JP5489863B2 - Wafer processing method - Google Patents

Description

  The present invention relates to a wafer processing method in which a back electrode of a wafer is ground and then a through electrode connected to an electrode of a device formed on the front surface of the wafer from the back surface of the wafer is formed.

  A semiconductor wafer formed on the surface by dividing a plurality of devices such as IC, LSI, etc. by grid-like division lines is divided into individual devices by a dicing apparatus, and the divided devices are various types such as mobile phones and personal computers. Widely used in electrical equipment.

  In recent semiconductor device technology, a stacked semiconductor package in which a plurality of semiconductor chips are stacked is effectively used to achieve high density, miniaturization, and thinning. In this semiconductor device technology, the back surface of the wafer is ground with a grinding wheel to reduce the thickness of the wafer to about 50 μm, and then a through electrode is formed from the back surface of the wafer to the device electrode formed on the surface. Before reinforcing the back surface of the wafer, a reinforcing plate is attached to the surface of the wafer via a bonding agent.

  However, since the wafer is exposed to a relatively high temperature environment when forming a through electrode connected to the electrode of the device, it has a strength capable of withstanding a high temperature of 250 ° C. as a bonding agent for attaching a reinforcing plate to the surface of the wafer. The epoxy-type bond agent which has is used.

  Since the bond agent has such a strength that it can withstand a high temperature of 250 ° C., conventionally, to remove the reinforcement plate from the surface of the wafer, the reinforcement plate is heated to raise the bond agent to a temperature of 250 ° C. or higher. The reinforcing plate is detached while being slid from the surface of the wafer so as not to put a burden on the wafer.

JP 2003-249620 A JP 2004-95849 A JP 2004-119593 A

  As described above, in the conventional wafer processing method, a heat-resistant bond agent having a strength capable of withstanding a high temperature of 250 ° C. is used as a bond agent for adhering the reinforcing plate to the wafer, so that a through electrode is formed on the wafer. After that, there is a problem that it is difficult to peel the reinforcing plate from the surface of the wafer.

  The present invention has been made in view of these points, and an object of the present invention is to provide a wafer processing method in which a reinforcing plate can be easily peeled off from the surface of the wafer.

  According to the present invention, there is provided a method for processing a wafer having a device in each region defined by a plurality of division lines formed in a lattice pattern on the surface, wherein the reinforcing plate is provided on the surface of the wafer via a heat-resistant bond agent. A reinforcing plate disposing step, a back surface grinding step of holding the reinforcing plate by a chuck table and grinding the back surface of the wafer with a grinding wheel, and from the back surface of the wafer disposed on the reinforcing plate to the front surface of the wafer. A through electrode forming step for forming a through electrode to be connected to the electrode of the formed device, and a plurality of depths reaching the heat resistant bond agent by holding the back surface of the wafer with a chuck table and cutting the reinforcing plate with a cutting blade A groove forming step for dividing the reinforcing plate into a plurality of pellets, and a melt for melting the heat resistant bond agent from the reinforcing plate side. A heat-resistant bond agent melting step for melting the heat-resistant bond agent, and a reinforcing plate removing step for removing the reinforcing plate divided into pellets from the surface of the wafer. A method for processing a wafer is provided.

  Preferably, in the wafer processing method, after the reinforcing plate removing step is performed, the back surface of the wafer is attached to a dicing tape having an outer peripheral portion attached to the annular frame, and the wafer is attached to the annular frame via the dicing tape. It further includes a wafer supporting step for supporting, and a wafer dividing step for dividing the wafer supported by the annular frame into individual devices.

  According to the present invention, the reinforcing plate is cut with a cutting blade to form a plurality of grooves having a depth reaching the heat-resistant bond agent, the reinforcing plate is divided into pellets, and then the solvent for melting the heat-resistant bond agent is reinforced. Since the heat-resistant bond agent is melted by supplying from the plate side and infiltrating into the groove, the reinforcing plate divided into pellets can be easily removed from the surface of the wafer, and productivity can be improved. it can.

It is a figure which shows a heat resistant bond agent supply process. It is a figure explaining a reinforcement plate arrangement | positioning process. It is a perspective view of the back surface grinding process of a wafer. It is explanatory drawing of a penetration electrode formation process. It is a perspective view which shows a groove | channel formation process. It is a perspective view of a solvent supply process. It is a perspective view which shows a wafer support process. It is a perspective view which shows a wafer division | segmentation process.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Referring to FIG. 1, a perspective view of a heat-resistant bond agent supplying process is shown. In the present embodiment, the heat-resistant bond agent 10 is supplied to the surface 2a of the wafer 2 by spin coating. First, a semiconductor wafer (hereinafter abbreviated as “wafer”) 2 is sucked and held on a rotatable chuck table 4.

  A plurality of streets (division lines) 3 are formed in a lattice pattern on the surface 2 a of the wafer 2, and devices 5 such as IC and LSI are formed in each region partitioned by the plurality of streets 3. . The wafer 2 has a device region 6 in which a plurality of devices 5 are formed on the surface 2 a and an outer peripheral surplus region 7 that surrounds the device region 6.

  In order to spin coat the heat-resistant bond agent on the surface 2a of the wafer 2, the heat-resistant bond agent 10 is applied to the wafer 2 from the heat-resistant bond agent dropping portion 8 while rotating the chuck table 4 in the arrow A direction at, for example, about 300 rpm. It is dripped on the surface 2a.

  When the chuck table 4 is rotated for at least 5 seconds or more, the dropped heat-resistant bond agent 10 is uniformly spin-coated on the surface 2a of the wafer 2, and the heat-resistant bond agent layer 11 is formed. The heat resistant bond agent 10 is formed of an epoxy resin and has a strength capable of withstanding a high temperature of 250 ° C.

  After the heat resistant bond agent layer 11 is formed on the surface 2a of the wafer 2, the reinforcing plate 12 and the surface 2a of the wafer 2 face each other as shown in FIG. It sticks to the surface 2a of the wafer 2.

  After sticking, the wafer 2 and the reinforcing plate 12 are integrally fixed by baking at a predetermined temperature for a predetermined time. The reinforcing plate 12 is made of, for example, a silicon wafer having a thickness of 700 μm, but is not limited thereto.

  Thus, after the reinforcing plate disposing step of disposing the reinforcing plate 12 on the surface 2a of the wafer 2, the reinforcing plate 12 is sucked and held by the chuck table 14 of the grinding device as shown in FIG. A back grinding process for grinding the back surface 2b of the wafer 2 is performed.

  In FIG. 3, the grinding unit 16 of the grinding apparatus is fastened by a spindle 18 that is rotationally driven by a motor (not shown), a wheel mount 20 that is fixed to the tip of the spindle 18, and a plurality of screws 27 that are detachably attached to the wheel mount 20. And a grinding wheel 26 to be operated.

  For example, as shown in FIG. 3, a plurality of grinding wheels 24 in which diamond abrasive grains having a grain size of 0.3 to 1.0 μm are hardened by vitrified bond or the like are fixed to the grinding wheel 26, as shown in FIG. 3. Configured.

  In the back surface grinding process of the wafer 2, the reinforcing plate 12 is sucked and held by the chuck table 14 of the grinding device to expose the back surface 2 b of the wafer 2. While rotating the chuck table 14 in the direction of arrow a at 300 rpm, for example, the grinding wheel 26 is rotated in the same direction as the chuck table 14, that is, in the direction of arrow b at 6000 rpm, for example, and a grinding unit feed mechanism (not shown) is operated to perform grinding. The grindstone 24 is brought into contact with the back surface 2 b of the wafer 2.

  Then, the grinding wheel 26 is ground and fed downward by a predetermined amount at a predetermined grinding feed rate (for example, 3 to 5 μm / second), and the wafer 2 is ground. While measuring the thickness of the wafer 2 with a contact-type thickness measurement gauge (not shown), the wafer 2 is finished to a desired thickness, for example, 50 μm. The wafer 2 is ground while supplying grinding water.

  After performing the grinding process, as shown in FIG. 4, the through electrode forming the through electrode 28 connected to the electrode of the device 5 formed on the front surface 2 a of the wafer 2 from the back surface 2 b of the wafer 2 adhered to the reinforcing plate 12. A forming step is performed.

  In this through electrode forming step, first, a plurality of through holes are formed in the wafer 2 by, for example, laser beam irradiation. As the laser beam, a laser beam having a wavelength (for example, 355 nm) having an absorptivity with respect to the wafer 2 is used, and preferably a third harmonic of a YAG laser or a YVO4 laser is used.

  Next, an insulator such as a polymer material is filled in the through hole. As a filling method, a liquid phase method is preferably used. Since the liquid phase method does not need to heat the wafer 2 to a high temperature, it can be used even for a wafer in which the device 5 is formed in advance.

  Next, a through hole is further formed in the insulator filled in the through hole by etching using a laser processing method or a lithography process. Furthermore, a conductive material such as copper, nickel, palladium, gold, or silver is embedded in the through hole.

  As the conductive material embedding method, dry plating, wet plating, jet painting method, conductive paste or molten metal film forming method, or the like can be used. The through electrode 28 is formed so as to penetrate both the front and back surfaces of the wafer 2, and is electrically connected to the electrode of the device 5 formed on the surface 2 a of the wafer 2.

  After carrying out the through electrode forming step, the reinforcing plate 12 is cut with a cutting blade of a cutting device to form a plurality of grooves that reach the heat-resistant bond agent, and the groove forming step for dividing the reinforcing plate 12 into pellets is performed. To do. In this groove forming step, as shown in FIG. 5, the reinforcing plate 12 is exposed by sucking and holding the wafer 2 with the chuck table 30 of the cutting apparatus.

  A cutting unit 32 of the cutting apparatus includes a spindle that is rotationally driven by a motor (not shown) housed in a spindle housing 34, and a cutting blade 36 that is detachably attached to the tip of the spindle.

  The cutting blade 36 is covered with a wheel cover 38, and a pipe 40 of the wheel cover 38 is connected to a cutting water supply source (not shown). Since the cutting blade 36 needs to form a relatively wide groove 44 in the reinforcing plate 12, for example, a cutting blade having a thickness of about 500 μm is used.

  The cutting water introduced from the pipe 40 is ejected from a cutting water nozzle 42 installed so as to sandwich the cutting blade 36, and the reinforcing plate 12 is cut. At the time of cutting the reinforcing plate 12, the reinforcing plate 12 is cut and turned into a heat-resistant bond agent by feeding the chuck table 30 in the X-axis direction while rotating the cutting blade 36 in the direction of arrow A at a high speed (for example, 30000 rpm). A plurality of grooves 44 having a depth to reach is formed.

  The formation of the groove 44 by the cutting blade 36 may be random. For example, a plurality of cutting grooves are formed while the cutting unit 32 is randomly fed in the Y-axis direction, and the chuck table 30 is further rotated about 90 degrees, and then the same cutting groove is formed. By forming 44, the reinforcing plate 12 is divided into a plurality of pellets. FIG. 6 shows a state in which the reinforcing plate 12 is divided into a plurality of pellets by the groove forming step.

  After the groove forming step, the wafer 2 and the reinforcing plate 12 are placed on the chuck table 46 with the back surface 2b side down on the chuck table 46 as shown in FIG. 6, and the solvent 50 such as methyl ethyl ketone is reinforced from the solvent supply device 48. The heat-resistant bond agent that is supplied onto the plate 12 and infiltrate the solvent into the grooves 44 of the reinforcing plate 12 to form the heat-resistant bond agent layer 12 is melted.

  When the heat-resistant bond agent is melted with a solvent in this manner, the sticking power of the heat-resistant bond agent is weakened. Next, a reinforcing plate removing step for removing the reinforcing plate 12 divided into pellets from the surface 2a of the wafer 2 is performed. To do.

  After the reinforcing plate 12 is removed from the surface of the wafer 2 in this way, the back surface of the wafer 2 is adhered on the dicing tape 52 whose outer peripheral portion is adhered to the annular frame 54 as shown in FIG. A wafer support process for supporting 2 on the annular frame 54 through the dicing tape 52 is performed.

  Next, as shown in FIG. 8, the wafer 2 is sucked and held by the chuck table 30 of the cutting device via the dicing tape 52, and the wafer 2 is fully cut along the planned division line 3 by the cutting blade 36 </ b> A of the cutting unit 32. A cutting groove 56 is formed, and a wafer dividing step for dividing the wafer 2 into the individual devices 5 is performed.

  Unlike the cutting blade 36 used in the groove forming step, the cutting blade 36A is a cutting blade having a cutting edge thickness of about 20 to 30 μm used in normal dicing. When all the streets 3 extending in the first direction have been cut while indexing the cutting blade 36A by street pitch, the chuck table 30 is rotated 90 degrees and then the second direction orthogonal to the first direction is reached. All the streets 3 extending in the direction are cut to divide the wafer 2 into individual devices D.

2 Semiconductor wafer 5 Device 10 Heat-resistant bond agent 11 Heat-resistant bond agent layer 12 Reinforcing plate 28 Through electrode 36, 36A Cutting blade 44 Groove 50 Solvent 52 Dicing tape 54 Annular frame

Claims (2)

A method of processing a wafer having a device in each region defined by a plurality of division lines formed in a lattice pattern on the surface,
A reinforcing plate disposing step of disposing a reinforcing plate on the surface of the wafer via a heat-resistant bond agent;
A back grinding process in which the reinforcing plate is held by a chuck table and the back surface of the wafer is ground with a grinding wheel;
A through electrode forming step of forming a through electrode connected to an electrode of a device formed on the front surface of the wafer from the back surface of the wafer disposed on the reinforcing plate;
A groove forming step of holding the back surface of the wafer with a chuck table, cutting the reinforcing plate with a cutting blade to form a plurality of grooves having a depth reaching the heat-resistant bond agent, and dividing the reinforcing plate into a plurality of pellets When,
Supplying a solvent for melting the heat-resistant bond agent from the side of the reinforcing plate and penetrating the groove into the groove to melt the heat-resistant bond agent; and
A reinforcing plate removing step for removing the reinforcing plate divided into pellets from the surface of the wafer;
A wafer processing method characterized by comprising: After performing the reinforcing plate removing step, a wafer supporting step of sticking the back surface of the wafer to a dicing tape having an outer peripheral portion attached to the annular frame, and supporting the wafer with the annular frame via the dicing tape;
A wafer dividing step of dividing the wafer supported by the annular frame into individual devices;
The wafer processing method according to claim 1, further comprising:

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