JP2012256653A - Method for processing wafer with electrodes buried therein - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for processing a wafer with electrodes buried therein by which electrodes can be exposed from the backside of a substrate by preparing the substrate to have a given thickness, and a gettering effect can be obtained.SOLUTION: The wafer processing method is for preparing a wafer to have a predetermined finished thickness, provided that the wafer includes a substrate and electrodes buried therein, and the electrodes are connected with bonding pads respectively provided on a plurality of devices formed on a surface of the substrate. The method comprises: a property-modification layer formation step where the substrate is irradiated with laser light of a wavelength which can permeate the substrate from the backside thereof, thereby forming a property-modification layer on the backside of a boundary portion for defining a finished thickness, which is located inside the substrate; a backside-grinding step where the substrate with the property-modification layer formed therein is ground from its backside to a point not reaching the property-modification layer; and an etching step where the substrate subjected to the backside grinding is etched from the backside thereof to arrange the electrodes protruding from the backside of the substrate.

Description

  The present invention relates to a wafer processing method in which electrodes connected to bonding pads provided in a plurality of devices formed on a surface of a substrate are embedded.

  In a semiconductor device manufacturing process, a plurality of regions are partitioned by dividing lines called streets arranged in a grid on the surface of a substantially disk-shaped silicon (Si) substrate, and ICs, LSIs are divided into these partitioned regions. A semiconductor device such as is formed. In this way, by cutting a wafer having a plurality of semiconductor devices formed on the surface of a silicon (Si) substrate along the streets, the regions where the semiconductor devices are formed are divided to manufacture individual semiconductor devices.

In order to reduce the size and increase the functionality of devices, a module structure in which a plurality of devices are stacked and bonding pads provided on the stacked devices are connected has been put into practical use. In this module structure, a hole (via hole) is formed in a silicon (Si) substrate where a bonding pad is provided, and an electrode such as copper or aluminum connected to the bonding pad is formed in silicon dioxide (SiO ₂ ). It is the structure which coat | covers and embeds with the insulating material which consists of. (For example, refer to Patent Document 1.)

  As described above, in order to expose the copper (Cu) electrode embedded in the silicon (Si) substrate on the back surface of the silicon (Si) substrate, the back surface of the silicon (Si) substrate is ground and copper (Cu) is formed on the back surface. The electrode is exposed, and then the back surface of the silicon (Si) substrate is etched using potassium hydroxide (KOH), which has a high etching rate for silicon (Si) and a low etching rate for copper (Cu), as an etchant. As a result, a silicon (Si) substrate is formed to a predetermined thickness, and a copper (Cu) electrode is projected from the back surface by about 30 μm.

JP 2003-249620 A

  As described above, when the back surface of the silicon (Si) substrate is ground to expose the copper (Cu) electrode, copper atoms penetrate into the silicon (Si) substrate when the copper (Cu) electrode is ground. There is a problem that the quality of the device is lowered. In addition, grinding the back surface of a silicon (Si) substrate to form a grinding strain on the back surface causes the gettering effect to suppress the migration of copper atoms, but etching the back surface of a silicon (Si) substrate causes the grinding strain to be reduced. Since there is no gettering effect after being removed, there is a problem in that the copper atoms move and reach the device to degrade the quality of the device.

  The present invention has been made in view of the above-mentioned facts, and a main technical problem thereof is that the substrate can be formed to a predetermined thickness to expose the electrode from the back surface of the substrate and obtain a gettering effect. Another object of the present invention is to provide a method of processing a wafer in which an electrode that can be embedded is embedded.

In order to solve the above-mentioned main technical problem, according to the present invention, a wafer in which electrodes connected to bonding pads provided in a plurality of devices formed on the surface of the substrate are embedded in the substrate is formed to a predetermined finished thickness. A method of processing a wafer to be formed,
A modified layer forming step of irradiating a laser beam having a wavelength transparent to the substrate from the back side of the substrate, and forming a modified layer on the back side of the boundary portion defining the finished thickness inside the substrate;
Grinding the back surface of the substrate on which the modified layer is formed, and finishing the grinding at a position not reaching the modified layer; and
Etching the back surface of the ground substrate, and causing the electrode to protrude from the back surface of the substrate.
A method for processing a wafer having an electrode embedded therein is provided.

  The electrode is made of copper (Cu), and the etching step is performed using tetramethylammonium hydroxide (TMAH) as an etchant.

  In the method of processing a wafer in which an electrode is embedded according to the present invention, a laser beam having a wavelength that is transparent to the substrate is irradiated from the back side of the substrate to a boundary that defines the finished thickness of the substrate, and the finish inside the substrate is finished. A modified layer forming step for forming a modified layer on the back surface side of the boundary defining the thickness, and the back surface of the substrate on which the modified layer is formed are ground, and the grinding is finished at a position not reaching the modified layer. Since it includes a back grinding process and an etching process in which the back surface of the substrate whose back surface is ground is etched and the electrode protrudes from the back surface of the substrate, the modified layer serves as a barrier and the back surface of the substrate and the modified layer The movement of metal atoms existing in the region between the two is constrained, and the metal atoms present in the region between the back surface of the substrate and the modified layer do not reach the device formed on the surface of the substrate. Then, by carrying out the etching step, the electrode can be projected from the back surface of the substrate, and metal atoms present on the back surface side of the substrate are also removed by etching. In the etching step, the gettering effect can be effectively obtained by leaving the modified layer on the back surface of the substrate.

The perspective view of the semiconductor wafer processed by the processing method of the wafer by which the electrode by this invention was embed | buried. Sectional drawing which expands and shows the principal part of the semiconductor wafer shown in FIG. Explanatory drawing of the protection member sticking process in the processing method of the wafer by which the electrode by this invention was embed | buried. The perspective view which shows the principal part of the laser processing apparatus for implementing the modified layer formation process in the processing method of the wafer by which the electrode by which this invention was embed | buried. Explanatory drawing of the modified layer formation process in the processing method of the wafer by which the electrode by this invention was embed | buried. Explanatory drawing of the back surface grinding process in the processing method of the wafer by which the electrode by this invention was embed | buried. The perspective view of the etching apparatus for implementing the etching process in the processing method of the wafer with which the electrode by this invention was embed | buried. Explanatory drawing which shows the state which located the spinner table of the etching apparatus shown in FIG. 7 in the workpiece carrying in / out position. Explanatory drawing which shows the state which located the spinner table of the etching apparatus shown in FIG. 7 in the working position. Explanatory drawing of the etching process in the processing method of the wafer by which the electrode by this invention was embed | buried.

  Preferred embodiments of a method for processing a wafer in which an electrode according to the present invention is embedded will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a perspective view of a semiconductor wafer to be processed by the method for processing a wafer in which an electrode according to the present invention is embedded. A semiconductor wafer 2 shown in FIG. 1 is divided into a plurality of regions by streets 211 formed in a lattice pattern on a surface 21a of a silicon (Si) substrate 21 having a thickness of, for example, 600 μm. Each device 212 is formed. A plurality of bonding pads 213 are provided on the surface of the device 212 thus formed. In the semiconductor wafer 2 thus formed, a copper (Cu) electrode 214 connected to the bonding pad 213 is embedded in a silicon (Si) substrate 21 as shown in FIG. The copper (Cu) electrode 214 embedded in the silicon (Si) substrate 21 has a length of, for example, 200 μm, and a silicon dioxide (SiO ₂ ) film 215 as an insulating film is covered with a thickness of about 150 nm. Has been.

  Hereinafter, a processing method in which the silicon (Si) substrate 21 constituting the semiconductor wafer 2 described above is formed to a predetermined thickness and the copper (Cu) electrode 214 protrudes and is exposed on the back surface of the silicon (Si) substrate 21 will be described. First, in order to protect the device 212 formed on the surface 21a of the silicon (Si) substrate 21 constituting the semiconductor wafer 2, a protective member 3 such as a protective tape is provided on the surface of the semiconductor wafer 2 as shown in FIG. The protective member sticking process to stick is implemented.

  If the above-described protective member attaching step is performed, a laser beam having a wavelength that is transmissive to the silicon (Si) substrate 21 from the back side of the silicon (Si) substrate 21 is applied to the finished thickness of the silicon (Si) substrate 21. A modified layer forming step of irradiating the defined boundary and forming a modified layer at the boundary defining the finished thickness inside the silicon (Si) substrate 21 is performed. This modified layer forming step is performed using a laser processing apparatus 4 shown in FIG. The laser processing apparatus 4 shown in FIG. 4 has a chuck table 41 that holds a workpiece, laser beam irradiation means 42 that irradiates a workpiece held on the chuck table 41 with a laser beam, and a chuck table 41 that holds the workpiece. An image pickup means 43 for picking up an image of the processed workpiece is provided. The chuck table 41 is configured to suck and hold a workpiece. The chuck table 41 is moved in a processing feed direction indicated by an arrow X in FIG. 4 by a processing feed means (not shown) and is also shown in FIG. 4 by an index feed means (not shown). It can be moved in the index feed direction indicated by the arrow Y.

  The laser beam application means 42 includes a cylindrical casing 421 arranged substantially horizontally. In the casing 421, pulse laser beam oscillation means including a pulse laser beam oscillator and repetition frequency setting means (not shown) are arranged. A condenser 422 for condensing the pulse laser beam oscillated from the pulse laser beam oscillating means is attached to the tip of the casing 421. The laser beam irradiating unit 42 includes a condensing point position adjusting unit (not shown) for adjusting the condensing point position of the pulsed laser beam condensed by the condenser 422.

  The imaging means 43 attached to the tip of the casing 421 constituting the laser beam irradiation means 42 is an infrared illumination means for irradiating a workpiece with infrared rays in addition to a normal imaging device (CCD) for imaging with visible light. And an optical system that captures infrared rays irradiated by the infrared illumination means, and an image sensor (infrared CCD) that outputs an electrical signal corresponding to the infrared rays captured by the optical system. It sends to the control means which is not illustrated. The control means (not shown) includes a memory for storing design values of the X and Y coordinates of the street 211 and the electrode 214 formed on the semiconductor wafer 2.

  Using the laser processing apparatus 4 described above, a laser beam having a wavelength that is transmissive to the silicon (Si) substrate 21 from the back side of the silicon (Si) substrate 21 constituting the semiconductor wafer 2 is applied to the silicon (Si) substrate 21. FIG. 4 and FIG. 5 are referred to regarding a modified layer forming step of irradiating a boundary portion that defines the finished thickness of the substrate and forming a modified layer at the boundary portion that defines the finished thickness inside the silicon (Si) substrate 21. I will explain.

  In order to carry out the modified layer forming step for forming the modified layer on the back surface of the boundary portion that defines the finished thickness inside the silicon (Si) substrate 21, first, the chuck of the laser processing apparatus 4 shown in FIG. On the table 41, the protective tape 3 attached to the surface of the semiconductor wafer 2 is placed. Then, by operating a suction means (not shown), the semiconductor wafer 2 is held on the chuck table 41 via the protective tape 3 (wafer holding step). Accordingly, the semiconductor wafer 2 held on the chuck table 41 has the back surface 21b of the silicon (Si) substrate 21 on the upper side. In this way, the chuck table 41 that sucks and holds the semiconductor wafer 2 is positioned directly below the imaging unit 43 by a processing feed unit (not shown).

  When the chuck table 41 is positioned immediately below the image pickup means 43, an alignment operation for detecting a processing region to be laser processed of the semiconductor wafer 2 is executed by the image pickup means 43 and a control means (not shown). That is, the imaging unit 43 and a control unit (not shown) perform alignment for detecting whether the street 211 formed in a predetermined direction of the semiconductor wafer 2 is parallel to the machining feed direction indicated by the arrow X (alignment process). ). At this time, the surface of the silicon (Si) substrate 21 on which the streets 211 in the semiconductor wafer 2 are formed is positioned on the lower side, but the streets 211 can be imaged from the back surface 21b side of the silicon (Si) substrate 21. it can.

  When the alignment process is performed as described above, a modified layer forming process is performed in which a modified layer is formed in the boundary portion that defines the finished thickness inside the silicon (Si) substrate 21. In this modified layer forming step, the laser beam is irradiated avoiding the copper (Cu) electrode 214 embedded in the silicon (Si) substrate 21. For this purpose, a laser beam is irradiated in parallel to the street 211, and copper (Cu) based on the design values of the X and Y coordinates in which the copper (Cu) electrode 214 stored in the memory of the control means (not shown) is disposed. Cu) The laser beam is irradiated while avoiding the electrode 214. That is, as shown in FIG. 5A, the chuck table 41 is moved to the laser beam irradiation area where the condenser 422 of the laser beam irradiation means 42 is located, and there is no copper (Cu) electrode 214 parallel to the street 211. One end of the straight line in the axial direction (the left end in FIG. 5A) is positioned directly below the condenser 422 of the laser beam irradiation means 42. When the finished thickness of the semiconductor wafer 2 is 100 μm, the condensing point P of the pulsed laser beam irradiated from the condenser 422 is set at a position of, for example, 115 μm from the surface 21a of the silicon (Si) substrate 21. In order to position the condensing point P of the pulse laser beam irradiated from the concentrator 422 at a predetermined position of the silicon (Si) substrate 21, it is held on a chuck table described in, for example, Japanese Patent Application Laid-Open No. 2009-63446. The height position of the upper surface of the silicon (Si) substrate 21 held on the chuck table 41 is detected using a height position detection device for the workpiece, and the detected height position of the upper surface of the silicon (Si) substrate 21 is detected. By operating a condensing point position adjusting means (not shown) with reference to, the condensing point P of the pulse laser beam is positioned at a predetermined position. Next, the chuck table 41 is processed by an arrow X1 in FIG. 5A while irradiating a pulsed laser beam having a wavelength transmissive to the silicon (Si) substrate 21 from the condenser 422 of the laser beam irradiation means 42. Move in the feed direction at a predetermined machining feed rate. When the other end of the street 211 (the right end in FIG. 5B) reaches the irradiation position of the condenser 422 of the laser beam irradiation means 42 as shown in FIG. 5B, the irradiation of the pulsed laser beam is stopped. At the same time, the movement of the chuck table 41 is stopped. As a result, a continuous modified layer 216 is formed on the substrate 20 constituting the semiconductor wafer 2 as shown in FIGS. 5B and 5C (modified layer forming step).

The processing conditions in the modified layer forming step are set as follows, for example.
Light source: Semiconductor pumped solid-state laser (Nd: YAG)
Wavelength: 1064 nm pulse laser Repeat frequency: 100 kHz
Average output: 0.3W
Pulse width: 12ps
Condensing spot diameter: φ1μm
Processing feed rate: 400 mm / sec

  By performing the modified layer forming step, the silicon (Si) substrate 21 has a thickness from the front surface 21a of the silicon (Si) substrate 21 that is the finished thickness of the semiconductor wafer 2 to the back surface 21b side, for example, from a position of 100 μm. The modified layer 216 having a thickness of approximately 30 μm is formed. The modified layer 216 formed in this way is located in the middle of the copper (Cu) electrode 214 in the illustrated embodiment.

  As described above, by forming the modified layer 216 inside the silicon (Si) substrate 21, the modified layer 216 serves as a barrier between the back surface 21 b of the silicon (Si) substrate 21 and the modified layer 216. The movement of copper atoms existing in the region is restricted, and copper atoms existing in the region between the back surface 21b of the silicon (Si) substrate 21 and the modified layer 216 are formed on the surface 21a of the silicon (Si) substrate 21. The device 212 is not reached.

  When the above-described modified layer forming step is performed, the back surface of the silicon (Si) substrate 21 constituting the semiconductor wafer 2 on which the modified layer 216 is formed is ground and is ground at a position that does not reach the modified layer 216. The back grinding process is completed. In the illustrated embodiment, this back grinding process is performed using a grinding apparatus 5 shown in FIG. A grinding apparatus 5 shown in FIG. 6A includes a chuck table 51 that holds a workpiece, and a grinding unit 52 that grinds the workpiece held on the chuck table 51. The chuck table 51 sucks and holds the workpiece on the upper surface and is rotated in the direction indicated by the arrow 51a in FIG. The grinding means 52 includes a spindle housing 521, a rotating spindle 522 that is rotatably supported by the spindle housing 521 and rotated by a rotation driving mechanism (not shown), a mounter 523 attached to the lower end of the rotating spindle 522, and the mounter And a grinding wheel 524 attached to the lower surface of 523. The grinding wheel 524 includes an annular base 525 and a grinding wheel 526 that is annularly attached to the lower surface of the base 525, and the base 525 is attached to the lower surface of the mounter 523 with fastening bolts 527. ing.

  In order to perform the back surface grinding process using the grinding apparatus 5 described above, the semiconductor wafer in which the modified layer forming process is performed on the upper surface (holding surface) of the chuck table 51 as shown in FIG. The protective member 3 side adhered to the surface of 2 is placed. Then, the semiconductor wafer 2 is sucked and held on the chuck table 51 via the protective member 3 by operating a suction means (not shown). Accordingly, in the semiconductor wafer 2 sucked and held on the chuck table 51, the back surface 21b of the silicon (Si) substrate 21 is on the upper side. If the semiconductor wafer 2 is sucked and held on the chuck table 51 in this way, the grinding wheel 524 of the grinding means 52 is moved while rotating the chuck table 51 in the direction indicated by the arrow 51a in FIG. In FIG. 6 (a), it is rotated at, for example, 6000 rpm in the direction indicated by the arrow 524a, and as shown in FIG. 6 (b), the grinding surface (lower surface) of the grinding wheel 526 is a silicon (Si) substrate 21 that is the work surface. 6 (a) and (b) in FIG. 6, the grinding wheel 524 is moved downward (the holding surface of the chuck table 51) at a predetermined grinding feed rate (for example, 3 μm / second) as indicated by an arrow 524 b in FIGS. For example, 470 μm grinding feed. At this time, the grinding water is supplied to the grinding portion of the grinding wheel 524 by the grinding wheel 526. In this back surface grinding step, the back surface 21b of the silicon (Si) substrate 21 constituting the semiconductor wafer 2 is ground by 470 μm, for example, and the grinding is finished at a position not reaching the modified layer 216. Accordingly, as shown in FIG. 6C, the thickness of the silicon (Si) substrate 21 constituting the semiconductor wafer 2 is 130 μm, and the copper (Cu) electrode 214 having a length of 130 μm is the back surface of the silicon (Si) substrate 21. Exposed to 21b.

  If the back surface grinding process described above is performed, the back surface 21b of the silicon (Si) substrate 21 whose back surface has been ground is etched, and the etching process for projecting the copper (Cu) electrode 214 from the back surface 21b of the silicon (Si) substrate 21 is performed. To implement. This etching step is performed using an etching apparatus shown in FIG. The etching apparatus 6 shown in FIG. 7 includes a spinner table mechanism 61 and an etchant receiving means 62 disposed so as to surround the spinner table mechanism 61. The spinner table mechanism 61 includes a spinner table 611, an electric motor 612 as a rotation driving unit that rotationally drives the spinner table 611, and a support unit 613 that supports the electric motor 612 so as to be movable in the vertical direction. . The spinner table 611 includes a suction chuck 611a formed of a porous material, and the suction chuck 611a communicates with suction means (not shown). Therefore, the spinner table 611 holds the wafer on the suction chuck 611a by placing a wafer as a workpiece on the suction chuck 611a and applying a negative pressure by a suction means (not shown). The electric motor 612 connects the spinner table 611 to the upper end of the drive shaft 612a. The support means 613 includes a plurality of (three in the illustrated embodiment) support legs 613a and a plurality of (three in the illustrated embodiment) attached to the electric motor 612 respectively connected to the support legs 613a. ) Air cylinder 613b. The support means 613 configured as described above operates the air cylinder 613b to move the electric motor 612 and the spinner table 611 to the workpiece loading / unloading position, which is the upper position shown in FIGS. Is located at the work position which is the lower position shown in FIG.

  The etching solution receiving means 62 includes an etching solution receiving container 621, three supporting legs 622 (two are shown in FIG. 7) that support the etching solution receiving container 621, and the electric motor 612. And a cover member 623 attached to the drive shaft 612a. As shown in FIGS. 8 and 9, the etching solution receiving container 621 includes a cylindrical outer wall 621a, a bottom wall 621b, and an inner wall 621c. A hole 621d through which the drive shaft 612a of the electric motor 612 is inserted is provided at the center of the bottom wall 621b, and an inner wall 621c protruding upward from the periphery of the hole 621d is formed. Further, as shown in FIG. 7, the bottom wall 621b is provided with a drain port 621e, and a drain hose 624 is connected to the drain port 621e. The cover member 623 is formed in a disc shape, and includes a cover portion 623a that protrudes downward from the outer peripheral edge thereof. When the electric motor 612 and the spinner table 611 are positioned at the work position shown in FIG. 8, the cover member 623 configured as described above has a gap on the outside of the inner wall 621 c that constitutes the etching solution receiving container 621. Is positioned to polymerize.

  The etching apparatus 6 in the illustrated embodiment includes an etching solution supply mechanism 64 that supplies an etching solution to a workpiece held on the spinner table 611. The etchant supply mechanism 64 includes an etchant supply nozzle 641 that supplies an etchant toward the workpiece held on the spinner table 611, and an electric motor that can be rotated forward and backward to swing the etchant supply nozzle 641. 642, and an etchant supply nozzle 641 is connected to the etchant supply means 640 (see FIGS. 8 and 9). The etching solution supply nozzle 641 includes a nozzle portion 641a extending horizontally and a support portion 641b extending downward from the nozzle portion 641a. The support portion 641b is provided on the bottom wall 621b constituting the etching solution receiving container 621. The etching hole supply means 640 (see FIGS. 8 and 9) is connected through an insertion hole (not shown). A seal member (not shown) that seals between the support portion 641b and the support hole 641b is attached to the periphery of the insertion hole (not shown) through which the support portion 641b of the etching solution supply nozzle 641 is inserted. The etching solution supply means 640 supplies tetramethylammonium hydroxide (TMAH) in the illustrated embodiment.

  The etching apparatus 6 in the illustrated embodiment includes a cleaning water supply mechanism 65 for supplying water to the workpiece held on the spinner table 611. The cleaning water supply mechanism 65 includes a cleaning water supply nozzle 651 that supplies cleaning water toward the workpiece held on the spinner table 611, and an electric motor that can be rotated forward and backward to swing the cleaning water supply nozzle 651. The cleaning water supply nozzle 651 is connected to the cleaning water supply means 650 (see FIGS. 8 and 9). The cleaning water supply nozzle 651 is composed of a nozzle portion 651a that extends horizontally and has a tip bent downward, and a support portion 651b that extends downward from the base end of the nozzle portion 651a, and the support portion 651b is the etching solution. An insertion hole (not shown) provided in the bottom wall 621b constituting the receiving container 621 is inserted and connected to the cleaning water supply means 650 (see FIGS. 8 and 9). Note that a seal member (not shown) that seals between the support portion 651b and the support hole 651b is attached to the periphery of the insertion hole (not shown) through which the support portion 651b of the cleaning water supply nozzle 651 is inserted.

  The etching apparatus 6 in the illustrated embodiment includes an air supply mechanism 66 for supplying air to the workpiece after cleaning held by the spinner table 611. The air supply mechanism 66 includes an air nozzle 661 that blows air toward the workpiece to be cleaned, which is held by the spinner table 611, and an electric motor 662 that can be rotated forward and backward to swing the air nozzle 661. The air nozzle 661 is connected to the air supply means 660 (see FIGS. 8 and 9). The air nozzle 661 is composed of a nozzle portion 661b that extends horizontally and has a distal end bent downward and has an injection port 661a at the distal end, and a support portion 661c that extends downward from the base end of the nozzle portion 661b. A reference numeral 661c is provided through an insertion hole (not shown) provided in the bottom wall 621b constituting the etching solution receiving container 621, and is connected to the air supply means 660 (see FIGS. 8 and 9). A seal member (not shown) that seals between the support portion 661c is attached to the periphery of an insertion hole (not shown) through which the support portion 661c of the air nozzle 661 is inserted.

  Hereinafter, the etching process implemented using the etching apparatus 6 mentioned above is demonstrated. In order to carry out the etching step, the spinner table 611 constituting the etching device 6 is adsorbed on the protective member 3 side of the semiconductor wafer 2 (the protective member 3 is stuck on the surface) on which the back grinding step described above has been carried out. Place on the chuck 611a. Then, the semiconductor wafer 2 is sucked and held on the suction chuck 611a via the protective member 3 by operating a suction means (not shown). Accordingly, in the semiconductor wafer 2 sucked and held on the suction chuck 611a via the protective member 3, the back surface 21b of the silicon (Si) substrate 21 is on the upper side. At this time, the spinner table 611 is positioned at the workpiece loading / unloading position shown in FIG. 8, and the etching solution supply nozzle 641, the cleaning water supply nozzle 651, and the air supply nozzle 661 are as shown in FIGS. It is positioned at a standby position spaced apart from above the spinner table 611.

If the semiconductor wafer 2 is sucked and held via the protective member 3 on the suction chuck 611a of the spinner table 611 constituting the etching apparatus 6, the silicon (Si) is etched and the etching rate with respect to silicon dioxide (SiO ₂ ). An etching process in which a silicon (Si) substrate is etched using a low etchant to cause the copper (Cu) electrode 214 covered with the silicon dioxide (SiO ₂ ) film 215 to protrude from the back surface 21 b of the silicon (Si) substrate 21. carry out. In order to perform this etching step, as shown in FIG. 10A, the etching solution supply nozzle 651 and the air supply nozzle 661 are positioned at the standby position, and the etching solution supply nozzle 641 is held on the spinner table 611. 2 is positioned above the central portion of the silicon (Si) substrate 21 constituting the substrate 2. Next, the electric motor 612 is operated to rotate the spinner table 611 in the direction indicated by arrow A at a rotation speed of, for example, 100 rpm, and the etching solution supply means 640 is operated to remove tetramethylammonium hydroxide (TMAH) as an etching solution. The supply nozzle 651 is supplied at a rate of 1 liter per minute (1 liter / minute). The tetramethylammonium hydroxide (TMAH) supplied to the etching solution supply nozzle 651 in this way is formed on the back surface 21b of the silicon (Si) substrate 21 constituting the semiconductor wafer 2 held by the spinner table 611 from the nozzle portion 651a. Supplied to the center. Thus, the tetramethylammonium hydroxide (TMAH) supplied to the central portion of the back surface 21b of the silicon (Si) substrate 21 moves toward the outer periphery by centrifugal force while moving the back surface 21b of the silicon (Si) substrate 21. Etch. By performing the etching process in this manner for 5 minutes, the back surface 21b of the silicon (Si) substrate 21 is etched by 30 μm, for example, as shown in FIG. 10B, and the silicon (Si) substrate 21 has a finished thickness. It is formed to 100 μm. Then, the copper (Cu) electrode 214 covered with the silicon dioxide (SiO ₂ ) film 215 is projected from the back surface 21 b of the silicon (Si) substrate 21 by 30 μm.

  By performing the etching process described above, the copper (Cu) electrode 214 can be protruded from the back surface 21b of the silicon (Si) substrate 21 by approximately 30 μm, and exists on the back surface 21b side of the silicon (Si) substrate 21. Copper atoms that are present are also removed by etching. In the above-described etching process, the gettering effect can be obtained by leaving the modified layer 216 on the back surface 21b of the silicon (Si) substrate 21.

  If the etching process is performed as described above, a cleaning process for cleaning the etched semiconductor wafer 2 is performed. In order to perform this cleaning step, the etching solution supply nozzle 641 is positioned at the standby position, and the nozzle portion 651a of the cleaning water supply nozzle 651 constituting the cleaning water supply mechanism 65 is placed on the spinner table 611. Located above the center. Then, the cleaning water supply unit 650 is operated while rotating the spinner table 611 at a rotation speed of, for example, 800 rpm, and the cleaning water is ejected from the nozzle portion 651 a of the cleaning water supply nozzle 651. If the nozzle portion 651a is constituted by a so-called two-fluid nozzle to supply cleaning water and supply air, the silicon (Si) substrate that forms the semiconductor wafer 2 by the cleaning water being ejected by the pressure of the air. The back surface 21b of 21 can be effectively cleaned. At this time, the electric motor 652 is actuated so that the cleaning water sprayed from the nozzle portion 651a of the cleaning water supply nozzle 651 reaches the required angle range from the position where it hits the center of the semiconductor wafer 2 held by the spinner table 611 to the position where it hits the outer periphery. Swing with. As a result, the back surface 21b of the silicon (Si) substrate 21 constituting the semiconductor wafer 2 can be reliably cleaned.

  If the cleaning process is performed as described above, a drying process for drying the cleaned semiconductor wafer 2 is performed. In order to perform this drying step, the cleaning water supply nozzle 651 is positioned at the standby position, and the nozzle portion 661a of the air nozzle 661 constituting the air supply mechanism 66 is located above the center portion of the semiconductor wafer 2 held on the spinner table 611. Position. Then, the air supply unit 660 is operated while rotating the spinner table 611 at a rotation speed of, for example, 3000 rpm, and air is ejected from the nozzle portion 661 a of the air supply nozzle 661. At this time, the electric motor 662 is actuated, and the cleaning water ejected from the nozzle portion 661a of the air nozzle 661 swings within a required angle range from a position where it hits the center of the semiconductor wafer 2 held by the spinner table 611 to a position where it hits the outer peripheral portion. Move it. As a result, the back surface 21b of the silicon (Si) substrate 21 constituting the semiconductor wafer 2 can be reliably dried.

  When the drying process is performed as described above, the rotation of the spinner table 611 is stopped and the air nozzle 661 is positioned at the standby position. Then, the spinner table 611 is positioned at the workpiece loading / unloading position shown in FIG. 8, and the suction and holding of the semiconductor wafer 2 held by the spinner table 611 is released. Next, the processed semiconductor wafer 2 on the spinner table 611 is transferred to the next step by an appropriate transfer means.

2: Semiconductor wafer 21: Silicon (Si) substrate 212: Device 213: bonding pad 214: copper (Cu) electrode 215: silicon dioxide (SiO ₂₎ film 3: protective member 4: laser processing apparatus 41: a chuck of a laser processing device Table 42: Laser beam irradiation means 422: Condenser 5: Grinding apparatus 51: Chuck table of grinding apparatus 52: Grinding means 524: Grinding wheel 6: Etching apparatus 61: Spinner table mechanism 611: Spinner table 62: Etching solution receiving means 64 : Etching solution supply mechanism 65: Cleaning water supply mechanism 66: Air supply mechanism

Claims (2)

A wafer processing method for forming a wafer in which electrodes connected to bonding pads respectively provided in a plurality of devices formed on a surface of a substrate are embedded in the substrate to a predetermined finished thickness,
A modified layer forming step of irradiating a laser beam having a wavelength transparent to the substrate from the back side of the substrate, and forming a modified layer on the back side of the boundary portion defining the finished thickness inside the substrate;
Grinding the back surface of the substrate on which the modified layer is formed, and finishing the grinding at a position not reaching the modified layer; and
Etching the back surface of the ground substrate, and causing the electrode to protrude from the back surface of the substrate.
A method for processing a wafer in which an electrode is embedded.   The method of processing a wafer with an embedded electrode according to claim 1, wherein the electrode is formed of copper (Cu), and the etching step is performed using tetramethylammonium hydroxide (TMAH) as an etching solution.

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