JP3021601B2 - MgO target - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an MgO target, and more particularly to an MgO target used for sputtering an underlying MgO film of a superconducting thin film.

[Prior Art] With the discovery of a Y-Ba-Cu-O-based high-temperature superconductor in 1986, research on a normal-temperature superconductor has been advanced, and as a part thereof, thinning of the superconductor has been studied. As a substrate for a superconducting thin film, MgO having a similar lattice constant is promising, but since single-crystal MgO is expensive, a crystalline MgO film is formed on a substrate such as Si,
It is practical to epitaxially grow a superconducting thin film on this.

The inventor sintered light-burned MgO as a target, and formed an MgO thin film by RF sputtering. The obtained thin film was amorphous (FIG. 4). Light burned MgO was used because it has high sinterability and it is easy to obtain a dense target. The relative density of the target used was 99%, the pores and specific surface area were small, and impurities such as adsorbed water should be small. Crystalline Mg from the viewpoint of dense and low impurities
O thin films should be easy to obtain, but the results were disappointing. The inventor sintered MgO clinker powder instead of lightly burned MgO and used it as a target, but again only an amorphous MgO thin film was obtained.

When a single crystal MgO target is used instead of lightly burned MgO, (2,
A thin film oriented in the (0,0) direction was obtained (FIG. 3). The crystallinity of the target and the crystallinity of the sputtering film should be originally unrelated. However, when the target is a single crystal, a crystalline MgO thin film is obtained, and the reason why the crystallinity of the target is related to the crystallinity of the sputtering film is unknown.

The inventor has proposed electrofusion as an alternative to single crystal targets.
MgO powder was sintered and used as a target. We focused on electrofused MgO because it is a material similar to a single crystal in that crystal growth is progressing. However, fused MgO has low sinterability and a relative density of 7
Only about 0% was obtained. Further, since electro-fused MgO is produced using arc discharge, the purity of the metal component is not high, and the purity of the metal component is lower than that of lightly burned MgO. In view of the low purity of the metal component, the large number of pores, and the large amount of adsorbed impurities, electrofused MgO is not a preferred target material.
However, when MgO was used as the target, an MgO thin film having the same crystallinity as the single crystal target was obtained. That is, also in this case, the relationship between the crystallinity of the target and the crystallinity of the obtained thin film was maintained.

[Problem of the Invention] An object of the present invention is to provide an MgO target that can easily produce a highly crystalline MgO thin film with an inexpensive material.

[Constitution of the Invention] In the present invention, an MgO target is prepared by using at least 60 wt% of the MgO component as electrofused MgO. Using this target,
The high-frequency sputtered MgO film is oriented in the (2,0,0) direction, and the crystallinity is the same as when a single-crystal MgO target is used. When the content of electrofused MgO is 70 wt% and 50 wt%, there is a large difference in the crystallinity of the obtained films. At 70 wt%, a thin film equivalent to a single crystal MgO target is obtained, and at 50 wt%, the peak intensity and the X-ray diffraction The half width decreases. From this, electrofused MgO
The minimum content was 60 wt%.

[Example] An electro-fused MgO powder (purity of about 99%) of 100 mesh over with a 50 mesh pass was mixed with light-burned MgO having an average particle size of 5.6 µm, and 700 Kgw / cm on a disk having a thickness of 10 mm and a diameter of 60 mm. ^It was press-molded in ² and sintered in air at 1700 ° C. for 1 hour. The particle size of the electrofused MgO as a main component is suitably about 20 to 200 mesh from the viewpoint of powder engineering. When the material has a mesh size of 20 mesh or more, the sinterability is low. The lightly burned MgO component is a crystallization agent for the target, and it can be changed to MgO clinker (magnesium hydroxide or magnesium carbonate sintered at about 1600 ° C) or electro-fused MgO pulverized to a particle size of 10 μm or less. good. If the particle size of the sintering agent exceeds 10 μm, the sinterability is reduced. Therefore, the particle size of the sintering agent is preferably 10 μm or less. The particle size of the main component of fused MgO is preferably 20 mesh to 200 mesh, and the particle size of the sintering agent is preferably 10 μm or less.
It is preferable that a part of O is pulverized to a particle size of 10 μm or less.

Using the obtained sintered body as a target, the substrate holder temperature was 150 ° C, the high-frequency power was 200 W, and the sputtering atmosphere was A.
High frequency sputtering was performed on the silicon substrate at a pressure of 20 mTorr and a flow rate of 15 scc / min at r. Ion beam sputtering may be used instead of high frequency sputtering, and the substrate may be sapphire, quartz, etc. in addition to silicon.
In addition to Ar, Xe or N ₂ may be used. However, the introduction of O ₂ into the atmosphere reduced the crystallinity of the sputtered film. The temperature of the substrate holder is 100 ° C, for example, to prevent water adsorption.
It is preferable to make the above.

Table 1 shows the relationship between the target composition used and the crystallinity in the (2,0,0) direction. Also, electrofused MgO 90wt% and lightly burned MgO 10wt%
Fig. 1 shows the X-ray diffraction pattern of the (2,0,0) peak with the target of Fig. 1. Fig. 2 shows the X-ray diffraction patterns of 50wt% of fused MgO and 50wt% of lightly burned MgO. The pattern is shown in FIG. 3, and the X-ray diffraction pattern with the 100% lightly burned MgO target is shown in FIG.

When a crystalline MgO thin film was obtained, MgO was oriented in the (2,0,0) direction, and X-ray diffraction peaks in other directions were not obtained. No cracks were found in the crystalline MgO film by observation with an electron microscope, and the film surface was a mirror-finished and entirely uniform film. These facts indicate that the crystalline MgO film manufactured using the electro-fused MgO target is a film oriented in the (2,0,0) direction and is suitable as a base for epitaxial growth. When examining the target materials, an MgO thin film with a strong orientation in the (2,0,0) direction was obtained with a fused MgO 90 wt% or single crystal MgO target. On the other hand, when light burned MgO is 100%, an amorphous thin film is obtained.
Even when the substrate holder temperature was changed from room temperature to 300 ° C., a crystalline thin film was not obtained. A thin film equivalent to a single crystal target can be obtained with 70% by weight of fused MgO, but 50% by weight.
Thus, a film having reduced crystallinity is obtained. For this reason, the content of electrofused MgO in the target is preferably 60% or more. Other than this, the target was adjusted by sintering at 1700 ° C by changing the lightly burned MgO to MgO clinker (average particle size 9 μm). 7
When the content was 0 wt% or more, a thin film equivalent to the single crystal target was obtained.

[Effects of the Invention] According to the present invention, a target is obtained, which contains inexpensive electrofused MgO as a main component and can provide an MgO thin film having high crystallinity. Although the target of the present invention is generally porous and the purity of the metal component is not high, an MgO thin film having high crystallinity can nevertheless be obtained.

[Brief description of the drawings]

FIG. 1 is an X-ray diffraction diagram of an MgO thin film using a sintered target of fused MgO of 90% by weight and lightly burned MgO of 10% by weight, and FIG. X-ray diffraction diagram of a MgO thin film using a conventional single crystal MgO target, FIG. 3 shows an X-ray diffraction diagram of a MgO thin film using a conventional single crystal MgO target, and FIG.
It is an X-ray diffraction diagram of a thin film.

────────────────────────────────────────────────── ─── Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C23C 14/00-14/58 C30B 29/22 C04B 35 / 00,35 / 04 H01L 39/24 JOIS

Claims (1)

(57) [Claims] 1. An MgO wherein at least 60 wt% of the MgO is electrofused MgO.
target.