JPH0196890A - Magnetic bubble memory element - Google Patents

Abstract

PURPOSE:To prevent the generation of a local unevenness in implanting an ion by forming an ion implanting layer of a magnetic bubble transfer path on a magnetic film by combining the ion driving with the irradiation of an electron. CONSTITUTION:A positive electric charge driving ion from an ion source via a mass analyzer tube 6 is driven on the magnetic bubble film 1. At such a time, the film 1 is irradiated by a secondary electron 11 based on a primary electron 9 from an electron source 8 to neutralize a stored positive electric charge by implanting the ion 7. Accordingly, the charge of the film 1 is prevented to prevent the generation of the local unevenness in implanting the ion and have good magnetic bubble transfer characteristic having no unevenness.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an ion implantation type magnetic bubble memory device, and particularly to the formation of transfer paths in a high-density ion implantation magnetic bubble device using a fine mask pattern. The present invention relates to a suitable method for forming an ion implantation layer.

[Conventional technology]

A magnetic bubble memory device (hereinafter referred to as an ion implantation device) using a conventional ion implantation method is disclosed in U.S. Pat.
As described in No. 828,329, a mask pattern is formed on the surface of the magnetic film using a polymer resin (photoresist) or a metal film, and ions are implanted into the surface of the magnetic film to create a transfer path for magnetic bubbles (ion implantation layer). It is configured to form a The magnetic film that holds the magnetic bubbles is usually a garnet crystal and is an insulator. In the ion implantation device, ions are implanted into the surface of the bubble garnet film to induce strain, and the magnetization of the ion implanted part is switched in the in-plane direction of the film using the magnetostrictive effect of the magnetic material. to form a driving layer for magnetic bubbles. Therefore, the properties of the ion-implanted layer, such as the shape of the strain depth distribution and the uniformity of the strain, are important parameters that greatly influence the operating characteristics of the magnetic bubble.

[Problem that the invention seeks to solve]

As mentioned above, since bubble garnet crystal is an insulator, when ions are implanted, charging occurs due to the accumulation of charges.

If this phenomenon is significant, the dielectric breakdown voltage of the substrate crystal is exceeded, causing dielectric breakdown or cracking of the substrate.

Therefore, in order to lower the potential of the wafer surface during ion implantation, methods have been taken such as mechanically grounding the wafer surface or using a conductive material in the ion implantation mask pattern.

However, even if such conventional charging rainproofing methods are used, they are less effective against local charging when the period of the ion implantation transfer path becomes small, and local non-uniformity in the properties of the ion implantation layer may occur. will occur. As a result, when attempting to increase the tolerance of memory devices, variations in the operating characteristics of the devices due to non-uniformity of strain occur, which poses a major problem.

In the above-mentioned conventional technology, when implanting ions into a magnetic film that can hold magnetic bubbles, no consideration is given to charging due to accumulation of ffi charges, and local non-uniformity of ion implantation occurs as a result of this charging. (Unevenness in implantation depth, nonuniformity in strained layer due to insufficient dose)
There was a problem in that element characteristics varied (there were parts where malfunctions occurred in the transfer of magnetic bubbles and parts where they did not).

The purpose of the present invention is to eliminate the local non-uniformity of the ion implantation layer due to the accumulation of charge caused by ion implantation, and to create a high-density layer with good reproducibility and no variation in the operating characteristics of magnetic bubbles. An object of the present invention is to provide an ion implantation type magnetic bubble memory device.

[Means for solving problems]

The above purpose is to simultaneously implant positively charged ions and irradiate negatively charged electrons (-secondary electrons, secondary electrons) into a magnetic film in the process of forming a magnetic bubble driving layer, that is, an ion implantation layer. This is achieved by

That is, implantation of positively charged ions.

The ion implantation forms a strained layer, and the irradiation with negatively charged electrons neutralizes the charging caused by the accumulation of positive charges, thereby preventing charging in the ion implantation layer formed in the magnetic film, that is, the driving layer of the magnetic bubble. This solves the problem of variations in transfer characteristics caused by local non-uniformity of ion implantation.

[Effect]

The implantation of positively charged ions having mass acts to form a strained layer, that is, an in-plane magnetized layer for driving magnetic bubbles by the magnetostrictive effect of the magnetic material. The irradiation with massless, negatively charged electrons acts to neutralize the charges of the positively charged ion-implanted layer.

At this time, the electron irradiation may be performed by directly scanning and irradiating the surface of the magnetic film with electrons in synchronization with the implantation of positively charged ions (-secondary electron irradiation).

Alternatively, when positively charged ions are implanted, electrons are irradiated to a second object other than the magnetic film (substrate wafer) near the surface of the magnetic film, and the secondary electrons generated by the irradiation effect on this object are indirectly The surface of the magnetic film may also be irradiated (secondary electron irradiation).

The secondary electrons generated here have no directionality, but when the surface of the magnetic film becomes positively charged by implanting positively charged ions,
Negatively charged secondary electrons are attracted to this positive charge and act to neutralize the charge of the positively charged ion implantation layer.

The neutralizing effect of electron irradiation as described above prevents charge accumulation in the driving layer of the magnetic bubble, that is, the ion implantation layer, and therefore malfunction of the magnetic bubble due to local nonuniformity of ion implantation occurs. It disappears.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. The diameter of the magnetic bubble is about 1 μm (YSrrrLu
A photoresist, a metal film, or S
An ion implantation mask pattern 2 for forming an ion implantation transfer path is formed using an iOx film or a Si film. Next, a magnetic bubble driving layer, ie, an ion implantation layer 3, is formed by a combination of ion implantation and electron irradiation. Ions 7 for forming a strained layer on the magnetic bubble film are generated by an ion source 5.

Here, impurity ions are removed using a mass spectrometer tube 6,
Desired implant ions 7 are selected. The conditions for ion implantation into the magnetic bubble film 1 at this time are 50KeV/], 3X
101B・Hz+/ffl and 68KeV/3.5X
This is a double implant of 10 k'-Hz+/a#.

The implanted ions 7 are scanned so as to cover the entire surface of the magnetic bubble film 1. In parallel with this H2+ ion implantation, the electron source 8 generates primary electrons 9, and the negative electrons are transferred to the second object 10 in the vicinity of the magnetic bubble film 1. For example, the inner wall of an ion implantation device, a Si substrate, or a conductor plate such as AQ or stainless steel is irradiated. Due to the irradiation effect of this negative electron, the second
A secondary child 11 is generated from the object 10. This secondary electron 1
Since the magnetic bubble film 1 has no directionality, it floats near the surface of the magnetic bubble film 1 where ions are implanted. Here, since the electrical property of the magnetic bubble film 1 described above is that of an insulator, the ion implantation layer 3 becomes charged as a positively charged VS stack 12 during the progress of ion implantation. When this charging occurs, the secondary electrons 11 floating in the vicinity of the surface of the magnetic bubble film are attracted to the positive charge storage portion and neutralize the positive charges. In this way, the ion-implanted layer 3 is formed by repeating a slight charge that attracts the secondary electrons 11 and neutralization by the secondary electrons 11. As a result, the dielectric strength of the magnetic bubble film 1 is not exceeded.
H2+ ion implantation on the order of 016 to 1017/d can be performed. In addition, since the secondary electrons 11 have no directionality,
It is also possible to neutralize local charging that occurs depending on the ion implantation mask pattern shape 2 on the surface of the magnetic bubble film 1, and to form an extremely uniform ion implantation layer, that is, a magnetic bubble driving layer. It becomes possible.

In addition, before the formation of the mask pattern 2 described above or after ion implantation/removal of the mask pattern, in order to suppress abnormal bubbles, the entire surface of the magnetic bubble film was coated.

1×10 H2+ ions accelerated at 25 K e V
By simultaneously implanting secondary electrons 11 at a dose of 16/d,
Forming an ion implantation element.

FIG. 3 represents another embodiment of the invention. The magnetic baffle film 1 is equipped with an ion source 5 for forming an ion implantation layer and an electron source 8 for performing electron irradiation in a dual system.
The accumulation layer of positively charged ions generated on the surface is forcibly irradiated with electrons while scanning to neutralize it and form an ion implantation magnetic bubble transfer path.

Next, the charge accumulation phenomenon in the conventional ion implantation transfer path forming method for devices will be explained, and the effects of the present invention will be described.

FIG. 4 shows a schematic diagram of conventional ion implantation transfer path formation. In the minor loop where the ion implantation transfer paths serve as a storage section for periodically arranged information, the ion implantation layer 3 is uniformly and positively charged on average by implanted ions having positive charges.

Therefore, in this case, non-uniformity in ion implantation does not occur. However, other than such a minor loop, for example, a major line section for configuring a functional section such as writing and reading information,
Alternatively, in a gate operating portion such as a connection portion as seen in a permalloy/ion implantation composite magnetic bubble memory element, there are portions that differ in size in the area into which ions are implanted, that is, the area of the ion implantation layer. For this reason, a strong positive charge accumulation layer 14 is formed in the wide ion implantation layer 13 compared to other parts, and as a result, the ion implantation is performed locally as shown in FIG. This results in significant heterogeneity. That is, in the minor loop part, the ion implantation transfer path which had a --like strain distribution shape 15 in the depth direction (FIG. 5(b)) has a large area,
Segmented shape 16 with small distortion due to strong positive charge storage layer 14
(Fig. 5 (C)), or shallow strain distribution shape 17 (
As shown in FIG. 5(d), an ion implantation transfer path having non-uniform ion implantation (the shape of the strain distribution is different) is formed.

This phenomenon occurs because, as shown in Fig. 6, the scanned ions 18 become ions 19 that are inhibited by charging due to the strong positive charge accumulation layer, and the ion dose in this region is reduced. This is caused by a decrease in the acceleration voltage or a drop in the acceleration voltage.

Due to the above-mentioned phenomenon, that is, local non-uniformity of the strain distribution shape in the ion implantation transfer path, in conventional elements, the operating characteristics of the magnetic bubbles vary.

The ion implantation magnetic bubble transfer path using the ion/electron neutralization implantation method of the present invention eliminates such local non-uniformity in the shape of strain distribution, and provides high-density transmission with extremely high reproducibility and no variation in device characteristics. There is an effect that an ion implantation element can be formed.

Furthermore, since there is no change in the local strain distribution shape caused by electrification, as in the case of conventional methods, there is no malfunction in the transfer characteristics of magnetic bubbles, and an ion implantation element with very small variation in operating characteristics can be formed. There is.

Here, the effects described above can be expressed quantitatively as shown in FIG. In other words, in conventional devices, the operating bias magnetic field margin of the magnetic bubbles (the allowable fluctuation range of the bias magnetic field for normal operation) varied widely, but in the device using neutralizing ion implantation of the present invention, the margin width is extremely large. This has the effect of realizing uniform memory index characteristics.

〔Effect of the invention〕

According to the present invention, by neutralizing ion implantation using electron irradiation, it is possible to prevent the magnetic bubble film, which is an insulating substrate, from being charged due to local accumulation of positive charges during ion implantation. The ion implantation has the effect of forming a magnetic bubble path.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an ion implantation device using an ion/electron neutralization implantation method according to an embodiment of the present invention, FIG. 2 is an enlarged view of a part of FIG. 1, and FIG. Another example of electron irradiation type ion implantation transfer is a schematic diagram of the transfer path, No. 4V is a diagram showing the charging layer on the surface of the magnetic bubble film of the prior art, and FIG. 5 is the result of charging in the same manner as in FIG. FIG. 3 is a diagram showing the non-uniformity of strain distribution shape. FIG. 6 is a diagram schematically showing the phenomenon of non-uniformity in FIG. 5, and FIG. 7 is a diagram showing the operating bias magnetic field margin of an element in which variations in operating characteristics are reduced by the effects of the present invention. DESCRIPTION OF SYMBOLS 1... Magnetic bubble film, 2... Ion implantation mask pattern, 3... Ion implantation layer, 4... Whole surface ion implantation layer, 5... Ion source, 6... Mass spectrometry tube, 7
...Implanted ions, 8.Electron source, 9.-secondary electrons, 10.Second object, 11.Secondary electrons, 12.
...Positive charge storage layer, 13...Wide ion implantation layer, 1
4... Strong positive charge storage layer, 15... Strain distribution shape,
16... Distribution shape of small strain, 17... Distribution shape of shallow strain, 18... Scanning ion, 19... Ion inhibited by charging, 20... Normal operation bias magnetic field width of magnetic bubble .

Claims (1)

[Claims] 1. In a magnetic bubble memory element having a magnetic bubble transfer circuit comprising an ion implantation layer on the surface of a magnetic film capable of holding magnetic bubbles, the ion implantation layer is a combination of ion implantation and electron irradiation. A magnetic bubble memory element characterized in that it is formed by. 2. Claim 1 is characterized in that the ion implantation layer on the entire surface of the magnetic film for suppressing abnormal bubble generation is formed by a combination of the ion implantation and the electron irradiation. Magnetic bubble memory element. 3. A magnetic bubble memory according to claim 1, characterized in that the implanted ions are H+, H_2+, D+, and D_2+.