JPS6115144A - Photomask - Google Patents

Abstract

PURPOSE:To improve the yield by using a glass plate, etc. as a base material, forming a thin film pattern for transmitting no ultraviolet rays, on its one main surface, and embedding a heating element heated by electric conduction, into the base material in the outside of an area in which said pattern exists. CONSTITUTION:In order that exposure is not obstructed, a line-shaped or tape- shaped heater 8 is placed in an area except an area 7 in which a mask pattern 6 exists, namely, the peripheral part of a photomask 5. An electric conduction terminal 9 for applying a current for heating to the heater 8 is provided, and the heater 8 is placed on the photomask 5 or embedded in the mask 5. Or the heater 8 is formed on the mask 5, and thereafter, coated with a resin.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a photomask for photolithography, and more particularly to a photomask suitable for photolithography of large area devices or devices.

(Structure of conventional example and its problems) Photo-etching technology is a technology that forms a photosensitive resin pattern that acts as a mask material when selectively etching a certain material to be etched. , photosensitive resin, photomask, and photosensitive resin development process. In devices such as semiconductor devices, various thin film etching processes are usually performed several times, so in the photo-etching process, relative positioning of P-turns, commonly known as mask alignment, is required for each process. be.

Figure 1 is an explanatory diagram to show the importance of mask alignment.
1 and 1' are setans formed on the substrate S such as silicone in the previous photolithography and etching process, and 2 and 2' are patterns for mask alignment formed on the photomask ( (commonly known as key).

Normally, a suitable margin a is provided so that the key 2 can be stored in the turf 1. In FIG. 1(a), for the sake of simplicity, the key 2 is shown aligned with the center of the pattern 1. Key 2 is provided for each chip, but in actual mask alignment, alignment is performed at two locations on the left and right, appropriately away from the center of the board, and the mask is aligned by moving the board or photomask while taking into account the balance of the entire board. will be carried out. If the photomask and the substrate do not expand or contract, the state shown in Figure 1(a) can be reproduced many times, but if the expansion of the substrate is greater in the relative relationship between the photomask and the substrate, It is easy to understand that the state shown in FIG. 1(b) will be obtained, and in the opposite case, the state shown in FIG. 1(C) will be obtained. Generally speaking, substrates are manufactured through long processes that include high-temperature processes, so it is impossible to avoid some degree of expansion, contraction, and warping, so it would be meaningless if the photomask were to expand or contract in terms of process control. Therefore, the photo-etching process is performed in a clean room with constant temperature and humidity.

Next, the relationship between alignment margin and ξ turn accuracy will be described. In FIG. 2, for example, when trying to form a 12 μm square contact 4 in patterns 3 and 3',
, ), the alignment margin is 4 μm, so the width of the P turf 3 can be set to 20 μm. In FIG. 2(b), the alignment margin is 6 μm, so unless the width of the turn 3' is 241Rn, the contact 4 will protrude from the turn 3'. That is, even if an attempt is made to form the same contact 4, if the alignment accuracy deteriorates, the pattern width must be increased. In other words, the precision of the P-turf decreases, preventing higher density.

As shown in FIG. 1, the relative expansion and contraction of the photomask and substrate reduces the alignment margin. However, the alignment margin is determined by the ability of the exposure device and, in the case of visual alignment, the skill level of the operator, and cannot be reduced unnecessarily. Therefore, if an attempt is made to maintain the alignment margin, the alignment margin between turn 1 and key 2 will be the sum of the alignment margin determined by the exposure device and the relative expansion/contraction, resulting in a significant drop in pattern accuracy.

A large number of silicon-based semiconductor devices such as ICs and LSIs are usually formed simultaneously on a single substrate as chips of 10 sides or less. Therefore, the average value of relative expansion/contraction for each chip is reduced to 1/n of the number n of chips arranged in the vertical or horizontal direction, and the larger n is, the smaller the reduction in alignment margin is. However, in the case of a large element or device where n=1, that is, one entire substrate constitutes a chip, the reduction in alignment margin largely depends on the expansion and contraction of the substrate. As such a large element or device, there is a liquid crystal display device, which has been actively developed in recent years. In a liquid crystal display device with a simple matrix configuration,
The minimum line width and turn width are several tens of micrometers, so this is hardly a problem.However, in an active matrix configuration, that is, one in which each picture element has a built-in switching element, the minimum line width is necessary to obtain good characteristics of the switching element. is required to have a value of several μm or less.

However, when the size of one chip exceeds several degrees, the expansion and contraction of the substrate often shows thermal expansion of 0.1 μm per 1° C. depending on the material. In particular, glass has a low softening point of several hundred degrees Celsius, and its plastic deformation is not reversible.
There is an example of In's chisozo] Ottrn being extended. Under such conditions, even if exposure/steeling with a pattern accuracy of 5 .mu.m is used, the alignment accuracy is required to be 10 .mu.m, and the design standard must be such that the minimum line width exceeds 15 .mu.m. 1. In other words, even if pattern accuracy can be improved in the photolithography process for large areas, if alignment accuracy is not improved, narrower patterns for higher density and improved device characteristics will not be realized. This means that it is difficult.

This tendency becomes stronger as the chip area becomes larger and as the substrate expands and contracts more easily.

(Objective of the Invention) The present invention was made in view of the above situation, and an object of the present invention is to provide an exposure/stem, particularly a photomask, that prevents a decrease in alignment accuracy in the photolithography process of large-area devices. do.

(Structure of the Invention) The main point of the present invention is to compress the relative difference between the photomask and the substrate by applying heat to the photomask and forcibly elongating the photomask against the phase 7 expansion and contraction. It's in a place where you can.

(Description of Embodiment) FIG. 3 shows a photomask according to an embodiment of the present invention. The area excluding the area 7 where the mask/gutter 76 is present so as not to interfere with exposure, that is, the photomask 5
A linear or tape-shaped heater 8 is arranged around the periphery of the heater. Reference numeral 9 denotes a current-carrying terminal that supplies current to the heater 8 for heating. Figures 3(b) and (c) show the third
h-t (cross-section shown in Figures (,), Figure 3 ()
In b), the heater is completely buried in the glass plate 5 that is the base material. Alternatively, a heater 8 is placed on one main surface of the glass plate 5.
After forming, it may be coated with a resin or the like.

In FIG. 3(C), the heater 8 is formed on one main surface of the glass plate 5 as a base material. Although the current-carrying terminal 9 and the heater 8 can be formed on either main surface of the photomask 5,
Unless the projection exposure method is used, the main surface on which the mask pattern 6 is formed will be in close contact with or come close to the sample coated with photosensitive resin, so it is generally provided on the main surface on which the mask pattern 6 is not formed. Would.

FIGS. 4 and 5 show photomasks according to other embodiments of the present invention, respectively. In this embodiment, since the transparent conductive layer 10 is used as a heating element, it can be formed over almost the entire mask surface regardless of the arrangement of the mask grooves 6, and the heating uniformity and speed are significantly improved compared to the previously described embodiments. is obtained. Figure 4(b) is Figure 4(a)
The transparent conductive layer 10, which is a heating element, is embedded in the glass plate 5, which is a base material. Alternatively, the transparent conductive layer 10 may be formed on one main surface of the glass plate 5 and then coated with a resin or the like.

If the transparent conductive layer 10 is not exposed, a metal current-carrying terminal 9 is also formed. Moreover, FIG. 5(b) shows the CC' cross section of FIG. 5(a), and shows that the transparent conductive layer 10, which is a heating element, is formed on one main surface of the base glass plate 5. However, for the reason mentioned above, it is convenient to provide it on the main surface where the mask pattern 6 is not formed. Since the transparent conductive layer 10 is exposed, the current-carrying terminal 10' can be easily obtained by turning, and current supply to the current-carrying terminal 10' is achieved by crimping a suitable metal terminal.

There are several other possible arrangements for the transparent conductive layer 10. For example, in the case of forming a plurality of chips where n = 2 or more, they may be selectively arranged in a scribe grid that is a gap between chips. A transparent conductive layer, for example ITO (Ind
ium-Tin, -0xide) and Nesa is last (5n
o4) etc., the transmittance decreases as the wavelength of ultraviolet rays becomes shorter, so if they are arranged in a scribe grid, the problem of long exposure time can be avoided.

Needless to say, when the photomask is heated due to energization or the temperature rises, it is necessary to release the fixation function of the photomask in the exposure equipment and allow the photomask to stretch freely. To prevent the sample and the sample stage supporting or fixing it from being heated, it is necessary to separate them or provide an insulating shield. After forcibly stretching the photomask to the extent that it does not interfere with mask alignment, of course the mask alignment is performed once while the photomask is fixed.

(Effects of the Invention) As is clear from the above description, the photomask according to the present invention has a function of adjusting its length by heating, unlike the conventional photomask. Therefore, a large area element!
Even if elongation occurs for some reason during the manufacturing process of the device, it will never be difficult or impossible to match the mask, and the yield will be significantly improved. As the alignment accuracy is improved, the ξ-turn accuracy is prevented from decreasing, making it easier to increase the density and performance of the element or device.

The application of the present invention is not necessarily limited to large-area devices, but can also be applied to ordinary integrated circuit devices, which improves yield by suppressing variations in characteristics between chips as alignment accuracy improves. It's not even a moat to do that.

[Brief explanation of drawings]

Figures 1(a) to (C) illustrate the concept of mask alignment ['nl
,th ′,′! Figures (a) and (b) show alignment accuracy and
FIG. 3 is a conceptual diagram showing the relationship between turn accuracy and FIG. 3 is a configuration diagram of an embodiment of the present invention, FIG. The p, -1 sectional view of FIG. 3(a), FIG. 4, and FIG. 5 are configuration diagrams of other embodiments of the present invention, respectively, and FIG. 4(a) and FIG. Each plan view, FIG. 4(b), and FIG. 5(b) are sectional views. 5...Photomask, 6...Mask A' turn, 8...
... Heating element, 9, 10'... Current-carrying terminal, 10...
Transparent conductive layer. Patent applicant Matsushita Electric Industrial Co., Ltd. Figure 1 Figure 2 Figure 3

Claims (2)

[Claims] (1) A glass plate or a quartz plate is used as a base material, and a thin film pattern that does not transmit ultraviolet rays is formed on one main surface of the base material, and a heating element that generates heat when energized is located outside the area where the thin film pattern exists, and the base material is a glass plate or a quartz plate. A photomask, characterized in that the photomask is embedded in the substrate or formed on one of the main surfaces of the substrate. (2) A glass plate or a quartz plate is used as a base material, and a thin film pattern that does not transmit ultraviolet rays is formed on one main surface of the base material, and a transparent conductive layer is formed in the base material including the area where the thin film pattern exists. 1. A photomask, characterized in that the transparent conductive layer is provided with a current-carrying terminal, which is embedded or formed on one of the main surfaces of the base material.