Wafer separation method

Abstract

The wafer separation method disclosed by the invention comprises the following steps: performing laser cutting on a predetermined area of a wafer to form a separation channel; the predetermined area is subjected to laser ablation, the depth of the separation channel is increased till the wafer is separated along the separation channel, the laser power of the laser cutting is larger than the laser power of the laser ablation, and the laser movement rate of the laser ablation is larger than the laser movement rate of the laser cutting. The method is low in cost, simple in operation and high in efficiency, can avoid overlarge stress caused by mechanical cutting, reduces the occurrence of wafer edge breakage, and improves the yield of products.

Description

Technical Field

[0001] This invention relates to the field of semiconductor manufacturing, and more particularly to a method for separating wafers. Background Technology

[0002] With the rapid advancements in semiconductor technology, the requirements for semiconductor manufacturing and processing are becoming increasingly stringent. Separating wafers into the required units is a necessary step in wafer fabrication. A common wafer separation method is mechanical separation. However, during mechanical separation, a cutting wheel is used to cut along the dicing lines of the semiconductor. Therefore, the area near the dicing lines experiences significant stress, which can easily cause edge chipping or even wafer breakage. Furthermore, mechanical separation is inefficient and unsuitable for large-scale operations.

[0003] Therefore, there is an urgent need to provide an improved wafer separation method to overcome the above-mentioned defects. Summary of the Invention

[0004] The purpose of this invention is to provide an improved wafer separation method that is low in cost, simple to operate, and highly efficient, and can avoid excessive stress caused by mechanical cutting, reduce wafer edge breakage, and thus improve product yield.

[0005] To achieve the above objectives, the wafer separation method of the present invention includes the following steps:

[0006] Laser cutting is performed on a predetermined area of ​​the wafer to form separation channels;

[0007] The predetermined area is subjected to laser ablation to increase the depth of the separation channel until the wafer is separated along the separation channel, wherein the laser power of the laser cutting is greater than the laser power of the laser ablation, and the laser movement rate of the laser ablation is greater than the laser movement rate of the laser cutting.

[0008] Compared with existing technologies, this invention uses lasers for wafer separation, combining two laser processes of different intensities: laser cutting and laser ablation. First, laser cutting is performed in a predetermined area of ​​the wafer to form separation channels. Then, laser ablation is applied to these channels, gradually increasing their depth until the wafer is separated along them. The laser power for cutting is strictly controlled to be greater than that for ablation, and the laser movement rate for ablation is greater than that for cutting. This approach has the advantage of using a stronger, slower laser initially to locally separate the wafer, improving efficiency. Then, a weaker, faster laser is used to further deepen the separation channels while simultaneously trimming and softening the wafer's edge breakage, further reducing the breakage rate and thus improving product yield. Therefore, the method of this invention is low-cost, simple to operate, and highly efficient. It also avoids excessive stress caused by mechanical cutting, reduces wafer breakage, and improves product yield, making it suitable for widespread industrial application.

[0009] Preferably, the laser power range for laser cutting is 12-15KW, and the laser power range for laser ablation is 7-8KW.

[0010] Preferably, the laser movement rate for laser cutting is 1-2 mm / s, and the laser movement rate for laser ablation is 5-10 mm / s.

[0011] Preferably, the laser wavelength range for the laser cutting and the laser ablation is 600-800nm.

[0012] Preferably, helium is used as a protective gas only in the laser cutting and laser ablation processes, and the helium flow rate is 120-160 L / min.

[0013] Preferably, after the laser cutting, the depth of the separation channel is 1 / 2 to 4 / 5 of the total separation depth.

[0014] Preferably, in the laser cutting, the laser spot diameter is 3-5 nm.

[0015] Preferably, in the laser ablation, the laser spot diameter is 30-35 nm. Detailed Implementation

[0016] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific implementation methods of this application are described in detail below with reference to some embodiments. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0017] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating orientation or positional relationships are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0018] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0019] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., 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, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0020] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0021] It should be noted that when an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0022] The wafer separation method of the present invention will be further described below with reference to embodiments, but this does not limit the present invention. The method of the present invention aims to provide an improved wafer separation method that is low in cost, simple to operate, and can avoid excessive stress caused by mechanical cutting, reduce wafer edge breakage, and thus improve product yield.

[0023] In one embodiment of the wafer separation method of the present invention, the following steps are included:

[0024] Laser cutting is performed on a predetermined area of ​​the wafer to form separation channels;

[0025] The predetermined area is subjected to laser ablation to increase the depth of the separation channel until the wafer is separated along the separation channel, wherein the laser power of the laser cutting is greater than the laser power of the laser ablation, and the laser movement rate of the laser ablation is greater than the laser movement rate of the laser cutting.

[0026] This invention employs laser-based wafer separation, combining laser cutting and laser ablation with two laser processes of different intensities. First, laser cutting is performed in a predetermined area of ​​the wafer to form separation channels. Then, laser ablation is applied to these channels, gradually increasing their depth until the wafer is separated along them. The laser power for cutting is strictly controlled to be greater than that for ablation, and the laser movement rate for ablation is greater than that for cutting. This approach has the advantage of using a stronger, slower laser initially to locally separate the wafer, improving efficiency. Subsequently, a weaker, faster laser is used to further deepen the separation channels while simultaneously trimming and softening the wafer's edge, further reducing the edge breakage rate and thus improving product yield. Therefore, this invention offers a low-cost, simple, and highly efficient method that avoids excessive stress caused by mechanical cutting, reduces wafer edge breakage, and improves product yield, making it suitable for widespread industrial application.

[0027] In this invention, a laser generator is used to emit laser light. Preferably, the laser generator is directly facing the separation surface of the wafer; for example, the laser beam is incident on the separation surface of the wafer at a 90° angle. Preferably, the laser generator is a laser pulser, using helium as a protective gas, with a helium flow rate of 120-160 L / min.

[0028] Optionally, the helium gas flow rate is 150 L / min during laser cutting. To ensure separation effect and efficiency, the intensity of the laser pulse during laser cutting must be greater than that of the subsequent laser ablation. Specifically, the laser power range for laser cutting is 12-15 kW, and the laser movement speed is 1-2 mm / s. The laser wavelength range is 600-800 nm, and the laser spot diameter is 3-5 nm. After ion etching, the depth of the separation channel accounts for 1 / 2 to 4 / 5 of the total separation depth. That is to say, most of the wafer separation depth is formed during this laser cutting process, which protects the separation edge while improving separation efficiency.

[0029] Next, the wafer undergoes laser ablation. Specifically, the laser power is controlled at 7-8 kW, and the laser movement speed along the separation path is 5-10 mm / s. The laser wavelength range is 600-800 nm, the laser spot diameter is 30-35 nm, and the laser defocusing amount is 5-10 mm. Under these conditions, the depth of the separation path on the wafer can be gradually increased until the wafer is completely separated along the separation path. As a preferred embodiment, helium is used as a protective gas during the laser ablation process, such as a helium flow rate of 120 L / min, to protect other surfaces of the wafer. Through this laser ablation step, the separation path can be deepened, and the wafer edge chipping can be trimmed simultaneously, softening the separation edge and reducing the chipping size, thereby further reducing the chipping rate. The wafer processed in this step has a chipping size reduced to below 1-2 micrometers, and a chipping rate below 0.01%.

[0030] In summary, this invention utilizes laser technology for wafer separation, combining laser cutting and laser ablation with different laser intensities. First, laser cutting is performed on a predetermined area of ​​the wafer to form separation channels. Then, laser ablation is applied to these channels, gradually increasing their depth until the wafer is separated along them. The laser power for cutting is strictly controlled to be greater than that for ablation, and the laser movement rate for ablation is greater than that for cutting. This approach has the advantage of using a stronger, slower laser initially to locally separate the wafer, improving efficiency. Subsequently, a weaker, faster laser is used to further deepen the separation channels while simultaneously trimming and softening the wafer's edge, further reducing the edge breakage rate and thus improving product yield. Therefore, this invention offers a low-cost, simple, and efficient method that avoids excessive stress caused by mechanical cutting, reduces wafer edge breakage, and improves product yield, making it suitable for widespread industrial application.

[0031] The above-disclosed embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of the present invention. Therefore, any equivalent variations made in accordance with the claims of the present invention are still within the scope of the present invention.

Claims

1. A method of separating a wafer, characterized by, The method comprises the following steps: laser cutting a predetermined region of a wafer to form a separation groove; laser ablation on the predetermined region to increase the depth of the separation groove until the wafer is separated along the separation groove, wherein the laser power of the laser cutting is greater than the laser power of the laser ablation, and the laser moving speed of the laser cutting is less than the laser moving speed of the laser ablation.

2. The wafer separating method according to claim 1, wherein The laser power of the laser cutting ranges from 12 to 15 KW, and the laser power of the laser ablation ranges from 7 to 8 KW.

3. The method of singulating a wafer of claim 1, wherein, The laser moving speed of the laser cutting ranges from 1 to 2 mm / s, and the laser moving speed of the laser ablation ranges from 5 to 10 mm / s.

4. The method of singulating a wafer of claim 1, wherein: The laser wavelength of the laser cutting and the laser ablation ranges from 600 to 800 nm.

5. The method of singulating a wafer of claim 1, wherein, Helium is used as the protective gas in the laser cutting and the laser ablation, and the gas flow of the helium ranges from 120 to 160 L / min.

6. The method of singulating a wafer of claim 1, wherein, After the laser cutting, the depth of the separation groove is 1 / 2 to 4 / 5 of the total separation depth.

7. The method of singulating a wafer of claim 1, wherein, In the laser cutting, the laser spot diameter ranges from 3 to 5 nm.

8. The method of singulating a wafer of claim 1, wherein, In the laser ablation, the laser spot diameter ranges from 30 to 35 nm.