VACUUM DEPOSITION APPARATUS USING ELECTRON BEAMS

Abstract: The invention provides a vacuum deposition apparatus, which comprises a vacuum chamber (31), an electron beam source (32) coupled to said vacuum chamber, a holder (34) provided in the vacuum chamber for holding a substrate (36) on which a film is to be deposited, a target (38) of deposition materials being placed opposite to the substrate, said target having at least the same area as the substrate, and magnets (39) provided at the back of the target for generating magnetic fields near a surface of the target. The target opposite to the substrate has at least the same area as the substrate and the magnetic fields are generated near the surface of the target. The electrons emitted from the electron beam source are therefore diffused and uniformly distributed over the surface of the target. The electrons enter into the target, and the materials on the surface of the target are uniformly sputtered.

Description: DESCRIPTION VACUUM DEPOSITION APPARATUS USING ELECTRON BEAMS Field of the invention The invention relates to a deposition apparatus using electron beams used for producing a film of a semiconductor device, a liquid crystal display device or others. Specifically, the invention relates to a vacuum deposition apparatus for depositing target materials onto a substrate opposite to the target by allowing electron beams to enter into a target. Background of the invention One of the apparatus for depositing a metal, an alloy or others on a semiconductor substrate is vacuum deposition apparatus using electron beams. Fig.l is a diagram illustrating such an apparatus. In a chamber 1 under a high vacuum of 10 "5 - 10 "6 torr, electron beams are emitted from an electron beam source 2 and deflected, and enter into a target 4 (source) in a pot 3, causing the target to be heated and evaporated locally. This method has advantages of preventing mixture of pollution from the pot 3 into the deposition and also preventing mixture of impurity since the target is locally heated and the peripheral regions are not heated. The target 4 may be automatically and consecutively supplied. It is also possible to control deposition of an alloy by providing a plurality of electron beam sources 2 and pots 3. Kokai 3-138358 discloses a vacuum deposition apparatus using electron beams wherein magnets are provided near an evaporation sample. The electron beams are perpendicularly emitted from an electron gun which is parallel to the evaporation sample. Due to magnetic fields generated by the magnets near the sample, the electron beams 2 travel along magnetic lines of force in a cycloid movement. Since the magnetic lines of force are perpendicular to the sample, the electron beams travel along the magnetic lines of force and enter into the sample perpendicularly. Kokai 3-138358 does not teach that the magnets are used to diffuse the electron beams. Kokai 5-255841 discloses a deposition plating method in which plating materials are evaporated or sublimated by a method of heating with electron beams. Kokai 5- 255841 tells that an incident angle of the electron beams into the plating materials are equal to or more than 20° to increase the efficiency. Kokai 5-255841, however, does not teach that the magnets are used in such a manner of diffusing the electron beams. Prior deposition methods using electron beams basically employ an evaporation source referred to as a point source, the evaporated atoms from such a source travel straight in a vacuum, causing poor step coverage on patterns of the substrate. Fig.2 illustrates step coverage according to the prior apparatus. A simple model is shown in the figure wherein an insulating layer 22 is formed on a silicone substrate 21 and a contact hole 23 is formed in the insulating layer 22. When an aluminum layer 24 for example deposits on the substrate by means of a deposition method using electron beams, nonuniform deposition is formed on side walls of the contact hole depending on relationship of positions between the substrate and the target. As an aspect ratio of patterns formed on the semiconductor substrate is increased, the problem of step coverage becomes more serious. Further, when a film is formed on a large-diameter or large substrate 21, each portion of the substrate 21 forms different angles and distances with the target, and accordingly the film is not uniformly formed. 3 Thus, it is an object of the invention to provide a vacuum deposition apparatus using electron beams which produces better step coverage. It is another object of the invention to provide a deposition apparatus using electron beams which is capable of forming a uniform film on a large-diameter or large substrate. Summary of the Invention In order to resolve the problems described above, the invention provides a vacuum deposition apparatus of claim 1, which comprises a vacuum chamber, an electron beam source coupled to said vacuum chamber, a holder provided in the vacuum chamber for holding a substrate on which a film is to be deposited, a target of deposition materials being placed opposite to the substrate, said target having at least the same area as the substrate, and magnets provided at the back of the target for generating magnetic fields near a surface of the target. In the apparatus described above, the target opposite to the substrate has at least the same area as the substrate and the magnetic fields are generated near the surface of the target. The electrons emitted from the electron beam source are therefore diffused and uniformly distributed over the surface of the target. The electrons enter into the target, and the materials on the surface of the target are uniformly sputtered. Thus, a uniform film on the substrate is obtained. The invention of claim 2 provides the vacuum deposition apparatus of claim 1 wherein a plurality of the magnets are arranged in a loop in such a manner that the same magnetic poles are inside of the loop, and rotate in a plane parallel to the target. According to the apparatus of claim 2, since distribution of magnetic fields having effect on the electron beams are uniform over the surface of the target, a more uniform film is produced. 4 The invention of claim 3 provides the vacuum deposition apparatus of claim 1 which further comprises means for applying DC bias to the target to attract electrons. Since the density of electrons toward the target is increased, the sputtering effect of the target materials is improved, and the deposition rate is increased. The invention of claim 4 provides the vacuum deposition apparatus of claim 1 wherein the substrate is connected to a RF bias source to attract materials sputtered from the target. Thus, deposition of the materials sputtered from the target onto the substrate is increased and the deposition rate is also increased. Brief description of the drawings Fig. 1 is a diagram showing a constitution of a prior deposition apparatus using electron beams. Fig. 2 is a cross sectional view of a film deposited in the prior deposition apparatus using electron beams. Fig. 3 is a diagram showing a constitution of a deposition apparatus using electron beams according to the embodiment of the invention. Fig. 4 is a diagram showing an embodiment of an arrangement of magnets. Fig. 5 is a diagram showing another embodiment of the arrangement of magnets. Detailed description of the invention An embodiment of the invention is described with reference to Fig.3. A substrate stage 34 is provided via an insulating material 35 in a chamber 31 where a high vacuum can be produced. A substrate 36 such as a semiconductor substrate (wafer) or a liquid crystal panel to be processed is placed on the stage 34. The stage 34 is connected to a RF source to bias the substrate. An electron gun 32 is coupled to the chamber 31. Electrons are emitted from the electron gun 32, converged by convergence 5 magnets 33 and introduced into the chamber 31. A shield 37 shields the process region in the chamber 13. The entry path of the electron beam into the chamber is shown in parallel to the target 38 in Fig. 3. However, the path may be inclined a little toward the target. Further, a plurality of electron guns 32 may be provided around the chamber 31. Providing a few electron guns 32 around the chamber 31 causes increased electron density, and increased deposition rate due to uniformity of the electron density over the target, resulting in depositing a uniform film on the substrate. The target 38 is a metal such as aluminum, titan, tungsten, or tantalum or an alloy of them, and is opposite to the substrate 36 where the surface of the target is equal to or larger than substrate 36. In an example of Fig.3, the target 38 is fixed in such a manner that the end of the target is clamped by an upper housing 43 of the apparatus and a flange 42 provided on the top of sidewalls of the chamber 31. Alternatively, the target 38 may be accommodated by a supporting means (a pot) provided in a chamber. The target 38 is connected to a DC source 41. Cooling water for cooling the target 38 is circulated in a space 44 inside of the upper housing. Magnets 39 are located at the back of the target 38 and allowed to rotate around an axis 40. The magnets 39 are provided for applying magnetic fields perpendicular to electric fields near the surface of the target 38 to trap the electrons. The magnets 39 may be such magnets that are used for magnetron plasma sputtering. The magnets 39 are arranged in such a manner that the electrons should uniformly enter into the overall surface of the target 38 and the surface of the target 38 be uniformly sputtered. In a preferred arrangement, a plurality of permanent magnets are arranged in a loop in such a manner that the same magnetic poles are inside of the loop. Fig 4 shows an embodiment of such an arrangement of magnets which is disclosed in Kokai 62-60866. Fig. 5 is a diagram showing another embodiment of the arrangement of 6 magnets which is disclosed in Kokai 4-80358. Deposition process in the deposition apparatus using electron beams shown in Fig. 3 is now described. The upper housing 43 is opened to place an aluminum target 38 on the flange 42 at ends of the sidewalls of the chamber 31. After the target is placed, the upper housing 43 is closed. As an alternative, the target 38 may be fixed to the upper housing 43. A wafer on which a film is to be deposited is placed on the stage 34 and the chamber 31 is evacuated to a high vacuum of for example 10 '6 torr. The magnets 39 rotate about the axis 40 which is driven by a motor. The electron gun 32 is operated, and the emitted electrons are converged by the convergence magnets 33 and introduced into the chamber 31. The electrons 31 introduced to the chamber are diffused by the rotating magnetic fields produced by the magnets 39, and simultaneously attracted toward the target 38 due to the DC bias applied to the target. Thus, the target 38 is sputtered and heated by the electrons which are diffused over the surface of the target. The materials sputtered from the surface of the target 38 are ionized under the influence of the magnetic fields and the electric fields. The mixed atoms, molecules and ions travel straight in the chamber 31 and deposit on the substrate 36. Since the substrate 36 is biased by the RF source 45, the ionized target materials are attracted toward the substrate 36, causing increased deposition rate. Thus, the uniform film of aluminum is formed on the overall surface of the substrate. According to the invention, a film is uniformly deposited on the substrate and the deposition rate is also increased.

Claims: 7 CLAIMS 1. Vacuum deposition apparatus, comprising: a vacuum chamber; an electron beam source coupled to said vacuum chamber; a holder provided in said vacuum chamber for holding a substrate on which a film is to be deposited; a target of deposition material placed opposite the substrate, said target having at least the same area as the substrate; and magnets provided at the back of said target for generating magnetic fields near the surface of the target. 2. The vacuum deposition apparatus of claim 1, wherein a plurality of said magnets are arranged in a loop in such a manner that the same magnetic poles face the inside of the loop, and rotate in a plane parallel to the target. 3. The vacuum deposition apparatus of claim 1, further comprising: means for applying DC bias to said target to attract electrons. 4. The vacuum deposition apparatus of claim 1, wherein said substrate is connected to an RF bias source to attract the materials sputtered from said target.

Inventors: ONO MASANORI, ONO, MASANORI
Applicants: APPLIED MATERIALS INC, ONO MASANORI, APPLIED MATERIALS, INC., ONO, MASANORI
Application year: 1999
Main classification: C23C14
IPC codes: C23C14, H01J37