JP6425431B2 - Sputtering method - Google Patents

Description

  The present invention relates to a sputtering method in which a substrate to be processed and a target are disposed in a vacuum chamber, a sputtering gas is introduced, power is supplied to the target, and the target is sputtered to deposit a thin film on the substrate surface. Relates to the magnetron type.

Sputtering of such magnetron method, sputtering surface a surface to be sputtered of the target, the sputtering surface side is lower, locally acting tunnel-like magnetic field on the sputter surface by a magnet unit disposed above the target By capturing ionized electrons below the target and secondary electrons generated by sputtering, the electron density in the space below the target, and hence the plasma density, can be increased, for example, the film formation rate can be improved, etc. There are advantages of In this case, the target areas magnetic field is applied (i.e., a region facing the high-density plasma), since a locally sputtering, the film thickness of the portion of the substrate facing the target is relatively thick . For this reason, it is general to rotate or reciprocate the magnet unit at the same speed on the same trajectory along the sputtering surface during film formation (see, for example, Patent Document 1). And, by optimizing the arrangement of the magnets constituting the magnet unit and the orbit and speed of the magnet unit in advance, it is possible to form a film with a substantially uniform film thickness on the substrate.

  However, if the target is replaced with the same or different one, the film thickness distribution may change. In general, there is a rolling process when producing a target made of metal, but when the target is rolled, sputtered particles when sputtering the target due to the difference in crystal orientation between the rolling direction and the direction orthogonal to the rolling direction This is because the distribution of scattering (sputtering gas flow) changes due to a change in the scattering distribution, and once the vacuum chamber of the sputtering apparatus is opened to the atmosphere. From this, it is desirable to be able to readjust the film thickness distribution without opening the vacuum chamber to the atmosphere.

JP-A-9-41137

  An object of the present invention is to provide a sputtering method capable of readjustment of a film thickness distribution without exposing the vacuum chamber to the atmosphere, in view of the above points.

In order to solve the above problems, a substrate to be processed and a target having an outer size slightly larger than the substrate are placed in static opposition in the vacuum chamber, a sputtering gas is introduced, and the target is powered on. In the sputtering method of the present invention for forming a thin film on a substrate surface by sputtering, the sputtering surface of the target is the sputtering surface, the sputtering surface side is the bottom, and two orthogonal directions along the sputtering surface are the X direction and the Y direction. in the film, together with the action of locally magnetic field on the sputter surface by a magnet unit disposed above the target, acting region is magnetic field by rotating the magnet unit to the rotation axis of the sputtering surface from the origin moving on the same circumference enclosing the center in which performs at least once a cycle back to the starting point, for one cycle, magnetic The unit is moved at a constant rate over a predetermined reference speed thin film is deposited on the substrate surface, and the information acquisition step of acquiring information about the film thickness distribution in the substrate plane, boiled 1 cycle, the area that acts magnetic field The moving circumference is divided into a plurality of zones in the circumferential direction, and at least one zone is used as a reference zone, and the acceleration amount or the deceleration amount from the reference speed is determined based on the acquired information for each zone other than the reference zone. and a speed determination step of the magnet unit is moved to the target at a velocity of each zone in one cycle determined by the rate determining step, characterized in that a film is formed. In the present invention, the information related to the film thickness includes not only the film thickness of the film actually formed on the substrate but also, for example, the output voltage applied to the target.

According to the present invention, based on the information acquired in the information acquiring step, in the zone thicker than the reference zone, the moving speed of the magnet unit is accelerated from the reference speed by a predetermined value to maintain the residence time of the magnet unit. Therefore, while the time for high density plasma to stay is shortened and the amount of sputtering target is reduced (sputtering rate), in the zone thinner than the reference zone, the moving speed of the magnet unit is calculated from the reference speed By being decelerated by a predetermined value, the residence time of the magnet unit, and hence the time for which the high density plasma stays, is extended and the amount of sputtering of the target (sputtering rate) is increased. Thus in the present invention can be carried out from a previously acquired information, by changing the residence time in the region where one cycle definitive magnetic field is applied to each zone readjustment film thickness distribution. In this case, it is not necessary to open the vacuum chamber to the atmosphere. In the present invention, the speed of the magnet unit in the reference zone is set as the reference speed, and the speed obtained by increasing the speed by a predetermined amount from medium speed or medium speed is reduced to a high speed, and the speed reduced by a predetermined amount Determine the average film thickness on the circumference where the region where it works moves, and set the zone where the film thickness becomes thinner than the average film thickness at low speed and the zone where the film thickness becomes thicker than the average film speed at high speed It is preferable to do.

  Further, in the present invention, preferably, the information on the film thickness distribution is an output voltage value applied to the target when constant power is supplied to the target for one cycle. According to this, information can be acquired without measuring the film thickness of the film formed on the substrate by the measuring device, which is advantageous.

BRIEF DESCRIPTION OF THE DRAWINGS The schematic diagram explaining the structure of the sputtering device which enforces the sputtering method of this invention. The schematic diagram explaining the acceleration amount and deceleration amount which are determined at the speed | rate determination process in the sputtering method of this invention. The graph which shows the experimental result which confirms the effect of this invention. The graph which shows the experimental result which confirms the effect of this invention. The graph which shows the experimental result which confirms the effect of this invention.

  Hereinafter, with reference to the drawings, the case where the magnet unit moves relative to the same circumference on the same circumference with respect to a substrate W to be treated with a silicon wafer and a circular target in plan view circularly arranged fixed to a sputtering apparatus is taken as an example. Embodiments of the sputtering method will be described. In the following, with reference to FIG. 1, the ceiling side of the vacuum chamber 1 will be described as “upper” and the bottom side as “lower”.

As shown in FIG. 1, a sputtering apparatus SM capable of carrying out the sputtering method of the present invention includes a vacuum chamber 1 defining a processing chamber 1a. A vacuum pump is connected to the wall surface of the vacuum chamber 1 via an exhaust pipe (not shown) so that the vacuum pressure can be reduced to a predetermined pressure (e.g., 10 ^-5 Pa). A gas pipe 13 in communication with the gas source 11 and having a mass flow controller 12 interposed therein is connected to a side wall of the vacuum chamber 1 and a sputtering gas (a target 2 is reactively sputtered with a rare gas such as Ar). The reactive gas (including the reactive gas) can be introduced into the processing chamber 1a at a predetermined flow rate. A cathode unit C is provided on the ceiling of the vacuum chamber 1.

The cathode unit C is disposed to face the processing chamber 1 a, and has a target 2 having an outer diameter slightly larger than the outer diameter of the substrate W, and a magnet unit 3 disposed above the target 2. The target 2 is appropriately selected according to the composition of the thin film to be deposited on the surface of the substrate W, and is a single metal selected from Cu, Ti, Co, Ni, Al, W or Ta, or two selected therefrom It can be made of an alloy of species or more, or an insulator such as alumina. Then, the target 2 is attached to the vacuum chamber 1 via an insulating plate I ₁ in a state of being bonded via the bonding material such as indium or tin to copper backing plate 21 for cooling the target 2 at the time of film formation. The target 2 is connected with an output from a DC power source of a known structure as a sputtering power source E so that DC power (for example, 1 to 30 kW) having a negative potential is supplied at the time of sputtering. As the sputtering power source E, when the target 2 is an insulator, a high frequency power source for supplying high frequency power is used.

The magnet unit 3 has a support plate (yoke) 31 made of a magnetic material and provided parallel to the back surface of the backing plate 21. The lower surface of the support plate 31 has a plurality of permanent magnets 32 with lower polarity. Are arranged in a predetermined pattern. Then, a tunnel-like magnetic field (not shown) is generated in the space below the target 2 to capture sputtered electrons scattered from the sputtering surface 22 of the target 2 by capturing electrons and the like ionized below the target 2 during film formation. Ionize efficiently. Note that electromagnets can be used instead of the permanent magnets 32. Also, as the arrangement of the permanent magnets 32, known ones having various forms can be used depending on the shape, area, etc. of the target 2, So, the detailed explanation is omitted. The motor 33 is connected to the support plate 31, by rotating the support plate 31 at a predetermined speed as the rotation around the rotating shaft 34 of the motor 33, the target 2 which magnetic field is applied area (i.e., the target 2 (The region facing the high density plasma) continuously changes on the same circumference (orbit).

  Further, a rotary plate 35 is extrapolated to the rotary shaft 34, and a projecting piece 36 projecting radially outward is attached to the rotary plate 35. Then, an optical sensor 37 is provided corresponding to the projecting piece 36 so that when the optical sensor 37 detects the projecting piece 36, it can be determined that the magnet unit 3 is at the starting position. In this case, the origin position and the position of the notch of the substrate W are correlated to acquire information described later.

At the bottom of the vacuum chamber 1, stage 4 for holding the substrate W in a position facing the target 2 is provided through an insulating material I _2. An electrostatic chuck (not shown) is provided on the upper surface of the stage 4 as a substrate mounting surface, and after the substrate W is positioned by the electrostatic chuck, it is held by suction. In the inside of the side wall of the vacuum chamber 1, an adhesion preventing plate 5 is provided. The sputtering apparatus M has control means 6 including a known microcomputer, sequencer, etc., and controls the operation of the sputtering power source E, the operation of the mass flow controller 12, the operation of the motor 33, the operation of the evacuation unit, etc. I am trying to control.

  The control means 6 includes an information acquisition unit 61 and a speed determination unit 62, the details of which will be described later. The information acquisition unit 61 is configured to be communicable with, for example, a film thickness meter provided in an EFEM (Equipment Front End Module) (not shown) for loading / unloading the substrate W to / from the sputtering apparatus SM. It is possible to obtain information on the film thickness distribution in the substrate surface measured in the above. The speed determination unit 62 determines an acceleration amount and a deceleration amount from the reference speed of the motor 34 based on the acquired information. As a film thickness meter, one having a known structure can be used. For example, when a metal film having a low resistance value is formed with a relatively thick film thickness, an eddy current film thickness is used In the case where the insulating film is formed to have a relatively small thickness, a spectral ellipsometer can be used. A laser displacement gauge can be used as another film thickness gauge. Hereinafter, a sputtering method using the sputtering apparatus SM will be described.

  First, the inside of the vacuum chamber 1 (processing chamber 1a) is evacuated to a predetermined degree of vacuum, the substrate W is transferred into the vacuum chamber 1 by the transfer robot not shown, and the substrate W is delivered to the substrate stage 7 A voltage is applied to the electrodes of the chuck plate to hold the substrate W by suction. Next, argon gas as sputtering gas is introduced at a predetermined flow rate (for example, 12 sccm) (the pressure at this time is 0.1 Pa), and processing is performed by supplying 30 kW of DC power from the sputtering power source E to the target 2, for example. While forming a plasma atmosphere in the chamber 1a, the magnet unit 3 is rotated at least one cycle (one rotation) at a predetermined reference speed (for example, 40 rpm). As a result, the target 2 facing the magnet unit 3 is sputtered, and the sputtered particles generated thereby are scattered and adhere to the surface of the substrate W, thereby depositing a thin film. The film-formed substrate W is unloaded from the processing chamber 1a, and the film thickness of the thin film in the peripheral portion of the substrate W is measured by the film thickness meter provided in the EFEM, thereby obtaining information on the film thickness distribution in the substrate surface. Be The obtained information is transmitted to the information acquisition unit 61 of the control means 6, and the information acquisition unit 61 acquires the information (information acquisition process).

Then, the circumference region where magnetic field is applied to move equally divided in the circumferential direction, with the zone that are respectively divided, and the reference zone position optical sensor 37 detects the protrusion 36 Do. Hereinafter, the case where the rotational movement of one rotation (360 °) of the magnet unit 3 is divided into 24 zones at intervals of 15 ° will be described as an example. Then, with the moving speed in the reference zone as a reference speed, the acceleration amount or the deceleration amount from the reference speed is determined based on the acquired information for each zone other than the reference zone (speed determination step). Here, in the zone where the film thickness is thinner than the reference zone, the moving time of the magnet unit 3 is decelerated from the reference speed by a predetermined value, whereby the residence time of the magnet unit 3 and hence the time for high density plasma stay longer. Thus, the amount of sputtering of the target 2 (sputtering rate) is increased. In addition, in the zone where the film thickness is thicker than the reference zone, the moving time of the magnet unit 3 is accelerated (increased) from the reference speed by a predetermined value, whereby the residence time of the magnet unit 3 and, consequently, high density plasma stay The time is shortened to reduce the amount of sputtering of the target 2 (sputtering rate).

  In the example shown in FIG. 2, in the zone advanced 180 ° from the reference zone, the film thickness is thick, and the acceleration and deceleration for each zone are set so that the rotational speed of this zone is maximum (for example, 54 rpm). It has been decided. More specifically, it rotates at a reference speed (for example, 40 rpm) from a reference zone to a zone advanced by 90 °, accelerates at a speed of 28.5 rpm / sec from there, and is at a zone advanced 180 ° from a reference zone The speed during one cycle is determined such that the maximum speed is 54 rpm, then the speed is reduced at a speed of 28.5 rpm / sec, and the speed is returned to the reference speed at a zone advanced 270 ° from the reference zone.

In addition, the average value (average film thickness) of the film thickness of all the zones is determined, the ratio of each zone to the average film thickness is determined, and in the zone where the determined ratio is low (that is, the zone whose film thickness is thinner than the average film thickness) While the reference speed decelerates the speed of the magnet unit 3 by a predetermined value, the reference speed of the magnet unit 3 is a predetermined value in a zone where the calculated ratio is high (that is, a zone where the film thickness is thicker than the average film thickness) Only acceleration (acceleration) may be made. The velocity in each zone can be determined, for example, using the following equation (1).
Rotation speed of each zone = reference speed + coefficient × (film thickness of each zone−average film thickness) / average film thickness (1)

  Although one coefficient is used in the above equation (1), the coefficient may be provided in each zone. In this case, the reference speed of the magnet unit 3 is set to two conditions or more (for example, three conditions of low speed, medium speed and high speed), and the correlation value between the rotation speed of the magnet unit and the film thickness is obtained in each zone. Accuracy can be increased.

  After the speed of the motor 33 is determined in this manner, the substrate W to be processed next is transported into the vacuum chamber 1 and held on the substrate stage 4 by adsorption, and argon gas is introduced under the same conditions as above. By turning on the power to 2, the plasma atmosphere is formed in the processing chamber 1a, and the magnet unit 3 is rotationally moved at the speed determined above.

According to the above-described embodiment, the moving speed of the magnet unit 3 is increased by a predetermined value from the reference speed in a zone thicker than the reference zone based on the information acquired in the information acquiring step. While the residence time of the magnet unit 3 and hence the time for which the high density plasma stays is shortened and the amount of sputtering of the target 2 (sputtering rate) decreases, in the zone thinner than the reference zone, the magnet unit By decelerating the moving speed of 3 by a predetermined value from the reference speed, the residence time of the magnet unit 3 and, consequently, the time for which the high density plasma stays is extended and the amount by which the target 2 is sputtered (sputtering rate) is Be increased. Therefore, from the previously acquired information, one cycle definitive magnetic field can re-adjust the film thickness distribution is varied for each zone a residence time of acting region. In this case, it is not necessary to open the vacuum chamber 1 to the atmosphere.

  Next, experiments were conducted to confirm the effects of the present invention using the sputtering apparatus SM. A substrate W is a silicon wafer of 300 mm in diameter, 12 sccm of argon gas is introduced into the stage processing chamber 1a in the processing chamber 1a (the pressure at this time is 0.1 Pa), and 30 kW of DC power is supplied to the aluminum target 2. A plasma atmosphere was formed, and while rotating the magnet unit 3 at a constant speed of 40 rpm, the target 2 was sputtered to form an aluminum film on the surface of the substrate W. The result of having measured the film thickness distribution in the circumferential direction in a substrate surface is shown in FIG. 3 (a measurement point is 3 mm from an edge). According to this, the maximum film thickness was 41.3 nm, the minimum film thickness was 39.7 nm, and the difference between the two film thicknesses was 1.6 nm. Based on this film thickness distribution, the velocity per 24 zones was determined as follows. That is, it rotates at a reference speed (40 rpm) from the reference zone where the protrusion 36 is detected, accelerates at an acceleration of 28.5 rpm 0.35 seconds after the detection of the protrusion 36 and accelerates to 53.7 rpm, and It was decided to decelerate to the reference speed at a deceleration of 28.5 rpm. The film was formed while rotating the motor 33 at the speed determined in this way, and the film was made an invention. About this invention, the result of having measured the film thickness distribution in the circumferential direction in a substrate surface is shown in FIG. According to this, it was found that the film thickness distribution can be readjusted so that the film thickness becomes substantially uniform. The film was formed under the same conditions as the above-mentioned invention except that acceleration was performed with an acceleration of 28.5 rpm 0.5 seconds after the detection of the projecting piece 36 (that is, the acceleration timing was intentionally shifted). As a comparative product. About this comparative product, the result of having measured the film thickness distribution in the circumferential direction in a substrate surface is shown in FIG. According to this, although different film thickness distribution can be obtained, it is confirmed that the in-plane distribution of film thickness is worse as compared with the inventive product.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to said thing. Although the case where the velocity of the magnet unit 3 is determined based on the film thickness has been described as an example in the above embodiment, the velocity of the magnet unit 3 may be determined based on information correlated with the film thickness. For example, the target voltage applied to the target 2 when the constant input power is applied to the target 2 may be measured for each zone, and the speed of the magnet unit 3 may be determined based on the measured target voltage. In this case, the target voltage corresponding to each zone is acquired, the average value (average voltage) of the target voltages of all zones including the reference zone is determined, and the ratio of the target voltage to the average voltage corresponding to each zone is calculated. It can be configured. The amount of acceleration or deceleration from the reference speed so that the speed of the magnet unit 3 is high so that the speed of the magnet unit 3 is low in the zone where the calculated ratio is high, and the speed of the magnet unit 3 is high in the zone where the calculated ratio is low. The amount may be determined (speed determination step).

  In the above embodiment, the target 2 is circular in plan view, and the case where the magnet unit 3 is rotationally moved has been described. However, the target is rectangular in plan view, and the direction along the sputtering surface of the target is the X direction and Y direction The present invention can also be applied to the case of translating the magnet unit in at least one of the X direction and the Y direction.

  DESCRIPTION OF SYMBOLS 1 ... Vacuum chamber, W ... Substrate, 2 ... Target, 22 ... Sputter surface, 3 ... Magnet unit.

Claims (3)

A substrate to be processed and a target having an outer size slightly larger than the substrate are disposed in a vacuum chamber in a stationary opposing manner, a sputtering gas is introduced, power is supplied to the target, and the target is sputtered to deposit a thin film on the substrate surface. A sputtering method for forming a film;
The sputtered surface of the target is the sputtered surface, the sputtered surface side is downward, the two orthogonal directions along the sputtered surface are the X direction and the Y direction, and the film is locally deposited on the sputtered surface by the magnet unit disposed above the target. with the action of magnetic field, the flow returns to magnet unit is rotated around the rotation axis, to the origin by moving on the same circumference area magnetic field acts containing the center of the sputtering surface from the origin cycle For those who perform at least once
An information acquisition step of forming a thin film on a substrate surface by moving a magnet unit at a predetermined reference speed for one cycle, and acquiring information on film thickness distribution in the substrate surface;
Boiled one cycle, the circumference region where magnetic field is applied to move is divided into a plurality of zones in the circumferential direction, a reference zone at least one zone, each zone other than the reference zone, based on the obtained information And determining the amount of acceleration or deceleration from the reference speed.
Sputtering method characterized by forming a film of the magnet unit is moved to the target at a velocity of each zone in one cycle determined by the rate determining step. Set the speed of the magnet unit in the reference zone as the reference speed, increase the speed by a predetermined amount from medium speed or medium speed to a high speed, set the speed after decelerating a predetermined amount from medium speed to low speed, The average film thickness on the moving circumference is determined, and in the speed determining step, a zone in which the film thickness is thinner than the average film thickness is set at low speed, and a zone in which the film thickness is thicker than the average film thickness is set at high speed. The sputtering method according to claim 1, wherein   The sputtering method according to claim 1, wherein the information about the film thickness distribution is a voltage value applied to the target when a predetermined power is applied to the target for one cycle.

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