An ion implantation method for a wafer

Abstract

The present invention provides a method for ion implantation of a wafer, comprising the following steps: placing the wafer on a wafer chuck of an ion implantation machine; performing N times of ion implantation on the wafer in sequence until a preset ion implantation dose is reached, where N is an integer greater than 1, and after each ion implantation is completed, the wafer is first rotated 360 / N degrees in the same direction around the central axis of the wafer before the next ion implantation is carried out, the central axis passes through the center of the wafer and is perpendicular to the plane where the wafer is located. The method for ion implantation of the wafer according to the present invention improves the process flow of the ion implantation process. The ion implantation process is divided into multiple times. After each ion implantation is completed, the wafer is rotated 360 / N degrees before the next ion implantation is carried out, which can effectively eliminate the influence of the small angular deviation of the beam current on the product, can simply and effectively improve the uniformity of ion implantation of the wafer, thereby improving the yield of the product, reducing the risk of product scrapping and the utilization rate of the equipment.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductor integrated circuit manufacturing and relates to an ion implantation method for a wafer. Background Art

[0002] The VIISta HCS high-beam ion implantation machine is widely used in the ion implantation process of 12-inch semiconductor manufacturing, mainly for large-dose implantation; but because the machine uses a swept beam for ion implantation, it has certain inherent defects, which can easily lead to poor ion implantation uniformity and striped pattern problems.

[0003] In actual operation of the machine, due to the existence of the first lens (to improve productivity and beam transmission at low energy) and the second lens (to improve beam focusing and deceleration performance) in the VIISta HCS ion implanter, when the beam passes through these two lenses, due to the optical refraction phenomenon, the edge beam will have a slight deviation from the initial set angle, resulting in fluctuations in the uniformity of the ion implantation dose during the wafer ion implantation process, resulting in poor uniformity of the block resistance Rs, which in turn affects important electrical parameters such as the product saturation current (Idsat) and N / P plug resistance. This problem is an inherent defect of the swept beam method of the VIISta HCS machine, and it is difficult to correct it by adjusting the hardware conditions.

[0004] Therefore, how to provide an improved ion implantation method to reduce or eliminate the impact of small beam angle deviations on products and further improve product yield has become an important technical problem that needs to be urgently solved by technical personnel in this field. Summary of the invention

[0005] In view of the shortcomings of the prior art described above, the object of the present invention is to provide an ion implantation method for a wafer, which is used to solve the problem in the prior art that due to a slight angle deviation of the beam, the uniformity of the ion implantation dose fluctuates, thereby causing the uniformity of the wafer's block resistance Rs to deteriorate, thereby affecting important electrical parameters such as the product saturation current (Idsat) and N / P plug resistance.

[0006] To achieve the above object and other related objects, the present invention provides a method for ion implantation of a wafer, comprising the following steps:

[0007] Placing the wafer on a wafer rake plate of an ion implantation machine;

[0008] The wafer is subjected to N ion implantations in sequence until a preset ion implantation dose is reached, where N is an integer greater than 1. After each ion implantation, the wafer is first rotated 360 / N degrees in the same direction around the central axis of the wafer before the next ion implantation. The central axis passes through the center of the wafer and is perpendicular to the plane where the wafer is located.

[0009] Optionally, 1 < N ≤ 10.

[0010] Optionally, 3 ≤ N ≤ 5.

[0011] Optionally, the wafer is subjected to 4 ion implantations in sequence until the preset ion implantation dose is reached. After each ion implantation, the wafer is first rotated 90 degrees clockwise or counterclockwise around the central axis of the wafer before the next ion implantation.

[0012] Optionally, in each of the N ion implantations, the dose used is 1 / N of the preset ion implantation dose.

[0013] Optionally, in each of the N ion implantations, the beam angle used is the same.

[0014] Optionally, in each of the N ion implantations, the ion implantation energy used is the same.

[0015] Optionally, in each of the N ion implantations, the duration of each ion implantation is the same.

[0016] Optionally, in the ion implantation, the ions generated by the ion source pass through at least two lenses before being incident on the wafer.

[0017] Optionally, the wafer includes one of a 6-inch wafer, an 8-inch wafer, and a 12-inch wafer.

[0018] As described above, the ion implantation method for the wafer of the present invention improves the process flow of the ion implantation process. The ion implantation process is divided into multiple times (for example, 4 times). After each ion implantation, by adjusting the menu parameters, the wafer is rotated 360 / N degrees (for example, 90 degrees) before the next ion implantation. During each ion implantation process, except for changing the wafer angle, the other parameters such as the beam angle, dose, and energy size should remain unchanged, so as to ensure that the time of multiple ion implantations is consistent. The present invention uses the method of optimizing the menu in the process to effectively eliminate the influence of the small beam angle deviation on the product, can simply and effectively improve the uniformity of wafer ion implantation, thereby improving the yield of the product and reducing the risk of product scrapping and the utilization rate of the equipment. Description of the Drawings

[0019] Figure 1It shows a process flow chart of the ion implantation method for the wafer of the present invention.

[0020] Figure 2 It shows a schematic diagram of placing the wafer on the wafer chuck of the ion implantation machine in the step S1.

[0021] Figure 3 It shows a schematic diagram of rotating the wafer 90 degrees clockwise around the central axis of the wafer by the chuck.

[0022] Figure 4 It shows the sheet resistance distribution map of the wafer obtained by the ion implantation scheme of performing one-time ion implantation to a preset ion implantation dose without rotating the wafer.

[0023] Figure 5 It shows the sheet resistance distribution map of the wafer obtained by the ion implantation scheme of performing four-time ion implantation to a preset ion implantation dose and rotating the wafer 90 degrees clockwise between two adjacent ion implantations.

[0024] Description of Component Labels

[0025] Steps S1 - S2

[0026] 1 Wafer

[0027] 2 Chuck Detailed Embodiment

[0028] The following uses specific specific examples to illustrate the embodiments of the present invention. Those skilled in the art can easily understand the 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. 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.

[0029] Please refer to Figures 1 to 5 . It should be noted that the diagrams provided in this embodiment only illustrate the basic concept of the present invention in a schematic manner. Therefore, only the components related to the present invention are shown in the diagrams, rather than being drawn according to the number, shape, and size of the components in actual implementation. The type, quantity, and ratio of each component in actual implementation can be arbitrarily changed, and the component layout type may also be more complex.

[0030] Embodiment 1

[0031] The present invention provides an ion implantation method for a wafer. Please refer to Figure 1 , which shows a process flow chart of the ion implantation method, including the following steps:

[0032] S1: Place the wafer on the wafer chuck of the ion implantation machine;

[0033] S2: Perform N ion implantations on the wafer in sequence until a preset ion implantation dose is reached, where N is an integer greater than 1. After each ion implantation, first rotate the wafer 360 / N degrees in the same direction around the central axis of the wafer before performing the next ion implantation. The central axis passes through the center of the wafer and is perpendicular to the plane where the wafer is located.

[0034] Specifically, an ion implanter is a key device in the front-end processes of integrated circuit manufacturing. Ion implantation is a technology for doping the region near the semiconductor surface, and its purpose is to change the carrier concentration and conductivity type of the semiconductor. An ion implanter usually consists of five parts: an ion source, an ion extraction and mass analyzer, an acceleration tube, a scanning system, and a process chamber, where:

[0035] (1) The hot electrons generated by the filament in the ion source bombard the gaseous impurity source under the action of an electric field to ionize it, generating charged atoms or molecules;

[0036] (2) In the ion extractor, all positively charged ions are repelled by the positive pressure of the ion source anode and are extracted from a slit. At this time, the electrons in the plasma are repelled by the cathode and are blocked, thus forming an ion beam composed of positive ions;

[0037] (3) Since the bombardment of the impurity source gas molecules by hot electrons will generate various ions, and the mass-to-charge ratio of each ion is different, when passing through the analyzing magnet of the mass analyzer, the movement orbits of the ions will be different. Therefore, the mass analyzer of the ion implanter can separate the required impurity ions from the mixed ion beam;

[0038] (4) After the positive ions come out of the mass analyzer, they still need to obtain the required speed through the high voltage of the acceleration tube. The acceleration tube is composed of a series of electrodes isolated by a medium, and the negative voltages on the electrodes increase sequentially. When the positive ions enter the acceleration tube, each negative electrode accelerates the ions, and the movement speed of the ions is the superposition of the accelerations at each stage. The higher the total voltage, the faster the movement speed of the ions, that is, the greater the kinetic energy;

[0039] (5) The scanning system of the ion implanter constitutes the relative movement between the ion beam and the wafer. In order to make the impurities on the wafer be evenly distributed and avoid the local overheating caused by the long-term bombardment of a single point by ions, resulting in irreparable damage, the ion implantation of the wafer all adopts a scanning method;

[0040] (6) The process chamber includes a target disk for placing the wafer, a wafer transfer component, and a process control component. The wafer transfer component transfers the wafer cassette from the atmospheric environment to the high-vacuum environment. A specific orientation of each wafer is placed on the target disk waiting for ion implantation. The process control component is used to display the ion beam distribution curve and detect the ion beam current, and is also used to control ion implantation.

[0041] Specifically, please refer to Figure 2 , which shows a schematic diagram of placing the wafer 1 on the wafer chuck 2 of the ion implantation machine in the step S1.

[0042] As an example, the ion implantation machine can be any one of a low-energy high-current implanter, a high-energy implanter, and a medium-current implanter. The wafer 1 includes, but is not limited to, any one of a 6-inch wafer, an 8-inch wafer, and a 12-inch wafer. The material of the wafer 1 includes, but is not limited to, materials such as silicon, germanium, silicon-germanium, and III-V compounds. In this embodiment, the ion implantation machine is taken as a VIISta HCS type high-current ion implantation machine, and the wafer 1 is taken as a silicon wafer. Among them, in the ion implantation, the ions generated by the ion source are incident on the wafer after passing through at least two lenses. One lens is used to improve the productivity and beam transmission at low energy, and the other lens is used to improve the beam focusing and deceleration performance.

[0043] As an example, in the step S2, the implanted ions include, but are not limited to, ions such as P, As, Sb, B, Ga, and In, and can be selected according to actual needs.

[0044] As an example, in the step S2, in the N times of ion implantation, the dose used for each ion implantation is the same, that is, each is one Nth of the preset ion implantation dose.

[0045] As an example, in the N times of ion implantation, the beam angle and ion implantation energy used for each ion implantation are the same.

[0046] As an example, in the N times of ion implantation, the duration of each ion implantation is the same.

[0047] As an example, in this embodiment, in the step S2, the ion implantation process is divided into four times, that is, the wafer 1 is sequentially subjected to four times of ion implantation until the preset ion implantation dose is reached. Among them, after each ion implantation is completed, the wafer 1 is first rotated 90 degrees clockwise or counterclockwise around the central axis of the wafer 1 and then the next ion implantation is carried out.

[0048] Please refer to Figure 3 , which shows a schematic diagram of rotating the wafer 1 90 degrees clockwise around the central axis of the wafer 1 by the chuck 2.

[0049] It should be noted that after the direction is selected for the first rotation, the subsequent rotations all use the same direction. For example, if the clockwise direction is used for the first rotation, the subsequent rotations all use the clockwise direction; if the counterclockwise direction is used for the first rotation, the subsequent rotations all use the counterclockwise direction.

[0050] In this embodiment, the preset ion implantation dose is 4E14 cm -2 as an example. By optimizing the parameters of the process menu, after injecting a dose of 1E14 cm -2 each time, the ion implantation is stopped, the wafer is rotated 90 degrees clockwise, and then the ion implantation continues, with a total of three rotations.

[0051] Please refer to Figure 4 and Figure 5 , where Figure 4 shows the sheet resistance distribution map of the wafer obtained by an ion implantation scheme with a single ion implantation to the preset ion implantation dose and the wafer not being rotated. Figure 5 shows the sheet resistance distribution map of the wafer obtained by an ion implantation scheme with four ion implantations to the preset ion implantation dose and the wafer being rotated 90 degrees clockwise between two adjacent ion implantations. The change in the color depth in the figure represents the change in the sheet resistance. From the comparison between Figure 4 and Figure 5 , it can be seen that the ion implantation uniformity of the wafer without adopting the ion implantation scheme of the present invention is poor, showing an overall strip-shaped pattern. After adopting the ion implantation scheme of the present invention, the strip-shaped pattern area is significantly reduced, effectively improving the uniformity of the sheet resistance Rs of the wafer during the monitoring process, correspondingly optimizing the uniformity of the ion implantation of the wafer, and being beneficial to improving the yield of the product.

[0052] Embodiment 2

[0053] This embodiment adopts basically the same technical solution as Embodiment 1. The difference is that in Embodiment 1, the wafer is sequentially subjected to four ion implantations until the preset ion implantation dose is reached. Among them, after each ion implantation, the wafer is first rotated 90 degrees clockwise or counterclockwise around the central axis of the wafer and then the next ion implantation is carried out, and the dose used for each ion implantation is one-fourth of the preset ion implantation dose. In this embodiment, the wafer is sequentially subjected to two ion implantations until the preset ion implantation dose is reached. Among them, after each ion implantation, the wafer is first rotated 180 degrees clockwise or counterclockwise around the central axis of the wafer and then the next ion implantation is carried out, and the dose used for each ion implantation is one-half of the preset ion implantation dose.

[0054] Embodiment 3

[0055] This embodiment adopts basically the same technical solution as Embodiment 1. The difference is that in this embodiment, the wafer is sequentially subjected to three ion implantations until the preset ion implantation dose is reached. Among them, after each ion implantation, the wafer is first rotated 120 degrees clockwise or counterclockwise around the central axis of the wafer and then the next ion implantation is carried out, and the dose used for each ion implantation is one-third of the preset ion implantation dose.

[0056] Example 4

[0057] This example adopts basically the same technical solution as Example 1. The difference is that in this example, the wafer is subjected to ion implantation 5 times, 6 times, 7 times, 8 times, 9 times or 10 times in sequence until the preset ion implantation dose is reached. Among them, after each ion implantation is completed, the wafer is first rotated clockwise or counterclockwise by 72 degrees, 60 degrees, 51.4 degrees, 45 degrees, 40 degrees or 36 degrees around the central axis of the wafer and then the next ion implantation is carried out. The dose used for each ion implantation is one-fifth, one-sixth, one-seventh, one-eighth, one-ninth or one-tenth of the preset ion implantation dose.

[0058] In summary, the ion implantation method of the wafer of the present invention improves the process flow of the ion implantation process. The ion implantation process is divided into multiple times (for example, 4 times). After each ion implantation is completed, by adjusting the menu parameters, the wafer is rotated by 360 / N degrees (for example, 90 degrees) and then the next ion implantation is carried out. During each ion implantation process, except for changing the wafer angle, the other parameters such as the beam angle, dose, and energy should remain unchanged, so as to ensure that the time of multiple ion implantation processes is consistent. The present invention uses the method of optimizing the menu in the process to effectively eliminate the influence of the small beam angle deviation on the product, can simply and effectively improve the uniformity of wafer ion implantation, thereby improving the yield of the product and reducing the risk of product scrapping and the utilization rate of the equipment. Therefore, the present invention effectively overcomes various disadvantages in the prior art and has high industrial utilization value.

[0059] The above embodiments are only illustrative of the principles and effects of the present invention, and are not used to limit the present invention. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes completed by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. An ion implantation method for a wafer, characterized in that, Including the following steps: Place the wafer on the wafer chuck of the ion implanter; Perform N times of ion implantation on the wafer in sequence until the preset ion implantation dose is reached, where N is an integer greater than 1. After each ion implantation, first rotate the wafer 360 / N degrees in the same direction around the central axis of the wafer, and then perform the next ion implantation. The central axis passes through the center of the wafer and is perpendicular to the plane where the wafer is located. The ion implantation uses a swept beam. In the N times of ion implantation, the dose used for each ion implantation is 1 / N of the preset ion implantation dose.

2. The ion implantation method for a wafer according to claim 1, characterized in that: 1＜N≤10。 3. The ion implantation method of a wafer according to claim 2, wherein: 3≤N≤5。 4. The ion implantation method of a wafer according to claim 3, characterized in that: Perform 4 times of ion implantation on the wafer in sequence until the preset ion implantation dose is reached. After each ion implantation, first rotate the wafer 90 degrees clockwise or counterclockwise around the central axis of the wafer, and then perform the next ion implantation.

5. The ion implantation method of the wafer according to claim 1, wherein: In the N times of ion implantation, the beam angle used for each ion implantation is the same.

6. The ion implantation method for a wafer according to claim 1, characterized in that: In the N times of ion implantation, the ion implantation energy used for each ion implantation is the same.

7. The ion implantation method of a wafer according to claim 1, characterized in that: In the N times of ion implantation, the duration of each ion implantation is the same.

8. The ion implantation method for a wafer according to claim 1, wherein: In the ion implantation, the ions generated by the ion source pass through at least two lenses before entering the wafer.

9. The ion implantation method for a wafer according to claim 1, characterized in that: The wafer includes one of a 6-inch wafer, an 8-inch wafer, and a 12-inch wafer.

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