CN111438444B

CN111438444B - Laser cutting method and system based on device array mass transfer

Info

Publication number: CN111438444B
Application number: CN201811623505.8A
Authority: CN
Inventors: 张珂殊
Original assignee: Beijing Surestar Technology Co ltd
Current assignee: Beijing Surestar Technology Co ltd
Priority date: 2018-12-28
Filing date: 2018-12-28
Publication date: 2022-08-12
Anticipated expiration: 2038-12-28
Also published as: CN111438444A

Abstract

The invention discloses a laser cutting method and a laser cutting system based on device array mass transfer. The method comprises the following steps: step 1, providing a wafer, wherein the wafer comprises a bearing plate and a plurality of electronic devices, the electronic devices are arranged on one surface of the bearing plate in an array mode, and each electronic device and part of the bearing plate bearing the electronic device form a device unit; step 2, attaching the wafer to a substrate; and 3, cutting the wafer along the side edge of the device unit, wherein the cutting needs to be carried out to the inner part of the substrate. The laser cutting method and the laser cutting system based on the device array bulk transfer can avoid the short circuit of the electronic device in the bulk transfer process, improve the yield of products, and have simple and convenient operation and low cost.

Description

Laser cutting method and system based on device array mass transfer

Technical Field

The present invention relates to a method for cutting a wafer, and more particularly, to a laser cutting method and system based on mass transfer of a device array.

Background

In the process of transferring the devices in the wafer to a circuit board (such as a PCB), the devices need to be bonded by dispensing to realize electrical connection, however, in the bulk transfer process of the device array, since the devices are integrally moved in an array manner, and directly disposed on the circuit board in a predetermined position relationship, and attached and fixed to the corresponding PAD of the circuit board, the conductive adhesive disposed at the PAD is easily overflowed, resulting in short circuit between adjacent devices.

Specifically, please refer to fig. 1A and 1B.

The wafer includes a carrier 10 and a plurality of electronic devices 20, wherein the carrier 10 is used for carrying the electronic devices 20. The carrier plate 10 is, for example, a sapphire substrate, a gallium nitride substrate, an aluminum nitride substrate, a silicon substrate, a gallium arsenide substrate, and a silicon carbide substrate, but the invention is not limited to the type of the substrate. The electronic devices are arranged on a surface of the carrier 10 in an array. Each electronic device 20 may be a light emitting element, a photoelectric conversion element APD, or other electronic device. Each electronic device and a part of the bearing plate bearing the electronic device form a device unit.

When the electronic devices 20 are attached to the substrate 30 as a whole, each electronic device needs to be aligned with a corresponding PAD31, and the conductive adhesive 32 is disposed at the PAD31, so that the electronic devices are electrically connected to the PAD31 through the conductive adhesive 32.

However, since all the electronic devices 20 are arranged in an array, in the process of approaching the substrate 30 to the carrier 10, the conductive adhesive 32 may be squeezed to spread and extend, so that the adjacent conductive adhesives 32 may be fused, and since the conductive adhesive 32 has conductivity, a short circuit may occur between the electronic devices 20.

Due to the small size of the electronic device, the short circuit detection and repair cost is high, the process is complex, the matched equipment is complex, the operation time is long, the maintenance cost is high, and the yield of the product is influenced. How to solve the problem of short circuit caused by mass transfer when large-area electronic devices on the wafer are transferred to the corresponding receiving circuit boards in a aligned manner is an urgent technical problem to be solved in the field.

Disclosure of Invention

The invention aims to provide a laser cutting method and a laser cutting system based on device array mass transfer, which can avoid short circuit of electronic devices in the mass transfer process.

Furthermore, based on the cutting method, the conductive adhesive can be greatly coated on the substrate or the wafer without fixed-point coating, so that the process requirement for coating the conductive adhesive is reduced, and the production efficiency is improved.

The invention discloses a laser cutting method based on device array mass transfer, which comprises the following steps:

step 1, providing a wafer, wherein the wafer comprises a bearing plate and a plurality of electronic devices, the electronic devices are arranged on one surface of the bearing plate in an array mode, and each electronic device and part of the bearing plate bearing the electronic device form a device unit;

step 2, attaching the wafer to a substrate;

and 3, cutting the wafer along the side edge of the device unit, wherein the cutting needs to be carried out to the inner part of the substrate.

The method also comprises the following steps between the steps 1 and 2:

and coating the conductive adhesive on the surface of the substrate or the surface of the wafer in a large area.

The method also comprises the following steps between the steps 1 and 2:

step 20, pre-cutting the wafer along the side edges of the device units so that each device unit is still connected with at least one adjacent device unit;

the cutting step of step 20 cuts along part or all of the side edges of the device elements in the length and/or width direction of the array.

The dicing step of step 20 effects partial or complete separation of adjacent device units in the thickness direction of the wafer.

Step 3 is followed by: and 4, purging and cooling the device unit by using inert gas.

Step 4 is followed by: and 5, performing a grinding process to remove burrs.

The method comprises the steps of attaching the wafer to the substrate by one side of the electronic device, and executing the step 3 from one side of the bearing plate; or, the wafer is attached to the substrate by a side of the carrier plate, and the step 3 is performed from the side of the electronic device.

The invention also discloses a laser cutting system for realizing the massive transfer of the device array for realizing the method, wherein the wafer comprises a bearing plate and a plurality of electronic devices, the electronic devices are arranged on one surface of the bearing plate in an array mode, each electronic device and part of the bearing plate for bearing the electronic device form a device unit, and the system comprises:

the wafer cutting device cuts the wafer attached to the substrate along the side edge of the device unit, and the cutting needs to be cut into the substrate.

The wafer cutting device pre-cuts the wafer along the side edges of the device units before the cutting, and each device unit is still connected with at least one adjacent device unit;

the system also comprises a cutting information recording device for recording the pre-cutting information;

and the wafer cutting device is also used for cutting the wafer attached to the substrate according to the cutting information.

The system further comprises:

the purging device is used for purging and cooling the device unit by using inert gas; and/or

And a grinding device for grinding the cut wafer to remove burrs.

The laser cutting method and the laser cutting system based on the device array bulk transfer can avoid the short circuit of the electronic device in the bulk transfer process, improve the yield of products, and have simple and convenient operation and low cost. Furthermore, based on the cutting method, the conductive adhesive can be coated on the substrate or the wafer in a large area, fixed-point coating is not needed, the process requirement for coating the conductive adhesive is reduced, and the production efficiency is improved.

Drawings

FIGS. 1A and 1B are schematic diagrams illustrating a bulk transfer process in the prior art.

Fig. 2A is a schematic cross-sectional view along AA' of a wafer.

Fig. 2B is a schematic view of a wafer structure.

Fig. 3A and 3B are schematic flow charts of the method.

Fig. 4A and 4B are schematic diagrams illustrating the cutting manner of the precut in the length and/or width direction of the wafer.

Fig. 5-7 are cross-sectional views corresponding to the partial cut of fig. 4A.

Fig. 8A and 8B are schematic views illustrating the attaching process of the present invention.

Fig. 8C is a schematic diagram of the re-cutting process of the present invention.

FIG. 9 is a schematic diagram of a laser dicing system for mass transfer of a device array according to the present invention.

Detailed Description

The following describes an implementation process of the technical solution of the present invention with reference to specific embodiments, which are not intended to limit the present invention.

Fig. 2A is a schematic cross-sectional view of a wafer along line AA'. Fig. 2B is a schematic view of a wafer structure.

The wafer 100 may utilize 6-inch wafers, not limited to the wafer size. The wafer 100 includes a carrier 10 and a plurality of electronic devices 20, wherein the carrier 10 is used for carrying the electronic devices 20. The carrier plate 10 is, for example, a sapphire substrate, a gallium nitride substrate, an aluminum nitride substrate, a silicon substrate, a gallium arsenide substrate, and a silicon carbide substrate, but the invention is not limited to the type of the substrate.

The electronic devices are arranged on a surface of the carrier 10 in an array. Each electronic device 20 may be a light emitting element, a photoelectric conversion element APD, or other electronic device, and the present invention is not limited to the kind of the electronic device 20 mounted on the wafer. Each electronic device and a part of the carrier for carrying the electronic device form a device unit 101, and fig. 2B illustrates an example of carrying 8 × 4 electronic devices on the wafer 100, but the actual number is not limited thereto. Fig. 2B includes 32 device cells adjacent to each other.

The invention discloses a laser cutting method based on device array mass transfer, and a flow schematic diagram of the method is shown in fig. 3A. The method comprises the following steps:

step 2, attaching the wafer to a substrate;

In the bulk transfer process, the required multiple device units are transferred integrally, attached to the substrate 30, and then cut, as shown in fig. 8C, the cutting depth needs to ensure that the adjacent electronic devices 101 are completely separated, and simultaneously, the cutting traces need to go deep into the substrate 30, so that the cutting process completely blocks the physical connection between the conductive adhesives 32 of the adjacent electronic devices, thereby completely blocking the possibility of short circuit.

Because the conductive adhesive which causes short circuit can be cut off in the cutting process, the conductive adhesive 32 can be coated on the substrate or the wafer in a large area before the cutting process, and is not required to be coated on the position corresponding to each device unit at a fixed point, so that the process requirement of coating the conductive adhesive is reduced, and the production efficiency is improved.

More specifically, the flow chart of the present invention is shown in fig. 3B. The method comprises the following steps:

step 2, transferring the wafer and attaching the wafer to a substrate;

Referring to fig. 4A, an example of 4 electronic devices is shown. Step 20 is to pre-cut the device cells such that semi-adhesion is achieved between adjacent device cells.

Specifically, as shown in fig. 4A, the position where the cutting is performed is indicated by a black solid line, only the side edge of each device unit is cut in the length and/or width direction of the array, taking four side edges of each device unit as an example, for example, a part of the left edge and a part of the top edge of each device unit are cut, and the remaining part is kept unchanged and is not cut. Alternatively, dicing is performed only on a portion of the left edge of each device cell. Alternatively, the dicing is performed only on a part of the upper edge of each electronic device. The location of the partial cut may be selected as desired. In the thickness direction, partial separation or complete separation of adjacent device cells is achieved.

As shown in fig. 4B, it is also possible to cut all of the side edges, but not all of the side edges through the thickness, and still have a portion of the side edges remain attached, or otherwise ensure that all of the device cells remain relatively fixed. Or one side edge is completely cut and completely cut through in thickness, the other side edge needs to be relied on to maintain connection with other device units.

As shown in fig. 5-7, which are cross-sectional views corresponding to the partial cut for the skirt of fig. 4A.

Fig. 4A shows the pre-cut in the length and/or width direction of the wafer, and fig. 6 and 7 show the pre-cut in the thickness direction of the wafer.

The pre-cutting is performed for the area between adjacent device cells 101, which is covered with some semiconductor layer. In the embodiment shown in fig. 5, the pre-cut is performed from one side of the electronic device, only down to the lower edge of the electronic device 20, and the semiconductor layer is cut without cutting the carrier plate 10, so that the separation between the adjacent electronic devices is achieved and the carrier plate remains connected.

In another embodiment, shown in fig. 7, the precut is cut down to the lower edge of the carrier plate 10 so that separation is achieved between adjacent electronic devices and the carrier plate.

The pre-cutting step enables the device units to be partially separated and have certain mobility, and the device units are kept connected with each other to form a whole body, so that the subsequent plate distinguishing step is convenient to realize.

The pre-cutting step may be performed for all device units in the wafer 100 or for some of the device units therein.

That is, the present invention cuts some or all of the side edges of the device elements in the length and/or width direction of the array and performs partial or full separation in the thickness direction, but each device element remains connected to at least one adjacent device element.

And 2, transferring the wafer and attaching the wafer to a substrate.

The wafer can be transferred to a substrate by the grabbing device to be jointed to assemble the required product, so as to realize mass transfer of electronic devices.

Each electronic device needs to be aligned to a corresponding PAD31 on the circuit board, and the conductive adhesive 32 is disposed at the PAD31, so that the electronic device is electrically connected to the PAD31 through the conductive adhesive 32. Fig. 8A and 8B are schematic views of the attaching process.

In the process of approaching the substrate 30 to the carrier plate 10, the conductive adhesive 32 is pressed to spread and extend, so that adjacent conductive adhesives 32 are fused.

The wafer is diced again at the portions (length/width/thickness direction) where the side edges are not diced. Such that adjacent device cells are completely separated.

Fig. 8C is a schematic diagram of the re-cutting process in step 3.

The cutting depth is required to ensure that the adjacent electronic devices 101 are completely separated, and at the same time, the cutting trace is required to go deep into the substrate 30, so that the cutting process completely blocks the physical connection between the conductive adhesives 32 of the adjacent electronic devices, thereby completely blocking the possibility of occurrence of short circuits.

The cutting steps in steps 20 and 3 can adopt a laser cutting method, and by utilizing the characteristics of high laser energy density and pulse, an extremely high temperature and thermal shock effect can be formed on the surface of the material to be removed, so that the material to be removed and the base material can be quickly peeled, and the laser energy density is high, so that the material to be removed on the surface can be instantly gasified, and the quick and deep cutting can be realized.

The cutting step in steps 20 and 3 may also be mechanical cutting, photochemical reaction or photophysical reaction.

In addition, in step 3, the wafer is diced from one side of the wafer to one side of the substrate, i.e. the wafer can be attached to the substrate 30 from one side of the electronic device, and the dicing is performed from one side of the carrier plate; the re-dicing may also be performed from the electronic device side by attaching the wafer to the substrate 30 with the carrier side.

The cut width needs to be less than the spacing between adjacent PADs PAD 31.

After the re-cutting step of step 3 is finished, further comprising:

and 4, purging and cooling the device unit by using inert gas. The inert gas is nitrogen or carbon dioxide. Therefore, the chips of the conductive adhesive and other chips left by the cutting process can be completely removed, and short circuit is avoided.

And 5, grinding each device unit to remove burrs.

After cutting, various burrs or protrusions can be generated on the device unit, and the burrs can be removed through a grinding process, so that the yield of products is improved.

The wafer is transferred integrally by the huge transfer of the device arrays, the internal device arrays are not completely separated, and the relative position relation of the internal device arrays is kept absolutely fixed, so that the position precision of the device arrays is high during the integral transfer, the alignment is carried out subsequently by taking the whole plate as a unit, the alignment difficulty is reduced, the yield of products is improved, the operation is simple and convenient, and the cost is low.

The precutting allows the partial areas between the adjacent electronic devices to be separated, and thus reduces the workload, the work intensity and the alignment time for re-cutting.

The laser cutting method based on the massive transfer of the device array avoids short circuit of electronic devices and improves the reliability of products.

Based on the above disclosure, the present invention further discloses a laser cutting system for realizing mass transfer of device arrays, a schematic structural diagram of the system is shown in fig. 9, and the system 200 includes:

the wafer dicing apparatus 21 is used to cut the wafer attached to the substrate along the side edge of the device unit, and the cutting is required to be performed inside the substrate.

Furthermore, as shown in fig. 3B, the wafer cutting device 21 is also used to pre-cut the wafer along the side edges of the device units, but each device unit remains connected to at least one adjacent device unit;

the system 200 further comprises a cutting information recording means 22 for recording the pre-cut cutting information;

the wafer cutting device 21 further cuts the transferred wafer along the side edges of the device units again according to the cutting information, so that the adjacent device units are completely separated from each other, and the wafer needs to be cut into the substrate again.

In addition, the system may further comprise a gripping device 23 for gripping the wafer or the plate.

In addition, the system may also include a purge device 24 for purging and cooling the device unit with an inert gas.

The system may further include a polishing device 25 for performing a polishing process on the cut wafer to remove burrs.

The above-mentioned embodiments are merely exemplary descriptions for implementing the present invention, and do not limit the scope of the present invention, which is defined by the claims appended hereto.

Claims

1. A laser cutting method based on device array bulk transfer is characterized by comprising the following steps:

step 10, coating the conductive adhesive on the surface of the substrate or the surface of the wafer in a large area;

step 2, attaching the wafer to the substrate, wherein each electronic device is aligned with a gasket of the substrate;

and 3, cutting the wafer along the side edge of the device unit, wherein the wafer is required to be cut into the substrate without cutting through the substrate, the cutting depth ensures that the adjacent electronic devices are completely separated, and the cutting width is smaller than the distance between the adjacent gaskets.

2. The method of claim 1, wherein the step 20 of cutting cuts along part or all of the side edges of the device elements in the length and/or width direction of the array.

3. A method according to claim 1 or 2, wherein the dicing step of step 20 effects partial or complete separation of adjacent device units in the thickness direction of the wafer.

4. The method of claim 1, wherein step 3 is further followed by:

and 4, purging and cooling the device unit by using inert gas.

5. The method of claim 4, wherein step 4 is further followed by:

and 5, performing a grinding process to remove burrs.

6. The method of claim 1, wherein the wafer is attached to the substrate with the electronic device side, and the step 3 is performed from the carrier side; or

The wafer is attached to the substrate with one side of the carrier plate, and the step 3 is performed from one side of the electronic device.

7. A laser dicing system for implementing the method of any one of claims 1 to 6, wherein the wafer comprises a carrier plate and a plurality of electronic devices arranged in an array on a surface of the carrier plate, each electronic device and a portion of the carrier plate carrying the electronic device forming a device unit, the system comprising:

8. The system of claim 7, wherein the wafer dicing apparatus pre-cuts the wafer along the side edges of the device units prior to said cutting, each device unit remaining connected to at least one adjacent device unit;

9. The system of claim 7, wherein the system further comprises:

And a grinding device for grinding the cut wafer to remove burrs.