KR20120076862A - Wafer cutting system using laser beam - Google Patents

Abstract

PURPOSE: A wafer cutting system using a laser beam is provided to prevent physical damage to a wafer by arranging a buffer member between the wafer and a stage. CONSTITUTION: A wafer cutting system using a laser beam comprises a stage(100), a laser beam generating unit(200), a moving unit, and a frozen nitrogen gas injection unit(300). A wafer(1) is loaded on the stage. The laser beam generating unit is located above the stage and projects a laser beam to the wafer. The moving unit moves the stage or the laser beam generating unit. The frozen nitrogen gas injection unit is formed in the shape of a nozzle(301) and injects frozen nitrogen gas to the position of the wafer irradiated with the laser beam.

Description

Wafer cutting system using laser beam

The present invention relates to a wafer cutting system using a laser beam, and more particularly, to a wafer cutting system using a laser beam capable of full cutting a wafer under optimum conditions while minimizing the physical effects of laser beam processing. .

In the semiconductor device manufacturing process, a substantially disk-shaped semiconductor wafer is partitioned into a plurality of regions by cutting lines, which are arranged in a lattice shape on the surface thereof. Circuits such as ICs and LSIs are formed in the divided regions, and the semiconductor wafers are separated by cutting the semiconductor wafers according to the cutting schedule lines, thereby manufacturing semiconductor chips.

That is, a silicon wafer in which various semiconductor elements are patterned on the surface is cut into semiconductor chips of a predetermined size along the boundary line of the patterning. As a method of cutting a silicon wafer into a semiconductor chip, methods such as dicing and scribing are known.

Among them, a technique is disclosed in which a silicon wafer is cut in a manner of simultaneously cooling while continuously irradiating a laser beam onto the surface of the silicon wafer. In this case, a laser beam of pulses including two or more kinds of wavelengths is collected and irradiated onto the silicon wafer, and a focus point of the laser beam is formed on the surface of the silicon wafer, and at the same time, one or a plurality of laser beams are formed inside the silicon wafer. Wafer cutting is performed by forming a light collecting point and irradiating a laser beam along the cutting direction.

However, due to the thermal and physical energy of the laser beam irradiated on an object such as a wafer, thermal damage of the wafer may occur, and debris such as dust may occur. Furthermore, although there is an optical form, depending on the irradiation of the laser beam, a certain physical impact may occur on the wafer, thereby causing a problem of damage to the precision element.

Therefore, the problem to be solved by the present invention is to provide a wafer cutting system using a laser beam that can minimize the side effects of the laser beam irradiation in the optimum conditions.

In order to solve the above problems, the present invention is a wafer cutting system using a laser beam, the system is a stage on which the wafer is cut; Laser beam generation means spaced above the stage at predetermined intervals for irradiating a laser beam to the wafer; Moving means for moving said stage or laser beam generating means; And cooling nitrogen gas injection means for injecting cooling nitrogen gas into the laser beam irradiation position of the wafer, wherein the cooling nitrogen gas injection means is in the form of a nozzle. do.

In one embodiment of the present invention, the system is provided with a buffer member for mitigating the physical impact of the laser beam irradiation between the stage and the laser beam, the system is nitrogen gas cooling means for cooling the incoming nitrogen gas It further comprises, the nitrogen gas injection means is connected to the nitrogen gas cooling means rear end.

In an embodiment of the present invention, the laser beam cuts the wafer in multiple paths within the cutting line of the wafer, and the multiple paths are combined in such a manner as to not be continuous with each other in one direction, thereby cutting the wafer. In addition, energy patterns of the laser beams of the plurality of paths overlap each other, and the overlap range is 0 to 10 μm. In addition, the moving speed of the laser beam is 0 to 400mm / s, the number of laser beam processing is less than 10 times.

The wafer cutting system according to the present invention blows cooled nitrogen gas, not the normal temperature, to the position where the laser beam is irradiated. This minimizes thermal damage to the wafer, and prevents physical damage to the wafer by providing a separate buffer member between the wafer and the stage. Furthermore, by setting a plurality of movement paths of the laser within a single cutting line and overlapping them, an optimum cutting effect is achieved.

1 is a schematic diagram of a wafer cutting system according to an embodiment of the present invention.
2 is a schematic diagram of a wafer cutting system according to an embodiment of the present invention.
3 is a view illustrating a moving path in a cutting line of a laser beam according to an exemplary embodiment of the present invention.
4 is a schematic diagram illustrating a wafer cutting method according to an embodiment of the present invention.
5 illustrates a case where the laser beam is moved along the X axis, and FIG. 6 illustrates a case where the laser beam is moved along the Y axis.
7 is a block diagram of a wafer cutting system in accordance with an embodiment of the present invention.
8 is a block diagram of a wafer cutting system according to an embodiment of the present invention.

Hereinafter, a wafer cutting method and system according to an embodiment of the present invention will be described in detail. However, the following drawings and examples are all intended to illustrate the invention and the scope of the invention is not limited by the following.

1 is a schematic diagram of a wafer cutting system according to an embodiment of the present invention.

Referring to FIG. 1, the wafer cutting system includes a laser beam generating means 200 and a stage 100 as described above, and includes a wafer 1 provided on the stage 100. In addition, the wafer cutting system according to the present invention is connected to the laser beam generating means 200, the cooling nitrogen gas for injecting the cooling nitrogen gas at the position (p) irradiated with the laser beam from the laser beam generating means 200 In addition, the injection means 300, wherein the cooling nitrogen gas injection means 300 is a nozzle type connected to the tube having a nozzle 301 is provided at one end, the nozzle 301 is a laser beam is irradiated Configured to blow cooling nitrogen gas into position. To this end, the cooling nitrogen gas injection means 300 is preferably in the form of a nozzle fixed to the laser beam generating means (200). In addition, the cooling nitrogen gas injection means 300 may be connected to the cooling means 302 for cooling the nitrogen gas since the cooling nitrogen gas is used instead of the normal temperature nitrogen gas to reduce thermal damage of the wafer. . Therefore, the nitrogen gas injected at a normal temperature is cooled by the cooling means 302, and the cooled nitrogen gas proceeds to the cooling nitrogen gas injection means 300 at the rear end of the cooling means 302, and the nozzle 301. Is injected onto the wafer.

In one embodiment of the present invention, the laser beam is a laser beam used for cutting a wafer, and the type of the laser beam is not limited in the present invention.

According to another embodiment of the present invention, a wafer cutting system may further include a damping member having a damper function to absorb a so-called shock, which is a physical impact caused by laser beam processing between the stage and the wafer. have. That is, when a buffer member such as paper is provided between the stage of the hard metal material and the wafer, it has been found that the physical impact of the wafer due to the laser beam irradiation can be alleviated. That is, the present invention inserts a buffer member such as a tape or a gap paper, which can absorb a physical shock caused by a laser beam, to mitigate the impact the wafer receives. In addition, polishing the back side of the wafer results in a difference of 5% or more in chip strength than without polishing.

2 is a schematic diagram of a wafer cutting system according to an embodiment of the present invention.

Referring to FIG. 2, a buffer member 800 such as paper is interposed between the stage 100 and the wafer 1, and effectively absorbs the physical impact of the wafer due to laser beam irradiation, so that the actual wafer and the stage come into contact with each other. This effectively prevents physical cracking and the like of the wafer.

According to another embodiment of the present invention, when the laser beam is moved along the cutting line of the wafer, a method of setting the plurality of laser beam paths is provided.

3 is a view illustrating a moving path in a cutting line of a laser beam according to an exemplary embodiment of the present invention.

Referring to Figure 3, the laser beam in the cutting line cuts the wafer in three paths A, B, C. At this time, it is preferable that the condensing densities (energy patterns) of the laser beams in each path touch each other or cross (overlap) to a predetermined level. In one embodiment of the present invention, the overlapping range of the laser beam in each path is preferably 0 to 10 μm, more preferably 3 to 8 μm. If the laser beam paths are spaced apart from each other, it is difficult to expect a sufficient cutting effect, and if the laser beam paths overlap more than the above range, a uniform cutting effect does not occur in the cutting line.

Furthermore, the present invention does not configure the movement path order of the laser beam in the cut line in a discontinuous manner, but in a continuous manner to the left or the right.

For example, a wafer in A-B-C paths may be cut first, then A, and finally C. Alternatively, the wafer may be cut into A first, then C, and finally B paths. In other words, the present invention does not continuously move the laser beam processing path like A-B-C or C-B-A, because it produces a uniform cutting effect by the laser beam.

Table 1 below shows the cutting sequence (number) for the A, B, and C paths according to one embodiment of the present invention.

A B C Example 1 2 One 3 Example 2 One 2 3 Example 3 One Example 4 1,4 3 2,5

In addition, for the present invention, an appropriate laser beam moving speed in each path was selected from 0 to 400 mm / s. If it is faster than the above speed, sufficient laser beam cutting effect cannot be expected.

In addition, in the case of the present invention, the number of laser beam irradiation is set to a plurality, and in the case of one embodiment of the present invention, the number of irradiation of the combined laser beam is set to 10 or less. The number of times the laser beam is irradiated is calculated once in a case where the laser beam is irradiated in the cut line in a combination as shown in Table 1.

The wafer cutting system according to the present invention provides the electrical power (Laser E-power (W)) and the physical power (Laser P-poer (W)) of the laser beam as shown in Table 2 below. In this case, the electrical power refers to the electrical and electronic power supplied from the laser, and the physical power means the power is changed by optically adjusting the size of the laser beam.

A B C Laser E-power (W) 6 6 6 5.5 5.5 5.50 5 5 5 Laser P-power (W) 5.5 5.5 5.5 5 5 5 4.5 4.5 4.5

Furthermore, the present invention found that the depth of focus (DOF) of the laser, the magnification of the focus lens, and the processing speed depend on the wafer cross-section depending on the thickness of the wafer. As a result, when the processing speed is 0 to 400 mm / s, the lens magnification is 2 to 50 times, and the depth of focus is 0 to 30um, the wafer cross-sectional state is improved, and the chip strength is improved.

The present invention is based on the fact that the cutting effect of the wafer varies considerably according to the above process conditions, that is, the combination of the process conditions such as the laser beam movement path order, speed, frequency, overlap level, and power of the laser beam within the cutting line. According to the present invention, cooling nitrogen injection and the buffer member are provided between the wafer and the stage together with the combination of the above fixed conditions, thereby effectively performing a full cutting of the wafer cross section, and in particular, the chip strength of the blade sawing level. Improved.

Another embodiment of the present invention provides a technical configuration in which the axis of light density and the direction of wafer movement direction of the laser beam are 45 degrees.

4 is a schematic diagram illustrating a wafer cutting method according to an embodiment of the present invention.

Referring to FIG. 4, the laser beam irradiated onto the wafer to be cut has an ellipse condensing density having a long axis x and a short axis y. That is, the shape of the laser beam is composed of S (horizontal) wave and P (vertical) wave. In this case, due to the energy density of two unequal waves, the laser beam is condensed and irradiated onto the wafer in the form of an ellipse rather than a circle. Here, the light collecting density corresponds to the energy pattern of the laser beam, and in the prior art, in spite of this characteristic of the energy pattern of the laser beam, the wafer is cut in an orthogonal shape, so that the profile of the cutting planes of the X and Y axes of the wafer cutting line There was a problem that changed. Therefore, the present invention finds the above-described problems of the prior art, and in order to solve the above problem, the cutting line of the wafer is configured to be inclined by 45 degrees with respect to the elliptic axis of the laser beam. That is, referring to FIG. 4, the x-axis and the y-axis, which are orthogonal axes of the cutting line, are 45 degrees with respect to the x-axis (long axis) and y-axis (short axis), which are the reference axis (ellipse axis) of the ellipse of the elliptic laser beam. Achieve. That is, when the irradiation point of the laser beam is moved along the cutting line, the laser beam moves the cutting line in a form inclined at 45 degrees, and thus, the light condensing density profiles in the X and Y axes are all inclined at 45 degrees. Form.

5 illustrates a case where the laser beam is moved along the X axis, and FIG. 6 illustrates a case where the laser beam is moved along the Y axis.

5 and 6, it can be seen that the laser beam pattern on the X-axis and the laser beam pattern on the Y-axis are equally inclined at 45 degrees. According to an embodiment of the present invention, the laser beam has a fixed orientation angle, and as the wafer is rotated 90 degrees, the wafer can be cut in the same pattern in a rectangular structure, which is cut in the form of tilting the wafer at 45 degrees. It is a unique effect of the present invention that can be achieved by advancing the process.

7 is a block diagram of a wafer cutting system in accordance with an embodiment of the present invention.

According to an embodiment of the present invention, a wafer cutting system includes a laser beam generating means (510) for generating a laser beam to cut a wafer, a stage (520) on which the laser beam is irradiated and cut, and the laser beam is generated. And a moving means 530 for moving the beam generating means or stage, wherein the moving means tilts and moves the laser beam generating means or stage to 45 with respect to a laser beam uniaxial having an elliptical condensing density. That is, the moving means may include the laser beam generating means such that an orthogonal cutting line (X-axis, Y-axis) of the wafer cut about the long axis (x axis) and the short axis (y axis) of the elliptical laser beam forms 45 degrees. Move the stage.

8 is a block diagram of a wafer cutting system according to an embodiment of the present invention.

Referring to FIG. 8, in the wafer cutting system according to the present invention, the semiconductor wafer 1 is provided with a stage 100 provided on a slide table reciprocating along a predetermined horizontal direction (X direction or Y direction). Is mounted on. The slide table is supported by a plurality of guide rails to be slidable in the X direction or the Y direction in a horizontal state. In addition, the stage 100 may use a rotatable table. That is, the stage 100 may be rotated to have an arbitrary rotation angle θ with respect to the reference position. In addition, the wafer 1 mounted on the upper surface of the stage 100 is positioned after being fixed to the stage 100 by, for example, a suction chuck. For convenience of description below, a configuration for moving the position of the stage such as a slide table and a plurality of guide rails is referred to as a 'moving means'. The laser beam generating means 200 including an optical system and a laser oscillator is disposed above the stage, and a laser beam having a single wavelength or a plurality of wavelengths is collected from the laser beam generating means 200, and the stage 100 is provided. It is irradiated to the wafer 1 of the upper surface. At this time, the movement direction of the stage 100 with respect to a fixed coordinate axis of the laser beam generating means 200 (this is based on an elliptic axis of the laser beam energy pattern having an elliptical shape, ie, the major axis x and the minor axis y). The coordinate axis of is 45 degrees. Alternatively, the laser beam generating means 200 may be moved at 45 degrees with respect to the vertical coordinate of the wafer, and in any case, the wafer cutting line cut by the focused laser beam is 45 with respect to the elliptic axis of the laser beam. It will constitute a diagram.

As described above, the present invention provides a configuration for installing and controlling a device for designing the shortest distance to the optical path of the laser, and for extending the beam to reduce the shock caused by the light and to mitigate the physical shock. It also facilitates precision machining by using a combination of measurement focusing using a displacement sensor to increase accuracy and more precise vision focusing to cover wafer variations.

As mentioned above, although preferred embodiment about this invention was described, this invention is not limited to the above-mentioned embodiment, It is defined by what was described in the claim, and it is clear that various deformation | transformation and adaptation are possible in the technical field to which this invention belongs. Do.

Claims (7)

A wafer cutting system using a laser beam, the system
A stage on which a wafer to be cut is mounted;
Laser beam generation means spaced above the stage at predetermined intervals for irradiating a laser beam to the wafer;
Moving means for moving said stage or laser beam generating means; And
And cooling nitrogen gas injection means for injecting cooling nitrogen gas into the laser beam irradiation position of the wafer, wherein the cooling nitrogen gas injection means is in the form of a nozzle. The method of claim 1,
The system is a wafer cutting system using a laser beam, characterized in that the buffer member is provided between the stage and the laser beam to mitigate the physical impact of the laser beam irradiation. The method of claim 1,
The system further comprises a nitrogen gas cooling means for cooling the incoming nitrogen gas, the nitrogen gas injection means is connected to the rear end of the nitrogen gas cooling means, the wafer cutting system using a laser beam. The method of claim 1,
And the laser beam cuts the wafer in a plurality of paths within the cutting line of the wafer. The method of claim 4, wherein
And the plurality of paths are combined in a non-continuous manner in one direction to cut the wafer. 6. The method of claim 5,
The energy pattern of the laser beam of the plurality of paths overlap each other, the overlap range is 0 to 10μm wafer cutting system using a laser beam, characterized in that. 6. The method of claim 5,
The moving speed of the laser beam is 0 to 400mm / s, and the laser beam cutting frequency is less than 10 times, the wafer cutting system using a laser beam.

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