JP5890767B2 - Semiconductor wafer thickness measuring method and semiconductor wafer processing apparatus - Google Patents

Description

  The present invention relates to a semiconductor wafer thickness measuring method and a semiconductor wafer processing apparatus.

  In the manufacturing process of a semiconductor device, in order to obtain a target thickness of the device, the back surface is ground and thinned at a stage of a semiconductor wafer (hereinafter simply referred to as “wafer”) which is an assembly of a large number of devices. Has been done. Further, after the grinding process, distortion is also removed by further polishing (polishing) the back surface of the wafer.

  In this grinding process and polishing process, a protective tape is applied to the surface of the wafer on which the circuit pattern is formed for protection, the surface side is chucked on the turntable with air, and the process proceeds while measuring the thickness. It is done.

  In such processing forms, it is important to know the thickness of the wafer being processed in real time, and various measurement methods have been proposed. Further, in the measurement format, a contact-type thickness measurement method (for example, refer to Patent Document 1) in which a measurement probe is brought into contact with the back surface of the wafer, which is a processing surface, or laser light is applied to the top surface (back surface) of the wafer. , A non-contact type thickness measurement method (for example, refer to Patent Document 2) and the like are known, in which reflected light from the front and back surfaces of the wafer is received and the waveform of the interference wave is analyzed. .

  However, as disclosed in Patent Document 1, in the contact-type thickness measurement method using a measurement probe, the surface to be processed is scratched by the contacting probe, and the scratch reduces the strength of the wafer. There is a problem that the thickness of the wafer cannot be detected except for the thickness of the tape.

  On the other hand, in the non-contact type thickness measuring method as in Patent Document 2, the wafer is not touched, so that the surface to be processed is not damaged, and the thickness of the wafer is excluded except for the thickness of the protective tape. There is an advantage that can be detected. However, in the non-contact type thickness measurement method, the detection range (for example, 100 μm or less) in which the wafer thickness can be detected may be limited. For this reason, when processing a wafer having a thickness exceeding the detection range of the non-contact type thickness detecting means, it is necessary to use a contact type thickness measuring method in combination.

  Therefore, the contact-type thickness measurement method and the non-contact type thickness measurement method were used in combination, and during the grinding process, the contact-type thickness measurement method was switched to the non-contact type thickness measurement method. A thickness measurement method is also known (see, for example, Patent Document 3).

Japanese Patent Application Laid-Open No. 2001-9716. JP2009-50944A. JP2011-224678A.

  By the way, in wafer grinding, a grinding wheel mounted on a grinding unit and a wafer fixedly held on a chuck table are arranged opposite to each other, and the grinding wheel is brought into contact with the wafer while the grinding wheel and the chuck table are rotated relative to each other. Grinding. In addition, during the grinding process, grinding water (hereinafter referred to as “processing water”) is supplied to the upper surface (back surface) of the wafer for the purpose of lubrication, cooling and cleaning of the processed part. Furthermore, when measuring the thickness of the wafer in a non-contact manner by irradiating the wafer being doped with laser light or the like, if the measurement is performed with the top surface of the wafer completely dry, the reflection from the top and bottom surfaces will occur. Some wafers have low light interference intensity and are difficult to measure. For such wafers, if a water film with a certain thickness is formed on the upper surface of the wafer, the interference intensity of the reflected light from the upper and lower surfaces becomes stronger and measurement is possible. Measurement may be performed while supplying processing water during grinding.

  However, the processing water supplied to the grinding portion includes grinding waste generated by the processing, and is drained by flowing on the processing surface (upper surface) by the centrifugal force rotating the chuck table. In addition, some are sprayed by a rotating tool and flow and drain in a sprayed state.

  When a laser beam for thickness measurement is irradiated to a wafer in such an environment, the film thickness of the processing water flowing on the wafer varies, or splashes pass through the laser beam. For this reason, fluctuations in the refractive index of the laser beam and situations in which the laser beam is difficult to transmit occur and the interference wave is not stable, resulting in a problem that the measured thickness value is not stable.

  Therefore, when measuring the thickness of a semiconductor wafer using an interference wave of a laser beam, a semiconductor wafer measurement method capable of obtaining a stable measurement value without being affected by processing water and the method are implemented. The technical problem which should be solved arises in order to provide the semiconductor wafer processing apparatus which enables it, and this invention aims at solving this problem.

The present invention has been proposed to achieve the above object, and the invention according to claim 1 is characterized in that the lower surface of the semiconductor wafer is held by holding means, and the upper surface is ground while supplying processing water with a grinding stone. At the same time, the upper surface of the semiconductor wafer being ground is irradiated with laser light, and the interference wave between the laser light reflected on the upper surface of the wafer and the laser light reflected on the lower surface is received to reduce the thickness of the semiconductor wafer. A method for measuring a thickness of a semiconductor wafer in a semiconductor wafer processing apparatus for measuring by contact, wherein air is blown perpendicularly to an upper surface of the wafer to be irradiated with the laser light, and the irradiated portion is irradiated with the air. Provided is a method for measuring a thickness of a semiconductor wafer, in which a thin film having a constant thickness is formed by processing water and the laser beam is irradiated to the semiconductor wafer through the thin film.

  According to this method, a thin film is formed by blowing air onto a surface to be processed (upper surface) of a semiconductor wafer and a portion to be irradiated with laser light. At the same time, grinding waste is blown away. Moreover, when the splash of processed water comes toward the irradiation site, the splash can be prevented from being blown off by air and entering the irradiation site. As a result, a thin film having a constant thickness is always made only at the irradiated portion by the machining water from which cutting waste and splashes are eliminated. The surface to be processed on which the thin film is formed is irradiated with laser light, and an interference wave between the laser light reflected on the upper surface of the semiconductor wafer and the laser light reflected on the lower surface is received, and the interference is received. Based on the wave, the thickness of the semiconductor wafer can be stably derived without contact. The grinding referred to in the present invention includes polishing.

According to a second aspect of the present invention, in a semiconductor wafer processing apparatus for holding a lower surface of a semiconductor wafer by a holding means and grinding the upper surface while supplying processing water with a grinding wheel, laser light is applied to the semiconductor wafer being ground. A semiconductor wafer thickness measuring means for irradiating and receiving an interference wave between the laser beam reflected on the upper surface of the semiconductor wafer and the laser beam reflected on the lower surface and measuring the thickness of the semiconductor wafer in a non-contact manner; comprising spraying vertically air to the irradiation region of the semiconductor wafer is irradiated with a laser beam to the upper surface of the wafer, and air blowing means for forming a thin film single Teiatsumi that by the processing water to the irradiation site, the A semiconductor wafer processing apparatus is provided.

  According to this configuration, when forming a thin film by blowing air onto a surface to be processed (upper surface) of a semiconductor wafer and a portion irradiated with laser light by the air blowing means, together with a part of the processing water at the irradiated portion. The grinding waste is blown off at the same time. Moreover, when the splash of processed water comes toward the irradiation site, the splash can be prevented from being blown off by air and entering the irradiation site. As a result, a thin film having a constant thickness is always made only at the irradiated portion by only the processing water from which cutting waste and splashes are eliminated. Then, the processing surface on which the thin film is formed is irradiated with a laser beam by means of a semiconductor wafer thickness measuring means, and the laser beam reflected on the upper surface of the semiconductor wafer and the laser beam reflected on the lower surface The interference wave is received, and the thickness of the semiconductor wafer can be stably derived without contact based on the interference wave. The grinding referred to in the present invention includes polishing.

According to a third aspect of the present invention, in the configuration of the second aspect, a laser irradiation unit that irradiates a laser beam by the thickness measuring unit of the semiconductor wafer and a light receiving unit that receives the laser beam reflected by the front and back surfaces of the semiconductor wafer. , a semiconductor wafer processing device formed by providing a true on the air outlet of said air blowing means.

  According to this configuration, when measuring the thickness of the semiconductor wafer using the interference of the laser beam, it is possible to apply the laser beam to substantially the center of the irradiation site where the thin film is formed.

According to a fourth aspect of the present invention, there is provided a semiconductor wafer processing apparatus according to the second or third aspect, wherein the thickness of the thin film is set to 10 μm.

  According to this configuration, a stable thickness measurement value can be obtained by setting the thickness of the thin film to approximately 10 μm.

  According to the first aspect of the present invention, when measuring the thickness of the semiconductor wafer using the interference wave of the laser beam, the cutting waste and the splash are eliminated on the processing surface (upper surface) and the irradiated portion to which the laser beam is applied. A thin film of a certain thickness is made only from the processed water, and the surface to be processed is irradiated with laser light, and the reflected wave is received and the thickness is measured from the interference wave. Stable measurement values can be obtained without being affected by grinding scraps and the like, and the effect of improving measurement accuracy is expected.

  According to the second aspect of the present invention, when measuring the thickness of the semiconductor wafer by using the interference wave of the laser beam, the cutting dust is applied to the surface to be processed (upper surface) and the irradiated portion to which the laser beam is applied by the air blowing means. Then, a thin film having a constant thickness is made only from the processing water from which splashes have been eliminated, and the processing surface provided with the thin film is irradiated with a laser beam by means of a semiconductor wafer thickness measuring device, and received from the interference wave. Since the thickness is measured, it is possible to obtain a stable measurement value without being affected by splashes of processing water or grinding scraps, and an effect of improving measurement accuracy is expected.

  In the invention according to claim 3, when measuring the thickness of the semiconductor wafer using the interference of the laser beam, the measurement can be performed by irradiating the laser beam to substantially the center of the irradiation site where the thin film is formed. In addition to the effect of the invention described in claim 2, it is expected that the measurement accuracy is further improved.

  In the invention described in claim 4, a stable thickness measurement value can be obtained by setting the thickness of the thin film to about 10 μm, and in addition to the effects of the invention described in claim 2 or 3, Moreover, the effect of further improving the measurement accuracy is expected.

An example of the semiconductor wafer ground back by the semiconductor wafer processing apparatus which concerns on one Embodiment of this invention is shown, (a) is a perspective view, (b) is a side view. 1 is a schematic configuration layout diagram of a semiconductor wafer processing apparatus according to an embodiment of the present invention. FIG. 3 is a schematic configuration layout diagram of a grinding wheel unit, a chuck table, a water nozzle for supplying processing water, and a thickness measuring instrument of the semiconductor wafer processing apparatus shown in FIG. 2. Sectional drawing explaining the structure of a to-be-contacted type thickness measuring device and an air spraying means. The figure explaining the effect | action of the air spraying means in the semiconductor wafer processing apparatus which concerns on one Embodiment of this invention.

The present invention relates to a semiconductor wafer measurement method capable of obtaining a stable measurement value without being affected by processing water in measuring the thickness of a semiconductor wafer using an interference wave of a laser beam, and the method In order to achieve the object of providing a semiconductor wafer processing apparatus capable of implementing the above, in a semiconductor wafer processing apparatus for holding a lower surface of a semiconductor wafer by a holding means and grinding the upper surface while supplying processing water with a grindstone, The semiconductor wafer being ground is irradiated with laser light, and an interference wave between the laser light reflected on the upper surface of the semiconductor wafer and the laser light reflected on the lower surface is received so that the thickness of the semiconductor wafer is contactless. the thickness measuring means of the semiconductor wafer to be measured, the blowing air to the irradiation site of the semiconductor wafer, one Teiatsumi that by the processing water to the irradiation site that irradiates the laser beam And air blowing means for forming a film was achieved with the construction comprising a.

  Hereinafter, an example of a semiconductor wafer processing apparatus according to an embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows an example of a semiconductor wafer that is back-ground by the semiconductor wafer processing apparatus of the present invention. In the figure, a semiconductor wafer 11 (hereinafter, simply referred to as “wafer 11”) is a silicon wafer or the like, and is a disk-shaped wafer that is thinned by grinding the back surface. The wafer 11 has a uniform thickness of, for example, about 700 μm before processing.

  As shown in FIG. 1A, a plurality of rectangular semiconductor chips 13 are partitioned on the surface 11 a of the wafer 11 by lattice-shaped scheduled division lines 12. An electronic circuit (not shown) such as an IC or an LSI is formed on the surface of the semiconductor chip 13. A V-shaped notch 14 indicating the crystal orientation of the semiconductor is formed at a predetermined location on the peripheral surface of the wafer 11.

  The wafer 11 is cut into a plurality of semiconductor chips 13 by being cut along the planned dividing line 12, but before that, the back surface (this surface becomes the top surface during grinding) 11b is ground. Then, the whole is thinned to the target thickness (for example, 10 to 100 μm) of the semiconductor chip 13 to be obtained. The back surface grinding of the wafer 11 is performed by a semiconductor wafer processing apparatus 21 shown as an embodiment in FIGS. 2 and 3.

  As shown in FIG. 1B, a protective tape 15 is attached in advance to the front surface 11a of the wafer 11 provided to the semiconductor wafer processing apparatus 21 for grinding the back surface 11b. As the protective tape 5, for example, a tape obtained by applying an acrylic adhesive or the like having a thickness of about 10 to 20 μm to one side of a base material such as polyethylene having a thickness of about 100 to 200 μm is used. The purpose of sticking the protective tape 15 is to prevent the electronic circuit formed on the surface of the semiconductor chip 13 from being damaged when the back surface 11b is ground.

  Next, the configuration of the semiconductor processing apparatus 21 for grinding the back surface 11b of the wafer 11 will be described with reference to FIGS. In the figure, a semiconductor wafer processing apparatus 21 includes a chuck table 22 as holding means for holding the wafer 11, a grinding wheel portion 23 for grinding the back surface 11b of the wafer 11, and a cutting surface (back surface 11b) of the wafer 11. A water nozzle 24 for supplying processing water 42 to the contact, a contact-type thickness measuring device 25 and a non-contact-type thickness measuring device 26 for measuring the thickness of the wafer 11 in the middle of grinding in real time, an air supply source 27, and a memory. A unit 28 and a control unit 29 are provided.

  The chuck table 22 is a rotating table that is rotationally driven in the direction of arrow R shown in FIG. 3 by a motor (not shown). On the upper surface of the chuck table 22, there is provided a vacuum chuck portion (not shown) for vacuum-sucking and holding the wafer 11 placed with the surface 11a facing downward so as to be integrally rotatable.

  The grinding wheel portion 23 is attached to the tip of an output shaft 31 of a motor 30 attached to an apparatus main body (not shown), and a grinding wheel 23 a is provided on the surface facing the wafer 11. The grinding wheel 23 and the grinding wheel 23 a are rotated in the direction of arrow R shown in FIG. 3 by the driving force of the motor 30.

  The grinding wheel 23 a is a grinding wheel for grinding the back surface (upper surface) 11 b of the wafer 11 held by suction on the chuck table 22, and for example, a diamond grinding stone using a liquid bond as a binder is used. By making the bonding material a liquid bond, the grindstone has elasticity, the impact force at the time of contact between the grinding grindstone 23a and the wafer 11 is reduced, and the wafer back surface 11b can be processed with high accuracy. The grinding wheel portion 23 is arranged with the grinding wheel 23 a facing the back surface 11 b of the wafer 11 sucked and held by the chuck table 22.

  As shown in FIG. 3, the water nozzle 24 discharges the processing water 42 to the rotation center O of the back surface 11 b of the wafer 11 with respect to the wafer 11 to be ground, fixed and held by the chuck table 22. In this way, the discharge port 24 c is discharged toward the first water nozzle 24 a disposed toward the rotation center O of the wafer 11 and the vicinity of the outer periphery of the wafer 11. And a second water nozzle 24b disposed downstream of the first water nozzle 24a and upstream of the grinding wheel portion 32 with respect to the rotation direction L of the chuck table 22. It becomes. Then, from the first water nozzle 24a and the second water nozzle 24b, the processing water 42 is supplied between the wafer 11 being ground and the grinding wheel 23a by lubrication, cooling, cleaning, and the like.

  Then, the processed water 42 discharged from the discharge port 24c of the first water nozzle 24a toward the rotation center O of the wafer 11 is rotated from the rotation center O toward the outer periphery by the centrifugal force generated by the rotation of the wafer 11. It flows on the back surface 11b while spreading as drawn, and grinding scraps and splashes generated by grinding are flowed to the outer peripheral side to be removed.

  On the other hand, the processing water 42 discharged from the discharge port 24 c of the second water nozzle 24 b toward the outer periphery of the wafer 11 is attracted between the grinding wheel 23 a and the wafer 11 by the rotation of the grinding wheel portion 23. Then, the machined part is lubricated and cooled. The position of the second water nozzle 24b shown in FIG. 3 differs depending on whether the diameter of the wafer 11 is 200 mm or 300 mm, for example, and FIG. 3 shows the case of the wafer 11 having a diameter of 200 mm.

  The contact-type thickness measuring device 25 is a pair of touch sensors 25a and 25b, and probes 32a and 32b are attached to the tips of the touch sensors 25a and 25b, respectively. Also, as shown in FIGS. 2 and 3, one touch sensor 25a is disposed in contact with the vicinity of the outer peripheral edge of the back surface 11b of the wafer 11 rotating the probe 32a, and the other touch sensor 25b is The probe 32b is disposed in contact with the upper surface 22a of the chuck table 22 rotating. More specifically, as shown in FIG. 3, the probe 32a of the touch sensor 25a and the probe 32b of the touch sensor 25b are affected by the processing water 42 discharged from the discharge port 24c of the second water nozzle 24b. In order to reduce this, the grinding wheel portion 23 is disposed downstream of the grinding wheel portion 23 in the rotation direction of the wafer 11 and in the vicinity of the discharge port 24c of the second water nozzle 24b. As in the case of the second water nozzle 24b, the position where the touch sensor 25a is arranged differs depending on whether the diameter of the wafer 11 is 200 mm or 300 mm. In FIG. The case of the wafer 11 is shown. In the case where the diameter is 300 mm, the position is set to a position moved to the outer side in the outer circumferential direction than in the case where the diameter is 200 mm.

  In each touch sensor 25a, 25b of the contact-type thickness measuring device 25, changes in the probes 32a, 32b are converted into voltage signals by a differential transformer. The conversion signal is input to the control unit 28, and the control unit 29 determines the distance between the upper surface 22 a of the check table 22 and the back surface 11 b of the wafer 11 based on the conversion difference voltage signal, that is, the wafer 11 and the protective tape 15. Measure the thickness in real time.

  As shown in FIG. 4, the non-contact type thickness measuring device 26 is integrated with the air blowing means 33. Further, the non-contact type thickness measuring device 26 is affected by the processing water 42 discharged from the discharge port 24c of the first water nozzle 24a and the processing water 42 discharged from the discharge port 24c of the second water nozzle 24b. In order to reduce receiving, the wafer 11 is disposed downstream of the grinding wheel portion 23 in the rotational direction of the wafer 11 and near the outer peripheral edge of the wafer 11 away from the discharge port 24c of the first water nozzle 24a. Has been. On the other hand, as shown in FIG. 2, the air blowing means 33 includes an air supply source 27 and an air nozzle 34 connected to the air supply source 27.

  As shown in FIG. 2, the air nozzle 34 is disposed at a position close to the back surface 11 b of the wafer 11 held on the chuck table 22. Further, as shown in FIG. 4, the first hole 34 a is perpendicular to the back surface 11 b of the wafer 11 and the second hole 34 b is connected to the first hole 34 a at one end side in the air nozzle 34. Yes. Note that the surface of the opening 35 in the first hole 34 a is provided substantially parallel to and opposite to the back surface 11 b of the wafer 11, and therefore air 41 to be described later blown out from the opening 35 is used for the wafer 11. The back surface 11b is substantially perpendicular to the back surface 11b.

  The non-contact type thickness measuring device 26 is provided on the upper end side of the first hole 34a in the air nozzle 34 so as to close the opening side on the upper end side of the first hole 34a. The other end of the second hole 34 b is connected to the air supply source 27. Therefore, in the air nozzle 34, when the second hole 34b receives the supply of the air 41 from the air supply source 27, the air 41 is sent to the first hole 34b side, and further on the lower surface side of the first hole 34b. It is sprayed from the opening 35 substantially perpendicularly to the back surface 11 b of the wafer 11. The portion to which the air 41 is blown is a range indicated by a symbol S in FIG. Hereinafter, this range S is referred to as “irradiation site S”. In addition, the position of the irradiation part S shown in FIG. 3 is also the case where the diameter of the wafer 11 is, for example, 200 mm and 300 mm, as in the case of the second water nozzle 24b and the probe 32a of the touch sensor 25a. FIG. 3 shows the case of the wafer 11 having a diameter of 200 mm. In the case where the diameter is 300 mm, the position is set at a position moved outward in the outer circumferential direction as compared with the case where the diameter is 200 mm. However, the positions of the irradiation point 36 and the probe 32 a in the irradiation site S are the same in each case. It is preferable to arrange on the circumference.

  Further, the air 41 blown to the irradiation site S blows away the processing water 42 and the processing waste in the irradiation site S to the outside. At the same time, as shown in FIG. A thin film t having a certain thickness is formed. In this embodiment, the diameter of the opening 35 is 2 to 3 mm, the amount of blown air 41 is about 100 liters / minute, and the irradiation site S formed by blowing the air 41 is shown in FIG. As shown, the outer periphery of an irradiation point 36 of a laser beam 40, which will be described later, is formed so as to largely surround, and the thickness of the thin film t is set to be approximately 10 μm.

  On the other hand, the non-contact type thickness measuring device 26 attached to the upper end side of the first hole 34a emits a laser beam 40 perpendicularly to the back surface 11b of the wafer 11 through the first hole 34a. A laser irradiation part (not shown) for irradiating the irradiation point 36; and a light receiving part (not shown) such as a photodiode for receiving the reflected light from the back surface 11b of the wafer 11 and the reflected light from the surface 11a. The non-contact type thickness measuring device 26 itself is a generally known measuring device. In addition, a control unit 29 is connected to the non-contact type thickness measuring device 26, and in the control unit 29, a waveform of an interference wave due to reflected waves from the front and back surfaces respectively received by the light receiving unit of the non-contact type thickness measuring device 26. Is detected by a detection circuit (not shown), and the thickness of the wafer 11 is detected according to the waveform.

  The light receiving unit of the non-contact type thickness measuring device 26 is connected to the storage unit 28 for storing the detection result by the light receiving unit. In addition to the detection results measured by the contact-type thickness measuring device 25 and the non-contact-type thickness measuring device 26, the storage unit 28 stores programs for the control unit 29 to execute various processes.

  Next, an example of operation | movement of the semiconductor processing apparatus 21 comprised in this way is demonstrated. The wafer 11 is fixed and held in a vacuum chucked state at a predetermined position on the chuck table 22 with the back surface 11b facing upward (grinding wheel portion 23 side), and along with the chuck table 22 in the direction of arrow L in FIG. Rotate.

  Simultaneously with the rotation of the chuck table 22, the processing water 42 is supplied from the water nozzle 24, and the air 41 is supplied from the air supply source 27 to the air blowing means 33. And this air 41 is sprayed on the back surface 11b of the wafer 11 from the lower surface opening 35 of the 1st hole 34a, and a part of the process water 42 of the irradiation site | part S is removed, and the thin film t is formed in the irradiation site | part S. . The thin film t is formed by removing grinding debris and preventing splash intrusion when the wafer 11 is ground. At the same time, the interference intensity between the reflected light from the back surface 11b of the wafer 11 and the reflected light from the front surface 11a in the thickness measurement by the non-contact type thickness measuring device 26 is increased, and the measurement accuracy by the non-contact type thickness measuring device 26 is improved.

  Further, simultaneously with the formation of the thin film t, the thickness measurement by the contact thickness meter 25 and the thickness measurement by the non-contact thickness meter 26 are performed in real time, and the measurement value by the contact thickness meter 25 and the non-contact thickness measurement. The measurement values obtained by the device 26 are stored in the storage unit 28 in real time. Further, the control unit 29 compares the measured value obtained by the contact-type thickness measuring device 25 with the measured value obtained by the non-contact-type thickness measuring device 26. Then, when the difference between the compared values is within an allowable range, and this state is continuously obtained, the control unit 29 performs a preparation condition for performing the measurement with the non-contact type thickness measuring device 26, that is, performs the measurement. It is judged that the conditions that do not cause any problems are in place.

  Then, the control unit 29 averages the measurement values obtained during a certain time stored in the storage unit 28 to obtain an average value A. Further, when the next average value B measured is more than the allowable range from the average value A, the average value A is adopted again. Further, when the measured average value B is shifted from the average value A by more than an allowable range for a certain time or longer, the measured value obtained by the non-contact thickness measuring device 26 is not adopted, and the contact-type thickness is measured. Grinding is performed based on the thickness measured by the measuring device 25. In other words, the measurement is switched from the non-contact measurement to the contact measurement. Therefore, in the measurement in the control unit 29, it is a preparation condition for performing the measurement that the measurement value itself obtained by the non-contact type thickness measuring device 26 is stable.

  When it is confirmed that the above preparation conditions are set, the value obtained by the non-contact type thickness measuring device 26 is stored in the storage unit 28 and the grinding wheel unit 23 is controlled by the control unit 29. The wafer 11 is lowered and grinding of the wafer 11 is performed until the finish target thickness is reached. Whether or not each of the above preparation conditions is satisfied is checked continuously during the processing, and when a state deviating from the conditions is repeated a predetermined number of times, the non-contact type thickness measuring device 26 is used. The measurement is switched from the measurement by the thickness measurement by the contact-type thickness measuring device 25, and the processing is performed until the target thickness is reached. By performing these controls, the measurement by the non-contact type thickness measuring device 26 can be performed more stably and accurately. Furthermore, even if the measurement by the non-contact type thickness measuring device 26 cannot be performed, the processing thickness of the wafer 11 can be accurately obtained by using the thickness measurement by the contact type thickness measuring device 25.

  As described above, according to the semiconductor wafer processing apparatus 21 of the present invention, when measuring the thickness of the wafer 11 using the interference wave of the laser beam 40, the air blowing means 33 is used to measure the thickness of the wafer 11 on the processing surface. In addition, a thin film t having a constant thickness is formed only by the processing water 42 from which cutting waste and splashes are eliminated at the irradiation site S to which the laser light 40 is applied, and the non-contact type thickness measuring device 26 is applied to the processing surface provided with the thin film t. Between the laser beam 40 reflected from the back surface 11b of the wafer 11 and the laser beam 40 reflected from the front surface 11a by the light receiving unit. Since the wave is received and the thickness is measured from the interference wave, a stable measurement value can be obtained without being affected by the processed water 42 and the waste. Thereby, the measurement accuracy is improved.

  It should be noted that the present invention can be variously modified without departing from the spirit of the present invention, and the present invention naturally extends to the modified ones.

  The present invention can also be applied to a measuring apparatus that applies a laser beam to measure other than the thickness of a semiconductor wafer.

11 Semiconductor wafer 11a surface (lower surface)
11b Back side (upper surface)
21 Semiconductor wafer processing device 22 Chuck table 23 Grinding wheel 23a Grinding wheel 24 Water nozzle 24a First water nozzle 24b Second water nozzle 25 Contact type thickness measuring instrument 25a Touch sensor 25b Touch sensor 26 Non-contact type thickness Measuring device 27 Air supply source 28 Storage unit 29 Control unit 30 Motor 31 Output shaft 32a Probe 32b Probe 33 Air blowing means 34 Air nozzle 34a First hole 34b Second hole 35 Opening 36 Laser light irradiation point 40 Laser light 41 Air 42 Processing Water L Chuck Table Rotation Direction R Grinding Wheel Rotation Direction S Irradiation Site t Thin Film O Wafer Rotation Center

Claims (4)

The lower surface of the semiconductor wafer is held by a holding means, and the upper surface is ground while supplying processing water with a grinding wheel, and the upper surface of the semiconductor wafer is irradiated with laser light and is reflected on the upper surface of the wafer. A method for measuring a thickness of a semiconductor wafer in a semiconductor wafer processing apparatus for receiving an interference wave between a laser beam and a laser beam reflected by a lower surface and measuring the thickness of the semiconductor wafer in a non-contact manner,
Air is blown perpendicularly to the upper surface of the wafer to irradiate the semiconductor wafer to be irradiated with the laser light, a thin film having a constant thickness is formed by the processing water on the irradiated portion, and the laser light is applied to the semiconductor wafer. Irradiating through the thin film, a method for measuring a thickness of a semiconductor wafer. In a semiconductor wafer processing apparatus for holding a lower surface of a semiconductor wafer by a holding means and grinding the upper surface while supplying processing water with a grinding wheel,
The semiconductor wafer being ground is irradiated with laser light, and an interference wave between the laser light reflected on the upper surface of the semiconductor wafer and the laser light reflected on the lower surface is received so that the thickness of the semiconductor wafer is contactless. Means for measuring the thickness of the semiconductor wafer to be measured;
And air blowing means blowing vertically, to form a thin film single Teiatsumi that by the processing water to the irradiated area to the top surface of the wafer to air on the irradiated part of the semiconductor wafer is irradiated with the laser beam,
A semiconductor wafer processing apparatus comprising: The light receiving portion for receiving the laser beam reflected by the front and back surfaces of the semiconductor wafer and the laser irradiation unit for irradiating a laser beam by the thickness measuring means of the semiconductor wafer, formed by providing the air outlet of the true on the air blowing means The semiconductor wafer processing apparatus according to claim 2. 4. The semiconductor wafer processing apparatus according to claim 2, wherein the thickness of the thin film is set to 10 [ mu] m.

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