JPS5841591B2 - Defect repair method for pattern transfer mask for magnetic bubble memory - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for correcting defects in a pattern transfer mask for magnetic bubble memory, and more particularly to a method for correcting defects in a pattern transfer mask used when forming a transfer pattern of magnetic bubbles.

In general, magnetic bubble memories are made of permalloy or other materials to suppress hard bubbles (abnormal bubbles) on the surface of a single crystal magnetic thin film epitaxially grown on a substrate such as a non-magnetic G-G-G (gadolium gallium garnet) crystal. A soft ferromagnetic material (hard bubble suppression film) is laminated by a method such as vapor deposition, and on the top surface there are thin film layers for a magnetic bubble generation circuit, a magnetic bubble transfer circuit, etc. as a magnetic bubble control circuit, and wiring for the above circuit group. The conductor layer is composed of layers with an insulating layer of silicon dioxide film (S 102 ) interposed between each layer.

By generating and transferring magnetic bubbles in this soft ferromagnetic thin film pattern, desired information is written, stored, read, etc.

Here, to create a fine pattern for transferring magnetic bubbles onto the non-magnetic substrate, first, a pattern transfer mask for the fine pattern, such as a photomask, is made, and then this photomask is used to perform photolithography. .

Therefore, the fine pattern formed on the substrate has the same shape as the fine pattern produced on the photomask.

The above photomask is manufactured as follows.

That is, first, a pattern 10 times the size of the desired fine pattern is created.

This pattern is called a reticle pattern.

It is made using a device called a generator.

Next, a desired photomask is produced by applying this reticle pattern to a device called a photorepeater.

Here, the photorepeater reduces the pattern on the reticle to one-tenth, and repeatedly forms an actual-sized fine pattern on the photomask.

FIG. 1 is an enlarged plan view of a main part showing an example of a photomask for producing a major/minor type transfer pattern, particularly a minor loop transfer pattern.

In the figure, 1 is a photomask, and on the surface of this photomask 1, fine TI patterns 2 consisting of a T pattern 2a and an I pattern 2b are sequentially arranged in a predetermined arrangement to form a transfer loop.

The photomask for forming a transfer pattern formed in this way is used to remove the pattern of the transfer loop when an unnecessary residual defect 3 as shown in the circular shape in the same figure occurs on the loop of the fine TI pattern 2 during pattern formation. It cannot be treated as a defective loop, and this causes chip failure.

This is because when the chip is operated as a memory when the chip is completed, unintended magnetic bubbles may be generated from the residual defect 3, resulting in a memory malfunction.

In other words, if the remaining defect 3 is present on the photomask 1, it will definitely be transferred onto the wafer.

Therefore, conventionally, in order to correct the above-mentioned residual defects,
A correction method was adopted that brought the pattern as close to a normal pattern as possible using generally known techniques such as spot exposure or laser beam.

Therefore, when correcting the unnecessary residual defect 3 shown in Fig. 1 by spot exposure, the spot exposure operation must be performed at least 11 times, once in each of the 11 areas indicated by the symbols 1 to 1 in the same figure. was being carried out.

For this reason, it has a drawback that it takes a lot of time to correct the unnecessary residual defect 3.

Furthermore, even at present, the gap between the T pattern 2a and the ■ pattern 2b is approximately 1.3 μm, and it is extremely difficult to correct this accurately by spot exposure.

Furthermore, even if the gap were to break, the gap would widen as shown by symbol A in FIG. 2, resulting in a defective magnetic bubble transfer margin.

Furthermore, as shown by symbol B in the figure, if the gaps are connected without being cut, this also results in a transfer failure.

Therefore, even if the unnecessary residual defects 3 are corrected, most of the chips end up with poor characteristics.

Furthermore, if the magnetic bubble diameter becomes approximately 1 μm or less in the future, the gap between the T pattern 2a and the ■ pattern 2b will be approximately 0.
It has the disadvantage that the door size is about 5μ, and it is completely impossible to correct it.

Therefore, an object of the present invention is to eliminate the above-mentioned drawbacks, and to provide a method for correcting defects in pattern transfer masks for magnetic bubble memories, which allows the above-mentioned unnecessary residual defects to be corrected accurately and in a short time. It's about doing.

In order to achieve such an objective, the defect correction method of a pattern transfer mask for magnetic bubble memory according to the present invention is based on a concept different from the conventional one, on the premise that loops having unnecessary residual defects are treated as defective loops. This method is to be corrected.

In other words, all the surrounding parts including the unnecessary remaining part are removed.

Hereinafter, a method for correcting defects in a pattern transfer mask for magnetic bubble memory according to the present invention will be described in detail with reference to the drawings.

3a and 3b are plan views of essential parts of a photomask for explaining an example of a method for correcting defects in a pattern transfer mask for magnetic bubble memory according to the present invention, particularly a method for correcting defects in a photomask, and are shown with the same symbols as in FIG. Since they are the same element, their explanation will be omitted.

In FIG.
The area including the outer periphery surrounded by the dotted line frame is removed by a spot exposure method, which is a known technique.

In this case, the pattern of the transfer loop after removal is as shown in the same figure.

At this time, this transfer loop and the transfer loops on both sides of it, a total of three transfer loops, become defective loops, but the chip is not defective, and these three transfer loops are treated as defective loops and are rendered unusable. This is what I was made to do.

According to such a defect correction method, spot exposure, which conventionally required at least 11 times, can be completed in one time, and the spots can be roughly aligned.
The correction time can be significantly shortened.

Here, in the above major-minor one-way transfer loop, the minor loop is formed as a backup in case a defective loop occurs for a predetermined number of transfer loops, so this backup Since the loop can be used in place of the defective loop, there is no problem at all in practice.

Note that the above defect correction method cannot be used for a simple shift type transfer pattern, but it can be applied when this simple shift type has a large number of simple shift type loops and has redundancy.

In addition, in the above embodiment, T is used as a mask pattern.
Although the case where the I pattern is used has been described, the present invention is not limited to this, and even if applied to a transfer pattern using a YI pattern, a Scheffron pattern, a half disk pattern, etc., the same effect as described above can be obtained. is obtained.

In addition, in the case of a mask for submicron bubbles, one bit is approximately 4μ door angle, and the gap is approximately 0.5μ door angle, so it is completely impossible to modify the pattern to bring it closer to the normal pattern. Corrections can be made in a similar manner.

Further, in the above embodiments, a photomask is used as the pattern transfer mask, but the present invention is not limited to this, and other transfer masks using electron beams or X-rays may also be used. The same effect as described above can be obtained.

As explained above, according to the method for correcting defects in pattern transfer masks for magnetic bubble memory chips according to the present invention, it is possible to significantly shorten the time required to correct unnecessary residual defects that have occurred on patterns, and to ensure that the correction is carried out reliably. As a result, there are no defects in the performance characteristics that occur due to defects in the transfer margin, and reliability can be greatly improved.

Furthermore, when the gap between patterns becomes as small as about 1 .mu.m or less due to the increase in the density of transfer loops, an excellent effect can be obtained such that defects can be repaired extremely easily.

[Brief explanation of the drawing]

FIG. 1 is an enlarged plan view of essential parts showing an example of a photomask for creating a transfer pattern for a magnetic bubble memory chip, FIG. 2 is an enlarged plan view of essential parts showing an example of correcting a pattern on a photomask using a conventional method, and FIG. Diagram a. b is an enlarged plan view of a main part of a photomask for explaining an example of a method for correcting defects in a pattern transfer mask for a magnetic bubble memory chip according to the present invention, particularly a method for correcting defects in a photomask; 1...Photomask, 2a...T pattern, 2b...I pattern, 2...TI
Pattern 3...Remaining defects.

Claims (1)

[Claims] 1. A magnetic bubble characterized in that, in a pattern transfer mask on which a magnetic bubble transfer pattern is formed, when an unnecessary residual defect on the transfer pattern is corrected, the entire peripheral area including the residual defect is removed. A method for correcting defects in pattern transfer masks for memory.