JPH0344915A - Manufacture of x-ray exposure mask - Google Patents

Abstract

PURPOSE:To reduce a lithographic error and to manufacture a mask having high resolution by forming a photomask having suitable magnification by an electron beam lithography, and patter-transferring on a X-ray mask material by a contraction projecting aligner having high resolution. CONSTITUTION:A circuit pattern is formed on a reticle 1 having suitable magnification by an electron beam exposure 2. Then, an SiN film 4 is provided on a silicon wafer 3, a X-ray transmission window is formed at part of the film 4 of a rear surface, and a Ta absorber 8 and a photoresist 7 are formed on the film 4. Then, a pattern of the reticle 1 is contraction-projected and transferred on the wafer 3 by using a laser light source and a contraction projecting lens 8 having 0.45 or more of numerical aperture. With the resist 7 as a mask the Ta 6 is etched, the resist 7 is removed, a substrate 3 is removed from a rear face to form a X-ray transmission window. Thus, the error in electron beam lithography is reduced, and a high resolution mask can be manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for manufacturing an X-ray mask used in an X-ray exposure apparatus for forming fine patterns of half a micron or less.

BACKGROUND OF THE INVENTION As semiconductor devices have become increasingly highly integrated, techniques for forming fine patterns have been actively developed. The optical reduction projection exposure technology that has supported mass production technology up until now has a limit to its resolution performance, which is determined by the light source wavelength and lens NA (numerical aperture), and is at the 0.25 μm level required for devices after 64 MDRAM. Electron beam exposure technology or X-ray exposure technology is considered to be promising for exposure technology (1). The figure shows a typical manufacturing method of an X-ray mask that has been used conventionally. First, a silicon wafer 10 is coated with a Si
An N film 11 having a thickness of about 1 μm is formed by the CVD method (FIG. 2(a)). Next, as a window 12 type for the X-ray transparent area,
The Sin film 11 on the back surface is removed by etching (second
Figure (b)). Next, low stress heavy metal Ta is used as an X-ray absorber.
13 is formed on the entire surface (FIG. 2(C)). Next, 5iOa 14, which is used as an intermediate layer in the two-layer resist process, is formed on the entire surface (FIG. 2(d)). Next, after applying an electron beam resist, the circuit pattern is exposed to light by electron beam drawing 15 (FIG. 2(e)). Next, using the resist pattern 16 as a mask, the intermediate layer is etched and the pattern is transferred onto 5i (h14) (Fig. 2(f)).
. Next, Ta13 is etched using 5iO214 as a mask to transfer the pattern (FIG. 2(g)). Finally, after removing the resist 16, the silicon substrate IC is etched from the back side to form an X-ray transparent window, completing the X-ray mask (FIG. 2(h)).

Problems to be Solved by the Invention The X-ray mask requires a fine circuit pattern of 5 .mu.m or less.The accuracy of pattern line width and position is required to be on the order of 0.1 .mu.m or less. However, with the above method (1) Since the electron beam pain drawing method was used to form the circuit pattern, there were the following problems (1) The problem of proximity effect where the Shunga pattern is deformed due to the scattering of the electron beam and the charge of the irradiated electrons. Especially in the case of X-ray masks, this effect is noticeable because heavy metals such as TaAu are used as absorbers, and it has been difficult to obtain sufficient accuracy even when using a multilayer resist process or correcting the proximity effect. Another problem is the inherent drawing errors of electron beam drawing equipment.
This invention has the disadvantage that it is difficult to perform highly accurate drawing over the entire area of the drawing pattern.In order to solve the above-mentioned problems, a circuit pattern is drawn and formed directly on an X-ray mask using an electron beam. Instead, the circuit pattern formed on the reticle is reduced and transferred using a reduction projection exposure device with sufficient resolution performance to form an X-ray mask pattern, improving the pattern accuracy that was a drawback of the conventional method. It is an object of the present invention to provide a method for manufacturing an X-ray exposure mask which is also excellent in productivity.

Means for Solving the Problems According to the present invention, a mask of N times the desired circuit pattern is formed on a reticle using an electron beam exposure device, and then a projection lens having a numerical aperture of 0.45 or more using a Hooker argon laser as a light source Using a reduction projection exposure device equipped with a
In general, the resolution performance of a reduction projection optical system is expressed by the following equation.

Resolution limit: R=k・λ/NA−(1) where λ is the light source wavelength, NA is the numerical aperture used as a measure of the resolution performance of the projection lens, and k is the process representing the overall performance in the lithography process. It is a coefficient. By adopting resist materials and processes that provide high resolution performance,
It is possible to reduce the value to about 0.5. Here, if a Hooker argon (ArF) laser is used as the light source wavelength ('L λ = 0.193μ) and if the NA of the projection lens is 0.45 or more, R = k・λ/NA≦0 from equation (1). .214.um, and it is possible to obtain resolution performance at the 0.25 μm level required for X-ray mass. It is possible to obtain a same-size X-ray mask with excellent pattern accuracy by reducing and transferring the image to 1/N on the mask material forming the X-ray mask using a reduction projection exposure device.
The pattern position accuracy when using a reticle of N times is as follows: The pattern is formed by electron beam exposure on a material such as Cr used as a photomask material.The influence of electron beam scattering is also small. If the distortion of the projection lens is ignored, the pattern position accuracy on the reticle can be reduced to 1/N.Embodiment FIG. 1 shows a method of manufacturing an X-ray exposure mask according to an embodiment of the present invention. FIG. The embodiment will be described in detail below with reference to FIG. First, a circuit pattern is formed by directly drawing on a reticle 1 at an appropriate magnification (for example, 5x) using electron beam exposure 2 (see Fig. 1(a)).
). The drawing accuracy at this time (electronic lens poetry) is a comprehensive accuracy that includes stage accuracy and process factors, and by optimization, an accuracy of 0.1 μm or less has been achieved.

Next, an SiN film 4, which is an X-ray transparent film, is buried and formed on the silicon wafer 3 by the CVD method (FIG. 1(b)).

Next, a part of the SiN film 4 on the back surface of the silicon wafer 3 is removed by etching to form a window 5 in the X-ray transparent region (FIG. 1(C)). Window 5 shape LL at this time,
In order to alleviate the local stress at the interface between SL and SiN, a polygon close to a circle is preferable to a square.Next, as an X-ray absorber, a low-stress heavy metal, such as Ta6, is formed on the entire surface by sputtering. (Figure 1(d)). Next? Q A
A photoresist 7 with sufficient sensitivity and high resolution for rF excimer laser light is applied to the entire surface (see Figure 1 (e).
)). Next, the circuit pattern on the reticle 1 is
93nm ArF laser as light source and LNA=0.45
Using a stepper equipped with the above reduction projection lens 8, reduction projection is performed all at once onto the silicon wafer 3 for forming the X-ray mask, and transfer is performed (FIG. 1(f)). X
The resolution performance required for a line mask is satisfied by this projection exposure method as mentioned above.The most important pattern position accuracy (σA) is also generally expressed by the following formula according to this method. The drawing accuracy of the exposure system, σL (Lens distortion due to the aberration of the projection lens, N is the reduction ratio of the reticle. Here, the commonly used N-5, t
If y EB=0.1, ty L-0.05pm, then ic a A-0.054μm, and 0.25. This almost satisfies the pattern position accuracy of 0°05 μm required for an X-ray mask according to the um rule. Therefore, by performing electron beam lithography on a reticle that is 5 times larger, the error in electron beam lithography can be reduced to a few fractions of a second. The accuracy can be further improved by improving the projection lens such as an aberration-free lens and by improving the drawing accuracy of the electron beam exposure device. Next, resist pattern 7 is used as a mask and IATa
By etching 6, a circuit pattern that acts as an absorber is formed (FIG. 1(g)). Finally, after removing the resist 7, the silicon substrate 3 is etched away from the back surface to form an X-ray transparent window, thereby completing an X-ray exposure mask (FIG. 1(h)). In this embodiment, the numerical aperture N of the projection lens is set to 5. The power is not limited to this value, but as the NA value increases, the error in electron beam lithography can be further reduced compared to the conventional method.

Effects of the Invention As is clear from the above explanation, according to the present invention, a photomask with an appropriate magnification is formed by electron beam lithography, and then a pattern is transferred to an X-ray mask material using a reduction projection exposure device having high resolution. It is possible to provide a method for manufacturing a high-resolution X-ray exposure mask that can reduce errors in electron beam lithography to a few fractions of a second and has excellent pattern position accuracy. In addition, if a -degree food mask is made, it will be possible to perform repeated exposure transfers as a master mask.
It is also effective in terms of industrial productivity.

[Brief explanation of drawings]

Figure 1 shows the process of forming the X-ray exposure mask of the present invention. Figure 2 is a process diagram showing the conventional method of forming the X-ray exposure mask. ...Electron beam exposure 3
...Silicone waeno\ 4...SiN style 5
...X-ray transmission type 6...Ta absorption dependent 7...
・Resist, 8... Reduced projection lens B

Claims (1)

[Claims] A mask N times the desired circuit pattern is formed on the reticle using an electron beam exposure device, and then a reduction projection exposure device equipped with a projection lens having a numerical aperture of 0.45 or more and using a Hooker argon laser as a light source is used. A method for manufacturing an X-ray exposure mask, characterized in that the pattern on the reticle is projected onto an X-ray mask in a reduced size of 1/N and transferred.