JPH0647723B2 - Sputtering method and apparatus - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a sputtering apparatus in a thin film manufacturing process for a semiconductor device or the like, and particularly to an increase in film formation rate and target life, and burying in fine grooves and the like. The present invention relates to a sputtering apparatus and method suitable for forming a flat film surface.

[Background of the Invention]

Sputter deposition is performed on the target material placed on the cathode.
This is a film forming method in which ions having a predetermined energy or more are made to collide with each other, and constituent atoms or particles of the target material emitted thereby are attached and deposited on a substrate to form a thin film.

As a sputtering device for performing the above sputter film formation,
As described in Japanese Patent Publication No. 53-19319, a pair of magnetic poles of a magnetic device is provided on the side opposite to the target material of the cathode having the target material, and arc-shaped magnetic lines of force are formed on the target, and a voltage is applied to the cathode. Is applied to generate plasma, and charged particles of the plasma are subjected to cyclotron motion by the magnetic force lines to be confined within the magnetic force lines to obtain high-density plasma, and a method of obtaining a high film formation rate as compared with a two-pole sputtering apparatus is known. Has been.

However, in this method, the plasma region becomes a ring-shaped narrow region, and since both the plasma generation and the ion collision energy to the target are supplied by the power applied to the cathode, the applied power is increased to increase the film formation speed. If it is increased, the plasma density has a certain limit, and the increase in the number of ions stops, and only the collision energy of the ions to the target tends to increase. When sputter deposition is performed in such a state, the erosion region of the target becomes a ring-shaped narrow region that almost coincides with the plasma region, and the collision of high-energy ions causes the surface temperature of the target surface in a limited range to rise. The temperature rises sharply, large thermal stress is generated in the target, cracking or peeling of the target occurs, and it becomes impossible to form a film. Further, in the above film forming method, the target erosion area is narrow, so that the target utilization efficiency is low and the number of substrates processed per target is small.

As one of the methods for reducing the ion collision energy of the above device, there is a method disclosed in Japanese Patent Laid-Open No. 58-75839 that uses microwave capable of generating high density plasma as the plasma generating power.

In this method, a microwave generation source is installed in the sputtering device described in the above Japanese Patent Publication No. 19319/1983, and the plasma region is a ring-shaped narrow region as in the above.
In this method, since the density of plasma is increased by microwaves, the limit of plasma density can be made higher than that of the above-mentioned device, but since the region where the ions collide with the target, that is, the erosion region is the same as that described above, it is applied to the cathode. When the electric power is increased, the surface temperature of the target in a limited range rises due to the ion collision, and the target is cracked or peeled off due to the thermal stress, so that the film cannot be formed. Also, the utilization efficiency of the target was low.

As another example of the sputtering apparatus to which the plasma by the microwave is applied, there is one described in JP-A-59-47728. This is because plasma generated by microwaves is transported by a divergent magnetic field, a cathode on which a target is placed is installed in the vicinity of the plasma transport return, and electric power is applied to the cathode to cause ions to collide with the target. Atoms or particles of the target material emitted by the above are ionized by the plasma used for the above-mentioned sputtering, and these are deposited on the substrate. In this method, the erosion of the target due to ion collision is almost all over the target, but since the atoms or particles emitted from the target are ionized to form a film, the target does not face the substrate and is emitted from the target. The atoms or particles are configured to jump into the plasma. It is known that the emission angle distribution of the atoms or particles emitted from the target generally follows the cosine law, which means that the amount of atoms or particles emitted from the target directly deposited on the substrate is small in the above method, The film formation can be said to be based on ionized atoms or particles. From this, the film formation rate depends on the ionization efficiency of the atoms or particles emitted from the target, and the ionization rate is generally said to be low, and is small. Further, in the above method, when the target size is increased, the plasma is not confined on the target surface, so the plasma density is high in the vicinity of the plasma transport window, but becomes lower as the distance from the plasma transport window increases, and the sputter deposition rate increases. When the film is formed, only the central part of the target is eroded much and the peripheral part is hardly eroded. As a result, when the power applied to the cathode is increased,
Ion collision concentrates in the center of the target, causing thermal stress in the target. Therefore, even in the above method, the problems of thermal stress and improvement of target utilization efficiency in obtaining high-speed film formation have not been solved.

[Object of the Invention]

The object of the present invention is to generate a high-density plasma over the entire surface of the target and use the entire area of the target as an erosion region to achieve high-speed growth with a small thermal stress in the target without extremely increasing the ion collision energy. (EN) A sputtering apparatus and method capable of forming a film, increasing target utilization efficiency, and applying electric power to a substrate to fill a fine groove and form a film surface at a high speed evenly. .

[Outline of Invention]

In order to achieve the above object, the present invention is a sputtering method in which a target is sputtered inside a vacuum container to form a thin film on the surface of a substrate placed on a substrate electrode facing the target, in the center of the target. An opening is provided in the portion, a cusp magnetic field is formed between the target and the substrate electrode, power is applied to the target, and the magnetic field lines that form the cusp magnetic field are narrowed to one point, that is, the point cusp side. By introducing a high-density plasma generated by the interaction between the microwave and the magnetic field between the target and the substrate electrode through the opening in the central part and confining the high-density plasma in a cusp magnetic field over a wide range, A wide range of the target is sputtered to form a thin film on the substrate.

First, the generation of high-density plasma using microwave discharge is important. How effectively the microwave is absorbed by the plasma is important for this, and this condition limits the plasma density.

That is, the electromagnetic wave in the plasma without static magnetic field has wave vector K Here, ω is the incident electromagnetic wave frequency ωp is given by the plasma frequency, and when ω <ωp, K becomes imaginary and the electromagnetic wave cannot propagate into the plasma. In other words, for example, the microwave of 2.45 GHz cannot propagate into the plasma whose plasma density exceeds 7.4 × 10 ¹⁰ / cm ³ , that is, the plasma generated by the microwave of 2.45 GHz has a plasma density of It can be seen that the value does not exceed 7.4 × 10 ¹⁰ / cm ³ .

In addition, electromagnetic waves in a plasma with a static magnetic field have different propagation states depending on the angle between the traveling direction of the electromagnetic waves and the magnetic field. Especially, when the electromagnetic waves enter the plasma in parallel to the magnetic field, they rotate clockwise. Circular polarization dispersion formula is Here, ωce is an electron cyclotron frequency, ωci is an ion cyclotron frequency, and an electromagnetic wave having a frequency of 0 <ω <ωce propagates in plasma regardless of the plasma density.

That is, by providing a static magnetic field, and injecting microwaves in parallel with the static magnetic field, and setting the intensity of the static magnetic field to electron cyclotron resonance (875 G at 2.45 GHz) or more,
Since the right-hand circularly polarized wave propagates in the plasma and supplies microwave power to the plasma, the plasma frequency ωp is ωp> ω
And the plasma density is much larger than 7.4 × 10 ¹⁰ / cm ³ (10 ¹² / cm ³ or more).

Further, the plasma generated as described above will diverge unless it is bound by a magnetic device,
The loss of microwave power becomes large and the plasma cannot be densified. Also, if this plasma is bound by a magnetic device and transported for a long distance, due to the diffusion of plasma during transport,
Plasma density decreases with increasing distance.

From the above, according to the present invention, a magnetic device is provided in the plasma generating part, and this magnetic device also constitutes a magnetic device for confining the plasma in the film forming part. The distance between the parts is shortened to reduce the diffusion during the transportation of plasma so that the plasma density of the generation part and the plasma density of the film formation part are almost equal.

That is, the film forming unit is provided with a magnetic device paired with the magnetic device of the plasma generation unit on the back side of the target, and is paired with the magnetic device paired around the substrate holder which holds the substrate facing the target. Of the plasma generator by forming a cusp magnetic field (a magnetic field formed by a combination of a pair of magnetic devices having mutually opposite lines of magnetic force) between the target and the substrate holder. The magnetic device also serves as a magnetic device that forms a cusp magnetic field, and the distance between the plasma generation unit and the sputtering film formation unit (target surface) is shortened. With such a configuration, the magnetic device of the plasma generating unit forms a point where the magnetic field lines forming the cusp magnetic field are narrowed down, that is, a point cusp in the plasma generating unit, and the microwave and the magnetic field are generated in the vicinity of this point cusp. High-density plasma is generated by the discharge caused by the interaction with. This high-density plasma is transported onto the target along the magnetic field lines that form the cusp magnetic field, and the cusp magnetic field formed by these magnetic field lines confine the plasma to create a high-density plasma over the entire target surface. did.

Further, in the present invention, the structure is such that power (high frequency power) can be applied also to the substrate side, and power is also applied to the substrate side when applying the power to the cathode on which the target is placed to form a film by sputtering. The structure is such that sputter etching can be performed.

In addition, by configuring the magnetic device on the back of the target with multiple magnetic circuits, the intensity distribution of the magnetic lines of force on the target,
The shape and the like can be controlled.

Example of Invention

An embodiment of the present invention will be described below with reference to FIGS. 1 to 6. 1 and 2 are sectional views showing the structure 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 is installed on the back surface of the target 4 in close contact with the cathode 4 via the backing plate 3, and the cathode 4 is installed in the vacuum chamber 6 via the insulator 5. Further, an earth shield 7 is installed in the vacuum chamber 6 on the outer circumference of the insulator 5. A power source 9 is installed between the cathode 4 and the vacuum chamber 6. Here is the center of target 1
Reference numeral 10 denotes a cavity, and a plasma generation chamber 11 is installed in this portion, and a waveguide 12 is installed on the outer periphery of the plasma generation chamber 11 on the cathode 4 via an insulator 13. Another waveguide 15 is attached to the waveguide 12 with a flange 14, and the waveguide 15
A microwave generation source 16 is installed at the other end of the. A magnetic device 18 is installed on the back surface of the cathode 4, and the magnetic device 18
18 is composed of a plurality of magnetic coils 18a, 18b, 18c.
Here, the plasma chamber 11 is made of a material (for example, quartz, alumina porcelain, etc.) that transmits microwaves but retains a vacuum, and is installed so that the cathode can retain the vacuum.

The substrate 2 is placed on the substrate holder 19, and the substrate holder 19 is electrically insulated by the shaft 20 via the insulator 21 and installed on the flange 22 so as to hold a vacuum. Is installed on a coil flange 25 to which a ring-shaped can 24 enclosing the porcelain device 23 is attached, and the coil flange 25 is installed in the vacuum chamber 6 so as to be able to hold a vacuum. A power source 26 is installed on the shaft 20 of the substrate holder 19 so that high frequency power can be applied to the substrate 2.

In the above configuration, the magnetic devices 18 and 23 form a cusp magnetic field, and the magnetic force lines generated by these magnetic devices are
As shown in the figure, the magnetic force line 28 extending from the magnetic device 18 to the target side repels the magnetic force line 29 of the magnetic device 23 on the substrate 2 side, and a line cusp L between the target 1 and the substrate holder 19,
A cusp magnetic field forming a point cusp P is formed at the center of the magnetic device 18. Here, the magnetic field strength of the central portion 27 (that is, the point cusp P) of the magnetic device 18 is set to electron cyclotron resonance conditions (magnetic field strength of 875 Gauss at a microwave frequency of 2.45 GHz) or more, and microwaves are introduced here to generate high-density plasma. The plasma is generated and transported from the point cusp P into the cusp magnetic field by the magnetic field lines 28.

In the above, the sputtering film forming chamber 30 is kept in a predetermined vacuum state (about 10 ⁻² to 10 ⁻⁴ Torr) in an inert gas (eg, argon gas) atmosphere. When microwaves are oscillated from the microwave source 16 here, the microwaves are guided by the waveguide.
It is guided by 15 and sent to the waveguide 12 and the plasma generation chamber 11
Enter The static magnetic field generated by the magnetic device 18 causes the microwaves to ionize the atmospheric gas in the plasma generation chamber to form a high-density plasma (plasma density ne = 10 ¹¹ 10 ¹³ cm ³ ). The plasma in the plasma generation chamber 11 is sent to the surface of the target 1 along the lines of magnetic force 28, and is confined between the target 1 and the substrate 2 by the cusp magnetic field generated by the magnetic devices 18 and 23, so that the plasma is generated on the surface of the target 1. A high density plasma state is set. Here, power is applied to the cathode 4 from the power source 9,
A negative electric field is generated on the surface of the target 1, which accelerates the ions in the plasma to collide with the surface of the target 1 and sequentially eject the atoms or particles from the surface of the target 1, which are deposited on the surface of the substrate 2. To form a thin film. Here, the power source 9 selects DC or high frequency depending on the material of the target 1.

As described above, the plasma on the surface of the target 1 is generated in the plasma generation chamber 11 under the static magnetic field higher than the electron cyclotron resonance condition by the microwave, and the magnetic line of force of the generating part 27 is the magnetic field line of the cusp magnetic field for confining the plasma. Since the plasma generation part and the surface of the target 1 are close to each other and the plasma transport distance is short, the density is high over the entire surface of the target 1. Therefore, the erosion region of the target 1 is also the entire region of the target 1, the number of ions colliding with the target is large, high-energy ions do not collide with the target, and the thermal stress in the target 1 is small.

Further, in the above sputtering film formation, high-frequency power is applied to the substrate holder 19 by the power source 26 to generate a negative electric field on the surface of the substrate 2, and the electric field accelerates ions in the plasma to collide with the surface of the substrate 2. The thin film deposited on the substrate surface is sputter etched. The state of the substrate at this time is shown in FIGS. 3 and 4. FIG. 3 (a) shows a state in which the substrate 31 having a groove is formed by sputtering, and when the groove width is reduced, the film 32 deposited by sputtering is a corner portion of the previously formed film 33. The overhang 34 and the opening 36 of the groove 35 become narrower as the film formation progresses, and the film formation of the groove 35 becomes impossible. Therefore, if electric power is applied to the substrate side and sputter etching is performed simultaneously with sputter film formation, as shown in FIG. 3B, the overhang 34 of FIG.
Are more easily etched than other parts, and the opening 36 of the groove 35
As shown in 36 ', it becomes possible to form a film on the groove. Further, FIG. 4 shows a state in which a film is further formed while the substrate is being sputter-etched during the sputter film formation. In sputter etching, the angle between the incident angle of ions and the normal to the surface to be etched is 70
Since the maximum etching value is shown in the range of 80 ° to 80 °, the angled portion 37 is etched more than other portions, and the fourth
It is known that the state becomes as shown in FIG. 4A and the surface of the deposited film 32 becomes flat as shown in FIG. 4B. In these conventional devices, the plasma density is low, and when the applied power is increased in order to perform the sputter etching of the substrate during film formation at a high speed, the energy of the colliding ions increases due to the small number of ions, and the substrate or element However, since the device of the present invention confines high-density plasma between the target and the substrate, the ion energy does not increase even when the power applied to the substrate is increased, and ion collision damage to the substrate can be reduced. Thus, it becomes possible to perform groove filling and flattening film formation at high speed film formation.

5 and 6 are sectional views showing the structure of the sputtering apparatus according to the second embodiment of the present invention. This embodiment is the same as the first embodiment except that the cathode 4 ', the insulator 5', the backing plate 3'and the target 1'are conical in shape, and is the same as the first embodiment. effective. According to this embodiment, in addition to the first embodiment, the target 1'has a conical shape and the surface of the target 1'is inclined so as to enclose the substrate. Because the emission angle distribution of atoms or particles that are repelled by the collision of the particles follows the cosine law (see, for example, "Sputtering Phenomenon" by Takeshi Kanehara, University of Tokyo Press (1984).
March issue))), the rate at which the released atoms or particles adhere to and deposit on the surface of the substrate 2 is improved, and the deposition rate of the conductive film on the substrate is increased when the target 1 is supplied with the same power. .

〔The invention's effect〕

According to the present invention, a microwave and a magnetic device are combined to generate high-density plasma (plasma density ne = 10 ¹¹ to 10 ¹³ / cm ³ ), and one of the plasma generating magnetic device and the plasma confining magnetic device is the same. Since the plasma generation part and the target are close to each other, the plasma loss due to transportation is small, and this plasma is confined between the target and the substrate by a magnetic device to create a high density plasma state over almost the entire surface of the target. By applying electric power to the target, the number of ions colliding with the target can be increased, and even if a large amount of power is applied, the collision energy of the ions can be suppressed, and since the ions collide with the entire target area, thermal stress on the target can be reduced, so high-speed It is possible to improve the utilization rate of the film and the target.

Also, when power is applied to the substrate and the surface of the substrate is sputter-etched during sputter deposition, the energy of ions colliding with the surface of the substrate can be lowered because the plasma density is high, and the substrate or element is not damaged. High-speed embedding in fine grooves and high-speed flattening film formation are possible.

Further, by making the shape of the target into a conical shape, it is possible to improve the deposition rate of the atoms or particles that are repelled by sputtering on the substrate.

Further, since plasma is generated by using a microwave and a separate power source is used for ion collision energy to the target, the number of collision ions to the target (incident ion current to the target) and its energy (incident ion voltage to the target) Can be controlled individually, and the sputtering conditions suitable for the target material can be set.

As described above, according to the present invention, the production efficiency, the material usage efficiency, and the power usage efficiency are improved and the damage to the element is reduced.

[Brief description of drawings]

1 is a sectional view of a sputtering apparatus according to a first embodiment of the present invention, FIG. 2 is a sectional view showing magnetic lines of force in FIG. 1, and FIG.
4 and 5 are cross-sectional views showing the substrate during sputtering film formation, and FIG.
FIG. 6 is a sectional view of a sputtering apparatus according to the second embodiment of the present invention, and FIG. 6 is a sectional view showing magnetic lines of force in FIG. 1,1 '... Target, 2 ... Substrate 4,4' ... Cathode, 7,7 '... Earth shield 14,15 ... Waveguide, 9 ... Power supply 16 ... Microwave source 18, 23 …… Magnetic device 26 …… Power supply

Front page continuation (72) Inventor Susumu Aiuchi 292 Yoshida-cho, Totsuka-ku, Yokohama, Kanagawa Prefecture Production Technology Research Laboratory, Hitachi, Ltd. (56) Reference JP-A-59-47728 (JP, A) JP-A-SHO 57-91734 (JP, A) JP-A-61-194174 (JP, A)

Claims (5)

[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, comprising:
The target has an opening in the center, forms a cusp magnetic field between the target and the substrate electrode, and the cusp magnetic field formed near the opening of the microwave introduction part connected to the opening. The high density plasma is generated by the interaction between the microwave and the magnetic field in the vicinity of the point cusp, and the high density plasma is introduced between the target and the substrate electrode along the magnetic line of force of the cusp magnetic field. While confining a wide range with a cusp magnetic field,
By applying electric power to the target, a wide range of the target is sputtered to form a thin film on the substrate. 2. The sputtering method according to claim 1, wherein a thin film is formed on the substrate by re-sputtering by applying bias power to the substrate electrode at the same time as sputtering the target. . 3. A target made of a material for forming a thin film inside a vacuum container, electrode means for supporting the target, power applying means for applying power to the electrode means, and a predetermined distance from the target. And a substrate electrode means facing each other, a first magnetic field generator on the back side of the target, and a second magnetic field generator on the substrate electrode side to generate a cusp magnetic field between the target and the substrate electrode. Magnetic field generating means and microwave supplying means for supplying microwaves from the outside of the vacuum container through an opening provided at the center of the target and the electrode means, and the cusp magnetic field is the microwave supplying means. Point cusps are formed in the vicinity of the opening of the plasma, and high-density plasma is generated in the vicinity of the point cusps due to the interaction between the microwave and the magnetic field. Is supplied into the cusp magnetic field along the magnetic field lines of the cusp magnetic field to confine it over a wide range in the cusp magnetic field, and the target is sputtered by applying power to the electrode means by the power applying means. A sputtering apparatus, wherein a thin film is formed on a surface of a substrate placed on the substrate electrode means. 4. The substrate electrode means comprises bias power applying means for applying bias power during the sputtering, and the bias power applying means applies bias power to the substrate electrode means during the sputtering. The sputtering apparatus according to claim 3, wherein the thin film is formed on the surface of the substrate by re-sputtering. 5. The sputtering apparatus according to claim 4, wherein the magnetic field strength of the point cusp is equal to or higher than a critical magnetic field strength satisfying an electron cyclotron resonance condition corresponding to the frequency of the microwave.