Plasma generating device and control method

Abstract

The invention provides a plasma generating device and a control method. The plasma generating device comprises a process cavity; the carrying table is used for carrying a substrate; the carrying platform is mounted at the bottom of the process cavity; the target material back plate is mounted at the top of the process cavity; a negative electrode of the direct-current power supply is connected with the target material back plate, and the direct-current power supply is used for outputting and applying a first negative high voltage Vnegative 1 to the target material back plate; the negative electrode of the controllable high-voltage power supply is connected with the high-voltage electrode plate, and the controllable high-voltage power supply is used for outputting and applying second negative high voltage V negative 2 to the high-voltage electrode plate; the first negative high voltage Vnegative 1 and the second negative high voltage Vnegative 2 are used for superposing to generate a high-voltage electric field on the surface of the target material; the controller is used for controlling the controllable high-voltage power supply to automatically adjust the second negative high voltage Vnegative 2 according to the voltage change of the first negative high voltage Vnegative 1; according to the invention, glow discharge of process gas is facilitated, and plasma formation is promoted; and the atom utilization rate and the step coverage rate of the hole filling process can be improved.

Description

Technical Field

[0001] The invention relates to the technical field of magnetron sputtering in PVD, in particular to a plasma generating device and a control method. Background Art

[0002] In magnetron sputtering technology, the directional distribution of sputtered atoms is related to the ion incident direction, ion energy, target surface morphology, etc. Experiments show that for higher ion energy sputtering, the directional distribution of sputtered atoms has little correlation with the ion incident direction. Test data show that the distribution of sputtered atoms in different directions usually follows the cosine function (cos n θ) law, where θ is the angle between the emission direction of the sputtered atoms and the target surface normal, and the index n is related to the ion energy. For a specific ion / atom combination, within a certain energy range, n=1, while for lower and higher energy ion sputtering, the n value is less than and greater than 1, respectively. Figure 1 A schematic diagram of this distribution is given; for the case of n = 1, the direction distribution of the sputtered atoms is similar to a circular sphere; the direction distribution of atoms sputtered by lower and higher energy ions is similar to an ellipsoid, but the former is offset laterally and the latter is offset longitudinally, such as Figure 1 shown.

[0003] When the ion energy is low, its incident direction may affect the distribution of the sputtered atoms; the distribution of atoms sputtered by oblique incident ions may move toward the direction of the reflection angle. Low-energy ion sputtering is mainly a surface elastic collision process, and the atoms impacted have strong directionality. Higher-energy ions penetrate deeper into the surface of the target material, and after multiple collisions and scattering, they lose their original directionality.

[0004] In magnetron sputtering, the incident direction and ion energy of positive ions (such as Ar+ ions) in the plasma are mainly determined by the sputtering voltage, which is mainly determined by the input power of the target material, the magnetic field strength, and the discharge gas concentration or flow rate.

[0005] In the prior art, the normal sputtering voltage of common target materials (titanium, copper, aluminum, molybdenum, etc.) is in the range of 300V to 600V, and generally does not exceed 650V. The existing target surface voltage cannot provide sufficient incident energy for the plasma incident ions, and the atomic distribution sputtered by the lower energy ions presents a laterally offset ellipsoidal surface, resulting in more atoms deposited in the area outside the substrate directly below, resulting in a waste of sputtered atoms; in addition, the vertical directionality of the sputtered atom deposition is also greatly reduced, and for the metal hole filling process, the step coverage of the film is significantly reduced.

[0006] In addition, the maximum output voltage of the existing magnetron sputtering DC power supply does not exceed 850V, which places certain requirements on the discharge gas concentration or flow rate, target surface magnetic field strength, etc. For example, when the target surface magnetic field strength is insufficient or the target material is ferromagnetic (such as iron, cobalt, nickel, etc.), or when the specific sputtering process places certain requirements on the process gas pressure (for example, the gas pressure is required to be lower, because the higher sputtering pressure enhances the scattering effect of the sputtered atoms of the target material, resulting in a much lower kinetic energy of the sputtered atoms and reduced film density), the glow discharge process is often difficult to start. Summary of the invention

[0007] In order to solve at least one technical problem in the prior art, the embodiment of the present invention provides a plasma generating device and control method, which is helpful for process gas glow discharge, more conducive to ignition, and promotes plasma formation; and makes the angle between the exit direction of sputtered atoms and the normal direction of the target surface smaller, so that more sputtered atoms fall on the substrate, which can improve the atomic utilization rate and the step coverage rate of the hole filling process. To achieve the above technical objectives, the technical solution adopted by the embodiment of the present invention is: In a first aspect, an embodiment of the present invention provides a plasma generating device, comprising: Process chamber; A carrier, used for carrying a substrate; the carrier is installed at the bottom of the process chamber; A target material backing plate, used for carrying the target material; the target material backing plate is installed on the top of the process chamber, opposite to the carrier; A DC power supply, the negative electrode of which is connected to the target back plate, for outputting and applying a first negative high voltage V to the target back plate 负1 ; The positive electrode of the DC power supply is grounded; A controllable high-voltage power supply, wherein the negative electrode of the controllable high-voltage power supply is connected to the high-voltage electrode plate, and is used to output and apply a second negative high voltage V to the high-voltage electrode plate. 负2 ; The high voltage electrode plate is parallel to the target surface and insulated from the target back plate; the first negative high voltage V 负1 and the second negative high voltage V 负2 Used to generate a high-voltage electric field on the surface of the target material by superposition; the positive electrode of the controllable high-voltage power supply is grounded; The controller is used to generate a negative high voltage V 负1 The voltage change controls the controllable high voltage power supply to automatically adjust the second negative high voltage V 负2 ; So that in the ignition stage, the first negative high voltage V 负1 With the second negative high voltage V 负2 The voltage and V 和 Be consistent.

[0008] Furthermore, the first negative high voltage V 负1 With the second negative high voltage V 负2The voltage and V 和 It is 1800V~2200V.

[0009] Furthermore, the high-voltage electrode plate is mounted on the side of the target material backing plate facing away from the target material, and is insulated from the target material backing plate by a gap or an insulating layer.

[0010] Furthermore, the high-voltage electrode plate is wrapped by an insulating layer and installed inside the target material back plate; the high-voltage electrode plate is connected to the negative electrode of the controllable high-voltage power supply through an insulated wire passing through the target material back plate.

[0011] Furthermore, the carrier is grounded.

[0012] Furthermore, the controller adopts a PLC controller; it is used to collect the output voltage of the DC power supply, that is, the first negative high voltage V 负1 , and is used to issue a control instruction to the controllable high voltage power supply to adjust the second negative high voltage V 负2 .

[0013] In a second aspect, an embodiment of the present invention provides a control method for a plasma generating device, which is applicable to the plasma generating device as described above, and comprises the following steps: Step S10, according to the ignition voltage V of the DC power supply 1 and the preset voltage and V 和 Set the second negative high voltage V output by the controllable high voltage power supply 负2 The initial voltage value HV 1 ; That is HV 1 =V 和 -V 1 ; Step S20, introducing process gas into the process chamber, at the beginning of the ignition stage, applying a first negative high voltage V to the target back plate 4 through a DC power supply 负1 Ignition voltage V 1 , a second negative high voltage V is applied to the high voltage electrode plate by a controllable high voltage power supply 负2 is the initial voltage value HV 1 ; V 1 +HV 1 =V 和 ; Step S30, monitoring the first negative high voltage V output by the DC power supply 负1 , when the first negative high voltage V 负1 Drop to sputtering voltage V 2 And keep a set judgment time, adjust the second negative high voltage V 负2 is the operating voltage value HV 2 ; V 2 +HV 2 =V 和; Enter the magnetron sputtering stage; perform the magnetron sputtering process according to the set magnetron sputtering time.

[0014] Furthermore, the ignition voltage V 1 It is 650V~850V.

[0015] Furthermore, the sputtering voltage V 2 200V~650V.

[0016] Furthermore, the setting judgment time length is 100ms to 200ms.

[0017] The technical solution provided by the embodiment of the present invention has the following beneficial effects: 1) The second negative high voltage V generated by the controllable high voltage power supply 负2 Able to follow the first negative high voltage V generated by the DC power supply 负1 The voltage changes are automatically adjusted, and the superimposed high-voltage electric field ensures that the target surface always maintains a stable high-voltage electric field.

[0018] 2) The electric field generated by the higher voltage is conducive to the glow discharge of the process gas, which is more conducive to ignition and promotes the formation of plasma, thereby allowing the magnetron sputtering process to proceed smoothly.

[0019] 3) Under the action of the enhanced high-voltage electric field, the argon ions in the plasma bombard the target with greater kinetic energy, and the angle between the exit direction of the sputtered atoms and the normal direction of the target surface is smaller, so that more sputtered atoms fall on the substrate, which can improve the atomic utilization rate and the step coverage rate of the hole filling process. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of the direction distribution of sputtered atoms in an embodiment of the present invention.

[0021] Figure 2 Schematic diagram of the structure of a plasma generating device in an embodiment of the present invention.

[0022] Figure 3 4 is a flow chart of a control method in an embodiment of the present invention.

[0023] Figure 4 Schematic diagram of film measurement points in an embodiment of the present invention.

[0024] Figure 5 Schematic diagram of film thickness distribution during sputtering with an applied high voltage electric field in an embodiment of the present invention.

[0025] Figure 6 Schematic diagram of film thickness distribution during sputtering without an external high voltage electric field in an embodiment of the present invention. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0027] In the description of the embodiments of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0028] In the description of the embodiments of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, it can also be the internal connection of two components, it can be a wireless connection, or it can be a wired connection. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0029] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0030] like Figure 2 As shown, an embodiment of the present invention provides a plasma generating device, comprising: Process chamber 1; The carrier 2 is used to carry the substrate 3; the carrier 2 is installed at the bottom of the process chamber 1; A target back plate 4 is used to carry a target 5; the target back plate 4 is installed on the top of the process chamber 1 and is opposite to the carrier 2; A DC power supply 6, the negative electrode of which is connected to the target back plate 4, for outputting and applying a first negative high voltage V to the target back plate 4 负1 ; The positive electrode of the DC power supply 6 is grounded; A controllable high-voltage power supply 7, wherein the negative electrode of the controllable high-voltage power supply 7 is connected to the high-voltage electrode plate 8, and is used to output and apply a second negative high voltage V to the high-voltage electrode plate 8. 负2 ; The high voltage electrode plate 8 is parallel to the target surface 5 and insulated from the target back plate 4; the first negative high voltage V 负1 and the second negative high voltage V负2 It is used to generate a high voltage electric field on the surface of the target material 5 by superposition; the positive electrode of the controllable high voltage power supply 7 is grounded; The controller 9 is used to generate a first negative high voltage V 负1 The voltage change controls the controllable high voltage power supply 7 to automatically adjust the second negative high voltage V 负2 ; So that in the ignition stage, the first negative high voltage V 负1 With the second negative high voltage V 负2 The voltage and V 和 Stay consistent; In some embodiments, the DC power supply 6 is an existing magnetron sputtering DC power supply, and its maximum output voltage is usually 650V to 850V; the controllable high-voltage power supply 7 and the high-voltage electrode plate 8 are components added in this embodiment; the controllable high-voltage power supply 7 can adopt a DC boost power supply, and the output voltage is controllable; the substrate 3 on the carrier 2 is usually a wafer; the target material back plate 4 needs to be conductive, usually a metal plate; the process chamber 1 is provided with a gas inlet 101 and a gas extraction port 102; before the PVD magnetron sputtering process is carried out, the process chamber 1 needs to be evacuated, and then a process gas such as argon is introduced; In some embodiments, the first negative high voltage V 负1 With the second negative high voltage V 负2 The voltage and V 和 1800V~2200V, typically, for example, 2000V; in this embodiment, no negative sign is added before the voltage value, but it should be understood that the target back plate 4 and the high voltage electrode plate 8 are applied with negative high voltage; In some embodiments, the high voltage electrode plate 8 is mounted on the side of the target back plate 4 facing away from the target 5 and is insulated from the target back plate 4 by a gap or an insulating layer; In some embodiments, the high-voltage electrode plate 8 is wrapped by an insulating layer and installed inside the target back plate 4; the high-voltage electrode plate 8 is connected to the negative electrode of the controllable high-voltage power supply 7 through an insulated wire passing through the target back plate 4; In some embodiments, the carrier 2 is grounded; in other embodiments, the carrier 2 may not be grounded; In some embodiments, the controller 9 is a PLC controller; it can collect the output voltage of the DC power supply 6, that is, the first negative high voltage V 负1 , and can also issue a control instruction to the controllable high voltage power supply 7 to adjust the second negative high voltage V 负2 ; An embodiment of the present invention further provides a control method for a plasma generating device, comprising the following steps: Step S10, according to the ignition voltage V of the DC power supply 6 1 and the preset voltage and V 和 Set the second negative high voltage V output by the controllable high voltage power supply 7 负2The initial voltage value HV 1 ; That is HV 1 =V 和 -V 1 ; In this embodiment, the ignition voltage V of the DC power supply 6 is 1 is 850V, the preset voltage and V 和 is 2000V, then the second negative high voltage V 负2 The initial voltage value HV 1 1150V; Step S20, introducing process gas into the process chamber 1, at the beginning of the ignition stage, applying a first negative high voltage V to the target back plate 4 through the DC power supply 6 负1 Ignition voltage V 1 , a second negative high voltage V is applied to the high voltage electrode plate 8 by the controllable high voltage power supply 7 负2 is the initial voltage value HV 1 ; V 1 +HV 1 =V 和 ; The ignition stage is very short, about hundreds of milliseconds; then it enters the magnetron sputtering stage; after the ignition is successful and the process gas glow discharges, the DC power supply 6 outputs the first negative high voltage V 负1 will quickly rise from the ignition voltage V 1 Drop to sputtering voltage V 2 ; At this time, the second negative high voltage V 负2 ; Step S30, monitoring the first negative high voltage V output by the DC power supply 6 负1 , when the first negative high voltage V 负1 Drop to sputtering voltage V 2 And keep a set judgment time, adjust the second negative high voltage V 负2 is the operating voltage value HV 2 ; V 2 +HV 2 =V 和 ; Enter the magnetron sputtering stage; carry out the magnetron sputtering process according to the set magnetron sputtering time; In a specific embodiment, when the sputtering voltage V 2 When the second negative high voltage V is adjusted to 600V, 负2 1400V, HV 2 1400V; Furthermore, the ignition voltage V 1 650V~850V; Furthermore, the sputtering voltage V 2 200v~650v; Furthermore, the setting judgment time is 100ms to 200ms; The time from the ignition stage to the stable magnetron sputtering stage is very short, in this embodiment, usually within 1s; in this embodiment, the first negative high voltage V 负1 With the second negative high voltage V 负2 The voltage and V 和 Keep it consistent, so that the target surface always maintains a stable high-voltage electric field; on the one hand, the electric field generated by the higher voltage is conducive to the glow discharge of the process gas, which is more conducive to the ignition and promotes the formation of plasma, so that the magnetron sputtering process proceeds smoothly; on the other hand, the external high voltage (the second negative high voltage V 负2 ) significantly enhances the electric field on the target surface. Under the action of the enhanced high-voltage electric field, the argon ions in the plasma are affected by the cathode sheath electric field (the first negative high voltage V 负1 generated) and an externally applied high voltage electric field (the second negative high voltage V 负2 The double acceleration (generated by the vertical acceleration) bombards the target with greater kinetic energy, the angle between the exit direction of the sputtered atoms and the normal direction of the target surface is small, and the direction distribution of the sputtered atoms tends to be an elliptical surface with a longitudinal offset, so that more sputtered atoms fall on the substrate, thereby improving the atomic utilization rate; moreover, the vertical directionality of the sputtered atoms is stronger, which has a significant effect on improving the step coverage of the hole filling process.

[0031] Embodiment 1 The SJI-SEMI Depomerits P188+ Pro PVD equipment was used. A titanium target with a target purity of 99.999% was selected. The target diameter was 320-321 mm. The distance between the target and the carrier was 90 mm. First, the wafer was transferred to the DC reactive magnetron sputtering process chamber. The temperature of the carrier substrate was set at 200 °C and the vacuum degree of the chamber was maintained at 5.0 × 10 -8 Torr or less; use 3000W sputtering power and pre-sputter the target for 10 minutes; Then, set the second negative high voltage V output by the controllable high voltage power supply 负2 The initial voltage value HV 1 1150V; ignition voltage V 1 The DC power supply is 850V, V 1 With HV 1 The sum is 2000V, then 25sccm of argon is introduced into the process chamber, and the chamber pressure is 1.3mToor; the sputtering power of the DC power supply is 3000w; after the ignition is successful, the sputtering voltage V of the DC power supply is obtained through the controller 2 , and adjust the second negative high voltage V output by the controllable high voltage power supply 负2 is the operating voltage value HV 2 ; Make V 2With HV 2 The sum is 2000V; the total magnetron sputtering time is 120s, and a titanium film is obtained. The film thickness is about 1500Å measured by scanning electron microscopy; In addition, when there is no controllable high-voltage power supply and only a DC power supply is used for magnetron sputtering, the film thickness measured by a scanning electron microscope is about 1200Å; it can be seen that the external high-voltage electric field makes the argon ions in the plasma bombard the target material with greater kinetic energy, and the angle between the emission direction of the sputtered atoms and the normal direction of the target surface is smaller, so that more sputtered atoms fall on the substrate; ultimately, the atomic utilization rate or deposition rate is increased by about 25%.

[0032] Embodiment 2 When sputtering metal films of the same thickness, the step coverage when sputtering with an external high voltage electric field is compared with the step coverage when sputtering without an external high voltage electric field; Thin film measurement points such as Figure 4 As shown, Figure 4 The five thick and short lines in the figure represent the measurement points of each film. The step coverage is defined as the ratio of the film thickness on the side wall or bottom of the micropore to the film thickness on the top plane of the substrate. The film thickness distribution in the cross section of the micropore of the substrate is observed under a scanning electron microscope. The step coverage when sputtering with a high voltage electric field is shown in Figure 5 The step coverage during normal sputtering, i.e., sputtering without an external high voltage electric field, is shown in Figure 6 ; The calculated step coverage is shown in Table 1; The step coverage of the side wall can be taken as the average value;

[0033] Table 1 When sputtering is performed in an external high-voltage electric field, argon ions bombard the target with greater kinetic energy, and the distribution direction of the sputtered atoms tends to be a longitudinally offset elliptical surface. The vertical directionality of the sputtered atoms is stronger, which significantly improves the step coverage of the hole filling process.

[0034] Finally, it should be noted that the above specific implementation methods are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A plasma generating device, characterized in that: include: Process chamber (1); A carrier (2) for carrying a substrate (3); the carrier (2) is installed at the bottom of the process chamber (1); A target material back plate (4) for carrying a target material (5); the target material back plate (4) is installed on the top of the process chamber (1) and is arranged opposite to the carrier (2); A direct current power supply (6), wherein a negative electrode of the direct current power supply (6) is connected to the target material back plate (4) and is used to output and apply a first negative high voltage V to the target material back plate (4). 负1 ; The positive electrode of the DC power supply (6) is grounded; A controllable high-voltage power supply (7), wherein the negative electrode of the controllable high-voltage power supply (7) is connected to the high-voltage electrode plate (8) and is used to output and apply a second negative high voltage V to the high-voltage electrode plate (8). 负2 ; The high voltage electrode plate (8) is parallel to the target surface of the target material (5) and is insulated from the target back plate (4); the first negative high voltage V 负1 and the second negative high voltage V 负2 Used to generate a high-voltage electric field on the surface of the target material (5) by superposition; the positive electrode of the controllable high-voltage power supply (7) is grounded; A controller (9) is used to generate a voltage according to a first negative high voltage V 负1 The voltage change of the controllable high voltage power supply (7) automatically adjusts the second negative high voltage V 负2 ; So that in the ignition stage, the first negative high voltage V 负1 With the second negative high voltage V 负2 The voltage and V 和 Be consistent.

2. The plasma generating device according to claim 1, characterized in that: The first negative high voltage V 负1 With the second negative high voltage V 负2 The voltage and V 和 It is 1800V~2200V.

3. The plasma generating device according to claim 1, characterized in that: The high-voltage electrode plate (8) is mounted on the side of the target material back plate (4) facing away from the target material (5), and is insulated from the target material back plate (4) via a gap or an insulating layer.

4. The plasma generating device according to claim 1, characterized in that: The high-voltage electrode plate (8) is wrapped by an insulating layer and installed inside the target material back plate (4); the high-voltage electrode plate (8) is connected to the negative electrode of the controllable high-voltage power supply (7) via an insulating wire passing through the target material back plate (4).

5. The plasma generating device according to claim 1, characterized in that: The carrier (2) is grounded.

6. The plasma generating device according to claim 1, characterized in that: The controller (9) is a PLC controller; it is used to collect the output voltage of the DC power supply (6), that is, the first negative high voltage V 负1 , and is used to issue a control instruction to the controllable high voltage power supply (7) to adjust the second negative high voltage V 负2 .

7. A control method for a plasma generator, applicable to the plasma generator according to any one of claims 1 to 6, comprising the following steps: Step S10, according to the ignition voltage V1 of the DC power supply (6) and the preset voltage and V 和 Set the second negative high voltage V output by the controllable high voltage power supply (7) 负2 The initial voltage value HV1; that is, HV1=V 和 -V1; Step S20, introducing process gas into the process chamber (1), and at the beginning of the ignition phase, applying a first negative high voltage V to the target back plate (4) through the DC power supply (6) 负1 The second negative high voltage V is applied to the high voltage electrode plate (8) by the controllable high voltage power supply (7). 负2 is the initial voltage value HV1; V1+HV1=V 和 ; Step S30, monitoring the first negative high voltage V output by the DC power supply (6) 负1 , when the first negative high voltage V 负1 When the voltage drops to the sputtering voltage V2 and remains for a set judgment time, adjust the second negative high voltage V 负2 is the working voltage value HV2; V2+HV2=V 和 ; Enter the magnetron sputtering stage; perform the magnetron sputtering process according to the set magnetron sputtering time.

8. The control method of a plasma generator according to claim 7, characterized in that: The ignition voltage V1 is 650V to 850V.

9. The control method of a plasma generator according to claim 7, characterized in that: The sputtering voltage V2 is 200V to 650V.

10. The control method of a plasma generator according to claim 7, characterized in that: The setting judgment time is 100ms to 200ms.

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