JPH09232220A - Resist pattern formation method - Google Patents

Abstract

(57) Abstract: When a resist pattern made of a photosensitive ultrathin film is to be formed at a desired position on a substrate having a metal film as a film to be processed, or the surface is flat or smooth by CMP or the like. When a reflective film such as a metalized film is formed on the alignment mark, the alignment mark pattern cannot be detected. SOLUTION: A photoresist 8 which is exposed to a light having a wavelength different from the pattern exposure light is applied on a photosensitive ultrathin film 7, the photoresist 8 on an alignment mark 6 is exposed, and etching is performed after development. The alignment mark 6 can be detected by removing the photosensitive ultra-thin film 7 and the metal film 5 or the reflective film that blocks the alignment mark detection light. Then, after removing the photoresist 8, the photosensitive ultrathin film is exposed and developed. [Effect] Since the alignment mark can be detected, it is possible to form a resist pattern at a desired position, particularly a resist pattern made of a photosensitive ultrathin film.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a lithography technique,
More specifically, it belongs to a resist pattern forming technique involving matching.

[0002]

2. Description of the Related Art With the demand for higher integration of ULSI, there is a demand for the formation of an extremely fine resist pattern. At present, resist pattern formation with a minimum dimension of 0.2 μm to 0.3 μm is being actively studied, and the need for further miniaturization is being emphasized. Optical lithography using ArF excimer laser light having a wavelength of 193 nm is in the spotlight as a method for enabling such fine pattern formation. The light source currently used in the mainstream is a g-line (wavelength 436 nm) or i-line (wavelength 365n) of an ultra-high pressure mercury lamp.
m), the resolution is high because the wavelength is shorter than these lights, and it is considered that the resist pattern of 0.2 μm or less can be formed by using this ArF excimer laser light. However, the ArF excimer laser light is strongly absorbed by the novolac resin and the sulfone resin used in the conventional resists, and when these resists are used, the exposure light does not reach the bottom of the resist and a sufficient pattern cannot be formed. There was a problem.

As a method for solving this problem of light absorption, there is a method using an ultrathin film photosensitive hard mask, which has been attracting attention. In this method, Si which is exposed to ArF excimer laser light such as polysilsesquioxane on a substrate to be processed is used.
Ultra-thin film containing oxides of Ge and Ge (eg film thickness 50n
m) is formed by spin coating, and then exposure and development are performed to form a resist pattern made of the ultrathin film. Since this material does not have high light absorption for ArF excimer laser light and is an extremely thin film, it has sufficient resolution. Although it is an ultra-thin film,
Since it contains a large amount of oxides of Ge and Ge, it has a sufficient selection ratio with respect to the substrate to be processed and has a sufficient function as a processing mask. Since this thin film is formed by spin coating, it has good compatibility with conventional lithography techniques and is advantageous in terms of throughput and cost. CVD (Chemic
Compared to the film formed by the al Vapor Deposition method, it has fewer particles, and therefore has fewer film defects and has a better yield. Incidentally, this method is disclosed in JP-A-6-267.
911.

[0004]

When a fine pattern of 0.3 .mu.m is formed by photolithography on a substrate having a step, the depth of focus is insufficient and pattern resolution defects are likely to occur. Therefore, the step difference of the substrate is reduced. The reduction of the substrate step is also important in preventing the disconnection of the wiring layer when manufacturing the LSI, and therefore, the CMP (Chemic) is particularly used for the pattern formation of the wiring layer and the wiring interlayer layer.
The surface pattern is reduced by using a technique such as al mechanical polishing, and the resist pattern is formed on the substrate having a smooth surface. In lithography for forming the wiring layer, the film to be processed becomes a metal film. At this time, a pattern (for example, via hole) formed on the base with a stepless reflecting surface.
However, since light is used to detect the alignment pattern (target) of the exposure apparatus, the alignment pattern formed under this metal is used. However, the fatal defect that the lane cannot be detected and thus the alignment cannot be performed at all is in the conventional ultra-thin film photosensitive hard mask method.

The present invention was conceived in view of the above-mentioned problems in the ultra-thin film photosensitive hard mask method, and is highly accurate even when a metal film subjected to CMP is used as a film to be processed. The present invention relates to a method for forming a resist pattern using an ultrathin film photosensitive hard mask that can perform various alignments. Further, even when a reflective film such as a metal film whose surface is flattened and smoothed by CMP or the like is formed on the alignment mark, a fine resist pattern with high alignment accuracy is provided on the substrate to be processed. It is what you want to form on.

[0006]

In order to solve the above-mentioned problems, according to the present invention, (1) a substrate to be processed on which an alignment mark for forming a resist pattern at a desired position is formed,
A thin film having photosensitivity to pattern exposure light is formed.

(2) On this photosensitive thin film, a photoresist film is formed which is sensitive to light having a wavelength different from the pattern exposure light (this light is referred to as target exposure light).

(3) The region including the alignment pattern is exposed and developed by the target exposure light, and the photoresist film on the alignment mark is removed.

(4) Etching is carried out using the photoresist film as a mask to remove the photosensitive thin film and a part of the substrate to be processed so that the alignment mark can be detected by light.

(5) The photoresist film is removed.

(6) After irradiating the photosensitive thin film with a pattern exposure light through a mask on which a desired pattern is formed, the photosensitive thin film is developed, and the desired position on the substrate to be processed is obtained. A desired photosensitive thin film pattern is formed.

The above steps solve the above problems.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1) Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.

As shown in FIG. 1A, the substrate (Si) 1,
Insulating film (oxide film) 2, wiring pattern (polysilicon)
A substrate composed of 3, an insulating film (oxide film) 4, and a metal film (W) 5 was prepared. The surface of the insulating film 4 was flattened by the CMP method, so that the surface of the metal film 5 was also sufficiently flat and smooth. Since the alignment pattern 6 is placed under the metal film 5 having a flat surface, alignment could not be performed at all in this state.

Next, as shown in FIG. 1B, a thin film sensitive to ArF excimer laser light was formed on the metal film 5.
Although it is an experimental condition, the film thickness of this photosensitive thin film is 50 n.
m, and polysilsesquioxane was used as the material. This photosensitive thin film becomes a positive resist for ArF exposure. Since the photosensitive thin film is as thin as 50 nm, it is possible to form an extremely fine pattern without deterioration due to resolution due to light absorption. Further, a resist 8 sensitive to UV light was applied on the photosensitive thin film 7, and thereafter, exposure to UV light was performed only in the vicinity of the alignment pattern. A normal UV light resist can be used as the resist 8, but a water-soluble resist is preferably used because it does not damage the photosensitive thin film 7 when the resist is applied and removed. In general, a water-soluble resist has a low resolution, but here it is intended for a large pattern of opening an opening in the vicinity of an alignment pattern, and this does not pose a problem because the required accuracy is not high. FIG. 1B shows a case of so-called proximity exposure in which the mask 9 is brought close to the substrate and the light 10 is irradiated, but the present invention is not limited to this, and projection exposure and scanning exposure can be used. . After that, the resist 8 is developed to form a resist pattern 8a in which openings are formed only in the vicinity of the alignment pattern, and then etching is performed to open the openings only in the vicinity of the alignment pattern as shown in FIG. 1 (c). Photosensitive thin film pattern 7a and metal film pattern 5a having No. 11 were formed.

Next, after removing the resist pattern 8a,
As shown in FIG. 1D, after the alignment mark 6 is detected and the wafer and the reticle are aligned with each other, the reticle pattern 12 is interposed in the middle of the ArF excimer light 1
3 was irradiated to expose a desired pattern at a desired position.
Although the alignment pattern could not be detected at the stage of FIG. 1 (a), the metal film on the alignment mark was removed at the stage of FIG. 1 (d), so that the highly accurate pattern could be obtained. Was detected. An oxide film 4 is coated on the alignment mark, but this is not a problem because it is transparent to the alignment pattern detection light. Although the optical system such as the lens is omitted in FIG. 1D, the stepper having the apparatus configuration shown in FIG. 2 is actually used.
However, this is an embodiment, and a scanner or a projection aligner may be used instead of the stepper.

The exposure apparatus used here will be described. Light emitted from a light source (ArF excimer laser light) 501 is a fly-eye lens 502 and condenser lenses 503 and 50.
5 and the mirror 504, the mask (reticle) 506.
Illuminate. A pellicle 507 is provided on the mask 506 to prevent pattern transfer failure due to foreign matter. The mask pattern drawn on the mask 506 is projected onto a wafer 509 which is a sample substrate via a projection lens 508. The mask 506 is placed on the mask stage 518 controlled by the mask position control means 517, and the center thereof and the optical axis of the projection lens 508 are accurately aligned. The wafer 509 is a sample table 510.
Vacuum adsorbed on top. The sample table 510 is mounted on a Z stage 511 that is movable in the optical axis direction of the projection lens 508, that is, the Z direction, and is further mounted on an XY stage 512. Z stage 511 and XY stage 5
12 is driven by the respective drive means 513, 514 according to the control command from the main control system 519,
It can be moved to a desired exposure position. The position is accurately monitored by the laser length measuring machine 515 as the position of the mirror 516 fixed to the Z stage 511. Further, the position of the wafer 509 in the XY directions is measured by an alignment pattern detecting means including a detection light generating section 520, detection light 523, and a light receiving section 521. Based on the detection result, the XY stage is moved to accurately align the reticle and the wafer.

Next, development is performed to form a photosensitive thin film pattern 7b as shown in FIG. 1 (e), and the photosensitive thin film pattern 7b is cured by baking. )
As shown in FIG. 5, the metal film was etched at the desired position by etching the metal film using the photosensitive thin film pattern 7b as an etching mask. Although the photosensitive thin film was as thin as 50 nm, it was a polysiloxane base, and since it was cured by baking, it worked sufficiently as an etching mask. Since the etching mask can be made thin, the microloading effect at the time of etching the metal film is reduced, and the highly accurate metal wiring pattern 5b can be formed.

With this method, it was possible to form a fine pattern at a desired position.

On the other hand, the conventional method cannot detect the alignment mark at all, and it is impossible to perform the alignment. According to the method of removing the metal film on the alignment mark in advance, the extremely thin photosensitive thin film of 50 nm causes severe coating unevenness in the part where the metal film is removed and its periphery (range of about 50 μm), It was the cause of poor pattern resolution. When the film thickness of the photosensitive thin film was made thick enough not to cause coating unevenness, the resolution became insufficient and the microloading effect at the time of etching also occurred, resulting in a large deterioration in the resolution dimensional accuracy.

In this method, the case where the surface of the substrate is a metal film is shown. However, although a transparent film such as an oxide film is deposited on the metal film, it is also possible that the surface of the metal film is flat. By applying this method, it was possible to form a fine and highly precise pattern with good alignment accuracy. Further, when the photosensitive thin film on the alignment mark is directly removed by ArF excimer laser exposure without using a UV resist, the photosensitive thin film is damaged by the etching when removing the metal film, The photosensitivity is lost or the resolution is extremely deteriorated.

(Embodiment 2) In the second embodiment, as shown in FIG. 3, element isolation SiO ₂ 102 and MISFET (Metal Insulator) formed on the surface of a p-type silicon substrate 101.
Semiconductor Field Effect Transistor) Gate Si
O ₂ 103, polycrystalline Si gate electrode 104, SiO ₂ 105 stacked on the gate electrode, SiO ₂ 106 formed on the side wall of the gate electrode, n-type impurity region 107 formed on the surface of the p-type silicon substrate, Si ₃ N ₄ 108 buried between the gate electrodes, polycrystalline Si 109 containing n-type impurities formed on the n-type impurity region, W electrode 110 formed by a substitution process, Ta formed on the surface thereof
_The semiconductor device functions as a memory element including a ₂ O ₅ film 111 and a TiN film 112, SiO ₂ 113 over these structures, a data line 114 formed of W, and the like.

FIG. 4 is a structural view of the semiconductor memory device as seen from above.

FIG. 4 shows an active region 201, a gate electrode 202, a W electrode and a T electrode surrounded by SiO ₂ for element isolation.
Charge storage capacitor 20 formed of a ₂ O ₅ film and TiN film
4. Connection hole 2 for connecting the charge storage capacitor and the active region
03, the data line 207, and the second connection hole 206 for connecting the data line and the active region. here,
Reference numeral 205 is a plane pattern of the TiN electrode used for the charge storage capacitance, that is, a plate. This element uses a two-intersection type layout and has a strong characteristic against electric noise.

When forming the data lines 114 and 207 of this element, the oxide film 113 was flattened by CMP. This eliminates the problem of the depth of focus when forming the data line, and although the resolution is high as in ArF excimer laser lithography, the data line pattern of 0.18 μm is obtained by the exposure method with a shallow allowable depth of focus. Could be formed. However, the conventional method cannot detect the alignment mark at all due to the W film on the surface,
It was not possible to align the mask with the wafer. Therefore, as shown in FIG. 5, this method was applied. Here, the left side of FIG. 5 shows the alignment mark portion, and the right side shows the memory element portion.

First, as shown in FIG. 5 (b), a photosensitive thin film 121 for ArF excimer laser light and a resist sensitive to UV light are placed on a substrate on which W serving as a data line is deposited on the entire surface of the wafer. After coating, only the vicinity of the alignment mark was exposed to UV light and developed to form a resist pattern 122a having an opening 130. The alignment when forming this opening was performed using the orientation flat or notch of the wafer. Although the alignment accuracy is about 10 μm, it is sufficient to open an opening for alignment mark detection. After that, as shown in FIG. 5C, the photosensitive organic film and the W metal film on the alignment mark were removed by etching.
After that, the UV resist was removed to expose the photosensitive thin film 121a on the surface as shown in FIG. 5 (d). By this step, it was possible to form the photosensitive thin film on the reflective substrate in a state that there was no step and there was no unevenness in the coating film thickness and the alignment mark could be detected. Incidentally, the matching here is the matching of 206 and 207 shown in FIG. Then, ArF excimer laser exposure was performed to form fine data lines with high dimensional accuracy and high alignment accuracy. When this method was not used, there was the same problem as in Example 1 and no matching was possible.

[0027]

EFFECTS OF THE INVENTION Even when a reflective film such as a metal film whose surface is flattened and smoothed by CMP or the like is formed on the alignment mark, a fine resist pattern composed of a photosensitive ultrathin film. Can be formed on the substrate to be processed with good alignment accuracy. Therefore, ULSI can be highly integrated. Further, since the chip area can be reduced, the number of chips acquired per wafer can be increased, and the cost can be reduced.

[Brief description of drawings]

FIG. 1 is a process drawing showing a method of the present invention.

FIG. 2 is a diagram showing a configuration of a projection exposure apparatus that realizes the present invention.

FIG. 3 is a sectional view showing a method for manufacturing a semiconductor device of the present invention.

FIG. 4 is a plan view of main patterns forming a semiconductor device of the present invention.

FIG. 5 is a cross-sectional view showing the method for manufacturing a semiconductor device of the present invention.

[Explanation of symbols]

1 ... Si substrate, 2 ... Insulating film (oxide film), 3 ... Wiring pattern
(Polysilicon), 4 ... Insulating film (oxide film), 5 ... Metal film (W), 5a, b ... Metal film pattern, 6 ... Alignment pattern, 7 ... Photosensitive thin film, 7a, b Photosensitive thin film pattern, 8 ... UV resist, 8a ... UV resist pattern, 7 ... Photosensitive thin film, 8 ... UV resist, 9 ... Mask, 10 ... Exposure light (UV), 11 ... Opening, 12 ... Reticle pattern -N, 13 ... ArF excimer laser light, 101 ...
p-type silicon substrate, 102 ... SiO ₂ for element isolation, 10
3 ... Gate SiO ₂ , 104 ... Gate electrode, 105 ... S
iO ₂ , 106 ... SiO ₂ , 107 ... N-type impurity region, 1
08 ... Si ₃ N ₄ , 109 ... Polycrystalline Si, 110 ... W electrode, 111 ... Ta ₂ O ₅ film, 112 ... TiN, 113 ... S
iO ₂ , 114 ... Data line (W), 114a ... W film for data line having an opening in the alignment mark part, 121 ... Photosensitive thin film, 121a ... Photosensitive film having an opening in the alignment mark part Thin film, 122 ... UV resist, 122a ... UV
Resist pattern, 201 ... Active region, 202 ... Gate electrode, 203 ... Connection hole, 204 ... Charge storage capacity, 205
... plate, 206 ... connection hole, 207 ... data line, 50
8 ... Projection lens, 512 ... XY stage, 501 ... Light source, 506 ... Mask, 509 ... Wafer, 517 ... Mask position control means, 518 ... Mask stage, 520 ... Alignment detection light generator, 523 ... Alignment detection light, 521 ... Alignment light detector.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Taku Morisawa 1-280, Higashi Koikekubo, Kokubunji, Tokyo Metropolitan Research Center, Hitachi, Ltd.

Claims (4)

[Claims] 1. A step of forming a thin film having photosensitivity to pattern exposure light on a substrate to be processed on which an alignment mark for forming a resist pattern at a desired position is formed. A step of forming a photoresist film on the photosensitive thin film which is exposed to a target exposure of a wavelength different from that of the pattern exposure light, and exposing the region including the alignment pattern by the target exposure light, The step of developing and removing the photoresist film on the alignment mark, and etching the photoresist film as a mask to remove the photosensitive thin film and a part of the substrate to be processed, and the alignment mark detects by light. And a step of removing the photoresist film, a step of irradiating the photosensitive thin film with a pattern exposure light through a mask on which a desired pattern is formed, Developing the film, the desired photosensitive thin film pattern at a desired position on the substrate to be processed - comprising the step of forming the emission resist pattern - down forming process. 2. The method of forming a resist pattern according to claim 1, wherein the surface of the substrate to be processed is smoothed. 3. The method for forming a resist pattern according to claim 1, wherein a metal film is deposited on the surface of the substrate to be processed. 4. The method of forming a resist pattern according to claim 1, wherein the photoresist film is made of a water-soluble material.