Monitoring method for ion implantation process

Abstract

The invention relates to the field of semiconductor manufacturing, and provides an ion implantation process monitoring method comprising the following steps: S1, providing a control wafer; s2, forming a photoresist pattern on the control wafer, wherein the photoresist pattern exposes a blank pattern unit; s3, ions are injected into the blank pattern units; s4, removing the light resistance pattern on the control wafer; s5, measuring the resistance value at the blank pattern unit; s6, judging whether the area use upper limit of the control wafer is reached or not, and if the area use upper limit is reached, recycling the control wafer; if the upper limit is not reached, the step S2 to the step S6 are repeatedly executed, the blank pattern units exposed by the photoresist pattern are arranged in a staggered mode when the step S2 is executed for any two times, the blank pattern units exposed by the photoresist pattern are arranged in a staggered mode, repeated use of the control wafer in the monitoring process is achieved, cost control is facilitated, and the yield of the control wafer is improved. And meanwhile, the resistance value monitored by the machine is not influenced.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor manufacturing, and particularly to a method for monitoring an ion implantation process. Background Art

[0002] Ion implantation technology is an important doping technology in the field of semiconductor manufacturing. It is carried out in a vacuum environment. Impurity ions are accelerated to obtain greater kinetic energy and then form an ion beam to bombard the surface of a semiconductor wafer, thereby doping a semiconductor device. With the continuous development of semiconductor technology, higher and higher requirements are placed on data such as the accuracy of doping ions in the ion implantation process. Therefore, it is necessary for an ion implantation process machine to monitor the quality of ion implantation.

[0003] In the prior art, there are many items to be monitored in the ion implantation process, including at least 4 or more types of monitor wafers, resulting in a large consumption of monitor wafers. On average, one piece of equipment needs to use 4 monitor wafers (4 pcs / unit) per day. Moreover, the monitor wafers used up in a single monitoring process cannot be reused in a wafer fab, resulting in insufficient utilization rate of monitor wafers and being unfavorable for cost control. Summary of the Invention

[0004] The present invention mainly provides a method for monitoring an ion implantation process to solve the technical problem of high input cost of monitor wafers in the ion implantation process monitoring method mentioned in the above background art.

[0005] The technical solution adopted by the present invention to solve the above technical problems is as follows:

[0006] A method for monitoring an ion implantation process includes: S1: providing a monitor wafer; S2: forming a photoresist pattern on the monitor wafer, and the photoresist pattern exposes a blank pattern unit; S3: implanting ions into the blank pattern unit; S4: removing the photoresist pattern on the monitor wafer; S5: measuring the resistance value at the blank pattern unit; S6: determining whether the area usage upper limit of the monitor wafer is reached. If the upper limit is reached, the monitor wafer is recycled; if the upper limit is not reached, steps S2 to S6 are repeatedly executed, and the blank pattern units exposed by the photoresist pattern are misaligned when step S2 is executed any two times.

[0007] Preferably, an annealing treatment is further included for the monitor wafer between step S4 and step S5.

[0008] Preferably, in step S2, the photoresist pattern formed on the monitor wafer is changed by translating a photomask.

[0009] Preferably, the translation includes left - right movement, up - down movement, or a combination of the above movements.

[0010] Preferably, in step S2, the photoresist pattern formed on the control wafer is changed by rotating the angle of the photomask.

[0011] Preferably, when step S2 is executed for the first time, the blank graphic units exposed by the photoresist pattern are arranged on the same radius of the control wafer.

[0012] Preferably, the rotation angle is 5 to 10 degrees.

[0013] Preferably, in the step of measuring the resistance value at the blank graphic unit, the resistance value is measured by measuring the sheet resistance through the four-probe method.

[0014] Preferably, the measurement area of the probe in the four-probe method is 0.8 to 1.2 square millimeters.

[0015] Preferably, the blank graphic units exposed by the photoresist pattern formed on the control wafer include a circle, a rectangle, a triangle, a trapezoid or a combination thereof.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0017] A monitoring method for an ion implantation process provided by the present invention realizes the reuse of the control wafer in the monitoring process by arranging the blank graphic units exposed by the photoresist pattern in a staggered manner. Compared with the monitoring process of the traditional ion implantation process, in which the control wafer can only be used once, the present invention improves the utilization rate of the control wafer, is beneficial to cost control, does not affect the resistance value monitored by the machine tool, and has a simple method and is suitable for practical use.

[0018] The present invention will be explained and described in detail below in conjunction with the accompanying drawings and specific embodiments. Description of the Drawings

[0019] Figure 1 : Schematic diagram of the overall process of some embodiments of the present invention;

[0020] Figure 2 : Schematic diagram of the photoresist pattern in Embodiment 1 of the present invention;

[0021] Figure 3 : Schematic diagram of the photoresist pattern in Embodiment 2 of the present invention;

[0022] Figure 4 : Schematic diagram of the photoresist pattern in Embodiment 3 of the present invention.

[0023] Description of the Reference Numerals:

[0024] 101, 102, 103 First openings;

[0025] 201, 202, 203 Second openings. Detailed implementation manners

[0026] For the purposes, technical solutions and advantages of the embodiments of the present invention to be clearer, the technical solutions in the embodiments of the present invention will be described clearly and completely hereinafter. Apparently, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts shall fall within the scope of protection of the present invention. Unless otherwise defined, the technical terms or scientific terms used herein shall have the ordinary meanings as understood by those of ordinary skill in the art in the field to which the present invention belongs. The words such as "including" used herein mean that the elements or items appearing before this word cover the elements or items listed after this word and their equivalents, without excluding other elements or items.

[0027] In the prior art ion implantation process monitoring method, a large amount of control wafers are used and cannot be reused, resulting in too high input costs for the control wafers.

[0028] In view of the above problems, the embodiments of the present invention provide a monitoring method for an ion implantation process. Please refer to the attached Figure 1 attachment Figure 1 which is the overall process schematic diagram of some embodiments of the present invention.

[0029] The monitoring method includes:

[0030] S1: Provide a control wafer.

[0031] It should be noted that currently in the ion implantation process, the performance stability and uniformity of the ion implantation machine are ensured by monitoring the control wafers of the machine, that is, non-product wafers (NonProduction Wafer, abbreviated as NPW wafer). Here, the control wafer can be any semiconductor material. Exemplarily, it can be silicon, it can be germanium, it can be gallium arsenide, it can be gallium nitride, or it can also be sapphire. In addition, the control wafer can be a blank wafer or a wafer with a doped layer. The wafer with a doped layer can be a wafer with a P-type doped layer or a wafer with an N-type doped layer.

[0032] S2: Form a photoresist pattern on the control wafer, and the photoresist pattern exposes blank graphic units.

[0033] Specifically, a photoresist pattern is formed on the control wafer through steps such as photoresist coating, exposure, and development. The photoresist pattern has openings, and the openings expose the blank graphic units of the control wafer. The shape of the openings of the photoresist pattern can include a circle, a rectangle, a triangle, a trapezoid, or a combination thereof, that is, the blank graphic units exposed by the photoresist pattern formed on the control wafer include a circle, a rectangle, a triangle, a trapezoid, or a combination thereof. Exemplarily, the blank graphic units exposed by the photoresist pattern can be a single circle, a combination of multiple rectangles, or a combination of a triangle and a trapezoid.

[0034] Furthermore, the blank graphic units exposed by the photoresist pattern should be regular in shape. Regular shapes can facilitate subsequent measurement of the resistance values at the corresponding positions of the blank graphic units. At the same time, it can also avoid the generation of shadow effects, that is, when the blank graphic units exposed by the photoresist pattern are too complex, it is easy to cause insufficient or excessive ion implantation dose in some areas.

[0035] S3: Inject ions into the blank graphic units.

[0036] Specifically, each time the photoresist pattern formed on the control wafer exposes at least 49 blank graphic units. Exposing a sufficient number of blank graphic units can improve the uniformity of doping.

[0037] S4: Remove the photoresist pattern on the control wafer.

[0038] Removing the photoresist pattern here is for two reasons. One is to improve the accuracy of subsequent resistance measurement, and the other is to facilitate the reuse of the control wafer.

[0039] In addition, in some specific embodiments of the present invention, after this step, annealing treatment of the control wafer is further included. After ion implantation, defects and damages will be introduced on the surface of the control wafer, and these defects and damages will affect the conductivity of the control wafer. Annealing treatment can eliminate these defects and damages and restore the surface of the control wafer to a normal state.

[0040] S5: Measure the resistance value at the blank graphic units.

[0041] Specifically, in some specific embodiments of the present invention, the measurement method is to measure the sheet resistance by the four-probe method. The four-probe method is to place four equally spaced probes on the surface of the control wafer. A small appropriate current is provided by a constant current source to the two outer probes, and then the voltage V between the two middle probes is measured, so as to obtain the resistance measured by this set of data. For the uniformity of measurement, generally, multiple sets of measurement points at different positions are selected at the corresponding positions of the blank graphic units on the control wafer, and the average resistance (Mean) value and the standard deviation value (Stdv) are obtained by averaging the sheet resistance values measured at the multiple sets of measurement points at different positions to judge the stability and uniformity of the machine.

[0042] S6: Determine whether the area usage limit of the control wafer is reached. If the limit is reached, go to step S8: Recycle the control wafer. If the limit is not reached, repeat steps S2 to S6, and the blank pattern units exposed by the photoresist pattern are misaligned during any two executions of step S2.

[0043] It should be noted that the misaligned setting of the blank pattern units means that there is no overlapping part between each blank pattern unit exposed by the photoresist pattern. That is, the photoresist pattern changes in each cycle. Specifically, the opening positions of the photoresist pattern do not overlap with the opening positions of the photoresist pattern in all previous cycles. Thus, the blank pattern units exposed by the photoresist pattern in each cycle do not overlap with all the existing blank pattern units before this cycle. With such a design, different blank pattern units on the same control wafer can be measured for resistance in each cycle, respectively achieving the monitoring of the injection machine, thereby realizing the repeated use of the same control wafer without affecting the results of the resistance values monitored for the machine.

[0044] In addition, the area usage limit of the control wafer means that the blank pattern units on the control wafer reach a 100% usage rate.

[0045] Exemplarily, the specific process of the present invention is described in detail as follows:

[0046] Form a first photoresist pattern on the control wafer. The first photoresist pattern has a first opening, and the first opening exposes a first blank pattern unit. Ion implantation is performed at the position of the first blank pattern unit, and then the first photoresist pattern is removed. After annealing, the resistance value at the corresponding position of the first blank pattern unit is measured to achieve the first monitoring of the injection machine, completing the first use of the control wafer.

[0047] Form a second photoresist pattern on the control wafer. The second photoresist pattern has a second opening misaligned with the first opening. Thus, the second blank pattern unit exposed by the second opening does not overlap with the first blank pattern unit exposed by the first photoresist pattern. Ion implantation is performed at the position of the second blank pattern unit, and then the second photoresist pattern is removed. After annealing, the resistance value at the corresponding position of the second blank pattern unit is measured to achieve the second monitoring of the injection machine, completing the second repeated use of the control wafer.

[0048] Continue to form a third photoresist pattern on the control wafer. Similarly, the third blank pattern unit exposed by the third photoresist pattern must not overlap with the first blank pattern unit and the second blank pattern unit exposed by the first photoresist pattern and the second photoresist pattern at the same time. Ion implantation is performed at the position of the third blank pattern unit, and then the third photoresist pattern is removed. After annealing, the resistance value at the corresponding position of the third blank pattern unit is measured to achieve the third monitoring of the injection machine, completing the third repeated use of the control wafer.

[0049] This process repeats in a similar manner. The control wafer is reused until the available area on the control wafer reaches its upper limit. At this point, the control wafer can enter the recycling process for recycling.

[0050] In the present invention, the control wafer can be reused, and the minimum number of reuse times can be 5 times. Generally, it can reach 5 to 10 times. Under different misalignment setting methods of the blank graphic units exposed by the photoresist pattern, the number of reuse times of the control wafer can also exceed 10 times.

[0051] A monitoring method for an ion implantation process provided by the present invention realizes the reuse of the control wafer in the monitoring process by misaligning the blank graphic units exposed by the photoresist pattern. Compared with the traditional monitoring process of the ion implantation process where the control wafer can only be used once, the present invention improves the utilization rate of the control wafer, is beneficial to cost control, does not affect the resistance value monitored by the machine tool, and has a simple method and is suitable for practical use.

[0052] Furthermore, considering the specific implementation of the misalignment setting of the blank graphic units, the present invention provides the following several embodiments for better understanding of the present invention.

[0053] Embodiment 1

[0054] Please refer to the attached Figure 2 attachment, and the attached Figure 2 is a schematic diagram of the photoresist pattern in Embodiment 1 of the present invention.

[0055] Please first refer to the left schematic diagram in the attached Figure 2 The left schematic diagram is the first photoresist pattern (the white part). The first photoresist pattern has a first opening 101 formed as five rectangles, thereby exposing five rectangular-shaped first blank graphic units (the shaded marked part). Ion implantation is performed in the first blank graphic units exposed by the first opening 101 of the first photoresist pattern. After removing the first photoresist pattern and annealing, the resistance value at the corresponding position of the first blank graphic units is measured to complete the first monitoring of the implantation machine tool and complete the first use of the control wafer.

[0056] Then, continue to form a second photoresist pattern on the control wafer, as shown in the attached Figure 2As shown by the white part of the right schematic diagram, the second photoresist pattern has second openings 201 formed as another five rectangles. The positions of the second openings 201 are offset from the positions of the first openings 101 in the first monitoring. Thus, the five rectangular second blank graphic units exposed by the second photoresist pattern are also arranged in a staggered manner with the first blank graphic units, without overlapping parts, so that ion implantation will not affect each other, ensuring the accuracy of subsequent resistance measurement. Subsequently, ion implantation is performed on the second blank graphic units, the second photoresist pattern is removed, and the resistance values at the corresponding positions of the second blank graphic units are measured after annealing, achieving the second monitoring of the implantation machine tool, completing the second use of the control wafer, and realizing the recycling of the control wafer.

[0057] Subsequently, the photoresist pattern can be changed again to realize the repeated use of the control wafer, improve the utilization rate of the control wafer, and control costs.

[0058] Embodiment 2

[0059] Please refer to the attached Figure 3 attachment, the attached Figure 3 is a schematic diagram of the photoresist pattern in Embodiment 2 of the present invention.

[0060] Please first refer to the left schematic diagram of the attached Figure 3 The left schematic diagram is the first photoresist pattern (white part). The first photoresist pattern has three circular first openings 102, and these three circular first openings 102 are arranged on a radius of the control wafer. Thus, the first blank graphic units exposed by the first openings 102 are also formed as three circles (shaded marked parts), and the exposed blank graphic units are arranged on a radius of the control wafer. Subsequently, similarly, ion implantation is performed on the first blank graphic units, the first photoresist pattern is removed, and the resistance values at the corresponding positions of the first blank graphic units are measured after annealing, achieving the first monitoring of the implantation machine tool, and completing the first use of the control wafer.

[0061] Then rotate the photomask to transform the first photoresist pattern into a second photoresist pattern, as shown in the attached Figure 3As shown by the white part of the right schematic diagram. The rotated second photoresist pattern has a second opening 202. Since the same photomask is used, the shape of the second opening 202 is the same as that of the first opening 102, which are still three circles arranged along the radius of the control wafer. However, the position of the second opening 202 has rotated compared to the position of the first opening 102. Thus, the second blank pattern units (the shaded marked parts) exposed are three circular blank pattern units arranged on another radius of the control wafer, and the second blank pattern units and the first blank pattern units are arranged in a staggered manner without overlapping parts. Subsequently, ion implantation is performed on the second blank pattern units, the second photoresist pattern is removed, and after annealing, the resistance value at the corresponding position of the second blank pattern units is measured to achieve the second monitoring of the implantation machine, complete the second use of the control wafer, and realize the recycling of the control wafer.

[0062] Subsequently, the photomask can be rotated again to change the opening position of the photoresist pattern to achieve the reuse of the control wafer, improve the utilization rate of the control wafer, and control costs.

[0063] It should be noted that in some specific embodiments of the present invention, the angle of rotating the photomask mentioned above is 5 to 10 degrees. Exemplarily, it can be rotated by 5 degrees, 7 degrees can be selected, or it can be rotated by 10 degrees.

[0064] Furthermore, in some specific embodiments of the present invention, the measurement area of the probe in the four-probe method is 1 square millimeter, and this measurement area is much smaller than the rotation and movement distance. Therefore, rotating the photomask to change the photoresist pattern will not affect the subsequent resistance value measurement.

[0065] The difference between Embodiment 2 and Embodiment 1 is that in Embodiment 2, the opening position of the photoresist pattern is changed by rotating the photomask. This method can avoid using multiple photomasks to change the photoresist pattern and further control costs.

[0066] Embodiment 3

[0067] Please refer to the attached Figure 4 , the attached Figure 4 is the schematic diagram of the photoresist pattern in Embodiment 3 of the present invention.

[0068] Please first refer to the left schematic diagram of the attached Figure 4 The left schematic diagram is the first photoresist pattern (the white part), and this first photoresist pattern has three circular first openings 103. The first blank pattern units exposed by the first openings 103 are formed as three circles (the shaded marked parts). Subsequently, similarly, ion implantation is performed on the first blank pattern units, the first photoresist pattern is removed, and after annealing, the resistance value at the corresponding position of the first blank pattern units is measured to achieve the first monitoring of the implantation machine and complete the first use of the control wafer.

[0069] Then, shift the photomask to the left as shown in the figure to transform the first photoresist pattern into a second photoresist pattern, as shown in the white part of the right schematic diagram of Figure 4 . The second photoresist pattern after shifting has a second opening 203. Since the same photomask is used, the shape of the second opening 203 is the same as that of the first opening 103, which is still three circles. However, the position of the second opening 203 has moved compared to the position of the first opening 103. The second blank graphic units (the shaded marked parts) exposed thereby are three circular blank graphic units at another position on the control wafer, and the second blank graphic units and the first blank graphic units are arranged in a staggered manner without overlapping parts. Subsequently, ion implantation is performed on the second blank graphic units, the second photoresist pattern is removed, and the resistance value at the corresponding position of the second blank graphic units is measured after annealing to achieve the second monitoring of the implantation machine, complete the second use of the control wafer, and realize the recycling of the control wafer.

[0070] Subsequently, the photomask can be shifted again to change the opening position of the photoresist pattern to achieve the repeated use of the control wafer, improve the utilization rate of the control wafer, and control costs.

[0071] It should be noted that the above-mentioned shifting of the photomask can be an up-and-down movement, a left-and-right movement, or a combination of the above movement methods. Exemplarily, when moving up and left simultaneously, it is transformed into a movement obliquely upward, or it can also be a first up-and-down movement and then a left-and-right movement, both of which belong to the combination of the above movement methods.

[0072] Although the embodiments of the present invention have been described in detail above, it is obvious to those skilled in the art that various modifications and changes can be made to these embodiments. However, it should be understood that such modifications and changes are all within the scope and spirit of the present invention described in the claims. Moreover, the present invention described herein can have other embodiments and can be implemented or realized in various ways.

Claims

1. A monitoring method for an ion implantation process, characterized in that, Including: S1: Provide a control wafer; S2: Form a photoresist pattern on the control wafer, and the photoresist pattern exposes blank graphic units; S3: Inject ions into the blank graphic units; S4: Remove the photoresist pattern on the control wafer; S5: Measure the resistance value at the blank graphic units; S6: Determine whether the upper limit of the area usage of the control wafer is reached. If the upper limit is reached, recycle the control wafer; if the upper limit is not reached, repeat steps S2 to S6, and the blank graphic units exposed by the photoresist pattern are arranged in a staggered manner during any two executions of step S2.

2. The monitoring method according to claim 1, characterized in that An annealing treatment is also included between step S4 and step S5 for the control wafer.

3. The monitoring method according to claim 1, wherein In step S2, the photoresist pattern formed on the control wafer is changed by translating the photomask.

4. The monitoring method according to claim 3, wherein The translation includes left - right movement, up - down movement, or a combination of the above movements.

5. The monitoring method according to claim 1, wherein In step S2, the photoresist pattern formed on the control wafer is changed by rotating the angle of the photomask.

6. The monitoring method according to claim 5, wherein When step S2 is executed for the first time, the blank graphic units exposed by the photoresist pattern are arranged on the same radius of the control wafer.

7. The monitoring method according to claim 5 or 6, characterized in that, The rotation angle is 5 to 10 degrees.

8. The monitoring method according to claim 1, characterized in that In the step of measuring the resistance value at the blank graphic units, the resistance value is measured by measuring the sheet resistance using the four - probe method.

9. The monitoring method according to claim 8, wherein The measurement area of the probes in the four - probe method is 0.8 to 1.2 square millimeters.

10. The monitoring method according to claim 1, characterized in that, The blank graphic units exposed by the photoresist pattern formed on the control wafer include circles, rectangles, triangles, trapezoids, or combinations thereof.

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