A laser annealing method and system
By annealing the wafer with laser beams of different wavelengths and adjusting the laser module power based on reflectivity ratio and temperature feedback, the problem of temperature non-uniformity inside the wafer was solved, achieving the ±1 degree Celsius temperature uniformity required in high-end integrated circuit manufacturing.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- BEIJING U PRECISION TECH
- Filing Date
- 2022-09-08
- Publication Date
- 2026-05-29
AI Technical Summary
The problem of uneven annealing temperature inside wafers in existing technologies is particularly difficult to achieve in high-end integrated circuit manufacturing, where it is challenging to meet the temperature uniformity requirement of ±1 degree Celsius.
The wafer is annealed using first and second laser beams with different wavelengths. By measuring the reflectivity ratio and annealing temperature, the power of the laser module is adjusted to stabilize the annealing temperature of the wafer, and the temperature uniformity is improved by utilizing the complementarity of reflectivity.
It improves the uniformity of wafer annealing temperature, reduces patterning effects, and achieves higher temperature stability and uniformity.
Smart Images
Figure CN116230509B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the technical field of integrated circuit manufacturing, and more specifically, to a laser annealing method and system. Background Technology
[0002] The uneven annealing temperature inside the wafer caused by patterning effects has always been a major challenge in the field of laser annealing. With the development of integrated circuits, the requirements for annealing temperature uniformity are becoming increasingly stringent. High-end integrated circuits even require temperature uniformity of ±1 degree Celsius across the entire wafer. To address this, the industry has proposed using mid-infrared laser annealing with wavelengths far exceeding the wafer film thickness to reduce the uneven annealing temperature caused by thin film interference—one of the patterning effects. However, this is far from sufficient, as the temperature variation within the wafer is still tens of degrees Celsius, and the annealing temperature uniformity remains poor. Summary of the Invention
[0003] The first objective of this invention is to provide a laser annealing method to solve the technical problem of poor uniformity of annealing temperature inside wafers in the prior art.
[0004] The laser annealing method provided by this invention includes the following steps:
[0005] A first laser module is used to emit a first laser beam with a first wavelength onto the wafer, and a second laser module is used to emit a second laser beam with a second wavelength onto the wafer, wherein the second wavelength is different from the first wavelength;
[0006] The reflectivity of the wafer to laser beams of the second wavelength and the first wavelength is measured, and the reflectivity ratio is obtained.
[0007] Measure the annealing temperature of the wafer;
[0008] Based on the measured annealing temperature and the target annealing temperature, the target total power is determined, and based on the reflectivity ratio and the target total power, the power of the first laser module and the second laser module is adjusted to stabilize the annealing temperature of the wafer at the target annealing temperature.
[0009] Furthermore, in the step of adjusting the power of the first laser module and the second laser module according to the reflectivity ratio and the target total power, the power of the first laser module and the second laser module are respectively adjusted as follows:
[0010]
[0011] Wherein, P is the target total power, P1 is the target power of the first laser module, and P2 is the target power of the second laser module; R is the reflectivity ratio, R1 is the reflectivity of the wafer to the laser beam of the first wavelength, and R2 is the reflectivity of the wafer to the laser beam of the second wavelength.
[0012] Furthermore, the first laser beam and the second laser beam converge into line spots on the surface of the wafer, and the two line spots are parallel and overlap along the width direction.
[0013] Furthermore, the laser annealing method further includes: acquiring the position and speed information of the wafer, and adjusting the movement speed of the wafer according to the position and speed information, so that the dwell time of the first laser beam and the second laser beam on the wafer is both between 100μs and 1000μs.
[0014] Furthermore, when measuring the reflectivity of the wafer to laser beams of the second wavelength and the first wavelength, an independent light source is used for measurement. The spectrum of the measurement beam emitted by the independent light source includes the first wavelength and the second wavelength, and all other parameters of the measurement beam emitted by the independent light source are the same except for the wavelength.
[0015] Furthermore, the wavelength of the measuring beam used to measure the annealing temperature of the wafer is different from both the first wavelength and the second wavelength.
[0016] Furthermore, before annealing the wafer using the first laser beam and the second laser beam, the wafer is uniformly heated to the base temperature.
[0017] Furthermore, the reflectivity of the wafer to the laser beam of the first wavelength and the laser beam of the second wavelength is measured at a first frequency, the annealing temperature of the wafer is measured at a second frequency, and the power of the first laser module and the second laser module is adjusted at a third frequency. The first frequency, the second frequency and the third frequency are all positively correlated with the ratio of the scanning speed and the minimum period of pattern change.
[0018] The laser annealing method provided by this invention can produce the following beneficial effects:
[0019] The laser annealing method provided by this invention uses a first laser beam and a second laser beam with different wavelengths to anneal a wafer. After determining the target total power based on the target annealing temperature and the measured annealing temperature, the power of the first laser module and the second laser module is adjusted according to the reflectivity of the wafer to the first and second wavelength laser beams and the target total power, thereby stabilizing the annealing temperature of the wafer at the target annealing temperature. The reflectivity of the wafer to the two wavelength laser beams is complementary to a certain extent, which can improve the patterning effect and thus improve the uniformity of the annealing temperature of the wafer. Adjusting the power of the first and second laser modules based on the measured annealing temperature and reflectivity makes the power used for heating by the two laser modules more similar. By correcting the unevenness of the annealing temperature of the wafer through feedback on the annealing temperature and reflectivity, the uniformity of the annealing temperature of the wafer can be further improved.
[0020] The second objective of this invention is to provide a laser annealing system to solve the technical problem of poor uniformity of annealing temperature inside wafers in the prior art.
[0021] The laser annealing system provided by this invention is used to implement the above-described laser annealing method, the laser annealing system comprising:
[0022] The motion module is used to drive the movement of the wafer;
[0023] The first laser module is used to emit a first laser beam with a wavelength of a first wavelength toward the wafer;
[0024] The second laser module is used to emit a second laser beam with a second wavelength onto the wafer, wherein the second wavelength is different from the first wavelength.
[0025] Temperature measurement module, used to measure the annealing temperature of wafers;
[0026] A reflectivity measurement module is used to measure the reflectivity of the wafer to a laser beam of the second wavelength and a laser beam of the first wavelength, and to obtain the reflectivity ratio; and
[0027] The feedback control module is used to determine the target total power based on the measured annealing temperature and the target annealing temperature, and to adjust the power of the first laser module and the second laser module based on the reflectivity ratio and the target total power, so as to stabilize the annealing temperature of the wafer at the target annealing temperature.
[0028] Furthermore, the laser annealing system also includes: a heating module, a motion stage installed on the motion module, used to support the wafer and to uniformly heat the wafer to a base temperature before annealing it using the first laser beam and the second laser beam.
[0029] Furthermore, the reflectivity measurement module includes a laser emitting component and a laser detection component. The spectrum of the measurement beam emitted by the laser emitting component includes the first wavelength and the second wavelength. The laser emitting component includes a laser-driven plasma source, and the laser detection component includes an integrating sphere detector.
[0030] The laser annealing system provided by this invention can realize the above-mentioned laser annealing method, and therefore can achieve all the beneficial effects of the above-mentioned laser annealing method, which will not be repeated here. Attached Figure Description
[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.
[0032] Figure 1 This is a schematic diagram of the laser annealing system provided in an embodiment of the present invention;
[0033] Figure 2 This is a schematic flowchart of the laser annealing method provided in an embodiment of the present invention.
[0034] Explanation of reference numerals in the attached figures:
[0035] 100-Motion module; 200-Heating module; 300-First laser module; 400-Second laser module; 510-Laser emitting component; 520-Laser detection component; 600-Temperature measurement module; 610-Dichroic beam splitter; 700-Feedback control module; 800-Host computer;
[0036] 900-Wafer. Detailed Implementation
[0037] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
[0038] This embodiment provides a laser annealing method, such as Figure 2 As shown, the method includes the following steps:
[0039] S200, a first laser module 300 emits a first laser beam with a first wavelength to the wafer 900, and a second laser module 400 emits a second laser beam with a second wavelength to the wafer 900, the second wavelength being different from the first wavelength.
[0040] Specifically, the first laser beam can be incident on the wafer at approximately Brewster angle 90°, with a polarization direction ( Figure 1 The direction indicated by the middle arrow ab) is approximately within the incident plane. The first wavelength can be in the mid-infrared band, such as the 10.6μm wavelength generated by a CO2 laser. The first laser beam converges into a line spot on the wafer surface, with the length of the spot approximately within the incident plane, typically 2–100 mm in length and 20 μm–2000 μm in width. The second laser beam is incident at 90° on the wafer, and the incident angle can be any spatially permissible angle, such as Brewster's angle or perpendicular incident (e.g., ...). Figure 1 As shown), polarization direction ( Figure 1 The direction indicated by the middle arrow (cd) can deviate from the incident plane, but the optimal direction is approximately within the incident plane. The second wavelength can be in the ultraviolet to infrared band, such as wavelengths like 350nm, 532nm, 650nm, 808nm, 880nm, 940nm, 986nm, and 1064nm.
[0041] S300, measure the reflectivity of wafer 900 to laser beams of the second and first wavelengths, and obtain the reflectivity ratio. If R is the reflectivity ratio, R1 is the reflectivity of wafer 900 to the first wavelength laser beam, and R2 is the reflectivity of wafer 900 to the second wavelength laser beam, then...
[0042] S400, measuring the annealing temperature of wafer 900. Preferably, the temperature signal is collected directly above wafer 900 during measurement, as the signal is stronger there, resulting in a more accurate temperature value. It should be noted that since wafer 900 moves with the workpiece stage, the measurement position also changes with the position of wafer 900.
[0043] S500 determines the target total power based on the measured annealing temperature and the target annealing temperature, and adjusts the power of the first laser module 300 and the second laser module 400 according to the reflectivity ratio and the target total power to stabilize the annealing temperature of the wafer 900 at the target annealing temperature.
[0044] The laser annealing method provided in this embodiment uses a first laser beam and a second laser beam with different wavelengths to anneal a wafer 900. After determining the target total power based on the target annealing temperature and the measured annealing temperature, the power of the first laser module 300 and the second laser module 400 is adjusted according to the reflectivity of the wafer 900 to the first and second wavelength laser beams and the target total power, thereby stabilizing the annealing temperature of the wafer 900 at the target annealing temperature. The reflectivity of the wafer 900 to the two wavelength laser beams is complementary to a certain extent, which can improve the patterning effect and thus improve the uniformity of the annealing temperature of the wafer 900. Adjusting the power of the first laser module 300 and the second laser module 400 based on the measured annealing temperature and reflectivity corrects the unevenness of the annealing temperature of the wafer 900 through feedback of the annealing temperature and reflectivity, thereby further improving the uniformity of the annealing temperature of the wafer.
[0045] Specifically, in this embodiment, in step S500, the power of the first laser module 300 and the second laser module 400 is adjusted according to the reflectivity ratio and the target total power, and the power of the first laser module 300 and the second laser module 400 is adjusted as follows:
[0046]
[0047] Where P is the target total power, P1 is the target power of the first laser module 300, and P2 is the target power of the second laser module 400.
[0048] Thus, the greater the reflectivity of the wafer 900 to the laser beam, the greater the power of the corresponding laser module, resulting in more similar power for the two laser modules to heat the wafer, and more uniform heating of the wafer 900 by the two laser modules.
[0049] Specifically, in this embodiment, the first laser beam and the second laser beam converge into line spots on the surface of wafer 900, and the two line spots are parallel and overlap along the width direction.
[0050] Specifically, in this embodiment, the laser annealing method further includes: S600, acquiring the position and velocity information of the wafer 900, and adjusting the movement speed of the wafer 900 according to the position and velocity information, so that the dwell time of the first laser beam and the second laser beam on the wafer 900 is both between 100μs and 1000μs. The dwell time is the ratio of the spot width to the scanning speed of the stage.
[0051] More specifically, during the scanning process, the position, speed, and acceleration information of the motion stage can be transmitted to the host computer 800, thereby controlling the movement of the motion module 100. This ensures that the movement speed of the motion module 100 during annealing effectively keeps the dwell time of both the first and second laser beams on the wafer 900 between 100μs and 1000μs. This dwell time is based on mid-infrared laser annealing and is the optimal dwell time required by current and future integrated circuit manufacturing processes.
[0052] Specifically, in this embodiment, when measuring the reflectivity of wafer 900 to laser beams of the second and first wavelengths, an independent light source is used for measurement. The spectrum of the measurement beam emitted by the independent light source includes both the first and second wavelengths, and all parameters of the measurement beam emitted by the independent light source are the same except for the wavelength. The first and second laser beams have different parameters such as incident angle, polarization, and wavefront form, and are easily affected by the wafer pattern. Therefore, measuring the reflectivity ratio using the reflected or scattered light from both beams has low accuracy. This embodiment uses an independent light source, ensuring that the two measurement beams used to measure the reflectivity ratio are approximately the same except for the wavelength. Therefore, this embodiment can significantly improve the measurement accuracy of reflectivity and the reflectivity ratio. It should be noted that although the incident angle of the independent light source is different from that of the annealing beam, there is a definite conversion relationship between the reflectivity at different incident angles, which can be achieved through calibration or conversion.
[0053] Specifically, in this embodiment, the wavelength of the measuring beam used to measure the annealing temperature of wafer 900 is different from both the first and second wavelengths. This effectively avoids interference from the thermal radiation signal generated after wafer 900 is heated by the first and second laser beams, thereby improving the accuracy of the annealing temperature measurement.
[0054] Specifically, in this embodiment, the laser annealing method further includes: S100, uniformly heating the wafer 900 to a base temperature before annealing the wafer 900 using the first laser beam and the second laser beam. By heating the wafer 900 to the base temperature, both the annealing efficiency and the power consumption of laser annealing can be improved, thereby reducing power consumption.
[0055] Specifically, in this embodiment, the reflectivity of the wafer 900 to a laser beam of a first wavelength and a laser beam of a second wavelength is measured at a first frequency; the annealing temperature of the wafer 900 is measured at a second frequency; and the power of the first laser module 300 and the second laser module 400 is adjusted at a third frequency. The first, second, and third frequencies are all positively correlated with the ratio of the scanning speed to the minimum period of pattern change. More specifically, the shorter the minimum period of pattern change and the faster the scanning speed, the higher the aforementioned frequencies.
[0056] This embodiment also provides a laser annealing system for implementing the above-described laser annealing method, such as... Figure 1 As shown, the laser annealing system includes:
[0057] Motion module 100 is used to drive the movement of wafer 900;
[0058] The first laser module 300 is used to emit a first laser beam with a wavelength of a first wavelength toward the wafer 900;
[0059] The second laser module 400 is used to emit a second laser beam with a second wavelength to the wafer 900, wherein the second wavelength is different from the first wavelength.
[0060] Temperature measurement module 600 is used to measure the annealing temperature of wafer 900;
[0061] A reflectivity measurement module is used to measure the reflectivity of wafer 900 against a second wavelength laser beam and a first wavelength laser beam, and to obtain the reflectivity ratio; and
[0062] The feedback control module 700 is used to determine the target total power based on the measured annealing temperature and the target annealing temperature, and to adjust the power of the first laser module 300 and the second laser module 400 based on the reflectivity ratio and the target total power, so as to stabilize the annealing temperature of the wafer 900 at the target annealing temperature.
[0063] In the above configuration, the motion stage can perform at least two-dimensional translational motion in the horizontal plane. The motion stage drives the wafer 900 to move. Apart from the wafer 900 and the motion stage, the spatial positions of other components and modules remain constant. The spatial positions of the first laser beam and the second laser beam also remain constant. Thus, as the motion stage moves, the first laser beam and the second laser beam complete the scanning annealing of the entire wafer 900.
[0064] In the above configuration, the thermal radiation signal is converted into a temperature signal within the temperature measurement module 600 and transmitted to the feedback control module 700 and the host computer 800. The temperature measurement module 600 can measure the average temperature of the annealing location, for example, using an infrared thermometer; it can also measure the distribution of the annealing location, for example, using an infrared thermal imager; if the annealing temperature exceeds a certain threshold, such as 900℃, a regular visible light camera or a visible-near-infrared camera can also be used.
[0065] In the above configuration, the measured annealing temperature and reflectivity signals are transmitted to the feedback control module 700 and the host computer 800 for feedback control. The feedback control module 700 uses the annealing temperature issued by the host computer 800 as the target annealing temperature and adjusts the power of the two laser modules based on the measurement results of the temperature measurement module 600.
[0066] Specifically, in this embodiment, the laser annealing system further includes: a heating module 200, a motion stage mounted on the motion module 100, used to support the wafer 900 and to uniformly heat the wafer 900 to a base temperature before annealing it using the first and second laser beams. In this configuration, during use, the wafer 900 is fixed to the heating module 200, which can be done through mechanical clamping or vacuum adsorption, etc.; the heating module 200 is mounted on the motion stage, and the heating module 200 is used to uniformly heat the wafer 900 from room temperature to the base temperature. Except for the wafer 900, the heating module 200, and the motion stage, the spatial positions of other components and modules remain constant, as do the spatial positions of the first and second laser beams.
[0067] Specifically, in this embodiment, the reflectivity measurement module includes a laser emitting component 510 and a laser detection component 520. The measurement beam emitted by the laser emitting component 510 has a spectrum including a first wavelength and a second wavelength. The laser emitting component 510 includes a laser-driven plasma source, and the laser detection component 520 includes an integrating sphere detector. In this configuration, the measurement beam emitted by the laser emitting component 510 has a spectrum including both the first and second wavelengths, requiring fewer lasers. The laser-driven plasma source has a wide spectrum and emits a wide wavelength range, meeting the requirements. The laser detection component 520 detects the reflected and scattered light from the two wavelength laser beams on the wafer 900, while the integrating sphere detector has a wide coverage area, capable of omnidirectionally covering both emitted and scattered light.
[0068] Specifically, in this embodiment, as Figure 1 As shown, when measuring the annealing temperature, a dichroic beam splitter 610 is also provided between the temperature measurement module 600 and the wafer 900 to filter the light beam and change the direction of light propagation, thereby making it easier to arrange the components.
[0069] Finally, it should be noted that in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.
[0070] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to the embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims
1. A laser annealing method, characterized in that, Includes the following steps: A first laser module (300) emits a first laser beam with a first wavelength to the wafer (900), and a second laser module (400) emits a second laser beam with a second wavelength to the wafer (900), wherein the second wavelength is different from the first wavelength; The reflectivity of the wafer (900) to laser beams of the second wavelength and the first wavelength is measured, and the reflectivity ratio is obtained; Measure the annealing temperature of the wafer (900); Based on the measured annealing temperature and the target annealing temperature, the target total power is determined, and based on the reflectivity ratio and the target total power, the power of the first laser module (300) and the second laser module (400) is adjusted so that the annealing temperature of the wafer (900) is stabilized at the target annealing temperature; Based on the reflectivity ratio and the target total power, the sum of the powers of the first laser module (300) and the second laser module (400) is the target total power. The powers of the first laser module (300) and the second laser module (400) are adjusted as follows: Wherein, P is the target total power, P1 is the target power of the first laser module (300), and P2 is the target power of the second laser module (400); R is the reflectivity ratio, R1 is the reflectivity of the wafer (900) to the laser beam of the first wavelength, and R2 is the reflectivity of the wafer (900) to the laser beam of the second wavelength.
2. The laser annealing method according to claim 1, characterized in that, The first laser beam and the second laser beam converge into line spots on the surface of the wafer (900), and the two line spots are parallel and overlap along the width direction.
3. The laser annealing method according to claim 1, characterized in that, The laser annealing method further includes: The position and velocity information of the wafer (900) are acquired, and the movement speed of the wafer (900) is adjusted according to the position and velocity information so that the dwell time of the first laser beam and the second laser beam on the wafer (900) is between 100μs and 1000μs.
4. The laser annealing method according to claim 1, characterized in that, When measuring the reflectivity of the wafer (900) to laser beams of the second wavelength and the first wavelength, an independent light source is used for measurement. The spectrum of the measurement beam emitted by the independent light source includes the first wavelength and the second wavelength, and all other parameters of the measurement beam emitted by the independent light source are the same except for the wavelength.
5. The laser annealing method according to claim 1, characterized in that, The wavelength of the measuring beam used to measure the annealing temperature of the wafer (900) is different from both the first wavelength and the second wavelength.
6. The laser annealing method according to claim 1, characterized in that, Before annealing the wafer (900) using the first laser beam and the second laser beam, the wafer (900) is uniformly heated to the base temperature.
7. The laser annealing method according to claim 1, characterized in that, The reflectivity of the wafer (900) to the laser beam of the first wavelength and the laser beam of the second wavelength is measured at a first frequency, the annealing temperature of the wafer (900) is measured at a second frequency, and the power of the first laser module (300) and the second laser module (400) is adjusted at a third frequency, wherein the first frequency, the second frequency and the third frequency are all positively correlated with the ratio of the scanning speed and the minimum period of pattern change.
8. A laser annealing system, characterized in that, For implementing the laser annealing method according to any one of claims 1-7, the laser annealing system comprises: Motion module (100) is used to drive the wafer (900) to move; The first laser module (300) is used to emit a first laser beam with a wavelength of a first wavelength to the wafer (900); The second laser module (400) is used to emit a second laser beam with a second wavelength to the wafer (900), wherein the second wavelength is different from the first wavelength; Temperature measurement module (600) is used to measure the annealing temperature of wafer (900); A reflectivity measurement module is used to measure the reflectivity of the wafer (900) to a laser beam of the second wavelength and a laser beam of the first wavelength, and to obtain the reflectivity ratio; and The feedback control module (700) is used to determine the target total power based on the measured annealing temperature and the target annealing temperature, and to adjust the power of the first laser module (300) and the second laser module (400) based on the reflectivity ratio and the target total power, so as to stabilize the annealing temperature of the wafer (900) at the target annealing temperature.
9. The laser annealing system according to claim 8, characterized in that, The laser annealing system further includes: a heating module (200), a motion stage installed on the motion module (100), used to carry the wafer (900) and to uniformly heat the wafer (900) to a base temperature before annealing the wafer (900) using the first laser beam and the second laser beam.
10. The laser annealing system according to claim 8, characterized in that, The reflectivity measurement module includes a laser emitting component (510) and a laser detection component (520). The spectrum of the measurement beam emitted by the laser emitting component (510) includes the first wavelength and the second wavelength. The laser emitting component (510) includes a laser-driven plasma source. The laser detection component (520) includes an integrating sphere detector.