JP5705689B2 - Phase change memory forming method and phase change memory forming apparatus - Google Patents

Description

  The present invention relates to a phase change memory forming apparatus and a phase change memory forming method for forming a phase change memory having a stacked body in which a plurality of metal chalcogenide films having different compositions including a metal element and a chalcogen element are stacked. .

  Conventionally, as described in Patent Document 1, for example, a phase change memory using a metal chalcogenide film containing a metal element and a chalcogen element is widely known as one of memory elements. A metal chalcogenide film reversibly changes between a crystalline phase and an amorphous phase, which show different resistance values, depending on the difference in thermal energy applied to them, and both phases are stably held at room temperature. It has the characteristic that For this reason, the metal chalcogenide film is used as an element capable of storing two different values because of the difference in resistance value. Thus, since the phase change memory has an element for storing information based on the difference in resistance value between two different phases, a new nonvolatile memory that does not require power supply to maintain the storage Has attracted attention as.

FIG. 8 shows a partial sectional structure of such a phase change memory. In the hole formed in the insulating film 51 of the phase change memory 50, a lower electrode 53 covered with a heat insulating layer 52 is embedded. On the insulating film 51, a laminated body of a single layer metal chalcogenide film 54 made of, for example, Ge ₂ Sb ₂ Te ₅ and the upper electrode 55 is formed at a position covering the surface of the lower electrode 53. The metal chalcogenide film 54 is heated by a current flowing between the lower electrode 53 and the upper electrode 55 sandwiching the metal chalcogenide film 54, and is cooled as the current supply is stopped. Phase change between

  According to such a single-layer type phase change, switching of the resistance value as described above, that is, reading and writing of information is certainly possible. However, the phase change requires physical movement of each atom constituting the metal chalcogenide film 54 in the thickness direction of the metal chalcogenide film 54. Therefore, the read / write speed is lower than that of other storage elements such as a DRAM that stores information by movement of electrons in the capacitive element. Thus, for example, as described in Non-Patent Document 1, a phase change memory using a stacked body of metal chalcogenide films having different compositions instead of the single metal chalcogenide film as described above has been proposed.

The stacked type phase change memory has, for example, a plurality of GeTe films and Sb ₂ Te ₃ films stacked alternately. According to the numerical calculation results in Non-Patent Document 1, the phase change between the crystalline phase and the amorphous phase is caused only by the movement of Ge atoms at the interface between the adjacent GeTe film and the Sb ₂ Te ₃ film. Arise. Therefore, in the above-described phase change memory, such a stacked structure is expected as one of the measures that can increase the writing speed.

International Publication No. 2008/090963

Japanese Journal of Applied Physics 48 (2009) 03A053, J. Tominaga, et al

  However, although the non-patent document 1 proposes the characteristics of the laminated body in which the phase change occurs on the principle as described above and the contribution to the performance of the phase change memory by the characteristics, It was only discovered by numerical calculation.

  For this reason, for example, conditions for depositing a laminate having the above-described characteristics by sputtering have not yet been sufficiently studied, and therefore, development of such deposition conditions is eagerly desired.

Such a problem is not limited to the case where the phase change memory has a stack of metal chalcogenide films composed of a GeTe film and an Sb ₂ Te ₃ film, but a stack of other metal chalcogenide films. Are generally common.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method of forming a phase change memory capable of increasing the speed of read / write operations in a phase change memory having a stack of metal chalcogenide films, and a phase change memory. An object of the present invention is to provide an apparatus for forming a change memory.

Hereinafter, means for solving the above-described problems and the effects thereof will be described.
One aspect of the present invention is a method of forming a phase change memory in which a phase change memory is formed by stacking two or more metal chalcogenide films having different compositions on a substrate. While heating the temperature to 250 ° C. or more and 350 ° C. or less, each of two or more metal chalcogenide targets having different compositions is sputtered with argon gas at different timings, and two or more metal chalcogenide targets having different compositions are sputtered. The gist is to stack a metal chalcogenide film on the substrate at a rate of 3 nm to 10 nm per second.

  The phase change of the metal chalcogenide film at the boundary between the metal chalcogenide films having different compositions is generated uniformly by simply forming different metal chalcogenide films at different timings. The present inventors have found that it is difficult.

  In other words, the inventors of the present application formed a film if all of the metal chalcogenide films constituting the laminate were not formed from crystals having a uniform plane orientation, particularly [111] orientation, in the plane during the film formation. It has been found that the phase change in the later laminate is also difficult to occur uniformly in the plane.

  In this respect, in one aspect of the present invention, when the metal chalcogenide film is formed by sputtering each target, the temperature of the substrate to which the sputtered particles reach is set to 250 ° C. to 350 ° C. The speed is 3 nm or more and 10 nm or less. For this reason, the sputtered particles emitted from each target can obtain energy that allows surface diffusion on the substrate by kinetic energy when sputtered and thermal energy received from the substrate. In addition, since the new sputtered particles arrive on the substrate at such a frequency that does not hinder the surface diffusion of the sputtered particles, the uniformity of the growth rate of the metal chalcogenide film within the surface of the substrate can be improved. As a result, the flatness of the metal chalcogenide film is increased, and as a result, the crystal plane orientation of the metal chalcogenide film is easily aligned with the [111] orientation. As a result, phase changes occur uniformly at the boundaries between different metal chalcogenide films, and the time required for such phase changes is shortened. As a result, the speed of read / write operations is increased in the phase change memory having the stacked body. be able to.

  One aspect of the present invention is that two or more metal chalcogenide films having different compositions are laminated on the substrate while rotating the substrate stage on which the substrate is placed.

  In one aspect of the present invention, the metal chalcogenide film is formed while rotating the substrate stage. Therefore, the uniformity of the amount of sputtered particles that reach the substrate in the circumferential direction is improved. Therefore, the growth and flatness of the metal chalcogenide film in the plane of the substrate are enhanced, and as a result, the uniformity of the plane orientation is enhanced. Therefore, the speed of the read / write operation in the phase change memory having the stacked body is increased.

One aspect of the present invention is that the mounting surface of the substrate in the substrate stage is a heating surface, and the substrate is heated while adsorbed to the heating surface.
In one aspect of the present invention, the substrate is adsorbed and heated by the mounting surface of the substrate stage. Therefore, temperature variations in the surface of the substrate can be reduced. Therefore, it is possible to reduce the variation in energy given from the substrate to the sputtered particles in the plane of the substrate, and to reduce the variation in the surface diffusion of the sputtered particles. Therefore, film growth and flatness within the surface of the substrate can be improved.

In one aspect of the present invention, the metal chalcogenide target includes a GeTe target and an Sb ₂ Te ₃ target, and the GeTe target has a Ge content of 9.13 mass% to 69.5 mass% and a Te content of 30. The Sb ₂ Te ₃ target contains 29 mass% or more and 89.6 mass% or less, and Te contains 10.4 mass% or more and 71 mass% or less. Each of the GeTe target and the Sb ₂ Te ₃ target is sputtered in an atmosphere of 0.05 Pa to 1 Pa, and the GeTe film and the Sb ₂ Te ₃ film are formed on the substrate at a rate of 3 nm to 10 nm per second. The gist is to laminate.

In one aspect of the present invention, the GeTe target comprises 9.13 mass% to 69.5 mass% Ge and 30.5 mass% to 90.87 mass% Te, while Sb ₂ The Te ₃ target contains 29 mass% or more and 89.6 mass% or less of Sb and 10.4 mass% or more and 71 mass% or less of Te. Then, when forming a GeTe film by sputtering a GeTe target and when forming a Sb ₂ Te ₃ film by sputtering an Sb ₂ Te ₃ target, each atmosphere is in an atmosphere of 0.05 Pa or more and 1 Pa or less. The films are stacked on the substrate at a rate of 3 nm or more and 10 nm or less per second, that is, the sputtering rate of each film is set to 3 nm or more per second. Therefore, the ratio of Ge to Te in the GeTe film and the ratio of Ge to Sb in the Sb ₂ Te ₃ film are almost stoichiometric compositions. Therefore, the GeTe film and the Sb2Te3 film are easily grown in a uniform plane orientation. Thereby, the orientation of the crystals constituting each film is easily aligned with the [111] orientation.

  One aspect of the present invention is to switch the sputtering target using a shutter that exposes the metal chalcogenide target to be sputtered among the metal chalcogenide targets and covers the metal chalcogenide targets other than the sputtering target. When performing, the gist is to switch the metal chalcogenide target exposed from the shutter.

  In one aspect of the present invention, the metal chalcogenide target exposed from the shutter is switched in conjunction with the switching of the sputtering target. Therefore, when one metal chalcogenide film is formed, it is possible to suppress the mixture of sputtered particles emitted from the metal chalcogenide target for forming the other metal chalcogenide film. Therefore, the composition of each metal chalcogenide film is easily maintained at a stoichiometric composition, and as a result, the crystal orientation constituting each metal chalcogenide film is easily aligned with the [111] orientation.

One aspect of the present invention is to equalize the temperature of the heating surface when switching the sputtering target between two or more metal chalcogenide targets and the temperature of the heating surface when sputtering the metal chalcogenide target. Is the gist.

  In one aspect of the present invention, the temperature of the heating surface of the substrate stage is made equal when the sputtering target is switched and when the metal chalcogenide target is sputtered. Therefore, the temperature of the substrate can be made substantially constant from the start to the stop of the lamination of the metal chalcogenide film. Therefore, a temperature difference is formed on the substrate at the boundary between the switching period and the sputtering period, so that the difference in energy given to the sputtered particles from the substrate immediately after the start of the sputtering period and the subsequent sputtering period is reduced. Can be suppressed. Thereby, it is possible to suppress the degree of surface diffusion of the sputtered particles reaching the substrate from changing within each sputtering period. Therefore, the growth of each metal chalcogenide film and the uniformity in the plane of the flat substrate can be improved.

  One aspect of the present invention is a phase change memory forming apparatus for forming a phase change memory by stacking two or more metal chalcogenide films having different compositions on a substrate. A sputtering source that sputters each of two or more metal chalcogenide targets with argon gas and a substrate stage that heats the substrate, and the substrate stage heated the temperature of the substrate to 250 ° C. to 350 ° C. In this state, the sputtering source sputters each of the two or more metal chalcogenide targets at different timings, so that two or more metal chalcogenide films having different compositions can be formed at a rate of 3 nm to 10 nm per second. The gist is to laminate on a substrate.

  In one aspect of the present invention, when each metal target is sputtered by a sputtering source to form a metal chalcogenide film, the substrate temperature at which the sputtered particles reach is heated to 250 ° C. to 350 ° C. by the substrate stage. The sputtering rate is 3 nm or more and 10 nm or less per second. For this reason, the sputtered particles emitted from each target can obtain energy that allows surface diffusion on the substrate by kinetic energy when sputtered and thermal energy received from the substrate. In addition, since the new sputtered particles arrive on the substrate at such a frequency that does not hinder the surface diffusion of the sputtered particles, the uniformity of the growth rate of the metal chalcogenide film within the surface of the substrate can be improved. As a result, the flatness of the metal chalcogenide film is increased, and as a result, the crystal plane orientation of the metal chalcogenide film is easily aligned with the [111] orientation. As a result, phase changes occur uniformly at the boundaries between different metal chalcogenide films, and the time required for such phase changes is shortened. As a result, the speed of read / write operations is increased in the phase change memory having the stacked body. be able to.

The figure which shows the whole structure of the sputtering device as one Embodiment in the formation apparatus of the phase change memory of this invention. The timing chart which shows the switching mode of a target. (A) Sectional drawing which shows the cross-sectional structure of the metal chalcogenide laminated body formed with the same sputtering device. (B) (c) The figure which shows the mode of the phase change in a laminated body. The graph which shows the relationship between a sputtering speed and the root mean square roughness in the surface of a GeTe film | membrane. The graph which shows the XRD peak intensity | strength of the low-speed GeTe film | membrane whose root mean square roughness is 0.2 nm or less, and the XRD peak intensity | strength of the high-speed GeTe film | membrane whose root mean square roughness is larger than 0.2 nm. The graph which shows the relationship between a sputtering rate and the composition of a GeTe film | membrane. The graph which shows the relationship between a sputtering speed and crystal orientation. The fragmentary sectional view which shows the partial cross-section of the conventional phase change memory.

  Hereinafter, an embodiment of a method for forming a phase change memory and an apparatus for forming a phase change memory according to the present invention will be described with reference to FIGS. First, a sputtering apparatus as an embodiment of a phase change memory forming apparatus will be described with reference to FIG.

[Configuration of sputtering equipment]
An upper lid 12 that seals the upper surface is fixed to a cylindrical vacuum chamber 11 provided in the sputtering apparatus 10. In the vacuum chamber 11, a substrate stage 13 that holds a disk-shaped processing substrate S to be processed is installed. The substrate stage 13 incorporates a chuck electrode 14 for electrostatically attracting the processing substrate S to the mounting surface 13 a of the substrate stage 13. A chuck power supply 15 for supplying a direct current to the chuck electrode 14 is connected to the chuck electrode 14. As a result, the processing substrate S is electrostatically attracted to the placement surface 13a of the substrate stage 13, so that, for example, a suction hole for vacuum suction is formed on the placement surface 13a, or mechanically by a mechanical chuck or the like. Compared to the configuration in which the processing substrate S is held, the area of the processing substrate S that contacts the placement surface 13a can be increased. Thereby, the dispersion | variation in the temperature in the surface of the process board | substrate S can be suppressed.

In addition, the substrate stage 13 incorporates a heater 16 for heating the processing substrate S placed on the placement surface 13a serving as a heating surface. A heater power supply 17 that supplies a DC voltage to the heater 16 is connected to the heater 16. The heater 16 is a resistance heater that radiates heat when a DC voltage is applied from the heater power supply 17. For example, the heater 16 heats the processing substrate S to a temperature of 250 ° C. or higher and 350 ° C. or lower. Incidentally, the temperature of the processing substrate S is set to a range in which the GeTe film and the Sb ₂ Te ₃ film can be formed in a crystal phase state. The substrate stage 13 is connected to a thermometer 18 that measures the temperature of the substrate stage 13. Further, a rotation mechanism 19 that rotates the substrate stage 13 in the circumferential direction of the processing substrate S is connected to the substrate stage 13. The rotation mechanism 19 includes a motor and a rotation shaft that transmits the rotation of the motor to the substrate stage 13.

  A first backing plate 21a and a second backing plate 21b made of metal are fitted into the upper lid 12 that seals the vacuum chamber 11 via an insulating material 12a. On the vacuum chamber 11 side of the first backing plate 21a, a GeTe target 22a is bonded so that the surface of the GeTe target 22a and the mounting surface 13a of the substrate stage 13 are substantially parallel. The GeTe target 22a includes 9.13% by mass to 69.5% by mass of Ge and 30.5% by mass to 90.87% by mass of Te.

  On the other hand, a first magnet unit 23a is disposed on the opposite side of the first backing plate 21a from the GeTe target 22a. The permanent magnet mounted on the first magnet unit 23a forms a magnetic field on the surface of the GeTe target 22a on the vacuum chamber 11 side.

The Sb ₂ Te ₃ target 22b is bonded to the second backing plate 21b on the vacuum chamber 11 side so that the surface of the Sb ₂ Te ₃ target 22b and the mounting surface 13a of the substrate stage 13 are substantially parallel to each other. Has been. The Sb ₂ Te ₃ target 22b contains 29 mass% or more and 89.6 mass% or less of Sb and 10.4% or more and 71 mass% or less of Te.

On the other hand, the second magnet unit 23b is disposed on the opposite side of the second backing plate 21b from the Sb ₂ Te ₃ target 22b. The permanent magnet mounted on the second magnet unit 23b forms a magnetic field on the surface of the Sb ₂ Te ₃ target 22b on the vacuum chamber 11 side.

  A high frequency power supply 24 and a DC power supply 25 connected in parallel are connected to the first backing plate 21a via a first switch SWa, while the second backing plate 21b is connected to a first switch SWb via a second switch SWb. The high frequency power supply 24 and the DC power supply 25 are connected. Each of the high frequency power supply 24 and the DC power supply 25 has a switch for starting or stopping the supply of power. The frequency of the high frequency power output from the high frequency power supply 24 is, for example, 13.56 MHz. With such a configuration, the backing plates 21a and 21b are supplied with power only from the high frequency power supply 24, supplied with power only from the DC power supply 25, or from both the high frequency power supply 24 and the DC power supply 25. Power can be supplied.

A shutter 26 that covers the GeTe target 22a and the Sb ₂ Te ₃ target 22b and can selectively expose the surface of one of the targets is disposed on the upper lid 12 side in the vacuum chamber 11. The shutter 26 covers the other target when the one target is being sputtered. As a result, it is possible to prevent particles sputtered from the two targets 22a and 22b from being mixed in a single film and to prevent particles sputtered from one target from adhering to the other target.

  An exhaust port 11a is formed through the lower surface of the vacuum chamber 11, and an exhaust unit 31 is connected to the exhaust port 11a. The exhaust unit 31 includes various vacuum pumps and a valve that adjusts the exhaust speed of the vacuum pump. A gas supply port 11b is formed through the side surface of the vacuum chamber 11, and an argon gas supply unit 32 for supplying argon (Ar) gas used for sputtering is connected to the gas supply port 11b. The argon gas supply unit 32 is a mass flow controller connected to a cylinder storing Ar gas, and adjusts the flow rate of Ar gas supplied to the vacuum chamber 11 to, for example, 5 sccm or more and 100 sccm or less.

  When the targets 22a and 22b are sputtered, the pressure in the vacuum chamber 11 is set to 0.05 Pa or more and 1 Pa or less depending on the flow rate of the argon gas supplied from the argon gas supply unit 32 and the exhaust speed of the exhaust unit 31. The

In the present embodiment, the high-frequency power source 24 and the argon gas supply unit 32 constitute a sputtering source.
[Operation of sputtering equipment]
Of the operations of the sputtering apparatus 10, operations performed when the sputtering apparatus 10 forms a stacked body of metal chalcogenide films will be described with reference to FIG. 2. FIG. 2 shows an output mode of drive commands from the control device mounted on the sputtering apparatus 10 to the argon gas supply unit 32, the high frequency power supply 24, the first switch SWa, the second switch SWb, and the shutter 26. Yes.

When forming the laminated body, first, the pressure in the vacuum chamber 11 is reduced to a predetermined pressure by the exhaust unit 31. When the pressure in the vacuum chamber 11 is reduced, the processing substrate S is carried into the vacuum chamber 11 from a carry-in / out port (not shown), and the processing substrate S is placed on the mounting surface of the substrate stage 13 heated by the heater 16. 13a. As shown in FIG. 8, the processing substrate S is, for example, an insulating film 51 made of silicon oxide (SiO ₂ ) formed on a silicon substrate and nitriding covering the side surfaces of holes formed in the insulating film 51. A heat insulating layer 52 made of silicon (SiN) and a lower electrode 53 made of tungsten (W) embedded in a hole so as to be covered with the heat insulating layer 52 are provided.

  When the processing substrate S is placed on the placement surface 13a, a drive command is output from the control device to the argon gas supply unit 32 at timing T1, as shown in FIG. Argon gas is supplied from the argon gas supply unit 32 into the vacuum chamber 11. Thereby, the pressure in the vacuum chamber 11 is set to 0.05 Pa or more and 1 Pa or less. At this time, a DC current is supplied from the chuck power supply 15 to the chuck electrode 14 so that the processing substrate S is electrostatically attracted to the mounting surface 13a. When the processing substrate S is electrostatically attracted, the rotation mechanism 19 rotates the substrate stage 13 to rotate the processing substrate S in the circumferential direction.

  At timing T2, a drive command is output from the control device to the shutter 26, so that only the surface of the GeTe target 22a is exposed in the vacuum chamber 11 from the opening of the shutter 26. When the surface of the GeTe target 22a is exposed, at timing T3, a drive command is output from the control device to the high frequency power supply 24, and the first switch SWa is switched from the control device to the first switch SWa. A drive command for turning on is output. As a result, predetermined high-frequency power is supplied from the high-frequency power source 24 to the first backing plate 21a and the GeTe target 22a via the first switch SWa. When the high frequency power is supplied to the GeTe target 22a in this way, the GeTe target 22a is sputtered by positive ions in the plasma generated around the GeTe target 22a.

  By sputtering the GeTe target 22a, a GeTe film as a metal chalcogenide film is formed on the entire surface of the insulating film 51 with a thickness of 1 nm, for example. When the GeTe film is formed, the high-frequency power output from the high-frequency power supply 24, the pressure in the vacuum chamber 11 and the like are set to values at which the sputtering rate of the GeTe film is 3 nm / sec or more and 10 nm / sec or less.

When the GeTe film is formed, the target of sputtering is switched from the GeTe target 22a to the Sb ₂ Te ₃ target 22b. In the switching period between the targets 22a and 22b, first, at timing T4, a drive signal for turning off the first switch SWa is output from the control device to the first switch SWa. The supply of high-frequency power via one switch SWa is stopped. Then, at timing T5, a drive signal is output from the control device to the shutter 26, whereby the surface of the GeTe target 22a is covered by the shutter 26 and only the surface of the Sb ₂ Te ₃ target 22b is exposed to the shutter 26. It is exposed in the vacuum chamber 11 from the opening.

When the switching of the sputtering target between the targets 22a and 22b is completed, at timing T6, a drive command for turning on the second switch SWb is output from the control device to the second switch SWb. As a result, predetermined high-frequency power is supplied from the high-frequency power source 24 to the second backing plate 21b and the Sb ₂ Te ₃ target 22b via the second switch SWb. As a result, the Sb ₂ Te ₃ target 22b is sputtered by the positive ions in the plasma generated around the Sb ₂ Te ₃ target 22b.

By sputtering the Sb ₂ Te ₃ target 22b, an Sb ₂ Te ₃ film as a metal chalcogenide film is formed on the entire surface of the GeTe film with a thickness of, for example, 1 nm. When the Sb ₂ Te ₃ film is formed, the high-frequency power output from the high-frequency power source 24, the pressure in the vacuum chamber 11 and the like set the sputtering rate of the Sb ₂ Te ₃ film to 3 nm / sec or more and 10 nm / sec or less. Set to a value.

When the Sb ₂ Te ₃ film is formed, the target of sputtering is switched from the Sb ₂ Te ₃ target 22b to the GeTe target 22a. In the switching period between the targets 22a and 22b, first, at timing T7, a drive signal for turning off the second switch SWb is output from the control device to the second switch SWb. The supply of high-frequency power via the two switch SWb is stopped. Then, at timing T8, a drive signal is output from the control device to the shutter 26, whereby the surface of the Sb ₂ Te ₃ target 22b is covered with the shutter 26 and only the surface of the GeTe target 22a is exposed to the shutter 26. It is exposed in the vacuum chamber 11 from the opening.

When the switching between the targets 22a and 22b is completed, at timing T9, a drive command for turning on the first switch SWa is output from the control device to the first switch SWa. As a result, predetermined high-frequency power is supplied from the high-frequency power source 24 to the first backing plate 21a and the GeTe target 22a via the first switch SWa. As a result, the GeTe target 22a is sputtered again, whereby a GeTe film is formed on the entire surface of the Sb ₂ Te ₃ film with a thickness of 1 nm, for example. At this time as well, from the timing T3 to the timing T4, the high-frequency power output from the high-frequency power source 24, the pressure in the vacuum chamber 11 and the like are set to values at which the sputtering rate is 3 nm / sec or more and 10 nm / sec or less. Is done.

When the GeTe film is formed, the target of sputtering is switched again from the GeTe target 22a to the Sb ₂ Te ₃ target 22b. From timing T10 to timing T12, which is a switching period of the targets 22a and 22b, the same operation as that from timing T4 to timing T6 is performed.

As described above, the GeTe target 22a and the Sb ₂ Te ₃ target 22b are sputtered at different timings, and the GeTe target 22a and the Sb ₂ Te ₃ target 22b are alternately sputtered a predetermined number of times, for example, 10 times. As a result, a laminate composed of 20 metal chalcogenide films is formed. When the stacked body is formed, at timing T13, a drive command for turning off the second switch SWb is output from the control device to the second switch SWb, so that the second switch SWb is passed through. The supply of high-frequency power is stopped. Next, at timing T <b> 14, a drive command is output from the control device to the argon gas supply unit 32 and the high frequency power supply 24, whereby supply of argon gas and supply of high frequency power are stopped. Similarly, at timing T14, the drive command is output from the control device to the shutter 26, so that the surface of the Sb ₂ Te ₃ target 22b is covered. As a result, the surfaces of both targets 22 a and 22 b are covered with the shutter 26.

Note that the control device maintains the temperature of the substrate stage 13 with respect to the heater power source 17 constant from timing T1 to timing T14 based on the measurement result input at a predetermined time interval from the thermometer 18. Such a drive signal is output. That is, the temperature of the substrate stage 13 is continuously controlled so that the temperature of the mounting surface 13a is maintained at a predetermined temperature in the range of 250 ° C. or higher and 350 ° C. or lower during the switching period and the sputtering period. Therefore, the temperature of the processing substrate S is maintained at the same temperature during the switching period and during sputtering of the GeTe target. Therefore, even if the composition causes a phase change due to thermal energy, such as a boundary surface between the GeTe film 44a and the Sb ₂ Te ₃ film 44b, the occurrence of the phase change due to the thermal energy can be suppressed.

  Incidentally, the switching period is from timing T4 to timing T6, from timing T7 to timing T9, and from timing T10 to timing T12. The sputtering periods are from timing T3 to timing T4, from timing T6 to timing T7, from timing T9 to timing T10, and from timing T12 to timing T13.

Further, as described above, when switching between the GeTe target 22a and _Sb 2 Te ₃ target 22b, the power to any of the GeTe target 22a and _Sb 2 Te ₃ target 22b is a state of not being fed. One of the targets is exposed from the opening of the shutter 26, and the other target is covered with the shutter 26, and then power is supplied to the target to be sputtered.

Therefore, at the boundary between the GeTe film and the Sb ₂ Te ₃ film, mixing of sputtered particles for forming each film can be suppressed. In addition, it is possible to prevent particles sputtered from one target from adhering to the surface of the other target. For this reason, in the film formed immediately after the sputtering of the targets 22a and 22b is started, it is possible to suppress mixing of particles sputtered from the two targets 22a and 22b.

  When the stacked body is formed on the processing substrate S, the rotation of the substrate stage 13 by the rotation mechanism 19 is stopped, and then the application of the DC voltage from the chuck power supply 15 to the chuck electrode 14 is stopped. Then, the processing substrate S is carried out of the vacuum chamber 11 from the carry-in / out port of the vacuum chamber 11.

  When the formation of the laminated body by the sputtering apparatus 10 is completed, an upper electrode is formed on the laminated body by a known film forming apparatus such as a sputtering apparatus, and then a part of the laminated body and the upper electrode is formed by a dry etching apparatus or the like. Are selectively removed. Thereby, a phase change memory having a stacked body of metal chalcogenide films sandwiched between the upper electrode and the lower electrode is formed.

[Operation of phase change memory]
Next, the phase change which occurs in the laminate will be described with reference to FIG. As shown in FIG. 3A, in the recess of the insulating film 41 made of SiO ₂ formed on the substrate, a heat insulating layer 42 made of SiN is formed on the inner peripheral surface of the recess, and the heat insulating layer 42 A lower electrode 43 made of W is embedded in the inside. A stacked body 44 is formed on the upper surface of the insulating film 41 so as to cover the upper end surface of the lower electrode 43. The stacked body 44 has a configuration in which GeTe films 44a having a thickness of 1 nm and Sb ₂ Te ₃ films 44b having a thickness of 1 nm are alternately stacked. An upper electrode 45 made of, for example, W is stacked on the stacked body 44. The stacked body 44 and the upper electrode 45 are formed on the entire top surface of the insulating film 41 and then patterned into a predetermined shape by dry etching or the like.

In the stacked body 44, since the GeTe film 44a and the Sb ₂ Te ₃ film 44b are alternately stacked, the Ge atom, Sb atom, and Te are formed at the boundary between the GeTe film 44a and the Sb ₂ Te ₃ film 44b. An atom exists. At such a boundary, only Ge atoms 44G out of Te atoms 44T and Ge atoms 44G constituting the GeTe film 44a are formed by the thermal energy of the lower electrode 43 according to the current flowing between the lower electrode 43 and the upper electrode 45. Moving. This reversibly changes the phase of the compound formed by the Ge, Sb, and Te atoms.

  More specifically, the GeSbTe compound is heated at a relatively low temperature for a long time and then gently cooled to change the amorphous phase shown in FIG. 3B to the crystalline phase shown in FIG. 3C. On the other hand, by being rapidly cooled after being heated at a relatively high temperature for a short time, the crystalline phase shown in FIG. 3C is changed to an amorphous phase as shown in FIG. The GeSbTe compound that has become an amorphous phase or a crystalline phase by such heat treatment is maintained in this state regardless of whether it is in an amorphous phase or a crystalline phase at a room temperature of about 20 ° C. to 25 ° C., for example.

However, the phase change of the GeSbTe compound at the boundary between the GeTe film 44a and the Sb ₂ Te ₃ film 44b as described above can be achieved by simply stacking the GeTe films 44a and the Sb ₂ Te ₃ films 44b alternately. In other words, the inventors of the present application have found that it does not easily occur in the plane of the processing substrate S.

That is, the inventors of the present invention have a uniform plane orientation, particularly [111] orientation, in the surface of the processing substrate S during the film formation of the GeTe film 44a and the Sb ₂ Te ₃ film 44b constituting the stacked body 44. It has been found that if it is not formed from crystals, the phase change in the laminate 44 is also difficult to occur uniformly in the plane of the processing substrate S after film formation. In addition, the inventors of the present application formed the GeTe film 44a and the Sb ₂ Te ₃ film 44b using the sputtering apparatus 10 to change the phase of the GeSbTe compound at the boundary between the GeTe film 44a and the Sb ₂ Te ₃ film 44b. It has also been found that it is expressed even during the course.

In this regard, in the present embodiment, when the stacked body 44 is formed using the sputtering apparatus 10, the temperature of the processing substrate S is maintained at a predetermined temperature in the range of 250 ° C. to 350 ° C. In addition, the sputtering rate when forming the GeTe film 44a and the sputtering rate when forming the Sb ₂ Te ₃ film are 3 nm / sec or more and 10 nm / sec or less.

According to this, the sputtered particles emitted from the targets 22a and 22b can be diffused on the surface of the processing substrate S by the kinetic energy when sputtered and the thermal energy received from the processing substrate S. You can get energy. In addition, since new sputtered particles arrive on the processing substrate S at a frequency that does not hinder the surface diffusion of the sputtered particles, the uniformity of the film growth rate within the surface of the processing substrate S is improved. As a result, the flatness of the film becomes high, and as a result, the plane orientation of the crystals constituting the film easily aligns with the [111] orientation. As a result, the phase change at the boundary between the GeTe film 44a and the Sb ₂ Te ₃ film occurs uniformly, and the time required for such a phase change is shortened. As a result, in the phase change memory having the stacked body 44, The reading / writing operation speed can be increased.

  When the sputtering rate is higher than 10 nm / sec, the sputtered particles can obtain energy that allows surface diffusion during sputtering and when reaching the processing substrate S. However, since the sputtered particles are combined with other sputtered particles that have reached the processing substrate S before the surface diffusion sufficiently, the film growth rate varies within the surface of the processing substrate S. As a result, the flatness of the film is lowered, and as a result, the uniformity of the plane orientation of the crystals constituting the film is also lowered.

  Further, for example, when the temperature of the processing substrate S is less than 250 ° C., the sputtered particles can only obtain energy from the processing substrate S such that the surface of the sputtered particles hardly diffuses on the processing substrate S. When the temperature of S exceeds 350 ° C., the degree of surface diffusion of the sputtered particles is large, so that the bonding with other sputtered particles easily proceeds. Therefore, even if the temperature of the processing substrate S is included in any range, the film growth rate varies within the surface of the processing substrate S. As a result, the flatness of the film is lowered, and as a result, the uniformity of the plane orientation of the crystals constituting the film is also lowered.

In addition, in this embodiment, when forming the laminated body 44 using the sputtering apparatus 10, the pressure in the vacuum chamber 11 is set to 0.05 Pa or more and 1 Pa or less. Further, as GeTe target 22a, Ge and 9.13 mass% or more 69.5% by mass or less, with those comprising 30.5 wt% or more 90.87 mass% of Te, and, _Sb 2 Te ₃ target As for Sb, 29% by mass or more and 89.6% by mass or less are used. In addition, the sputtering rate when forming the GeTe film 44a and the sputtering rate when forming the Sb ₂ Te ₃ film 44b are set to 3 nm / sec or more.

Under these conditions, the ratio of Ge to Te in the GeTe film 44a and the ratio of Ge to Sb in the Sb ₂ Te ₃ film 44b are almost stoichiometric compositions. This is because, according to the above conditions, when the GeTe film 44a is formed, the amount of Ge that has reached the substrate and the amount of Te that has been volatilized relatively easily with respect to Ge from the amount of Te that has reached the substrate. This is because the difference obtained by subtracting the amount is substantially equal. On the other hand, when the Sb ₂ Te ₃ film is formed, the difference obtained by subtracting the amount of Te that has volatilized from the amount of Te that has reached the substrate is approximately 3/2 times the amount of Sb that has reached the substrate. It is to become. Therefore, the GeTe film 44a and the Sb ₂ Te ₃ film 44b are easy to grow in a uniform plane orientation, and as a result, the orientation of the crystals constituting each film is easily aligned with the [111] orientation.

[Test example]
A GeTe film was formed on a silicon substrate having a diameter of 200 mm under the following conditions.
-GeTe target Ge: 36.3 mass%, Te: 63.7 mass%
・ Ar gas flow rate 50sccm
・ Pressure in the vacuum chamber 0.2-0.5Pa
・ Target power 50W-1000W
・ Silicon substrate temperature 300 ℃
・ Film thickness 10nm
The sputtering rate was changed in the range of 1 nm / sec or more and 13 nm / sec or less, and the root mean square roughness (JIS B 0601) (nm) on the surface of each GeTe film was calculated. FIG. 4 shows the relationship between the calculated value of the root mean square roughness and the sputtering rate. Further, the crystallinity of each GeTe film was evaluated using X-ray diffraction (XRD). Of the above sputtering rates, the diffraction peak observed in the low-speed GeTe film of 3 nm / sec or more and 10 nm / sec or less is shown by the solid line L1 in FIG. 5, and the diffraction peak recognized in the high-speed GeTe film having a sputtering rate exceeding 10 nm / sec. Is shown by a one-dot chain line L2 in FIG.

  Also, using energy dispersive X-ray spectroscopy (EDX), the composition ratio of each GeTe film, specifically, the amount of Te with respect to the sum of the amount of Ge and the amount of Te The ratio of was measured. FIG. 6 shows the relationship between the composition ratio of the GeTe film and the sputtering rate. Furthermore, the ratio of [111] orientation strength (Ifcc) in each GeTe film to other orientation strengths in the GeTe film was measured using the XRD measurement result. The relationship between [111] orientation strength and sputtering rate is shown in FIG. When this ratio is 20 or more, it can be considered that the orientation of the crystals constituting the GeTe film is aligned with the [111] orientation.

  As shown in FIG. 4, the root mean square roughness of the GeTe film formed at a sputtering rate of 3 nm / sec or more and 10 nm / sec or less is substantially the same value, and is 0.1 nm or more and 0.2 nm. It was within the following range. On the other hand, when the sputtering rate exceeds 10 nm / sec, the root mean square roughness when the sputtering rate is 11 nm / sec is 0.24 nm and the root mean square when the sputtering rate is 12 nm / sec. The root mean square roughness when the roughness was 0.3 nm and the sputtering rate was 13 nm / sec was 0.5 nm. As described above, when the sputtering rate exceeds 10 nm / sec, the root mean square roughness of the GeTe film also increases as the sputtering rate increases.

Incidentally, by using the _Sb 2 Te ₃ target was formed of _Sb 2 Te ₃ film under the same conditions as described above, similar results as when creating the GeTe film was observed. This is because the ratio of the proportion of Sb that reaches the substrate as sputtered particles to the proportion of Te that contributes to film formation among the Te that reaches the substrate as sputtered particles is Ge and Te. This is because it is the same as that.

  As shown in FIG. 5, in the low-speed GeTe film, the intensity of X-rays at 2θ when θ = 25.5 ° is the highest, so the crystal having the [111] orientation of the face-centered cubic crystal is the most. It was recognized that many were included. In addition, in the low-speed GeTe film, the intensity of X-rays at 2θ when θ = 52.5 ° is the second highest, and therefore the second most crystals with [222] orientation of face-centered cubic crystals are included. It was recognized that In addition, when the angle of θ was other than the above, almost no X-ray reflection was observed at 2θ.

  On the other hand, as shown in FIG. 5, in the high-speed GeTe film, as in the low-speed GeTe film, it was recognized that the intensity of X-rays at 2θ when θ = 25.5 ° was the highest. . However, since the intensity of X-rays at 2θ when θ = 29.5 is as high as when θ = 22.5 °, the high-speed GeTe film has a face-centered cubic [200]. It was confirmed that relatively many crystals were oriented. In the high-speed GeTe film, similar to the low-speed GeTe film, reflection of X-rays at 2θ when θ = 52.5 ° is observed, and further, X at 2θ when θ = 42.5 ° is observed. Line reflection was also observed. That is, it was confirmed that the high-speed GeTe film also includes a crystal having a [220] orientation of face-centered cubic.

From these results, GeTe films formed at a relatively low speed are mostly [111] oriented crystals, whereas GeTe films formed at a relatively high speed are [111] oriented crystals. However, it is recognized that many crystals with other orientations are also contained, that is, the variation in orientation is relatively large. Incidentally, by using the _Sb 2 Te ₃ target was formed of _Sb 2 Te ₃ film under the same conditions as described above, similar results as when forming a GeTe film was observed.

As shown in FIG. 6, when the sputtering rate is 1 nm / sec or more and less than 3 nm / sec, it was recognized that the value of Te / (Ge + Te) increases as the sputtering rate increases. On the other hand, when the sputtering rate was 3 nm / sec or more, it was confirmed that the value of Te / (Ge + Te) was almost constant, and that Ge and Te were included approximately 1: 1. That is, it was recognized that the composition of the GeTe film was almost stoichiometric. As in Test Example 1, when an Sb ₂ Te ₃ film was formed under the same conditions as described above using an Sb ₂ Te ₃ target, the same results as when a GeTe film was formed were observed.

As shown in FIG. 7, it was recognized that the ratio was 20 or more when the sputtering rate was 3 nm / sec or more and 10 nm / sec or less. In accordance with these results, in view of the results shown in FIG. 6 above, it was confirmed that when the GeTe film has a substantially stoichiometric composition, the crystals constituting the GeTe film are aligned with the [111] orientation. . In addition to the results shown in FIG. 7, in consideration of the results shown in FIG. 5, when the root mean square roughness of the GeTe film is 0.2 nm or less, the crystals constituting the GeTe film are [111] It was confirmed that the alignment was aligned. Incidentally, by using the _Sb 2 Te ₃ target was formed of _Sb 2 Te ₃ film under the same conditions as described above, similar results as when forming a GeTe film was observed.
[Example]
Of the above film forming conditions, the GeTe film and the Sb ₂ Te ₃ film are alternately stacked on the condition that the sputtering rate is 3 nm / sec or more and 10 nm / sec or less, whereby the phase change memory of Example 1 is obtained. Obtained. Moreover, the phase change memory of Comparative Example 1 was obtained by alternately stacking GeTe films and Sb ₂ Te ₃ films on the condition that the sputtering rate was less than 3 nm / sec among the above film forming conditions. . Further, among the film forming conditions, by the sputtering rate is laminated under conditions of greater than 10 nm / sec GeTe film and _Sb 2 Te ₃ film are alternately ten layers, to obtain a phase change memory of Comparative Example 2. Further, by the Ge ₂ Sb ₂ Te ₅ film formed under the following conditions and the phase change layer, to obtain a phase change memory of Comparative Example 3.

・ Ar gas flow rate 50sccm
・ Pressure in vacuum chamber 0.5Pa
・ Target power 500W
・ Silicon substrate temperature 250 ℃
・ Thickness 200nm
Then, the set time, which is the time until the phase changes from the amorphous state to the crystalline state, and the reset time, which is the time until the phase changes from the crystalline state to the amorphous state, in each phase change memory were measured. . The measurement results are shown in Table 1 below.

As described above, according to the phase change memory of Example 1 including the GeTe film and the Sb ₂ Te ₃ film formed at the above-described preferable sputtering rate, the comparative example 3 including the single Ge ₂ Sb ₂ Te ₅ film. It was found that both the set time and the reset time are shorter than the phase change memory, that is, the time required for the read / write operation is shortened. In contrast, although the using a stack of GeTe film and _Sb 2 Te ₃ film, if it is GeTe film and _Sb 2 Te ₃ film formed by not included in the preferred range described above sputter rate, the above-mentioned It was recognized that such an effect could not be obtained.

As described above, according to the phase change memory forming apparatus and the phase change memory forming method of the present embodiment, the following effects can be obtained.
(1) Sputtered particles emitted from the targets 22a and 22b can obtain energy that allows surface diffusion on the processing substrate S when they are sputtered and when they reach the processing substrate S. it can. In addition, since new sputtered particles arrive on the processing substrate S at a frequency that does not hinder the surface diffusion of the sputtered particles, the uniformity of the film growth rate within the surface of the processing substrate S is improved. As a result, the flatness of the GeTe film 44a and the Sb ₂ Te ₃ film 44b increases, and as a result, the plane orientation of the crystals constituting the film easily aligns with the [111] orientation. As a result, the phase change at the boundary between the GeTe film 44a and the Sb ₂ Te ₃ film occurs uniformly, and the time required for such a phase change is shortened. As a result, in the phase change memory having the stacked body 44, The reading / writing operation speed can be increased.

(2) The GeTe film 44a and the Sb ₂ Te ₃ film 44b are formed while the substrate stage 13 is rotated. Therefore, the uniformity of the amount of sputtered particles that reach the processing substrate S in the circumferential direction is improved. Therefore, the growth and flatness of the GeTe film 44a and the Sb ₂ Te ₃ film 44b in the plane of the processing substrate S are improved, and as a result, the uniformity of the plane orientation is improved. Therefore, the speed of the read / write operation in the phase change memory having the stacked body 44 is increased.

  (3) The processing substrate S is attracted and heated by the mounting surface 13 a of the substrate stage 13. Therefore, the temperature variation in the surface of the processing substrate S can be reduced. Therefore, variation in energy given to the sputtered particles from the processing substrate S in the plane of the processing substrate S can be reduced, and consequently, variation in surface diffusion of the sputtered particles can be reduced. Therefore, film growth and flatness within the surface of the processing substrate S can be enhanced.

(4) The GeTe target 22a includes 9.13% by mass to 69.5% by mass of Ge and 30.5% by mass to 90.87% by mass of Te, while the Sb ₂ Te ₃ target 22b includes , Sb is 29 mass% or more and 89.6 mass% or less, and Te is 10.4 mass% or more and 71 mass% or less. Then, when the GeTe target 22a is sputtered to form the GeTe film 44a and when the Sb ₂ Te ₃ target 22b is sputtered to form the Sb ₂ Te ₃ film 44b, an atmosphere of 0.05 Pa to 1 Pa is formed. Each film is laminated on the substrate at a rate of 3 nm or more per second, that is, the sputtering rate of each film is set to 3 nm or more and 10 nm or less per second. Therefore, the ratio of Ge and Te in the GeTe film 44a and the ratio of Ge and Sb in the Sb ₂ Te ₃ film 44b are almost stoichiometric compositions. Therefore, the GeTe film 44a and the Sb ₂ Te ₃ film 44b are easily grown in a uniform plane orientation. Thereby, the orientation of the crystals constituting each film is easily aligned with the [111] orientation.

  (5) The targets 22a and 22b exposed from the shutter 26 are switched together with the switching of the sputtering target. Therefore, when one metal chalcogenide film is formed, it is possible to suppress the mixture of sputtered particles emitted from the metal chalcogenide target for forming the other metal chalcogenide film. Therefore, the composition of each metal chalcogenide film is easily maintained at a stoichiometric composition, and as a result, the crystal orientation constituting each metal chalcogenide film is easily aligned with the [111] orientation.

  (6) The temperature of the mounting surface 13a of the substrate stage 13 is made equal when the sputtering target is switched and when the targets 22a and 22b are sputtered. Therefore, the temperature of the processing substrate S can be made substantially constant from the start to the stop of the lamination of the metal chalcogenide film. Therefore, by forming a temperature difference in the processing substrate S at the boundary between the switching period and the sputtering period, the processing substrate S gives the sputtered particles immediately after the start of the sputtering period and in the subsequent sputtering period. The difference in energy can be suppressed. Thereby, it is possible to suppress the degree of the surface diffusion of the sputtered particles reaching the processing substrate S from changing within each sputtering period. Therefore, the growth of each metal chalcogenide film and the uniformity in the plane of the flat substrate can be improved.

In addition, the said embodiment can be changed and implemented suitably as follows.
The GeTe film 44a and the Sb ₂ Te ₃ film 44b may be formed without rotating the substrate stage 13. Even if it is such a structure, the effect according to said (1) and (3)-(6) can be acquired.

  The whole processing substrate S may be heated by heating the processing substrate S on a part of the mounting surface 13 a included in the substrate stage 13. Even if it is such a structure, the effect according to (1), (2), (4)-(6) can be acquired.

The composition of the GeTe target 22a may be a composition other than the above as long as the composition of the GeTe film 44a formed by sputtering is as described above, and the composition of the Sb ₂ Te ₃ target 22b is A composition other than the above may be used as long as the composition of the Sb ₂ Te ₃ film formed by sputtering has the above-described composition. Even if it is such a structure, the effect according to said (1)-(3), (5), (6) can be acquired.

The pressure in the vacuum chamber 11 may be a pressure not included in the above range as long as the composition of the GeTe film 44a formed on the processing substrate S and the Sb ₂ Te ₃ film 44b have the above composition. . Also by this, the effect according to said (1)-(3), (5), (6) can be acquired.

  -The shutter 26 does not need to be mounted. Even if it is such a structure, while being able to acquire the effect according to said (1)-(4) and (6), it can simplify the structure of the sputtering device 10 by the part which omits the shutter 26. FIG. it can.

The temperature of the mounting surface 13a during the switching period of the sputtering target and the temperature of the mounting surface 13a during the sputtering period can form the GeTe film 44a and the Sb ₂ Te ₃ film 44b in a crystalline phase state. If it is, it does not need to be the same temperature. Even if it is such a structure, the effect as described in said (1)-(5) can be acquired.

The stacked body 44 is configured by the GeTe films 44a and the Sb ₂ Te ₃ films 44b that are alternately stacked by 10 layers. However, the number of layers of the GeTe film 44a and the Sb ₂ Te ₃ film can be arbitrarily changed.

The GeTe target 22a and the Sb ₂ Te ₃ target 22b are arranged so as to be substantially parallel to the placement surface 13a of the substrate stage 13, but have a predetermined angle with respect to the normal direction of the placement surface 13a. You may arrange.

The sputtering apparatus 10 may supply nitrogen gas or oxygen gas in addition to the argon gas when sputtering the GeTe target 22a and the Sb ₂ Te ₃ target 22b.

-When sputtering the GeTe target 22a and the Sb ₂ Te ₃ target 22b, a DC voltage may be applied from the DC power source 25 to each of the targets 22a and 22b. Alternatively, the voltage may be applied simultaneously from both the high-frequency voltage from the high-frequency power supply 24 and the DC voltage from the DC power supply 25.

The target exposed from the opening of the shutter 26 is switched in a state where neither the first switch SWa nor the second switch SWb is connected to the high frequency power supply 24. However, the target exposed from the opening of the shutter 26 may be switched after the connection with the high frequency power supply 24 is switched from one switch to the other switch. In short, the switches SWa and SWb and the shutter 26 may be switched so that the surface of the GeTe target 22a and the surface of the Sb ₂ Te ₃ target 22b are not sputtered simultaneously.

-Elements such as carbon, silicon, aluminum, tin, phosphorus, arsenic, silver, and indium may be added to the targets 22a and 22b.
-GeTe films 44a and Sb ₂ Te ₃ films 44b were alternately stacked to form a GeSbTe compound at the boundary between these films. However, the present invention is not limited to this, and two metal chalcogenide targets may be configured such that an AgInSbTe compound or a GeCuTe compound is formed at the boundary between metal chalcogenide films having different compositions. In this case, as a combination of metal chalcogenide targets, for example, a combination of an AgInTe ₂ target and an AgSbTe ₂ target, or a combination of a GeTe target and a CuTe target can be employed. Even if it is such a structure, the effect according to said (1)-(3) can be acquired.

  The opening of the shutter 26 corresponding to each target 22a, 22b may be closed at the timing when the switches SWa, SWb are turned off, specifically, at the timing T4, the timing T7, and the timing T10. .

At the timing T13, the second switch SWb is turned off, and at the same time, the supply of Ar gas and power is stopped, and the opening corresponding to the Sb ₂ Te ₃ target in the shutter 26 is closed. Also good.

  The power supply from the high frequency power supply 24 is started after the first switch SWa is turned on at the timing T2, but after the power supply from the high frequency power supply 24 is started, the first switch SWa may be turned on.

  In addition to omitting the switches SWa and SWb, the high frequency power supply 24 may start and stop the supply of high frequency power when starting and stopping the formation of each film.

  Although the processing substrate S is adsorbed by the electrostatic force of the chuck electrode 14 mounted on the substrate stage 13, the processing substrate S may be adsorbed by another adsorption method such as vacuum adsorption.

  The target 22a, 22b may be supplied with power from the DC power supply 25, or may be supplied with power from both the high-frequency power supply 24 and the DC power supply 25, thereby supplying power from the high-frequency power supply 24. The same effect can be obtained if the sputtering rate is the same as in the above case.

The sputtering apparatus 10 has two metal chalcogenide targets, that is, a GeTe target 22a and an Sb ₂ Te ₃ target 22b, but has three or more metal chalcogenide targets, for example, a GeTe target, an SbTe target, and a GeSb target. It may be.

DESCRIPTION OF SYMBOLS 10 ... Sputtering device, 11 ... Vacuum chamber, 11a ... Exhaust port, 11b ... Gas supply port, 12 ... Upper lid, 12a ... Insulating material, 13 ... Substrate stage, 13a ... Mounting surface (heating surface), 14 ... Chuck electrode, 15 ... chuck power supply, 16 ... heater, 17 ... heater power source, 18 ... temperature measuring unit, 19 ... rotation mechanism, 21a ... first backing plate, 21b ... second backing plate, 22a ... GeTe target, 22b ... _Sb 2 Te ₃ Target, 23a ... 1st magnet unit, 23b ... 2nd magnet unit, 24 ... High frequency power supply, 25 ... DC power supply, 26 ... Shutter, 31 ... Exhaust part, 32 ... Argon gas supply part, 41, 51 ... Insulating film, 42 , 52 ... insulation layer, 43, 53 ... lower electrode, 44 ... laminate, 44a ... GeTe film, 44b ... _Sb 2 Te ₃ film, 44G ... germanium atoms, 44 ... tellurium atom, 50 ... phase change memory, 54 ... metal chalcogenide film, 55 ... upper electrode, S ... substrate, SWa ... first switch, SWb ... second switch.

Claims (7)

A phase change memory forming method for forming a phase change memory by laminating two or more metal chalcogenide films having different compositions on a substrate,
While heating the temperature of the substrate to 250 ° C. or more and 350 ° C. or less,
Two or more metal chalcogenide targets having different compositions are sputtered with argon gas at different timings, and two or more metal chalcogenide films having different compositions are sputtered at a rate of 3 nm to 10 nm per second. A method of forming a phase change memory, comprising stacking on a substrate. The method of forming a phase change memory according to claim 1, wherein two or more metal chalcogenide films having different compositions are stacked on the substrate while rotating a substrate stage on which the substrate is placed. The mounting surface of the substrate in the substrate stage is a heating surface,
The method of forming a phase change memory according to claim 2, wherein the substrate is heated while adsorbed on the heating surface. The metal chalcogenide target includes a GeTe target and a Sb ₂ Te ₃ target,
The GeTe target includes 9.13% by mass to 69.5% by mass of Ge and 30.5% by mass to 90.87% by mass of Te.
The Sb ₂ Te ₃ target comprises 29 mass% or more and 89.6 mass% or less of Sb, and 10.4 mass% or more and 71 mass% or less of Te,
Each of the GeTe target and the Sb ₂ Te ₃ target is sputtered in an atmosphere of 0.05 Pa to 1 Pa, and the GeTe film and the Sb ₂ Te ₃ film are stacked on the substrate at a rate of 3 nm to 10 nm per second. The method for forming a phase change memory according to claim 1. Among the metal chalcogenide targets, using the shutter that exposes the metal chalcogenide target that is a sputtering target and covers the metal chalcogenide target other than the sputtering target,
The method for forming a phase change memory according to claim 1, wherein when the sputtering target is switched, the metal chalcogenide target exposed from the shutter is switched. 4. The phase change memory according to claim 3 , wherein the temperature of the heating surface at the time of switching the sputtering target between two or more metal chalcogenide targets is made equal to the temperature of the heating surface at the time of sputtering of the metal chalcogenide target. Forming method. A phase change memory forming apparatus for forming a phase change memory by laminating two or more metal chalcogenide films having different compositions on a substrate,
A sputtering source for sputtering each of two or more metal chalcogenide targets having different compositions with argon gas;
A substrate stage for heating the substrate;
With the substrate stage heated to a temperature of 250 ° C. or higher and 350 ° C. or lower, the sputtering source sputters each of the two or more metal chalcogenide targets at different timings, thereby having different compositions. Two or more metal chalcogenide films are stacked on the substrate at a rate of 3 nm to 10 nm per second.

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