JP3711416B2 - Semiconductor wafer chemical wrapping equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a semiconductor wafer chemical wrap apparatus used in a semiconductor wafer processing process.
[0002]
[Prior art]
  In a semiconductor wafer manufacturing method, a semiconductor wafer obtained by cutting a cylindrical semiconductor (silicon) single crystal rod in a slicing step is lapped (mechanically polished) to remove saw marks and the like. Then, this semiconductor wafer is subjected to etching (chemical treatment) to remove the work-affected layer, and is further mirror-finished by polishing (mechanical chemical polishing).
  However, in the semiconductor wafer manufactured through the lapping process in this way, although the surface flatness is high to some extent, it is accompanied by a work-affected layer, and etching is performed to remove this work-affected layer. It is necessary to increase the etching amount (removal allowance) of, for example, about 20 to 30 μm. As a result, the unevenness (flatness) of the etched surface was increased to about 1 μm, for example. Furthermore, the amount of mirror polishing after etching has increased to, for example, about 10 to 20 μm.
[0003]
  Therefore, in order to further increase the flatness of the semiconductor wafer, it is conceivable to directly grind the wafer surface after slicing. By the way, conventionally used grinding machines have an annular grinding blade and are configured to grind semiconductor wafers placed and fixed on a table by vacuum suction one by one. For this reason, even if one side of the semiconductor wafer after slicing is ground and then the other side is ground, saw marks due to slicing remain on the front and back surfaces of the semiconductor wafer. Then, when the semiconductor wafer having both sides ground in this way is etched and further polished (polished) on one side, the saw mark is raised. Thus, if single-side grinding is performed instead of lapping, the saw marks in the slice cannot be completely removed from the wafer surface. In this way, lapping is not possible with single-side grinding.
[0004]
  Therefore, double-sided simultaneous rackIsHas been done. A feature of double-sided simultaneous wrapping is that it is not necessary to place a reference surface for processing on the material (semiconductor wafer) side. It can be said that the reference surface of the lap is constituted by an active virtual surface (effective action surface) of the surface plate surface on the apparatus side. But it depends on the stiffness of the material. Consider each finish using a model in which the surface shape of the semiconductor wafer is a sine curve.
  As shown in FIG. 8 (a), the surface of the sliced semiconductor wafer has irregularities, and these irregularities are shown in FIG. 8 (b) and FIG. 8 (c). It consists of “swelling ingredients”. The waviness component was an intermediate line on the front and back surfaces of the wafer.
  When the semiconductor wafer of FIG. 8B is processed from one side to make the thickness uniform (see FIG. 8D-1), the uneven surface on the non-processed side is formed as shown in FIG. 8D-2. The copied surface is created (backside transfer).
  Further, when both sides of the semiconductor wafer are pressed and processed simultaneously from both sides (see FIG. 8 (e-1)), the thick part is processed from both sides (see FIG. 8 (e-2)), and unevenness of the thickness component is observed. Although the semiconductor wafer is an elastic body, when the processing pressure is released after processing, a swell component remains as shown in FIG. 8 (e-3).
[0005]
  Here, an outline of a conventional lapping apparatus and chemical etching will be sequentially described.
(About wrapping device)
  Lapping is a process for removing the concavo-convex layer on the wafer surface caused by slicing to increase the flatness of the surface and the parallelism of the wafer. The sliced semiconductor wafer is placed between upper and lower lap surface plates made of cast iron kept parallel to each other. Usually, an alumina abrasive solution is poured between a lapping platen and a semiconductor wafer, and both surfaces of the wafer are mechanically processed by rotation and sliding under pressure.
[0006]
(About chemical etching)
  A silicon wafer that has undergone block cutting, outer diameter grinding, slicing, and lapping machining processes has a damaged layer, that is, a work-affected layer on the surface. The work-affected layer must be removed completely because it induces crystal defects such as slip dislocations in the device manufacturing process, lowers the mechanical strength of the wafer, and adversely affects the electrical properties. The work-affected layer introduced into the silicon wafer by the machining process is completely removed by chemical etching. As described above, the main purpose of chemical etching is to remove the work-affected layer, but it also has the purpose of precise control of the wafer thickness.
[0007]
  Typical etchants for the above chemical etch are etchant (HF) and nitric acid (HNO).₃) Mixed acid in water (H₂O 2) or acetic acid (CH₃Si, which is an acid etching solution with ternary elements diluted with COOH 3), is etched in the following two steps (a) and (b).
  (A) Oxidation of Si with nitric acid:
    Si + 4HNO₃→ SiO₂+ 4NO₂+ 2H₂O
  (B) SiO with hydrofluoric acid₂Dissolution removal
    SiO₂+ 6HF → H₂SiF₆+ 2H₂O
[0008]
[Problems to be solved by the invention]
  However, the prior art has a number of problems (1) to (6) as described below.
  (1) A semiconductor wafer is sliced by slicing a cylindrical semiconductor crystal rod, and lapping using abrasive grains having an average particle size of about 13 μm is performed to remove a surface damage layer at the time of slicing. After the lapping process, the damaged layer leaves a damaged layer of about 7 to 12 μm. Furthermore, because of this damaged layer, it is necessary to remove this processed layer in the next etching step.
  In this etching, since the damaged layer is deep, a smooth surface is not obtained, and the machining allowance must be removed deeply (damage depth (10 μm) + undulation reduction treatment depth (20 μm)).
[0009]
  (2) Since lapping and etching are performed by separate devices, the cost increases, and it takes a long time to complete both lapping and etching, and the productivity of the semiconductor wafer is low.
  (3) Since pressure crushing machining is performed with abrasive grains, machining damage remains remarkably, and the allowance for etching, which will be described later, must be increased to about 20 to 40 μm.
  (4) As described above, since both surfaces of the semiconductor wafer are wrapped in a pressurized state, processing is performed from a thick portion, and the unevenness of the thickness component is removed. At this time, the semiconductor wafer is temporarily treated by the processing pressure. Therefore, when the processing pressure is released after processing, the swell component remains.
  (5) Regarding the warpage of the semiconductor wafer, even if the semiconductor wafer after cutting is warped, the semiconductor wafer becomes flat between the parallel surface plates even with a small processing pressure. Assuming that this constant working pressure is Fc, if lapping is performed in the condition of 0 <F <Fc, as shown in FIG. 7B, the original shape changes due to pressurization, and the warp remains after lapping. The general processing pressure F is larger than F. In the case of F ≧ Fc, as shown in FIG. 7C, the semiconductor wafer becomes thin while maintaining the original pattern. That is, in practice, it is difficult to correct the deformation of the wafer typified by warpage caused by slicing by lapping or subsequent etching or polishing.
  (6) Since the lapping liquid adheres to the semiconductor wafer after lapping, it takes time and effort to remove the lapping solution, and the load on the semiconductor wafer due to cleaning is large. In addition, disposal processing such as condensation / precipitation / solidification of the lap liquid is costly.
[0010]
  The present invention has been made in view of the above-described problems of the prior art, and is intended to reduce the apparatus cost and improve the productivity,WrapThe total allowance is small, and further, swell・ SleighAn object of the present invention is to provide a chemical wrapping apparatus for a semiconductor wafer, which can reduce the components and easily perform the subsequent polishing.
[0011]
[Means for Solving the Problems]
The chemical wrapping apparatus for semiconductor wafers of the present invention cuts the concavo-convex layer on the wafer surface generated by slicing in a semiconductor wafer sliced and cut out from a semiconductor single crystal rod to increase the flatness of the surface and the parallelism of the wafer and at the time of slicing Chemical wrapping of a semiconductor wafer that chemically wraps both wafer surfaces simultaneously to remove the surface damage layer A device,
A casing,
Provided in the casing in parallel with each other, at least the opposite surfaces are surface plate surfaces formed of heat-resistant and alkali-resistant resin, respectively, and in contact with both wafer surfaces of the semiconductor wafer on the surface plate surface, respectively. And upper and lower surface plates
Relative motion means for causing the upper surface plate and the semiconductor wafer to move relative to each other in a direction along the wafer surface, and for causing the lower surface plate and the semiconductor wafer to move relative to each other in a direction along the wafer surface;
A heater in the casing;
Means for pouring free abrasive grains made of alumina between the surface plate surface and the semiconductor wafer,
In the casing, at least the semiconductor wafer and each surface plate surface are immersed, and an alkaline solution having a concentration of 5% or more is supplied,
The chemical wrap speed is 4.0 μm / min or more,
The alkaline solution in the casing is controlled to a constant temperature of about 45 ° C. to 80 ° C. by the heater,
The contact pressure when the platen surface is brought into contact with the semiconductor wafer is 5-50 g / cm so that the semiconductor wafer does not press and extend and the warp and swell do not elastically deform during processing. ² The above-mentioned problem was solved by setting the size to a certain level.
In the present invention, the semiconductor wafer is held by a carrier having outer peripheral teeth, while the upper surface plate and the lower surface plate each have a center hole,
The relative motion means is
A sun gear provided in the center hole so as to mesh with the outer peripheral teeth of the carrier; and provided on the outer side of the upper surface plate and the lower surface plate so as to mesh with the outer peripheral teeth of the carrier. A ring-shaped inner peripheral gear for revolving and rotating around the sun gear;
It is preferable that the driving mechanism is configured to rotate the sun gear and the ring-shaped inner peripheral gear.
In the present invention, the surface plate surface may be provided with a plurality of grooves in a grid pattern or in the radial direction and the circumferential direction.
In the present invention, the concentration of the alkaline solution may be 5 to 6%.
[0012]
To achieve the above object, the present invention provides a semiconductor wafer chemical lapping apparatus for simultaneously chemically polishing both wafer surfaces of a semiconductor wafer obtained by slicing a semiconductor single crystal rod. Provided in the casing in a parallel state, at least opposing surfaces are surface plate surfaces formed of heat-resistant resin, and upper surfaces that are in contact with both wafer surfaces of the semiconductor wafer on the surface plate surface, respectively. And a relative movement for moving the upper surface plate and the semiconductor wafer relative to each other in a direction along the wafer surface, and to move the lower surface plate and the semiconductor wafer relative to each other in a direction along the wafer. And at least the semiconductor wafer and each surface plate surface in the casing. As immersed, supplies temperature-controlled alkaline solution, 5 to 50 g / cm, such as contact pressure is not extended to press the semiconductor wafer when contacting the surface plate surface to the semiconductor wafer ² It is characterized by having a size of about.
  Further, the semiconductor wafer is held by a carrier having outer peripheral teeth, while the upper surface plate and the lower surface plate each have a center hole, and the relative movement means is engaged with the outer peripheral teeth of the carrier. The sun gear provided in the center hole and the outer surface plate of the upper surface plate and the lower surface plate so as to mesh with the outer peripheral teeth of the carrier, and the carrier revolves and rotates around the sun gear. A ring-shaped inner peripheral gear, and a drive mechanism for rotating the sun gear and the ring-shaped inner peripheral gear.
[0013]
  In addition, loose polishing is applied to the surface plate surface.Pour grainsOr a large number of grooves on the surface plate surface. And it is preferable that the temperature and density | concentration of the said alkaline solution are 45 degreeC or more and 5% or more, respectively.
  The contact pressure when the surface plate surface is brought into contact with the semiconductor wafer is 5 to 50 g / cm.² Can be of the order of magnitude.
[0014]
  The operation of the present invention will be described below.
  In the present invention, the alkaline solution reacts with both wafer surfaces, and the semiconductor wafer is chemically treated.WrapAnd a reaction product is produced. At this time, both wafer surfaces of the semiconductor wafer are applied to the upper and lower surface plates with a small processing pressure.ScrapedMicroscopic damage is given to the convex part of both wafer surfaces, and the chemicalWrapIs promoted. chemicalWrapBy using as a main component, the processing pressure can be reduced, thereby reducing the processing damage layer (non-damage or little shallow damage).
  As described above, since the upper surface plate and the lower surface plate are merely brought into contact with both the wafer surfaces of the semiconductor wafer or are brought into contact with each other under a small processing pressure, swell and warpage are reduced. Further, assuming that the processing pressure between the lapping surface plate and the wafer is infinitely small, as shown in FIG. 7A, the warp of the semiconductor wafer disappears, and both wafer surfaces have the same flatness as the surface plate surface. Get closer to. Further, since the semiconductor wafer has a small elastic deformation (it cannot be said that it is not deformed at all by the action of gravity), the swell component is also reduced.
[0015]
  In the present invention, both the wafer surfaces of the semiconductor wafer are made uniform by rotating and revolving the carrier holding the semiconductor wafer by simple relative motion means composed of a sun gear and a ring gear (internal gear). Can be polished. In the present invention, the surface plate surface of each surface plate (the upper surface plate is the lower surface and the lower surface plate is the upper surface)PlayBy providing the abrasive grains, the application of the micro damage is promoted. Furthermore, in the present invention, by providing grooves on each surface of the upper and lower surface plates, for example, in a lattice shape or a radial shape, the alkaline solution on both wafer surfaces of the semiconductor wafer moves in the grooves, so that the alkaline solution is replaced. (Replacement of reaction products) is continuously promoted and chemicalWrapSpeeds up. In the present invention, the temperature and concentration of the alkaline solution are 45 ° C. or more and 5% or more, respectively.WrapCan be increased so that the present invention is sufficiently industrially beneficial.
  In the present invention, chemicalWrapSince the semiconductor wafer surface is simultaneously ground at a low processing pressure by the upper and lower surface plates, warpage and undulation do not occur, and a highly flat semiconductor wafer can be obtained. In addition, since the processing pressure can be reduced as compared with the conventional pressure crushing machining, the processing damage layer is reduced. As a result, the damage layer on both wafer surfaces is 0 to 2 μm compared to the conventional 10 μm. Can be very small.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
  Next, an embodiment of the present invention will be described with reference to the drawings.
  1 is a longitudinal sectional view of an embodiment of a chemical wrapping apparatus for a semiconductor wafer of the present invention, FIG. 2 is a schematic plan view (top view) of an embodiment of a chemical wrapping apparatus for a semiconductor wafer of the present invention, FIG. These are the figures which expanded the carrier and semiconductor wafer between an upper and lower surface plate in this embodiment example.
[0017]
  As shown in FIGS. 1 and 2, reference numeral 1 denotes a bottomed cylindrical casing (device main body), and a leg portion 23 is attached to the outer bottom surface of the casing 1. The casing 1 can be placed in a horizontal state on a horizontal plane via the leg portion 23. The casing 1 is provided with a lid (motor base cover) 15 that can be freely opened and closed. That is, a pair of brackets 30 a and 30 b are fixed to the outer periphery on one end side of the casing 1, and the upper lid support portion 18 on one end side of the lid 15 is connected to the pair of brackets 30 a and 30 b via the support shaft 19. It is supported so as to be rotatable (see arrow A in FIG. 1). A handle (grip handle) 16 is provided on the other end side of the lid 15. By lifting the handle 16 from the state of FIG. 1, the lid 15 can be rotated about the support shaft 19 (see arrow A), and the upper end opening of the casing 1 can be opened.
[0018]
  A disc-shaped lower surface plate base member 10 having a center hole is mounted on the inner bottom surface of the casing 1. On the lower surface plate base member 10, a disk-shaped lower surface plate 3 having a center hole 3a is mounted. A plurality of pin members 20 a and 20 b are integrally projected on the bottom surface of the casing 1, and the pin members 20 a and 20 b pass through the lower surface plate base member 10 and fit into holes on the lower surface of the lower surface plate 3. Accordingly, the lower surface plate base member 10 and the lower surface plate 3 are not displaced in the horizontal direction. Above the lower surface plate 3, an upper surface plate 2 having a center hole 2 a is provided in parallel with the lower surface plate 3.
[0019]
  A first drive motor 11 is fixed to the upper surface of the lid 15 via a bracket 21, and a drive pin 8 is coaxial with a rotary shaft (output shaft) 11 a extending downward from the first drive motor 11. It is fixed integrally with. A sun gear 7 described later is engaged with the lower end of the drive pin 8 in the circumferential direction via the engagement pin 22. The engagement pin 22 is supported through the lower end portion of the drive pin 8. A sun gear support shaft 5 projects from the center of the inner bottom portion of the casing 1, and a sun gear 7 is rotatably fitted and supported on the sun gear support shaft 5. The sun gear 7 has outer peripheral teeth 7a on the outer periphery thereof, and the outer peripheral teeth 7a mesh with outer peripheral teeth 33a, 33b, 33c of a plurality of (three in this example) wafer carriers 4a, 4b, 4c described later. ing.
[0020]
  When the upper lid 15 is closed after the upper lid 15 is opened, the engagement pin 22 of the drive pin 8 enters the engagement groove 7 b of the sun gear 7. Then, by driving the first drive motor 11, the drive pin 8 rotates around its axis, and the sun gear 7 can be rotated via the engagement pin 22. Thereby, the three wafer carriers 4a, 4b, 4c can be rotated (see arrows Y, Z, W in FIG. 2). Reference numeral 6 denotes an O-ring on which the sun gear support shaft 5 is fitted. The O-ring 6 prevents an alkaline solution described later from entering the inner peripheral surface of the sun gear 7.
[0021]
  A ring-shaped inner peripheral gear (internal gear) 9 is rotatably provided in the casing 1, and the internal gear 9 has outer peripheral teeth 9 b and inner peripheral teeth 9 a on the entire outer periphery and the entire inner periphery, respectively. Is formed. Three wafer carriers 4a, 4b, and 4c, which will be described later, mesh with the inner peripheral teeth 9a of the internal gear 9. Thereby, the wafer carrier 4a, 4b, 4c can be revolved and rotated around the sun gear 7 by rotating the internal gear 9 around its central axis (see arrow X in FIG. 2). As a result, the wafer carriers 4a, 4b, and 4c move while drawing a planetary orbit around the sun gear 7. Thus, the semiconductor wafers 32a, 32b, and 32c move relative to the upper surface plate 2 and the lower surface plate 3 in the horizontal plane.
  As is clear from the above description, the first and second drive motors 11 and 25, the sun gear 7, the sun gear support shaft 5, the ring gear 9 and the like constitute relative motion means. The wafer carriers 4a, 4b, and 4c are not limited to those that move relative to the upper surface plate 2 and the lower surface plate 3 as in this example, but the upper and lower surfaces of the wafer carriers 4a, 4b, and 4c that are fixedly arranged are fixed. You may make it the structure which carries out the relative motion of the board 2 and the lower surface plate 3 synchronizing.
[0022]
  The upper surface plate 2 has a disk shape having a center hole 2a like the lower surface plate 3, and the support mechanism of the upper surface plate 2 is equidistant from the upper surface of the upper surface plate 2 in the circumferential direction. In this case, one end of a plurality of (three in this example) balance shafts 12a, 12b, 12c is fixed. The balance shafts 12a, 12b, and 12c penetrate the upper lid 15 so as to be movable in the vertical direction. On the outer periphery of each balance shaft 12a, 12b, 12c, a thread portion is formed from the upper end to the lower end portion. Balance adjustment nuts 13a, 13b, and 13c are screwed into the thread portions of the balance shafts 12a, 12b, and 12c, respectively. Further, balance coil springs 14a and 14b (one balance coil spring is not shown) are inserted through the balance shafts 12a, 12b and 12c. The upper surface plate 2 can be held by the elastic force of each balance coil spring 14a, 14b. Then, by adjusting the screwing amount of each balance adjustment nut 13a, 13b, 13c, the upper surface plate 2 can be surely brought into a horizontal state, and the pressure according to the distance between the upper surface plate 2 and the lower surface plate 3 is set. Can be adjusted.
[0023]
  The outer peripheral teeth 9b of the internal gear 9 are meshed with a gear 27 that is rotatably provided so as to penetrate the side portion of the casing 1. The gear 27 projects from the leg portion 23 of the casing 1. The second drive motor 25 fixed to the bracket 24 is rotationally driven. Reference numeral 26 indicates a rotation shaft (output shaft) of the second drive motor 25. With such a configuration, the internal gear 9 can be rotated to revolve and rotate each wafer carrier 4a, 4b, 4c. Reference numeral 28 denotes a sealing member for sealing the through portion of the gear 27 of the casing 1.
  An alkaline solution (for example, an aqueous potassium hydroxide solution or an aqueous sodium hydroxide solution) is accommodated in the casing 1 (the liquid level of this solution is indicated by reference numeral 29 in FIG. 1). In this example, since the temperature of the alkaline solution is high, as will be described later, a heat-resistant / alkali-resistant resin is used for at least the surface plate surfaces of the upper and lower surface plates 2 and 3, whereby the upper and lower surface plates 2. , 3 has a long life. In particular, the chemicals described belowWrapIn order to promote this, the temperature and concentration of the alkaline solution are preferably 45 ° C. or higher and 5% or higher, respectively. In order to reliably maintain the temperature of the alkaline solution at 45 ° C. or higher, it is preferable to provide a heater (not shown) in the casing 1 to control the temperature and to stir with a stirrer.
  In order to easily discharge this alkaline solution after chemical wrapping, a drain hose connection fitting 17 is screwed into the bottom of the casing 1. A drainage hose (not shown) is connected to one end of the drainage hose connection fitting 17, and the alkaline solution in the casing 1 is discharged via the drainage hose connection fitting 17 and the drainage hose by opening a valve provided on the drainage hose. be able to. Further, the alkaline solution can be supplied into the casing 1 through the drain hose and the drain hose connection fitting 17.
[0024]
  As shown in FIG. 2, outer peripheral teeth 33a, 33b, and 33c are formed on the outer circumferences of the wafer carriers 4a, 4b, and 4c, respectively, and wafer receiving holes 31a, 31b, and 31c are provided at substantially central portions, respectively. Is formed. Semiconductor wafers 32a, 32b, and 32c are loaded in the wafer receiving holes 31a, 31b, and 31c of the wafer carriers 4a, 4b, and 4c, respectively. The thickness of the wafer carriers 4a, 4b, 4c is slightly smaller than the thickness of the semiconductor wafers 32a, 32b, 32c.
[0025]
  As shown in FIGS. 3 to 5, the upper and lower surface plates 2, 3 are formed with heat-resistant / alkali-resistant resin at least at portions facing each other (surface surface surfaces 34, 35). That is, for example, a heat-resistant / alkali-resistant resin plate (not shown) is attached to the lower surface of the upper surface plate 2 and the upper surface of the lower surface plate 3 in a replaceable manner. Surface plate surface of upper surface plate 2 and lower surface plate 3 (WrapSurfaces 34 and 35 are uniformly provided with abrasive grains (fixed abrasive grains or loose abrasive grains).
  In addition, the upper surface plate 2 and the lower surface plate 3WrapAs shown in FIGS. 5 and 6A, a large number of grooves 38 are formed on the surfaces 34 and 35 in a lattice shape. The width B and pitch P of the grooves 38 are about 3 to 10 mm and 6 to 30 mm, respectively. Further, instead of forming the lattice-shaped grooves 38, as shown in FIG. 6B, a structure in which a large number of grooves 40 and 39 are formed in the radial direction and the circumferential direction may be used.
[0026]
  Next, the use method and operation of the above-described semiconductor wafer chemical wrap apparatus will be described with reference to the drawings.
  First, in a state where the upper lid 15 is opened, the lower carrier plate 4a, 4b, 4c holding the semiconductor wafers 32a, 32b, 32c is engaged with the sun gear 7 and the internal gear 9 as shown in FIG. 3 is arranged. The semiconductor wafers 32a, 32b, and 32c are obtained by slicing semiconductor single crystal rods.
  An alkaline solution is supplied into the casing 1. The supply amount of the alkaline solution is preferably an amount in which the upper surface plate 2 and the lower surface plate 3 are immersed to keep their temperatures constant (for example, about 60 ° C. or about 80 ° C.), but at least the semiconductor wafers 32a and 32b are provided. 32c and the surface plate surfaces 34 and 35 are required to be more than the amount to be immersed. The temperature of the alkaline solution is preferably controlled by the heater or stirred.
  Here, by closing the upper lid 15, the upper surface plate 2 supported by the upper lid 15WrapA surface (surface plate surface) 34 is brought into contact with each semiconductor wafer 32a, 32b, 32c. The contact pressure (processing pressure) at this time is a processing pressure (for example, 170 g / cm) by conventional mechanical polishing.²5 to 50 g / cm so that the semiconductor wafers 32a, 32b, and 32c are not extended by pressing.²It is about the size. That is, as shown in FIG. 4, the upper surface plate 2 and the lower surface plate 3WrapThe surfaces 34 and 35 are in contact with the convex portions 41 of both the wafer surfaces 36 and 37 of the semiconductor wafers 32a, 32b and 32c, and are close to no load.
[0027]
  Here, the first and second drive motors 11 and 27 are driven to rotate and revolve the wafer carriers 4a, 4b, and 4c, respectively, so that the semiconductor wafers 32a, 32b, and 32c are moved to the upper surface plate 2 respectively. And relative movement in the horizontal plane with respect to the lower surface plate 3. In this example, the revolution speed of the wafer carriers 4a, 4b, 4c is preferably as large as possible in order to efficiently remove hydrogen generated by the following reaction formula from the semiconductor wafers 32a, 32b, 32c. In this example, since the semiconductor wafers 32a, 32b, 32c, 32d are held one by one on the wafer carriers 4a, 4b, 4c, the rotation of the wafer carriers 4a, 4b, 4c is less important, but the wafer carrier 4a , 4b, 4c, in which the plurality of semiconductor wafers are held, the rotation speed of the wafer carriers 4a, 4b, 4c is opposite to the revolution speed, and is adjusted to the same value as the revolution speed. Is preferred.
[0028]
  As a result, the following phenomenon occurs.
  That is, the surface of each semiconductor wafer 32a, 32b, 32c reacts with alkalinity,Chemical wrapIs done. chemicalLappiThe reaction proceeds according to the following reaction formula, and sodium silicate (reaction product) and hydrogen are generated.
Reaction formula: Si + 2NaOH + H₂O → Na₂SiO₃+ 2H₂
      2Na₂SiO₃+ H₂O → (←) Na₂Si₂O₅+2 NaOH (hydrolysis)
  In this embodiment, the temperature and concentration of the alkaline solution are 45 ° C. or higher and 5% or higher, soChemical wrapProceeds at a speed of 0.5 to 4.0 μ / min or more, and there is no problem in industrial productivity. On the other hand, at a conventional temperature of 40 ° C. or lower and 5% or lower, the progress of chemical etching is slow and the productivity is poor.
  Further, the convex portions 41 of both the wafer surfaces 36 and 37 of the semiconductor wafers 32a, 32b and 32c are formed by the upper surface plate 2 and the lower surface plate 3, respectively.SharpenedMicro damage D is given, and the alkaline solution penetrates from the portion of the damage D andChemical wrapGoes further. chemicalWrapIn order to keep the working pressure constant, the screwing amounts of the balance adjusting nuts 13, 13b, 13c of the support mechanism of the upper surface plate 2 are adjusted. For reference, in the chemical etching in the etching tank without using a surface plate, the polishing rate is as slow as 5 μ / min or less. FIG. 9 is an example of an experimental result showing the rate of chemical etching (vertical axis) with respect to the temperature of the alkaline solution on the horizontal axis when the concentration of the alkaline solution is 6%.
  In addition, chemicalWrapThe wafer surfaces 36 and 37 are simultaneously processed at a low processing pressure by the upper and lower surface plates 2 and 3.processingTherefore, warpage and undulation do not occur, and a semiconductor wafer with high flatness can be obtained. In addition, since the processing pressure can be reduced as compared with the conventional pressure crushing machining, the processing damage layer is reduced. As a result, the damage layer on both wafer surfaces is 0 to 2 μm compared to the conventional 10 μm. Can be very small.
[0029]
  In this embodiment, the working pressure of the upper surface plate 2 and the lower surface plate 3 is small, so that the life of the upper surface plate 2 and the lower surface plate 3 is long.
  Abrasive grains on the surface plates 34 and 35 of the upper and lower surface plates 2 and 3(Play(Abrasive grains) can be provided, so that the micro damage can be effectively imparted to the semiconductor wafers 32a, 32b, 32c.
  Furthermore, by forming a large number of grooves 38 on the surface plates 34 and 35, the replacement of the alkaline solution on both wafer surfaces 36 and 37 is promoted through the grooves 38, and the reaction product generated by the above reaction formula is The wafer surfaces 36 and 37 can be effectively excluded.
  Although the alkaline solution adheres to the semiconductor wafers 32a, 32b, and 32c chemically-wrapped as described above, since the wrap solution is not used as in the prior art, for example, water washing (cleaning) is easily performed using ultrasonic waves. In addition, the burden on the semiconductor wafers 32a, 32b, and 32c due to cleaning can be reduced.
  In order to discharge the used alkaline solution from the casing 1, the alkaline solution is drained by opening a valve of the drain hose. The reaction product is Na₂SiO₃And Na₂Si₂O₅Therefore, pollution control processing is easier than before.
[0030]
  Chemical as aboveWrapThe semiconductor wafers 32a, 32b, and 32c that have completed the above are flattened microscopically, but in order to secure macroscopic flatness, it is necessary to perform a mirror polishing process at a later stage. In the present invention, since the wafer surfaces 36 and 37 can be finished with high accuracy in a state close to a mirror surface by chemical wrapping, the subsequent mirror polishing process can be easily completed.
[0031]
  In the conventional lapping machine, it is difficult to maintain the mechanical accuracy of the surface plate surface by simply raising the temperature of the cast iron lap surface plate, and the polishing cloth on the surface plate surface is weak in heat resistance. The life is shortened. In contrast, a chemical like the present inventionWrapIs the main component, the processing pressure can be low and the life of the upper and lower surface plates is long.
[0032]
【The invention's effect】
  Since the present invention is configured as described above, the following effects can be obtained.
  BookThe invention provides a single device for lapping and chemicalWrapBy performing the above, it is possible to reduce the apparatus cost and improve the productivity. Also chemicalWrapAnd both sides of the semiconductor wafer at the same time with a small processing pressureWrapBy doing so, the processing damage layer becomes small and the machining allowance of both wafer surfaces can be extremely reduced. Furthermore, the swell component and warpage are reduced in the semiconductor wafer.
  BookIn addition to the above effects, the invention adopts a simple relative motion means composed of a sun gear and a ring-shaped inner peripheral gear, etc., to rotate and revolve the semiconductor wafer so that both wafer surfaces of the semiconductor wafer are UniformlyWrapcan do.
  BookThe invention is the surface of the upper and lower surface plate (the upper surface plate is the lower surface, the lower surface plate is the upper surface)PlayBy providing the abrasive grains, the application of the micro damage is promoted.
  BookIn the invention, by providing grooves on the surface plates of the upper and lower surface plates in a lattice or radial manner, when the micro damage is given to both wafer surfaces, the replacement of the alkaline solution on both wafer surfaces is continuously promoted. ,Chemical reaction(Chemical wrap) Is faster.
  BookThe invention makes the temperature and concentration of the alkaline solution 45 ° C. or more and 5% or more, respectively.Chemical wrapCan be further promoted to make the present invention sufficiently useful in the industry.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of an embodiment of a chemical wrapping apparatus for a semiconductor wafer according to the present invention.
FIG. 2 is a schematic plan view (top view) of an embodiment of a semiconductor wafer chemical wrap apparatus according to the present invention.
FIG. 3 is an enlarged view of the carrier between the upper and lower surface plates and the semiconductor wafer in the embodiment.
FIG. 4 is an enlarged cross-sectional view of a main part showing upper and lower surface plates and a semiconductor wafer in the embodiment.
FIG. 5 is a longitudinal sectional view of a main part of upper and lower surface plates in the present embodiment example.
FIG. 6 is a view showing the surface plate surfaces of the upper and lower surface plates in the embodiment.
FIG. 7 is a diagram showing a deformation mode of a semiconductor wafer by lapping.
FIG. 8 is a diagram for explaining a swell component of a semiconductor wafer.
FIG. 9 is a graph showing the rate of chemical polishing with respect to the temperature of an alkaline solution.
[Explanation of symbols]
D Micro damage
1 Casing (device body)
2 Upper surface plate
2a, 3a Center hole
3 Lower surface plate
4a, 4b, 4c Wafer carrier
5 Sun gear support shaft
6 O-ring
7 Sun gear
7a peripheral teeth
7b Engaging groove
8 Drive pin
9 Ring-shaped inner gear (inter
Null gear)
9a Internal teeth
9b peripheral teeth
10 Lower surface plate base
11 First drive motor
11a Rotating shaft (output shaft)
12a, 12b, 12c Balance shaft
13a, 13b, 13c Balance adjustment nut
14a, 14b Balance coil spring
15 Top cover (motor base cover)
16 Handle (grip handle)
17 Drain hose fitting
18 Upper lid support
19 Spindle
20a, 20b Pin member
21 Motor support bracket
22 engaging pin member
23 legs
24 Bracket
25 Second drive motor
26 Rotating shaft (output shaft)
27 Gear
28 Seal member
29 Liquid level of alkaline solution
30a, 30b Bracket
31a, 31b, 31c Wafer accommodation hole
32a, 32b, 32c Semiconductor wafer
33a, 33b, 33c outer peripheral teeth
34, 35 Surface plate (Wrapsurface)
36, 37 Wafer surface
38, 39, 40 groove
41 Convex

Claims (4)

In order to increase the flatness of the wafer surface and the parallelism of the wafer, and to remove the surface damage layer at the time of slicing, the surface of both wafers is removed by slicing the rugged layer on the wafer surface of the semiconductor wafer sliced and cut from the semiconductor single crystal rod. A chemical wrapping device for semiconductor wafers that chemically wraps at the same time,
A casing,
Provided in the casing in parallel with each other, at least the opposite surfaces are surface plate surfaces formed of heat -resistant and alkali- resistant resin, respectively, and on both surface of the semiconductor wafer in the surface plate surface respectively With upper and lower surface plates in contact,
Relative motion means for causing the upper surface plate and the semiconductor wafer to move relative to each other in a direction along the wafer surface, and for causing the lower surface plate and the semiconductor wafer to move relative to each other in a direction along the wafer surface ;
A heater in the casing;
Means for pouring loose abrasive grains made of alumina between the surface plate surface and the semiconductor wafer ,
In the casing, at least the semiconductor wafer and each surface plate surface are immersed, and an alkaline solution having a concentration of 5% or more is supplied,
The chemical wrap speed is 4.0 μm / min or more,
The alkaline solution in the casing is controlled to a constant temperature of about 45 ° C. to 80 ° C. by the heater,
The contact pressure when contacting the surface plate surface on the semiconductor wafer, the not extended to press the semiconductor wafer, during processing warping or waviness is UNA'm not elastically deformed 5 to 50 g / cm ² The degree of being set to a size Chemical wrap device of a semiconductor wafer, comprising Rukoto. The semiconductor wafer is held by a carrier having outer peripheral teeth, while the upper surface plate and the lower surface plate each have a center hole,
The relative motion means is
A sun gear provided in the central hole so as to mesh with the outer peripheral teeth of the carrier, and provided on the outer side of the upper surface plate and the lower surface plate so as to mesh with the outer peripheral teeth of the carrier. A ring-shaped inner peripheral gear for revolving and rotating around the sun gear;
The semiconductor wafer chemical wrap apparatus according to claim 1, comprising: a driving mechanism for rotating the sun gear and the ring-shaped inner peripheral gear. 3. The chemical wrapping apparatus for a semiconductor wafer according to claim 1, wherein a plurality of grooves are provided on the surface plate surface in a lattice shape or in a radial direction and a circumferential direction . 4. The chemical wrapping apparatus for a semiconductor wafer according to claim 1 , wherein the concentration of the alkaline solution is 5 to 6% .

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