JPH025403A - Dummy wafer for aligner - Google Patents

Abstract

PURPOSE:To accurately measure an irregularity in illuminance on a surface to be radiated by employing a dummy wafer provided with a photosensitive material for varying the optical property of a light having a second wavelength band by the irradiation of a light having a first wavelength band. CONSTITUTION:When an irregularity in illuminance of a surface to be radiated is measured, a reticle 2 is retreated from an optical path by a command of a controller 20, an exposed wafer is removed from a wafer holder 11, and a dummy wafer is transferred to the holder 11. In this case, an illuminance distribution is stored on the face of the dummy wafer by the wafer in which a photosensitive material capable of writing and erasing to vary its optical properties with a light having a second wavelength band such as a photochromatic material is provided on a board by the radiation of a light having a first wavelength band on the face of the board of the wafer, and the illuminance distribution formed on the face of the photosensitive material is measured with a light having a wavelength different from that of the radiated light. Thus, the irregularity in the illuminance on the surface to be radiated can be rapidly and accurately measured.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a dummy wafer for an exposure apparatus used in the manufacture of semiconductor devices such as ICs and LSIs, and in particular to dummy wafers for use in dummy wafers such as reticles and masks (hereinafter referred to as "reticles"). Illumination of a pattern area on a second object surface such as a wafer surface when a pattern such as an electronic circuit formed on one object is exposed and transferred directly or through optical means such as a projection lens onto a second object surface such as a wafer surface. The present invention relates to a dummy wafer for an exposure apparatus for detecting unevenness.

(Prior Art) Continuously oscillating light sources such as ultra-high pressure mercury lamps have conventionally been used as illumination light sources in exposure apparatuses for manufacturing semiconductor devices such as ICs and LSIs. At this time, the illuminance unevenness on the irradiated surface is measured by moving the light receiver, which consists of a hole plate that approximately matches the image plane position of the projection lens and a light receiving element placed behind it, within the irradiated surface in the direction of the image plane. , by detecting the amount of light at each position.

Shortening the exposure wavelength is one effective means for achieving finer projection patterns in exposure apparatuses. An example of a light source that oscillates light with a relatively short wavelength (around 248r++++) is an excimer laser. Excimer lasers emit pulses of 10 to 20 n5ec and are characterized by high coherence.

For this reason, when an excimer laser is used in an exposure device, speckles occur on the irradiated surface due to the coherence of light, resulting in uneven illuminance. For this reason, it is necessary to average the speckles by performing multi-pulse oscillation using an oscillating method.

Furthermore, when measuring the uneven illuminance on the irradiated surface, there are the following problems.

(b) Because the wavelength is short, the sensitivity of the light receiving element is low, resulting in insufficient sensitivity.

(b) Responsiveness to pulse oscillation is low.

(c) The life of the excimer laser is shortened because each measurement point is exposed every time. Furthermore, the density decreases due to variations in the amount of light for each exposure.

In addition, a conventional illuminance unevenness measuring device is fixedly placed on an XY stage near a wafer chuck that supports a wafer.

For this reason, if the image plane of the projection lens moves up and down due to the influence of atmospheric pressure, the measuring instrument will not be able to follow this movement, and mismatch between the image plane and the hole will result in measurement errors due to the occurrence of symmetrical distortion, for example. There were some problems, such as causing problems.

(Problems to be Solved by the Invention) In the present invention, instead of directly measuring the light intensity distribution on the irradiated surface with a light receiving element and converting it into an electrical signal, the light intensity distribution on the irradiated surface is irradiated with exposure light in the first wavelength band. Using a dummy wafer on which a photosensitive material, such as a photochromic material, whose optical properties (for example, transmittance) change with respect to light is provided on the substrate surface, the illuminance distribution is memorized on the surface of the dummy wafer, and the illuminance distribution is recorded on the surface of the photosensitive material. In particular, semiconductor manufacturing equipment that can quickly and accurately measure illuminance unevenness on an irradiated surface by measuring the formed illuminance distribution using light with a wavelength different from the wavelength of the illumination light. The purpose of the present invention is to provide a dummy wafer for an exposure apparatus suitable for

(Means for Solving the Problems) A dummy wafer for an exposure apparatus according to the present invention aligns a first object and a second object so that they face each other, and transfers a pattern on the first object surface to a second object surface. A dummy wafer for use in an exposure device that performs exposure transfer using light in a first wavelength band on the substrate surface, the substrate surface being irradiated with the light in the first wavelength band, optically transferred to the light in the second wavelength band. It has a reversible photosensitive material that can be written and erased with changing properties.

(Example) FIG. 1 is a schematic diagram of an example in which a dummy wafer for an exposure apparatus according to the present invention is applied to an exposure apparatus, and FIG.
FIG. 2 is a plan view of a portion including the wafer stage and wafer transport system shown in the figure.

This embodiment takes a so-called off-axis alignment type exposure apparatus as an example.

In FIG. 1, a light beam from an illumination system 4 illuminates a reticle 2 as a first object held by a platen 6. In FIG. Then, a pattern such as an electronic circuit formed on the second surface of the reticle is projected and transferred by the projection lens 1 onto the third surface of the wafer as a second object.

The reticle 2 and the wafer 3 can be exchanged by means of transport means (not shown). A reticle reference mark 5 is arranged around the lower part of the reticle 2 with a slight gap from the reticle 2 for correctly arranging the reticle 2 with respect to the coordinate system of the apparatus. A reticle microscope 7 for aligning the reticle 2 with respect to the reticle reference mark 5 is provided at a position facing the reticle 2 therebetween. Note that the reticle microscope 7 and the reticle reference mark 5 are provided, for example, at two locations symmetrically about the center of the reticle.

For reticle alignment, a reticle microscope 7 reads the relative positional error between the reticle set mark and the reticle reference mark 5 provided on the 2nd surface of the reticle, and a reticle stage 8 movable in the XYθ directions adjusts the relative positional error between the reticle 2 and the platen 6. This is done by driving in a direction where the value approaches zero. Then, when the relative position error at this time falls within a predetermined tolerance range, the process ends.

A wafer alignment microscope 10 is arranged near the projection lens 1. The wafer 3 is held by vacuum suction on a wafer holding table 11, and the wafer holding table 11 is held on a θZ stage 12 which is movable in the rotation direction and the vertical direction, and the OZ stage 12 is movable in the XY force directions. It is configured so that Note that the O direction here indicates the H direction of rotation around Z#1.

At the end of the XY stage 13, there are an optical mirror 14Y for detecting positional coordinates and a mirror 14Y for detecting positional coordinates.
A laser interferometric length measuring device (hereinafter referred to as "interferometer") 15Y is arranged to make a light beam incident on the laser beam. Similarly, an optical mirror (not shown) for detecting position coordinates in the X direction + 4
, Lj (not shown) 1-4 in total 15X are arranged. Then, using these two interferometers 15X and 15Y. position of XY stage 13 and wafer 3ζ”)X
Y(1'7 position coordinates +A; 7j, take -J.

Above reticle 7 → alignment, wafer 7 alignment,
C) Data processing such as stage position information is performed on a routine basis. In addition, the S.--K.] and other operations are performed by a control device 20 within the controller 100. Creating jobs, commands to devices,
- Settings for the tarpaulin are done manually by going to the display 2 and keyboard 22 in the Torola 100.

In FIG. 2, reference numeral 30 indicates the optical axis of the projection lens 1, and for convenience, it will be explained below by aligning it with the origin 0 of the XY stage 13.

YIlt, the X axis is an optical mirror t 4 X,, 14
This is represented by the directions of Y::R planes 31X and 31Y.

In this embodiment, the optical axis 32 (P, φ,) of the wafer microscopist 0 is arranged at the position of the Y axis (X=O, Y=-R,) for convenience.

19: Optical axis 30 of i-sanshins 1 and wafer microscope 100
The distance Hx with Kusuke 32 is the so-called Lt=”Pi V (L
ise I inc>. The stroke of the XY stage 13 is
In the Y direction, the wafer microscope 10 is set to ``(D+!2.) or a value close to it.
Therefore, the entire surface of the wafer 3 and the parent dormitory on the entire surface of the wafer 3 are exposed.

The projectable area of the projection lens 1 is Fl 3 over the entire wafer 3.
5, the Raykle 2 has a rectangular shape in -R24. This area 36 is an area where the pattern of the reticle 2 [page 1F is projected and transferred onto the surface of the sea urchin A3 in one exposure.

The XY stage 13 is drawn so that the center of the sea urchin A 3 mounted on the horizon coincides with the optical axis 30 of the projection lens 1. It is movable within the range of +D/2-(D/2+4) in the D/2 and Y directions.

In this embodiment, in order to collect the exposed wafer 2 and place the unexposed wafer on the wafer cha vine, the XY stage 13 is moved to point Q, x = -D/
2, Y = - (El/2 + n) (7).

On the other hand, for a normal continuous wafer processing routine, a wafer cassette 23 containing unexposed wafers is supplied to a heald 24.
The wafer is transferred to the pre-alignment stage 2 using a transport means such as
5.1: After being approximately positioned on the pre-alignment stage 25 based on the outer shape of the wafer, the wafer is placed on the wafer holding table 11 at the wafer delivery position Q by the supply hunt 26.

On the other hand, the wafers that are on the XY stage 13F and have already been exposed are placed on collection bells 1 to 28 from collection hunt number 27 and stored in a cassette 29 to the collection side urchin. A dummy wafer 40 (hereinafter referred to as "dummy wafer 4") for the exposure apparatus of the present invention is used for measuring illuminance unevenness on the irradiated surface l-.
0". ) is stored in the standby stage 41,
The dummy wafer 40 is configured to have a reversible material such as a phytochromic material on its substrate.

When measuring the illuminance unevenness on the irradiated surface at the end of the exposure process or at any time, the reticle 2 is moved out of the optical path and the exposed wafer is removed from the wafer holding table 11 according to a command from the control device 20. Thereafter, the dummy wafer 40 is transferred to the wafer holding table 11 by the supply hand 26.

In this case, the dummy wafer 40 is substantially concave with the manufacturing wafer.
It is preferable that it be a circular thin plate with the same shape and medium diameter.

Thereafter, the surface of the dummy wafer 40 is adjusted using the XY stage 13 so that it matches the image plane position of the projection lens 1. Then, the illumination system 4 exposes the dummy wafer 40 at once with light in the first wavelength band, which is the exposure light, through the projection lens 1 to record information regarding illuminance unevenness on the dummy wafer surface, and the xYZ stage 13 records the exposed dummy wafer 4
0 is moved to the transfer position Q, and is moved from the XY stage 13 to a transmittance measuring device (not shown) by a supply belt 26 for supply and collection.

FIGS. 3A, 3B, and 3G are a plan view, a cross-sectional view, and an enlarged cross-sectional view of the dummy wafer 40 in this embodiment. In the figure, 42 is a substrate, 43 is an absorption layer, and 4
4 is a photochromic layer. The substrate 42 has a thickness of about 1 mm.
The front and rear are made of materials with a low coefficient of thermal expansion like quartz.
Furthermore, materials with good processability are preferred.

In addition, a material having a coefficient of thermal expansion substantially concave to that of the Si wafer, such as L E (Low Expansion) glass, a metal material, or the Si wafer itself may be used.

An exposure light absorption layer 43 is formed on the surface of the substrate 42 . The absorption layer 43 has a large absorption coefficient for exposure light (e.g., 250 nm light) in the first wavelength band, and has a large absorption coefficient for the measurement light (e.g., 500 to 600 nm) as light in the second wavelength band.
It is made of a material that has a high transmittance for light (m).

This prevents measurement errors caused by differences in absorption of exposure light depending on location due to film thickness interference between photochromic layers and film unevenness. The photochromic layer 44 provided on the surface of the absorption layer 43 is made of, for example, sudokudoran-based, fulgide-based, dihydrodrene-based, thioindigo-based, aziridine-based,
Bipyridine, polycyclic aromatic, tetrabenzopentacene, etc. are dissolved in a base material such as PMMA and applied to a thickness of about 1 μm using a method such as sudon coating.

When these photochromic materials are irradiated with light in a first wavelength band, the structural formula of the substance changes, and the optical properties, such as transmittance, change with respect to light in a second wavelength band. Furthermore, it has reversibility, allowing it to return to its original state by irradiating it with light of a different wavelength or by heating it. For example, spiropyrans turn from colorless to purple when irradiated with ultraviolet light, and return to their original colorless color when irradiated with light around 570 nm or heated.

FIG. 4 shows that the photochromic layer 44 according to this embodiment has a wavelength of 2.
FIG. 3 is an explanatory diagram showing changes in absorption spectrum when irradiated with a 48 nm excimer laser. With respect to the initial state (sp, large solid line), as the excimer laser is repeatedly fired at 2 mJ/cm2 per pulse, the wavelength at the center of 570 nm (
The figure shows how the absorbance changes from peak to peak).

FIG. 5 is an explanatory diagram when absorbance is plotted against irradiation energy, focusing on a wavelength of 570 nm in FIG. 4. As shown in the figure, the absorbance changes linearly between about 20 rnJ/cm2 and 200 mJ/cm2, with a rate of change of k=0.25%/mJ/cm2.

In this embodiment, by utilizing this characteristic, the dummy wafer 40 is held on the chuck surface of the stage, and the entire effective projection area of the projection lens is exposed to light of about 100 [IIJ/cm2. It is stored on the surface of a dummy wafer in the form of uneven locations, and after being removed from the chuck of the XY stage 13, it is stored in the exposure apparatus.
Or an absorbance measuring device (transmittance measuring device) installed outside the exposure equipment
The illuminance unevenness is measured.

FIG. 6 is a schematic diagram of an embodiment of the transmittance measuring device according to the present embodiment. In the same figure, a chuck 61 holding an exposed dummy wafer 40 is moved to a predetermined position (x, , 3/+) by an XY stage 13, and a light source that oscillates light with a wavelength of approximately SOO to 700 nm as a second wavelength band. 62 is turned on. A portion L1 of the luminous flux from the light source 62 is received by the light receiving element 63 using the half mirror 66 and the lens 67.

Also, the light beam from the light source 62 that has passed through the half mirror 66 is directed to the dummy wafer 40 by lenses 68a, 68b, and 68c.
It is input to. The light beam L2 that has passed through the dummy wafer 40 is received by the light receiving element 64.

Next, information on the point (x+, y+) and the light amounts Ll and L2 is sent to the controller 65. The controller 65 points (x+
, y, ) is determined from T = L2/Tl and stored. The transmittance distribution is determined by repeating the same method and measuring the entire exposed area.

If the illuminance distribution on the irradiated surface determined by the above method is outside the predetermined range, the controller 65
For example, the operator is notified by a warning lamp or a warning sound, and the system is controlled so that exposure is not possible on all eight sides of the sea urchin, and when the exposure is within a predetermined range, normal exposure operation is automatically started. .

On the other hand, the dummy wafer automatically returns the photochromic layer to its initial state (sp) by, for example, heating or irradiating with a specific wavelength.

Note that the present invention can be similarly applied even when an ultra-high pressure mercury lamp (g-line) is used as a light source instead of an excimer laser. Further, the present invention can be similarly applied to an exposure apparatus using a proximity method.

(Effects of the Invention) As described above, using a dummy wafer provided with a photosensitive material whose optical properties (transmittance) change with respect to light in a second wavelength band by irradiation with a first wavelength band, the surface of the dummy wafer is exposed at once. If a method is adopted in which the illuminance distribution is formed using the dummy wafer, information about the illuminance distribution is stored, the dummy wafer is removed from the stage, and the transmittance distribution is measured, it is possible to use short wavelength and extremely short pulse light such as an excimer laser. It is possible to quickly and accurately measure illuminance unevenness on the irradiated surface when using the irradiation method.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an embodiment in which a dummy wafer for an exposure apparatus according to the present invention is applied to an exposure apparatus, FIG. Figures (A), (B), and (C) are a plan view, a cross-sectional view, and an enlarged cross-sectional view of one embodiment of a dummy wafer according to the present invention, and Figures 4 and 5 are photochromic materials used in the present invention. FIG. 6 is a schematic diagram of a transmittance measuring device. In the figure, 1 is a projection lens, 2 is a reticle, 3 is a wafer, and 4
is the illumination system, 5 is the reticle reference mark, 6 is the platen, 7
8 is a reticle microscope, 8 is a reticle stage, 10 is a wafer microscope, 11 is a wafer holder, 12 is a θZ stage,
13 is an xY stage, 40 is a dummy wafer, 23 is a wafer cassette, 24 is a supply belt, 25 is a pre-alignment stage, 26 is a supply hand, 27 is a recovery node,
28 is a collection belt, 29 is a wafer cassette, and 100 is a controller.

Claims (2)

[Claims] (1) An exposure device for aligning a first object and a second object so that they face each other, and transferring the pattern on the first object surface onto the second object surface by exposure using light in a first wavelength band. A dummy wafer, which has a reversible photosensitive material that can be written and erased, and whose optical properties change with respect to light in a second wavelength band when irradiated with light in the first wavelength band on the substrate surface. A dummy wafer for exposure equipment that is characterized by: (2) The dummy wafer for an exposure apparatus according to claim 1, wherein the photosensitive material is a photochromic material.