JPH0340497B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an optical exposure apparatus used for manufacturing semiconductor devices.

More specifically, the present invention relates to a reduction projection excimer exposure apparatus devised to realize ultrafine processing in a photolithography process in semiconductor device manufacturing.

2. Description of the Related Art Conventionally, reduction projection exposure apparatuses (steppers) using ultra-high pressure mercury lamps as light sources have already been commercially available for microfabrication of semiconductor devices, particularly LSIs, VLSIs, etc. However, conventional stepper
G-line (436nm) and i-line (365nm) of ultra-high pressure mercury lamps
Because of this, the resolution was limited to about 1.2 μm for the g-line and 0.8 μm for the i-line. At these wavelengths, it is nearly impossible to obtain the 0.5 μm resolution required for future 4MbitRAM and 16MbitRAM production.

Therefore, in recent years, XeCl (308 nm), KrF (249 nm), and ArF (193 nm), which have shorter wavelengths than g-lines and i-lines, have been
The development of exposure apparatuses using excimer light sources such as m) has begun to be considered.

Problems to be Solved by the Invention However, reduction projection exposure using an excimer laser has the following two problems.

(1) Problems with the half-width of the wavelength distribution of excimer laser light and achromatization of the reduction projection lens (relationship between speckle and resolution).

(2) The problem of selecting the alignment wavelength The former problem may be solved by creating an optical system that disturbs the transverse mode of the excimer laser beam while aligning the longitudinal mode, but in the latter case, the problem of selecting the alignment wavelength may be solved. When it comes to selection issues, in order to improve alignment accuracy, we adopt a method (through-the-lens; abbreviated as TTL method) in which the exposure wavelength is used to pass through a reduction projection lens to directly align the reticle (mask) and the mark on the wafer. This is preferable and has the advantage of facilitating lens design, but since the exposure wavelength is in the ultraviolet region, there is a problem that alignment cannot be performed using visible light pattern recognition as in conventional video cameras. Therefore, in the present invention, when using light of the same wavelength as the exposure wavelength for alignment in excimer reduction projection exposure,
The purpose is to enable alignment using the TTL method.

Means to solve the problem Namely, the configuration of the optical path order is as follows: an excimer laser optical system as a light generation source, a mirror and integrator system for uniformity of laser light and beam shaping, and a quartz system for illuminating the reticle. A main optical system consisting of a condenser lens, a reticle, a quartz beam splitter, a quartz reduction projection lens, a wafer on an XYZ stage, the beam splitter, an optical path perpendicular to the exposure optical path, an alignment lens, an alignment beam splitter, Image intensifier (IIT) for image amplification and wavelength conversion, video camera for image processing (e.g. CCD
(camera) alignment optical system (the vertical optical path of the alignment beam splitter is accompanied by an alignment light source for illumination). Note that the alignment optical system is accompanied by an XY system drive system in order to illuminate any location on the wafer. The alignment optical system and the XY stage on which the wafer is mounted are configured to be interfaced with a computer for image processing and alignment signal processing.

Therefore, in the present invention, by using a beam splitter and an IIT for image amplification and wavelength conversion, the alignment of the reticle and wafer can be performed directly using excimer laser light or light with a wavelength close to it to achieve TTL alignment. This has the effect of making it possible to achieve highly accurate alignment.

Examples Examples of the present invention will be described below with reference to the drawings.
That is, as a light source part, for example, a KrF excimer laser light source 1 and an integrator 2 that shapes and homogenizes the light oscillated and emitted from the laser light source.
and a large total reflection mirror 3 that makes the optical path perpendicular, a quartz condenser lens 4 for illuminating the reticle 5 and the reduction lens 7, a reticle 5, a large beam splitter 6 for alignment, and a quartz mirror. With the configuration of the optical system consisting of the reduction projection lens 7,
At the image forming point, there is a main optical system of a reduction projection exposure apparatus that transfers images onto a wafer 9 placed on an XYZ stage 8, and an alignment lens 1 in the order of the optical path on the optical axis perpendicular to the beam splitter 6 and the exposure optical path.
0, Beam splitter 11 for alignment, IIT 12 for image processing/wavelength conversion, CCD for image processing
The alignment optical system consists of a camera 13, and an alignment light source 14 for illuminating the alignment mark (for example, light from an ultra-high pressure mercury lamp separated by a cut filter or monochromator, or a laser) perpendicular to the alignment beam splitter 11. It is held by an XY drive system 15 for illuminating any location on the wafer. Then, install the alignment optical system and wafer 9.
The XYZ stage 8 is interfaced with a control computer 16 for image processing and alignment signal processing.

The alignment optical system will be explained in more detail.
Alignment illumination system 14 For example, a cut filter is used to illuminate the light of around 250 nm from a Xe-Hg ultra-high pressure lamp (when the reduction projection lens 7 and excimer laser light source 1 are KrF), and the alignment lens 10 is illuminated by the alignment beam splitter 11. The beam splitter 6 of the main optical system is illuminated through the beam splitter 6 of the main optical system. At this time, the alignment system is adjusted according to the alignment mark position on the reticle and wafer.
Illumination can be performed arbitrarily by the XY drive system 15. The alignment illumination light passes through the beam splitter 6 to capture an image of the alignment mark on the reticle 5 and the alignment mark on the wafer 9 in the ultraviolet region around 250 nm, and the reflected light is further passed through the beam splitter 6. Through this process, the images of the alignment marks on the wafer 9 and reticle 5 are returned to the alignment lens 10. At this time, the images on the wafer 9 and reticle 5 are magnified by the reduction projection lens 7 and the alignment lens 10, making it possible to obtain a very high resolution. Furthermore, an image of ultraviolet light (visual or
Image intensifier (IIT) 12 is equipped with a microchannel plate (MCP) that converts wavelengths (which cannot be observed in the ultraviolet region) into visible video and amplifies image signals to improve the S/N ratio. The image will be processed using . At this time, the wavelength of the image is usually 500n
By increasing the number of pixels to m or more, observation in the visible range becomes possible, and finally, the CCD camera 13 performs pattern recognition processing of picture elements. In addition
It goes without saying that the higher the resolution of a CCD camera, the better it is, but with the effects of image magnification, visible light, etc., there is not much of a problem.

Image intensifiers include the V1506 (Hamamatsu Photonics Co., Ltd. model name), which has Cs-Te on the photocathode and is sensitive to 150 to 320 nm, and microchannel plates include the F1217 (Hamamatsu Photonics Co., Ltd.). ) etc. can be used.

Effects of the Invention In an excimer laser exposure device, by installing the configuration of the present invention, that is, an IIT including an MCP in front of a video camera, it is possible to convert ultraviolet light into visible light and amplify the image by about ¹⁰⁴ times, resulting in a high Accurate TTL alignment is possible.

For the above reasons, it is possible to complete an excimer exposure device with a resolution of 0.5 μm, which is necessary for ultra-super LSI at a practical level. Note that the excimer light source is not limited to KrF. It will also be clear that the same effect can be obtained with a catoptric reduction projection exposure apparatus.

[Brief explanation of the drawing]

The figure is a conceptual diagram of an embodiment for explaining the excimer exposure apparatus of the present invention. 1...Excimer light source, 2...Integrator, 3...Mirror, 4...Condenser lens, 5
...Reticle, 6...Beam splitter, 7...
...Reduction projection lens, 8...XYZ stage, 9...
...Wafer, 10...Alignment lens, 1
1...Beam splitter for alignment, 12
...IIT for image processing and wavelength conversion, 13...CCD camera, 16...control computer.

Claims (1)

[Scope of Claims] 1. In an optical exposure apparatus for manufacturing semiconductor devices including a reduction projection lens, a wafer stage, a reticle stage, and an excimer laser light source, a beam splitter is disposed between the optical path of the reticle stage and the reduction projection lens, In an optical path perpendicular to the exposure optical axis of the projection lens, an alignment lens, an alignment beam splitter, an image processing/wavelength conversion unit,
An exposure apparatus comprising: a camera section arranged in this order; an alignment optical system having an alignment ultraviolet light illumination section; and a drive section for the alignment optical system. 2. The exposure apparatus according to claim 1, wherein the image processing/wavelength conversion section includes a multi-channel plate.