JPS6235102B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an exposure method for obtaining different projection patterns on a photoresist film using a single transfer mask pattern.

The minute electronic circuits currently used in bubble memory chips, IC boards, etc. are formed on crystals using photolithography.

That is, a pattern-forming film made of metal or resin is deposited on the surface of a wafer made of magnetic garnet single crystal in the case of bubble memory chips or silicon single crystal in the case of IC chips, and then a projection exposure device is used to deposit the film. The wafer is moved a certain distance at a time to expose a large number of mask patterns on the photoresist film. When using a positive type photoresist film, the pattern is formed using the phenomenon that the light irradiated part becomes soluble in the developer, and in the case of a negative type, the pattern is formed using the phenomenon that the light irradiated part becomes insoluble. Each chip is formed by forming a fine circuit pattern from a pattern-forming film on a wafer using etching or dry etching, and dividing this pattern into unit circuits.

There is no problem if the electronic circuit patterns formed on the photoresist film are the same, but if the unit circuit consists of two patterns, A and B, and these cannot be displayed with a single mask pattern, the projected pattern will be extremely difficult. Since it is small, alignment is difficult and it is difficult to obtain a highly reliable circuit pattern.

The present invention was made to solve this problem.
A, B2 where the unit pattern has a partially different circuit configuration
When the mask pattern consists of two patterns, it is possible to form a unit pattern using one mask pattern by changing the moving distance of the wafer.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described below with reference to the drawings, taking pattern formation for a magnetic bubble memory as an example, while comparing them with a conventional example.

As bubble memory chips progress in manufacturing technology and materials, the storage capacity of magnetic bubbles (hereinafter referred to as bubbles) stored in one chip increases over time, while the diameter of the bubbles that serve as the storage medium decreases, and - Conductive patterns made of Cu alloys and transfer patterns made of permalloy are becoming smaller.

For example, in the case of a memory chip with a storage capacity of 1M bits, the minimum pattern size is about 1 μm, and the entire pattern of the electronic circuit is formed on a magnetic garnet crystal film of 10 mm square.

Regarding this, the currently used pattern forming method is that when using a high-performance projection exposure machine, the possible transfer area is 10 mm square. A 5 x 10 mm pattern area was exposed twice and 10
It is practiced to form a mm square circuit pattern and make it into one chip.

Here, in the current circuit configuration using the block replicate transfer method, in order to speed up the access time, the left and right sides have different configurations, and the bubble signal corresponding to the input information is processed separately into even and odd columns. A method is being adopted.

FIG. 1 is a schematic diagram of an exposure mask for forming a conventional permalloy pattern circuit, which includes a writing major line 2, a minor loop 3, a reading major line 4, having generator forming ends 1a and 1b.
It has a mask pattern for obtaining the bubble detector 5, etc., and the pattern shape is actually composed of T-I patterns, half disk patterns, etc. arranged in a row.

The feature of this exposure mask pattern is that the writing measure line 2 has two generator forming ends 1a and 1b, and the detector 5 is also composed of three permalloy detection elements 5a, 5b, and 5c in the shape of a fishbone or serpentine, including a dummy. It is being formed.

Figure 2 shows that using this mask pattern, the wafer was moved 5 mm and projection exposure was performed twice to create two 500K-bit memory patterns, creating a 1M-bit bubble memory chip with an odd-even circuit configuration. FIG.

In this memory chip, an insulating film is first deposited on a wafer on which a magnetic garnet single crystal is formed, and then a conductive pattern for bubble control is formed on the surface of the insulating film by photo-etching, for example, a conductive pattern 1c for forming a generator, Make 1d. After that,
It is manufactured by depositing an insulating film on the conductor pattern and then forming a permalloy pattern on the conductor pattern using the exposure mask shown in FIG.

In the figure, 1 and 1' are 2 formed by overlapping the ends 1a and 1b of the write major line 2 made of a permalloy pattern and the conductor patterns 1c and 1d.
bubble generator. Also, pattern 6 on the left
Pattern 7 on the right side is an even block that processes and stores the even numbered columns, and these two blocks 6 and 7 form a one-chip circuit configuration.

That is, in this circuit having a major/minor configuration, a large number of minor loops 3 and 3' are arranged at every other bit of the transfer pattern constituting the major lines 2 and 2'. When writing the bubble signal, the bubble signal is propagated on the major lines 2 and 2' by the driving magnetic field, but at this time, the odd-numbered bubbles making up the bubble signal correspond to the minor loop 3 of the odd-numbered block 6. At the same time, the even-numbered bubbles are transported to the respective bit positions of the major line 2' corresponding to the minor loop 3' of the even-numbered block 7.

Thereafter, in this state, each bubble on the major lines 2 and 2' is transported all at once to each minor loop 3 and 3' by the action of a transfer gate made of a conductor pattern (not shown), and writing is performed.

Here, generators 1 and 1' of even and odd blocks that generate bubble signals are operated by the same power supply to simplify the drive circuit, but in order to perform the above writing, generators 1 and 1' are operated by the same power supply to simplify the drive circuit. The number of bits in the transfer path from 1' to the write major lines 2 and 2' is determined by using two generators for the odd block 6 and the even block 7, respectively.

That is, as shown in Fig. 2, the generator 1 on the right side is used in the odd block 6, and the generator 1' on the left side is used in the even block 7, and both are connected by external electrode terminals 8, 8' connected to the drive circuit. This changes the number of bits sent from generators 1, 1' to major lines 2, 2' by 1 bit.

The same thing needs to be done during readout, and this is accomplished by using detection elements 5a, 5b, and 5c that are adjacent to each other with a one-bit difference in the detector 5.

This is because, as shown in Fig. 2, in the odd block 6, the bubble signal from the readout major line 4 is extracted by the inner detection element 5a, while in the even numbered block 7, the bubble signal from the readout major line 4' is extracted from the central detector 5b. This achieves a 1-bit difference.

The reason why the dummy detection elements 5b for the odd block 6 and the dummy detection elements 5c for the even block 7 are required is that the bubble signal is detected by a differential amplifier with high detection efficiency. The signals from the dummy detection elements 5b and 5c are sent to one terminal of the differential amplifier, and the detection signals from the detection element 5a of the odd block 6 and the signals from the detection element 5b of the even block 7 are sent to external electrode terminals 9 and 9. ' becomes a continuous signal and is connected to the other terminal of the differential amplifier.

In the bubble memory chip using the conventional pattern forming method described above, the positional relationship of the detection elements used in the even-numbered block detector and the odd-numbered block detector is slightly different, resulting in differences in characteristics and redundant generation. The device requires a detection element, which is disadvantageous in terms of pattern density, and it is also easy to make mistakes when bonding the generator and detection element used and their external electrode terminals, and incorrect connections can lead to malfunctioning chips. There were problems such as the large amount of

The present invention proposes an exposure method that eliminates such variations in characteristics due to differences in the position of the detection elements, relaxation of pattern density, and erroneous bonding connections. In order to do this, the mask has a main pattern area for forming a main pattern, and at least one variable pattern area formed within the main pattern area, and the variable pattern is provided in the vicinity outside the main pattern area. The area has a sub-pattern area for providing a predetermined pattern, and the predetermined pattern in the sub-pattern area is composed of at least two unit patterns having different shapes, and when the transfer exposure is performed by moving relatively, the main pattern is During the exposure process of the pattern area, the variable pattern area formed within the main pattern area is left unexposed, and during the previous or next exposure process of the adjacent main pattern area, the variable pattern area is exposed by the sub pattern area. In addition, the sub-pattern area is achieved by an exposure method in which one of the unit patterns is selected at a predetermined position by adjusting the amount of movement.

Next, embodiments of the present invention will be described with reference to FIGS. 3 to 5.

FIG. 3 shows an exposure mask according to the invention, which includes a writing major line 10 with one generator-forming end 10a, a reading major line 11, a minor loop 23, and two sensing elements 24a, 24b. A mask pattern through which light passes is provided to obtain a bubble detector 24 having a bubble detector. Also, main pattern 1 in which mask patterns 10, 11, 23, 24 for obtaining each of these functional elements are located.
The major lines 10 and 11 in 4 have variable pattern areas 12 and 13, and the main pattern area 14
Sub-pattern regions 15 and 16 are formed above and below on both sides. This exposure mask directs light to the main and sub pattern areas during projection exposure.
A photoresist film is irradiated from 4, 15, and 16, developed to obtain a predetermined resist pattern, and then the permalloy film is etched to form a permalloy pattern circuit according to the resist pattern, which will be described later.

By the way, the four partial views A, B, C, and D shown around FIG.
This is an enlarged view of the configuration of 16 parts.

Here, sub-pattern areas 15 and 16 in figures c and D
As shown in the figure, a mask pattern through which light passes to obtain a half-disk-shaped permalloy pattern for transfer is formed; Unit patterns 15b and 16b are arranged in parallel to obtain two permalloy patterns whose size is 1/2 and corresponds to 2 bits. Also, variable pattern area 1 in figures A and B
2 and 13 represent the light in which the mask patterns 10b and 11a through which the light passes to obtain the half-disc-shaped permalloy pattern for transfer forming the major lines 10 and 11 are missing by 2 bits (2 permalloy patterns) as shown in the figure. It is given as an area that does not allow transmission.

In the exposure mask according to the embodiment shown in FIG. 3, when performing projection exposure while moving the wafer left and right by a fixed distance, the operation of changing the moving distance slightly more than the fixed distance is repeated every other time. Accordingly, one or two unit patterns 15a, 15b, 16a, 16b can be selectively projected into the variable pattern regions 12, 13 to obtain a half-disc-shaped permalloy pattern of the sub-pattern regions 15, 16.

In this way, in this embodiment, the major line 1
Patterns having different numbers of constituent bits of 0 and 11 are continuously formed, and this will be explained in more detail with reference to FIG.

FIG. 4 shows an embodiment of the present invention, in which a photoresist film on a wafer is exposed by projection using the exposure mask shown in FIG. 3, and a resist pattern is formed to obtain permalloy pattern circuits having different transfer bit arrangements. It is an explanatory diagram of a process.

In this pattern forming method, first, a first projection exposure is performed on the right end of the wafer through the exposure mask shown in FIG. unit patterns 15a, 15b, 1
6a and 16b are exposed to a photoresist film.

As a result, the photoresist film has a photosensitive resist pattern 17 corresponding to the mask pattern in the main pattern area 14, a unit resist pattern 19a corresponding to the unit pattern in the sub pattern areas 15 and 16,
A photosensitive resist pattern 19 consisting of 19b (the unit resist pattern of region 16 is omitted for illustration purposes) is formed.

Next, after moving the wafer to the right in a dimension slightly narrower than the area length of the main pattern area 14, a second projection exposure is performed using the exposure mask shown in FIG. 11,2
3, 24 and unit patterns 15a, 15b, 1
6a and 16b are exposed to a photoresist film. When the main pattern area 14 irradiated onto the wafer is defined as, for example, 5 mm horizontally and 10 mm vertically, the wafer moving distance during the second exposure corresponds to the horizontal dimension in the wafer moving direction. Now, the 4.99mm wafer, which is slightly narrower than that, is moved to the right. Also, at this time, the main pattern area 14 is formed on the photoresist film as in the first time.
The photosensitive resist pattern 18 corresponding to the mask pattern in the area and the unit resist patterns 20a, 20 corresponding to the unit patterns in the sub pattern areas 15, 16
A photoresist pattern 20 consisting of the resist pattern 20 and a photoresist pattern 21 consisting of the unit resist patterns 21a and 21b are formed.

Now, the photosensitive resist patterns 20 and 21 are formed by the sub-pattern areas 15 and 16 formed during this second projection exposure, but as mentioned above, the wafer moving distance at this time is 10 μm narrower than the main pattern area length, so the photosensitive resist patterns 20 and 21 are formed during the second projection exposure. The patterns 17 and 18 are formed by exposure with the main pattern regions 14 overlapping each other. For this reason, the unit resist patterns 20a and 20b are an unexposed area 20' corresponding to the variable pattern area 12 of the exposure mask when the photosensitive resist pattern 17 is formed, and the 1-bit unit resist pattern 20a is formed by the mask pattern 10b for the first time. Measure line 1 formed during exposure
It is given in accordance with the photosensitive resist pattern 20c for 0. Also, at this time, unit resist patterns 19a and 19b formed during the first exposure are located in the area 19 corresponding to the variable pattern area 13 of the exposure mask, and the 2-bit unit resist pattern 19b is located in the area 19 corresponding to the variable pattern area 13 of the exposure mask. Mask pattern 1
A photoresist pattern 18a for the major line 11 given by 1a is provided in correspondence therewith.

Next, the wafer is moved 5 mm from the center line 22 of the photoresist pattern 18 that was previously projected and exposed, and then a third exposure is performed in the same manner as before to form a photoresist pattern corresponding to the mask pattern in the main pattern area 14. 25 and sub pattern area 15,1
Photosensitive resist pattern 2 consisting of unit resist patterns 26a and 26b corresponding to unit patterns in 6
A photoresist pattern 27 consisting of 6 and unit resist patterns 27a and 27b is formed on the photoresist film. In this exposure, unlike the second exposure, the wafer movement distance is equal to the area length of the main pattern area 14, so the unit resist pattern 26
a and 26b are the 2-bit unit resist pattern 2 in the unexposed area 26' given during the second exposure.
6b is provided in alignment with the photoresist pattern 26c for the measure line 10 that has already been formed. Also, at this time, a photosensitive resist pattern 25a for the major line 11 is provided to match the 1-bit unit resist pattern 25a already formed in the region 21'.

Next, the fourth projection exposure was carried out by moving the wafer 4.99 mm from the center line 28 of the photosensitive resist pattern 25 in the same manner as the second, and
photosensitive resist pattern 30 and unit resist pattern 29a by sub-pattern region 15,
A unit resist pattern similar to the photosensitive resist pattern 21 (not shown) is formed in the photoresist by forming the photoresist pattern 29b and the sub-pattern region 16.

As a result, the unexposed area 29' of the photosensitive resist pattern 25 is replaced by the unit resist buttons 29a, 2.
9b, and a 1-bit unit resist pattern 29a is provided continuously to the already formed photosensitive resist pattern 29c for the major line 10. Also, at this time, major line 1
One photosensitive resist pattern 30a is provided in correspondence with the 2-bit unit resist pattern 27b already formed in the region 27'.

In this way, by exposing the wafer by alternately moving the wafer by the length of the main pattern area and the length of a slightly narrower area, the sub-pattern area within the variable pattern area of the main pattern area is exposed. Unit patterns of 1 bit or 2 bits in the pattern area are alternately and selectively positioned. Thereafter, this photoresist film is developed to leave only the photoresist pattern on the permalloy film, and this is etched to obtain a permalloy pattern circuit along the photoresist pattern.

When looking at the photosensitive resist patterns 18 and 25 in FIG. 4, which constitute one chip of this permalloy pattern circuit, both of them have a difference in the number of bits transferred from the write major line from the bubble generator and the number of bits transferred from the read major line to the detector. They are formed with one bit difference, and as a result, a bubble memory chip with block replicate transfer control based on an odd-even method is obtained.

Incidentally, when forming a pattern by this method, unnecessary unit resist patterns 19a, 19b, 2 are formed on the sides of the write and read major lines.
Permalloy patterns formed by 1b, 26a, 27a, and 29b remain, but even if they exist, they do not affect the bubble transfer function.

Now, FIG. 3 above shows an example of an exposure mask in which the transfer bits from the bubble generator to the write major line and the transfer bits from the read major line to the bubble detector are changed using a vertical transfer path. , FIG. 5 shows another embodiment of the present invention using transfer paths in the lateral direction.

Variable pattern area 34 in the case of the main exposure mask,
Numeral 35 is placed in the main pattern area 31 at the write major line close to the generator and the read major line close to the detector, as in FIG. It is placed.

Further, the sub-pattern areas 32 and 33 consist of one and two half-disk mask patterns as in the previous embodiment, but the difference is that these are arranged in parallel in the horizontal direction.

Here, pattern C is an enlarged view of the sub-pattern area 32, and pattern D is an enlarged view of the sub-pattern area 33.

Further, the variable pattern areas 34 and 35 are shown as white in the figure, but these provide areas that are not exposed during projection exposure, and are used for pattern B.
and Pattern A are enlarged views of variable pattern regions 34 and 35 including the peripheral portions, respectively.

Next, as for the pattern forming method in this example, the lateral movement distance of the wafer is always 5 mm, and
On the other hand, when moving, move the wafer vertically from the reference position.
The operation of shifting by 10 μm may be repeated every other time.

According to the present invention as described above, by selecting an exposure mask having a variable pattern area in the main pattern area and a sub pattern area consisting of a group of unit patterns in order to provide a predetermined pattern in the variable pattern area, and the wafer movement distance. , it is possible to easily and continuously form patterned circuits whose shapes differ from each other between adjacent and remote areas by exposure, and the practical effects thereof are remarkable.

Incidentally, in the above embodiment, an example in which the present invention is applied to forming a permalloy pattern circuit of a bubble memory has been described, but the present invention is not limited to this and can be used for various types of circuit patterns.

Note that the exposure method according to the present invention can be applied to both positive type and negative type photoresist films on the substrate by using an exposure mask in which black and white are reversed.

[Brief explanation of the drawing]

Figure 1 is a block diagram of a mask pattern used in conventional magnetic bubble memory chip formation, Figure 2 is an example of conventional circuit formation using this, and Figures 3 to 5.
The figure is a diagram for explaining an exposure method according to the present invention. [Explanation of symbols] 14, 31... Main pattern area, 15, 16, 32, 33... Sub pattern area, 12, 13, 34, 35... Variable pattern area.

Claims (1)

[Claims] 1. An exposure method in which a pattern provided on a mask is transferred and exposed at least twice to a photoresist film on a substrate surface using a projection exposure machine by relatively moving the mask or a substrate, wherein the mask forms a main pattern. a main pattern area for applying a predetermined pattern to the variable pattern area, and at least one variable pattern area formed within the main pattern area; a pattern area, and the predetermined pattern in the sub-pattern area has at least two different shapes.
When performing transfer exposure by moving relatively, the variable pattern area formed within the main pattern area is left unexposed during exposure processing of the main pattern area, and the variable pattern area formed in the main pattern area is left unexposed and the adjacent pattern is During exposure processing of the main pattern area, the variable pattern area is exposed by the sub pattern area, and the sub pattern area selects one of the unit patterns at a predetermined position by adjusting the amount of movement. An exposure method characterized by the following: