Thin wafer cutting method

Abstract

The invention relates to the technical field of chips, in particular to a thin wafer cutting method. Comprising the following steps: S1, performing front surface shallow cutting on a wafer, and selecting an ultrathin cutter with a V-shaped edge as a cutting knife to form a V-shaped cutting groove; s2, attaching a front surface protective film to the front surface of the wafer; s3, thinning the back surface of the wafer; s4, attaching a through cutting film to the back surface of the wafer, and removing the front surface protection film; s5, placing the wafer on a flexible platform of an invisible cutting machine in a manner that the front surface of the wafer faces downwards, performing laser invisible cutting on the back surface of the wafer, and separating the wafer into a plurality of chips; s6, expanding the wafer, and expanding the distance between the chips; s7, carrying out ultraviolet irradiation on the penetrating and cutting film; and S8, taking away the chip. Compared with the prior art, the ultra-thin V-shaped edge cutting knife is utilized to perform shallow cutting in the cutting channel on the front surface of the wafer, and the V-shaped pre-slotting guides the invisible cutting crack to extend, so that the risk of disordered extension of the crack in invisible cutting is reduced, and the process cost of wafer cutting is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the chip technical field, specifically a thin wafer cutting method. BACKGROUND

[0002] Chip packaging is essential in the process of semiconductor device manufacturing, and wafer cutting as the core process in the packaging process has an important influence on the quality and reliability of the final chip. In particular, with the increase of storage capacity, multi-chip function and continuous miniaturization of advanced packaging all require thinner wafer slices. The use of traditional mechanical cutting processing methods inevitably produces chip side collapse and back collapse, which greatly affects the chip strength of ultra-thin chips. In order to reduce the influence of side collapse and back collapse in mechanical cutting on chip strength, laser stealth cutting process is usually used, which forms a modified layer and a crack in the material inside in a very short time with high energy through ultrafast laser, and then completes the cutting through crack propagation caused by external stress. However, the increasingly thick metal structure in the cutting path leads to the inability to crack in the specified direction after stealth cutting, increasing the risk of chip collapse and other abnormalities.

[0003] To solve the above problems, the current conventional method performs multiple laser slotting processes before stealth cutting, and thins to the preset thickness after stealth cutting. However, multiple laser slotting increases the risk of thermal damage and increases the process cost of wafer cutting. In the process, multiple film reversal is required, which is complicated and increases the risk of wafer cracking. SUMMARY

[0004] The present application is to overcome the shortcomings of the prior art and provide a thin wafer cutting method.

[0005] To achieve the above purpose, a thin wafer cutting method is designed, which includes the following steps: S1, shallow cutting the front surface of the wafer, the cutting knife selects an ultra-thin knife with a V-shaped edge to form a V-shaped cutting groove; S2, sticking a front protective film on the front surface of the wafer; S3, thinning the back surface of the wafer; S4, sticking a through-cut film on the back surface of the wafer and removing the front protective film; S5, placing the front surface of the wafer downward on the soft platform of the stealth cutting machine, laser stealth cutting the back surface of the wafer, and separating it into several chips; S6, expanding the wafer to enlarge the spacing between the chips; S7, irradiating the through-cut film with ultraviolet light; S8, taking out the chips.

[0006] The cutting depth in step S1 is 5-15um, the cutting speed is 10-40mm / s, the rotating speed is 30000-60000rpm, and the cutting width is 10-20um.

[0007] The front protective film in step S2 is BG film.

[0008] In step S3, the thickness of the wafer is reduced to 40-775um.

[0009] In step S6, the spacing between adjacent chips is 15-100um.

[0010] Compared with the prior art, the present application has the following beneficial effects: 1. The wafer is pre-slotted on the front surface by mechanical cutting, which reduces the thickness of the metal layer in the cutting path, reduces the difficulty of crack propagation, guides the propagation of the invisible cutting crack, improves the propagation effect of the invisible cutting crack, and reduces the quality risk caused by the disordered extension of the crack.

[0011] 2. The shallow cutting is performed by using an ultrathin bevel cutting knife, which forms a chamfer during the cutting process, reduces the risk of front surface collapse, and realizes high mold strength and high quality processing. Compared with multiple laser slotting and cutting, there is no risk of thermal damage, and the process cost is reduced.

[0012] 3. After the wafer is thinned to the target thickness, the back surface is pasted with a through-cut film, and the invisible cutting is directly performed through the through-cut film. Compared with the conventional process, the number of grinding is reduced, the process flow of multiple film turning is reduced, and the risk of crack during film turning is reduced, and the processing efficiency is improved. BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1 The figure is a schematic diagram of step S1 of the present application.

[0014] Figure 2 The figure is a schematic diagram of step S2 of the present application.

[0015] Figure 3 The figure is a schematic diagram of step S3 of the present application.

[0016] Figure 4 The figure is a schematic diagram of step S4 of the present application.

[0017] Figure 5 The figure is a schematic diagram of step S5 of the present application.

[0018] Figure 6 The figure is a schematic diagram of step S6 of the present application. DETAILED DESCRIPTION

[0019] The present application will be further described below with reference to the accompanying drawings.

[0020] AsFigures 1 to 6 As shown, the thin wafer cutting method of the present application comprises the following steps: S1, shallow cutting on the front surface of the wafer 1, the cutting knife is selected as an ultrathin knife 2 with a V-shaped edge, forming a V-shaped cutting groove 3, and forming a chamfer during cutting, which can realize high mold strength and high-quality processing. The cutting depth is 5-15um, the cutting speed is 10-40mm / s, the rotation speed is 30000-60000rpm, and the cutting width is 10-20um.

[0021] S2, the front surface of the wafer 1 is attached to the front protective film 4. The front protective film 4 is selected as a BG film to prevent the front surface of the wafer 1 from being damaged during the thinning process in the subsequent step S3.

[0022] S3, the back surface of the wafer 1 is thinned to reduce the thickness of the wafer 1 to 40-775um.

[0023] S4, the wafer 1 is attached to the back surface of the wafer 1, and the front protective film 4 is removed, and the through-cut film 5 plays a protective and supporting role on the back surface of the wafer 1.

[0024] S5, the wafer 1 is placed on the soft platform of the invisible cutting machine with the front surface downward, and the back surface of the wafer 1 is laser invisible cut to separate into several chips 6.

[0025] S6, the wafer 1 is expanded to expand the spacing between the chips 6 and the chips 6, and the spacing between the adjacent chips 6 is 15-100um.

[0026] S7, the through-cut film 5 is irradiated with ultraviolet light to remove the adhesion between the through-cut film 5 and the wafer 1.

[0027] S8, the chip 6 is taken out.

[0028] The present application uses an ultrathin V-shaped edge cutting knife on the front surface of the wafer to perform shallow cutting in the cutting groove, guides the invisible cutting crack propagation through the V-shaped pre-slot, reduces the risk of disordered propagation of the crack in invisible cutting, and reduces the process cost of wafer cutting. The through-cut film is attached to the back surface of the wafer for invisible cutting process, which reduces the repeated film flow process in the invisible cutting process and improves the processing efficiency.

Claims

1. A thin wafer dicing method characterized by: It comprises the following steps: S1, shallow cutting on the front side of the wafer (1), the cutting knife is selected as a super-thin knife (2) with a V-shaped edge to form a V-shaped cutting groove (3); S2, the wafer (1) is attached to the front side with a front protective film (4); S3, the wafer (1) is thinned on the back side; S4, the wafer (1) is attached to the back side with a through-cut film (5), and the front protective film (4) is removed; S5, the wafer (1) is placed on the soft platform of the invisible cutting machine with the front side down, the wafer (1) is laser invisible cut on the back side, and is separated into a plurality of chips (6); S6, the wafer (1) is expanded to increase the spacing between the chips (6); S7, the through-cut film (5) is irradiated with ultraviolet light; S8, the chip (6) is taken away.

2. The thin wafer dicing method of claim 1, wherein: In the step S1, the cutting depth is 5-15 um, the cutting speed is 10-40 mm / s, the rotating speed is 30000-60000 rpm, and the cutting width is 10-20 um.

3. The method of claim 1, wherein: In the step S2, the front protective film (4) is selected as a BG film.

4. The method of claim 1, wherein: In the step S3, the thickness of the wafer (1) is thinned to 40-775 um.

5. The method of claim 1, wherein: In the step S6, the spacing between the adjacent chips (6) is 15-100 um.

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