Wafer annealing method

Abstract

A wafer annealing method relates to the technical field of semiconductor manufacturing, and comprises the following steps: obtaining waiting time before a wafer enters annealing equipment; when the waiting time length is greater than or equal to a preset time length, cleaning the wafer so as to remove precursor attachments formed by the wafer during the waiting time length; wherein the cleaning treatment comprises acid cleaning. And when the waiting time length before the wafer is annealed is greater than the preset time length, the cleaning treatment is added to remove the precursor attachment formed by the wafer during the waiting time length, so that the wafer can be effectively prevented from generating the viscous attachment after the wafer is annealed. And the mechanical arm is influenced to take out the wafer from the annealing equipment, so that the risk that the wafer is damaged or fails to be scrapped in the taking-out process is reduced.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor manufacturing technology, and in particular to a wafer annealing method. Background Art

[0002] Wafer annealing is a critical process in semiconductor manufacturing. It optimizes the physical and chemical properties of the wafer by precisely controlling the heating and cooling processes, thereby improving its performance and reliability in subsequent processing and final applications.

[0003] During wafer manufacturing, stress is generated within the wafer due to various physical and chemical processing steps, such as ion implantation, etching, and metal deposition. If left unaddressed, these stresses can cause the wafer to fracture or deform during subsequent processing or use. Annealing effectively relieves these stresses by rearranging the crystal lattice through heating. High-energy particles introduced during ion implantation can disrupt the lattice structure, creating defects and damage. Annealing repairs these defects, allowing atoms to rearrange themselves into their proper positions within the lattice and thereby restore the material's electrical properties. Furthermore, dopant atoms do not take effect immediately after ion implantation. Annealing allows them to move to their proper positions and integrate into the crystal lattice, activating the dopant and altering the semiconductor's electrical properties. This process is crucial to the performance of semiconductor devices. Annealing can also improve the electrical properties of semiconductor materials, such as reducing resistance and increasing carrier mobility. It also enhances the material's mechanical properties, making the wafer more durable.

[0004] With the continuous development of semiconductor manufacturing technology, rapid thermal annealing technology is also constantly innovating to meet the process requirements of smaller feature sizes and higher performance requirements.

[0005] However, there are still many problems in the process of rapid thermal annealing of wafers. Summary of the Invention

[0006] The problem solved by the present invention is to provide a wafer annealing method to prevent the wafer from generating sticky attachments after annealing, ensure that the robotic arm can smoothly remove the wafer, and reduce the risk of the wafer being damaged or failing during the removal process.

[0007] To solve the above problems, the technical solution of the present invention provides a wafer annealing method, including: obtaining the waiting time of the wafer before entering the annealing equipment; when the waiting time is greater than or equal to the preset time, cleaning the wafer to remove precursor attachments formed on the wafer during the waiting time; wherein, the cleaning treatment includes acid cleaning.

[0008] Optionally, the annealing equipment includes: rapid thermal annealing equipment, furnace annealing equipment, flash annealing equipment or laser annealing equipment.

[0009] Optionally, the preset duration is obtained based on historical waiting time data of several historical wafers that have completed annealing processing.

[0010] Optionally, the method for obtaining the preset time length includes: obtaining a first waiting time length corresponding to the historical wafer with the largest value and no sticky attachment generated from several historical waiting time length data; obtaining a second waiting time length corresponding to the historical wafer with the smallest value and sticky attachment generated from several historical waiting time length data; and obtaining the preset time length based on the first waiting time length and the second waiting time length.

[0011] Optionally, the method for obtaining the preset duration based on the first waiting duration and the second waiting duration includes: taking a median value between the first waiting duration and the second waiting duration as the preset duration.

[0012] Optionally, the parameters of the acid cleaning include: the cleaning solution is a mixed solution of sulfuric acid and hydrogen peroxide; and the cleaning time is 5 minutes to 15 minutes.

[0013] Optionally, the volume ratio of sulfuric acid to hydrogen peroxide is 3:1~5:1.

[0014] Optionally, the cleaning process further includes alkaline cleaning, and the alkaline cleaning is performed after the acid cleaning.

[0015] Optionally, the parameters of the alkaline cleaning include: the cleaning solution is a mixed solution of ammonia water and hydrogen peroxide; and the cleaning time is 3 minutes to 7 minutes.

[0016] Optionally, the volume ratio of ammonia water and hydrogen peroxide is 1:1:5 or 1:2:7.

[0017] Optionally, when the waiting time is less than the preset time, the wafer is transferred to the annealing equipment.

[0018] Compared with the prior art, the technical solution of the present invention has the following advantages:

[0019] In the wafer annealing method of the technical solution of the present invention, when the waiting time of the wafer before annealing is greater than the preset time, the cleaning process is added to remove the precursor attachments formed on the wafer during the waiting time, thereby effectively avoiding the generation of sticky attachments on the wafer after annealing, which affects the robot arm's removal of the wafer from the annealing equipment, thereby reducing the risk of damage or failure of the wafer during the removal process.

[0020] Furthermore, the parameters of the acid cleaning include: a cleaning solution of sulfuric acid and hydrogen peroxide mixed solution; and a cleaning time of 5 to 15 minutes. The acid cleaning can effectively remove the pre-attachment formed on the wafer while not damaging the device structure formed on the wafer itself, thereby ensuring the yield of the wafer after annealing.

[0021] Furthermore, the cleaning process also includes an alkaline cleaning process, performed after the acid cleaning process. The parameters of the alkaline cleaning process include a cleaning solution consisting of a mixture of ammonia and hydrogen peroxide and a cleaning time of 3 to 7 minutes. By performing the alkaline cleaning process after the acid cleaning process, the alkaline cleaning process can remove microparticles formed on the wafer after the acid cleaning process, preventing residual microparticles from affecting the wafer yield after annealing. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 1 is a schematic flow chart of a wafer annealing method according to an embodiment of the present invention;

[0023] Figure 2 1 is a schematic structural diagram of a wafer in a wafer annealing method according to an embodiment of the present invention;

[0024] Figure 3 FIG. 2 is a schematic diagram of the assembly structure of a wafer and an edge ring 200 in a wafer annealing method according to an embodiment of the present invention. DETAILED DESCRIPTION

[0025] To make the above-mentioned objects, features, and advantages of the present invention more clearly understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0026] In the description of the present invention, it should be understood that the terms "upper," "lower," "top," and "bottom" and the like, indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the positions or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations of the present invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0027] As described in the background art, there are still many problems in the process of rapid thermal annealing of wafers, which will be described in detail below.

[0028] Rapid thermal annealing (RTA) is a process used in semiconductor device fabrication and materials research during semiconductor manufacturing. It works by rapidly heating and cooling a material to alter its properties or structure. RTA is commonly used in applications such as ion implantation annealing, rapid annealing after IO coating, and oxide and nitride growth.

[0029] However, the applicant has found that some wafers will produce glue-like sticky attachments on the edges after annealing. The sticky attachments will adhere to the components in the annealing equipment. When the robotic arm enters the cavity of the annealing equipment to remove the wafer, the robotic arm cannot remove the wafer normally due to the adhesion between the wafer and the components of the annealing equipment. It is also easy for the wafer to slip in the equipment cavity, the robotic arm to scratch the surface of the wafer, or even the wafer to fall into pieces from the robotic arm. The above problems will all lead to damage or failure of the wafer.

[0030] The applicant has discovered that the above-mentioned problem arises when the waiting time of the wafer before entering the annealing equipment exceeds a certain period of time, the surface of the wafer will undergo subtle changes, resulting in some precursor attachments that are difficult to observe with the naked eye. After high-temperature annealing treatment, the precursor attachments will generate sticky attachments, which will cause the components of the annealing equipment to adhere to them, resulting in the wafer being unable to be removed normally by the robotic arm, and even causing the wafer to fail and be scrapped.

[0031] The applicant has further discovered that when the waiting time of the wafer before entering the annealing equipment exceeds a certain length of time, if the wafer is cleaned before annealing to remove the precursor attachments, then after annealing, no sticky attachments will be generated on the edge of the wafer, and the wafer can be removed smoothly by the robotic arm, and there will be no problem of wafer failure and scrap. In addition, the applicant also found that ordinary water washing cannot remove the precursor attachments, and sticky attachments will still be generated after annealing. Acidic cleaning is required to remove the precursor attachments, thereby solving the problem of sticky attachments generated after wafer annealing, thereby avoiding adhesion between the wafer and the components of the annealing equipment, ensuring that the wafer is removed smoothly by the robotic arm, and at the same time avoiding the risk of wafer failure and scrap.

[0032] Figure 1 1 is a schematic flow chart of a wafer annealing method according to an embodiment of the present invention, comprising:

[0033] Step S101, obtaining the waiting time of the wafer before entering the annealing equipment;

[0034] Step S102 , when the waiting time is greater than or equal to a preset time, performing a cleaning process on the wafer to remove precursor attachments formed on the wafer during the waiting time; wherein the cleaning process includes acid cleaning.

[0035] The steps of the wafer annealing method are described in detail below with reference to the accompanying drawings.

[0036] Figure 2 1 is a schematic structural diagram of a wafer in a wafer annealing method according to an embodiment of the present invention; Figure 3 Schematic diagram of the assembly structure of the wafer and edge ring in the wafer annealing method according to an embodiment of the present invention

[0037] Please refer to Figure 2 , obtain the waiting time of wafer 100 before entering the annealing equipment.

[0038] It should be noted that in modern semiconductor manufacturing plants, the production management system (MES) records in detail the transit time of each wafer through each process step, including the waiting time at the pre-annealing station. Specifically, the MES queries the entry and exit times of the wafer 100 at the pre-annealing station, with the difference between the two times representing the waiting time. Alternatively, in smaller plants or under specific circumstances, manual recording of wafer transit time may be necessary. Specifically, the time is recorded when the wafer 100 enters the pre-annealing station and again when the wafer 100 is transferred to the annealing furnace. The difference between the two times represents the waiting time. Alternatively, many semiconductor production equipment are equipped with monitoring systems that record equipment operating status and wafer processing time. Specifically, the monitoring system monitors the waiting time of the wafer 100 at the pre-annealing station. For example, rapid thermal annealing (RTA) equipment typically begins heating the wafer 100 immediately after entering the equipment. Therefore, the waiting time is the time from the wafer 100 entering the equipment to the start of heating.

[0039] In this embodiment, the annealing equipment utilizes rapid thermal annealing (RTA), an advanced heat treatment process used in semiconductor manufacturing. It uses a high-intensity light source (such as a halogen lamp or flash lamp) to heat the wafer 100 to a high temperature (typically around 1000°C) within a very short period of time (typically a few seconds to tens of seconds), followed by rapid cooling. The primary advantage of this process is that it can complete the annealing process in a short time, minimizing dopant diffusion while simultaneously repairing lattice damage and activating dopant atoms.

[0040] Rapid thermal annealing (RTA) technology is suitable for processes in modern semiconductor manufacturing that require extremely high precision and speed, such as ultra-shallow junction formation and surface defect repair. Compared to traditional furnace annealing, RTA offers faster heating and cooling rates, enabling better control of the thermal budget and thus improving device performance. Furthermore, RTA allows for flexible adjustment of heating time and temperature to meet diverse process requirements.

[0041] Rapid thermal annealing techniques also include various variants, such as laser annealing and flash annealing. Laser annealing utilizes a high-energy laser beam to locally heat the wafer 100, making it suitable for applications requiring high-precision and localized processing. Flash annealing, on the other hand, uses high-intensity pulsed light to heat the wafer 100 within an extremely short time (on the order of milliseconds), further reducing the thermal budget.

[0042] In other embodiments, the annealing equipment may also be a furnace annealing equipment, a flash annealing equipment or a laser annealing equipment.

[0043] Please refer to Figure 3 When the waiting time is greater than or equal to a preset time, the wafer 100 is cleaned to remove precursor attachments formed on the wafer 100 during the waiting time; wherein the cleaning process includes acid cleaning.

[0044] It should be noted that in this embodiment, after the wafer 100 is fed into the rapid thermal annealing (RTA) equipment, an edge ring 200 is placed at the edge of the wafer 100 to support and protect the wafer 100 during the thermal treatment process. The edge ring 200 is typically made of high-purity materials such as quartz, ceramic, or silicon. During the RTA process, the edge ring 200 helps evenly distribute heat, ensuring consistent temperature of the wafer 100 during heating and cooling. The edge ring 200 also acts as a barrier to prevent particles or impurities from entering sensitive areas of the wafer 100, thereby reducing contamination. During the thermal annealing process, the edge ring 200 provides a stable support platform, preventing the wafer 100 from shifting during rotation or heating. In certain processes, the edge ring 200 can also be used to regulate the electric field distribution, particularly during plasma etching, to prevent excessive plasma bombardment of the wafer 100 edge.

[0045] The edge ring 200 typically has an annular sidewall, and the distance between its upper surface and the base plate is greater than the thickness of the wafer 100 to ensure that the wafer 100 can be stably placed. In some designs, the edge ring 200 is provided with a gas flow channel for passing a temperature-regulating gas (such as helium) to control the temperature of the edge of the wafer 100. To further reduce contamination, the surface of the edge ring 200 may be coated with a special coating. Therefore, the edge ring 200 is an indispensable component in rapid thermal annealing equipment. It not only helps to improve the stability and repeatability of the process, but also significantly reduces the defects of the wafer 100 and improves the production yield.

[0046] If the wafer 100 forms adhesive deposits after annealing, the adhesive deposits will adhere to the edge ring 200 and the wafer 100, thereby preventing the robotic arm from removing the wafer 100 from the rapid thermal annealing equipment. Common phenomena include wafer slippage, scratches on the surface of the wafer 100 by the robotic arm, and fragments of the wafer 100 falling from the robotic arm. These problems can damage or render the wafer 100 useless.

[0047] Therefore, when the waiting time of the wafer 100 before annealing is greater than the preset time, the cleaning process is added to remove the precursor attachments formed on the wafer 100 during the waiting time, thereby effectively avoiding the generation of sticky attachments on the wafer 100 after annealing, preventing the wafer 100 from sticking to the edge ring 200, and affecting the robot arm's removal of the wafer 100 from the annealing equipment, thereby reducing the risk of the wafer 100 being damaged or failing during the removal process.

[0048] In other embodiments, when the waiting time is less than the preset time, the wafer is directly transferred to the annealing equipment.

[0049] In this embodiment, the preset duration is obtained based on historical waiting time data of several historical wafers 100 that have completed annealing. Specifically, the method for obtaining the preset duration includes: obtaining a first waiting time corresponding to the historical wafer 100 with the maximum waiting time and no adhesive deposits from the several historical waiting time data; obtaining a second waiting time corresponding to the historical wafer 100 with the minimum waiting time and adhesive deposits from the several historical waiting time data; and obtaining the preset duration based on the first waiting time and the second waiting time. Specifically, the method for obtaining the preset duration based on the first waiting time and the second waiting time includes: using the median between the first waiting time and the second waiting time as the preset duration.

[0050] In this embodiment, the acid cleaning parameters include: a sulfuric acid-hydrogen peroxide mixture (SPM) as the cleaning solution; and a cleaning time of 5 to 15 minutes. The volume ratio of sulfuric acid to hydrogen peroxide is 3:1 to 5:1, with a 4:1 ratio being the most common. For example, 1000 mL of sulfuric acid and 250 mL of hydrogen peroxide are used. While water is typically not added, the dilution ratio can be adjusted based on the process, such as a 3:1:1 volume ratio of sulfuric acid, hydrogen peroxide, and deionized water. The temperature of the sulfuric acid-hydrogen peroxide mixture is between 120 and 150 degrees Celsius, and temperature control is required to heat the sulfuric acid to boiling.

[0051] In this embodiment, the acid cleaning can effectively remove the pre-attachments generated on the wafer 100 while not damaging the device structure already formed on the wafer 100 itself, thereby ensuring the yield of the wafer 100 after annealing.

[0052] In this embodiment, the cleaning process further includes alkaline cleaning, and the alkaline cleaning is performed after the acid cleaning.

[0053] In this embodiment, the alkaline cleaning parameters include: the cleaning solution is a mixture of ammonia and hydrogen peroxide (Standard Clean 1, SC1); the cleaning time is 3 to 7 minutes. The volume ratio of ammonia, hydrogen peroxide, and deionized water is 1:1:5 or 1:2:7. For example, 100 mL of ammonia, 100 mL of hydrogen peroxide, and 500 mL of deionized water are used. The temperature of the ammonia and hydrogen peroxide mixture ranges from 70°C to 80°C.

[0054] In this embodiment, by adding the alkaline cleaning after the acid cleaning, the alkaline cleaning can remove the tiny particles formed on the wafer 100 after the acid cleaning, thereby preventing the residual tiny particles from affecting the yield of the wafer 100 after annealing.

[0055] It should be understood that the examples and embodiments herein are merely illustrative and that those skilled in the art may make various modifications and corrections without departing from the spirit and scope of the present invention as defined in this application and the appended claims.

Claims

1. A wafer annealing method, characterized in that: include: Get the waiting time of the wafer before entering the annealing equipment; When the waiting time is greater than or equal to a preset time, the wafer is cleaned to remove precursor attachments formed on the wafer during the waiting time; wherein, The cleaning treatment includes acid cleaning.

2. The wafer annealing method according to claim 1, wherein: The annealing equipment includes: rapid thermal annealing equipment, furnace tube annealing equipment, flash annealing equipment or laser annealing equipment.

3. The wafer annealing method according to claim 1, wherein: The preset waiting time is obtained based on provided historical waiting time data of several historical wafers that have completed annealing processes.

4. The wafer annealing method according to claim 3, wherein: The method for obtaining the preset time length includes: obtaining a first waiting time length corresponding to the historical wafer with the largest waiting time length and no sticky attachment generated from a number of the historical waiting time length data; obtaining a second waiting time length corresponding to the historical wafer with the smallest waiting time length and sticky attachment generated from a number of the historical waiting time length data; and obtaining the preset time length based on the first waiting time length and the second waiting time length.

5. The wafer annealing method according to claim 4, wherein: The method for obtaining the preset duration based on the first waiting duration and the second waiting duration includes: taking a median value between the first waiting duration and the second waiting duration as the preset duration.

6. The wafer annealing method according to claim 1, wherein: The parameters of the acid cleaning include: the cleaning solution is a mixed solution of sulfuric acid and hydrogen peroxide; and the cleaning time is 5 minutes to 15 minutes.

7. The wafer annealing method according to claim 6, wherein: The volume ratio of sulfuric acid and hydrogen peroxide is 3:1~5:

1.

8. The wafer annealing method according to claim 1, wherein: The cleaning process further includes alkaline cleaning, and the alkaline cleaning is performed after the acid cleaning.

9. The wafer annealing method according to claim 8, wherein: The parameters of the alkaline cleaning include: the cleaning solution is a mixed solution of ammonia water and hydrogen peroxide; and the cleaning time is 3 minutes to 7 minutes.

10. The wafer annealing method according to claim 9, wherein: The volume ratio of ammonia water, hydrogen peroxide and deionized water is 1:1:5 or 1:2:

7.

11. The wafer annealing method according to claim 1, wherein: When the waiting time is less than the preset time, the wafer is transferred to the annealing equipment.

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