JPH036649B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to improvements in reduction projection exposure methods.

As the density of semiconductor devices has increased, lithography technology, which is the basis of microfabrication, has made remarkable progress. The exposure method for transferring a photomask pattern onto a substrate has changed from the conventional contact exposure method to a reduction projection exposure method that reduces the pattern by a ratio of 10:1 or 5:1. This is because, compared to the contact exposure method, it has the advantage of superior resolution and highly accurate alignment. In such reduction projection exposure methods, the pattern original plate is a mask that has been enlarged (usually 10x), so it is called a reticle, but the reticle also has multiple identical patterns formed on it. This is to improve the efficiency of exposure processing on larger substrates.

However, the photo process to print the pattern on the semiconductor substrate takes several to ten or more times.
Further, there are many heat treatments and etching treatments as well, and it is necessary to detect during these wafer processing steps whether or not elements with desired characteristics are being formed without fail. Therefore, several monitor patterns for testing electrical characteristics are formed at arbitrary positions on the substrate, and transistor characteristics, dielectric strength voltage, contact resistance, and other wiring layer resistances are also tested using the monitor patterns. In addition, when a semiconductor element with the required characteristics cannot be obtained after the wafer processing process, characteristic analysis is performed, but the regular pattern is so minute that it is impossible to detect it with a prober, and in that case, the monitor pattern is also used. . Therefore, it is necessary to form several monitor patterns on the substrate, and in the conventional contact exposure method, the same number of patterns as the substrate are formed on the photomask, so it is necessary to form these many regular patterns. It was easy to form several monitor patterns within the pattern. However, in the reduction projection exposure method, it is better for mass production to form a plurality of regular patterns on one reticle and transfer the plurality of regular patterns in one exposure. However, in such a reduction projection exposure method, even if only one monitor pattern is placed on the reticle, at least one monitor pattern will be formed in each transfer, and the surface of the wafer to be transferred will be affected. In this case, an unnecessarily large number of monitor patterns are formed. For example, if 4 regular patterns are formed on the reticle and 200 integrated circuit patterns are formed on the exposed substrate, the step repeat will be repeated 50 times, for a total of 50 integrated circuit patterns. This results in the formation of a monitor pattern of 1,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000. At most, only a few monitor patterns are required, so in the reduction projection exposure method, a reticle with only the monitor pattern formed is prepared separately, and is occasionally exchanged with a reticle on which the regular pattern is formed, so that the necessary A monitor pattern is formed at the position.

However, the throughput of exchanging the reticle is lower than expected, and the effectiveness of the exposure process is drastically reduced. That is, the reticle is cleaned each time it is replaced, its position is adjusted when it is installed in an exposure device, and furthermore, after installation, the test substrate is printed and inspected for foreign matter adhesion, which significantly increases the number of processing steps. Furthermore, the more frequently the reticle pattern is replaced, the greater the risk of damaging the reticle pattern.

Conventionally, for example, one normal pattern and one monitor pattern were formed together as a reticle pattern, and when a monitor pattern was not required, a shutter was used to cover only the surface of the monitor pattern on the reticle surface to form multiple monitor patterns. Methods have been used to prevent this. According to this method, only the required amount of monitor patterns are formed, and wafers are not wasted. However, since only one regular pattern is formed in one exposure, it is not suitable for mass production.

The present invention proposes a reduction projection exposure method that solves these problems, and uses a reticle having a monitor pattern and a plurality of regular patterns to form a transferred image of the regular pattern of the reticle on the surface of a substrate to be exposed. and a second step of forming a transfer image of the monitor pattern of the reticle on the surface of the substrate to be exposed using the reticle, so that no empty pattern area is formed. In the reduction projection exposure method, in the first step, among the plurality of regular patterns, one of the regular patterns that overlaps a position where the monitor pattern is transferred in the second step is shielded, while the remaining regular patterns are shielded. This is a reduction projection exposure method characterized by transferring a pattern so that the regular pattern and the monitor pattern are not formed overlapping each other, and will be described in detail below with reference to Examples.

Figure 1 shows a plan view of a conventional reticle 1. Nine regular patterns P ₁ to _{P 9} are formed in the center, the effective area of the reticle is approximately 100 mm square, and the surrounding area is shielded from light by vapor-deposited chromium. . When such a reticle is attached to an exposure device as described above, it is first printed onto a substrate for inspection, inspected for abnormalities such as dust adhesion and damage, and then printed (transferred) onto the substrate to be exposed. Ru. FIG. 2 is a plan view of the semiconductor substrate 2 to be exposed, where M indicates a monitor pattern, and shows an example in which three monitor patterns are formed on the substrate by a contact exposure method. Semiconductor substrate 2 has a diameter of 4
If the size is inch (100 mm), when transferring the reticle at a reduction rate of 1/10 as shown in Figure 1, step repeat exposure will be performed nearly 100 times.
During this time, it becomes impossible to print three monitor patterns as shown in FIG. Although it is possible to print nine monitor patterns in one shot, it takes time to change the reticle and wastes the chip.

FIG. 3 shows a reticle according to the present invention, which is a reticle 11 in which one monitor pattern M is formed around nine regular patterns _P1 to _P9 . Then, as shown in the model diagram shown in FIG. 4, pattern shutters 12 and 13 are provided on both sides of the reticle 11, and by sliding them left and right, the regular pattern is
_P1 and the monitor pattern M are alternately covered or exposed, and the monitor pattern is appropriately transferred onto the substrate 2 to be exposed. 5a, b, and c show the relationship between these patterns and the shutter, and FIG. 5a shows the position where only the regular pattern is printed, and the pattern shutter 13 shields the monitor pattern M. Figure 5b shows the relevant position for printing the monitor pattern M, where the pattern shutter 12 is the regular pattern.
_P1 is shielded, and the pattern shutter 13 is opened to expose the monitor pattern M. In FIG. 5c, the pattern shutter 12 shields the regular pattern, and the pattern shutter 13 shields the monitor pattern M. In addition to these three related positions, there is a related position where all regular patterns and monitor patterns are printed without blocking anything.

When step repeating the reticle pattern and continuing to transfer it from left to right on the wafer surface,
In the first transfer, only the monitor pattern is covered with a shutter to obtain the condition shown in FIG. 5a. Next, a relative position is taken where nothing is shielded, and a single monitor pattern is formed for the first time. Thereafter, if the third pattern to be transferred is adjacent to the second pattern to be transferred, the wafer can be used without waste. To do this, next, select the state shown in FIG. 5c and join the outline of the third pattern to the outline of the second transferred monitor pattern section.

Alternatively, as another example, first transfer is performed at a related position that does not block anything, and then the transfer is continued in the order of FIG. 5c, FIG. 5a, and FIG. 5a.

In this way, when changing the shielding and exposure using two pattern shutters and transferring a part of the regular pattern overlappingly to the monitor pattern transfer position, the regular pattern in the part of the pattern that overlaps with the monitor pattern is shielded. By transferring the remaining regular pattern, the unevenness of the outline of the transfer pattern created by forming the monitor pattern can be successfully joined together. Therefore, there is less wastage of wafers than in reduction projection exposure performed using a conventional pattern shutter.

Such pattern shutters 12 and 13 are attached to the main body of the reduction projection exposure apparatus, and when you want to print a monitor pattern, you can switch to manual operation and transfer it, but of course you can operate the shutter automatically and print it on the computer. It is also possible to incorporate it into the control program by manipulation. In addition, in Figure 4,
14 indicates a reduction lens system.

The above is one embodiment of the present invention. Moreover, the present invention is not limited to this one embodiment, but can be modified in many ways. For example, the monitor pattern to be formed on the outer periphery of a reticle pattern consisting of a regular pattern is arranged at the corner of a large rectangular pattern formed by the regular pattern, but there is no problem with the monitor pattern being placed at the center of the outer periphery. As is clear from the above, according to the present invention, in addition to being able to eliminate the need to change the reticle for transferring a monitor pattern, the patterns to be transferred can be closely bonded to each other, and the area of the wafer to be transferred can be reduced. It has the effect of being able to be used effectively without waste.

[Brief explanation of the drawing]

FIG. 1 is a plan view of a reticle of a conventional method, FIG. 2 is a plan view of a substrate on which a monitor pattern is formed, FIG. 3 is a plan view of a reticle according to the present invention, and FIG. 4 is a plan view of a reticle according to the present invention. A model diagram of the method, FIG. 5, is a diagram showing the relative position between the pattern shutter and the pattern. In the figure, 1 and 11 are reticles, 2 is a substrate, 12,
13 is a pattern shutter, 14 is a reduction lens system,
P indicates a regular pattern, and M indicates a monitor pattern.

Claims (1)

[Scope of Claims] 1. A first step of forming a transferred image of the regular pattern of the reticle on the surface of the substrate to be exposed using a reticle having a monitor pattern and a plurality of regular patterns; A second step for forming a transferred image of the monitor pattern of the reticle on the surface of the exposed substrate.
In the reduction projection exposure method performed by step repeat in such a manner that no empty pattern area is formed, in the first step, out of the plurality of regular patterns, in the second step, the monitor pattern is The reduction projection is characterized in that the regular pattern and the monitor pattern are prevented from being formed overlapping each other by transferring the remaining regular pattern while shielding the regular pattern that overlaps the position where the regular pattern is transferred. Exposure method.