JP2005277284A - Exposure method and manufacturing method of semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exposure method for securing the light quantity of reflected light required for focus control, and to provide a manufacturing method of a semiconductor device. <P>SOLUTION: In the exposure method, the focus of an exposure beam to a workpiece is adjusted based on reflected light. The method includes a process for forming on the workpiece a reflection film having a reflection factor larger than that of the workpiece, a process for forming a resist layer on the reflection film, and a process for irradiating the workpiece with beams for focus adjustment from above the resist layer and adjusting the focus of the exposure beam based on reflected light reflected by the reflection film. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an exposure technique, and more particularly to an exposure method for performing focusing by a focus adjustment mechanism and a method for manufacturing a semiconductor device.

  2. Description of the Related Art In recent years, TIR (Total Internal Reflection) type holographic exposure technology has attracted attention in the patterning process of semiconductor devices. This exposure technique includes a recording process for recording a desired pattern on a hologram mask and an exposure process for irradiating the hologram mask with reproducing light to expose a semiconductor pattern photoresist.

  In the recording step, first, a mask pattern (original reticle) corresponding to the pattern of the semiconductor device is irradiated with a recording beam of laser light to generate diffracted light, which is emitted onto the recording surface of the hologram mask. On the other hand, the reference light is irradiated from the back side of the hologram mask at a fixed angle with respect to the recording surface of the hologram mask, and interferes with the diffracted light from the original reticle. As a result, an interference pattern is generated on the recording surface of the hologram mask, and this is recorded on the hologram recording surface.

  In the exposure process, a hologram mask is placed at the same position as the original reticle, and the exposure beam, which is the reproduction light, is irradiated from the opposite direction to the time of recording, and the diffracted light that reproduces the original pattern is coupled to the photoresist formed on the substrate. Image and expose the photoresist.

For example, as described in Non-Patent Document 1, in the exposure process, in general, in order to focus the exposure beam as reproduction light, a reflection beam obtained by irradiating the substrate with a focus beam and reflecting it is reflected. The focus of the exposure beam is controlled by detecting light.
F. Clube et al., "0.5mm Enabling Lithography for Low-temperature Polysilicon Displays", Information Display Society 2003 International Symposium Technical Paper Digest, 34, Book I, p. 350-353 (SOCIETY FOR INFORMATION DISPLAY, 2003 INTERNATIONAL SYMPOSIUM, DIGEST OF TECHNICAL PAPERS, VOLUME XXXIV, BOOK I, pp.350-353), May 20, 2003

  However, for example, in a method of manufacturing a semiconductor device, when a contact hole is formed in an insulating layer made of silicon oxide or the like by the above exposure method, the focus beam is reduced because the insulating layer has a low reflectance. There is a problem that the focus control cannot function effectively because the insulating layer is transmitted and sufficient reflected light cannot be obtained.

  Accordingly, an object of the present invention is to provide an exposure method and a semiconductor device manufacturing method in which the amount of reflected light necessary for focus control is ensured.

  In order to solve the above-mentioned problems, the present invention is an exposure method for adjusting the focus of an exposure beam on a workpiece based on reflected light, and has a higher reflectance on the workpiece than the workpiece. And a step of forming a resist layer on the reflective film. The workpiece is irradiated with a focus adjusting beam from the resist layer and reflected by the reflective film. An exposure method for adjusting the focus of the exposure beam based on the reflected light is provided.

  According to this, since a reflective film having a larger reflectance than the workpiece is formed on the workpiece, the amount of reflected light necessary for focus control when the focus adjustment beam is irradiated. Can be secured. Therefore, for example, even when the workpiece is made of a material that cannot reflect the focus adjustment beam in an amount necessary for focus adjustment, it is possible to perform focus adjustment with high sensitivity, and to perform exposure with high accuracy. Can be done.

  Another aspect of the present invention is a holographic exposure method that adjusts the focus of an exposure beam on a workpiece based on light reflected from the hologram mask and the workpiece, the workpiece being processed on the workpiece. A step of forming a reflective film having a larger reflectance than an object, and a step of forming a resist layer on the reflective film, and a hologram mask placed above the resist layer, via the hologram mask An exposure method for irradiating the workpiece with a focus adjustment beam and adjusting the focus of the exposure beam on the basis of interference light of reflected light reflected from the hologram mask and the reflection film is provided. is there.

  Thus, even when the present invention is used for hologram exposure, a reflective film having a higher reflectance than the workpiece is formed on the workpiece, so that when the beam for focus adjustment is irradiated, Therefore, it is possible to secure the amount of reflected light necessary for focus control. Therefore, for example, even when the workpiece is made of a material that cannot reflect the focus adjustment beam in an amount necessary for focus adjustment, it is possible to perform focus adjustment with high sensitivity, and to perform exposure with high accuracy. Can be done.

  It is preferable that the wavelength of the beam for focus adjustment is 800 to 900 nm, and the reflection film has a reflectivity that can secure a minimum reflected light amount capable of focus adjustment with respect to the wavelength. The focus adjustment beam having a wavelength in the above-mentioned range is preferably used. In such a wavelength region, the reflective film can secure the amount of reflected light necessary for the focus adjustment, so that the focus can be adjusted with high sensitivity. Adjustments can be made.

  Here, the amount of reflected light necessary for focus adjustment varies depending on the sensitivity of the focus beam detector provided in the exposure apparatus. For example, when the reflectance of the reflective film is about 20% or more, the sensitivity is high. Focus adjustment can be performed.

  Another aspect of the present invention is a method of manufacturing a semiconductor device using an exposure method that adjusts the focus of an exposure beam on a processing target layer based on reflected light, and is formed on the processing target layer from the processing target layer. A step of forming a reflective film having a high reflectance; a step of forming a resist layer on the reflective film; and irradiating the processing target layer with a focus adjusting beam from the resist layer, and the reflective film The step of exposing and patterning the resist layer while adjusting the focus based on the reflected light reflected by the step, and performing the etching process using the patterned resist layer as an etching mask, thereby forming a recess or a groove in the processing target layer. And a step of forming a semiconductor device.

  According to this, since the reflection film having a larger reflectance than the processing target layer is formed on the processing target layer, the amount of reflected light necessary for focus control when the focus adjustment beam is irradiated. Can be secured. Therefore, for example, even when the processing target layer is made of a material that cannot reflect the focus adjustment beam in an amount necessary for focus adjustment, the focus adjustment can be performed with high sensitivity, and exposure can be performed with high accuracy. Can be done. Therefore, the degree of freedom in designing the semiconductor device is expanded. Here, examples of the semiconductor device include a device including a thin film element such as a thin film transistor.

  The present invention can also be suitably applied when the concave portion or the groove portion is a contact hole, a via hole, or a wiring groove. Usually, a contact hole, a via hole, or a wiring trench is often formed in an insulating layer such as an interlayer insulating film. Such an insulating layer is often translucent like a silicon oxide film, for example, and there are cases where a sufficient amount of reflection cannot be expected. Even in such a case, it can be suitably formed according to the production method of the present invention.

  The reflective film is made of a wiring material, and the step of filling the recess or groove with the wiring material and forming the wiring layer on the workpiece layer using the wiring material; Forming a resist layer on the wiring layer, patterning the resist layer, and etching the wiring layer using the resist layer as an etching mask, and etching the wiring layer, It is preferable to remove the reflective film together with the wiring layer. According to this, since the reflective film is made of the wiring material, it is possible to remove the reflective film at unnecessary portions at the same time in the step of etching the wiring layer. Accordingly, since a process for removing an unnecessary reflection film is not required, the manufacturing process can be simplified and the production efficiency of the semiconductor device can be improved.

Hereinafter, an exposure method according to an embodiment of the present invention will be described with reference to the drawings.
First, an exposure apparatus used in this embodiment will be described.
FIG. 1 is a view showing the overall configuration of an example of an exposure apparatus used in the present embodiment.

  As shown in FIG. 1, the holographic exposure apparatus used in this embodiment includes a prism 201, a stage apparatus 222 including a stage 220, a first information processing apparatus 230, a distance measurement optical system 240, a film thickness measurement optical system 250, The light source 260, the second information processing device 270, the exposure light source 280, and the exposure light source driving device 282 are configured.

  The stage device 222 holds an exposed substrate 216, on which a resist layer (photosensitive material film) 212 is formed on a substrate 210 as a workpiece, is held on the stage 220 with a vacuum chuck or the like, and moves in the vertical direction (Z direction). In addition, the position of the stage 220 can be adjusted in the horizontal direction (XY plane).

  The light source 260 is configured to be able to emit measurement light beams from the distance measurement optical system 240 and the film thickness measurement optical system 250. The distance measuring optical system 240 will be described in detail later. The film thickness measurement optical system 250 includes a beam splitter, a photodetector, an amplifier, an A / D converter, and the like, and has a configuration for measuring the film thickness of the resist layer 212 formed on the substrate 210. The second information processing device 270 moves the exposure light source 280 so that the exposure beam irradiated from the exposure light source 280 scans within the appropriate exposure region, and the second information processing device 270 outputs the resist layer 212 output by the film thickness measurement optical system 250. The exposure light quantity is controlled based on the relative value of the film thickness. The exposure light source 280 is configured to be able to irradiate the hologram recording surface 202 of the hologram mask 200 with an exposure beam. The exposure light source driving device 282 is related to the driving device of the present invention, and is configured to move the exposure light source 280 to scan and expose a desired exposure area on the substrate 216 to be exposed. Further, the exposure apparatus includes a prism 201 on which a hologram mask 200 on which an interference pattern corresponding to a predetermined reticle pattern is recorded is mounted on the surface facing the substrate 216 to be exposed.

Next, the distance measuring optical system 240 will be described.
FIG. 2 is a diagram for explaining the distance measuring optical system 240. The distance measuring optical system 240 includes a beam splitter 310, a diffraction grating 312, a linear CCD array 314 (Linear Charge-Coupled Devices Array) as an optical sensor, an error signal detector 316, and the like.

  The mechanism of the distance measuring optical system 240 will be described. A focus adjusting beam emitted from the light source 260 (also referred to as a focus beam; for example, a beam having a wavelength of 800 to 900 nm is used) is reflected on the hologram mask 200 and the substrate 210 via the prism 201. Reflected lights having different wavelengths respectively reflected by the hologram mask 200 and the substrate 210 are guided to the diffraction grating 312 by the beam splitter 310. Thereafter, the light is dispersed by the diffraction grating 312 and concentrated on the linear CCD array 314. The intensity distribution when passing through the CCD changes due to the interference wave of the reflected light from the hologram mask 200 and the substrate 210. A change in intensity distribution obtained from the linear CCD array 314 is detected by an error signal detector 316, and a change in the distance between the hologram mask 200 and the substrate 210 is calculated. Thereafter, the calculated error information is transmitted to the first information processing device 230. In the first information processing apparatus 230, the position of the stage 220 is set so that the focus is appropriate based on the distance between the hologram recording surface measured by the distance measuring optical system 240 and the resist layer surface formed on the exposed substrate. Position information to be sent to the stage device 222. The stage device 222 adjusts the position of the stage 220 in the vertical direction (Z direction) based on the position information for setting the position of the stage 220. By such a mechanism, it is possible to adjust the distance between the hologram recording surface 202 and the resist layer surface 214 applied on the substrate to be exposed, and it is possible to perform exposure with high accuracy.

  Next, the exposure method of the present embodiment will be described with reference to FIGS. 3 and 4 taking a semiconductor device manufacturing method as an example. 3 and 4 are views for explaining the method for manufacturing the semiconductor device of this embodiment. In this example, the process for forming a wiring layer of a semiconductor device will be described as an example.

  First, as shown in FIG. 3A, for example, a p-Si layer 12 (example: 50 nm) on a substrate 10 such as glass, a silicon oxide film 14 (example: 800 nm) as a processing target layer, and a reflective film A substrate 216 to be exposed is prepared by laminating a titanium nitride film 16 (example: 50 nm) and a resist layer 212 (example: 1 μm) in this order. Here, a laminated structure including the substrate 10, the p-Si layer 12, the silicon oxide film 14 as a processing target layer, and the titanium nitride film 16 corresponds to the base 210. A stacked structure including the base 210 and the resist layer 212 corresponds to the substrate to be exposed 216.

  Specifically, the p-Si layer 12 may be an active layer such as a thin film transistor, and is formed by various film forming methods such as a PECVD method, an LPCVD method, and a sputtering method. The silicon oxide film 14 can be formed by a film forming method such as an electron cyclotron resonance PECVD method (ECR-PECVD method) or a PECVD method. The titanium nitride film 16 can be formed by a film forming method such as a sputtering method or a CVD method. Although not shown, a base insulating layer such as a silicon oxide film may be formed between the substrate 10 and the p-Si layer 12.

The resist layer 212 is patterned by irradiating the exposure substrate 20 with the exposure beam 20. Thereby, the desired area 18 irradiated with the exposure beam 20 is exposed.
Specifically, in this embodiment, the planned region 18 in which the contact hole is to be formed is exposed with the exposure beam 20. At this time, in order to perform focus control of the exposure beam 20, the substrate 216 to be exposed is simultaneously irradiated with the focus adjusting beam as described above.

  Here, the silicon oxide film 14 which is a processing target layer has high light transmittance. Therefore, for example, when a focus adjustment beam having a wavelength of 800 to 900 nm is irradiated, the reflectivity is low, so that the amount of reflected light necessary for focus adjustment of the exposure beam 20 cannot be obtained sufficiently. However, in this embodiment, since the titanium nitride film 16 having a higher reflectance than the silicon oxide film 14 is formed, a reflected light amount sufficient for focus adjustment can be obtained.

  Here, although the titanium nitride film 16 is used as the reflective film, the present invention is not limited to this, and it is sufficient that at least a minimum reflected light amount necessary and sufficient for focus adjustment is obtained. The amount of reflected light necessary for focus adjustment also varies depending on the sensitivity of the focus beam detection device provided in the exposure apparatus. For example, the reflectance of the reflective film is about 20% or more, for example, 20 to 80%. It is preferable that When the reflectance is in the above range, focus adjustment can be performed with high sensitivity, and irradiation of the exposure beam 20 is not hindered. In this embodiment, a hologram exposure apparatus manufactured by Holtronic Technologies is used as an exposure apparatus (including a focus system).

  However, if it is necessary to remove the reflective film after forming the wiring layer in a later step, the reflective film can be removed at the same time as the etching process after patterning the wiring layer, so it is used to form the wiring layer. It is preferable to form the reflective film with the same wiring material as that used. Examples of the wiring material used to form such a reflective film include barrier metal and metal. More specifically, for example, when the wiring layer is made of a metal such as aluminum, it can be removed by etching at a later step by using, for example, Ti or TiN as the reflective film. Further, it is preferable that the reflective film does not substantially affect the exposure beam irradiation. For example, when Ti or TiN is used as the reflective film, it is preferable because the exposure beam can be accurately exposed without substantially affecting the exposure beam. Further, it is preferable that the reflective film has sufficient light shielding properties (attenuation rate) with respect to the wavelength of the focus adjustment beam. When the reflective film is a highly transmissive film (a film having a low attenuation rate, such as a-Si), the film formed under the reflective film is patterned under the reflective film. The focus system may pick up the influence of the focus adjustment beam reflected by the film as noise. In this case, focus control accuracy may be lowered, which is not preferable. In the case of Ti or TiN, it has been confirmed that there is no influence by such noise.

  In the exposure apparatus used in this embodiment, as described above, the focus adjustment beam is irradiated perpendicularly to the substrate 216 to be exposed, so that it is particularly difficult to obtain reflected light. Accordingly, in such an apparatus, it is necessary to particularly increase the detection sensitivity of the reflected light of the focus adjustment beam, and the use of the reflective film is particularly useful in such an apparatus.

  Next, as shown in FIG. 3B, the resist layer 212 is developed. Subsequently, as shown in FIG. 3C, using the developed resist layer 212 as an etching mask, the titanium nitride film 16 and the silicon oxide film 14 as a reflective film are etched. At this time, the etching process may be performed by wet etching or dry etching, for example. Thereafter, the contact hole 21 is formed by removing the resist layer 212.

  Next, as shown in FIG. 3D, a wiring layer 28 is formed. The wiring material constituting the wiring layer 28 is not particularly limited, and for example, a metal such as tantalum or aluminum is used. In the present embodiment, the wiring layer 28 includes a titanium layer 22 (example: 50 nm), an aluminum layer 24 (example: 800 nm), and a titanium nitride layer 26 (example: 50 nm). The wiring layer 28 is formed by depositing a metal material constituting the wiring layer 28 by a method such as sputtering.

  Next, as shown in FIG. 4A, a resist layer 30 is formed on the wiring layer 28, and the resist layer 30 is patterned and developed. Thereafter, as shown in FIG. 4B, the wiring layer 28 is etched. At this time, the titanium nitride film 16 formed in an unnecessary region can be etched simultaneously with the wiring layer 28. Thereafter, by removing the resist layer 30, it is possible to obtain a semiconductor device in which the wiring layer 28 having a desired pattern is formed (see FIG. 4C).

  According to the present embodiment, since the reflective film 16 is formed below the resist layer 212, it is possible to secure the amount of reflected light necessary for focus control when the focus beam is irradiated. Therefore, even when the workpiece is made of a material that cannot reflect the required amount of the focus beam, focus adjustment can be performed with high sensitivity, and exposure can be performed with high accuracy. In addition, when the focus beam is incident vertically as in the exposure apparatus used in the present embodiment, it is difficult to obtain reflected light, and it is often difficult to obtain a reflected light amount sufficient for detection. Therefore, the present invention is particularly useful for such an exposure apparatus.

Further, according to the present embodiment, since the material of the reflective film 16 is the same as the material constituting the wiring layer, the reflective film 16 formed in an unnecessary region can be simultaneously formed with the etching process of the wiring layer. Is good.
In the present embodiment, the contact hole formation process has been described as an example. However, the method of the present invention can also be applied to the formation of a via hole or a groove.

  The semiconductor device manufacturing method of the present invention is applied to, for example, formation of a pixel circuit that constitutes each pixel in an electro-optical device such as an EL display device or a liquid crystal display device, or a driver (integrated circuit) that controls the pixel circuit. can do. In addition to the manufacture of such an electro-optical device, the present invention can be applied to various device manufacturing. For example, various memories such as FeRAM (ferroelectric RAM), SRAM, DRAM, NOR type RAM, NAND type RAM, floating gate type non-volatile memory, magnetic RAM (MRAM) can be manufactured. In addition, the present invention can also be used for sensors integrated using thin film transistors, bank cards equipped with CPUs, and the like. Further, in a non-contact communication system using microwaves, the present invention can also be applied to manufacturing an inexpensive tag mounted with a minute circuit chip (IC chip).

FIG. 1 is a view showing the overall configuration of an example of an exposure apparatus used in the present embodiment. FIG. 2 is a diagram for explaining the distance measuring optical system 240. FIG. 3 is a view for explaining the method for manufacturing the semiconductor device of this embodiment. FIG. 4 is a view for explaining the method for manufacturing the semiconductor device of this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Substrate, 12 ... p-Si layer, 14 ... Silicon oxide film, 16 ... Titanium nitride film, 18 ... Exposure region, 20 ... Exposure beam, 21 ... Contact Hole: 22 ... titanium layer, 24 ... aluminum layer, 26 ... titanium nitride layer, 28 ... wiring layer, 30 ... resist layer, 110 ... light shielding device, 200 ... hologram Mask, 201 ... prism, 202 ... hologram recording surface, 210 ... substrate, 212 ... resist layer, 214 ... resist layer surface, 216 ... substrate to be exposed, 220 ... stage , 222 ... stage device, 230 ... information processing device, 240 ... distance measurement optical system, 250 ... film thickness measurement optical system, 260 ... light source, 270 ... information processing device, 280 ... Exposure light source, 28 ... exposure light source driving unit, 310 ... beam splitter, 312 ... diffraction grating, 314 ... linear CCD array, 316 ... error signal detector

Claims (6)

An exposure method for adjusting the focus of an exposure beam on a workpiece based on reflected light,
Forming a reflective film having a greater reflectance than the workpiece on the workpiece;
Forming a resist layer on the reflective film,
An exposure method comprising: irradiating the workpiece with a focus adjustment beam from above the resist layer, and adjusting a focus of the exposure beam based on reflected light reflected by the reflection film. A holographic exposure method for adjusting a focus of an exposure beam on a workpiece based on a hologram mask and reflected light from the workpiece,
Forming a reflective film having a greater reflectance than the workpiece on the workpiece;
Forming a resist layer on the reflective film,
Interference of reflected light reflected from the hologram mask and the reflection film by irradiating the hologram mask placed above the resist layer and the workpiece through the hologram mask for focus adjustment. An exposure method comprising adjusting the focus of the exposure beam based on light.   The wavelength of the beam for focus adjustment is 800 to 900 nm, and the reflective film has a reflectance that can secure a minimum reflected light amount that allows focus adjustment with respect to the wavelength. The exposure method as described. A method for manufacturing a semiconductor device using an exposure method for adjusting a focus of an exposure beam on a processing target layer based on reflected light,
Forming a reflective film having a larger reflectance than the processing target layer on the processing target layer;
Forming a resist layer on the reflective film;
Irradiating the processing target layer from above the resist layer with a beam for focus adjustment, exposing the resist layer while adjusting the focus based on the reflected light reflected by the reflective film, and patterning;
A step of forming a recess or a groove in the layer to be processed by etching using the patterned resist layer as an etching mask;
A method for manufacturing a semiconductor device, comprising:   The method for manufacturing a semiconductor device according to claim 4, wherein the recess or the groove is a contact hole, a via hole, or a wiring groove. The reflective film is made of a wiring material, and
Filling the recess or groove with the wiring material and forming the wiring layer on the workpiece layer using the wiring material;
Forming a resist layer on the wiring layer and patterning the resist layer;
Etching the wiring layer using the resist layer as an etching mask;
Including
6. The method of manufacturing a semiconductor device according to claim 4, wherein the reflective film is removed together with the wiring layer in the step of etching the wiring layer.

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