JP5541681B2 - Wafer flattening method - Google Patents

Description

  The present invention relates to a wafer flattening method for flattening a surface of a wafer such as a silicon wafer cut out from an ingot.

  For example, a silicon wafer forming a device such as an IC or LSI is manufactured by cutting (slicing) a silicon ingot with a wire saw or the like, and flattening both sides of the cut wafer by grinding, lapping, or the like. Yes.

  A substrate wafer obtained by slicing an ingot has fine irregularities and undulations. In addition, there is distortion generated at the time of cutting near the surface. This fine unevenness, waviness and distortion are removed by a flattening process.

  As this flattening processing technique, for example, a flattening method using a grinding apparatus as described in JP-A-2006-261527 is known. In this wafer flattening method, a substrate having excellent flatness is placed on a chuck table, and the wafer is bonded to the substrate via a fluid adhesive to obtain a combined wafer comprising the substrate and the wafer. . By applying ultrasonic vibration to the entire combined wafer, in the curing process of the flowable adhesive, the force for flattening the wafer is suppressed and the adhesive is cured.

  Next, the exposed surface of the wafer is ground and flattened while the substrate is sucked and held by the chuck table. Remove the wafer that has been ground and flattened from the substrate by softening and fluidizing the fluid adhesive and grinding the other surface while holding the flattened surface side with a chuck table. Flatten.

JP 2006-261527 A

  However, in the wafer flattening method disclosed in Patent Document 1, when the wafer is bonded to the substrate using a fluid adhesive, the swell in the cut-out state of the wafer is caused by the viscosity of the fluid adhesive. Even if the flowable adhesive is hardened while being deformed and the ultrasonic wave is applied to the entire wafer and the wafer is bonded to the substrate, the waviness of the wafer is not fully restored due to the viscosity of the flowable adhesive, and the wafer surface is not restored. There is a problem that the back surface cannot be ground sufficiently by grinding the back surface.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a wafer flattening method capable of completely removing waviness from the front and back surfaces of the wafer and flattening the wafer. Is to provide.

According to the present invention, a method for flattening a wafer by grinding both surfaces of a wafer cut out from an ingot to finish it into a flat wafer, and measuring the undulation of one surface and the other surface of the wafer cut out from the ingot A waviness measuring step for recording data, a permeable film having a larger area than the wafer on a surface plate having permeability, and a resin layer formed by applying a liquid resin to be solidified by irradiation of ultraviolet rays on the film. formed, and the wafer adhering step of adhering the one side of the wafer to the resin layer, based on said undulation data obtained by the undulation measurement step, the liquid resin selectively applying ultrasonic waves to the wafer A waviness restoration process in which the viscosity of the wafer is partially reduced to restore the waviness of the wafer; A liquid resin solidifying step of, the film side grinding the other surface of the wafer while holding a chuck table waviness is removed, a first planarization step of finishing flat surfaces of said other, the wafer The film is peeled off from the one surface together with the resin layer, and the other surface of the wafer is held by a chuck table, and the one surface of the wafer is ground to remove waviness, and the one surface is flattened. And a second planarization step for finishing the wafer. A method for planarizing a wafer is provided.

  According to the present invention, after attaching one surface of the wafer to the liquid resin, the ultrasonic wave is selectively applied to the wafer based on the waviness data to partially reduce the viscosity of the liquid resin, and the wafer waviness. Since the waviness restoring process for restoring the waviness is performed, the liquid resin can be solidified and the wafer can be adhered to the film in a state where the waviness of the wafer is sufficiently restored. Next, since the other surface of the wafer is ground while the film side is sucked and held by the chuck table, the waviness can be sufficiently removed from the other surface and the surface can be flattened.

  Next, since one surface is ground while the other surface of the sufficiently ground wafer is sucked and held by the chuck table, waviness can be sufficiently removed from one surface, and the wafer can be formed flat. .

It is a figure which shows the base wafer cut out from an ingot and an ingot. It is explanatory drawing of a waviness measurement process. It is a disassembled perspective view explaining a wafer adhesion process. It is explanatory drawing of a wafer adhesion process. It is explanatory drawing of a wave | undulation restoration process. It is explanatory drawing of a liquid resin solidification process. It is explanatory drawing of a 1st planarization process. It is explanatory drawing of a 2nd planarization process.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Referring to FIG. 1, an ingot 4 such as a silicon ingot and a substrate wafer 2 cut from the ingot 4 by a wire saw or the like are shown. The substrate wafer 2 is cut to a thickness of about 2 mm, and there are fine irregularities, distortions, etc. on the sliced surface, and further, there is a waviness when cutting the wire saw as a whole.

  In the wafer flattening method of the present invention, first, as shown in FIG. 2, the waviness measuring device 6 is used to measure the waviness of the substrate wafer 2, and this waviness data is recorded in a recording device. The substrate wafer 2 has one surface 2a and the other surface 2b, and the substrate wafer is obtained by the undulation measuring device 6 having the measurement head 8a facing the one surface 2a and the measurement head 8b facing the other surface 2b. 2 swell is measured (measured). As a device capable of measuring the undulation of the substrate wafer 2, a bow / warp measuring device SWB-330 manufactured by Kobelco Kaken Co., Ltd. can be used.

  After the waviness measurement process, the wafer adhesion process is performed. In this wafer attaching step, a platen made of a transparent resin such as glass or polycarbonate as shown in FIG. 3 and having a number of suction holes 12 is used. The suction hole 12 of the surface plate 10 is selectively connected to the suction source 14.

  Reference numeral 16 denotes a transparent film such as PET (polyethylene terephthalate), and a resin layer 18 is formed by applying a liquid resin on the transparent film 16 with the transparent film 16 sucked and held by the surface plate 10 as shown in FIG. To do.

  As the liquid resin, an ultraviolet curable hot water wet type resin (manufactured by Three Bond Co., Ltd., trade name “30Y-632D-3”, Toyo Adtech Co., Ltd., trade name “TEMPLOC series”) can be used. Thus, after forming the resin layer 18 which consists of liquid resin on the transparent film 16, the one surface 2a of the base wafer 2 is made to adhere to the resin layer 18. FIG.

  When the wafer attaching step is performed, the state of the undulation of the substrate wafer 2 is changed from the original undulation state by the wafer 2 being pulled by the viscosity of the liquid resin. Therefore, in the present invention, the waviness restoration process for restoring the waviness of the wafer 2 to the original state is performed next.

  In the undulation restoration process, as shown in FIG. 5, the ultrasonic wave generation member 20 formed of a piezoelectric vibrator or the like connected to the high frequency power source 22 is brought into contact with the other surface 2b of the wafer 2 and recorded in the undulation measurement process. Based on the waviness data, ultrasonic vibration is selectively applied to the wafer 2 to partially reduce the viscosity of the liquid resin and restore the waviness of the wafer 2 to the original state. For example, the ultrasonic vibration is selectively applied to the undulation valley portion of the undulation data to restore the undulation of the wafer 2 to the original state.

  After the waviness restoration process is performed, a liquid resin solidification process for solidifying the liquid resin is performed. In this liquid resin solidifying step, as shown in FIG. 6, the liquid resin is solidified by irradiating ultraviolet rays from below the surface plate 10 with an ultraviolet lamp 24.

  When the liquid resin is solidified, a combined wafer 26 in which the substrate wafer 2 is bonded to the transparent film 16 is obtained as shown in FIG. The transparent wafer 16 side of the combined wafer 26 is sucked and held by the chuck table 28 of the grinding device, and the first flattening step of grinding the other surface 2b of the substrate wafer 2 is performed.

  In the first planarization step, as shown in FIG. 7B, the grinding wheel 36 of the grinding unit (grinding means) 30 is positioned on the substrate wafer 2 sucked and held by the chuck table 28 as shown in the drawing.

  The grinding unit 30 has a wheel mount 34 fixed to the tip of a spindle 32 that is rotationally driven by a motor, and a grinding wheel 40 is annularly disposed on the wheel mount 34 at the free end of an annular base 38. The ground grinding wheel 36 is detachably mounted.

  While rotating the chuck table 28 in the direction of the arrow a at 300 rpm, for example, the grinding wheel 36 is rotated in the direction of the arrow b at 6000 rpm, for example, and the grinding unit feed mechanism is driven to move the grinding wheel 40 to the other surface 2b of the substrate wafer 2. Contact.

  Then, the grinding wheel 30 is ground and fed downward by a predetermined grinding feed rate, and the other surface of the substrate wafer 2 is ground. Thereby, the waviness of the other surface 2b of the wafer 2 is removed, and the other surface 2b is finished flat.

  After the first flattening step is performed, the ground union wafer 26 is removed from the chuck table 28, and the union wafer 26 is immersed in warm water filled in a container (not shown) to bond the wafer 2 to the transparent film 16. Since the resin layer 18 swells and its adhesive strength disappears, the wafer 2 can be peeled from the transparent film 16.

  Next, as shown in FIG. 8, the other surface 2b side of the peeled wafer 2 is sucked and held by the chuck table 28, and one surface 2a of the wafer 2 is ground to remove waviness, and the one surface 2a is removed. A second flattening step for flattening is performed.

  In the second flattening step, as in the first flattening step, the grinding wheel 36 is rotated in the arrow b direction at 6000 rpm while the chuck table 28 is rotated in the arrow a direction at 300 rpm, for example. The grinding feed mechanism is driven to bring the grinding wheel 40 into contact with one surface 2 a of the wafer 2.

  Then, the grinding wheel 36 is ground and fed downward by a predetermined amount at a predetermined grinding feed speed, and the one surface 2a of the wafer 2 is ground. One surface 2a of the wafer 2 is ground while measuring the thickness of the wafer 2 with a contact type or non-contact type thickness gauge, and the wafer 2 is finished to a desired thickness, for example, 700 μm.

  According to the above-described embodiment, the waviness of the wafer 2 cut out from the ingot 4 is measured, waviness data is recorded, and after one surface 2a of the wafer is adhered to the liquid resin, the wavy data is applied to the wafer based on the recorded waviness data. The ultrasonic wave is selectively applied to partially reduce the viscosity of the liquid resin, and the wavy state of the wafer 2 is restored to the original state.

  Since the swell of the wafer 2 is sufficiently restored to its original state, the liquid resin is solidified by irradiation with ultraviolet rays, and the other surface 2b of the wafer 2 is ground while sucking and holding the transparent film 16 side with the chuck table. Waviness can be completely removed from the surface 2b.

  Next, since one surface 2a of the wafer 2 is ground while the other surface 2b of the wafer 2 ground sufficiently flat is sucked and held by the chuck table, the waviness can be completely removed from the one surface 2a. The wafer 2 can be formed flat with a thickness of about 700 μm.

2 Substrate wafer 4 Ingot 6 Waviness measuring device 10 Surface plate 16 Transparent film 20 Ultrasonic vibrator 24 Ultraviolet lamp 28 Chuck table 30 Grinding unit 36 Grinding wheel 40 Grinding wheel

Claims (1)

A wafer flattening method in which both sides of a wafer cut out from an ingot are ground to finish a flat wafer,
A waviness measuring step of measuring waviness of one side and the other side of the wafer cut out from the ingot and recording waviness data;
A transparent film having an area larger than the wafer is laid on a transparent platen, and a liquid resin that is solidified by irradiation of ultraviolet rays is applied on the film to form a resin layer. and the wafer adhering step of adhering the one side said,
Based on the waviness data obtained by the waviness measurement step, a waviness restoration step for selectively reducing the viscosity of the liquid resin by selectively applying ultrasonic waves to the wafer to restore the waviness of the wafer;
A liquid resin solidification step of solidifying the liquid resin by irradiating ultraviolet rays from the surface plate side;
The film side grinding the other surface of the wafer while holding a chuck table waviness is removed, a first planarization step of finishing flat surfaces of said other,
The film is peeled together with the resin layer from the one surface of the wafer, and the other surface of the wafer is held by a chuck table to grind the one surface of the wafer to remove waviness. A second planarization step of finishing the surface flatly;
A method for flattening a wafer, comprising:

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