JPH07147230A - Reduction projection aligner and manufacture of semiconductor - Google Patents

Abstract

PURPOSE:To provide a new aligner capable of making the reduction of manufacturing cost compatible with the improvement of productivity. CONSTITUTION:The title reduction projection aligner consists of the following; a mask stage 1 for retaining a mask on which a transfer pattern is formed, wafer stages 50, 51, 52 for retaining a wafer, an illuminating means for illuminating the mask retained by the mask stage with an exposure light, reduction projection optical systems M1, M2, M3 which reduction-project the transfer pattern of the illuminated mask on the wafer, and contain a plurality of reflection surfaces wherein at least one out of the reflection surfaces is not spherical, and means which controls at least the moving of the mask stage 1 so that the reduction transfer pattern of the mask is sequentially exposed and transfered to a plurality of regions of the wafer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection exposure apparatus for printing with high resolution and a semiconductor manufacturing method using the same.

[0002]

2. Description of the Related Art Conventionally, in a semiconductor manufacturing process, an exposure apparatus such as a mask aligner or a stepper is often used to print a circuit pattern of a mask or a reticle on a wafer.

In recent years, as the integration of semiconductor chips such as ICs and LSIs has increased, an exposure apparatus capable of printing with high resolution has been required, and the present far ultraviolet region (Deep UV).
The research and development of an apparatus that replaces the exposure apparatus that uses the above-mentioned light is actively performed. Generally, in this type of exposure apparatus, particularly in a projection exposure apparatus such as a stepper, the minimum line width of printing called resolution (or resolution) is determined by the wavelength of light used and the numerical aperture of the projection optical system.

Regarding the numerical aperture, the larger the numerical aperture is, the higher the resolution is. However, if the numerical aperture is too large, there is a problem that the depth of focus becomes shallow and the image is blurred by a slight defocus. It is difficult to obtain high resolution by changing the number. Therefore, attempts have generally been made to obtain higher resolution by using light obtained from an excimer laser or the like or light having a short wavelength such as X-rays as the light used for printing.

[0005]

DISCLOSURE OF THE INVENTION Problem to be Solved by the Invention
It has been difficult to obtain a high resolution on the order of submicrons with high precision in the manufacture of VLSIs after bit DRAM.

It is an object of the present invention to provide a novel reduction projection exposure apparatus and a semiconductor manufacturing method which have a high resolution on the order of submicrons and which enables highly accurate printing.

[0007]

A reduction projection exposure apparatus of the present invention that achieves the above object is a mask stage for holding a mask on which a transfer pattern is formed, a wafer stage for holding a wafer, and the mask stage. Illumination means for illuminating the exposed mask with exposure light, and a plurality of reflective surfaces for reducing and projecting the transferred pattern of the illuminated mask onto the wafer, at least one of the reflective surfaces having an aspherical shape. And a means for controlling the movement of at least the wafer stage so as to sequentially expose and transfer the reduced transfer pattern of the mask onto a plurality of regions of the wafer.

In the semiconductor manufacturing method of the present invention, the process of holding the mask on which the transfer pattern is formed on the mask stage, the process of holding the wafer on the wafer stage, and the exposure light on the mask held on the mask stage are used. And a reduction projection optical system including a plurality of reflection surfaces and at least one of the reflection surfaces having an aspherical shape reduces the projection pattern of the mask illuminated by the exposure light onto the wafer. And a step of controlling at least the movement of the wafer stage so as to sequentially expose and transfer the reduced transfer pattern of the mask onto a plurality of regions of the wafer.

[0009]

1 is a schematic diagram of a projection exposure apparatus according to an embodiment of the present invention. In the figure, reference numeral 1 denotes a mask stage that supports the mask MS, which can be moved in a two-dimensional direction by a driving device (not shown). Reference numeral 2 is a mask stage alignment mark provided on the mask stage 1, and in this embodiment, it is formed at three different points on the mask stage 1 as shown in the figure and is used for alignment. Reference numeral 3 denotes a light guide member through which X-rays pass, and directs X-rays emitted from an X-ray source (not shown) and transmitted through the mask MS to a projection optical system described later. Reference numeral 4 denotes a lens barrel that houses a projection optical system including a plurality of reflecting mirrors, and is connected to the light guide member 3. 10 and 11
And 12 are the first stage alignment scope,
A second stage alignment scope, a third stage alignment scope, and 20 and 21 respectively indicate a first mask / wafer alignment scope and a second mask / wafer alignment scope, which correspond to the mask MS and the wafer W side. By observing the position of the alignment mark through the projection optical system, the mask MS and the wafer W
Perform alignment. M ₀ , M ₁ , M ₂ and M ₃ are reflecting mirrors, and in particular, M ₁ and M ₂ and M ₃ constitute a projection optical system, and the reflecting mirror M ₀ passes through the light guide member 3 and the inside of the lens barrel 4. It is a bending mirror for directing X-rays incident on the reflecting mirror M ₁ at a predetermined angle.

Next, reference numerals 50, 51 and 52 denote stage constituent members constituting a wafer stage, and the constituent member 50 has a wafer chuck for supporting and fixing the wafer W, and an upper surface thereof has a stage alignment target used for alignment. 6 is provided. The constituent member 51 is the constituent member 5
It is fixed at 0 and can move on the component member 52 in the X direction as indicated by an arrow in the figure. The constituent member 52 is movable in the Y direction as shown by the arrow in the figure, and the constituent members 51 and 52 constitute a so-called XY stage. Reference numerals 70 and 71 denote drive devices for moving the constituent member 50 and the constituent member 51 in the X and Y directions, respectively, and are composed of step motors and the like.
The component member 50 or the wafer stage composed of the component members 50, 51, and 52 as a whole is rotatable in the θ direction by a driving device (not shown). Reference numerals 90, 91, and 92 are length measuring instruments for stage control, which can measure the position or movement amount of the wafer displaced in the X, Y, and θ directions with high accuracy. As the length measuring devices 90, 91, and 92 for stage control, interferometer type length measuring devices and the like, which can perform length measurement without contact, are suitable.

The projection exposure apparatus shown in FIG. 1 is an apparatus that exposes the wafer W by surface projection by forming a reduced image of the pattern image of the mask MS by the reflecting mirrors M ₁ , M ₂ and M ₃ , which is a so-called step & repeat method. By the method, printing is performed for each chip or for each of a plurality of chips separated by a scribe line on the wafer W. Further, the mask MS is supported by a mask holder (not shown) of the mask stage 1, and the wafer W is attracted to a wafer chuck (not shown) and fixed to the wafer stage. After the alignment of the wafer W and the mask MS, which will be described later, is completed, the following exposure is performed.

X-rays emitted from an X-ray source (not shown) illuminate the mask MS, and the circuit pattern of the mask MS is from the light guide member 3, the reflecting mirror M ₀ , and the reflecting mirrors M ₁ , M ₂ , M _3. An image is formed on a predetermined area on the wafer W through the projection optical system. That is, according to the present apparatus, the information about the circuit pattern of the mask MS is transmitted on the wafer W in the form of the intensity distribution of X-rays, and the circuit pattern is applied to the X-ray photoconductor (resist) coated on the wafer W. Will form a latent image of. The X-ray used may be of any wavelength range depending on the characteristics of the photoconductor or projection optical system, but if an X-ray source that emits X-rays of the desired wavelength range cannot be obtained, BN (boron The mask MS may be illuminated through an X-ray filter having a predetermined absorption characteristic such as nitroxide). After the baking of one chip or a plurality of chips is completed by one shot, the wafer stage is moved by the driving devices 70 and 71 (step
p) and send an area adjacent to the effective printing area of the projection optical system, which is composed of chips or a plurality of chips, align the mask MS and the wafer W to be printed again, and then print this chip by X-ray. To do. (Repea
t), this operation is performed on a plurality of chips on the wafer W in a predetermined order, and all of the plurality of chips separated by the scribe line on the wafer W are exposed by a large number of shots. The exposed wafer W is automatically replaced with the unexposed wafer W, and the above-described exposure process is performed again.

An example of the alignment procedure in this embodiment will be described below.

In FIG. 1, the wafer stage composed of the constituent members 50, 51 and 52 is moved by the driving devices 70 and 71, and the stage alignment target 6 on the constituent member 50 is moved to the reflecting mirrors M ₁ , M ₂ and M. _It is positioned so that it can be observed by the stage alignment scopes 10, 11 and 12 via the projection optical system composed of ₃ . Here, based on the information obtained from the stage alignment scopes 10, 11, and 12 so that the marks on the stage alignment target 6 and the stage alignment marks 2 on the mask holder 1 match or have a predetermined positional relationship, The position of the stage alignment target 6 is adjusted using the drive devices 70 and 71 and a drive device for rotating the wafer stage (not shown). Stage alignment scope 10, 1
The information on the alignments from 1 and 12 can be obtained visually or photoelectrically, and various conventionally known methods may be used.

Now, of the exposure area on the wafer W held on the constituent member 51, the constituent member 51 of the area exposed in the first one shot, for example, the area for one chip divided by orthogonal scribe lines. By determining the positional relationship between the upper position and the stage alignment target 6 in advance, after the alignment of the stage alignment target 6 described above is completed, the component member 50 based on the positional relationship,
The wafer stage consisting of 51 and 52 is moved to mask the area on the wafer W to be exposed in the first shot.
It can be sent near the image forming position of the S projection optical system. Area to be exposed in the first shot on the wafer W,
For example, a predetermined alignment mark is provided around the area of one chip divided by the scribe line (for example, on the scribe line), and the alignment mark and the alignment mark formed on the mask MS are used for mask / wafer alignment. Alignment with higher accuracy is performed by visually or photoelectrically observing through the scopes 20 and 21.

After the above alignment is completed, the above-mentioned exposure process is started. The positional relationship between the area exposed in the first one shot and each area exposed by step & repeat and the exposure If the order is given to a controller (not shown), the exposure area after the first one-shot exposure area can be accurately moved at all times by moving the wafer stage with high accuracy through the controller. The mask MS and the wafer W do not have to be aligned for each shot as described above. In particular, in order to improve the throughput, only the first shot is aligned and the rest of the shots are staged, as compared with the method of aligning the mask MS and the wafer W for each shot (die-by-die alignment). It is preferable to use a method of accurately sending the exposure area due to the mechanical accuracy of.

The projection exposure apparatus shown in FIG. 1 is used with the inside of the apparatus in a vacuum state in order to perform exposure using X-rays. For example, the inside of the apparatus is evacuated by an evacuation means (not shown) such as a vacuum pump, and exposure is performed in a vacuum state of about 10 ⁻⁶ Torr. It is desirable that the degree of vacuum inside the apparatus is high, and in this projection exposure apparatus, exposure is performed from a high vacuum state to an ultra-high vacuum state. Further, instead of evacuating the inside of the apparatus, the atmosphere consisting of N ₂ or O ₂ in the apparatus is replaced with a light element such as H or He, and the light element is filled into the apparatus to perform exposure. Is also good. Since these light elements have substantially zero absorption of X-rays, exposure can be performed by such a method and effective use of X-rays can be achieved.

Further, when the wavelength of X-ray used for exposure is large, the absorption of various substances is large, so that the influence on the human body is small, and the X-ray to the outside is shielded by a shield that holds the apparatus in vacuum. There are almost no leaks. On the other hand, the shorter the X-ray wavelength, the smaller the absorption of various substances. Therefore, it is preferable to provide an X-ray shield depending on the wavelength of the X-ray used.

As described above, according to the projection exposure apparatus as shown in FIG. 1, the pattern of the mask illuminated by the X-rays is imaged on the wafer through the projection optical system to perform exposure, so that the projection optical system is reduced. By using the one having the magnification, the accuracy of the mask pattern is relaxed as compared with the conventional proximity method, and the mask is easily manufactured.
Needless to say, the resolution can be improved by performing the reduced projection. Furthermore, the degree of freedom of the X-ray source that can be used is increased, and the device becomes highly versatile. Further, accurate gap measurement and gap adjustment between the mask and the wafer, which are required by the proximity method, become unnecessary.

The mask used in this embodiment is roughly classified into two types, a reflection type and a transmission type X-ray mask. The transmissive X-ray mask is composed of an X-ray absorber and a mask substrate that supports the X-ray absorber, and the mask substrate is patterned by the X-ray absorber. As the material of the X-ray absorber, Au, Ta, W or the like, which has a high X-ray absorptance and is easy to process, can be used. On the other hand, examples of the material of the mask substrate include organic polymers and inorganic substances. Organic polymers include polyimide, mylar, and Kapton, and inorganic substances include B-diffused Si, SiC, Si ₃ N ₄ , and T.
i and BN. Further, a SiN substrate or a composite substrate of polyimide and BN can be used.

The reflection type X-ray mask is a mask in which a pattern is drawn with a material having a high reflectance on a mask substrate having a low reflectance, and for example, a material having a low electron density (light element material) such as Si is used. On a thick mask substrate made of Au, a pattern with a substance having a high electron density (heavy element substance) such as Au, or Ti and Ni.
It is possible to use a mask obtained by patterning a multi-layer reflection film or the like composed of and on a mask substrate.

The mask MS used in this embodiment must be appropriately selected according to the wavelength of X to be used.
For example, the X-rays having a wavelength of several Å to several tens of Å can be selected from the above-mentioned mask materials, but the X-rays having a relatively long wavelength of several tens of Å to several hundred Å have the above-mentioned mask materials. Is not preferable because the absorption is too large. These dozens of Å ~ several hundred Å
As a mask for X-rays of a certain degree, it is preferable that the X-ray absorbing member or the reflecting member is formed with a hole corresponding to a circuit pattern to form a mask.

As the X-ray source used in this embodiment,
A so-called electron beam excitation type radiation source for generating X-rays by irradiating an electron beam to a solid metal, which is well known in the past, a radiation source using laser plasma, rare gas plasma or creeping discharge plasma, SOR (Synchrotron Orbit)
al Radiation) and a radiation source using synchrotron radiation.

Further, the photoconductor for X-rays used in the exposure, that is, the resist, has a high sensitivity to a relatively low sensitivity according to the energy density of the X-rays for exposure which differs depending on the X-ray source used. Various materials can be selected. For example, negative-type X-ray resist materials include polyglycidyl methacrylate-CO-ethyl acrylate (COP),
Polyglycidyl methacrylate maleic acid adduct (SE
L-N), polydiaryl orthophthalate, epoxidized polybutadiene, polystyrene TTF-based, metal-containing salt resist material, halogen-containing polyvinyl ether-based resist material, halogen-containing polyacrylate-based resist material, and the like, and positive X-ray resist Materials include polymethylmethacrylate (PMMA), polyhexafluorobutylmethacrylate, polytetrafluoropropylmethacrylate, polymethacrylonitrile, poly (MMA-CO).
-Trichloroethyl methacrylate), polybutene-1
-Sulfone, metal salt-containing resist material, polytrichloroethyl methacrylate, polymethyl methacrylate-
CO-dimethylmethylene malonate (PMMA-CO-
DMM), a copolymer of n-hexylaldehyde and n-butyraldehyde, and polychloroacetaldehyde.

Next, an example of the projection optical system used in the projection exposure apparatus shown in FIG. 1 will be shown.

FIG. 2 is a schematic configuration diagram showing an example of the projection optical system, and shows a reflection type projection optical system including three reflecting mirrors. In the figure, MS is a mask, W is a wafer, M ₁ , M ₂ , M
Reference numeral ₃ denotes a reflecting mirror, and r ₁ , r ₂ and r ₃ are reflecting mirrors M ₁ and M ₃ , respectively.
Paraxial radii of curvature of M ₂ and M ₃ , d ₁ and d ₂ are the surface distances between the reflecting mirrors M ₁ and M ₂ , and the reflecting mirrors M ₂ and M ₃ , respectively, and S ₁ is the reflecting mirror M ₁
To the object, that is, the mask MS, and l ₁ denotes the distance from the reflecting mirror M ₁ to the image plane, that is, the wafer W.
The values of d ₁ , d ₂ , S ₁ and l ₁ are assumed to be measured along the optical axis 0.

The reflective projection optical system shown in FIG. 2 is a mask MS.
A concave reflecting mirror M ₁ (hereinafter, referred to as “concave mirror M ₁ ”), a convex reflecting mirror M ₂ (hereinafter, referred to as “convex mirror M ₂ ”), and a concave reflecting mirror M ₃ (hereinafter, “Concave mirror M ₃ ”), and the circuit pattern of the mask MS is formed on the wafer W.
Above, more specifically, reduction projection is performed on the resist applied on the surface of the wafer W.

Generally, in an exposure apparatus used for manufacturing a 64 Mbit or 256 Mbit class super LSI, a main specification required for a projection optical system for performing surface projection as shown in FIG. 2 is a super high resolution large image. The surface size is distortion-free, and the minimum line width of 0.35 μm and 2 for 64 Mbit class.
Image plane size of 8 x 14 mm ² is required, 256 Mbit
It is said that a minimum line width of 0.25 μm and an image plane size of 40 × 20 mm ² are required for the class. These requirements are generally contradictory, and no conventional optical system of this type satisfies the above specifications at the same time. However, by using the projection optical system shown in FIG. 1, the above-mentioned specifications can be satisfied, and the present invention can be achieved.

In order to obtain a large image plane size in this type of optical system, it is most important that the image plane is excellent in flatness, that is, the field curvature is well corrected. Therefore, in the projection optical system shown in FIG. 1, the values of the paraxial radii of curvature r ₁ , r ₃ and r ₂ of the concave mirrors M ₁ and M ₃ and the convex mirror M ₂ are the following (1).
The selection is made to satisfy the formula. _{0.9 <r 2 / r 1 +} r 2 / r 3 <1.1 ... (1)

The above formula (1) is a conditional formula for reducing the Petzval sum. If the range of the formula (1) is exceeded, the required resolving power cannot be obtained over the entire image surface size, and the above-mentioned specifications are required. Exposure that satisfies the above condition becomes impossible. The closer the value of r ₂ / r ₁ + r ₂ / r _{3 in} the formula (1) is to 1, the closer the Petzval sum is to 0, so r ₂ / r ₁ + r ₂ / r ₃ = 1 is the most ideal. It can be said to be in a state.

Further, in order to satisfy the above-mentioned specifications, it is necessary that aberrations other than field curvature, that is, spherical aberration, coma aberration, astigmatism, and distortion aberration are also well corrected. In the system, the light emitted from the object is reflected by the concave mirror M ₁ , the convex mirror M ₂ , and the concave mirror M ₃ in this order, and the above-mentioned aberrations are corrected by using the convex mirror M ₂ as an aperture stop. In addition to these, each of the above-mentioned aberrations can be corrected more favorably by making at least one of the three reflecting mirrors of the concave mirrors M ₁ and M ₃ and the convex mirror M ₂ an aspherical surface. In particular, it is desirable to form the concave mirrors M ₁ and M ₃ as aspherical surfaces in order to improve the imaging performance. That is, in order to remove the above-mentioned aberrations, so-called Seidel's five aberrations, in the projection optical system of FIG. 2, the paraxial radius of curvature of each of the concave mirrors M ₁ and M ₃ and the convex mirror M ₂ is appropriately determined. Thus, the Petzval sum is kept small and distortion is mainly removed, and other coma aberration, astigmatism, and spherical aberration are well corrected by using an aspherical surface. Moreover, FIG.
The projection optical system of 1 basically forms a coaxial optical system, and only one mirror surface of the concave mirrors M ₁ and M ₃ is used. Incidentally, by further removing at least one of the concave mirrors M ₁ and M ₃ and the convex mirror M ₂ from the coaxial relationship and slightly tilting it with respect to the optical axis 0 in the figure, it is possible to further correct the aberration. .

FIG. 3 is an explanatory view showing the image plane when the projection optical system of FIG. 2 is used. In the figure, y indicates the image height, y _max indicates the maximum image height, and y _min indicates the minimum image height. Usually, a portion of y _min ≤y≤y _max is used as the image plane. The light flux reaching this portion has substantially no vignetting, and a uniform light amount distribution with an aperture efficiency of 100% can be obtained. FIG. 3 shows, as an example of the image plane used, a rectangular area having a maximum area of a ratio of long sides to short sides of 2: 1. Of course,
In this region, the above-mentioned various aberrations are well corrected. When assuming such a rectangular area as an image plane to be used, the short side of the rectangle is y _max −y _min and the long side is

[0033]

[Outer 1] Given in.

Further, it is preferable to provide a reflecting film on the reflecting surfaces of the concave mirrors M ₁ and M ₃ and the convex mirror M _{2 in} the projection optical system shown in FIG. 2 in order to reflect X-rays efficiently. This reflective film is formed of a multi-layered film of several tens of layers and significantly improves the reflectance as compared with the case where no reflective film is provided. This kind of multilayer reflective film is a combination of different materials such that the difference in refractive index between adjacent layers is large, for example, a multilayer film composed of a transition metal element having a high melting point and a semiconductor element, or a low melting point metal element. It can be formed from a multilayer film composed of a semiconductor element or a light metal element, a multilayer film composed of a white metal element and a semiconductor element, or the like. Specifically, tungsten W, carbon C, tantalum T
a and silicon Si, gold Au and carbon C, rhenium Re and carbon C, lead Pb and silicon Si, ruthenium Ru and silicon Si, palladium Pd and silicon Si, rhodium Rh
And silicon Si, ruthenium Ru and beryllium Be, ruthenium Ru and boron B, rhodium Rh and boron B, palladium Pd and boron B, and the like. Hereinafter, specific examples of the multilayer reflective film will be described.

<Multilayer Reflective Film for X-Rays with Wavelength 114.0Å> Example 1 If the different substances constituting the multilayer film are the first substance and the second substance, the first substance is Ru and the second substance is Si. , And the respective film thicknesses were 36.4 Å and 23.5 Å, and 41 layers were laminated to obtain a reflectance of 38.6% at an incident angle of 0 °. As a result of laminating C as a protective film on the 5Å top layer,
A reflectance of 37.9% was obtained at an incident angle of 0 °. By stacking 41 layers with the film thicknesses of 39.1Å and 25.2Å, a reflectance of 40.1% was obtained at an incident angle of 20 °. As a result of laminating C as the protective film on the 5Å uppermost layer, a reflectance of 39.4% was obtained at an incident angle of 20 °.

Example 2 Pd was used as the first substance, Si was used as the second substance, and the film thickness was 31.3Å and 28.0Å, and 41 layers were laminated to reflect 26.1% at an incident angle of 0 °. The rate was obtained.
By setting the respective film thicknesses to 33.3Å and 30.1Å, a reflectance of 26.7% was obtained at an incident angle of 20 °.

<Multilayer Reflective Film for X-Rays with Wavelength 112.7Å> Example 3 41 layers are laminated with Ru as the first substance and Be as the second substance, and the film thicknesses are 26.6Å and 30.6Å, respectively. As a result, a reflectance of 77.2% was obtained at an incident angle of 0 °.
By laminating 41 layers with the respective film thicknesses of 27.4Å and 33.4Å, a reflectance of 79.9% was obtained at an incident angle of 20 °.

<Multilayer reflective film for X-rays having a wavelength of 108.7Å> Example 4 A first substance is Rh and a second substance is Si, and the respective film thicknesses are 33.4Å and 23.4Å, and 41 layers are laminated. As a result, a reflectance of 33.2% was obtained at an incident angle of 0 °.
By laminating 41 layers with respective film thicknesses of 48.2Å and 28.8Å, a reflectance of 38.7% was obtained at an incident angle of 40 °.

<Multilayer Reflective Film for X-Rays with Wavelength 82.1Å> Example 5 41 layers are laminated with Ru as the first substance and B as the second substance, and the film thicknesses are 20.1Å and 21.8Å, respectively. As a result, a reflectance of 18.0% was obtained at an incident angle of 0 °. By laminating 41 layers with the respective film thicknesses of 21.3Å and 23.4Å, a reflectance of 21.6% was obtained at an incident angle of 20 °.

Example 6 Ru was used as the first substance, B was used as the second substance, and the film thickness was set to 20.0Å and 21.9Å, and 41 layers were laminated to reflect 15.7% at an incident angle of 0 °. The rate was obtained. By laminating 41 layers with the respective film thicknesses of 21.0Å and 23.6Å, a reflectance of 18.8% was obtained at an incident angle of 20 °.

Example 7 Pd was used as the first substance, B was used as the second substance, and the film thickness was 19.4Å and 22.4Å, and 41 layers were laminated to reflect 13.2% at an incident angle of 0 °. The rate was obtained. By laminating 41 layers with the respective film thicknesses of 20.6Å and 24.0Å, a reflectance of 15.7% was obtained at an incident angle of 20 °.

Although the multilayer reflective film shown above is for X-rays having a wavelength of 80 to 120Å, the multilayer reflective film for X-rays having other wavelengths is designed by appropriately selecting the combination of the above-mentioned substances. Can be obtained by doing. Further, the first substance and the second substance may not only be composed of individual elements, but may be composed of synthetic materials of a plurality of elements.

Next, a specific example of the projection optical system shown in FIG. 2 will be described in detail with reference to the drawings and numerical data.

FIG. 4 is an optical path diagram for showing a concrete example of the projection optical system. Reference numerals M ₁ , M ₂ and M ₃ in the drawing are concave mirrors, convex mirrors and concave mirrors, respectively, as in FIG. 2, and W is a wafer. ing.
Further, it is assumed that a mask (reticle) (not shown) is present at a predetermined position in the left-hand direction on the paper surface. The X-rays directed to the projection optical system via the light transmitting portion or the reflecting portion of the mask are sequentially reflected by the concave mirror M ₁ , the convex mirror M ₂ , and the concave mirror M ₃ to form an image of the mask on the wafer W. . The projection optical system in FIG. 4 is an optical system corresponding to Numerical Example 4 described later, and has a projection magnification of 1 /.
5, effective F number 13, image plane size 28x14m
m ² , image height is 20 to 37 mm, and resolution is 0.35 μm. Therefore, it has a performance that can be sufficiently used for manufacturing a 64 Mbit DRAM.

5 (A), 5 (B) and 6 (A)-
6D is an aberration diagram of the projection optical system in FIG. 4. Figure 5
6 (A) and 6 (B), (A) shows astigmatism, (B) shows distortion, and FIGS. 6 (A) to 6 (D) show lateral aberrations at different object heights. Shows. In FIG. 6, (A) has a height of 0, (B) has a height of 130 mm, and (C) has a height of 16
0 mm and (D) show the case where the object height is 185 mm. 5A and 5B, the vertical axis represents the object height, M indicates the meridional surface, and S indicates the sagittal surface.

As can be seen from the aberration diagrams of FIGS. 5 and 6, sufficient aberration correction is made for this type of projection optical system,
Especially, the distortion aberration is almost zero. Further, aberration correction could be achieved over a wide range so as to be sufficiently satisfied as an optical system applicable to a surface projection type exposure apparatus which requires a wide exposure area. Further, as shown in specific examples described later, an optical system having an MTF characteristic sufficient to obtain a resolution on the order of submicron is provided.

Numerical examples of the projection optical system shown in FIGS. 2 and 4 will be shown below. In the projection optical system used in the present invention, in order to satisfactorily correct various aberrations, it is preferable that at least one of the concave mirrors M ₁ , M ₃ and convex mirror M ₂ is an aspherical surface. In each of the numerical examples, at least 1
It has a structure including a single aspherical reflector.

In the following numerical examples, Ki (i = 1,
2, 3) are aspherical coefficients of the i-th surface counted from the object side, and the aspherical shape can be expressed by the following equation.

[0049]

[Outside 2]

Here, X is the coordinate in the optical axis direction, H is the distance from the optical axis in the vertical direction, and ri (i = 1, 2, 3) is the paraxial curvature of the ith surface counted from the object side. It represents a radius. Further, S ₁ , l ₁ , d ₁ , and d ₂ are the distance from the concave mirror M ₁ to the mask MS, the distance from the reflecting mirror M ₁ to the wafer W, and the concave mirror M _{1 as described} with reference to FIG. spacing of the convex mirror M _2, shows the spacing of the convex mirror M ₂ and the concave mirror M _3.

Example 1 [Magnification = 1/5 times, effective F number = 30, image plane size = 28 mm × 14 mm, resolution = 0.35 μm, image height =
5 mm to 24 mm] S ₁ = -1288.7 mm l ₁ = -298.9 mm r ₁ = -635.99 mm r ₂ = -213.51 mm r ₃ = -321.40 mm d ₁ = -165.00 mm d ₂ = 165 0.00 mm K ₁ = −2.26097 K ₂ = −0.12295 K ₃ = 0.11246 [Performance] ・ MTF at spatial frequency 1500 lp / mm When wavelength = 0, 85% 13.3Å 80% ・ Distortion Rate = -0.3%

Embodiment 2 [Magnification = 1/5 times, effective F number = 30, image plane size = 40 mm × 20 mm, resolution = 0.25 μm, image height =
10 mm to 40 mm] S ₁ = −2577.4 mm l ₁ = −597.9 mm r ₁ = −1271.98 mm r ₂ = −427.01 mm r ₃ = −642.81 mm d ₁ = −330.00 mm d ₂ = 330 0.00 mm K ₁ = −2.26097 K ₂ = −0.12295 K ₃ = 0.11246 [Performance] ・ MTF at spatial frequency of 2000 lp / mm When wavelength = 0, 75% When 13.3Å 75% ・ Distortion Rate = -0.24%

Embodiment 3 [Magnification = 1/5 times, effective F number = 15, image plane size = 28 mm × 14 mm, resolution = 0.35 μm, image height =
20mm~37mm] _{S 1 = -2577.4mm l 1 = -597.9mm} r 1 = -1271.98mm r 2 = -427.01mm r 3 = -642.81mm d 1 = -330.00mm d 2 = 330 0.00 mm K ₁ = −2.26097 K ₂ = −0.12295 K ₃ = 0.11246 [Performance] ・ MTF at spatial frequency 1500 lp / mm When wavelength = 0, 70% 13.3Å 70% 100Å When 60% When 200Å 40% ・ Strain curvature = -0.2%

Example 4 [Magnification = 1/5 times, effective F number = 13, image plane size = 28 mm × 14 mm, resolution = 0.35 μm, image height =
20 mm to 37 mm] S ₁ = -3000.0 mm l ₁ = -602.5 mm r ₁ = -1181.91 mm r ₂ = -325.97 mm r ₃ = -448.92 mm d ₁ = -449.68 mm d ₂ = 210 0.01 mm K ₁ = −0.94278 K ₂ = −0.07146 K ₃ = 0.14283 [Performance] ・ MTF at spatial frequency 1500 lp / mm When wavelength = 0, 80% When 13.3Å 80% 100Å When 65% When 200Å 45% ・ Strain curvature = -0.00005% or less

Example 5 [Magnification = 1/5 times, effective F number = 13, image plane size = 40 mm × 20 mm, resolution = 0.25 μm, image height =
27 mm to 52 mm] S ₁ = -4500.0 mm l ₁ = -903.6 mm r ₁ = -1772.60 mm r ₂ = -488.89 mm r ₃ = -673.46 mm d ₁ = -674.44 mm d ₂ = 315 .17 mm K ₁ = −0.94301 K ₂ = −0.08049 K ₃ = 0.14261 [Performance] ・ 50% at MTF wavelength = 0 at spatial frequency 2000 lp / mm 13.3Å 50% at 100Å When 40% When 200Å 35% ・ Strain curvature = -0.00004% or less

Example 6 [Magnification = 1/5, effective F number = 13, image plane size = 28 mm × 14 mm, resolution = 0.35 μm, image height =
20 mm to 37 mm] S ₁ = -3000.0 mm l ₁ = -602.7 mm r ₁ = -1182.14 mm r ₂ = -325.53 mm r ₃ = -449.22 mm d ₁ = -449.96 mm d ₂ = 210 _{.66mm K 1 = -0.93900 K 2 =} -0. (Spherical surface) K ₃ = 0.14403 [Performance] ・ MTF at spatial frequency 1500 lp / mm When wavelength = 0, 60% 13.3Å 60% 100Å 55% 200Å 45% ・ Distortion 0.01 μm Less than

Embodiment 7 [Magnification = 1/2 times, effective F number = 26, image plane size = 34 mm × 17 mm, resolution = 0.35 μm, image height =
40 mm-60 mm] S ₁ = -1431.1 mm l ₁ = -719.0 mm r ₁ = -847.10 mm r ₂ = -309.30 mm r ₃ = -486.35 mm d ₁ = -263.73 mm d ₂ = 130 0.56 mm K ₁ = -1.72866 K ₂ = -1.60 435 K ₃ = 0.78100 [Performance] -MTF at spatial frequency of 1500 lp / mm When wavelength = 0, 80% When 13.3Å 75% 100Å When 45% When 200Å 14% ・ Distortion 0.1 μm

Embodiment 8 [Magnification = 1 ×, effective F number = 39, image plane size = 3]
6 mm × 18 mm, resolution = 0.35 μm, image height = 70
mm to 90 mm] S ₁ = −934.6 mm l ₁ = −1054.2 mm r ₁ = −834.76 mm r ₂ = −306.69 mm r ₃ = −483.92 mm d ₁ = −266.67 mm d ₂ = 107 .85 mm K ₁ = -1.82882 K ₂ = -1.83789 K ₃ = -1.19285 [Performance] -MTF at spatial frequency 1500 lp / mm When wavelength = 0, 70% 13.3Å 65% 100Å When 30% 200 Å 0% ・ Distortion 0.1 μm

Examples 1 to 3 show the case where the concave mirrors M ₁ and M ₃ are arranged at the same position with substantially the same distance with respect to the convex mirror M ₂ , and Examples 1 and 3 are for manufacturing a 64 Mbit class LSI,
The second embodiment is designed for the purpose of manufacturing a 256 Mbit class LSI. The projection optical systems of Examples 1 to 3 are relatively compact and have high resolving power, but distortion tends to remain slightly. In this case, the mask pattern itself can be corrected by giving a distortion opposite to the distortion that cannot be corrected by the projection optical system.

[0060] The distance between Examples 4 to 8 the concave mirror M ₁ and shows a case where the concave mirror M ₃ is disposed between the convex mirror M _2, each example both the concave mirror M ₁ and the convex mirror M ₂ Almost half
A concave mirror M ₃ is arranged at a position separated by a distance of. Example 4 and Example 5 are 64 Mbit class and 256 Mb, respectively.
Designed for it-class LSI manufacturing, it provides a bright optical system that almost completely eliminates distortion and has an effective F number of 13. In the sixth embodiment, when the convex mirror M ₂ is a spherical surface and is designed for manufacturing a 64-Mbit class LSI,
In the seventh embodiment, the projection magnification is ½ and the 64 Mbit class L
In the case of being designed for SI manufacture, the embodiment 8 shows an example in which the projection magnification is set to 1 × and the case is designed for 64Mbit class LSI manufacture. It should be noted that Examples 1 to 6 are all examples in which the reduction ratio is ⅕, and all other examples except Example 6 have three reflecting mirrors (M ₁ , M ₂ , M ₃ ) with aspherical surfaces. It is a configuration example.

The projection optical system described above has M ₁ , M ₂ , M ₃
However, the projection optical system applicable to the present projection exposure apparatus is not limited to the above embodiments. For example, it may be performed optical design by adding a fourth reflector formed of M _4. In order to reflect X-rays efficiently, a multilayer reflective film may be used as described above, but even if a multilayer reflective film is used, the loss of X-rays will inevitably increase as the number of reflecting mirrors increases. Therefore, it is desirable that the number of reflecting mirrors constituting the projection optical system is small.

Further, the present projection optical system is not only used in the above-mentioned surface projection, but also a predetermined image height with a small aberration is projected through an arc slit or the like, and the mask and the wafer are simultaneously scanned to form a mask pattern. It may be used for a method of transferring onto a wafer.

[0063]

As described above, according to the present invention, the reduction projection optical system having the aspherical reflecting surface is used to sequentially expose and transfer the reduction pattern to a plurality of regions of the wafer. It is possible to achieve both simplification of the above and relaxation of the pattern accuracy required for the mask, contribute to cost reduction of production from both sides of the mask and the device, and enable semiconductor production with high productivity.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of a projection exposure apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing an example of a projection optical system used in an embodiment of the present invention.

3 is an explanatory diagram showing an image plane when the projection optical system of FIG. 2 is used.

FIG. 4 is an optical path diagram showing a specific example of the projection optical system of FIG.

5 is a diagram showing astigmatism and distortion of the projection optical system of FIG.

FIG. 6 is a lateral aberration diagram at different object heights.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 mask stage 2 stage alignment mark 3 light guide member 4 lens barrel 6 stage alignment target 10, 11, 12 stage alignment scope 20, 21 mask / wafer alignment scope 50, 51, 52 wafer stage constituent member 70, 71 drive device 90, 91, 92 Stage control length measuring devices M ₁ , M ₂ , M ₃ , M ₄ reflector MS mask W wafer

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication location G03F 9/00 H 9122-2H G21K 5/02 X (72) Inventor Shigetaro Ogura Shimomaruko Ota-ku, Tokyo 3-30-2 Canon Inc. (72) Inventor Keiaki Fukuda 3-30-2 Shimomaruko, Ota-ku, Tokyo Incorporated (72) Yutaka Watanabe 3-30 Shimomaruko, Ota-ku, Tokyo No. 2 within Canon Inc. (72) Inventor Yasuo Kawai 3-30-2 Shimomaruko, Ota-ku, Tokyo Within Canon Inc. (72) Inventor Takuo Kariya 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Within the corporation

Claims (2)

[Claims] 1. A mask stage that holds a mask on which a transfer pattern is formed, a wafer stage that holds a wafer, an illuminating unit that illuminates the mask held on the mask stage with exposure light, and the illuminated mask. A reduction projection optical system including a plurality of reflecting surfaces for reducing and projecting the transfer pattern of the image onto a wafer, at least one of the reflecting surfaces having an aspherical shape; And a means for controlling the movement of at least the wafer stage so as to sequentially expose and transfer the reduced transfer pattern of the mask. 2. A step of holding a mask on which a transfer pattern is formed on a mask stage, a step of holding a wafer on a wafer stage, a step of illuminating the mask held on the mask stage with exposure light, A step of reducing and projecting the transfer pattern of the mask illuminated with the exposure light onto a wafer by a reduction projection optical system including a reflection surface and at least one of the reflection surfaces having an aspherical shape; A step of controlling at least the movement of the wafer stage so that the reduced transfer pattern of the mask is sequentially exposed and transferred onto the area.