Laser annealing system, laser annealing method and exposure equipment
By introducing a wafer body heating unit and multiple modes of timing control into the laser annealing system, combined with the use of modulated waveforms and pulsed lasers, the problem of annealing non-uniformity in laser annealing was solved, and the manufacturing quality of memory devices was improved.
Patent Information
- Application Number
- CN202410705122.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-05-31
- Publication Date
- 2025-12-09
AI Technical Summary
In the manufacturing process of memory devices such as dynamic random access memory and flash memory, traditional laser annealing technology has problems such as local microscopic annealing inhomogeneity of wafers and non-uniform crystallization of annealing at the edge of the laser spot.
A laser annealing system comprising a wafer body heating unit, a first irradiation unit, and a second irradiation unit is employed. Through timing control of synchronous mode, delay mode, and secondary annealing mode, combined with the use of modulated waveform laser and pulsed laser, the temperature gradient and spot distribution are optimized.
This method achieves a temperature field distribution with smaller temperature gradient changes during wafer annealing, improves the microscopic local uniformity and crystallization degree of annealing, and reduces the risk of fragmentation caused by thermal stress.
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Figure CN121096901A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the field of exposure technology, in particular to a laser annealing system, a laser annealing method and an exposure apparatus. BACKGROUND
[0002] In the manufacturing process of memory devices such as dynamic random access memory (DRAM) and flash memory (NAND), local annealing treatment is usually required for specific film materials, for example, to convert amorphous materials into polycrystalline or single-crystal state, so as to achieve improvement and enhancement of material properties. Due to the limitation of heat budget, traditional annealing technologies such as rapid thermal processing (RTP) cannot meet the requirement of precise control of heat-affected zone, therefore, laser annealing, especially nanosecond laser anneal (NLA) technology, is introduced into the process. However, NLA usually adopts pulsed laser light source, and the annealing effect is discontinuous in time and space, the temperature gradient of temperature field distribution changes greatly, resulting in local microscopic annealing non-uniformity of the wafer. In addition, in the laser annealing process, due to the limitation of the optical system, the spot shape is not ideal and there are accompanying beams around, which also causes the non-uniformity of annealing crystallization at the edge of the spot. SUMMARY
[0003] The present application aims to provide a laser annealing system, a laser annealing method and an exposure apparatus, to solve at least one of the problems of local microscopic annealing non-uniformity of the wafer and non-uniformity of annealing crystallization at the edge of the spot in the laser annealing process.
[0004] To solve the above technical problems, the present application provides a laser annealing system, comprising a first irradiation unit, a second irradiation unit and a wafer body heating unit, the wafer body heating unit is used to heat the wafer to an initial temperature, the second irradiation unit is used to provide modulated waveform laser to preheat the local annealing area of the wafer, the first irradiation unit is used to provide pulsed laser to heat anneal the wafer, at least one of the synchronization mode, the time delay mode and the secondary annealing mode is used to control the timing of the first irradiation unit and the second irradiation unit, and when the synchronization mode is used, the spot area generated by the second irradiation unit is larger than the spot area generated by the first irradiation unit.
[0005] Optionally, the synchronization mode is that the first irradiation unit and the second irradiation unit are turned on at the same time; the delay mode is that the second irradiation unit is turned on first, then the first irradiation unit is turned on, and there is a delay between the first irradiation unit and the second irradiation unit; and the secondary annealing mode is that after the second irradiation unit completes full wafer annealing scanning, the first irradiation unit performs full wafer annealing on the wafer.
[0006] Optionally, the wafer shallow layer temperature in the synchronization mode and the delay mode is higher than the wafer shallow layer temperature when only the first irradiation unit acts, and the wafer deep layer temperature in the synchronization mode and the delay mode is higher than the wafer deep layer temperature when only the first irradiation unit acts.
[0007] Optionally, the wafer shallow layer temperature in the delay mode is higher than the wafer shallow layer temperature in the synchronization mode.
[0008] Optionally, in the synchronization mode and the delay mode, when the wafer body heating unit temperature is at a first temperature, the wafer shallow layer temperature is higher than the wafer shallow layer temperature when the wafer body heating unit temperature is at a second temperature, and when the wafer body heating unit temperature is at the first temperature, the wafer deep layer temperature is higher than the wafer deep layer temperature when the wafer body heating unit temperature is at the second temperature, wherein the first temperature is higher than the second temperature.
[0009] Optionally, the parameters of the second irradiation unit include at least one of wavelength, power, duty cycle and delay time; and the parameters of the first irradiation unit include at least one of wavelength, pulse width, pulse energy density and frequency.
[0010] Optionally, when the pulse energy density of the first irradiation unit increases, the temperature rising amplitude of the wafer surface layer and the temperature rising amplitude of the wafer shallow layer are both greater than the temperature rising amplitude of the wafer deep layer.
[0011] Optionally, when the power of the second irradiation unit increases, the temperature rising amplitude of the wafer shallow layer and the temperature rising amplitude of the wafer deep layer are both greater than the temperature rising amplitude of the wafer surface layer, and are less than the amplitude of the temperature rising of the wafer surface layer and the wafer shallow layer in the first irradiation unit with the increase of the pulse energy density.
[0012] Optionally, the initial temperature range is room temperature to 600 degrees Celsius, the preheating temperature range provided by the second irradiation unit is 600 degrees Celsius to 800 degrees Celsius, and the annealing temperature range provided by the first irradiation unit is 1200 degrees Celsius to 1600 degrees Celsius.
[0013] Optionally, when the wafer body heating unit and the first irradiation unit act together, as the temperature of the wafer body heating unit increases, the temperature increase amplitude of the wafer surface layer, the wafer shallow layer and the wafer deep layer are all greater than the temperature increase amplitude of the wafer surface layer.
[0014] Optionally, when the wafer body heating unit and the second irradiation unit act together, as the temperature of the wafer body heating unit increases, the temperature of the wafer surface layer, the wafer shallow layer and the wafer deep layer increases synchronously.
[0015] Optionally, the laser annealing system further comprises a first optical unit, a second optical unit and a focusing unit, the first optical unit performs beam expansion and uniformity modulation on the outgoing light of the first irradiation unit, the second optical unit performs beam expansion and uniformity modulation on the outgoing light of the second irradiation unit, and the focusing unit focuses the light spots modulated by the first optical unit and the second optical unit on the surface of the wafer, and focuses the light spots of different wavelengths on the wafer through achromatic design.
[0016] Optionally, the long side of the light spot modulated by the first optical unit and the second optical unit is flat-top distributed, and the short side is Gaussian distributed or flat-top distributed; the long side length of the light spot of the second irradiation unit is greater than the long side length of the light spot of the first irradiation unit, and the short side length of the light spot of the second irradiation unit is greater than the short side length of the light spot of the first irradiation unit.
[0017] Optionally, the laser annealing system further comprises a workpiece table unit, the workpiece table unit has multiple degrees of freedom of motion and is used to drive the wafer to perform scanning and stepping motion, so that the light spot covers the entire surface of the wafer during the annealing process.
[0018] Optionally, the laser annealing system further comprises an annealing temperature monitoring unit, the annealing temperature monitoring unit is used to measure the real-time annealing temperature of the wafer and control the temperature change during the annealing process through the control unit.
[0019] Based on the same inventive concept, the present application also provides a laser annealing method, which uses the laser annealing system of any one of the above to anneal a wafer, comprising:
[0020] heating the wafer by the wafer body heating unit to an initial temperature;
[0021] The second irradiation unit outputs modulated waveform laser to locally preheat the wafer, and the first irradiation unit outputs pulsed laser to anneal the wafer; wherein at least one of the synchronous mode, the delay mode and the secondary annealing mode is used to time sequence control the first irradiation unit and the second irradiation unit, and the spot area generated by the second irradiation unit is larger than the spot area generated by the first irradiation unit when the synchronous mode is used.
[0022] Based on the same inventive concept, the application further provides an exposure apparatus comprising the laser annealing system.
[0023] In the laser annealing system provided by the application, the wafer body heating unit heats the wafer to an initial temperature, the second irradiation unit provides modulated waveform laser to preheat the local annealing area of the wafer, and the first irradiation unit provides pulsed laser to rapidly heat and anneal the wafer. The wafer body heating unit provides an initial temperature, which reduces the temperature gradient change of the first irradiation unit and the second irradiation unit, and at least one of the synchronous mode, the delay mode and the secondary annealing mode is used to time sequence control the first irradiation unit and the second irradiation unit, and the spot area of the second irradiation unit is larger than the spot area of the first irradiation unit when the synchronous mode is used, so that a temperature field distribution with smaller temperature gradient change is obtained, and better annealing microscopic local uniformity and better crystallization degree are obtained, and the possibility of fragments caused by thermal stress in the laser annealing process is reduced. BRIEF DESCRIPTION OF DRAWINGS
[0024] Those skilled in the art will understand that the provided drawings are for better understanding of the application, and do not constitute any limitation on the scope of the application. Among them:
[0025] Figure 1 is a structure schematic diagram of a laser annealing system according to an embodiment of the application.
[0026] Figure 2 is a loading time sequence schematic diagram of a 527nm laser pulsed signal and an 808nm laser waveform modulation signal in a synchronous mode according to an embodiment of the application.
[0027] Figure 3 is a loading time sequence schematic diagram of a 527nm laser pulsed signal and an 808nm laser waveform modulation signal in a delay mode according to an embodiment of the application.
[0028] Figure 4 is a loading time sequence schematic diagram of a 527nm laser pulsed signal and an 808nm laser waveform modulation signal in a secondary annealing mode according to an embodiment of the application.
[0029] Figure 5is the highest temperature of the wafer at different depths corresponding to different wafer body heating unit temperatures when only the 527nm pulsed laser of the embodiment of the present application acts.
[0030] Figure 6 is the highest temperature of the wafer at different depths corresponding to different wafer body heating unit temperatures when only the 808nm modulated waveform laser of the embodiment of the present application acts.
[0031] Figure 7 is the highest temperature of the wafer at different depths corresponding to different loading timing when the wafer body heating unit temperature T0 of the embodiment of the present application is 0℃.
[0032] Figure 8 is the highest temperature of the wafer at different depths corresponding to different loading timing when the wafer body heating unit temperature T0 of the embodiment of the present application is 400℃.
[0033] Figure 9a is the temperature of the wafer at 1μm depth over time corresponding to different loading timing modes of the first irradiation unit and the second irradiation unit of the embodiment of the present application.
[0034] Figure 9b is the temperature of the wafer at 8μm depth over time corresponding to different loading timing modes of the first irradiation unit and the second irradiation unit of the embodiment of the present application.
[0035] Figure 9c is the temperature of the wafer at 100μm depth over time corresponding to different loading timing modes of the first irradiation unit and the second irradiation unit of the embodiment of the present application.
[0036] Figure 10 is the highest temperature of the wafer at different depths corresponding to different pulse energy densities of the 527nm laser of the embodiment of the present application.
[0037] Figure 11 is the highest temperature of the wafer at different depths corresponding to different power densities of the 808nm laser of the embodiment of the present application.
[0038] In the drawings:
[0039] 100 - workpiece table unit; 101 - wafer body heating unit; 102 - wafer; 103 - focusing unit; 104 - first reflecting unit; 105 - annealing temperature monitoring unit; 106 - second irradiation unit; 107 - second optical unit; 108 - first irradiation unit; 109 - first optical unit; 110 - control unit; 111 - second reflecting unit. DETAILED DESCRIPTION
[0040] In order to make the objects, advantages and features of the present application more clearly, the following further describes the present application in conjunction with the drawings and specific embodiments. It should be noted that the drawings are very simplified and not drawn to scale, and are only used to facilitate and clearly assist the purpose of describing the embodiments of the present application. In addition, the structures shown in the drawings are often part of the actual structures. In particular, the emphasis shown in each drawing is different, and sometimes different scales are used.
[0041] As used in the present application, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. The term "or" is generally employed in its sense including "and / or" unless the context clearly dictates otherwise. The term "plurality" is generally employed in its sense including "at least two" unless the context clearly dictates otherwise. The terms "first," "second," "third," etc. are used only to describe the objects and are not to be construed as indicating or implying relative importance or a specific number of the indicated technical features. Thus, features defined with "first," "second," "third" can explicitly or implicitly include one or at least two of the features. In addition, as used in the present application, an element disposed on another element generally only indicates a connection, coupling, cooperation or transmission relationship between the two elements, and the two elements can be directly or indirectly connected, coupled, cooperated or transmitted, and cannot be understood as indicating or implying a spatial positional relationship between the two elements, i.e. one element can be in any orientation inside, outside, above, below or one side of another element, unless the context clearly indicates otherwise. For those skilled in the art, the specific meanings of the above terms in the present application can be understood according to the specific circumstances.
[0042] Figure 1 is a schematic structural diagram of a laser annealing system according to an embodiment of the present application. As shown in Figure 1 , a laser annealing system includes a first irradiation unit 108, a second irradiation unit 106 and a wafer body heating unit 101.
[0043] The wafer body heating unit 101 is used to heat the wafer 102 to an initial temperature T0, which is in the range of, for example, room temperature to 600 degrees Celsius. The wafer body heating unit 101 is, for example, a hot plate. The initial temperature provided by the wafer body heating unit 101 reduces the temperature gradient change of the wafer 102 and the first irradiation unit 108 and the second irradiation unit 106.
[0044] The second irradiation unit 106 is configured to provide modulated waveform laser to pre-heat the local annealing area of the wafer 102. The pre-heat temperature range provided by the second irradiation unit 106 is, for example, 600-800 degrees Celsius. The first irradiation unit 108 is configured to provide pulsed laser to rapidly heat and anneal the wafer 102. The annealing temperature range provided by the first irradiation unit 108 is, for example, 1200-1600 degrees Celsius. The first irradiation unit 108 and the second irradiation unit 106 are controlled in at least one of a synchronous mode, a time-delay mode and a double annealing mode, and the spot size of the second irradiation unit 108 is larger than that of the first irradiation unit 106 in the synchronous mode to reduce the temperature gradient variation of the temperature field distribution of the wafer 102. In the embodiment, the wafer has a specific film layer material formed thereon, and the local annealing process is performed on the specific film layer material to, for example, convert amorphous material into polycrystalline or single-crystal material to improve and enhance the material properties. The laser annealing system provided in the embodiment can provide the wafer with a temperature field distribution having a smaller temperature gradient variation during the annealing process, better micro-local uniformity and better crystallization degree.
[0045] Specifically, the first irradiation unit 108 includes a solid laser, and the second irradiation unit 106 includes a semiconductor laser. The light source of the first irradiation unit 108 has a wavelength different from that of the second irradiation unit 106. The wavelength of the light source of the first irradiation unit 108 is, for example, 300-1500 nm, and preferably 500-600 nm. The wavelength of the light source of the second irradiation unit 106 is, for example, 300-1060 nm, and preferably 800-900 nm. The first irradiation unit 108 is in a pulse mode, and the second irradiation unit 106 can be in a pulse mode, a continuous wave (CW) mode or other modes. In the embodiment, the first irradiation unit 108 includes, for example, two integrated 527 nm solid lasers, and the second irradiation unit 106 includes, for example, an 808 nm semiconductor laser. The two integrated 527 nm pulse lasers are time-delayed by a time of, for example, 50 μs. The modulation waveform period of the 808 nm laser is the same as the pulse period of the 527 nm laser, i.e., the pulse periods of the first irradiation unit 108 and the second irradiation unit 106 are the same. The short side length of the spot generated by the second irradiation unit 106 is larger than that of the spot generated by the first irradiation unit 108, and the long side length of the spot generated by the second irradiation unit 106 is larger than that of the spot generated by the first irradiation unit 108. Preferably, the spot size generated by the first irradiation unit 108 is, for example, 3 mm x 0.2 mm, and the spot size generated by the second irradiation unit 106 is, for example, 3.5 mm x 0.25 mm.
[0046] Figure 2 This is a schematic diagram of the loading timing of the 527nm laser pulse signal and the 808nm laser waveform modulation signal in synchronous mode according to an embodiment of the present invention. Figure 3 This is a schematic diagram of the loading timing of the 527nm laser pulse signal and the 808nm laser waveform modulation signal in delay mode according to an embodiment of the present invention. Figure 4 This is a schematic diagram of the loading timing of a 527nm laser pulse signal and an 808nm laser waveform modulation signal in a double annealing mode according to an embodiment of the present invention. The first irradiation unit 108 and the second irradiation unit 106 include three loading timing sequences, such as synchronous mode, delay mode, and double annealing mode.
[0047] Furthermore, such as Figure 2 As shown, the synchronization mode involves the simultaneous activation of the first irradiation unit 108 and the second irradiation unit 106, for example, the simultaneous activation of a 527nm laser and an 808nm laser. Since the pulse periods of the first irradiation unit 108 and the second irradiation unit 106 are the same (e.g., both are 200μs), and the pulse duration of the second irradiation unit 106 is longer than that of the first irradiation unit 108 (e.g., the pulse duration of the second irradiation unit 106 is 50μs, while the total duration of the two pulses and delay of the first irradiation unit 108 is 2.1μs), and the short side length of the light spot generated by the second irradiation unit 106 is greater than that of the light spot generated by the first irradiation unit 108, and the long side length of the light spot generated by the second irradiation unit 106 is greater than that of the light spot generated by the first irradiation unit 108, in the synchronization mode, only the preheating effect of the second irradiation unit 106 due to the difference in light spot size occurs. The area of the light spot produced by the second irradiation unit 106 is larger than that produced by the first irradiation unit 108. The preheating effect of the second irradiation unit 106 can reduce the non-uniformity of the edge of the light spot produced by the first irradiation unit 108.
[0048] Furthermore, such as Figure 3As shown, the delay mode involves first activating the second irradiation unit 106, then activating the first irradiation unit 108, with a delay between the first irradiation unit 108 and the second irradiation unit 106. The delay time is, for example, 50 μs. Specifically, there is a delay between the loading sequence of the 527nm laser and the 808nm laser. After the 808nm laser preheats the wafer 102, the 527nm laser is immediately activated to heat the wafer 102. In the delay mode, since the 808nm laser has just finished preheating the wafer 102, the temperature of the wafer 102 reaches its maximum value within the cycle, at which point the absorbance is at its maximum. Therefore, when the 527nm laser continues rapid heating and annealing, the absorption depth of heat on the wafer 102 will relatively increase, allowing the heat to penetrate deeper into the interior of the wafer 102, resulting in a better degree of crystallization and thus improving the microscopic local uniformity of the wafer annealing.
[0049] Furthermore, such as Figure 4 As shown, the secondary annealing mode involves the first irradiation unit 108 performing full-wafer annealing on wafer 102 after the second irradiation unit 106 completes the full-wafer annealing scan. For example, after the 808nm laser performs full-wafer annealing scan on wafer 102, the 527nm laser then performs full-wafer annealing on wafer 102. Compared with the synchronous mode and the delayed mode, the secondary annealing mode uses the 808nm laser to preheat the entire wafer 102 to change the crystal distribution of the entire wafer 102, and then the 527nm laser performs annealing on the wafer 102 on this basis. This can effectively improve the uniformity of the annealed crystallization of wafer 102 and obtain a better degree of crystallization.
[0050] The inventors conducted simulation experiments on the operation of the described laser annealing system under different control modes. The basic parameters used in the simulation experiments are as follows: the pulse width of the first irradiation unit 108 (527nm solid-state laser) is 300ns, the frequency is 5000Hz, the spot size is 3mm×0.2mm, and the pulse delay time is 50μs; the modulation waveform of the second irradiation unit 106 (808nm semiconductor solid-state laser) is a square wave, the duty cycle is 25%, the spot size is 3.5mm×0.25mm, and the period of the second irradiation unit 106 is the same as that of the first irradiation unit 108; the scanning speed of the workpiece stage unit 100 is 250mm / s, and the annealing dwell time is 800μs, where the annealing dwell time is the ratio of the spot width to the scanning speed of the workpiece stage unit 100. The laser pulse period is 200μs, and there are 4 pulse periods during the dwell time.
[0051] Scenario 1: The wafer body heating unit 101 works in conjunction with a 527nm laser or an 808nm laser.
[0052] First, the influence of the temperature of the wafer body heating unit 101 on the annealing temperature of the wafer 102 when only the 527 nm pulsed laser is used is simulated. The energy density (ED) of the 527 nm pulsed laser is, for example, 1 J / cm 2 , and the power density (PD) of the 808 nm modulated waveform laser is 0 kW / cm 2 . Figure 5 is the maximum temperature of the wafer at different depths corresponding to different wafer body heating unit temperatures when only the 527 nm pulsed laser is used. Figure 5 The abscissa of is the depth of the wafer in μm. The ordinate is the maximum temperature in °C. Table 1 is the maximum temperature of the wafer at 1 μm, 8 μm and 100 μm corresponding to different wafer body heating unit temperatures when only the 527 nm pulsed laser is used.
[0053] Table 1: Maximum temperature of the wafer at 1 μm, 8 μm and 100 μm corresponding to different wafer body heating unit temperatures when only the 527 nm pulsed laser is used;
[0054] Depth \ Hot Plate Temperature T＝0℃ T＝250℃ T＝400℃ 1 μm 1406.1 1414.2 1416.5 8 μm 643.2 828.6 923.1 100 μm 148.9 387.1 524.1
[0055] From Figure 5 and Table 1, it can be seen that when only the 527 nm pulsed laser is used, that is, when only the first irradiation unit 108 is used, as the temperature of the wafer body heating unit 101 increases, the maximum temperature of the wafer surface layer (0-3 μm) hardly increases, and the temperature of the wafer shallow layer (3 μm-8 μm) and the wafer deep layer (8 μm-100 μm) increases more. That is, when the wafer body heating unit and the first irradiation unit act together, as the temperature of the wafer body heating unit increases, the temperature increase amplitude of the wafer shallow layer and the wafer deep layer is greater than that of the wafer surface layer.
[0056] Then, the influence of the temperature of the wafer body heating unit 101 on the annealing temperature of the wafer 102 when only the 808 nm modulated waveform laser is used is simulated. The simulation conditions are: the energy density ED of the 527 nm pulsed laser is 0, and the power density PD of the 808 nm modulated waveform laser is 44.57 kW / cm 2 . Figure 6 is the maximum temperature of the wafer at different depths corresponding to different wafer body heating unit temperatures when only the 808 nm modulated waveform laser is used. Figure 6The abscissa is the depth of the wafer, in units of pm, and the ordinate is the maximum temperature, in units of °C. Table 2 is the maximum temperature of the wafer at 1 pm, 8 pm and 100 pm under different wafer body heating unit temperatures when only 808 nm modulated waveform laser is used.
[0057] Table 2: The maximum temperature of the wafer at 1 pm, 8 pm and 100 pm under different wafer body heating unit temperatures when only 808 nm modulated waveform laser is used.
[0058] Depth \ Hot Plate Temperature T＝0℃ T＝250℃ T＝400℃ 1 μm 216.2 466.2 616.2 8 μm 209.7 459.7 609.4 100 μm 100.5 350.5 500.5
[0059] From Figure 6 and Table 2, it can be seen that only under the action of 808 nm modulated waveform laser, i.e. only under the action of the second irradiation unit 106, the temperature of the wafer surface layer, the wafer shallow layer and the wafer deep layer all increase more as the temperature of the wafer body heating unit increases. That is, when the wafer body heating unit and the second irradiation unit act together, as the temperature of the wafer body heating unit increases, the temperature of the wafer surface layer and the wafer shallow layer and the wafer deep layer increases synchronously.
[0060] From the above simulation results, it can be seen that under the condition of the same pulse energy density or power density, the temperature of the wafer body heating unit has different effects on the annealing temperature of the wafer at different depths when the first irradiation unit 108 and the second irradiation unit 106 act alone. Within the allowable temperature range of the wafer, setting appropriate wafer body heating unit temperature can obtain different temperature intervals.
[0061] Case two: 527 nm laser and 808 nm laser are controlled by different loading time sequences.
[0062] Case two simulates the effects of 808 nm modulated waveform laser alone, 527 nm pulsed laser alone, and 808 nm modulated waveform laser and 527 nm pulsed laser acting together under different loading time sequences on the annealing temperature of the wafer. The pulse energy density ED of the 527 nm pulsed laser is 1 J / cm 2 , and the power density PD of the 808 nm modulated waveform laser is 44.57 kW / cm 2 .
[0063] Figure 7 is the maximum temperature of the wafer at different depths under different loading time sequences when the temperature T0 of the wafer body heating unit is 0°C. Figure 8 is the maximum temperature of the wafer at different depths under different loading time sequences when the temperature T0 of the wafer body heating unit is 400°C. Figure 7 and Figure 8The horizontal coordinate in the above figures is the depth of the wafer, in units of μm. The vertical coordinate is the maximum temperature, in units of °C. Table 3 is the maximum temperature of the wafer at 1 μm, 8 μm and 100 μm corresponding to the first irradiation unit and the second irradiation unit under different loading sequences.
[0064] Table 3 is the maximum temperature of the wafer at 1 μm, 8 μm and 100 μm corresponding to the first irradiation unit and the second irradiation unit under different loading sequences.
[0065]
[0066] From Figure 7 and Figure 8 and Table 3, the wafer shallow layer temperature in the synchronization mode and the delay mode is higher than the wafer shallow layer temperature under the action of only the 527 nm pulsed laser, and the wafer deep layer temperature in the synchronization mode and the delay mode is higher than the wafer deep layer annealing temperature under the action of only the 527 nm pulsed laser; that is, the wafer shallow layer temperature in the synchronization mode and the delay mode is higher than the wafer shallow layer temperature under the action of only the first irradiation unit, and the wafer deep layer temperature in the synchronization mode and the delay mode is higher than the wafer deep layer temperature under the action of only the first irradiation unit. The preheating by the 808 nm modulated waveform laser increases the absorption depth of the 527 nm pulsed laser, and improves the annealing temperature, that is, the wafer shallow layer temperature in the delay mode is higher than the wafer shallow layer temperature in the synchronization mode. In addition, the wafer shallow layer temperature when the wafer body heating unit temperature is T0=400 °C is higher than the wafer shallow layer temperature when the wafer body heating unit temperature is T=0 °C, and the wafer deep layer temperature when the wafer body heating unit temperature is T0=400 °C is higher than the wafer deep layer temperature when the wafer body heating unit temperature is T=0 °C.
[0067] Figure 9a is the temperature change of the wafer at a depth of 1 μm over time under different loading sequence modes of the first irradiation unit and the second irradiation unit of the embodiment of the present application. Figure 9b is the temperature change of the wafer at a depth of 8 μm over time under different loading sequence modes of the first irradiation unit and the second irradiation unit of the embodiment of the present application. Figure 9c is the temperature change of the wafer at a depth of 100 μm over time under different loading sequence modes of the first irradiation unit and the second irradiation unit of the embodiment of the present application. The temperature change of the wafer at a depth of 1 μm, 8 μm and 100 μm over time in the synchronization mode and the delay mode within the residence time. Figure 9a Figure 9b and Figure 9c The horizontal coordinate in the above figures is time, in units of μs, and the vertical coordinate is temperature, in units of °C.
[0068] In the delay mode, the wafer temperature reaches the maximum after the 808 nm modulated waveform laser is fully loaded. Compared with the synchronous mode, the 527 nm pulsed laser has a higher absorption rate, resulting in a superposition effect, and the temperature of the shallow layer of the wafer is higher. At the same time, since the action time of the 527 nm pulsed laser is short enough, the total energy loaded is small, and the temperature has not had time to conduct to the deep part of the wafer, so the temperature difference between the upper and lower parts of the wafer is larger.
[0069] In the synchronous mode, the 808 nm modulated waveform laser only has a preheating effect on the edge of the 527 nm pulsed laser spot. In actual cases, due to the limitation of the optical system, the spot shape is not ideal and there is a companion around the edge of the spot, that is, the edge of the spot shape is curved. The preheating effect of the synchronous mode can make the size of the wafer annealing crystallization on the edge of the spot more uniform, because the short side length and the long side length of the 808 nm modulated waveform spot are both larger than the short side length and the long side length of the 527 nm pulsed laser spot, that is, the 808 nm modulated waveform spot can completely cover the 527 nm pulsed laser spot, and the preheating effect of the 808 nm modulated waveform spot can reduce the non-uniformity of the wafer annealing crystallization caused by the companion on the edge of the 527 nm pulsed laser spot. The laser annealing system can obtain a temperature field distribution with smaller temperature gradient change and provide a larger temperature difference between the shallow layer of the wafer and the deep layer of the wafer through the wafer body heating unit, the second irradiation unit and the first irradiation unit loading time sequence control.
[0070] Case three: the influence of the annealing parameters of the first irradiation unit and the second irradiation unit on the wafer annealing temperature.
[0071] Taking the delay mode as an example, the temperature T0 of the wafer body heating unit is 400℃, the pulse energy density ED of the 527 nm pulsed laser is 1 J / cm 2 , and the power density PD of the 808 nm modulated waveform laser is 44.57 kW / cm 2 . The power density of the 808 nm modulated waveform laser is unchanged, and the pulse energy density of the 527 nm laser is set to 1 J / cm 2 , 2 J / cm 2 , and 3 J / cm 2 , respectively. The pulse energy density of the 527 nm pulsed laser is unchanged, and the power density of the 808 nm laser is set to 44.57 kW / cm 2 , 59.43 kW / cm 2 , and 74.29 kW / cm 2 , respectively. Figure 10 is the maximum temperature of the wafer at different depths under different pulse energy densities of the 527 nm laser. Figure 11 is the maximum temperature of the wafer at different depths under different power densities of the 808 nm laser. Figure 10 andFigure 11 The horizontal axis represents the wafer depth in μm, and the vertical axis represents the maximum temperature in °C. Table 4 shows the maximum temperatures of the wafer at 1 μm, 8 μm, and 100 μm under different pulse energy densities and power densities.
[0072] Table 4. Maximum temperatures of wafers at 1μm, 8μm, and 100μm under different pulse energy densities and power densities;
[0073]
[0074] Depend on Figure 10 As shown in Table 4, with the increase of pulse energy density in the first irradiation unit, the wafer surface temperature increased from 1418.7℃ to 1975.1℃. In the parameter adjustments within the first irradiation unit, with the increase of pulse energy density, the temperature changes of the wafer surface and shallow layers were greater than those of the deep layers, thus providing a larger temperature difference between the upper and lower layers. Figure 11 As shown in Table 4, with the increase of power density in the second irradiation unit, the temperature in the shallow and deep layers of the wafer rises slowly, while the temperature of the wafer surface remains almost unchanged. That is, in the parameter adjustment within the second irradiation unit, with the increase of power density, the temperature increase in the shallow and deep layers of the wafer is greater than that of the wafer surface, but less than the temperature increase in the surface and shallow layers of the wafer with increasing pulse energy density in the first irradiation unit.
[0075] The parameters of the second irradiation unit also include wavelength, duty cycle, and delay time; the parameters of the first irradiation unit include wavelength, pulse width, and frequency. In other embodiments, the relationship between the wavelength, duty cycle, and delay time of the second irradiation unit and the wafer annealing temperature, as well as the relationship between the wavelength, pulse width, and frequency of the first irradiation unit and the wafer annealing temperature, can be studied.
[0076] Please continue to refer to this. Figure 1, the laser annealing system further comprises a first optical unit 109, a second optical unit 107 and a focusing unit 103, the first optical unit 109 performs beam expanding and uniformity modulation on the light emitted by the first irradiation unit 108, the second optical unit 107 performs beam expanding and uniformity modulation on the light emitted by the second irradiation unit 106, the focusing unit 103 focuses the light spots modulated by the first optical unit 109 and the second optical unit 107 on the surface of the wafer 102, and the focusing unit 103 is designed to be achromatic so as to ensure that light spots of different wavelengths can be focused on the wafer 102. The long side of the light spot modulated by the first optical unit 109 and the second optical unit 107 is, for example, flat-top distributed, and the short side of the light spot is, for example, Gaussian distributed or flat-top distributed, and the length of the long side and the length of the short side of the light spot generated by the second irradiation unit 106 are greater than the length of the long side and the length of the short side of the light spot generated by the first irradiation unit 108.
[0077] Please continue to refer to Figure 1 , the laser annealing system further comprises a first reflection unit 104 and a second reflection unit 111. The first reflection unit 104 is used for reflecting the light beam of the first irradiation unit 108 to the wafer 102, and the second reflection unit 111 is used for reflecting the light beam of the second irradiation unit 106 to the wafer 102.
[0078] Please continue to refer to Figure 1 , the laser annealing system further comprises a workpiece table unit 100, the workpiece table unit 100 has multiple degrees of freedom and is used for driving the wafer 102 to perform scanning and stepping motion, so that the light spot in the annealing process can cover the entire surface of the wafer 102.
[0079] Please continue to refer to Figure 1 , the laser annealing system further comprises a control unit 110. The annealing temperature monitoring system 105 measures the real-time annealing temperature of the wafer and feeds back the annealing temperature measurement value to the control unit 110. The control unit 110 synchronizes the control signals of the workpiece table unit 100, the first irradiation unit 108 and the second irradiation unit 106 according to a control algorithm. The control unit 110 adjusts the pulse energy density of the pulsed laser of the first irradiation unit 108 and the modulation waveform power density ratio of the second irradiation unit 106 in real time according to the real-time annealing temperature of the wafer 102, so as to improve the stability of the temperature in the annealing process.
[0080] The laser annealing system further comprises an annealing temperature monitoring unit 105, the annealing temperature monitoring unit 105 is used for measuring the real-time annealing temperature of the wafer 102 and feeding back the real-time annealing temperature to the control unit 110, and the control unit 110 controls the change of the temperature in the annealing process, so as to improve the stability of the temperature in the annealing process.
[0081] The embodiment also provides a laser annealing method, which anneals a wafer by using the laser annealing system according to any one of the above.
[0082] The wafer body heating unit heats the wafer to an initial temperature.
[0083] The second irradiation unit outputs modulated waveform laser to preheat a local area of the wafer, and the first irradiation unit outputs pulsed laser to anneal the wafer; wherein the first irradiation unit and the second irradiation unit are controlled in time sequence by using at least one of a synchronous mode, a time delay mode and a secondary annealing mode, and the spot area generated by the second irradiation unit is larger than the spot area generated by the first irradiation unit when the synchronous mode is used.
[0084] Specifically, the initial temperature range provided by the wafer body heating unit is, for example, room temperature to 600 degrees Celsius, the preheating temperature range provided by the second irradiation unit 106 is, for example, 600 degrees Celsius to 800 degrees Celsius, and the annealing temperature range provided by the first irradiation unit 108 is, for example, 1200 degrees Celsius to 1600 degrees Celsius. The parameters of the second irradiation unit 106 include wavelength, power, duty cycle and time delay, and the parameters of the first irradiation unit 108 include wavelength, pulse width, pulse energy density and frequency. When the wafer 102 is annealed by using the laser annealing system, the wavelength, power, duty cycle and time delay of the second irradiation unit 106 and the wavelength, pulse width, pulse energy density and frequency of the first irradiation unit 108 are adjusted, so that the first irradiation unit 108 and the second irradiation unit 106 cooperate with each other, the wafer 102 can obtain a temperature field distribution with smaller temperature gradient change in the annealing process, better annealing microscopic local uniformity and better crystallization degree.
[0085] The embodiment also provides an exposure device, which comprises the laser annealing system.
[0086] In the laser annealing system, the laser annealing method and the exposure apparatus provided by the embodiment of the present application, the wafer body heating unit heats the wafer to an initial temperature, the second irradiation unit provides modulated waveform laser to preheat the local annealing area of the wafer, and the first irradiation unit provides pulsed laser to rapidly heat and anneal the wafer. The wafer body heating unit provides an initial temperature, which reduces the temperature gradient variation of the first irradiation unit and the second irradiation unit, and at least one of the synchronization mode, the time delay mode and the secondary annealing mode is used to time control the first irradiation unit and the second irradiation unit, and the spot area generated by the second irradiation unit is larger than the spot area generated by the first irradiation unit when the synchronization mode is used, so that a temperature field distribution with smaller temperature gradient variation is obtained, and better annealing microscopic local uniformity and better crystallization degree are obtained, and the possibility of fragments caused by thermal stress in the laser annealing process is reduced. The annealing temperature monitoring unit in the present application measures the real-time annealing temperature of the wafer to control the temperature variation in the annealing process, and the stability of the temperature in the annealing process can be improved.
[0087] In addition, it should be appreciated that, although the present application has been disclosed with the preferred embodiments as above, the above embodiments are not intended to limit the present application. For any skilled person in the art, many possible changes and modifications or equivalent embodiments of the above disclosed technical content can be made without departing from the scope of the technical solutions of the present application. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present application without departing from the content of the technical solutions of the present application shall still fall within the scope of protection of the technical solutions of the present application.
Claims
1. A laser annealing system, characterized in that, The device includes a first irradiation unit, a second irradiation unit, and a wafer body heating unit. The wafer body heating unit is used to heat the wafer to an initial temperature. The second irradiation unit is used to provide modulated waveform laser to preheat the local annealing area of the wafer. The first irradiation unit is used to provide pulsed laser to heat and anneal the wafer. The timing control of the first irradiation unit and the second irradiation unit is performed using at least one of a synchronous mode, a delayed mode, and a secondary annealing mode. When the synchronous mode is used, the spot area generated by the second irradiation unit is larger than the spot area generated by the first irradiation unit.
2. The laser annealing system according to claim 1, characterized in that, The synchronous mode is that the first irradiation unit and the second irradiation unit are turned on simultaneously; the delay mode is that the second irradiation unit is turned on first, and then the first irradiation unit is turned on, with a delay between the first irradiation unit and the second irradiation unit; the secondary annealing mode is that after the second irradiation unit completes the full-wafer annealing scan of the wafer, the first irradiation unit performs full-wafer annealing on the wafer again.
3. The laser annealing system according to claim 2, characterized in that, The wafer shallow temperature in the synchronous mode and the delayed mode is higher than the wafer shallow temperature when only the first irradiation unit is applied, and the wafer deep temperature in the synchronous mode and the delayed mode is higher than the wafer deep temperature when only the first irradiation unit is applied.
4. The laser annealing system according to claim 2, characterized in that, The wafer shallow temperature in the delay mode is higher than that in the synchronization mode.
5. The laser annealing system according to claim 2, characterized in that, In the synchronous mode and the delayed mode, the wafer body heating unit temperature at the first temperature is higher than the wafer body heating unit temperature at the second temperature, and the wafer body heating unit temperature at the first temperature is higher than the wafer body heating unit temperature at the second temperature, wherein the first temperature is higher than the second temperature.
6. The laser annealing system according to claim 1, characterized in that, The parameters of the second irradiation unit include at least one of wavelength, power, duty cycle, and delay time; the parameters of the first irradiation unit include at least one of wavelength, pulse width, pulse energy density, and frequency.
7. The laser annealing system according to claim 6, characterized in that, When the pulse energy density of the first irradiation unit increases, the temperature rise of the wafer surface and the shallow layer of the wafer is greater than that of the deep layer of the wafer.
8. The laser annealing system according to claim 6, characterized in that, When the power of the second irradiation unit increases, the temperature rise of the shallow layer of the wafer and the temperature rise of the deep layer of the wafer are both greater than the temperature rise of the surface layer of the wafer, but less than the temperature rise of the surface layer and the shallow layer of the wafer in the first irradiation unit as the pulse energy density increases.
9. The laser annealing system according to claim 1, characterized in that, The initial temperature range is from room temperature to 600 degrees Celsius, the preheating temperature range provided by the second irradiation unit is from 600 degrees Celsius to 800 degrees Celsius, and the annealing temperature range provided by the first irradiation unit is from 1200 degrees Celsius to 1600 degrees Celsius.
10. The laser annealing system according to claim 1, characterized in that, When the wafer body heating unit works together with the first irradiation unit, as the temperature of the wafer body heating unit increases, the temperature increase of the shallow layer and the deep layer of the wafer are both greater than the temperature increase of the surface layer of the wafer.
11. The laser annealing system according to claim 1, characterized in that, When the wafer body heating unit and the second irradiation unit work together, as the temperature of the wafer body heating unit increases, the temperature of the wafer surface layer, the shallow layer of the wafer, and the deep layer of the wafer also increase synchronously.
12. The laser annealing system according to claim 1, characterized in that, The laser annealing system further includes a first optical unit, a second optical unit, and a focusing unit. The first optical unit expands and modulates the emitted light from the first irradiation unit, the second optical unit expands and modulates the emitted light from the second irradiation unit, and the focusing unit focuses the light spot modulated by the first and second optical units onto the surface of the wafer, and focuses light spots of different wavelengths onto the wafer through an achromatic design.
13. The laser annealing system according to claim 12, characterized in that, The long side of the light spot shape modulated by the first optical unit and the second optical unit is flat-topped, and the short side is Gaussian or flat-topped; the long side length of the light spot of the second irradiation unit is greater than the long side length of the light spot of the first irradiation unit, and the short side length of the light spot of the second irradiation unit is greater than the short side length of the light spot of the first irradiation unit.
14. The laser annealing system according to claim 1, characterized in that, The laser annealing system also includes a workpiece stage unit, which has multiple degrees of freedom of motion and is used to drive the wafer to perform scanning and stepping motion so that the laser spot during the annealing process covers the entire surface of the wafer.
15. The laser annealing system according to claim 1, characterized in that, The laser annealing system also includes an annealing temperature monitoring unit, which measures the real-time annealing temperature of the wafer and controls the temperature change during the annealing process through a control unit.
16. A laser annealing method, characterized in that, Annealing a wafer using the laser annealing system as described in any one of claims 1 to 15, comprising: The wafer body heating unit heats the wafer to its initial temperature; The second irradiation unit outputs modulated waveform laser to preheat a local area of the wafer, while the first irradiation unit outputs pulsed laser to heat and anneal the wafer. In this process, at least one of the following modes—synchronization mode, delay mode, and secondary annealing mode—is used to perform timing control on the first irradiation unit and the second irradiation unit. When the synchronization mode is used, the area of the light spot generated by the second irradiation unit is greater than the area of the light spot generated by the first irradiation unit.
17. An exposure apparatus, characterized in that, Including the laser annealing system as described in any one of claims 1 to 15.