Method for monitoring energy contamination of an ion implanter

Abstract

The present application provides a method for monitoring energy contamination of an ion implanter. A wafer is subjected to low energy ion implantation. A laser annealing process is used to activate surface ions of the wafer. A sheet resistance value RS1 of the wafer is measured. The wafer is subjected to rapid high temperature annealing. A sheet resistance value RS2 of the wafer is measured. A standard sheet resistance value of the wafer is provided. The sheet resistance value RS1 and the sheet resistance value RS2 are compared with the standard sheet resistance value, respectively. If the deviation of the sheet resistance value RS1 from the standard sheet resistance value is greater than 5% and the deviation of the sheet resistance value RS2 from the standard sheet resistance value is less than 5%, the ion implanter has energy contamination.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and in particular to a method for monitoring energy pollution in ion implanters. Background Technology

[0002] The development of highly integrated circuits requires smaller feature size and closer spacing between circuit devices. However, thermal diffusion limits the production of advanced circuits. These limitations stem from lateral diffusion, ultra-shallow junctions, poor doping control, interference from surface contamination, and dislocation generation.

[0003] Ion implantation overcomes the limitations of diffusion and offers additional advantages. There is no lateral diffusion during ion implantation, the process is performed near room temperature, impurity atoms are placed below the wafer surface, and a wide range of doping concentrations are possible. Ion implantation allows for better control over the location and amount of dopants within the wafer. Therefore, ion implantation plays a crucial role in semiconductor manufacturing. Diffusion is a chemical process, while ion implantation is a physical process. Ion implantation uses gaseous and solid impurity source materials. During ion implantation, dopant atoms are ionized, separated, and accelerated (gaining kinetic energy) to form an ion beam that sweeps across the wafer. Impurity atoms physically bombard the wafer, penetrating the wafer surface and stopping below it.

[0004] An ion implanter is a device used in ion implantation processes, and it is an integration of several extremely complex and precise subsystems. Commonly used ion implantation methods include medium-current ion implantation, high-current ion implantation, and high-energy ion implantation. In the ion implantation process, the number of atoms (implantation dose) is determined by the ion beam current density (the number of ions per square centimeter) and the implantation time. The dose can be precisely controlled by measuring the ion current. During ion implantation, the wafer crystal structure is damaged due to collisions with incident ions. Crystal damage can be repaired by heating and annealing the wafer.

[0005] With the continuous development of semiconductor manufacturing technology, higher requirements have been placed on the process stability of ion implanters. Effectively monitoring ion implanters and accurately reflecting their status and the causes of malfunctions is crucial for maintaining the stability of existing semiconductor manufacturing processes and for the research and development of new processes.

[0006] Energy contamination in ion implanters refers to a deviation between the energy of doped ions implanted into the wafer and the set energy. This deviation can lead to an unintended doping depth, resulting in electrical deviations in the device and consequently, reduced device yield. As semiconductor process dimensions continue to shrink, controlling the implantation depth is crucial to meeting ultra-shallow junction requirements, making energy contamination increasingly significant, especially for low-energy ion implantation technologies where the resulting electrical deviations are very pronounced. Current technologies typically use secondary ion mass spectrometry (SIMS) to analyze for energy contamination. SIMS uses a primary heavy ion beam to bombard the wafer surface and collects secondary ion mass spectra at different times, measuring the doping ion concentration and depth profiles. The presence of energy contamination is determined by comparing the profiles with a standard curve. However, SIMS testing is typically time-consuming (around a week) and destructive to the wafer, making it generally unsuitable for monitoring actual production processes. Summary of the Invention

[0007] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a method for monitoring energy pollution in ion implanters, which solves the problem that the SIMS testing technology in the prior art has a long testing time and cannot be applied to the monitoring of energy pollution in actual production processes.

[0008] To achieve the above and other related objectives, the present invention provides a method for monitoring energy pollution in an ion implanter, comprising at least:

[0009] Step 1: Provide a wafer and perform low-energy ion implantation on the wafer;

[0010] Step 2: Perform surface ion activation on the wafer using laser annealing process;

[0011] Step 3: Measure the sheet resistance value RS1 of the wafer;

[0012] Step 4: Perform rapid high-temperature annealing on the wafer;

[0013] Step 5: Measure the sheet resistance value RS2 of the wafer;

[0014] Step 6: Provide the standard sheet resistance value of the wafer, and compare the sheet resistance values ​​RS1 and RS2 with the standard sheet resistance value respectively; if the deviation of the sheet resistance value RS1 from the standard sheet resistance value is greater than 5%, while the deviation of the sheet resistance value RS2 from the standard sheet resistance value is less than 5%, then there is energy contamination in the ion implanter.

[0015] Preferably, the wafer in step one is a light wafer.

[0016] Preferably, the ions implanted in step one are boron ions; the ion implantation energy is 1-5 keV; the ion implantation dose is 5E13-2E14 Ions / cm2; and the implantation angle is 0-7 degrees.

[0017] Preferably, the peak temperature of the laser annealing in step two is 1100℃~1300℃.

[0018] Preferably, in step three, the sheet resistance value RS1 of the wafer is measured using the four-probe method.

[0019] Preferably, the measurement range in step three is 3-5 mm, and the number of measurement points is 49-121.

[0020] Preferably, the annealing temperature of the rapid high-temperature annealing in step four is 950–1150°C, and the annealing time is 30–50 seconds.

[0021] Preferably, in step five, the sheet resistance value RS2 of the wafer is measured using the four-probe method.

[0022] Preferably, the deviation between the sheet resistance value RS1 and the standard sheet resistance value in step six refers to the sheet resistance value RS1 being larger than the standard sheet resistance value.

[0023] Preferably, the deviation between the sheet resistance value RS1 and the standard sheet resistance value in step six refers to the sheet resistance value RS1 being smaller than the standard sheet resistance value.

[0024] As described above, the method for monitoring energy contamination in an ion implanter according to the present invention has the following beneficial effects: The present invention first implants a wafer with low-energy ions, then uses laser annealing to activate surface ions, tests the wafer sheet resistance value RS1, and then continues with high-temperature rapid annealing to test the wafer sheet resistance value RS2. If energy contamination exists, the sheet resistance value RS1 will differ from the standard value, while the difference in RS2 will be minimal. This method can quickly determine whether there is an energy contamination problem in the implanter, and the process is basically similar to the daily monitoring process of the implanter, making it applicable in actual production. Furthermore, compared to SIMS testing, this method does not damage the wafer. The tested wafer can be recycled and reused, effectively reducing monitoring costs. Attached Figure Description

[0025] Figure 1 The diagram shows a flowchart of the method for monitoring energy pollution from an ion implanter in this invention. Detailed Implementation

[0026] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0027] Please see Figure 1 It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of the present invention. Therefore, the drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0028] This invention provides a method for monitoring energy pollution in ion implanters, such as... Figure 1 As shown, Figure 1 The flowchart shown is a method for monitoring energy pollution in an ion implanter according to the present invention, the method comprising at least:

[0029] Step 1: Provide a wafer and perform low-energy ion implantation on the wafer;

[0030] Furthermore, in step one of this embodiment, the wafer is a light wafer, meaning that no processing has been performed on the wafer.

[0031] In a further embodiment of the present invention, the ions implanted in step one are boron ions; the ion implantation energy is 1-5 keV; the ion implantation dose is 5E13-2E14 Ions / cm2; and the implantation angle is 0-7 degrees.

[0032] Step 2: Perform surface ion activation on the wafer using laser annealing process;

[0033] Furthermore, in this embodiment, the peak temperature of laser annealing in step two is 1100℃~1300℃.

[0034] Step 3: Measure the sheet resistance value RS1 of the wafer; that is, after laser annealing, measure the sheet resistance value RS1 of the wafer.

[0035] Furthermore, in step three of this embodiment, the sheet resistance value RS1 of the wafer is measured using the four-probe method.

[0036] Furthermore, in step three of this embodiment, the measurement range for edge removal is 3-5mm, and the number of measurement points is 49-121.

[0037] Step 4: Perform rapid high-temperature annealing on the wafer;

[0038] Furthermore, in step four of this embodiment, the rapid high-temperature annealing annealing temperature is 950–1150°C, and the annealing time is 30–50 seconds.

[0039] Step 5: Measure the sheet resistance value RS2 of the wafer; that is, after rapid high-temperature annealing, measure the sheet resistance value RS2 of the wafer.

[0040] In a further step of this invention, the sheet resistance value RS2 of the wafer is measured using a four-probe method in step five of this embodiment.

[0041] Step 6: Provide the standard sheet resistance value of the wafer, and compare the sheet resistance values ​​RS1 and RS2 with the standard sheet resistance value respectively; if the deviation of the sheet resistance value RS1 from the standard sheet resistance value is greater than 5%, while the deviation of the sheet resistance value RS2 from the standard sheet resistance value is less than 5%, then there is energy contamination in the ion implanter.

[0042] Furthermore, in step six of this embodiment, the deviation between the sheet resistance value RS1 and the standard sheet resistance value refers to the fact that the sheet resistance value RS1 is larger than the standard sheet resistance value.

[0043] In further embodiments of the present invention, the deviation between the sheet resistance value RS1 and the standard sheet resistance value in step six may also be that the sheet resistance value RS1 is smaller than the standard sheet resistance value.

[0044] In other words, the deviation between the sheet resistance value RS1 and the standard sheet resistance value in this invention can be either that the sheet resistance value RS1 is larger than the standard sheet resistance value, or that the sheet resistance value RS1 is smaller than the standard sheet resistance value.

[0045] In step six of this invention, the sheet resistance values ​​RS1 and RS2 are compared with the standard sheet resistance value. If the deviations of the sheet resistance values ​​RS1 and RS2 from the standard sheet resistance value are both less than 5%, then the ion implanter is free from energy pollution. If the deviations of the sheet resistance values ​​RS1 and RS2 from the standard sheet resistance value are both greater than 5%, then there is a deviation in the implantation dose or angle.

[0046] When ion implanters suffer from energy contamination, the energy of doped ions implanted into the wafer deviates from the set energy. This energy contamination is typically more pronounced in low-energy ion implanters, where some doped ions have higher energies than the target energy, resulting in a deeper implantation depth. SIMS (Simultaneous Metal Oxidation) testing often reveals a significant deviation in ion concentration from the standard value in these deeper implanted areas. As feature sizes continue to shrink, controlling the implantation depth is crucial to meeting ultra-shallow nodule requirements. This deviation in doped ions can lead to electrical deviations in the device, causing yield losses.

[0047] Routine monitoring of ion implanters typically involves testing sheet resistance. After implanting dopant ions into the wafer, an annealing process is used to activate the dopant ions, and then the sheet resistance is measured to monitor the implanter's stability. This monitoring method usually employs a rapid annealing (RTA) process, with an annealing time generally between 20 and 40 seconds, ensuring that all dopant ions are fully activated. Under this monitoring method, the dopant ions have sufficient time to complete diffusion and activation, and the energy contamination problem caused by some ions cannot be effectively monitored.

[0048] Laser annealing is a powerful tool for monitoring energy contamination. The laser annealing system uses laser energy to rapidly heat the wafer surface to its critical melting point and then quickly cools it down. Laser annealing activates dopant ions with minimal impurity diffusion after ion implantation, forming ultra-shallow junctions. Laser annealing is widely used in process nodes below 45nm. Regarding energy contamination from ion implanters, controlling the laser annealing process can effectively activate the surface layer of dopant ions. However, in cases of energy contamination, deeply implanted ions cannot be activated. When energy contamination is present, the wafer resistance after laser annealing shows significant differences, typically exceeding 10%. Therefore, sheet resistance testing can clearly reveal these resistance deviations, allowing for the determination of whether energy contamination is present.

[0049] To eliminate the influence of injection dosage or angle on sheet resistance (SRT), a combination of laser annealing and rapid high-temperature annealing is used. Measuring the SRT after both laser annealing and rapid annealing effectively determines whether there is energy contamination in the injection equipment. If the SRT values ​​measured in both measurements fluctuate within the normal range, the injection dosage or angle is normal, and there is no energy contamination issue. If the SRT measurement after laser annealing has a large deviation, while the SRT after rapid high-temperature annealing is within the normal range, then energy contamination is considered to exist in the injection equipment. If both SRT measurements are too high or too low, the primary suspicion is a deviation in the injection dosage or angle.

[0050] In summary, this invention first implants a wafer with low-energy ions, then uses laser annealing to activate the surface ions, tests the wafer sheet resistance (RS1), and then performs high-temperature rapid annealing to test the wafer sheet resistance (RS2). If energy contamination is present, the sheet resistance (RS1) will differ from the standard value, while the difference in RS2 will be minimal. This method can quickly determine if there is energy contamination in the implanter, and the process is basically similar to the daily monitoring process of the implanter, making it applicable in actual production. Furthermore, compared to SIMS testing, this method does not damage the wafer. The tested wafer can be recycled and reused, effectively reducing monitoring costs. Therefore, this invention effectively overcomes the various shortcomings of existing technologies and has high industrial applicability.

[0051] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for monitoring energy pollution in an ion implanter, characterized in that, At least including: Step 1: Provide a wafer and perform low-energy ion implantation on the wafer; the implanted ions are boron ions; the ion implantation energy is 1-5 keV; the ion implantation dose is 5E13-2E14 ions / cm 2 The injection angle is 0 to 7 degrees. Step 2: Perform surface ion activation on the wafer using laser annealing; the peak temperature of laser annealing is 1100℃~1300℃; Step 3: Measure the sheet resistance value RS1 of the wafer; Step 4: Perform rapid high-temperature annealing on the wafer; the annealing temperature for rapid high-temperature annealing is 950-1150℃, and the annealing time is 30-50 seconds; Step 5: Measure the sheet resistance value RS2 of the wafer; Step 6: Provide the standard sheet resistance value of the wafer, and compare the sheet resistance values ​​RS1 and RS2 with the standard sheet resistance value respectively; if the deviation of the sheet resistance value RS1 from the standard sheet resistance value is greater than 5%, while the deviation of the sheet resistance value RS2 from the standard sheet resistance value is less than 5%, then there is energy contamination in the ion implanter.

2. The method for monitoring energy pollution in an ion implanter according to claim 1, characterized in that: The wafer mentioned in step one is a light wafer.

3. The method for monitoring energy pollution in an ion implanter according to claim 1, characterized in that: In step three, the sheet resistance value RS1 of the wafer is measured using the four-probe method.

4. The method for monitoring energy pollution in an ion implanter according to claim 3, characterized in that: In step three, the measurement range for the edge removal is 3-5mm, and the number of measurement points is 49-121.

5. The method for monitoring energy pollution in an ion implanter according to claim 1, characterized in that: In step five, the sheet resistance value RS2 of the wafer is measured using the four-probe method.

6. The method for monitoring energy pollution in an ion implanter according to claim 1, characterized in that: The deviation between the sheet resistance value RS1 and the standard sheet resistance value mentioned in step six refers to the fact that the sheet resistance value RS1 is larger than the standard sheet resistance value.

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