 3003, radicals formed in the plasma using a gas containing a halogen element preferentially reach the wafer to be etched 3005. Therefore, etching mainly caused by radicals in the plasma generated by the gas containing a halogen element can be achieved.

[0103] In step 602, if a deposited film 106 with a sufficient thickness has been formed in step 601, the plasma may be generated in the second space 3004. In this case, the plasma is directly irradiated onto the wafer 3005 to be etched, increasing the amount of radicals formed in the plasma and the processing speed of the conductive material 101. However, since ions generated in the plasma are also irradiated onto the wafer 3005 to be etched, it becomes difficult to selectively process the conductive material 101 relative to the first insulating film 103 or the second insulating film 104. Therefore, it is necessary to form a deposited film 106 with a sufficient thickness in step 601 so that the energy of the irradiated ions is attenuated by the deposited film 106. Specifically, it is desirable to form a deposited film 106 with a thickness of 3 nm or more in step 601, and then generate plasma in the second space 3004 in step 602.

[0104] When radical-based etching is performed using a gas containing Cl, F, or Br as a halogen element, radicals generated by the gas containing the halogen element pass through the deposition film 106 formed in step 601 and further etch the conductive material 101 below the deposition film 106. Here, the expansion of the seam 102 during dry etching is caused by the fact that the diffusion rate of radicals diffusing in the gas phase is faster than the diffusion rate of radicals in solids such as the conductive material 101, and therefore the radicals reach the seam 102 more quickly. In other words, if the entire seam 102 can be covered with the solid deposition film 106 in step 601, the diffusion rate of radicals in the deposition film 106 is slower, and therefore the expansion of the seam 102 during dry etching can be suppressed. In other words, even if radical etching having a high selectivity with respect to the surrounding materials (103, 104) is used, radicals generated by plasmatizing halogen elements can penetrate the deposited film 106 formed in step 601, and the conductive material 101 can be continuously processed while maintaining the thickness of the deposited film 106 formed in step 601.

[0105] The halogen gas containing Cl, F or Br is BCl ３ and Cl ２ and science fiction ６ and NF３ It is desirable to use a gas containing a halogen element gas such as HF or HBr. In order to make the plasma distribution uniform, these gases may be mixed with Ar, He, Xe, or N. ２ and H ２ However, if a gas containing Si or C elements is used, the thickness of the deposited film formed in step 601 increases, so it is preferable not to use a gas containing Si or C elements.

[0106] Next, after the conductive material 101 has been processed to a predetermined processing depth, the introduction of the thermal conduction gas between the wafer 3005 to be etched and the wafer stage 3006 is stopped, and then plasma is generated in the second space 3004 below to release the electrical fixation between the wafer 3005 to be etched and the wafer stage 3006. That is, after the conductive material 101 has been etched to a predetermined depth, the application of the DC voltage for electrostatically attracting the sample 3005 to the sample stage 3006 is stopped while maintaining the plasma generated in the second space 3004 between the shielding plate 3002 and the sample stage 3006. Here, if the first electrode 3013 and the second electrode 3014 have the same area and the applied voltage is turned off at the same time, the electrical fixation can, in principle, be released even without plasma.

[0107] However, there may be slight differences in the areas of the two due to differences in the plasma processing apparatus 1, or slight discrepancies in the timing of turning off the applied voltage, which may cause charges to accumulate on the wafer 3005 to be etched and the wafer stage 3006. In this case, the electrical fixation may not be completely released, and the wafer 3005 may occasionally be damaged when being unloaded, which becomes an issue during mass production.

[0108] Therefore, it is desirable to generate plasma in the second space 3004 directly above the wafer 3005 to be etched and form an electrical path with electrons and ions in the plasma to release the electric charges accumulated in the wafer 3005 to be etched and the wafer stage 3006. In other words, it is desirable to turn off the DC voltage applied to the first electrode 3013 and the second electrode 3014 while the plasma is generated in the second space 3004. With this configuration, damage to the wafer 3005 when the wafer 3005 is unloaded can be suppressed, and a process suitable for mass production can be realized.

[0109] When the DC voltage applied to the first electrode 3013 and the second electrode 3014 is turned off, in order to more easily remove the accumulated charge, the voltage value applied to both electrodes (3013, 3014) may be changed or the pusher pin may be moved up and down while plasma is still being generated in the second space 3004.

[0110] It is desirable to select a gas for generating plasma in this process that does not significantly affect the shape of the wafer 3005 to be etched, such as a rare gas.

[0111] However, if generating plasma in the second space 3004 changes the etching shape, the DC voltage applied to the first electrode 3013 and the second electrode 3014 may be turned off without generating plasma in the second space 3004. In this case, however, in order to prevent damage to the wafer 3005, it is necessary to give particular consideration to the speed at which the pusher pins are raised and lowered, and to select materials for the pusher pins and wafer stage 3006 that are less likely to accumulate electric charge.

[0112] Next, the plasma is extinguished, and all gases are stopped from being introduced into the vacuum vessel 3001. Thereafter, the wafer 3005 to be etched is carried out from the wafer stage 3006.

[0113] When the wafer 3005 is unloaded, for example, three or more pusher pins provided in the wafer stage 3006 are raised to lift the wafer 3005 to be etched, and the wafer 3005 is then loaded from the transfer chamber by a transfer arm. At this time, in order to prevent contact between the wafer 3005 to be etched and the transfer arm, the wafer 3005 to be etched needs to be lifted to a position higher than the transferred transfer arm. Thereafter, the pusher pins are lowered into the wafer stage 3006, so that the wafer 3005 to be etched can be held by the transfer arm. Thereafter, the transfer arm is retracted into the transfer chamber, so that the wafer 3005 to be etched can be unloaded from the vacuum chamber 3001.

[0114] In this method, in order to prevent the generation of foreign matter due to wear between the back surface of the wafer 3005 and the pusher pin, it is desirable to select the optimum operating speed, tip shape and material of the pusher pin.

[0115] In this process, the temperature may be changed to another temperature during etching. However, since changing the temperature of the wafer stage 3006 increases the process time, it is desirable not to change the temperature of the wafer stage 3006. Specifically, it is desirable to set and maintain the temperature of the wafer stage 3006 at any temperature within the range of -50°C to +150°C. In other words, the temperature of the sample stage 3006 on which the sample 3005 on which the conductive material 101 is formed is set to a temperature within the range of -50°C to 150°C.

[0116] In this method, the wafer to be etched 3005 is carried out from the inside of the vacuum chamber 3001 with the deposition film 106 deposited on the pattern. However, this deposition film 106 can be removed by wet etching such as SC1 cleaning using a mixed solution of ammonia water and hydrogen peroxide water, or HF cleaning, and it has been confirmed that this does not cause any problems in subsequent processes.

[0117] Furthermore, this deposition film 106 may be removed by dry etching inside the vacuum chamber 3001. For example, before the wafer 3005 to be etched is carried out, a gas containing a halogen element is introduced into the vacuum chamber 3001 in the case of a Si-based deposition film 106, and a gas containing an oxygen element is introduced into the vacuum chamber 3001 in the case of a C-based deposition film 106, and plasma is generated to remove the film by dry etching (plasma etching).

[0118] In this case, the space in which the plasma is generated may be either above (first space 3003) or below (second space 3004) the separation plate 3002. However, if plasma is generated below (second space 3004) the separation plate 3002 and the wafer 3005 to be etched is directly irradiated with the plasma, a self-bias is generated between the plasma and the wafer 3005 to be etched. As a result, ions generated in the plasma are accelerated by the self-bias and enter the wafer 3005 to be etched. This may damage the conductive material 101 and insulating films 103 and 104 of the wafer 3005 to be etched. For this reason, it is desirable to use dry etching in which plasma is generated above (first space 3003) the separation plate 3002.

[0119] Alternatively, the deposition film 106 may be removed by dry etching using only gas without using plasma.

[0120] The process of removing this deposited film 106 does not necessarily have to be performed inside the same vacuum vessel 3001; as long as the deposited film can be removed, the wafer to be etched 3005 may be moved to the vacuum vessel 3001 of another plasma processing apparatus 1 and then the deposited film 106 may be removed.

[0121] However, if the deposited film 106 is thick, there is a concern that the process time required to remove the deposited film 106 after etching will be long. However, by using the two-stage etching method described in this second embodiment, it is possible to independently control the thickness of the deposited film 106 in step 601 and the processing depth of the conductive material 101 in step 602. This makes it possible to realize a plasma processing method as a process for etching the conductive material 101 to a predetermined depth while maintaining the target thickness of the deposited film 106.

[0122] Furthermore, when processing a plurality of wafers 3005 to be etched repeatedly, it is also possible to periodically perform a cleaning sequence using plasma between the first wafer 3005 to be etched and the next wafer 3005 to be etched. In this cleaning sequence, it is desirable to use a sequence for removing reaction products from the material to be etched that have adhered to the inner wall of the vacuum vessel 3001 during etching, or a sequence for forming a protective film on the inner wall of the vacuum vessel 3001 in order to maintain the inner wall in a constant state.

[0123] In the cleaning sequence, it is desirable to generate plasma in the second space 3004 below the separation plate 3002, where reaction products from the wafer 3005 to be etched are likely to adhere. However, because reaction products from the wafer 3005 to be etched may also adhere to the first space 3003 above the separation plate 3002, it is desirable to perform a cleaning sequence in which plasma is generated in both the first space 3003 and the second space 3004. Here, the order may be such that either the first space 3003 or the second space 3004 is performed first, and the first space 3003 and the second space 3004 may be alternated during the cleaning sequence. In other words, after the conductive material 101 is etched to a predetermined depth, it is desirable to clean the processing chamber 3101 using plasma generated in the first space 3003 between the dielectric plate 3102 and the shielding plate 3002, or plasma generated in the second space 3004 between the shielding plate 3002 and the sample stage 3006.

[0124] When performing this cleaning sequence, a wafer to be cleaned may be placed on the wafer stage 3006. However, in order to reduce the cost of the wafer to be cleaned, it is desirable to perform the cleaning sequence without placing the wafer to be cleaned on the wafer stage 3006. In other words, when cleaning the processing chamber 3101, it is desirable not to place the sample 3005 on the sample stage 3006.

[0125] The gas used in this cleaning is BCl 2 to remove deposits formed in the vacuum vessel 3001. ３ and Cl２ and science fiction ６ and NF ３ It is desirable to use a plurality of halogen element gases such as HF and HBr. ２ YaCO ２ When forming a protective film, an oxygen-containing gas such as SiCl ４ and SiH ４ and CH ４ It is desirable to use a gas containing Si element or C element such as the above.

[0126] As an example of using the wafer processing method (plasma processing method) according to the second embodiment of the present disclosure, a TiN film is used as the conductive material 101 to be etched, and SiCl is used as the gas containing a deposition element and a halogen element used in step 601. ４ and Cl ２ A mixed gas of these elements was introduced to generate plasma, and the conductive material 101 was etched while forming a deposition film 106. Thereafter, a gas containing a halogen element, Cl, was introduced in step 602. ２ The results of an experiment in which a gas was introduced to generate plasma and the conductive material 101 was etched while maintaining the thickness of the deposited film 106 formed in step 601 will be described.

[0127] First, a wafer 3005 on which a TiN film, which is the conductive material 101, is formed is placed on a wafer stage 3006 inside the vacuum chamber 3001 using a transfer arm and pusher pins, and the wafer 3005 is electrically fixed on the wafer stage 3006. Next, the stage temperature is set to −5° C. using the temperature control function provided in the wafer stage 3006.

[0128] Next, as shown in step 601, a predetermined flow rate of SiCl ４ and Cl ２Gas is introduced, and microwave power 3007 with a power of 500 W is supplied from a waveguide 3008, generating plasma above the separation plate 3002 (first space 3003) by electron cyclotron resonance. At this time, the pressure inside the vacuum vessel 3001 is maintained at 0.8 Pa. Furthermore, by generating plasma above the separation plate 3002 inside the vacuum vessel 3001 (first space 3003), only neutral radicals formed in the plasma are preferentially supplied to the wafer 3005. Thereafter, by processing for a predetermined time, a deposition film 106 of a desired thickness is formed on the conductive material 101, while etching the conductive material 101.

[0129] Next, as shown in step 602, a predetermined flow rate of Cl ２ Gas is introduced, microwave power 3007 with a power of 500 W is supplied from a waveguide 3008, and plasma is generated above the separation plate 3002 (first space 3003) by electron cyclotron resonance. At this time, the pressure inside the vacuum vessel 3001 is maintained at 0.8 Pa. Furthermore, by generating plasma above the separation plate 3002 inside the vacuum vessel 3001 (first space 3003), only neutral radicals formed in the plasma are preferentially supplied to the wafer 3005. Thereafter, by processing for a predetermined time, the conductive material 101 is etched to the desired thickness while maintaining the film thickness of the deposition film 106 formed in step 601. Note that between steps 601 and 602, the discharge is stopped once, and the gas inside the vacuum vessel 3001 is evacuated, and then Cl is again introduced into the vacuum vessel 3001. ２ Although it is possible to introduce gas and generate plasma, it is preferable to replace only the gas while maintaining the discharge in order to improve throughput.

[0130] Thereafter, the conductive material 101 is processed to the desired etching depth, and then Ar gas is introduced to generate plasma below the separation plate 3002 (second space 3004), releasing the electrical fixation of the wafer 3005 to be etched, and then the wafer 3005 to be etched is carried out.

[0131] 7 shows the change in the etching amount (FIG. 7(a)) and the change in the film thickness of the deposited film 106 (FIG. 7(b)) with respect to the processing time of step 602, with the processing time of step 601 fixed at 300 seconds. From FIG. 7(a), it can be seen that the etching amount increases as the processing time of step 602 increases. Also, from FIG. 7(b), it can be seen that even if the processing time increases, the film thickness of the deposited film 106 formed in step 601 remains unchanged. This is because the halogen element passes through the deposited film 106 and reaches the conductive material 101, thereby causing etching of the conductive material 101 to proceed. In other words, SiCl containing the deposition element Si and the halogen element Cl ４ and Cl ２ After forming a predetermined thickness of the deposition film 106 in a process using a mixed gas of the above, a Cl containing Cl, which is a halogen element, is ２ By carrying out a process using gas, it is possible to realize continuous etching with high throughput, in which the thickness of the deposited film 106 and the etching depth of the conductive material 101 are independently controlled.

[0132] The deposited film 106 formed on the pattern needs to be removed after etching, and if the deposited film 106 is too thick, there is a concern that the process time required to remove the deposited film 106 after etching will be long. However, by using the two-stage etching method described in this second embodiment, the thickness of the deposited film 106 and the processing depth of the conductive material 101 can be controlled independently. This makes it possible to provide a plasma processing method that realizes a process of etching the conductive material 101 to a predetermined depth while maintaining the target thickness of the deposited film 106.

[0133] The disclosure made by the present inventor has been specifically described above based on examples, but it goes without saying that the present disclosure is not limited to the above examples and can be modified in various ways without departing from the spirit of the present disclosure. For example, the above examples have been described in detail to clearly explain the present disclosure, and the present disclosure is not necessarily limited to those having all of the described configurations. Furthermore, it is possible to add, delete, or replace part of the configuration of the examples with other known configurations.

[0134] 101: conductive material, 102: seam, 103: first insulating film, 104: second insulating film, 105: seam width, 106: deposited film, 107: radicals, 201: ions, 3001: vacuum vessel, 3002: separation plate, 3003: first space, 3004: second space, 3005: wafer to be etched, 3006: wafer stage, 3007: high frequency power, 3008: waveguide, 3009: cavity resonator, 3010: process gas, 3011: exhaust direction, 3012: static magnetic field coil, 3013: first electrode, 3014: second electrode.

Claims

1. A plasma processing method for etching back a conductive material that has been surrounded by an insulating film and has developed a seam, comprising the steps of generating plasma using a gas containing a depositing element and a halogen element, and etching the conductive material with radicals from the generated plasma while forming a deposited film containing the depositing element on the conductive material.

2. A plasma processing method for etching back a conductive material that has been surrounded by an insulating film and has developed a seam, comprising: a first step of generating plasma using a gas containing a depositing element and a halogen element, and etching the conductive material with radicals from the generated plasma while forming a deposition film containing the depositing element on the conductive material; and a second step of etching the conductive material with plasma generated using a gas containing a halogen element, wherein the gas containing a halogen element does not contain the depositing element.

3. A plasma processing method according to claim 1 or 2, wherein the deposition element is a silicon element or a carbon element.

4. The plasma processing method according to claim 1 or 2, wherein the halogen element is a chlorine element, a fluorine element or a bromine element.

5. In the plasma processing method according to claim 1 or 2, the gas containing a deposition element and a halogen element is SiCl ４ Gas, SiF ４ gas 、 CF ４ Gas, CHF ３ Gas, CH ３ F gas, C ４ F ６ Gas or C ５ F ８ A plasma processing method characterized in that the gas is a plasma.

6. In the plasma processing method according to claim 1 or 2, the plasma generated by using a gas containing a deposition element and a halogen element is a gas containing an Ar gas, a He gas, a Xe gas, a N gas, or a N ２ Gas or H ２ A plasma processing method characterized in that a plasma is generated by further adding a gas.

7. In the plasma processing method according to claim 1 or 2, the plasma generated using a gas containing a deposition element and a halogen element is SiCl ４ Gas and Cl ２ 1. A plasma processing method, comprising: generating a plasma using a mixed gas of gases, wherein the ratio of chlorine elements to silicon elements is equal to or greater than 80% and less than 100%.

8. A plasma processing method according to claim 1 or 2, characterized in that the pressure in the processing chamber in which the conductive material is etched is within the range of 0.05 Pa to 100 Pa.

9. A plasma processing method according to claim 1 or 2, characterized in that the temperature of the sample stage on which the sample having the conductive material film formed thereon is placed is within the range of -50°C to 150°C.

10. A plasma processing method according to claim 1 or 2, wherein the thickness of the deposited film when the conductive material is etched to a predetermined depth is within the range of half the width of the seam to 60 nm.

11. A plasma processing method according to claim 1 or 2, wherein the conductive material is titanium nitride (TiN), tungsten (W), polysilicon (Poly-Si), ruthenium (Ru), cobalt (Co) or iridium (Ir).

12. A plasma processing method according to claim 1 or 2, characterized in that after the conductive material has been etched to a predetermined depth, the deposited film is removed by wet etching or plasma etching.

13. The plasma processing method according to claim 12, wherein the deposited film is removed by wet etching using SC1 cleaning or HF cleaning.

14. A plasma processing method according to claim 12, characterized in that, when the deposited film contains silicon, the deposited film is removed by plasma generated using a gas containing a halogen element, and when the deposited film contains carbon, the deposited film is removed by plasma generated using a gas containing an oxygen element.

15. A plasma processing method according to claim 1, wherein the plasma processing apparatus in which the plasma is generated comprises a processing chamber in which the conductive material is etched and on which a dielectric plate for airtight sealing is placed above, a high frequency power supply for supplying high frequency microwave power for generating plasma, a magnetic field forming mechanism for forming a magnetic field within the processing chamber, a sample stage on which a sample having a film of the conductive material formed thereon is placed, and a shielding plate for blocking ions from entering the sample stage, wherein the plasma is generated between the dielectric plate and the shielding plate.

16. A plasma processing method according to claim 2, wherein the plasma processing apparatus in which the plasma is generated comprises a processing chamber in which the conductive material is etched and on which a dielectric plate for airtight sealing is placed, a high-frequency power supply that supplies high-frequency microwave power for generating plasma, a magnetic field forming mechanism that forms a magnetic field within the processing chamber, a sample stage on which a sample having a film of the conductive material formed thereon is placed, and a shielding plate that blocks ions from entering the sample stage, characterized in that the plasma in the first step is generated between the dielectric plate and the shielding plate, and the plasma in the second step is generated between the shielding plate and the sample stage.

17. A plasma processing method according to claim 15 or 16, characterized in that after the conductive material has been etched to a predetermined depth, the processing chamber is cleaned using plasma generated between the dielectric plate and the shielding plate or plasma generated between the shielding plate and the sample stage.

18. The plasma processing method according to claim 17, wherein when the processing chamber is cleaned, the sample is not placed on the sample stage.

19. A plasma processing method according to claim 15 or 16, characterized in that after the conductive material has been etched to a predetermined depth, the application of a DC voltage for electrostatically attracting the sample to the sample stage is stopped while maintaining the plasma generated between the shielding plate and the sample stage.

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