Copper layer etching method and substrate processing apparatus

Abstract

The invention relates to a method for etching a copper layer and a substrate processing apparatus. The present invention suppresses a decrease in shape controllability when a copper layer is formed into a desired shape, and also suppresses a decrease in etching rate of the copper layer. When etching a thin copper layer (41) formed on the surface of a substrate (G) disposed inside a processing chamber (11) of a substrate processing apparatus (10), in a primary reaction, copper chloride (II) (44) is generated from the copper layer (41) by using chlorine radicals generated from a first processing gas containing a chlorine-containing gas and not containing hydrogen gas, and in a secondary reaction, copper chloride (II) (44) is generated from the copper layer (41) by using chlorine radicals generated from a second processing gas containing chlorine gas and not containing hydrogen gas. The trimer of copper chloride (I) is generated from copper chloride (II) (44) by means of hydrogen radicals generated from a second treatment gas that contains hydrogen gas and does not contain a chlorine-containing gas and another chlorine-containing gas, and the primary reaction and the secondary reaction are alternately repeated for a predetermined number of times.

Description

Technical Field

[0001] The present disclosure relates to a copper layer etching method and a substrate processing device. Background Art

[0002] As display devices become larger and higher resolution, copper (Cu) is used as a low-resistance wiring material in display elements. However, wet etching is usually used in the copper wiring formation process, and the copper layer on the substrate is etched according to a predetermined pattern. However, with the recent miniaturization and high density, it is sometimes difficult to control the shape in the wet process, so accurate patterning using dry etching is required.

[0003] Conventionally, in the dry etching method of copper, chlorine plasma generated from chlorine (Cl)-based gas is used. In this etching method, copper chloride is generated as a reaction product from copper and chlorine plasma, and the copper chloride is vaporized to etch the copper. The vapor pressure of the copper chloride generated at this time is low, so it is necessary to heat it with a lamp or the like for vaporization (for example, refer to Patent Document 1).

[0004] On the other hand, an OLED (Organic Light Emitting Diode), which is a display element used in display devices in recent years, has a light-emitting layer formed of an organic substance. Therefore, an etching method for a copper layer that does not require heating in the manufacturing process of a display element is sought. As such an etching method, the following method is known: using a processing gas containing hydrogen chloride (HCl) gas and hydrogen (H2), in an ECR (electron cyclotron resonance) type plasma processing device, chlorine radicals and hydrogen radicals are generated by the processing gas. In this etching method, copper (II) chloride (CuCl2) is generated from the copper layer using chlorine radicals, and a trimer (Cu3Cl3) of copper (I) chloride (CuCl) is generated from copper (II) chloride using hydrogen radicals. Moreover, since the vapor pressure of the trimer of copper (I) chloride is high, it is vaporized approximately simultaneously with its generation. As a result, the copper layer can be etched without heating (for example, refer to Patent Document 2).

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 01-160035

[0008] Patent Document 2: U.S. Patent Application Publication No. 2019 / 0103287 Summary of the invention

[0009] Problem that the invention aims to solve

[0010] The technology disclosed herein suppresses a decrease in shape controllability when a copper layer is formed into a desired shape, and also suppresses a decrease in the etching rate of the copper layer.

[0011] Solutions for solving problems

[0012] A technical scheme of the technology of the present invention is a method for etching a copper layer, which is an etching method for a copper layer formed on a substrate inside a processing chamber arranged in a substrate processing device, wherein the method for etching the copper layer comprises: a first step of supplying a first processing gas containing at least a chlorine-containing gas and not containing hydrogen into the processing chamber, and generating a first product from the copper layer using a first plasma generated by the first processing gas; and a second step of supplying a second processing gas containing at least the hydrogen gas and not containing the chlorine-containing gas and other chlorine-containing gases into the processing chamber, and generating a second product from the first product using a second plasma generated by the second processing gas, and alternately repeating the first step and the second step a predetermined number of times.

[0013] Effects of the Invention

[0014] According to the technology disclosed in the present invention, it is possible to suppress a decrease in shape controllability when forming a copper layer into a desired shape, and also suppress a decrease in the etching rate of the copper layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a cross-sectional view schematically showing the structure of a substrate processing apparatus as one embodiment of the technology disclosed herein.

[0016] Figure 2 It means the observation from the processing space side Figure 1 A diagram showing a metal window provided in a substrate processing apparatus.

[0017] Figure 3 This is a process diagram for explaining a reaction utilized in a method for etching a copper layer according to one embodiment of the technology of the present invention.

[0018] Figure 4 This is a flowchart showing a method for etching a copper layer according to one embodiment of the technology of the present invention.

[0019] Figure 5 It is a partially enlarged cross-sectional view schematically showing a partial SEM image of a cross section of a test piece of a comparative example and an example.

[0020] Description of Reference Numerals

[0021] G, substrate; U, processing space; 10, substrate processing device; 11, processing chamber; 12, metal window; 13, mounting table; 21, dividing sheet; 24, inductively coupled antenna; 44, copper (II) chloride; 40, control unit. DETAILED DESCRIPTION

[0022] In the technology described in the above-mentioned patent document 2, if the generated copper chloride (II) is vaporized due to heat, the copper chloride (II) solidifies again inside the processing chamber and is deposited at a relatively low temperature position, which becomes the cause of the generation of particles. Therefore, the temperature rise of copper chloride (II) is suppressed by absorbing heat when generating the trimer of copper chloride (I), thereby suppressing the vaporization of copper chloride (II). Therefore, it is necessary to simultaneously generate copper chloride (II) and generate the trimer of copper chloride (I). Corresponding to this, the chlorine radical used for the generation of copper chloride (II) and the hydrogen radical used for the generation of the trimer of copper chloride (I) are simultaneously present inside the processing chamber of the ECR plasma processing device. As a result, the hydrogen chloride gas as the generation source of the chlorine radical is present inside the processing chamber during the etching of the copper layer.

[0023] However, hydrogen chloride gas corrodes the hard mask used as an etching mask. Therefore, if hydrogen chloride gas exists in the processing chamber for a long time, the shape of the hard mask is deformed by the hydrogen chloride gas, resulting in reduced shape controllability when forming a desired shape of the copper layer.

[0024] In addition, since the formation of copper (II) chloride and the formation of copper (I) chloride trimers are performed simultaneously, it is difficult to optimize the formation conditions of copper (II) chloride and the formation conditions of copper (I) chloride trimers, and it is impossible to promote the formation of copper (II) chloride and the formation of copper (I) chloride trimers at the same time. As a result, the etching rate of the copper layer is reduced, and the etching execution time for forming a desired shape on the copper layer becomes longer, for example, the etching execution requires 120 seconds to 300 seconds.

[0025] In contrast, the technology disclosed in the present invention suppresses a decrease in shape controllability when forming a copper layer into a desired shape, and also suppresses a decrease in the etching rate of the copper layer.

[0026] Hereinafter, one embodiment of the technology of the present invention will be described with reference to the drawings. Figure 1 is a cross-sectional view schematically showing the structure of a substrate processing apparatus according to this embodiment. Figure 2 It means the observation from the processing space side Figure 1 FIG. 1 is a diagram showing a metal window provided in a substrate processing apparatus 10 .

[0027] Figure 1The substrate processing apparatus 10 is an inductively coupled plasma processing apparatus. The substrate processing apparatus 10 uses high-density plasma generated by a processing gas to etch a thin film copper layer formed on the surface of a rectangular substrate, such as a glass substrate G (hereinafter referred to as "substrate G") for FPD (Flat Panel Display).

[0028] The substrate processing apparatus 10 includes a processing chamber 11 in a square cylindrical shape. The processing chamber 11 is made of a conductive material, such as aluminum or an alloy containing aluminum. The processing chamber 11 accommodates a substrate G and is electrically grounded. The upper portion of the processing chamber 11 is airtightly sealed by a metal window 12. In addition, a mounting table 13 on which the substrate G is mounted is arranged at the lower portion of the processing chamber 11, and the mounting table 13 is opposite to the metal window 12. In addition, in the processing chamber 11, a processing space U is formed between the mounting table 13 and the metal window 12. In the processing space U, as described later, a high-density plasma is generated by a processing gas.

[0029] An electrostatic holding disk (not shown) is provided on the upper surface of the mounting table 13, and the substrate G mounted on the mounting table 13 is held on the mounting table 13 by adsorption by the electrostatic holding disk. In addition, a temperature control mechanism, such as a cooler using a refrigerant and a heat transfer gas supply mechanism (both not shown) are provided inside the mounting table 13 to control the temperature of the mounted substrate G by controlling the temperature of the mounting table 13. In addition, the mounting table 13 is provided on the bottom surface of the processing chamber 11 via an insulating frame 14.

[0030] A metal frame 15 is provided at the upper end of the side wall of the processing chamber 11, and a side wall portion 16 is provided on the upper surface of the metal frame 15. The side wall portion 16 supports a top plate 17 and is electrically grounded, and the top plate 17 covers the metal window 12 from above. In addition, a sealing member 18 such as an O-ring is provided between the side wall of the processing chamber 11 and the metal frame 15 to keep the processing space U airtight. In addition, a feed-in / feed-out port 19 for feeding the substrate G into and out of the processing space U and a gate valve 20 for opening and closing the feed-in / feed-out port 19 are provided on the side wall of the processing chamber 11.

[0031] like Figure 2As shown, the metal window 12 is rectangular in shape and is divided into a plurality of segments 21. In the present embodiment, the metal window 12 is divided into 24 segments 21, but the number of the segments 21 is not limited to 24 and varies according to the size of the metal window 12, the controllability of the distribution of the plasma, and the like. Each segment 21 is composed of, for example, a non-magnetic and conductive metal, aluminum, or an alloy containing aluminum. In the metal window 12, a partition member 22 composed of an insulator is respectively arranged between each adjacent segment 21. The partition member 22 separates the adjacent segments 21 and electrically insulates them from each other. Considering that the processing space U is kept airtight via the metal window 12 with the antenna chamber 23 described later, the partition member 22 is preferably composed of an integral body.

[0032] return Figure 1 In the substrate processing apparatus 10, a space surrounded by the metal window 12, the side wall portion 16, and the top plate 17 constitutes an antenna chamber 23. In the antenna chamber 23, an inductive coupling antenna 24 is arranged so as to face the substrate G placed on the mounting table 13 via the metal window 12. The inductive coupling antenna 24 is arranged to be separated from the metal window 12 via, for example, a spacer made of an insulator (not shown).

[0033] The inductive coupling antenna 24 is composed of a plurality of antenna segments, each of which is arranged in the circumferential direction of the metal window 12 to form a ring-shaped antenna as a whole. In addition, each antenna segment is configured in the same plane, so the inductive coupling antenna 24 has a flat antenna shape. Depending on the processing content, each antenna segment can be configured to span across each segment 21, or it can be configured not to span across each segment 21 but to converge to the projection range of the corresponding segment 21. In addition, the inductive coupling antenna 24 can also be composed of a single antenna wire or a plurality of antenna wires bundled together. In this case, the inductive coupling antenna 24 spans the area opposite to each segment 21 and is configured in a spiral shape along the circumferential direction of the metal window 12. In addition, multiple inductive coupling antennas 24 can also be configured in a concentric shape.

[0034] like Figure 1 As shown, a plurality of gas holes 25 opening toward the processing space U are formed in each segment 21. A gas supply pipe 26 is connected to each segment 21, and the gas supply pipe 26 is connected to a gas supply device 27. In addition, a gas diffusion chamber 28 is formed inside each segment 21, and the gas supply device 27 introduces a processing gas into the gas diffusion chamber 28 via the gas supply pipe 26. The processing gas introduced into the gas diffusion chamber 28 is supplied to the processing space U from each gas hole 25. Therefore, each segment 21 has a gas nozzle structure composed of each gas hole 25 and the gas diffusion chamber 28.

[0035] The gas supply device 27 is connected to a hydrogen chloride gas supply source 29 for supplying hydrogen chloride gas as a chlorine-containing gas, a chlorine gas supply source 30 for supplying chlorine gas (Cl2) as a chlorine-containing gas, and a boron trichloride gas supply source 50 for supplying boron trichloride (BCl3) gas as a chlorine-containing gas. In addition, only one or both of hydrogen chloride gas, chlorine gas, and boron trichloride gas may be used as the chlorine-containing gas, and accordingly, only one or both of the hydrogen chloride gas supply source 29, the chlorine gas supply source 30, and the boron trichloride gas supply source 50 are connected to the gas supply device 27. In addition, the gas supply device 27 is connected to a hydrogen gas supply source 31 for supplying hydrogen gas and an argon gas supply source 32 for supplying argon gas (Ar) as a diluent gas. In addition, the diluent gas is not limited to argon gas as long as it has a function of diluting the gas supplied together. The gas supply device 27 has pipes connected to the gas supply sources 29, 30, 31, 32, and 50, and flow control devices (not shown) and valves (not shown) of the gases disposed on the pipes. The pipes are combined downstream of the corresponding flow control devices and valves, so that the gases merge in the gas supply device 27. The gas supply device 27 controls the flow of the gases flowing from the gas supply sources 29, 30, 31, 32, and 50 to the gas supply device 27 using the flow control devices based on instructions from the control unit 40 described later, and then merges the gases to generate the processing gas. In addition, instead of providing the gas supply device 27 in order to merge the gases, flow control devices and valves may be provided on the pipes connected to the gas supply sources 29, 30, 31, 32, and 50, and the pipes may be combined downstream of them. In addition, as the chlorine-containing gas, other chlorine-containing gases other than hydrogen chloride gas, chlorine gas, and boron trichloride gas may be used, and a gas supply source corresponding to other chlorine-containing gases may be connected to the gas supply device 27 .

[0036] In addition, in the substrate processing apparatus 10, a high-frequency power source 34 is connected to the inductive coupling antenna 24 via a matching device 33. The high-frequency power source 34 supplies, for example, 13.56 MHz high-frequency power for plasma generation to the inductive coupling antenna 24. As a result, eddy currents swirling from the upper surface (the inductive coupling antenna 24 side) to the lower surface (the processing space U side) are induced in each of the divided pieces 21 constituting the metal window 12, and an electromagnetic field is formed in the processing space U by the eddy currents. Then, the electromagnetic field is applied to the processing gas supplied to the processing space U, so that the processing gas is excited and a high-density plasma is generated from the processing gas.

[0037] In addition, in the substrate processing apparatus 10 , a dielectric window made of a dielectric may be used instead of the metal window 12 . In this case, the electromagnetic field formed by the inductive coupling antenna 24 passes through the dielectric window and is directly applied to the processing gas.

[0038] Furthermore, a high frequency power supply 36 is connected to the mounting table 13 via a matching device 35. The high frequency power supply 36 supplies, for example, 3.2 MHz high frequency power for bias to the mounting table 13. Thus, various ions in the high density plasma of the processing space U can be attracted to the substrate G, and various plasma processes can be performed on the substrate G.

[0039] In addition, in the substrate processing apparatus 10, each segment 21 is electrically insulated from other segments 21 by the partition member 22, so that eddy currents are independently induced in each segment 21 of the metal window 12, and induced electric fields are independently generated in the regions facing each segment 21. Therefore, by changing the size and configuration of each segment 21, the distribution of the electromagnetic field generated in the processing space U can be controlled. As a result, the degree of plasma processing performed on the substrate G (for example, the etching rate in etching processing, etc.) can be locally controlled.

[0040] Furthermore, in the substrate processing apparatus 10, a temperature control flow path 37 is formed inside each of the divided pieces 21. A cooling medium or a heating medium is introduced into the temperature control flow path 37 to adjust the temperature of each of the divided pieces 21. The degree of a certain plasma processing is also affected by temperature, and therefore, the degree of plasma processing applied to the substrate G can be locally controlled by independently adjusting the temperature of each of the divided pieces 21.

[0041] In addition, in the substrate processing apparatus 10, an exhaust port 38 is formed on the bottom surface of the processing chamber 11. An exhaust device 39 such as a turbomolecular pump or a dry pump is connected to the exhaust port 38. When performing various plasma processes, the exhaust device 39 maintains the processing space U at a predetermined pressure lower than the atmospheric pressure. In addition, a control unit 40 is provided for the substrate processing apparatus 10. The control unit 40 is composed of a computer having at least a CPU and a memory, and a process (program) for performing various plasma processes including the copper layer etching process described later is recorded in the memory.

[0042] Figure 3 1 is a process diagram for explaining the reaction used in the etching method of the copper layer of this embodiment. Figure 3 , an enlarged cross section of a part of the substrate G is shown. In addition, a thin film copper layer 41 is formed on the surface of the substrate G, and a hard mask 42 is formed on the copper layer 41. The hard mask 42 is formed in a pattern that exposes a part of the copper layer 41. In addition, the hard mask 42 is composed of, for example, a silicon oxide film. The etching method of the copper layer of this embodiment is performed in the substrate processing device 10.

[0043] In the copper layer etching method of this embodiment, first, as a primary reaction, copper (II) chloride (first product) is generated from a part of the copper layer 41 (first step). Specifically, an electromagnetic field is applied to a first processing gas containing a chlorine-containing gas to generate chlorine radicals (indicated by "Cl" in the figure) (first plasma), and the chlorine radicals react with the exposed copper layer 41 ( Figure 3 At this time, first, copper (I) chloride (CuCl) 43 ( Figure 3 Then, if the first processing gas continues to generate chlorine radicals, the further generated chlorine radicals react with copper (I) chloride 43 to generate copper (II) chloride (CuCl2) 44 ( Figure 3 (C)).

[0044] The chemical reaction formulas for generating copper (I) chloride and copper (II) chloride in this primary reaction are represented by the following formulas (1) and (2).

[0045] Cu+Cl→CuCl…(1)

[0046] CuCl + Cl → CuCl2… (2)

[0047] The chlorine-containing gas of the first processing gas used for the primary reaction is composed of a single substance of hydrogen chloride gas, a single substance of chlorine gas, a single substance of boron trichloride gas, or a mixed gas of hydrogen chloride gas, chlorine gas and boron trichloride gas, or a mixed gas of any two of hydrogen chloride gas, chlorine gas and boron trichloride gas. In addition, the first processing gas does not contain hydrogen gas, but may contain argon gas in order to adjust the flow rate.

[0048] Next, as a secondary reaction, a trimer (Cu3Cl3) of copper (I) chloride is generated from copper (II) chloride 44 (second product) (second step). Specifically, an electromagnetic field is applied to the second processing gas containing hydrogen gas to generate hydrogen radicals (indicated by "H" in the figure) (second plasma), which react with copper (II) chloride 44 ( Figure 3 (D)). At this time, copper (II) chloride 44 generates a trimer of copper (I) chloride and hydrogen chloride. Since the vapor pressure of copper (I) chloride trimer and hydrogen chloride is high, they are directly vaporized and scattered. As a result, the exposed copper layer 41 is removed (etched) ( Figure 3 (E)).

[0049] The chemical reaction formulas for generating the trimer of copper (I) chloride and hydrogen chloride in the secondary reaction are represented by the following formulas (3) and (4).

[0050]

Formula 1

[0051] 3CuCl2+3H→Cu3Cl3↑+3HCl↑…(3)

[0052]

[0053] The second processing gas for the secondary reaction is composed of a single substance of hydrogen and does not contain chlorine-containing gases, such as chlorine, hydrogen chloride gas, and boron trichloride gas. In addition, the second processing gas does not contain only the chlorine-containing gas contained in the first processing gas, but also does not contain other chlorine-containing gases not contained in the first processing gas. Other chlorine-containing gases can be gases among chlorine, hydrogen chloride gas, and boron trichloride gas that are not contained in the first processing gas, or can be chlorine-containing gases other than chlorine, hydrogen chloride gas, and boron trichloride gas. However, the second processing gas can also contain argon gas to adjust the flow rate.

[0054] Figure 4 2 is a flowchart showing the etching method of the copper layer according to the present embodiment. In the etching method of the copper layer, the control unit 40 executes according to a predetermined recipe.

[0055] Initially, the control unit 40 performs a primary reaction (step S41). In the primary reaction, first, the gas supply device 27 controls the flow rate of each gas flowing in from the hydrogen chloride gas supply source 29, the chlorine gas supply source 30, the boron trichloride gas supply source 50, and the argon gas supply source 32, and mixes each gas in the gas supply device 27 to generate a first processing gas.

[0056] Next, the first processing gas is supplied to the processing space U from the air holes 25 of each segment 21, and high-frequency power for plasma generation is supplied to the inductively coupled antenna 24 from the high-frequency power supply 34. At this time, the electromagnetic field formed in the processing space U is applied to the first processing gas to generate chlorine radicals. The chlorine radicals react with the exposed copper layer 41 in the substrate G that is not covered by the hard mask 42, and copper (I) chloride 43 is generated from the copper layer 41. Then, the chlorine radicals continue to be generated, and copper (II) chloride 44 is generated from the copper (I) chloride 43 using the generated chlorine radicals.

[0057] After that, the supply of the first process gas to the process space U is stopped to interrupt the generation of chlorine radicals, interrupt the material change from the copper layer 41 to the copper (II) chloride 44, and thus temporarily terminate the primary reaction. At this time, the duration from the start of the supply of the first process gas to the process space U to the stop of the supply is set to be shorter than the time required for the exposed copper layer 41 to be completely changed into the copper (II) chloride 44. In addition, the duration from the start of the supply of the first process gas to the stop of the supply is set based on the results of a previous experiment, etc., or is determined in real time by observing the plasma emission intensity, etc.

[0058] In addition, in the primary reaction, the substrate G is heated by the heat input of the plasma and the reaction heat, and a part of the copper chloride (I) and copper chloride (II) may be vaporized. Therefore, in the present embodiment, the vaporization of copper chloride (I) and copper chloride (II) is suppressed by cooling the substrate G in the primary reaction. Specifically, the temperature of the substrate G is maintained below 50°C using the cooler of the mounting table 13. At this time, the set temperature of the refrigerant of the cooler is set to below -40°C.

[0059] Next, the control unit 40 executes the secondary reaction (step S42 ). In the secondary reaction, first, the gas supply device 27 controls the flow rates of the gases flowing in from the hydrogen gas supply source 31 and the argon gas supply source 32 , and mixes the gases in the gas supply device 27 to generate a second process gas.

[0060] Next, the second processing gas is supplied to the processing space U from the air holes 25 of each partition 21. At this time, the electromagnetic field formed in the processing space U is applied to the second processing gas to generate hydrogen radicals. The hydrogen radicals react with the copper (II) chloride 44, and the copper (II) chloride 44 generates a trimer of copper (I) chloride and hydrogen chloride. When the trimer of copper (I) chloride and hydrogen chloride are generated, they are directly vaporized and scattered. As a result, the copper (II) chloride 44 generated in the first reaction is removed, and the unreacted copper layer 41 is newly exposed.

[0061] After that, the supply of the second process gas to the processing space U is stopped to interrupt the generation of hydrogen radicals. At this time, the duration from the start of the supply of the second process gas to the processing space U to the stop of the supply is set to be longer than the time required to completely remove the copper (II) chloride 44 generated in the primary reaction. In addition, the duration from the start of the supply of the second process gas to the stop of the supply is also set based on the results of a previous experiment, etc., or is determined in real time by observing the plasma emission intensity, etc.

[0062] In addition, even in an environment where hydrogen radicals exist, the substrate G is heated by the heat input of the plasma and the heat of reaction, and part of the copper chloride (I) and copper chloride (II) may be vaporized. Therefore, during the secondary reaction, the substrate G is also cooled. Specifically, during the secondary reaction, the temperature of the substrate G is maintained below 50° C. using the cooler of the mounting table 13. At this time, the set temperature of the refrigerant of the cooler is set to below -40° C.

[0063] Next, it is determined whether the primary reaction and the secondary reaction are repeated alternately for a set number of times (predetermined number of times) or more (step S43). In the case where the primary reaction and the secondary reaction are repeated alternately for a set number of times or more, the etching method is terminated. In the case where the primary reaction and the secondary reaction are not repeated alternately for a set number of times or more, the method returns to step S41. In addition, the set number of times of step S43 is set to be more than the number of repetitions of the primary reaction and the secondary reaction required to completely remove the exposed copper layer 41. The set number of times is set based on the results of previous experiments, etc.

[0064] According to the present embodiment, in order to etch the exposed copper layer 41, a primary reaction using a first processing gas containing chlorine gas and a secondary reaction using a second processing gas containing hydrogen gas and not containing hydrogen chloride gas are repeatedly performed. That is, when etching the copper layer 41, a period in which no hydrogen chloride gas exists in the processing space U of the processing chamber 11 (a period in which the secondary reaction is performed) occurs, and hydrogen chloride gas does not exist for a long time in the processing space U. Thus, the shape of the hard mask can be prevented from being deformed by the hydrogen chloride gas, and the reduction in shape controllability when forming a desired shape, such as a groove or a taper, on the copper layer can be suppressed.

[0065] In addition, in the present embodiment, the primary reaction and the secondary reaction are not performed simultaneously, but are performed independently. Thus, the generation conditions of copper chloride (II) in the primary reaction can be optimized, and the generation conditions of the trimer of copper chloride (I) in the secondary reaction can be optimized. As a result, it is possible to promote the generation of copper chloride (II) and promote the generation of the trimer of copper chloride (I), thereby suppressing the reduction of the etching rate of the exposed copper layer 41.

[0066] Furthermore, in the present embodiment, an ECR type plasma processing apparatus is not used, but a substrate processing apparatus 10 which is an inductively coupled type plasma processing apparatus is used. Although an ECR type plasma processing apparatus can generate high-density plasma, it is difficult to maintain a constant resonance region of microwaves and magnetic fields over a large area, and therefore, high-density plasma cannot be generated from a processing gas over a large area. Therefore, in order to perform plasma processing on a substrate G for a large display device using an ECR type plasma processing apparatus, a scanning mechanism or the like for scanning the surface of the substrate G using a plasma generation source is required, and the plasma processing apparatus cannot be avoided from being large-scaled and complicated.

[0067] On the other hand, as described above, the inductively coupled plasma processing apparatus can form plasma uniformly over a large area by using a flat antenna, so that high-density plasma can be generated from the processing gas over a large area. Therefore, when performing plasma processing on the substrate G for a large display device, a scanning mechanism like that of the ECR type plasma processing apparatus is not required. Therefore, in this embodiment, the enlargement and complexity of the substrate processing apparatus 10 can be avoided.

[0068] Next, the experimental results are described. First, the applicant prepared the following test piece 45: a film with a thickness of A copper layer 41 is formed, and a hard mask 42 ( Figure 5 In addition, Figure 5 (A)~ Figure 5 (C) is a partially enlarged cross-sectional view schematically showing a partial SEM image of a cross section of the test piece 45 .

[0069] In addition, even if the processing gas is only hydrogen chloride gas, when the processing gas is excited, hydrogen radicals are generated to a certain extent while chlorine radicals are generated, so although the etching rate is low, copper is still etched. Therefore, as a comparative example for comparing the degree of consumption of the hard mask 42, the applicant continuously supplies a processing gas containing hydrogen chloride gas and not containing hydrogen gas to the processing space U in the substrate processing device 10, and etches the copper layer 41 of the test piece 45. That is, the processing step based on hydrogen gas is not performed, and the copper layer 41 is etched only by the processing step based on hydrogen chloride gas.

[0070] In the comparative example, as the processing conditions, the pressure of the processing space U is set to 1 mTorr, the output of the high-frequency power for plasma generation (source power) is set to 4 kW, and the output of the high-frequency power for bias (bias power) is set to 4 kW. In addition, the flow rate of the hydrogen chloride gas is set to 36 sccm, and in order to maintain the temperature of the substrate G below 50°C, the set temperature of the refrigerant of the cooler of the mounting table 13 is set to below -40°C. And, the processing gas is continuously supplied to the processing space U for 300 seconds. That is, the etching of the copper layer 41 is performed only by the processing step based on hydrogen chloride for 300 seconds.

[0071] In addition, as an example of this embodiment, the applicant performs in the substrate processing device 10 Figure 4 The copper layer 41 of the test piece 45 was etched using the etching method for the copper layer.

[0072] The processing conditions of the embodiment are substantially the same as those of the comparative example. However, although the output of the source power and the output of the bias power are both set to 4 kW in the same manner as in the comparative example, the processing conditions of the embodiment are different from those of the comparative example in that the processing step based on hydrogen chloride (primary reaction) and the processing step based on hydrogen (secondary reaction) are repeated alternately. In addition, in the primary reaction, a single substance of hydrogen chloride gas is used as the chlorine-containing gas of the first processing gas, and its flow rate is set to 36 sccm. In addition, in the secondary reaction, the flow rate of hydrogen gas of the second processing gas is set to 150 sccm. Furthermore, the primary reaction and the secondary reaction are repeated alternately for a predetermined number of times within 300 seconds.

[0073] In the comparative example, Figure 5 As shown in (B), although the copper layer 41 is reduced, the shape of the hard mask 42 is deformed. As a result, the shape of the remaining portion of the copper layer 41 does not reflect the shape of the hard mask 42 before etching (refer to Figure 5 The reason for this is that, in the comparative example, since the processing gas containing hydrogen chloride gas is continuously supplied to the processing space U, the hard mask 42 is corroded by the hydrogen chloride gas for a long time. In addition, as a result of the deformation of the shape of the hard mask 42, the portion of the copper layer 41 that should have been covered by the hard mask 42 is chlorinated and swelled, and remains as a swollen layer 46.

[0074] On the other hand, in an embodiment, Figure 5 As shown in (C), the copper layer 41 is reduced while the hard mask 42 maintains its shape, and the shape of the remaining portion of the copper layer 41 also reflects the shape of the hard mask 42 before etching. This is considered to be because the hydrogen chloride gas does not exist in the processing space U for a long time by alternately repeating the primary reaction and the secondary reaction in the embodiment, and the hard mask 42 is not corroded by the hydrogen chloride gas.

[0075] The etching rate of the hard mask 42 in the comparative example is 2.2 times higher than that in the example. This result also confirms that the hard mask 42 is etched by the hydrogen chloride gas in the comparative example, but not in the example.

[0076] From the above, it can be confirmed that by performing the copper layer etching method of this embodiment and repeating the primary reaction and the secondary reaction alternately, the shape deformation of the hard mask 42 can be suppressed, and the reduction in shape controllability when forming the copper layer 41 into a desired shape can be suppressed.

[0077] In addition, in the comparative example and the embodiment, although the processing conditions are substantially the same, the etching rate of the copper layer 41 of the comparative example is 0.5 times the etching rate of the copper layer 41 of the embodiment. It is believed that the reason is that in the comparative example, since only hydrogen chloride gas is used, chlorine radicals are present in large quantities relative to hydrogen radicals. That is, it is believed that this is due to the high presence of chlorine radicals relative to hydrogen radicals. Specifically, it is believed that the reason is that if chlorine radicals are present in large quantities relative to hydrogen radicals, chlorine radicals will hinder hydrogen radicals from contacting with copper chloride (II) 44, and hydrogen radicals are insufficient for making copper chloride (II) 44 become trimers of copper chloride (I). This is because, as a result of the obstruction of contact and the deficiency of hydrogen radicals, the trimer of copper chloride (I) generated by copper chloride (II) 44 is suppressed.

[0078] In addition, if deposits are generated inside the processing chamber 11, it will cause problems such as the formation of particles, so the generation of deposits must be suppressed as much as possible. For example, in a primary reaction, even when hydrogen chloride gas is used as the chlorine-containing gas, the generation of deposits can be suppressed by reducing the output of bias power, but the etching rate will also decrease at the same time. However, the applicant has found that when boron trichloride gas is used as the chlorine-containing gas, the generation of deposits can be suppressed while maintaining a high etching rate compared to the case of using hydrogen chloride gas.

[0079] First, as a standard HCl condition, the applicant used hydrogen chloride gas, set the output of the source power and the output of the bias power to 4 kW, and set the gas flow rate to 36 sccm. Figure 4 The etching method of the copper layer was used to etch the copper layer. The deposition ratio obtained by dividing the amount of the deposit generated at this time by the etching amount of the copper layer was used as the standard deposition ratio, and the etching rate at this time was used as the standard etching rate. The number of repetitions of the primary reaction and the secondary reaction under the standard HCl condition was 5 times, and the setting temperature of the cooler of the mounting table 13 was -40°C.

[0080] Next, as low bias HCl conditions, the applicant set the output of the source power to 6kW, the output of the bias power to 0kW, the number of repetitions of the primary reaction and the secondary reaction to 9 times, and the other conditions to be the same as the standard HCl conditions, and then etched the copper layer. In addition, under the low bias HCl conditions, the deposition ratio and etching rate obtained by dividing the amount of deposits produced by the etching amount of the copper layer were also obtained. As a result, it can be seen that under the low bias HCl conditions, the deposition ratio was reduced by 25% relative to the standard deposition ratio, which was improved, but the etching rate was also greatly reduced relative to the standard etching rate, reduced by 52%.

[0081] Under low bias HCl conditions, the output of source power and the number of repetitions of primary and secondary reactions are increased relative to standard HCl conditions, so the deposition amount and etching rate are expected to increase. However, contrary to expectations, under low bias HCl conditions, both the deposition amount and etching rate are reduced, which is believed to be due to the greater effect of setting the bias power to 0 kW.

[0082] On the other hand, under low bias HCl conditions, the etching rate drops to about half of the standard HCl conditions, so it is necessary to improve the etching rate. Therefore, as a low bias BCl3 condition, the applicant uses boron trichloride gas as a chlorine-containing gas, sets other conditions to be the same as the low bias HCl conditions, and etches the copper layer on this basis. In addition, under low bias BCl3 conditions, the deposition ratio and etching rate obtained by dividing the amount of deposits produced by the etching amount of the copper layer are also obtained. The result can be confirmed that under low bias BCl3 conditions, the deposition ratio becomes a value equal to that of the low bias HCl conditions, which is 25% lower than the standard deposition ratio, and the etching rate becomes a value increased by 72% relative to the low bias HCl conditions. That is, under low bias BCl3 conditions, the deposition ratio is the same as the low bias HCl conditions, and the etching rate of the copper layer is lower than the standard HCl conditions, but it becomes a value more than 70% higher than the low bias HCl conditions.

[0083] As described above, it is understood that the use of boron trichloride gas as the chlorine-containing gas has the effect of suppressing a decrease in the etching rate and also suppressing the generation of deposits.

[0084] In addition, in this embodiment, the case where the copper layer is etched by first performing the first step, then performing the second step, and then repeating the first step and the second step is described, but the third step may be additionally performed before performing the first step. The third step is a step in which the second processing gas is supplied and performed under the same processing conditions as the second step. That is, in this case, after the substrate is treated with hydrogen by performing the third step, the first step is performed, then the second step is performed, and then the first step and the second step are repeated. By performing the third step initially in this way, the surface of the copper layer is modified by hydrogen to promote the primary reaction and the secondary reaction.

[0085] As mentioned above, the etching method of the copper layer which is a preferred embodiment of the present disclosure has been described, but the embodiment of the present disclosure is not limited to the above-mentioned embodiment and the like, and various modifications and improvements can be made within the scope of the present disclosure.

Claims

1. A method for etching a copper layer, which is a method for etching a copper layer formed on a substrate disposed inside a processing chamber of a substrate processing device, wherein: The copper layer etching method has the following features: In a first step, a first processing gas containing at least a chlorine-containing gas and no hydrogen gas is supplied into the processing chamber, and a first product is generated from the copper layer using a first plasma generated by the first processing gas; and In a second step, a second process gas containing at least the hydrogen gas and excluding the chlorine-containing gas and other chlorine-containing gases is supplied into the processing chamber, and a second product is generated from the first product using a second plasma generated by the second process gas. The first step and the second step are repeatedly performed alternately a predetermined number of times.

2. The method for etching a copper layer according to claim 1, wherein: The chlorine-containing gas is a single substance of hydrogen chloride gas, a single substance of chlorine gas, a single substance of boron trichloride gas, or a mixed gas of the hydrogen chloride gas, the chlorine gas and the boron trichloride gas, or a mixed gas of any two of the hydrogen chloride gas, the chlorine gas and the boron trichloride gas.

3. The method for etching a copper layer according to claim 1, wherein: In the first step and the second step, the temperature of the substrate is maintained at 50° C. or less.

4. The method for etching a copper layer according to claim 1, wherein: The substrate processing device comprises: a mounting table on which the substrate is mounted; a metal window facing the mounting table and including a plurality of split pieces; and an inductive coupling antenna facing the mounting table across the metal window and including a plurality of antenna segments. In the first step, the first plasma is generated by applying an electromagnetic field from the inductively coupled antenna to the first process gas through the metal window. In the second step, the second plasma is generated by applying an electromagnetic field from the inductive coupling antenna to the second process gas through the metal window.

5. The method for etching a copper layer according to claim 1, wherein: A third step is performed before the first step, in which the second process gas is supplied into the processing chamber and the substrate is processed using the second plasma generated from the second process gas.

6. A substrate processing device for etching a copper layer formed on a substrate, wherein: The substrate processing device comprises: a mounting table on which the substrate is mounted; a processing chamber having the mounting table therein; a metal window, which is opposite to the mounting platform and includes a plurality of split pieces; an inductive coupling antenna, which is opposite to the mounting platform across the metal window and includes a plurality of antenna segments; and Control Department, The control unit executes a copper layer etching method, which includes: a first step of supplying a first processing gas containing at least a chlorine-containing gas and not containing hydrogen into the processing chamber, and generating a first product from the copper layer using a first plasma generated by the first processing gas; and a second step of supplying a second processing gas containing at least the hydrogen and not containing the chlorine-containing gas and other chlorine-containing gases into the processing chamber, and generating a second product from the first product using a second plasma generated by the second processing gas. In the copper layer etching method, the first step and the second step are repeatedly performed alternately a predetermined number of times.

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