JPH0583632B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a sputtering apparatus used in the process of producing thin films for semiconductor devices, etc., and is particularly suitable for increasing the sputtering deposition rate and target life, and making the thickness of thin films uniform. Regarding the source of spatter.

[Background of the invention]

In sputtering film formation, a target material placed on a cathode is bombarded with ions having an energy of more than a predetermined value, and the constituent atoms or particles of the target material released thereby adhere and deposit on a semiconductor substrate to form a thin film. This is done by forming.

As a device for sputtering film formation,
There is one described in Publication No. 19319. According to this device, a pair of magnetic poles of a magnetic device are provided on the back side of the target material surface of the cathode, and arc-shaped lines of magnetic force are formed by the magnetic device along the cathode surface. By applying a voltage between the anode and cathode electrodes and holding the charged particles in the plasma in cyclotron motion using the magnetic lines of force, a higher density plasma is generated than in a two-pole sputtering device, resulting in a higher growth rate. It was becoming possible to obtain membrane speed.

In this method, the plasma region is ring-shaped, and high frequency or DC power is used to generate plasma and supply the energy for collision of ions to the target. When the ions are increased, the energy of collision of ions with the target becomes excessive, leading to an increase in the temperature of the target surface, and destruction of the target due to large temperature stress occurs. Furthermore, in this method, the plasma region has a ring shape and the eroded region of the target also has a similar shape, so that only a part of the target material contributes to film formation, and the target life is short.

As one method of reducing ion collision energy, as shown in Japanese Patent Application Laid-open No. 75839/1983,
Some use microwaves to generate plasma. In this method, microwaves are supplied to the cathode, which holds the charged particles of the plasma by magnetic field lines, and the energy is absorbed to generate high-density plasma, while the voltage applied between the positive and negative electrodes charges the plasma. Sputter film deposition is performed by accelerating the particles and causing them to collide with the target.

In this method, the number of ions colliding with the target increases as the plasma density increases, so a faster film formation rate can be obtained than with the above-mentioned apparatus.
Problems such as the low contribution rate of the target material to film formation remain unsolved.

[Purpose of the invention]

The purpose of the present invention is to generate high-density plasma over almost the entire surface of the target, to make the erosion region of the target almost the entire surface of the target, and to create a state of low temperature stress within the target without extremely increasing the collision energy of ions. enables high-speed film deposition and increases target usage efficiency.
Another object of the present invention is to provide a sputtering apparatus that can achieve uniform thickness of a thin film during sputtering film formation.

[Summary of the invention]

The present invention is a sputtering method for forming a thin film on the surface of a substrate placed on a substrate electrode facing the target by sputtering a target inside a vacuum container, wherein the target has an opening in the center. , generating a magnetic field covering the vicinity of the surface of the target in an arc shape, applying electric power to the target, and generating a high-density field through the interaction between the microwave and the magnetic field between the target and the substrate electrode through the opening. Introducing the plasma of
A sputtering method and apparatus thereof, characterized in that a thin film is formed on the substrate by sputtering the target while confining the high-density plasma near the surface of the target using a magnetic field covering the vicinity of the surface in an arc shape. .

That is, the present invention injects microwaves in a direction parallel to or along the static magnetic field (mirror magnetic field) of the plasma generation part, and adjusts the strength of the static magnetic field under electron cyclotron resonance conditions (microwave frequency 2.45G).
By using a part of the magnetic device that generates this mirror magnetic field to generate a magnetic field to restrain the plasma on the target surface, the plasma transport distance can be minimized and the plasma diffusion can be minimized. In addition to being small in size, this magnetic device is constructed with a plurality of magnetic circuits, thereby making it possible to control the intensity distribution, shape, etc. of the magnetic lines of force on the target.

Next, a supplementary explanation will be given regarding the generation and density of plasma.

In the generation of plasma by microwaves,
It is important how effectively microwaves contribute to plasma generation, and this determines plasma density.

Electromagnetic waves in a plasma without a magnetic field are expressed by a wave number vector κ, κ=ω ² −ω _p ² /c ² where ω is the incident electromagnetic wave frequency ω _p is the plasma frequency, and when ω < ω _p , κ becomes negative and electromagnetic waves cannot propagate into the plasma. In other words, for example, with a 2.45GHz microwave, the plasma density is 7.4
It cannot propagate into plasma exceeding ×10 ¹⁰ /cm ³ . In other words, plasma generated by 2.45GHz microwave has a plasma density of 7.4 in the absence of a magnetic field.
It can be seen that it does not exceed ×10 ¹⁰ /cm ³ .

On the other hand, electromagnetic waves in a plasma with a static magnetic field are
The propagation state differs depending on the angle between the direction of travel of the electromagnetic wave and the magnetic field. In particular, when electromagnetic waves are introduced into the plasma parallel to the magnetic field, the dispersion formula for right-handed circularly polarized waves is κ ² C ² /ω ² =1−ω _p ² /(ω−ω _ce )(ω -ω _ci ) However, ω _ce : Electron cyclotron frequency ω _ci : Ion cyclotron frequency, and electromagnetic waves with a frequency of 0<ω<ω _ce propagate in the plasma regardless of the plasma density.

In other words, if a static magnetic field is provided and a microwave is incident parallel to this static magnetic field, the strength of this static magnetic field can be adjusted to electron cyclotron resonance (2.45G
875G in Hz) or more, the right-handed circularly polarized wave propagates in the plasma and supplies microwave power to the plasma, so the plasma frequency, ω _p , becomes ω _p
>ω, and the plasma density is known to be much larger than 7.4×10 ¹⁰ /cm ³ (more than 10 ¹² /cm ³ ).

The plasma generated as described above needs to be restrained by a magnetic device. If this is not done, the plasma will diverge and will not be dense, resulting in large microwave power losses. Furthermore, after the plasma is generated, it must be quickly transported to the vicinity of the target. This is because the plasma density decreases due to diffusion during transportation.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to FIGS. 1 to 4.

FIGS. 1 and 2 are cross-sectional views showing the structure of the sputter film forming section of the sputtering apparatus of the first embodiment. The target 1 and the substrate 2 face each other in a plane, and the target 1 has a packing plate 3 on the back side.
The cathode 4 is placed in close contact with a cathode 4 via an insulator 5, and the cathode 4 is placed in a vacuum chamber 6 via an insulator 5. Further, a cathode 7 is installed on the cathode 4 with an insulator 5 interposed therebetween, and the anode 7 is installed in a vacuum chamber 6 with an insulating plate 8 interposed therebetween. A power source 9 is installed between the positive and negative electrodes. Here, the center part 10 of the target 1 is hollow, and a plasma generation chamber 11 is disposed in this part.A waveguide 12 is connected to the cathode through an insulator 13 on the outer periphery of the plasma generation chamber 11. It is set at 4. Another waveguide 15 is attached to the waveguide 12 by a flange 14, and a microwave generation source 16 is installed at the other end of the waveguide 15.
Further, a magnetic device 17 is installed on the outer periphery of the flange 14 of the waveguide 15, and another magnetic device 18
is installed on the back surface of the cathode 4. Here, the magnetic device 18 includes a plurality of magnetic coils 18a, 1
8b and 18c, the magnetic field strength of which can be controlled independently.

The plasma generation chamber 11 is made of a material (for example, quartz, alumina porcelain, etc.) that allows microwaves to pass through but maintains a vacuum, and is installed in the vacuum chamber so as to maintain a vacuum.

Further, the substrate 2 is placed on the substrate holder 19,
The substrate holder 19 is electrically insulated by a shaft 20 via an insulator 21 and installed in a state in which a vacuum can be maintained.

In the above configuration, the magnetic devices 17 and 18 constitute a mirror magnetic field, and the magnetic lines of force are as shown in FIG.
The magnetic flux density decreases and expands in the middle between 2 and 3, and narrows again at the center of the magnetic device 18, and furthermore, on the target 1, the magnetic field lines 23 are formed in the cavity 1 of the target 1.
From 0 to almost target 1 on target 1
The magnetic device is constructed so that it is parallel to the surface and enters the cathode 4 at one end of the target. Here, the sputtering film forming chamber 24 is kept in a predetermined vacuum state (10 ^-2 to 10 ^-4 Torr) of atmospheric gas (for example, argon gas, etc.).
Exhaust the air to a certain level.

When microwaves are oscillated from the microwave generation source 16, the microwaves are guided by the waveguide 15,
It is sent to the waveguide 12 and further to the plasma generation chamber 11.
pass through. At this time, due to the static magnetic field created by the magnetic devices 17 and 18, the microwave ionizes the atmospheric gas in the plasma generation chamber 11 and turns it into a plasma state.

Here, by making the center magnetic field strength of the magnetic device 17 larger than the center magnetic field strength of the magnetic device 18, the plasma is directed to the target 1 along the magnetic field lines 22.
The plasma 25 is sent to the cavity 10 of the target 1, and further transported to the entire surface of the target 1 along the lines of magnetic force 23, and a plasma 25 is generated on the surface of the target 1. here,
The plasma in the plasma generation chamber 11 has a static magnetic field and the lines of magnetic force 22 are along the direction of propagation of the microwaves, so the plasma has a high density (plasma density
n _e = 10 ¹¹ /cm ³ or more). Due to the proximity of the surfaces of the plasma generation chamber 11 and the target 1 and the application of electric power to the cathode 4, the charged particles undergo cyclotron motion along the lines of magnetic force 23 and rotate while drifting in the circumferential direction of the target 1. The plasma 25 on the surface of the target 1 also becomes a high-density plasma state.

By applying power to the positive and negative electrode tubes from the power source 9, a negative electric field is generated on the surface of the target 1, which accelerates ions in the plasma and
Collision with a surface. As a result, atoms or particles ejected from the surface of the target 1 adhere and deposit on the surface of the substrate 2 to form a thin film.

Since the plasma 25 on the surface of the target 1 has a high density, the number of ions in the plasma is large, and a low voltage is sufficient to be applied by the power source 9. As a result, the negative electric field on the surface of the target 1 does not become excessively strong, and since the plasma 25 covers almost the entire surface of the target, the erosion area of the target 1 is also large, and the temperature stress applied to the target 1 is small.

In addition, since the target is hollow in the center, there are no atoms or particles flying from the center, which was conventionally seen, and even if the entire surface of the target becomes an erosion area, the thickness of the thin film deposited on the surface of the substrate 2 is uniform. It is not necessary to make the target diameter extremely large, and the rate at which atoms or particles ejected from the target 1 are deposited on the substrate 2 is high, resulting in good sputtering film formation efficiency.

A plurality of magnetic coils 18a, 1 of the magnetic device 18
It is possible to control each of 8b and 18c independently. Therefore, the intensity of the magnetic field parallel to the target 1 in the radial direction of the target can be controlled, thereby making it possible to control the radial density distribution of the plasma 25. As a result, the higher the plasma density, the greater the number of atoms or particles ejected from the target 1, and the higher the plasma density.
The thickness of the film deposited on the substrate in the radial direction can be controlled.

Next, a second embodiment of the present invention will be described with reference to FIGS. 3 and 4. The configuration of the sputter film forming section of the sputtering apparatus of this embodiment is the same as that of the first embodiment, but the target 1' has a conical shape, and a packing plate 3' is attached to the outer peripheral surface of the target 1'. A cathode 4' is disposed closely on the outer peripheral surface of the cathode 4'. The cathode 4' is installed in a vacuum chamber 6 via an insulator 5', and a cathode 7' is also installed in the vacuum chamber 6 via an insulator 8, via the insulator 51. There is. A power source 9 is installed between the positive and negative electrodes. Center part 1 of target 1'
0' is a cavity as in the first embodiment,
A plasma generation chamber 11 made of a material through which microwaves pass and maintains a vacuum, a waveguide 12 and an insulator 1
3' to the cathode 4', another waveguide 15 is attached to the waveguide 12 by a flange 14, and a microwave generation source 16 is installed at the other end of the waveguide 15. . A magnetic device 17 is installed on the outer circumference of the flanges 14 of the waveguides 12 and 15, and another magnetic device 18 is provided on the conical outer circumferential surface of the cathode 4' and is composed of a plurality of magnetic coils 18a, 18b, and 18c. and each is installed in the same way on the cathode 4'. The substrate 2 is the same as in the first embodiment. Furthermore, the configuration of the magnetic devices 17 and 18 is similar to that of the first embodiment, and forms a mirror magnetic field, and the lines of magnetic force are 22' in the plasma generation chamber 11, and the lines of magnetic force are 23' passing through the cavity of the central part 10' of the target 1'. ', and enters into the cathode 4' at the outer periphery of the target 1'.

In the above configuration, plasma 25' is generated by microwave discharge and sputter film formation is performed as in the first embodiment.

In this embodiment, in addition to the features of the first embodiment, the target 1' has a conical shape,
These surfaces are inclined so as to surround the substrate.

As a result, the rate of deposition on the surface of the substrate 2 is increased, and even when the same power is supplied and the same target atoms or particles are repelled from the target, the rate of deposition of the thin film on the substrate is increased.

It is known from experimental results that the cosine law holds for the flight direction and amount of atoms or particles ejected from the surface of the target 1' (for example, the University of Tokyo Press, "Sputtering Phenomenon" by Kanehara Kou, 1984). Published in March).

〔Effect of the invention〕

According to the present invention, a high-density plasma (plasma density n _e =10 ¹¹ /cm ³ or more) using a combination of microwave and magnetic field
The charged particles are generated and transported over a short distance to the target surface, and the charged particles are confined by a plasma generation magnetic field and electric power applied to the target, making it possible to create a high-density plasma state over almost the entire area on the target surface. As a result, the number of ions in the plasma increases, so even if high power is applied between the positive and negative electrodes,
By increasing the current, the voltage can be suppressed to a low level, and therefore the collision energy of ions can be kept low, and sputtering can be performed with less thermal shock to the target. Furthermore, since the eroded area of the target can be increased by ions, the number of atoms or particles ejected from the target increases, which not only speeds up sputtering film deposition, but also increases the target utilization rate by increasing the target eroded area. It can be significantly improved.

Furthermore, by tilting the target in consideration of the flying direction and amount of atoms or particles, it is possible to increase the rate at which atoms or particles ejected from the target adhere to and deposit on the substrate. Furthermore, since microwaves are used to generate plasma and a separate power source is used to generate the energy of ions colliding with the target, the number of ions colliding with the target and their energy can be individually controlled, making it possible to set sputtering conditions that suit the target material. Therefore, there is an effect of improving production efficiency, material usage efficiency, and power usage efficiency.

[Brief explanation of drawings]

1 is a sectional view showing the structure of a film forming section of a sputtering apparatus according to a first embodiment of the present invention; FIG. 2 is a sectional view showing magnetic lines of force and plasma in the film forming section of FIG. 1; The figure is a sectional view showing the structure of the film forming part of the sputtering apparatus according to the second embodiment of the present invention.
The figure is a cross-sectional view showing magnetic lines of force and plasma in the film forming part of FIG. 3. 1, 1'...Target, 2...Substrate, 4,
4'...Cathode, 7,7'...Anode, 11...Plasma generation chamber, 14,15...Waveguide, 16...Microwave source, 9...Power supply, 17, 18...Magnetic device , 6... Vacuum chamber, 22, 22', 23, 2
3'...Magnetic field lines, 25,25'...Plasma.

Claims (1)

[Scope of Claims] 1. A sputtering method for forming a thin film on the surface of a substrate placed on a substrate electrode facing the target by sputtering a target inside a vacuum container, the target having an opening in the center. generating a magnetic field that covers the vicinity of the surface of the target in an arc shape, applying electric power to the target, and generating the magnetic field between the target and the substrate electrode through the opening by interaction between the microwave and the magnetic field. A thin film is formed on the substrate by introducing high-density plasma and sputtering the target by confining the high-density plasma near the surface of the target using a magnetic field covering the vicinity of the surface in an arc shape. sputtering method. 2. A target made of a material that forms a thin film inside the vacuum vessel, electrode means for supporting the target, power application means for applying electric power to the electrode means from outside the vacuum vessel, and a target at a predetermined distance from the target. substrate electrode means facing each other with a distance between them; magnetic field generating means for generating a magnetic field on the back side of the target in which lines of magnetic force cover the vicinity of the surface of the target in an arc shape; and plasma generated by microwaves at the center of the target. a microwave plasma supply means for supplying into the vacuum vessel through an opening provided therein, and confining the plasma supplied from the microwave plasma supply means near the surface of the target with the magnetic field, so that the plasma near the surface of the target is generating high-density plasma, and applying electric power to the target via the electrode means by the electric power applying means,
A sputtering apparatus characterized in that the target is sputtered with the high-density plasma to form a thin film on the surface of a substrate placed on the substrate electrode means. 3. The microwave plasma supply means has a magnetic field generation section near a part that supplies the plasma into the vacuum container, and the magnetic field generation section forms a pair with the magnetic field generation means, and the microwave plasma generation means has a magnetic field generation section. 3. The sputtering apparatus according to claim 2, wherein a mirror magnetic field is formed inside, and plasma is generated by interaction of the mirror magnetic field and microwaves. 4. The magnetic field strength inside the microwave plasma generating means generated by the magnetic field generating section and the magnetic field strength inside the microwave plasma generating means generated by the magnetic field generating means both depend on the frequency of the microwave. 3. The sputtering apparatus according to claim 2, wherein the magnetic field strength is greater than or equal to a critical magnetic field strength that satisfies the electron cyclotron resonance conditions. 5. Claims characterized in that the magnetic field strength inside the microwave plasma generating means generated by the magnetic field generating section is stronger than the magnetic field strength inside the microwave plasma generating means generated by the magnetic field generating means. The sputtering device according to item 2. 6. The sputtering apparatus according to claim 2, wherein the diameter of the opening provided at the center of the target is less than or equal to the microwave blocking dimension. 7. The sputtering apparatus according to claim 2, wherein the magnetic field generating means on the back side of the target is constituted by a plurality of magnetic field generating sections.