KR20070117747A - Apparatus for sputtering - Google Patents

Abstract

A sputtering apparatus is provided to prevent particles from being generated from the edge of a wafer by using an electrostatic chuck for fixing a wafer electrostatically instead of a clamp. A chamber(110) has a space separated from the outside. A plurality of electrodes are formed in the upper and lower portions in a chamber, confronting each other. A target(116) is formed in the upper portion of the inside of the chamber having the plurality of electrodes. An electrostatic chuck(118) is formed in the lower portion of the chamber corresponding to the target to support a wafer(W), electrically chucking the wafer. The electrostatic chuck includes a plurality of chucking electrodes for electrostatically fixing the wafer.

Description

Sputtering Device {Apparatus for sputtering}

1 is a sectional view schematically showing a sputtering apparatus according to the prior art.

Figure 2 is a schematic cross-sectional view showing a sputtering apparatus according to an embodiment of the present invention.

3 is a cross-sectional view illustrating the electrostatic chuck of FIG. 2.

4 is a plan view showing the multiple electrodes of the electrostatic chuck of FIG.

Explanation of symbols on the main parts of the drawings

110: chamber 112: cathode electrode

114: anode electrode 116: target

118: electrostatic chuck 120: heater

The present invention relates to a semiconductor manufacturing apparatus, and more particularly, to a sputtering apparatus for physically depositing a metal thin film on a wafer.

In recent years, the semiconductor manufacturing industry has steadily reduced the minimum line width applied to the semiconductor integrated circuit process in order to increase the operation speed of the semiconductor chip and increase the information storage capability per unit area. Accordingly, the size of active and passive devices including transistors integrated on semiconductor wafers has been reduced to sub-half microns or less.

In addition, although semiconductor devices are becoming more integrated, research and development of metal wiring processes for electrically connecting the semiconductor devices are more demanding than in the past. For example, in the case of metal deposits such as aluminum, tungsten, and titanium, a large amount of semiconductor products are produced through physical vapor deposition (PVD) processes such as sputtering or evaporation. In particular, the sputtering method specifically looks at, in a vacuum state to inert gas ions in the plasma state to the target (target) made of a material to be deposited on the wafer. At this time, the component particles constituting the target are peeled off and deposited on the wafer. In this case, the wafer positioned to correspond to the target should be fixed so as not to swing when the inert gas ions are generated in the plasma state. In addition, the wafer is fixed such that the target and the wafer are positioned to face each other so that the metal deposit that is peeled off and dropped from the target at a uniform area ratio may be uniformly deposited on the front surface of the wafer. For example, the sputtering apparatus according to the prior art is fixed by a clamp that clamps the outer circumferential surface of the wafer.

 Hereinafter, a sputtering apparatus according to the prior art will be described with reference to the accompanying drawings.

1 is a schematic cross-sectional view showing a sputtering apparatus according to the prior art.

As shown in FIG. 1, the conventional sputtering apparatus includes a chamber 10 in which a metal thin film forming process is performed by providing a closed and independent space from the outside, and receiving a power voltage of a direct current applied from the outside of the chamber ( 10) the cathode electrode 12 and the anode electrode 14 formed to face each other in the upper and lower portions of the chamber 10 to excite the inert gas filled in the plasma state, the lower portion of the cathode electrode 12 and the A target 16 formed at an upper end of the chamber 10, a chuck 18 formed at a lower end of the chamber 10 corresponding to the target 16 to support a wafer, and supported on the chuck 18; It is configured to include a clamp 20 for clamping the outer peripheral surface of the wafer.

Here, the chuck 18 supports the wafer in a horizontal state at the lower end of the chamber 10. For example, the chuck 18 has a larger area than the wafer and is formed to support the rear surface of the wafer. At this time, the chuck 18 is formed to support the rear surface of the wafer by the load of the wafer.

In addition, the target 16 is formed in parallel with each other at a predetermined distance from the wafer at the upper end of the chamber 10 facing the wafer on the chuck 18. For example, the target 16 and the wafer may have the same or similar average travel distance between the wafers at the target 16 so that the metal deposits peeled off from the target 16 are uniformly deposited on the entire surface of the wafer. mean free path).

The clamp 20 clamps the outer circumferential surface of the wafer to prevent the wafer supported on the chuck 18 from being moved in the horizontal direction, and covers the wafer edge to prevent the metal deposit from being formed at the edge of the wafer. can do. For example, the clamp 20 is formed to have a ring type covering the edge of the wafer.

Accordingly, the sputtering apparatus according to the prior art chucks the wafer so that the wafer and the target 16 face each other when a metal deposit that is separated from the target 16 by the inert gas ions in the plasma state is deposited on the wafer. It can be fixed on (18).

However, the sputtering apparatus according to the prior art has the following problems.

In the conventional sputtering apparatus, a large amount of deposition material is induced on the clamp 20 that surrounds and clamps the outer circumferential surface of the wafer so that the deposition material may act as a contaminant such as a particle in a subsequent process, thereby causing a defect in the metal deposition process. There was a problem that the production yield is falling.

An object of the present invention for overcoming the above problems is to provide a sputtering apparatus that can increase or maximize the production yield by preventing particles caused at the edge of the wafer.

A sputtering apparatus according to an aspect of the present invention for achieving the above object, the chamber provides a space independent from the outside; A plurality of electrodes formed to face each other at upper and lower portions of the chamber; A target formed on an upper end of the chamber in which the plurality of electrodes are formed; And an electrostatic chuck formed at a lower end of the chamber corresponding to the target to support the wafer and electrostatically chuck the wafer.

Hereinafter, a sputtering apparatus according to an embodiment of the present invention with reference to the drawings as follows. The embodiments of the present invention may be modified in various forms, and the scope of the present invention should not be construed as being limited by the embodiments described below. This embodiment is provided to more completely explain the present invention to those skilled in the art. Therefore, the shape of the elements in the drawings are exaggerated to emphasize a clearer description.

Figure 2 is a schematic cross-sectional view showing a sputtering apparatus according to an embodiment of the present invention.

As shown in FIG. 2, the sputtering apparatus according to the present invention includes a chamber 110 that is sealed from the outside and provides an independent space, and a direct current voltage applied from the outside to an inert gas filled in the chamber 110 from outside. The cathode electrode 112 and the anode electrode 114 formed to face each other in the upper and lower portions of the chamber 110 to form a plasma state by using, and the cathode electrode 112 is formed on the top of the chamber 110 is formed And a target 116 and an electrostatic chuck 118 formed at a lower end of the chamber 110 corresponding to the target 116 to support a wafer and electrostatically chuck the wafer.

Although not shown, a magnet formed on the rear surface of the target 116 to focus the inert gas ions excited in the plasma state by the cathode electrode 112 and the anode electrode 114 to the target 116. It is configured to further include.

Here, the chamber 110 is sealed so as to be filled with only the inert gas excluding contaminants in the atmosphere therein. In this case, the chamber 110 is connected to an exhaust line communicating with a vacuum pump for pumping air containing the inert gas to a predetermined pressure therein. For example, the vacuum pump includes a dry pump or a rotary pump for pumping air in the chamber 110 to have a degree of vacuum of about 1 × 10 −3 torr or less. Although not shown, the chamber 110 is formed to receive the wafer from the robot arm through a door or slit valve formed on a sidewall, and the load lock chamber 110 or the transfer chamber 110 in which the robot arm is formed. It is commonly connected by cluster type.

The cathode electrode 112 and the anode electrode 114 are plasma electrodes for separating the inert gas existing between the target 116 and the wafer into a plasma state and separating ions having positive charges into electrons. . For example, the cathode electrode 112 and the anode electrode 114 may be generally formed above and below the chamber 110, but in some cases, both of the cathode electrode 112 and the anode electrode 114 may be formed at the bottom of the electrostatic chuck 118. The inert gas flowing on the wafer may be excited in a plasma state. In addition, the power supply voltage applied to the cathode electrode 112 and the anode electrode 114 is matched and supplied from a matching box formed outside the chamber 110. In addition, a plasma reaction of a corresponding color is induced in the chamber 110 according to the type of the inert gas filled in the chamber 110. For example, when the inert gas is made of argon, the green plasma-based reaction is maintained inside the chamber 110, and when the inert gas is made of nitrogen, the blue-based plasma reaction is induced inside the chamber 110. Can be.

The magnet is formed to impinge the inert gas ions onto the target 116 facing the wafer. For example, the magnet forms a magnet in a counterclockwise direction in a direction in which the outer circumferential surface of the wafer or target 116 is wound based on a position corresponding to the center of the wafer or the target 116, so that the magnet is positive according to the left hand rule of Fleming. The inert gas ions having a charge are formed to strike the target 116. In this case, the magnet can be adjusted according to the magnitude of the voltage applied to the magnet, it is possible to control the amount of collision between the target 116 and the inert gas ions. In addition, a magnetron sputtering technique may be used as a method of inducing the existence zone so that secondary electrons generated by the inert gas ions colliding with the target 116 can be efficiently used to ionize the inert gas again. . In this technique, a magnet is installed not only at the rear of the target but also at the side of the target 116 so as to limit and induce the secondary electrons to a certain area.

The target 116 is formed such that a metal deposit is deposited on the wafer while the surface is peeled off by the collision of the inert gas ions in the plasma state. For example, the target 116 is made of a metal material such as aluminum, tungsten, titanium, tantalum, or the like formed on the wafer as metal wires. In this case, the target 116 may further be heated to a high temperature by the collision of the inert gas ions, further comprising a backing plate (backing plate) through which a coolant having a predetermined temperature flows from the rear surface of the target 116. Is done. At this time, the metal deposit is separated from the target 116 is deposited on the wafer with a predetermined thickness while continuously falling to the surface of the wafer located on the bottom of the chamber 110 by the load. In this case, since the deposit is separated from the target 116 is electrically neutral, it may be free from the inert gas ions in the plasma state.

Although not shown, the metal deposits peeled off the target 116 and falling beyond the edges of the wafer may be deposited on the inner wall of the chamber 110 to prevent deposition as they flow onto the sidewall of the chamber 110. A plurality of shields surrounding the edge of the target 116 may be formed while shielding the wafer edge from the metal deposit in a horizontal direction.

The electrostatic chuck 118 has a support surface corresponding to the wafer of a predetermined size and is formed to electrostatically fix the wafer on the support surface. At this time, the electrostatic chuck 118 using electrostatic attraction forces to hold the wafer has several advantages over other types of chucks (eg, mechanical chucks and vacuum chucks). As one of such advantages, the electrostatic chuck 118 can reduce particle related contamination often caused by mechanical clamps and reduce stress-related cracks. Such electrostatic chucks 118 are described in U.S. Pat. Patent No. 4,665,463, entitled "METHOD OF AND APPARATUS FOR APPLYING VOLTAGE TO ELECTROSTATIC CHUCK". Patent No. 5,117,121 and titled "ELECTROSTATIC CHUCK HAVING A THERMAL TRANSFER REGULATED PAD." Patent No. 5,978,202, respectively.

3 is a cross-sectional view illustrating the electrostatic chuck 118 of FIG. 2, wherein the electrostatic chuck 118 press-fixes the wafer W with a constant power of a predetermined size by using the Johnson-Labeck effect. For example, the Johnson-Lavec effect is a phenomenon in which a dielectric plate polished by a weak conductive material, such as agate or slate rock, by Johnson and Lavec in 1920. Found. In the absence of charge, this bond is easily broken. This phenomenon occurs in some ways because the metal is in contact with the weak conductive material. This occurs because the resistance in the transition region is large and the resistance between the cross sections of the metal plate and in the metal plate itself is small. Therefore, if there is any electric field in the transition space between the metal and the object, a large voltage is generated. Since the distance between the metal and the object is as small as about 1 nm, a large voltage is generated between these spaces. The electrostatic chuck 118 is a consumable part capable of attaching and detaching the wafer W without contacting the wafer W using the electrostatic force induced by the Johnson-Labeck effect. In addition, the force associated with the Johnson-Labeck effect increases with the time that the potential difference is applied. On the other hand, when the potential difference is removed from the chucking electrode 117, the remaining force will gradually decrease with time. This may not immediately disconnect the wafer W from the electrostatic chuck 118 if the force of the Johnson-Labeck effect is too large. Therefore, the wafer W may be grounded through the dielectric member so that the charge remaining in the wafer W may be reduced to a predetermined level or less to dechuck. In this case, as the number of the chucking electrodes increases or decreases, the electrostatic chuck 118 may have a different clamping force and a different degree of dechucking.

As described above, the characteristics of the Johnson-Label effect according to the number of chucking electrodes 117 to which the chucking voltage is applied are shown in Table 1.

Table 1

Where A is the area of the wafer W supported on the electrostatic chuck 118, and the permittivity is the dielectric constant 119 between the wafer W and the chucking electrode 117, V is the chucking voltage, d Is the distance from the chucking electrode 117 to the wafer (W).

Therefore, the clamping force by the Johnson-Labeck effect is proportional to the area of the wafer W, proportional to the square of the chucking voltage, and inversely proportional to the square of the distance from the chucking electrode 117 to the wafer W. In this case, since the multi-electrode such as the double electrode or the triple electrode includes at least one or more chucking electrodes 117 to which a reverse voltage is applied to the chucking voltage, the clamping force may be canceled and induced to be smaller than the single electrode. However, the plasma chucking step is required because a single electrode induces a plasma reaction with the wafer W therebetween, so that chucking is possible only when there is an electrical connection. In addition, since the wafer W is electrostatically charged from the plasma reaction according to the plasma chucking step, a large amount of charges induced in the wafer W are required, so that a plurality of dechucking times are required.

Thus, the electrostatic chuck 118 may employ multiple electrodes, such as double electrodes or triple electrodes, to fix the wafer on the electrostatic chuck 118, and the wafer from the electrostatic chuck 118 upon unloading of the wafer. Can be easily dechucked.

4 is a plan view illustrating multiple electrodes of the electrostatic chuck 118 of FIG. 2, wherein the electrostatic chuck 118 has a plurality of electrodes to which a chucking voltage is applied in a radial shape at a center thereof. In this case, the position of the chucking electrode 117 is based on the distance r from the center of the electrostatic chuck 118 and the direction from the center of the electrostatic chuck 118 to the flat zone of the wafer W. It can be represented by the made azimuth angle θ.

Here, the electrostatic chuck 118 further comprises a heater 120 for heating the wafer to a predetermined temperature. For example, the wafer fixed on the electrostatic chuck 118 is heated to a temperature of about 180 ° C. during the sputtering process. In addition, the heater 120 is radially formed to diverge in the direction of the edge from the center of the electrostatic chuck 118.

Accordingly, the electrostatic chuck 118 may fix the wafer using the plurality of chucking electrodes 117 symmetrically formed at a position corresponding to the center of the wafer, and radially from the center of the wafer to the edge direction. By using the formed heater 120, a metal deposit having a uniform thickness may be deposited on the entire surface of the wafer.

In addition, the electrostatic chuck 118 electrostatically fixes the rear surface of the wafer, and can reduce spatial constraints compared to clamps that cover and clamp the wafer edge. For example, the electrostatic chuck 118 may expose the edge of the wafer while holding the wafer to prevent the wafer from being contaminated by contaminants such as particles caused by conventional clamps.

As a result, the sputtering apparatus according to the embodiment of the present invention includes an electrostatic chuck 118 that fixes the wafer electrostatically to prevent the clamping of the conventional wafer edge or the particles induced at the edge of the wafer. Production yields can be increased or maximized.

In addition, the description of the above embodiment is merely given by way of example with reference to the drawings in order to provide a more thorough understanding of the present invention, it should not be construed as limiting the present invention. In addition, for those of ordinary skill in the art, various changes and modifications are possible without departing from the basic principles of the present invention.

As described above, according to the present invention, an electrostatic chuck that electrostatically fixes a wafer can be provided to prevent a clamp from clamping a conventional wafer edge or particles generated at the edge of the wafer, thereby increasing production yield or There is an effect that can be maximized.

Claims (3)

A chamber providing a space independent from the outside; A plurality of electrodes formed to face each other at upper and lower portions of the chamber; A target formed on an upper end of the chamber in which the plurality of electrodes are formed; And And an electrostatic chuck formed at a lower end of the chamber corresponding to the target to support a wafer and electrostatically chuck the wafer. The method of claim 1, The target while shielding the wafer edge from the metal deposit in a horizontal direction at the inner wall of the chamber to prevent deposition of metal deposits that delaminate from the target and fall off the edge of the wafer onto the sidewall of the chamber Sputtering apparatus, characterized in that it further comprises a plurality of shields surrounding the edge. The method of claim 1, And the electrostatic chuck comprises a plurality of chucking electrodes that electrostatically fix the wafer.

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