阅读说明：本技术 一种准分子激光器绝对波长校准方法 (Absolute wavelength calibration method for excimer laser ) 是由 殷青青 刘广义 江锐 张华� 赵江山 刘海东 于 2020-04-30 设计创作，主要内容包括：本公开提供了一种准分子激光器绝对波长校准方法,包括以下步骤：在扫描区间Δλ1内进行连续式扫描；在扫描区间Δλ2内进行步进式扫描；通过连续式扫描和步进式扫描对准分子激光器绝对波长进行校准；其中,Δλ2＜＜Δλ1。本公开采用连续式扫描和步进式扫描相结合的方式,既能在波长偏移较大时进行大范围的峰值扫描,确保能够找到吸收峰位置,又能在吸收峰附近小范围内进行精确扫描,提高了绝对波长校准的精度。(The present disclosure provides an excimer laser absolute wavelength calibration method, which includes the following steps: carrying out continuous scanning in a scanning interval delta lambda 1; step-by-step scanning is carried out in a scanning interval delta lambda 2; aligning the absolute wavelength of the molecular laser by continuous scanning and step-by-step scanning; wherein Δ λ 2 < Δ λ 1. The method adopts a mode of combining continuous scanning and step-by-step scanning, can perform large-range peak value scanning when the wavelength is greatly deviated, ensures that the position of an absorption peak can be found, can perform accurate scanning in a small range near the absorption peak, and improves the accuracy of absolute wavelength calibration.)

1. An excimer laser absolute wavelength calibration method is characterized by comprising the following steps:

carrying out continuous scanning in a scanning interval delta lambda 1;

step-by-step scanning is carried out in a scanning interval delta lambda 2;

aligning the absolute wavelength of the molecular laser by continuous scanning and step-by-step scanning; wherein Δ λ 2 < Δ λ 1.

2. The method of claim 1, wherein the continuously scanning over a scan interval Δ λ 1 comprises: and taking the theoretical peak wavelength as a center, and continuously scanning in a scanning interval delta lambda 1 to obtain first scanning wavelength data.

3. The method of claim 2, further comprising, after the continuous scanning during the scanning interval Δ λ 1 and before the step-wise scanning during the scanning interval Δ λ 2: a coarse peak wavelength λ p1 is determined using the first scan wavelength data.

4. The method of claim 3, wherein the step-wise scanning over a scan interval Δ λ 2 comprises: and taking the lambdap 1 as a center, and performing step scanning in a scanning interval delta lambada 2 to acquire second scanning wavelength data.

5. The method of claim 4, wherein after the step-scanning within the scanning interval Δ λ 2 and before the calibration of the absolute wavelength of the excimer laser by the continuous scanning and the step-scanning, further comprising: the second scan wavelength data is used to determine the exact peak wavelength λ p 2.

6. The method of excimer laser absolute wavelength calibration according to claim 3, wherein determining a coarse peak wavelength λ p1 using the first scan wavelength data comprises: and carrying out integral peak searching algorithm processing on the first scanning wavelength data to obtain the rough peak wavelength lambdap 1.

7. The method of excimer laser absolute wavelength calibration of claim 5, wherein determining a precise peak wavelength λ p2 using the second scanned wavelength data comprises: and carrying out single-interval peak searching algorithm processing on the second scanning wavelength data to obtain a peak wavelength average value serving as the accurate peak wavelength lambdap 2.

8. The method of claim 1, wherein the wavelength tuning module is continuously rotated at a speed during the continuous scan.

9. The method of claim 1, wherein the wavelength tuning module is rotated stepwise at a minimum speed during the step scan.

10. The method of claim 1, wherein multiple reciprocal scans or a single scan is used during the step scan.

Technical Field

The disclosure relates to the technical field of laser, in particular to a high-precision excimer laser absolute wavelength calibration method.

Background

The accurate control of the wavelength of an excimer laser is one of important technologies in the preparation of an integrated circuit chip, and the central wavelength is a key parameter of the excimer laser, which can influence the imaging quality of a subsequent illumination imaging system and a final photoetching resolution node. In the long-time use process of the excimer laser, the central wavelength can have a drift phenomenon due to the influence of external factors such as temperature, mechanical stress and the like. Absolute wavelength calibration is an important technical approach to improve wavelength accuracy and reduce the influence of external factors on the center wavelength.

Absolute wavelength calibration means providing one or more known wavelengths with high stability and high precision as absolute wavelengths for calibrating the error of a wavelength measurement control system, and the prior art mentions calibration using an elemental hollow cathode lamp having one or more absorption lines in wavelength calibration of a KrF laser of 248nm and an ArF laser of 193nm, for example, the ArF laser performs wavelength calibration using the absorption line 193.2243nm or 193.4369nm of a Pt hollow cathode lamp, while the KrF laser performs calibration using the 248.3271nm or 248.4187nm of an Fe hollow cathode lamp.

However, due to the comprehensive influence of the factors of the laser, such as frequency, energy stability, response of the detector, stability of the element lamp, and the like, the position of the reference center wavelength is severely jittered, so that the absolute wavelength calibration accuracy is not high. In addition, the existing single fast continuous scanning speed is fast but the precision can not meet the requirement, and the single step interval scanning precision is high but the speed is slow and the interval is too small, so that the scanning can not cause the absorption peak.

Disclosure of Invention

Technical problem to be solved

In view of the above problems, it is a primary object of the present disclosure to provide a high-precision excimer laser absolute wavelength calibration method so as to solve at least one of the above problems.

(II) technical scheme

In order to achieve the above object, as one aspect of the present disclosure, there is provided an excimer laser absolute wavelength calibration method, comprising the steps of:

carrying out continuous scanning in a scanning interval delta lambda 1;

step-by-step scanning is carried out in a scanning interval delta lambda 2;

aligning the absolute wavelength of the molecular laser by continuous scanning and step-by-step scanning; wherein Δ λ 2 < Δ λ 1.

Further, the performing the continuous scanning within the scanning interval Δ λ 1 includes: and taking the theoretical peak wavelength as a center, and continuously scanning in a scanning interval delta lambda 1 to obtain first scanning wavelength data.

Further, after the continuous scanning is performed in the scanning interval Δ λ 1 and before the step-by-step scanning is performed in the scanning interval Δ λ 2, the method further includes: a coarse peak wavelength λ p1 is determined using the first scan wavelength data.

Further, the step-by-step scanning within the scanning interval Δ λ 2 includes: and taking the lambdap 1 as a center, and performing step scanning in a scanning interval delta lambada 2 to acquire second scanning wavelength data.

Further, after the step scanning is performed within the scanning interval Δ λ 2 and before the calibration is performed on the absolute wavelength of the molecular laser by the continuous scanning and the step scanning, the method further includes: the second scan wavelength data is used to determine the exact peak wavelength λ p 2.

Further, determining a coarse peak wavelength λ p1 using the first scan wavelength data comprises: and carrying out integral peak searching algorithm processing on the first scanning wavelength data to obtain the rough peak wavelength lambdap 1.

Further, determining a precise peak wavelength λ p2 using the second scan wavelength data comprises: and carrying out single-interval peak searching algorithm processing on the second scanning wavelength data to obtain a peak wavelength average value serving as the accurate peak wavelength lambdap 2.

Further, the wavelength adjusting module continuously rotates at a certain speed in the continuous scanning process.

Further, the wavelength adjustment module is rotated stepwise at a minimum speed during the step-by-step scanning.

Further, multiple reciprocating scans or a single scan may be used in the step-by-step scanning process.

(III) advantageous effects

According to the technical scheme, the absolute wavelength calibration method of the high-precision excimer laser disclosed by the invention has at least one of the following beneficial effects:

(1) the method adopts a mode of combining continuous scanning and step-by-step scanning, can perform large-range peak value scanning when the wavelength is greatly deviated, ensures that the position of an absorption peak can be found, can perform accurate scanning in a small range near the absorption peak, and improves the accuracy of absolute wavelength calibration.

(2) According to the method, aiming at the characteristics that the scanning data obtained by different scanning modes are different, the effective peak value is screened by respectively utilizing the integral peak searching algorithm and the single-interval peak searching algorithm, and the influence of an interference peak value on an absolute wavelength calibration result is avoided.

(3) The present disclosure uses multiple scanning cycles in the step-by-step peak scanning process, which is beneficial to further improving the accuracy of absolute wavelength calibration.

Drawings

Fig. 1 is an overall flowchart of a high-precision absolute wavelength calibration method according to an embodiment of the present invention.

Fig. 2 is a flowchart of a specific implementation method of the high-precision absolute wavelength calibration method according to the embodiment of the present invention.

FIG. 3 is a continuous scan local absorption peak diagram according to an embodiment of the present invention.

FIG. 4 is a step scan local absorption peak diagram according to an embodiment of the present invention.

Detailed Description

For the purpose of promoting a better understanding of the objects, aspects and advantages of the present disclosure, reference is made to the following detailed description taken in conjunction with the accompanying drawings.

The invention provides an excimer laser absolute wavelength calibration method, which comprises the following steps:

carrying out continuous scanning in a scanning interval delta lambda 1;

step-by-step scanning is carried out in a scanning interval delta lambda 2;

aligning the absolute wavelength of the molecular laser by continuous scanning and step-by-step scanning; wherein Δ λ 2 < Δ λ 1.

Compared with the existing single continuous scanning and single step scanning, the method for calibrating the absolute wavelength of the high-precision excimer laser can improve the speed and precision of absolute wavelength calibration.

Specifically, the performing the continuous scanning within the scanning interval Δ λ 1 includes: and taking the theoretical peak wavelength as a center, and continuously scanning in a scanning interval delta lambda 1 to obtain first scanning wavelength data.

Further, the method for calibrating the absolute wavelength of the excimer laser further includes, after the continuous scanning is performed in the scanning interval Δ λ 1 and before the step-by-step scanning is performed in the scanning interval a λ 2: a coarse peak wavelength λ p1 is determined using the first scan wavelength data. On the basis, the step scanning in the scanning interval Δ λ 2 includes: and taking the lambdap 1 as a center, and performing step scanning in a scanning interval delta lambada 2 to acquire second scanning wavelength data.

Further, the method for calibrating the absolute wavelength of the excimer laser, after the step-scanning is performed within the scanning interval Δ λ 2 and before the calibration is performed by aligning the absolute wavelength of the excimer laser through the continuous scanning and the step-scanning, further includes: the second scan wavelength data is used to determine the exact peak wavelength λ p 2.

Determining a coarse peak wavelength λ p1 using the first scan wavelength data comprises: and carrying out integral peak searching algorithm processing on the first scanning wavelength data to obtain the rough peak wavelength lambdap 1. Determining a precise peak wavelength λ p2 using the second scan wavelength data comprises: and carrying out single-interval peak searching algorithm processing on the second scanning wavelength data to obtain a peak wavelength average value serving as the accurate peak wavelength lambdap 2. Therefore, according to the characteristics that scanning data obtained by different scanning modes are different, the method and the device screen effective peaks respectively by using the integral peak searching algorithm and the single-interval peak searching algorithm, and avoid the influence of interference peaks on absolute wavelength calibration results.

In summary, the method for calibrating the absolute wavelength of the high-precision excimer laser mainly comprises a continuous scanning peak value, an integral peak searching algorithm process, a step scanning peak value and an interval peak searching algorithm process. The method comprises the steps of scanning a peak value in a continuous mode, carrying out interval peak searching algorithm processing on the peak value in a small range, carrying out interval peak searching algorithm processing on the peak value in a step mode, and carrying out continuous scanning peak value and integral peak searching algorithm processing on the peak value in the large range.

Embodiments of the present disclosure are described in detail below with reference to fig. 1-4.

In the excimer laser absolute wavelength calibration technology, the position of a reference center wavelength is a main factor influencing the calibration precision, and in the absolute wavelength calibration process, in order to reduce wavelength fluctuation caused by the performance of a laser, the disclosure provides a high-precision excimer laser absolute wavelength calibration method. As shown in fig. 1, firstly, a continuous scanning peak value is used to perform a rapid continuous wavelength scanning in a large range, and then the obtained scanning data is processed by an overall peak searching algorithm to obtain a coarse peak wavelength, the continuous scanning has the advantages of a large scanning range and a high speed, but in the continuous scanning process, the wavelength jitter may be large due to insufficient response speed of an optical device or an electronic device, so that after the coarse peak wavelength is obtained, fine scanning is performed in a small range by a step-wise peak scanning mode, and then the scanning data is processed by an interval peak searching algorithm to obtain a precise peak wavelength. Therefore, the peak wavelength can be obtained quickly and accurately by a mode of combining continuous scanning and step scanning.

More specifically, as shown in fig. 2, the method for calibrating the absolute wavelength of the high-precision excimer laser comprises the following steps:

s1: taking the theoretical peak wavelength as the center, and rapidly and continuously scanning within a range delta lambda 1, namely, rapidly and continuously scanning the laser output by the high-precision excimer laser within the range delta lambda 1 by the wavelength measuring device; the continuous scanning means that in the peak value scanning process, a wavelength adjusting module (such as a motor) continuously rotates at a certain speed, and scanning wavelength data are recorded in real time; after the scanning interval delta lambda 1 is set, the wavelength scanning interval does not exceed the working range of the laser;

s2: carrying out integral peak searching algorithm processing on data stored in continuous scanning to obtain a rough peak value wavelength lambda p1, wherein the integral peak searching algorithm processing is to carry out peak searching processing on the data stored in the continuous scanning process at the same time, and screening out an effective peak value, namely lambda p1, through effective peak value judgment conditions such as absorption peak intensity, half-height width and the like;

s3: taking λ p1 as a center, performing step scanning within a range Δ λ 2, that is, performing step scanning on the laser output by the high-precision excimer laser within the range Δ λ 2 by the wavelength measuring device; specifically, a plurality of reciprocating scanning modes or a single scanning mode can be adopted, wherein the step scanning mode refers to that in the peak value scanning process, the wavelength adjusting module (such as a motor) performs step rotation at a minimum speed, scanning wavelength data is recorded once per step, λ p1 is a rough peak value wavelength obtained by continuous scanning, a scanning interval Δ λ 2 < Δ λ 1, Δ λ 1 is, for example, a certain set value to the full scanning range of the laser wavelength, and Δ λ 2 is, for example, 1% -2% of Δ λ 1, but is not limited thereto; preferably, in order to further improve the scanning accuracy, the step-by-step scanning in the cell can adopt a mode of reciprocating multiple scanning;

meanwhile, the step scanning has more sampling points in the scanning interval and high signal-to-noise ratio, and the step scanning local absorption peak diagram shown in fig. 4 is helpful for improving the accuracy of absolute wavelength calibration; the continuous scanning signal has high noise and low signal-to-noise ratio, and the continuous scanning local absorption peak map is shown in fig. 3, wherein the signal-to-noise ratio (SNR) is equal to the maximum value minus the minimum value of the scanning interval signal divided by the standard deviation of the signal noise.

S4: and carrying out single-interval peak searching algorithm processing on the scanning data to obtain the average value lambda p2 of all peak wavelengths, wherein the single-interval peak searching algorithm is to search for an effective peak within the range of each scanning interval, if the scanning is repeated for multiple times, carrying out interval division according to the scanning start and stop wavelengths, then carrying out effective peak screening from each interval, and carrying out absolute wavelength calibration by taking the average value of all the peaks as the final peak wavelength.

It should be noted that the wavelength measuring device of the present invention may be any existing wavelength measuring device, and is not limited to a specific wavelength measuring device, and is used for scanning the laser output by the high-precision excimer laser to obtain the wavelength of the laser. The wavelength adjusting module may also be any existing wavelength adjusting module, and is configured to adjust the wavelength of the laser output by the high-precision excimer laser, so that the wavelength of the laser output by the laser approaches an absolute wavelength, which is not limited to a specific wavelength adjusting module.

In summary, in the present embodiment, a combination of continuous scanning and step-by-step scanning is adopted, so that not only can peak scanning be performed in a large range when the wavelength shift is large, and it is ensured that the position of the absorption peak can be found, but also accurate scanning can be performed in a small range near the absorption peak, and the accuracy of absolute wavelength calibration is improved. In addition, effective peak values are screened according to the characteristics that the scanning data obtained by different scanning modes are different through the integral peak searching algorithm and the single-interval peak searching algorithm, and the influence of interference peak values on absolute wavelength calibration results is avoided.

Further, the above definitions of the various elements and methods are not limited to the various specific structures, shapes or arrangements of parts mentioned in the examples, which may be easily modified or substituted by those of ordinary skill in the art.

It should be noted that directional terms, such as "upper", "lower", "front", "rear", "left", "right", and the like, mentioned in the embodiments are only directions referring to the drawings, and are not intended to limit the scope of the present disclosure. Throughout the drawings, like elements are represented by like or similar reference numerals. Conventional structures or constructions will be omitted when they may obscure the understanding of the present disclosure. And the shapes and sizes of the respective components in the drawings do not reflect actual sizes and proportions, but merely illustrate the contents of the embodiments of the present disclosure. Furthermore, in the claims, any reference signs placed between parentheses shall not be construed as limiting the claim.

Furthermore, the word "comprising" or "comprises" does not exclude the presence of elements or steps other than those listed in a claim. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements.

The use of ordinal numbers such as "first," "second," "third," etc., in the specification and claims to modify a corresponding element does not by itself connote any ordinal number of the element or any ordering of one element from another or the order of manufacture, and the use of the ordinal numbers is only used to distinguish one element having a certain name from another element having a same name.

Similarly, it should be appreciated that in the foregoing description of exemplary embodiments of the disclosure, various features of the disclosure are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of one or more of the various disclosed aspects. However, the disclosed method should not be interpreted as reflecting an intention that: that is, the claimed disclosure requires more features than are expressly recited in each claim. Rather, as the following claims reflect, disclosed aspects lie in less than all features of a single foregoing disclosed embodiment. Thus, the claims following the detailed description are hereby expressly incorporated into this detailed description, with each claim standing on its own as a separate embodiment of this disclosure.

The above-mentioned embodiments are intended to illustrate the objects, aspects and advantages of the present disclosure in further detail, and it should be understood that the above-mentioned embodiments are only illustrative of the present disclosure and are not intended to limit the present disclosure, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present disclosure should be included in the scope of the present disclosure.