JP2007254827A - Sputtering system and sputtering method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sputtering system and a sputtering method capable of forming a ferroelectric film having satisfactory orientation properties for a long period of time. <P>SOLUTION: While temperature control is performed by a cooling/temperature controlling unit before and after the generation of plasma, cooling water is allowed to flow through water flowing paths 6a to 6f in a cooling part 1 via piping 2a to 2f. At that time, as it goes to the part in which the thickness of a target is more reduced in the case cooling is not performed, the temperature of the cooling water flowing therethrough is lowered. For example, the temperature of the cooling water flowing through the water flowing paths 6a and 6f located in the outer circumferential part and the central part of the target is made lower, and the temperature of the cooling water flowing through the water flowing path 6b located at the inside than the water flowing path 6a is made higher. Since the temperature of the target can be controlled in accordance with the distance from the center, the degree of erosion can be also adjusted in accordance with the distance from the center. In this way, even in the case a ferroelectric film is formed, the one having satisfactory orientation properties can be stably formed over a long period. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a sputtering apparatus and a sputtering method suitable for forming a ferroelectric film.

  A ferroelectric capacitor used in a ferroelectric memory or the like includes a ferroelectric film. The ferroelectric film can be formed by various methods. One of them is a sputtering method using a magnetron type sputtering apparatus. In the magnetron type sputtering apparatus, a magnetron unit that forms a magnetic field in the vicinity of the target is provided above the target that is a film forming raw material. The magnetron unit is provided with a magnet assembly including a plurality of magnets, a drive motor for rotating the magnet assembly, and the like.

  In forming a thin film using a magnetron sputtering apparatus, Ar gas is supplied into the chamber and a DC voltage is applied between the target and the stage to generate plasma in the chamber. As a result, Ar ions in the plasma collide with the target, particles are ejected from the target, and the particles are deposited on the semiconductor wafer. In this way, a thin film is formed.

  In the conventional magnetron type sputtering apparatus, the temperature of the target rises with the progress of sputtering. As the target temperature rises, erosion proceeds. Thus, techniques for cooling the temperature of the target have been proposed (Patent Documents 1 to 3).

  Patent Document 1 discloses a technique for cooling a target using an inert gas such as Ar gas.

  Patent Document 2 discloses a technique for forming a radial groove in a target in accordance with a location where erosion occurs and improving the cooling efficiency there.

  Patent Document 3 discloses a technique in which cooling water is introduced from one place into a frame provided on the target and discharged from one place for the purpose of suppressing erosion on the back surface of the target.

However, these techniques cannot sufficiently suppress the erosion of the target when forming a ferroelectric film that requires particularly high orientation. High orientation is required for the ferroelectric film constituting the ferroelectric capacitor. The orientation is easily affected by target erosion. However, the conventional technique cannot suppress erosion to such an extent that good orientation can be secured for a long time. For this reason, when the target is used over a long period of time, the orientation is extremely lowered from the middle.
JP-A-6-25844 JP-A-9-143708 JP 2003-73827 A

  An object of the present invention is to provide a sputtering apparatus and a sputtering method capable of forming a ferroelectric film with good orientation over a long period of time.

  When the inventor of the present application conducted an experiment on the distribution of erosion, results as shown in FIG. 5 were obtained. FIG. 5 is a graph showing erosion in a semiconductor wafer having a diameter of 300 mm. The horizontal axis in FIG. 5 indicates a position on an arbitrary straight line passing through the center of the semiconductor wafer, and the vertical axis indicates the thickness of the PZT target after performing sputtering for 600 hours. As a result of this test, the present inventor has found that the thickness of the PZT target varies greatly depending on the distance from the center of the PZT target due to erosion.

  FIG. 6 is a graph showing the relationship between the target usage time and the data retention performance. The data retention performance shown on the vertical axis in FIG. 6 was evaluated based on the PT ratio. The PT ratio indicates the ratio of the yield of ferroelectric capacitors that can be read correctly when heat treatment is performed after writing and the data is inverted after the yield of ferroelectric capacitors that can be read correctly after writing. PT ratio is 0 or 1 data written and then heat treated, then 0 or 1 can be read as it is, and 1 or 0 inverted data is written and then heat treated Thereafter, it is confirmed whether 1 or 0 can be read as it is. For example, when the number of normally operating chips is 10, and the number of normally operating chips finally becomes 8, the PT ratio is 8/10 = 80 (%). The PT ratio should be high, and if there is a chip that tends to become a defective chip, the PT ratio deteriorates. As shown in FIG. 6, when a ferroelectric capacitor is formed using a conventional magnetron sputtering apparatus, the PT ratio rapidly decreases when the target usage time exceeds 400 k hours. This indicates that the orientation of the ferroelectric film is lowered.

  Based on these findings, the inventor of the present application has intensively studied to solve the above problems, and as a result, has arrived at the following aspects of the invention.

  The sputtering apparatus according to the present invention includes a chamber, an electric field forming unit that forms an electric field in the chamber, and a magnetic field forming unit that forms a magnetic field around a target arranged in the chamber. . The sputtering apparatus further includes two or more flow paths for refrigerants independent from each other, a cooling means for cooling the target, and a temperature control means for individually controlling the temperature of the refrigerant flowing through the two or more flow paths. , Is provided.

  In the sputtering method according to the present invention, an electric field is formed in a chamber, and a magnetic field is formed around a target disposed in the chamber. Then, the target is cooled by flowing the refrigerant through a cooling means having two or more flow paths for refrigerants independent from each other, and the temperature of the refrigerant flowing through the two or more flow paths is individually controlled. Note that the order of these steps is not particularly limited.

  According to the present invention, erosion of a target can be appropriately controlled. For this reason, when a ferroelectric target such as a PZT target is used, a ferroelectric film having a good orientation can be stably formed over a long period of time.

  Hereinafter, embodiments of the present invention will be specifically described with reference to the accompanying drawings.

(First embodiment)
First, a first embodiment of the present invention will be described. FIG. 1 is a diagram showing an internal structure of a magnetron sputtering apparatus according to the first embodiment of the present invention.

  In the magnetron sputtering apparatus according to the first embodiment, as shown in FIG. 1, an electrostatic chuck 17 for fixing a semiconductor wafer 16 is provided in a chamber 11, and an earth block 18 is disposed around the electrostatic chuck 17. . Below the electrostatic chuck 17, an electrode 19 connected to the negative electrode of the DC power supply 20 is provided. Further, an electrode 13 connected to the positive electrode of the DC power supply 20 is disposed so as to face the semiconductor wafer 16. A target 14 is fixed below the electrode 13. Furthermore, a deposition preventing plate 15 that isolates the space between the semiconductor wafer 16 and the target 14 and the inner wall of the chamber 11 is provided.

  In the present embodiment, the cooling unit 1 for cooling the target 14 is provided on the electrode 13, and the magnet 12 is provided thereon. A cooling / temperature adjustment unit 3 is connected to the cooling unit 1 via a pipe bundle 2. The pipe bundle 2 is provided so as to extend above the cooling unit 1. FIG. 2 is a diagram illustrating a configuration of the cooling unit 1 according to the first embodiment. The pipe bundle 2 is composed of, for example, six pipes (tubes) 2a, 2b, 2c, 2d, 2e, and 2f. The pipes 2a to 2f are independent from each other, and the cooling / temperature adjustment unit 3 individually adjusts the temperature of the cooling water flowing through the pipes 2a to 2f. Further, in the cooling section 1, flowing water channels 6a, 6b, 6c, 6d, 6e and 6f are formed, which are connected to the pipes 2a, 2b, 2c, 2d, 2e and 2f, respectively. The flowing water channels 6 a to 6 f are arranged concentrically in the cooling unit 1. And in the cooling water introduction part 4, the pipes 2a to 2f connected to the water flow paths 6a to 6f are connected to the discharge side of the cooling / temperature control unit 3, and in the cooling water discharge part 5, the pipe 2a connected to the water flow paths 6a to 6f. ˜2f is connected to the introduction side of the cooling / temperature control unit 3.

  Next, the operation (sputtering method) of the magnetron sputtering apparatus configured as described above will be described. Here, a ferroelectric film is formed on the semiconductor wafer 16 using a target containing Pb atoms, Zr atoms, Ti atoms, Ca atoms, Sr atoms, and O atoms.

  First, the semiconductor wafer 16 is carried into the chamber 11 and fixed by the electrostatic chuck 17. Next, the pressure inside the chamber 11 is reduced to a predetermined degree of vacuum using a vacuum pump, and a process gas such as Ar gas is introduced into the chamber 11 from the gas supply port. Next, a predetermined voltage is applied between the DC power source 20 and the electrodes 13 and 19 while rotating the magnet 12. Thereby, glow discharge is generated in the space surrounded by the deposition preventing plate 15, and Ar ions 21 in the plasma 23 collide with the target 14. As a result, the particles 22 are ejected from the target 14 and deposited on the semiconductor wafer 16. The particle 22 is an atom constituting the target 14. Then, the deposition of the particles 22 is repeated, and a ferroelectric film is formed.

  Further, before and after the generation of the plasma 23, the cooling water is caused to flow through the water flow paths 6 a to 6 f in the cooling unit 1 through the pipes 2 a to 2 f while performing temperature control by the cooling / temperature control unit 3. At this time, the temperature of the cooling water flowing therethrough is lowered as the decrease in the thickness of the target 14 increases when cooling is not performed. For example, when the distribution shown in FIG. 5 is obtained, the temperature of the cooling water flowing through the water flow paths 6a and 6f located at the outer peripheral part and the center part of the target 14 is lowered, and the position is located inside the water flow path 6a. The temperature of the cooling water flowing through the flowing water channel 6b is increased. For example, since a large amount of PZT target is consumed around the pipe 2a, cooling water of 10 ° C. is flowed, and since a PTT target is hardly consumed around the pipe 2b, cooling water of 20 ° C. is flowed. Also, since the PZT target is consumed near the average value around the pipe 2c, 18 ° C. cooling water flows, and since much PZT target is consumed around the pipe 2d, the cooling water is 14 ° C. Shed. Also, since the PZT target is consumed near the average value around the pipe 2e, a cooling water of 16 ° C. flows, and the P2T target is consumed a lot around the pipe 2f because the PZT target is consumed around 10 ° C. Shed.

  According to the first embodiment, the degree of cooling of the target 14 can be adjusted according to the distance from the center of the target 14. Therefore, since the temperature of the target 14 can be controlled according to the distance from the center, the degree of erosion can also be adjusted according to the distance from the center. For this reason, even when a ferroelectric film is formed, a film having good orientation can be stably formed over a long period of time.

(Second Embodiment)
Next, a second embodiment of the present invention will be described. FIG. 3 is a diagram showing an internal structure of a magnetron sputtering apparatus according to the second embodiment of the present invention.

  In the first embodiment, the pipe bundle 2 is provided so as to extend above the cooling part 1. However, in the second embodiment, the pipe bundle 2 is provided so as to extend to the side of the cooling part 1. It has been. Other configurations are the same as those of the first embodiment.

  According to the second embodiment as described above, the same effect as that of the first embodiment can be obtained.

(Third embodiment)
Next, a third embodiment of the present invention will be described. FIG. 4 is a diagram illustrating a configuration of the cooling unit 1 according to the third embodiment of the present invention.

  In the first embodiment, six flow channels 6 a to 6 f are arranged concentrically in the cooling unit 1, but in the third embodiment, a large number of annular flow channels 6 g are installed in the cooling unit 1. Has been placed. Further, the plurality of water channels 6g are arranged to form a circle, and six such circles are formed with different diameters. These six circles are arranged concentrically. Further, although not shown, the pipe bundle 2 is composed of the same number of pipes as the flowing water passages 6 g, and the temperature of the cooling water flowing through each pipe is individually controlled by the cooling / temperature control unit 3. Other configurations are the same as those of the first embodiment.

  According to such 3rd Embodiment, compared with 1st Embodiment, more precise temperature control is attained. In many cases, the erosion is considered to be the same if the distance from the center of the target is the same, but the erosion may be different within the same circle. According to the third embodiment, since it is possible to individually control the temperature of the flowing water channel 6g located on the same circle, even in such a case, erosion over the entire target is possible. The degree can be made uniform.

  In the above-described embodiment, cooling water is used as the refrigerant, but other refrigerants such as gas may be used. Further, as a target, in addition to a ferroelectric material, an Al target or the like may be used.

  Moreover, it is preferable that the cooling / temperature control unit 3 changes the temperature of the cooling water according to the elapsed time. For example, when a target containing Pb atom, Zr atom, Ti atom and O atom is used as the target 14, the temperature (° C.) of the cooling water is within a range of 10% with respect to the initial set value according to the elapsed time. It is preferable to change within.

  As described above, Patent Document 2 discloses a technique for forming a groove in a target in accordance with an erosion occurrence location, but the groove is formed in a radial shape, and since the flow channel is single, Erosion cannot be properly controlled. Furthermore, it is necessary to form a groove in the target each time the target is exchanged, and this operation is complicated.

  Hereinafter, various aspects of the present invention will be collectively described as supplementary notes.

(Appendix 1)
A chamber;
An electric field forming means for forming an electric field in the chamber;
Magnetic field forming means for forming a magnetic field around a target disposed in the chamber;
Two or more flow paths for refrigerants independent from each other, a cooling means for cooling the target,
Temperature control means for individually controlling the temperature of the refrigerant flowing through the two or more flow paths;
A sputtering apparatus comprising:

(Appendix 2)
The sputtering apparatus according to appendix 1, wherein the two or more flow paths are arranged concentrically with each other.

(Appendix 3)
A plurality of flow paths included in the two or more flow paths are arranged on the first circle,
A plurality of other channels included in the two or more channels are disposed on the second circle;
The sputtering apparatus according to appendix 1, wherein the center of the first circle coincides with the center of the second circle.

(Appendix 4)
Any one of Supplementary notes 1 to 3, wherein the temperature control means controls the temperature of the refrigerant flowing through a flow path located near a portion where the progress of erosion is remarkable when the target is not cooled, to be lower. 2. A sputtering apparatus according to item 1.

(Appendix 5)
The sputtering apparatus according to any one of appendices 1 to 4, wherein a coolant is used as the refrigerant.

(Appendix 6)
The temperature control means mixes a positive gradient and a negative gradient in the temperature gradient between adjacent flow paths while controlling the temperature of the refrigerant according to the distance from the center of the target. The sputtering apparatus according to any one of appendices 1 to 5.

(Appendix 7)
The sputtering apparatus according to any one of appendices 1 to 6, wherein the cooling unit is disposed between the target and the magnetic field forming unit.

(Appendix 8)
When a target containing Pb atom, Zr atom, Ti atom and O atom is used as the target,
The temperature control means changes the temperature (° C.) of the refrigerant within a range of 10% with respect to an initial set value according to an elapsed time. Sputtering equipment.

(Appendix 9)
An electric field forming step for forming an electric field in the chamber;
A magnetic field forming step for forming a magnetic field around a target disposed in the chamber;
A cooling step of cooling the target by flowing the refrigerant through a cooling means having two or more flow paths for refrigerant independent from each other;
A temperature control step of individually controlling the temperature of the refrigerant flowing through the two or more flow paths;
A sputtering method comprising:

(Appendix 10)
The sputtering method according to appendix 9, wherein the two or more flow paths are arranged concentrically with each other.

(Appendix 11)
A plurality of flow paths included in the two or more flow paths are arranged on the first circle,
A plurality of other channels included in the two or more channels are disposed on the second circle;
The sputtering method according to appendix 9, wherein the center of the first circle coincides with the center of the second circle.

(Appendix 12)
Any one of appendices 9 to 11, wherein, in the temperature control step, when the target is not cooled, the temperature of the refrigerant flowing in the flow path located near the portion where the erosion progresses significantly is controlled to be lower. 2. The sputtering method according to item 1.

(Appendix 13)
As the target, a substance containing Pb atom, Zr atom, Ti atom and O atom is used.
13. The additional control 9 to 12, wherein in the temperature control step, the temperature (° C.) of the refrigerant is changed within a range of 10% with respect to an initial set value according to an elapsed time. Sputtering method.

It is a figure which shows the internal structure of the magnetron type | mold sputtering apparatus which concerns on the 1st Embodiment of this invention. It is a figure which shows the structure of the cooling unit 1 in the 1st Embodiment of this invention. It is a figure which shows the internal structure of the magnetron type | mold sputtering apparatus which concerns on the 2nd Embodiment of this invention. It is a figure which shows the structure of the cooling unit 1 in the 3rd Embodiment of this invention. It is a graph which shows the erosion in the semiconductor wafer whose diameter is 300 mm. It is a graph which shows the relationship between the usage time of a target, and data retention performance.

Explanation of symbols

1: Cooling unit 2: Pipe bundle 2a-2f: Piping 3: Cooling / temperature control unit 4: Cooling water introduction unit 5: Cooling water discharge unit 6a-6g: Flow channel

Claims (5)

A chamber;
An electric field forming means for forming an electric field in the chamber;
Magnetic field forming means for forming a magnetic field around a target disposed in the chamber;
Two or more flow paths for refrigerants independent from each other, a cooling means for cooling the target,
Temperature control means for individually controlling the temperature of the refrigerant flowing through the two or more flow paths;
A sputtering apparatus comprising:   The sputtering apparatus according to claim 1, wherein the two or more flow paths are arranged concentrically with each other. A plurality of flow paths included in the two or more flow paths are arranged on the first circle,
A plurality of other channels included in the two or more channels are disposed on the second circle;
The sputtering apparatus according to claim 1, wherein a center of the first circle and a center of the second circle coincide with each other.   4. The temperature control unit controls the temperature of the refrigerant that flows through a flow path located near a portion where erosion progresses significantly when the target is not cooled, to lower the temperature. 5. A sputtering apparatus according to claim 1. An electric field forming step for forming an electric field in the chamber;
A magnetic field forming step for forming a magnetic field around a target disposed in the chamber;
A cooling step of cooling the target by flowing the refrigerant through a cooling means having two or more flow paths for refrigerant independent from each other;
A temperature control step of individually controlling the temperature of the refrigerant flowing through the two or more flow paths;
A sputtering method comprising:

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