SiC laser annealing apparatus and control method

Abstract

The application discloses a SiC laser annealing device, which comprises a laser annealing process cavity, a laser device and an EPD detector; the laser annealing process cavity comprises a workpiece table for bearing a SiC wafer. The laser device is used for emitting laser to the surface of the SiC wafer and realizing laser annealing of the SiC wafer. The EPD detector is used for detecting the C content in the internal environment of the laser annealing process cavity and detecting the energy of the laser annealing in real time according to the C content, and alarming when the energy of the laser annealing is higher than a set value. The application further discloses a SiC laser annealing control method. The application can detect the energy of the laser annealing in real time and alarm when the energy of the laser annealing is over the standard, and can prevent the adverse effects caused by C precipitation.

Description

Technical Field

[0001] This invention relates to the field of semiconductor integrated circuit manufacturing, and in particular to a SiC laser annealing apparatus. This invention also relates to a SiC laser annealing control method. Background Technology

[0002] SiC devices require the formation of ohmic contacts. The commonly used method is to deposit metal layers such as Ni / Ti / Al and then form SiNi alloys through laser annealing.

[0003] The laser annealing window depends mainly on two factors: First, the energy level is too low to form an alloy. Secondly, excessively high energy levels can lead to carbon precipitation and cluster formation, which negatively impacts device performance. For low energy levels, which are relatively easy to test, the metal contact resistance can be measured directly after annealing to determine the issue.

[0004] However, once the laser annealing energy is normal, the metal contact resistance reaches its minimum value. When the energy is subsequently increased, the metal contact resistance remains almost unchanged. Therefore, the energy cannot be determined to be too high by measuring the metal contact resistance.

[0005] Therefore, existing methods lack a direct quantitative detection method for carbon precipitation caused by excessively high energy. Currently, online detection relies on macroscopic visual inspection to check for black dotted / blocky spots, or on cross-sectioning to examine the alloy layer for carbon clusters. However, this method is inherently uncertain. Macroscopic visual inspection depends on the inspector's subjective judgment, and cross-sectioning can damage the wafer. Furthermore, both existing methods are post-annealing inspections and cannot detect excessively high energy levels during laser annealing in real time. Summary of the Invention

[0006] The technical problem to be solved by this invention is to provide a SiC laser annealing device that can detect the laser annealing energy in real time and alarm when the laser annealing energy exceeds the limit, thereby preventing the adverse effects caused by C precipitation. This invention also provides a SiC laser annealing control method.

[0007] To address the aforementioned technical problems, the SiC laser annealing apparatus provided by this invention includes: a laser annealing process cavity, a laser device, and an EPD detector. EPD is short for end point detection.

[0008] The laser annealing process cavity includes a workpiece stage, which is used to support SiC wafers.

[0009] The workpiece stage is used to support SiC wafers.

[0010] The laser device is used to emit laser light onto the surface of the SiC wafer and to perform laser annealing on the SiC wafer.

[0011] The EPD detector is used to detect the C content in the internal environment of the laser annealing process cavity and to detect the energy of the laser annealing in real time based on the C content. An alarm is triggered when the energy of the laser annealing is determined to be higher than a set value.

[0012] A further improvement is that the detection point of the EPD detector is located above the SiC wafer and / or at the vent of the laser annealing process cavity.

[0013] A further improvement is that a metal layer is formed on the surface of the SiC wafer, and the laser annealing is used to achieve a silicide reaction between the metal of the metal layer and the Si of the SiC wafer to form a metal silicide.

[0014] A further improvement is that the metal layer includes a Ni layer, and the metal silicide is a nickel silicide.

[0015] A further improvement is that the metal layer also includes a Ti layer and an Al layer located on top of the Ni layer.

[0016] A further improvement is that the EPD detector detects the laser annealing energy in real time based on the C content, including: When the C content is ND, it means that C was not detected and the laser annealing energy is normal. ND is short for Not Detectable.

[0017] When the C content is higher than 5e-10cm -3 ~1e-9cm -3 When the ratio of the intensity of the characteristic spectral line of C in the spectrum detected by the EPD detector to the intensity of the substrate of the SiC wafer is greater than 3, it is determined that the energy of the laser annealing is higher than the set value.

[0018] To solve the above-mentioned technical problems, the SiC laser annealing control method provided by the present invention includes the following steps: Step 1: Place the SiC wafer on the workpiece stage of the laser annealing process chamber.

[0019] Step 2: Laser annealing is performed by emitting a laser beam onto the surface of the SiC wafer using a laser device.

[0020] Step 3: During the laser annealing process, an EPD detector is used to detect the C content in the internal environment of the laser annealing process cavity in real time and to detect the laser annealing energy in real time based on the C content. An alarm is triggered when the laser annealing energy is determined to be higher than a set value.

[0021] A further improvement is that the detection point of the EPD detector is located above the SiC wafer and / or at the vent of the laser annealing process cavity.

[0022] A further improvement is that a metal layer is formed on the surface of the SiC wafer, and the laser annealing is used to achieve a silicide reaction between the metal of the metal layer and the Si of the SiC wafer to form a metal silicide.

[0023] A further improvement is that the metal layer includes a Ni layer, and the metal silicide is a nickel silicide.

[0024] A further improvement is that the metal layer also includes a Ti layer and an Al layer located on top of the Ni layer.

[0025] A further improvement is that the EPD detector detects the laser annealing energy in real time based on the C content, including: When the C content is ND, it means that no C was detected and the energy of the laser annealing is normal.

[0026] When the C content is higher than 5e-10cm -3 ~1e-9cm -3 When the ratio of the intensity of the characteristic spectral line of C in the spectrum detected by the EPD detector to the intensity of the substrate of the SiC wafer is greater than 3, it is determined that the energy of the laser annealing is higher than the set value.

[0027] A further improvement is that, when it is determined that the energy of the laser annealing is higher than a set value, the following additional steps are included: The machine is stopped to confirm the energy of the laser annealing, the atmosphere and vacuum level inside the laser annealing process cavity, and the inside of the laser annealing process cavity is cleaned by C.

[0028] A further improvement is that, when it is determined that the energy of the laser annealing is higher than a set value, the following additional steps are included: Macroscopic inspection is performed on the SiC wafer. If the macroscopic inspection confirms the presence of black or dark dot-like or block-like spots on the surface of the SiC wafer, it indicates the presence of C precipitation and an abnormality in the equipment and the SiC wafer.

[0029] A further improvement is that, when it is determined that the energy of the laser annealing is higher than a set value, the following additional steps are included: The SiC wafer is cleaved and subjected to SEM inspection. If the SEM inspection confirms the presence of C clusters at the interface between the SiC wafer and the metal layer, then C precipitation and equipment and SiC wafer malfunctions are confirmed.

[0030] A further improvement is that, when it is determined that the energy of the laser annealing is higher than a set value, the following additional steps are included: The SiC wafer is reworked, and the rework steps include: The metal layer and the metal silicide are removed by mechanical grinding or chemical etching, exposing the surface of the SiC wafer; A second metal layer is redeposited on the surface of the SiC wafer, and the second metal layer has the same structure as the metal layer before laser annealing. Then, repeat steps one through three, and adjust the laser annealing energy during the repeat of step two to prevent the laser annealing energy from exceeding the set value.

[0031] This invention utilizes the characteristic that excessively high annealing energy during SiC wafer annealing will cause C precipitation. An EPD detector is added to this invention. The EPD detector monitors the C content in the internal environment of the laser annealing process cavity in real time and, based on the C content, monitors the laser annealing energy in real time. An alarm is triggered when the laser annealing energy exceeds a set value. This allows for timely detection of C precipitation caused by excessively high laser annealing energy, thus preventing the adverse effects of C precipitation. For example, if the laser annealing energy is detected to be higher than the set value, the laser annealing process cavity and the SiC wafer can be processed promptly to eliminate problems caused by C precipitation. Attached Figure Description

[0032] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments: Figure 1 This is a schematic diagram of the SiC laser annealing apparatus according to an embodiment of the present invention; Figure 2 This is a flowchart of the SiC laser annealing control method according to an embodiment of the present invention. Detailed Implementation

[0033] like Figure 1 The diagram shown is a structural schematic of the SiC laser annealing apparatus according to an embodiment of the present invention. The SiC laser annealing apparatus according to an embodiment of the present invention includes: a laser annealing process cavity 101, a laser device (not shown), and an EPD detector (not shown).

[0034] The laser annealing process cavity 101 includes a workpiece stage 102. Figure 1 In the present invention, the cross-sectional structure of the laser annealing process cavity 101 is square. In practical applications, the shape of the laser annealing process cavity 101 can be modified according to actual needs, such as being set to a bowl shape.

[0035] The workpiece stage 102 is used to support SiC wafers.

[0036] The laser device is used to emit laser light onto the surface of the SiC wafer and to perform laser annealing on the SiC wafer.

[0037] The EPD detector is used to detect the C content in the internal environment of the laser annealing process cavity 101 and to detect the energy of the laser annealing in real time based on the C content. An alarm is triggered when the energy of the laser annealing is determined to be higher than a set value.

[0038] In this embodiment of the invention, the detection point 104 of the EPD detector is located above the SiC wafer and / or at the vent 103 of the laser annealing process cavity 101. Figure 1 The image shows two symmetrical exhaust ports 103. Figure 1 As shown, the arrows represent the atmospheric flow diagram inside the laser annealing process cavity 101. It can be seen that the C content can be detected relatively accurately above the SiC wafer and at the vent 103.

[0039] In this embodiment of the invention, a metal layer is formed on the surface of the SiC wafer, and the laser annealing is used to achieve a silicide reaction between the metal of the metal layer and the Si of the SiC wafer to form a metal silicide. In some embodiments, the metal layer includes a Ni layer, and the metal silicide is a nickel silicide. The metal layer also includes a Ti layer and an Al layer located on top of the Ni layer.

[0040] The EPD detector detects the energy of the laser annealing in real time based on the C content, including: When the C content is ND, it means that no C was detected and the energy of the laser annealing is normal.

[0041] When the C content is higher than 5e-10cm -3 ~1e-9cm -3 When the ratio of the intensity of the characteristic spectral line of C in the spectrum detected by the EPD detector to the intensity of the substrate of the SiC wafer is greater than 3, it is determined that the energy of the laser annealing is higher than the set value.

[0042] This invention utilizes the characteristic that excessively high annealing energy during SiC wafer annealing will cause C precipitation. An EPD detector is added to this invention. The EPD detector monitors the C content in the internal environment of the laser annealing process cavity 101 in real time and detects the laser annealing energy based on the C content. An alarm is triggered when the laser annealing energy exceeds a set value. This allows for timely detection of C precipitation caused by excessively high laser annealing energy, thus preventing the adverse effects of C precipitation. For example, if the laser annealing energy exceeds the set value, the laser annealing process cavity 101 and the SiC wafer can be processed promptly to eliminate problems caused by C precipitation.

[0043] like Figure 2The diagram shown is a flowchart of the SiC laser annealing control method according to an embodiment of the present invention; the SiC laser annealing control method according to an embodiment of the present invention includes the following steps: Step 1: Place the SiC wafer on the workpiece stage 102 of the laser annealing process cavity 101.

[0044] Step 2: Laser annealing is performed by emitting a laser beam onto the surface of the SiC wafer using a laser device.

[0045] In the method of this invention embodiment, a metal layer is formed on the surface of the SiC wafer, and the laser annealing is used to realize the silicide reaction between the metal of the metal layer and the Si of the SiC wafer to form metal silicide.

[0046] In some embodiments, the metal layer includes a Ni layer, and the metal silicide is a nickel silicide. The metal layer also includes a Ti layer and an Al layer located on top of the Ni layer.

[0047] Step 3: During the laser annealing process, an EPD detector is used to detect the C content in the internal environment of the laser annealing process cavity 101 in real time and to detect the laser annealing energy in real time based on the C content. An alarm is triggered when the laser annealing energy is determined to be higher than a set value.

[0048] In the method of this embodiment of the invention, the detection point 104 of the EPD detector is located above the SiC wafer and / or at the exhaust port 103 of the laser annealing process cavity 101.

[0049] In the method of this invention embodiment, the EPD detector detects the energy of the laser annealing in real time based on the C content, including: When the C content is ND, it means that no C was detected and the energy of the laser annealing is normal.

[0050] When the C content is higher than 5e-10cm -3 ~1e-9cm -3 When the ratio of the intensity of the characteristic spectral line of C in the spectrum detected by the EPD detector to the intensity of the substrate of the SiC wafer is greater than 3, it is determined that the energy of the laser annealing is higher than the set value.

[0051] In the method of this embodiment of the invention, when it is determined that the energy of the laser annealing is higher than a set value, the method further includes: The machine is stopped to confirm the energy of the laser annealing, the atmosphere and vacuum level inside the laser annealing process cavity 101, and the inside of the laser annealing process cavity 101 is cleaned by C.

[0052] In some embodiments, when it is determined that the energy of the laser annealing is higher than a set value, the method further includes: Macroscopic inspection is performed on the SiC wafer. If the macroscopic inspection confirms the presence of black or dark dot-like or block-like spots on the surface of the SiC wafer, it indicates the presence of C precipitation and an abnormality in the equipment and the SiC wafer.

[0053] In some embodiments, when it is determined that the energy of the laser annealing is higher than a set value, the method further includes: The SiC wafer is cleaved and subjected to SEM inspection. If the SEM inspection confirms the presence of C clusters at the interface between the SiC wafer and the metal layer, then C precipitation and equipment and SiC wafer malfunctions are confirmed.

[0054] In some embodiments, when it is determined that the energy of the laser annealing is higher than a set value, the method further includes: The SiC wafer is reworked, and the rework steps include: The metal layer and the metal silicide are removed by mechanical grinding or chemical etching, exposing the surface of the SiC wafer; A second metal layer is redeposited on the surface of the SiC wafer, and the second metal layer has the same structure as the metal layer before laser annealing. Then, repeat steps one through three, and adjust the laser annealing energy during the repeat of step two to prevent the laser annealing energy from exceeding the set value.

[0055] In this embodiment of the invention, an EPD detector is introduced into the SiC laser annealing apparatus. The EPD detector monitors the content of C in the spectrum. When the laser energy is too high and a large amount of C is precipitated, the EPD detector will detect a sharp increase in the spectral peak of a large amount of C in the atmosphere above the silicon wafer, i.e., the SiC wafer. In this way, the problem of C precipitation can be monitored.

[0056] The present invention has been described in detail above through specific embodiments, but these are not intended to limit the invention. Many modifications and improvements can be made by those skilled in the art without departing from the principles of the invention, and these should also be considered within the scope of protection of the present invention.

Claims

1. A SiC laser annealing apparatus, characterized in that, include: Laser annealing process cavity, laser device and EPD detector; The laser annealing process cavity includes a workpiece stage, which is used to support the SiC wafer. The laser device is used to emit laser light onto the surface of the SiC wafer and to perform laser annealing on the SiC wafer; The EPD detector is used to detect the C content in the internal environment of the laser annealing process cavity and to detect the laser annealing energy in real time based on the C content. An alarm is triggered when the laser annealing energy is determined to be higher than a set value.

2. The SiC laser annealing apparatus as described in claim 1, characterized in that: The detection point of the EPD detector is located above the SiC wafer and / or at the vent of the laser annealing process cavity.

3. The SiC laser annealing apparatus as described in claim 1, characterized in that: A metal layer is formed on the surface of the SiC wafer, and the laser annealing is used to realize the silicide reaction between the metal of the metal layer and the Si of the SiC wafer to form metal silicide.

4. The SiC laser annealing apparatus as described in claim 3, characterized in that: The metal layer includes a Ni layer, and the metal silicide is a nickel silicide.

5. The SiC laser annealing apparatus as described in claim 4, characterized in that: The metal layer also includes a Ti layer and an Al layer located on top of the Ni layer.

6. The SiC laser annealing apparatus as described in claim 1, characterized in that: The EPD detector detects the energy of the laser annealing in real time based on the C content, including: When the C content is ND, it means that no C was detected and the energy of the laser annealing is normal; When the C content is higher than 5e-10cm -3 ~1e-9cm -3 When the ratio of the intensity of the characteristic spectral line of C in the spectrum detected by the EPD detector to the intensity of the substrate of the SiC wafer is greater than 3, it is determined that the energy of the laser annealing is higher than the set value.

7. A method for controlling SiC laser annealing, characterized in that, The steps include the following: Step 1: Place the SiC wafer on the workpiece stage of the laser annealing process cavity; Step 2: Laser annealing is performed by emitting a laser beam onto the surface of the SiC wafer using a laser device; Step 3: During the laser annealing process, an EPD detector is used to detect the C content in the internal environment of the laser annealing process cavity in real time and to detect the laser annealing energy in real time based on the C content. An alarm is triggered when the laser annealing energy is determined to be higher than a set value.

8. The SiC laser annealing control method as described in claim 7, characterized in that: The detection point of the EPD detector is located above the SiC wafer and / or at the vent of the laser annealing process cavity.

9. The SiC laser annealing control method as described in claim 8, characterized in that: A metal layer is formed on the surface of the SiC wafer, and the laser annealing is used to realize the silicide reaction between the metal of the metal layer and the Si of the SiC wafer to form metal silicide.

10. The SiC laser annealing control method as described in claim 9, characterized in that: The metal layer includes a Ni layer, and the metal silicide is a nickel silicide.

11. The SiC laser annealing control method as described in claim 10, characterized in that: The metal layer also includes a Ti layer and an Al layer located on top of the Ni layer.

12. The SiC laser annealing control method as described in claim 7, characterized in that: The EPD detector detects the energy of the laser annealing in real time based on the C content, including: When the C content is ND, it means that no C was detected and the energy of the laser annealing is normal; When the C content is higher than 5e-10cm -3 ~1e-9cm -3 When the ratio of the intensity of the characteristic spectral line of C in the spectrum detected by the EPD detector to the intensity of the substrate of the SiC wafer is greater than 3, it is determined that the energy of the laser annealing is higher than the set value.

13. The SiC laser annealing control method as described in claim 1, characterized in that: When it is determined that the energy of the laser annealing is higher than a set value, the method further includes: The machine is stopped to confirm the energy of the laser annealing, the atmosphere and vacuum level inside the laser annealing process cavity, and the inside of the laser annealing process cavity is cleaned by C.

14. The SiC laser annealing control method as described in claim 9, characterized in that: When it is determined that the energy of the laser annealing is higher than a set value, the method further includes: Macroscopic inspection is performed on the SiC wafer. If the macroscopic inspection confirms the presence of black or dark-colored dot-like or block-like spots on the surface of the SiC wafer, it confirms the presence of C precipitation and an abnormality in the equipment and the SiC wafer.

15. The SiC laser annealing control method as described in claim 9, characterized in that: When it is determined that the energy of the laser annealing is higher than a set value, the method further includes: The SiC wafer is cleaved and subjected to SEM inspection. If the SEM inspection confirms the presence of C clusters at the interface between the SiC wafer and the metal layer, then C precipitation and equipment and SiC wafer malfunctions are confirmed.

16. The SiC laser annealing control method as described in claim 9, characterized in that: When it is determined that the energy of the laser annealing is higher than a set value, the method further includes: The SiC wafer is reworked, and the rework steps include: The metal layer and the metal silicide are removed by mechanical grinding or chemical etching, exposing the surface of the SiC wafer; A second metal layer is redeposited on the surface of the SiC wafer, and the second metal layer has the same structure as the metal layer before laser annealing. Then, repeat steps one through three, and adjust the laser annealing energy during the repeat of step two to prevent the laser annealing energy from exceeding the set value.

Images