Nanosecond laser annealing device

Abstract

The invention relates to the technical field of semiconductor manufacturing processes and equipment, in particular to a nanosecond laser annealing device, which can realize miniaturization of laser annealing equipment, ensure the stability of a laser process and improve the technical reliability and the yield of products. Wafer annealing is carried out based on 10.6 mu m long-wave laser, and miniaturization of laser annealing equipment is achieved; the temperature conversion unit and the acquisition equipment are combined for use, feedback regulation is performed through the automatic control unit, so that the annealing process flow is stable and reliable, a stable ns-level annealing process can be realized, specifically, the acquisition equipment is adopted to collect infrared radiation and perform nanosecond-level infrared radiation temperature measurement, and the automatic control unit is combined, so that the production efficiency is improved. The laser pulse energy is regulated and controlled, the stability of the laser process is ensured, and the technical reliability and the product yield are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor manufacturing processes and equipment, and particularly relates to a nanosecond laser annealing device. Background Art

[0002] Laser Annealing is a technology that uses laser to heat the surface of materials to improve their physical and chemical properties. This technology has been widely used in fields such as semiconductor manufacturing and materials science. Its technical principle is to irradiate the surface of materials with a high-intensity laser beam, and through processes such as light absorption, heat conduction, and thermal radiation, the materials are rapidly heated to a high temperature and then rapidly cooled. This heat treatment process can improve the crystal structure of materials, eliminate defects, or change the physical and chemical properties of materials.

[0003] In the laser annealing process, it is very important to select a suitable laser as the annealing light source. Currently, the relatively mature annealing light sources in application are excimer lasers, semiconductor lasers, and CO 2 lasers. The output wavelength of excimer lasers is between 200 - 350 nm, and they have the characteristics of high-energy and high-repetition-rate laser output, and can achieve rapid annealing at the ms or even ns level. However, the production and maintenance costs of the equipment corresponding to this annealing technology are relatively high, which limits its use in large-scale production. Moreover, semiconductor materials have a relatively high absorption rate for the light beam in this wavelength band, and it is easy to cause damage to the materials during the annealing process, reducing the yield. Semiconductor lasers have a relatively low manufacturing cost, are structurally compact, and can perform long-term continuous heating. However, the peak power output of this type of laser is relatively low, and there are technical bottlenecks in achieving rapid annealing. CO 2 lasers can provide a relatively high power density, and the technology is mature and controllable. They are suitable for rapid annealing of non-metallic materials such as ceramics, silicon, and germanium, and can process a relatively large area, and have been relatively widely used in the field of rapid annealing. For example, the LSA series annealing equipment of the American company Vecco all uses CO 2 lasers as the light source of the annealing equipment and has been successfully applied to the production line of the 14nm node process. However, the LSA series annealing equipment is relatively large in volume and high in cost. Summary of the Invention

[0004] In view of this, the present invention provides a nanosecond laser annealing device, which can miniaturize the laser annealing equipment, ensure the stability of the laser process, and improve the technical reliability and the excellent rate of products.

[0005] To achieve the above object, the technical solution of the present invention is as follows:

[0006] A nanosecond annealing device, comprising a base, a laser, a mirror I, a mirror II, a beam shaper I, a translation base, a wafer fixture, an infrared radiation collection module, a collection device, a temperature conversion unit, a semiconductor laser, a beam shaper II and an automatic control unit;

[0007] The beam output by the laser passes through the mirror I, the mirror II, and the beam shaper I, and is incident on the wafer to be annealed at the Brewster angle; the infrared radiation collection module collects the infrared radiation of the wafer to the collection device; the collection device receives the infrared radiation via the infrared radiation collection module, converts the collected infrared radiation photon signal into an electrical signal, generates a pulse and transmits it to the temperature conversion unit; the temperature conversion unit obtains temperature data according to the pulse, transmits it to the automatic control unit as a feedback value, and the automatic control unit calculates the error between the target temperature and the actual temperature according to the feedback value, and automatically adjusts the output power of the semiconductor laser and the laser;

[0008] The base is used to place the annealing device; the semiconductor laser is used for preheating before annealing; the beam shaper II focuses the beam emitted by the semiconductor laser in the X and Y directions; the translation base is used to install and carry the device.

[0009] Among them, the mirror I is a high-reflection mirror, which transmits the beam output by the laser to the mirror II; the mirror II is a high-reflection mirror, which transmits the beam reflected by the mirror I to the beam shaper I; the mirror II is used to control the transmission direction of the laser, so that the laser is incident on the wafer to be annealed in the P polarization state.

[0010] Among them, the beam shaper I includes a beam expander, a Fresnel lens and a ZnSe focusing lens group. After the laser beam reflected by the mirror II passes through the beam shaper I, the output optical axis remains unchanged; the beam shaper II adjusts the beam shape into a rectangular light spot and irradiates it onto the preheating area of the wafer while ensuring that the output optical axis remains unchanged.

[0011] Among them, an X-Y translation component is directly connected to the translation base. The X-Y translation component is in a gantry configuration, with the Y axis as the lower axis and an open structure. The guide rail and the linear motor are directly fixed on the translation base; the X axis is the upper axis, and the guide rail and the linear motor are horizontally mounted above the X axis.

[0012] Among them, the automatic control unit uses a PID control algorithm to automatically adjust the output power of the laser to keep the temperature of the preheating area and the annealing area constant.

[0013] Among them, the laser is a sealed-off RF-excited CO2 laser with an integrated closed design.

[0014] Among them, the infrared radiation collection module includes a ZnSe filter and a focusing mirror, which receive infrared radiation. The filter is used to screen infrared radiation near 1μm, and the working wavelength range of the detector is 800 - 1100nm.

[0015] Among them, the beam shaper II is a quartz focusing lens group. A lens group composed of two cylindrical lenses focuses the beam in the X and Y directions to obtain a linear light spot, realizing the shaping of the laser beam.

[0016] Among them, the scanning methods of the preheating area and the annealing area are selected as linear reciprocating scanning. The preheating laser beam is shaped and adjusted to a rectangular area of 11mm × 0.15mm, and the CO2 laser beam is shaped and adjusted to a rectangular area of 8.4mm × 0.075mm.

[0017] Among them, it also includes an infrared pyrometer and a beam expander. The infrared pyrometer collects the thermal radiation during the preheating process of laser irradiation through the beam expander.

[0018] Beneficial effects:

[0019] 1. The present invention is based on a 10.6μm long-wave laser for wafer annealing, realizing the miniaturization of the laser annealing equipment; the temperature conversion unit and the acquisition device are combined and feedback-regulated by the automatic control unit, making the annealing process stable and reliable. A stable ns-level annealing process can be achieved. Specifically, the acquisition device is used to collect infrared radiation for nanosecond-level infrared radiation temperature measurement, and combined with the automatic control unit, the laser pulse energy is regulated to ensure the stability of the laser process, improving the technical reliability and the excellent rate of products.

[0020] 2. The present invention uses a sealed-off radio frequency excited CO 2 laser to emit nanosecond pulse CO 2 laser, with a corresponding pulse width of 120ns. Under the condition of ensuring the pulse energy, this pulse width is 1 / 83 of the pulse width of the existing laser annealing device using this wavelength laser. The peak power corresponding to the laser is high, and it can heat the surface temperature of the wafer to be annealed to the annealing temperature within the nanosecond time level, meeting the annealing process requirements for aspects such as ultra-shallow junction activation below the 7nm node.

[0021] 3. The preheating laser of the present invention can also use a solid-state laser, such as a Nd:YAG laser with a wavelength of 1064nm, which generates green light at 532nm through frequency doubling. Or a near-infrared laser such as an indium gallium arsenide (InGaAs) laser (900nm to 1700nm), which is small in volume and low in cost, and is suitable for preheating applications with low to medium power and relatively high spatial resolution requirements.

[0022] 4. In the device of the present invention, through the combination of the translation stage and the rotation stage, the workpiece can achieve an arc scanning effect during movement. When annealing circular arc materials, arc scanning can preferably avoid the edge effect and heating non-uniformity especially at the corners brought by linear scanning, and can cover a large area in a single pass, avoiding the repeatability of the scanning route.

[0023] 5. In terms of the annealing time, the device of the present invention can achieve a stable ns-level annealing process, and compared with the ms-level annealing, it can achieve more precise control of the processing area and reduce the thermal damage to the surrounding materials.

[0024] 6. In the device of the present invention, during the rapid thermal cycle process, the wafer maintains a high doping concentration, generates a steeper doping profile, and improves its electrical performance and reliability. At the same time, due to the greatly increased annealing speed, while reducing energy consumption, the production efficiency is also improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of an embodiment of the nanosecond annealing device of the present invention.

[0026] Figure 2 It is a schematic diagram of the annealing route of the device of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0027] The following combines the drawings and gives embodiments to describe the present invention in detail.

[0028] The development of laser annealing technology has shortened the annealing time to the nanosecond level. This process uses a high-intensity laser beam to instantaneously heat the surface of the material, making it quickly reach a high temperature and then cool down. By precisely controlling the power and irradiation time of the laser, the crystal structure and physical properties of the material can be effectively improved, while avoiding problems such as overheating and local melting. Nanosecond annealing not only improves the process efficiency but also meets the requirements of rapid heat treatment for increasingly smaller semiconductor nodes. With the gradually increasing requirements for thermal budget control, the relatively mature ms-level annealing process urgently needs to be improved. The present invention proposes a nanosecond annealing device that uses a 10.6 μm laser, which has many advantages during the laser annealing process due to its wavelength characteristics. First, due to the longer wavelength, compared with short-wave lasers such as excimer lasers, the degree of scattering and diffraction of the light beam on the material surface is lower. At the same time, since the interference fringe spacing is proportional to the wavelength, the interference fringes or interference effects formed by the long-wave laser on the material surface are significantly weakened compared with short-wave lasers (such as ultraviolet lasers). This means that when the laser beam irradiates the wafer, it can maintain good irradiation uniformity, improving the controllability and yield of the annealing process.

[0029] The nanosecond annealing device of this embodiment is as Figure 1As shown in the figure, it includes a base, a laser, a mirror I, a mirror II, a beam shaper I, a translation base, a wafer fixture, an infrared radiation collection module, a collection device, a temperature conversion unit, a semiconductor laser, a beam shaper II, and an automatic control unit.

[0030] Specifically, in this embodiment, the base of the entire nanosecond annealing device is a marble base, which is used to place the annealing device to ensure the long-term working stability of the annealing device. Its material is Jinan green marble, which has the characteristics of high hardness and low stress. Its typical size is 900mm×500mm×130mm.

[0031] In this embodiment, the laser is a high-energy pulsed CO 2 laser. The typical type of the laser is a sealed-off radio-frequency excited CO 2 laser. It adopts an integrated closed design, and its compact structure realizes the miniaturization of the laser annealing equipment. Through the excitation of gas molecules by a high-frequency electric field, a more uniform excitation distribution is achieved. It can still maintain a high efficiency under high-power output, and the same or higher output can be achieved with a relatively small volume. At the same time, due to the gas seal, almost no maintenance is required during use, avoiding the cumbersome process of frequently replacing gas in the traditional transverse excitation atmospheric pressure CO 2 laser. This laser can output pulsed laser with a frequency of 100Hz / 120ns / 5J, and the typical wavelength is 10.6μm. The polarization direction is consistent with the P polarization direction of the wafer annealing working plane. The beam output by this laser passes through mirror I, mirror II, and beam shaper I, and is incident on the wafer to be annealed at the Brewster angle (74.3°), providing laser beam and energy for the annealing process. Among them, this laser wavelength is more than 30 times that of the light source wavelength (200 - 350nm) used in the existing nanosecond annealing device, greatly weakening the beam scattering and diffraction effects in the existing nanosecond laser annealing, being beneficial to the temperature uniformity of the annealing area of the wafer to be annealed, and ensuring the yield rate during the annealing process.

[0032] Mirror I is a high-reflection mirror, which has a high reflection for CO 2 laser and transmits the beam output by the CO 2 laser to mirror II. The typical reflectivity of mirror I for CO 2 laser is more than 99%.

[0033] Mirror II is a high-reflection mirror, which has a high reflection for CO 2 laser and transmits the beam reflected by mirror I to beam shaper I. At the same time, mirror II is used to control the transmission direction of CO 2 laser, so that the CO 2 laser is incident on the wafer to be annealed in a P polarization state.

[0034] The beam shaper I includes a beam expander, a Fresnel lens, and a ZnSe focusing lens group. The CO laser beam reflected by the mirror 2 passes through the beam shaper I, and the output optical axis remains unchanged. Compared with the commonly used clipping method in current laser annealing equipment, the Fresnel lens realizes the flat-topping processing of the CO laser through optical transmission transformation, improving the utilization efficiency of laser energy. It ensures that the spot size of the CO laser on the wafer is rectangular and has a flat-top intensity distribution, and the non-uniformity of the intensity distribution ≤ 5%. This intensity distribution characteristic is used to ensure the temperature consistency in the irradiation area of the wafer to be annealed. 2 After the 2 laser beam passes through the beam shaper I, the output optical axis remains unchanged. Compared with the commonly used clipping method in current laser annealing equipment, the Fresnel lens realizes the flat-topping processing of the 2 laser through optical transmission transformation, improving the utilization efficiency of laser energy. 2 It ensures that the 2 laser has a rectangular spot size and a flat-top intensity distribution on the wafer, and the non-uniformity of the intensity distribution ≤ 5%. 2 This intensity distribution characteristic is used to ensure the temperature consistency in the irradiation area of the wafer to be annealed.

[0035] The semiconductor laser is an 880nm laser, which is used for preheating before annealing. In this embodiment, it can output 440W of pulsed laser. The output beam is incident on the preheating area of the wafer through the beam shaper II to provide energy, and it can be well absorbed by the silicon wafer. The beam shaper II is a quartz focusing lens group. A lens group composed of two cylindrical lenses focuses the beam emitted by the semiconductor laser in the X and Y directions to obtain a linearly shaped spot of appropriate size, realizing the shaping of the 880nm laser beam. While ensuring that the output optical axis remains unchanged, the beam shape is adjusted to a rectangular spot and incident on the preheating area of the wafer.

[0036] The translation base is used to install and carry devices such as the translation motor, wafer fixture, and wafer. Its material is Jinan Qing marble, which has high hardness and a small thermal expansion coefficient, avoiding adverse factors such as vibration during wafer movement and providing a good working environment. Its typical dimensions are 550mm × 250mm × 150mm.

[0037] Directly connected to the translation base is the X-Y translation assembly. The X-Y translation assembly has a gantry configuration. The Y-axis is the lower axis with an open structure. The guide rail and linear motor are directly fixed on the translation base. The typical parameters can ensure a moving space of 600mm. The X-axis is the upper axis. The guide rail and linear motor are horizontally mounted above the X-axis. The typical parameters are a total stroke of 1500mm, a maximum movement speed of 5m / s in the uniform speed section, and a stroke ≥ 800mm. The straightness error of the XY-axis movement is ±3μm (within the 800mm movement range), the orthogonality error of the XY-axis is ±3μm (within the 800mm movement range), the flatness error of the movement plane is ±2μm (within the 800mm movement range), and the XY two-way repeat positioning accuracy is ±1μm.

[0038] The infrared radiation collection module collects the infrared radiation of the wafer to the collection device. In this embodiment, the collection device uses a single-photon detector array, and it can also be replaced by a high-speed ICCD camera. In this embodiment, as Figure 1As shown in the figure, the single-photon detector array receives infrared radiation through an infrared radiation collection module composed of a ZnSe filter and a focusing mirror. The filter has a transmittance of 85% @ 1.0μm ± 50nm and has a highly cutoff characteristic for radiation light of other wavelengths, which can effectively filter out the 880nm laser radiation for preheating and the 10.6μm laser radiation for annealing, as well as the influence of other background stray light, and screen the infrared radiation near 1μm. Then, it is converged onto the single-photon detector by a high-transmission focusing mirror with a focal length f = 10cm and an aperture of 50mm. The working wavelength range of the detector is 800 - 1100nm, the detection efficiency is 75%, the response time ≤ 100ps, and the quantum efficiency ≥ 80%. The infrared radiation photon signal collected is converted into an electrical signal by the single-photon detector and generates a pulse to be transmitted to the temperature conversion unit. First, it is amplified by a low-noise amplifier to enhance the signal intensity and overcome the noise in subsequent circuit processing. Then, it is converted into a digital signal by a shaping circuit and an analog-to-digital converter for counting and logical processing, and the radiation intensity at the corresponding wavelength is obtained according to the response function and spectral resolution of the detector. According to Planck's blackbody radiation law:

[0039]

[0040] In the formula, M (λ,T) is the blackbody spectral radiance, and its unit is W / m 3 ; C 1 is the first radiation constant, with a value of 3.7415×10 8 W·μm 4 / m 2 ; C 2 is the second radiation constant, with a value of 1.43879×10 4 μm·K; λ is the wavelength of spectral radiation, with the unit of μm; T is the thermodynamic temperature of the blackbody, with the unit of K. According to the relationship between radiation intensity and wavelength, the temperature is obtained by fitting experimental data (radiation intensity and wavelength), and fitting methods such as the least squares method are often used to calculate the actual temperature value. Before the implementation of this scheme, the temperature conversion relationship was calibrated with a blackbody source with a known temperature to ensure the accuracy of the results.

[0041] The temperature data of the temperature conversion unit is transmitted to the automatic control unit as a feedback value. The automatic control unit calculates the error between the target temperature (set point) and the actual temperature (feedback value) according to the feedback value, and uses the PID control algorithm to automatically regulate the output power of the semiconductor laser and the CO 2 laser. The feedback system adjusts the system behavior in real time according to the change of the error. If there are fluctuations or deviations from the expectation, the feedback mechanism can automatically correct them to ensure the stability and reliability of the system.

[0042] By continuously inputting verified error values and monitoring the feedback effect, the system can gradually optimize its performance and respond quickly to environmental changes. This enables the two to maintain an ideal heating power, thereby ensuring a constant temperature in the preheating area and the annealing area. In terms of the scanning method, this solution selects linear reciprocating scanning. The preheating laser beam is shaped and adjusted to a rectangular area of 11 mm × 0.15 mm, and the CO 2 laser beam is shaped and adjusted to a rectangular area of 8.4 mm × 0.075 mm. The preheating area sweeps through a position slightly ahead of the annealing area to provide a temperature condition above 400 °C for laser annealing, and then the CO 2 laser beam performs the annealing treatment. The specific schematic is as shown in Figure 2 . Through the combination of a translation stage and a rotation stage, the workpiece can achieve an arc scanning effect during movement. When annealing circular arc materials, arc scanning can preferably avoid the edge effect and heating non-uniformity, especially at the corners, caused by linear scanning, and can cover a relatively large area in a single pass, avoiding the repeatability of the scanning route.

[0043] Furthermore, the device of the present invention may further include an infrared pyrometer and a beam expander.

[0044] The infrared pyrometer collects the thermal radiation during the preheating process of LD laser irradiation through the beam expander, and then performs high-frequency temperature measurement based on Planck's blackbody radiation law. The beam expansion ratio of the beam expander is 20 times, and the damage threshold is 7.5 J / cm 2 , with a transmittance of 96% @ 980 nm - 1050 nm. The temperature measurement range of the infrared pyrometer is 300 - 1200 °C, the response band is 0.7 - 1.1 μm, the response time is 120 μs, the measurement accuracy within the temperature measurement range is 0.3% ± 2 °C of the reading, and the repeatability accuracy is 0.15% of the reading. The selection of the wavelength range corresponds to the vicinity of the maximum value of the surface emissivity of the wafer to be annealed at the preheating temperature.

[0045] The temperature data of the infrared pyrometer and the temperature conversion unit are transmitted to the automatic control unit for mutual reference, and the weighted average result is taken as the feedback value to ensure that the data input into the system is as accurate as possible.

[0046] Furthermore, the device of the present invention may further include a signal processing and amplification unit for amplifying the signals acquired by the acquisition device and then inputting them into the temperature conversion unit.

[0047] Furthermore, the pulsed CO 2 laser can also be other types of pulsed long-wave lasers, such as long-wave infrared lasers generated by nonlinear optical frequency conversion technology, which are characterized by high peak power and narrow pulses (1 ns - 200 ns).

[0048] Furthermore, the preheating laser can also be a solid-state laser, such as a Nd:YAG laser with a wavelength of 1064 nm, which generates green light at 532 nm through frequency doubling. Or a near-infrared laser such as an indium gallium arsenide (InGaAs) laser (900 nm to 1700 nm). It is small in size and low in cost, and is suitable for preheating applications with low to medium power and relatively high spatial resolution requirements.

[0049] In summary, the above are only the preferred embodiments of the present invention and are not intended to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A nanosecond annealing device, characterized in that: It includes a base, a laser, a reflector I, a reflector II, a beam shaper I, a translation base, a wafer fixture, an infrared radiation collection module, a collection device, a temperature conversion unit, a semiconductor laser, a beam shaper II and an automatic control unit; The beam output by the laser passes through reflector I, reflector II, and beam shaper I, and is incident on the wafer to be annealed at the Brewster angle; the infrared radiation collection module collects the infrared radiation of the wafer to the collection device; The acquisition device receives infrared radiation via the infrared radiation collection module, converts the collected infrared radiation photon signal into an electrical signal, generates a pulse and transmits it to the temperature conversion unit; The temperature conversion unit obtains temperature data according to the pulse and transmits it to the automatic control unit as a feedback value. The automatic control unit calculates the error between the target temperature and the actual temperature according to the feedback value and automatically adjusts the semiconductor laser and the laser output power. The base is used for placing the annealing device; the semiconductor laser is used for preheating before annealing; the beam shaper II focuses the light beam emitted by the semiconductor laser in the X and Y directions; and the translation base is used for installing and carrying components.

2. A nanosecond annealing device according to claim 1, characterized in that: Mirror I is a high reflector, which transmits the light beam output by the laser to reflector II; reflector II is a high reflector, which transmits the light beam reflected by reflector I to beam shaper I; reflector II is used to control the transmission direction of the laser so that the laser is incident on the wafer to be annealed in a P polarization state.

3. A nanosecond annealing device according to claim 2, characterized in that: The beam shaper I includes a beam expander, a Fresnel lens and a ZnSe focusing lens group. After the laser beam reflected by the reflector II passes through the beam shaper I, the output optical axis remains unchanged; while ensuring that the output optical axis remains unchanged, the beam shape is adjusted by the beam shape into a rectangular spot to be incident on the preheating area on the wafer.

4. The nanosecond annealing device according to claim 1, characterized in that: The translation base is directly connected to the translation base with an XY translation assembly. The XY translation assembly is a gantry configuration, the Y axis is the lower axis, the open structure, the guide rail and the linear motor are directly fixed on the translation base; the X axis is the upper axis, and the guide rail and the linear motor are horizontally mounted on the X axis.

5. The nanosecond annealing device according to claim 4, characterized in that: The automatic control unit uses a PID control algorithm to automatically adjust the laser output power to keep the temperatures of the preheating area and the annealing area constant.

6. The nanosecond annealing device according to any one of claims 1 to 5, characterized in that: The laser is a sealed radio frequency excited CO2 laser with an integrated closed design.

7. The nanosecond annealing device according to claim 6, characterized in that: The infrared radiation collection module includes a ZnSe filter and a focusing lens to receive infrared radiation. The filter is used to screen infrared radiation near 1 μm, and the working wavelength range of the detector is 800-1100 nm.

8. The nanosecond annealing device according to claim 6 or 7, characterized in that: The beam shaper II is a quartz focusing lens group, which uses a lens group composed of two cylindrical lenses to focus the light beam in the X and Y directions to obtain a linear light spot, thereby realizing the shaping of the laser beam.

9. The nanosecond annealing device according to claim 8, characterized in that: The scanning mode of the preheating area and the annealing area is linear reciprocating scanning. The preheating laser beam is shaped and adjusted to a 11mm×0.15mm rectangular area, and the CO2 laser beam is shaped and adjusted to a 8.4mm×0.075mm rectangular area.

10. The nanosecond annealing device according to claim 1, characterized in that: It also includes an infrared pyrometer and a beam expander, wherein the infrared pyrometer collects thermal radiation during the laser irradiation preheating process through the beam expander.

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