Monitoring Method for Wafer Cleaning Machine

Abstract

The present invention provides a monitoring method for a wafer cleaning machine tool, including: forming a stacked first buffer layer, a second buffer layer, a seed layer and a metal layer on the front surface of a bare wafer to obtain a test chip; transferring the test chip to the wafer cleaning machine tool; cleaning the back surface of the test chip; obtaining an electron beam imaging grayscale map of the test chip; analyzing the distribution of metal ions on the edge and side wall of the test chip. This application uses a test chip with a metal layer grown on the front surface to simulate the cleaning operation process of the BSC machine tool for product wafers. According to the electron beam imaging grayscale map of the test chip, the distribution of metal ions on the edge and side wall of the test chip is analyzed, and the cleaning operation state of the BSC machine tool is monitored in advance to determine whether it has changed, thereby avoiding the particle dispersion defect caused by the cleaning operation with the changed state of the BSC machine tool, avoiding damage to the metal layer on the front surface of the wafer, and improving the late-stage yield of the wafer.

Description

Technical Field

[0001] This application relates to the field of semiconductor manufacturing technology, and particularly to a monitoring method for a wafer cleaning machine. Background Art

[0002] The BSC (Backside Clean) machine is a wafer backside cleaning machine used to clean the backside of the wafer. After depositing some film layers (such as oxide layers, metal layers, etc.) on the front side of the wafer, the backside of the wafer is prone to adhering some impurities such as particles and metal elements. The BSC machine mainly removes the contamination, particles, and metal elements on the back of the wafer.

[0003] The BSC machine flips the wafer through a wafer flipping device so that the front side of the wafer is facing down and the back side of the wafer is facing up, and uses a cleaning reagent to clean the back side of the wafer. During the process of cleaning the back side of the wafer, the wafer carrier of the BSC machine will pass an inert gas (such as nitrogen) to protect the front side of the wafer, preventing the cleaning reagent from flowing onto the downward-facing front side of the wafer and thus eroding the front side of the wafer. When the BSC machine is in a process interval where the metal layer (such as copper) or other film layers are exposed, if the cleaning operation state of the BSC machine has changed, at this time, performing the cleaning operation process of the BSC machine is likely to cause damage to the metal layer (or other film layers) on the front side of the wafer, resulting in metal ion diffusion (such as CU Diffuse, copper ion diffusion) defects or other impurity particle diffusion defects. Currently, the particle diffusion defects caused by the cleaning operation due to the state change of the BSC machine cannot be effectively monitored in advance, resulting in damage to the film layer on the front side of the wafer and abnormal yield of the wafer in the later stage. Summary of the Invention

[0004] This application provides a monitoring method for a wafer cleaning machine, which can solve the problem that the particle diffusion defects caused by the cleaning operation of the BSC machine when the operation state changes cause damage to the film layer on the front side of the wafer.

[0005] On the one hand, an embodiment of this application provides a monitoring method for a wafer cleaning machine, including:

[0006] Providing a bare wafer, and sequentially forming a stacked first buffer layer, a second buffer layer, a seed layer, and a metal layer on the front side of the bare wafer to obtain a test chip;

[0007] Transferring the test chip to a wafer cleaning machine, and flipping the test chip so that the back side of the test chip is facing up;

[0008] Cleaning the back side of the test chip;

[0009] Obtaining an electron beam imaging grayscale map of the test chip, wherein the electron beam imaging grayscale map at least covers the edge region and the sidewall region of the test chip;

[0010] According to the electron beam imaging grayscale map, analyze the distribution of metal ions on the edge and sidewall of the test chip to monitor whether the cleaning operation of the wafer cleaning machine damages the metal layer on the front side of the test chip.

[0011] In the monitoring method of the wafer cleaning machine, the metal layer is a copper layer.

[0012] In the monitoring method of the wafer cleaning machine, according to the electron beam imaging grayscale map, analyze the distribution of copper ions on the edge and sidewall of the test chip to monitor whether the cleaning operation of the wafer cleaning machine damages the copper layer on the front side of the test chip.

[0013] In the monitoring method of the wafer cleaning machine, the step of cleaning the back side of the test chip includes:

[0014] Fix the edge of the test chip with the jaw of the wafer cleaning machine;

[0015] Inject nitrogen gas onto the front side of the test chip through the gas pipeline inside the carrier of the wafer cleaning machine;

[0016] Drive the test chip to rotate with the rotating base of the wafer cleaning machine;

[0017] Inject a cleaning reagent onto the back side of the test chip through the chemical solution pipeline above the carrier;

[0018] At the end of the cleaning operation, stop injecting nitrogen gas through the gas pipeline, stop the rotation of the rotating base, stop injecting the cleaning reagent through the chemical solution pipeline, and release the jaw to take out the test chip from the wafer cleaning machine.

[0019] In the monitoring method of the wafer cleaning machine, the cleaning reagent includes: HF and HNO 3 .

[0020] In the monitoring method of the wafer cleaning machine, after cleaning the back side of the test chip and before obtaining the electron beam imaging grayscale map of the test chip, the monitoring method of the wafer cleaning machine further includes:

[0021] Provide a plurality of identical test chips, and clean the back sides of the plurality of test chips under different cleaning conditions; wherein, the cleaning conditions at least include: the rotation speed of the rotating base of the wafer cleaning machine, and the flow rate of nitrogen gas injected through the gas pipeline inside the carrier of the wafer cleaning machine.

[0022] In the monitoring method of the wafer cleaning machine, the rotation speed of the rotating base of the wafer cleaning machine is set to 400 rpm; the flow rate of nitrogen gas injected by the gas pipeline inside the carrier stage of the wafer cleaning machine is set to 150 L / min.

[0023] In the monitoring method of the wafer cleaning machine, the rotation speed of the rotating base of the wafer cleaning machine is set to 800 rpm; the flow rate of nitrogen gas injected by the gas pipeline inside the carrier stage of the wafer cleaning machine is set to 200 L / min.

[0024] In the monitoring method of the wafer cleaning machine, the step of analyzing the distribution of metal ions on the edge and sidewall of the test chip according to the electron beam imaging grayscale map to monitor whether the cleaning operation of the wafer cleaning machine damages the metal layer on the front side of the test chip includes:

[0025] Compare the electron beam imaging grayscale maps of the test chips under different cleaning conditions, and analyze the distribution of metal ions on the edge and sidewall of the test chip to monitor whether the cleaning operation of the wafer cleaning machine damages the metal layer on the front side of the test chip.

[0026] In the monitoring method of the wafer cleaning machine, the first buffer layer is a tantalum nitride layer; the second buffer layer is a tantalum layer; the seed layer is a copper layer.

[0027] The technical solution of the present application has at least the following advantages:

[0028] The present application uses a test chip (wafer) that grows a first buffer layer, a second buffer layer, a seed layer, and a metal layer on the front side to simulate the BSC machine cleaning operation process of the product wafer. According to the electron beam imaging grayscale map of the test chip, analyze the distribution of metal ions on the edge and sidewall of the test chip to monitor whether the cleaning operation of the wafer cleaning machine damages the metal layer on the front side of the test chip, so as to monitor in advance whether the cleaning operation state of the BSC machine has changed, thereby avoiding the particle dispersion defect caused by the cleaning operation with the changed state of the BSC machine, thereby avoiding damage to the metal layer (or other film layers) on the front side of the wafer, and improving the late-stage yield of the wafer. Description of the Drawings

[0029] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0030] Figure 1 is a flowchart of the monitoring method for the wafer cleaning machine in the embodiment of the present invention;

[0031] Figure 2 is a schematic structural diagram of the test chip in the embodiment of the present invention;

[0032] Figure 3 is a schematic diagram of the cleaning operation process of the wafer cleaning machine in the embodiment of the present invention;

[0033] Among them, the reference numerals are explained as follows:

[0034] 10 - test chip, 11 - front side of the test chip, 12 - back side of the test chip, 101 - bare wafer, 102 - first buffer layer, 103 - second buffer layer, 104 - seed layer, 105 - metal layer;

[0035] 20 - wafer cleaning machine, 21 - gas pipeline, 22 - carrier stage, 23 - chemical liquid pipeline, 24 - rotating base. Detailed implementation manners

[0036] Next, the technical solutions in the present application will be clearly and completely described in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts shall fall within the protection scope of the present application.

[0037] In the description of the present application, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present application. In addition, the terms "first", "second", "third" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0038] In the description of the present application, it should be noted that unless otherwise clearly specified and limited, the terms "installed", "connected", "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, and can also be the communication inside two elements. It can be a wireless connection or a wired connection. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific situations.

[0039] In addition, the technical features involved in different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0040] An embodiment of the present application provides a monitoring method for a wafer cleaning machine. Refer to Figure 1 , Figure 1 which is a flowchart of the monitoring method for the wafer cleaning machine according to an embodiment of the present invention. The monitoring method for the wafer cleaning machine includes:

[0041] Step S10: Refer to Figure 2 , Figure 2 which is a schematic structural diagram of a test chip according to an embodiment of the present invention. Provide a bare wafer 101, and sequentially form a stacked first buffer layer 102, a second buffer layer 103, a seed layer 104, and a metal layer 105 on the front surface of the bare wafer 101 to obtain a test chip 10. Specifically, the metal layer 105 covers the seed layer 104, the seed layer 104 covers the second buffer layer 103, the second buffer layer 103 covers the first buffer layer 102, and the first buffer layer 102 covers the front surface of the bare wafer 101.

[0042] In this embodiment, the first buffer layer 102, the second buffer layer 103, and the seed layer 104 are sequentially formed on the front surface of the bare wafer 101 by using a PVD machine; further, the metal layer 105 is formed on the seed layer 104 by using an ECP machine.

[0043] Preferably, the first buffer layer 102 can be a tantalum nitride layer, and the thickness of the first buffer layer 102 can be For example The second buffer layer 103 can be a tantalum layer, and the thickness of the second buffer layer 103 can be For example The seed layer 104 can be a copper layer, and the thickness of the seed layer 104 can be For example The metal layer 105 can be a copper layer, and the thickness of the metal layer 105 can be For example

[0044] In this embodiment, the main functions of the first buffer layer 102 and the first buffer layer 102 are to make the bare wafer 101 bond better with the subsequently formed metal layer 105. The seed layer 104 is the seed layer of the metal layer 105. When the metal layer 105 is formed using an ECP machine later, it must grow along the crystal phase of the seed layer 104. The metal layer 105 is the main source of the metal layer in the subsequent simulation of the cleaning operation process of the wafer cleaning machine (BSC machine). The metal layer 105 formed in this way has high crystal quality and can well simulate and restore the BSC machine cleaning operation process of the product wafer later.

[0045] Step S20: Refer to Figure 3 , Figure 3 is a schematic diagram of the cleaning operation process of the wafer cleaning machine according to an embodiment of the present invention. Transfer the test chip 10 to the wafer cleaning machine 20 and flip the test chip 10 so that the back surface 12 of the test chip faces upward.

[0046] Step S30: Clean the back surface 12 of the test chip. In this embodiment, the specific steps for cleaning the back surface of the test chip may include:

[0047] Preset a certain cleaning duration;

[0048] Fix the edge of the test chip 10 using the jaws (not shown) of the wafer cleaning machine 20;

[0049] Inject nitrogen gas onto the front surface 11 of the test chip using the gas pipeline 21 inside the carrier 22 of the wafer cleaning machine 20;

[0050] Drive the test chip 10 to rotate using the rotating base 24 of the wafer cleaning machine 20;

[0051] Inject a cleaning reagent onto the back surface 12 of the test chip using the chemical liquid pipeline 23 above the carrier 22;

[0052] When the cleaning operation ends, stop the nitrogen gas injection of the gas pipeline 21, stop the rotation of the rotating base 24, stop the injection of the cleaning reagent of the chemical liquid pipeline 23, release the jaws, and take out the test chip from the wafer cleaning machine 10. Specifically, the cleaning reagent may include: a mixed solution of HF and HNO 3 3.

[0053] In this embodiment, a test chip (wafer) 10 with a grown copper metal layer is used to simulate the BSC machine cleaning operation process of the product wafer. Since HF and HNO 3The mixed solution causes relatively large damage to copper. Therefore, it is easier to discover problems by using the test chip (wafer) 10 with a metal copper layer grown on it to simulate the BSC machine cleaning operation process of the product chip, which improves the accuracy and reliability of early monitoring of the wafer cleaning machine.

[0054] Further, after cleaning the back surface 12 of the test chip, the monitoring method of the wafer cleaning machine may further include:

[0055] Provide a plurality of exactly the same test chips 10, perform the operations of steps S10 - S30 on these test chips 10, and clean the back surfaces 12 of different test chips under different cleaning conditions; wherein, the cleaning conditions at least include: the rotation speed of the rotating base 24 of the wafer cleaning machine, and the flow rate of nitrogen gas sprayed by the gas pipeline 21 inside the carrier stage 22 of the wafer cleaning machine.

[0056] Under one cleaning condition, the rotation speed of the rotating base 24 of the wafer cleaning machine can be set to 400 rpm; the flow rate of nitrogen gas sprayed by the gas pipeline 21 inside the carrier stage 22 of the wafer cleaning machine can be set to 150 L / min.

[0057] Under another cleaning condition, the rotation speed of the rotating base 24 of the wafer cleaning machine can be set to 800 rpm; the flow rate of nitrogen gas sprayed by the gas pipeline 21 inside the carrier stage 22 of the wafer cleaning machine can be set to 200 L / min.

[0058] Step S40: Obtain the electron beam imaging grayscale map of all the test chips 10 through measurement, wherein the electron beam imaging grayscale map at least covers the edge region and the sidewall region of the test chip 10. The area covered by the electron beam imaging grayscale map can be the entire surface of the test chip 10, and the entire surface can include the central region and the edge region near the upper surface of the test chip 10 and the sidewall region of the test chip 10. In this embodiment, a photo can be taken along one circle of the periphery (bevel) of the test chip 10 to form a long strip-shaped electron beam imaging grayscale map around one circle.

[0059] Step S50: Compare all the electron beam imaging grayscale maps, and analyze the distribution of copper ions on the edge and sidewall of the test chip to monitor whether the cleaning operation of the wafer cleaning machine 20 causes damage to the copper layer on the front surface 11 of the test chip. Specifically, the step of analyzing the distribution of metal ions on the edge and sidewall of the test chip according to the electron beam imaging grayscale map to monitor whether the cleaning operation of the wafer cleaning machine causes damage to the metal layer on the front surface of the test chip includes:

[0060] By comparing the electron beam imaging grayscale images of the test chip 10 under different cleaning conditions, the distribution of metal ions on the edge and sidewall of the test chip is analyzed to monitor whether the cleaning operation of the wafer cleaning machine causes damage to the metal layer on the front of the test chip.

[0061] The inventors found that during the cleaning process, the diffused ions are particularly likely to fall on the edge of the wafer where the clamps are used to fix the wafer. After multiple experiments to observe the particle performance of the wafer with a metal copper layer grown on the front side on the BSC machine, the inventors found that there were obvious 6 clamp marks composed of diffused copper ions of the BSC machine on the edge and sidewall (also understood as the bevel) of the test chip, which can well detect the distribution differences of diffused copper ions of multiple test chips under different experimental conditions, thereby determining that the cleaning operation status of the BSC machine has changed.

[0062] Furthermore, after monitoring whether the cleaning operation of the wafer cleaning machine 20 causes damage to the copper layer on the front side 11 of the test chip, the monitoring method of the wafer cleaning machine may further include:

[0063] The cleaning operation parameters / conditions of the wafer cleaning machine 20 are adjusted to perform a cleaning operation on the back side of the product wafer.

[0064] In the present application, before using the wafer cleaning machine 20 to clean the back of the product wafer, a test chip (wafer) 10 with the first buffer layer 102, the second buffer layer 103, the seed layer 104 and the metal layer 105 grown on the front is used to simulate the BSC machine cleaning process of the product wafer. According to the electron beam imaging grayscale image of the test chip 10, the distribution of metal ions on the edge and side wall of the test chip 10 is analyzed to monitor whether the cleaning operation of the wafer cleaning machine 20 causes damage to the metal layer 105 on the front side 11 of the test chip, thereby monitoring in advance whether the cleaning operation state of the BSC machine changes, thereby avoiding particle diffusion defects of the product wafer caused by the cleaning operation of the BSC machine due to the change in state, thereby avoiding damage to the metal layer (or other film layer) on the front side of the product wafer, and improving the later yield of the wafer.

[0065] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection created by this application.

Claims

1. A monitoring method for a wafer cleaning machine, characterized in that, it includes: providing a bare wafer, and sequentially forming a stacked first buffer layer, a second buffer layer, a seed layer, and a metal layer on the front surface of the bare wafer to obtain a test chip; transferring the test chip to the wafer cleaning machine, and flipping the test chip so that the back surface of the test chip faces upward; cleaning the back surface of the test chip; acquiring an electron beam imaging grayscale map of the test chip, wherein the electron beam imaging grayscale map at least covers the edge region and the sidewall region of the test chip; analyzing the distribution of metal ions on the edge and sidewall of the test chip according to the electron beam imaging grayscale map to monitor whether the cleaning operation of the wafer cleaning machine damages the metal layer on the front surface of the test chip.

2. The monitoring method for a wafer cleaning machine according to claim 1, characterized in that, the metal layer is a copper layer.

3. The monitoring method for a wafer cleaning machine according to claim 2, characterized in that, analyzing the distribution of copper ions on the edge and sidewall of the test chip according to the electron beam imaging grayscale map to monitor whether the cleaning operation of the wafer cleaning machine damages the copper layer on the front surface of the test chip.

4. The monitoring method for a wafer cleaning machine according to claim 1 or 2, characterized in that, the step of cleaning the back surface of the test chip includes: fixing the edge of the test chip by using the jaws of the wafer cleaning machine; spraying nitrogen gas onto the front surface of the test chip through the gas pipeline inside the carrier stage of the wafer cleaning machine; driving the test chip to rotate by using the rotating base of the wafer cleaning machine; spraying a cleaning reagent onto the back surface of the test chip through the liquid medicine pipeline above the carrier stage; when the cleaning operation ends, stopping the nitrogen gas spraying of the gas pipeline, stopping the rotation of the rotating base, stopping the spraying of the cleaning reagent of the liquid medicine pipeline, and loosening the jaws, and taking out the test chip from the wafer cleaning machine.

5. The monitoring method for a wafer cleaning machine according to claim 4, characterized in that, The cleaning reagent includes: HF and HNO 3 .

6. The monitoring method for a wafer cleaning machine according to claim 4, characterized in that, before acquiring the electron beam imaging grayscale map of the test chip after cleaning the back surface of the test chip, the monitoring method of the wafer cleaning machine further includes: providing a plurality of identical test chips, and cleaning the back surfaces of the plurality of test chips under different cleaning conditions; wherein, the cleaning conditions at least include: the rotation speed of the rotating base of the wafer cleaning machine, the flow rate of nitrogen gas sprayed by the gas pipeline inside the carrier stage of the wafer cleaning machine.

7. The monitoring method for a wafer cleaning machine according to claim 6, characterized in that, the rotation speed of the rotating base of the wafer cleaning machine is set to 400 rpm; the flow rate of nitrogen gas sprayed by the gas pipeline inside the carrier stage of the wafer cleaning machine is set to 150 L / min.

8. The monitoring method for a wafer cleaning machine according to claim 6, characterized in that, The rotation speed of the rotating base of the wafer cleaning machine is set to 800 rpm; the flow rate of nitrogen gas injected by the gas pipeline inside the carrier stage of the wafer cleaning machine is set to 200 L / min.

9. The monitoring method of the wafer cleaning machine according to claim 6, characterized in that the step of analyzing the distribution of metal ions on the edge and side wall of the test chip according to the electron beam imaging grayscale map to monitor whether the cleaning operation of the wafer cleaning machine damages the metal layer on the front side of the test chip includes: comparing the electron beam imaging grayscale maps of the test chips under different cleaning conditions, and analyzing the distribution of metal ions on the edge and side wall of the test chip to monitor whether the cleaning operation of the wafer cleaning machine damages the metal layer on the front side of the test chip.

10. The monitoring method of the wafer cleaning machine according to claim 1, characterized in that the first buffer layer is a tantalum nitride layer; the second buffer layer is a tantalum layer; the seed layer is a copper layer.

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