JP3618643B2 - Film forming apparatus and method - Google Patents

Description

[0001]
[Field of the Invention]
The present invention relates to a film forming apparatus and method for performing ion plating using plasma.
[0002]
[Prior art]
There are various film forming apparatuses using an ion beam. There are two types of film forming apparatuses: one that uses the ion beam itself as film forming particles and the other that generates film forming particles using an ion beam. In the film forming apparatus classified as the former, for example, material particles are generated by sputtering a target, and the ionization rate is increased by some method to be incident on a substrate that is a film formation target. In this case, for example, an RF coil is used as a means for increasing the ionization rate. Further, in the film forming apparatus classified as the latter, for example, an ion beam is extracted from an ion source, the ion beam is applied to a target to form film forming particles, and the film forming particles are incident on a substrate to be formed. . As such an apparatus, for example, an apparatus called ion beam sputtering (IBS) exists.
[0003]
[Problems to be solved by the invention]
However, any of the film forming apparatuses as described above is complicated, and the apparatus itself is expensive.
[0004]
Accordingly, an object of the present invention is to provide a film forming apparatus that can efficiently increase the ionization rate of particles for film formation by a simple method and has excellent controllability during film formation.
[0005]
[Means for Solving the Problems]
In order to solve the above problems, a film forming apparatus of the present invention is disposed in a film forming chamber to hold a film material, and is disposed opposite to the material evaporation source and is applied with a positive bias. A reflective electrode; and plasma supply means for locally supplying plasma in the vicinity of the reflective electrode.
[0006]
In this case, since the plasma supply means locally supplies the plasma in the vicinity of the reflective electrode, electrons in the plasma are attracted to the reflective electrode to which a positive bias is applied, and a sheath electric field is formed on the surface of the reflective electrode. In this state, when neutral film material particles from the material evaporation source enter the region of the sheath electric field, the film material particles collide with electrons accelerated by the sheath electric field and are positively ionized with high probability. The film material particles thus cationized are reflected by the potential gradient in the reflective electrode to which the positive bias is applied and the sheath region, so that the substrate to be deposited is placed in the traveling direction of the reflected film material particles. If arranged, it becomes possible to form a film with a very high ionization rate by a simple method.
[0007]
According to a preferred aspect of the apparatus, the positive bias is a voltage higher by a predetermined amount than a voltage corresponding to an ionization potential for ionizing film material particles evaporated from the material evaporation source. The film-forming apparatus of description.
[0008]
In this case, the film material particles can be reliably ionized by the electrons accelerated by the positive bias applied to the reflective electrode, and the film material particles having a width of kinetic energy corresponding to the predetermined amount can be generated. The energy homogenization of the film material particles becomes possible.
[0009]
According to a preferred aspect of the above apparatus, the apparatus further comprises a discharge chamber that generates plasma outside the film formation chamber, and the plasma supply means is an opening provided between the discharge chamber and the film formation chamber. To do. In this case, plasma can be locally and stably supplied only to the vicinity of the reflective electrode.
[0010]
Further, according to a preferred aspect of the above apparatus, the reflective electrode has a flat plate shape, and the film material particles from the material evaporation source are reflected by the reflective electrode, and are formed at positions facing the reflective electrode. A substrate support member for supporting the substrate is disposed. In this case, a film having a relatively uniform film thickness can be easily formed on the substrate.
[0011]
Moreover, according to the preferable aspect of the said apparatus, it further has the extraction electrode which has a small hole between a reflective electrode and a board | substrate support member. In this case, it is possible to prevent plasma from entering the substrate and causing plasma damage and temperature rise of the substrate, and the velocity of the evaporated particles that enter the substrate through the small holes, that is, the energy, is set to a desired value. be able to.
[0012]
Moreover, according to the preferable aspect of the said apparatus, the extraction electrode is mesh shape or honeycomb shape. In this case, the film formation can be performed while stably evaporating the evaporated particles.
[0013]
Moreover, according to the preferable aspect of the said apparatus, a material evaporation source heats and evaporates film | membrane material. In this case, the evaporated particles emitted from the material evaporation source have a low energy of about 0.2 eV or less and the energy is uniform. Therefore, the energy of the evaporated particles incident on the substrate can be easily controlled, and the film formation conditions can be easily set.
[0014]
In addition, the film forming method of the present invention includes a step of heating a material evaporation source that holds a film material, a step of applying a positive bias to a reflective electrode disposed opposite to the material evaporation, and a plasma in the vicinity of the reflective electrode. A step of supplying locally.
[0015]
In this case, since plasma is locally supplied in the vicinity of the reflective electrode, electrons in the plasma are attracted to the reflective electrode to which a positive bias is applied, and a sheath electric field is formed on the surface of the reflective electrode. In this state, when neutral, uniform and low energy film material particles from the material evaporation source enter the region of the sheath electric field, the film material particles have a high probability due to electrons accelerated by the sheath electric field on the surface of the reflective electrode. It becomes cationized at. The film material particles thus cationized are reflected by the potential gradient in the reflective electrode to which the positive bias is applied and the sheath region, so that the substrate to be deposited is placed in the traveling direction of the reflected film material particles. If arranged, film formation with film material particles having uniform kinetic energy and an extremely high ionization rate can be performed by a simple method.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the structure of a film forming apparatus according to an embodiment of the present invention will be described. FIG. 1 is a diagram schematically illustrating the overall structure of a film forming apparatus according to an embodiment. This film forming apparatus includes a first vacuum container 10 that is a film forming chamber for forming a film on a substrate W, and a second vacuum container 20 that forms a discharge chamber for supplying plasma into the first vacuum container 10. With.
[0017]
An evaporation crucible 11 is disposed in the lower part of the first vacuum vessel 10 as a material evaporation source for storing the film material. Above the evaporating crucible 11, a flat plate-like reflective electrode 12 for reflecting the film material particles EP evaporated from the evaporating crucible 11 in the horizontal direction is disposed in an inclined manner. A substrate support member 14 that vertically supports the substrate W that is the target of film formation is disposed on the side of the reflective electrode 12 via the extraction electrode 13. The first vacuum vessel 10 is maintained at an appropriate degree of vacuum by the vacuum exhaust device 54.
[0018]
The evaporating crucible 11 contains a film material such as Cu, and melts the film material inside to a melt at a desired temperature by induction heating that supplies high-frequency power from the heating power supply 51 to the coil 11b provided in the periphery. Can be evaporated.
[0019]
The reflective electrode 12 is a flat metal plate and is biased to a positive potential by applying a voltage from the electric field control power supply 52. An opening 30 for communicating the first vacuum container 10 and the second vacuum container 20 is formed on the side of the reflective electrode 12. The opening 30 constitutes a plasma supply means, and serves as a plasma introduction window for supplying plasma generated in the space between the first and second vacuum vessels 10 and 20 into the first vacuum vessel 10. As a result, electrons in the plasma are attracted to the reflecting surface 12a of the reflecting electrode 12, and a thin sheath electric field is formed. Here, the back surface of the reflective electrode 12 is supported by an insulating member (not shown). Thereby, a sheath electric field can be formed only on the reflective surface 12a on the front side of the reflective electrode 12, and the film material particles EP can be ionized.
[0020]
The reflective electrode 12 is held at an angle of about 45 ° with respect to the horizontal plane, but can be swung during film formation. This is because the film material particles EP emitted substantially vertically upward from the evaporation crucible 11 are cationized by the sheath electric field in the vicinity of the reflecting surface 12a of the reflecting electrode 12, reflected by the reflecting surface 12a, and then proceed substantially in the horizontal direction. It is a thing.
[0021]
The extraction electrode 13 is a mesh having a large number of small holes, and the diameter of the small holes is about several tens of μm to 2 mm. The extraction electrode 13 is biased to a negative potential by voltage application from the electric field control power supply 52. As a result, the film material particles EP ionized by the reflective electrode 12 are accelerated to a desired speed and enter the substrate W held at the same potential as the extraction electrode 13. The extraction electrode 13 is not limited to a mesh shape, and the shape is not limited as long as it has a small hole and can appropriately extract the film material particles EP by an electric field, such as a honeycomb electrode. Is optional.
[0022]
The substrate support member 14 not only simply supports the substrate W but also incorporates a heater and a cooling device, and can maintain the temperature of the substrate W during film formation at a desired constant temperature.
[0023]
The second vacuum container 20 accommodates the first vacuum container 10 so as to wrap it. A part of the space where the first vacuum vessel 10 does not exist is a space for forming plasma, that is, a plasma forming region PS, and a pair of discharge electrodes 21 are disposed at both ends thereof. A voltage from the high frequency power supply 61 is applied to these discharge electrodes 21, and plasma having a desired density is formed in the plasma forming region PS therebetween. The second vacuum container 20 is connected to a gas source 63 that supplies argon gas or the like and a vacuum exhaust device 64 that exhausts the gas in the second vacuum container 20. The space around the first vacuum vessel 10 is maintained at an appropriate atmosphere and degree of vacuum necessary for forming the plasma having the desired density described above.
[0024]
FIG. 2 is a diagram for explaining the positional relationship between the first and second vacuum vessels 10 and 20 and the flow of plasma into the first vacuum vessel 10. A large amount of plasma is formed in the plasma formation region PS between the pair of discharge electrodes 21 provided in the second vacuum vessel 20. The plasma thus formed diffuses into the gap between the vacuum vessels 10 and 20, and flows into the first vacuum vessel 10 having a higher degree of vacuum through a pair of openings 30 that are plasma introduction windows. The plasma that has flowed into the first vacuum vessel 10 through both openings 30 is locally supplied to the vicinity of the reflective electrode 12 and diffuses throughout the interior of the first vacuum vessel 10. That is, a distribution of plasma that is unevenly distributed in the vicinity of the reflective electrode 12 is formed in the first vacuum vessel 10.
[0025]
Here, the first vacuum container 10 is set to a vacuum degree of 1 × 10 ⁰ Pa to 1 × 10 ⁻² Pa, for example, and the second vacuum container 20 is set to a vacuum degree of 1 × 10 ⁻³ Pa or less, for example. . That is, the two vacuum vessels 10 and 20 are differentially evacuated.
[0026]
FIG. 3 is a diagram for explaining a microscopic phenomenon in the vicinity of the reflection surface of the reflection electrode 12 that is an ionization electrode. In the vicinity of the reflective surface 12a of the reflective electrode 12, an extremely thin sheath electric field region SF is formed. The thickness of the sheath electric field region SF (sheath thickness) varies depending on the plasma density around the reflective electrode 12 and the voltage applied to the reflective electrode 12, but the ambient plasma density is about 10 ⁹ to 10 ¹⁰ pieces / cm ³ . When a voltage of about +10 V is applied to the reflective electrode 12, the thickness is several tens to several hundreds of micrometers.
[0027]
A large amount of electrons that have entered the sheath electric field region SF from the boundary region SB are accelerated by the sheath electric field, are incident on and collide with the reflecting surface 12a, and become a current. At this time, since a voltage of about 10 V is applied to the reflective electrode 12, electrons incident on the reflective surface 12a obtain a kinetic energy of about 10 eV. Such electrons collide with neutral copper particles (film material particles EP) incident from the boundary region SB, and ionize them with high probability. Here, considering that the ionization energy of copper is about 7.7 eV, it can be seen that if electrons accelerated to about 7.7 eV or more collide with copper particles, this can be changed to copper ions.
[0028]
When the copper particles, which are the film material particles EP, are ionized by the electrons accelerated in the sheath electric field region SF, the copper particles maintain the momentum in the direction parallel to the reflecting surface 12a, and the Coulomb force between the reflecting electrode 12 and the copper particles. Rebounded and reflected. As a result, the ionized copper particles travel substantially in a direction perpendicular to the reflective electrode 12.
[0029]
Thus, the copper ions reflected by the reflective electrode 12 have low energy and uniform energy. That is, the neutral copper particles that evaporate from the evaporating crucible 11 only by heating have a kinetic energy of about 0.1 eV. In addition, when a voltage of about 10 V is applied to the reflective electrode 12, the kinetic energy acquired by the copper particles is about 10 eV at the maximum. Therefore, the energy of copper ions reflected by the reflective electrode 12 is in the range of about 0 to 10 eV, which is much smaller than the energy at the time of film formation by normal sputtering or the like. Further, the copper ions reflected by the reflective electrode 12 pass through the plasma when going to the substrate W, but the plasma potential is low, and the influence of the plasma can be almost ignored. As a result, the energy of the copper ions is about 10 eV at the maximum, and is accelerated to the film material particles EP having an arbitrary energy by the extraction electrode 13 and enters the substrate W.
[0030]
Hereinafter, the operation of the film forming apparatus of FIG. 1 will be described. In this film forming apparatus, plasma is formed in the second vacuum container 20, and this plasma is supplied to the first vacuum container 10 through the opening 30. The plasma supplied from the opening 30 diffuses in the vicinity of the reflective electrode 12 to which a positive bias is applied. Thereby, a sheath electric field region is formed along the reflective surface 12a of the reflective electrode 12. In this state, when the neutral film material particle EP is evaporated from the evaporation crucible 11 and is incident on the reflective electrode 12, the neutral film material particle EP is ionized almost 100% by the electrons accelerated by the sheath electric field. The ions of the film material particles EP thus formed are repelled by the reflective electrode 12 and accelerated by the extraction electrode 13. The ions of the film material particles EP that have passed through the extraction electrode 13 enter the substrate W, and film formation by an ion beam having a desired energy is performed on the substrate W.
[0031]
As described above, the present invention has been described based on the embodiment, but the present invention is not limited to the above embodiment. For example, the film material to be formed on the substrate W is not limited to Cu, and other metals can be used. Further, a nonmetal film can be formed as long as it becomes a cation by ionization.
[0032]
Moreover, the heating method of the evaporating crucible 11 is not limited to induction heating as in the embodiment, and may be various methods such as resistance heating using a heater.
[0033]
The voltage applied to the reflective electrode 12 is determined in consideration of the ionization potential of the film material. At a voltage that is not very different from the ionization potential, the density of electrons with sufficient kinetic energy for ionization tends to decrease and the ionization efficiency of the film material tends to decrease, but the energy of the ionized film material particles decreases, And it is uniform and controllability increases. On the other hand, at a voltage much higher than the ionization potential, the energy of the ionized film material increases and tends to be random, but reliable ionization is possible.
[0034]
Further, the plasma formed in the second vacuum vessel 20 does not need to be generated by high frequency discharge as in the embodiment, and is also formed by DC glow discharge or the like.
[0035]
Further, the shape of the opening 30 formed in the first vacuum vessel 10 may be arbitrary as long as plasma can be efficiently introduced in the vicinity of the reflective electrode 12.
[0036]
Furthermore, the second vacuum container 20 is not limited to a structure that wraps the first vacuum container 10, and can have any structure as long as plasma can be supplied from the pair of openings 30.
[0037]
【The invention's effect】
According to the film forming apparatus of the present invention, since the plasma supply means locally supplies the plasma in the vicinity of the reflective electrode, electrons in the plasma are attracted to the reflective electrode to which a positive bias is applied, and the sheath is formed on the surface of the reflective electrode. An electric field is formed. In this state, when neutral film material particles from the material evaporation source enter the sheath, they are cationized by electrons accelerated by the sheath electric field on the surface of the reflective electrode. The film material particles thus cationized are reflected by the potential gradient in the reflective electrode to which the positive bias is applied and the sheath region, so that the substrate to be deposited is placed in the traveling direction of the reflected film material particles. If arranged, it becomes possible to form a film with a very high ionization rate by a simple method.
[0038]
In addition, according to the film forming method of the present invention, since plasma is locally supplied in the vicinity of the reflective electrode, electrons in the plasma are attracted to the reflective electrode to which a positive bias is applied, and a sheath electric field is generated on the surface of the reflective electrode. It is formed. In this state, when neutral, uniform and low-energy film material particles from the material evaporation source enter the sheath, they are cationized by electrons accelerated by the sheath electric field on the surface of the reflective electrode. The film material particles thus cationized are reflected by the potential gradient in the reflective electrode to which the positive bias is applied and the sheath region, so that the substrate to be deposited is placed in the traveling direction of the reflected film material particles. If it arrange | positions, the film-forming by the film | membrane material particle | grains of the uniform kinetic energy with a very high ionization rate will be attained by a simple method.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a structure of a film forming apparatus according to an embodiment of the present invention.
FIG. 2 is a perspective view illustrating supply of plasma to a film formation chamber.
FIG. 3 is a diagram schematically illustrating a phenomenon in the vicinity of a reflective electrode.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 1st vacuum vessel 11 Evaporation crucible 11b Coil 12 Reflective electrode 12a Reflective surface 13 Extraction electrode 14 Substrate support member 20 Second vacuum vessel 21 Discharge electrode 30 Opening EP Film material particle PS Plasma formation region SF Sheath electric field region W Substrate

Claims (8)

A material evaporation source disposed in the film forming chamber to hold the film material;
A reflective electrode disposed opposite the material evaporation source and applied with a positive bias;
A film forming apparatus comprising plasma supply means for locally supplying plasma in the vicinity of the reflective electrode. 2. The film forming apparatus according to claim 1, wherein the positive bias is a voltage higher by a predetermined amount than a voltage corresponding to an ionization potential for ionizing film material particles evaporated from the material evaporation source. The discharge chamber for generating the plasma is further provided outside the film formation chamber, and the plasma supply means is an opening provided between the discharge chamber and the film formation chamber. 3. The film forming apparatus according to any one of 2 and 2. The reflective electrode has a flat plate shape, and a substrate support that supports a substrate that is a film formation target at a position opposite to the reflective electrode where the film material particles from the material evaporation source are reflected by the reflective electrode. The film forming apparatus according to claim 1, wherein a member is disposed. The film forming apparatus according to claim 4, further comprising an extraction electrode having a small hole between the reflective electrode and the substrate support member. 6. The film forming apparatus according to claim 5, wherein the extraction electrode has a mesh shape or a honeycomb shape. 7. The film forming apparatus according to claim 1, wherein the material evaporation source heats and evaporates the film material. Heating the material evaporation source holding the membrane material;
Applying a positive bias to the reflective electrode disposed opposite the material evaporation;
Supplying plasma locally in the vicinity of the reflective electrode;
A film forming method comprising:

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