Etching method of copper layer and substrate processing apparatus

Abstract

To suppress deterioration of an etch rate of a copper layer while suppressing deterioration of a shape control property when forming a desired shape to the copper layer.SOLUTION: When etching a copper layer 41 with a thin film formed onto a front surface of a substrate G arranged into an internal part of a processing chamber 11 of a substrate processing apparatus 10, a copper chloride (II) 44 is generated from the copper layer 41 by a chlorine radical generated from a first processing gas containing a chlorine-containing gas and excluding a hydrogen gas in a primary reaction, and generates a trimer of a copper chloride (I) from the copper chloride (II) 44 by a hydrogen radical generated by a second processing gas containing the hydrogen gas and excluding the other chlorine-containing gas and the chlorine-containing gas in a secondary reaction. The primary and secondary reactions are alternately and repeatedly executed at a predetermined number of times.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present disclosure relates to a method for etching a copper layer and a substrate processing apparatus. [Background technology]

[0002] As display devices become larger and have higher resolution, copper (Cu) is used as a low-resistance wiring material in display elements, and wet etching is usually used to form copper wiring, and the copper layer on the substrate is etched to follow a predetermined pattern. However, with the recent trend toward finer patterns and higher densities, it can be difficult to control the shape using wet processes, so accurate patterning using dry etching is required.

[0003] Conventionally, a copper dry etching method uses chlorine plasma generated from a chlorine (Cl)-based gas. 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. Since the copper chloride generated at this time has a low vapor pressure, heating with a lamp or the like is required for vaporization (see, for example, Patent Document 1).

[0004] On the other hand, OLEDs (Organic Light Emitting Diodes) as display elements used in recent display devices have a light-emitting layer formed of an organic material. Therefore, a method for etching a copper layer that does not require heating is required in the manufacturing process of a display element. As such an etching method, a method is known in which a process gas containing hydrogen chloride (HCl) gas and hydrogen (H2) gas is used to generate chlorine radicals and hydrogen radicals from the process gas in an ECR (Electron Cyclotron Resonance) type plasma processing device. In this etching method, copper chloride (II) (CuCl2) is generated from the copper layer by chlorine radicals, and furthermore, a copper chloride (I) (CuCl) trimer (Cu3Cl3) is generated from the copper chloride (II) by hydrogen radicals. And, since the copper chloride (I) trimer has a high vapor pressure, it vaporizes almost at the same time as it is generated. This makes it possible to etch the copper layer without the need for heating (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 01-160035 [Patent Document 2] US Patent Application Publication No. 2019 / 0103287 Summary of the Invention [Problem to be solved by the invention]

[0006] The technology according to the present disclosure suppresses a decrease in the etch rate of the copper layer while suppressing a decrease in shape controllability when forming a desired shape in the copper layer. [Means for solving the problem]

[0007] One aspect of the technology disclosed herein is a method for etching a copper layer formed on a substrate disposed inside a processing chamber of a substrate processing apparatus, comprising: a first step of supplying a first processing gas containing at least a chlorine-containing gas and not containing hydrogen gas into the processing chamber, and generating a first product from the copper layer by a first plasma generated from 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 by a second plasma generated from the second processing gas, wherein the first step and the second step are alternately repeated a predetermined number of times. Effect of the Invention

[0008] According to the technique of the present disclosure, it is possible to suppress a decrease in the etching rate of the copper layer while suppressing a decrease in shape controllability when forming a desired shape in the copper layer. [Brief description of the drawings]

[0009] [Figure 1] 1 is a cross-sectional view illustrating a schematic configuration of a substrate processing apparatus according to an embodiment of the technology disclosed herein. [Diagram 2] 2 is a diagram showing a metal window provided in the substrate processing apparatus of FIG. 1, as viewed from the processing space side. FIG. [Diagram 3] FIG. 2 is a process diagram for explaining reactions used in a copper layer etching method according to an embodiment of the technology disclosed herein. [Figure 4] 1 is a flowchart showing a method for etching a copper layer according to an embodiment of the technology disclosed herein. [Diagram 5] 1A to 1C are enlarged partial cross-sectional views each showing a schematic partial SEM image of the cross section of a test piece of a comparative example and an example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] In the technology described in the above-mentioned Patent Document 2, when the generated copper chloride (II) is vaporized by heat, the copper chloride (II) resolidifies and accumulates in a place with a low temperature inside the processing chamber, which causes the generation of particles. For this reason, the temperature rise of the copper chloride (II) is suppressed by utilizing the heat absorption when the copper chloride (I) trimer is generated, and the vaporization of the copper chloride (II) is suppressed. Therefore, it is necessary to generate the copper chloride (II) and the copper chloride (I) trimer simultaneously. In response to this, the chlorine radicals used to generate the copper chloride (II) and the hydrogen radicals used to generate the copper chloride (I) trimer are simultaneously present inside the processing chamber of the ECR plasma processing apparatus. As a result, the hydrogen chloride gas, which is the source of the chlorine radicals, is present inside the processing chamber while the copper layer is being etched.

[0011] However, hydrogen chloride gas corrodes a hard mask used as an etching mask, and therefore, if hydrogen chloride gas is present inside a processing chamber for a long period of time, the hydrogen chloride gas will cause the hard mask to lose its shape, resulting in reduced shape controllability when forming a desired shape in a copper layer.

[0012] In addition, since the copper chloride (II) and the copper chloride (I) trimer are generated simultaneously, it is difficult to optimize the conditions for generating copper chloride (II) and the conditions for generating the copper chloride (I) trimer, and the promotion of the generation of copper chloride (II) and the promotion of the generation of the copper chloride (I) trimer are not compatible. As a result, the etching rate of the copper layer is reduced, and the etching time required to form a desired shape on the copper layer is extended, for example, 120 to 300 seconds are required to perform the etching.

[0013] In contrast, the technique disclosed herein suppresses a decrease in the etch rate of the copper layer while suppressing a decrease in shape controllability when forming a desired shape in the copper layer.

[0014] Hereinafter, an embodiment of the technology according to the present disclosure will be described with reference to the drawings. Fig. 1 is a cross-sectional view showing a schematic configuration of a substrate processing apparatus according to the present embodiment, and Fig. 2 is a view showing a metal window provided in the substrate processing apparatus 10 of Fig. 1 as viewed from the processing space side.

[0015] The substrate processing apparatus 10 in Fig. 1 is an inductively coupled plasma processing apparatus. The substrate processing apparatus 10 etches a thin copper layer formed on a surface of a rectangular substrate, for example, a glass substrate G (hereinafter referred to as "substrate G") for a flat panel display (FPD), by using high-density plasma generated from a processing gas.

[0016] The substrate processing apparatus 10 includes a rectangular cylindrical processing chamber 11 made of a conductive material, for example, aluminum or an alloy containing aluminum. The processing chamber 11 accommodates a substrate G and is electrically grounded. The upper part of the processing chamber 11 is airtightly sealed by a metal window 12. A mounting table 13 for mounting the substrate G thereon is disposed at the lower part inside the processing chamber 11, and the mounting table 13 faces the metal window 12. 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, high-density plasma is generated from a processing gas, as described below.

[0017] An electrostatic chuck (not shown) is provided on the upper surface of the mounting table 13, and the substrate G placed on the mounting table 13 is attracted and held to the mounting table 13 by the electrostatic chuck. A temperature control mechanism, for example, a chiller using a refrigerant or a heat transfer gas supply mechanism (neither of which are shown), is provided inside the mounting table 13 to control the temperature of the mounting table 13 and thereby control the temperature of the substrate G placed thereon. The mounting table 13 is installed on the bottom surface of the processing chamber 11 via an insulating frame 14.

[0018] A metal frame 15 is provided at the upper end of the sidewall of the processing chamber 11, and a sidewall portion 16 is provided on the upper surface of the metal frame 15. The sidewall portion 16 supports a top plate 17 and is electrically grounded, and the top plate 17 covers the metal window 12 from above. A seal member 18 such as an O-ring is provided between the sidewall of the processing chamber 11 and the metal frame 15 to keep the processing space U airtight. In addition, a load / unload port 19 for loading / unloading the substrate G into / from the processing space U and a gate valve 20 for opening / closing the load / unload port 19 are provided on the sidewall of the processing chamber 11.

[0019] As shown in FIG. 2, the metal window 12 has a rectangular shape and is divided into a plurality of segments 21. In this embodiment, the metal window 12 is divided into 24 segments 21, but the number of segments 21 is not limited to 24 and is changed depending on the size of the metal window 12, the controllability of the plasma distribution, and the like. Each segment 21 is made of, for example, a non-magnetic and conductive metal, aluminum, or an alloy containing aluminum. In the metal window 12, a partition member 22 made of an insulator is disposed between each of the adjacent segments 21. The partition member 22 separates the adjacent segments 21 and electrically insulates them from each other. It is preferable that the partition member 22 is made of a single piece, considering that the processing space U and the antenna chamber 23 described later are kept airtight across the metal window 12.

[0020] 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 disposed so as to face the substrate G placed on the mounting table 13 via the metal window 12. The inductive coupling antenna 24 is disposed at a distance from the metal window 12 via, for example, a spacer made of an insulator (not shown).

[0021] The inductive coupling antenna 24 is composed of a plurality of antenna segments, and the antenna segments are arranged in the circumferential direction of the metal window 12 to form a ring-shaped antenna as a whole. Since the antenna segments are arranged on the same plane, the inductive coupling antenna 24 has a flat antenna shape. Depending on the processing content, each antenna segment may be arranged across each divided piece 21, or may be arranged so as to fit within the projection range of the corresponding divided piece 21 without spanning across each divided piece 21. The inductive coupling antenna 24 may be composed of a single antenna wire or a bundle of multiple antenna wires, and in this case, the inductive coupling antenna 24 spans the areas facing each divided piece 21 and is arranged in a spiral shape along the circumferential direction of the metal window 12. Furthermore, a plurality of inductive coupling antennas 24 may be arranged concentrically.

[0022] 1, each divided piece 21 has a number of gas holes 25 formed therein, which open toward the processing space U. A gas supply pipe 26 is connected to each divided piece 21, and the gas supply pipe 26 is connected to a gas supply device 27. A gas diffusion chamber 28 is formed inside each divided piece 21, and the gas supply device 27 introduces 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 from each gas hole 25 to the processing space U. Therefore, each divided piece 21 has a gas shower structure consisting of each gas hole 25 and the gas diffusion chamber 28.

[0023] The gas supply device 27 is connected to a hydrogen chloride gas supply source 29 that supplies hydrogen chloride gas as a chlorine-containing gas, a chlorine gas supply source 30 that supplies chlorine (Cl2) gas as a chlorine-containing gas, and a boron trichloride gas supply source 50 that supplies boron trichloride (BCl3) gas as a chlorine-containing gas. As the chlorine-containing gas, only one or two of hydrogen chloride gas, chlorine gas, and boron trichloride gas may be used, and only one or two of the hydrogen chloride gas supply source 29, the chlorine gas supply source 30, and the boron trichloride gas supply source 50 may be connected to the gas supply device 27 accordingly. Furthermore, the gas supply device 27 is connected to a hydrogen gas supply source 31 that supplies hydrogen gas, and an argon gas supply source 32 that supplies argon (Ar) gas as a diluent gas. The diluent gas is not limited to argon gas as long as it has a function of diluting the gases supplied together. The gas supply device 27 includes pipes connected to the gas supply sources 29, 30, 31, 32, and 50, and flow rate control devices (not shown) and valves (not shown) for each gas arranged on the pipes. The pipes are connected downstream of the corresponding flow rate control devices and valves, so that the gases join together in the gas supply device 27. The gas supply device 27 uses the flow rate control devices to control the flow rates of the gases flowing from the gas supply sources 29, 30, 31, 32, and 50 to the gas supply device 27 based on instructions from the control unit 40, which will be described later, and further joins the gases to generate a process gas. Instead of providing the gas supply device 27 to join the gases, flow rate 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 joined downstream of the flow rate control devices and valves. In addition, as the chlorine-containing gas, a chlorine-containing gas other than hydrogen chloride gas, chlorine gas, and boron trichloride gas may be used, and further, a gas supply source corresponding to the other chlorine-containing gas may be connected to the gas supply device 27.

[0024] In the substrate processing apparatus 10, a high-frequency power supply 34 is connected to the inductively coupled antenna 24 via a matching box 33. The high-frequency power supply 34 supplies high-frequency power for generating plasma, for example, 13.56 MHz, to the inductively coupled antenna 24. As a result, in each of the divided pieces 21 constituting the metal window 12, an eddy current is induced circulating from the upper surface (the inductively coupled antenna 24 side) to the lower surface (the processing space U side), and an electromagnetic field is formed in the processing space U by this eddy current. Then, when this electromagnetic field is applied to the processing gas supplied to the processing space U, the processing gas is excited and high-density plasma is generated from the processing gas.

[0025] In addition, in the substrate processing apparatus 10, a dielectric window made of a dielectric material 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 applied directly to the processing gas.

[0026] Furthermore, a high frequency power supply 36 is connected to the mounting table 13 via a matching box 35. The high frequency power supply 36 supplies, for example, a high frequency bias power of 3.2 MHz to the mounting table 13. This allows various ions in the high density plasma in the processing space U to be attracted to the substrate G, and various plasma processes can be performed on the substrate G.

[0027] Furthermore, in the substrate processing apparatus 10, each divided piece 21 is electrically insulated from the other divided pieces 21 by the partition members 22, so that eddy currents are induced individually in each divided piece 21 of the metal window 12, and an electromagnetic field is generated individually in the area facing each divided piece 21. Therefore, by changing the size and arrangement of each divided piece 21, it is possible to control the distribution of the electromagnetic field generated in the processing space U. As a result, it is possible to locally control the degree of plasma processing performed on the substrate G (for example, the etch rate in an etching process, etc.).

[0028] Furthermore, in the substrate processing apparatus 10, a temperature control flow path 37 is formed inside each divided piece 21. A cooling medium or a heating medium is introduced into the temperature control flow path 37 to adjust the temperature of each divided piece 21. Since the degree of some plasma processing is also influenced by temperature, the degree of plasma processing applied to the substrate G can also be locally controlled by individually adjusting the temperature of each divided piece 21.

[0029] Furthermore, in the substrate processing apparatus 10, an exhaust port 38 is formed in the bottom surface of the processing chamber 11. An exhaust device 39 such as a turbo molecular pump or a dry pump is connected to this exhaust port 38. When performing various plasma processes, the exhaust device 39 maintains the processing space U at a predetermined pressure lower than atmospheric pressure. The substrate processing apparatus 10 is also provided with a control unit 40. The control unit 40 is composed of a computer having at least a CPU and a memory, and recipes (programs) for performing various plasma processes including a copper layer etching process described below are recorded in the memory.

[0030] Fig. 3 is a process diagram for explaining reactions used in the copper layer etching method according to this embodiment. Fig. 3 shows an enlarged cross section of a portion of a substrate G. A thin copper layer 41 is formed on the surface of the substrate G, and a hard mask 42 is formed on the copper layer 41 in a pattern that exposes a portion of the copper layer 41. The hard mask 42 is made of, for example, a silicon oxide film. The copper layer etching method according to this embodiment is performed in a substrate processing apparatus 10.

[0031] In the copper layer etching method according to the present embodiment, first, as a primary reaction, copper chloride (II) (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 are reacted with the exposed copper layer 41 (FIG. 3(A)). At this time, copper chloride (I) (CuCl) 43 is first generated as a reaction product from the copper layer 41 (FIG. 3(B)). Thereafter, when the generation of chlorine radicals from the first processing gas is continued, the generated chlorine radicals further react with the copper chloride (I) 43 to generate copper chloride (II) (CuCl2) 44 (FIG. 3(C)).

[0032] The chemical reaction equations for the production of copper(I) chloride and copper(II) chloride in this primary reaction are expressed by the following equations (1) and (2).

[0033] Cu + Cl → CuCl … (1) CuCl + Cl → CuCl2… (2)

[0034] The chlorine-containing gas of the first process gas used in the primary reaction is composed of hydrogen chloride gas alone, chlorine gas alone, boron trichloride gas alone, 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. The first process gas does not contain hydrogen gas, but may contain argon gas to adjust the flow rate.

[0035] Next, as a secondary reaction, a copper(I) chloride trimer (Cu3Cl3) (second product) is generated from copper chloride (II) 44 (second step). Specifically, an electromagnetic field is applied to a second process gas containing hydrogen gas to generate hydrogen radicals (indicated by "H" in the figure) (second plasma), which react with copper chloride (II) 44 (FIG. 3(D)). At this time, copper chloride (I) chloride trimer and hydrogen chloride are generated from copper chloride (II) 44. Then, because the copper chloride (I) trimer and hydrogen chloride have high vapor pressure, they vaporize and scatter. As a result, the exposed copper layer 41 is removed (etched) (FIG. 3(E)).

[0036] The chemical reaction equations for the production of copper(I) chloride trimer and hydrogen chloride in this secondary reaction are expressed by the following equations (3) and (4).

[0037]

number

[0038] The second process gas used in the secondary reaction is composed of hydrogen gas alone and does not contain chlorine-containing gas, such as chlorine gas, hydrogen chloride gas, or boron trichloride gas. The second process gas does not contain not only the chlorine-containing gas contained in the first process gas, but also other chlorine-containing gases not contained in the first process gas. The other chlorine-containing gas may be a gas among chlorine gas, hydrogen chloride gas, and boron trichloride gas that was not contained in the first process gas, or a chlorine-containing gas other than chlorine gas, hydrogen chloride gas, and boron trichloride gas. However, the second process gas may also contain argon gas to adjust the flow rate.

[0039] 4 is a flowchart showing a method for etching a copper layer according to the present embodiment. This method for etching a copper layer is carried out by the control unit 40 according to a predetermined recipe.

[0040] First, the control unit 40 executes a primary reaction (step S41). In the primary reaction, the gas supply device 27 controls the flow rates of the gases 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 the gases in the gas supply device 27 to generate a first process gas.

[0041] Next, the first process gas is supplied to the process space U from the gas holes 25 of each divided piece 21, and high frequency power for generating plasma is supplied from the high frequency power supply 34 to the inductively coupled antenna 24. At this time, the electromagnetic field formed in the process space U is applied to the first process gas, generating chlorine radicals. The chlorine radicals react with the exposed copper layer 41 on the substrate G that is not covered by the hard mask 42, generating copper chloride (I) 43 from the copper layer 41. The generation of chlorine radicals continues, and copper chloride (II) 44 is generated from the copper chloride (I) 43 by the generated chlorine radicals.

[0042] Thereafter, the supply of the first process gas to the processing space U is stopped to interrupt the generation of chlorine radicals, and the transformation of the copper layer 41 to copper (II) chloride 44 is interrupted, thereby temporarily terminating the primary reaction. The duration from the start of the supply of the first process gas to the processing space U to the stop of the supply is set to be shorter than the time required for all of the exposed copper layer 41 to transform to copper (II) chloride 44. 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 or the like, or is determined in real time by observing the plasma emission intensity or the like.

[0043] However, in the primary reaction, the substrate G is heated by the plasma heat input or the reaction heat, and there is a risk that some of the copper chloride (I) and copper chloride (II) will evaporate. Therefore, in this embodiment, the substrate G is cooled in the primary reaction to suppress the evaporation of the copper chloride (I) and copper chloride (II). Specifically, the temperature of the substrate G is maintained at 50°C or lower using a chiller of the mounting table 13. At this time, the set temperature of the coolant of the chiller is set to -40°C or lower.

[0044] Next, the control unit 40 executes a secondary reaction (step S42). In the secondary reaction, first, the gas supply device 27 controls the flow rate of each gas 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.

[0045] Next, the second process gas is supplied to the process space U from the gas holes 25 of each divided piece 21. At this time, the electromagnetic field formed in the process space U is applied to the second process gas, generating hydrogen radicals. These hydrogen radicals react with copper chloride (II) 44, generating copper chloride (I) trimers and hydrogen chloride from copper chloride (II) 44. Once generated, the copper chloride (I) trimers and hydrogen chloride vaporize and scatter. As a result, the copper chloride (II) 44 generated in the first reaction is removed, and the unreacted copper layer 41 is newly exposed.

[0046] Thereafter, the supply of the second process gas to the processing space U is stopped to interrupt the generation of hydrogen radicals. 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 for the copper (II) chloride 44 generated in the first reaction to be completely removed. 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 or the like, or is determined in real time by observing the plasma emission intensity or the like.

[0047] However, even in an environment where hydrogen radicals are present, the substrate G is heated by the plasma heat input or reaction heat, and there is a risk that some of the copper chloride (I) or copper chloride (II) may evaporate, so the substrate G is cooled in the secondary reaction as well. Specifically, the temperature of the substrate G is maintained at 50°C or lower using the chiller of the mounting table 13 in the secondary reaction as well. At this time, the set temperature of the coolant of the chiller is set to -40°C or lower.

[0048] Next, it is determined whether the primary reaction and the secondary reaction have been alternately repeated a set number of times (a predetermined number of times) or more (step S43). If the primary reaction and the secondary reaction have been alternately repeated a set number of times or more, the present etching method is terminated. If the primary reaction and the secondary reaction have not been alternately repeated a set number of times or more, the process returns to step S41. The set number of times in step S43 is set to be greater than the number of times the primary reaction and the secondary reaction are repeated that are necessary to completely remove the exposed copper layer 41. This set number is set based on the results of a previous experiment or the like.

[0049] According to this embodiment, a first reaction using a first process gas containing a chlorine-containing gas and a second reaction using a second process gas containing hydrogen gas but not containing hydrogen chloride gas are repeatedly performed to etch the exposed copper layer 41. That is, when etching the copper layer 41, a period (period in which the second reaction is performed) occurs in which hydrogen chloride gas is not present in the process space U of the process chamber 11, and hydrogen chloride gas does not exist in the process space U for a long period of time. This prevents the shape of the hard mask from being distorted by the hydrogen chloride gas, and suppresses deterioration of shape controllability when forming a desired shape, such as a trench or a taper, in the copper layer.

[0050] In addition, in this embodiment, the first and second reactions are not performed simultaneously, but are performed separately. This makes it possible to optimize the conditions for generating copper chloride (II) in the first reaction while optimizing the conditions for generating the trimer of copper chloride (I) in the second reaction. As a result, it is possible to simultaneously promote the generation of copper chloride (II) and the generation of the trimer of copper chloride (I), thereby suppressing a decrease in the etch rate of the exposed copper layer 41.

[0051] Furthermore, in this embodiment, the substrate processing apparatus 10 is an inductively coupled plasma processing apparatus, not an ECR plasma processing apparatus. Although the ECR plasma processing apparatus can generate high-density plasma, it is difficult to keep the resonance region between the microwave and the magnetic field constant over a large area, and therefore the high-density plasma cannot be generated over a wide area from the processing gas. Therefore, in order to perform plasma processing on the substrate G used in a large display device using the ECR plasma processing apparatus, a scanning mechanism for scanning the surface of the substrate G with a plasma generation source is required, and the plasma processing apparatus is inevitably enlarged and complicated.

[0052] On the other hand, as described above, the inductively coupled plasma processing apparatus can generate a plasma uniformly over a large area by using a flat antenna, and can generate a high-density plasma from the processing gas over a wide area. This makes it possible to eliminate the need for a scanning mechanism as in the ECR plasma processing apparatus, even when performing plasma processing on a substrate G used in a large display device. Therefore, in this embodiment, it is possible to avoid the substrate processing apparatus 10 becoming larger and more complicated.

[0053] Next, the experimental results will be described. First, the applicant prepared a test piece 45 (FIG. 5(A)) in which a copper layer 41 having a thickness of 5000 Å was formed on the surface of a substrate G, and a hard mask 42 was further formed on the copper layer 41 to expose a part of the copper layer 41. Note that FIGS. 5(A) to 5(C) are enlarged partial cross-sectional views that are schematic partial SEM images of the cross section of the test piece 45.

[0054] However, even if the processing gas is only hydrogen chloride gas, when the processing gas is excited, hydrogen radicals are generated to a certain extent along with chlorine radicals, so that copper is etched even though the etching rate is low. Therefore, as a comparative example for comparing the degree of wear of the hard mask 42, the applicant etched the copper layer 41 of the test piece 45 by continuously supplying a processing gas containing hydrogen chloride gas but not hydrogen gas to the processing space U in the substrate processing apparatus 10. That is, the copper layer 41 was etched only by the processing step using hydrogen chloride gas, without performing the processing step using hydrogen gas.

[0055] In the comparative example, the processing conditions were as follows: the pressure in the processing space U was set to 1 mTorr, the output of the high frequency power for plasma generation (source power) was set to 4 kW, and the output of the high frequency power for bias (bias power) was set to 4 kW. The flow rate of the hydrogen chloride gas was set to 36 sccm, and the set temperature of the coolant of the chiller of the mounting table 13 was set to -40°C or lower in order to maintain the temperature of the substrate G at 50°C or lower. Furthermore, the processing gas was continuously supplied to the processing space U for 300 seconds. That is, the copper layer 41 was etched only by the processing step using hydrogen chloride for 300 seconds.

[0056] Moreover, as an example of this embodiment, the applicant etched copper layer 41 of test piece 45 by carrying out the copper layer etching method of FIG.

[0057] The processing conditions of the embodiment are basically the same as those of the comparative example. However, the output of the source power and the output of the bias power were set to 4 kW, respectively, as in the comparative example, but the processing conditions of the embodiment are different from those of the comparative example in that a processing step using hydrogen chloride (first reaction) and a processing step using hydrogen (second reaction) are alternately and repeatedly performed. In the first reaction, hydrogen chloride gas alone was used as the chlorine-containing gas of the first processing gas, and the flow rate was set to 36 sccm. In the second reaction, the flow rate of hydrogen gas of the second processing gas was set to 150 sccm. Then, the first reaction and the second reaction were alternately and repeatedly performed a predetermined number of times for 300 seconds.

[0058] In the comparative example, as shown in FIG. 5(B), although the copper layer 41 was scraped off, the shape of the hard mask 42 was distorted, and as a result, the shape of the remaining part of the copper layer 41 did not reflect the shape of the hard mask 42 (see FIG. 5(A)) before etching. This was thought to be because in the comparative example, the processing gas containing hydrogen chloride gas was continuously supplied to the processing space U, and as a result, the hard mask 42 was eroded by the hydrogen chloride gas for a long period of time. In addition, as a result of the deformation of the hard mask 42, the copper layer 41 in the area that should have been covered by the hard mask 42 was chlorinated and swelled, and remained as a swollen layer 46.

[0059] 5(C), in the example, the copper layer 41 was etched away while the hard mask 42 maintained its shape, and the shape of the remaining portion of the copper layer 41 also reflected the shape of the hard mask 42 before etching. This was believed to be because, in the example, the first reaction and the second reaction were alternately and repeatedly performed, so that hydrogen chloride gas did not remain in the processing space U for a long period of time, and the hard mask 42 was not eroded by the hydrogen chloride gas.

[0060] Moreover, the etch rate of the hard mask 42 in the comparative example was 2.2 times or more that of the example. From this result, it was confirmed that the erosion of the hard mask 42 by the hydrogen chloride gas progressed in the comparative example, whereas the erosion of the hard mask 42 by the hydrogen chloride gas did not progress in the example.

[0061] From the above, it has been confirmed that by carrying out the copper layer etching method according to the present embodiment and alternately repeating the primary and secondary reactions, it is possible to suppress deformation of the shape of the hard mask 42 and to suppress deterioration of shape controllability when forming a desired shape in the copper layer 41.

[0062] In addition, although the processing conditions were almost the same in the comparative example and the embodiment, the etching rate of the copper layer 41 in the comparative example was 0.5 times that of the copper layer 41 in the embodiment. This was thought to be because only hydrogen chloride gas was used in the comparative example, and therefore a large amount of chlorine radicals existed relative to hydrogen radicals. In other words, this was thought to be because the abundance ratio of chlorine radicals to hydrogen radicals was high. Specifically, this was thought to be because, when a large amount of chlorine radicals exist relative to hydrogen radicals, the chlorine radicals interfere with the contact of the hydrogen radicals with copper chloride (II) 44, and there is a shortage of hydrogen radicals for the copper chloride (II) 44 to change to a copper chloride (I) trimer. This is because the interference with the contact and the shortage of hydrogen radicals result in the suppression of the generation of a copper chloride (I) trimer from copper chloride (II) 44.

[0063] However, if deposits are generated inside the processing chamber 11, they may cause problems such as particles, and therefore the generation of deposits must be suppressed as much as possible. For example, even when hydrogen chloride gas is used as the chlorine-containing gas in the first reaction, the generation of deposits can be suppressed by lowering the output of the bias power, but at the same time, the etching rate also decreases. However, the present applicant has found that when boron trichloride gas is used as the chlorine-containing gas, it is possible to suppress the generation of deposits while maintaining a high etching rate, as compared to when hydrogen chloride gas is used.

[0064] First, the applicant etched the copper layer by carrying out the copper layer etching method of Fig. 4 under standard HCl conditions, using hydrogen chloride gas, setting both the source power output and the bias power output to 4 kW, and setting the gas flow rate to 36 sccm. The amount of deposits generated at this time was divided by the amount of the copper layer etched to obtain a standard deposit ratio, and the etching rate at this time was determined as the standard etching rate. Under these standard HCl conditions, the first and second reactions were repeated five times, and the chiller temperature of the mounting table 13 was set to -40°C.

[0065] Next, the applicant etched the copper layer under low bias HCl conditions with a source power output of 6 kW, a bias power output of 0 kW, and a number of repetitions of the first and second reactions of 9 times, with the other conditions being the same as the standard HCl conditions. Then, even under the low bias HCl conditions, the deposition ratio, which is the amount of deposition generated divided by the amount of etching of the copper layer, and the etching rate were obtained. As a result, it was found that under the low bias HCl conditions, the deposition ratio was improved by 25% compared to the standard deposition ratio, but the etching rate was also significantly reduced by 52% compared to the standard etching rate.

[0066] Under low bias HCl conditions, both the source power output and the number of repetitions of the first and second reactions are increased compared to standard HCl conditions, so an increase in the amount of deposition and the etching rate is expected. However, contrary to expectations, both the amount of deposition and the etching rate decreased under low bias HCl conditions, which is thought to be largely due to the effect of setting the bias power to 0 kW.

[0067] On the other hand, since the etching rate under the low bias HCl condition was reduced to about half that under the standard HCl condition, it was necessary to improve the etching rate. Therefore, the applicant etched the copper layer under the low bias BCl3 condition using boron trichloride gas as the chlorine-containing gas and setting other conditions to the same as those under the low bias HCl condition. Then, under the low bias BCl3 condition, the deposition ratio and etching rate obtained by dividing the amount of deposition generated by the amount of etching of the copper layer were obtained. As a result, it was confirmed that under the low bias BCl3 condition, the deposition ratio was 25% lower than the standard deposition ratio, which was equivalent to that under the low bias HCl condition, and the etching rate was 72% higher than that under the low bias HCl condition. That is, under the low bias BCl3 condition, the deposition ratio was the same as under the low bias HCl condition, and the etching rate of the copper layer was lower than that under the standard HCl condition, but was more than 70% higher than that under the low bias HCl condition.

[0068] From the above, it was found that the use of boron trichloride gas as the chlorine-containing gas has the effect of suppressing the decrease in etching rate while also suppressing the generation of deposits.

[0069] In this embodiment, the first step is performed first, the second step is performed next, and then the first and second steps are repeated to etch the copper layer. However, the third step may be added before the first step. The third step is a step in which the second processing gas is supplied and is performed under the same processing conditions as the second step. That is, in this case, after the third step is performed to process the substrate with hydrogen gas, the first step is performed, the second step is performed next, and then the first and second steps are repeated. In this way, by performing the third step first, the surface of the copper layer is modified by hydrogen, and the effect of promoting the primary reaction and the secondary reaction is obtained.

[0070] The above describes a method for etching a copper layer as a preferred embodiment of the present disclosure. However, the present disclosure is not limited to the above-described embodiment, and various modifications and improvements are possible within the scope of the present disclosure. [Explanation of symbols]

[0071] G board U Processing Space 10 Substrate processing equipment 11 Processing chamber 12 Metal Windows 13 Placement table 21 Split pieces 24 Inductively Coupled Antenna 44 Copper(II) chloride 40 Control section

Claims

1. 1. A method for etching a copper layer formed on a substrate disposed within a processing chamber of a substrate processing apparatus, comprising: a first step of supplying a first process gas containing at least a chlorine-containing gas and not containing hydrogen gas into the process chamber, and generating a first product from the copper layer by a first plasma generated from the first process gas; a second step of supplying a second process gas containing at least the hydrogen gas and not containing the chlorine-containing gas and other chlorine-containing gases into the process chamber, and generating a second product from the first product by a second plasma generated from the second process gas; A method for etching a copper layer, comprising repeating the first step and the second step alternately a predetermined number of times.

2. 2. The method for etching a copper layer according to claim 1, wherein the chlorine-containing gas is a hydrogen chloride gas alone, a chlorine gas alone, a boron trichloride gas alone, 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. 2. The method for etching a copper layer according to claim 1, wherein the temperature of the substrate is maintained at 50[deg.] C. or less in the first and second steps.

4. the substrate processing apparatus includes a mounting table on which the substrate is mounted, a metal window facing the mounting table and made of a plurality of divided pieces, and an inductively coupled antenna facing the mounting table via the metal window and made of 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; 2. The method for etching a copper layer according to claim 1, wherein in the second step, the second plasma is generated by applying an electromagnetic field from the inductively coupled antenna to the second process gas through the metal window.

5. 2. The method for etching a copper layer according to claim 1, further comprising the steps of: supplying the second process gas into the processing chamber before the first process; and processing the substrate with the second plasma generated from the second process gas.

6. A substrate processing apparatus for etching a copper layer formed on a substrate, comprising: a mounting table for mounting the substrate; a processing chamber having the mounting table therein; a metal window facing the mounting table and made up of a plurality of divided pieces; an inductively coupled antenna facing the mounting table across the metal window and including a plurality of antenna segments; A control unit, The control unit executes a method for etching a copper layer, the method including: a first step of supplying a first process gas containing at least a chlorine-containing gas and not containing hydrogen gas into the process chamber, and generating a first product from the copper layer by a first plasma generated from the first process gas; and a second step of supplying a second process gas containing at least the hydrogen gas and not containing the chlorine-containing gas and other chlorine-containing gases into the process chamber, and generating a second product from the first product by a second plasma generated from the second process gas; In the copper layer etching method, the first step and the second step are alternately repeated a predetermined number of times.

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