Patent Application
20240105511
The present invention relates to a processing method of a substrate, the method performing processing of the substrate with use of a laser beam having a wavelength that transmits through the substrate and being focusable in a region of a greater length along a thickness direction of the substrate than a width along a direction perpendicular to the thickness direction, and also to a manufacturing method of chips, the method performing manufacture of the chips from the substrate with use of the processing method.
Chips of semiconductor devices such as integrated circuits (ICs) or optical devices like light-emitting diodes (LEDs) or laser diodes (LDs) are manufactured using a disk-shaped substrate made from a single crystal material such as, for example, silicon, silicon carbide, or sapphire.
Described specifically, such chips are manufactured by forming a function layer, which includes a conductive film, a semiconductor film, and/or an insulation film, on a front surface of the substrate to constitute the devices, and then dividing the substrate along boundaries of the devices.
Known as a method for dividing a substrate is a method which uses a laser beam having a wavelength that transmits through a material constituting the substrate and being focusable in a region of a greater length along a thickness direction of the substrate than a width along a direction perpendicular to the thickness direction (see, for example, JP 2014-168790A).
In this method, the laser beam is first applied to the substrate along the boundaries of the devices with the region, in which the beam is focused, positioned inside the substrate. As a consequence, shield tunnels (filaments), each of which includes a fine pore and an amorphous portion surrounding the fine pore, are formed inside the substrate. In this method, etching is applied to the substrate such that the shield tunnels are removed. As a result, chips are manufactured from the substrate.
If a laser beam is applied from a side of a front surface of a substrate with a function layer formed on the front surface, the advancing direction of the laser beam may change in the function layer, thereby causing a possible problem in that desired shield tunnels may be hardly formed in the substrate. If the laser beam is applied from a side of a back surface of the substrate, on the other hand, there is a possible problem in that the function layer may be damaged by the laser beam reaching the side of the front surface of the substrate.
With these possible problems in view, the present invention has as objects thereof the provision of a processing method of a substrate, which can form desired shield tunnels in the substrate without damaging a function layer for a configuration of a plurality of devices, and a manufacturing method of chips, which manufactures the chips from the substrate with use of the processing method.
In accordance with a first aspect of the present invention, there is provided a processing method of a substrate, the method performing processing of the substrate with use of a laser beam having a wavelength that transmits through a material constituting the substrate and focused in a region of a greater length along a thickness direction of the substrate than a width along a direction perpendicular to the thickness direction. The processing method includes a shield tunnel forming step of forming shield tunnels, each of which includes a fine pore opening in at least one of a front surface or a back surface of the substrate and an amorphous portion surrounding the fine pore, by applying the laser beam to the substrate such that at least a part of the region is positioned inside the substrate, and a function layer forming step of, after the shield tunnel forming step, forming a function layer on the front surface of the substrate.
Preferably, the processing method may further include, between the shield tunnel forming step and the function layer forming step, an etching step of etching the shield tunnels from the at least one of the front surface or the back surface, the at least one having the fine pore opening therein.
In accordance with a second aspect of the present invention, there is provided a manufacturing method of chips, the method performing manufacture of the chips from a substrate with use of a laser beam having a wavelength that transmits through a material constituting the substrate and focused in a region of a greater length along a thickness direction of the substrate than a width along a direction perpendicular to the thickness direction. The manufacturing method includes a shield tunnel forming step of forming shield tunnels, each of which includes a fine pore opening in at least one of a front surface or a back surface of the substrate and an amorphous portion surrounding the fine pore, by applying the laser beam to the substrate such that at least a part of the region is positioned inside the substrate, an etching step of, after the shield tunnel forming step, etching the shield tunnels from the at least one of the front surface or the back surface, the at least one having the fine pore opening therein, a function layer forming step of, after the etching step, forming a function layer on the front surface of the substrate, and a dividing step of, after the function layer forming step, dividing the substrate by applying an external force to the substrate.
In the present invention, the fine pore may preferably open in only one of the front surface or the back surface of the substrate.
In the present invention, before the function layer forming step of forming the function layer on the front surface of the substrate, the shield tunnel forming step is performed to form the shield tunnels, each of which includes the fine pore opening in the at least one of the front surface or the back surface of the substrate and the amorphous portion surrounding the fine pore, respectively.
In other words, the shield tunnels in the present invention are formed in the substrate in a state that the function layer has not been formed on its front surface. In the present invention, it is therefore possible to form the shield tunnels in the substrate as desired without damaging the function layer for the configuration of a plurality of devices.
The above and other objects, features and advantages of the present invention and the manner of realizing them will become more apparent, and the invention itself will best be understood from a study of the following description and appended claims with reference to the attached drawings showing some preferred embodiments of the invention.
With reference to the attached drawings, embodiments of the present invention will be described.
On the substrate 11, a plurality of intersecting scribe lines 13 is arranged in a grid pattern. The substrate 11 is defined into a plurality of regions 15 by the scribe lines 13, and on the front surface 11a in each region 15, a function layer is formed to constitute a device as will be mentioned below.
The chips are manufactured by dividing the substrate, in each region 15 of which the function layer is formed, along the respective scribe lines 13. It is to be noted that no limitations are imposed on the material, shape, construction, size, and the like of the substrate 11. For example, the substrate 11 may be made from another single crystal material such as sapphire.
The laser processing machine 2 has a disk-shaped holding table 4. The holding table 4 has an upper surface (holding surface) of, for example, a circular shape. The holding table 4 also has a disk-shaped porous plate (not illustrated), an upper surface of which is exposed in the holding surface.
Further, the porous plate is in communication with a suction source (not illustrated) such as an ejector via a flow channel formed inside the holding table 4. When this suction source is activated, a suction force acts on a space in a vicinity of the holding surface of the holding table 4. As a consequence, it is possible to hold, for example, the substrate 11, which is placed on the holding surface, on the holding table 4.
The holding table 4 is also connected to a horizontal direction moving mechanism (not illustrated). This horizontal direction moving mechanism includes, for example, a ball screw, a motor, and the like. When this horizontal direction moving mechanism is activated, the holding table 4 is moved along a horizontal direction.
Above the holding table 4, a head 6 of a laser beam irradiation unit is disposed. The laser beam irradiation unit also has a laser oscillator (not illustrated). This laser oscillator has, for example, Nd:YAG or the like as a laser medium.
The laser oscillator applies a pulsed laser beam LB of a wavelength that transmits through a material constituting the substrate 11 (for example, a wavelength of 1,064 nm). This pulsed laser beam LB has, for example, a pulse width of 10 ps, and a frequency of 50 kHz.
After this laser beam LB has been adjusted in power at an attenuator (not illustrated) (for example, its average power has been reduced to 2 W), the laser beam LB is applied directly downwards from the head 6 via an optical system (not illustrated) that includes a condenser lens 6a and the like disposed in the head 6.
Further, the optical system also imposes, for example, aberration (in particular, longitudinal aberration) on the laser beam LB. As a consequence, the laser beam LB is focused in a region R of a greater length along its advancing direction (a thickness direction of the substrate 11) than a width along a direction perpendicular to the advancing direction.
The head 6 of the laser beam irradiation unit is connected to a vertical direction moving mechanism (not illustrated). This vertical direction moving mechanism includes, for example, a ball screw, a motor, and the like. When this vertical direction moving mechanism is activated, the head 6 is moved along a vertical direction.
When forming the shield tunnels 19 inside the substrate 11 in the laser processing machine 2, the substrate 11 that has a protective tape 17 bonded to the front surface 11a thereof is first placed on the holding table 4 such that the back surface 11b is directed upwards. It is to be noted that the protective tape 17 is made, for example, from a resin, and has a disk shape of substantially the same diameter as the substrate 11.
Alternatively, no protective tape 17 may be bonded to the front surface 11a of the substrate 11 in the shield tunnel forming step S1. In other words, the substrate 11 may be placed on the holding table 4 such that the front surface 11a comes into direct contact with the holding surface of the holding table 4.
The suction source that is in communication with the porous plate exposed in the holding surface of the holding table 4 is next activated. As a consequence, the substrate 11 is held on the holding table 4. The holding table 4 and/or the head 6 is then adjusted in position such that an end of desired one of the scribe lines 13 on the substrate 11 and the region in which the laser beam LB is to be focused overlap each other.
While applying the laser beam LB from the head 6, the holding table 4 is next moved along a direction in which the desired one scribe line 13 extends (see
The above-mentioned operations are repeated further until the shield tunnels 19 are formed in all the elongated zones along the respective scribe lines 13. As a consequence, the substrate 11 is obtained with the shield tunnels 19 formed in a grid pattern as seen in a plan view.
After the shield tunnel forming step S1, a function layer is formed on the front surface 11a of the substrate 11 (function layer forming step S2). In this function layer forming step S2, a function layer made of a single metal film is formed on the front surface 11a of the substrate 11 using, for example, physical vapor deposition (PVD). It is to be noted that this function layer is used, for example, as back surface electrodes for power devices.
The sputtering system 8 has a housing 10 that defines a chamber C. A through-hole is formed in a bottom wall of the housing 10, and a support member 12 is disposed extending through the through-hole. The support member 12 supports a holding table 14 with an electrostatic chuck disposed on a side of an upper surface thereof.
Above the holding table 14, a target 16 made from a metal material is disposed, and the target 16 is attached to an electrode 18. In a vicinity of the target 16, an exciting member 20 is disposed to excite the target 16. The target 16 is connected to a radio frequency power supply 22 via the electrode 18.
Formed in left and right side walls, respectively, of the housing 10 are a gas inlet 10a and a gas outlet 10b. The gas inlet 10a can be brought into communication with a supply source of sputtering gas (for example, argon or the like) via a valve (not illustrated) or the like, while the gas outlet 10b can be brought into communication with a suction source for depressurizing the chamber C.
When forming the metal film on the front surface 11a of the substrate 11 in the sputtering system 8, the protective tape 17 bonded to the front surface 11a of the substrate 11 is first removed, and a protective tape 21 similar to the protective tape 17 is bonded to the back surface 11b.
The substrate 11 is next placed on the holding table 14 with the protective tape 21 interposed therebetween such that the exposed front surface 11a is directed upwards. The electrostatic chuck disposed on the side of the upper surface of the holding table 14 is then activated. As a consequence, the substrate 11 is held on the holding table 14.
The suction source that is in communication with the gas outlet 10b is then activated to evacuate the chamber C, and the chamber C is depressurized until its internal pressure drops to 10−2 to 10−4 Pa. The radio frequency power supply 22 is then activated such that radio frequency power, for example, of 40 kHz is applied via the electrode 18 to the target 16 excited by the exciting member 20, and at the same time, the sputtering gas is supplied from the supply source into the chamber C via the valve or the like, the gas inlet 10a, and the like.
As a consequence, a plasma that contains ions of the sputtering gas is generated in the chamber C, and these ions strike the target 16. Metal particles sputtered from the target 16 by the striking of the ions of the sputtering gas then deposit on the front surface 11a of the substrate 11 to form the metal film.
In the processing method of the substrate as illustrated in
In other words, the shield tunnels 19 are formed in the substrate 11 in a state that the function layer 23 has not been formed on its front surface 11a. In this method, it is therefore possible to form the shield tunnels 19 in the substrate 11 as desired without damaging the function layer 23 for a configuration of a plurality of devices.
It is to be noted that the details mentioned above are those relating to the first embodiment of the first aspect of the present invention, and the present invention is therefore not limited to the above-mentioned details. In the shield tunnel forming step S1 of the processing method of the first embodiment, for example, the shield tunnels 19 may not be required to be formed extending through the substrate 11 in the thickness direction thereof, insofar as the substrate 11 can be divided in a dividing step, which will be mentioned subsequently herein, or the like.
Described specifically, these shield tunnels 19 include fine pores 19a opening in only a back surface 11b of the substrate 11 and amorphous portions 19b surrounding the fine pores 19a, respectively. As an alternative, these shield tunnels 19 may include fine pores 19a opening in only a front surface 11a of the substrate 11 and amorphous portions 19b surrounding the fine pores 19a, respectively.
Further, the construction of a laser processing machine for use in the shield tunnel forming step S1 of the processing method is not limited to the construction of the above-mentioned laser processing machine 2. For example, the shield tunnel forming step S1 may be performed using a laser processing machine that is provided with a vertical direction moving mechanism for moving the holding table 4 in a vertical direction and a horizontal direction moving mechanism for moving the head 6 of a laser beam irradiation unit in a horizontal direction.
As another alternative, the shield tunnel forming step S1 of the processing method may also be performed using a laser processing machine in which a scanning optical system that can change the direction of a laser beam LB emitted from the head 6 is disposed in the laser beam irradiation unit. It is to be noted that this scanning optical system includes, for example, a galvano scanner, an acoustic optical device (AOD), a polygon mirror, and/or the like.
In the shield tunnel forming step S1 of the processing method, it is therefore only required that the substrate 11, which is held on the holding table 4, and the region, in which the laser beam LB applied from the head 6 is to be focused, can be relatively moved along each of the horizontal direction and the vertical direction, and no limitations are imposed on the construction for their relative movement.
In the processing method, the shield tunnels 19 may be removed in part, for example, as much as 65% to 75% before the function layer forming step S2.
In the processing method of the second embodiment as illustrated in
The etching system 24 has a holding table 26 similar to the holding table 4 illustrated in
When this suction source is activated, a suction force acts on a space in a vicinity of a holding surface of the holding table 26. As a consequence, the substrate 11 placed on the holding surface can be held on the holding table 26.
The holding table 26 is connected to a rotary drive mechanism (not illustrated). This rotatory drive mechanism includes, for example, a spindle, a motor, and the like. When this rotary drive mechanism is activated, the holding table 26 is rotated about, as an axis of rotation, a straight line that passes through a center of the holding surface and extends along a vertical direction.
Above the holding table 26, a nozzle 28 is arranged to supply the etchant E to the substrate 11 held on the holding table 26. This etchant E contains, for example, hydrofluoric acid or the like.
When etching the shield tunnels 19 in part with the etchant E in the etching system 24, the substrate 11 on a front surface 11a of which a protective tape 17 is bonded is first placed on the holding table 26 such that the back surface 11b is directed upward.
Alternatively, no protective tape 17 may be bonded to the front surface 11a of the substrate 11 in the etching step S3. In other words, the substrate 11 may be placed on the holding table 26 such that the front surface 11a comes into direct contact with the holding surface of the holding table 26.
The suction source that is in communication with the porous plate exposed in the holding surface of the holding table 26 is next activated. As a consequence, the substrate 11 is held on the holding table 26. While supplying the etchant E to the back surface 11b of the substrate 11, the rotary drive mechanism is then activated such that the substrate 11 is spined over a predetermined period of time.
As a consequence, the shield tunnels 19 are etched in part on the side of the back surface 11b.
On the side of the back surface 11b of the substrate 11, grooves 11c are formed in elongated zones along the scribe lines 13 by this etching. It is to be noted that, in this etching, the substrate 11 may be etched at portions thereof where the shield tunnels 19 have not been formed, that is, at portions thereof overlapping the regions 15 (see
In the etching step S3, etching may be continued until the shield tunnels 19 are removed in their entirety, in other words, until the substrate 11 is divided along the scribe lines 13.
In the etching step S3, the shield tunnels 19 may be removed in part on the side of the front surface 11a. In other words, the shield tunnels 19 may be etched in the etching step S3 from the front surface 11a exposed by separating the protective tape 17.
The present invention also relates to a manufacturing method of chips, which includes the above-mentioned processing method of the substrate.
After the function layer forming step S2, the substrate 11 is then divided by applying an external force to the substrate 11 (dividing step S4).
Described specifically, in each of
It is to be noted that, before the dividing step S4, the protective tape 21 is separated from the back surface 11b of the substrate 11, and a disk-shaped dicing tape 25 of a greater diameter than the substrate 11 is newly bonded at a central area thereof to the back surface 11b of the substrate 11. Also bonded to an outer peripheral area of the dicing tape 25 is an annular frame 27 in which a circular opening of a greater diameter than the substrate 11 is formed.
The expansion machine 30 has a cylindrical drum 32. Around the drum 32, a frame support unit 34 is disposed. The frame support unit 34 has an annular frame support base 34a disposed such that it surrounds an upper end portion of the drum 32.
On an upper surface of the frame support base 34a, a plurality of clamp portions 34b is disposed at substantially equal angular intervals along a peripheral direction of the frame support base 34a. When the substrate 11 integrated with the frame 27 with the dicing tape 25 interposed therebetween is loaded onto the expansion machine 30, the frame 27 is placed on the frame support base 34a with the dicing tape 25 interposed therebetween, and the frame 27 is clamped by the frame support base 34a and the clamp portions 34b.
On a lower surface of the frame support base 34a, on the other hand, a plurality of rods 34c is disposed at substantially equal angular intervals along the peripheral direction of the frame support base 34a. The rods 34c are, for example, rods of air cylinders, respectively, and are movable up and down. When the rods 34c are moved up and down, the frame support base 34a and clamp portions 34b are also moved up and down along with the rods 34c.
When dividing the substrate 11 along the scribe lines 13 on the expansion machine 30, the rods 34c are first moved up such that the upper surface of the frame support base 34a is positioned on the same plane as an upper end of the drum 32.
The substrate 11 integrated with the frame 27 via the dicing tape 25 is then loaded onto the expansion machine 30 such that the function layer 23 is directed upwards, and the frame 27 is clamped by the frame support base 34a and the clamp portions 34b (see
As a consequence, the dicing tape 25 is expanded by a distance over which the upper end of the drum 32 and the frame support base 34a are separated from each other. At this time, an external force acts on the substrate 11 and also on the function layer 23 such that they are expanded. As a result, the substrate 11 and the function layer 23 are divided along the scribe lines 13 (see
It is to be noted that, in the manufacturing method, the function layer 23 may be divided along the scribe lines 13 before the dividing step S4.
In the manufacturing method according to the second embodiment as illustrated in
Moreover, the constructions, methods, and the like according to the above-mentioned embodiments can be practiced with appropriate changes or modifications within the scope not departing from the object of the present invention.
The present invention is not limited to the details of the above-described preferred embodiments. The scope of the invention is defined by the appended claims and all changes and modifications as fall within the equivalence of the scope of the claims are therefore to be embraced by the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2022-154396 | Sep 2022 | JP | national |
