Laser source device and extreme ultraviolet lithography device

A device includes a laser source, an amplifier, an optical sensor and a spectrometer. The laser source is configured to produce a seed laser beam. The amplifier includes gain medium and a discharging unit. The discharging unit is configured to pump the gain medium for amplifying power of the seed laser beam. The optical sensor is coupled to the amplifier and configured for sensing an optical emission generated in the amplifier while the gain medium is discharging. The spectrometer is coupled with the optical sensor and configured to measure a spectrum of the optical emission.

BACKGROUND

In semiconductor fabrication processes, increased density of integrated circuits has increased the complexity of processing and manufacturing ICs. There is a need to perform lithography processes with higher resolution. One of the leading lithography techniques is an extreme ultraviolet (EUV) lithography. Others include X-Ray lithography, ion beam projection lithography, and electron-beam projection lithography. EUV light with a wavelength around 5-100 nm or less can be used in photolithography processes to produce extremely small patterns on semiconductor wafers.

DETAILED DESCRIPTION

FIG. 1is a schematic diagram of a device100, in accordance with some embodiments of the present disclosure.

As illustratively shown inFIG. 1, the device100includes a laser source110, an amplifier120, an optical sensor130, a spectrometer140, a processor150, a beam transport system (BTS)160, a laser focus unit170and an extreme ultraviolet (EUV) generating vessel180. In some embodiments, the device100is a laser produced plasma extremely ultra violet (LPP-EUV) light source which is capable of generating an extreme ultraviolet light EUVL. The extreme ultraviolet light EUVL has a wavelength about 5 nm to about 100 nm. In some embodiments, the extreme ultraviolet light EUVL has a wavelength about 13.5 nm.

As illustratively shown inFIG. 1, in some embodiments, the device100further includes optical components190, and the extreme ultraviolet light EUVL is guided through optical components190onto a wafer WF. In some embodiments, the device100is an extreme ultraviolet lithography equipment, which is capable of generating the extreme ultraviolet light EUVL and utilizing the extreme ultraviolet light EUVL to form a pattern onto the wafer WF.

The laser source110is configured to produce a seed laser beam SLB. Reference is further made toFIG. 2.FIG. 2is a schematic diagram of the laser source110inFIG. 1, in accordance with some embodiments of the present disclosure. As illustratively shown inFIG. 2, in some embodiments, the laser source110includes a pre-pulse laser generator111, a main pulse laser generator112, a beam combiner113and a pre-amplifier114. The pre-pulse laser generator111is configured to produce a pre-pulse laser beam PLB. The main pulse laser generator112is configured to produce a main pulse laser beam MLB. The pre-pulse laser beam PLB has a wavelength different from a wavelength of the main pulse laser beam MLB. In some embodiments, the wavelength of the pre-pulse laser beam PLB and the main pulse laser beam MLB are in a range from about 9 μm to about 12 μm. In some embodiments, the pre-pulse laser generator111and the main pulse laser generator112can be gas-discharge CO2laser generators. In other embodiments, other suitable laser generators, for examples, an excimer or molecular fluorine laser, may be used for the pre-pulse laser generator111and the main pulse laser generator112shown inFIG. 2.

As illustratively shown inFIG. 2, in some embodiments, the beam combiner113is configured for combining the main pulse laser beam MLB and the pre-pulse laser beam PLB onto one optical path to form the seed laser beam SLB. In the embodiments illustratively shown inFIG. 2, the seed laser beam SLB is a combination of the main pulse laser beam MLB and the pre-pulse laser beam PLB. In some other embodiments, the seed laser beam SLB includes one laser beam, for example the main pulse laser beam MLB or the pre-pulse laser beam PLB, produced by one gas-discharge laser generator. The pre-amplifier114is configured to enhance power of the seed laser beam SLB. In some embodiments, the pre-amplifier114is able to modulate the power of the seed laser beam SLB to about 1 kW to about 5 kW.

As illustratively shown inFIG. 1, the seed laser beam SLB produced by the laser source110transmits through the amplifier120to the beam transport system (BTS)160. Afterward, the seed laser beam SLB is utilized to excite a target droplet DP in the extreme ultraviolet generating vessel180for producing the extreme ultraviolet light EUVL. In order to effectively excite a target droplet DP in the extreme ultraviolet generating vessel180, the seed laser beam SLB is required to have enough power. The amplifier120is utilized to amplify power of the seed laser beam SLB. In some embodiments, the amplifier120is able to modulate the power of the seed laser beam SLB to about 5 kW to about 15 kW.

As illustratively shown inFIG. 1, in some embodiments, the amplifier120includes four stages of amplifier components121,122,123and124positioned along an optical path of the seed laser beam SLB, but the present disclosure is not limited in this regard. The number and configuration of the amplifier120in following embodiments are given for illustrative purposes. In some other embodiments, the amplifier120includes at least one amplifier component to amplify power of the seed laser beam SLB.

The seed laser beam SLB after processed by the amplifier120is transmitted through the beam transport system160to the extreme ultraviolet generating vessel180. In some embodiments, the laser source110and the amplifier120may be implemented at one location, for example a ground floor or underground of a factory, and the extreme ultraviolet generating vessel180and the optical components190may be implemented at another location, for example a first floor or a second floor of the factory. In some embodiments, the beam transport system160is configured to transport the seed laser beam SLB between two locations with minimum leakage.

As illustratively shown inFIG. 1, in some embodiments, the laser focus unit170is disposed between the beam transport system160and the extreme ultraviolet generating vessel180. The laser focus unit170is configured to make the seed laser beam SLB converge at a point precisely to excite the target droplet DP in the extreme ultraviolet generating vessel180.

As illustratively shown inFIG. 1, in some embodiments, the extreme ultraviolet generating vessel180includes a droplet generator182, a droplet catcher184, an extreme ultraviolet collector186and an intermediate focus unit188. The droplet generator182is configured to provide the target droplet DP. In some embodiments, the target droplet DP is a tin-doped droplet. The droplet catcher184is configured to catch and remove the target droplet DP after being impacted by the seed laser beam SLB. The target droplet DP excited by the seed laser beam SLB will become laser-produced plasma, and the laser-produced plasma will produce the extreme ultraviolet light EUVL in different directions. The extreme ultraviolet collector186is configured to gather the extreme ultraviolet light EUVL onto the intermediate focus unit188. The intermediate focus unit188is configured to make the seed laser beam SLB converge the extreme ultraviolet light EUVL onto one optical path. The extreme ultraviolet light EUVL converged by the intermediate focus unit188can be utilized by optical components190for extreme ultraviolet lithography. As illustratively shown inFIG. 1, in some embodiments, the optical components190include at least one illuminator mirror and at least one reticle mask for forming a pattern on the wafer WF.

In some embodiments, the optical sensor130is coupled to the amplifier120and is configured for sensing an optical emission generated in the amplifier120. As illustratively shown inFIG. 1, in some embodiments, the amplifier120includes four stages of amplifier components121,122,123and124. As a demonstrational example, the optical sensor130is disposed in the amplifier component122of the amplifier120. As illustratively shown inFIG. 1, in some embodiments, the optical sensor130is able to sense the optical emission at the second stage, i.e., the amplifier component122, while the seed laser beam SLB is amplifying in the four consequent stages of the amplifier120.

In some other embodiments, the optical sensor130can be disposed at least one of the amplifier components121-124. For example, the optical sensor130can be disposed in the amplifier component121,123or124in some embodiments. Alternatively, two or more optical sensors can be disposed two of more amplifier components121-124. The optical sensor130disposed in the amplifier component122in following embodiments are given for illustrative purposes. However, the disclosure is not limited thereto. Reference is further made toFIG. 3.FIG. 3is a schematic diagram of the amplifier component122inFIG. 1, in accordance with some embodiments of the present disclosure. As illustratively shown inFIG. 1andFIG. 3, in some embodiments, the amplifier component122is located between the amplifier component121and the amplifier component123. The amplifier component122receives the seed laser beam SLB amplified by the amplifier component121. The amplifier component122is configured to further amplify the seed laser beam SLB and send the seed laser beam SLB to the amplifier component123.

As illustratively shown inFIG. 3, the amplifier component122includes a shielding210, glass tubes GT1, GT2, GT3and GT4, connection chambers CHB1, CHB2, CHB3and CHB4, a discharging unit, gain medium GM and an ultraviolet blocking cover250. The shielding210is an external surface of the amplifier component122. The glass tubes GT1, GT2, GT3and GT4are disposed in the shielding210and configured to accommodate the gain medium GM. In some embodiments, the glass tubes GT1, GT2, GT3and GT4are quartz tubes. In some embodiments, the gain medium GM is a gas mixture includes carbon dioxide, CO2, and nitrogen, N2. In some embodiments, the gas mixture accommodated inside the glass tubes GT1, GT2, GT3and GT4further includes helium, He, for stabilizing the gas mixture. Helium is not utilized as an active gain medium. The discharging unit includes a power source240and electrodes241and242disposed adjacent to the glass tubes GT1-GT4.

In some embodiments, the electrodes241are utilized as anode electrodes and the electrodes241are utilized as cathode electrodes242on each of the glass tubes GT1-GT4. The power source240provides radio-frequency signals RF. The radio-frequency signals RF are applied on the electrodes241and242disposed on opposite sides of each of the glass tubes GT1-GT4for pumping the gain medium GM. In order to keep brevity ofFIG. 3, wirings for transmitting the radio-frequency signals RF between the power source240to the electrodes241and242on the glass tube GT1is illustrated, and similar wirings for transmitting the radio-frequency signals RF to the electrodes241and242on the glass tubes GT2-GT4are not shown inFIG. 3. The radio-frequency signals RF are configured to boost an energy level of the gain medium GM in the glass tubes GT1, GT2, GT3and GT4. When the seed laser beam SLB travels through the glass tubes GT1, GT2, GT3and GT4, the seed laser beam SLB will absorb energy from the gain medium GM, such that the power of the seed laser beam SLB will be amplified.

As illustratively shown inFIG. 3, the connection chambers CHB1, CHB2, CHB3and CHB4are configured to connect the glass tubes GT1, GT2, GT3and GT4and guide the optical path of the seed laser beam SLB. As illustratively shown inFIG. 3, in some embodiments, a fluid inlet GMi is implemented at the connection chamber CHB1and a fluid outlet GMo is implemented at the connection chamber CHB4. In some embodiments, the gain medium GM is provided from a gas pipeline, not shown in figures, to the fluid inlet GMi. The gain medium GM flows from the fluid inlet GMi to the fluid outlet GMo.

In the embodiment illustratively shown inFIG. 3, the amplifier component122includes four glass tubes GT1-GT4and four connection chambers CHB1-CHB4for connecting between the glass tubes GT1-GT4. However, the number and configuration of the glass tubes and the connection chambers in the amplifier component122are given for illustrative purposes. In some other embodiments, the amplifier component122includes at least one glass tube and corresponding connection chambers. In some embodiments, the amplifier component122may include twelve glass tubes or more for further amplifying the power of the seed laser beam SLB.

As illustratively shown inFIG. 3, in some embodiments, the optical sensor130is disposed in the amplifier component122. There is at least one opening formed on the shielding210. As illustratively shown inFIG. 3, there are six openings211-216formed on different positions on the shielding210. As illustratively shown inFIG. 3, in some embodiments, an upper end of the optical sensor130is disposed inside the shielding130and a lower end of the optical sensor130penetrates the shielding210through the opening211. The optical sensor130disposed in the shielding210of the amplifier component122is able to sense an optical emission generated in the amplifier component122while the gain medium GM is discharging, and the optical sensor130will generate an optical emission signal SOES describing the optical emission. As illustratively shown inFIG. 3, the ultraviolet blocking cover250is disposed over the openings211-216on the shielding210for blocking a leakage of the seed laser beam SLB or the optical emission.

As illustratively shown inFIG. 3, in some embodiments, the optical sensor130is disposed at the opening211, which is relatively adjacent to the fluid inlet GMi and relatively away from the fluid outlet GMo. In this configuration illustratively shown inFIG. 3, the optical sensor130is able to sense the optical emission adjacent to the fluid inlet GMi, such that the optical emission signal SOES is highly related to an inlet flow rate of the gain medium GM. In some other embodiments, the optical sensor130can be adjusted to be implement at different opening212-216to sense the optical emission from different locations of the amplifier component122, and the optical emission signal SOES can reflect more information about different conditions, e.g., an outlet flow rate, of the amplifier component122. In some embodiments, the optical sensor130includes Optical Emission Spectrometry (OES) sensor head. The Optical Emission Spectrometry sensor head is able to generate the optical emission signal SOES with a sample rate about 10 samples per second to about 15 samples per second.

As illustratively shown inFIG. 1andFIG. 3, in some embodiments, an optical fiber cable132is configured for transmitting the optical emission signal SOES generated by the optical sensor130to the spectrometer140. One end of the optical fiber penetrates through the ultraviolet blocking cover250and is connected to the optical sensor130. Another end of the optical fiber cable132is connected to the spectrometer140.

As illustratively shown inFIG. 1andFIG. 3, the spectrometer140is coupled with the optical sensor130and configured to measure a spectrum of the optical emission. The processor150is coupled with the spectrometer140, and the processor150is configured to determine an operational status of the amplifier120according to the spectrum of the optical emission. Further details about how to determine the operational status of the amplifier120according to the spectrum will be explained and discussed in following paragraphs.

As illustratively shown inFIG. 1, in some embodiments, the processor150is coupled to the spectrometer140and a storage medium152. In various embodiments, the processor150is a central processing unit (CPU), an application specific integrated circuit (ASIC), a multi-cores processor, a distributed processing system, or a suitable processing unit. Various circuits or units to implement the processor150are within the contemplated scope of the present disclosure.

The storage medium152stores one or more program codes for performing some tasks on the processor150. For illustration, the storage medium152stores program codes encoded with executable instructions for performing some tasks on the processor150. The processor150is able to access the program codes stored in the storage medium152.

In some embodiments, the storage medium152is a non-transitory computer readable storage medium encoded with, i.e., storing, a set of executable instructions for performing aforesaid tasks on the processor150. In some embodiments, the non-transitory computer readable storage medium is an electronic, magnetic, optical, electromagnetic, infrared, and/or a semiconductor system (or apparatus or device). For example, the computer readable storage medium includes a semiconductor or solid-state memory, a magnetic tape, a removable computer diskette, a random access memory (RAM), a read-only memory (ROM), a rigid magnetic disk, and/or an optical disk. In one or more embodiments using optical disks, the computer readable storage medium includes a compact disk-read only memory (CD-ROM), a compact disk-read/write (CD-R/W), and/or a digital video disc (DVD).

Reference is now made toFIG. 4.FIG. 4is a flow chart of a method400suitable to be applied on the device100inFIG. 1,FIG. 2andFIG. 3, in accordance with some embodiments of the present disclosure. For ease of understanding, as an example, the method400is described below with reference toFIG. 1,FIG. 2andFIG. 3.

For illustration, the method400inFIG. 4includes operations S402-S410. In operation S402, the laser source110is configured to produce a seed laser beam SLB. In operation S404, the amplifier120is configured to amplify the power of the seed laser beam SLB. During operation S404, as illustratively shown inFIG. 3andFIG. 4, the power source240applies the radio-frequency signals RF on the electrodes241and242for pumping the gain medium GM. The seed laser beam SLB is directed through the gain medium GM. The seed laser beam SLB absorb the energy from the gain medium GM, such that the power of the seed laser beam SLB is amplified. As illustratively shown inFIG. 3andFIG. 4, in operation S406, the optical sensor130disposed in the amplifier component122senses the optical emission generated in the amplifier component122while the gain medium GM is discharging. In operation S408, the spectrometer140measures the spectrum of the optical emission. In operation S410, the processor150determines an operational status of the amplifier120according to the spectrum of the optical emission.

Reference is further made toFIG. 5, which is a schematic diagram illustrating a spectrum SP1of the optical emission measured by the spectrometer140, in accordance with some embodiments of the present disclosure. As illustratively shown inFIG. 5, in some embodiments, the spectrum SP1of the optical emission indicates intensities of the optical emission at different wavelengths. The spectrum SP1reflects the optical emission include different beam components at different wavelengths mainly ranged from about 200 nm to about 1100 nm.

In some embodiments, the processor is configured to analyze the spectrum SP1based on the waveform and a peak distribution of the spectrum SP1. As illustratively shown inFIG. 5, the spectrum SP1has four peaks P1-P4. The peak P1is located at about 315 nm corresponding to an emission band induced by carbon dioxide, CO2. The peak P2is located at about 336 nm corresponding to an emission band induced by carbon dioxide, CO2. The peak P3is located at about 357 nm corresponding to another emission band induced by carbon dioxide, CO2. The peak P4is located at about 375 nm corresponding to still another emission band induced by carbon dioxide, CO2. The four peaks P1-P4are listed for demonstration. The processor150may capture and analyze further peaks, for example, peaks from about 300 nm to about 800 nm in the spectrum SP1for more details.

In some embodiments, the spectrum SP1is a standard spectrum recorded when the device100and the amplifier120operating in a normal status. The spectrum SP1can be stored in the storage medium152for reference.

Reference is further made toFIG. 6, which is a schematic diagram illustrating another spectrum SP2of the optical emission measured by the spectrometer140, in accordance with some embodiments of the present disclosure. As illustratively shown inFIG. 6, in some embodiments, the spectrum SP2of the optical emission indicates intensities of the optical emission at different wavelengths. As illustratively shown inFIG. 6, the spectrum SP2has corresponding four peaks P1-P4. The peak P1is located at about 315 nm corresponding to an emission band induced by nitrogen, N2. The peak P2is located at about 336 nm corresponding to an emission band induced by carbon dioxide, CO2.

In some embodiments, when the spectrum SP2is measured by the spectrometer140, the processor150is configured to compare the spectrum SP2in reference with the spectrum SP1stored in the storage medium152. Because the spectrum SP2is different from the spectrum SP1regard as the standard spectrum, the processor150is able to determine that the device100or the amplifier120is currently in an abnormal status.

Compared to the spectrum SP1regarded as the standard spectrum inFIG. 5, an intensity of the peak P2of the spectrum SP2inFIG. 6is lower than an intensity of the peak P2of the spectrum SP1, and intensities of the peaks P1and P3of the spectrum SP2inFIG. 6is higher than intensities of the peak P1and P3of the spectrum SP1. Accordingly, the processor150is able to determine that the abnormal status can be related to an inlet flow rate of the gain medium GM is currently lower than a standard rate, or the abnormal status can be a ratio of the carbon dioxide, CO2in the gas mixture of the gain medium GM is lower than a standard ratio. In some embodiments, the processor150is able to analyze the abnormal status according to a difference between the spectrum SP2inFIG. 6and the spectrum SP1inFIG. 5. In some embodiments, the processor150is able to analyze a setting of the radio-frequency signals RF, which are applied on the electrodes of the glass tubes GT1-GT4inFIG. 3for pumping the gain medium GM, according to the difference between the spectrum SP2inFIG. 6and the spectrum SP1inFIG. 5.

Reference is further made toFIG. 7, which illustrates a waveform diagram of a waveform WVF of the optical emission plotted by the spectrometer140, in accordance with some embodiments of the present disclosure. InFIG. 7, the waveform WVF reflects an amplitude variation of the optical emission over time. The waveform WVF in a period P1between a time point T0and another time point T1reflects the amplitude variation of the optical emission when the device100is operating. During the period P1, the laser source110and the amplifier120is activated to work. The waveform WVF of the optical emission will have a characteristic of a glowing light. The amplitude of the waveform WVF varies up and down periodically in the period P1. It is assumed that the laser source110and the amplifier120at the time point T1, and the amplitude of the waveform WVF during a period P2returns to a low level, e.g., zero. It is assumed that the laser source110and the amplifier120restarts at a time point T2. It can be observed that the waveform WVF during a period P3starts to climb up to a high level. The waveform WVF during a period P4will resume to a normal status, similar to the period P1, with the characteristic of the glowing light.

In some embodiments, the period P3is regarded as an ignition phase of the laser source110and the amplifier120. The ignition phase can be observed in the period P3of the waveform WVF because the optical sensor130, in some embodiments, including the Optical Emission Spectrometry (OES) sensor head with the sample rate about 10 samples per second to about 15 samples per second. In some approaches, a rejected power returned from the amplifier120can be measured at an interface between the laser source110and the amplifier120, and the rejected power is measured at a sample rate about 1 sample every 12 seconds. In those approaches, it is hard to observe the ignition phase in the rejected power returned from the amplifier120to the laser source110. As illustratively shown inFIG. 7, the waveform WVF during the period P3of the optical emission plotted by the spectrometer140is able to reflect the ignition phase of the laser source110and the amplifier120. The processor150is able to analyze the ignition phase of the laser source110and the amplifier120according to the waveform WVF during the period P3.

The predetermined sequences, including the ascending numerical order and/or the descending numerical order, are given for illustrative purposes only. Various kinds of orders are within the contemplated scope of the present disclosure.

For ease of understanding, the embodiments above are given with an application of fabricating two switches. The embodiments above are able to be applied to fabricate a single switch or two more switches. For illustrative purposes, the embodiments above are described as implementing the switches. The present disclosure is not limited thereto. Various elements are able to be implemented according to the embodiments above, and thus are the contemplated scope of the present disclosure.

In this document, the term “coupled” may also be termed as “electrically coupled,” and the term “connected” may be termed as “electrically connected”. “Coupled” and “connected” may also be used to indicate that two or more elements cooperate or interact with each other.

In some embodiments, a device including a laser source, an amplifier, an optical sensor and a spectrometer is disclosed. The laser source is configured to produce a seed laser beam. The amplifier includes gain medium and a discharging unit. The discharging unit is configured to pump the gain medium for amplifying power of the seed laser beam. The optical sensor is coupled to the amplifier and configured for sensing an optical emission generated in the amplifier while the gain medium is discharging. The spectrometer is coupled with the optical sensor and configured to measure a spectrum of the optical emission.

Also disclosed is a method that includes the operation below. A seed laser beam is produced by a laser source. Power of the seed laser beam by an amplifier is amplified. An optical emission is sensed by an optical sensor disposed in the amplifier. A spectrum of the optical emission is measured. An operational status of the amplifier is determined according to the spectrum of the optical emission.

Also disclosed is a device that includes a laser source, an extreme ultraviolet generating vessel, an optical component, an optical sensor and a spectrometer. The laser source is configured to produce a seed laser beam. The seed laser beam being is directed to the extreme ultraviolet generating vessel to form laser-produced plasma. The laser-produced plasma is configured to generate an extreme ultraviolet light. The extreme ultraviolet light transmitting through the optical component is utilized to in lithographing a wafer. The optical sensor is configured for sensing an optical emission generated while the seed laser beam is amplified before entering the extreme ultraviolet generating vessel. The spectrometer is coupled with the optical sensor and configured to measure a spectrum of the optical emission.