JPH08195335A - Exposure method and exposure system - Google Patents

Abstract

PURPOSE: To manufacture a device after the 0.1μm rule by measuring deviations such as strain produced between the image pattern of a first substrate substrate and that of a second substrate in an exposure plane, calculating their correcting values and by relatively changing the shape of either of them to correct the deviations in a plane direction. CONSTITUTION: The positions of a reticle 17 and a wafer 14 are measured by position detectors 24 and 25 respectively and they are placed so as to eliminate the misalignment by driving a stage 20. The array error is previously measured and the data for correcting the error are stored. Next the wafer 14 is loaded and vacuum-chucked. After that the wafer 14 is strained by a the prescribed value by driving a piezoelectric element by a quantity previously stored. As a result a pattern to be transferred next is aligned with the pattern already formed on the wafer 14, thus manufacturing a devise after the 0.1μm rule.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor manufacturing method,
The present invention relates to an exposure method suitable for improving the alignment accuracy of an X-ray exposure apparatus, a reduction projection exposure apparatus, or an electron beam drawing apparatus, and the structure of the exposure apparatus.

[0002]

2. Description of the Related Art In a process of transferring a semiconductor integrated circuit pattern (lithography process), how to accurately superimpose an original image pattern formed on a mask or the like on a pattern already processed on a wafer (alignment)
is important. To improve the alignment accuracy, in addition to improving the mechanical positioning accuracy, the deformation of the wafer substrate caused by the wafer process, the image distortion of the exposure optical system, the original pattern of the mask and the original image of the reticle. It is effective to reduce the alignment error caused by the pattern alignment error and the like.

Conventionally, as described in Japanese Patent Laid-Open No. 63-70420, a mark alignment method is used to correct a change in magnification due to expansion and contraction of the wafer, or
Magnification correction is performed by deforming the reticle substrate as described in JP-A-4-138465, or magnification correction using thermal deformation of the entire wafer as described in JP-A-53-98782. By doing so, the error was reduced and the device was manufactured.

[0004]

In the above prior art,
It was unsuitable for manufacturing devices after the 0.1 μm rule. This is because the alignment accuracy higher than 30 nm is required for manufacturing the device after the 0.1 μm rule. To exceed this accuracy, the array error 5 of the original image pattern on the mask and the image distortion 22 of the exposure optical system shown in FIGS.
It is necessary to reduce the alignment error due to the local process distortion of the wafer 14. However, in the above conventional technique,
Since the magnification correction is performed by using the thermal deformation of the entire wafer, the alignment error due to the local deformation of the wafer and the image distortion of the exposure optical system cannot be reduced. These error factors were at a level that can be ignored in the conventional device processing process. For example, the image distortion of the currently mainstream i-line stepper is about 50 nm in the exposure field, and the pattern arrangement accuracy of the reticle is about 12 nm on the wafer.
Up to the 0.2 μm rule (required alignment accuracy of 60 nm) was acceptable. However, there was a problem that cannot be ignored under the 0.1 μm rule.

The present invention solves the above-mentioned problems and solves the problem of 0.1 μm.
An object of the present invention is to provide an exposure method and an exposure apparatus capable of manufacturing devices following the rule.

[0006]

The present invention is an exposure method for transferring a pattern of a first substrate onto a second substrate by using a radiation source, and an image formation pattern of the first substrate pattern and a second image pattern.
Step of obtaining a deviation amount such as distortion in the exposure surface generated between the pattern on the substrate and the pattern on the substrate, a step of calculating a correction amount for correcting the deviation amount, an image formation pattern and a surface of the pattern on the second substrate. It is characterized by including a step of correcting the deviation of the direction by relatively deforming the first substrate or the second substrate.

The present invention also provides an exposure apparatus for transferring a pattern of a first substrate onto a second substrate using a radiation source,
It has a correction means such as a local temperature control means for correcting the relative deviation in the exposure surface before the transfer of the pattern, and a radiation source of any one of ultraviolet rays, extreme ultraviolet rays, X-rays, electron beams and ion sources. And

When the exposure method and the exposure apparatus having the above-mentioned structures are used, first, the deviation amount between the image forming position of the pattern formed on the reticle and the pattern position formed on the wafer is calculated as one sheet. Measure by exposing the preceding wafer. A long dimension measuring device may be used for the measurement.

Next, the wafer, the reticle, and the mask are mounted on the means for independently holding the wafer, reticle, and mask with a plurality of actuators, or on the means for giving a local temperature distribution to the wafer, reticle, and mask. The correction amount required to cancel the deviation amount obtained by the previous measurement is calculated by using the control means, and the actuator is driven by the drive means by this correction amount to deform the wafer, or the wafer, reticle, The amount of deviation can be corrected by causing a local heat distribution in the mask and deforming it. If a normal exposure operation is performed after this, the image forming position of the pattern formed on the reticle and the pattern position formed on the wafer can be favorably superposed with no deviation.

The above-mentioned problems can be solved by using the exposure method and the exposure apparatus having the above constitution.

[0011]

The operation of the present invention will be described in detail with reference to FIGS. 5 and 10. FIG. 5 is a view showing an exposure apparatus of the present invention,
FIG. 10 is a diagram showing a flow chart of exposure in the present invention.

The exposure is carried out along the flow shown in FIG. 10. First, the dummy wafer is loaded into the exposure apparatus shown in FIG. A pattern of the previous layer is formed on this dummy wafer, and there is also a mark for alignment evaluation in the pattern. On the other hand, the exposure apparatus has a reticle 17 on which the following pattern and marks for alignment evaluation are formed.
Is installed. The mark for alignment evaluation is effectively a box-in-box type, but another type may be used.

Next, the pattern is transferred after the normal alignment process. After that, the dummy wafer is unloaded, and the deviation amount in the exposure surface is measured by a dimension measuring device or the like. In addition to this, the deviation amount outside the exposure surface, that is, the deviation amount of the image formation point is also obtained. This data is the field curvature of the exposure optical system,
It is necessary to take into consideration the step structure of the device.

These data are sent from the data input / output means 40 of the exposure apparatus shown in FIG. 5 to the main control means 41, and the correction amount of the wafer chuck 1 is calculated. This correction amount is
It is transferred to the chuck control means 42. Here, the next wafer is loaded into the exposure apparatus. And the driver 43
Thus, the wafer chuck 1 is driven and the deviation amount is corrected. The wafer position detector 25 evaluates whether or not this correction amount is appropriate. It is preferable to use the two-beam type wafer back surface position detector shown in FIG. 11 for the wafer position detector 25, because high position detection accuracy without influence of the wafer process and wafer thickness can be obtained. As a result of the evaluation, if the predetermined correction is completed, the process proceeds to the exposure process, but if it is defective, the operation of releasing the wafer chuck 1 and chucking it again is repeated. After the exposure process is completed, the presence or absence of the remaining wafer is confirmed, and if there is any remaining wafer, the next wafer is loaded and the process of correcting the wafer chuck 1 is repeated. If no wafer remains, the exposed wafer is unloaded and all steps are completed.

Next, a specific structure of the wafer chuck 1 will be described. A case where distortion is corrected by holding a local area of the wafer 14 will be described with reference to FIG. It is assumed that the area d holding the wafer is 5 mm square and the pitch p of the area is 6 mm. Generally, elastic deformation is expressed by the following equation.

[0016]

[Equation 1]

Here, σ is stress, ε is strain, and E is Young's modulus. Assuming that there is a strain Δp of 15 nm between the pitches p, 3.25 ×
It suffices to displace the actuator having a holding force capable of withstanding the stress σ of 10 ⁵ N / m ² by 15 nm. The holding force F required at this time is that Si (E = 1.3 × 10 ¹¹ N /
m ² ), thickness t is 400 μm, static friction coefficient μ is 0.3
Then it becomes as follows.

[0018]

[Equation 2]

Therefore, it is sufficient if the holding power is 2.17N. When the wafer chuck 1 by vacuum suction is used, since the area d for holding the wafer is 5 mm square, the suction force in this area is the product of the atmospheric pressure 1.01325 × 10 ⁵ Pa and the area of the area d, that is, 2 It turns out to be 0.53 N, which exceeds the required holding force and withstands use.

Next, a method of generating a local temperature distribution and reducing the local strain by thermal deformation will be described with reference to FIG. Before loading the wafer 14 on the exposure apparatus, it is loaded on the illustrated local temperature control means. Wafer 1
The entire unit 4 is kept at a constant temperature by the temperature control unit 7 and, at the same time, is locally heated by the laser beam 38 focused on the wafer 14. The heating section expands its area by thermal expansion. The distortion is corrected by utilizing the deformation caused by the thermal expansion. It is measured in advance how much the strain amount exists, and the laser irradiation amount and irradiation region for reducing the strain amount are calculated. For example, since the linear expansion coefficient α of Si is 0.0000026 (1 / ° C) at 20 degrees Celsius, it is necessary to heat 1.15 degrees to expand a 5 mm square area by 15 nm per side. After loading the local temperature control means, a predetermined amount of laser is irradiated to a predetermined position.
After that, the wafer may be loaded into the exposure device and the normal exposure may be performed. By doing so, even if there is a process distortion, an array error of the original image pattern formed on the mask, an image distortion of the exposure optical system, or the like, highly accurate alignment can be performed.

[0021]

【Example】

(Embodiment 1) In the example shown in FIG. 1, the present invention is applied to a wafer chuck 1. An enlarged view of the chuck portion is shown on the right side of the figure. Each block has a suction unit (suction block) 2 having a vacuum suction port. This adsorption block 2
Are supported by piezo elements 3-1 and 3-2, one side of which is fixed to the chuck 1. The wafer chuck 1 has a plurality of suction blocks 2 having such a structure. After the wafer is loaded on the chuck 1 and vacuum chucked, the piezoelectric elements 3-1 and 3-2 are driven by a predetermined amount to distort the wafer into a desired shape. A shape memory alloy may be used instead of the piezo elements 3-1 and 3-2. As a practical material, titanium and nickel-based shape memory alloys called Nitinol have a deformation force of 600N.
It is as strong as / mm ^2, and the deformation speed is comparable to the speed of sound.

The actual process will be described step by step. The case of using the optical lithography apparatus shown in FIG. 5 will be described in detail. The present exposure apparatus is an apparatus for reducing and transferring the original image pattern formed on the reticle 17 onto the wafer 14. Prior to exposure, position of reticle 17 and wafer 1
The positions are detected by position detectors 24 and 25, respectively, and the stage 20 is driven and positioned so as to eliminate the relative displacement between the two substrates. After that, the light source 15
The reticle 17 is illuminated by the illumination optical system 16 by opening a shutter (not shown) between the illumination optical system 16. The original pattern image is reduced by the exposure optical system 18 and transferred onto the wafer 14. After that, the stage 20 is driven to the next shot position to move the wafer 14, and the same operation is repeated. When such a lithographic apparatus is used, it is necessary to (1) correct the alignment error of the original image pattern drawn on the reticle 17 and (2) correct the image distortion of the exposure optical system 18. As shown in FIG. 2, the array error of the original image pattern is a drawing error or a process distortion such as etching when the pattern is formed by an electron beam drawing apparatus or the like. Here, the image distortion refers to a phenomenon in which, when a reticle pattern having an ideal lattice is transferred as shown in FIG. 3, the transferred pattern has an array error due to the aberration of the exposure optical system 18. Further, the deviation amount of the image forming point refers to the deviation of the image forming point caused by the curvature of field of the exposure optical system 18 and the step structure of the device to be manufactured.

These array errors are measured in advance, and data for canceling these array errors is stored in the wafer chuck control means 12. Next, the wafer 14 is loaded and vacuum-adsorbed. After that, the piezo element 3-1 by the amount stored in advance,
3-2 is driven to distort the wafer 14 by a predetermined amount.
By doing so, the pattern to be newly transferred and the pattern already formed on the wafer 14 can be accurately overlapped. In this embodiment, the example using the optical lithography apparatus has been described, but the present invention can be applied to the X-ray reduction exposure apparatus having the structure shown in FIG.
It may be applied to direct drawing by an electron beam drawing apparatus having the structure shown in FIG.

(Second Embodiment) In the first embodiment, the wafer chuck 1 is provided with the distortion correcting mechanism, but in the present embodiment, the distortion correcting mechanism is provided only in the exposure field. By adopting such a configuration, complicated mechanism can be reduced. FIG. 6 is a diagram showing the structure of this embodiment. Wafer 1
No. 4 is sucked by a hollow flat plate (hollow chuck) 27, and inside the hollow flat plate (hollow chuck) 27, there is a chuck 28 with a distortion correction mechanism. The main chuck 28 is fixed to the base 21 of the apparatus, and is constantly exposed to the exposure optical system 1.
Directly below 8. The chuck 28 has a built-in alignment sensor for aligning the wafer 14 and the transfer pattern. FIG. 7 is a view of the main chuck 28 seen from above. The chuck 28 has an alignment hole 36, which penetrates the alignment hole 36, and detects the position of an alignment mark (not shown) formed on the back surface of the wafer 14 from this opening. Although not shown, each suction block is supported by a piezo element or the like and can be finely moved.

When the position detection of the wafer 14 is completed, the first
The wafer 14 is moved to the shot position, and the chuck 28
Adsorb to. Precise positioning can be performed by using signals from the laser length measuring device 19 and the alignment sensor 25 for positioning at this time. Then, like the first embodiment, the distortion is corrected and then the transfer is performed. Wafer chuck 1 after the first shot
Is removed, the wafer 14 is moved to the next shot position, and the same process is repeated. This makes it possible to obtain a similar effect with a simpler configuration than the first embodiment.

(Embodiment 3) Another embodiment will be described with reference to FIG. In the above embodiment, the wafer 1
Although the elastic deformation of No. 4 was used, the thermal deformation of the wafer 14 is used in this embodiment. It is the same as the above-described embodiment until the strain of the wafer 14 is measured in advance before performing the strain correction. After that, the wafer 14 is attached to the local temperature control device shown in FIG.
Is loaded on the uniaxial stage 9. This stage 9
Is movable in one axis direction and can be driven in synchronization with the oscillation of the laser beam 37. Also, the wafer 14
The temperature control unit 7 is provided to control the temperature of the liquid crystal to a specific constant temperature. The laser beam 37 passes through the lens 13 to the wafer 1
4 is adjusted so as to be condensed on the surface of the wafer 4, and is reflected by the oscillating mirror 10 through the shutter 38 to reach the surface of the wafer 14. The surface of the wafer 14 is heated by the laser beam 37, and local thermal deformation occurs. For example, the linear expansion coefficient α of Si
Is 0.0000026 (1 / ° C.) at 20 degrees Celsius, so 1.15 degrees heating is required to expand a 5 mm square area by 15 nm per side. The relationship between the deformation amount and the laser irradiation amount may be obtained in advance and a predetermined amount may be irradiated to a predetermined position. The processed wafer 14 is loaded into the lithographic apparatus and subjected to a normal exposure process before being re-deformed due to heat dissipation. In this way, by deforming the wafer 14 before exposure to cancel the distortion, it is possible to accurately superimpose the pattern to be newly transferred and the pattern already formed on the wafer 14.

Although not shown here, the reticle or mask may be corrected for local temperature instead of the wafer. The correction process is not limited to immediately before exposure, and it is obvious that the same effect can be obtained during exposure.

[0028]

According to the present invention, the alignment accuracy is remarkably improved over the entire exposure field even when the image distortion of the optical system exists in the lithographic apparatus or the distortion due to the wafer process occurs. Further, according to the present invention, it becomes possible to manufacture a device having a 0.1 μm rule or later.

[Brief description of drawings]

FIG. 1 is a diagram illustrating the present invention.

FIG. 2 is a diagram showing an array error of a reticle pattern on a wafer.

FIG. 3 is a diagram showing image distortion of an exposure optical system.

FIG. 4 is a diagram illustrating another embodiment of the present invention.

FIG. 5 is a diagram illustrating an example in which the present invention is applied to an optical lithography apparatus.

FIG. 6 is a diagram illustrating another embodiment of the present invention.

FIG. 7 is a diagram supplementing the description of another embodiment of the present invention.

FIG. 8 is a diagram illustrating an example in which the present invention is applied to an X-ray reduction exposure apparatus.

FIG. 9 is a diagram illustrating an example in which the present invention is applied to an electron beam drawing apparatus.

FIG. 10 is a diagram showing an exposure method of the present invention.

FIG. 11 is a diagram showing an example of a wafer back surface position detector used in the exposure apparatus of the present invention.

[Explanation of symbols]

1 ... Wafer chuck, 2 ... Suction block, 3-1 ... Piezo element, 3-2 ... Piezo element, 4 ... Vacuum suction groove, 5 ... Reticle pattern arrangement error, 6 ... Laser, 7 ... Temperature control unit, 8 ... Stage driving means, 9 ... Stage, 10 ... Oscillating mirror, 11 ... Oscillating mirror driving means, 12 ... Wafer chuck control means, 13 ... Lens, 14 ... Wafer, 15 ...
Exposure light source, 16 ... Illumination optical system, 17 ... Reticle, 18
... exposure optical system, 19 ... laser length measuring device, 20 ... stage,
21 ... Base, 22 ... Image distortion of exposure optical system, 23 ... Reticle stage, 24-1 ... Reticle position detector, 24
-2 ... Reticle position detector, 25 ... Wafer position detector, 26 ... Mirror, 27 ... Hollow-out chuck, 28 ... Chuck, 29 ... X-ray source, 30 ... Illumination optical system, 31 ... Mask, 32 ... Mask stage, 33-1 ... Exposure optical system, 3
3-2 ... Exposure optical system, 33-3 ... Exposure optical system, 33-4
Exposure optical system 34 Electron gun 35 Electromagnetic optical system 36
... Alignment hole, 37 ... Laser beam, 38 ... Shutter, 39-1 ... Aperture, 39-2 ... Aperture, 40 ... Data input / output means, 41 ... Main control means, 42 ... Chuck control means, 43 ... Driver.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshio Kawamura 1-280 Higashi Koigokubo, Kokubunji, Tokyo Inside the Central Research Laboratory, Hitachi, Ltd.

Claims (10)

[Claims] 1. An exposure method for transferring a pattern on a first substrate onto a second substrate, the step of detecting a deviation amount between an image formation pattern of the pattern on the first substrate and a pattern on the second substrate. And a step of calculating a correction amount for correcting the deviation amount, and by relatively deforming the first substrate or the second substrate with respect to the deviation in the plane direction between the image formation pattern and the pattern on the second substrate. And a correction step. 2. The method according to claim 1, further comprising the step of detecting in-plane strain as a deviation amount between the image formation pattern of the pattern on the first substrate and the pattern on the second substrate. Exposure method. 3. The exposure method according to claim 1, further comprising a step of correcting a relative error in the exposure surface so as to reduce image distortion of an exposure optical system used for the transfer. 4. The exposure method according to claim 1, further comprising a step of correcting a relative deviation in the exposure surface so as to reduce a pattern alignment error of the first substrate. 5. A light source, an illumination optical system that illuminates a light beam from the light source onto a first substrate, and a pattern of the first substrate formed by a light beam transmitted through the first substrate is reduced.
An exposure optical system that transfers to a second substrate, a chuck that holds the second substrate, a first position detector that detects the position of the first substrate, and a position of the second substrate. And a stage for determining the exposure position of the second substrate, and the chuck is provided with a second position detector for correcting the relative deviation between the first substrate and the second substrate. A structure having a plurality of vacuum holding portions, and the plurality of vacuum holding portions being independently movable in the in-plane direction of the wafer, wherein the correction means includes the first position detector and the second position detector.
Exposure apparatus comprising: input means for inputting a position signal detected by the position detector, control means for controlling a correction amount of the chuck from the input signal, and moving means for moving the chuck. . 6. The relative correction of the exposure surface so as to reduce image distortion in an exposure field of an exposure optical system used for transfer and positional deviation of a pattern formed on the first substrate, or magnification error. 6. The exposure apparatus according to claim 5, wherein the exposure apparatus has a structure for correcting a general error. 7. The exposure apparatus according to claim 5, wherein the moving means comprises an electrostrictive element (piezo). 8. The exposure apparatus according to claim 5, wherein the moving means is made of a shape memory alloy. 9. The correction means comprises a local temperature control means for producing a local temperature distribution in the exposure field in the exposure surface of the second substrate. The exposure apparatus according to any one of 1. 10. The radiation source is ultraviolet light, extreme ultraviolet light, X-ray,
7. The exposure apparatus according to claim 5, wherein the exposure apparatus is one of an electron beam and an ion source.