JP2012219330A - Apparatus of forming phase change memory and method of forming phase change memory - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an apparatus of forming a phase change memory that enhances the speed of reading and writing operations in the phase change memory including laminated metallic chalcogenide films, and to provide a method of forming the change memory.SOLUTION: A sputtering apparatus 10 includes a GeTe target 22a and an SbTetarget 22b having mutually different compositions. In addition, the sputtering apparatus 10 includes a substrate stage 13 which has a heating surface for heating a substrate S and heats the substrate S while sucking it to the heating surface, and a rotary section 18 for turning the substrate stage 13 in the circumferential direction of the substrate S. While the substrate stage 13 sucks and heats the substrate S and the rotary section 18 turns the substrate stage 13, the sputtering apparatus 10 sputters the GeTe target 22a and SbTetarget 22b at different timings from each other to stack two metallic chalcogenide films having mutually different compositions on the substrate S.

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 laminate in which a plurality of metal chalcogenide films having different compositions including a metal element and a chalcogen element are laminated. .

  Conventionally, for example, as described in Patent Document 1, a phase change memory that is a memory element using a metal chalcogenide film containing a metal element and a chalcogen element is widely known. A metal chalcogenide film has a characteristic that it reversibly changes between a crystalline phase and an amorphous phase due to a difference in thermal energy applied thereto, and that both phases are stably held at room temperature. ing. In addition, the crystalline metal chalcogenide film and the amorphous metal chalcogenide film have different resistance values. 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. As described above, since the memory element stores information based on the difference in resistance value between two different phases, it has attracted attention as a new nonvolatile memory that does not require power supply to maintain the memory. ing.

FIG. 6 shows a partial cross-sectional structure of such a phase change memory. In the hole formed in the interlayer insulating film 51 of the phase change memory 50, a lower electrode 53 covered with a heat insulating layer 52 is embedded. On the interlayer 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 when the current supply is stopped. Phase change between amorphous phase.

  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 low as compared with other storage elements such as a DRAM that stores information by the 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.

A stacked phase change memory has, for example, a plurality of GeTe layers and Sb ₂ Te ₃ layers that are alternately stacked. According to the numerical calculation results in Non-Patent Document 1, the phase change between the crystalline phase and the amorphous layer is caused only by the movement of Ge atoms at the interface between the adjacent GeTe layer and Sb ₂ Te ₃ layer. 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 stacked body of metal chalcogenide films composed of GeTe layers and Sb ₂ Te ₃ layers, but has a stacked body composed 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 phase change memory forming apparatus 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. It is to provide a method for forming a change memory.

  Hereinafter, means for solving the above-described problems and the effects thereof will be described.

  The invention according to claim 1 is 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, wherein the compositions are different from each other. A sputtering source for sputtering each of two or more metal chalcogenide targets having a rare gas, a substrate stage having a heating surface for heating the substrate, and heating the substrate while adsorbing to the heating surface; A rotating unit that rotates the substrate stage in the circumferential direction of the substrate, and the sputtering unit rotates the substrate stage while the substrate stage sucks and heats the substrate, and the sputtering source includes the two sputtering sources. Two or more metals having different compositions by sputtering each of the above metal chalcogenide targets at different timings. The Rukogenaido film and summarized in that the stacking by the substrate.

  The inventors of the present application have studied diligently a laminated structure in which two metal chalcogenide films having different compositions are laminated, and the plane orientation of each metal chalcogenide film constituting the laminated structure is in-plane of the substrate at the time of film formation. If not uniform, it has been found that the phase change at the boundary of each metal chalcogenide film is also difficult to occur uniformly in the plane of the substrate after film formation. The inventors have found that the characteristic that the phase structure of the metal chalcogenide easily changes depending on the transition of the thermal energy given to the metal chalcogenide is the same as that of the metal chalcogenide in the middle of film formation.

  In this regard, in the first aspect of the invention, the phase change memory forming apparatus includes a sputtering source that sputters each of two or more metal chalcogenide targets with a rare gas, a substrate stage that performs adsorption and heating of the substrate, And a rotating unit that rotates the substrate stage. The phase change memory forming apparatus includes two or more metals having different compositions by sputtering of the metal chalcogenide target while rotating the substrate stage by the rotating unit while the substrate is attracted and heated by the substrate stage. A chalcogenide film is stacked.

  Therefore, the number of sputtered particles reaching the substrate surface is uniform in the plane of the substrate as compared with a configuration in which the position of the substrate is fixed. In addition, the temperature of the substrate surface becomes uniform in the plane of the substrate as compared with a configuration in which the substrate stage does not adsorb the substrate. Therefore, the heat per sputtered particle given from the substrate surface becomes uniform in the plane of the substrate. With such a configuration, even when a metal chalcogenide whose phase structure is greatly changed by heat, the plane orientation of the metal chalcogenide film formed on the substrate can be easily maintained in the plane of the substrate during film formation. . Therefore, in the phase change memory having such a stack of metal chalcogenide films, a phase change is likely to occur at the boundary of each metal chalcogenide film, and as a result, the read / write operation speed in the phase change memory can be increased.

  According to a second aspect of the present invention, there is provided the phase change memory forming apparatus according to the first aspect, wherein the substrate stage adsorbs the substrate by electrostatic force on the heating surface.

  If the suction hole for sucking the substrate is provided on the heating surface of the substrate stage, the substrate can be sucked to the heating surface by the suction force of the suction hole. However, in such a configuration, since it becomes difficult for the substrate to be heated at a portion facing the suction hole, there is a limit to suppressing temperature variations in the plane of the substrate. In this regard, in the invention according to claim 2, since the substrate is electrostatically adsorbed on the heating surface of the substrate stage, the area of the substrate in contact with the heating surface is compared with a configuration in which suction holes are formed on the heating surface. Can be increased. Therefore, it is possible to suppress variations in temperature in the plane of the substrate, so that the read / write speed of the phase change memory including the laminated structure of the metal chalcogen film can be more reliably increased.

According to a third aspect of the present invention, in the phase change memory forming device according to the first or second aspect, the two or more chalcogenide targets are a first target composed of GeTe and a _second target composed of Sb ₂ Te ₃ . The sputtering source alternately switches the sputtering target to the first target and the second target, and when switching the sputtering target, puts a switching period, in the switching period The substrate stage further includes a shutter that exposes a target to be sputtered and covers a target other than the target, and the substrate stage includes a temperature of the heating surface during a period during which the sputtering source sputters the target, and a switching period. The gist is to control the temperature of the heating surface so that the temperature of the heating surface becomes equal.

  When the second target is sputtered after the first target is sputtered, if the interval between the end of one sputter and the start of the other sputter is shortened, sputtering is performed from different targets at such an interval. Particles are likely to mix on the substrate. In a phase change memory having a stacked structure, a memory function is manifested by movement of atoms at the interface between adjacent metal chalcogenide films, and therefore the crystal plane orientation at such an interface greatly affects the quality of the memory function.

In a third aspect of the invention, the metal chalcogenide target is composed of a first target made of GeTe and a _second target made of Sb ₂ Te ₃ . Therefore, at the boundary between the film formed by sputtering of the GeTe target and the film formed by sputtering of the Sb ₂ Te ₃ target, the ratio of Ge to SbTe is set to “Ge: Sb: Te = 2: 2: 5”. It can be. Thereby, since a GeSbTe structure having a stable composition can be formed at the boundary of the film, a phase change due to heat in the GeSbTe structure can also be stably performed.

  Then, in order to suppress the mixture of particles sputtered from different targets, the target other than the target to be sputtered is covered by the shutter during the switching period in which the target to be sputtered is switched. In addition, the temperature of the heating surface is adjusted so that the temperature of the heating surface during the period during which the sputtering source sputters the target is equal to the temperature of the heating surface during such a switching period. Therefore, mixing of the sputtered particles from different targets on the substrate can be suppressed by securing the switching period, and the change in the substrate temperature during the switching period can reduce the substrate temperature during the switching period and the substrate temperature during the sputtering period. It can be suppressed by making it equal. As a result, it is possible to suppress mixing of particles sputtered from different targets at the interface between adjacent chalcogenide films.

  According to a fourth aspect of the present invention, in the phase change memory forming apparatus according to the third aspect, the diameter of the substrate is not less than 150 mm and not more than 300 mm, and the temperature variation in the plane of the substrate is −10 ° C. The gist is that the temperature is + 10 ° C. or less, and the rotation speed of the substrate stage is 60 times or more and 250 times or less per minute.

  When the diameter of the substrate is 200 mm or more and 300 mm or less, the inventors of the present application have a temperature variation in the plane of the substrate of −10 ° C. or more and + 10 ° C. or less, and the rotation speed of the substrate stage is 60 to 250 times per minute. It has been found that substantially the entire metal chalcogenide film is formed as a film composed of crystals having a uniform plane orientation when: Therefore, in the invention described in claim 4, the substrate stage sets the temperature variation in the plane of the substrate to −10 ° C. or higher and + 10 ° C. or lower. The rotating unit rotates such a substrate stage at a speed of 60 times or more and 250 times or less per minute. As a result, the uniformity of the plane orientation of the crystal forming the metal chalcogen film can be improved more reliably. As a result, the read / write speed of the phase change memory having the laminated structure of the metal chalcogen film can be increased more reliably.

  The invention according to claim 5 is a method of forming a phase change memory by forming a phase change memory by laminating two or more metal chalcogenide films having different compositions on a substrate. Sputtering each of two or more metal chalcogenide targets having different compositions while being adsorbed on the heating surface of the substrate stage and rotating the substrate stage with a rare gas at different timings. Thus, the gist is to stack two or more metal chalcogenide films having different compositions on the substrate.

  In the invention according to claim 5, two or more metal chalcogenides having different compositions by sputtering of two or more metal chalcogenide targets while rotating the substrate stage while the substrate is adsorbed and heated by the substrate stage. The films are stacked.

  Therefore, the number of sputtered particles reaching the substrate surface is uniform in the plane of the substrate as compared with a configuration in which the position of the substrate is fixed. In addition, the temperature of the substrate surface becomes uniform in the plane of the substrate as compared with a configuration in which the substrate stage does not adsorb the substrate. Therefore, the heat per sputtered particle given from the substrate surface becomes uniform in the plane of the substrate. With such a configuration, even when a metal chalcogenide whose phase structure is greatly changed by heat, the plane orientation of the metal chalcogenide film formed on the substrate can be easily maintained in the plane of the substrate during film formation. . Therefore, in the phase change memory having such a stack of metal chalcogenide films, a phase change is likely to occur at the boundary of each metal chalcogenide film, and as a result, the read / write operation speed in the phase change memory can be increased.

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. (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 showed the relationship between the distance from a substrate center, and an X-ray diffraction (XRD) peak intensity according to the temperature variation in a substrate surface. The graph which showed the relationship between the distance from a substrate center, and a XRD peak intensity according to the rotation speed of a board | substrate. XRD peak intensity of the stack 1 formed by the phase change memory forming apparatus of the present embodiment, the stack 2 formed by another phase change memory forming apparatus, and the metal chalcogenide film provided in the conventional phase change memory Graph showing. Sectional drawing which shows the cross-section of the conventional phase change memory.

  Hereinafter, an embodiment of a phase change memory forming apparatus and a phase change memory forming method 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.

(Device configuration)
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 substrate S to be processed is installed. The substrate stage 13 incorporates a chuck electrode 14 for electrostatically attracting the substrate S to the mounting surface 13 a of the substrate stage 13. A chuck power supply 15 that supplies a DC voltage to the chuck electrode 14 is connected to the chuck electrode 14. Since the substrate S is electrostatically attracted to the placement surface 13a of the substrate stage 13, for example, a suction hole for vacuum suction is formed on the placement surface 13a, or the substrate S is mechanically held by a mechanical chuck or the like. Compared with the structure to perform, it is possible to enlarge the area | region of the board | substrate S which contacts the mounting surface 13a. Thereby, the dispersion | variation in the temperature in the surface of the board | substrate S can be suppressed.

  Further, the substrate stage 13 incorporates a heater 16 for heating the substrate S placed on the placement surface 13a, which serves as a heating surface. The heater 16 is, for example, a resistance heater that radiates heat when a DC voltage is applied, and heats the substrate S to 250 ° C., for example. A heater power supply 17 that supplies a DC voltage to the heater 16 is connected to the heater 16. The substrate stage 13 is connected to a rotating unit 18 that rotates the substrate stage 13 in the circumferential direction of the substrate S. The rotating unit 18 includes a motor and a rotating shaft that transmits the rotation of the motor to the substrate stage 13.

  The substrate stage 13 heats the substrate S placed on the placement surface 13a while being attracted by electrostatic force, thereby setting the temperature variation in the surface of the substrate S to −10 ° C. or more and + 10 ° C. or less. Further, the substrate stage 13 is rotated in the circumferential direction of the substrate S by the rotating unit 18, thereby rotating the substrate S at a speed of 60 to 250 revolutions per minute. Note that if the rotation speed of the substrate S exceeds 250 rotations per minute, the rotation of the motor constituting the rotation unit 18 becomes unstable, and thus the variation in the rotation speed of the substrate S increases.

  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 as a first target is bonded so as to be substantially parallel to the mounting surface 13a of the substrate stage 13. 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 first magnet unit 23a includes a permanent magnet that forms a magnetic field on the surface of the GeTe target 22a on the vacuum chamber 11 side.

An Sb ₂ Te ₃ target 22b as a _second target is bonded to the vacuum chamber 11 side of the second backing plate 21b so as to be substantially parallel to the mounting surface 13a of the substrate stage 13. 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 second magnet unit 23b includes a permanent magnet that 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 the first switch SWa, and to the second backing plate 21b via the second switch SWb. ing. Each of the high frequency power supply 24 and the DC power supply 25 has a switch for starting or stopping the application of voltage. The frequency of the high frequency power supplied from the high frequency power supply 24 is, for example, 13.56 MHz.

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. When one target is sputtered, the shutter 26 covers the other target, so that particles sputtered from the two targets 22a and 22b are mixed in a single film, or sputtered from one target. Particles are prevented from adhering to the other target.

An exhaust unit 31 is connected to an exhaust port 11 a formed through the lower surface of the vacuum chamber 11. The exhaust unit 31 includes a valve for adjusting the pressure in the vacuum chamber 11 and various vacuum pumps. A rare gas supply unit 32 for supplying argon (Ar) gas for sputtering the targets 22a and 22b is connected to the gas supply port 11b formed through the side surface of the vacuum chamber 11. The rare gas supply unit 32 is a mass flow controller connected to a cylinder storing argon gas, and adjusts the flow rate of the argon gas supplied to the vacuum chamber 11 to, for example, 5 sccm or more and 100 sccm or less. The gas supply port 11b is connected to an additive gas supply unit 33 for supplying an additive gas added to the argon gas, for example, nitrogen (N ₂ ) gas or oxygen (O ₂ ) gas. The additive gas supply unit 33 is a mass flow controller connected to a cylinder storing nitrogen gas or oxygen gas, and adjusts the flow rate of the additive gas supplied to the vacuum chamber 11 to, for example, 0.1 sccm or more and 10 sccm or less.

  When the targets 22a and 22b are sputtered, the pressure in the vacuum chamber 11 is set to a predetermined pressure by the flow rate of the argon gas supplied from the rare gas supply unit 32, the flow rate of the additive gas, and the exhaust flow rate of the exhaust unit 31. Maintained.

  In the present embodiment, the high-frequency power source 24 and the rare gas supply unit 32 constitute a sputtering source.

(Function)
Of the operations of the sputtering apparatus 10, an operation performed when the sputtering apparatus 10 forms a stacked body of metal chalcogenide films constituting a phase change memory will be described with reference to FIG.

  When forming the laminated body, first, the substrate S carried from the unillustrated carry-in / out port into the vacuum chamber 11 decompressed by the exhaust unit 31 is placed on the placement surface 13a of the substrate stage 13 heated by the heater 16. Placed. As shown in FIG. 2A, the substrate S has an insulating layer that covers, for example, an interlayer insulating film 41 formed on a silicon substrate having a diameter of 150 mm or more and 300 mm or less, and a side surface of a hole formed in the interlayer insulating film 41. The layer 42 and the lower electrode 43 embedded in the hole so as to be covered with the heat insulating layer 42 are provided.

  When the substrate S is placed on the placement surface 13a, the argon gas is supplied from the rare gas supply unit 32 into the vacuum chamber 11, and then a DC voltage is applied to the chuck electrode 14 from the chuck power source 15. The substrate S is electrostatically attracted to the placement surface 13a. Next, the rotating unit 18 rotates the substrate stage 13 so that the substrate S is rotated in the circumferential direction.

  The high frequency voltage from the high frequency power supply 24 is applied to the first backing plate 21a and the GeTe target 22a via the first switch SWa with the shutter 26 exposing only the surface of the GeTe target 22a in the vacuum chamber 11. Is done. As a result, the GeTe target 22a is sputtered by the positive ions in the plasma generated around the GeTe target 22a. When the GeTe target 22a is sputtered, a GeTe film 44a as a metal chalcogenide film is formed on the entire surface of the interlayer insulating film 41.

When the GeTe film 44a 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, after both the first switch SWa and the second switch SWb are turned off, the shutter 26 covers the GeTe target 22a and the surface of the Sb ₂ Te ₃ target 22b is vacuumed. It is exposed in the tank 11. The heater 16 keeps the temperature of the substrate stage 13 so that the temperature of the mounting surface 13a is the same during the switching period and during sputtering of the GeTe target. Therefore, the temperature of the substrate S is maintained at the same temperature during the switching period and during sputtering of the GeTe target.

When the switching between the targets 22a and 22b is completed, a high frequency voltage is applied from the high frequency power supply 24 to the second backing plate 21b and the Sb ₂ Te ₃ target 22b via the second switch SWb. Thus, the positive ions in the plasma generated in the neighborhood of _Sb 2 Te ₃ target 22b, _Sb 2 Te ₃ target 22b is sputtered. When the Sb ₂ Te ₃ target 22b is sputtered, an Sb ₂ Te ₃ film 44b as a metal chalcogenide film is formed on the entire surface of the GeTe film 44a formed on the interlayer insulating film 41.

When the Sb ₂ Te ₃ film 44b is formed, the sputtering target 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, similarly to the switching period from the GeTe target 22a to the Sb ₂ Te ₃ target 22b, the shutter 26 is moved after both the first switch SWa and the second switch SWb are turned off. The Sb ₂ Te ₃ target 22 b is covered and the surface of the GeTe target 22 a is exposed in the vacuum chamber 11. Similarly, the heater 16 continues to adjust the temperature of the substrate stage 13 so that the temperature of the mounting surface 13a is the same during the switching period and during the sputtering of the Sb ₂ Te ₃ target 22b. Therefore, the temperature of the substrate S is maintained at the same temperature during the switching period and during the sputtering of the Sb ₂ Te ₃ target 22b.

When the switching between the targets 22a and 22b is completed, the high frequency power is applied from the high frequency power source 24 to the first backing plate and the GeTe target 22a via the first switch SWa. As a result, the GeTe target 22a is sputtered again, whereby the GeTe film 44a is formed on the entire surface of the Sb ₂ Te ₃ film 44b.

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 each. A laminated body 44 made of 20 metal chalcogenide films is formed.

The temperature of the mounting surface 13a of the substrate stage 13 during the switching period is the same as the temperature of the mounting surface 13a during the sputtering period of the GeTe target 22a and the sputtering period of the Sb ₂ Te ₃ target 22b, which are the sputtering periods before and after the switching period. Adjusted as follows. 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.

Further, as described above, but when switching sputtering target with the GeTe target 22a and _Sb 2 Te ₃ target 22b is not any in the voltage of the GeTe target 22a and _Sb 2 Te ₃ target 22b is applied state And The target to be sputtered is exposed from the opening of the shutter 26, while the target that is not to be sputtered is covered by the shutter 26, and then a voltage is applied to the target to be sputtered. Therefore, mixing of sputtered particles for forming each film can be suppressed at the boundary between the GeTe film 44a and the Sb ₂ Te ₃ film 44b, which are metal chalcogen films having different compositions. In addition, since particles sputtered from one target are also prevented from adhering to the surface of the other target, two films are formed in the film formed immediately after the sputtering of each target 22a, 22b is started. Mixing of particles sputtered from the targets 22a and 22b can be suppressed.

  When the stacked body 44 is formed on the substrate S, the application of the DC voltage from the chuck power supply 15 to the chuck electrode 14 is stopped after the rotation of the substrate stage 13 by the rotating unit 18 is stopped. Then, the 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 stacked body 44 by the sputtering apparatus 10 is completed, an upper electrode is formed on the stacked body 44 by a known film forming apparatus such as a sputtering apparatus, and then the stacked body 44 and the upper electrode are formed by a dry etching apparatus or the like. Is selectively removed. As a result, a phase change memory having a stack of metal chalcogenide films sandwiched between the upper electrode and the lower electrode 43 is formed.

A phase change occurring in the laminate 44 will be described with reference to FIGS. 2B and 2C. As described above, the stacked body 44 has a configuration in which the GeTe films 44a and the Sb ₂ Te ₃ films 44b are alternately stacked. Therefore, at the boundary between the GeTe films 44a and the Sb ₂ Te ₃ films 44b, Ge atoms, Sb atoms and Te atoms will be present. At such a boundary, among the Te atoms 44T and Ge atoms 44G constituting the GeTe film 44a, only the Ge atoms 44G move by thermal energy based on the voltage applied between the lower electrode 43 and the upper electrode. , Ge, Sb, and Te atoms change the phase of the compound reversibly. More specifically, the GeSbTe compound formed by Ge atoms, Sb atoms, and Te atoms is heated at a relatively high temperature for a short time and then rapidly cooled to form an amorphous phase shown in FIG. On the other hand, after being heated at a relatively low temperature for a long time and then gently cooled, the crystal phase 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 substrate S. That is, the inventors of the present application have found that all of the GeTe film 44a and the Sb ₂ Te ₃ film 44b constituting the stacked body 44 are crystals having a uniform plane orientation, particularly [111] orientation, in the plane of the substrate S at the time of film formation. It was found that the phase change in the laminate 44 would not occur evenly in the plane of the substrate 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 in the sputtering apparatus 10, the target 22 a is rotated while the substrate stage 13 is rotated by the rotating unit 18 while the substrate S is attracted and heated by the substrate stage 13. , 22b are sputtered to form the GeTe film 44a and the Sb ₂ Te ₃ film 44b.

Therefore, compared to the configuration in which the position of the substrate S is fixed, the number of sputtered particles reaching the substrate surface is uniform in the plane of the substrate. In addition, the temperature of the substrate surface is uniform in the plane of the substrate S as compared with the configuration in which the substrate stage 13 does not adsorb the substrate S. Therefore, the heat per sputtered particle given from the substrate surface becomes uniform in the plane of the substrate S. That is, the composition and phase structure of the GeTe film 44a and the Sb ₂ Te ₃ film 44b are easily maintained. As a result, the GeTe film 44a and the Sb ₂ Te ₃ film 44b are easy to grow in a uniform plane orientation. Thereby, the said laminated body 44 can be formed as a crystal phase with which the orientation of the crystal | crystallization which comprises each film | membrane matched [111] orientation.

  Next, the relationship between the temperature variation in the plane of the substrate S and the plane orientation of the crystals constituting the stacked body 44 will be described with reference to FIG. In the present embodiment, the plane orientation of the crystals constituting the stacked body 44 is analyzed by X-ray diffraction (XRD). The peak intensity in XRD is proportional to the volume of crystal grains having orientation in the plane orientation corresponding to the diffraction angle. Therefore, in the present embodiment, the [111] orientation is a main phase, the other is a different phase, and the crystal oriented in the main phase exceeds 95% of the crystals constituting the laminate 44, that is, the main phase. When the intensity of the peak is 20 times or more of the intensity of the peak corresponding to the different phase, the plane orientation of the laminated body 44, that is, each film constituting the laminated body 44 is considered to be substantially uniform.

  As shown by a solid line in FIG. 3, when the temperature variation in the surface of the substrate S is −10 ° C. or more and + 10 ° C. or less, that is, the substrate S is electrostatically applied to the mounting surface 13 a of the substrate stage 13. When adsorbing, it was recognized that the peak intensity of the main phase was larger than 20 times the peak intensity of the different phase in the entire substrate S. On the other hand, as shown by a broken line in FIG. 3, when the temperature variation in the surface of the substrate S is −20 ° C. or more and + 20 ° C. or less, that is, known with respect to the placement surface 13 a of the substrate stage 13. When the mechanical chuck is used to mechanically hold, the peak intensity of the main phase is recognized to be 20 times or more of the peak intensity of the different phase only in the range where the distance from the center of the substrate S does not exceed 50 mm. . The laminated body 44 analyzed by XRD shown in FIG. 3 has a substrate S having a diameter of 300 mm and a set temperature in the substrate stage 13 of 250 ° C., and the substrate S is rotated 100 times per minute in the circumferential direction. It is formed while rotating at a speed.

  The relationship between the rotation speed of the substrate S when forming the stacked body 44 and the plane orientation of the crystals constituting the stacked body 44 will be described with reference to FIG. As shown in FIG. 4, when the rotation speed of the substrate S is 60 revolutions per minute, the peak intensity of the main phase is larger than 20 times the peak intensity of the different phase in the entire substrate S. It was confirmed that the higher the rotation speed of S, the larger the average value of the peak intensity ratio. On the other hand, when the rotation speed of the substrate S was lower than 60 revolutions per minute, it was confirmed that the peak intensity of the main phase was 20 times or more of the peak intensity of the different phase only on the center side of the substrate S. More specifically, when the rotation speed of the substrate S is 40 rotations per minute, when the distance from the center of the substrate S is within 60 mm, on the other hand, when the rotation speed of the substrate S is 20 rotations per minute, When the distance from the center of the substrate S was within 40 mm, it was confirmed that the peak intensity of the main phase was 20 times or more the peak intensity of the different phase. Note that the laminated body 44 analyzed by XRD shown in FIG. 4 is formed by adsorbing the substrate S having a diameter of 300 mm by the substrate stage 13 and setting the temperature to 250 ° C.

Thus, at the time of forming the stacked body 44, the substrate S is heated while being electrostatically attracted by the substrate stage 13, whereby the temperature variation in the surface of the substrate S is set to −10 ° C. or more and + 10 ° C. or less. It is preferable that the number of rotations of the substrate S by the rotating unit 18 is 60 to 250 rpm. As a result, it is possible for the entire substrate S to align the plane orientation of the crystals forming each of the GeTe film 44a and the Sb ₂ Te ₃ film 44b constituting the stacked body 44 with the [111] orientation.
[Example]
[Example 1]
Ten layers of GeTe films and SbTe films were alternately formed on a silicon substrate having a diameter of 300 mm under the following conditions.
○ GeTe film ・ Target GeTe target (diameter 125mm)
・ Supply power 500W
・ Argon gas flow rate 50sccm
・ Vacuum chamber pressure 0.5Pa
・ Board setting (mounting surface) temperature 250 ℃
・ Substrate temperature variation ± 10 ℃ (electrostatic adsorption)
・ Substrate rotation speed: 100 revolutions per minute ・ Film thickness: 10 nm
○ Sb ₂ Te ₃ film ・ Target Sb ₂ Te ₃ target (diameter 125 mm)
・ Supply power 500W
・ Argon gas flow rate 50sccm
・ Vacuum chamber pressure 0.5Pa
・ Board setting (mounting surface) temperature 250 ℃
・ Substrate temperature variation ± 10 ℃
・ Substrate rotation speed: 100 revolutions per minute ・ Film thickness: 10 nm

[Comparative Example 1]
Ten layers of GeTe films and SbTe films were alternately formed on a silicon substrate having a diameter of 300 mm. The film forming conditions were the same as those in Example 1 except that the substrate temperature variation was ± 20 ° C. and the substrate rotation speed was 20 rotations per minute. The substrate was held on the mounting surface of the substrate stage by a known mechanical chuck.
[Comparative Example 2]
A single Ge ₂ Sb ₂ Te ₅ film was formed on a silicon substrate having a diameter of 300 mm under the following conditions.
・ Target Ge ₂ Sb ₂ Te ₅ target (diameter 125 mm)
・ Supply power 500W
・ Argon gas flow rate 50sccm
・ Vacuum chamber pressure 0.5Pa
・ Board setting (mounting surface) temperature 250 ℃
・ Substrate temperature variation ± 10 ℃ (electrostatic adsorption)
・ Substrate rotation speed 0 rotation per minute ・ Film thickness 200nm
FIG. 5 shows the result of XRD analysis of the metal chalcogen film formed under the conditions of Example 1, Comparative Example 1, and Comparative Example 2. In FIG. 5, peak A is a peak indicating [111] orientation, peak B is a peak indicating [200] orientation, peak C is a peak indicating [220] orientation, and peak D is a peak indicating [222] orientation. is there.

  As shown in FIG. 5, most of the crystals forming the laminate 1 formed under the conditions of Example 1 have [111] orientation, and other crystals having other orientations are hardly formed. Admitted. On the other hand, the laminate 2 formed under the conditions of Comparative Example 1 includes [111] oriented crystals, but also includes [200] oriented crystals to the same extent, and [220] oriented and It was also observed that [222] oriented crystals were included. Further, the conventional metal chalcogenide film formed under the conditions of Comparative Example 2 contains almost no [111] -oriented crystals, and [200] -oriented crystals and [220] -oriented crystals account for the majority. It was recognized that In addition, it was confirmed that the conventional metal chalcogenide film also includes [222] oriented crystals.

  A phase change memory using a metal chalcogenide film formed under the same conditions as in Example 1 and Comparative Example 1 and Comparative Example 2 was created, and the phase change from an amorphous state to a crystalline state in each of them was made. The set time, which is the time, and the reset time, which is the time until the phase changes from the crystalline state to the amorphous state, were measured. The measurement results are shown in Table 1 below.

表１に示されるように、実施例１の条件で形成された積層体１を用いた相変化メモリによれば、比較例１及び比較例２の条件で形成された積層体２あるいは従来の金属カルコゲナイド膜を用いた相変化メモリと比較して、セット時間、及びリセット時間のいずれもが短縮された。

As shown in Table 1, according to the phase change memory using the laminated body 1 formed under the conditions of Example 1, the laminated body 2 formed under the conditions of Comparative Example 1 and Comparative Example 2 or the conventional metal Both the set time and the reset time were shortened compared with the phase change memory using a chalcogenide film.

  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) The sputtering apparatus 10 includes a substrate stage 13 that performs adsorption and heating of the substrate S, and a rotating unit 18 that rotates the substrate stage 13. The sputtering apparatus 10 alternately stacks the GeTe films 44 a and the Sb ₂ Te ₃ films while rotating the substrate stage 13 by the rotating unit 18 while the substrate S is attracted and heated by the substrate stage 13. ing. Therefore, the distribution of the number of sputtered particles emitted from the GeTe target 22a and the Sb ₂ Te ₃ target 22b is such that the relative positions of the targets 22a and 22b and the substrate S are fixed in the plane of the substrate S. As compared with the above, it becomes uniform in the plane of the substrate S. In addition, the temperature uniformity in the substrate S is enhanced in the plane of the substrate S as compared with a configuration in which the substrate stage 13 does not attract the substrate S. Therefore, the uniformity of the quantity per unit area of the sputtered particles reaching the surface of the substrate S is increased in the plane of the substrate S. That is, the composition of the GeTe film 44a and the Sb ₂ Te ₃ film 44b is uniform in the plane. Further, the size per unit area of the thermal energy given to the sputtered particles from the surface of the substrate S also increases in the plane of the substrate S. With such a configuration, even GeTe films 44a and _Sb 2 Te ₃ film 44b with a large change in the crystal structure by variations in temperature, GeTe films 44a and _Sb 2 Te ₃ film formed on a substrate S The crystal structure 44b is easily maintained uniformly. As a result, the GeTe film 44a and the Sb ₂ Te ₃ film 44b are easy to grow in a uniform plane orientation. Therefore, in the phase change memory having a stack 44 of GeTe films 44a and _Sb 2 Te ₃ film 44b, it tends to occur the phase change at the boundary between the GeTe film 44a and _Sb 2 Te ₃ film 44b, and thus, in the phase change memory The reading / writing operation speed can be increased.

  (2) The substrate S is electrostatically attracted to the mounting surface 13 a of the substrate stage 13. Therefore, the area | region of the board | substrate S which contacts the mounting surface 13a can be enlarged. Therefore, since the temperature variation in the plane of the substrate S can be suppressed, the read / write speed of the phase change memory having the stacked body 44 can be more reliably increased.

(3) When switching the sputtering target between the GeTe target 22a and the Sb ₂ Te ₃ target 22b, the sputtering apparatus 10 sets a switching period and exposes the target to be sputtered during the switching period. And a shutter that covers other targets. Therefore, particles sputtered from the GeTe target 22a and the Sb ₂ Te ₃ target 22b are mixed in a single film formed by the sputtering period sandwiched between the switching period and the next switching period. Can be suppressed. Therefore, at the boundary between the film formed by sputtering of the GeTe target 22a and the film formed by sputtering of the Sb ₂ Te ₃ target 22b, the ratio of Ge to SbTe is expressed as “Ge: Sb: Te = 2: 2”. : 5 ". As a result, since a GeSbTe structure having a stable composition can be formed at the boundary of the film, a phase change due to heat in the GeSbTe structure can also be stably performed.

(4) The substrate stage 13 is mounted so that the temperature of the mounting surface 13a during the sputtering period of the GeTe target 22a or the Sb ₂ Te ₃ target 22b is equal to the temperature of the mounting surface 13a during the switching period. The placement surface 13a is temperature-controlled. Therefore, a change in the substrate temperature during the switching period can be suppressed. Therefore, it is possible to prevent the crystal structure from changing at the boundary between the GeTe film 44a and the Sb ₂ Te ₃ film 44b based on the temperature change, and as a result, from the particles sputtered from the GeTe target 22a and the Sb ₂ Te ₃ target 22b. It is possible to prevent the sputtered particles from being mixed at the interface between the GeTe film 44a and the Sb ₂ Te ₃ film 44b.

(5) The substrate stage 13 sets the temperature variation in the plane of the substrate S to −10 ° C. or higher and + 10 ° C. or lower. The rotating unit 18 rotates the substrate stage 13 at a speed of 60 to 250 times per minute. Therefore, the uniformity of the plane orientation of the crystals forming the GeTe film 44a and the Sb ₂ Te ₃ film 44b, which are metal chalcogen films, can be improved more reliably. As a result, the read / write speed of the phase change memory having the laminated structure of the metal chalcogen film can be increased more reliably.

  In addition, the said embodiment can be changed and implemented suitably as follows.

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 rare gas supply unit 32 is configured to supply argon gas as a sputtering gas, but a rare gas other than argon, for example, helium (He) gas, neon (Ne) gas, krypton (Kr) gas, and xenon (Xe) ) Gas may be supplied.

· GeTe during sputtering of the target 22a and _Sb 2 Te ₃ target 22b, may be adapted to supply nitrogen gas or oxygen gas is added gas from the additive gas supply unit 33.

  The sputtering apparatus 10 may have a configuration that does not include the additive gas supply unit 33.

-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 source 24. The target exposed from the opening of the shutter 26 may be switched after switching the connection 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.

  The elements 22a and 22b include elements such as carbon (C), silicon (Si) aluminum (Al), tin (Sn), phosphorus (P), arsenic (As), silver (Ag), and indium (In). May be added.

-The diameter of the board | substrate S is not restricted to 300 mm, You may make it use the board | substrate of another magnitude | size. Regardless of the size of the substrate S used, the GeTe film 44a and Sb ₂ Te formed on the substrate S are rotated as long as the substrate S is rotated in the circumferential direction while adsorbing and heating the substrate S. It is possible to easily align the plane orientations of the crystals forming the _three films 44b.

Even if the temperature variation is not included in the range of −10 ° C. or higher and + 10 ° C. or lower, and the rotation speed of the substrate S is not included in the range of 60 to 250 rotations per minute, adsorption, heating, and rotation of the substrate S If the GeTe film 44a and the Sb ₂ Te ₃ film 44b are formed, the plane orientation in the crystals forming these films 44a and 44b can be made uniform. That is, even if the range of temperature variation and the range of rotation speed are not included in the above-described preferable range, the film 44a is compared with the configuration in which any of these is missing as long as the substrate is rotated, adsorbed, and heated. 44b can be made uniform in plane orientation.

-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.

-When changing the target to be sputtered without providing the switching period, there may be a period during which both the surface of the GeTe target 22a and the Sb ₂ Te ₃ target 22b are sputtered. Even in such a configuration, when sputtering the targets 22a and 22b, the GeTe film 44a and the Sb ₂ are rotated while the substrate S is rotated in the circumferential direction while the substrate S is attracted and heated by the substrate stage 13. As long as the Te ₃ film 44b is formed, it is possible to obtain the effects equivalent to the above (1) and (2).

The temperature of the mounting surface 13a is adjusted so that the temperature of the mounting surface 13a of the substrate stage 13 is equal between the sputtering time of the GeTe target 22a and the Sb ₂ Te ₃ target 22b and the sputtering target switching period. I did it. Not limited to this, the temperature of the mounting surface 13a changes within a range in which the GeSbTe compound formed at the boundary between the GeTe film 44a and the Sb ₂ Te ₃ film 44b does not change from the crystalline phase to the amorphous phase. May be.

The sputtering apparatus 10 may not have the shutter 26. Even in such a configuration, when sputtering the targets 22a and 22b, the substrate S is adsorbed and heated by the substrate stage 13 while the substrate S is rotated in the circumferential direction thereof, and the GeTe film 44a and Sb _2. As long as the Te ₃ film 44b is formed, it is possible to obtain the effects equivalent to the above (1) and (2).

  Although the substrate S is adsorbed to the mounting surface 13a of the substrate stage 13 by electrostatic force, the substrate S may be adsorbed by another adsorption method such as vacuum adsorption.

The sputter 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 ... rotary unit, 21a ... first backing plate, 21b ... second backing plate, 22a ... GeTe target (first target), 22b ... _Sb 2 Te ₃ Target (second target), 23a ... first magnet unit, 23b ... second magnet unit, 24 ... high frequency power supply, 25 ... DC power supply, 26 ... shutter, 31 ... exhaust section, 32 ... rare gas supply section, 33 ... Addition gas supply unit, 41, 51 ... interlayer insulation film, 42, 52 ... heat insulation layer, 43, 53 ... lower electrode, 44 ... metal chalcogenide laminate, 44a ... GeT Film, 44b ... _Sb 2 Te ₃ film, 44G ... germanium atom, 44T ... tellurium atom, 50 ... phase change memory, 54 ... metal chalcogenide film, 55 ... upper electrode, S ... substrate, SWa ... first switch, SWb ... first 2 switches.

Claims (5)

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 a rare gas;
A substrate stage having a heating surface for heating the substrate and heating the substrate while adsorbing the substrate to the heating surface;
A rotating unit that rotates the substrate stage in the circumferential direction of the substrate;
With the substrate stage sucking and heating the substrate, the sputter source sputters each of the two or more metal chalcogenide targets at different timings while rotating the substrate stage. An apparatus for forming a phase change memory, wherein two or more metal chalcogenide films having different compositions are stacked on the substrate. The apparatus for forming a phase change memory according to claim 1, wherein the substrate stage attracts the substrate by electrostatic force on the heating surface. The two or more chalcogenide targets are composed of a first target made of GeTe and a _second target made of Sb ₂ Te ₃ ,
The sputtering source alternately switches the sputtering target to the first target and the second target, and when switching the sputtering target, put a switching period,
A shutter that exposes a target to be sputtered and covers a target other than the target in the switching period;
The substrate stage controls the temperature of the heating surface so that the temperature of the heating surface during a period during which the sputtering source sputters a target is equal to the temperature of the heating surface during the switching period. Or an apparatus for forming a phase change memory according to 2; The substrate has a diameter of 150 mm to 300 mm,
The temperature variation in the plane of the substrate is -10 ° C or higher and + 10 ° C or lower,
The phase change memory forming device according to claim 3, wherein the rotation speed of the substrate stage is not less than 60 times per minute and not more than 250 times per minute. 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 the substrate is adsorbed to the heating surface of the substrate stage and heated by the heating surface, and the substrate stage is rotated, each of the two or more metal chalcogenide targets having different compositions is mixed with a rare gas at different timings. And forming two or more metal chalcogenide films having different compositions on the substrate by sputtering.

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