Method for reducing wafer edge defects in CMP copper process

Abstract

The invention provides a method for reducing wafer edge defects in a CMP copper process, and the method comprises the steps: carrying out the pre-cleaning of a wafer at a wafer conveying-out position of a grinding cavity at the end of grinding, conveying the wafer to a cleaning cavity, and carrying out the cleaning of a groove, used for clamping the wafer, of a clamping jaw finger at the wafer conveying-out position; and starting and stopping of the cleaning device for implementing the cleaning process are automatically controlled by the PLC according to the state of the clamping jaw fingers judged by the correlation type laser sensor. The method has the following beneficial effects: (1) the defect probability is reduced, and the wafer yield of the copper process is improved; (2) the pressure of the cleaning cavity consumables is reduced, the service life of the cleaning cavity consumables is prolonged, the replacement frequency of the cleaning cavity consumables is reduced, and the cost is saved; and (3) the workload of an engineer for processing product abnormity is reduced.

Description

Technical Field

[0001] The present application relates to the field of semiconductor technology, and in particular to a method for reducing wafer edge defects in a CMP copper process. Background Art

[0002] like Figure 1 As shown, taking the Reflexion LK 300MM CMP polishing machine as an example, the wafer located at the wafer input position of the wafer exchanger device (WaferExchangerArm) is polished by three grinding plates in the polishing chamber. Before being sent to the cleaning chamber, it will undergo preliminary cleaning in the wafer output device of the wafer exchanger and then enter the cleaning chamber for further cleaning.

[0003] like Figure 2 As shown in the figure, the wafer exchange device mainly consists of gripper A (Gripper A), gripper B (Gripper B), gripper finger (Gripper Finger), dual finger wing (Dual Finger Wing), etc. Gripper A uses the three gripper fingers fixed on its device (the other two gripper fingers are located at both ends of the dual finger wing) to grab the edge of the wafer and send it to the grinding plate for grinding. After the grinding is completed and the copper process is completed, gripper B uses the three gripper fingers fixed on its device to grab the edge of the wafer and send it to the wafer out position ( Figure 2 The wafer is located in the middle of the wafer for preliminary cleaning.

[0004] The grinding process of copper processing is prone to produce by-products under the action of other chemicals and consumables, such as Figure 3 As shown in Figure 2, this byproduct easily adheres to the wafer surface (especially the edge of the wafer grasped by the gripper fingers). When the gripper fingers grasp the edge of the wafer, the byproduct at the edge of the wafer easily adheres to the groove of the gripper fingers (such as Figure 4 As shown in the figure, byproducts still cling to the edges of wafers after initial cleaning. When the wafers enter the cleaning chamber for further cleaning, the cleaning chamber consumables reach the end of their service life and their cleaning capacity weakens, preventing them from fully cleaning the wafer surface (especially the edges). This leads to wafer defects and a decrease in wafer yield. This shortens the service life of the cleaning chamber consumables and increases the frequency of their replacement, hindering cost savings. Summary of the Invention

[0005] In view of the above-mentioned shortcomings of the prior art, the purpose of this application is to provide a method for reducing wafer edge defects in the CMP copper process, so as to solve the problem of poor removal effect of byproducts adhered to the wafer edge during the polishing process of the copper process in the prior art.

[0006] To achieve the above object and other related objects, the present application provides a method for reducing wafer edge defects in a CMP copper process, which comprises the following steps: after the polishing is finished at the wafer transmission position of the polishing cavity, the wafer is pre-cleaned and transmitted to a cleaning cavity, the recess for clamping the wafer of the gripper finger at the wafer transmission position is cleaned, and the start and stop of the cleaning device for the cleaning process are automatically controlled by PLC according to the state of the gripper finger determined by the light emitting and receiving laser sensor.

[0007] Preferably, the light emitting and receiving laser sensor has a transmitting end and a receiving end, the transmitting end is opposite to the receiving end, the transmitting end is located beside the recess for clamping the wafer of the gripper finger arranged at one end of the double finger wing, and the receiving end is located beside the recess for clamping the wafer of the gripper finger arranged at the other end of the double finger wing.

[0008] Preferably, when the gripper finger clamps the wafer, the wafer blocks the path of the laser emitted from the transmitting end of the light emitting and receiving laser sensor, the receiving end cannot detect the optical signal, and the light emitting and receiving laser sensor determines that the state of the gripper finger is the grabbing state.

[0009] Preferably, when the gripper finger does not clamp the wafer, the path of the laser emitted from the transmitting end of the light emitting and receiving laser sensor is restored, the receiving end detects the optical signal, and the light emitting and receiving laser sensor determines that the state of the gripper finger is the releasing state.

[0010] Preferably, after the light emitting and receiving laser sensor determines that the state of the gripper finger is the grabbing state, the PLC cannot receive the signal emitted by the light emitting and receiving laser sensor, and the electromagnetic valve in the cleaning device is in the off state.

[0011] Preferably, after the light emitting and receiving laser sensor determines that the state of the gripper finger is the releasing state, the PLC receives the signal emitted by the light emitting and receiving laser sensor, starts a timer to determine whether the signal emitted by the light emitting and receiving laser sensor remains stable, if the signal remains stable, the PLC outputs a 24V DC signal to the electromagnetic valve in the cleaning device, and the electromagnetic valve is in the on state.

[0012] Preferably, if the light emitting and receiving laser sensor continuously outputs the signal within 20ms, it is determined that the signal remains stable.

[0013] Preferably, the light emitting and receiving laser sensor emits visible red laser with a wavelength of 650nm, and the light cluster is smaller than the thickness of the wafer.

[0014] Preferably, the cleaning device is located below the central position of the gripper, and has three cleaning nozzles with openings arranged at a certain angle to the back surface of the gripper.

[0015] Preferably, the cleaning nozzle is a solid cone nozzle, and the opening aperture is 0.3mm-0.5mm.

[0016] As described above, the method for reducing wafer edge defects in a copper CMP process provided by the present application has the following beneficial effects:

[0017] (1) Defect probability is reduced, improving the yield of copper process wafers; (2) Reducing the pressure of cleaning cavity consumables, increasing the service life of cleaning cavity consumables, reducing the replacement frequency of cleaning cavity consumables, which is conducive to cost saving; (3) Reducing the workload of engineers in handling product abnormalities. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the specific embodiments or prior art of the present application, the drawings needed in the description of the specific embodiments or prior art will be briefly introduced. Obviously, the drawings in the following description are some embodiments of the present application, and those skilled in the art can obtain other drawings according to these drawings without creative labor.

[0019] Figure 1 The internal structure of the polishing cavity is shown as a schematic diagram;

[0020] Figure 2 The photo of the wafer exchange device in the polishing cavity is shown;

[0021] Figure 3 The electron photo of the by-product adhering to the surface of the wafer in the polishing process of the copper process is shown;

[0022] Figure 4 The photo of the groove of the gripper finger is shown;

[0023] Figure 5 The schematic diagram of the emitting end and receiving end of the through-beam sensor and the position of the cleaning device in the wafer transmission position provided by the embodiment of the present application is shown;

[0024] Figure 6 The schematic diagram of the through-beam laser sensor and the cleaning device provided by the embodiment of the present application working together is shown. DETAILED DESCRIPTION

[0025] The embodiments of the present application are described below through specific, concrete examples. Those skilled in the art can easily understand other advantages and effects of the present application from the content disclosed in the present specification. The present application can also be implemented or applied through other different specific embodiments, and each detail in the present specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present application.

[0026] With reference to the drawings, the technical solutions in the present application will be clearly and completely described. Obviously, the described embodiments are only part of the embodiments of the present application, but not all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of the present application.

[0027] In the description of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", and the like indicate the orientation or positional relationship, which are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation of the present application. In addition, the terms "first", "second", "third" are only for the purpose of description, and cannot be understood as indicating or implying relative importance.

[0028] In the description of the present application, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connecting" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the communication between two elements, or it can be wireless connection, or it can be wired connection. For those of ordinary skill in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0029] In addition, the technical features involved in the different embodiments of the present application described below can be combined with each other as long as there is no conflict.

[0030] The embodiment of the present application provides a method for reducing wafer edge defects in a CMP copper process. After the pre-cleaning of the wafer at the wafer transmission-out position of the polishing cavity and the transmission of the wafer to the cleaning cavity, the recess of the gripper finger for clamping the wafer at the wafer transmission-out position is cleaned, and the start and stop of the cleaning device for implementing the cleaning process are automatically controlled by PLC according to the state of the gripper finger determined by the opposite laser sensor.

[0031] Please refer to Figure 5 which shows the schematic diagram of the transmission end and the receiving end of the opposite laser sensor and the position of the cleaning device in the wafer transmission-out position.

[0032] As Figure 5As shown, the through-beam laser sensor has a transmitter 1 and a receiver 2, with transmitter 1 facing receiver 2. Transmitter 1 is located next to the wafer-holding groove of gripper finger 31, located at one end of a double-finger wing 3, and receiver 2 is located next to the wafer-holding groove of gripper finger 32, located at the other end of the double-finger wing 3. The cleaning device is located below the center of gripper 6 and has three cleaning nozzles 7, whose openings form a certain angle with the back of gripper 6. When gripper fingers 31, 32, and 33 grip a wafer, the cleaning nozzles 7 do not come into contact with the wafer. The openings of the three cleaning nozzles 7 face gripper fingers 31, 32, and 33, respectively.

[0033] The through-beam laser sensor and the cleaning device work together, such as Figure 6 As shown, the collaboration works as follows:

[0034] like Figure 6 (a) and Figure 6 (b)(From Figure 6 As shown in the rear side view of (a), when the gripper fingers 31, 32, and 33 grip the wafer 5, the wafer 5 blocks the path of the laser light emitted from the transmitting end 1 of the through-beam laser sensor. The receiving end 2 cannot detect the light signal, and the through-beam laser sensor determines that the gripper fingers 31, 32, and 33 are in the grasping state. The PLC (programmable logic controller) cannot receive the signal from the through-beam laser sensor, the solenoid valve in the cleaning device is in the off state, and the cleaning nozzle 7 does not spray high-pressure water.

[0035] like Figure 6 (c) and Figure 6 (d)(From Figure 6 As shown in the rear side view of (c), when the gripper fingers 31, 32 and 33 do not clamp the wafer 5, the path of the laser 8 emitted from the transmitting end 1 of the through-beam laser sensor is restored, the receiving end 2 detects the light signal, and the through-beam laser sensor determines that the state of the gripper fingers 31, 32 and 33 is the released state. After receiving the signal from the through-beam laser sensor, the PLC starts the timer to determine whether the signal emitted by the laser sensor remains stable within a period of time (usually 20ms). If the signal remains stable, a 24V DC signal is output to the solenoid valve in the cleaning device, so that the solenoid valve is in the open state, and the high-pressure water flow 9 is sprayed at a certain inclination angle through the cleaning nozzle 7 to the grooves of the gripper fingers 31, 32 and 33 for clamping the wafer.

[0036] In order to ensure that the wafer 5 blocks the path of the laser emitted from the emitting end 1 of the through-beam laser sensor when the gripper fingers 31 , 32 and 33 clamp the wafer 5 , the through-beam laser sensor is required to emit a visible red laser 8 with a wavelength of 650 nm, and the light cluster is smaller than the wafer thickness.

[0037] To ensure that the high-pressure water flow sprayed by the cleaning nozzle 7 can cover the recesses of the gripper fingers 31, 32 and 33 for clamping the wafer and reduce splashing, the cleaning nozzle 7 is a solid conical nozzle, and the water flow rate is increased to 15 m / s (at the nozzle outlet) by the nozzle design, forming a strong impact force. When the spraying pressure is 0.3 MPa, the impact force of the high-pressure water flow 9 (flow rate 15 m / s) sprayed by the cleaning nozzle 7 reaches 7.5 N, which is sufficient to remove the polishing by-products adhered to the recesses of the gripper fingers 31, 32 and 33 for clamping the wafer.

[0038] To ensure that the wafer 5 does not contact the cleaning nozzle 7 when the gripper fingers 31, 32 and 33 clamp the wafer 5, the opening aperture of the cleaning nozzle 7 is preferably 0.3-0.5 mm.

[0039] For example, the cleaning nozzle 7 is made of stainless steel, the water curtain formed by the high-pressure water flow 9 has a fan angle of 60°, and the spraying pressure is accurately controlled by a PLC controller. The spraying pressure is preferably 0.3-0.5 MPa.

[0040] For example, the electromagnetic valve has a response time of less than 15 ms and a flow coefficient of 1.2.

[0041] For example, the pair of laser sensors has a detection distance of 50 mm and a resolution of 0.1 mm.

[0042] Through the cooperation of the above-mentioned pair of laser sensors and the cleaning device, it can be ensured that each wafer completing the copper polishing process is pre-cleaned at the wafer transmission position in the polishing cavity and sent to the cleaning cavity, and the recesses of the gripper fingers for clamping the wafer are timely and sufficiently cleaned, and the polishing by-products adhered to the recesses are completely removed, thereby avoiding the pollution of the subsequent wafers completing the copper polishing process by the polishing by-products.

[0043] It should be noted that the drawings provided in the embodiments only schematically illustrate the basic concepts of the present application, and only the components related to the present application are shown in the drawings, rather than being drawn according to the number, shape and size of the components in actual implementation. The actual implementation of each component may be a random change, and the component layout pattern may be more complex.

[0044] In summary, the method for reducing the edge defects of wafers in a CMP copper process has the following beneficial effects: (1) the defect probability is reduced, and the yield of the copper process wafers is improved; (2) the pressure on the consumables of the cleaning cavity is reduced, the service life of the consumables of the cleaning cavity is increased, and the replacement frequency of the consumables of the cleaning cavity is reduced, which is beneficial to cost saving; (3) the workload of engineers in handling product abnormalities is reduced. Therefore, the present application effectively overcomes the various shortcomings in the prior art and has a high industrial utilization value.

[0045] The above embodiments are merely illustrative of the principles and effects of this application and are not intended to limit this application. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of this application. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical concepts disclosed herein shall be covered by the claims of this application.

Claims

1. A method for reducing wafer edge defects in a CMP copper process, characterized in that: After grinding is completed, the wafer is pre-cleaned at the wafer exit position of the grinding chamber and the wafer is transferred to the cleaning chamber. The grooves of the gripper fingers located at the wafer exit position for clamping the wafer are cleaned. The start and stop of the cleaning device that implements the cleaning process are automatically controlled by PLC according to the status of the gripper fingers determined by the through-beam laser sensor.

2. The method according to claim 1, characterized in that The opposing laser sensor has a transmitting end and a receiving end, the transmitting end is opposite to the receiving end, the transmitting end is located next to the groove of the clamping finger set at one end of the double-finger wing for clamping the wafer, and the receiving end is located next to the groove of the clamping finger set at the other end of the double-finger wing for clamping the wafer.

3. The method according to claim 2, characterized in that When the gripper fingers grip the wafer, the wafer blocks the path of the laser emitted from the transmitting end of the through-beam laser sensor, the receiving end cannot detect the light signal, and the through-beam laser sensor determines that the state of the gripper fingers is a grasping state.

4. The method according to claim 2, characterized in that When the gripper fingers do not grip the wafer, the path of the laser emitted from the transmitting end of the through-beam laser sensor is restored, the receiving end detects the light signal, and the through-beam laser sensor determines that the state of the gripper fingers is a released state.

5. The method according to claim 3, characterized in that After the through-beam laser sensor determines that the state of the gripper finger is the grasping state, the PLC cannot receive the signal sent by the through-beam laser sensor, and the solenoid valve in the cleaning device is in the off state.

6. The method according to claim 4, characterized in that After the through-beam laser sensor determines that the state of the gripper finger is in the released state, the PLC starts the timer after receiving the signal sent by the through-beam laser sensor to determine whether the signal sent by the through-beam laser sensor remains stable. If the signal remains stable, the PLC outputs a 24V DC signal to the solenoid valve in the cleaning device to put the solenoid valve in the open state.

7. The method according to claim 6, characterized in that If the through-beam laser sensor continuously outputs a signal within 20 ms, it is determined that the signal remains stable.

8. The method according to claim 1, characterized in that The incident laser sensor emits visible red laser light with a wavelength of 650 nm, and the light cluster is smaller than the thickness of the wafer.

9. The method according to claim 1, characterized in that The cleaning device is located below the center of the clamping jaw and has three cleaning nozzles whose opening directions form a certain angle with the back of the clamping jaw.

10. The method according to claim 9, characterized in that The cleaning nozzle is a solid conical nozzle with an opening diameter of 0.3mm-0.5mm.

Images