Method for improving laser girdling effect

Abstract

The invention discloses a method for improving a laser ring cutting effect, and the method comprises the steps: S1, providing a wafer of which the back surface is provided with a taiko ring, and placing the wafer on a bearing disc; s2, the wafer is subjected to an annular cutting process, and the annular cutting process comprises the steps that S21, the wafer is cut through by using a first laser beam until the wafer is cut through, and a first cutting channel is formed; s22, a second laser beam concentric with the first laser beam is used for cleaning the first cutting channel; wherein the spot diameter of the second laser beam is larger than that of the first laser beam, and the power of the second laser beam is smaller than that of the first laser beam. According to the technical scheme, the problem that the wafer cracks during ring removal due to silicon chip residues in the cutting channel in the related technology can be solved.

Description

Technical Field

[0001] The present application relates to the technical field of wafer cutting technology, and in particular to a method for improving the effect of laser ring cutting. Background Art

[0002] Taiko process is a wafer thinning technology, which is the name of the back grinding of wafers used in new generation packaging technology. This technology is different from the previous back grinding. When grinding the wafer, the edge ring part of the wafer will be retained and only the inside of the wafer will be ground and thinned. By introducing this technology, it is possible to reduce the risk of handling thin wafers and reduce the problem of warping.

[0003] As one of the important steps in Taiko wafer process, the ring cutting and de-ringing process is mainly used to maintain the integrity of the wafer edge, which is convenient for Dicing and packaging. Laser cutting is one of the main methods of ring cutting. It uses a laser beam to bombard the wafer surface, causing the contacted part to quickly heat up and melt or vaporize. Through the relative movement of the laser beam and the wafer, a cutting seam is formed to achieve the cutting purpose.

[0004] However, during the laser cutting process, some of the melted high-temperature silicon chips cannot be removed from the cutting seam in time. After cooling and solidifying in the cutting path, they merge with the wafer, which easily leads to cracks during subsequent ring removal. Summary of the invention

[0005] In order to solve the above problems, the present application provides a method for improving the effect of laser circumcision.

[0006] The present application provides a method for improving the effect of laser cutting, including: S1: providing a wafer with a taiko ring formed on the back side, wherein the wafer is placed on a carrier plate; S2: performing a ring cutting process on the wafer, the ring cutting process comprising: S21: using a first laser beam to cut the wafer until the wafer is cut through and a first cutting line is formed; S22: using a second laser beam concentric with the first laser beam to clean the first cutting path; The spot diameter of the second laser beam is larger than that of the first laser beam, and the power is smaller than that of the first laser beam.

[0007] In some embodiments, the spot diameter of the first laser beam is 20 um, and the spot diameter of the second laser beam is 30 um.

[0008] In some embodiments, the power of the second laser beam is half of that of the first laser beam.

[0009] In some embodiments, the circumcision process is suitable for band circumcision.

[0010] In some embodiments, the thickness of the wafer ranges from 20um to 250um.

[0011] The technical solution of this application has at least the following advantages: 1. By setting the wafer ring cutting process as step-by-step cutting, and in the first step of cutting, using the first laser beam with a small spot and high power to cut the wafer to ensure that the wafer is cut through, and in the second step of cutting, using the second laser beam with a large spot and low power to clean the first cutting path to ensure that the residual high-temperature silicon chips are removed, the ring removal window is enlarged, the cutting effect of the wafer ring cutting process is improved, and cracks are avoided in the subsequent ring removal of the Taiko thinned wafer. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In order to more clearly illustrate the specific implementation methods of the present application or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0013] Figure 1 A method for improving the effect of laser circumcision is provided by an exemplary embodiment of the present application; Figure 2 is a schematic diagram provided by an exemplary embodiment of the present application for reflecting that a first laser beam irradiates a wafer; Figure 3 It is a schematic diagram provided by an exemplary embodiment of the present application for reflecting that the second laser beam irradiates the wafer. DETAILED DESCRIPTION

[0014] The following will be combined with the accompanying drawings to clearly and completely describe the technical solutions in this application. Obviously, the described embodiments are part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0015] In the description of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present application. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0016] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, it can also be the internal connection of two components, it can be a wireless connection, or it can be a wired connection. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0017] 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 they do not conflict with each other.

[0018] The present application provides a method for improving the effect of laser cutting. Figure 1 , the method comprises the following steps: S1: A wafer having a taiko ring formed on the back side is provided, and the wafer is placed on a carrier plate.

[0019] For example, refer to Figure 2 , providing a wafer with a taiko ring formed on the back side (i.e., the wafer in the figure), which is placed on a carrier plate (i.e., the Chuck table in the figure) in the laser cutting machine, waiting for subsequent processes.

[0020] Furthermore, the thickness of the wafer mentioned above ranges from 20um to 250um.

[0021] S2: performing a ring cutting process on the wafer.

[0022] Among them, this step includes the following contents: S21: using a first laser beam to cut the wafer until the wafer is cut through and a first cutting line is formed.

[0023] Exemplarily, by adjusting the software settings in the laser cutting machine, it generates a first laser beam, and uses the first laser beam to irradiate a designated position of the wafer, such as Figure 2Afterwards, through the relative movement of the first laser beam and the wafer, the first laser beam is used to cut the wafer for several circles until the wafer is cut through to form a first cutting path.

[0024] The designated position may be a position on the surface of the wafer where the horizontal distance from the edge of the taiko ring is a fixed value. Afterwards, by rotating the carrier, the first laser beam cuts a number of circles on the wafer to form a circular first cutting path. The specific number of cutting circles of the first laser beam can be set according to the actual thickness of the wafer. The thicker the wafer, the more cutting circles.

[0025] S22: Cleaning the first cutting path using a second laser beam concentric with the first laser beam.

[0026] For example, in S21, the wafer is cut through and a first cutting path is formed. In order to remove the high-temperature silicon chips that may remain in the first cutting path, the software settings in the laser cutting machine are adjusted to generate a second laser beam concentric with the first laser beam, and the second laser beam is used to clean the first cutting path for several circles, such as Figure 3 In order to ensure the cutting effect of the first laser beam on the wafer, the power of the first laser beam is set to be higher than that of the second laser beam. At the same time, in order to make the second laser beam fully clean the high-temperature silicon chips in the first cutting path, the spot diameter of the second laser beam is set to be larger than that of the first laser beam.

[0027] Furthermore, the spot diameter of the second laser beam may be 30 um, and the spot diameter of the first laser beam may be 20 um.

[0028] Furthermore, the power of the second laser beam is half of the power of the first laser beam. For example, when forming the first laser beam, the laser power of the laser cutting machine is adjusted to 100%, and when forming the second laser beam, the laser power of the laser cutting machine is adjusted to 50%.

[0029] Furthermore, the ring cutting process described above is applicable to ring cutting with film, that is, during the cutting process, the back side of the wafer is still covered with the back film.

[0030] The method for improving the laser ring cutting effect provided by the embodiment of the present application is to set the wafer ring cutting process as step-by-step cutting, and in the first step of cutting, use a first laser beam with a small spot and high power to cut the wafer to ensure that the wafer is cut through, and in the second step of cutting, use a second laser beam with a large spot and low power to clean the first cutting path to ensure that residual high-temperature silicon chips are removed, thereby increasing the ring removal window, improving the cutting effect of the wafer ring cutting process, and avoiding cracks in the Taiko thinned wafer during subsequent ring removal.

[0031] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection created by this application.

Claims

1. A method for improving the effect of laser ring cutting, characterized in that: include: S1: providing a wafer with a taiko ring formed on the back side, wherein the wafer is placed on a carrier plate; S2: performing a ring cutting process on the wafer, the ring cutting process comprising: S21: using a first laser beam to cut the wafer until the wafer is cut through and a first cutting line is formed; S22: using a second laser beam concentric with the first laser beam to clean the first cutting path; The spot diameter of the second laser beam is larger than that of the first laser beam, and the power is smaller than that of the first laser beam.

2. The method for improving the effect of laser ring cutting according to claim 1, characterized in that: The spot diameter of the first laser beam is 20 um, and the spot diameter of the second laser beam is 30 um.

3. The method for improving the effect of laser ring cutting according to claim 1, characterized in that: The power of the second laser beam is half of that of the first laser beam.

4. The method for improving the effect of laser ring cutting according to claim 1, characterized in that: The circumcision process is suitable for circumcision with membrane.

5. The method for improving the effect of laser circumcision according to claim 1, characterized in that: The thickness of the wafer ranges from 20um to 250um.

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