Laser annealing energy control method and laser annealing apparatus

Abstract

The present invention provides a laser annealing energy control method and a laser annealing apparatus. In the laser annealing energy control method, when a laser spot moves relative to a substrate with a first laser power, the laser power of the laser spot is reduced to a second laser power at a first position relative to the substrate; when the laser spot moves relative to the substrate to a second position, and then moves from the second position to a third position relative to the substrate, the laser power is increased to a third laser power; and the laser spot performs scanning annealing on the substrate with the third laser power. By moving the laser spot to the edge of the substrate and reducing the laser power, energy spike problems and chipping problems due to thermal stress at the edge of the substrate are prevented.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and particularly to a laser annealing energy control method and a laser annealing apparatus.

Background Art

[0002] In recent years, as the process node of integrated circuits has been developing towards smaller sizes (40 mm or less), the junction depths of the source region, drain region, and lightly doped drain (LDD) region have become smaller and smaller, and the manufacturing of corresponding shallow junctions has become an increasingly important process module. In order to solve the short-channel effect caused by the reduction of the gate length, it is necessary to shallowly implant ions into the source and drain to form an ultra-shallow junction (USJ). Since the junction depths and lateral dimensions of the source-drain PN junction and the lightly doped drain PN junction are determined by the annealing process, in the annealing process, it is required to have a high annealing temperature and a low annealing thermal budget to meet the requirements of advanced manufacturing processes such as low stress, low diffusion, high activation, and high uniformity.

[0003] Laser Annealing is an annealing process commonly used in integrated circuit technology. Laser Annealing utilizes a laser beam with a certain amount of energy to quickly scan the surface of the substrate, thereby realizing an annealing effect in microseconds in a certain differential region on the substrate. When performing laser scanning, the heat in the middle part of the substrate may be dissipated to the edge region of the substrate, but the situation in the edge region of the substrate is relatively complex. On the one hand, since there is a lack of a heat dissipation surface at the edge of the substrate, heat dissipation is difficult, the annealing time becomes longer, and the thermal budget increases. On the other hand, since there are some potential defects at the edge of the substrate, when excited by thermal stress, cracks are likely to occur in the substrate from the defect sites.

[0004] The current solution to the above problem involves installing guard rings at the edges of the substrate. However, when annealing is performed from the edges of the substrate, chipping occurs at the edges due to high power intrusion, edge defects, or thermal stress. This is because, during the annealing process, energy spikes occur due to thermal diffusion in the intermediate region of the substrate, edge defects, and switching of energy control at the substrate edges. When excited by thermal stress, these spikes are likely to cause chipping of the substrate or a decrease in yield.

[0005] Another solution to the above problem involves constant power control via a software interface, controlling the laser power output (high-level light emission, low-level light closure) during the annealing process using a gate signal. However, this method has the problem of mutations occurring due to excessively high power after large energy switching, resulting in energy spikes in energy control at the substrate edge, uneven temperature distribution on the annealed surface, and increased susceptibility to abnormal traces, leading to reduced yield and chipping problems. [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] The object of the present invention is to provide a laser annealing energy control method and a laser annealing apparatus that reduce or avoid the possibility of substrate chipping or yield reduction occurring during the laser annealing process. [Means for solving the problem]

[0007] To solve the above technical problems, the present invention provides A laser annealing energy control method is provided, comprising: moving a laser spot with a first laser power relative to a substrate, reducing the laser power of the laser spot to a second laser power at a first position relative to the substrate; increasing the laser power to a third laser power when the laser spot moves from the second position relative to the substrate to a third position relative to the substrate; and the laser spot performing scanning annealing on the substrate with the third laser power.

[0008] Optionally, the laser spot moves from the first position relative to the substrate to the second position relative to the substrate using the second laser power.

[0009] In the process in which the laser spot moves from the second position on the substrate to the third position on the substrate, optionally, the second laser power is first increased to the fourth laser power, and then further increased to the third laser power.

[0010] Optionally, the rate at which the laser power is increased from the second laser power to the fourth laser power is greater than the rate at which it is increased from the fourth laser power to the third laser power.

[0011] Optionally, the fourth laser power is 50% to 150% of the first laser power.

[0012] Optionally, the first position relative to the substrate is an outer edge contact of the substrate or in front of an outer edge contact of the substrate along the direction of movement of the laser spot relative to the substrate; the second position relative to the substrate is an inner edge contact of the substrate or in behind an inner edge contact of the substrate along the direction of movement of the laser spot relative to the substrate.

[0013] Optionally, the first laser power is one-third to two-thirds of the third laser power, and the second laser power is less than one-third of the third laser power.

[0014] Based on a similar inventive concept, the present invention further provides a laser annealing apparatus for performing the laser annealing energy control method described in any one of the preceding paragraphs.

[0015] In the laser annealing energy control method and laser annealing apparatus according to the present invention, when a laser spot moves with respect to a substrate at a first laser power, the laser power of the laser spot is reduced to a second laser power at a first position relative to the substrate; when the laser spot moves to a second position relative to the substrate, and then moves from the second position to a third position relative to the substrate, the laser power is increased to a third laser power; and the laser spot performs scanning annealing on the substrate at the third laser power. By switching from the first laser power to the second laser power when the laser spot moves to a first position on the substrate, the laser power is reduced to prevent chipping of the substrate.

[0016] Furthermore, when the laser spot moves to a second position on the substrate, the second laser power is first increased to the fourth laser power. The power increases rapidly to preheat the lens in the output optical path, reducing the expansion effect and improving spot uniformity, allowing higher spot quality to enter the scan and improving annealing uniformity. In addition, increasing the fourth laser power to the third laser power prevents energy spike problems at the substrate edges and chipping problems due to thermal stress. [Brief explanation of the drawing]

[0017] Those skilled in the art will understand that the accompanying drawings are provided to better understand the present invention and do not limit its scope. Here,

[0018] [Figure 1] This is a diagram illustrating the process of a laser annealing energy control method according to an embodiment of the present invention. [Figure 2] This diagram shows the process structure of substrate position and laser power change in a laser annealing process according to an embodiment of the present invention. [Figure 3] This diagram shows the process curve of the changes in substrate position and laser power in the laser annealing process according to an embodiment of the present invention. [Figure 4] This is a drawing showing the structure of the substrate scanning region in the laser annealing process according to an embodiment of the present invention. [Modes for carrying out the invention]

[0019] To further clarify the purpose, advantages, and features of the present invention, the invention will be described in more detail below with reference to the drawings and specific embodiments. It should be noted that the drawings are in a highly simplified form, are not drawn proportionally, and are merely supplementary to easily and clearly illustrate the purpose of the embodiments of the present invention. Furthermore, the structures shown in the drawings are often only parts of the actual structures. In particular, the key points shown in each drawing vary, and different scales may be used.

[0020] In this invention, the singular forms "one," "one," and "the said" include multiple objects; the term "or" is usually used to mean "and / or"; the term "several" is usually used to mean "at least one"; the term "at least two" is usually used to mean "two or more than two"; and the terms "first," "second," and "third" are merely for descriptive purposes and should not be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. Therefore, the features that are limited by “first,” “second,” and “third” may explicitly or implicitly include one or at least two such features, the terms “one end” and “the other end” and “near end” and “far end” usually refer to two corresponding parts, including endpoints, and the terms “attachment,” “connected to one another,” and “connection” should be understood broadly, for example, they may be fixedly connected, detachably connected, or become one; they may be mechanically connected, electrically connected; they may be directly connected, indirectly connected via an intermediate medium, or be internal communication between two elements or an interaction relationship between two elements. Also, as used in the present invention, one element is attached to another element, and there is usually a connection, coupling, mating or transmission relationship between the two elements, and the connection, coupling, mating or transmission between the two elements may be direct or indirectly via an intermediate element, and should not be understood to indicate or imply a spatial positional relationship between the two elements. In other words, unless otherwise explicitly stated in the content, one element may be in any orientation, such as inside, outside, above, below, or to one side of another element. Those skilled in the art will be able to understand the specific meaning of the above terms in this invention depending on the specific situation.

[0021] Figure 1 is a diagram illustrating the process of a laser annealing energy control method according to an embodiment of the present invention. As shown in Figure 1, this embodiment provides a laser annealing energy control method comprising the following steps: Step S10: When the laser spot moves on the substrate at the first laser power, the laser power of the laser spot at the first position with respect to the substrate is reduced to the second laser power; Here, the reduction of the first laser power to the second laser power may be a gradual reduction or an immediate reduction.

[0022] Step S20: The laser spot moves to the second position with respect to the substrate; when the laser spot moves from the second position with respect to the substrate to the third position with respect to the substrate, the laser power is increased to the third laser power, and the laser spot performs scanning annealing on the substrate at the third laser power.

[0023] Here, the laser spot may move from the first position with respect to the substrate to the second position with respect to the substrate at the second laser power. During the movement, the power may be increased or decreased.

[0024] Furthermore, in the process of the laser spot moving from the second position with respect to the substrate to the third position with respect to the substrate, first, the second laser power is increased to the fourth laser power, and then further increased to the third laser power. The increase rate of increasing the laser power from the second laser power to the fourth laser power is greater than the increase rate of increasing from the fourth laser power to the third laser power.

[0025] Step S30: When the laser spot moves on the substrate at the third laser power, the laser power of the laser spot at the fourth position with respect to the substrate is reduced to the second laser power.

[0026] Step S40: When the laser spot moves on the substrate at the second laser power, the laser power of the laser spot at the fifth position with respect to the substrate is switched to the first laser power, and the first field scanning is ended.

[0027] In step S50, the field scanning process is repeated until the annealing process for the entire substrate is completed.

[0028] In this embodiment, the laser annealing process can be controlled by increasing or decreasing the laser power using an analog signal. Laser modulation uses light as a carrier, loading a signal onto the light to transmit the signal according to the application requirements. Generally, modulation is divided into external modulation and internal modulation. External modulation refers to mechanical modulation or acousto-optic modulation performed outside the laser, while internal modulation refers to power-driven modulation. Here, internal modulation is further divided into TTL (Transister-Transister-Logic) modulation and analog modulation. In the prior art, TTL modulation outputs closed light at low levels and full power at high levels when a DC signal of a constant frequency and high or low level (0V or 5V) is input to the laser from an external source, and the amplitude at high levels cannot be adjusted. In this embodiment, the laser modulation can freely adjust the waveform and amplitude of the input signal using analog modulation, and the laser output power changes linearly with the input analog voltage signal.

[0029] As shown in Figure 2, before performing the laser annealing process on the substrate, the laser is positioned in a safe location. That is, there is no positive film under the laser, and either a test film or a shielding device that will not be burned by the laser is placed under the laser. The laser power is increased to the annealing power, and after detecting the power stability, it is set to the safe power. The laser power is reduced to the safe shutter power, and then switched to the travel power. When the laser spot moves to the first position on the substrate at the travel power (first laser power), the laser power is reduced from the travel power to the safe power. When the laser spot moves to the second position on the substrate, it is immediately increased to the travel power, and then further increased to the annealing power by the lamp control function. In other words, when the laser spot moves to a third position relative to the substrate, the laser power is annealing power. When the laser spot moves to a fourth position relative to the substrate, the annealing power is switched to safety power. When the laser spot moves to a fifth position relative to the substrate, the first field scan is completed, and the power is switched to inter-field switching power to perform the next field scan. Immediately increasing the power to inter-field switching power when the laser spot moves to a second position relative to the substrate means that the laser device increases from safety power to inter-field switching power within the fastest possible response time.

[0030] Specifically, as shown in Figure 2, a substrate 10 is provided, and when the laser spot is moved to a first position A on the substrate with a first laser power P1, the first laser power P1 is reduced to a second laser power P2, which may be immediate or gradually. The first position A on the substrate 10 is located in front of the first external contact outside the edge of the substrate 10 or the first external contact outside the edge of the substrate, along the direction of movement of the laser spot on the substrate, and the distance between the first position A on the substrate and the first external contact outside the edge of the substrate is, for example, 0 to 5 mm. In this embodiment, the distance between the first position A on the substrate 10 and the first external contact outside the edge of the substrate is, for example, 0.5 mm. That is, even when the laser spot has not yet moved to the edge of the substrate 10, the first laser power P1 has already been reduced to the second laser power P2. The first laser power P1 is a field-to-field switching power, and the first laser power P1 (Travel Power) can be configured as a mechanical constant depending on the process requirements. These configuration parameters are used to switch the inter-field transition power during the scanning process. The first laser power P1 is, for example, 1000W to 2000W. The first laser power P1 is one-third to two-thirds of the third laser power P3. The second laser power P2 is a safe power, and the second laser power P2 (Safe Power) can be configured as a mechanical constant according to process requirements. These configuration parameters are used for annealing protection power at the substrate edge. The second laser power P2 is, for example, 0 to 1000W. The second laser power P2 is less than one-third of the third laser power P3. By employing a safe laser power at the substrate edge and moving the laser spot onto the substrate, it is ensured that the power inside the laser remains stable, thus preventing a decrease in laser power stability due to power switching.

[0031] As shown in Figures 2 and 3, when the laser spot moves from the first position A on the substrate 10 to the second position B on the substrate with a second laser power P2, the second laser power P2 immediately increases to the fourth laser power P4, and then increases to the third laser power P3 within a predetermined time. That is, when the laser spot moves from the second position B on the substrate to the third position C on the substrate, the second laser power P2 is first increased to the fourth laser power P4, and then to the third laser power P3. The rate of increase from the second laser power P2 to the fourth laser power P4 is greater than the rate of increase from the fourth laser power P4 to the third laser power P3. The fourth laser power P4 is 50% to 150% of the first laser power P1. In this embodiment, the fourth laser power P4 is 100% of the first laser power P1, that is, the second laser power P2 immediately increases to the first laser power P1.

[0032] The second position B on the substrate 10 is located at or behind the first inner contact point within the edge of the substrate along the direction of movement of the laser spot relative to the substrate. That is, after the laser spot moves to the first inner contact point on the edge of the substrate relative to the substrate, the laser power is immediately increased to the first laser power P1. When the laser spot moves to the first inner contact point within the edge of the substrate relative to the substrate at low power, the second laser power P2 is immediately increased to the first laser power P1. The rapid increase in power preheats the lens in the output optical path, reduces the expansion effect, improves spot uniformity, allows for higher spot quality scanning, and improves annealing uniformity. The laser power is increased to the third laser power P3, and the substrate is scanned to the annealing start point, for example, a position 2 mm away from the edge of the substrate. The substrate within a range 2 mm away from the edge of the substrate does not need to be annealed, and the third laser power P3 is the annealing power. The third laser power P3 is, for example, 2000W to 3000W. The third laser power P3 can be modified according to process requirements, and this configuration parameter is used for the annealing process power and is not limited in this embodiment. A ramp power control function is employed to increase the first laser power P1 to the third laser power P3. The time it takes to immediately increase the second laser power P2 to the first laser power P1 is shorter than the time it takes to increase the first laser power P1 to the third laser power P3.

[0033] The predetermined time for increasing the first power P1 to the third power P3 is, for example, less than 50 ms. In this embodiment, the predetermined time for increasing the first power P1 to the third laser power P3 is 0.01 ms to 10 ms. Since the ramp power control time is within 50 ms, laser energy spike problems and substrate chipping problems can be effectively prevented, and a power increase rate of 500 W / ms is most preferable. The first field scanning annealing process is started. The ramp power control can be configured with mechanical constants according to process requirements. These configuration parameters are used for power control during the process in which the first laser power P1 increases to the third laser power P3 during the scanning field switching process. By adjusting the power increase time, the scanning start position is preheated, and the energy overshoot problem during high power switching can be avoided. By switching the state of the first laser power P1 and the third laser power P3, trace abnormalities and chipping phenomena at the scanning start position of the substrate 10 caused by the first pulse power being too high during the high-energy switching process can be reduced. The lamp power control function preheats the starting position of the substrate 10 where the laser spot moves relative to the substrate, while simultaneously reducing energy overshoot, avoiding chipping problems, and improving the uniformity of annealing.

[0034] The lamp power control function prevents energy spikes that occur when switching energy levels, allowing for a smooth transition and output of laser beam energy, thus preventing chipping problems caused by edge defects or thermal stress.

[0035] Next, referring to Figures 2 and 3, when the laser spot moves from the third position C on the substrate 10 to the fourth position D on the substrate 10 at the third laser power P3, the third laser power P3 is switched to the second laser power P2. The fourth position D on the substrate 10 is located at or in front of the second inner contact point within the edge of the substrate along the direction of movement of the laser spot relative to the substrate. That is, even when the laser spot has not yet moved to the second inner contact point within the edge of the substrate, the laser power has already been reduced to the second laser power. In this embodiment, the first field scan ends at a position 0.5 mm before the inscribed position on the edge of the substrate, and the laser power is switched to the second laser power P2.

[0036] When the laser spot moves to the fifth position E on the substrate 10 with the second laser power P2, the second laser power P2 is switched to the first laser power P1, and the first field scan is terminated. The fifth position E on the substrate 10 is located behind the second outer contact or second outer contact outside the edge of the substrate, along the direction of movement of the laser spot relative to the substrate, and the distance between the fifth position E on the substrate and the second outer contact outside the edge of the substrate is 0 to 5 mm. In other words, the second laser power P2 is switched to the first laser power P1 after the laser spot has moved to the second outer contact outside the edge of the substrate relative to the substrate. Specifically, after moving outside the edge of the substrate in synchronization with the scan, the first field receives a scan synchronization termination signal, and then the laser power is controlled by an analog signal to decrease to the first laser power P1. To address the problem of damage caused by light emitted from the same point while the work stage is relatively stationary during deceleration and acceleration when switching between fields, after scanning is completed between scanning fields, there is a section where the speed is relatively stationary at the start of deceleration and acceleration of the work stage. By controlling the laser power so that the laser power is reduced from the first laser power P1 to the second laser power P2 during the stationary stage, static annealing at the same position is reduced, and the appearance of abnormal traces at the annealing position of the substrate edge is reduced. At the start of the acceleration phase of the work stage, the laser is increased to the first laser power P1, maintaining a good spot shape while preserving the stability of the laser power and thermal deformation of the lens.

[0037] The field scanning process is repeated until the annealing process for the entire substrate is completed. Specifically, as shown in Figures 1 and 4, the substrate has multiple field scans, including, for example, a first field scan 10a and a second field scan 10b. Once the first field scan 10a is completed, the second field scan 10b proceeds. Specifically, in the second field scan 10b, the energy is switched to the second laser power P2 (safe power) at the first position on the substrate, and when the laser spot moves to an in-bound position within the edge of the substrate at low power, the second laser power P2 (safe power) is immediately increased to the first laser power P1 (Travel Power). The lamp power control function increases the laser output power to the third laser power P3, initiating the scanning annealing process for the second field, and the above scanning process is repeated until the last field.

[0038] In Figure 4, the outer contact is the point where the laser spot contacts the outer edge of the substrate, and the inner contact is the point where the laser spot contacts the inner edge of the substrate. In this embodiment, the first position A of the substrate 10 is located at or in front of the first outer contact outside the edge of the substrate 10 along the direction of movement of the laser spot relative to the substrate, and the distance between the first position A of the substrate and the first outer contact outside the edge of the substrate is, for example, 0 to 5 mm. The second position B of the substrate 10 is located at or behind the first inner contact inside the edge of the substrate along the direction of movement of the laser spot relative to the substrate. The third position C of the substrate 10 is located at the position where the direction of movement of the laser spot relative to the substrate is switched to the third laser power. The fourth position D of the substrate 10 is located at or in front of the second inner contact inside the edge of the substrate along the direction of movement of the laser spot relative to the substrate. The fifth position E of the substrate 10 is located behind the second outer contact or second outer contact outside the edge of the substrate, along the direction of movement of the laser spot relative to the substrate, and the distance between the fifth position E of the substrate and the second outer contact outside the edge of the substrate is 0 to 5 mm.

[0039] This embodiment further provides a laser annealing apparatus for performing the laser annealing energy control method described above.

[0040] As described above, in the laser annealing energy control method and laser annealing apparatus according to one embodiment of the present invention, when the laser spot moves with a first laser power on the substrate, the laser power of the laser spot is reduced to a second laser power at a first position on the substrate; when the laser spot moves with respect to the substrate to a second position on the substrate, and then moves from the second position to a third position on the substrate, the laser power is increased to a third laser power; and the laser spot performs scanning annealing on the substrate at the third laser power. When the laser spot moves with respect to the substrate to a first and fourth position on the substrate, the laser power is reduced by switching from the first laser power to the second laser power to prevent chipping of the substrate. When the laser spot moves with respect to the substrate to a second position on the substrate, the second laser power is increased to a fourth laser power, and the rapid increase in power preheats the lens in the output optical path, reducing the expansion effect, improving the uniformity of the spot, allowing a higher spot quality to enter the scan, and improving the uniformity of the annealing. The laser power is increased to the third laser power by a ramp power control method to prevent energy spike problems at the substrate edges and chipping problems due to thermal stress. During the scanning field switching process, there is a period of near-stationary state between the deceleration or acceleration of the work stage, and by switching the laser power to a safety power, abnormalities and damage to the energy trace at the stationary position are prevented.

[0041] In this specification, each example is described progressively, focusing on the differences between each example and others. Identical or similar parts between examples may be referenced to one another. Furthermore, different parts between examples may be used in combination, and the present invention is not limited thereto.

[0042] Furthermore, while the present invention has been disclosed in preferred embodiments, it should be recognized that these embodiments do not limit the present invention. Those skilled in the art can, without departing from the scope of the technical means of the present invention, utilize the technical content disclosed above to make various possible variations and modifications to the technical means of the present invention, or modify them into equivalent embodiments of equivalent changes. Accordingly, all simple modifications, equivalent changes, and modifications made to the above embodiments based on the technology of the present invention, without departing from the scope of the technical means of the present invention, should all be considered to fall within the scope of protection of the technical means of the present invention. [Explanation of symbols]

[0043] 10-Substrate; 10a-First field scan; 10b-Second field scan

Claims

1. A laser annealing energy control method characterized by: reducing the laser power of the laser spot to a second laser power at a first position relative to the substrate when the laser spot moves relative to the substrate with a first laser power; increasing the laser power to a third laser power when the laser spot moves relative to the substrate to a second position relative to the substrate, and then moves from the second position relative to the substrate to a third position relative to the substrate; and having the laser spot perform scanning annealing on the substrate with the third laser power.

2. The laser annealing energy control method according to claim 1, characterized in that the second laser power causes the laser spot to move from a first position relative to the substrate to a second position relative to the substrate.

3. The laser annealing energy control method according to claim 1, characterized in that, in the process of the laser spot moving from the second position on the substrate to the third position on the substrate, the second laser power is first increased to the fourth laser power, and then further increased to the third laser power.

4. The laser annealing energy control method according to claim 3, characterized in that the rate of increase in the laser power from the second laser power to the fourth laser power is greater than the rate of increase in the laser power from the fourth laser power to the third laser power.

5. The laser annealing energy control method according to claim 3, characterized in that the fourth laser power is 50% to 150% of the first laser power.

6. The laser annealing energy control method according to claim 1, characterized in that the first position with respect to the substrate is an outer edge contact of the substrate or in front of an outer edge contact of the substrate along the direction of movement of the laser spot with respect to the substrate; and the second position with respect to the substrate is an inner edge contact of the substrate or in behind an inner edge contact of the substrate along the direction of movement of the laser spot with respect to the substrate.

7. The laser annealing energy control method according to claim 1, characterized in that the first laser power is one-third to two-thirds of the third laser power, and the second laser power is less than one-third of the third laser power.

8. A laser annealing apparatus characterized by being used to perform the laser annealing energy control method described in any one of claims 1 to 7.

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