JPS5823671B2 - Bubble domain device manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to continuous transfer (propagation).
n) method of manufacturing a bubble domain device with an element, more specifically, the size of the cell is determined by the loss point (
cusp), but rather by the mask-to-bump alignment accuracy during sequential exposures through the mask.

Magnetic bubble domain devices using contiguous transfer elements are well known in the art and can be understood, for example, by reference to US Pat. No. 3,967,002.

The above literature describes a contiguous transfer device using ion implantation to form a contiguous transfer element in a magnetic material.
Describes disk bubble domain devices.

Contiguous elements can take many different shapes, such as circles, diamonds, etc.

As the magnetic field reorients in the plane of the ion-implanted transfer element, a magnetic channel
arged wall ) moves around the element and attracts bubble domains along it.

In this way, the bubble domain is transferred through a structure approximately four times as large as the bubble domain.

Therefore, the storage density in terms of cell size increases.

Contiguous transfer element devices are usually formed by implanting ions into a magnetic material through a suitable (metallic) mask or by providing a pattern of adjacent openings in the magnetic material.

In both of these methods, a resist layer is patterned by exposing it through a mask.

Thus, during ion implantation, the part to be implanted is exposed to the incident ion particles, and the part not to be implanted is protected by a metal mask.

The bubble domain moves along the edge of the ion implanted region thus formed in accordance with the reorientation of the magnetic field within the plane of the ion implanted layer.

The transfer elements are therefore the edges of adjacent ion implantation regions.

Contiguous transfer elements are characterized by loss regions located between adjacent transfer elements.

In prior art continuous element devices, the size of the storage cell was dependent on the size of the loss.

This is because this is the smallest resolvable feature in the transfer pattern.

When forming a contiguous transfer element by exposing a resist layer through a mask with a light or electron beam,
The effect of interference limits the sharpness of goals conceded.

For example, a loss of size close to a transfer element is influenced by spatial relationships and distortions from adjacent transfer elements due to diffraction effects (when exposure is by light) or proximity effects (when exposure is by an electron beam). Ru.

In other words, exposure through a mask having adjacent apertures is subject to a diffraction effect or a proximity effect depending on the nature of the mask in the lost point area between adjacent apertures, making it difficult to create a sharp lost point area with sharp outlines. It is.

Therefore, due to this effect, the contiguous element bubble tome does not limit the cell size.

It is desirable to provide technology to create in-device devices.

Therefore, the main object of the present invention is to provide a method for manufacturing a contiguous element bubble transfer device in which the loss area between adjacent transfer elements is sharply formed.

Another object of the present invention is to provide a method for manufacturing a contiguous element bubble transfer pattern in which the size of a cell in a transfer path is not determined by the size of points lost between adjacent transfer elements.

Another object of the invention is an improved method for manufacturing contiguous element bubble transfer patterns in which the ultimate size of the cell is related solely to the size of the basic components (e.g. disks, diamonds, circles, etc.). It is to give.

Another object of the present invention is to provide an improved method for manufacturing continuous element bubble transfer patterns in which the ultimate size of the cells is determined by the accuracy of mask pattern alignment during successive exposures.

Another object of the invention is to provide an improved method of manufacturing a contiguous element bubble transfer device that is suitable for many different types of phosphorography.

The present invention relates to an improved method for manufacturing bubble domain devices with contiguous element transfer patterns.

The shape of the individual transfer elements in the pattern is not important; circular,
It may include any of the well-known shapes, such as a diamond.

Contiguous transfer elements are typically made by ion implantation of magnetic materials, but other methods can also be used.

For example, a continuous transfer element can be provided by forming a pattern on a magnetic layer having in-plane magnetization.

This example is a magnetic body with adjacent apertures, and the transfer element corresponds to the edge of the aperture.

This latter type of structure is shown in US Pat. No. 3,988,722.

In contrast to prior art techniques that involve a single exposure through a mask to provide a contiguous device transfer pattern,
The present invention performs multiple exposures.

The mask (and/or weber) is displaced prior to each exposure.

If the mask contains isolated elements, such as isolated apertures, no diffraction will occur.

In other words, diffraction due to lost points can be avoided.

The ultimate cell size is then a function of the accuracy of the alignment prior to each successive exposure.

However, alignment is easier to achieve than high resolution and can be easily aligned over distances smaller than the size of the individual transfer elements (ie, the size of the apertures in the mask).

In a preferred embodiment, the resist layer is exposed at least twice sequentially through a mask (usually the same mask), and the mask is spatially displaced prior to a new exposure.

When two exposures are used to form a continuous pattern, the first exposure defines every other transfer element of the transfer pattern and the second exposure defines the transfer elements created by the first exposure. A transfer element is defined between the two.

In this way, a complete transfer pattern is given.

The spatial displacement is generally equal to, slightly larger, or slightly smaller than the size of the individual transfer elements, depending on design requirements.

These objects, features and advantages will become apparent from the more specific description of the preferred embodiments below.

FIG. 1A and FIG. 1B show a plan view and a cross-sectional view of a bubble domain storage device that uses a contiguous transfer element to move bubbles.

Although the storage device of FIG. 1A is arranged in the familiar tiger/minor loop organization, this is for illustrative purposes only.

Here, the input/output major loop 10 gives bubbles to the minor loop 12 when writing, and receives and takes bubble B from the minor loop 12 when continuing.

Bubble domain B is magnetic layer 1 for magnetic bubble domain.
Exist in 4.

This is an engineered magnetic material that can maintain a stable bubble domain under the stabilizing bias magnetic field Hb.

The movement of the bubble around the major loop 10 and the minor loop 12 occurs when the driving magnetic field HXy reorients within the plane of the magnetic layer 140.

This movement is due to the presence of magnetically charged domain walls around the major and minor loops.

The magnetically charged domain wall moves around the loops 10 and 120 and attracts the bubble domain B along it.

In this example, ion implantation region 16 is shown with diagonal lines.

As is well known, the magnetic layer 14. The top surface (or bottom surface) is implanted with ions, such as He+ ions.

Therefore, the magnetization of the ion-implanted thin layer changes to in-plane magnetization in the implanted region.

However, as the bubble domain size decreases, it often becomes difficult to implant ions into the bubble domain magnetic bilayer 14.

A separate driving layer must then be used to provide the ion implantation region.

This matter is stated in Japanese Patent Application No. 51-147217.

The use of alternative drive layers is illustrated in FIG. 1B.

where the magnetic: layer 14 has a layer 20 on which ions can be implanted.
have.

Region 16 of layer 20 is implanted to produce an in-plane magnetization Md in the implanted region of drive layer 20.

The magnetization M8 of the bubble domain magnetic layer 14 is perpendicular to the plane of the layer 14.

Shown in layer 14. The bubble domain B has a magnetization Mb opposite to the magnetization M8 of the remainder of the bubble magnetic layer.

In FIG. 1B, an adjacent metal disk 18 overlies portions of drive layer 200 that have not been implanted.

The metal disk 18 typically has a Ti/
Approximately 60 mm plated on the Au metal plated base 22
Consists of money from 00 people.

Thus, the transfer elements of the major loop 10 and the minor loop 12 are the edges of ion implanted regions formed by implanting ions into the driving layer 20 through a mask consisting of the gold layer 18.

Although metal 18 is disk-shaped in FIG. 1A, any other shape may be used to form the continuous transfer element.

For example, metal 18 may be diamond-shaped.

Regardless of its shape, a contiguous transfer element of this structure consists of ion-implanted regions adjacent to each other, along which the bubble domain B has a magnetic field H
It moves while reorienting within the 0 plane.

It is a common practice to provide a mask for forming an adjacent metal disk 18 to create the ion implantation region 16.

The drive layer 20 is then implanted over its entire surface with suitable ions to create the ion implantation region 16.

Masking metal 18 serves to protect portions of the underlying drive layer from damage by incident ions.

It is customary to first provide a thin plating base 22 over the drive layer 20 to form the metal disk 18.

Thereafter, a resist layer with a thickness of 1-2 μm is applied to the entire plating base layer 22 (5 pins).

The resist layer is exposed in the areas where the metal disk 18 is to be formed.

Exposure of the resist layer is performed through a mask having adjacent openings corresponding to adjacent metal disks 18.

The resist is thus exposed to the pattern of adjacent discs.

After chemical development, the exposed portions of the resist layer are removed, exposing the plating base 22.

A masking layer 18 of gold is then plated onto the exposed portions of layer 22.

, after which the drive layer 20 is ion-implanted through the masking layer 18 to form a region 16 with in-plane magnetization Md.

When a mask with adjacent apertures is used to expose the resist layer, the smallest resolvable feature is cusp C (FIG. 1A).

Light passing through the mask is affected by spatial relationships due to diffraction and distortions from adjacent adjacent apertures.

These interference effects cause distortions in the vicinity of the lost points created in the resist layer.

Therefore, the size of the basic cell of the continuous transfer pattern is not simply related to the size of the basic components (for example, the size of the transfer element such as a disk or a diamond), but is determined by the size of the points conceded.

Even if the resist layer is made of Dupont E, I, DeN
PMMA (polymethyl methacrylate) manufactured by emours
Even if the exposure irradiation was an electron beam in a resist that is sensitive to electron beams, the size of the spot would still determine the size of the cell.

In this case there is scattering of the incident electrons in what is known as the "proximity effect".

Due to the non-uniform intensity profile of the electron beam in the resist, the lapses smooth out as the size of the transfer element decreases.

In practicing the present invention, the size of the loss is removed from being the primary determinant of cell size when a contiguous element baton is formed.

A prior art mask 24 with three different types of adjacent apertures is shown in FIG.

Mask 24 is typically a metal mask such as chrome.

The top row 26 of adjacent apertures consists of circular apertures 28.

A mask using adjacent circular apertures is suitable for forming the structures of FIGS. 1A and 1B.

However, as is clear from the second row 28, which includes diamond-shaped apertures 30, the continuous transfer elements need not be circular.

Yet another variation is the bottom row 32 of hexagonal openings 34.

In mask 24 of FIG. 2, cusp regions C exist between adjacent adjacent apertures in each row of apertures.

When light enters through the mask 24, diffraction and interference effects occur in the lost-point region C.

As a result, defects in the exposed underlying resist are not sharply defined and affect the integrity of the contiguous transfer elements fabricated in the drive layer 20.

The net effect is that the points conceded are not sharply defined and the memory register 1
This has an adverse effect on the size of cells in cells 0 and 12 (FIG. 1A).

An improved mask 36 is shown in FIG.

This is also a metal mask such as chrome.

This mask 36 differs from the mask of FIG. 2 in that the apertures in each row 38.40 and 42 are spaced apart from each other.

For example, the top row 38 includes isolated circular apertures 44 and the middle row 40 includes isolated diamond-shaped apertures 46.

The bottom row 42 includes isolated hexagonal apertures 48 .

When the mask 36 is used, the minimum resolvable line width W of the formed continuous transfer pattern corresponds to the size of the element itself.

For example, the diameter W of the circular aperture 44 is a fundamental determinant of the size of the cells in a continuous transfer batten comprised of circular transfer elements.

Similarly, the size W of apertures 46 and 48 is a determinant of the cell size of the continuous transfer pattern using rows 40 and 42, respectively, with respect to the definition of individual transfer elements in the batten.

Adjacent openings in each row of mask 36 are spaced 2W'-distance apart from each other.

However, W/ is the final, 7. The transfer is the center-to-center distance between adjacent elements of the tangent (FIG. 4).

Mask 36 can be used to provide contiguous transfer elements.

For this purpose, multiple exposures are made through this mask,
The mask is moved laterally between each exposure.

Travel distance is WIC: Yes.

This may be equal to, slightly larger or smaller than the element size W, depending on design requirements.

That is, W' is chosen according to the amount of overlap the designer wishes to obtain with the bubble transfer button.

From the point of view of mask matching (well, there is no problem regardless of W).

5 is because, as will be pointed out later, alignment can be easily performed up to a distance smaller than W.

For example, if the overlap region of adjacent discs (that is, the constriction between adjacent discs) overlaps so that it has a width of about 1/4 of the disc diameter, Wl is selected.
You can make disk elements.

Because the apertures 44, 46, and 48 are separated from other apertures in the same row, there are no longer any interference effects that cause distortion around the lapses between adjacent apertures.

The size of the cell is therefore not determined by the size of the points conceded, but is simply related to the size of the basic component, namely W.

This results in a continuous bubble transfer button of cell size W2.

FIG. 4 shows the process of processing a contiguous element bubble chip.

In this case a resist layer 50 is present on the lower drive layer 20.

This resist layer is exposed through mask 36 to form an ion implantation mask.

The area of the resist 50 exposed during the first exposure using the mask 36 is shown by a solid line, and after being displaced by W′
The areas of resist 50 that have been exposed through are shown in dashed lines.

The reference number is the third one except that it is primed to indicate that it is part of the exposed resist layer 50.
The same numbers are used as in the figure.

A single prime indicates the first exposed area, and a double prime indicates the second exposed area.

Thus, during the initial exposure of layer 50, light (or electrons) passes through mask 36 and illuminates regions 44', 46', and 48'.

After the first exposure, mask 36 is moved to the right by W'.

The resist layer 50 is then exposed a second time with the same mask to form exposed regions 44'', 46' and 48''.

Adjacent regions of exposed portions of layer 50 are then created using the same mask 36.

3 is equal to W, so the continuous patterns 44', 44", 44', . . . in FIG. 4 are patterns in which adjacent circular areas touch each other.

The other two contiguous patterns in Figure 4 are W/
is smaller than W in rows 40 and 42 of mask 36, so they have overlapping adjacent regions.

If W/ is thicker than W, the final pattern of resist 50 will contain isolated exposed areas.

Light passing through a mask with lapsed regions is subject to both coherent and incoherent diffraction effects, as is well known in the field of optics.

The technique of the present invention provides coherent diffraction and reduces the total diffraction by a significant amount (easily over 50%).

The final cell size for the bubble transfer pattern is determined by the accuracy of mask 36 alignment between two sequential exposures.

It is well known that isolated circles are very easily created in resist layers.

This is because ostia of any shape tend to create a circular image.

Therefore, the minimum structure size obtained using this technique is very small.

It is relatively easy to optically fabricate a continuous disk transfer element in the range of 0.1 to 0.25 .mu. with fine, sharp defects.

Of course, smaller geometries are possible when higher resolution lithographic techniques (such as X-ray phosphorography) are used.

The mask can be aligned to a distance smaller than the size W) of the elementary element to be formed.

This is because it is easier to center an image than to resolve it.

Displacements of 0.1-0.25μ can be achieved using handy mask alignment equipment.

Many techniques for mask alignment are known and mechanical mask alignment devices are commercially available for this purpose.

These devices have the ability to move the mask or the web (or both) in one or more directions and are manufactured by several companies.

A comprehensive report describing the current Weber exposure equipment (mask alignment equipment) is published in Electronics: 197.
It's on page 134 of the October 27, 2017 issue.

Other relevant references describing shadow matching techniques include IBM T
electricalDisclosure Bullet
tin, Vol, 20, no, 2, (July 1977)
, p, 856.

The present invention can be practiced using these known techniques and commercially available equipment.

After exposing resist layer 50, the remainder of the process used to fabricate the continuous element bubble transfer device is the same as previously described.

For example, exposed portions of resist layer 50 may be chemically removed to expose underlying plating base layer 22.

A metal layer 18 is then plated onto the exposed plating base layer.

Thereafter, ion implantation is performed in the unmasked regions of the drive layer 20.

A typical ion implantation is with He+ ions at 100 KeV to a concentration of 3 x 10''5He''/crA.

Finally, another masking layer is applied and appropriate conductors are deposited where needed, as fully described in the aforementioned US Pat. No. 3,967,002.

The magnetic sensing device is deposited with another masking step.

The principles of the invention were used to create a 2.5μ diameter continuous disk transfer device.

This has an opening with a diameter of 2.5μ and they are connected to each other by 2W.
This was done using masks 36 separated by '-W = 2.5μ.

Resist layer 50 was approximately 1 micron thick and was PMMA.

The wavelength of the exposure light was 2000-2600 nm.

It should be recognized by those skilled in the art that when practicing the present invention, the same mask can be used for more than one exposure to produce a contiguous transfer device.

The number of exposures required depends on the direction of the transferred pattern or the initially resolved isolated array? Depends on the number.

Moreover, the size and shape of the individual transfer elements are not important to the invention, as is the selection of other driving layers for the formation of the transfer pattern.

It is also immaterial whether the transfer element is made by ion implantation of the magnetic layer or by forming openings in the magnetic layer.

An example of the latter is a contiguous transfer element consisting of a magnetic edge with adjacent apertures.

In this latter example, the magnetic layer has in-plane magnetization and the bubble domains move along paths along the edges of adjacent apertures.

In other embodiments of the invention, more than one mask may be used for the sequential exposures required to create a contiguous device pattern.

Also, the mask and webber can be moved in more than one direction relative to each other.

For example, to create a two-dimensional bubble shift register based on horizontal and vertical shift registers, it may be advantageous to use two masks, one vertically and one horizontally displaced.

However, alignment of a single mask is generally easier than alignment of two masks.

The present invention provides the greatest improvement when resist layer 50 is exposed to light.

This is because the effects of diffraction and interference are most pronounced when the wavelength of the resist exposure radiation is relatively long.

For example, for exposure at far ultraviolet (2000-2600) or near ultraviolet (3000-4300) wavelengths,
An improvement of more than 0% is shown.

Of course, since electrons are also subject to interference due to the proximity effect, improvements can be obtained even when exposure is performed using an electron beam.

[Brief explanation of drawings]

FIG. 1A is a top view of a contiguous element bubble storage device in a tiger/minor loop configuration; FIG. 1B is a cross-sectional view of the device of FIG. 1A along line IB-IB; and FIG. 2 is a contiguous element transfer pattern. FIG. 3 is a diagram of the mask of the present invention used to create a contiguous device transfer pattern;
FIG. 4 is a diagram illustrating how to use the mask of FIG. 3. 10... Major loop, 12...
・Minor loop, 14... Magnetic layer for bubble, 16... Ion implantation region, 18...
Au layer, 20...Magnetic layer for ion implantation, 22.
...Ti/Au plating base, 24,36...
...Mask, 50...Resist layer, B...
...Bubble Domain, C... Conceded points.

Claims (1)

Claims: 1. A radiation-sensitive layer on a substrate comprising a thin film in which bubble domains can move is subjected to a first exposure to radiation through a mask having spaced apart apertures; performing a second exposure of the radiation-sensitive layer to radiation through a mask having spaced apertures to form exposed areas adjacent to the areas exposed in the first exposure; A method for manufacturing a bubble domain device having a contiguous transfer element, comprising the step of forming a magnetic layer pattern having in-plane magnetization using the exposed region of the radiation-sensitive layer.