TW201712748A - Wafer processing method - Google Patents

Abstract

Provides an SDBG that prevents grinding debris from remaining on the side of the component wafer The method of processing wafers. a segmentation in which multiple bars intersect each other A method of processing a wafer in which a component is formed in each region of a surface drawn by a predetermined line, characterized by comprising: a frame unit forming step of attaching a surface of the wafer to an expansion tape that blocks an opening of the annular frame And forming a frame unit; the reforming layer forming step of irradiating a laser beam having a wavelength transparent to the wafer from a back surface of the wafer constituting the frame unit, and forming a predetermined segmentation along the surface of the inside of the wafer a modified layer of the wire; a first grinding step, after performing the frame unit forming step and the reforming layer forming step, grinding the back surface of the wafer with a grinding stone while supplying the grinding water to follow the The reforming layer divides the wafer into individual component wafers; and a second grinding step, after performing the first grinding step, expanding the expansion tape and providing a spacer crystal between adjacent ones of the component wafers The round side is supplied with grinding water while grinding the back side of the wafer with a grinding stone to thin the wafer to the finished thickness.

Description

Wafer processing method Field of invention

The present invention relates to a method of processing a wafer such as a semiconductor wafer.

Background of the invention

In the process of the semiconductor device, a plurality of predetermined dividing lines called dicing streets formed in a lattice shape are divided into a plurality of lines on the surface of a semiconductor wafer such as a substantially circular disk-shaped germanium wafer or a gallium arsenide wafer. Areas, and components such as ICs and LSIs are formed in the divided areas.

A semiconductor wafer (hereinafter sometimes referred to simply as a wafer) is processed into a predetermined thickness after grinding the back surface by a grinding device, and then divided into individual pieces by a cutting device (cutting device). The component wafer and the divided component wafer are widely used in various electronic devices such as mobile phones and personal computers.

In recent years, electronic devices such as mobile phones and computers have been demanding to be lighter and smaller, and to require thinner component chips. As a division technique for thinning a wafer and dividing it into a component wafer having a high flexural strength, a division technique called a pre-cut method has been developed and put into practical use (for example, refer to Japanese Patent Laid-Open No. Hei 11-40520) .

The first dicing method is a dividing groove formed from a surface of a semiconductor wafer along a predetermined dividing line to a predetermined depth (corresponding to a depth of a finished wafer thickness of the element wafer), and a back surface of the semiconductor wafer on which the dividing groove is formed on the surface Grinding is performed to expose the dividing groove to the back surface to divide the wafer into individual element wafers, and the thickness of the element wafer can be processed to about 50 μm.

On the other hand, in recent years, a technique of using a laser beam to divide a wafer into individual component wafers has been developed and put into practical use. One of the laser processing methods is to position a condensing point of a laser beam having a wavelength (for example, 1064 nm) having a penetrating wavelength to the inside of a wafer corresponding to a dividing line, and to divide along the division. A method in which a line is irradiated with a laser beam to form a modified layer inside the wafer, and then an external force is applied to the wafer by the dividing device to divide the wafer into individual element wafers using the modified layer as a starting point of the division. This processing method is called SD (Stealth Dicing) processing.

In order to achieve narrow scribe line, a SDBG processing method composed of a combination of the SD processing method and the grinding method has been developed and put into practical use.

Prior technical literature Patent literature

Patent Document 1: Japanese Patent Laid-Open No. 11-40520

Patent Document 2: Japanese Patent Laid-Open Publication No. 2005-064232

Summary of invention

However, in the SDBG processing method, there is a problem that the grinding debris intrudes into a slight gap (about 1 μm) between the component wafers which are divided by the back surface of the ground wafer, and the grinding debris remains. On the side of the completed component wafer.

The present invention has been made in view of the above problems, and an object thereof is to provide a method for processing a wafer formed by the SDBG method which can prevent grinding debris from remaining on the side surface of an element wafer.

According to the present invention, there is provided a method of processing a wafer in which respective elements are formed in respective regions of a surface drawn by a plurality of intersecting dividing lines, and the wafer processing method is characterized by a frame unit forming step of attaching a surface of the wafer to an expansion tape that blocks an opening of the annular frame to form a frame unit; and a reforming layer forming step of irradiating the wafer from a back surface of the wafer constituting the frame unit a laser beam having a penetrating wavelength, and forming a reforming layer along a dividing line in the vicinity of a surface inside the wafer; a first grinding step, performing the frame unit forming step and the reforming layer forming step Thereafter, while grinding the water, grinding the grinding stone to grind the back surface of the wafer to divide the wafer into individual element wafers along the modified layer; and performing the first grinding step in the second grinding step After the grinding step, the expansion tape is expanded and the back surface of the wafer is supplied with grinding water and the back surface of the wafer is ground with a grinding stone to thin the wafer to Finished product thickness .

Preferably, the wafer processing method further includes a wafer transfer step and a film breaking step, and the wafer transfer step is performed on the back surface of the wafer after the second grinding step is performed. Attaching a film and attaching a dicing tape to the adhesive film, and supporting the outer peripheral portion of the dicing tape by an annular frame, and peeling off the expanded tape attached to the surface of the wafer, the adhesive film breaking step is After the wafer transfer step is performed, the adhesive film exposed between the element wafers is irradiated with a laser beam to break the adhesive film.

According to the method for processing a wafer of the present invention, by grinding the element wafers apart from each other in the second grinding step and performing the fine grinding, the grinding debris that has entered the space between the element wafers can be ground by grinding. The water is easily washed away, so that the effect of preventing the grinding debris from remaining on the side of the component wafer can be exerted.

2‧‧‧Laser beam irradiation unit

20, 66‧‧‧Working table

21‧‧‧Component chip

22, 68‧‧‧ fixture

23‧‧‧ interval

25‧‧‧DAF

32‧‧‧ grinding device

34‧‧‧Base

34a‧‧‧ recess

36‧‧‧ pillar

38‧‧‧rails

4‧‧‧Laser beam generating unit

40‧‧‧ grinding unit

40‧‧‧Retractable shield

42‧‧‧ spindle housing

44‧‧‧Support

46‧‧‧Mobile abutments

48‧‧‧ Spindle

49‧‧‧Motor

50‧‧‧ wheel seat

52‧‧‧ grinding wheel

54‧‧‧ wheel abutment

56‧‧‧grinding grindstone

58‧‧‧Ball screw

6‧‧‧concentrator (laser head)

60‧‧‧pulse motor

62‧‧‧ grinding unit feed mechanism

64‧‧‧Working table mechanism

72‧‧‧Operator panel

74‧‧‧Clamp support member

76‧‧‧ grinding water supply nozzle

78‧‧‧ grinding water

8‧‧‧Laser oscillator

10‧‧‧Repeat frequency setting device

11‧‧‧Semiconductor wafer

11a‧‧‧ surface

11b‧‧‧Back

12‧‧‧ pulse width adjustment equipment

13‧‧‧Division line

14‧‧‧Power adjustment equipment

15‧‧‧ components

16‧‧‧Mirror

17‧‧‧Frame unit

18‧‧‧ concentrating objective lens

19‧‧‧Modified layer

A‧‧‧ wafer loading and unloading position

B‧‧‧ grinding position

A, a, b, X, Y, Z, X1, X2‧‧‧ arrows

T1‧‧‧Expanding tape

T2‧‧‧ cutting tape

F‧‧‧Ring frame

1 is a perspective view of a surface side of a semiconductor wafer.

2 is a perspective view of a frame unit.

Figure 3 is a block diagram of a laser beam irradiation unit.

Figure 4 is a partial cross-sectional side view showing the step of forming a modified layer.

Figure 5 is a perspective view of the grinding device.

6 is a partial cross-sectional side view showing the first grinding step, and shows a state in which (A) is a state before grinding and (B) a state in which the wafer is divided into component wafers in order to perform the first grinding step.

Fig. 7 is a partial cross-sectional side view showing the second grinding step.

Figure 8 is a partial cross-sectional side view showing the step of breaking the film.

Form for implementing the invention

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Referring to Fig. 1, a front side perspective view of a semiconductor wafer (hereinafter, simply referred to as a wafer) 11 which is a target of the processing method of the present invention is shown.

On the surface 11a of the semiconductor wafer 11, a plurality of predetermined dividing lines 13 are formed in a lattice shape, and elements 15 such as ICs and LSIs are formed in each of the areas divided by the dividing line 13 to be formed.

In the wafer processing method of the present embodiment, as shown in FIG. 2, first, a frame unit forming step of attaching the surface 11a of the wafer 11 to the ring frame F is performed. The frame unit 17 is formed by attaching the expansion tape T1 that blocks the opening of the annular frame F. In the frame unit 17, the wafer 11 attached to the expansion tape T1 exposes the back surface 11b.

After the back surface 11b of the wafer 11 is exposed to hold the wafer 11 of the frame unit 17 on the work chuck 20, a reforming layer forming step of irradiating the back surface 11b of the wafer 11 is performed. A laser beam having a penetrating wavelength (for example, 1064 nm) is applied to the wafer 11 to form a reforming layer 19 along the dividing line 13 near the surface inside the wafer 11.

Referring to Fig. 3, a block diagram of the laser beam irradiation unit 2 is shown. The laser beam irradiation unit 2 is composed of a laser beam generating unit 4 and a concentrator (laser head) 6.

The laser beam generating unit 4 includes a laser oscillator 8 that oscillates to generate a YAG pulse laser or a YVO4 pulse laser, and a repetition frequency setting device 10. Pulse width adjustment device 12 and power adjustment device 14.

The pulsed laser beam, which is adjusted to a predetermined power by the power adjusting device 14 of the laser beam generating unit 4, is reflected on the mirror 16 of the concentrator 6 to further converge and illuminate the objective lens 18 by collecting light. Up to the semiconductor wafer 11 held on the work chuck 20.

The reforming layer forming step will be described in further detail with reference to FIG. The wafer 11 is sucked and held by the expansion tape T1 on the working chuck 20 of the laser processing apparatus, and the annular frame F of the frame unit 17 is sandwiched and fixed by the jig 22.

The condensing point of the laser beam having a wavelength that is transparent to the wafer 11 is positioned near the surface of the wafer 11 by the concentrator 6, and the laser beam is irradiated from the side of the back surface 11b of the wafer 11, and The working chuck 20 is fed in the direction of the arrow X1, whereby the reforming layer 19 is formed inside the wafer 11 along the dividing line 13 elongated in the first direction.

Then, by feeding the working clamping table 20 of the holding wafer 11 and indexing the laser beam to the adjacent dividing line 13 and processing the working chuck 20 in the direction of the arrow X2, The reforming layer 19 is formed inside the wafer 11.

In this manner, the machining feed direction of the work chuck 20 is alternately changed to the X1 direction or the X2 direction, and the reforming layer 19 is formed inside the wafer 11 along all the planned dividing lines 13 elongated in the first direction.

Next, after the work chuck 20 is rotated by 90 degrees, the reforming layer 19 is formed inside the wafer 11 along all the planned dividing lines 13 elongated in the second direction orthogonal to the first direction.

The processing conditions of this reforming layer forming step are set as follows, for example.

Light source: LD-excited Q-switch Nd: YVO4 pulse laser

Wavelength: 1064nm

Average output: 0.1W

Repeat frequency: 50kHz

Processing feed rate: 200mm / sec

After the reforming layer forming step is performed, a grinding step of grinding the back surface 11b of the wafer 11 to divide the wafer 11 along the reforming layer 19 into individual element wafers is performed. In the present embodiment, it is characterized in that the grinding step is divided into a first grinding step and a second grinding step.

Referring to Figure 5, a perspective view of a grinding device 32 that can perform a grinding step is shown. 34 is a base of the grinding device 32, and a pillar 36 is erected behind the base 34. A pair of guide rails 38 extending in the up and down direction are fixed to the stays 36.

A grinding unit (grinding device) 40 is mounted along the pair of guide rails 38 so as to be movable in the up and down direction. The grinding unit 40 has a main shaft housing 42 and a support portion 44 that holds the main shaft housing 42, and the support portion 44 is mounted on a moving base 46 that is movable in the vertical direction along the pair of guide rails 38.

The grinding unit 40 includes a spindle 48 rotatably housed in the spindle housing 42, a motor 49 that rotationally drives the spindle 48, a wheel mount 50 fixed to the front end of the spindle 48, and a grinding wheel that is bolted to the wheel housing 50. Rounding wheel 52. As shown in FIG. 6, the grinding wheel 52 is a wheel base 54 and a plurality of fixed bases. The grinding grindstone 56 on the outer periphery of the lower end of the table 54 is formed.

The grinding device 32 is provided with a grinding unit feeding mechanism 62 which is constituted by a ball screw 58 and a pulse motor 60 that move the grinding unit 40 in the vertical direction along the pair of guide rails 38. . When the pulse motor 60 is driven, the ball screw 58 is rotated, and the grinding unit 40 is moved in the up and down direction.

A recess 34a is formed on the upper surface of the base 34, and a work chuck mechanism 64 is disposed in the recess 34a. The work chuck mechanism 64 has a work chuck 66 and is movable between a wafer loading and unloading position A in the Y-axis direction and a grinding position B facing the grinding unit 40 by a moving mechanism (not shown).

It is provided with a plurality of clamps 68 adjacent to the work clamping table 66 and clamping the annular frame. 40 is a telescopic shield for covering and protecting the shaft portion of the working chuck feeding mechanism. An operation panel 72 to which an operator of the grinding device 32 inputs grinding conditions or the like is disposed on the front side of the susceptor 34.

Next, the first grinding step will be described with reference to Fig. 6 . As shown in FIG. 6(A), the jigs 68 disposed around the work chuck 66 are supported by the jig support members 74, and the jig support members 74 are selectively fixed to the first position shown in FIG. Between the second position shown in FIG. 7 which is lowered by a predetermined distance from the first position.

In the first grinding step, the jig support member 74 is fixed to the first position, and the ring frame F of the frame unit 17 is pulled down by a predetermined distance by the jig 68 and fixed. 76 is a grinding water supply nozzle, and in the first grinding step, the grinding water 78 is supplied to the wafer 11 and the grinding stone 56 from the grinding water supply nozzle 76, and the back surface 11b of the wafer 11 is ground. cut.

In the first grinding step, the grinding wheel 52 is rotated in the direction of the arrow a at a rotation speed of, for example, 300 rpm, and the grinding wheel 52 is rotated in the same direction as the working table 66, that is, in the direction of the arrow b at, for example, 6000 rpm. The grinding unit feed mechanism 62 is rotated and the grinding stone 56 is brought into contact with the back surface 11b of the wafer 11.

Then, while the grinding water 78 is supplied from the grinding water supply nozzle 76, the grinding wheel 52 is ground downward by a predetermined amount at a predetermined grinding feed speed, and the wafer is ground by the grinding stone 56. The back surface 11b of the film 11 is divided into individual element wafers 21 along the reforming layer 19 by the grinding pressure. FIG. 6(B) shows a state in which the first grinding step is performed and the wafer 11 is divided into individual element wafers 21.

After the first grinding step, the second grinding step is performed to expand the expansion tape T1 and supply the grinding water to the wafers 11 provided between the adjacent element wafers 21 while supplying the grinding water. The back surface 11b of the wafer 11 is ground with a grinding stone 56 to thin the wafer 11 to the finished thickness.

In the second grinding step, as shown in FIG. 7, the jig support member 74 is moved from the first position in the direction of the arrow A and is fixed at the second position after moving from the first position to the lower side of the predetermined distance. Thereby, the expansion tape T1 of the frame unit 17 is expanded in the radial direction, and an interval of about 5 to 20 μm is formed between the adjacent element wafers 21, preferably about 10 to 15 μm.

Similarly to the first grinding step, in the second grinding step, the grinding wheel 52 is rotated at a rotation speed of, for example, 300 rpm in the direction of the arrow a, and the grinding wheel 52 is rotated at a direction of arrow b, for example, at 6000 rpm. Rotating and moving the grinding water while supplying the grinding water 78 from the grinding water supply nozzle 76 The element feeding mechanism 62 brings the grinding stone 56 into contact with the back surface 11b of the wafer 11.

Then, while the grinding water 78 is supplied from the grinding water supply nozzle 76, the grinding wheel 52 is ground downward by a predetermined amount at a predetermined grinding feed rate to grind the back surface 11b of the wafer 11, and The wafer 11 is thinned to the thickness of the finished product.

In this second grinding step, since the expansion tape T1 is radially expanded by pulling down the annular frame F of the frame unit 17 by the jig 68, it is possible to form a predetermined between the element wafers 21 as described above. Interval.

As a result, the grinding debris that has entered between the component wafers 21 can be washed away by the grinding water 78, and the grinding debris can be prevented from remaining on the side surface of the component wafer 21. The finished thickness of the element wafer 21 is about 20 to 75 μm, preferably about 30 to 60 μm.

After performing the fine grinding step, a wafer transfer step is performed in which a die attach film (DAF) 25 as a bonding film is mounted on the back surface 11b of the wafer 11, and on the DAF 25 The dicing tape T2 is attached, and the outer peripheral portion of the dicing tape T2 is supported by the annular frame F, and then the expanded tape T1 attached to the surface 11a of the wafer 11 is peeled off. It is also possible to attach a dicing tape having a layer of DAF 25 laminated on the back surface 11b of the wafer 11.

After the wafer transfer step is performed, an adhesive film breaking step of breaking the DAF 25 by irradiating the DAF 25 exposed between the element wafers 21 to the DAF 25 is performed. In the subsequent film breaking step, as shown in FIG. 8, the annular frame F after the wafer transfer step is held by the jig 22 and fixed, and the working chuck 20 is attracted by the dicing tape T2. The wafer 11 is held to expose the surface 11a of the wafer 11.

Then, the DAF 25 exposed between the element wafers 21 is irradiated from the concentrator 6 with a laser beam having a wavelength (for example, 355 nm) which is absorptive to the DAF 25, and is processed by the working chuck 20 in the direction of the arrow X1. The dividing line 13 which is elongated in the first direction by the DAF 25 is broken.

Next, the working chuck 20 is indexed to irradiate the laser beam between the element wafers 21 corresponding to the adjacent dividing line 13 and the working chuck 20 is fed in the direction of the arrow X2 to Broken DAF25.

While the machining feed direction is alternately changed to the X1 direction or the X2 direction, the DAF 25 is broken along all of the planned dividing lines 13 elongated in the first direction by the irradiation of the laser beam.

Next, after the work chuck 20 is rotated by 90 degrees, the same laser beam is irradiated along all of the planned dividing lines 13 elongated in the second direction orthogonal to the first direction, and the DAF 25 is placed in the second direction. The upper predetermined dividing line 13 is broken.

The processing conditions of the film breaking step are set to, for example, the following.

Light source: LD-excited Q-switch Nd: YVO4 pulse laser

Wavelength: 355nm

Output: 0.2W

Repeat frequency: 200kHz

Processing feed rate: 200mm / sec

11‧‧‧Semiconductor wafer

21‧‧‧Component chip

23‧‧‧ interval

40‧‧‧ grinding unit

48‧‧‧ Spindle

50‧‧‧ wheel seat

52‧‧‧ grinding wheel

54‧‧‧ wheel abutment

56‧‧‧grinding grindstone

66‧‧‧Working table

68‧‧‧Clamp

74‧‧‧Clamp support member

76‧‧‧ grinding water supply nozzle

78‧‧‧ grinding water

A, a, b‧‧‧ arrows

T1‧‧‧Expanding tape

F‧‧‧Ring frame

Claims (2)

A method for processing a wafer, wherein the wafer is formed with an element in each of a region of a surface drawn by a plurality of mutually intersecting dividing lines, the wafer processing method characterized by: a frame unit forming step Forming a surface of the wafer on the expansion tape that blocks the opening of the annular frame to form a frame unit; and modifying the layer forming step to illuminate the wavelength of the wafer from the back surface of the wafer constituting the frame unit Laser beam, and a modified layer along a predetermined dividing line is formed near the inner surface of the wafer; a first grinding step, after performing the frame unit forming step and the reforming layer forming step, supplying the grinding Grinding the back side of the wafer with a grinding stone to divide the wafer into individual component wafers along the modified layer; and a second grinding step, after performing the first grinding step, The expanded tape is expanded and the back surface of the wafer is ground by grinding the grindstone while supplying the spacer wafer between the adjacent element wafers to thin the wafer to the finished thickness. The processing method of the wafer of claim 1, further comprising a wafer transfer step and a subsequent film breaking step of attaching on the back surface of the wafer after the second grinding step is performed Next, a film is attached to the adhesive film, and a dicing tape is attached to the adhesive film, and the outer peripheral portion of the dicing tape is supported by the annular frame, and the expanded tape attached to the surface of the wafer is peeled off. In the adhesive film breaking step, after the wafer transfer step is performed, the adhesive film exposed between the element wafers is irradiated with a laser beam to break the adhesive film.