Magnetron sputtering apparatus and mask

(42) Date of commencement of the patent: 15. 2.1997 (45) Date of issue: 25. 9.1997 (515 Int.Cl.⁶ : C23C 14/04 C23C 14/35 (30) Priority:

(73) Patent owner:

19th 1.1994 JP P06-003950 claimed.

(56) Documents:

EP 229914A2 EP 496036A1 LS 4469719A OE 3919147A1

SONY CISC TECHNOLOGY INC. TOKYO (JP).

(54) Magnetron sputtering apparatus (57) A magnetron sputtering apparatus for forming a thin layer of metal on a major surface of a translucent disk-shaped substrate, such as an optical disk substrate, wherein magnetic field intersecting magnetic fields are applied from a magnetic-fat-anilage stage is provided at the back of a baffle electrode. The apparatus has a central mask closely contacted with the outer peripheral part of a main surface of the disk substrate on which the thin film is formed so as to cover the center part of the substrate, and an outer peripheral mask provided with the outer peripheral part of the one main surface of the disk substrate the thin film is formed, closely in contact to cover the outer edge part. The outer edge mask is separate from the center mask and independent.

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AT 402 944

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AT 402 944 Β

The present invention relates to a magnetron sputtering apparatus for forming a thin film on a main surface of a disk-shaped substrate under the application of mutually orthogonal magnetic fields having a magnetic field applying step provided on the back surface of a beating electrode.

Optical discs, such as compact discs (CDs), are widely used for recording digital audio or video information. Such optical disks have a support of a transparent synthetic resin, such as a polycarbonate, on the surface of which a thin layer of high reflectivity aluminum is vapor-deposited or dusted. On that surface of the carrier carrying the thin aluminum layer, a pattern of minute projections and recesses is formed, the holes (pits) can be mentioned, and the digital information of 1 or 0, respectively. The light beam is thrown onto these holes by the carrier, whereby the information recorded on the optical disc is read out due to the light beam reflected from the thin film.

From EP 229 914 A2 a mask for two disks to be coated has been known, wherein the mask portions substantially lie directly on the surfaces of the disc-shaped carrier to be coated. In this known device, an uncooled crash electrode is provided. Due to the heat occurring during operation of the device considerable problems arise in these known solutions.

The aim of the invention is to avoid these disadvantages and to propose a device of the type mentioned, in which these problems are avoided.

According to the invention this is achieved in a magnetron sputtering apparatus in that the apparatus comprises:

a beating electrode for forming a thin film on a main surface of a disc-shaped carrier;

A collision electrode cooling device mounted on the opposite side of the impingement electrode for cooling the impingement electrode;

a magenta field application stage arranged at the backside of the plunger electrode for applying perpendicular magnetic fields;

a center mask, which is mounted insulated on the impact electrode cooling means and in close contact with the central part of a main surface of the disk substrate on which the thin film is formed to cover the center part of the substrate;

an outer edge mask, the inner diameter of which is smaller than the outer diameter of the disc-shaped carrier and which abuts a stationary part of a layer forming chamber forming chamber and is in close contact with the outer edge part of the one main surface of the carrier; on which the thin film is formed, to cover the outer edge part, the outer edge mask, is independent of the middle mask; and a carrier holding device, to vertically move the carrier to and from the center mask and the outer rim mask and provide an insulating member, to isolate the center mask to the impingement electrode and the impact electrode cooling device.

The proposed measures ensure that the temperature of the impact electrode rises uncontrollably during the sputtering process, which could lead to inaccuracies due to the thermal expansion of the materials, in particular the areas of the support to be covered. Furthermore, it is possible by the carrier-holding device and the independent central mask and outer edge mask possible to keep the surface to be pollinated of the carrier completely free, so that the layer can be applied over the entire area to be dusted in a uniform thickness.

Further, it may be provided that the insulating member includes an insulating fastener which is inserted in the impact electrode cooling means in a through hole formed along the central axis of the center mask, and an insulating holder which sits on the outer peripheral surface of that end of the central mask, the the contact surface is opposite to the carrier.

By these measures, a heat flow from the impact electrode to the central mask is largely prevented, whereby uncontrolled thermal expansion of the center mask can be avoided.

In this case, it may further be provided that the insulating member has a first insulator inserted into a through hole formed along the center axis of the center mask and fixed to the impingement cooling means, and a second insulator attached to the outer peripheral surface of that end the center mask sits, which is opposite to the contact surface with the carrier, resulting in a structurally simple solution.

It is particularly advantageous if the middle mask is cooled via a fastening element, the holder and the carrier-holding device, whereby thermal expansions of the central mask are largely minimized

AT 402 944 Β.

The invention will now be explained in more detail with reference to the drawing, which shows schematically a device according to the invention.

The magnetron sputtering apparatus according to this invention mainly consists of a beating electrode 1, a center mask 3 and an outer edge mask 4 for covering predetermined parts of a plate-shaped carrier 2, and a magnet 5 for applying mutually overlapping electric and magnetic fields, as shown in FIG. 5 shows. The plate carrier used here is made of a translucent material, with the smallest recesses and elevations, ie Holes, which correspond to the information signals.

The collision electrode 1, which serves as a cathode, is used to support on that surface of the plate carrier 2 which carries the holes, ie on that surface of the plate carrier to be pollinated to form a thin film. In the manufacture of an optical disk, a baffle 1 made of aluminum is used. The impact electrode 1 is formed as a plate whose diameter is greater than the diameter of the plate carrier 2, wherein it has a reduced thickness only in its outer edge part. That is, the beating electrode is formed as a plate having a projecting center portion facing the disc carrier 2.

On the surface of the impact electrode 1, which is on the other side like the baffle 1a hit by the atoms, for example, argon atoms, a collision electrode cooling means 6 is provided to cool the collision electrode 1. The impact electrode cooling device 6 is formed in the form of a plate having an outer diameter which is substantially equal to the outer diameter of the impingement electrode 1.

The impact electrode cooling device 6 has a hollow channel in a central part of the plate thickness to circulate cooling water therein. An inlet and an outlet of the hollow channel to circulate cooling water are connected to a cooling water supply 7 for supplying fresh cooling water and a cooling water discharge 8, respectively, for discharging the water circulated through the channel.

The introduced via the cooling water supply line 7 cold water thus passes through the cooling water channel of the impact electrode cooling device 6, whereupon, after it has cooled the impingement electrode 1, which is in contact with the impact electrode cooling device 6, via the cooling water discharge. 8 is drained. This prevents the temperature from rising during the sputtering process.

The magnet 5 applies mutually overlapping electric and magnetic fields to atoms which strike the impact electrode 1 under the argon gas atmosphere. The magnet 5 is arranged in a rear, offset to the end of a rotating shaft 9 area on the opposite side of the baffle electrode 1, with the impact electrode cooling device 6 is located therebetween. The applied magnetic field is kept uniform by causing the magnet to make a staggered rotation, thereby improving the yield of the impact electrode 1.

The center mask 3 is used to cover the central part of the disc carrier 2, being constructed so as to hold the carrier 2 by being in close contact with the central part thereof. Such a center mask 3 is in the form of a flared cylinder having a larger diameter on that side which is in contact with the plate carrier 2.

Along the center axis of the center mask 3, a through hole 11 is formed which serves to receive a screw 10 which is made insulating or made of an insulating material to fix the center mask 3 to the impact electrode cooling means 6. At the open end of the through hole 11, there is formed a fitting part 17 which serves to contact a disk centering member, which will be described later, as well as the center mask 3. The fitting part 17 is formed as a recess in which the Plattenzentrierelement has a seat.

If the screw 10 is made of an insulating material, this may be a ceramic material, a plastic or polytetrafluoroethylene.

That part of the center mask 3 introduced into the impact electrode 1 has a slightly smaller diameter to form a step surface. Between the step surface and the impact electrode surface 1 a is an annular spacer 12, which is made insulating or made of an insulating material to isolate between the impingement electrode 1 and the central mask 3. If this spacer 12 is made of an insulating material, this may be the same insulating material as in the screw 10.

On the outer circumference of the smaller diameter portion of the center mask 3 is seated a support 13 which is made insulating or made of an insulating material to insulate the center mask 3 from the impact electrode 1 and the impact electrode cooling means 6. The bracket 13, which consists of a cylinder having a bottom located on the smaller-diameter portion of the center mask 3 and open at one end, is inserted into a bracket attachment hole 15 bored in the center of the impact electrode 1. If such a holder 13 is made of an insulating material, the

AT 402 944 Β same insulating material as the spacer 12 are used.

In the bottom surface of the holder 13, a circular screw insertion hole 14 is formed, through which the end of the screw 10 passes, which is inserted through the through hole 11 of the center mask 3. The underside of the center mask 3 is provided with a flange 16 to prevent the holder 13 from disengaging from the attachment opening 15 when the holder 13 is seated in the attachment opening 15.

The outer edge mask 4 serves to cover the outer peripheral part of the disc base 2 by being in close contact with the outer edge part, being fixed to an outer case constituting the layer forming chamber independently of the center mask 3, not shown here FIG. 2 will be shown. The outer peripheral mask 4 is provided as a disk with a blind hole 18 having the same size as the outer diameter of the projecting part of the beating electrode 1 and a central opening 19 which is a circular through hole having a diameter slightly smaller than the outer diameter of the disc carrier 2 is.

Between the inner wall surface of the center opening 19 of the outer peripheral mask 4 and the outer periphery of the free end of the center mask 3 provided with a contact surface 3a, a cavity 25 is formed in the thickness direction of the masks 3 and 4 over the entire circumference of the inner wall surface of the central opening 19 as shown in FIG. 5 shows. The outer edge mask 4 and the middle mask 3 are completely separated from each other by the cavity 25 and insulated. About this cavity 25 atoms can be dusted by the impact electrode 1 on the support 2. A contact surface 4a of the outer edge mask 4, which serves to come into close contact with the outer peripheral part of the disc carrier 2, is aligned with the contact surface 3a of the center mask 3 to hold the disc carrier 2 in a horizontal position and to spatter a uniform layer.

The disc carrier 2 is in close contact with the contacting surface 3a of the center mask 3 and with the contacting surface 4a of the outer peripheral mask 4 via a carrier holding unit 20. The carrier support unit 20 is attached to the free end of a shaft 22 of a cylinder 21 which serves to adjust the plate carrier 2 thereon and to move the plate carrier 2 to and from the center mask 3 and the outer edge mask 4, as shown by the arrows X. , The carrier holding unit 20 is held at the anode potential via the shaft 22.

The carrier holding unit 20 has a disc centering member 23 serving to be inserted into the circular through hole formed in the center of the disc carrier 2 and a disc table 24 for holding the centered disc carrier 2.

The disk centering member 23 is disposed so as to face a through hole formed in the center of the disk base 2 to center the disk base 2, being frustoconical so as to project from the disk table 24 and gradually to its free end rejuvenated. A disc-shaped disc table 24 is provided on the side of the disc centering member 23 to stably hold the disc carrier 2.

During the sputtering operation, the disc carrier 2 is lifted by the cylinder 21 in a state where it lies on the disc table 24. The plate support 2, which is moved upwards in this manner, projects with its middle part and outer edge part with the middle mask 3 or the outer edge mask 4 in close contact. Thus, the surface 2a of the disc carrier 2 to be dusted is completely exposed without being covered by the masks 3 and 4, whereby the layer formed on the surface to be dusted has a uniform thickness.

At this time, the disc centering member 23 of the carrier holding unit 20 is seated in the fitting portion 17 in the center mask 3 and is in contact therewith so that the center mask 3 is maintained at anode potential. The center mask 3 is forcibly insulated with the screw 10, the spacer 12 and the holder 13 for the impact electrode 1 and the impact electrode cooling means 6, whereby it is forcibly maintained at the anode potential.

During the sputtering process, the center mask 3 is exposed to an elevated temperature. However, it is cooled by the impact electrode cooling device 6 via the screw 10 and the holder 13, which are in contact with the impact electrode cooling device 6.

Although the present invention has been described in connection with preferred embodiments, it is not confined to the details described herein, it is intended to cover all modifications which are within the scope of the invention as set forth in the appended claims.