JP6270520B2 - Wafer processing method - Google Patents

Description

The present invention relates to a wafer processing method, in particular, a low dielectric constant insulating film (Low-k) as an interlayer insulating film.
The present invention relates to a wafer processing method using a film.

  In the semiconductor device manufacturing process, a plurality of regions are defined by divided planned lines called streets formed in a lattice shape on the surface of a semiconductor wafer such as a silicon wafer or a gallium arsenide wafer having a substantially disk shape, A device such as an IC or LSI is formed in the region.

  After such a semiconductor wafer is ground to a predetermined thickness by a grinding device, it is divided into individual devices by a cutting device or a laser processing device, and the divided devices are various electric devices such as mobile phones and personal computers. Widely used in equipment.

  As a cutting device, a cutting device generally called a dicing device is used. In this cutting device, a cutting blade having a cutting blade having a thickness of 20 to 30 μm is obtained by hardening superabrasive grains such as diamond and CBN with metal or resin. Cutting is performed by cutting into a semiconductor wafer while rotating at a high speed such as 30000 rpm.

A semiconductor device formed on the surface of a semiconductor wafer has a plurality of layers of metal wirings that transmit signals, and each metal wiring is insulated by an interlayer insulating film formed mainly of SiO ₂ . .

  In recent years, with the miniaturization of the structure, the distance between wirings has become shorter, and the electric capacity between adjacent wirings has increased. Due to this, a problem that signal delay occurs and power consumption increases has become prominent.

In order to reduce the parasitic capacitance between the layers, the device (circuit) prior to each layer when forming an interlayer insulating film for insulating primarily had adopted the SiO ₂ insulating film, than recently become SiO ₂ insulating film dielectric A low dielectric constant insulating film (Low-k film) having a low rate has been adopted.

As the low dielectric constant insulating film, a material having a dielectric constant lower than that of the SiO ₂ film (dielectric constant k = 4.1) (for example, about k = 2.5 to 3.6), for example, an inorganic material such as SiOC, SiLK, etc. Examples thereof include organic films such as films, polyimide-based, parylene-based, and polytetrafluoroethylene-based polymer films, and porous silica films such as methyl-containing polysiloxane.

  When a laminated body including such a low dielectric constant insulating film is cut along a line to be divided by a cutting blade, the low dielectric constant insulating film is very brittle like mica, which causes a problem that the laminated body is peeled off.

  In order to solve this problem, for example, in Japanese Patent Application Laid-Open No. 2005-064230 or Japanese Patent Application Laid-Open No. 2005-209719, prior to cutting with a cutting blade, the laminated body on the planned division line is removed in advance by laser beam irradiation. Then, a method for processing a semiconductor wafer that is then divided into chips with a cutting blade has been proposed.

  In the case of a processing method that forms a processing groove by removing the laminated body on the division line in advance by laser beam irradiation, the wafer is irradiated prior to the laser beam irradiation so that debris generated when forming the processing groove does not adhere to the device portion. A method has been proposed in which a protective film is applied to the surface of the film, and the protective film is washed and removed after the grooves are formed (see, for example, Japanese Patent No. 4471632).

  On the other hand, a laser processing device is used to divide a semiconductor wafer, and a pulsed laser beam having a wavelength that is transparent to the wafer is irradiated to the inside of the wafer with a converging point, and the wafer is modified along the planned division line. A method is also known in which a wafer is divided into individual device chips using a modified layer as a starting point by applying an external force to a planned dividing line whose strength has been reduced in the modified layer by forming a quality layer (for example, JP 2009-10105 A).

Japanese Patent Laying-Open No. 2005-064230 JP 2005-209719 A Japanese Patent No. 4471632 JP 2009-10105 A

  In the case of a processing method in which a modified layer is formed inside a wafer and the wafer is divided into individual device chips with the modified layer as a starting point, the stacked body stacked on the surface of the wafer is difficult to be divided including the low-k film. When formed from a material, there has been a problem that the division position of the laminated body portion is shifted or the laminated body is peeled off from the upper surface of the wafer substrate.

  The present invention has been made in view of such a point, and the object of the present invention is to efficiently and reliably ensure that a laminated body including a low-k film is laminated on the substrate surface of the wafer. To provide a method for processing a wafer that can be divided into individual device chips.

A wafer processing method for dividing a wafer, on which a plurality of devices are formed by a laminate laminated on a surface of a substrate, along a predetermined division line that divides the plurality of devices, and a protective member is provided on the surface of the wafer the protective member disposed step of disposing, after implementing the protection member disposed step, a laser beam having an absorption wavelength to respect laminate has a permeability to said protective member and said wafer Irradiate the wafer along the planned dividing line from the laminated body side through the protective member , partially remove the laminated body to form a laser processing groove on the surface of the wafer, and start the fracture of the wafer inside the wafer. A laser processing step for simultaneously forming the modified layer to be formed, and after performing the laser processing step, an external force is applied to the wafer along the line to be divided. Comprising a dividing step of dividing the Doha into individual device chips, and in the laser processing step, position the focal point of the laser beam to the wafer inside the neighboring laminate, in the dividing step, through the protection member holding the wafer by a chuck table Te, you divide into individual device chips along the wafer to the dividing lines and the reforming layer in fracture starting point with by grinding the back surface of the wafer is formed into a predetermined thickness A wafer processing method characterized by the above.

  In the wafer processing method of the present invention, the laser beam is focused by positioning a condensing point of a laser beam having a wavelength that is transmissive to the wafer and absorbable to the laminated body within the wafer in the vicinity of the laminated body. The laser beam is irradiated from the body side along the planned dividing line to form the laser processing groove and the modified layer at the same time, so it is possible to divide the wafer into individual device chips without causing a division failure. There is an effect that it is possible in the processing step.

It is a surface side perspective view of a semiconductor wafer. It is a perspective view of the state which affixed the surface of the semiconductor wafer on the dicing tape with which the outer peripheral part was affixed on the cyclic | annular flame | frame. It is sectional drawing which shows a laser processing step. It is a block diagram of a laser beam irradiation unit. It is a perspective view of the division | segmentation step of 1st Embodiment. It is a perspective view which shows the grinding step which grinds the back surface of a wafer. It is sectional drawing which shows a laser processing step. It is sectional drawing which shows the division | segmentation step of 2nd Embodiment.

  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 11 (hereinafter sometimes simply referred to as a wafer) 11 is shown. The semiconductor wafer 11 is configured by laminating a laminated body 15 for forming a plurality of semiconductor devices 19 on a silicon substrate 13 having a predetermined thickness (for example, 700 μm).

  Each device 19 is formed in a region defined by a plurality of division lines 17 formed in a lattice shape. In the semiconductor wafer 11 of this embodiment, a low dielectric constant insulating film (Low-k film) is used as an interlayer insulating film when the device 19 is formed.

  In the wafer processing method according to the first embodiment of the present invention, first, as shown in FIG. 2, the surface 11 a of the wafer 11 is attached to a dicing tape T whose outer peripheral portion is attached to the annular frame F. The back surface 11b is exposed.

  In the present embodiment, the dicing tape T functions as a protective member that protects the device 19 formed on the surface 11 a of the wafer 11. Therefore, this will be referred to as a protective member disposing step.

  After carrying out the protective member arranging step, as shown in FIG. 3, the back surface 11b side of the wafer 11 is sucked and held by the chuck table 10 of the laser processing apparatus, and the second annular frame having the same shape is formed on the annular frame F. 50, the outer peripheral portion of the dicing tape T is sandwiched, and the second annular frame 50 is clamped and fixed by the clamp 52 in this state.

  After performing the protective tape attaching step, as shown in FIG. 3, a laser beam having a wavelength that is transmissive to the dicing tape T and the wafer 11 and absorbable to the laminate 15 is applied to the dicing tape T. Then, the wafer 11 is irradiated, and the laminated body 15 is partially removed to form a laser processing groove 23 along the division line 17 on the surface of the wafer 11. A laser processing step for simultaneously forming the modified layer 25 is performed.

  In this laser processing step, it is important to irradiate the laser beam with the condensing point of the laser beam positioned inside the wafer 11 in the vicinity of the laminate 15. For example, the condensing point of the laser beam is positioned at a depth of about 20 to 30 μm from the surface 11 a of the wafer 11 and the laser beam is irradiated onto the wafer 11 through the dicing tape T.

  As a result, the laminate 15 is partially removed to form a laser processing groove 23 on the surface of the wafer 11 and a modified layer 25 is simultaneously formed to a depth of about 20 to 30 μm from the surface 11a of the wafer 11. The

  3 and 4, the laser beam irradiation unit 12 includes a laser beam generating unit 16 housed in a casing, and a condenser (laser head) 18 attached to the tip of the casing.

  As shown in FIG. 4, the laser beam generating unit 16 includes a laser oscillator 22 that oscillates a YAG pulse laser or a YVO4 pulse laser, a repetition frequency setting means 24, a pulse width adjusting means 26, and a power adjusting means 28. It is out. Although not particularly illustrated, the laser oscillator 22 has a Brewster window, and the laser beam emitted from the laser oscillator 22 is a linearly polarized laser beam.

  The pulse laser beam adjusted to a predetermined power by the power adjusting means 28 of the laser beam generating unit 16 is reflected by the mirror 30 of the condenser 18 and further condensed by the condenser objective lens 32 and held on the chuck table 10. The wafer 11 is irradiated through the dicing tape T.

  Before performing the laser processing step, an alignment step is performed in which the planned dividing line 17 is parallel to the processing feed direction and aligned with the light collector 18. The alignment step is performed by detecting the planned division line 17 through the dicing tape T using an infrared imaging means of an imaging unit (not shown). This alignment step is performed for the planned division line 17 extending in the first direction and the planned division line 17 orthogonal to the first direction.

  After performing the alignment step, the condenser 18 is aligned with the planned division line 17 to be laser-processed, and has transparency to the dicing tape T and the silicon substrate 13 of the wafer 11, and to the laminated body 15 of the wafer 11. A laser beam having an absorptive wavelength is irradiated onto the wafer 11 through the dicing tape T, and the chuck table 10 is processed and fed in the direction of the arrow X1, thereby partially removing the stacked body 10 of the wafer 11 and dividing the line. A laser processing step is performed in which a laser processing groove 23 is formed along 17 and a modified layer 25 is simultaneously formed in the wafer 11.

  While the chuck table 10 is indexed and fed in the direction orthogonal to the machining feed direction X1 at intervals of the planned division lines 17, the same laser machining grooves 23 are formed in the laminate 15 along the planned division lines 17 extending in the first direction. At the same time, the modified layer 25 is formed one after another inside the wafer 11.

  After completing the formation of the laser processing groove 23 and the modified layer 25 along all the division lines 17 extending in the first direction, the chuck table 10 is rotated by 90 °, and the second direction orthogonal to the first direction is obtained. The laser processing grooves 23 are formed in the stacked body 15 of the wafer 11 along all the planned division lines 17 extending in the direction, and the modified layer 25 is simultaneously formed in the wafer 11.

  The laser processing conditions in the laser processing step are, for example, as follows.

Wavelength: 500 nm to 1000 nm
Average output: 0.5W
Repetition frequency: 100 kHz
Feeding speed: 300mm / s

After performing the laser processing step, the back surface 11b of the wafer 11 is ground to thin the wafer 11 to a finished thickness, and the wafer 11 is divided into individual device chips with the modified layer 25 as a starting point by grinding pressing force. A division step for dividing is performed.

  This division step will be described with reference to FIG. In the dividing step, as shown in FIG. 5A, the front surface 11a side of the wafer 11 is sucked and held through the dicing tape T by the chuck table 36 of the grinding apparatus, and the back surface 11b side of the wafer 11 is exposed.

  The grinding unit 38 of the grinding apparatus includes a spindle 40 that is rotationally driven by a motor, a wheel mount 42 that is fixed to the tip of the spindle 40, and a grinding wheel 44 that is detachably fixed to the wheel mount 42 with a plurality of screws 43. Is included. The grinding wheel 44 includes an annular wheel base 46 and a plurality of grinding wheels 48 that are annularly fixed to the outer periphery of the lower end of the wheel base 46.

  In the dividing step, while rotating the chuck table 36 in the direction of arrow a at 300 rpm, for example, the grinding wheel 44 is rotated in the same direction as the chuck table 36, that is, in the direction of arrow b at 6000 rpm, for example, and a grinding unit feed mechanism (not shown) is provided. Driven to bring the grinding wheel 48 into contact with the back surface 11 b of the wafer 11.

  Then, the grinding wheel 44 is ground and fed by a predetermined amount at a predetermined grinding feed speed, and the wafer 11 is ground and processed to a desired thickness. Since grinding pressing force is applied to the back surface 11b of the wafer 11 during grinding of the wafer 11, the wafer 11 starts with the modified layer 25 whose strength has been reduced as a starting point for splitting, as shown in FIG. Is divided into individual device chips 29 defined in (1).

  In the wafer processing method of this embodiment, the modified layer 25 is formed inside the wafer 11 in the laser processing step, and the laser processing groove 23 along the planned division line 17 is formed in the laminate 15 of the wafer 11. Therefore, even when the stacked body 15 includes a material that is difficult to separate, such as a low-k film, the division position of the stacked body 15 is shifted, or the stacked body 15 is separated from the surface of the substrate 13 of the wafer 11. The problem does not occur.

  Next, a wafer processing method according to the second embodiment of the present invention will be described with reference to FIGS. In the processing method of this embodiment, first, a grinding step is performed in which the back surface 11b of the wafer 11 is ground to process the wafer 11 to a predetermined thickness. In this grinding step, as shown in FIG. 6, the wafer 11 is sucked and held via the dicing tape T by the chuck table 36 of the grinding device to expose the back surface 11 b of the wafer 11.

  Preferably, at this time, the annular frame F is clamped by a clamp of a grinding device (not shown) and the annular frame F is pulled downward so that the annular frame F does not get in the way in the grinding step of the wafer 11.

  In the grinding step, while rotating the chuck table 36 in the direction of arrow a at 300 rpm, for example, the grinding wheel 44 is rotated in the same direction as the chuck table 36, that is, in the direction of arrow b at 6000 rpm, for example. Driven to bring the grinding wheel 48 into contact with the back surface 11 b of the wafer 11.

  Then, the grinding wheel 44 is ground by a predetermined amount at a predetermined grinding feed speed, and the wafer 11 is ground. While measuring the thickness of the wafer 11 with a contact-type or non-contact-type thickness measurement gauge, the wafer 11 is finished to a desired thickness, for example, 100 μm.

  After the grinding step is performed, a laser beam having a wavelength that is transmissive to the dicing tape T and the substrate 13 of the wafer 11 and absorbs the laminated body 15 passes through the dicing tape T to the division line 17 of the wafer 11. The laser processing is performed to form a laser processing groove 23 on the surface of the wafer by partially removing the laminate 15 and simultaneously forming a modified layer 25 serving as a starting point for breaking the wafer 11 inside the wafer 11. Perform the steps.

  Since this laser processing step is the same as the laser processing step of the first embodiment described with reference to FIGS. 3 and 4, detailed description thereof is omitted here.

  After performing the laser processing step, a dividing step is performed in which an external force is applied to the wafer 11 on which the laser processing groove 23 and the modified layer 25 are formed, and the wafer 11 is divided into individual device chips 29 along the dividing line 17. carry out.

  In this dividing step, a dividing device 60 as shown in FIG. 8 is used. 8A, the dividing device 60 includes a frame holding unit 62 that supports the annular frame F, and an expansion drum 64 that extends the dicing tape T attached to the annular frame F held by the frame holding unit 62. ing.

  The frame holding unit 60 includes an annular frame holding member 66 and a plurality of clamps 68 as fixing means disposed on the outer periphery of the frame holding member 66. An upper surface of the frame holding member 66 forms a mounting surface 66a on which the annular frame F is mounted, and the annular frame F is mounted on the mounting surface 66a.

  The frame holding unit 62 is driven by a driving means 70 including an air cylinder 72, and the annular frame holding member 66 has a reference position where the mounting surface 66 a is substantially flush with the upper end of the expansion drum 64, and the expansion drum 64. It moves in the vertical direction between the extended positions below the upper end by a predetermined amount. A piston rod 74 of the air cylinder 72 is connected to the lower surface of the frame holding member 66.

  In the dividing step, as shown in FIG. 8A, the annular frame F that supports the wafer 11 via the dicing tape T is placed on the placement surface 66a of the frame holding member 66, and the frame is held by the clamp 68. The member 66 is fixed. At this time, the frame holding member 66 is positioned at a reference position where the placement surface 66 a is substantially the same height as the upper end of the expansion drum 64.

  Next, the air cylinder 72 is driven to lower the frame holding member 66 to the extended position shown in FIG. As a result, the annular frame F fixed on the mounting surface 66a of the frame holding member 66 is also lowered, so that the dicing tape T attached to the annular frame F abuts on the upper end edge of the expansion drum 64 and mainly has a radius. Expanded in the direction.

  As a result, a tensile force acts radially on the wafer 11 adhered to the dicing tape T. When a tensile force is applied to the wafer 11 in a radial manner in this way, the strength of the modified layer 25 formed inside the wafer 11 is reduced, so that the modified layer 25 serves as a division starting point and the wafer 11 is scheduled to be divided. Divided into individual device chips 29 along line 17.

  Also in the present embodiment, since the laser processing groove 23 along the planned dividing line 17 is formed in the laminated body 15 of the wafer 11 at the same time as the modified layer 25 formed inside the wafer 11 in the laser processing step, the laminated body 15 However, even when the material contains a difficult-to-separate material such as a low-k film, there is a problem that the division position of the laminated body 15 is shifted or the laminated body 15 is peeled off from the upper surface of the substrate 13 of the wafer 11. It does not occur.

  In the first embodiment described above, the laser processing step shown in FIG. 3 and the dividing step shown in FIG. 5 can be performed without the need to replace the dicing tape T attached to the annular frame F.

  Further, in the second embodiment, the dicing tape T attached to the annular frame F is replaced in order to perform the grinding step shown in FIG. 6, the laser processing step shown in FIG. 7, and the dividing step shown in FIG. There is no need to Therefore, the processing method is efficient and productivity is improved.

  In the first and second embodiments described above, the laser beam is irradiated onto the wafer 11 through the dicing tape T, and the laminated body 15 is partially removed to form the laser processing groove 23 along the division line 17. The dicing tape T disposed on the surface of the wafer can prevent the debris from being scattered on the device portion. Since the laser beam is irradiated through the dicing tape T, a protective film coating step that has been conventionally required is not necessary.

DESCRIPTION OF SYMBOLS 11 Semiconductor wafer 12 Laser beam irradiation unit 13 Silicon substrate 15 Laminate body 16 Laser beam generating unit 17 Dividing line 18 Condenser 19 Device 23 Laser processing groove 25 Modification layer 27 Dividing groove 29 Device chip 38 Grinding unit 42 Frame holding unit 44 Grinding wheel 60 Dividing device 64 Expansion drum

Claims (1)

A wafer processing method for dividing a wafer, on which a plurality of devices are formed by a laminate laminated on a surface of a substrate, along a predetermined division line that divides the plurality of devices, and a protective member is provided on the surface of the wafer A protective member disposing step for disposing;
After performing the protective member disposing step, a laser beam having a wavelength that is transmissive to the protective member and the wafer and absorbs the laminated body is split from the laminated body side through the protective member. A laser that irradiates a wafer along a predetermined line, partially removes the laminate, forms a laser processing groove on the surface of the wafer, and simultaneously forms a modified layer in the wafer as a starting point for breaking the wafer. Processing steps;
A step of dividing the wafer into individual device chips along the planned dividing line by applying an external force to the wafer after performing the laser processing step; and
In the laser processing step, the condensing point of the laser beam is positioned inside the wafer in the vicinity of the laminate ,
In the dividing step, the wafer is held by the chuck table via the protective member, and the back surface of the wafer is ground to a predetermined thickness, and the modified layer is used as a starting point for breakage to bring the wafer into the planned dividing line. wafer processing methods, wherein that you divided into individual device chips along.

Images