KR19980080158A - Scan exposure method and scanning exposure apparatus - Google Patents

Abstract

The exposure is always performed in the shortest time irrespective of the set exposure dose.

The main controller 50 sets the maximum scanning speed of the mask R and the photosensitive substrate W by the main scanning unit 50 in accordance with the number of exposure pulses per one point determined by the relationship between the set exposure and the measured average pulse energy at the time of scanning exposure The oscillation frequency of the light source 16 is controlled so as to maintain at least one of the maximum oscillation frequency of the pulse laser light source 16 and the maximum oscillation frequency of the pulse laser light source 16. Therefore, scan exposure can be performed at the maximum scan speed regardless of the set exposure dose in a high sensitivity region where the set exposure dose is small and the oscillation frequency does not need to be increased as much. On the other hand, when the set exposure dose is increased, the oscillation frequency must be increased accordingly. However, since the maximum oscillation frequency is the upper limit, the oscillation frequency is set to the maximum oscillation frequency in the low sensitivity region where the set exposure amount is large and the scan maximum speed can not be maintained. And exposure is performed.

Description

Scan exposure method and scanning exposure apparatus

The present invention relates to a scanning exposure method and a scanning type exposure apparatus and more particularly to a pulse laser light source used in a lithography process for manufacturing semiconductor devices, liquid crystal display devices, imaging devices (CCDs, etc.), thin film magnetic heads, A scanning exposure method used and a scanning type exposure apparatus.

Conventionally, when a semiconductor device or the like is manufactured, a projection exposure apparatus for transferring and exposing a pattern of a reticle as a mask to each shot area on a wafer (or a glass plate or the like) coated with a photoresist through a projection optical system is used. As one basic function in such a projection exposure apparatus, there is an exposure amount control function for accepting an integrated exposure dose (integrated exposure energy) for each point in each shot area of the wafer within an appropriate range.

In a batch exposure type projection exposure apparatus such as a conventional stapler (apparatus for collectively performing exposure in a state in which a wafer stage on which a wafer is mounted is exposed when a reticle pattern is exposed in a shot area on a wafer), ultra- In the case of using either a continuous light source such as a lamp or a pulse laser light source such as an excimer laser light source, cutoff control is basically adopted as the exposure amount control method. In the cut-off control, a part of the exposure light is branched during the irradiation of the exposure light to the wafer coated with the photosensitive material (photoresist) and guided to a photoelectric detector called an integrator sensor, And the laser emission is performed until the integrated value of the detection result exceeds a predetermined level (critical level) corresponding to the integrated exposure amount (hereinafter referred to as " set exposure amount ") required for the photosensitive material (In the case of the continuous light, the shutter is started to be closed when it exceeds the critical level).

Further, in the case of using a pulsed laser light source as an exposure light source, since energy is disturbed for each pulse laser light, exposure is performed with a plurality of pulsed laser lights of a predetermined number (hereinafter referred to as " minimum exposure pulse number & And the reproducibility of the desired exposure amount control precision is obtained. In this case, for example, when the high-sensitivity resist is exposed, since the set exposure dose is small, exposure using the laser beam from the pulse laser source at the minimum exposure pulse number can not be performed. Thus, when the set exposure amount is small, exposure of the pulse laser light to the minimum number of exposure pulses is enabled by, for example, exposing the pulsed laser light by the photosensitive means provided in the optical path.

In order to transfer a pattern of a larger area onto the wafer with high accuracy without imposing too much burden on the projection optical system in recent years, in a state in which a part of the reticle pattern is projected onto the wafer through the projection optical system A scanning projection exposure apparatus such as a step-and-scan system in which a pattern of a reticle is successively transferred to each shot area on a wafer by scanning the reticle and wafer synchronously with the projection optical system is developed. In such a scanning exposure type apparatus, since the exposure amount control focused on one point on the wafer can not be applied, the above cut-off control can not be applied. Therefore, conventionally, as a first control method, a system (an open exposure amount control system) for simply controlling the exposure amount by integrating the light amount of each pulse illumination light has been used. As a second control method, for example, as disclosed in Japanese Unexamined Patent Application Publication No. 6-252022, there is proposed an exposure method in which an exposure area in the form of a slit (a region that is a space in a slit-shaped illumination area on a reticle , The wafer is subjected to relative scanning with respect to the area), and the target energy of the next pulse illumination light is individually calculated based on the integrated exposure dose, and each pulse illumination light (The exposure amount control method for each pulse) is also considered, but the algorithm is complicated.

In the first control scheme of the former, it is necessary to finely adjust the pulse energy so that the following relationship is established in order to obtain the linearity of the desired exposure amount control, that is, the number of exposure pulses is an integer.

Here, the average energy of one pulse is a value measured by the integrator sensor immediately before exposure. For this reason, a pulse energy fine modulator is provided in the optical path.

11A and 11B show an example of a conventional energy fine modulator. In the double-grading fine modulator shown in FIG. 11A, a fixed grating plate 72 having a transmitting portion and a shielding portion formed at a predetermined pitch on the optical path of the pulsed laser beam LB, and a movable The grating plates 74 of the grating plates 72 and 74 are overlapped with each other and the two grating plates 72 and 74 are shifted relative to each other so that the transmissivity of the laser beam LB can be finely modulated. In the fine modulator shown in Fig. 11 (B), two glass plates 76, 78 on both sides of which the antireflection coating is applied on the optical path of the laser beam LB are symmetrically arranged at a variable inclination angle? And are arranged in an inclined state. The overall transmittance of the laser beam LB is finely adjusted by controlling the inclination angle? By using the characteristic that the transmittance of the glass plates 76 and 78 changes according to the incident angle of the laser beam LB have. In addition, there is an example in which the set energy of the laser itself, which is a light source, is modulated.

However, in the case of the scanning type exposure apparatus, the following expression must be satisfied.

V is the scanning speed at the time of scanning exposure of the wafer (wafer stage), Ws is the width of the slit-shaped exposure area in the scanning direction (slit width), N is the number of exposure pulses per one point, f Shows the laser oscillation frequency.

As the flow of the conventional exposure sequence, the exposure amount is set, the average energy on the image plane is measured, the number of pulses per point is calculated, and the slit width Ws, the laser oscillation frequency f, . In this case, the laser oscillation frequency f is the maximum oscillation frequency f (f), which is speed-controlled by the maximum scan speed (scan maximum speed) defined by the performance of the stage control system of the exposure apparatus ₀ ).

That is, in the conventional scanning type exposure apparatus, the slit width Ws is a fixed value determined on the optical design, and the laser oscillation frequency f is the maximum value corresponding to the scan maximum speed V _max determined on the performance of the stage control system when the oscillation frequency (f ₀₎ which has been fixed to (f = f ₀ was a) to be from the exposure pulse number (N) of the minimum exposure pulse length per interval (N _min), that is, when the N = N _min, ( 2), the scanning speed V is determined to be V _max .

In the case of the scanning type exposure apparatus, like the above-described batch type exposure apparatus, it is necessary to expose a plurality of pulsed laser beams at a certain number (minimum exposure pulse number) or more per point in order to obtain a predetermined exposure amount reproducibility. Also in this case, when the set exposure amount is small, as in the case of exposure of a high-sensitivity resist, for example, pulsed laser light is exposed by a photosensitive means (energy coarse adjustment device) provided on the optical path to satisfy the minimum exposure pulse condition .

As the energy coarse adjuster in this case, for example, a plurality of ND filters 84 having different transmittance (= 1-light sensitivity ratio) on a rotatable disk 80 called a revolver as shown in Fig. 11 (C) Is arranged at one end or in a plurality of stages, and the transmittance of the laser beam LB incident on the laser beam LB by rotating each revolver 80 is changed from 100% in a plurality of stages (in the case of FIG. 11 (C) 6 占 6 = 36 steps). That is, the setting of the transmittance by such an energy rough adjuster is discrete (usually isoquant series).

For this reason, depending on the set exposure dose, it may be difficult to set the (relative) exposure rate corresponding to the setting exposure dose. In the case of such a preset exposure dose, in the combination of the rate of photosensitivity corresponding to the set exposure dose It is only necessary to select the ND filter having the near light sensitivity and the number N of exposure pulses per one point is set to be equal to the discrete amount of the ND filter light transmittance (the difference from the light sensitivity ratio corresponding to the set exposure amount set by the ideal continuous variable energy modulator) It is inevitable to set it to a value larger than the minimum exposure pulse number (N _min ). Therefore, as is evident from the relationship of the expression (2), the scanning speed V can not always be maintained at the maximum speed V _max , and consequently the exposure time T _exp (= Ws / V) And the ideal throughput was lowered at a certain set exposure dose. That is, the relationship between the set exposure amount (S ₀₎ of the exposure time (T _exp) was supposed, as illustrated in broken lines Fig.

An object of the present invention is to provide a scanning exposure method capable of always performing exposure in the shortest time irrespective of a high sensitivity region and a low sensitivity region.

The object of the second aspect of the present invention is to provide an image forming apparatus capable of always performing exposure in the shortest time in the high sensitivity region without being influenced by the discrete light sensitivity of the photosensitive means and improving the throughput even in the low sensitivity region And to provide a scanning type exposure apparatus.

The object of the third aspect of the present invention is to perform exposure such that a desired integrated exposure amount is obtained for the next shot while maintaining the scanning speed when the pulse energy during exposure varies in the high sensitivity exposure area And to provide a possible scanning exposure method.

The object of the invention set forth in claim 4 is to perform exposure such that a desired integrated exposure amount is obtained for the next shot while maintaining the scanning speed when the pulse energy during exposure varies in the high sensitivity exposure area And to provide a possible scanning exposure apparatus.

The invention described in claim 1 is characterized in that a predetermined illumination area on a mask R is illuminated by a pulse light from a pulsed laser light source 16 to project the mask R and the photosensitive substrate W onto a projection optical system PL, And a step of successively projecting a pattern formed on the mask R onto the photosensitive substrate W while performing relative scanning with respect to the pulse laser light source 16. The step of measuring the average pulse energy of the pulsed light from the pulsed laser light source 16 and; The maximum scanning speed between the mask R and the photosensitive substrate W and the maximum scanning speed between the mask R and the photosensitive substrate W are determined in accordance with the number of exposure pulses per one point determined by the relationship between the set exposure amount and the measured average pulse energy, And controlling the oscillation frequency of the pulse laser light source so as to maintain at least one of the maximum oscillation frequency of the light source (16).

According to this, the average pulse energy of the pulse light from the pulse laser light source is measured prior to the scan exposure, and according to the number of exposure pulses per one point determined by the relationship between the set exposure amount and the measured average pulse energy, , The oscillation frequency of the pulse laser light source is controlled so as to keep at least one of the maximum scanning speed of the mask and the photosensitive substrate and the maximum oscillation frequency of the pulse laser light source. That is, according to the present invention, the oscillation frequency f of the pulsed laser light source, which has been conventionally fixed, is set to the maximum scanning speed (scan maximum speed) of the mask and the photosensitive substrate, And is controlled to maintain at least one of the maximum oscillation frequency. Therefore, in the region where the set exposure amount is small and the oscillation frequency necessary for obtaining the maximum speed is within the maximum oscillation frequency, scanning exposure can be performed at the scan maximum speed at least irrespective of the set exposure dose, do. In this case, the oscillation frequency of the pulse laser light source is controlled based on the relationship of the above-mentioned expression (2). On the other hand, if the set exposure dose is increased, the laser oscillation frequency must also be increased accordingly, but the laser oscillation frequency can not be higher than the maximum oscillation frequency which is the upper limit. Therefore, in a region where the set exposure amount is large and the scan maximum speed can not be maintained (in this specification, the region is referred to as a "low sensitivity region"), the laser oscillation frequency is set to the maximum oscillation frequency, The exposure is performed at a predetermined scanning speed. In this case, as is apparent from the expression (2), when the maximum oscillation frequency is f _max , the scanning speed is set to f _max / f ₀ times the conventional one, and the exposure time per one point is suppressed to f ₀ / f _max , Clearly f _max > f ₀ , the throughput is improved even in the low sensitivity region. Further, even when considering the case where the energy of the pulse laser light source can be continuously modulated, since f _max? F ₀ , the width of the set exposure dose to be exposed at the maximum scanning speed becomes wider than the conventional one.

The invention described in claim 2 is characterized in that a predetermined illumination area on a mask R is illuminated by pulse light from a pulsed laser light source 16 to project the mask R and the photosensitive substrate W onto a projection optical system PL, And a mask stage which is movable in a predetermined scanning direction while holding the mask R. The scanning exposure apparatus according to claim 1, (RST); A substrate stage (14) holding the photosensitive substrate (W) and movable in at least the scanning direction; A stage control system (48, 50, 54R, 54W, 56) for relatively scanning the mask stage (RST) and the substrate stage (14) with respect to the projection optical system (PL) at a predetermined speed ratio; Frequency changing means (16d) for changing the oscillation frequency of the pulse laser light source (16); A photodetecting means (20) for separating the pulsed light from the pulsed laser light source (16) and having a photosensitivity of discrete values; An energy measuring means (46) for measuring an average pulse energy of the pulsed light from the pulsed laser light source (16) that is photographed by the photosensitive means (20); (RST, 14) by the stage control system (48, 50, 54R, 54W, 56) in accordance with the number of exposure pulses per one point determined by the relationship between the set exposure amount and the average pulse energy And a control means (50) for controlling the frequency changing means (16d) so as to maintain at least one of a maximum oscillation frequency of the pulse laser light source (16) and a maximum oscillation frequency of the pulse laser light source (16).

According to this, when the minimum exposure pulse number can not be secured in the state where the set exposure amount is small and the photosensitive rate is 0% (transmittance is 100%), the pulse light from the pulse laser light source is exposed by the photosensitive means. The average pulse energy of the pulsed light from the pulsed laser light source that is photographed by the photosensitive means is measured by the energy measuring means. However, since the photosensitivity of the photosensitive means is discrete, the number of exposure pulses per one point determined by the set exposure dose and the measured average pulse energy is not always limited to the minimum exposure pulse number, and when it is greater than the minimum exposure pulse number . Therefore, as the control means, the frequency changing means is controlled so as to maintain at least one of the maximum scanning speed of both stages and the maximum oscillation frequency of the pulse laser light source by the stage control system in accordance with the number of exposure pulses per one point.

That is, according to the present invention, the oscillation frequency f of the pulse laser light source, which has conventionally been fixed, is controlled by the control means in accordance with the number of exposure pulses N, and the maximum scan speed (scan maximum speed) Or at least one of the maximum oscillation frequency of the pulse laser light source. Therefore, even if the number of exposure pulses per one point increases due to the discrete amount of the photosensitivity in the high sensitivity region where the set exposure amount is reduced and the laser oscillation frequency does not need to be increased as much, the laser oscillation frequency is increased Therefore, regardless of the set exposure dose, both stages are scanned at the scan maximum speed by the stage control system at the time of exposure, and it becomes possible to maintain the throughput at the highest level. In this case, the oscillation frequency of the pulse laser light source is controlled based on the relationship of the above-mentioned expression (2). On the other hand, if the set exposure dose is increased, the number of exposure pulses per point must increase and the laser oscillation frequency must also be increased accordingly. However, the laser oscillation frequency can not be made higher than the maximum oscillation frequency which is the upper limit. Therefore, in the low sensitivity region where the set exposure amount is increased and the scan maximum speed can not be maintained (in this region, the photosensitive rate by the photosensitive means is set to 0% (transmittance 100%)), the laser oscillation frequency is set to the maximum oscillation frequency , And exposure is performed at a scanning speed determined based on the relationship of the above-mentioned expression (2). In this case, as is apparent from the expression (2), when the maximum oscillation frequency is f _max , the scanning speed becomes the conventional f _max / f ₀ times, and the exposure time per one point is suppressed to the conventional f ₀ / f _max , Clearly f _max > f ₀ , the throughput is improved even in the low sensitivity region. Further, even when considering the case where the energy of the pulse laser light source can be continuously modulated, the width of the set exposure dose that can be exposed at the maximum scanning speed becomes wider than the conventional one because f _max? F ₀ .

The present invention described in claim 3 is characterized in that the mask R is illuminated by the pulse light from the pulse laser light source 16 and the mask R and the photosensitive substrate W are scanned relative to the projection optical system PL And a scanning exposure method for successively projecting and exposing a pattern formed on the mask R to a plurality of shot areas on a photosensitive substrate W, the method comprising the steps of: measuring a degree of exposure of the mask pattern with respect to each shot area on the photosensitive substrate (W) The average pulse energy of the pulse laser light source 16 is detected and the cumulative exposure amount up to that time is calculated and the average pulse energy of the pulse laser light source 16 fluctuates. And controls the oscillation frequency of the pulse laser light source 16 to secure the required number of exposure pulses per one point.

According to this, every time the mask pattern is exposed to each shot area on the photosensitive substrate, the average pulse energy of the pulse laser light source is detected and the integrated exposure amount up to that is calculated. When the average pulse energy of the pulse laser light source fluctuates, the oscillation frequency of the pulse laser light source, in which the required number of exposure pulses per required point is secured, is controlled based on the integrated exposure amount of the immediately preceding shot area. As described above, according to the present invention, when the exposure of the mask pattern to each shot area on the photosensitive substrate is sequentially performed, the average pulse energy of the pulse laser light source fluctuates, and as a result of this fluctuation, Based on the total exposure amount of the immediately preceding shot area, in which the required number of exposure pulses per one necessary point, that is, the set exposure amount and the number of exposure pulses per one point determined by the measured average pulse energy, The oscillation frequency of the pulse laser light source is controlled. As a result, as is apparent from the above-described expression (2), when the exposure is performed at the scan maximum speed in, for example, the high sensitivity region by changing the number of exposure pulses without changing the scan speed, It is possible to perform exposure to obtain the desired integrated exposure amount while maintaining the scan maximum speed for the next shot without being influenced by the fluctuation in the average pulse energy of the pulse laser light source during exposure or after exposure.

According to a fourth aspect of the invention, the mask R is illuminated by the pulsed light from the pulsed laser light source 16, and the mask R and the photosensitive substrate W are scanned relative to the projection optical system PL Type exposure apparatus for successively projecting a pattern formed on the mask R onto a plurality of shot areas on a photosensitive substrate W, the apparatus comprising: a frequency changing unit 16d for changing an oscillation frequency of the pulse laser light source 16; and; An energy measuring means (46) for measuring an average pulse energy of the pulse light from the pulse laser light source (16); Detecting an average pulse energy of the pulse laser light source (16) every time the master pattern is exposed to each shot area on the photosensitive substrate (W), and calculating an integrated exposure amount up to the detected pulse energy, And control means (50) for controlling the frequency changing means (16d) to secure the required number of exposure pulses per one necessary point based on the integrated exposure amount of the immediately preceding shot region when the average pulse energy fluctuates.

According to this, the average pulse energy of the pulse light from the pulse laser light source is measured by the energy measuring means. As the control means, the average pulse energy of the pulse laser light source is detected via the energy measuring means every time the master pattern is exposed to each shot area on the photosensitive substrate, and the integrated exposure amount up to this is calculated, And controls the frequency changing means to secure the required number of exposure pulses per required point based on the total exposure amount of the shot area immediately before the energy has changed. As described above, according to the present invention, when the exposure of the master pattern to each shot area on the photosensitive substrate is carried out sequentially, the average pulse energy of the pulse laser source fluctuates and as a result of this fluctuation, Based on the total exposure amount of the shot area immediately before the required number of exposure pulses per one necessary point, that is, the set exposure amount and the number of exposure pulses per one point determined by the measured average pulse energy, , And the oscillation frequency of the pulse laser light source is controlled. Therefore, for example, when the exposure is performed at the scan maximum speed in a high sensitivity region by changing the number of exposure pulses without changing the scan speed, the average pulse energy of the pulse laser light source changes during exposure or after exposure of a shot region In this case, without being affected by this, it becomes possible to expose the next shot to obtain the desired integrated exposure amount while maintaining the scan maximum speed.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a view schematically showing the configuration of a scanning exposure apparatus according to a first embodiment; Fig.

Fig. 2 is a block diagram schematically showing the configuration of an exposure amount control system of the apparatus of Fig. 1; Fig.

3 is a diagram showing an example of correlation data between the throughput of the integrator sensor and the output of the energy monitor.

4 is a flowchart showing an exposure amount control algorithm of the CPU in the main controller according to the first embodiment;

Figure 5 is a comparative example and at the same time a view showing relationship between the set exposure amount (S ₀₎ and the first exposure time (T _exp) of the bet in the exposure amount control sequence according to the flowchart of FIG.

Fig. 6 is a view for explaining an example in which the exposure amount control sequence of Fig. 4 exerts a greater effect by accepting an illumination condition with E (E < 1) for the standard illumination condition.

7 is a view schematically showing the configuration of a scanning type exposure apparatus according to the second embodiment;

8 is a diagram showing a relationship between a control amount externally and a variation amount of transmittance for a driving apparatus in an energy fine modulator according to the second embodiment.

FIG. 9 is a flowchart showing a part of an exposure amount control algorithm of the CPU in the main controller according to the second embodiment. FIG.

10 is a flowchart showing a part of the remainder of the exposure amount control algorithm of the CPU in the main controller according to the second embodiment;

Fig. 11 (A) and Fig. 11 (B) are views each showing an example of an energy fine modulator, and Fig. 11 (C) is an explanatory view showing an example of an energy coarse regulator.

Description of the Related Art [0002]

10: Scanning type exposure apparatus

14: XY stage (substrate stage)

16: Excimer laser light source (pulse laser light source)

16d: Energy controller (frequency changing means)

20: Energy attenuator (photosensitive means)

46: integrator sensor (energy measuring means)

48: Reticle stage driving part (part of stage control system)

50: main controller (part of stage control system, control means)

54R: Laser interferometer (part of stage control system)

54W: Laser interferometer (part of stage control system)

56: Wafer stage driving part (part of stage control system)

70: Scanning type exposure apparatus

R: reticle (mask)

W: photosensitive substrate

PL: projection optical system

RST: Reticle stage (mask stage)

(First Embodiment)

A first embodiment of the present invention will be described below with reference to Figs. 1 to 6. Fig.

Fig. 1 shows a schematic configuration of a scanning type exposure apparatus 10 according to the first embodiment. The scanning type exposure apparatus 10 is a step-and-scan scanning type exposure apparatus using an excimer laser light source as a pulse laser light source for an exposure light source.

The scanning type exposure apparatus 10 includes an illumination system 12 including an excimer laser light source 16, a mask stage 12 for holding a reticle R as a mask illuminated by the illumination system 12, A projection optical system PL for projecting a pattern of the reticle R onto the wafer W as a photosensitive substrate, an XY stage (not shown) for holding the wafer W and moving a horizontal plane (in the XY plane) 14, and a control system thereof.

The illumination system 12 includes an excimer laser light source 16, a beam shaping optical system 18, an energy rough adjuster 20, a fly's eye lens 22, an illumination system aperture plate 24, a beam splitter 26, A relay lens 28A, a second relay lens 28B, a fixed reticle blind 30A, an movable reticle blind 30B, an optical path bending mirror M, a condenser lens 32, and the like.

Here, the constituent parts of the illumination system 12 will be described. As the excimer laser light source 16, a KrF excimer laser light source (oscillation wavelength 248 nm) or an ArF excimer laser light source (oscillation wavelength 193 nm) is used. Instead of the excimer laser light source 16, a pulsed light source such as a metal vapor laser light source or a harmonic generator of a YAG laser may be used as an exposure light source.

The beam shaping optical system 18 shapes the sectional shape of the laser beam LB pulsed from the excimer laser light source 16 to efficiently enter the fly's eye lens 22 provided behind the optical path of the laser beam LB For example, a cylinder lens or a beam extract panda (not shown).

The energy rough adjuster 20 is disposed on the optical path of the laser beam LB behind the beam shaping optical system 18 and a plurality of (Two ND filters 36A and 36D shown in Fig. 1 are shown in Fig. 1), and by rotating the rotary plate 34 with the drive motor 38, It is possible to change the transmittance of the laser beam LB from 100% to a plurality of steps in an isoquadratic manner. The drive motor 38 is controlled by a main controller 50 to be described later. It is also possible to arrange two rotary plates such as the rotary plate 34 so that the transmittance can be finely adjusted by combining two ND filters (see Fig. 11 (C)).

The fly's eye lens 22 is disposed on the optical path of the laser beam LB behind the energy rough adjuster 20 to form a plurality of secondary light sources for illuminating the reticle R with a uniform illumination distribution. The laser beam emitted from the secondary light source is hereinafter referred to as " pulse illumination light IL ".

Near the exit surface of the fly-eye lens 22, an illumination system aperture preparation plate 24 made of a disc-shaped member is disposed. The illumination system aperture preparation plate 24 is provided with an aperture tightening with a uniform circular aperture, for example, a regular circular aperture, and a small circular aperture to tighten the aperture to reduce the value σ, which is a coherence factor, (Only two types of opening fastening are shown in Fig. 1) formed by arranging a plurality of openings eccentrically and arranged in a ring-shaped opening and tightening and deforming light source for illumination. The illumination system aperture preparation plate 24 is rotated by a driving device 40 such as a motor controlled by a main controller 50 to be described later. .

A beam splitter 26 having a small reflectance and a high transmittance is disposed on the optical path of the pulsed illumination light IL behind the illumination system aperture plate 24 and the fixed reticle blind 30A and the movable reticle A relay optical system including a first relay lens 28A and a second relay lens 28B is disposed via the blind 30B.

The fixed reticle blind 30A is disposed on a surface that is barely defocused in the conjugate plane with respect to the pattern surface of the reticle R and has a rectangular opening that defines the illumination area 42R on the reticle R. A movable reticle blind 30B having an opening portion with a variable position and width in the scanning direction is disposed in the vicinity of the fixed reticle blind 30A so that the movable reticle blind 30B is moved By further limiting the illumination area 42R, it is possible to prevent exposure of an unnecessary part.

A bending mirror (not shown) for reflecting the pulse illumination light IL passing through the second relay lens 28B toward the reticle R is provided on the optical path of the pulse illumination light IL behind the second relay lens 28B constituting the relay optical system And a condenser lens 32 is disposed on the optical path of the pulse illumination light IL behind the mirror M. [

The laser beam LB pulsed from the excimer laser light source 16 is incident on the beam shaping optical system 18 where it is incident on the rear fly eye lens 22, And enters into the energy rough adjuster 20 after the cross-sectional shape is shaped. The laser beam LB transmitted through any of the ND filters in the energy rough adjuster 20 is incident on the fly-eye lens 22. As a result, a plurality of secondary light sources are formed at the emitting end of the fly-eye lens 22. The pulse illumination light IL emitted from the plurality of secondary light sources passes through any aperture stop on the illumination system aperture cooking aperture 24 and then reaches the beam splitter 26 having a high transmittance and a low reflectance. The pulsed illumination light IL as the exposure light transmitted through the beam splitter 26 passes through the rectangular opening of the fixed reticle blind 30A and the movable reticle blind 30B via the first relay lens 28A, 2 relay lens 28B and the optical path is bent vertically downward by the mirror M and then passes through the condenser lens 32 to form a rectangular illumination on the reticle R held on the reticle stage RST And illuminates the region 42R with a uniform illuminance distribution.

The pulsed illumination light IL reflected by the beam splitter 26 is received by an integrator sensor 46 constituted by a photoelectric conversion element via a condenser lens 44 and is subjected to photoelectric conversion of the integrator sensor 46 Signal is supplied to the main controller 50 as an output DS (digit / pulse) through the peak hold circuit and the A / D converter not shown in the drawing. As the integrator 46, for example, a PIN type photodiode or the like having sensitivity to an out-of-atom region and having a high response frequency for detecting pulse emission of the excimer laser light source 16 can be used. The correlation coefficient between the output DS of the integrator sensor 46 and the illuminance (exposure amount) of the pulse illumination light IL on the surface of the wafer W is obtained in advance and is stored in a memory 51).

The reticle R is placed on the reticle stage RST and held by a vacuum chuck or the like not shown in the drawing. The reticle stage RST can be slightly driven within a horizontal plane (XY plane), and at the same time, the reticle stage driving unit 48 can perform scanning in a predetermined stroke range in a scanning direction (here, . The position of the reticle stage RST during the scan is measured by an external laser interferometer 54R through a moving mirror 52R fixed on the reticle stage RST, And is supplied to the apparatus 50.

The projection optical system PL is composed of a plurality of lens elements having an optical axis AX in the common Z-axis direction arranged to be optically arranged as both side telecentric. Further, as the projection optical system PL, a projection magnification? (? Is, for example, 1/4 or 1/5) is used. Therefore, when the illumination region 42R on the reticle R is illuminated by the pulsed illumination light IL as described above, the pattern formed on the reticle R is projected by the projection optical system PL to the projection magnification? And the reduced image is projected and exposed to a slit-shaped exposure area 42W on the wafer W coated with a resist (photosensitive agent) on its surface.

The XY stage 14 is two-dimensionally driven by the wafer stage driving unit 56 in the Y direction as the scanning direction and the X direction (the direction perpendicular to the plane of FIG. 1) in the XY plane. A Z tilt stage 58 is mounted on the XY stage 14 and the wafer W is held on the Z tilt stage 58 by a vacuum suction or the like through a wafer holder not shown. The Z tilt stage 58 has a function of adjusting the position (focus position) of the wafer W in the Z direction and adjusting the inclination angle of the wafer W with respect to the XY plane. The position of the XY stage 14 is measured by an external laser interferometer 54W via a moving mirror 52W fixed on the Z tilt stage 58 so that the measurement value of the laser interferometer 54W is transmitted to the main controller (Not shown).

The control system is mainly constituted by the main controller 50 as a control means in Fig. The main controller 50 includes a so-called microcomputer (or a minicomputer) including a CPU (central processing unit), a ROM (read only memory), a RAM (random access memory) For example, the synchronous scanning of the reticle R and the wafer W, the stepping of the wafer W, the exposure timing, and the like are controlled collectively.

Concretely, in synchronization with the scanning of the reticle R through the reticle stage RST at the speed V _R in the + Y direction (or -Y direction), for example, during the scanning exposure, The wafer W is moved in the -Y direction (or the + Y direction) with respect to the exposure area 42W through the XY stage 14 at a speed of? V _R (? Is the distance from the reticle R to the wafer W) The positions and velocities of the reticle stage RST and the XY stage 14 through the reticle stage driving section 48 and the wafer stage driving section 56, respectively, based on the measurement values of the laser interferometers 54R and 54W, Respectively. During stepping, the main controller 50 controls the position of the XY stage 14 through the wafer stage driver 56 based on the measured value of the laser interferometer 54W. As described above, in the first embodiment, the stage control system is constituted by the main controller 50, the laser interferometers 54R and 54W, the reticle stage driver 48 and the wafer stage driver 56. [

The main control device 50 also controls the emission timing and emission power of the excimer laser light source 16 by supplying the control information TS to the excimer laser light source 16. [ The main controller 50 controls the energy coarse adjuster 20 and the illumination system aperture cooking aperture 24 through the motor 38 and the driving device 40 and also controls the movable reticle Thereby controlling the opening and closing operation of the blind 30B. As described above, in the present embodiment, the main controller 50 also has the tasks of the exposure controller and the stage controller. It goes without saying that these controllers may be provided separately from the main controller 50.

Next, the configuration of the exposure amount control system of the scanning-type exposure apparatus 10 of the present embodiment will be described based on Fig.

Fig. 2 shows the constituent parts related to the exposure amount control of the scanning type exposure apparatus 10 of Fig. 2, a laser resonator 16a, a beam splitter 16b, an energy monitor 16c, an energy controller 16d, and a high voltage power source 16e are installed inside the excimer laser light source 16 have.

2, the laser beam emitted pulsed from the laser resonator 16a is incident on a beam splitter 16b having a high transmittance and a slight reflectance, and the laser beam LB transmitted through the beam splitter 16b And is injected outside. The laser beam reflected by the beam splitter 16b is incident on an energy monitor 16c constituted by a photoelectric conversion element and the photoelectric conversion signal from the energy monitor 16c is output through a peak hold circuit And is supplied to the energy controller 16d as an electric power source ES. The unit of the energy control amount corresponding to the output (ES) of the energy monitor 16c is mJ / pulse. The energy controller 16d controls the energy controller 16d so that the output ES of the energy monitor 16c becomes a value corresponding to the target value of the energy per pulse of the control information TS supplied from the main controller 50, And the power supply voltage in the power source 16e is feedback-controlled. The energy controller 16d also changes the oscillation frequency by controlling the energy supplied to the laser resonator 16a through the high voltage power source 16e. That is, the energy controller 16d sets the oscillation frequency of the excimer laser source 16 to the frequency designated by the main controller 50 in accordance with the control information (TS) from the main controller 50, Feedback control of the power supply voltage of the high-voltage power supply 16e is performed so that the energy per one pulse in the main controller 16 becomes the value indicated by the main controller 50. [

A shutter 16f for shielding the laser beam LB in accordance with control information from the main controller 50 is also disposed outside the beam splitter 16b in the excimer laser light source 16. [

The output ES of the energy monitor 16c is supplied to the main controller 50 through the energy controller 16d so that the output of the energy controller 16c in the main controller 50 (ES) and the output (DS) of the integrator sensor (46). The main controller 50 sends predetermined control information TS to the energy controller 16c to cause the excimer laser light source 16 to emit pulses at the time of scanning exposure, 46 to obtain an integrated exposure amount at each point on the wafer W in order. The main controller 50 adjusts the transmittance of the energy coarse adjuster 20 and adjusts the transmittance of the excimer laser light source 16 so that the total exposure light amount of each point becomes the set exposure amount of the photoresist on the wafer W Fine adjustment of the energy per pulse is performed before exposing the wafer.

Next, an example of the exposure amount control operation in the scanning type exposure apparatus 10 configured as described above will be described.

First, a description will be given of a procedure for creating a control table as a premise of exposure amount control. Here, in order to create the control table around the integrator sensor 46, the unit (the unit of the energy control amount) of the output ES of the energy monitor 16c in the excimer laser light source 16 is mJ / pulse . As described above, the unit of the output DS of the integrator sensor 46 (unit of the energy control amount) is (digit / pulse).

Here, the output DS of the integrator sensor 46 corresponds to the output of the reference illuminometer not shown in the drawing provided at the same height as the top surface (i.e., the surface of the wafer) on the Z tilt stage 58 in Fig. 1 It is assumed that it is calibrated (calibrated) in advance. A data processing unit of the reference light meter is (mJ / (cm ² · pulse)), and the physical quantity, the integrator sensor 46, the calibration is, integrator sensor 46, the output (DS) (digit / pulse of the (MJ / (cm ² pulse pulse)) on the upper surface of the photosensitive drum, or a conversion function. By using the conversion coefficient or the conversion function, it is possible to measure the amount of exposure given on the image plane indirectly from the output DS of the integrator sensor 46. Therefore, in the following description, the amount of exposure on the upper surface, which is indirectly obtained from the output DS of the integrator sensor 46, is used as the processing amount P (mJ / (cm ² · pulse)) by the integrator sensor 46, ).

The amount of exposure P on the upper surface, that is, the throughput P (mJ / (cm2 占 pulse) of the integrator 46) and the output ES of the energy monitor 16c in the excimer laser light source 16, (mJ / pulse). As a precondition for this, it is assumed that the energy E per pulse of the laser beam LB from the excimer laser light source 16 of FIG. 1 is stabilized with a predetermined center energy E ₀ . It is also assumed that the transmittance of the energy rough adjuster 20 is set to 100% (closed space).

Then, the energy E of the laser beam LB is changed above and below the center energy E ₀ as follows. However, the number of data used for correlation data acquisition is N _DATA .

&Quot; (3) "

Where E _R is the required energy modulation range, typically E _R / E ₀ is 0.02 to 0.03. Also, i is an integer, and the value of i varies in the range of, for example, 0 to N _DATA .

The value P _i of the throughput P of the integrator sensor 46 and the output ES of the energy monitor 16c are compared with each other by causing the excimer laser light source 16 to perform pulse light emission while actually changing the value of _i . the value (E _i) of a) is written as a correlation data (P _i, E _i). One data may be a single pulse or an average value of a plurality of pulses or any data that is simultaneously measured.

Fig. 3 shows the correlation data (P _i , E _i ) obtained as described above. 3, the axis of abscissas is a value (P _i ) of the throughput of the integrator sensor 46, and the axis of ordinates is the value (E _i ) of the output of the energy monitor 16c. And, for example, by an interpolation a correlation data of Figure 3 example, the integrator output (ES) of the radar sensor 46, the throughput (P) (mJ / (cm ² · pulse)) Energy Monitor (16c) from (mJ / (P) for calculating the output (ES) of the output signal (P), or a transform coefficient for obtaining the output (ES) at the throughput (P) And stores it in the memory 51 shown in Fig. Thereafter, in the main controller 50, the output ES of the corresponding energy monitor 16c can be accurately calculated based on the control table and the throughput P of the integrator sensor 46,

In the following description, it is assumed that the correlation between the integrator sensor 46 and the energy monitor 16c is very linear and the correlation data (P _i , E _i ) is the same as the solid line of FIG. 3 , And the offset thereof can be regarded as 0, and it is assumed that the inclination can be handled as the transformation coefficient beta. (MJ / pulse) of the energy monitor 16c in the following equation using the throughput P (mJ / (cm ²占 pulse) of the integrator sensor 46 and the conversion coefficient? It is assumed that it can be calculated.

Therefore, as the main controller 50, the conversion coefficient beta is obtained by, for example, the least square approximation in the correlation data of Fig. 3, and the conversion coefficient beta is stored in the memory 51 as a control table. This completes the creation of the control table.

Next, the basic exposure amount control sequence of the scanning-type exposure apparatus 10 of the present embodiment will be described with reference to the flow chart of Fig. 4 showing the CPU control algorithm in the main control apparatus 50. Fig. The transmittance of the laser beam LB from the excimer laser light source 16 by the energy roughness adjuster 20 may be set only so that the number of exposure pulses is equal to or greater than the required number of exposure pulses. ) Will be described below.

First, the amounts used in the following description are defined as follows.

(a) S ₀ : An exposure amount (set exposure dose) to be given to the photoresist on the wafer W set by the operator.

(b) N: number of pulses (number of exposure pulses) of pulse illumination light IL irradiated per one point on the wafer.

(c) p: Average pulse energy density (mJ / (cm ² · pulse)) on the image surface that is indirectly measured by the integrator sensor 46 before exposure.

(d) A _t is the target error of the average exposure amount error within each shot area on the actual wafer with respect to the set exposure amount (accuracy of the exposure amount target value precision).

(e) P _t : set pulse energy (mJ / (cm ² · pulse)) based on the integrator sensor 46.

(f) E _t is the energy set value (mJ / pulse) of the laser beam LB received from the main controller 50 by the excimer laser light source 16. That is, the following equation is established in correspondence with the expression (4).

(g) V _max : maximum scan speed of the XY stage 14 (mm / s).

(h) N _min : Minimum number of exposure pulses per point.

(i) Ws: Effective exposure slit width (mm) on the wafer surface.

(j) f _max : Actual maximum oscillation frequency (Hz) of the excimer laser light source 16.

As a precondition, the neutral value of the laser oscillation frequency f is f ₀ . f ₀ is calculated from the following expression. This is the same as the fixed oscillation frequency in the conventional exposure amount control.

In this embodiment it is assumed, and f ₀ <f _max, f ₀ the oscillation frequency in the range of <ff _max which is possible modulation.

It is also assumed that the transmittance of the energy rough adjuster 20 is designed so that the discrete transmittance becomes an equilibrium series so as to minimize the exposure time in the entire set exposure dose. When the above azimuth is r, it is assumed that rf ₀ / f _max in the present embodiment.

The normal exposure amount control sequence is as follows.

First, in FIG. Step 4 (100), when waiting for the set exposure amount (S ₀₎ is set through the input device 62 (see Fig. 1) such as a console by the operator, set an exposure amount (S0) is set , and it sets the process proceeds to the next step 101, the set exposure amount (S _0), the center of energy (E _0), the first set point energy per pulse of the laser beam (LB) (E _t) in accordance with.

In the next step 102, pulse light emission is performed a plurality of times (for example, several hundred times) to the excimer laser light source 16, and the output of the integrator sensor 46 is integrated, measures the average pulse energy density _{^{p (mJ / (cm 2 ·}} pulse)). The measurement is performed, for example, in a state in which the reticle movable blind 30B is driven to completely close the opening and prevent the illumination light IL from reaching the reticle R side. Of course, the XY stage 14 may be driven to retract the wafer W.

In the next step 103, the number of exposure pulses N is calculated from the following equation.

Here, the function cint is to represent the rounding of the first digit below the decimal point.

It is determined whether the exposure if the number of pulses (N) is the minimum number of exposure pulses for obtaining the exposure amount control accuracy required to reproduce (N _min) or higher in the following step 104. The Here, the minimum exposure pulse number (N _min ) is a ratio (? P /?) Of the pulse energy dp (? P) p).

When the determination in step 104 is negative, that is, when the number of exposure pulses N is smaller than the minimum number of exposure pulses N _min , the process proceeds to step 105, after the closest, and set by selecting a transmission so as to satisfy the N≥N _{min 0} to S / (N × P _min) from the configurable transmittance by the ND filter of the regulator 20, wherein said step (102, 103) If the determination in step 104 is affirmed or the determination in step 104 is affirmed from the beginning (N &gt; = N _min ), the process proceeds to step 106, The measured value (A _tgt ) of the target value precision of the exposure amount is calculated by the food,

Here, the function ABS is a function for obtaining an absolute value.

In the next step 107, it is judged whether fine modulation of the pulse energy in the excimer laser light source 16 is necessary or not, that is, whether or not the measured value A _tgt of the exposure amount target value precision is equal to or more than the above described exposure amount target value precision A _t . When the determination is negative, that is, when the measured value A _tgt is smaller than the exposure amount target value precision A _t , the _routine proceeds to step 109 where the scan speed V = the laser oscillation frequency V _max as the scan maximum speed V _max f) is calculated by the following equation.

Here, the function int (a) is assumed to represent the largest integer not exceeding the real number (a).

On the other hand, if the determination in step 107 is affirmative, that is, if A _tgt &gt; = A _t , fine modulation of the pulse energy is required. In step 108, the set pulse energy P _t (mJ / (cm ² · pulse)) based on the integrator sensor 46 is calculated as follows.

Next, the energy setting value Et (mJ) of the laser beam LB in the excimer laser light source 16 from the expression (5) is obtained by using the conversion coefficient? Retained as the control table in the memory 51 / pulse) to the energy set value (E _t) is calculated and then supplied to the energy controller (16d), the process proceeds to step 109, as the scan rate (V) = scanning maximum speed (V _max) as described above And the laser oscillation frequency f is calculated.

In the next step 110, it is determined whether or not the laser oscillation frequency f calculated above is equal to or less than the maximum oscillation frequency f _max of the laser. If the determination is affirmative, the process proceeds to step 111 to set the laser oscillation frequency to a value calculated from the above through the energy controller 16d, and at the same time, sets the scan target speed (scan speed) (V _max ). On the other hand, if the determination in step 110 is negative, the process proceeds to step 112. The laser oscillation frequency f is set to the maximum oscillation frequency f _max via the energy controller 16d and the process proceeds to step 113 And the scan speed V is set based on the following equation.

Then, in step 114, the exposure is performed with the setting conditions (V, f, P _t ) determined by the steps up to that point.

FIG. 5 shows the relationship between the set exposure dose S ₀ and the exposure time per one point (T _exp ) in the exposure amount control sequence according to the flow chart of FIG. 4 described above. In Fig. 5, the solid line represents the case of this embodiment, and the dotted line represents the case of the conventional case for comparison.

As can be seen from FIG. 5, according to the present embodiment, in the region corresponding to the high-sensitivity resist (the region of the set exposure dose S _0? P N _min (f _max / f ₀ ) for without being affected by the discrete photosensitive rate, is always (set exposure amount (regardless of the value of S ₀₎₎ is capable of the exposure as a scanning maximum speed (V _max), the minimum exposure time (T _exp). Further, since the low sensitivity to the exposure of the area (on the exposure amount _{(S 0) PN min · (} f max / area of the f ₀₎₎ up to the oscillation frequency (f _max) laser having also corresponding to the resist, the conventional example inclination of the broken line (∂T / ∂N = 1 / f 0) and by comparing the slope (∂T / ∂N = 1 / f max) of the solid line represents the present embodiment clear, the exposure time is shortened, as shown a do. That is, it becomes possible to obtain the maximum as a wide range of setting exposure area throughput. Further, the range of the set exposure dose that can be exposed at this scan maximum speed is also widened from S ₀ = PN _min to PN _min (f _max / f ₀ ).

In this embodiment, since the pulse energy of the excimer laser light source 16 is finely modulated, the exposure amount of the laser beam LB to the wafer W can be controlled with high speed and high accuracy, The desired integrated exposure dose can be obtained at each point on the image.

Incidentally, the exposure amount control sequence described above exerts even greater effects depending on the illumination condition in which the surface roughness is low. As to the power loss at the time of changing the illumination condition by the illumination system aperture plate 24, an illumination optical system which does not deteriorate the energy transfer efficiency has been proposed. However, it is difficult to achieve a perfect proposition in which the difference between illumination conditions is zero, Average pulse energy) is inevitable.

Here, as an example, an example in which the exposure amount control sequence of the present embodiment exerts an even greater effect, taking as an example an illumination condition in which E (E1) is an efficiency for a standard illumination condition in which the average pulse energy becomes maximum 6 will be described. In FIG. 6, it is assumed that an attenuator (modulator) having a continuously variable transmittance is used in order to simplify the explanation.

And In, the minimum exposure time length per interval of, the illumination condition to appear as case 1 in FIG. 6 _{(Ws / V max) = (} N min / f 0) in standard lighting conditions in the conventional sequence, the minimum The maximum amount of exposure that can be exposed at the exposure time can be expressed as PN _min . On the other hand, in the illumination condition of the efficiency E, the maximum exposure amount that can be exposed at the minimum exposure time becomes EPN _min as shown in the case (2) in FIG. 6, and in the illumination condition where the efficiency E is small, The throughput at the time of the operation is poor.

On the other hand, when adapting a sequence of the present embodiment for the lighting conditions of the efficiency (E), the minimum exposure time as shown in case 3 in Fig. 6 does not change as a Ws / V _max, the conventional example, if , The maximum set exposure dose S ₀ that can be exposed at the minimum exposure time is expanded to EPN _min x (f _max / f ₀ ), which is equivalent to the case of the standard exposure condition setting an exposure amount of the maximum S = ₀ is growing by the PN _mim. This is because, in the present embodiment, it is possible to increase the effective illuminance by raising the laser oscillation frequency (repetition frequency), and to compensate for the decrease in the average pulse energy due to the change of the illumination condition. In this way, according to the sequence, illumination is the exposure time is shortened to a modulation of the oscillation frequency (f) range _{(EPN min ≥ S 0 EPN min} (f max / f 0)) that in the low-light conditions, Throughput is improved in the entire low sensitivity region.

In the above embodiment, the case where the pulse energy of the excimer laser light source 16 is fine-modulated has been described. However, the present invention is not limited to this, and instead of this or at the same time, It is needless to say that the pulse energy may be finely modulated by using an energy fine modulator as shown in FIGS. In this case, the fine modulator is arranged on the optical path of the laser beam LB between the energy roughness adjuster 20 and the fly's eye lens 22 of FIG. 1, for example, It is controlled by the main controller 50 so that the desired integrated exposure amount is obtained.

(Second Embodiment)

Next, a second embodiment of the present invention will be described based on Figs. 7 to 10. Fig. Here, the same reference numerals are used for constituent parts which are the same as or equivalent to those of the first embodiment, and the description thereof is simplified or omitted.

7 schematically shows the configuration of the scanning exposure apparatus 70 according to the second embodiment. The scanning type exposure apparatus 70 is a scanning type exposure apparatus (first embodiment) of the first embodiment described above in which the point of fine modulation of the pulse energy using the energy fine modulator is finely modulated by the output pulse energy of the excimer laser light source 16 10).

7, an energy fine modulator 21 is provided on the optical path of the laser beam LB between the energy rough adjuster 20 and the fly's eye lens 22, Respectively. As the energy fine modulator 21, for example, a double-gradation fine modulator shown in Fig. 11 (A) or a fine modulator with fine tuning of transmittance according to two incident angles shown in Fig. 11 (B) It is possible to use an energy fine modulator comprising a drive device for adjusting the crossing angle of the optical filter plate and the two optical filter plates within a predetermined range. The fine adjustment amount T _F by the energy fine modulator 21 is controlled by the main controller 50.

Further, by using an acoustooptic modulator using, for example, a Raman's diffraction (a divisor effect) or the like as the energy fine modulator 21, the modulation type in the acoustooptic modulator is controlled so that the amount of transmitted light is continuously changed .

8 shows the relationship between the control amount externally and the amount of change of the transmittance with respect to the driving device (not shown) in the energy fine modulator 21 as a straight line Q. In Fig. In FIG. 8, the light amount of the laser beam emitted is divided by the light amount of the incident laser beam, and the transmittance obtained by dividing the light amount is the fine adjustment amount T _F. In the present embodiment, the adjustment range of the fine adjustment amount T _F is a continuous range between the predetermined minimum value T _min and the maximum value T _max , and the control amount for the internal drive device is set to a median value The fine adjustment amount T _F is adjusted to be a median value T ₀ between the minimum value T _min and the maximum value T _max . Further, when the energy fine modulator 21 is reset, the control amount is set to the neutral point, and the fine adjustment amount T _F is set to the median value T ₀ .

The configuration of the other parts is the same as that of the scanning-type exposure apparatus 10 of the first embodiment, except that the CPU control algorithm in the main controller 50 is different.

Next, the basic exposure amount control sequence of the scanning-type exposure apparatus 70 of the present embodiment will be described with reference to the flowcharts of Figs. 9 and 10 showing the CPU control algorithm in the main control apparatus 50. Fig. The transmittance of the laser beam LB from the excimer laser light source 16 by the energy tuning regulator 20 may be set only so that the number of exposure pulses becomes equal to or greater than the necessary number of exposure pulses. The energy fine modulation operation of FIG.

The exposure amount control in the present embodiment is performed by the pulse count method in each shot area, but the predetermined energy modulation is performed in the shot area.

First, in step 201 of FIG. 9, an operator, for example, obtains the center coordinates (FIG. 7) of a plurality of shot areas to be exposed on the wafer W through the input / output device 62 (Scanning length) L in the scanning direction of the wafer W when performing exposure to each shot area and a target integrated exposure amount (set exposure amount) to be irradiated per one point on the wafer W, S ₀ (mJ / cm ² ) or the like is set. Then, when the set exposure dose S ₀ is set, the process proceeds to the next step 202 to cause the excimer laser light source 16 to perform pulse light emission a plurality of times (for example, several hundred times) The pulse energy density p (mJ / (cm ² · pulse)) on the wafer W is indirectly measured by integrating the output of the pulse generator 46. The measurement is performed, for example, in a state in which the reticle movable blind 30B is driven to completely close the opening and prevent the illumination light IL from reaching the reticle R side. Of course, the XY stage 14 may be driven to retract the wafer W. In measuring the average pulse energy density, the ratio (difference)? P of 3 times (3?) Of the standard deviation of the pulse energy of the laser beam LB to the average pulse energy density p ? P / p) can be obtained.

In the next step 203, the number of exposure pulses N is calculated in the same manner as in the step 103 described above.

Although not shown in the figure, the CPU in the main control device 50 calculates the difference (3σ value) of the pulse energy (the value of 3σ) ΔP N) necessary for suppressing the variation of the integrated exposure dose within each shot area on the wafer W to within a predetermined tolerance, based on the ratio (P / P) of the average pulse energy density (p) _min . Further, the minimum number of exposure pulses (N _min ) may be obtained based on? P / p obtained in the above step (202). In the method of successively exposing pulse light from one excimer laser light source 16 as in the present embodiment, the distribution of the integrated exposure amount S per point on the wafer is, for example, disclosed in Japanese Patent Laid-Open Publication No. 8-250402 As described above, the value of 3σ at the average value Np is a normal distribution of N ^1/2 · δP. Assuming that the reproducibility of the integrated exposure amount in each shot area on the wafer W is A ₀ and the reproducibility of the integrated exposure amount required at each point on the wafer W is A _rep , The minimum number of exposure pulses (N _min ) necessary to accommodate the reproducibility in the A _rep is determined to satisfy the following condition.

In a next step 204 determines whether that the minimum exposure pulse number (N _min) or more for obtaining the exposure pulse number of the exposure amount control accuracy required to reproduce the (N) calculated in the step 203.

When the determination in step 204 is negative, that is, when the number of exposure pulses N is smaller than the minimum number of exposure pulses Nmin, the process proceeds to step 205, where the energy roughness adjuster 20 ) of the closest, then also set to select the transmittance to meet N≥N _min, treatment of the step (202, 203) to _{S 0 / (N min × p} ) in a settable transmission by the ND filter If the determination in step 204 is affirmative, or if the determination in step 204 is affirmative (N &gt; = N _min ), the process proceeds to step 206, and in step 206 The actual value A _tgt of the exposure amount target value precision is calculated.

In the next step 207, it is determined whether or not fine modulation of the pulse energy is necessary, that is, whether the measured value A _tgt of the exposure amount target value precision is equal to or more than the above described exposure amount target value precision A _t . If the determination is negative, that is, if the measured value A _tgt is smaller than the exposure amount target value precision A _t , the process advances to step 209 to set the scan speed V = scan maximum speed V _max to the laser oscillation frequency f) are calculated in the same manner as in step 109 described above. That is, the laser oscillation frequency f is calculated by the above-mentioned formula (9) as the scan speed V = the scan maximum speed V _max . Exposure pulses Accordingly, (N) by the exposure greater than the minimum pulse (N _min), by increasing the laser transmission frequency (f) to maintain the scanning maximum speed (V _max).

On the other hand, if the determination in step 207 is affirmative, the process proceeds to step 208 to set the fine adjustment amount T _F in the energy fine modulator 21 in FIG. 7 as follows, After adjusting the value of the pulse energy p, the process proceeds to step 209. [

The fine adjustment amount (transmittance) T _{F in the} energy fine modulator 21 varies between the minimum value T _min and the maximum value T _max as described above with reference to FIG. 8, The maximum value T _max and the minimum value T _min can be expressed as follows using the pulse number N _min and the exposure amount target value accuracy A _t .

Further, the value of the fine adjustment amount T _F in the initial state and resetting is set to (T _max + T _min ) / 2, that is, T ₀ .

In the next step 210, it is determined whether or not the laser oscillation frequency f calculated above is equal to or lower than the maximum oscillation frequency fmax of the laser. If the determination is affirmative, the process advances to step 211 to set the laser oscillation frequency to a value calculated from the above via the energy controller 16d and to set the scan target speed (scan speed) to the scan maximum speed V _max ). On the other hand, if the determination in step 210 is negative, the process proceeds to step 212. The laser oscillation frequency f is set to the maximum oscillation frequency fmax through the energy controller 16d and the routine proceeds to step 213. In step 213, And the scan speed V is set in the same manner as the step 113 described above.

In the next step 214 (step 214 in Fig. 10), the pattern image of the reticle R is exposed in the scanning exposure method at the exposure amount set in the designated shot area on the wafer W. [

The CPU in the main controller 50 calculates the integrated exposure amount on the shot area on the wafer W by the laser beam LB from the excimer laser light source 16 via the integrator sensor 46 during the scan exposure do. In this case, since the number of exposing pulses for each point on the wafer W is N, the integrator 46 (see FIG. 7) is scanned in the period in which the corresponding shot area on the wafer W is scanned with respect to the exposure area 42W (M is an integer equal to or larger than 2) M pulses per N pulses to calculate a sequential integrated exposure amount S, as shown in FIG. As a result, the integrated exposure dose S _j at M positions Y _j (j = 1 to M) arranged at substantially equal intervals in the Y direction on the wafer W is calculated. In addition, because the disclosed method for the integrated amount of exposure (S _j) the specific calculation, for example, in Japanese Patent Publication No. 8-250402 discloses, is omitted here for further description.

In the next step 215, the average value S _rst of the M integrated exposure amounts S _j is calculated and the average pulse energy p 'in the exposure is calculated.

In the next step 216, the target value error ABS (S _rst / S ₀ -1), which is an error with respect to the target integrated exposure amount S ₀ of the average value (S _rst ) of the actual integrated exposure dose in the exposed shot area, Is greater than the exposure amount target value precision (A _t ). And, if the judgment is affirmative, that is, when the target value of the error exceeds the target amount of exposure accuracy (A _t), the process proceeds to step 217, the correction amount of the exposure amount required is calculated. More specifically, the correction amount T _add , which is a value obtained by dividing the exposure amount after correction for each pulse of the laser beam LB by the current exposure amount, is set as follows.

In this case, the rough adjustment amount (transmittance) T _R of the exposure amount in the energy coarse adjustment unit 20 for the shot area in which exposure has been completed and the fine adjustment amount T of the exposure amount in the energy fine modulation unit 21 _F are stored in the memory 51 as information of the pre-shot area.

Therefore, in the next step 218, it is determined whether the value obtained by multiplying the fine adjustment amount T _F of the energy fine modulator 21 by the correction amount T _add is within the adjustable range of the energy fine modulation unit 21 .

When the equation (18) is satisfied, the process proceeds to step 219 to change the fine adjustment amount T _F of the energy fine modulator 21 to T _add · T _F (= T _F '), (230). If there is a shot area to be exposed, the process returns to step 214 and the fine adjustment amount T _F (T _F ) of the newly set energy fine modulator 21 is determined '), The exposure is performed by the scanning exposure method. At this time, since the exposure amount is corrected based on the actual integrated exposure amount in the immediately preceding shot area, the obtained integrated exposure amount becomes close to the target integrated exposure amount (set exposure amount) S ₀ .

On the other hand, if the judgment in the step 216 is negative, i.e., the target value error (ABS), when the (S _rst / S ₀ -1) is less than the target value exposure accuracy _(t A), there is no need to change the exposure conditions Therefore, the process directly proceeds to step 230, and exposure to the next shot area is performed. Then, when a shot area to be exposed disappears, a series of processing of this routine ends.

On the other hand, when the product of the fine adjustment amount T _F and the correction amount T _add is not within the range of the formula (8) in the step 218, the process proceeds to the step 220, The number N of exposing pulses per point is changed to N '. Further, the average pulse energy p 'is an actual average pulse energy obtained by the equation (16).

In the next step 221, it is determined whether or not the number of exposure pulses N 'after correction is equal to or greater than the minimum necessary number of exposure pulses N _min . When the determination is negative, that is, when N' is smaller than N _min , was set to 222, the amount of energy fine modulator fine adjustment by resetting the (21) (T _F), a median value (T ₀₎ in, Figure 9 back to step 205, so that rough energy N'≥N _min Adjusts the rough adjustment amount of the regulator 20, and then returns to step 202. [

On the other hand, when the determination in step 221 is affirmative, that is, when N '&gt; N _min holds, the process proceeds to step 223 to calculate the target integrated exposure dose S (N' ₀ ) is larger than the above-described exposure amount target value precision (A _t ).

And, if the determination is affirmative, that is, when the target value the error exceeds the target amount of exposure accuracy (A _t), the process proceeds to step 224, the correction amount of the exposure amount required is calculated. Specifically, the fine adjustment amount T _F in the energy fine modulator 21 is changed to the next T _F '.

Then, in the following steps 225 to 229, the same processing as the above-mentioned steps 209 to 213 is performed. That is, the laser oscillation frequency f corresponding to the new exposure pulse number N 'is calculated with the scan speed at the maximum speed, and if the calculated f is not more than the laser maximum oscillation frequency f _max , through changing the lasing frequency to that frequency, and at the same time, by setting the scan rate to scan the maximum speed (V _max), when the calculated f exceeds the laser maximum oscillation frequency (f _max), a laser oscillation frequency of the laser the maximum oscillation To the frequency ( _fmax ), and sets the scan speed (V) in accordance with _fmax and N '. Thereafter, the operation proceeds to step 230 to perform exposure of the next shot area.

On the other hand, if less than or equal to step 223 of the judgment in this case is negative, that is, the target value error (ABS) (N '· p ' / S 0 -1) The target exposure accuracy (A _t) is estimated according to the energy fine modulator The setting of the laser oscillation frequency and the scan speed are set in the same manner as described above, and thereafter, the process proceeds to step 230 and the next shot area Exposure is performed.

According to the exposure amount control sequence according to the flowcharts shown in Figs. 9 and 10 as described above, in order to obtain the stability of the exposure amount between the shots on the wafer W, as shown in steps 215 to 230 (except step 222) (Running window data) is acquired based on the output of the integrator sensor 46 during exposure to each shot area, and when the average integrated exposure amount of the immediately preceding shot is out of tolerance, Since the pulse energy is corrected by adjusting the fine adjustment amount T _{F in the} energy fine modulator 21 based on the integrated exposure amount measured in the exposed shot area, the integrated exposure amount of each shot area can be accurately corrected to the target integrated exposure amount .

According to the above embodiment, the average power of the laser light source 16 is high in the middle of the exposure of one wafer W coated with the high-sensitivity resist (in this case, scanning exposure is performed at the scan maximum speed) In order to obtain the same amount of exposure as before the decrease in power fluctuation corresponding to one pulse and in the case where the power fluctuation is out of the fine adjustment dynamic range of the fine modulator 21 (the judgment in step 218 is negative) Even when the number of exposure pulses at one point on the wafer is changed in step 220 and a change made from, for example, the number of pulses N to N + 1 is calculated, the laser light source 16, The oscillation frequency f of the photodetector is set to (N + 1) / N times of the previous shot, and consequently, a desired exposure amount can be obtained without changing the scan speed. Therefore, even in such a case, there is no increase in the exposure time and the throughput can be maintained.

The exposure amount control as described above is repeated until the average pulse energy of the laser beam from the excimer laser light source 16 is actually measured (this is called &quot; energy check &quot;) as in step 202. [ When the rough adjustment amount T _R in the energy rough adjuster 20 is changed by the flow of step 221 → step 222 → step 205, the energy check is performed in step 202 , The frequency of changing the rough adjustment amount T _R in the energy rough adjustment unit 20 between exposure to the shot area is considerably low. Further, the ordinary energy check is performed at intervals such as every time the wafer is exchanged or every lot of wafers exchanged. Therefore, for example, it is not necessary to perform a normal energy check during exposure to one wafer, and the throughput of the exposure process (the number of wafers processed per unit time) is also kept high in this respect.

In step 215, the total average value S _rst of the M integrated exposure quantities S _j (j = 1 to M) is calculated in the equation (15), but m (mM) (S _rst ') of the integrated exposure dose S _j may be used. This makes it possible to control the exposure amount corresponding to the shorter-term output fluctuation of the excimer laser light source 16.

In the second embodiment, the energy rough adjuster 20 and the energy fine modulator 21 are used as a pulse energy modulator. However, the present invention is not limited to this, and similarly to the first embodiment, the excimer laser light source 16 It goes without saying that the power (applied voltage) may be controlled. In this case, since the energy loss of the (1-T ₀ ) portion is eliminated based on the fine adjustment amount (transmittance) T ₀ in the initial state of the energy fine modulator 21, .

In the above embodiment, as shown in steps 216 and 217, the exposure amount is corrected when the integrated exposure exposure amount (P) average value (S _rst ) exceeds the allowable value, but even when the average value (S _rst ) by continuously each exposure of the shot area storing data of the average value (S _rst), if there is increasing or decreasing trend in the average value (Srst) is to pre-correct the exposure amount prior to exceeding the average value (S _rst) is allowable . Such a prediction control has an advantage in that the number of shot areas in which the integrated exposure dose is out of tolerance is reduced.

In the above embodiment, the exposure amount is modulated between the exposure to each shot area via the energy fine modulator 21 and the like. However, the energy fine modulator 21 is controlled based on the partial integrated exposure amount up to the pulse exposure, The exposure amount may be modulated. This makes it possible to more accurately bring the integrated exposure dose in each shot area closer to the target integrated exposure dose.

As described above, according to the invention described in claim 1, there is provided a scanning exposure method capable of always performing exposure in the shortest time irrespective of the high sensitivity area and the low sensitivity area.

In addition, according to the invention described in claim 2, exposure can be always performed in the shortest time in the high sensitivity area without being affected by the discrete light sensitivity of the photosensitive means, and at the same time, It is possible to provide an excellent scanning type exposure apparatus which is not conventional.

According to the invention described in claim 3, when the pulse energy during exposure varies in the high-sensitivity exposure area, it is possible to perform exposure such that a desired integrated exposure dose is obtained for the next shot while maintaining the scanning speed A scanning exposure method is provided.

According to the fourth aspect of the present invention, when the pulse energy during exposure varies in the high-sensitivity exposure region, it is possible to perform exposure such that a desired integrated exposure amount is obtained for the next shot while maintaining the scanning speed It is possible to provide an excellent scanning type exposure apparatus.

Claims (4)

A scanning exposure method for illuminating a predetermined illumination area on a mask with pulse light from a pulsed laser light source and successively projecting a pattern formed on the mask onto a photosensitive substrate while scanning the mask and the photosensitive substrate relative to the projection optical system In this case, Measuring an average pulse energy of the pulse light from the pulse laser light source; Wherein the maximum scanning speed between the mask and the photosensitive substrate and the maximum oscillation frequency of the pulse laser light source at the time of scanning exposure are determined in accordance with the number of exposure pulses per one point determined by the relationship between the set exposure amount and the measured average pulse energy. And controlling the oscillation frequency of the pulsed laser light source so as to maintain at least one side of the pulse laser light source. A scanning exposure apparatus for sequentially projecting a pattern formed on a mask onto a photosensitive substrate while illuminating a predetermined illumination area on the mask with pulse light from a pulsed laser light source and scanning the mask and the photosensitive substrate relative to the projection optical system, In the exposure apparatus, A mask stage which holds the mask and is movable in a predetermined scanning direction; A substrate stage which holds the photosensitive substrate and is movable in at least the scanning direction; A stage control system for relatively scanning the mask stage and the substrate stage at a predetermined speed ratio with respect to the projection optical system; Frequency changing means for changing an oscillation frequency of the pulse laser light source; A photosensitive means for discrete pulsed light from the pulsed laser light source, the photosensitive means being discrete in sensitivity; Energy measuring means for measuring an average pulse energy of pulse light from the pulsed laser light source that is photographed by the photosensitive means; At least one of the maximum scanning speed of both stages by the stage control system and the maximum oscillation frequency of the pulse laser light source is maintained in accordance with the number of exposure pulses per one point determined by the relationship between the set exposure amount and the average pulse energy And control means for controlling said frequency changing means so that said frequency changing means is controlled. A scanning exposure method for illuminating a mask with pulsed light from a pulsed laser source and successively projecting a pattern formed on the mask to a plurality of shot areas on a photosensitive substrate while scanning the mask and the photosensitive substrate relative to the projection optical system As a result, Detecting an average pulse energy of the pulse laser light source and calculating an integrated exposure amount up to the exposure pulse pattern for each exposure of the master pattern with respect to each shot area on the photosensitive substrate; And controlling the oscillation frequency of the pulse laser light source in which the required number of exposure pulses per required point is secured based on the integrated exposure amount of the immediately preceding shot area when the average pulse energy of the pulse laser light source fluctuates Wherein the scanning exposure method comprises the steps of: A scanning type exposure apparatus which illuminates a mask with pulse light from a pulsed laser light source and sequentially exposes a pattern formed on the mask to a plurality of shot areas on a photosensitive substrate while scanning the mask and the photosensitive substrate relative to the projection optical system In this case, Frequency changing means for changing an oscillation frequency of the pulse laser light source; An energy measuring means for measuring an average pulse energy of the pulse light from the pulse laser light source; An average pulse energy of the pulse laser light source is detected for each exposure of the master pattern with respect to each shot area on the photosensitive substrate, and an integrated exposure amount up to the detected pulse energy is calculated. When the average pulse energy of the pulse laser light source fluctuates And control means for controlling the frequency changing means to secure the necessary number of exposure pulses per one point on the basis of the integrated exposure amount of the shot area immediately before.