JPS61185929A - X-ray exposure mask - Google Patents

Abstract

PURPOSE:To prevent the effect of an adjoining shot by a method wherein a material, which is transparent for a visible light and absorbs the X-rays to be used for exposure, is filled in the aperture region of the Si substrate whereon an alignment mark is formed. CONSTITUTION:In the structure diagram of a cross section, the X-ray absorbing pattern 21, which constitutes a transfer pattern, the mask pattern 25 consisting of an Si3N4 film to be used for selective removal by etching of the prescribed region of an alignment mark 22, an X-ray transmitting thin film 23, and an Si frame 24 using the anisotropic etchant such as a KO aqueous solution and the like, for example, and the organic material 26 which is filled to attenuate the X-rays to be made incident on the aperture region provided on the Si frame 24 of the region whereon the alignment mark 22 is formed, are indicated respectively. As a result, the superpositional exposure of the adjoining shots in a step-and-repeat X-ray exposure can be prevented, and the X-rays pass through the aperture part on the circumference of the alignment mark, thereby enabling to prevent the effect affecting on the adjoining shot region.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to an X-ray exposure mask used in X-ray exposure, which is expected to be a highly accurate transfer technology for fine patterns. Problem) X-ray exposure method uses soft x# with short wavelength! Since it is used as a pattern transfer medium, it is possible to perform high-precision batch transfer of fine patterns using gloximity exposure.

For this reason, it has the advantage that the mask is less likely to become contaminated and that highly accurate mask positioning is possible. On the other hand, in an X-ray exposure apparatus using an electron beam excitation type X-ray source, soft X! Since it is used as a T-pattern transfer medium, there is a problem in that warpage and distortion of the mask and wafer greatly affect the positional deviation and blurring of the transferred pattern. However, increasing the diameter of the wire is also essential for increasing the productivity and yield of semiconductor devices. For this reason, conventionally, a large-diameter X-ray exposure mask (hereinafter referred to as a glass mask) with a thin film of plastic such as Mylar, Kapton, polyimide, or Parylene-N as a support layer for the transferred pattern has been used for contact exposure. Attempts have been made to transfer the image to a larger diameter Eva.

However, to date, these plastic masks have problems such as changes in the dimensions of the plastic thin film over time, changes in dimensions due to fluctuations in temperature and humidity, and distortion that occurs when the plastic thin film that is in close contact with the wafer is separated even during use. Therefore, it is extremely difficult to overlay and expose ultra-fine patterns of around 1 μm or less with the desired precision. On the other hand, as shown in Figure 3, heavy metals such as humans that absorb X4I Desired transfer pattern 31t-8i formed by
'P 8i1N4, 8i01, 8iC, BN, u
The xan has a structure in which the thin film 32 is supported by a thin film 32 made of an inorganic material having a high transmittance for soft X-rays such as Y-Om, and the thin film 32 is reinforced and supported by an 8i7 frame 34 formed by selectively etching away using a protective film 33. The development of original masks (hereinafter referred to as inorganic masks) is also active.@Koshi9 Inorganic masks generally have almost no change in dimensions over time, and small fluctuations in dimensions due to changes in temperature and humidity. It is suitable for manufacturing ultra-L8I etc. that require extremely high precision alignment.

The disadvantages of inorganic masks are that they generally cause cracking due to the stress acting on the interface between the thin film 32 and the Si frame 34, and that their mechanical strength is lower than that of plastic masks.
It is difficult to expose large-diameter wafers all at once. However, the above-mentioned problems when exposing large-diameter wafers are due to the step-by-step process using an inorganic mask with a relatively small diameter and high flatness. This problem can be solved by adopting an AND-REPIE exposure method. This is because by doing this, the mask area can be small, and because the mask dimensions are small, the warpage is small, and the decrease in pitch accuracy of the mask due to changes in temperature and humidity is kept to a minimum. Furthermore, since the spacing and parallelism between the X-ray exposure mask and the wafer can be finely adjusted for each exposure step, highly accurate alignment is possible regardless of the wafer diameter. When considering the case of manufacturing an X-ray exposure mask for the step-and-repeat method, pattern formation of an X-ray source mask using fine pattern writing technology such as electron beam exposure technology also requires a large number of patterns to be drawn on the surface. ,
The step-and-repeat X-ray exposure method, which has many advantages as mentioned above, has the advantage of being easier because it requires less, but it also has the following problems. Recently, it has begun to be recognized that there are points. FIG. 4 shows a schematic planar structure of a conventional general front X-ray exposure mask. In this mask, a mask pattern for four chips is formed.

ing. In the figure, reference numeral 41 denotes a thin film (hereinafter referred to as an XH transparent layer) made of a material that transmits XS well, and supports a chip pattern 42 made of a material that absorbs XS well and an alignment mark 43i of the mask.

Furthermore, the thin film 41 is supported entirely by a frame 44 made of Si, and this frame 44 serves as a part for fixing the XAI exposure mask to the X@ exposure device or as a gripped part during handling. 0 Using a conventional X-ray exposure mask with the structure described above, the step-and-repeat method
PjA Yazan #Otori Mohe I ∆ ^11, lbeh, the number of chips that can be taken (yield b > t - in order to get as many chips as possible,
As shown in FIG. 5, it is necessary to perform exposure with the chip interval between adjacent 71 bits as small as possible. However, in this case, as shown in FIG.

Since the margin area 52 around the chip 51 cannot be made so small, there is an inconvenience that adjacent silts overlap as shown in the shaded area 53, resulting in the exposure of parts that should not be exposed in the first place. Ta. For example, the size of the chip pattern 42 is 8 x 8 mm, the width of the outer periphery where the alignment mark 43 is located is f 2 mm, and the space between the chip patterns 42 is 07 my
The chip spacing between the two patterns is as shown above. (Since we want to increase the number of small patterns, the spacing between the chip patterns 42 is 100 μm, which is the same as the spacing between the chip patterns 42.
m, and all chips on the wafer are lined up at intervals of 100 μm, as shown in the shaded area 53 in FIG.
Overlapping exposure source regions with a width of m to 100 μm are created.

The above-mentioned outer periphery and tb margin area 52t-hair is coated with an X-ray absorber pattern forming material.Generally, the intensity of XfIs transmitted through the X-ray absorber is from several orders of magnitude to more than ten orders of magnitude, so this X-ray It is impossible to prevent the effects of overlapping exposures. As can be seen from the fact that the hatched area 53 overlaps in the center of Fig. 5 and there are 9 parts, there are 4
The IK influence is large◎ This problem can be solved by covering the outer periphery with the I-frame 44, but the alignment mark 43
Due to restrictions on the outer diameter of the objective microscope for t-detection, it is necessary to set the distance between the alignment marks on the X-ray exposure mask to a certain value or more. Also, the alignment mark 43
must be formed at least in the opening area of the S1 frame, so depending on the size of the chip pattern 4217), it is inevitable that there will be a blank area around it where there is no chip pattern and X-rays will pass through. Therefore, when step-and-repeat exposure is performed using a conventional X-ray exposure mask as shown in FIG. ) It is necessary to reduce the overlapped lines between the exposed areas, and as a result, the yield of chips of 61 or more sea urchins is significantly reduced. In the above example, if only the blank area with a width of 21 pixels overlaps between shots, the yield will be 162/202 = 0.64, which is certainly lower than when the chip spacing can be made all 100 μm. do.

(Objective of the Invention) The object of the present invention is to improve the drawbacks of the conventional X-ray exposure mask as described above, and to
It is an object of the present invention to provide a step-and-repeat X-ray exposure mask that can always expose chips with sufficiently close intervals without being influenced by adjacent shots.

(Structure of the Invention) The X-ray exposure mask of the present invention includes an X-ray transparent thin film, an 8i substrate that is in close contact with one surface of the X-ray transparent thin film and has a plurality of opening areas, and the X-ray transparent thin film. A mask pattern formed and arranged on the other surface of the thin film so as to be included in the first opening area of the 8i substrate, and another opening area provided separately from the opening area where the mask pattern is placed. The Si substrate has at least four alignment marks formed therein, and the opening area of the Si substrate where the alignment marks are formed is filled with a material that is transparent to visible light and absorbs XJie for exposure. .

(Detailed Description of Configuration) In the configuration of the present invention, the X-ray transparent thin film is used as a substrate for forming a heavy metal pattern constituting a desired transfer pattern and an alignment mark. In order to transfer the heavy metal pattern with high precision and in as short a time as possible by X-ray exposure, the film should have the following properties: 8i, N, 0.
It is preferable to use a material whose main component is a light element such as B, C, or H having an atomic weight of at least 30 or less. In addition, it is desirable that the film thickness be as small as the mechanical strength allows (@The Xls-permeable thin film itself is fragile) 1. Since it is almost impossible to mechanically grip it, the surrounding area should be shaped like a window frame, etc. of Si
Reinforce and support with the board. The first feature of the X-ray exposure mask provided by the present invention is that this window frame-shaped 8i substrate has a blanking function to prevent unnecessary exposure areas from occurring during X-ray exposure. The opening area of the Si substrate provided in the heavy metal pattern portion constituting the desired transfer pattern is set to the minimum necessary size.

On the other hand, when using an X-ray exposure mask for the manufacture of semiconductor devices, accurate alignment is required with respect to the pattern on the semiconductor substrate, so at least two alignments are required for one X-ray exposure mask. In the X-ray exposure mask provided by the present invention that requires a mark, the alignment mark is not restricted by either the chip size or the outer diameter of the objective microscope for mask alignment. It is formed in an opening region of the heavy metal pattern section provided independently of the opening of the 8i substrate. Furthermore, in the step-and-repeat exposure using a single X-ray exposure mask, the opening area of the alignment mark portion may be exposed so that the adjacent exposure area is overlapped with the X-rays transmitted through the opening area. Soft xlfst-
It is characterized by being filled with a transparent material that sufficiently absorbs and transmits visible light used for mask alignment. For example, a general resist such as polymethyl methacrylate (PMMA) is suitable for the above material.If this resist is filled to a thickness of 100 μm, for example, a wavelength of 7 The transmittance of the 8iKa line of .1X is 0.1% or less, and the influence of overlapping exposure in step-and-repeat exposure is improved to the point where it can be ignored. The above material is not limited to PMMA, and similar effects can be obtained by using polystyrene, polyimide, silica liquid, or the like.

(Example) Next, an example of the present invention will be explained in detail with reference to the drawings.0 Figure 1 is a schematic plan view of an X-ray exposure mask of the present invention.
1 is Au, Pt so as to form a desired transfer pattern.
, W, or Ta are mainly formed. The distance between each of the four chips is 100 μm. Compared to the conventional example explained in FIG. 〇Therefore, since the chips can be arranged on the wafer at intervals of 100 μm, the yield is 110.0 μm compared to the case shown in FIG.
This is an improvement of 1656 times out of 64. 12 is an alignment mark formed using the same material as the above X-ray absorber pattern, Si2N3, BN, stc, Si0g
Since the lower alignment marks, each supported by an X-ray transparent thin film 13 made of either a diamond-shaped carbon film or a plastic film, are not placed in the same opening as the transfer pattern 11, the spacing between the alignment marks can be reduced. It can be made wide enough to match the outer diameter of the objective lens. The X-ray transparent thin film 13 is reinforced and supported by a t8i7 frame 14 around it.

FIG. 2 is a schematic structural diagram of a cross section taken along the plane indicated by A-AI in FIG.
Reference numeral 23 denotes an X-ray transparent thin film, 24 denotes a Si frame, and 25 denotes a film used to selectively etch a predetermined region of the S1 frame using an anisotropic etchant such as a KOH aqueous solution. A mask pattern 26 made of N4 film is
The organic material filled in order to attenuate the XSi incident on the opening area provided in the 8i frame 24 in the area where the alignment mark 22 is formed is shown. The X-ray exposure mask of the above embodiment can be obtained as follows.

First, on one surface of an 8i single crystal substrate with a thickness of several hundred μm to 1 mm, an 8i1N film with a thickness of several hundred to several thousand micrometers is formed by the usual CVD method, and then a film of 8i1N with a thickness of several hundred to several thousand is formed using the usual Photoring 2 film technique. A desired pattern 25t is formed using the following method. Next, the 8i
CVD method or plasma CV on the other surface of the single crystal substrate
By method such as D method or sputtering method s 8t
, N, , BN, 8tC, Si, etc., or a composite film thereof.
- Au, pt, W are formed on this X-ray transparent layer 23.
or Ta to form a desired transfer pattern 21 and alignment mark 22. Next, the transfer pattern 21 and alignment mark 22 are protected using an arbitrary jig.

For example, using an etching liquid such as a 30% KOH aqueous solution, a predetermined area of the 8i single crystal substrate is etched into a core 8i1NJ pattern 2.
5 is used as a protective film and removed by etching to form a window frame-shaped reinforcing support z4ft consisting of a part of the single crystal substrate 4. Finally, by heating and curing the area of the alignment mark 22, an X-ray exposure mask provided by the present invention as shown in FIGS. 1 and 2 can be obtained. According to the X-ray exposure mask, the dimensions of the Si7 frame can be determined according to the placement area of the transferred chip pattern without being constrained by the outer diameter of the objective microscope for mask alignment of the X-ray exposure device, and the 8i frame t
- Since it can be used as a blanking mask in X-ray exposure, it is possible to prevent the influence of overlapping exposure of adjacent shots in step-and-repeat X-ray exposure, and it is also possible to prevent alignment marks and their Since an organic film is provided in the peripheral area that allows only visible light to pass through and absorbs most of the Nor. As a result, the yield of semiconductor devices obtained from one wafer (per wafer) has been significantly improved compared to the conventional method, and the design of X-ray exposure masks has also become easier.

[Brief explanation of the drawing]

Fig. 1 is a schematic plan view of the X-ray exposure mask of the present invention, Fig. 2 is a schematic cross-sectional view on the plane indicated by A- in Fig. 1, and Fig. 3 is a schematic cross-section of a conventional xsm original mask. Figure 4 is a schematic plan view of a conventional general X-ray exposure mask, and Figure 5 is a schematic plan view of a conventional general X-ray exposure mask.
Schematic diagrams are shown to show the influence of adjacent marks when step-and-repeat exposure is performed using the conventional X-ray exposure mask shown in the figure. Each number in the figure indicates the following. 11.21, 31.42...X-ray absorber pattern. 12.22, 43... Alignment mark, 13° film, 51... Chip pattern, 52... Margin area, 5
3...Superimposed g-light region. Tei 3 Illustration 4 Written amendment of bile procedure (voluntary) 1. Display of case 1985 Patent application No. 254
No. 83 No. 2, Name of the invention Column 6 of Detailed Description of the Invention of the Book, Contents of Amendment

Claims (1)

[Claims] an X-ray transparent thin film, a Si substrate in close contact with one surface of the thin film and having a plurality of opening areas, and a molded arrangement on the other surface of the thin film so as to be included in the opening area of the Si substrate. and an alignment mark formed in another opening area provided separately from the opening area where this mask pattern is arranged, and an opening area of a Si substrate in which this alignment mark is formed. The X is characterized by being filled with a material that is transparent to alignment light and absorbs exposure X-rays.
Line exposure mask.