JPH0496315A - Exposure device - Google Patents

Abstract

PURPOSE:To make high-accuracy overlay exposure with little alignment error possible even if a wafer and a wafer holder expand during exposure by correcting the position to an exposure position found with an alignment apparatus based on the quantity of irradiation energy absorbed by a substrate or its holder in exposure. CONSTITUTION:A reticle R is mounted on a reticle stage RS and located so that the central point of a pattern area PA may be aligned with an optical axis AX. The reticle R is set first by fine control of the reticle stage RS based on a mark detection signal from a reticle alignment system to photo-electrically detect an alignment mark around the reticle. Reflection light emitted from a wafer W by applying illumination light IL enters a photo detector 10, such as a PIN photodiode, through a mirror 3. The reflection amount monitor 10 photo-electrically detects the reflection light and transmits light information RS to a main control system 20. The information RS acts as fundamental data to correct EGA data in the main control system 20.

Description

[Detailed Description of the Invention] [The invention in the field of industrial application relates to an exposure apparatus for manufacturing semiconductor elements and liquid crystal display elements, and in particular, to an exposure apparatus for manufacturing semiconductor elements and liquid crystal display elements. The present invention relates to an improvement in an alignment system for aligning a mask pattern and a wafer pattern formed on a substrate with high precision during exposure.

1. Prior Art] Conventionally, in exposure equipment, more than ten f! Lay the similar mask or 1/ticle pattern on top of the sea urchin in sequence (4-
When exposing the reticle pattern, the circuit pattern already formed on the wafer (hereinafter referred to as
(referred to as a shot area) (improving the accuracy of the alignment 11 was an extremely important issue; however, this method of overlapping exposure can be roughly divided into two types.

The first is the die-by-die (D/D) or die-by-sight (S/S) method, which uses alignment marks formed along with the shot area to Overlapping exposure is performed while aligning.

The second method is called the global alignment method, in which all shots on the wafer are considered as one block, the alignment marks of several shots are detected and the wafer is precisely aligned, and then the shot areas on the wafer are aligned. Move the stage uniquely according to the coordinates, and
This method performs overlapping exposure while controlling the direction movement using a laser interferometer on the stage.

Currently, the alignment method of exposure equipment is, for example,
Extended wafer global alignment (hereinafter referred to as Enhancement Global Alignment: EGA) has become mainstream, as disclosed in Japanese Patent Laid-Open No. 1-44429 or Japanese Patent Application Laid-Open No. 62-84516.

In the EGA method, when exposing a single square, first the positions of alignment marks attached to multiple shot areas on the wafer are measured (sample alignment), and then the offset (x , y direction), wafer expansion/contraction degree (X, Y direction), remaining rotation amount to the square, and orthogonality of the wafer stage (or orthogonality of the shot area arrangement). This is determined by a statistical method based on the difference between the measured position of the mark and the measured position of the mark. Then, based on the values of the determined parameters, the position of the overlapping exposure shot area is corrected from the designed position, and the wafer stage is sequentially stepped.

The advantage of this EGA method is that the number of shots (approximately 3 to 16) is small compared to the total number of shots on the wafer prior to wafer exposure.
After measuring the mark position, mark detection and position measurement are no longer required, which can improve throughput.If a sufficient number of marks are sampled and aligned, individual mark detection errors will be statistically reduced. As a result, alignment accuracy equivalent to or higher than alignment for each shot, that is, alignment using the die-by-die method, can be expected for all shot areas on the entire wafer surface. That's true.

[iJU to be Solved by the Invention] However, in this EGA method, several shot coordinates are obtained before overlapping exposure is performed, and an arrangement map (coordinate values) of shot areas on the wafer is determined. For this reason, if, for example, the wafer or wafer holder stretches due to the thermal energy of the exposure light during overlay exposure, the shot interval changes and the exposure shot position shifts, so even if the stage is moved according to the array map determined by EGA,
There is a problem in that the projected image of the reticle pattern and the shot area do not overlap accurately.

The present invention was made in view of these conventional problems, and even if the wafer or wafer holder stretches during exposure,
The purpose is to enable highly accurate overlay exposure with almost zero alignment error.

[Means for Solving the Problems] The exposure apparatus of the present invention is an exposure apparatus having an alignment device for overlapping a pattern on a mask with a pattern on a substrate. Alternatively, it is provided with an irradiation amount measuring means for measuring the amount of irradiation energy absorbed by the holding member, and a correction means for performing positional correction for the exposure position determined by the alignment device based on the amount of irradiation energy.

[Function] As described above, the exposure apparatus of the present invention includes a irradiation amount measuring means for measuring the amount of irradiation energy absorbed by the substrate or its holding member during exposure, and a irradiation amount measuring means for measuring the amount of irradiation energy absorbed by the substrate or its holding member during exposure, and a radiation amount measuring means for measuring the amount of irradiation energy absorbed by the substrate or its holding member during exposure, and an alignment device that measures the amount of irradiation energy based on the amount of irradiation energy. Since it is equipped with a correction means that performs position correction for the exposure position, even if the substrate or its holding member stretches during exposure, the measured irradiation amount can be adjusted.
This elongation can be calculated and the exposure position can be corrected. For this reason, advanced superposition +! Accuracy is obtained.

[Embodiment] FIG. 1 is a diagram showing a schematic configuration of an r-light device according to an embodiment of the present invention.

In FIG. 1, an illumination light source 1 such as an ultra-high pressure mercury lamp or an excimer 1 noser device is an illumination light IL for H light in a wavelength range that sensitizes the resist layer, such as g-line, i-line, or K rF excimer laser light. The illumination light 11 is incident on the illumination optical system 2, which includes an optical integrator (not shown) (prior eye lens), a variable blind 28, etc. The surface of the variable blind 2a is aligned with the reticle R. Therefore, by opening and closing the movable plate constituting the variable blind 2a and changing the aperture position and shape, the observation and field of view (illuminated field at the time of exposure) of one nodicle R can be arbitrarily selected. be able to. The illumination light IL whose illumination light flux has been concentrated, speckles reduced, etc. by the illumination optical system 2 reaches the mirror 5 via the mirror 3 and the main condenser lens 4, where it is directed downward almost vertically. It is reflected and illuminates the reticle R with uniform illuminance. The I-noticle R is placed on the 1-noticle stage RS, and is positioned so that the center point of the pattern area PA coincides with the optical axis AX. Furthermore, l
The initial setting of the noticle R is based on the mark detection signal from the 1/ticle alignment system (not shown) that charges and detects the alignment mark provided around the 1/ticle.
This is done by slightly moving the nozzle stage RS. Here, the mirror 3 has a reflectance of 90% or more for the illumination light 12 in the exposure wavelength range.7 In this embodiment, the reflected light generated from the wafer W by the illumination light IL is 3 via PIN721-)-
The light is configured to be incident on a photodetector (reflection amount monitor) 10 such as a diode. The reflection jl monitor 10 emits the reflected light and sends the light information (intensity value) R3 to the main control system 20r.
This information R3 becomes basic data for correcting EGA data in the main control system 20 (details will be described later).

Now, the illumination light IL that has passed through the batten area pA1 is incident on both sides of the projection lens PL, which is connected to the projection lens P1. The projected image of the circuit pattern of 1/ticle R is superimposed on one shot area of the wafer W on which the 1/cyst layer is formed on the surface, and a beam is carved (imaged). On the wafer W, an alignment mark (diffraction grating mark) WMx is located near the wafer W in a constant positional relationship with the area.
, WMy (only WMy is shown) are formed. The projection lens PL properly corrects chromatic aberration with respect to the wavelength of the illumination light IL, and the reticle R and the wafer W are arranged so that they are conjugate (ζ) to each other under that wavelength. This is Koehler illumination, and a light source image is formed at the center of the dark Ep of the projection 1 PL.The wafer W is vacuum-adsorbed to the wafer holder 7, and is stepped through the holder 7 by the driver 9.・The wafer stage WS is placed on a wafer stage WS that moves two-dimensionally in an Andori bead type.
There is. When the transfer exposure of one notch R to one shot area of the wafer W is completed, the wafer stage WS starts stepping at the end of the next shot position. The two-dimensional position of wafer stage WS is constantly detected by optical interference length measuring device (laser interference side) 8 with a resolution of, for example, 0.01/), t+. At the end of fS5, irradiation I1. 1,000 units (for example, projection 1/units P
An image field of I-4 or a projection area of 1/ticle pattern (a photoelectric detector with a light-receiving surface 11 having the same area as the sky) 6 is also set up, and information L regarding the irradiation amount is provided.
S is also sent to the control system 20 and serves as basic data for correcting the EGA data.

FIG. 2 is a plan view showing the arrangement of the shot areas SA, wafer WMx, and WIWIy on the wafer WJ2, and each shot area SA is a thin cloth-like scribe area extending in the X and Y directions. It is divided by CL.

Further, each shot area SA corresponds to a size that allows a circuit pattern area of 1/dicle R1 to be projected and exposed in one exposure in the exposure apparatus.

The configuration of the alignment system included in the exposure apparatus of this embodiment will be described below. This exposure system RJ, as shown in Figure 1, is a through-the-lens used for EGA measurement.
It is equipped with alignment systems (11 to 18) of the gh The Lense; T T L) type. In this embodiment, alignment marks provided on a mask or reticle are not detected, and only marks attached to a shot area on a wafer are directly observed or detected through a projection lens.

In addition, the following mark detection method is used in this alignment system. In other words, a one-dimensional diffraction grating mark formed on a wafer is irradiated with coherent parallel beams from two directions to create one-dimensional interference fringes on the diffraction grating mark, and the irradiation of these interference fringes causes diffraction. In this embodiment, which photoelectrically detects the intensity of diffracted light (interference light) generated from a grating mark, a heterodyne method is adopted that gives a certain frequency difference to parallel beams from two directions, and The phase difference between the photoelectric signal (optical beat signal) detected by intensity modulating the interference light from the diffraction grating mark at the beat frequency and the optical beat signal of the reference interference light separately created from the two transmitted light beams. (within ±180°)
By determining this, a positional deviation within ±P/4 of the grating pitch P is detected.

This type of alignment system (hereinafter referred to as Laser I
interferometric alignment:
The LIA system (referred to as the LIA system) is capable of extremely high-resolution mark position detection, but it is necessary to position the diffraction grating mark in advance within ±P/4 with respect to the interference fringes created by two parallel beams. There is a need.

For this reason, in this embodiment, an off-axis type wafer alignment system 21 is provided separately from the projection lens PL and exclusively detects the alignment mark on the wafer W. The wafer alignment system 21 performs global alignment of the wafer W. For example, the alignment mark on the wafer W is irradiated with illumination light that has extremely low sensitivity to the resist layer and has a broad spectral distribution in the wavelength range necessary for mark detection, or has multiple sharp spectra. The index mark on the index board (
An image pickup device (ITV) captures the image of the alignment mark which is re-imaged on the index plate together with the image sensor (not shown).

By forming an image on the light receiving surface of a CCD camera, etc.
This is to find the amount of deviation of the alignment mark with respect to the index mark.

Now, regarding the configuration of the LIA system, etc., for example,
Since it is disclosed in Japanese Patent Application Laid-open No. 215905 and Japanese Patent Application Laid-Open No. 62-56818, it will be briefly explained here. still,
Actually, the wafer mark WMx attached to the shot area,
Although two sets of LIA systems are provided corresponding to each of WMy, only the LIA system that detects the mark position in the Y direction will be described here. Regarding the other set of LIA systems that detect the mark position in the X direction, only the mirror M2'' corresponding to the mirror M2 is illustrated.Linearly polarized light oscillated from the laser light source 1 (for example, a He-Ne laser with a wavelength of 633 nm) The laser beam LB enters a two-beam frequency shifter 12 that includes two sets of acousto-optic modulators (hereinafter referred to as AOMs, but optical waveguides may also be used), half-plane beam splitters, etc. Frequency f+, f2
The first-order light beams are driven by high-frequency signals SFI and SF2 of (f2=fr-Δf) and are deflected by a diffraction angle determined by the frequency f, . . . f2 as beams LB, LB2. Furthermore, in a half-plane beam splitter that is placed at or near the pupil plane of the LIA system and has a total reflection mirror deposited on half of the cemented surface, the beams LB and LB2 are spaced apart by a predetermined distance and are almost parallel to each other. It is synthesized as follows. As a result, the chief rays of the two beams LB, LB2 become parallel to each other and are positioned symmetrically across the optical axis of the LIA system.

Two beams LB with a frequency difference △f are emitted from the two-beam frequency shifter 12 with the principal rays parallel, (frequency r+)
and LB2 (f) are partially branched to the photoelectric detector 14 of the reference signal generation section by the beam splitter BS. The two beams L B + and L B 2 reflected by the beam splitter BS are sent to different reference diffraction gratings 13 fixed on the device via a lens system (inverse Fourier transform lens) not shown. Parallel light beams from two directions form a large sword at a predetermined intersection angle O and form an image (intersect). The photoelectric detector 14 has a two-split light-receiving element, and for example, interference light between the 0th-order light of the beam LB that has passed through the reference diffraction grating 13 and the -1st-order diffracted light of the beam 13B that travels coaxially therewith, The interference light of the 1st-order diffracted light of beams 1 and LB and the 0-order light of beams 1 and B2 traveling coaxially therewith is received (photoelectrically converted) independently.The intensity of these two interference lights is The corresponding sinusoidal photoelectric signals are added by an amplifier (not shown), and the photoelectric signal SR written as a result is:
A frequency roar proportional to the difference frequency Δf between the beams LBhLB, becomes an optical beat signal. Here, the grating pitch of the reference diffraction grating 13 is determined to be equal to the pitch of the grid set made by the beams LB, LB2.

On the other hand, two linearly polarized (for example, S-polarized) beams I, B1. LB2 passes through a field stop AP arranged at a position 1-'' conjugate with the wafer W, is reflected by a polarizing beam splitter 15, and then
The light is converted into circularly polarized light by a 74-wave plate 16 and reaches a telnocentric objective lens 17 for alignment. 2
Wooden beam [−B + , i.

B2 (circularly polarized light) crosses once at the focal point of the objective lens 17 and then enters the projection lens PL via mirrors M, M2. Further 1. At or near the pupil plane Ep of the Z projection lens PL, the beam L B 1. I-82 is once focused into a spot, and each spot is centered on the pupil (light #1
AX) and passes through the pupil plane Ep almost symmetrically.

Two beams LB, L are emitted from the projection lens Pi.
B, (circularly polarized light) is a wafer mark W as shown in FIG.
With respect to the lattice arrangement direction (Y direction) of M, the attribute light beams are tilted at mutually symmetrical angles across the optical axis AX, and are incident on the wafer mark WMy from two different directions at an intersection angle θ and are condensed. The beam LB is formed to be substantially point symmetrical with respect to the optical axis AX on both sides of the optical axis AX in the pupil plane Ep.

The direction of the straight line connecting each sub-box 1- of 1, B2 and the direction of marking arrangement of wafer marks WM31 (Y direction) are approximately -
We are doing so.

When the beams L B r and L B 2 are incident on the wafer mark WMy at a predetermined crossing angle O (Fig. 3),
In the spatial region where the beams L B , , L, , B intersect, the optical axis AX and perpendicular lQ (in any plane (wafer), 1 / m times (m is integer) bitp'(P' = r'/2 on the wood grain side)
), one-dimensional interference fringes are created. This interference fringe causes the beam +-B, in the Y direction. ! , B, difference frequency Δf
It will move (flow) corresponding to the velocity V
is expressed by the relational expression ■・−△f−P′.

When the beams LB, LB2 (circularly polarized light) are emitted from the secondary beam, the beams LB, LB2 (circularly polarized light) are emitted from the mark WMy by 1. 1st-order diffracted light (interference light) BTI is generated as it travels along the path, and this interference light BTL repeats periodic 1ζ changes in brightness and darkness due to the movement of interference fringes (, :').・Has a wave front. The interference light BTL passes through the projection lens PL1 and the objective 1/lens 17 again,
After being converted into p-polarized light by the wave plate 16, it passes through the polarizing beam splitter 15 and is transmitted to the photoelectric detector 18 via a spatial filter FT arranged on a plane that is approximately conjugate to the pupil plane Ep of the projection lens PL. The light is received by Charging detector 1
8 is a photoelectric power supply No. 3 5D4- according to the intensity of the interference light 13TL.
This photoelectric No. 3 SD is the cycle of the change in interference fringes (,: 17 or 17, or the sine wave-like AC No. 3 SD (previous beat signal).
SD and ZIN are output from the phase detection section 191ζ.

The phase detection unit 19 inputs the light beam from the photoelectric detector 18], the signal SD, and the light beam outputted from the photoelectric detector 14h as a reference signal (X SR), and outputs the light beam, signal SD, etc.
Find the phase difference △ψ on the waveform of the quantity signal SR,,"l) with R as the reference. This phase difference △ψ (±180°) is the positional deviation amount of the wafer mark wMy within the horizontal P/4. Unique to 1
ζ, and its positional deviation ΔY is calculated using the following formula: Assuming that the detection resolution is 0.2°, the measurement resolution of positional deviation is 0°0022μ
It also becomes m. In reality, since it is affected by noise and the like, the practical measurement resolution is about o, oi μm (0.9° in phase).

The main control system 20 performs EGA calculation based on the mark position found from the phase difference information (positional deviation amount) from the phase detection section 19 and the position information from the laser interferometer 8.
The motor 9 is servo-controlled in accordance with the data and data LS and RS from the irradiation monitor 6 and the reflection monitor 10 to sequentially position the shot areas on the wafer W at predetermined positions, as well as to control the entire exposure apparatus.

Next, the operation related to EGA alignment will be explained.

First, pre-alignment is performed by the wafer alignment system 21. First, two holes are formed near the outer circumference of the wafer W and at positions symmetrical to the left and right (Y axis) with respect to the wafer center.
shot areas (for example, SA l, S in Fig. 2)
Detect the position of A2) in the Y direction. Furthermore, the wafer W
Near the outer periphery of and the above two shot areas SA, %S
The position of shot area SA, which is approximately equidistant from A2, in the X direction is detected. Then, the main control system 20 calculates the amount of positional deviation (including rotational error) of the wafer W with respect to the coordinate system Perform alignment. From this, if the wafer stage is stepped according to the alignment pressure PA (design value) of the shot area, the wafer marks WM x, W M y will always be aligned with the beam LBI,
It will be positioned within ±P/4 with respect to LB2 (interference fringes).

At this time, for example, the wafer W may be stretched by various processes after exposure. 1ii (runout) occurs and the scaling error increases, even if the wafer stage is stepped according to the above array coordinates, it is not possible to position the wafer marks WMx and WMy within ±P/4 of the beams LBl and LB2. .

In such a case, the wafer alignment system 21 is used again to measure at least two shot Fg target values (positions in the x and y directions) on the wafer W. At this time, if the shot area SA cannot be measured or the measurement result is questionable due to random errors due to surface roughness of the wafer W, the measurement is performed again, or the shot area SA in the vicinity is measured again. . Then, based on this measurement result, the array coordinates (design values) of the shot area are
, and memorize this new position information as an array map), this will remove the scaling error, and if the wafer stage WS is stepped according to the array map, the wafer mark will always be WMx, WMy are beams L B r , L B 2
It is positioned within ±P/4 with respect to. Note that the alignment map may be calculated using the measurement results (mark position information) in the pre-alignment operation. In this case, it is possible to improve the calculation accuracy of the alignment map, or to determine the shot area to be measured. The number of SAs can be reduced.

Second, EGA measurement using the LIA system, that is, wafer W
Sample alignment is performed for a plurality of (approximately 5 to 10) shot areas SA located near the center and the outer periphery of the area SA. Therefore, based on the designed array coordinate values of the shot area (or the array map mentioned above), the wafer stage WS is stepped, and the wafer marks WMY of the shot area whose coordinate values are to be measured are beamed to B, L.
Position within distance P/4 with respect to B2. Next, the beams L B 1 and L B 2 are directed onto the wafer mark WMy, and the photoelectric detector 18 receives the diffracted light BTL generated from the wafer mark WMy. The phase detection section 19 inputs the optical beat signal SD from the photoelectric detector 18 and the optical beat signal (reference signal) SR from the photoelectric detector 14, and receives both signals S.
The phase difference △ψ (±180 degrees) between D and SR is detected, and this P
The positional deviation amount ΔY of the wafer mark WMy is determined from the phase difference Δψ within /2. Thereafter, the above operation is repeated to perform sample alignment of all the selected shot areas, and then the main control system 20 calculates the shot arrangement by a statistical method (EGA calculation). Than this,
EGA measurement using the LIA system is completed.

In conventional exposure equipment, the main control system 2
0, the wafer stage WS is stepped, and exposure is performed by overlapping the projected image of the reticle pattern with the shot area SA.

Regarding the relative rotational error between the projected image of the reticle pattern and the shot area, the reticle R is rotated by an amount approximately equal to the wafer rotation amount obtained from the EGA calculation, and the error is reduced by 1. It is desirable to set it to τ.

In the exposure apparatus according to the present invention, by newly adding the following process to the above alignment process, higher precision t2 can be achieved.
This allows superimposition.

That is, in this embodiment, the elongation of the wafer W and the wafer holder 7 during overlapping exposure is determined using the irradiance measuring means consisting of a 1,200 yen dose and a 10,000 yen reflector, and the previously calculated EGA data is used. This is corrected by a correction means.

A more detailed explanation will be given below with reference to the drawings. FIG. 4 shows the case where a conventional exposure device is used, and the overlap is 8't! This is based on the assumption that no scaling occurs during exposure. Figure 4 (
a) is a wafer W with 9 sheets and 1 region of 3 rows and 3 columns.
Sl indicates what was exposed. Here, the area surrounded by the solid square is the l5tff light shot area 24.

FIG. 4(b) shows a state in which the wafer W in FIG. 4(a) undergoes scaling through various processes, and the shot interval is widened. - The part indicated by the Braille translation line is 2 n dg before light EG
This is the array coordinate 23 of the shot area determined by A measurement. The 2nd exposure is performed according to these coordinates, so as shown in the figure, IS (, tF light shot start; 24 and 2
The nd exposure shot areas 25 completely overlap (the shot centers coincide).

Next, FIG. 5 shows the case where a speed-dependent exposure device is used, and 2 n
This is based on the assumption that dg will occur when light is ahead. Fifth
In Figure (a), IS'l-exposure of 9 shot areas of 3 rows and 3 columns of wafer W1ζ was performed and the process was completed. Here, 26 indicates the 1st exposure shot area, and 27 indicates the shot/array coordinates of the 1st exposure. 6 Figure 5 (1)
) is the result of performing 2nd exposure on the wafer in (a). As exaggeratedly shown in the figure, the wafer W and wafer boulder 7 extended into the 2n4g light, so the 1st
, the H light shot area moves to a ratio compared to the case of (a), and the shot interval widens to the position shown by the solid line square 26T. , and the 2nd exposure is E G before the 2nd exposure.
Since it cannot be carried out according to the shot array coordinates 28 determined by the AH measurement, the 2nrJ exposure area is at the position indicated by the dotted square 29 in the figure. Like this 2n
dDuring exposure, the hole W and hole holder 7 extend,
Even if accurate EGA measurement is performed, a gap will occur between the 1 stl$ light shot area 26 and the 2nd exposure shot area 29.This deviation amount (irradiation) - energy j (corresponding to this amount of scaling) is shown in the figure by an arrow 30 in its direction and magnitude.In addition, this overlay error becomes a scaling error as shown in the figure.

Next, the disc alignment exposure method of the present invention will be explained using FIG.

FIG. 6(a) shows the various processes in which the first exposure of nine shot areas of 3 rows by 3 columns is performed on the wafer W. Here, 31 is the 1st exposure shot/area, and 32 is the 2nd exposure area.
8 shows the shot arrangement coordinates of 1s14 exposure by IEGA cutting before 2nd exposure. The calculation is based on the amount of energy irradiated on the wafer and the reflected image from the wafer (opposite plan).

The amount of irradiation energy is determined by the above-mentioned irradiation amount measuring means of the present invention. It has a light-receiving surface with an aperture approximately equal to H. By moving the T-station WS using the drive motor 9, the irradiance monitor 6 and
Jx penetrates almost into the center of the projection lens PI-, and the Ugoha W
All of the exposure light IL irradiated onto the wafer W is received and photoelectrically detected, and the irradiation amount of the exposure light IL that reaches the wafer W via the first notch R etc. is calculated. The irradiation amount is the illumination light intensity, 1.
・Transmittance of Dikuru R, chrome butter on reticle R・=-
This depends on the window occupancy rate, the serrations of the variable blind 2a, etc.

Further, the amount of reflection from the wafer W (or its amount of reflection) is measured by the above-mentioned reflection amount monitor 10 which is the reflector measurement means of the present invention.
Find it by The reflection amount monitor 10 photoelectrically detects all or a part of the amount of reflected light from the imaging position (surface of the sea urchin) of the projection lens PL. By measuring in advance, it is possible to obtain the reflectance of a desired wafer whose reflectance is unknown.

Specifically, a material with high reflectance (α%) is placed in the imaging plane of the projection lens PL, for example, a reference member (a glass substrate, a reference member) placed on the wafer stage WS for baseline measurement, etc. Along with the mark, a part having a reflective surface made of chromium or the like) and one having a low reflectance (β%), for example, the surface of the irradiance monitor 6 (the light receiving surface of the detector) are arranged in sequence. Thereafter, the reflection amount monitor 10 photoelectrically detects the reflected light generated from these surfaces by the irradiation of the exposure light IL, and the pressure voltage values V, , V2 are determined according to the amount of reflected light.
seek. Then, from this detection result, a linear relationship between the reflectance γ and the output voltage value V, that is, a relational expression (−order number) of γ==(α−β)/(Vl−v2)×v, is calculated, It is stored in a memory (not shown).

Therefore, in this embodiment, by irradiating the resist-coated wafer (which may have an aluminum film, an oxide film, etc. formed on the surface) to be exposed with the exposure light IL in the same manner as described above, A desired wafer reflectance can be calculated from the above relational expression using the voltage value output from the reflection amount monitor 10. Here, in this embodiment, the reflectance to the square including the material of the wafer, the type and film thickness of the base and resist, etc., is determined by the above operation. Note that it is desirable to calculate the above relational expression, for example, every time the reticle R is replaced, or when the output of a sensor that monitors the intensity of the illumination light from the illumination light source 1 changes.

Now, in this embodiment, prior to overlay exposure, the exposure light IL reaching the wafer W is monitored by the irradiation amount monitor 6 as described above.
The irradiation amount is measured and this data is output to the main controller 20. On the other hand, the reflectance cannot be determined before exposure because the resist layer is exposed to light by irradiation with the exposure light IL. Therefore, in this embodiment, the reflectance is determined using the reflection amount monitor 10 during overlay exposure for the first shot area on the wafer W. This is because, as a matter of course, no scaling error occurs due to the irradiation of the exposure light IL in the shot area to be overlapped and exposed first.

The information R3 (voltage value) output from the reflection amount monitor 10 is immediately sent to the main control system 20, where the reflectance of the wafer W is calculated based on the above-mentioned relational expression, and the irradiation amount of the exposure light IL is calculated. and stored in memory. The main control system 20 is
Based on the irradiation amount during wafer exposure determined by the irradiation amount monitor 6 and the reflectance of the wafer W and data such as exposure time, step pitch, wafer size, etc. stored in the memory,
The amount of energy absorbed by the wafer W is calculated, and the elongation of the wafer W and wafer holder 7 is determined from this calculated value.

Furthermore, the amount of scaling for each 1st exposure shot area of the wafer W is calculated based on the amount of elongation (details will be described later).
After that, the EGA data obtained by the LIA system is corrected. As a result, as soon as the reflectance of the wafer is determined during the overlapping exposure of the first shot area, the EGA
The data is corrected and “@2nd and subsequent 1s on wafer W”
The coordinate values of the t-exposure shot area (shot center) are calculated. After the exposure of the first shot area is completed, the main control system 2o steps the wafer stage ws according to the corrected EGA data. As a result, the alignment error between the projected image of the reticle pattern and the 1st exposure shot area, which is caused by the amount of scaling due to absorption of the exposure light IL, becomes almost zero.
Highly accurate overlapping exposure of the second and subsequent layer reticles becomes possible.

Now, as a calculation formula for determining whether a displacement occurs in the array coordinates of the shot area due to the elongation of the wafer, etc., as described above, the following formula may be considered, for example. The amount of scaling of the 1st exposure shot area caused by the elongation of the wafer W and wafer holder 7 due to heat during the 2nd exposure is [S
] 2nd, [S Y] 2nd, 2 n d 3'
The amount of energy absorbed per unit area on the Ugoha W during f light is Eab = The proportional coefficient of the scaling ball caused by the amount of absorbed energy is αx (x direction), ay (y direction) (of the wafer) τ is the time constant at which the energy stored in the wafer W and wafer boulder 7 flows to the outside. , the time it takes to expose one horizontal row is tO)1
+ If the time required to expose one vertical column is reduced by 1°, then lsx]znd=αX E Mh×exp(-tox
/τo) ”'■[5ylznd d = α y
E, b x exp (-toy/
It can be expressed as τ o) -... ■.

Here, Eab: I o (1-r)X T x1/LXX
1/Ly...■■o: Irradiation dose, r・
Reverse lA rate, T: 2nd exposure time, 1. , +x step pitch in the force direction, L: step pitch in the y direction.

As is clear from the formula 0, the EibO value is a known value in the wood system because NO (irradiation amount) and r (foul rate) are measured in advance. Also, toll of ■ and ■ expressions
The value of +t09 can also be determined from appropriate exposure time, stage speed, and number of shots. As for C1, αa, and τ0 in equation 010, they can be determined by experimentally obtaining the first +S data and -(g).In actual cases, the equations % and % There is no problem in handling it with the formula %.

Also, 2. nd exposure light row 11 Umoe's skate song iSR
*The value of S y can be expressed by the following formula.

SX = I'sxE+ [Sx]2y
”'■s, = csy] +
[syco 2nd
... ■Here, [S x] and [s y] are the values obtained by conventional EGA measurement, [S x] 2nd,
[S y]2nd is a term for correcting elongation during the 2nd exposure according to the present invention.

The elongation of the wafer W and wafer boulder 7 due to heat during the 2nd exposure is calculated using the above formula, and the arrangement coordinates of the 7 loam new shot area obtained by correcting this scaling are indicated by the dotted line in FIG. 6(a). 33 is shown.

So, using this new shot area array coordinates, 2
Figure 6 (11) shows the rhinoceros that has been exposed to ND light. - Show. Is it indicated by a solid square?154. , g light 3 1-
- It is located at position 31, and as shown in the figure, scaling has occurred due to the 2nd exposure. The 2nd exposure shot indicated by the dotted square is located at position 34 on the rod mentioned above.
Since the elongation of the 1st shot W etc. due to the 2n6g light was considered and corrected, as shown in (1) in the figure, the 1st exposure shot position 31 was completely 1. = will match.

In this way, in the present invention, the irradiation amount I. , wafer reflectance r
is measured before the 2nd exposure, so even if the illuminance of the illumination light is lowered, the one-noticle pattern occupancy is different, the size of the blind, etc. is different, and wafers with different base materials, resist types, and film thicknesses are used. Therefore, the system can cope with changes in reflectance. If the wafer material is not silicon, but Garihiso, for example, the wafer material N
The coefficient αII + ay corresponding to αII + ay is measured in advance in an experiment and set at 2, and the coefficient α8. Change αa1, that's good.

As described above, in one embodiment of the present invention, the amount of scaling caused by absorption of exposure light is calculated by calculation ζ:, and wafer stage WS is stepped in accordance with EGA data corrected based on the calculation result. However, the reticle stage R3 shown in FIG. The amount of scaling caused by absorption of exposure light in the shot area may be corrected each time the reticle stages R and S are driven. Therefore, the C1 main control system 20 operates according to the EGA data obtained by the LIA system.
As the wafer stage WS is stepped, the scaling amount calculated from the above formulas 1 to 2 or 2 and 3 is adjusted so that the alignment error due to the above scaling amount is almost zero in the second and subsequent sheet regions. Accordingly, reticle stage R5 may be driven for each shot.

By the way, in the present invention, the elongation of the wafer holder 7 is taken into consideration, but if the wafer holder 7 is made of a heat insulating material (such as ceramic) or a material with a low expansion coefficient (such as Invar), there is no need to take the elongation of the wafer holder 7 into consideration. , it becomes possible to simplify the arithmetic expression for calculating the scaling amount.

Further, in the above embodiment, when calculating the scaling amount of the first exposure shot area, the reflectance obtained during exposure of the first shot area on the wafer was used. However, for example, when exposing multiple shot areas from the second shot area, only the scaling amount of the multiple shot areas is calculated using the reflectance obtained during exposure of the first shot area. However, for subsequent shot areas, the scaling amount for the remaining shot areas is calculated using the average of the reflectances obtained during exposure of multiple shot areas starting from the first shot area. I don't mind. Here, it is considered that the processing conditions (for example, the type and film thickness of the base and resist) are almost the same for wafers in the same lot, so the reflectance of the first wafer in the loft ( The reflectance of the first shot or the average reflectance above) is
The scaling amount may be calculated by directly using it for the second and subsequent wafers. Also, when overlay exposure is performed on the first wafer in the loft, the reflectance is determined for all shot areas on the wafer, and the averaged reflectance is applied to the second and subsequent wafers. In this case, there is an advantage that it is possible to prevent a decrease in the calculation accuracy of the scaling amount that may occur due to a difference in reflectance for each shot area due to uneven thickness of the resist layer or the like. Note that for the first wafer, the reflectance is determined and averaged for each shot, and this average value is used to determine the scaling amount, that is, the nth shot area (n≧2) on the wafer is When exposing, the amount of scaling is calculated using the average reflectance of the (n-1)th shot area, and the EGA data is corrected for each shot, or the scaling is performed by driving the reticle stage. All you have to do is correct the alignment error caused by this. It is also possible to divide the shot area on the wafer into several blocks and change the reflectance for each block.
The reflectance in each block may be, for example, the reflectance of the first shot area within the block.

In addition, in the above embodiment, in order to simplify the explanation, FIG. 6 (
a) As is clear from (arrow in the figure), the amount of scaling of the first exposure shot area due to exposure light absorption during the second exposure is equally balanced around the scissor area (wafer center) located approximately in the center of the wafer W. The explanation was given as something that was occurring. However, in reality, the heat distribution within the wafer differs depending on the order of overlapping exposure of the 1st exposure shot area on the wafer, etc.
Accurately determining the amount of scaling from the equation can be difficult. Therefore, the exposure positions X, Y of the 1st exposure shot area on the wafer (array position 1jil! in FIG. 6(a)) are determined.
33) and the exposure order, the coefficients α, (X, Y), α of the above equations
, (X, Y), it is possible to obtain the scaling amount with higher accuracy and to improve the overlay accuracy. At this time, the coefficient αx for every l shot
(x, y).

Even if α, (X, Y) are not changed, the first exposure shot area on the wafer is divided into a plurality of blocks considering the exposure order of the shot areas, etc., and the above coefficients α, α,
It is okay to specify. In addition, especially large diameter wafers (e.g. 8
Since the heat distribution can vary greatly for (inch wafers), it is desirable to determine the coefficients α8 and α for each shot or block using the same method as described above.

In addition, although scaling correction has been described in the above embodiment, in reality, the size of the 1st exposure shot area fluctuates depending on the elongation of the wafer and wafer holder due to the irradiation amount during the 2nd exposure, and even linear and nonlinear distortions occur. may also occur. Therefore, in such a case, the 1st exposure shot corresponding to the above-mentioned irradiation amount → the elongated ball (
The scaling (corresponding to -ring (2)) is obtained from equations (2) and (2) in the same manner as in the above embodiment. 1: From the elongation amount, t
s is calculated by calculating the size and distortion of the exposed shot area t/, and the projection magnification of the 1-notch butterfly and the image distortion shell are adjusted according to the results.
This makes it possible to perform alignment exposure more accurately.

The ability to adjust the projection magnification and the amount of distortion can be achieved by, for example, moving at least some of the lens elements of the projection lens PL three-dimensionally, or
A two-dimensional IC tilt is applied to a plane approximately perpendicular to AX, an air chamber is provided between the two lens elements and the pressure is changed, and the distance between 1/ticle R and projection 1 nons PL is changed. +, or) two-dimensionally inclining the noticle R with respect to a plane substantially perpendicular to the optical axis AX.

Here, in the above embodiment, T is used as an alignment sensor.
Although a TL type LIA system was used, any type of alignment sensor may be used in the present invention. Furthermore, the alignment method suitable for applying the present invention is not limited to the EGA method, but any method that performs alignment prior to overlay exposure may be used. 7
The present invention can be applied even to a method in which Furthermore, the present invention can be applied not only to an exposure apparatus for manufacturing semiconductor elements, but also to an exposure apparatus for manufacturing liquid crystal display elements, and the same effects as in the actual example can be obtained. Needless to say, it's 12.

Further, T T R (Throu) (h Th
When performing continuous exposure using the DID method using an LIA system using the eRet, 1cle) method, the wafer stage may be stepped to the next exposure shot area in consideration of the above scaling amount. In this case, there is an advantage that the five and seven half marks can always be positioned within P/4 of the interference fringes for alignment. In addition, when using an air micrometer as a focus detection means (AF sensor) that detects the position of the surface of the sea urchin in the height direction (optical axis AX direction), scaling should be done taking into consideration the cooling of the wafer by air. It is desirable to determine the amount.

[Effects of the Invention] As described above, the exposure apparatus of the present invention includes an irradiation i measuring means for measuring the irradiation energy ball absorbed by the substrate or its holding member when selling π, and an alignment method based on the amount of irradiation energy. Since the apparatus is equipped with a correction means for correcting the exposure position determined by the apparatus, a high degree of overlay accuracy can be obtained even if the substrate or substrate holding member stretches during exposure. In addition, since exposure can be performed using the high-precision EGA method, the die-pie-die exposure apparatus 1. ``In comparison, it has the advantage of being highly efficient and guaranteeing high throughput.

A plan view of the Ugoha suitable for exposure, Figure 3 is 1.
Diagram explaining the alignment principle of IA system, 4th...
FIG. 6 is a diagram for explaining the exposure position correction method according to the present invention.

[Explanation of symbols of main parts]

Claims (2)

[Claims] (1) In an exposure apparatus having an alignment device that superimposes a pattern on a mask onto a pattern on a substrate, the irradiation amount measuring means measures the amount of irradiation energy absorbed by the substrate or its holding member during exposure, and the irradiation An exposure apparatus comprising: a correction means for correcting the exposure position determined by the alignment apparatus based on the amount of energy. (2) The irradiation amount measuring means includes an incident amount measuring means for measuring the amount of exposure light incident on the substrate, and a reflection amount measuring means for measuring the amount of exposure light reflected by the substrate. The exposure apparatus according to claim 1, characterized in that: