A method of laser anneal monitoring

Abstract

Embodiments of the present application provide a laser annealing monitoring method, comprising: ion implantation on a wafer at a set angle; wherein the set angle is an angle between an ion implantation direction and a crystal axis of the wafer, and the set angle is greater than 0; laser annealing on the wafer; measuring an electrical parameter of the wafer; and determining a process state of the laser annealing according to the electrical parameter. Embodiments of the present application can improve the monitoring precision of the annealing process.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and in particular to a laser annealing monitoring method. Background Technology

[0002] In semiconductor manufacturing, ion implantation damages the wafer's crystal lattice by bombarding atoms out of it. Annealing heats the implanted wafer, repairing lattice defects and activating impurity atoms by moving them to lattice points. Therefore, annealing significantly impacts the performance of semiconductor devices, necessitating monitoring of the annealing process. However, current technologies for monitoring the annealing process lack sufficient accuracy. Summary of the Invention

[0003] This invention provides a laser annealing monitoring method to improve the monitoring accuracy of the annealing process.

[0004] According to one aspect of the present invention, a laser annealing monitoring method is provided, comprising: Ion implantation is performed on a wafer at a set angle; wherein the set angle is the angle between the ion implantation direction and the crystal axis of the wafer, and the set angle is greater than 0. The wafer is subjected to laser annealing; Measure the electrical parameters of the wafer; The process state of laser annealing is determined based on the electrical parameters.

[0005] Optionally, the set angle is greater than or equal to 6 degrees and less than or equal to 8 degrees.

[0006] Optionally, the wafer is a silicon wafer or a silicon carbide wafer.

[0007] Optionally, the laser annealing depth is greater than or equal to the ion implantation depth, and less than or equal to 110% of the ion implantation depth.

[0008] Optionally, the laser used for laser annealing has a wavelength greater than or equal to 248 nm and less than or equal to 532 nm.

[0009] Optionally, determining the process state of laser annealing based on the electrical parameters includes: The process state of laser annealing is determined based on the electrical parameters and the wafer electrical parameters obtained from n previous measurements, where n is an integer greater than or equal to 1.

[0010] Optionally, the process state of laser annealing is determined based on the electrical parameters and the wafer electrical parameters obtained from n previous measurements, including: The laser annealing process state is determined based on the differences between the electrical parameters and the wafer electrical parameters obtained from the previous n measurements.

[0011] Optionally, the laser annealing process state is determined based on the differences between the electrical parameters and the wafer electrical parameters obtained from the previous n measurements, including: When the difference between the electrical parameters and the wafer electrical parameters obtained from the previous n measurements meets the set requirements, the energy of laser annealing is determined to be stable. When the difference between the electrical parameters and the wafer electrical parameters obtained from the previous n measurements does not meet the set requirements, the energy attenuation of laser annealing is determined.

[0012] Optionally, the electrical parameters include resistance values.

[0013] Optionally, measuring the electrical parameters of the wafer includes: The resistance value of the wafer was measured using a four-probe resistance meter.

[0014] In this embodiment, ion implantation is performed on the wafer at a set angle. The set angle is the angle between the ion implantation direction and the crystal axis of the wafer. The set angle is greater than 0, which can avoid the channel effect. This allows impurities and damage to be densely distributed near the surface after ion implantation, which can be covered by the laser annealing depth. When the laser energy density decays, some doped regions are not fully activated, resulting in a large change in the wafer's electrical parameters. By measuring the wafer's electrical parameters, the change in laser annealing energy can be accurately monitored, improving the monitoring accuracy.

[0015] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of the present invention, nor is it intended to limit the scope of the invention. Other features of the invention will become readily apparent from the following description. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a flowchart of a laser annealing monitoring method provided in an embodiment of this application.

[0018] Figure 2 This is a schematic diagram of ion implantation of a wafer provided in an embodiment of this application.

[0019] Figure 3 This is a carrier distribution curve provided in this application after ion implantation.

[0020] Figure 4This is a schematic diagram of atomic distribution provided in an embodiment of this application.

[0021] Figure 5 This is another carrier distribution curve after ion implantation provided in this application.

[0022] Figure 6 This is another schematic diagram of atomic distribution provided in the embodiments of this application. Detailed Implementation

[0023] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0024] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0025] This application provides a laser annealing monitoring method. Figure 1 This is a flowchart of a laser annealing monitoring method provided in an embodiment of this application, see reference. Figure 1 Laser annealing monitoring methods include: S110. Ion implantation is performed on the wafer at a set angle; wherein, the set angle is the angle between the ion implantation direction and the crystal axis of the wafer, and the set angle is greater than 0.

[0026] S120, Laser annealing of the wafer.

[0027] S130, Measure the resistance of the wafer.

[0028] S140. Determine the process state of laser annealing based on the resistance value.

[0029] The wafer can be a silicon wafer or a silicon carbide wafer, etc. This application does not limit the specific material of the wafer. Figure 2 This is a schematic diagram of ion implantation on a wafer provided in an embodiment of this application, with reference to... Figure 2 The dashed line in the figure shows the crystal axis of wafer 10, and the line with the arrow indicates the ion implantation direction, with the angle A set to be greater than 0. Figure 2 The illustration only shows, by way of example, that the crystal axis of wafer 10 is perpendicular to the surface of wafer 10, and is not intended to limit the scope of this application. In other embodiments, the crystal axis may not necessarily be perpendicular to the surface of wafer 10.

[0030] The inventors discovered through research that laser annealing is characterized by extremely short processing times (nanoseconds) and shallow high-temperature phase transition melting depths (surface layer). This means that conventional laser annealing can only repair shallow implantation damage and activate shallow doping. During this process, a decrease in reflectivity and transmittance is a hallmark signal of the molten state. Fluctuations in laser energy density affect the surface thermal melting depth, thereby affecting the activation depth, the number of charge carriers in the conductive layer, and the wafer resistance value Rs. When ions are implanted into a crystal, the ion distribution is strongly dependent on the implantation angle. Figure 3 This is a carrier distribution curve provided in this application after ion implantation. Figure 4 This is a schematic diagram of atomic distribution provided in an embodiment of this application, for reference. Figure 3 and Figure 4 , Figure 4 The red circles represent injected atoms, while the black circles represent the original atoms on the wafer. Figure 4 An exemplary illustration of atomic distribution is provided. When ion implantation is performed in a direction parallel to the wafer's crystal axis, i.e., 0-degree ion implantation, ions are implanted along the main crystal axis. The ion distribution is dominated by the channeling effect, the doping depth distribution is deep, gentle, and long-tailed, and the damage distribution is sparse, widely distributed, and has a deep damage peak. Figure 3 As shown in the figure, after ion implantation, the peak damage is located at 7-8 μm. Laser annealing, on the other hand, is adept at repairing surface damage, such as... Figure 4 Laser annealing only repairs damage in the shallow region 11; atoms deeper remain inactive and non-conductive. Therefore, the final measured wafer resistance value Rs mainly depends on the shallow activated layer. When the laser energy density fluctuates within a small range, the melting depth changes slightly. However, the number of activated atoms distributed in the shallow region is limited, and the small change in laser energy cannot affect the deep inactive atoms. Therefore, the change in laser energy has little impact on the overall number of conductive particles, and the wafer resistance value Rs changes little. Consequently, the change in laser energy cannot be reflected by the wafer resistance value RS.

[0031] When ions deviate from the main crystal axis during ion implantation, the ion distribution is dominated by random scattering collisions, exhibiting a shallow, steep, near-Gaussian distribution, with damage densely distributed near the surface. When ions deviate from the main crystal axis during ion implantation, both impurities and damage are densely distributed near the surface, while activated atoms are distributed in the shallow region, which can be covered by the laser annealing depth. As the laser energy density decreases, the thermal melting depth decreases, resulting in some doped regions not being fully activated. Due to the high density of doped atoms in the shallow region, many atoms remain unactivated and unable to conduct electricity, causing a sharp increase in the wafer resistance value Rs. The change in laser annealing energy can be monitored by measuring the wafer resistance value Rs.

[0032] For example, Figure 5 This is another carrier distribution curve after ion implantation provided in this application. Figure 6 This is another schematic diagram of atomic distribution provided in the embodiments of this application, see reference. Figure 5 and Figure 6 With the angle set at 7 degrees, after ion implantation, the implanted atoms (red circles) are mainly distributed on the surface. The maximum damage peak of 7° implantation is located at 2μm. After laser annealing, laser annealing can repair ion implantation damage. When the laser energy decays, the thermal melting depth decreases, the doped region is not fully activated, and the wafer resistance value Rs will increase sharply.

[0033] In this embodiment, ion implantation is performed on the wafer at a set angle. The set angle is the angle between the ion implantation direction and the crystal axis of the wafer. The set angle is greater than 0, which can avoid the channel effect. This allows impurities and damage to be densely distributed near the surface after ion implantation, which can be covered by the laser annealing depth. When the laser energy density decays, some doped regions are not fully activated, resulting in a significant increase in the wafer resistance value Rs. By measuring the wafer resistance value Rs, the change in laser annealing energy can be accurately monitored, thus improving the monitoring accuracy.

[0034] Based on the above embodiments, optionally, the angle is set to be greater than or equal to 6 degrees and less than or equal to 8 degrees.

[0035] For details, please refer to Figure 5 and Figure 6 When the implantation angle is set to 6-8 degrees, the ions deviate from the crystal axis, the damage distribution is closest to the surface, and the implanted atomic distribution density is the highest. When the laser energy density decays, resulting in some doped regions not being fully activated, the wafer resistance value Rs changes the most. By measuring the change in resistance value, the annealing process can be monitored more accurately.

[0036] Based on the above embodiments, optionally, the wafer is a silicon wafer or a silicon carbide wafer.

[0037] Based on the above embodiments, optionally, the laser annealing depth is greater than or equal to the ion implantation depth, and less than or equal to 110% of the ion implantation depth.

[0038] Specifically, when the ion implantation depth is greater than the laser annealing depth, the implanted atomic density is lower, and the impact of laser energy fluctuations on the wafer resistance value Rs is smaller, resulting in a smaller change in Rs. Conversely, when the laser annealing depth is too large, even with minimal laser energy attenuation, the wafer resistance value Rs remains relatively stable as long as the laser depth is greater than or equal to the ion implantation depth. By setting the laser annealing depth to be greater than or equal to the ion implantation depth, and less than or equal to 110% of the ion implantation depth, a larger change in wafer resistance value Rs is ensured when laser energy changes, thereby improving the accuracy of laser annealing process monitoring.

[0039] For example, the depth of ion implantation can be adjusted by adjusting the energy of ion implantation, and the depth of laser annealing can be adjusted by adjusting the laser wavelength and energy.

[0040] Based on the above embodiments, optionally, the wavelength of the laser used for laser annealing is greater than or equal to 248nm and less than or equal to 532nm.

[0041] This configuration ensures that the laser penetration depth is greater than or equal to the ion implantation depth, and less than or equal to 110% of the ion implantation depth, thus ensuring that the wafer resistance value Rs changes significantly when the laser energy fluctuates.

[0042] Based on the above embodiments, optionally, determining the process state of laser annealing according to the resistance value includes: The process state of laser annealing is determined based on the resistance value and the wafer resistance values ​​obtained from n previous measurements, where n is an integer greater than or equal to 1.

[0043] Specifically, the resistance value of the wafer is measured at regular intervals after annealing. The resistance value obtained in this measurement is compared with the resistance values ​​obtained in the previous n measurements to determine the annealing process status. For example, the resistance value of the wafer can be measured daily or weekly to monitor the annealing process status in real time. n can be 2, 3, 4, 5, 6, 7, etc.

[0044] Based on the above embodiments, optionally, the process state of laser annealing is determined according to the resistance value and the wafer resistance values ​​obtained from the previous n measurements, including: determining the process state of laser annealing according to the difference between the resistance value and the wafer resistance values ​​obtained from the previous n measurements.

[0045] Specifically, the resistance value measured this time can be subtracted from the resistance values ​​measured in the previous n measurements to obtain n difference values. These n differences are then compared with a set difference value, and the annealing process state is determined based on the comparison results. Alternatively, the variance and standard deviation of the n differences can be calculated, and the process state can be determined based on the calculation results.

[0046] Optionally, the laser annealing process state is determined based on the differences between the electrical parameters and the wafer electrical parameters obtained from the previous n measurements, including: When the difference between the electrical parameters and the wafer electrical parameters obtained from the previous n measurements meets the set requirements, the energy of laser annealing is determined to be stable. When the difference between the electrical parameters and the wafer electrical parameters obtained from the previous n measurements does not meet the set requirements, the energy attenuation of laser annealing is determined.

[0047] Specifically, if the difference between the measured resistance value and the wafer resistance values ​​obtained from the previous n measurements is too large, it is determined that the laser energy attenuation during laser annealing is significant, indicating energy attenuation in the laser annealing process. If the difference between the measured resistance value and the wafer resistance values ​​obtained from the previous n measurements is within a set range, it is determined that the laser energy attenuation during laser annealing is small or non-existent, indicating stable energy during laser annealing.

[0048] Based on the above embodiments, optionally, measuring the resistance value of the wafer includes: The resistance value of the wafer was measured using a four-probe resistance meter.

[0049] Specifically, the four-probe resistor meter has high resistance measurement accuracy, which can accurately measure the resistance of the wafer, reduce the monitoring error caused by resistance measurement error, and further improve the monitoring accuracy of the laser annealing process.

[0050] It should be understood that the various forms of processes shown above can be used, with steps reordered, added, or deleted. For example, the steps described in this invention can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution of this invention can be achieved, and this is not limited herein.

[0051] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A laser annealing monitoring method, characterized in that, include: Ion implantation is performed on a wafer at a set angle; wherein the set angle is the angle between the ion implantation direction and the crystal axis of the wafer, and the set angle is greater than 0. The wafer is subjected to laser annealing; Measure the electrical parameters of the wafer; The process state of laser annealing is determined based on the electrical parameters.

2. The monitoring method according to claim 1, characterized in that: The set angle is greater than or equal to 6 degrees and less than or equal to 8 degrees.

3. The monitoring method according to claim 1, characterized in that: The depth of laser annealing is greater than or equal to the implantation depth of ion implantation, and less than or equal to 110% of the implantation depth of ion implantation.

4. The monitoring method according to claim 1, characterized in that: The laser used in laser annealing has a wavelength greater than or equal to 248nm and less than or equal to 532nm.

5. The monitoring method according to claim 1, characterized in that, Determining the laser annealing process state based on the electrical parameters includes: The process state of laser annealing is determined based on the electrical parameters and the wafer electrical parameters obtained from n previous measurements, where n is an integer greater than or equal to 1.

6. The monitoring method according to claim 5, characterized in that, The laser annealing process state is determined based on the electrical parameters and the wafer electrical parameters obtained from n previous measurements, including: The laser annealing process state is determined based on the differences between the electrical parameters and the wafer electrical parameters obtained from the previous n measurements.

7. The monitoring method according to claim 6, characterized in that, The laser annealing process state is determined based on the differences between the electrical parameters and the wafer electrical parameters obtained from the previous n measurements, including: When the difference between the electrical parameters and the wafer electrical parameters obtained from the previous n measurements meets the set requirements, the energy of laser annealing is determined to be stable. When the difference between the electrical parameters and the wafer electrical parameters obtained from the previous n measurements does not meet the set requirements, the energy attenuation of laser annealing is determined.

8. The monitoring method according to claim 1, characterized in that, The electrical parameters include resistance values.

9. The monitoring method according to claim 8, characterized in that, Measuring the electrical parameters of the wafer includes: The resistance value of the wafer was measured using a four-probe resistance meter.

10. The monitoring method according to claim 1, characterized in that: The wafer is a silicon wafer or a silicon carbide wafer.

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