JPS58194339A - Preparation of x-ray mask - Google Patents

Abstract

PURPOSE:To practically manufacture many masks for exposure by X-ray with good transfer accuracy from a sheet of original mask and attain improvement of throughput by utilizing an X-ray mask having a low contrast to the wavelength of X-ray used for manufacturing a device as the original mask and by duplicating a pattern from the original mask using the synchrotron X-ray. CONSTITUTION:An X-ray mask of which Au absorbing pattern thickness is as comparatively thin as several thousands Angstrom is manufactured as an original mask. The X-ray mask having a thin Au absorbing pattern can be usually manufactured with excellent size accuracy. The parallel and extensive soft X-ray 22 is extracted from the synchrotron orbit irradiation beam source 21 and the duplication X-ray exposing mask 24 is manufactured with the original mask 23 used as the mask. Since the X-ray is irradiated in parallel, the X-ray is accurately focused without any deviation and simultaneously a large allowance is given to the gap between the mask and wafer.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an X-ray exposure method in the field of X1M lithography, which is effective in transferring fine patterns of 1 μm or less.

XI! One important key to the practical application of phosphorography is to establish a technology for producing X-ray masks that can be used in practical applications.
And lots of x! The goal is to prepare for the supply of I-masks. The latter is especially important in production lines that process a large number of wafers. In order to take full advantage of the advantage of improving throughput by batch or partial transfer using X-ray exposure, it is essential that XS masks be supplied at low cost and in large quantities.

In the production of X-ray masks, which is widely practiced, there is a resist pattern engraving process using electron beam exposure, which is considered to be an essential process that consumes a large amount of time and considerably increases the cost of producing an XIS master. Currently and in the future, electron and i*m light are considered to be the most effective drawing techniques for forming fine patterns of 1 μm or less.Therefore, drawing using electron IIa11 light is indispensable in the production of X!I masks. It is probably a common knowledge that electron beam exposure takes a long time, that is, the throughput F is poor.Especially in the area of submicron line widths, this tendency is even more pronounced. In other words, with the widely used method of patterning the resist by electron beam exposure for each X-ray mask, it is almost impossible to supply xII masks in large quantities at low cost. It would be impossible.

One possible method for solving this problem is to prepare all the master masks (fi!L masks) for xil exposure masks. X! including electron beam lithography process! One original mask is manufactured by the I mask manufacturing process, and a large number of working masks for xm exposure are provided by xis exposure transfer using this original mask. However, this method also has the following strict conditions:

(1) When producing a large number of X-ray exposure masks using an IN mask, no damage is caused to the original mask.

(2) In the process of producing a large number of X-ray exposure masks, the transfer accuracy from the original mask is sufficiently high and a sufficient throughput of mask production can be obtained to be practical.

If a large number of xmm optical working masks are produced under such conditions, it is possible to improve the throughput for producing the intended device and reduce the production cost.

By the way, the idea of preparing original masks itself is not so novel as an idea, but in a sense it can be said to be an easy idea to come up with. An example shown in the literature is shown in FIG.

Publication published in 1979 Journal of Vacuum Science and Technology (J, V
ac-Sei, 'I'eehno1. ), Volume 16, No. 6.

Similar figures appear on pages 1965-1967.

First, the thickness of 4000X (2) PMMA was obtained by electron beam exposure.
A resist pattern 1 is formed, and an Au@container pot body 2 having a thickness of 300X is formed by electroplating. In order to be able to form a fine pattern at this time, a method was adopted in which PHMA was applied to a polyimide film mask substrate with a thickness of 2 μm. This is because the amount of secondary reflected electrons can be reduced by a thin organic film.
A master mask (original mask) is formed (Fig. 1 (1)
)figure).

Next, using the original mask as a mask, Ou Lclil (
X11 transfer is performed using a wavelength of 13.34 A) to create an inversion mask. In other words, PMMA resist 3 is applied to a thickness of soooXm, buttered, and the areas where the resist is removed are electroplated to a thickness of 6000X.
An I pot body pattern 4 is formed (FIG. 1(2)).

Next, using the inversion mask, the mu IKα ray (wavelength 8.3
41) XI! A resist pattern 5 is formed on the wafer 6 by transfer (FIG. 1(3)).

The main point of this process is 0uLa! The only point is to create an inversion mask using i['. In other words, ■ The original mask is created under conditions that allow the formation of as fine a pattern as possible during electron beam exposure. ■ As a result, the film thickness of the An absorber is 3000X thinner than that of a normal X-ray mask, but the inversion The transmission X! is sufficiently large for the long wavelength CuLa line used for mask creation. This means that a contrast of I can be obtained.

However, such conventional technology has the following drawbacks. Although the idea of creating an inversion mask using CuLa wire is interesting, there are various practical problems. In the case of Ou La line, the wavelength is long, so the normal X1
aflll (using Be foil) is difficult to configure as an X-ray exposure device, and X! It is necessary to adopt a vacuum exposure method in which the i1 generation source and the exposed sample are in the same vacuum.

For example, a commonly used Be foil with a thickness of 30 μm is ! When used as an extraction window, the 0uLa line passing through this window (
The wavelength (13.34X) is attenuated to just over 4%. The fact that exposure is performed in a vacuum rather than in the atmosphere is a very big disadvantage from the perspective of throughput.

The trouble of setting up and removing the exposed wafer from the vacuum exposure chamber, the consumption of extra evacuation time, the problem of contamination due to the exposure of the X-ray source to the atmosphere every time exposure, and the fixation of the mask and wafer in vacuum problems (vacuum suction cannot be used), damage to the mask when using mechanical fixing means because the mask cannot be fixed by vacuum suction, and problems such as the need for extra vacuum exhaust equipment. occurs.

Furthermore, there are many resists whose characteristics deteriorate during exposure in vacuum. One of these is the extra crosslinking phenomenon (commonly seen in negative resists, called the post-polymerization effect) caused by leaving the material in vacuum after irradiation, 1 m (electron beam, XM).

In short, in the case of 0uLa radiation, it is necessary to use an exposure method in vacuum using an X-ray exposure device without an The first drawback is that it is difficult to raise.

Next, although it is related to the first drawback, the fact that the am that generates the CuLa rays is an electron beam excitation source produces the following second drawback. The so-called electron beam excitation method for xi generation has a long history, and there is no doubt that it is the only practical X-ray (including hard X-ray and soft Xm) generation method currently established. This will continue to be the case in the future, and although it has not been developed yet, a practical XM exposure apparatus will naturally have an electron beam excitation source as an Xls source. However, this electron beam excitation source has the following serious drawbacks.

An electron beam excitation source is one in which a metal target is convergently irradiated with a high-pressure accelerated electron beam to generate excitation X-rays from a nearly point source.
l is a divergent X-ray emitted in all solid angle directions. This divergence Xts is a serious defect. That is, Ou'l, a for producing a X1m exposure mask from the original mask.
In line transcription.

This will lead to a significant deterioration in transfer accuracy. The well-known penumbra blur δ and geometric shift Δ in XS transcription are expressed by the following equations.

Δ=8-unit D Here, S represents the gap between the mask and the wafer, d represents the diameter of the radiation source, D represents the distance between the radiation source and the mask, and W represents the diameter of the wafer. As the value of S, when transferring the X-ray exposure mask from the original mask, the original mask pKJi[t4'''-a
c゛t=t=i"766"゛6.1. 120 μm is necessary. d is 5m, D is 30511, and W
Assuming that the step-and-repeat method reduces the exposed area, a value of about 2 mw would be appropriate. Substituting these values into the above formula, a becomes 0.33
0.66 μm is obtained as μm and Δ. These values are very large and lead to a significant deterioration in transfer accuracy. Especially 1
Considering the formation of μm or even submicron patterns, the above values of a and Δ will result in an X
It turns out that it is impossible to make a mask for line exposure.

The purpose of the present invention is to eliminate such conventional drawbacks, to produce a large number of X-ray photomasks from a single original mask with good transfer accuracy and with practical productivity, and to achieve an improvement in throughput. An object of the present invention is to provide a method for manufacturing a new X-ray mask.

According to the present invention, there is provided a method for manufacturing an XS mask, in which an XLS mask having a low contrast with respect to the Xm wavelength used for device manufacturing is used as an original mask, and a working mask is manufactured by transferring the original mask Karachtatern. Synchrotron orbital radiation xI as an X-ray source for transferring patterns! A method for manufacturing an XII mask is obtained, which is characterized by using the method.

The present invention will be described in detail below with reference to the drawings. Fig. 2 is a drawing showing one configuration of the present invention. First, the film thickness of AI @ storage container is relatively thin, several thousand times.
Manufacture M mask as original mask (Figure 2 (1))
. XI with an Au absorber pattern with a thin film thickness of several thousand
The fabrication of 1 masks can be accomplished without much difficulty. It is a natural prerequisite that the original mask has excellent dimensional accuracy. Needless to say, the production of this original mask includes the step of forming a fine resist pattern using an electronic III exposure tip, and the total time and cost involved in producing this original mask is considerable. This is unavoidable.

Next, using the original mask as a mask, a large number of working masks for X-ray exposure for X1s transfer are prepared using zinc a-orbital synchrotron radiation (FIG. 2(2)). The use of synchrotron orbital synchrotron radiation as a source for X-ray exposure has only been slightly experimentally investigated.

In reality, the cost of constructing a synchrotron orbital radiation source is enormous (it is thought to cost at least several billion yen), and the equipment operation and maintenance costs are considerable. Due to the considerable size of this device (the radiation ring is at least 10 m in diameter), it is completely impractical to apply this device to X-ray exposure. Good too. For those involved in the actual research and development of X-ray exposure,
It is true that synchrotron orbital radiation sources are hardly ever in mind.

However, synchrotron orbital radiation sources have other
It has the following three important advantages compared to 11i. It is possible to obtain parallel radiation X&l, it is high intensity, and it is a long wavelength radiation source. These advantages can be effectively utilized in the present invention. Parallel and high-intensity soft X from the synchrotron orbital radiation source 21 in Figure 2 (2)! 22 is taken out, and using the original mask 23 as a mask, a transfer x and 111g light mask 24 is produced. Since it is parallel Xm, the above-mentioned deflection δ
This produces the effect that the deviation Δ becomes completely zero, and at the same time produces the effect that a large tolerance is given to the gap between the mask and the wafer. Even if a gap of several tens of μm to several hundred μm is provided, the transfer accuracy will not be impaired in the slightest. The tolerance of this gap is that ■ it does not damage the original mask;
This means that it is basically an important point for the method of producing a large number of XM dew filling masks by transferring from the original mask. In addition, the high intensity of the synchrotron orbital radiation source means that a large number of
This will be a great help in improving productivity when manufacturing M exposure masks. Another feature of the synchrotron orbital radiation source is the long wavelength property of the synchrotron orbital radiation Is source. The wavelength range is usually from several tens of times to hundreds of times (or even several thousand μm), but for such long wavelengths, a thickness of several thousand 100 μm of Au absorber is sufficient.

In the wavelength range (IX to 10 WkX) of the commonly used electron beam excitation source, the contrast is low and good transfer characteristics cannot be obtained. In short, one important advantage is that a relatively easy-to-manufacture low-lift mask can be used as the original mask.

In the process explained in FIG.
Produced at high throughput. (Figure 2 (3)) The X-ray exposure mask used during device fabrication is required to have high contrast. Since it is assumed that an electron beam excitation source or the like in the mX to tens of tens of wavelength range is used as the X-ray source, a high contrast mask with an Au film thickness of approximately 60,001 mm or more is required. Due to the high intensity feature of the synchrotron orbital radiation source, it is easy to form a high aspect pattern of a thick film resist, and a thick film Au absorber pattern can also be easily formed using this resist pattern. In other words, we have manufactured a large number of high-quality (high-precision, high-contrast) xmm optical masks that are suitable for manufacturing devices by Xi & transfer, and use these to create X! ! The transfer results in the production of devices at -C high throughput.

It is clear from the above description that by adopting such a new X-ray exposure method, the above-mentioned problems can be solved and the object of the present invention can be achieved.

The effects of the present invention will be described. If the present invention is applied, firstly, high-contrast You can make the most of its features! Thirdly, it is possible to improve throughput, which is the most important goal in the production of devices with fine patterns such as VLSIs, and fourthly, synchrotrons are unrealistic as sources for X-ray exposure! The advantages of I sources can be utilized very skillfully and effectively.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a conventional X-ray exposure method, and FIG. 2 is a diagram showing an XSG light method according to the present invention. In the figure, 1 and 3.5 are resist patterns. 2.4 is the Aui storage pot, 6 is the wafer, 21 is the synchrotron orbital radiation source, 22 is the radiation soft X, I[,2
3 is an original mask, and 24 is a transfer X-ray exposure mask. Spear I

Claims (1)

[Claims] Xi! used for device fabrication! X which has low contrast with respect to the wavelength! ! Using the mask as the original mask, transfer the pattern from the wrinkle mask to create a working mask. ! A method for manufacturing a mask, in which sink ptosine orbital radiation x! is used as an X-ray source for transferring a pattern. A method for producing an XII mask characterized by using I.