JPH0660392B2 - Thin film forming equipment - Google Patents

Description

TECHNICAL FIELD The present invention relates to an apparatus for forming thin films of various materials on a sample substrate, and in particular, it utilizes sputtering of high density plasma to form various thin films. The present invention relates to a new thin film manufacturing apparatus for forming at high speed and high efficiency.

[Conventional technology]

BACKGROUND ART Conventionally, a so-called sputtering device for forming a film by sputtering a target as a thin film forming element in plasma has been widely used in various fields for forming a thin film of various materials. Among them, a normal two-pole (rf, dc) sputter device in which the target 1 and the substrate 2 are opposed to each other as shown in FIG. 4 or a two-electrode sputter device has a third electrode for electron emission as shown in FIG. 3 pole spatter device provided with 3, and further 6th
As shown in the figure, a magnetron sputtering method is widely known in which a high-density low-temperature plasma is generated by applying an appropriate magnet field to a target by using a magnet 5, and eventually a high-speed film formation is realized. Each of these devices mainly comprises a vacuum tank 4 having a target 1 as a film constituent and a substrate 2 to which a thin film is attached, a gas introduction system and an exhaust system, and generates plasma inside the vacuum tank 4. .

[Problems to be solved by the invention]

In order to form a film at a high speed with a conventional device, it is necessary to keep the plasma at a high density, but in the bipolar electrode sputtering device represented by FIG. 4, the higher the density of the plasma, the more the target is applied. The voltage also rises sharply, and at the same time, the temperature of the substrate rises sharply due to the impact of high-energy particles on the substrate and the high-speed electrons in the plasma, and damage to the formed film also increases. It can only be applied to material and film composition. Further, in the case of the three-pole sputter device typified by FIG. 5, the plasma density is increased by the supply of electrons from the third electrode into the plasma, but as in the case of the above-mentioned two-pole sputter device, it should be formed at high speed. In that case, the substrate temperature rises sharply, and the resulting film material and the substrate to be formed are limited in number.

On the other hand, the magnetron high-speed sputtering apparatus typified by FIG. 6 confines the γ (gamma) electrons emitted from the target necessary for ionizing the gas in the plasma to the target surface by a magnetic field and an electric field, thereby lowering the plasma. It is widely used for high-speed formation of various thin films because it can be generated and densified by gas pressure and can realize high-speed sputtering even at low gas pressure of 10 ^-3 Torr level. However, in such a sputtering device, ion bombardment (mainly Ar ⁺ ions) in the plasma is applied to the film during film deposition.
In addition, the impact of high-speed neutral particles (mainly recoil particles on the target surface of Ar) and negative ions from the target is often present, causing the composition shift of the film and the damage of the film and the substrate.
It is also known that, when a ZnO film or the like is formed, the film quality of the part directly above the eroded part of the target is completely different from that of the other part, and the substrate impact of such high-energy particles is a big problem. In addition, since the erosion part of the target is localized, the utilization efficiency of the target is extremely low, and there is a drawback in productivity on an industrial scale.

Further, in the film formation by the conventional sputtering device, the ionization of the gas and particles in the plasma is not sufficient in all cases, and the neutral particles as the film deposition elements sputtered are mostly neutral particles. Since it is incident on the substrate, the activity is not sufficient from the viewpoint of reactivity, so that a high substrate temperature of about 500 ° C to 800 ° C was required to obtain some oxides and thermal nonequilibrium substances. Moreover, most of the electric power supplied to the plasma is consumed as heat energy, and the ratio of the electric power used for plasma formation (ionization) to make the supplied electric power is low, resulting in a low power efficiency.

Furthermore, none of the sputter methods has the drawback that a discharge cannot be stably formed at a low gas pressure of 10 ^-3 Torr or less, and that much impurities are trapped in the film.

That is, in forming a thin film by sputtering, the following things are desired.

(1) High-speed film formation without damage to the film or substrate or rapid temperature rise, (high density plasma), (2) particle energy control over a wide range, (3) particle Energy dispersion is as small as possible, (4) Plasma ionization rate is high and active, (5) Plasma can be generated even at low gas pressure. On the other hand, recently, as shown in Fig. 7, electron cyclotron resonance and magnetic flux A sputtering device and a CVD device have been proposed in combination with a divergent magnetic field whose density gradually decreases.
(For example, Japanese Patent Application No. 55-57877 and Japanese Patent Application Laid-Open No. 56-155535), high-speed formation of a good quality film is realized. First in Figure 7
The same reference numerals as those in the figure indicate the same parts. 6 is a plasma generator,
Reference numeral 7 is a microwave waveguide, and 8 is an electron cyclotron resonance electromagnet. In the example of FIG. 7, the microwave propagating in the waveguide as a microwave introducing mechanism is introduced into the vacuum chamber 4 through the microwave introducing window such as quartz, and the vacuum chamber itself resonates with the microwave. Need to be designed to satisfy. ． That is, the vacuum chamber 4
However, there is a drawback in that the degree of freedom in the device configuration is so small that it is determined depending on the wavelength of the microwave used. When the film to be formed is a metal such as Al or Fe, or another conductive material, it also adheres to the microwave introduction window, so that the microwave is absorbed in the microwave introduction window. Since it is reflected, and as a result, the discharge cannot be stably connected, it can only be applied to the formation of an insulating film with SiO ₂ or Al ₂ O ₃ .

[Means for solving problems]

In order to solve the conventional problems, the present invention relates to a thin film forming apparatus for forming a thin film of various materials on a sample substrate, in which a vacuum having a gas inlet provided with a plasma generating part, a sputter part and a substrate supporting part which are sequentially coupled. The plasma generating unit comprises a cylindrical coil with slits as an exciter for causing electron cyclotron resonance connected to a microwave introducing mechanism provided outside the vacuum chamber, and the plasma generating unit and the substrate supporting unit are In the vicinity of the slitted cylindrical coil in the vacuum chamber, a pair of magnetic field densities necessary for causing electron cyclotron resonance is formed and a mirror magnetic field or an asymmetric magnetic field gradient is formed to minimize the magnetic flux density in the spatula section. An electromagnet is provided, and a target to be sputtered is arranged in the spatula portion.

[Work]

According to the present invention, a high-density plasma with high activity is locally generated, and a high-quality thin film can be formed at high speed, high efficiency, and high stability while keeping the sample substrate at a low temperature. That is, according to the present invention, plasma is generated and heated by electron thyrotron resonance using a cylindrical coil (rigitano coil) in a mirror magnetic field or an asymmetric magnetic field, and the plasma is confined by a magnetic field gradient of the mirror magnetic field or the asymmetric magnetic field, or effective. A high-density plasma is locally formed by diverging into the plasma, and a target to which a negative voltage is applied is placed in front of the high-density plasma to effectively draw ions in the plasma to the target, thereby achieving a high-speed, high-efficiency sputtering. In addition to realizing the above, it is possible to form a high-purity film on a low-temperature substrate at low gas pressure with particles having energy with little dispersion while suppressing damage to the film or substrate and rapid temperature rise. Embodiments will be described below with reference to the drawings.

〔Example〕

FIG. 1 is a schematic sectional view of a thin film device of the present invention, and FIG. 2 is an embodiment of the present invention. The vacuum chamber 4 includes a plasma generating unit 6 in which a cylindrical coil with slits (resitano coil) 10 as a microwave exciter is arranged, a sputtering unit 12 in which a target 1 for sputtering is arranged, and a substrate supporting unit in which a substrate 2 is arranged. It consists of 13. Further, the slitted cylindrical coil 10 is provided with a microwave waveguide 9 and is further provided with a microwave waveguide 9 for introducing a microwave from a microwave source including a matching device, a microwave power meter, an isolator, etc. Supply the waves. In the embodiment, a coaxial line is used as the microwave waveguide 9, and a 2.45 GHz magnetron, for example, is used as the microwave source (not shown).

The vacuum chamber 4 and the target 1 are water-cooled to prevent temperature rise due to plasma generation, and the gas introduction system is directly connected to the vacuum chamber 4. The plasma generation unit 6 in the vacuum chamber 4
The substrate 2 is arranged at a position facing the slitted cylindrical coil 10 inside, and a shutter (not shown) is arranged on the substrate 2 so as to block the spatter particles. Further, the substrate holder has a built-in heater so that the substrate 2 can be heated.

Furthermore, a DC or AC voltage can be applied to the substrate 2, and substrate bias during film formation and sputter cleaning of the substrate 2 can be performed.

The plasma generating unit 6 does not need to satisfy the resonance condition for microwaves, and the slitted cylindrical coil 10 arranged therein may be matched with the microwave used. For example, for 2.45GHz microwave,
The slit length of the slit-equipped cylindrical coil 10 may be a half wavelength of the microwave, that is, about 12 cm.

The target 1 is placed in the spatula part 12, and -1.5K
Negative voltage up to V, 10A can be applied.

Electromagnets 11 are provided around both ends of the vacuum chamber 4, and the strength of the magnetic field generated by the electromagnets 11 is increased by the cylindrical coil with slits.
It is determined so that the condition of the electron cyclotron resonance by the microwave is satisfied near 10.

For example, for microwaves with a frequency of 2.45 GHz, the condition for electron cyclotron resonance is a magnetic flux density of 875 G, so the electromagnets 11 on both sides were designed to obtain a maximum magnetic flux density of about 3000 G. The currents flowing through the two electromagnets 11 are independently controlled to control the magnetic flux density obtained from each electromagnet 11. Further, by placing an appropriate distance between the two electromagnets 11, it is possible to realize a so-called mirror magnetic field arrangement in which the magnetic flux density is the weakest in the vacuum chamber 4, while the electromagnets of the two electromagnets 11 arranged on the side of the substrate 2 are realized. 11
An asymmetric magnetic field arrangement can be realized in the vacuum chamber 4 by setting the power supply for flowing 0 to 0, weak or strong.

The arrangement of the mirror magnetic field as described above not only efficiently gives energy to the electrons by electron cyclotron resonance, but also prevents the generated ions and electrons from being dissipated in the magnetic field direction, and further plasma is generated by the mirror magnetic field. It has the effect of being trapped inside.

FIG. 3 shows the principle of the present invention.

The parameters for forming plasma are the gas pressure in the plasma generation part, the applied voltage of the microwave power target, and the gradient of the mirror magnetic field (maximum magnetic flux density of the electromagnet).
Ratio of minimum magnetic flux density B ₀ in the vacuum chamber between Bm and both magnets: Bm /
B ₀ ), and the symmetry of the mirror magnetic field (the ratio of the maximum hourly velocity density Bm of one electromagnet to the maximum magnetic flux density Bmo of the other electromagnet)
Bm / Bmo) and the distance between both electromagnets.

Here, for example, using a microwave with a frequency of 2.45 GHz,
Assuming that it is located at the center of one of the electromagnets of the slit-equipped cylindrical coil 10 as the microwave exciter, as described above, the magnetic flux density (in this case, Bm) in the vicinity of the slit-equipped cylindrical coil in the plasma generation unit 6 is calculated. A magnetic field gradient may be formed as 875G. When such a magnetic field is spatially gently changing, the charged particles in the plasma are accelerated by the magnetic force lines 14 and move spirally around the magnetic force lines 14 while maintaining angular momentum.

When plasma is formed in the mirror magnetic field, the charged particles are reflected by the portion having a high magnetic flux density, and as a result, the charged particles reciprocate in the mirror magnetic field and eventually confine. The above-mentioned gradient of the mirror magnetic field, Bm / B _0, has a great influence on the plasma confinement efficiency. By applying a negative voltage to the target 1 facing the high-density plasma confined as described above, the ions in the high-density plasma are efficiently drawn into the target 1 to cause the spatter. Furthermore, most of the particles sputtered from the target 1 are partially ionized in a high-density plasma having a high electron temperature. On the other hand, since the electron is much lighter than the ion, the velocity of motion in the direction of the magnetic field is larger for the electron than for the ion. Therefore, many electrons escape from the end of the mirror magnetic field, positive ions are left behind in the mirror magnetic field, charge separation occurs, and an electric field is inevitably induced near the end of the mirror magnetic field. Equilibrium occurs when the internal and external potential difference (Vp) is equal to the average energy of electrons, and this electric field acts as a decelerating electric field for electrons and an accelerating electric field for ions, so that the emission amounts of both species are almost the same. Become. That is, the loss due to the space charge effect due to the mirror magnetic field means that, from the viewpoint of the thin film forming apparatus, the plasma can extract ions having energy corresponding to the potential difference.

On the other hand, when an asymmetric magnetic field is used and one of the magnetic flux densities Bmo eliminates the effect of confining charged particles in the plasma,
The charged particles in the plasma are bound around the magnetic field lines 14 and move toward the substrate. The electrons and ions obtained in this way fly onto the substrate, effectively forming a film.
The energy of these particles greatly depends on the microwave power, gas pressure, magnetic field gradient and its symmetry,
It can be controlled freely over a wide range from eV to several hundred eV.

Moreover, since the target and the substrate are in the orthogonal position, it is possible to avoid the substrate impact of negative ions and neutral high-energy particles from the target, and the substrate of various high-energy particles which has been a problem in the conventional sputtering method. Impact can be suppressed.

In addition, since there is scattering of particles due to collisions between particles in the plasma in the mirror magnetic field, the relaxation time for the time decrease of the plasma density due to the collision scattering is smaller as the ion energy in the plasma is smaller. The average energy of the particle group escaping from the end of the mirror magnetic field is a fraction of the average energy of the particle group inside the plasma. That is, higher energy (high activity) for ionization in plasma
When it is carried out and taken out to form a film, it means that the ions can be taken out with a smaller energy of a fraction, and a sputtering device having this magnetic field arrangement is used as a thin film forming device. It shows that it has an ideal property.

Further, the present invention is characterized in that since the plasma is activated, the discharge can be stably formed even at a lower gas pressure (10 ⁻⁵ Torr), and a film with less impurities can be realized.

Further, in the present invention, since the heating by electron cyclotron resonance is utilized, the electron temperature in plasma can be freely controlled. Therefore, an electron temperature sufficient to generate multiply charged ions can be realized, and as a result, a chemically unstable material can be synthesized using the multiply charged ions.

On the other hand, in the thin film forming apparatus of the present invention, since the ionization rate of the plasma is extremely high as described above, the neutral sputter particles released from the target have a feature that the ionization rate in the plasma is high. The ionized target constituent elements are also accelerated by the potential of the target,
Further, the proportion of so-called self-sputtering that sputters the target becomes extremely large. That is, even if the gas for plasma generation (for example, Ar) is extremely dilute or is not used, the above-mentioned self-sputtering can be maintained, and as a result, ultra-high purity film formation can be realized.

Further, in the present invention, since the cylindrical coil with slit is used for exciting the microwave without using the conventional method of introducing the microwave from the waveguide through the microwave introducing window, the microwave introducing window which is a problem in the conventional type is used. It completely solves the instability of discharge due to cloudy weather, and has an excellent feature that metal and other conductive materials can be stably formed over an extremely long period of time.

In addition, in the present invention, the slit length of the above-mentioned slitted cylindrical coil can be efficiently realized by only matching the half-wavelength of the microwave used, so that the vacuum chamber can be resonated under conventional resonance conditions. Since it can be designed in any size without the need to adjust to, it has an extremely excellent feature that it can easily cope with both upsizing and downsizing.

Next, the result of forming an Al film using the device of the present invention will be described.

Example 1: After evacuating the vacuum degree in a vacuum chamber to 5 × 10 ⁻⁷ Torr in a symmetrical mirror magnetic field arrangement, Ar gas was introduced, and the gas pressure in the spatula portion was 2 × 10 ⁻⁴ Torr. Power 10
0-1000W, Al target applied voltage 300-1200V,
The film was formed under the condition of the mirror magnetic field gradient (875G / 20G). At this time, the cylindrical coil with slit and the substrate were arranged at the centers of the respective electromagnets, and the substrate was sputtered without being particularly heated.

At this time, a film could be formed efficiently at a deposition rate of 150 to 2200Å / min. As compared with the conventional sputter film, a good quality film could be stably formed without cracking or peeling.

On the other hand, the average energy of the ions at this time is 5eV to 30
Ions accounted for 10 to 30% of the particles that changed to eV and flew toward the substrate.

Embodiment 2 In the embodiment of the thin film forming apparatus of the present invention (FIG. 2), the degree of vacuum in the vacuum chamber is set by a complete divergent magnetic field arrangement (Bm = 875G, Bmo = 180G) in which no current flows through one electromagnet. 5x
After evacuating to 10 ^-7 Torr, Ar gas was introduced, and the gas pressure in the sputter part was set to 2.5 × 10 ^-4 Torr and the microwave power was 100 to 100 〜.
The film was formed under the conditions of 800 W, Al target applied voltage of 300 to 1200 V.

At this time, the cylindrical coil with slit and the substrate were arranged at the centers of the respective electromagnets, and the substrate was sputtered without being particularly heated.

At this time, a film could be formed efficiently and stably at a deposition rate of 200 to 2400Å / min. Since the internal stress of the film is smaller than that of the conventional sputtering film, a film having a thickness of 2 μm or more can be stably formed without causing cracking or peeling.

On the other hand, the average energy of the ions at this time is 5eV to 25eV.
10 to 30% of the particles that change up to the direction of the substrate
Was Ion.

The thin film forming apparatus of the present invention can be used not only for forming an Al film, but also for forming almost all thin films, and a reactive sputtering can be realized by using a reactive gas or a mixed gas thereof as an introduced gas. .

Further, the thin film forming apparatus of the present invention can be used without spattering the target, that is, by generating plasma while flowing the reaction gas or its mixed gas, the CV can be obtained.
It can also be used as a D device.

In addition, the thin film forming apparatus of the present invention can also be used as an ion limit, and several ions are extracted at the position of the substrate of this embodiment, and ions are selectively applied by applying a voltage to the grid. You can take it out.

〔The invention's effect〕

As described in detail above, the present invention uses the high-density microwave discharge under the electron cyclotron resonance condition in which a cylindrical coil with slits (a Ligitano coil) is used for plasma generation, and efficiently confines the plasma by a mirror magnetic field or an asymmetric magnetic field. Alternatively, by diverging the ions, the ions in the high-density plasma can be efficiently drawn into the target to realize a spatula. A plasma with high activity can be obtained at a low gas pressure, and it has an extremely high ionization rate compared to conventional sputter devices. Particles can be stably formed at a high speed in a low gas pressure, the energy of the particles can be freely controlled in a wide range from several eV to several hundred eV, and the energy is less dispersed. Since the thin film deposition equipment has this equipment, it is possible to use this equipment to obtain extremely high-purity, high-quality films with low damage at high substrate temperatures at high temperatures. Not only can it be formed with high speed and high efficiency and stability, but it is also possible to form a stable equilibrium material at low temperature, which could not be realized by the conventional method.

Further, in the present invention, a magnetic coil is used to obtain a mirror magnetic field or an asymmetric magnetic field. However, even if various permanent magnets are used or they are combined to form a mirror magnetic field or an asymmetric magnetic field, the same effect is obtained. It is clear that

[Brief description of drawings]

FIG. 1 is a block diagram of a thin film forming apparatus of the present invention, FIG. 2 is an embodiment of the thin film forming apparatus of the present invention, FIG. 3 is a magnetic field layout of the thin film forming apparatus of the present invention, and ions generated thereby. Movement (principle diagram), FIG. 4 is a block diagram of a 2-pole sputter device, FIG. 5 is a block diagram of a 3-pole sputter device, FIG. 6 is a block diagram of a magnetron sputter device, and FIG. 7 is a divergent magnetic field type spatter device. It is a block diagram of an apparatus or a CVD apparatus. 1 ... Target, 2 ... Substrate, 3 ... Electron emission third
Electrodes, 4 ... Vacuum chamber, 5 ... Magnet, 6 ... Plasma generator, 7 ... Microwave waveguide, 8 ... Electron cyclotron resonance electromagnet, 9 ... Microwave waveguide, 10 ... Cylindrical coil with slit (rigitano coil), 11 …… electromagnet, 12 …… sputter part, 13 …… substrate support part, 14 …… magnetic field line

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A 61-87869 (JP, A) JP-A 61-60881 (JP, A) JP-A 60-50167 (JP, A) Yoshinobu Kawai Applied Physics 54 (12) (1985) P. 1291-1292

Claims (1)

[Claims] 1. A thin film forming apparatus for forming a thin film of various materials on a sample substrate, comprising a vacuum chamber having a gas inlet having a plasma generating part, a sputter part, and a substrate supporting part, which are sequentially coupled, The generator includes a cylindrical coil with a slit as an exciter that causes electron cyclotron resonance and is connected to a microwave waveguide that introduces microwaves from a microwave source provided outside the vacuum chamber, and the plasma generator and The substrate supporting part is necessary for inducing electron cyclotron resonance at both outer ends of the vacuum chamber at positions where the slit-equipped cylindrical coil and the substrate arranged facing the slit-equipped cylindrical coil in the vacuum chamber are included. A pair of electromagnets that form a magnetic flux density and that form a mirror magnetic field or an asymmetric magnetic field gradient that minimizes the magnetic flux density in the sputter part are provided. , The sputter unit, a thin film forming apparatus characterized by comprising placing a Tagetsuto to sputter.