JP2810061B2 - Method for manufacturing semiconductor device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to a lithography technique performed in a manufacturing process of a semiconductor element, a magnetic bubble element, and the like, and more particularly, to a method of manufacturing a semiconductor device having a fine pattern.

[Conventional technology]

With the miniaturization and high integration of semiconductor elements and magnetic bubbles, projection exposure equipment used in the lithography process includes:
There is a demand for miniaturization and high resolution of patterns that can be transferred. The resolution which indicates how fine a pattern can be transferred by a projection exposure apparatus is evaluated based on whether or not two adjacent bright portions can be separated when a pattern on a reticle is transferred onto a wafer. It is known that as one method of improving the resolving power, a phase difference may be given to exposure light at two adjacent transmission portions on the reticle. Conventionally, a reticle pattern for giving a phase difference to exposure light is disclosed in, for example, JP-A-58-173744. This conventional example does not disclose a reticle structure that can be put to practical use and a manufacturing method thereof. Japanese Patent Laid-Open Publication No.
-231851, but does not describe pattern formation using a phase shift mask.

[Problems to be solved by the invention]

In the above prior art, no consideration is given to the prevention of electrification at the time of drawing a phase shift pattern using electron beam exposure.Electrons are charged on a substrate to be drawn at the time of drawing an electron beam, fluctuations in pattern dimensions, and errors in pattern position errors. Occurrence was a problem.

When drawing the original pattern, the entire surface of the glass substrate is usually Cr
Since there is a film (light shielding film), it is grounded through the Cr film, so that no charging occurs. On the other hand, the drawing of the phase shift pattern becomes a transmission part having almost no Cr film, so that charging occurs.

An object of the present invention is to construct a process that does not cause charging when drawing a phase shift pattern. Another object of the present invention is to form a fine repetitive pattern of a semiconductor device with high resolution. It is another object of the present invention to provide a technique capable of forming a capacitor having as large a capacity as possible within a limited occupation area when forming a charge storage capacitor of a semiconductor device.

[Means for solving the problem]

The above objective is for electron beam exposure of the phase shift pattern,
This is achieved by using a process with antistatic means.

Antistatic can be achieved by imparting conductivity to any of the glass substrate, the phase shift film, and the electron beam resist, or by interposing a conductive film between each layer or on the resist. That is, it is necessary to make the structure such that the potential is grounded. The present invention also relates to a method of manufacturing a semiconductor device including a step of forming a pattern group of a charge storage capacitor of the semiconductor device, wherein the phase of the transmitted light is set in a light transmitting region surrounded by a light shielding portion. The phase shift part that inverts the phase of the light transmitted through the part is arranged in a checkered pattern,
The outermost phase shift portion irradiates light to a photomask formed at a position where an end portion is in contact with the light-shielding region, and transmits light of the phase shift portion having a phase inverted with respect to the light-shielding portion and the phase shift portion. It is characterized in that the semiconductor wafer is exposed to a pattern group of the capacitor of the stored charge corresponding to the phase shift section of the photomask to form a pattern by interference of transmitted light in a light transmission area where a shift section is not formed. This is achieved by a method of manufacturing a semiconductor device described below.

〔Example〕

 Reference Example An embodiment of the present invention will be described below with reference to FIG.

As shown in FIG. 1A, a light-shielding film 2 made of Cr is formed on a glass substrate 1 by an ordinary method. Next, the target pattern 2-4 is simultaneously formed with the original pattern composed of the transmission portions 2-1 2-2, 2-3 by a usual method. Next, the phase shift layer 3 was applied on the entire surface.

Next, as shown in FIG. 1B, a resist 4 was applied on the entire surface, and the resist and the phase shift layer were removed only from the alignment target portion 5. After a while, match target pattern 2
The glass substrate 1 was etched using the -4 Cr film as a mask to form a concave matching target pattern 6. After the resist 4 was removed, as shown in FIG. 1C, an electron beam resist 7 was formed on the entire surface, and an Al film was formed thereon with a thickness of 50 nm. The Al film is for antistatic and has a film thickness of 10
0 nm or less is sufficient. Thereafter, a phase shift pattern was drawn at a desired position with the electron beam 9. At this time, the target pattern 6 was used for pattern alignment. Since the target pattern 6 is a deep concave pattern, the secondary electron image from the target was clear and good alignment accuracy was obtained. A good signal image could not be obtained with a target consisting only of the Cr pattern, and pattern matching was difficult.

Next, as shown in FIG. 1D, an alkali-based developer was prepared at a concentration lower than the developing sensitivity of the electron beam resist 7, and the Al film 8 was removed with this solution. Next, the concentration of the developing solution was adjusted to a concentration suitable for resist development, and development was performed to form a resist pattern 4 '. At this time, the removal of the Al film was performed by diluting the resist developing solution, so that the next development could be performed with good characteristics without deterioration of the resist. Next, the phase shift layer 3 was etched using the resist pattern 4 'as a mask to form a phase shift pattern 3'. Next, the resist pattern 4 'was removed, and a phase shift type reticle was produced.

In the above embodiment, a coating silicon compound was used for the phase shift layer 3, and the film thickness t was a value satisfying the phase inversion condition 1 of the illumination light.

Here, λ = 365 nm and n = 1.47. At this time, t = 388 nm, and in this embodiment, it is 390 nm. Electron beam resist is RD
-2000N (Hitachi Kasei Kogyo KK) using NMD-3
(Tokyo Ohka Kogyo KK) was used.

A dilute solution of hydrofluoric acid was used for etching the phase shift layer 3 using the resist as a mask. When the etching of the phase shift layers on the patterns 2-3 and 2-1 is finished, there is a concern that the substrate glass is exposed and etched, but the etching speed of the coated silicon compound as the phase shift material is about 10 times that of the substrate glass. It was no longer a problem. Depending on the material, the etching selectivity with the substrate may be small.
In this case, it is desirable to interpose an etching stop layer between the phase shift layer and the substrate.

Although the present embodiment is performed under the above conditions, the present invention is not limited to this. For example, a similar effect can be obtained by forming a conductive film between the glass substrate and the Cr film or on the entire surface after forming the Cr pattern. Alternatively, it is also effective to use the single-layer electron beam resist 7 as a multilayer resist and to use any one of the multilayer films as a conductive film. Also, the exposure wavelength is not limited to 365 nm, and it goes without saying that other ultraviolet rays, excimer laser light, and the like are also effective.

In addition, as a modification of the present embodiment, a phase shift type reticle can be created in substantially the same process even when the phase shift layer 3 is provided between the light shielding film 2 and the glass substrate 1. For example, the structure of the reticle brace used is a glass substrate,
A typical example is a four-layer structure of Si ₃ N ₄ , SiO ₂ , and Cr. Here, the Si ₃ N ₄ film serves to prevent the etching of the glass substrate when the unnecessary portion of SiO _{2 serving as} the phase shift layer is removed by etching. SiO ₂ is a phase shift layer, and Cr is a light shielding film. The above structure is an example, and the present invention is not limited to this. When the etching selectivity between the glass substrate and the phase shift material is sufficiently large, the etching stopper is unnecessary. Further, the above materials are not limited thereto, and other materials may be used as long as the objects of the present invention are satisfied.

Embodiment 1 A second embodiment of the present invention will be described below. Here, a phase shift mask structure particularly suitable for forming a fine space is shown. FIG. 2 shows the mask structure of the present invention, the amplitude of the transmitted light obtained by this mask, and the corresponding light intensity on the wafer. As shown in FIG. 2 (a), a glass substrate
A light-shielding film 11 made of Cr is formed on 10, and a phase shifter 13 made of a transparent film is formed in the transmission part 12. As shown in FIG. 2B, the amplitude distribution of the light transmitted through the mask is such that the phase of the portion having the phase shifter is inverted. When this light is projected on the wafer, the light intensity becomes 0 at the phase inversion portion as shown in FIG. 2 (c), and an extremely fine groove is formed in the pattern formation using the negative resist.

As an improved example of this embodiment, by providing a light-shielding film at the boundary of phase inversion, it becomes possible to form a pattern with good line width control.

Second Embodiment An example in which the mask structure of the second embodiment is applied to the manufacture of a semiconductor memory device will be described. The phase shift type mask of the second embodiment was used to form a pattern of a storage capacitor portion in a manufacturing process of a stacked capacitor type cell having a typical cell structure of a DRAM dynamic random access memory (Dynamic Random Access Memory).

FIG. 3 shows the planar shapes of the pattern obtained by the conventional method and the pattern according to the present invention. FIG. 3A shows a pattern shape obtained by using a conventional mask. Storage capacity section
Although the interval 14 of 13 could be miniaturized to the resolution limit of lithography, shorts occurred between patterns with dimensions smaller than that. The i-line (365 nm) lens having a numerical aperture of 0.42 used here had a resolution limit of 0.5 μm. On the other hand, as shown in FIG. 3 (b), in the example to which the present invention is applied, the resolution can be reduced to below the resolution limit of the lens of the interval 14 'of the storage capacitor portion 13', and the interval of 0.1 μm can be resolved. did it.

Therefore, according to the present invention, the area of the storage capacitor section can be greatly increased despite the same pitch as the arrangement pitch 15 of the storage capacitor section in the conventional method. As a result of measuring the storage capacity of the DRAM manufactured in this example, it was 38 fF per bit of memory in the present invention, which was about double the capacity of 20 fF of the conventional method, and a highly reliable element was manufactured. . From another viewpoint, when the same storage capacity area as that of the conventional method is sufficient, the interval 15 can be made smaller, the cell area can be reduced, and the chip size can be reduced.

〔The invention's effect〕

As described above, according to the present invention, the substrate is not charged during the electron beam exposure of the phase shift pattern, and a good phase shift pattern can be formed. For example, in the present embodiment, the displacement between the original image pattern and the phase shift pattern is 0.
3μm or less, and the dimensional accuracy of the obtained pattern is ± 0.2
μm or less.

In addition, a mask structure that makes full use of the characteristics of the phase shift mask makes it possible to form ultra-fine patterns,
It is also effective for improving characteristics or reducing the area of a semiconductor memory element or the like.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a manufacturing process of a photomask of the present invention,
FIG. 2 is a cross-sectional view showing the mask structure of the present invention and a diagram showing the amplitude distribution and light intensity of the obtained transmitted light, and FIG. 3 is a plan view of a formed pattern according to the conventional example and the embodiment of the present invention. . 1,10: glass substrate, 2,11: light-shielding film Cr, 3,13: phase shift layer, 7: electron beam resist, 8: Al, 13: storage capacitor section.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tsuneo Terasawa 1-280 Higashi-Koikekubo, Kokubunji-shi, Tokyo Inside the Hitachi, Ltd. Central Research Laboratory (72) Inventor Shinichiro Kimura 1-280 Higashi-Koikekubo, Kokubunji-shi, Tokyo Hitachi, Ltd. (56) References JP-A-55-79447 (JP, A) JP-A-62-195120 (JP, A) JP-A-61-292463 (JP, A) JP-A-58-173744 (JP, A) A) JP-A-62-92438 (JP, A) JP-A-62-189468 (JP, A) JP-A-2-34854 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) ) G03F 1/00-1/16 H01L 21/30

Claims (4)

(57) [Claims] 1. A method of manufacturing a semiconductor device, comprising: forming a pattern group of a charge storage capacitor of a semiconductor device, wherein a phase of a transmitted light in a light transmitting region surrounded by a light shielding portion is set in the light transmitting portion. A phase shift portion that inverts the phase of the light transmitted therethrough is arranged in a checkered pattern, and the outermost phase shift portion irradiates light to a photomask formed at a position where an end portion is in contact with the light shielding region, The semiconductor wafer corresponds to the phase shift portion of the photomask on the semiconductor wafer due to interference between transmitted light of the phase shift portion having a phase inverted with respect to the light shielding portion and transmitted light of a light transmission region where the phase shift portion is not formed. A method of manufacturing a semiconductor device, comprising: exposing a pattern group of a capacitor of the stored charge to form a pattern. 2. The method of manufacturing a semiconductor device according to claim 1, wherein a light-shielding film for controlling line width is provided at a boundary between the phase shift portion and the phase inversion of the light transmitting region. . 3. A method for manufacturing a semiconductor device, comprising a step of forming a pattern group of a charge storage capacitor of a semiconductor device, wherein a phase of transmitted light is set in a light transmitting region surrounded by a light shielding portion. A plurality of two-dimensionally arranged phase shift units that invert the phase of light transmitted therethrough, and the outermost phase shift unit is
By irradiating light to a photomask formed at a position where an end portion is in contact with the light shielding region, interference between light transmitted through the phase shift portion and light transmitted through a light transmission region where the phase shift portion is not formed is caused. Forming a pattern in which the stored charge capacitors are arranged in a grid pattern on the semiconductor wafer. 4. The light-shielding region, the first light-transmitting region, and the phase of the transmitted light is inverted from the phase of the light transmitted through the first light-transmitting region, and the first light-transmitting region and the light-shielding film are separated from each other. A method of manufacturing a semiconductor device, comprising irradiating a mask having a second light transmissive region adjacent thereto through a light to form a pattern in which charge storage capacitors of the semiconductor device are arranged in a grid pattern.