Magnetic film processing method, magnetic device manufacturing method, and processing apparatus

Abstract

To provide a magnetic film processing method, a magnetic device manufacturing method, and a processing apparatus suitable for mass production of magnetic devices.SOLUTION: A magnetic film processing method includes a first step of performing plasma etching using oxygen plasma on a magnetic device 600 having a magnetic film 602 laminated thereon, and a second step of performing gas etching using a mixed gas containing oxygen and a diketone after the first step, and a cycle consisting of the first step and the second step is repeated multiple times, and in the second step, the mixed gas is irradiated from a direction facing the surface of the magnetic device 600.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a magnetic film processing method, a magnetic device manufacturing method and a processing apparatus, and more particularly to a magnetic film processing method, a magnetic device manufacturing method and a processing apparatus that can be applied to, for example, a magnetic memory. [Background technology]

[0002] With the explosive increase in data processing capacity in recent years, there is an urgent need for semiconductor devices to not only increase speed and integration density, but also reduce power consumption. Conventionally, static random access memory (SRAM) and dynamic random access memory (DRAM) have been widely used as working memory. As these devices become smaller, it becomes more difficult to trap electrons, and standby power consumption for data retention tends to increase. Therefore, nonvolatile memory has been proposed to reduce standby power consumption, making it possible to significantly reduce standby power consumption in standby mode.

[0003] Among nonvolatile memories, spin transfer torque magnetic random access memory (STT-MRAM) boasts excellent processing speed and rewrite endurance. However, numerous challenges remain before it can replace SRAM and DRAM. One of these challenges is the need for high integration. While traditional semiconductor device miniaturization has been achieved using reactive ion etch (RIE) processing, the magnetic materials used in STT-MRAM are difficult to process using conventional RIE processing. One of the reasons for this is the high vapor pressure of chlorides and fluorides in magnetic materials, which makes them difficult to sublimate after chemical reactions. Furthermore, degradation of magnetic properties due to chemical reactions has been reported during magnetic film processing. For example, numerous reports of degradation of electrical properties due to processing damage have been reported for STT-MRAM using perpendicularly magnetized films.

[0004] Given this background, Ion Beam Etch (IBE), which utilizes the physical sputtering phenomenon, is commonly used to process STT-MRAM. IBE processing is a physical sputtering method in which physical etching is promoted by irradiating the material to be etched (magnetic film) with Ar ions, for example. IBE processing has the advantages of not causing chemical damage due to etching and being able to process materials that are difficult to process with RIE. On the other hand, there is a disadvantage in ion milling, in that particles generated by physical sputtering adhere to the side of the device, causing short circuits.

[0005] For this reason, ion milling typically involves changing the angle of incidence of the Ar ion beam to remove redeposited material from the side of the device. However, if the angle of incidence of the Ar ions is set in a direction that is not perpendicular to the surface of the material being etched, a shadowing effect occurs in which the ions are blocked by structures such as mask patterns, making it difficult to process narrow-pitch patterns. Due to these backgrounds and challenges in magnetic film processing, progress in achieving high integration of STT-MRAM has not progressed to date. [Prior art documents] [Non-patent literature]

[0006] [Non-Patent Document 1] S. Fujisaki et. al., “Thermal-cyclic atomic layer etching of cobalt with smooth etched surface by plasma oxidation and organometallization”, Applied Physics Letters, September (2022) Summary of the Invention [Problem to be solved by the invention]

[0007] As mentioned above, there are many problems with applying conventional RIE etching to the processing of magnetic films. In recent years, etching techniques using metal complex reactions have been proposed for the processing of magnetic films. For example, in the case of cobalt etching, as described in Non-Patent Document 1, selective etching of difficult-to-etch materials has been successfully achieved by irradiating cobalt oxide with acetylacetone gas.

[0008] The method described in Non-Patent Document 1 is a processing method in which cobalt is oxidized with oxygen plasma and then irradiated with the diketone acetylacetone under certain temperature conditions to promote metal complex reaction and desorption of the reaction product. Non-Patent Document 1 describes a method in which, since the temperature ranges for the oxidation reaction and the desorption reaction are different, cyclic processing is performed to ensure flatness after etching. This method etches at the atomic layer level, allowing for very precise control of the etching amount, but also has the disadvantage of requiring a very long processing time. Therefore, it is not suitable for mass production of magnetic devices such as STT-MRAM.

[0009] The embodiments described below have been made in consideration of the above, and other problems and novel features will become apparent from the description of this specification and the accompanying drawings. [Means for solving the problem]

[0010] A method for processing a magnetic film according to one embodiment includes a first step of performing plasma etching using oxygen plasma on a workpiece on which a magnetic film has been formed, and a second step of performing gas etching using a mixed gas containing oxygen and a diketone after the first step, in which a cycle consisting of the first and second steps is repeated multiple times, and in the second step, the mixed gas is irradiated from a first direction which is a direction opposite to the surface of the workpiece.

[0011] A magnetic device manufacturing method according to one embodiment includes the steps of: manufacturing a multilayer film in which at least a pinned layer, a tunnel barrier layer, a free layer, and a mask layer are sequentially stacked on a substrate; patterning the mask layer into a predetermined pattern; after the patterning step, processing the free layer by plasma etching with oxygen plasma using the patterned mask layer as a mask; after the step of processing the free layer by plasma etching, processing the free layer by gas etching with a mixed gas containing oxygen and a diketone; after the step of processing the free layer by gas etching, processing the tunnel barrier layer and the pinned layer by plasma etching with oxygen plasma; after the step of processing the tunnel barrier layer and the pinned layer by plasma etching, processing the pinned layer by gas etching with a mixed gas containing oxygen and a diketone; after the step of processing the pinned layer by gas etching, forming an interlayer insulating film; and performing a planarization treatment on the interlayer insulating film formed in the step of forming the interlayer insulating film.

[0012] A processing apparatus according to one embodiment includes a container having a first gas inlet and a first gas outlet, a sample stage on which a workpiece is placed within the container, a plasma inducing section that induces plasma within the container from the gas introduced from the first gas inlet, an oxygen supplying section that supplies oxygen to the first gas inlet, a diketone supplying section that supplies diketone to the first gas inlet, and a first regulating section that regulates the supply of diketone from the diketone supplying section to the first gas inlet, wherein the first gas inlet is provided on a wall surface facing the surface of the workpiece placed on the sample stage, and the first gas outlet is provided on a wall surface facing the wall surface on which the first gas inlet is provided, and the first regulating section regulates the supply of diketone from the diketone supplying section to supply only oxygen to the first gas inlet when the plasma inducing section is operating, and regulates the supply of diketone from the diketone supplying section to supply a mixed gas of oxygen and diketone to the first gas inlet when the plasma inducing section is not operating. [Effects of the Invention]

[0013] According to the embodiment, processing suitable for mass production can be realized. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 shows a magnetic film processing method described in Non-Patent Document 1, which involves a cycle of oxidation reaction and metal complex reaction using diketone. [Figure 2] FIG. 2 is a schematic diagram of a processing apparatus for carrying out the magnetic film processing method according to the first embodiment. [Figure 3] FIG. 3 is a diagram showing a state in which plasma is induced in the processing apparatus of FIG. [Figure 4] FIG. 4 is a diagram showing a state in which plasma is not induced in the processing apparatus of FIG. [Figure 5] FIG. 5 is a chart showing processing conditions in the processing apparatus of FIG. [Figure 6] FIG. 6 is a diagram showing an example of processing a magnetic device using the processing apparatus of FIG. [Figure 7] FIG. 7 is a schematic diagram of a processing apparatus for carrying out the magnetic film processing method according to the second embodiment. [Figure 8] FIG. 8 is a chart showing processing conditions in the processing device of FIG. [Figure 9] FIG. 9 is a diagram showing an example of processing a magnetic device using the processing apparatus of FIG. [Figure 10] FIG. 10 is a diagram showing an example of processing a magnetic device using the processing apparatus of FIG. [Figure 11] FIG. 11 is a schematic diagram of a processing apparatus for carrying out the magnetic film processing method according to the third embodiment. [Figure 12A] FIG. 12A is a diagram showing a state in which plasma is induced in the processing apparatus of FIG. [Figure 12B] FIG. 12B is a diagram showing a state in which plasma is not induced in the processing apparatus of FIG. [Figure 13] FIG. 13 is a diagram showing a state in which plasma is not induced in the processing apparatus of FIG. [Figure 14]FIG. 14 is a diagram showing an example of processing a magnetic device using the processing apparatus of FIG. [Figure 15] FIG. 15 is a diagram showing an example of processing a magnetic device using the processing apparatus of FIG. [Figure 16] FIG. 16 shows the results of the etching reaction of cobalt using oxygen and a diketone. [Figure 17] FIG. 17 is a diagram showing the effect on the magnetic device pattern. [Figure 18] FIG. 18 shows the results of elemental analysis of the sample shown in FIG. [Figure 19] FIG. 19 is a schematic diagram showing the manufacturing process of an MTJ element. DETAILED DESCRIPTION OF THE INVENTION

[0015] In the following embodiments, when necessary for convenience, the description will be divided into multiple sections or embodiments, but unless otherwise specified, they are not unrelated to each other, and one is a partial or complete modification, detail, supplementary explanation, etc. of the other. Furthermore, in the following embodiments, when the number of elements, etc. (including the number, numerical value, amount, range, etc.) is mentioned, it is not limited to that specific number, and may be more or less than the specific number, unless otherwise specified or when it is clearly limited in principle to a specific number.

[0016] Furthermore, in the following embodiments, it goes without saying that the components (including element steps, etc.) are not necessarily essential unless otherwise specified or considered to be clearly essential in principle. Similarly, in the following embodiments, when referring to the shape, positional relationship, etc. of components, etc., it is intended to include those that are substantially similar or similar to the shape, etc., unless otherwise specified or considered to be clearly not essential in principle. The same applies to the above numerical values ​​and ranges.

[0017] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In all drawings for explaining the embodiments, the same components are generally designated by the same reference numerals, and repeated description thereof will be omitted.

[0018] (Outline of the embodiment) In the following embodiment, we propose a magnetic film processing method that combines anisotropic processing using oxygen ions and isotropic processing by metal complex formation. Figure 1 shows the magnetic film processing method described in Non-Patent Document 1, which involves a cyclic process of oxidation reaction and metal complex reaction using diketone.

[0019] In the first step, the surface of the initial magnetic film 101 is oxidized using an oxidation plasma or thermal oxidation to form an oxide magnetic film layer 102. In the second step, the oxide magnetic film layer 102 is irradiated with a diketone to cause a complex reaction, forming a metal complex layer 103. According to Non-Patent Document 1, acetylacetone (hacac) is known to be effective for cobalt. In the third step, the formed metal complex layer 103 is desorbed from the magnetic film 101 by ion irradiation or heat treatment. According to Non-Patent Document 1, the cobalt metal complex is known as Co(acac)2, and it has been reported that the metal complex reaction and desorption reaction occur simultaneously in the temperature range of 200 to 250°C.

[0020] In this way, by repeating the oxidation reaction, metal complex reaction, and desorption reaction, it becomes possible to etch the magnetic film. However, the method described in Non-Patent Document 1 involves a reaction at the atomic layer level, and the etching speed is a bottleneck. Therefore, in the following embodiment, a mixed gas of oxygen and diketone is simultaneously irradiated, enabling high-speed etching of the magnetic film.

[0021] (First embodiment) A schematic diagram of a processing apparatus for carrying out the magnetic film processing method according to this embodiment is shown in Fig. 1. As shown in Fig. 1, the processing apparatus 1 includes a vacuum vessel 201, an antenna coil 202, a stage 203, high-frequency matching circuits 204 and 205, high-frequency power supplies 206a and 206b, MFCs (flow controllers) 208 and 209, a vacuum valve 210, and pipes 231 and 232.

[0022] The vacuum vessel 201 has a processing chamber 2011, which is a space in which a workpiece 207 is placed and plasma is generated. A stage 203 on which the workpiece 207 is placed is installed in the processing chamber 2011. The vacuum vessel 201 is also provided with an inlet 221, to which a piping 231 (described later) is connected and which introduces oxygen gas or a mixed gas (described later) into the processing chamber 2011. The vacuum vessel 201 is also provided with an outlet 222 which discharges the gas introduced from the inlet 221. The inlet 221 is provided on a wall surface 201a facing the surface of the workpiece 207 placed on the stage 203. The outlet 222 is provided on a wall surface 201b facing the wall surface 201a. That is, the inlet 221 irradiates the gas from a first direction facing the surface of the workpiece 207. The irradiated gas is discharged from the outlet 222 in the same direction as the first direction.

[0023] The antenna coil 202 is a coil (plasma inducing unit) for inducing plasma inside the vacuum vessel 201 (inside the processing chamber). In this embodiment, an example of an inductively coupled plasma (ICP) method using the antenna coil 202, which is a high-frequency induction coil, is shown, but the plasma generation method is not necessarily limited to this method.

[0024] In this embodiment, the stage 203 is configured by, for example, an electrostatic chuck. As described above, the stage 203 is a sample stage that fixes the placed workpiece 207. The stage 203 also has a built-in heater for heating the placed workpiece 207. However, the heating of the workpiece 207 is not limited to contact heating such as a heater, and non-contact heating such as irradiation with an infrared halogen lamp may also be used.

[0025] The high-frequency matching circuit 204 is connected to a high-frequency power supply 206a and applies a high-frequency voltage to the antenna coil 202. The high-frequency power supply 206a is a power supply for supplying source power that generates plasma inside the vacuum vessel 201 (processing chamber 2011). The high-frequency matching circuit 205 is connected to a high-frequency power supply 206b and applies a high-frequency voltage to the stage 203. The high-frequency power supply 206b is a power supply for applying a bias electric field to the workpiece 207.

[0026] The MFC 208 is provided midway through the pipe 231 connected to the introduction part 221. The MFC 208 adjusts the flow rate of oxygen gas as described below. That is, the MFC 208 serves as an oxygen supply part that supplies oxygen to the introduction part 221. The MFC 209 is provided upstream of the pipe 232. The MFC 209 adjusts the flow rate of diketone as described below. The MFC 209 also serves as a diketone supply part that supplies diketone to the introduction part 221.

[0027] The vacuum valve 210 is provided downstream of the MFC 209 in the pipe 232. The vacuum valve 210 is controlled to be open when no plasma is induced, and closed when plasma is induced. The vacuum valve 210 may be of any type, such as compressed air or a solenoid valve. In other words, the vacuum valve 210 serves as a first regulator that regulates the supply from the MFC 209 to the introduction part 221.

[0028] Pipe 231 is a pipe that introduces oxygen or a mixed gas of oxygen and diketone, which will be described later, into vacuum vessel 201. Oxygen gas is supplied to pipe 231 from the upstream side. The flow rate of oxygen gas in pipe 231 is adjusted by MFC 208 installed midway, and the adjusted oxygen gas is introduced into vacuum vessel 201 from introduction part 221. Pipe 231 is also connected to pipe 232 downstream of MFC 208. Therefore, pipe 231 can mix oxygen and diketone from pipe 232 and supply the mixed oxygen to introduction part 221.

[0029] Pipe 232 is a pipe that supplies diketone to vacuum vessel 201. Diketone is supplied to pipe 232 from the upstream side. The flow rate of diketone is adjusted by MFC 209 installed midway through pipe 232, and when vacuum valve 210 is controlled to be open, diketone is supplied to introduction section 221 via pipe 231. Therefore, oxygen gas or a mixed gas of oxygen and diketone is introduced from introduction section 221 into vacuum vessel 201 depending on the operation of processing apparatus 1.

[0030] Next, a processing method using the processing apparatus 1 will be described with reference to Figures 3 and 4. Figure 3 shows a state in which plasma is induced. In Figure 3, when the vacuum valve 210 is controlled to be closed and only oxygen gas adjusted by the MFC 208 is introduced, a high-frequency voltage is applied to the antenna coil 202 from the high-frequency matching circuit 204, and oxygen plasma is induced in the processing chamber 2011. That is, when the antenna coil 202 is operating, the vacuum valve 210 restricts the supply of diketone from the MFC 209, and only oxygen is supplied to the introduction part 221.

[0031] The frequency and output intensity of the high-frequency power supply 206a for inducing the plasma may be determined as appropriate. When a high-frequency voltage is applied to the stage 203 from the high-frequency matching circuit 205 while the oxygen plasma is induced, oxygen ions are accelerated from the oxygen plasma in a direction perpendicular to the workpiece 207. In general, the incidence velocity of the oxygen ions can be controlled by the magnitude of the bias electric field applied to the stage 203.

[0032] Fig. 4 shows a state in which plasma is not induced. As shown in Fig. 4, for example, when no high-frequency voltage is applied to antenna coil 202, vacuum valve 210 is controlled to be open, and oxygen gas and diketone are simultaneously supplied to vacuum chamber 201. In other words, a mixed gas of oxygen gas and diketone is supplied into vacuum chamber 201. In other words, when antenna coil 202 is not operating, vacuum valve 210 supplies diketone from MFC 209, causing the mixed gas of oxygen and diketone to be supplied to introduction section 221.

[0033] In the state shown in FIG. 4, the temperature of the workpiece 207 on the stage 203 is maintained at a predetermined temperature. For example, if the workpiece 207 to be processed is made of cobalt and acetylacetone is selected as the diketone, a temperature of approximately 200 to 400°C is appropriate for the workpiece 207 during gas etching. In addition, in this process, the pressure inside the vacuum chamber 201 is ideally kept constant by adjusting the exhaust rate, and an example pressure range is approximately 100 to 5000 Pa. Under these conditions, gas etching using a mixed gas of oxygen and diketone is possible.

[0034] Next, an example of a chart of the processing conditions described above is shown in Figure 5. From the top, Figure 5 shows the changes over time in oxygen flow rate, diketone flow rate, source power, and bias power. The plasma etch (plasma etching) shown in Figure 5 represents the state in which plasma is induced, as shown in Figure 3, and the gas etch (gas etching) shown in Figure 5 represents the state in which plasma is not induced, as shown in Figure 4.

[0035] As shown in Figure 5, plasma etching is performed as the first step from time t1 to time t2, from time t3 to time t4, and from time t5 to time t6. Meanwhile, gas etching is performed as the second step from time t2 to time t3, from time t4 to time t5, and from time t6 to time t7. Therefore, plasma etching and gas etching are performed alternately. Or, it can be said that multiple cycles of plasma etching and gas etching are performed in that order.

[0036] As shown in FIG. 5, oxygen gas is continuously supplied, but the MFC 208 controls the gas flow rates optimized for each etching process during the plasma etching shown in FIG. 3 and the gas etching shown in FIG. 4. Meanwhile, diketone is supplied only when the source power for plasma induction and bias power are not supplied (t2-t3, t4-t5, t6-t7). The flow rate is controlled by the MFC 209 to achieve an appropriate mixture ratio with oxygen. Operating in this sequence allows for alternating plasma etching and gas etching, enabling anisotropic processing with oxygen ions in the plasma etching step and isotropic processing in the gas etching step. The duration of each step can be determined appropriately depending on the workpiece 207 to be processed.

[0037] Fig. 6 shows an example of processing a magnetic device when the above-mentioned processing method is applied. First, the left side of Fig. 6 shows the initial state of a magnetic device 600. In the magnetic device 600, a magnetic film 602 and a nonmagnetic metal oxide film 601 are stacked in this order on a nonmagnetic metal film 603. The nonmagnetic metal oxide film 601 has been patterned in advance.

[0038] Examples of the nonmagnetic metal oxide film 601 include materials that can be formed into nonmagnetic oxide films, such as aluminum oxide, silicon oxide, and magnesium oxide. During the plasma etching process, the magnetic film 602 is etched by oxygen ions using the nonmagnetic metal oxide film 601 as a mask. However, because some of the etched magnetic material adheres to the sidewalls of the pattern, the processed shape becomes tapered (center of Figure 6). Furthermore, because the nonmagnetic metal oxide film 601 has high etching resistance to oxygen ions, the mask height is not significantly reduced during the plasma etching process. Then, a mixed gas of oxygen and diketone is irradiated using a downflow. In other words, the mixed gas is irradiated from a direction facing the surface of the magnetic device 600, which is the workpiece. This selectively induces a metal complex reaction only in the tapered portion, resulting in the tapered angle of the sidewalls approaching vertical (right side of Figure 6).

[0039] This is because the mixed gas is irradiated only to the tapered portion not covered with the nonmagnetic metal oxide film 601, causing the metal complex reaction to proceed preferentially. In the gas etching process using oxygen and diketone, the etching selectivity with respect to the nonmagnetic metal film 603 is important, and by appropriately selecting the target material, it is possible to remove only the tapered portion of the magnetic film 602. As an example, if cobalt is used as the magnetic film 602 and tantalum, tungsten, titanium, or the like is used as the nonmagnetic metal film 603, the etching reaction using the metal complex reaction with acetylacetone in diketone is limited to cobalt, enabling highly selective etching of the magnetic film 602.

[0040] According to this embodiment, a magnetic device 600 having a magnetic film 602 formed thereon is subjected to a first step of plasma etching using oxygen plasma, followed by a second step of gas etching using a mixed gas containing oxygen and a diketone. The cycle consisting of the first and second steps is then repeated multiple times. In the second step, the mixed gas is irradiated from a direction facing the surface of the magnetic device 600 (downflow). This allows for selective removal of the tapered portion of the magnetic device 600. The improved tapered shape of the magnetic device 600 allows, for example, higher integration. Furthermore, gas etching using a mixed gas allows for faster etching than the method of Non-Patent Document 1, thereby realizing processing suitable for mass production.

[0041] Furthermore, the mixed gas irradiated in the downflow is discharged from the discharge part 222, so that it can be discharged efficiently without changing the gas flow.

[0042] (Second embodiment) Next, a second embodiment will be described. In the following, explanations of parts that overlap with the above-described embodiment will be omitted in principle.

[0043] Fig. 7 is a schematic diagram of a processing apparatus 1A according to this embodiment. In the processing apparatus 1A of this embodiment, the vacuum vessel 201 of the processing apparatus 1 shown in Fig. 2 is changed to a vacuum vessel 201A. Furthermore, MFCs 709, 711, and 713, a vacuum valve 714, and pipes 731 and 732 are added. Furthermore, the MFC 209 is changed to an MFC 209A.

[0044] 2, the vacuum vessel 201A is provided with an inlet 223 and an outlet 224. The inlet 223 is provided on a wall surface 201c that is perpendicular to the wall surface 201b. The outlet 224 is provided on a wall surface 201d that faces the wall surface 201c. The inlet 223 is connected to a pipe 732 and introduces a mixed gas of oxygen and diketone into the processing chamber 2011A. The outlet 224 exhausts the gas introduced from the inlet 223. The inlet 223 and the outlet 224 are preferably provided on the wall surfaces 201c and 201d at positions (heights) close to the stage 203.

[0045] MFC 709 is provided upstream of MFC 209A in pipe 233. MFC 709 adjusts the flow rate of diketone as described below. MFC 209A adjusts the flow rate of a mixed gas of oxygen gas and diketone. MFC 711 is provided midway through pipe 731 and adjusts the flow rate of oxygen gas. MFC 713 is provided midway through pipe 732 and adjusts the flow rate of a mixed gas of oxygen gas and diketone.

[0046] Vacuum valve 714 is provided downstream of MFC 713 on pipe 732. Vacuum valve 714 is controlled to be open when plasma is not induced, and conversely, closed when plasma is induced. Similar to vacuum valve 210, vacuum valve 714 may be of any type, such as compressed air or an electromagnetic valve. In other words, vacuum valve 714 serves as a second regulating unit that regulates the introduction of the mixed gas from introduction unit 223.

[0047] Pipe 731 branches off from pipe 231 upstream of MFC 208 provided in pipe 231. Pipe 731 joins pipe 233 between MFC 209A and MFC 709 provided in pipe 233. Pipe 732 branches off from pipe 233 between the junction of pipe 233 with pipe 731 and MFC 209A. Pipe 732 is connected to introduction part 223, and introduces the mixed gas branched off from pipe 233 from introduction part 223 into vacuum chamber 201A.

[0048] While the processing apparatus 1 shown in FIG. 2 has only one gas inlet, the processing apparatus 1A shown in FIG. 7 has multiple gas inlet ports. The processing apparatus 1A includes an inlet port 221 (first gas inlet port) for introducing oxygen gas or a mixed gas of oxygen and diketone into a vacuum chamber 201A, as well as an inlet port 223 (second gas inlet port) for introducing the mixed gas. Furthermore, an outlet port 222 (first gas outlet port) and an outlet port 224 (second gas outlet port) are provided corresponding to the inlet ports 221 and 223, respectively. The outlet port 222 is provided facing the inlet port 221, and the outlet port 224 is provided facing the inlet port 223. Therefore, the inlet port 223 can introduce (irradiate) the mixed gas from a second direction different from the inlet port 221. In FIG. 7, the mixed gas can be irradiated from the side of the workpiece 207 placed on the stage 203.

[0049] Furthermore, the MFCs 209A and 713 can adjust the direction of gas flow within the vacuum vessel 201. Furthermore, the MFCs 709 and 711 can adjust the mixing ratio of the mixed gas.

[0050] An example of a chart of processing conditions using the processing apparatus 1A of this embodiment is shown in Fig. 8. Fig. 9 shows, from top to bottom, the oxygen flow rate at the first gas inlet (inlet 221), the mixed gas flow rate at the first gas inlet, the mixed gas flow rate at the second gas inlet (inlet 223), the source power, and the bias power over time.

[0051] In the example of FIG. 8, the flow rate of oxygen flowing through the first gas introduction part (introduction part 221) is set to a constant value regardless of whether the source power and the bias power are on or off. On the other hand, the mixed gas flowing through the first gas introduction part and the second gas introduction part is introduced only when the source power and the bias power are off. That is, the vacuum valve 714 restricts the introduction of the mixed gas from the introduction part 223 when the antenna coil 202 operates, and allows the mixed gas to be introduced from the introduction part 223 when the antenna coil 202 is not operating.

[0052] Also, let the flow rate of the mixed gas flowing through the first gas introduction part be m1, and the flow rate of the mixed gas flowing through the second gas introduction part be m2. When m1 >> m2, the flow of the mixed gas flowing from the first gas introduction part (introduction part 221) becomes dominant. Conversely, when m1 << m2, the influence from the second gas introduction part (introduction part 223) becomes dominant.

[0053] Similar to FIG. 5 in the case of FIG. 8, plasma etching is performed between time t1 and time t2, between time t3 and time t4, and between time t5 and time t6. On the other hand, gas etching is performed between time t2 and time t3, between time t4 and time t5, and between time t6 and time t7. Therefore, plasma etching and gas etching are performed alternately.

[0054] FIGS. 9 and 10 show examples of processing a magnetic device when the processing method of this embodiment is applied. FIGS. 9 and 10 are the same as FIG. 6 in that the left side shows the initial state of the magnetic device 600. Also, the configuration (materials, etc.) of the magnetic device 600 to be processed is the same as that in FIG. 6.

[0055] In FIG. 9, the plasma etching (in the center of FIG. 9) is the same as that in FIG. 6. And in the gas etching process on the right side of FIG. 9, under the condition of m1 >> m2, only the tapered part of the magnetic film 602 (indicated by the arrow in the figure) can be etched in the same way as described in FIG. 6.

[0056] In FIG. 10, the plasma etching (in the center of FIG. 10) is the same as that in FIG. 6. In the gas etching process on the right side of FIG. 10, under the condition of m1 << m2, the side wall portion of the magnetic film 602 (indicated by the arrow in the figure) can be selectively etched according to the relative angle between the second gas introduction part and the magnetic device 600. Therefore, in the processing of the magnetic device 600, by changing the flow rate ratio of the mixed gas flowing through the first gas introduction part and the second gas introduction part, the processing shape can be arbitrarily controlled.

[0057] According to the present embodiment, the introduction part 223 and the discharge part 224 are provided in the processing apparatus 1A so that the mixed gas of oxygen and diketone can be irradiated from the side of the workpiece 207 (magnetic device 600) from the introduction part 223. Therefore, by arbitrarily changing the ratio between the mixed gas irradiated from above the workpiece 207 and the mixed gas irradiated from the side, the processing shape can be controlled.

[0058] In the present embodiment, one of the introduction parts 223 is provided as the second gas introduction part, but the second gas introduction part may be provided at another position.

[0059] (Third Embodiment) Next, the third embodiment will be described. In the following, the description of the parts overlapping with the above-described embodiments will be omitted in principle.

[0060] FIG. 11 shows a schematic diagram of the processing apparatus 1B according to the present embodiment. The present embodiment is an application example to a plasma processing apparatus using an ion beam. The processing apparatus 1B includes a vacuum chamber 1101, a filament 1102, a rotary stage 1103, an acceleration voltage power supply 1104, a deceleration voltage power supply 1105, an AC power supply 1106, an acceleration grid 1111, a deceleration grid 1112, MFCs 208 and 209, a vacuum valve 210, and pipes 231 and 232.

[0061] Of the above-described configuration, the MFCs 208 and 209, the vacuum valve 210, and the pipes 231 and 232 are the same as those in the first embodiment. The vacuum vessel 1101 has a processing chamber 1101A, which is a space in which a workpiece 207 is placed and plasma is generated. The processing chamber 1101A is provided with a filament 1102, an acceleration grid 1111, and a deceleration grid 1112 on the side of a gas inlet 1121 (described later). The processing chamber 1101A is also provided with a rotation stage 1103 on which the workpiece 207 is placed on the side of a gas outlet 1122 (described later). The vacuum vessel 1101 is also provided with an inlet 1121 connected to the pipe 231, which introduces oxygen gas or a mixed gas into the processing chamber 1101A. The vacuum vessel 1101 is also provided with an outlet 1122 which exhausts the gas introduced from the inlet 1121. The inlet 1121 is provided on a wall surface 1101a that faces the surface of the workpiece 207 placed on the rotary stage 1103. The outlet 1122 is provided on a wall surface 1101b that faces the wall surface 1101a.

[0062] The filament 1102 is provided in the vacuum vessel 1101 (processing chamber 1101A). The filament 1102 serves as a plasma ignition source by power supplied from an AC power supply 1106, and induces plasma. The acceleration grid 1111 is electrically connected to an acceleration voltage power supply 1104. The deceleration grid 1112 is electrically connected to a deceleration voltage power supply 1105. The acceleration grid 1111 and the deceleration grid 1112 serve as acceleration sections that accelerate ions generated within the induced plasma.

[0063] The rotation stage 1103 is rotatable about a rotation axis C that extends in a direction perpendicular to the mounting surface on which the workpiece 207 is placed. The rotation stage 1103 fixes the workpiece 207 using, for example, a mechanical chuck. The rotation stage 1103 is capable of changing the angle of the rotation axis C from a direction coaxial with the introduction section 1121 (the direction in which the ions are accelerated and travel). In addition, since the rotation stage 1103 is electrically grounded, the accelerated ions can cause a sputtering phenomenon on the workpiece 207.

[0064] Next, a processing method using the processing apparatus 1B will be described with reference to FIGS. 12 and 13. FIG. 12A shows the state in which plasma is induced. In FIG. 12A, the vacuum valve 210 is closed, and only oxygen gas adjusted by the MFC 208 is introduced. When the AC power supply 1106 supplies power to the filament 1102, oxygen plasma is induced within the vacuum chamber 1101. Then, by applying appropriate acceleration and deceleration voltages from the acceleration voltage power supply 1104 and deceleration voltage power supply 1105, physical sputter etching (plasma etching) using oxygen ions becomes possible. By appropriately adjusting the angle of the rotation stage 1103, it is possible to reduce redeposits due to physical sputter etching. If the relative angle θ between the ion traveling direction (shown by the dashed line D in FIG. 12A) and the rotation axis C of the rotation stage 1103 is θ, it is generally preferable that θ = 30 to 60 degrees, but this may be determined appropriately depending on the material of the workpiece 207, etc. FIG. 12A shows the case where the relative angle is 30 degrees.

[0065] Fig. 12B shows a state in which plasma is not induced. As shown in Fig. 12B, for example, when power is not supplied to filament 1102 from AC power supply 1106, vacuum valve 210 is controlled to be open, and oxygen gas and diketone are simultaneously supplied to vacuum vessel 1101. Also, in Fig. 12B, the above-mentioned relative angle θ is set to 0 degrees.

[0066] Fig. 13 shows a state in which plasma is not induced, similar to Fig. 12B. A state in which plasma is induced may be the same as Fig. 12A, for example. In Fig. 13, the relative angle is 30 degrees.

[0067] 14 and 15 show an example of processing a magnetic device when the processing method of this embodiment is applied. In Fig. 14 and Fig. 15, the left side is the initial state of the magnetic device 600, just like Fig. 6. The configuration (materials, etc.) of the magnetic device 600 to be processed is the same as Fig. 6.

[0068] In Fig. 14, the plasma etching (center of Fig. 14) is the same as in Fig. 6. In the gas etching process on the right side of Fig. 14, by rotating the rotary stage 1103 under the condition of relative angle θ = 0 degrees and performing etching, only the tapered portion of the magnetic film 602 can be etched, as explained in Fig. 6.

[0069] In Fig. 15, the plasma etching (center of Fig. 10) is the same as in Fig. 6. Then, in the gas etching process on the right side of Fig. 15, the sidewall of the magnetic film 602 can be selectively etched by rotating the rotary stage 1103 under the condition of a relative angle θ = 30 degrees.

[0070] According to this embodiment, by changing the angle of the rotary stage 1103 during gas etching, it is possible to arbitrarily control the processed shape.

[0071] (Example) Here, Fig. 16 shows the results of the etching reaction of cobalt using oxygen and diketone. The following three conditions were adopted in this example. Gas etch condition 1 (hereinafter referred to as condition 1) is a low temperature (200°C) and a high pressure (1000 Pa). Gas etch condition 2 (hereinafter referred to as condition 2) is a high temperature (400°C) and a high pressure (1000 Pa). Gas etch condition 3 (hereinafter referred to as condition 3) is a high temperature (400°C) and a low pressure (100 Pa). The gas flow rates of both diketone and oxygen were constant.

[0072] In Figure 16, the upper row of the photographs showing the shape shows the cross section, and the lower row shows the surface state. The surface state also shows the results of analysis using an atomic force microscope (AFM). As is clear from these photographs and analysis results, the etching amount and surface state varied depending on the processing conditions. Under condition 1, surface oxidation was dominant, and no cobalt etching was observed. On the other hand, under conditions 2 and 3, which were high temperature and high pressure, and high temperature and low pressure, respectively, the cobalt film thickness decreased after etching, indicating that the etching reaction progressed. Furthermore, when comparing conditions 2 and 3, the etching amount was similar, but the surface was found to be smoother under the lower pressure. From these results, it was determined that condition 3 was the most appropriate of the three conditions used in this example.

[0073] Next, we verified the effect on the magnetic device pattern (see Figure 17). The magnetic device used was made by laminating titanium (Ti) and cobalt (Co) layers, with alumina (Al2O3) layered on top as a mask. Figure 17 shows an example of processing using the processing equipment 1B. From top to bottom, Figure 17 shows cross-sectional views of the processed surfaces after three types of processing: plasma etching only, plasma etching + gas etching (condition 1), and plasma etching + gas etching (condition 3). The gas etching conditions used were those shown in Figure 16. As shown in Figure 17, with plasma etching only, the cobalt sidewalls had a tapered shape. However, by applying gas etching, this shape was observed to approach a vertical shape. In particular, when condition 3 was applied for gas etching, the cobalt near the alumina mask was selectively removed.

[0074] To verify the details of this etching, elemental analysis was performed using TEM-EDX (energy dispersive X-ray spectroscopy). The results are shown in Figure 18. The upper row of Figure 18 shows the case without gas etching, and the lower row of Figure 18 shows the case with gas etching. The right side of each row of Figure 18 shows the analysis results for the elements oxygen (O), cobalt (Co), aluminum (Al), and titanium (Ti).

[0075] According to Figure 18, without gas etching, oxygen was detected widely along the side of the pattern, but with gas etching, oxidation progressed only in the tapered parts of the cobalt. Further analysis revealed that a metal complex reaction was progressing in the tapered parts, and as a result, it was shown that gas etching using alumina as a mask is possible.

[0076] Finally, we will show an example of applying the above-mentioned processing method (processing apparatus) to the manufacturing process of STT-MRAM. That is, we will show a magnetic device manufacturing method. Figure 19 shows a schematic diagram of the manufacturing process of an MTJ (magnetic tunnel junction) element, which is a key component of STT-MRAM. Note that the manufacturing process of the upper and lower electrodes that make up STT-MRAM can be done using well-known technology, so we will not explain it here.

[0077] 19, a resist mask 1901 is patterned by an exposure device on a multilayer film for an MTJ element. The multilayer film for an MTJ element is composed of mask layers 1902 and 1903, a free layer 1904, a tunnel barrier layer 1905, and a fixed layer 1906 stacked in this order. A substrate (not shown) is located below the fixed layer 1906.

[0078] In the example of FIG. 19, Al2O3 was used for the mask layer 1902. Ta was used for the mask layer 1903. CoFeB / Ta / CoFeB was used for the free layer 1904. MgO was used for the tunnel barrier layer 1905. CoFeB / Ru / [Co / Pt stacked film] was used for the fixed layer 1906. That is, the magnetic film can be made of a single metal such as cobalt, iron, or nickel, or an alloy containing at least one of cobalt, iron, and nickel.

[0079] The resist pattern was a circular shape with a diameter of 30 nm, and exposure was carried out with a pattern pitch of 60 nm.

[0080] In the mask processing step shown in 19-2, the resist mask 1901 is first transferred to a non-magnetic oxide mask, Al2O3. The transfer method is RIE processing using a mixed gas of BCl3 and Cl2. Then, Ta is patterned using Al2O2 as a mask. For Ta patterning, RIE processing using Cl2 is performed.

[0081] In processing the free layer 1904 of 19-3, anisotropic etching (plasma etching) with oxygen ions 1907 was performed by the processing device 1 using the multilayer mask of Al2O2 and Ta formed in 19-3. The etching with oxygen ions 1907 was terminated at the portion directly above the tunnel barrier layer 1905 by using an end point determination system.

[0082] Next, as shown in 19-4, gas etching was performed using a mixed gas of acetylacetone and oxygen using the processing equipment 1. The mixed gas was irradiated from above the device in a downflow manner (reference numeral 1908). The pressure and temperature conditions used in the gas etching were P = 600 Pa and T = 400 °C. Under these conditions, selective improvement of the tapered shape at the bottom of the pattern generated in 19-3 was confirmed.

[0083] Subsequently, the process of plasma etching 19-5 and gas etching 19-6 was carried out to complete the creation of the fixed layer 1906. The processing conditions used for the plasma etching and gas etching were the same as those for forming the free layer 1904. During the etching with oxygen ions 1907 in 19-5, an altered layer due to oxidation was observed on the sidewall of the MTJ, but the altered layer could be removed by gas etching with a mixed gas in 19-6.

[0084] Next, in the interlayer insulating film formation process 19-7, SiO2 was used as the interlayer insulating film 1909, and in process 19-8, planarization was performed using CMP (chemical mechanical polishing). At this time, the planarization process was performed until part of the Ta mask was exposed by the CMP process. Through these processes, we succeeded in creating a highly integrated MTJ element with a diameter of 30 nm and a pitch of 60 nm.

[0085] According to the magnetic device manufacturing method described above, the tapered shapes formed in the free layer 1904 and the fixed layer 1906 can be improved, and a highly integrated MTJ element can be fabricated.

[0086] The invention made by the inventor has been specifically described above based on an embodiment, but it goes without saying that the present invention is not limited to the above embodiment and can be modified in various ways without departing from the gist of the invention. [Explanation of symbols]

[0087] 1 Processing equipment 201 Vacuum vessel (vessel) 201a wall 201b wall 201c Wall 201d wall 202 Antenna coil (plasma induction section) 203 Stage (sample stage) 207 Workpiece 208 MFC (Oxygen Supply Unit) 209 MFC (Diketone Supply Department) 210 Vacuum valve (first regulation part) 221 Introduction section (first gas introduction section) 222 Exhaust section (first gas exhaust section) 223 Introduction section (second gas introduction section) 224 Exhaust section (second gas exhaust section) 1103 Rotating stage (sample stage) C rotation axis

Claims

1. a first step of performing plasma etching using oxygen plasma on a workpiece on which a magnetic film has been formed; a second step of performing gas etching using a mixed gas containing oxygen and a diketone after the first step, A cycle consisting of the first step and the second step is repeated a plurality of times; In the second step, the mixed gas is irradiated from a first direction facing the surface of the workpiece. A method for processing magnetic films.

2. 2. The method for processing a magnetic film according to claim 1, In the second step, the mixed gas is irradiated from the first direction and also from a second direction different from the first direction. A method for processing magnetic films.

3. 2. The method for processing a magnetic film according to claim 1, The mixed gas is exhausted from the same direction as the direction in which the mixed gas is irradiated. A method for processing magnetic films.

4. 2. The method for processing a magnetic film according to claim 1, a non-magnetic oxide film patterned in advance on the magnetic film, and the first and second steps are performed on the magnetic film using the non-magnetic oxide film as a mask; A method for processing magnetic films.

5. 2. The method for processing a magnetic film according to claim 1, acetylacetone is used as the diketone, The magnetic film is made of a single metal selected from the group consisting of cobalt, iron, and nickel, or an alloy containing at least one of cobalt, iron, and nickel. A method for processing magnetic films.

6. A step of manufacturing a multilayer film in which at least a fixed layer, a tunnel barrier layer, a free layer, and a mask layer are sequentially stacked on a substrate; patterning the mask layer into a predetermined pattern; After the patterning step, using the patterned mask layer as a mask, processing the free layer by plasma etching with oxygen plasma; After the step of processing the free layer by the plasma etching, a step of processing the free layer by gas etching using a mixed gas containing oxygen and a diketone; after the step of processing the free layer by gas etching, processing the tunnel barrier layer and the fixed layer by plasma etching using oxygen plasma; after the step of processing the tunnel barrier layer and the fixed layer by plasma etching, processing the fixed layer by gas etching using a mixed gas containing oxygen and a diketone; forming an interlayer insulating film after processing the fixing layer by gas etching; a step of performing a planarization process on the interlayer insulating film formed in the step of forming the interlayer insulating film; A method for manufacturing a magnetic device comprising:

7. a container including a first gas inlet and a first gas outlet; a sample stage on which a workpiece is placed within the container; a plasma inducing section that induces plasma in the container from the gas introduced from the first gas inlet section; an oxygen supply unit that supplies oxygen to the first gas introduction unit; a diketone supply unit that supplies a diketone to the first gas introduction unit; a first restricting unit that restricts the supply of the diketone from the diketone supply unit to the first gas introduction unit; Equipped with the first gas inlet is provided on a wall surface facing a surface of the workpiece placed on the sample stage, the first gas exhaust portion is provided on a wall surface opposite to the wall surface on which the first gas introduction portion is provided, the first regulating unit regulates the supply of the diketone from the diketone supply unit when the plasma inducing unit is operating, thereby supplying only the oxygen to the first gas inlet, and when the plasma inducing unit is not operating, allows the diketone to be supplied from the diketone supply unit, thereby supplying a mixed gas of the oxygen and the diketone to the first gas inlet. Processing equipment.

8. The processing device according to claim 7, The container comprises: a second gas inlet provided on a wall surface perpendicular to the first gas inlet, and a second gas outlet provided on a wall surface opposite to the second gas inlet, a second restriction part that restricts the introduction of the mixed gas from the second gas inlet part, the second regulating unit regulates the introduction of the mixed gas from the second gas inlet unit when the plasma inducing unit is operating, and allows the mixed gas to be introduced from the second gas inlet unit when the plasma inducing unit is not operating. Processing equipment.

9. The processing device according to claim 7, the plasma inducing unit further includes an accelerating unit that accelerates ions generated in the induced plasma, the sample stage is rotatable along a rotation axis extending in a direction perpendicular to a surface on which the workpiece is placed, and the relative angle between the rotation axis and the traveling direction of the ions is changeable. Processing equipment.

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