Control of laser output, laser device and exposure device

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention relates to a laser output control method for controlling a laser output such as an excimer laser that charges each pulse and oscillates the laser, a laser device, and an exposure device using the laser device as a pulse light source.

【0002】

[Conventional technology]

Conventionally, when a semiconductor element, a liquid crystal display element, an image pickup element (CCD, etc.), a thin film magnetic head, or the like is manufactured by using photolithography technology, an image of a pattern in a reticle as a mask via a projection optical system is photoresist. A projection exposure apparatus is used that exposes a wafer (or a glass plate or the like) coated with the above. Generally, a pulse oscillation type laser such as a KrF excimer laser or an ArF excimer laser used as an exposure source of an exposure apparatus is provided with a high voltage charge control unit having a charging circuit, and charges a high voltage to the charging circuit for each pulse. Laser emission is performed by switching at a desired timing and discharging between the two electrodes installed inside the gas chamber.

【0003】

As a means of controlling the laser output to give or determine the high voltage value to be charged for each pulse How to give the target charging voltage value itself from the outside A method in which a target energy value is given from the outside, calculation processing is performed from the past output energy history and gas state inside the laser, and the charging voltage of the next pulse is calculated / converted. Etc., conventionally The setting of the target charging voltage from the outside is completed. The calculation of the target charging voltage is completed internally. When the preprocessing such as is completed, the charging operation is started so as to reach the target charging voltage value required for the next pulse.

【0004】

In recent years, in semiconductor exposure apparatus, a pulse oscillation type laser having a higher emission repetition frequency is required as an exposure light source for the purpose of improving the number of wafers processed (throughput) per unit time. On the other hand, the accuracy and stability of key characteristics such as output energy, wavelength and full width at half maximum are also required to be improved, and the control inside the laser tends to be more complicated and lead to an increase in processing time. Shortening occupies a greater weight.

【0005】

[Problems to be Solved by the Invention]

However, the conventional laser output control means still has the following problems. That is, in order to reduce the time related to charging, The state where the setting of the target charging voltage from the outside is not completed The state where the calculation of the target charging voltage is not completed internally If the charging process is attempted in, charging for the next pulse cannot be started, or charging is started with the target charging voltage value of the previous pulse as it is. As a means to meet this challenge, As a way to speed up the charging time itself, it is conceivable to develop an improved charging device and shorten the charging time by changing the hardware (laser device). To shorten the calculation time of the charging voltage and speed up the setting timing of the command energy or charging voltage from the outside. a) How to shorten the charging voltage calculation time inside the laser b) How to shorten the charging voltage calculation time for external devices (Increased calculation speed, simplified algorithm, faster interface, etc.) can be considered. However, according to these means, it is necessary to change the device configuration of hardware such as a charging device and an arithmetic circuit, which causes an increase in cost.

【0006】

The present invention has been made in view of the above-mentioned problems, and is a laser output control method capable of shortening the time required for charging for laser oscillation without changing the device configuration such as conventional hardware. It is an object of the present invention to provide a laser apparatus and an exposure apparatus.

【0007】

[Means for solving problems]

The present invention has adopted the following configuration in order to solve the above problems. That is, to explain in association with FIGS. 1 and 2, the laser output control method according to claim 1 is a method of controlling the output of a laser that charges each pulse and oscillates the laser. The precharging step of starting the charging with the temporary charging voltage value set in advance as a target, the target voltage calculating step of calculating the target charging voltage value required for the next pulse during the precharging step, and the said. When the target charging voltage value is calculated in the target voltage calculation process, a technology is adopted that includes a fine charging process in which the charging is performed with the target charging voltage value as the target instead of the temporary charging voltage value in the precharging process. To.

【0008】

Further, the laser device according to claim 3 is a pulse oscillation type laser device (1) that charges each pulse and oscillates the laser, and the charge control means (13) that controls the charge for each pulse. The charge control means includes a target voltage calculation means (14) for calculating a target charge voltage value required for the next pulse, and targets a temporary charge voltage value preset for the next pulse. The target charging voltage value is calculated by the target voltage calculation means during charging up to the temporary charging voltage value after starting charging, and when the target charging voltage value is calculated, the target charging voltage is replaced with the temporary charging voltage value. The technology that is set to charge with the value as the target is adopted.

【0009】

In this laser output control method and the laser device, charging is started with a target of a temporary charge voltage value set in advance for the next pulse, and a target required for the next pulse during charging to the temporary charge voltage value. The charging voltage value is calculated, and when the target charging voltage value is calculated, charging is performed with the target charging voltage value as the target instead of the temporary charging voltage value, so the previous pulse emission ends for the next pulse. Charging is started immediately after, and the target is switched from the temporary charging voltage value to the target charging voltage value in a state where charging is performed to some extent, so that the time until charging is completed is significantly shortened. Moreover, since it is only necessary to change the charging algorithm and it is not necessary to change the device configuration such as hardware, it can be realized at low cost.

【0010】

The exposure apparatus according to claim 4 is an exposure apparatus that illuminates a mask (R) with pulsed light of a pulse light source (1) and transfers and exposes a pattern formed on the mask onto a photosensitive substrate (W). A technique in which the laser apparatus according to claim 3 is provided as the pulse light source is adopted.

【0011】

Since this exposure apparatus includes the laser apparatus (1) as a pulse light source, the pulse interval can be shortened, and the throughput can be improved by the high emission repetition frequency.

【0012】

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, an embodiment of an exposure apparatus using the laser apparatus according to the present invention will be described with reference to FIG.

【0013】

FIG. 1 is an overall configuration diagram of the exposure apparatus of the present embodiment. The exposure apparatus is a step-and-scan type projection exposure apparatus having a pulse light source (laser apparatus) 1 which is a pulse oscillation type exposure light source as a light source. As the pulse light source 1, an excimer laser light source that performs pulse oscillation such as a KrF excimer laser (wavelength 248 nm) or an ArF excimer laser (wavelength 193 nm) is used, and a charge control unit that charges for pulse oscillation is built-in. ing.

【0014】

The laser beam IL emitted from the pulse light source 1 is shaped by the beam shaping optical system 2 composed of a cylinder lens, a beam expander, etc. so that the cross-sectional shape of the beam is efficiently incident on the subsequent fly-eye lens 4. Will be done. The fly-eye lens 4 forms a number of secondary light sources to illuminate the subsequent field diaphragm 8 and the reticle (mask) R with a uniform illuminance distribution. An aperture diaphragm 5 of an illumination system is arranged on the ejection surface of the fly-eye lens 4, and a laser beam emitted from a secondary light source in the aperture diaphragm 5 enters the beam splitter 6 and passes through the beam splitter 6. The beam passes through the opening of the field diaphragm (fixed reticle blind) 8 via the first relay lens 7A.

【0015】

The laser beam that has passed through the field diaphragm 8 illuminates the reticle R on the reticle stage 11 with a uniform illuminance distribution via the second relay lens 9A, the optical path bending mirror 9, and the main condenser lens 10. The image of the pattern in the illumination region 24 on the reticle R via the projection optical system 15 is projected and exposed on the wafer (board) W. At this time, the reticle stage 11 is scanned in the scanning direction by the reticle stage driving unit 12.

【0016】

The reticle stage drive unit 12 is controlled by a main control system (charge control means) 13 that collectively controls the operation of the entire device. In addition, a length measuring device (laser interferometer, etc.) for detecting the coordinates in the scanning direction (X direction) of the reticle stage 11 is incorporated, and the coordinates in the scanning direction of the reticle stage 11 measured by this are the main control system 13. Is supplied to.

【0017】

On the other hand, the wafer W is placed on the XY stage 17 which can scan at least in the scanning direction via the wafer holder 16. A Z stage (not shown) for positioning the wafer W in the Z direction is provided between the XY stage 17 and the wafer holder 16.

【0018】

The laser beam reflected by the beam splitter 6 is received by an integrator sensor 20 composed of a photoelectric conversion element (for example, a PIN photodiode) via a condenser lens 19, and the photoelectric conversion signal of the integrator sensor 20 is an amplifier and an analog (not shown). / It is supplied to the calculation unit (target voltage calculation means) 14 in the main control system 13 via the digital converter. The calculation unit 14 measures the variation in the pulsed light amount of the pulsed light output from the pulse light source 1 from the photoelectric conversion signal of the integrator sensor 20, integrates the photoelectric conversion signals for each pulsed light, and sequentially integrates the photoelectric conversion signals of each of the wafers W. Obtain the integrated exposure amount at the point. Further, the calculation unit 14 calculates the target charging voltage value required for each pulse based on the output from the integrator sensor 20.

【0019】

The main control system 13 controls the light emission timing of the pulse light source 1 by supplying the light emission trigger signal TP to the pulse light source 1 via the trigger control unit 21. A beam splitter 25 is arranged on the optical path of the laser beam between the pulse light source 1 and the beam shaping optical system 2, and the laser beam reflected by the beam splitter 25 is received by the energy monitor 26 composed of a photoelectric conversion element. .. The photoelectric conversion signal of the energy monitor 26 is supplied to the main control system 13 via an amplifier and an analog / digital converter (not shown), and the main control system 13 outputs the pulse light source 1 from the photoelectric conversion signal from the energy monitor 26. Adjust the power.

【0020】

Next, the output control method of the pulse light source 1 by the main control system 13 will be described with reference to FIGS. 2 and 3.

【0021】

[Precharge step] After the pulse emission before, as shown in FIG. 2, the pulse light source 1 has the minimum charging voltage required to obtain the lower limit energy of the actual use level, that is, the voltage value set during the exposure of the wafer W. Precharge is started with the precharge voltage value (temporary charge voltage value), which is the estimated lower limit, as the target. Further, the estimated lower limit value is determined based on the number of pulsed lights emitted during the exposure of the wafer W and the resist sensitivity attached on the wafer W.

【0022】

[Target voltage calculation process] The exposure energy of the previous pulse is detected by the integrator sensor 20 output in parallel with the precharge time of the pulse light source 1, and the calculation unit 14 is based on the past monitor history (energy information of exposure energy). The target charging voltage value of the next pulse is calculated in.

【0023】

[Fine charge process] When the target charge voltage value of the next pulse is calculated, the main control system 13 notifies (communicate) to the pulse light source 1. When the pulse light source 1 receives the target charge voltage value from the main control system 13, the final target value of the charge control unit is corrected to the target charge voltage value of the next pulse instead of the precharge voltage value, and fine charge is performed. I do. When the target charging voltage value is reached by fine charging, the main control system 13 sends a light emitting trigger signal TP to the pulse light source 1 via the trigger control unit 21 to oscillate the laser.

【0024】

In the conventional control method described above, as shown in FIG. 3, when the target charging voltage value of the next pulse is calculated, the pulse light source is notified (communication of the target charging voltage value command), and the pulse light source receives the pulse light source. At this stage, the target value of the charge control unit is updated from the target charge voltage value of the previous pulse for the next pulse, and charging is started, so it takes time by the amount of the calculation time added. On the other hand, according to the present embodiment, as shown in FIG. 2, charging is started immediately after the end of the previous pulse light source for the next pulse, and the precharge voltage is charged to some extent. Since the target is switched from the value to the target charging voltage value, it can be seen that the charging completion time of the pulse light source 1 between pulses can be significantly shortened as compared with the conventional case. Therefore, according to the present embodiment, the charging completion time for the next pulse can be shortened, so that the laser output control can be highly repeated by the charging voltage or energy command for each pulse, and the laser frequency can be increased. be able to.

【0025】

Further, since the estimated lower limit value of the voltage value set during the exposure of the wafer W is used as the precharge voltage value, there is no possibility that the precharge voltage value exceeds the target charging voltage value. Further, the estimated lower limit is determined based on the number of pulsed lights emitted during the exposure of the wafer W and the resist sensitivity attached on the wafer W, and the energy of each pulsed light actually irradiated is determined. However, it is determined by the resist sensitivity and how many pulsed lights are applied to the resist.

【0026】

The present invention also includes the following embodiments. (1) In the above embodiment, an example in which the target charging voltage of the laser for each pulse is given in the main control system 13 is shown, but in addition, the target energy of the laser of the next pulse between the main control system 13 and the pulse is shown. The amount may be commanded, and the target energy amount may be converted into a target charging voltage value inside the pulse light source 1 and calculated.

【0027】

(2) As the exposure apparatus of the above embodiment, it can also be applied to a step-and-repeat type exposure apparatus in which a mask pattern is exposed while the mask and the substrate are stationary and the substrate is sequentially moved step by step. (3) As the exposure apparatus of the above embodiment, it can also be applied to a proximity exposure apparatus that exposes a mask pattern by bringing the mask and a substrate into close contact with each other without using a projection optical system.

【0028】

(4) The application of the exposure device is not limited to the exposure device for semiconductor manufacturing. For example, an exposure device for liquid crystal that exposes a liquid crystal display element pattern on a square glass plate and a thin film magnetic head are manufactured. It can also be widely applied to an exposure device for performing. (5) The light sources of the exposure apparatus of the above embodiment are KrF excimer laser (248 nm), ArF excimer laser (193 nm), and F.₂Not only a laser (157 nm) but also a charged particle beam such as an X-ray can be used.

【0029】

(6) The magnification of the projection optical system may be not only a reduction system but also an equal magnification system and an enlargement system. (7) When using far infrared rays such as excimer laser as the projection optical system, use a material that transmits far infrared rays such as quartz and fluorite as the glass material, and use F.₂When a laser or X-ray is used, a catadioptric system or a catadioptric system (a reflective type reticle is also used) may be used.

【0030】

(8) When using a linear motor (see USP5,623,853 or USP5,528,118) for the wafer stage or reticle stage, use either the air levitation type using air bearings or the magnetic levitation type using Lorentz force or reactance force. You may. Further, the stage may be a type that moves along a guide, or a guideless type that is not provided with a guide.

【0031】

(9) The reaction force generated by the movement of the wafer stage may be mechanically released to the floor (ground) using a frame member (as described in USP 5,528,118). (10) The reaction force generated by the movement of the reticle stage may be mechanically released to the floor (ground) using a frame member (as described in US S / N 416558).

【0032】

(11) Illumination optics and projection optics consisting of multiple lenses are incorporated into the exposure equipment body to make optical adjustments, and a reticle stage or wafer stage consisting of many mechanical parts is attached to the exposure equipment body for wiring and piping. The exposure apparatus of the present embodiment can be manufactured by connecting the above and further performing comprehensive adjustment (electrical adjustment, operation check, etc.). It is desirable that the exposure device is manufactured in a clean room where the temperature, cleanliness, etc. are controlled.

【0033】

(12) For a semiconductor device, a step of designing the function and performance of the device, a step of manufacturing a reticle based on this design step, a step of manufacturing a wafer from a silicon material, and a reticle pattern by the exposure device of the above-described embodiment are used. Manufactured through a wafer exposure step, a device assembly step (including a dicing step, a bonding step, a packaging step), an inspection step, and the like.

【0034】

[Effect of the invention]

According to the present invention, the following effects are obtained. (1) According to the laser output control method according to claim 1 and the laser apparatus according to claim 3, the charging is started and the temporary charging is performed with a target of a temporary charging voltage value set in advance for the next pulse. The target charging voltage value required for the next pulse is calculated during charging to the voltage value, and when the target charging voltage value is calculated, the target charging voltage value is used as the target instead of the temporary charging voltage value. Because charging starts immediately for the next pulse and switches to fine charging during charging, the time to complete charging can be greatly shortened, and charging control with plenty of processing time At the same time, it is possible to realize a system capable of high repetitive light emission in terms of energy control. Further, since it is only necessary to change the charging algorithm and it is not necessary to change the device configuration such as hardware, it can be realized at low cost.

【0035】

(2) According to the laser output control method according to claim 2, the target charging voltage value is calculated based on the energy information of at least one previously oscillated pulse, that is, in consideration of the pulse history. It is possible to suppress the variation in energy for each pulse, and it is possible to obtain an appropriate integrated exposure amount when used as an exposure light source.

【0036】

(3) According to the exposure apparatus according to claim 4, since the laser apparatus is provided as a pulse light source, the pulse interval can be shortened, and the throughput can be improved by the high emission repetition frequency. Further, when a voltage command or an energy command is given for each pulse, the time constraint can be relaxed.

【0037】

(4) According to the exposure apparatus according to claim 5, since the estimated lower limit of the voltage value set during the exposure of the substrate is used as the temporary charging voltage value, the temporary charging voltage value exceeds the target charging voltage value. There is no risk, and stable laser output control is possible even if the calculation time is long.

【0038】

(5) According to the exposure apparatus according to claim 6, the estimated lower limit value is determined based on the number of pulsed lights emitted during the exposure of the substrate and the resist sensitivity attached on the substrate. It is possible to set a temporary charging voltage value corresponding to the energy of each pulsed light required for actual irradiation.

[Simple explanation of drawings]

[Figure 1]

It is an overall block diagram which shows one Embodiment of the exposure apparatus which concerns on this invention.

[Figure 2]

It is a graph which shows the charge curve of the pulse light source in one Embodiment of the exposure apparatus which concerns on this invention.

[Fig. 3]

It is a graph which shows the charge curve in the conventional example of the pulse light source in the exposure apparatus which concerns on this invention.

[Explanation of symbols]

1 Pulse light source (laser device) 13 Main control system (charge control means) 14 Calculation unit (target voltage calculation means) W wafer (photosensitive substrate) R reticle (mask)