A method of dicing a bonded wafer

Abstract

The application discloses a bonded wafer cutting method and relates to the technical field of semiconductor processing. The bonded wafer cutting method comprises the following steps: forming a first groove on a first surface of a silicon layer by using laser burning, and extending the first groove to a first surface of a glass lens; forming a crack corresponding to the first groove on a second surface of the glass lens by using laser cutting, and extending the crack to a second surface of the silicon layer; and applying force to the crack to split the glass lens. The bonded wafer cutting method solves the problems that, in the prior art, directly cutting with a blade will cause too large edge collapse due to the difference in material between the upper and lower layers of the bonded wafer, and directly cutting with the same kind of laser will cause low yield due to the difference in ablation effect of the same kind of laser on silicon and glass, and can simultaneously ensure the cutting effect of silicon and glass and improve the cutting yield of the bonded wafer.

Description

Technical Field

[0001] This invention relates to the field of semiconductor processing technology, and more particularly to a method for cutting bonded wafers. Background Technology

[0002] High-purity quartz glass is widely used in image sensors, displays, and nanofluidic devices due to its excellent optical, mechanical, and chemical properties. By combining silicon and quartz glass wafers through plasma-activated bonding processes to form bonded wafers, ultra-miniaturized hermetically sealed packaging of high-sensitivity electronic components can be achieved, which is widely used in medical implants, aerospace, microelectromechanical systems, and micro-optical components.

[0003] In the existing technology, the packaging and dicing process of bonded wafers uses either direct blade cutting or direct cutting with the same type of laser. However, when performing the packaging and dicing process of bonded wafers, direct blade cutting can lead to excessive edge chipping due to the different materials of the upper and lower layers of the bonded wafer. Direct cutting with the same type of laser can also result in low yield due to the different ablation effects of the same laser on silicon and glass.

[0004] Therefore, there is an urgent need for a method for dicing bonded wafers to solve the above problems. Summary of the Invention

[0005] The purpose of this invention is to provide a method for dicing bonded wafers that can simultaneously ensure the dicing effect of silicon and glass, thereby improving the dicing yield of bonded wafers.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] A method for dicing a bonding wafer, the bonding wafer comprising a silicon layer and a glass lens stacked thereon, the dicing method comprising:

[0008] A first groove is formed by burning the first surface of the silicon layer with a laser, and the first groove extends to the first surface of the glass lens;

[0009] The second surface of the glass lens is cut with a laser to form a crack corresponding to the first groove, and the crack extends to the second surface of the silicon layer.

[0010] A force is applied to the crack to split the glass lens.

[0011] As a preferred technical solution for the dicing method of the bonding wafer, before forming a first groove on the first surface of the silicon layer by laser ablation and extending the first groove to the surface of the glass lens, the method further includes:

[0012] A first cutting film is attached to the second surface of the glass lens.

[0013] As a preferred technical solution for the dicing method of the bonding wafer, the method further includes, before using a laser to cut the first surface of the glass lens to form a crack corresponding to the first groove, and before extending the crack to the second surface of the silicon layer:

[0014] A second dicing film is attached to the first surface of the silicon layer.

[0015] A preferred embodiment of a method for dicing bonded wafers further includes, before applying force to the crack to split the glass lens:

[0016] The bonding wafer is fixed on the stage.

[0017] As a preferred embodiment of a method for dicing bonded wafers, applying force to the crack to split the glass lens includes:

[0018] The glass lens can be split by applying a cleaver to the crack; or by splitting the glass lens by cold spalling and thermal expansion.

[0019] As a preferred technical solution for a bonding wafer dicing method, the laser ablation frequency is set to 110KHZ-130KHZ, the average power is 2W-2.5W, and the grooving speed is set to 300mm / s-500mm / s.

[0020] As a preferred technical solution for cutting bonded wafers, the glass lens is cut using an ultrafast laser.

[0021] As a preferred technical solution for a bonding wafer dicing method, the ultrafast laser dicing speed is set to 40mm / s-60mm / s, the dicing frequency is set to 40kHz-60kHz, and the average power is 15W-20W.

[0022] As a preferred technical solution for a bonding wafer cutting method, the ultrafast laser is used to cut the glass lens, forming a plurality of wire holes in the glass lens, and the plurality of wire holes form the crack.

[0023] In a preferred embodiment of a method for dicing bonded wafers, the aperture of the wire holes is 2µm-5µm, and the spacing between the wire holes is 4µm-6µm.

[0024] The beneficial effects of this invention are:

[0025] This invention provides a method for dicing bonded wafers, comprising: forming a first groove by ablation of a first surface of a silicon layer with a laser, and extending the first groove to a first surface of a glass lens; forming a crack corresponding to the first groove by cutting a second surface of the glass lens with a laser, and extending the crack to the second surface of the silicon layer; and applying force to the crack to split the glass lens. This method for dicing bonded wafers solves the problems in the prior art where direct cutting with a blade results in excessive chipping due to the different materials of the upper and lower layers of the bonded wafer, and where direct cutting with the same laser results in low yield due to differences in the ablation effect of the same laser on silicon and glass. It can simultaneously ensure the cutting effect of silicon and glass, thereby improving the dicing yield of bonded wafers. Attached Figure Description

[0026] Figure 1 This is a flowchart of the main steps in the bonding wafer dicing method of the present invention;

[0027] Figure 2 This is a schematic diagram of forming a first groove on the first surface of a silicon layer using laser ablation in the wafer cutting method of the present invention;

[0028] Figure 3 This is a schematic diagram of attaching a second dicing film to the first surface of the silicon layer in the dicing method of the bonding wafer of the present invention; Figure 4 This is a schematic diagram of removing the first dicing film in the dicing method of the bonding wafer of the present invention;

[0029] Figure 5 This is a schematic diagram of forming a crack corresponding to the first groove on the second surface of a laser-cut glass lens in the wafer cutting method of the present invention.

[0030] Figure 6 This is a schematic diagram of applying force to the crack to split the glass lens in the bonding wafer cutting method of the present invention.

[0031] In the picture:

[0032] 1. Silicon layer;

[0033] 2. Glass lens;

[0034] 3. First cutting membrane;

[0035] 4. Second cutting membrane;

[0036] 5. Platform;

[0037] 6. Laser;

[0038] 7. Chopping knife. Detailed Implementation

[0039] To make the technical problems solved by the present invention, the technical solutions adopted, and the technical effects achieved clearer, the technical solutions of the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0040] In the description of this invention, unless otherwise explicitly specified and limited, the terms "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0041] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0042] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0043] like Figure 1 and Figure 2 As shown, the bonding wafer in this embodiment includes a silicon layer 1 and a glass lens 2 stacked together. The silicon layer 1 is an IC functional wafer with a thickness of 40um-80um, and the glass lens 2 has a thickness of 300um-400um. The dicing method for the bonding wafer provided in this embodiment mainly includes:

[0044] A first groove is formed by burning the first surface of the silicon layer 1 with a laser, and the first groove extends to the first surface of the glass lens 2;

[0045] A crack corresponding to the first groove is formed on the second surface of the glass lens 2 by laser cutting, and the crack extends to the second surface of the silicon layer 1.

[0046] Apply force to the crack to split the glass lens 2.

[0047] This wafer cutting method solves the problems in the prior art, such as excessive chipping due to the different materials of the upper and lower layers of the wafer when cutting directly with a blade, and low yield due to the different ablation effects of the same laser on silicon and glass when cutting directly with the same laser. It can simultaneously ensure the cutting effect of silicon layer 1 and glass lens 2, thereby improving the wafer cutting yield.

[0048] The detailed steps of the bonding wafer dicing method provided in this embodiment include:

[0049] like Figure 2 As shown, step one involves attaching the first cutting film 3 to the second surface of the glass lens 2.

[0050] Step 2: Fix the bonding wafer onto a platform with a fixture, with silicon layer 1 facing upwards.

[0051] Specifically, since the glass lens 2 cannot be placed directly on the platform, the first cutting film 3 needs to be attached to the second surface of the glass lens 2. The first cutting film 3 is attached to the second surface of the glass lens 2. The edge of the first cutting film 3 is provided with an iron ring, which makes it easy to fix the first cutting film 3 and the bonding wafer on it on the platform with a fixture. The first cutting film 3 with the iron ring is placed on the platform with a fixture, with the silicon layer 1 facing upward.

[0052] Step 3: Use a laser to burn the first surface of the silicon layer 1 to form a first groove, and make the first groove extend to the first surface of the glass lens 2.

[0053] Further, laser 6 is used for laser ablation, with the laser ablation frequency set to 110kHz-130kHz, the average power to 2W-2.5W, and the grooving speed set to 300mm / s-500mm / s. Optionally, the laser ablation frequency is set to 110kHz, 120kHz, and 130kHz, preferably 120kHz. Optionally, the average laser ablation power is 2.1W, 2.2W, 2.3W, 2.4W, and 2.5W, preferably 2.2W. Optionally, the grooving speed is set to 300mm / s, 400mm / s, and 500mm / s, preferably 400mm / s. Laser 6 is fixed on a support. The bonding wafer is aligned with the laser. After alignment, the platform with clamps that holds the glass lens 2 moves at a uniform speed according to the program, causing the laser to ablate each kerf in the silicon layer 1. The depth of the laser grooving is about 20µm, and the width can be less than 10µm, which can completely ablate the silicon layer 1. When laser cutting the glass lens 2 later, it can cut through the entire bonding wafer, thereby improving the problem of excessive edge chipping caused by laser power mismatch.

[0054] like Figure 3 and Figure 4 As shown, in step four, since the silicon layer 1 cannot be placed directly on the platform, a second cutting film 4 needs to be attached to the first surface of the silicon layer 1. The first cutting film 3 attached to the second surface of the glass lens 2 is removed.

[0055] Step 5: Fix the bonding wafer onto the platform with the fixture, with glass lens 2 facing upwards.

[0056] Step 6: Use a laser to cut the second surface of the glass lens 2 to form a crack corresponding to the first groove, and extend the crack to the second surface of the silicon layer 1.

[0057] Specifically, a second cutting film 4 is attached to the first surface of the silicon layer 1, the first cutting film 3 attached to the second surface of the glass lens 2 is removed, an iron ring is provided on the edge of the second cutting film 4, and the second cutting film 4 with the iron ring is placed on a platform with a clamp, with the glass lens 2 facing upward.

[0058] The platform with the fixture is also equipped with a vacuum chuck. After alignment, the vacuum chuck adsorbs the second cutting membrane 4, and then laser cutting is performed.

[0059] Furthermore, an ultrafast laser is used to cut the glass lens 2, with the laser head being an infrared picosecond laser head.

[0060] The ultrafast laser cutting speed is set to 40mm / s-60mm / s, the cutting frequency is set to 40kHz-60kHz, and the average power is 15W-20W. Optionally, the ultrafast laser cutting speed can be set to 40mm / s, 50mm / s, and 60mm / s.

[0061] Furthermore, an ultrafast laser is used to cut the glass lens 2, forming several pores in the glass lens 2, and these pores form cracks.

[0062] The aperture of the wire holes is 2µm-5µm, and the spacing between the wire holes is 4µm-6µm. Optionally, the aperture diameter of the wire holes is 2µm, 3µm, 4µm, and 5µm, and the spacing between the wire holes is 4µm, 5µm, and 6µm. Preferably, the aperture diameter of the wire holes is 3µm, and the spacing between the wire holes is 5µm. When the ultrafast laser beam propagates through the glass material, it will form micron-sized wire holes in the material. The aperture diameter is controlled at 3µm, and the spacing is controlled at about 5µm. These wire holes can penetrate the glass lens 2 of the bonded wafer, forming a dense pore on the glass lens 2. Ultrafast lasers interact with the material to be cut in an extremely short time and in a very small space. The temperature in the interaction area rises sharply in an instant, and the material to be cut is removed in the form of plasma ejection. The thermal impact is very small, which weakens and eliminates the thermal effects in traditional machining. The interaction time between ultrafast laser micromachining and the material is very short, so the energy is instantly carried away in the form of plasma. The heat does not have time to diffuse inside the material, and no recast layer is formed. It is a cold process, which presents sharp processing edges and high processing precision.

[0063] Step 7: Fix the bonding wafer onto the stage 5 with the glass lens 2 facing upwards.

[0064] Furthermore, the stage 5 of the cleaver is provided with a groove. When the glass lens 2 is placed on the stage 5 of the cleaver, the crack of the glass lens 2 is aligned with the groove, which facilitates the subsequent splitting of the glass lens 2.

[0065] Step 8: Apply force to the crack to split the glass lens 2.

[0066] Furthermore, applying force to the crack to split the glass lens 2 includes using a chopping tool to act on the crack to split the glass lens 2; or splitting the glass lens 2 by cold collapse and thermal expansion.

[0067] In this embodiment, the glass lens 2 is split by applying a chopping blade 7 to the crack. Pressure is applied to the cutting path using the chopping blade 7, which is less than 10µm wide, increasing the stress at the crack and causing the glass lens 2 to fracture along the crack, thus achieving the purpose of cutting. This processing method also ensures that the surrounding materials within the affected space are not affected during processing, thereby achieving ultra-precision machining.

[0068] Compared with traditional blade cutting or laser cutting methods for bonded wafers, the cutting method of this embodiment reduces the front and back edge chipping of the cuts on the glass lens 2. Traditional blade cutting methods generally result in front edge chipping greater than 50µm, and laser cutting of the glass lens 2 is difficult to ablate the silicon layer 1, which can easily cause abnormalities such as incomplete cutting or excessive burning. Using the cutting method of this embodiment, the front edge chipping size can be less than 10µm, greatly reducing problems such as incomplete cutting or excessive burning.

[0069] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for dicing a bonding wafer, the bonding wafer comprising a silicon layer (1) and a glass lens (2) stacked together, characterized in that, The cutting method includes: A first groove is formed by burning the first surface of the silicon layer (1) with a laser, and the first groove extends to the first surface of the glass lens (2); The second surface of the glass lens (2) is cut with a laser to form a crack corresponding to the first groove, and the crack extends to the second surface of the silicon layer (1); A force is applied to the crack to split the glass lens (2); When the glass lens (2) is laser-cut, it can cut through the entire bonded wafer, thereby improving the problem of excessive edge chipping; The glass lens (2) was cut using an ultrafast laser. The cutting speed of the ultrafast laser is set to 40 mm / s-60 mm / s, the cutting frequency is set to 40 kHz-60 kHz, and the average power is 15 W-20 W. The glass lens (2) is cut using the ultrafast laser to form a plurality of wire holes in the glass lens (2), and the plurality of wire holes form the crack.

2. The method for dicing a bonding wafer according to claim 1, characterized in that, Before forming a first groove on the first surface of the silicon layer (1) by laser ablation, and before extending the first groove to the first surface of the glass lens (2), the process further includes: A first cutting film (3) is attached to the second surface of the glass lens (2).

3. The method for dicing a bonding wafer according to claim 1, characterized in that, The process further includes forming a crack corresponding to the first groove on the first surface of the glass lens (2) using a laser, and before the crack extends to the second surface of the silicon layer (1): A second dicing film (4) is attached to the first surface of the silicon layer (1).

4. The method for dicing a bonding wafer according to claim 1, characterized in that, Before applying force to the crack to split the glass lens (2), the following steps are also included: The bonding wafer is fixed on the stage (5) so that the groove on the stage (5) is aligned with the crack.

5. The method for dicing a bonding wafer according to claim 1, characterized in that, Applying force to the crack to split the glass lens (2) includes: Use a chopping tool (7) to split the glass lens (2) at the crack; or split the glass lens (2) by cold collapse and thermal expansion.

6. The method for dicing a bonding wafer according to claim 1, characterized in that, The laser ablation frequency was set to 110 kHz-130 kHz, the average power was 2 W-2.5 W, and the grooving speed was set to 300 mm / s-500 mm / s.

7. The method for dicing a bonding wafer according to claim 1, characterized in that, The diameter of the wire holes is 2 μm - 5 μm, and the spacing between the wire holes is 4 μm - 6 μm.

Images