Method for monitoring whether bonding bubbles are damaged or not in chip manufacturing wafer bonding process

Abstract

The invention discloses a method for monitoring whether bonding bubbles are damaged in a chip manufacturing wafer bonding process. The method comprises the following steps: bonding and fixing the front surface of a first wafer to the back surface of a second wafer to obtain a bonded wafer; grinding the back surface of the first wafer of the bonded wafer through a grinding machine table; when the grinding operation on the back surface of the first wafer of the bonded wafer is completed, the wafer appearance detection device detects the appearance of the back surface of the first wafer and identifies whether bubble damage exists or not, and if the bubble damage exists, a bubble damage signal is sent to the processor; the processor controls to send the bonding wafer which completes the grinding operation out of the grinding machine table; in addition, if the damage signal is received, the processor controls and triggers the alarm device to give an alarm. According to the invention, on the premise that the wafer grinding process is not influenced, the bubble damage condition in the grinding process can be simply, conveniently, effectively and timely monitored at low cost.

Description

Technical Field

[0001] The invention relates to semiconductor manufacturing technology, and in particular to a method for monitoring whether bonding bubbles are broken in a chip manufacturing wafer bonding process. Background Art

[0002] BSI (backside illuminated) process is a semiconductor manufacturing process used to improve the performance of image sensors.

[0003] In order to make CIS (Contact Image Sensor) chips have better light sensitivity, back side illumination (BSI) CIS technology came into being. The light sensing path of this type of product is to collect light on the back of the chip after it is thinned to a few microns, thereby greatly improving the light sensing ability.

[0004] The front-end process of back-side illumination (BSI) CIS is similar to that of front-side illumination (FSI) CIS, and the main difference lies in the back-end chip docking and thinning process. The BSI CIS process is similar to the FSI CIS process, and the front side of the CIS chip is bonded to the carrier wafer. After the bonded wafer, the back side of the CIS chip is back-grinded to a thickness of several microns to further improve the light collection efficiency, and the BSI CIS is completed.

[0005] In the BSI process, bubble defects may occur after two wafers are bonded, that is, small bubbles exist between the two bonded wafers. When the wafer with bubble defects passes through the grinding station, the bubble may burst during the grinding process. After the bubble bursts, the crystal slag falls randomly, which will cause machine contamination and scratch the subsequent wafers, such as Figure 1 As shown in the figure, when the broken wafer enters other machines, slag may fall and contaminate other machines. Therefore, in order to reduce the impact on more wafers and machines, it is particularly important to monitor whether the bubble is broken after grinding.

[0006] Traditionally, monitoring whether bubbles are broken is done after Si CMP (chemical mechanical polishing). After the front side of the CIS wafer is butted against the carrier wafer to form a bonded wafer, the back side of the CIS wafer of the bonded wafer is back-grinded. After going through multiple processes, it arrives at the CMP station for Si CMP operation. Then, a defect inspection machine or an appearance inspection machine is used to inspect the bonded wafer after the CMP operation to check whether the bubbles are broken. Since there are multiple stations from back-grinding the CIS wafer of the bonded wafer to CMP, a wafer with broken bubbles after back-grinding will affect subsequent wafers and machines. Summary of the invention

[0007] The technical problem to be solved by the present invention is to provide a method for monitoring whether the bonding bubble is damaged in the chip manufacturing wafer bonding process, which can monitor the bubble damage status in the grinding process in a low-cost, simple, effective and timely manner without affecting the wafer grinding process.

[0008] In order to solve the above technical problems, the present invention provides a method for monitoring whether bonding bubbles are broken in a chip manufacturing wafer bonding process, which comprises the following steps:

[0009] S1. Provide the required first wafer and second wafer, and bond the front side of the first wafer to the back side of the second wafer to obtain a bonded wafer;

[0010] S2. The back of the first wafer of the bonded wafer is ground by a grinding machine, wherein the grinding machine is provided with a wafer appearance detection device, a processor and an alarm device;

[0011] S3. When the grinding operation on the back side of the first wafer of the bonded wafer is completed, the wafer appearance detection device detects the appearance of the back side of the first wafer and identifies whether there is bubble damage, and sends a bubble damage signal to the processor if there is bubble damage;

[0012] S4. The processor controls the bonded wafer that has completed the grinding operation to be sent out of the grinding machine; and if a damage signal is received, the processor also controls the alarm device to be triggered to sound an alarm.

[0013] Preferably, in step S4, if a damage signal is received, the processor controls the alarm device to be triggered to sound an alarm and controls the grinding machine to stop.

[0014] Preferably, in step S3, the wafer appearance inspection device further sends the bubble damage position on the back side of the first wafer to the processor;

[0015] The processor controls outputting the bubble collapse position to a display or a memory.

[0016] Preferably, the wafer appearance detection device uses infrared detection or ultrasonic detection scanning to determine the appearance of the back side of the first wafer and identify whether there is bubble damage.

[0017] Preferably, the chip is a back-illuminated contact image sensor chip;

[0018] A photodiode and a plurality of pixel transistors of a contact image sensor are formed on the first wafer;

[0019] The second wafer has a signal processing logic circuit of the contact image sensor formed thereon.

[0020] Preferably, the chip is a back-illuminated contact image sensor chip;

[0021] The contact image sensor is a 4T structure CMOS image sensor, the photodiode, transfer gate transistor and first floating diffusion region of the pixel unit of which are formed on the first wafer;

[0022] The photodiode is located on the vertical back of the first wafer;

[0023] The transfer gate transistor and the first floating diffusion region are located on the vertical front side of the photodiode;

[0024] The first floating diffusion region is located at the lateral peripheral side of the transfer gate transistor;

[0025] The source follower transistor, reset transistor, row selection transistor and second floating diffusion region of the pixel unit are formed on the second chip;

[0026] The first floating diffusion region and the second floating diffusion region are connected together through a through silicon via to form a floating diffusion region of a pixel unit;

[0027] The second wafer also has a signal processing logic circuit for the contact image sensor formed thereon.

[0028] Preferably, the first floating diffusion region and the second floating diffusion region have an overlapping area in vertical projection.

[0029] The method for monitoring whether a bonding bubble is broken in a chip manufacturing wafer bonding process of the present invention can monitor the bubble breakage status in the grinding process in a low-cost, simple, effective and timely manner without affecting the wafer grinding process, thereby reducing the possibility of scratching subsequent wafers when the grinding machine grinds subsequent wafers, reducing pollution to subsequent machines, improving factory production efficiency and reducing economic losses. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solution of the present invention, the following briefly introduces the drawings required for use in the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0031] Figure 1 This is a schematic diagram of the crystal slag after the bubble bursts, which contaminates the machine and causes subsequent wafers to be scratched;

[0032] Figure 2 It is a schematic flow chart of an embodiment of a method for monitoring whether a bonding bubble is broken in a chip manufacturing wafer bonding process of the present invention. DETAILED DESCRIPTION

[0033] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] The words "first", "second" and similar terms used in this application do not indicate any order, quantity or importance, but are only used to distinguish different components. Words such as "include" or "comprises" and similar terms mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. Words such as "connect" or "connected" and similar terms are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right", "front", "back" and the like are only used to indicate relative position relationships. When the absolute position of the object being described changes, the relative position relationship may also change accordingly.

[0035] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0036] Embodiment 1

[0037] A method for monitoring whether a bonding bubble is broken in a chip manufacturing wafer bonding process, such as Figure 2 As shown, the following steps are included:

[0038] S1. Provide the required first wafer and second wafer, and bond the front side of the first wafer to the back side of the second wafer to obtain a bonded wafer;

[0039] S2. Grinding the back of the first wafer of the bonded wafer by a grinding machine, wherein the grinding machine is provided with a wafer appearance detection device, a processor and an alarm device;

[0040] S3. When the grinding operation on the back side of the first wafer of the bonded wafer is completed, the wafer appearance detection device detects the appearance of the back side of the first wafer and identifies whether there is a bubble (bubble) broken, and if there is a bubble (bubble) broken, sends a bubble break signal to the processor;

[0041] S4. The processor controls the bonded wafer that has completed the grinding operation to be sent out of the grinding machine; and if a damage signal is received, the processor also controls the alarm device to be triggered to sound an alarm.

[0042] The method for monitoring whether the bonding bubble is broken in the chip manufacturing wafer bonding process of the first embodiment can monitor the bubble breakage status in the grinding process in a low-cost, simple, effective and timely manner without affecting the wafer grinding process, thereby reducing the possibility of scratching the subsequent wafer when the grinding machine grinds the subsequent wafer, reducing the pollution to the subsequent machine, improving the factory production efficiency and reducing economic losses.

[0043] Embodiment 2

[0044] Based on the method for monitoring whether the bonding bubble is broken in the chip manufacturing wafer bonding process of the first embodiment,

[0045] In step S4, if a damage signal is received, the processor controls the alarm device to be triggered to alarm and controls the grinding machine to stop.

[0046] Preferably, in step S3, the wafer appearance inspection device further sends the bubble damage position on the back side of the first wafer to the processor;

[0047] The processor controls outputting a bubble break position to a display or a memory.

[0048] Embodiment 3

[0049] Based on the method for monitoring whether a bonding bubble is broken in a chip manufacturing wafer bonding process of the first embodiment, the wafer appearance detection device uses infrared detection or C-SAM (ultrasonic detection) scanning to determine the appearance morphology of the back side of the first wafer and identify whether there is a bubble broken.

[0050] Embodiment 4

[0051] A method for monitoring whether a bonding bubble is broken in a chip manufacturing wafer bonding process based on the first embodiment, wherein the chip is a back side illumination (BSI) CIS (Contact Image Sensor) chip;

[0052] The first wafer is formed with a CIS (Contact Image Sensor) photodiode (PD) and a plurality of pixel transistors.

[0053] A signal processing logic circuit of a CIS (Contact Image Sensor) is formed on the second wafer.

[0054] Embodiment 5

[0055] A method for monitoring whether a bonding bubble is broken in a chip manufacturing wafer bonding process according to the fourth embodiment, wherein the chip is a back side illumination (BSI) CIS (Contact Image Sensor) chip;

[0056] The contact image sensor is a 4T structure CMOS image sensor, in which the photodiode PD, the transfer gate transistor TG and the first floating diffusion region of the pixel unit are formed on the first wafer;

[0057] The photodiode PD is located at the vertical back of the first wafer;

[0058] The transfer gate transistor TG and the first floating diffusion region are located on the vertical front side of the photodiode PD;

[0059] The first floating diffusion region is located at the lateral peripheral side of the transfer gate transistor TG;

[0060] The source follower transistor SF, the reset transistor RST, the row selection transistor RS and the second floating diffusion region of the pixel unit are formed on the second chip;

[0061] The first floating diffusion region and the second floating diffusion region are connected together through TSV (through silicon via) to form a floating diffusion region FD of the pixel unit;

[0062] A signal processing logic circuit of a CIS (Contact Image Sensor) is also formed on the second wafer.

[0063] Preferably, the first floating diffusion region and the second floating diffusion region have an overlapping area in vertical projection.

[0064] In the fifth embodiment of the chip manufacturing wafer bonding process, the bonding bubble (bonding bubble) is broken. Since the photodiode PD of the CIS (Contact Image Sensor) and other pixel transistors other than the transmission gate transistor TG of the pixel unit are respectively located on the first wafer and the second wafer, the photodiode PD area can be greatly increased, thereby greatly increasing the full well capacitance of the image sensor (can be increased by about one time), and increasing the dynamic range. At the same time, since other pixel transistors other than the transmission gate transistor TG of the pixel unit are formed on the second wafer, the photodiode PD area only needs to strengthen the isolation with the transmission gate transistor TG and other pixel units, and the P-type well isolation width can be expanded to improve the isolation effect, so that the dark current and image noise are greatly reduced, and the dark line noise and full well capacitance can be improved at the same time, so that the CMOS image sensor generates less image noise in night and other dim scenes. Moreover, since the substrate where the source follower tube SF is located does not form a transfer gate transistor TG and a photodiode PD, the size of the source follower tube SF can be increased. By increasing the size of the source follower tube SF, the optical signal processing capability of the image sensor under dark light can be improved, and the amplification performance of the source follower tube SF can be improved, so that the overall saturation signal amount of the image sensor is greatly increased (can be doubled) compared with traditional image sensors, thereby expanding the dynamic range, reducing dark current, and improving image noise.

[0065] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for monitoring whether a bonding bubble is broken in a chip manufacturing wafer bonding process, characterized in that: The following steps are involved: S1. Provide the required first wafer and second wafer, and bond the front side of the first wafer to the back side of the second wafer to obtain a bonded wafer; S2. The back of the first wafer of the bonded wafer is ground by a grinding machine, wherein the grinding machine is provided with a wafer appearance detection device, a processor and an alarm device; S3. When the grinding operation on the back side of the first wafer of the bonded wafer is completed, the wafer appearance detection device detects the appearance of the back side of the first wafer and identifies whether there is bubble damage, and sends a bubble damage signal to the processor if there is bubble damage; S4. The processor controls the bonded wafer that has completed the grinding operation to be sent out of the grinding machine; and if a damage signal is received, the processor also controls the alarm device to be triggered to sound an alarm.

2. The method for monitoring whether bonding bubbles are broken in a chip manufacturing wafer bonding process according to claim 1, characterized in that: In step S4, if a damage signal is received, the processor controls the alarm device to be triggered to alarm and controls the grinding machine to stop.

3. The method for monitoring whether bonding bubbles are damaged in a chip manufacturing wafer bonding process according to claim 1, characterized in that: In step S3, the wafer appearance inspection device also sends the bubble damage position on the back side of the first wafer to the processor; The processor controls outputting the bubble collapse position to a display or a memory.

4. The method for monitoring whether bonding bubbles are broken in a chip manufacturing wafer bonding process according to claim 1, characterized in that: The wafer appearance detection device uses infrared detection or ultrasonic detection scanning to determine the appearance of the back side of the first wafer and identify whether there is bubble damage.

5. The method for monitoring whether bonding bubbles are broken in a chip manufacturing wafer bonding process according to claim 1, characterized in that: The chip is a back-illuminated contact image sensor chip; A photodiode and a plurality of pixel transistors of a contact image sensor are formed on the first wafer; The second wafer has a signal processing logic circuit of the contact image sensor formed thereon.

6. The method for monitoring whether bonding bubbles are broken in a chip manufacturing wafer bonding process according to claim 1, characterized in that: The chip is a back-illuminated contact image sensor chip; The contact image sensor is a 4T structure CMOS image sensor, the photodiode, transfer gate transistor and first floating diffusion region of the pixel unit of which are formed on the first wafer; The photodiode is located on the vertical back of the first wafer; The transfer gate transistor and the first floating diffusion region are located on the vertical front side of the photodiode; The first floating diffusion region is located at the lateral peripheral side of the transfer gate transistor; The source follower transistor, reset transistor, row selection transistor and second floating diffusion region of the pixel unit are formed on the second chip; The first floating diffusion region and the second floating diffusion region are connected together through a through silicon via to form a floating diffusion region of a pixel unit; The second wafer also has a signal processing logic circuit for the contact image sensor formed thereon.

7. The method for monitoring whether bonding bubbles are broken in a chip manufacturing wafer bonding process according to claim 1, characterized in that: The first floating diffusion region and the second floating diffusion region have an overlapping area in vertical projection.

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