JPH0469984A - superconducting element - Google Patents

Abstract

PURPOSE:To improve yield and to obtain an oxide superconducting element having high reproducibility and high integration by miniaturizing the element to be miniaturized at the same position by a focused ion beam in an ultrahigh vacuum state therefor. CONSTITUTION:A superconducting thin film 20 is formed in an MBE chamber, and three elements are simultaneously deposited by K-cell by using metals of yttrium 10, barium 11 and copper 12 as substances to be deposited. Then, the film is transferred into an FIBE device 2 evacuated in vacuum to pressure of the same degree as that in the chamber by opening a valve 7, and miniaturized. The miniaturization is conducted by using Au<+> ions of 130keV of beam energy and forming source and drain electrodes in size of 10mum square. After the miniaturization is finished, the valve 7 is opened, a substrate is overturned, returned to the MBE device, and an insulting layer of AlOy 18 is formed. Then, the K-cell is used as a gate electrode 19, and Ag 13 is deposited.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to superconducting devices.

[Conventional technology]

In order to fabricate highly integrated superconducting devices, microfabrication technology is almost always required, just as in the case of semiconductor devices.

In the conventional microfabrication process for producing oxide superconducting elements, film formation and microfabrication are performed independently.

That is, after the layer is formed, the film is taken out from the completed film and subjected to microfabrication. For example, in the fabrication of oxide superconducting transistors as described in "IEICE Technical Research Report", Vol. 88, No. 146, 1988, pages 47-52, a superconducting thin film is formed and removed from the film forming chamber. microfabricated using A, and then A for forming source and drain electrodes on top of it.
g is vapor-deposited, taken out again, and microfabricated. Further, to form a gate electrode, Al is deposited and taken out for fine processing.

In addition, microfabrication technology for oxide superconducting thin film layers involves taking the film out of the deposition chamber after forming the superconducting thin film, for example, "JAp
ANEsEJOURNAL OF A, PPL Engineering EDF
HYS Engineering O3J, Volume 26, No. 9, 1987 L15
Phosphoric acid (H,
P 04-) Wet process using solution or “JAPANKSE JOURNAL 0FAPPL
Engineering ED PEYSICsJ, Volume 27, No. 8, 198
Ion beam etching as described on pages L1521 to L1525 (hereinafter abbreviated as E)
Microfabricated using a dry process. In the wet process, in addition to H5po4, hydrochloric acid (HC engineering), nitric acid (uNp3), sulfuric acid (HzSO+) solutions, etc. are used, and in the dry process, in addition to E, ion implantation is used.

Laser etching, reactive ion etching (RE
), focused ion beam etching (from V to E), etc. are used.

[Problem to be solved by the invention]

However, in the conventional microfabrication for fabricating oxide superconducting electrons as described above, each layer is deposited and removed each time, making the process complicated. Furthermore, exposure to the atmosphere contaminates the surface of the film, and at the same time, oxide superconductors are sensitive to moisture, and even a small amount of moisture can cause their properties to deteriorate, especially after microfabrication, as the surface area increases. The impact is significant. Therefore, there is a problem that reproducibility and yield are poor.

Regarding microfabrication of oxide superconducting thin films, unlike the other methods mentioned above, ion implantation and F to E require patterning and
Since it does not require a mask, it is advantageous in that there is no contamination of the film surface by the resist.Furthermore, it is possible to miniaturize to the submicron order in F/EE and ion implantation, making it possible to return highly integrated elements. I can do it. However, even if contamination by the resist can be prevented, if the film is exposed to the atmosphere for microfabrication after film formation, the surface may be contaminated by the atmosphere and the characteristics may deteriorate due to moisture, as described above. Therefore, there is a problem in obtaining stable reproducibility and yield.

Therefore, the present invention is intended to solve these conventional problems.The purpose of the present invention is to perform microfabrication on the spot after forming a thin film without exposing it to the atmosphere, and to repeat this process to improve yield and further reproducibility. The object of the present invention is to provide a highly integrated oxide superconducting element with good performance.

[Means to solve the problem]

The superconducting element of the present invention does not expose the oxide superconducting thin film to the atmosphere (in a superconducting element manufactured by continuous in-situ microfabrication, the in-situ microfabrication is performed using a focused ion beam in an ultra-high vacuum state). It is characterized by

〔Example〕

Examples of the present invention will be described below.

FIG. 1 is a diagram showing an apparatus in which a thin film production apparatus and a microfabrication apparatus are combined via a conveyance path 50, which is an embodiment of the present invention. Molecular beam epitaxy (hereinafter abbreviated as MBE) 1 is used as a thin film production device, and a focused ion beam device 2 without a patterning mask is used as a microfabrication device.
Use. Since this is a clean process that does not use a resist, it can be easily combined with high vacuum crystal growth techniques such as MBK. Further, each device is equipped with a vacuum pump 3, and the E device can be isolated from the MBE device and F by a load lock system and evacuated separately, and the conveyance path can also be kept in a vacuum state.

FIG. 2 shows an example of a superconducting field effect transistor (hereinafter abbreviated as 5UFET) in which the source 16 and drain electrode 17 are made of oxide superconductors, which is an example fabricated using this apparatus.

) is shown. FIG. 6 shows the manufacturing process. The crystal substrate 15 must be a semiconductor and one on which an oxide superconductor can easily grow epitaxially. It is known that strontium titanate is easily epitaxially grown as an oxide superconductor, and can be turned into an n-type semiconductor by adding a group V element such as niobium (Hb). Therefore, a single crystal (IOO) of 5rTiO is used as a crystal substrate, and niobium ions (Nb+) are implanted and diffused to convert it into a semiconductor. As an oxide superconductor, Rin crystal is easily obtained YB
a2 C! Use u30y.

First, in FIG. 5(α), a superconducting thin film 20 is formed in an MBm chamber. At this time, the initial degree of vacuum in the chamber is around 10-1 Torr. Yttrium (y) 1o and barium (Ea) 111 as vapor deposition substances
Steel (cu) 12 metals are used for each -(1! eLL
Three-dimensional simultaneous vapor deposition is performed. Since the inside of the chamber is in a high vacuum state, oxygen is efficiently introduced into the film (in order to enter the film, active oxygen is supplied near the substrate by Et? plasma 8. At this time, the film thickness is 1000 mm). The surface of the thin film is very smooth and is grown epitaxially in the C-axis direction.

Next, the pulp 7 is evacuated to the same pressure as in the MEE chamber. The FE equipment is evacuated (this saves time compared to performing film formation and microfabrication separately. For movement, use a transport bar whose tip is structured to hold the substrate holder). 31 for each substrate holder.

At this time, turn over the board together with the board holder. The substrate holder is common to both the MBE device and the FEE device, and has a structure that allows the substrate to be held therein, so that the substrate will not fall out even if it is turned over. After conveyance, the pulp 7 is closed.

The beam energy for microfabrication of superconducting thin films is 160Ke.
Using Au+ ions of V, the source and drain electrodes are each 10 μm square in size. Naturally, patterning is carried out.
I don't use your credit card. Since it is a high vacuum process, Au+
Ion operates stably and can be used for a long time.

After the microfabrication is completed, open the pulp 7 again and turn the substrate over for MBI.
Return it to the IC device. A10y shown in Figure 5(C)
Form an insulating layer of is. First, a metal mask 21 is introduced directly under the substrate, and A19 is placed in a 50mm increments using K-Cell.
Deposit. The rotation speed of the mask and substrate should be the same. Since the molecular beams fly in parallel, there is almost no wraparound to other parts. This is sufficiently oxidized in oxygen plasma to obtain an Al0y insulating layer. Next, in FIG. 5Cd), K-Oe 11 is used as the gate electrode 19 in the shape shown in the figure.
Deposit gl 5. At this time, the film thickness is 1000 mm. Note that before vapor deposition, the metal mask 22 was replaced in vacuum for forming the gate electrode.

When fabricated using the above method, the conventional yield was about 50%, but the yield was as high as 80%. Therefore, it is possible to highly integrate the device size to several μm.The example mentioned here is just one example, and other than 5UFET and SQU
Than.

It can also be applied to various superconducting devices such as weakly coupled Josephson junction devices and superconducting wiring.

〔Effect of the invention〕

As described above, according to the present invention, by continuously performing in-situ microfabrication after forming a thin film without exposing it to the atmosphere, yield can be improved and reproducibility can be improved (highly integrated superconducting elements can be provided). In addition, the time can be reduced compared to when film formation and microfabrication are performed independently.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an apparatus in which a thin film production apparatus and a microfabrication apparatus are combined via a conveyance path, which is an embodiment for producing a superconducting element of the present invention. FIG. 2 is a sectional view of a superconducting field effect transistor that is an embodiment of the present invention. FIG. 3 is a diagram showing the manufacturing process of the superconducting field effect transistor shown in FIG. 2. 1......MBE device 2...F to E device 3...Vacuum pump 4...Crystal substrate 5...Metal mask 6...Shutter 7...Pulp 8...RF plasma 9... ...A1 and -Cθ1110...
・・・・・・Ytoniichi0el111・・・・・・・・・B
a and K -Oe 'l 112・・・・・・・・・Ou
and K -Os 1115...A, g and K -Oe 1114... Ion source 5... S r T made into a semiconductor i
0゜6......Source electrode 7...Drain electrode 8...A10y Insulating layer 9...Al Gate electrode 0... Oxide superconducting thin film 1...
・・・Metal mask for insulating layer 2・・・・・・Metal mask for gate electrode 0・・・・・・Transport path 1・・・・・・Transport bar Applicant Seiko Epson Co., Ltd. Agent Patent Attorney Kizobe Suzuki (and 1 other person) Figure 7 Figure 2/. ／ ＼

Claims (1)

[Claims] A superconducting device manufactured by continuous in-situ microfabrication of an oxide superconducting thin film without exposing it to the atmosphere, characterized in that the in-situ microfabrication is performed using a focused ion beam in an ultra-high vacuum state. superconducting element.