JPH06192829A - Thin film forming device - Google Patents

Abstract

PURPOSE:To suppress the generation of impurities and to easily and inexpensively produce high-purity thin films by using the sputtered particles generated in a sputtering chamber having a cooling wall and emitting these particles to a film forming chamber connected by a hole via this hole. CONSTITUTION:Gaseous Ar 10 is converted to plasma in the sputtering chamber 3 evacuated to a vacuum and opposite targets 1 are sputtered to generate the sputtered particles. On the other hand, the film forming chamber 7 is dispoosed adjacent to the sputtering chamber 3 and both chambers are connected by the hole 2. The sputtered particles mentioned above are emitted from the sputtering chamber 3 through the hole 2 to the film forming chamber 7 and are deposited on a substrate arranged there to form the thin films. A cooling means 4 consisting of the wall 6, etc., having the low-temp. surface connected to a liquid nitrogen reservoir 5 is disposed in the sputtering chamber 3 of the thin film forming device. As a result, the desorption of the impurities sticking to the wall is prevented and the effect of getter sputtering is enhanced. The formation of the thin films having the high purity and high quality is enabled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film forming apparatus for forming a high purity thin film.

[0002]

2. Description of the Related Art A thin film forming method utilizing a sputtering phenomenon of a glow discharge of a rare gas and a mixed gas of oxygen, nitrogen and the like has been widely used industrially and is also used for basic research. Came. Particles evaporated from the cathode surface (target) by sputtering can be expected to grow crystals that cannot be obtained by the vapor deposition method due to high kinetic energy. Further, in the vapor deposition method, since the vapor pressures of the raw materials are different, a multi-element thin film requires a sophisticated control device to obtain a desired composition, but the sputtering method is relatively easy.

[0003]

However, in spite of these advantages, the mechanism of sputtering has not been completely elucidated as compared with the vapor deposition method, and since discharge is used, high energy generated by plasma is generated. Ions and electrons collide with the wall of the vacuum chamber, and the Joule heat (usually several 100 W to several KW) generated by plasma is adsorbed on the walls of the vacuum chamber and other equipment such as H2 O, O2, N2 and C. Start tapping and pollute the vacuum. Therefore, in the present circumstances, it is usual that impurities of about several percent are mixed in the thin film, which is a big problem of the sputtering method.

As a countermeasure against this, an attempt is being made to produce a highly pure thin film by using an ultra-high vacuum device instead of a normal high-vacuum device to reduce adsorbed substances as much as possible and maintain clean discharge. However, the ultra-high vacuum device requires extremely expensive equipment and advanced technology, and its maintenance requires time and labor. Further, in order to obtain an ultrahigh vacuum, it is necessary that the vacuum chamber has a simple structure with a small surface area.

[0005]

The present invention has been made to solve the above-mentioned problems, and the thin film forming apparatus of the present invention can realize clean sputtering by a normal high vacuum technique. .

That is, according to the present invention, a sputter chamber having a coolable wall and a film forming chamber for forming a thin film are provided adjacent to each other, and sputtered particles generated by sputtering in the sputter chamber are transferred from the sputter chamber to the film forming chamber. The present invention provides a thin film production apparatus characterized in that an injection hole is provided and the sputtering chamber and the film formation chamber are connected by this hole.

The particles evaporated from the target by sputtering are in the form of atoms, molecules, or ions, and are chemically highly active. Therefore, when these sputtered particles collide with the above-mentioned impurities, they combine with them and are deposited on the walls of the sputtering chamber. This is called getter sputtering and has long been used for vacuum cleaning. However, since the plasma has high energy, impurities are strongly generated from the wall, and thus normal getter sputtering is not popular.

In order to obtain clean sputtering in a high vacuum, the following improvements can be considered. 1) Cool the walls of the sputtering chamber to suppress the generation of impurities. 2) A part of the particles evaporated in the sputtering chamber is injected into another vacuum chamber (film formation chamber) adjacent to the sputtering chamber through a hole of an appropriate size, and the film is formed at a higher degree of vacuum and in the absence of plasma. Form.

In 1), the sputtering chamber is cooled in order to further reduce the amount of impurities generated from the wall. The rate Vd of desorption of impurities adsorbed on the wall is Vd with respect to the temperature of the wall.
There is a relationship of ∝ exp (-D / T) (D: coefficient depending on the kind of adsorbate and wall, T: temperature). The temperature of the wall close to the plasma is usually about 100 ° C., and water cooling is thought to be about 40 to 50 ° C. However, assuming that this can be cooled to 0 ° C., the desorption amount is 1/3 to 1 / 4. Further, when it is cooled to -200 ° C by liquid nitrogen or the like, it becomes about 1/107, and the amount of desorption from the wall disappears. Therefore, in order to reduce the amount of desorption and enhance the effect of getter sputtering, it is preferable to cool to at least 0 ° C. or lower.

2) is a device for depositing the clean sputtered particles thus obtained on the substrate as a film in a cleaner vacuum chamber. 1) and 2) independently contribute to cleaning.

Further, in order to obtain cleaner sputtering, it is preferable to make the following improvements. 3) Use a magnetron target that applies a magnetic field horizontally to the cathode (target) surface, or an opposed target that uses two cathodes (targets) to speed up the sputtering and increase the getter action several times to several tens of times. Raise to. 4) By reducing the size of the sputtering chamber, the surface area in the vacuum chamber is reduced and the rate of impurity generation is reduced.

In 3), the sputtering is sped up to increase the number of collisions with impurities and obtain a cleaner plasma. In 4), the vacuum chamber itself is made small in order to reduce the amount of impurities generated from the wall.

[0013]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a schematic sectional view of an example of the device of the present invention. Reference numeral 1 is a facing target for increasing the sputtering speed in 3). Electric discharge occurs between the upper and lower flat plate targets, and high-speed sputtering occurs on the target surface. However, for the purpose of 2), a hole is provided in the center of the lower target, which is different from the normal facing target. (In the present invention, an ordinary opposed target may be used.)

Reference numeral 3 denotes a sputtering chamber which is made small for the purpose of 4). Reference numeral 4 is a cooling means for cooling liquid nitrogen in 1) with a liquid nitrogen reservoir 5 in the sputtering chamber and a wall 6 having a low temperature surface. Reference numeral 7 denotes a film forming chamber for forming a film by the sputtered particles ejected from the hole 2. The vacuum pump 9 having a large exhaust amount exhausts up to 10 −8 Torr level, and its cleanliness is always controlled by the mass spectrometer 8. It Reference numeral 11 is a substrate on which a film is formed.

The film was formed as follows. First, an iron target was placed in the sputtering chamber 3, and the sputtering chamber and the film forming chamber were evacuated by the vacuum pump 9, respectively. The ultimate vacuum was 2 × 10 −7 Torr in the sputtering chamber and 5 × 10 −8 Torr in the film forming chamber. Next, Ar gas 10 was introduced to start sputtering. H2O, N2, O2 generated by sputtering in the film forming chamber at the start of sputtering
The partial pressures of 4 × 10 -8 Torr and 9 × 10 -9 T, respectively
Orr was around 6 × 10 -9 Torr.

FIG. 2 shows the results of measuring the crystal grain size of the produced iron thin film sample by X-ray diffraction and examining the relationship between the substrate temperature (Ts) and the heat treatment temperature (Ta) during film formation.
For comparison, FIGS. 2 to 4 show the measurement results (R of the sample by a normal sputtering device (radio frequency (RF) sputtering device)).
(Denoted as F). As is clear from FIG. 2, the sample according to the present invention has a large crystal even as it is manufactured, and it is understood that a further rapid crystal growth occurs due to the heat treatment. This indicates that the crystal growth is less suppressed by impurities in iron.

FIG. 3 shows the electric resistance ρ (mΩ ·
cm) is the result of measurement. In general, the electric resistance of a thin film increases when there are impurities in the film, irregularity of crystal grain boundaries due to the impurities, defects in the crystal, and the like, and does not decrease even at low temperatures. The sample of the present invention in FIG. 3 has a size of about 1.4 times that of pure iron at 300K, and the decrease at a low temperature is remarkable.
The results show that crystals with high purity and high quality are growing. On the other hand, RF (comparative example) in the figure shows electric resistance several times higher, and does not decrease even at low temperatures.

FIG. 4 shows the coercive force (Hc
, Unit Oe) shows the change due to heat treatment. In general, the coercive force Hc becomes a low value of 1 (Oe) or less after the heat treatment for removing strain in a normal iron plate or the like which is not a thin film, but in the thin film, the grain boundary is irregular, defects in the crystal or slight crystal growth causes It is known that complicated distortion is introduced and increases up to several tens (Oe). However, in FIG.
It has fallen to about (Oe). On the other hand, the film (indicated by RF) formed by the ordinary sputtering apparatus shows a complicated change due to the heat treatment as expected, and the value is also large.

Further, in FIG. 1, when a thin film is formed in the film forming chamber 7 without using the cooling means 4 and when the substrate is placed in the sputtering chamber 3 by cooling using the cooling means 4. When a thin film was formed, both showed remarkable crystal growth as compared with the sample by the ordinary sputtering device.
The best quality thin film was obtained when the thin film was formed in the film forming chamber 7 while being cooled by the cooling means 4 as in the above experiment. That is, it was found that the above 1) and 2) have individual effects, but when they are combined, more remarkable effects are obtained.

[0020]

As described above, according to the present invention, the generation of impurities is suppressed by cooling the wall of the sputter chamber, and a part of the particles evaporated in the sputter chamber is separated from another part adjacent to the sputter chamber. High-purity and high-quality crystals can be grown by injecting into a vacuum chamber (film formation chamber) through holes of appropriate size and forming a film in a higher vacuum and in the absence of plasma. In addition, there is an effect of reducing distortion due to irregularities of crystal grain boundaries, defects in crystals, and the like, and time and labor for maintaining and managing the device can also be reduced. Therefore, the thin film characteristics can be improved at low cost, and the present invention has great industrial value.

[Brief description of drawings]

1 is a conceptual cross-sectional view of the device of the present invention.

FIG. 2 is a graph showing crystal grain size heat treatment temperature dependence of an iron thin film formed according to the present invention.

FIG. 3 is a graph showing temperature dependence of electric resistance in an iron thin film formed by the present invention.

FIG. 4 is a graph showing the heat treatment temperature dependence of the coercive force of the iron thin film formed by the present invention.

[Explanation of symbols]

 1: Opposite target 2: Hole 3: Sputtering chamber 4: Cooling means 5: Liquid nitrogen reservoir 6: Wall with low temperature surface 7: Film forming chamber 8: Mass spectrometer 9: Vacuum pump 10: Ar gas 11: Substrate

Claims (3)

[Claims] 1. A hole in which a sputter chamber having a coolable wall and a film forming chamber for forming a thin film are provided adjacent to each other, and sputter particles generated by sputtering in the sputter chamber are ejected from the sputter chamber to the film forming chamber. The thin film forming apparatus is characterized in that the sputtering chamber and the film forming chamber are connected by this hole. 2. A sputtering chamber and a film forming chamber for forming a thin film are provided adjacent to each other, and a hole is provided through which sputtered particles generated by sputtering in the sputtering chamber are ejected from the sputtering chamber to the film forming chamber. A thin film forming apparatus characterized by connecting a sputtering chamber and a film forming chamber. 3. A thin film forming apparatus having a sputtering chamber having a coolable wall.