JP2009088073A - Method for measuring thickness of semiconductor substrate in grinding stage - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To measure the in-situ thickness of a semiconductor substrate having a thickness of 20-100 μm at an error range of 0.5 μm or smaller, by using an optical thickness measuring instrument during grinding. <P>SOLUTION: The thickness of a semiconductor substrate W, which is being ground on a semiconductor holder table of a grinding stage, is measured by a thickness measuring instrument 100, which is provided with a sensor head holder 101 having a fluid channel to supply pressurized gas to the outer periphery of a sensor head 102 with a laser light floodlight and a photodetector, a control unit 110 and a data analysis means 120. Midway of grinding or after the completion of grinding, while the pressurized air is being supplied onto the silicon substrate surface of the semiconductor substrate through the sensor head holder 101, a laser light is directed with the floodlight to the surface of the silicon substrate, to which the air is supplied, and a reflection factor from the silicon substrate surface, wherein an air film is formed is used, to calculate the thickness of the silicon substrate of the semiconductor substrate. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to a method for measuring an in-situ thickness of a thin semiconductor substrate in a grinding stage. The substrate thickness measurement method of the present invention is effective for detecting the end point of grinding of a semiconductor substrate on a grinding stage.

There is a demand for an extremely thin semiconductor substrate having a diameter of 300 mm or 450 mm and a thickness of 20 to 80 μm. The silicon substrate surface of the semiconductor substrate whose wiring printed surface is covered with the protective tape is ground with a grinding wheel, and then the ground silicon surface is polished or / and etched to reduce the thickness of the substrate to 20 to 80 μm. As a flattening device for forming a mirror and a mirror surface, a plurality of substrate holder tables capable of holding a substrate by vacuum suction are arranged below, a rotary spindle provided with a rough grinding wheel above each substrate holder table, and a rotary spindle provided with a finish grinding wheel , And a rotating spindle equipped with a polishing tool, and an articulated transfer robot that transfers the substrate stored in the substrate storage cassette to the temporary placement table for alignment, and the substrate on the substrate holder table to the next processing stage And a flattening device equipped with a substrate cleaning equipment It is.

For example, four substrate holder tables that can vacuum chuck five small-diameter semiconductor substrates on one index-type rotary table partitioned into a loading / unloading stage, a first rough grinding stage, a second finish grinding stage, and a polishing stage are described above. Using surface grinding / polishing devices arranged at equal intervals on the same circumference with respect to the axis of the index rotation table, each rotation of the index rotation table with respect to each substrate holder table is 90 degrees. Loading of a semiconductor substrate by an articulated transfer robot, rough grinding of the back side of the substrate by a rough grinding flat grindstone, finish grinding of the back side of the substrate by a flat grinding grindstone, mirror polishing by a polishing pad, and unloading by a transfer device It is known to sequentially perform the processes (see, for example, Patent Document 1). ).

Further, in a flattening apparatus provided with a substrate storage stage outdoors, an articulated transfer robot, an alignment temporary placement table, a grinding stage, a movable transfer pad, a polishing stage, and a cleaning stage, the flattening apparatus A substrate storage stage is provided on the right side of the room from the front side to the back side of the room, and in the room, an articulated transfer robot is installed at a position near the substrate storage stage in the front row of the room. On the right side of the rear row, a temporary positioning table and a movable transfer pad are installed on the center side of the rear row. In the last row, a substrate loading / unloading stage, a rough grinding stage, and a finish grinding stage are arranged in the clockwise direction. Grinding processing stage in which the substrate holder table constituting one stage is concentrically arranged on the first index type rotary table A cleaning device including a rotary chuck cleaner for cleaning the upper surface of the substrate loading table and a pair of rotary cleaning brushes for cleaning the ground substrate surface is moved in a vertical direction and a parallel direction with respect to the upper surface of the substrate holder table. A spindle provided with a rough grinding cup wheel type diamond grinding wheel is provided above the substrate holder table constituting the rough grinding stage so as to be movable up and down relative to the upper surface of the substrate holder table, and above the substrate holder table constituting the finish grinding stage. A spindle having a finish grinding cup wheel type diamond grindstone is provided so as to be movable up and down with respect to the upper surface of the substrate holder table, and a substrate loading / unloading stage is constituted by the cleaning device having the cleaner and the rotary cleaning brush. And a rough grinding cup wheel diamond wheel are used to form a rough grinding stage, and a substrate holder table and a finish grinding cup wheel diamond wheel are used to form a finishing grinding stage. A polishing stage in which a substrate holder table constituting a loading / finish polishing stage and a substrate holder table constituting a rough polishing stage are arranged concentrically on another second index-type rotary table is provided, Above the substrate holder table that constitutes the polishing stage, a spindle for rotatably supporting the cleaning liquid supply mechanism and the polishing pad is provided so as to be movable up and down in parallel with the upper surface of the substrate holder table. A pad, a cleaning liquid supply mechanism, and the movable transfer pad; A substrate holder table with a spindle for rotatably supporting the polishing slurry liquid supply mechanism and the polishing pad above the substrate loading / unloading table by the robot and an articulated transfer robot or another transfer pad or an articulated transfer robot There is also known a semiconductor substrate flattening device which is provided so as to be movable up and down and swingable in parallel with respect to the upper surface, and which comprises a substrate rough polishing stage with this substrate holder table, polishing pad and abrasive slurry liquid supply mechanism (for example, See Patent Document 2. ).

In both of the above-described flattening apparatuses described in Patent Document 1 and Patent Document 2, a two-point indicator substrate thickness meter (two points) is used to determine the end point of grinding of the silicon substrate surface in the rough grinding stage and the finish grinding stage. Formula in-process gauge) is used.

On the other hand, a polishing end point detection device for in-situ polishing of a wiring circuit thin film layer of a semiconductor substrate of a CMP apparatus has a wiring circuit thin film of a semiconductor substrate through a transparent window provided with a laser beam emitted from a laser light source on a polishing pad. Of the optical thin film (wiring circuit thin film layer) deposited on the silicon substrate by receiving the reflected light or transmitted light from the wiring circuit thin film layer with a light receiver and changing the reflectance or transmittance. A method of measuring the thickness in-situ is used (see, for example, Patent Document 3).

Furthermore, the measurement device using a semiconductor laser that measures after grinding and polishing processing with a semiconductor substrate grinding device, polishing device, etc., irradiates a laser beam, measures the reflected laser beam, and an optical triangular distance measurement method However, the spot diameter measured by the semiconductor laser is several tens of microns, and if there is a fine tilt or fine unevenness within the spot diameter range, there will be an error in the average value measurement. In order to prevent the occurrence, a non-contact automatic measurement device using a semiconductor laser beam is used to dispose the upper measurement unit and the lower measurement unit relative to each other vertically, and the upper measurement unit and the lower measurement unit. There has also been proposed a method in which measurement is performed by rotating on the same axis and passing a semiconductor wafer to be measured while rotating between an upper measurement unit and a lower measurement unit (for example, see Patent Document 4).

On the other hand, in the market for measurement equipment attached to semiconductor manufacturing equipment, near-infrared light (wavelength: 1.3 μm) is irradiated on one side of a silicon substrate on a measurement stage, and the reflected light is detected by a photoreceiver to determine the thickness of the silicon substrate. The silicon substrate thickness measuring device for calculating the value is the product name LTM1001 from Presize Gauge Co., Ltd., the product name of the thickness measuring device C8125 from Photogenic Co., Ltd. It has been on sale since 2004.

In addition, a non-contact optical thickness measuring instrument F20-XT using reflectance spectroscopy was put on the market in 2007 by FILMETRICS, INC. (See Non-Patent Document 1).

JP 2000-254857 A US Pat. No. 7,238087 JP 2003-519361 A JP 2000-193425 A Filmetrics Co., Ltd. (Japan), “ADVANCED THIN-FILM MEASUREMENTS SYSTEMS” catalog, published in January 2007, p1-p7

In the substrate flattening apparatus described in Patent Documents 1 and 2, a two-point indicator substrate thickness meter is used to determine the end point of grinding of the silicon substrate surface. The two-point indicator substrate thickness meter measures and measures the thickness distribution variation of the protective tape (approximately 5 to 10 μm) and the thickness distribution variation of the wiring circuit thin film (several nanos to several tens of nanos). The said thickness variation rate with respect to thickness (20-80 micrometers) is large. In addition, the silicon substrate surface due to the gauge may be damaged. The use of a semiconductor substrate thickness measuring means that is a measurement error of a semiconductor element manufacturing μm or less is expected.

In the conventional backside grinding process in which the silicon substrate surface of the semiconductor substrate having a thickness of 100 to 700 mm is reduced by 50 to 500 μm, the thickness of the silicon substrate of the semiconductor substrate subjected to finish grinding is as thick as 50 to 300 μm. The effect of error due to was small. The thickness measuring device using laser light sold after the above-mentioned 2004 can measure the thickness of the silicon substrate layer of the semiconductor substrate, but the grinding process is interrupted during the grinding, Transferring the semiconductor substrate to the measurement stage and measuring the thickness of the silicon layer there is a need to return the semiconductor substrate to the grinding stage again and restart the grinding process if the silicon layer thickness is different from the desired thickness. It is troublesome.

To measure the thickness of the semiconductor substrate in-situ during grinding of the silicon substrate surface of the semiconductor substrate, an end point detection device using the aforementioned spectral reflectance or a displacement sensor using a single laser light reflectance is used. The thickness measuring instrument used is optimal. However, the thickness measuring instrument using the reflection of these infrared laser light and near-infrared laser light is affected by the reflection of grinding droplets scattered during the thickness measurement and the influence of irregular reflection by grinding dust adhering to the semiconductor substrate. As a result, errors are likely to occur in the measured values. The sensor head of the thickness measuring device using these laser light reflectivities is not used on the grinding stage. Since the non-contact automatic measuring device using a pair of upper and lower semiconductor laser beams described in Patent Document 4 is not provided with a hole through which a laser beam passes in a substrate holder table that vacuum chucks a semiconductor substrate, It cannot be applied to the stage.

The present invention provides a thickness measuring device using a spectral reflectance or a thickness measuring device using a single laser light reflectance sensor in a grinding stage of a substrate flattening apparatus described in Patent Document 1 and Patent Document 2, etc. The present invention relates to a method for measuring the thickness of a semiconductor substrate, in which the silicon substrate thickness of the semiconductor substrate on the grinding stage can be measured in-situ within a measurement error of 0.5 μm or less.

According to the first aspect of the present invention, there is provided a substrate holder table supported by a spindle, a grinding wheel supported by a spindle that can be moved up and down above the substrate holder table, and mounted on the substrate holder table. A grinding stage comprising a grinding liquid supply means capable of supplying a grinding liquid while the semiconductor substrate surface and the lower surface of the grinding wheel are rubbed, and a fluid capable of supplying gas to the outer periphery of a sensor head including a laser light projector and a light receiver A thickness measuring device including a sensor head holder provided with a passage, a control unit, and data analysis means is used to place a semiconductor substrate on the substrate holder table so that the silicon substrate surface faces upward, and the spindle of the substrate holder table The grinding wheel is lowered while rotating the spindle that supports the grinding wheel while rotating the wheel. Grinding is performed to reduce the thickness of the silicon substrate by grinding the silicon substrate surface by supplying a grinding fluid to the surface on which the silicon substrate surface and the lower surface of the grinding wheel rub from the grinding fluid supply means while rubbing. During the grinding process or after the grinding process is completed, the laser light is projected from the projector onto the surface of the silicon substrate supplied with gas while the gas is supplied from the sensor head holder of the thickness measuring device to the silicon substrate surface of the semiconductor substrate. Then, the light receiver receives the reflected light from the silicon substrate surface on which the gas film is formed, and transmits it as an electrical signal to the data analysis means via the control unit. The data analysis means determines the thickness of the silicon substrate of the semiconductor substrate. The present invention provides a method for measuring a thickness of a semiconductor substrate.

The invention of claim 2 is a thickness measuring device in which the thickness measuring device independently projects a laser beam having a laser wavelength of 1.3 μm, the laser beam spot diameter is 1.2 to 250 μm ψ, and the rotation speed of the substrate holder table is 20 ～100Min ^-1, the distance between the rotational speed 1,000～4,000Min ^-1, the lower surface and the silicon substrate surface of the sensor head holder of the grinding wheel is 10 to 150 mm, the gas supply amount to the silicon substrate surface 1, The method of measuring a thickness of a semiconductor substrate according to claim 1, wherein the thickness is from 000 to 10,000 cc / min.

The invention of claim 3 is a spectroscopic thickness measuring device in which the thickness measuring device projects near infrared light with a wavelength of 650 nm to 1,700 nm, the rotation speed of the substrate holder table is 20 to 100 min ⁻¹ , The rotational speed is 1,000 to 4,000 min ⁻¹ , the distance between the lower surface of the sensor head holder and the silicon substrate surface is 10 to 150 mm, and the gas supply amount to the silicon substrate surface is 1,000 to 10,000 cc / min. It exists in the thickness measuring method of the semiconductor substrate of Claim 1 characterized by the above-mentioned.

Gas is supplied to the light projecting spot on the silicon substrate surface of the semiconductor substrate, and grinding scraps are washed away, and the centrifugal force of the rotation of the substrate holder table prevents the grinding liquid from entering the light projecting spot. Since a gas transparent film is formed on the measurement spot surface between the sensor head and the silicon substrate surface to be measured, irregular reflection of the projected laser beam is prevented. Therefore, the thickness of the silicon substrate can be measured without capturing irregular reflections caused by grinding scraps or scattered grinding droplets.

Hereinafter, the present invention will be described in more detail with reference to the drawings. FIG. 1 is a plan view of a flattening device, FIG. 2 is a front view with a part of the back surface finishing grinding device cut away, and FIG. 3 is a cross-sectional view of a sensor head holder of the thickness measuring device.

In the planarization apparatus 10 for a semiconductor substrate shown in FIG. 1, the planarization apparatus 10 includes substrate storage stages 13, 13 outside the chamber partition wall 12, and an articulated type on the base 11 inside the chamber partition wall 12. The transfer robot 14, the temporary positioning table 15, the grinding stage 20, the movable transfer pad 16, the polishing stage 70, and the cleaning device 38 are provided in the room. In the storage cassette of the substrate storage stage 13, 25 substrates can be stored.

Each stage is provided with substrate storage stages 13 on the right side of the room from the front side to the back side of the flattening apparatus 10, and a suction arm 14 a is provided near the substrate storage stage in the front row in the room. The articulated transfer robot 14 is provided with a temporary positioning table 15 on the right side of the rear row of the multi-joint transfer robot and a movable transfer pad 16 on the center side of the rear row. The substrate holders 30a, 30b, and 30c constituting the three stages of the loading / unloading stage S ₁ , the rough grinding stage S ₂ , and the finish grinding stage S ₃ are concentrically arranged on the first index type rotary table 2. Is provided with a grinding stage 20 disposed on the surface. Then, on the left side of the articulated transfer robot 14, and the substrate holder table 70a constituting the substrate loading / unloading / finish polishing stage ps _1, the substrate holder table 70b constituting the rough grinding stage _ps 2 (70) first A polishing stage 70 disposed concentrically on a two-index rotary table 71 is provided.

Wherein the upper substrate holder table 30a constituting the substrate loading / unloading stage S ₁ provided on the first index rotary table 2, the rotary chuck cleaner and grinding processed substrate surface to clean the substrate holder table 30a upper surface A cleaning device 38 is provided in which a pair of rotary cleaning brushes for cleaning the substrate is movably movable in a direction perpendicular to and parallel to the upper surface of the substrate holder table.

The substrate holder table 30b upward constituting the rough grinding stage S _2, the spindle 90b provided with a rough grinding cup wheel type diamond grindstone 90a movable up and down relative to the substrate holder table 30b upper surface, constituting the finish grinding stage S ₃ Above the substrate holder table 30c, a spindle 91b provided with a finish grinding cup wheel type diamond grindstone 91a is provided so as to be movable up and down with respect to the upper surface of the substrate holder table. The support plates 90c and 91c of the spindles 90b and 91b can be moved in the vertical direction along the guide guides 90e and 91e. The support plates 90c and 91c are screwed into ball screws that are driven to rotate by the servo motors 90d and 91d. It has become. In the figure, 6 is a two-point indicator substrate thickness meter, and 101 is a sensor head holder of the thickness measuring device 100.

The Configure substrate loading / unloading stage S ₁ by the substrate holder table 30a and articulated transfer robot 14 and the mobile conveyor pad 16 and rotating the chuck cleaning device 38 comprises a cleaner and a rotating cleaning brush, the substrate holder configure the rough grinding stage S ₂ in the table 30b and the rough grinding cup wheel type diamond grindstone 90a, constituting a grinding stage S ₃ finish at said substrate holder table 30c and fine grinding cup wheel type diamond grindstone 91a. The substrate loading / unloading stage S ₁ can be regarded as the cleaning stage since the substrate and the substrate holder table 30a is cleaned.

As the rough grinding cup wheel type diamond grinding wheel 90a, a resin bond diamond grinding wheel having a grinding number (JIS general abrasive grain size) 800 to 1,800 is used, and as a finish grinding cup wheel type diamond grinding wheel, grinding number 2,000 to 8, 000 metal bond diamond wheels or vitrified bond diamond wheels are preferred. The cup wheel type diamond grindstones 90a and 91a are provided with a grinding fluid supply guide as disclosed in FIG. 1 of JP-A No. 2004-167617. As shown in FIG. 2 of Japanese Patent Application Laid-Open No. 2003-218079, the finish grinding stage S ₃ includes a finish grinding cup wheel type diamond grindstone 91a and a silicon substrate surface of a semiconductor substrate from a grinding liquid supply nozzle provided outside the substrate holder table. You may make it supply a grinding fluid to the grinding process point which contact | abuts.

Each of the substrate holder tables 30a, 30b, and 30c of the grinding stage 20 is arranged on the first index type rotary table 2 at equal intervals of 120 degrees on the same circumference.

The grinding stage of the back grinding apparatus is shown in FIG. The substrate holder table (vacuum chuck) 30 includes a porous ceramic disk-shaped mounting table 30 having a diameter substantially the same as the diameter of the workpiece w, and a non-breathable material supporting table 5 having a large and small two-dimensional annular space in the upper part. The upper surface of the porous ceramic disk-shaped mounting table and the upper surface of the non-breathable material support table are placed flush with each other, and the non-breathable material support table is hollowed via the upper surface concave support frame 51 and the bearing 51a. The spindle 52 is rotatably supported. Substrate holder table 30 and 30, motor - is journalled on a spindle shaft 57 which is rotated by one 120 degrees motor M _3. When the substrate is placed on the substrate holder table 30a, the pipe 59 leading to the suction hole is sucked by a vacuum pump (not shown), and the substrate is fixed on the substrate holder table 30. Each substrate holder table 30 and 30 mode - is rotated horizontally by motor M _4, M _5. When the spindle shaft 57 is rotated, the index table 2 is rotated 120 degrees or -120 degrees clockwise, each of the substrate holder table 30a, 30b, 30c following stage position _{S 1,} S 2, _{S 3} Moved to.

Sensor head holder 101 of the thickness gauge 100, finish grinding stage S ₃ of the base third laser beam is projected from the projector to the arm 110 that is erected from the top downwards, preferably in a vertical (90 °) Fixed to face.

The finish grinding cup wheel type diamond grindstone 91 a is supported by an air spindle 42, and the air spindle 42 is rotated by a built-in motor 43. Tighten or tilt bolt 46 with data, - 44 spindle casing, 45 is a bearing, 46 the X-axis (left-right) direction of the tilt adjusting bolt, 46 'Y-axis (longitudinal) direction of the tilt adjusting bolt, _{M 3} is Mo Loosen. Reference numeral 47 is a mounting portion for mounting the casing 44 to the lifting mechanism 48, and 49 is a rail having a concave groove that allows the lifting mechanism to be vertically lifted. A hemispherical concave portion 47a is provided at the lower portion of the attachment portion 47, and a hemispherical convex portion 48a that fits into the hemispherical concave portion 47a is provided at the lower portion of the lifting mechanism 48, between the hemispherical concave portion 47a and the hemispherical convex portion 48a. A gap of 0.05 to 0.1 mm is formed in the.

The tilt adjusting bolt 46, 46 'motor - motor M, before hemispherical recess 47a of the subordinate unit mounted around the lower portion of the hemispherical protrusion 48a of the elevating mechanism 48 by tightening and loosening the driving force of M ₃ The spindle 42 is tilted using the provided gap. 48b ball screw, 48c grinding cup wheel type diamond grindstone 91a finish which is journalled to the spindle 42 by raising or lowering the lifting mechanism by driving the AC servomotor M ₂ at screw coalescence is up and down.

The vacuum means for sucking the void under the porous ceramic substrate holder table 30 is arranged in a vacuum pump, a pipe 59 connected to the vacuum pump, a switching valve 59a, a rotary joint, and a hollow spindle 52 connected to the rotary joint. Composed of pipes. A pure water supply pipe is connected to the switching valve.

Further, in the hollow spindle 52, a pipe that communicates with the concave portion of the upper concave support frame is disposed, and is connected to a rotary joint and a pump that supplies pure water for cooling via a pipe connected thereto. The pure water supplied to the concave support frame recess cools the bottom of the non-breathable material support.

By operating the vacuum means, the semiconductor substrate w placed on the porous ceramic substrate holder table 30 is fixed to the porous ceramic substrate holder table 30 under reduced pressure with the silicon substrate surface facing upward. After the vacuum of the vacuum means is stopped, when the switching valve 60a is switched to the pure water supply side, the pressurized pure water cleans the porous ceramic holder table 30.

The polishing stage 70 is provided on the left side of the articulated transfer robot 14. The polishing stage 70 includes a substrate holder table 70a constituting a substrate loading / unloading / finish polishing stage (ps ₁ ) and a substrate holder table 70b constituting a rough polishing stage (ps ₂ ) as a second index type rotary table 71. Are arranged symmetrically on a concentric circle. Above the substrate holder table 70a constituting the finish polishing stage, a spindle 74 that rotatably supports the cleaning liquid supply mechanism 72 and the finish polishing pad 73 swings up and down with respect to the upper surface of the substrate holder table 70a and can swing linearly. Provided on the arm 77.

The substrate holder table 70a, the finish polishing pad 73, the cleaning liquid supply mechanism 72, and the movable transfer pad 16 constitute a substrate loading / unloading / finish polishing stage (ps ₁ ). The substrate loading / unloading / finish polishing stage ps ₁ and the rough polishing stage ps ₂ are provided with a substrate loading / unloading / finish polishing stage ps ₁ closer to the transfer position to the next tape mounter processing stage (not shown). . Therefore, in the planarization apparatus of FIG. 1, the substrate loading / unloading / finish polishing stage ps ₁ is provided closer to the grinding stage 20. The substrate loading / unloading / finish polishing stage ps ₁ can also be said to be a cleaning stage for cleaning a substrate.

The above substrate holder table 70b constituting the rough grinding stage ps _2, liftable and parallel spindles 74 journalled rotatably abrasive slurry supply mechanism 72 'and coarse polishing pad 73' to the substrate holder table 70b upper surface pendulum swinging or linearly swingably provided, constituting the substrate rough grinding stage ps ₂ out with the substrate holder table 70b and rough polishing pad 73 'and the abrasive slurry supply mechanism 72' to. Substrate loading / unloading / finish polishing stage ps ₁ of the rough polishing pad 73 'is on the swing trajectory of the pad conditioner 75 is provided, the rough polishing pad 73' scraping the lower surface of the dressing grinding stone 75a, causes fluffed, The cleaning water 75b is supplied to the rough polishing pad surface and cleaned. Although not shown, another pad conditioner 75 may be installed on the swinging locus of the finishing polishing pad 73 if necessary.

As the abrasive slurry liquid, a slurry liquid in which abrasive grains such as colloidal silica, cerium oxide, alumina, boehmite, and manganese dioxide are dispersed in pure water is used. If necessary, a surfactant, a chelating agent, a pH adjuster, an oxidizing agent, and a preservative are blended in the slurry liquid. The abrasive slurry liquid is supplied to the polishing cloth surface at a rate of 50 to 1,500 cc / min.

As the cleaning liquid, pure water, distilled water, deep seawater, deionized exchange water, surfactant-containing pure water, or the like is used.

In the substrate flattening apparatus shown in FIG. 1, the rough polishing pad 73 ′ and the finish polishing pad 73 are rotatably fixed in front of an arm 77 supported by a rotation shaft 76. With the rotation of the rotation shaft 76, the polishing pad position (standby position) indicated by the phantom line in FIG. The rotational speed of the polishing heads 70a and 70b is 10 to 150 rpm (min ⁻¹ ), the rotational speed of the substrate holder tables 70a and 70b is 10 to 150 rpm, and the pressure at which the polishing pad is applied to the substrate is 0.05 to 0.3 kg / cm ² , preferably 100 to 200 g / cm ² .

In the polishing pads 73 and 73 ′ of the polishing stage 70 disclosed in FIG. 1, a screwed body 79 screwed with a ball screw 78 rotated by a motor M ₂ moves along the linear guide 80 in the front-rear direction. As a result, the hollow spindle 74 that supports the polishing pad linearly swings on the substrate holder tables 70a and 70b, thereby being retracted to the polishing pad position (standby position) indicated by the phantom line. The spindle 95 of the holder table and the spindle 7 of the index type rotary table 71 are installed upright in the through hole 109 portion of the base 20. The rotation of the hollow spindle 74 is performed by the pulley 81 receiving the rotational drive of the motor M ₁ and transmitting it to the pulley 83 via the belt 82 to rotate the hollow spindle 74. The hollow spindle 74 is raised and lowered by an air cylinder 84. A liquid supply pipe 85 is provided at the center of the hollow spindle 74 and is connected to a rotary joint 86 and further connected to a cleaning liquid supply mechanism 72 or an abrasive slurry liquid supply mechanism 72 ′. A pressurized air supply pipe 88 is connected to the space 87 formed inside the hollow spindle 74 and the liquid supply pipe 85 via the rotary joint 86.

The structure of the second index type rotary table 71 of the polishing stage 70 is similar to the structure of the first index type rotary table 2 of the grinding stage 20 except that there are two substrate holder tables 70a and 70b. That is, in FIG. 5, the substrate holder tables (vacuum chucks) 70a and 70b are made of ceramic disk-like mounting tables 70a and 70b, which are perforated (having a hole diameter of 0.3 to 1 mm) having substantially the same diameter as the workpiece w. The non-breathable material support base 92 is mounted so that the upper surfaces of the perforated ceramic disk-like mounting tables 70a and 70b and the upper surface of the non-breathable material support base 92 are flush with each other. Vacuum means for causing the hollow spindle 95 to be rotatably supported through the upper concave support frame 94 and for reducing the pressure of the annular space 96 of the non-breathable material support base on the bottom surface of the perforated ceramic disk-like mounting base 97. Substrate holder table 70a, 70b are journalled to the spindle 7, the spindle can be rotated by the driving of the motor M _3. The substrate holder table (perforated ceramic disk-shaped mounting table) 70a, 70b may be the same kind of porous ceramic disk used in the grinding stage.

By operating the vacuum means, the semiconductor substrate w placed on the perforated ceramic disk-shaped mounting tables 70a and 70b is fixed to the perforated ceramic disk-shaped mounting tables 70a and 70b under reduced pressure with the substrate surface facing upward. . After the vacuum of the vacuum means is stopped, when the switching valve is switched to the pure water supply side, the pressurized pure water cleans the perforated ceramic disk-like mounting tables 70a and 70b (so-called back flush).

The substrate loading / unloading / finish polishing stage ps ₁ and the rough polishing stage ps ₂ of the polishing stage 70 are filled with abrasive slurry liquid and cleaning liquid scattered due to the presence of the partition wall 108 provided on the second index type rotary table 71. Do not scatter on the opponent's stage.

A thickness measuring device 100 shown in FIG. 3 supplies gas such as pressurized air, nitrogen gas, carbon dioxide gas, etc. between the outer wall of the sensor head 102 and the inner wall of the outer shell 103 by the outer shell 103 surrounding the outer periphery of the sensor head 102 having a laser beam projector and a light receiver. This is a thickness measuring device including a sensor head holder 101 provided with a fluid passage 104 having an annular cross section, a control unit 110, and data analysis means 120. The annular gap width of the fluid passage 104 is 1 to 5 mm. The fluid passage 104 is supplied with a pressurized gas of 0.2 to 0.4 MPa through a pipe by a compressor or a pump (not shown).

As shown in FIGS. 1 and 2, the sensor head holder 101 is installed above the substrate holder 30 c of the finish grinding stage S ₃ of the back grinding apparatus provided on the index table 2. The distance between the lower surface of the sensor head holder 101 and the silicon substrate surface is preferably 10 to 150 mm. Rotational speed of the substrate holder table 20~100rpm ^{(min -1),} the rotational speed of the grinding wheel 1,000~4,000min ^-1, gas supply amount to the silicon substrate surface 1,000～10,000Cc / min It is.

The thickness measuring instrument 100 obtains a thickness measuring instrument including a sensor head 102, a control unit 110, and a data analyzing means 120 of a thickness measuring instrument utilizing the reflectance of the laser beam from the market. A sensor head holder 101 provided with a fluid passage 104 having an annular cross section capable of supplying gas between the inner walls is used by remodeling.

As a thickness measuring device using the reflectance of such commercially available laser light, near infrared light (wavelength 1.3 μm) is irradiated to one side of a silicon substrate on a measurement stage with a laser beam spot diameter of 1.2 to 250 μmφ, As a silicon substrate thickness measuring device that detects the reflected light with a light receiver and calculates the thickness of the silicon substrate, the product name is LTM1001 from Presize Gauge Co., Ltd. and the product name is Thickness Measurement Device C8125 from Photogenic Co., Ltd. Available from FRONTIER SEMICONDUCTOR, USA under the trade name FSM413-300. In addition, as a non-contact optical thickness measuring instrument using reflectance spectroscopy using near infrared light having a wavelength of 650 nm to 1,700 nm with a beam spot diameter of 100 to 1,000 μmψ, non-contact optical from FILMETRICS, INC. It can be obtained from Otsuka Electronics Co., Ltd. under the trade name MCPD5000. White light (420 to 720 nm wavelength) is used as the spectral wavelength for measuring the thickness of the printed wiring board surface of the semiconductor substrate, and 650 nm or 1.3 μm wavelength is used as the spectral wavelength for measuring the thickness of the silicon substrate. .

As the gas supplied to the silicon substrate surface, pressurized gas such as air, nitrogen gas, carbon dioxide gas, helium gas is used.

In the finish grinding stage S ₃ of the grinding apparatus shown in FIG. 1 or FIG. 2, a substrate thickness gauge 100 shown in FIG. 3, the work of performing thinning grinding of the rear surface of the semiconductor substrate is performed through the following steps. Prior to the processing, advance the desired thickness t of the silicon substrate on at finish grinding stage S ₃ input from memory to the operation panel of the control unit 110 of the thickness gauge 100, the data analysis unit 120 is a silicon substrate thickness Is determined by the finish grinding processing and the processing program.

1) The semiconductor substrate w stored in the storage cassette of the substrate storage stage 13 is sucked to the suction pad 14a of the articulated transfer robot 14 and transferred onto the temporary placement table 15 for alignment, where the semiconductor substrate is centered. Make adjustments.

2) the aligned substrate top surface is sucked by the suction pads 14a of the articulated transfer robot then substrate B provided in the first index rotary table 2 - constituting the di S ₁ - loading / unloading stearate The substrate is transferred onto the substrate holder table 30a.

3) by rotating 120 degrees to the first index rotary table 2 clockwise, the substrate being vacuum-chucked to the substrate loading / unloading stage S ₁ position of the substrate holder table 30a of the rough grinding stage S ₂ substrate Transfer to the holder table 30b position.

4) rough grinding the back surface of the substrate which has moved to the rough grinding stage S ₂ using a diamond cup wheel type grinding wheel 90a. During this time, the first and second steps using a multi-joint type transport robot 14 is carried out, a new substrate w is carried onto the substrate loading / unloading stage S _1.

5) by rotating 120 degrees to the first-index the turntable 2 clockwise, while transferred to the substrate holder table 30c position of the grinding stage S ₃ finish a rough grinded substrate, the substrate loading / unloading row ing stage transferring the substrate on the substrate holder table 30a of S ₁ position to the rough grinding stage S _2.

6) In the finish grinding stage S ₃ for finish grinding the rough grinded back surface of the substrate using a cup wheel type diamond grindstone 91a. During this time, the back surface of the substrate at the rough grinding stage S ₂ together with the rough grinding using a cup wheel type diamond grindstone 90a, substrate loading with new substrate via the positioning provisional table 15 by articulated transfer robot 14 / it is conveyed unloading stage S ₁ position on the substrate holder table 30a to.

7) is rotated 120 degrees first index rotary table 2 clockwise or by rotating 240 degrees in a clockwise reverse around direction, transferring the substrates from the fine grinding to the substrate loading / unloading stage S ₁ above At the same time, the roughly ground substrate is transferred to the finish grinding stage S ₃ .

8) lowering the rotating cleaning brush to fine grinding top surfaces of the substrate on the substrate holder table 30a in the substrate loading / unloading stage S ₁ position of the first index rotary table 2, while supplying a cleaning liquid to the upper surface of the substrate The top surface of the substrate is cleaned, and then the ground and cleaned substrate top surface is suctioned to the suction pad 16a surface of the movable transfer pad 16, and then moved to the position indicated by the imaginary line, and then moved again and moved again. 2 index type rotary tape - and transferring the substrate on the substrate holder table 70a located on the substrate loading / unloading / finish polishing stage ps ₁ provided in table 71. The substrate holder table 30a the upper surface in the substrate loading / unloading stage S ₁ position of the first index rotary table 2 during the transfer of the substrate is cleaned by rotating a ceramic chuck cleaner. After washing the substrate holder -30a top, new substrate by articulated transfer robot 14 is transported through the provisional table 15 for positioning on the substrate loading / unloading stage S ₁ position of the substrate holder table 30a described above The first step and the second step are performed. The first index rotary Te - substrate on the substrate holder table 30b located rough grinding stage S ₂ of the table, along with the rough grinding of the fourth step described above is carried out, the finishing of the first index rotary table grinding substrate on the substrate holder table 30c positioned on the stage S ₃ is performed finish grinding of the foregoing sixth step.

9) After the rough grinding of the substrate, the second index-type rotary table 71 is rotated 180 degrees clockwise or clockwise, and the ground and cleaned substrate is roughly polished provided on the second index-type rotary table. It is moved to the stage ps ₂ position. In parallel with this operation, the aforementioned seventh step is executed.

10) The coarse polishing pad 73 ′ rotating on the upper surface of the substrate held on the substrate holder table 70 b located on the coarse polishing stage ps ₂ provided on the second index type rotary table 71 is lowered and rubs the substrate surface. . During the rubbing of the substrate and the rough polishing pad, an abrasive slurry liquid 72 ′ in which abrasive grains are dispersed in water is passed from the abrasive slurry liquid supply mechanism via the polishing pad of the rough polishing pad or the urethane foam sheet pad. The coarse polishing pad 73 ′ is supplied to the upper surface of the substrate and the pendulum swings or linearly swings. At the same time, the aforementioned eighth step is executed. During rough polishing of the substrate, in-situ polishing end point detection of the semiconductor substrate is performed by the spectroscopic photoelectric sensor 120c, and when the polishing end point is detected, the rough polishing process is finished.

11) The second index type rotary table 71 is rotated 180 degrees clockwise or clockwise, and the substrate subjected to the rough polishing is loaded into the second index type rotary table 71 at the substrate loading / unloading / finish polishing stage ps ₁ position. Moved to. Simultaneously in parallel, the first index type rotary table 2 is rotated 120 ° clockwise or 240 ° counterclockwise to transfer the finish-ground substrate onto the substrate loading / unloading stage S ₁ and rough. transferred to the grinding stage S ₃ finish grinding is substrate, transferring the substrate on the substrate loading / unloading stage S ₁ to the rough grinding stage S _2.

12) In the substrate loading / unloading / finish polishing stage ps _{1 of} the second index type rotary table 71, the finish polishing pad 73 rotating on the upper surface of the rough polishing substrate held on the substrate holder table 70a is lowered, and the substrate surface Rub. At the time of rubbing the substrate with the finish polishing pad, a cleaning liquid 72 containing no abrasive grains, such as pure water, is supplied from the cleaning liquid supply mechanism to the upper surface of the substrate via the polishing cloth of the finishing polishing pad 73 or the urethane foam sheet pad. At the same time, the finish polishing pad 73 is swung. Since the finish polishing surface is dried by raising the finish polishing pad 73 and rotating the substrate holder table, the finish polished substrate is dried by the CCD sensor while rotating the substrate holder table. In addition to monitoring (observing) the presence or absence of chipping (breakage), the substrate thickness measurement laser displacement sensor 120b is swung to measure the thickness distribution in the radial direction of the finished polished semiconductor substrate. The semiconductor substrate that has been subjected to finish polishing is transferred to the next mounter processing stage (not shown) using a substrate transfer device having an adsorption pad on the arm or an articulated transfer robot.

13) When finish polished semiconductor substrate is a substrate loading / unloading / finish polishing stage ps ₁ position of the substrate holder table 70a of the second index rotary table 71 becomes free by which is transferred to the stage of the next step, the grinding and cleaned substrate on the substrate holder table 30a in the substrate loading / unloading stage S ₁ position of the first index rotary table 2 adsorbed in a mobile suction pad 16, then the second index rotary table 71 Situated in substrate loading / unloading / finish polishing stage ps ₁ provided to transfer onto the substrate holder table 70a. At the same time, in the respective stages S ₁ , S ₂ , S ₃ of the first index type rotary table 2 and the rough polishing stage ps _{2 of} the second index type rotary table 71, the tenth process including the aforementioned eighth process is executed. Is done.

14) Thereafter, the above-described eleventh step, twelfth step and thirteenth step are repeated, and the substrate surface of the semiconductor substrate is ground, washed and polished, and the operation of thinning and flattening the substrate is continuously performed.

Example 1 Using the substrate flattening apparatus shown in FIG. 1, FSM413-300 (trade name) sensor head “Eco-probe” of US FRONTIER SEMICONDUCTOR as a thickness measuring device (length 50 mm, diameter 25 mm, 1. Using a 3 μm wavelength) A sensor head holder modified so that pressurized air can be supplied to the outer periphery was used, and the sensor head was fixed at a distance of 25 mm between the lower surface of the sensor head holder and the silicon substrate surface. As the semiconductor substrate, a semiconductor substrate having a 300 mm diameter with a polyimide protective film attached to the printed wiring surface and a silicon substrate thickness of about 220 μm is used, and the thickness is reduced by about 180 μm by rough grinding with a cup wheel diamond grindstone with a grinding number of 2000. The thickness was reduced by about 10 μm by finishing with a cup wheel diamond grindstone with a grinding wheel number of 4000, and the finish grinding process was terminated when the silicon substrate thickness fell below 30 μm.

Rotational speed of the substrate holder table 30c is 50min ^-1, rotation speed of the finishing grinding wheel 91a is at 2000 ^-1, compressed air supply amount to the silicon substrate surface was performed finish grinding at 3,000 cc / min.

The 8-point average thickness of the in-situ measurement silicon substrate (Air Dry) at the end of finish grinding was 29.32 μm, and the thickness fluctuation width (σ) was 0.008 μm. Wet measurement finish grinding The ground surface of the semiconductor substrate was washed with pure water, spin-dried, and the thickness of the silicon substrate was measured (dry) on the measurement stage of FSM413-300 (trade name) of US FRONTIER SEMICONDUCTOR. The point average thickness was 29.45 μm, and the thickness fluctuation width (σ) was 0.010 μm.

The deviation between the Air Dry value measured in-situ and the thickness of the silicon substrate measured on the measurement stage is 0.13 μm, and it is understood that the in-situ measured value is reliable.

Comparative Example 1 Finish grinding of a semiconductor substrate was performed in the same manner as in Example 1 except that pure water was not supplied from the sensor head holder. The 8-point average thickness of the in-situ measurement silicon substrate (wet) at the end of finish grinding was 29.28 μm, and the thickness fluctuation width (σ) was 2.583 μm.

Example 2 In Example 1, pressurized air can be supplied to a sensor head of a film thickness measuring device MCPD-5000 (fiber length 2000 mm, diameter 12 mm, using a spectral wavelength of 650 nm) manufactured by Otsuka Electronics Co., Ltd. as a thickness measuring device. The semiconductor substrate was ground in the same manner except that the sensor head holder thus modified was used and the sensor head was fixed at a distance of 15 mm between the lower surface of the sensor head holder and the silicon substrate surface.

The 8-point average thickness was 29.26 μm, and the thickness fluctuation width (σ) was 0.0013 μm. The ground surface of the ground semiconductor substrate was washed with pure water, spin-dried, and the thickness of the silicon substrate was measured (dry) on the measurement stage of a film thickness measuring device MCPD-5000 (trade name) manufactured by Otsuka Electronics Co., Ltd. The 8-point average thickness was 29.68 μm, and the thickness fluctuation width (σ) was 0.0005 μm. The deviation between the Air Dry value measured in-situ and the thickness of the silicon substrate measured on the measurement stage is 0.38 μm, and it is understood that the in-situ measured value is reliable.

Example 3 Using the substrate flattening apparatus shown in FIG. 1, FSM413-300 (trade name) of sensor head “Eco-Probe” manufactured by FRONTIER SEMICONDUCTOR as a thickness measuring instrument (length 50 mm, diameter 25 mm, 1. Using a 3 μm wavelength) A sensor head holder modified so that pressurized air can be supplied to the outer periphery was used, and the sensor head was fixed at a distance of 25 mm between the lower surface of the sensor head holder and the silicon substrate surface. As the semiconductor substrate, a semiconductor substrate having a 300 mm diameter with a polyimide protective film attached to the printed wiring surface and a silicon substrate thickness of about 220 μm is used, and the thickness is reduced by about 130 μm by rough grinding with a cup wheel diamond grindstone with an abrasive number of 8000. The thickness was reduced by about 10 μm by finishing with a cup wheel diamond grindstone with a grinding wheel of 4000, and the finish grinding was terminated when the silicon substrate thickness fell below 81 μm.

The rotation speed of the substrate holder table 30c is 50 mi.
Finish grinding was performed with n ⁻¹ , a rotational speed of the finishing grinding wheel 91a of 2,500 min ⁻¹ , and an air supply amount to the silicon substrate surface of 5,000 cc / min.

The 8-point average thickness of the in-situ measurement silicon substrate (Air Dry) at the end of finish grinding was 81.15 μm, and the thickness fluctuation width (σ) was 0.0012 μm. The ground surface of this finished ground semiconductor substrate was washed with pure water, spin-dried, and the thickness of the silicon substrate was measured (dry) on the FSM413-300 (trade name) measurement stage of FRONTIER SEMICONDUCTOR, USA. The thickness was 81.70 μm and the thickness fluctuation width (σ) was 0.0052 μm.

The in-situ thickness measurement method on the grinding stage of the silicon substrate at the time of finish grinding of the thin semiconductor substrate of the present invention is reliable in the thickness of the silicon substrate without being affected by irregular reflection of the grinding fluid and grinding debris. Measurement results can be presented.

It is a top view of a board | substrate planarization apparatus. It is the front view which notched a part of back surface finishing grinding apparatus. It is sectional drawing of the sensor head holder of a thickness measuring apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Substrate flattening apparatus w Semiconductor substrate S ₃ Finish grinding stage 30 Substrate holder table 100 Thickness measuring device 101 Sensor head holder 102 Sensor head 110 Control unit 120 Data analysis means

Claims (3)

A substrate holder table supported by a spindle, a grinding wheel supported by a spindle provided so as to be movable up and down above the substrate holder table, a semiconductor substrate surface mounted on the substrate holder table, and the grinding wheel A sensor head holding provided with a grinding stage comprising a grinding fluid supply means capable of supplying a grinding fluid while the lower surface of the surface is rubbed, and a fluid passage capable of supplying gas to the outer periphery of the sensor head including a laser beam projector and a light receiver Using a thickness measuring instrument equipped with a tool, a control unit and data analysis means, a semiconductor substrate is placed on the substrate holder table so that the silicon substrate surface faces upward, and a grinding wheel is rotated while rotating the spindle of the substrate holder table. Grinding while grinding the grinding wheel against the silicon substrate surface by rotating and lowering the bearing spindle Grinding is performed to reduce the thickness of the silicon substrate by supplying a grinding liquid to the surface where the silicon substrate surface and the lower surface of the grinding wheel rub against each other from the supply means, and during the grinding process, Alternatively, after the grinding process is completed, a gas film is formed by projecting laser light from the projector onto the surface of the silicon substrate supplied with gas while supplying gas from the sensor head holder of the thickness measuring instrument to the silicon substrate surface of the semiconductor substrate. The light receiving device receives the reflected light from the surface of the silicon substrate, transmits it as an electrical signal to the data analysis means via the control unit, and calculates the thickness of the silicon substrate of the semiconductor substrate by the data analysis means. A method for measuring a thickness of a semiconductor substrate. The thickness measuring device is a thickness measuring device that independently projects laser light having a laser wavelength of 1.3 μm, the laser beam spot diameter is 1.2 to 250 μmφ, the rotation speed of the substrate holder table is 20 to 100 min ⁻¹ , grinding The rotational speed of the grindstone is 1,000 to 4,000 min ⁻¹ , the distance between the lower surface of the sensor head holder and the silicon substrate surface is 10 to 150 mm, and the gas supply amount to the silicon substrate surface is 1,000 to 10,000 cc / The method of measuring a thickness of a semiconductor substrate according to claim 1, wherein the thickness is a minute. The thickness measuring device is a spectroscopic thickness measuring device that projects near-infrared light having a wavelength of 650 nm to 1,700 nm, the rotation speed of the substrate holder table is 20 to 100 min ⁻¹ , and the rotation speed of the grinding wheel is 1,000 to 4,000 min ⁻¹ , the distance between the lower surface of the sensor head holder and the silicon substrate surface is 10 to 150 mm, and the gas supply amount to the silicon substrate surface is 1,000 to 10,000 cc / min. The method for measuring a thickness of a semiconductor substrate according to claim 1.

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