JP7262235B2 - Sputtering apparatus and sputtering method - Google Patents

Description

The present invention comprises a vacuum chamber in which a target and a substrate to be processed are arranged to face each other. By forming a plasma atmosphere in the vacuum chamber and sputtering the target, the sputtered particles scattered from the target adhere to the substrate surface. The present invention relates to a sputtering apparatus and a sputtering method for forming a film by deposition, and more particularly, to a device suitable for forming a film with good bottom coverage on a substrate to be processed in which concave portions such as via holes and trenches are previously formed on the surface.

In the manufacturing process of semiconductor devices, for example, a silicon wafer having recesses such as via holes and trenches formed on the surface thereof is used as a substrate to be processed, and Cu as a seed layer is applied to the surface of the substrate to be processed including the inner surfaces (inner walls and bottom surface) of the recesses. There is a process of forming a film. A sputtering apparatus used for such film formation is known, for example, from Patent Document 1. This conventional sputtering apparatus includes a vacuum chamber capable of forming a vacuum atmosphere. A target selected according to the thin film to be formed is provided on the upper wall portion of the vacuum chamber, and a stage for holding the substrate to be processed facing the target is arranged in the vacuum chamber. Then, after setting the substrate to be processed on the stage, a rare gas is introduced into a vacuum chamber in a vacuum atmosphere, and power having a negative potential, for example, is applied to the target to form plasma in the vacuum chamber. The target is sputtered by the ions of the rare gas in the atmosphere, and the sputtered particles scattered from the target are adhered and deposited on the surface of the substrate to be processed including the inner surface of the recess to form a predetermined thin film.

Here, when the target is sputtered, the sputtered particles are scattered from the surface of the target according to a predetermined cosine law, but the amount of the sputtered particles obliquely incident on the surface of the substrate to be processed exceeding a predetermined angle with respect to the vertical direction increases. As a result, it is generally known that a so-called overhang occurs and the bottom coverage is lowered. As a solution to this problem, a collimator is provided between the substrate and the target to regulate sputtered particles scattered from the target that obliquely impinge on the surface of the substrate over a predetermined angle with respect to the vertical direction. and applying bias power to the stage and thus to the substrate to be processed during deposition by sputtering.

By the way, if a collimator is provided between the substrate to be processed and the target, and a predetermined bias power is supplied to the substrate to be processed during film formation by sputtering, the bottom coverage may be rather deteriorated. found. Therefore, the inventors of the present application have made intensive studies and have come to the following findings.

That is, in the process in which the sputtered particles scattered from the target pass through the collimator through the plasma atmosphere and reach the surface of the substrate to be processed, particularly the ions of the sputtered particles (for example, Cu ions) ionized in the plasma atmosphere pass through the collimator. When this happens, the trajectory is bent, and the number of sputtered particles obliquely incident at an angle that should have been regulated by the collimator increases, thereby deteriorating the bottom coverage. This is because when the collimator arranged between the substrate to be processed and the target is arranged in an electrically floating state, ions (for example, Cu ions) of sputtered particles in the plasma atmosphere flow into the collimator (or are charged). ), the collimator itself becomes a positive potential.

JP 2010-111892 A

The present invention has been made based on the above findings, and an object of the present invention is to provide a sputtering apparatus and a sputtering method capable of forming a film with good bottom coverage on a substrate to be processed having recesses formed on its surface. is.

In order to solve the above problems, a vacuum chamber in which a copper target and a substrate to be processed are arranged facing each other and a sputtering power source for supplying power to the copper target are provided, and power is supplied to the copper target to generate plasma in the vacuum chamber. By forming an atmosphere and sputtering a copper target, the sputtering apparatus of the present invention forms a film by depositing sputtered particles scattered from the copper target on the surface of the substrate to be processed. It is arranged in the space between the substrate to be processed and the copper target with the direction toward the target facing upward, and the sputtered particles scattered from the copper target exceed a predetermined angle with respect to the vertical direction and reach the surface of the substrate to be processed. A collimator for regulating oblique incidence and a first power supply for applying bias power to the substrate to be processed are further provided, and the pressure in the vacuum chamber is set to 0.8 when a copper target is sputtered to form a film. × 10 ^-2 Pa to 1.6 × 10 ^-2 Pa, the power supplied from the sputtering power supply is in the range of 20 kW to 25 kW, the bias power supplied from the first power supply is in the range of 100 W to 600 W, and the collimator is electrically and a second power source that applies a positive potential to the collimator. do.

According to the present invention, during film formation by sputtering, a predetermined positive potential is applied from the second power supply to maintain the collimator itself at a positive potential, so that ions of sputtered particles (for example, Cu ions) can be prevented from bending their trajectories when passing through the collimator. In addition to this, by applying a predetermined bias power to the substrate to be processed from the first power supply, the ions of the sputtered particles that have passed through the collimator are drawn into the substrate to be processed while maintaining their straightness. As a result, it is possible to form a film with good bottom coverage on a substrate to be processed having recesses formed on its surface.

In addition, in the present invention, it is preferable that the second power supply maintains the potential of the collimator at a positive potential of +40 V or less. According to this, when the ions of the sputtered particles (for example, Cu ions) pass through the collimator, it is possible to reliably prevent the trajectory from being bent. In this case, if a positive potential exceeding +40 V is applied to the collimator, ions (for example, Cu ions) of the sputtered particles are repulsed when passing through the collimator, causing a problem that the trajectory is greatly changed. If the collimator is at a negative potential lower than 0 V, ions (for example, Cu ions) of the sputtered particles are trapped when passing through the collimator, resulting in a problem that the film cannot be formed with good bottom coverage.

In order to solve the above-mentioned problems, a copper target and a substrate to be processed are arranged opposite to each other in a vacuum chamber, and power is supplied to the copper target by a sputtering power source to form a plasma atmosphere in the vacuum chamber, thereby forming a copper target. The sputtering method of the present invention, in which sputtered particles scattered from a copper target are adhered to the surface of a substrate and deposited to form a film by sputtering a target, is a copper target with the direction from the substrate to be processed facing the copper target facing upward. During film formation by sputtering of the target, sputtered particles scattered from the copper target pass through a collimator arranged in the space between the substrate to be processed and the copper target, and the sputtered particles exceed a predetermined angle in the vertical direction of the substrate to be processed. The pressure in the vacuum chamber is set to 0.8×10 ⁻² Pa or more when the object obliquely incident on the surface is regulated, bias power is applied to the substrate to be processed, and a copper target is sputtered to form a film. In the range of 1.6×10 ⁻² Pa, the power supplied from the sputtering power supply is in the range of 20 kW to 25 kW, and the bias power supplied from the first power supply is in the range of 100 W to 600 W. During film formation by sputtering a copper target, It is characterized in that the collimator arranged in an electrically floating state is held at a positive potential of +40 V or less.

1 is a schematic cross-sectional view showing a sputtering apparatus according to an embodiment of the invention; FIG. The graph which shows the experimental result of this invention. (a) and (b) are SEM photographs showing the effects of the present invention.

Hereinafter, referring to the drawings, the target is copper, and the substrate to be processed (hereinafter simply referred to as "substrate Sb") is a silicon wafer. A sputtering apparatus and a sputtering method according to an embodiment of the present invention will be described by taking as an example a case where fine recesses with an aspect ratio of 3 or more are formed in a predetermined pattern and a copper film is formed on the surface of the substrate Sb including the inner surfaces of the recesses. do. Hereinafter, it is assumed that the sputtering apparatus is set in the attitude shown in FIG. 1, and terms indicating directions are based on FIG.

Referring to FIG. 1, SM is the sputtering apparatus of this embodiment. A sputtering apparatus SM includes a vacuum chamber 1 . An exhaust pipe 11 is connected to the bottom of the vacuum chamber 1 and communicates with an evacuation means Pu composed of a turbomolecular pump, a rotary pump, or the like. A gas introduction pipe 12 for introducing a rare gas (sputtering gas) such as argon is connected to the side wall of the vacuum chamber 1 . A mass flow controller 13 is interposed in the gas introduction pipe 12 so that the sputter gas whose flow rate is controlled can be introduced into the vacuum chamber 1 which is evacuated at a constant evacuation speed by the evacuation means Pu. In FIG. 1, reference numeral 2 denotes an anti-adhesion plate for preventing adhesion and deposition of sputtered particles on the inner wall surface of the vacuum chamber 1 and the like.

A cathode unit 3 having a copper target 31 and a magnet unit 32 is provided in the upper portion of the vacuum chamber 1 . The target 31 is manufactured by a known method so as to have a contour (circular in plan view in this embodiment) larger than that of the substrate Sb. A backing plate 33 made of Cu is bonded to the upper surface of the target 31 via a bonding material (not shown) such as indium. The target 31 is attached to the top opening of the vacuum chamber 1 via the insulator 14 with the sputtering surface 31a facing the inside (downward) of the vacuum chamber 1 . The target 31 is also connected to an output from a sputtering power supply 4 composed of a DC power supply, so that a predetermined power having a negative potential is applied to the target 31 . The magnet unit 32 arranged above the target 31 generates a leakage magnetic field in the space below the sputtering surface 31a, and since such a magnet unit 32 itself can be used, a detailed description will be given here. omitted.

A stage 5 capable of holding the substrate Sb in a posture facing the target 31 is provided at the bottom of the vacuum chamber 1 via an insulator 15 . The stage 5 is composed of, for example, a base 51 made of aluminum and an electrostatic chuck 52 provided on the upper surface of the base 51. After setting the substrate Sb with its film forming surface facing upward, the stage 5 can be held by suction. It's becoming Further, the base 51 is connected to the output from the first power supply 6 composed of an AC power supply, so that a predetermined bias power can be supplied to the base 51 and the substrate Sb. Since a known electrostatic chuck 52 itself can be used, detailed description thereof is omitted here. Further, the base 51 may be provided with a known mechanism for heating or cooling the substrate Sb attracted and held by the electrostatic chuck 52 .

In the space between the target 31 and the stage 5 in the vacuum chamber 1, as will be described later, among the sputtered particles scattered from the target 31, the substrate Sb A collimator 7 is provided in an electronically floating state for regulating obliquely incident light on the surface of . The collimator 7 has a metal plate member having a predetermined thickness, and a plurality of through holes 71 are formed vertically through the plate member at predetermined positions. Since a known collimator can be used as the collimator 7 itself, a detailed description of the configuration of the through hole 71, the distance from the substrate Sb, and the like is omitted here. The collimator 7 is connected to an output from a second power supply 8 composed of a DC power supply, a positive potential is applied to the collimator 7, and the collimator 7 is at a positive potential of +40 V or less during film formation by sputtering the target 31. so that it is retained. In this case, if a positive potential exceeding +40 V is applied to the collimator 7, Cu ions are repulsed when passing through the collimator 7, causing a problem that the trajectory is greatly changed. If the collimator 7 is at a negative potential lower than 0 V, Cu ions are trapped when passing through the collimator 7, causing a problem that the film cannot be formed with good bottom coverage.

Further, the sputtering apparatus SM has a control means 9 having a microcomputer, a sequencer, etc., and controls the operations of the sputtering power supply 4, the first power supply 6, the second power supply 8, the mass flow controller 13, and the evacuation means Pu. can be controlled. The deposition of the Cu film on the substrate Sb by the sputtering method using the sputtering apparatus SM will be described below.

First, after setting the substrate Sb on the stage 5 in the vacuum chamber 1, the evacuation means Pu is operated to evacuate the inside of the vacuum chamber 1. As shown in FIG. When the pressure in the vacuum chamber 1 reaches a predetermined value (eg, 1×10 ⁻⁵ Pa), the mass flow controller 13 is controlled to introduce argon gas at a predetermined flow rate (eg, 10 to 20 sccm) (at this time, The pressure in the vacuum chamber 1 is 0.8×10 ⁻² to 1.6×10 ⁻² Pa). At the same time, a predetermined power (for example, 20 to 25 kW) having a negative potential is applied from the sputtering power source 4 to the target 31 made of Cu, and a predetermined bias power (for example, 100 kW) is applied to the stage 5 from the first power source 6. ~ 600 W) is turned on. Then, a plasma atmosphere Pl is formed in the vacuum chamber 1 (for example, a space below the sputtering surface 31a and above the collimator 7), and the sputtering surface 31a of the target 31 is formed by argon ions in the plasma atmosphere Pl. Sputtered. Then, the sputtered particles scattered from the sputtering surface 31a pass through the plasma atmosphere P1 and the through hole 71 of the collimator 7, and pass through the substrate including the inner surface of fine recesses formed in a predetermined pattern on the surface to which the bias power is applied. A Cu film is formed by adhering and depositing on the surface of Sb.

Here, in the process in which the sputtered particles scattered from the sputtering surface 31a of the target 31 pass through the plasma atmosphere Pl, pass through the through hole 71 of the collimator 7, and reach the surface of the substrate Sb, especially the Cu ions ionized in the plasma atmosphere Pl When passing through the through-hole 71 of the collimator 7, if its trajectory is bent, the number of sputtered particles obliquely incident at an angle that should be restricted by the through-hole 71 of the collimator 7 increases, resulting in deterioration of bottom coverage. invite. On the other hand, in the present embodiment, the voltage is applied to the collimator 7 by the second power supply 8 so that the potential of the collimator 7 is maintained at a positive potential of +40 V or less during the deposition of the target 31 by sputtering.

According to the above, during film formation, by applying a predetermined positive potential from the second power supply 8 and maintaining the collimator 7 itself at a positive potential, Cu ions ionized in the plasma atmosphere P1 pass through the collimator 7. Sometimes it can be suppressed that the trajectory is bent. By applying a predetermined bias power to the substrate Sb from the first power source 6, the Cu ions that have passed through the through hole 71 of the collimator 7 are drawn into the substrate Sb while maintaining their straightness. As a result, it is possible to form a film with good bottom coverage on the substrate Sb having the recesses formed on the surface thereof.

Next, in order to confirm the effect of the present invention, the following experiment was conducted to form a Cu film on the surface of the substrate Sb using the sputtering apparatus SM. In this experiment, the substrate Sb was a silicon wafer having a diameter of 300 mm, and concave portions having an aspect ratio of 3 were formed in a predetermined pattern. (Note that the Ta film and the Cu film are deposited in a vacuum atmosphere while being properly transported). As conditions for forming the Cu film, the collimator 7 having a height of 75 mm was used, the distance between the substrate Sb and the target 31 made of Cu was set to 400 mm, and the distance between the collimator 7 and the substrate Sb was set to 55 mm. bottom. The flow rate of the argon gas introduced into the vacuum chamber 1 was set to 10 sccm (the pressure at this time was 0.8×10 ⁻² Pa), the input power to the target 31 was set to 21 kW, and the bias power input to the substrate Sb was set to 300 W. set. Then, the potential of the collimator 7 is held at a predetermined potential in the range of -5 V to +60 V by the second power supply 8 (when the collimator 7 is not energized, the potential of the collimator 7 during film formation was +60 V), A Cu film was formed under the above conditions, and the bottom coverage after the film formation was evaluated. The evaluation results of these bottom coverages are shown in FIG. According to this, it was confirmed that the bottom coverage can be increased to 60% or more if the collimator 7 is held at a positive potential of +40 V or less. In this case, it can be seen that the collimator 7 should preferably be held at a positive potential in the range of +5V to +40V, more preferably at a positive potential in the range of +10V to +30V.

Next, the bias power was set to 300 W, and the collimator 7 was held at a positive potential of +20 V when the collimator 7 was not energized (when the potential of the collimator 7 was +60 V: corresponding to the conventional example), and the film was formed. A comparison of SEM photographs of the depressions after film formation is shown in FIGS. 3(a) and 3(b). According to this, it can be seen that the overhang is suppressed and the film can be formed with good bottom coverage in the case shown in FIG. 3A as compared with the conventional example shown in FIG. 3B. This is believed to be because the potential of the collimator 7 is lowered from +60 V to +20 V during film formation, thereby reducing the effect of bending the trajectory of the Cu ions due to their repulsion when passing through the collimator 7. .

Although the embodiments of the present invention have been described above, the present invention is not limited to the above. In the above embodiment, an example of forming a Cu film using the target 31 made of Cu has been described. The present invention can also be applied when using a target made of a metal or alloy selected from Cr, Mo and W.

Sb: substrate to be processed, SM: sputtering apparatus, 1: vacuum chamber, 6: first power source, 7: collimator, 8: second power source, 31: target.

Claims (2)

A vacuum chamber in which a copper target and a substrate to be processed are arranged to face each other , and a sputtering power supply for supplying power to the copper target are provided, and power is supplied to the copper target to form a plasma atmosphere in the vacuum chamber, thereby forming the copper target. A sputtering apparatus for depositing and depositing sputtered particles scattered from a copper target on the surface of a substrate to be processed by sputtering,
Placed in the space between the substrate to be processed and the copper target with the direction from the substrate to be processed toward the copper target facing upward, and sputtered particles scattered from the copper target exceeding a predetermined angle with respect to the vertical direction A device further comprising a collimator for regulating obliquely incident light on the surface of the substrate to be processed, and a first power supply for applying bias power to the substrate to be processed,
When forming a film by sputtering a copper target, the pressure in the vacuum chamber is in the range of 0.8×10 −2 ^Pa to 1.6×10 ⁻² Pa, and the power supplied from the sputtering power source is in the range of 20 kW to 25 kW. , the bias power supplied from the first power supply is in the range of 100 W to 600 W, the collimator is arranged in an electrically floating state, and a second power supply is further provided for applying a positive potential to the collimator. A sputtering apparatus , wherein the potential of the collimator is held at a positive potential of +40 V or less by a second power supply . A copper target and a substrate to be processed are placed opposite each other in a vacuum chamber, power is supplied to the copper target from a sputtering power source, a plasma atmosphere is formed in the vacuum chamber, and the copper target is sputtered . A sputtering method for depositing and depositing sputtered particles scattered from a substrate surface to form a film,
Sputtered particles scattered from the copper target through a collimator placed in the space between the substrate to be processed and the copper target during film formation by sputtering of the copper target, with the direction from the substrate to be processed toward the copper target facing upwards. of which oblique incidence on the surface of the substrate to be processed exceeding a predetermined angle with respect to the vertical direction is regulated, and bias power is supplied to the substrate to be processed,
When forming a film by sputtering a copper target, the pressure in the vacuum chamber is in the range of 0.8×10 −2 ^Pa to 1.6×10 ⁻² Pa, and the power supplied from the sputtering power source is in the range of 20 kW to 25 kW. , The bias power supplied from the first power supply is in the range of 100 W to 600 W, and the collimator arranged in an electrically floating state is held at a positive potential of +40 V or less during film formation by sputtering a copper target. and sputtering method.

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