Double-side processing method and double-side processing apparatus for wafer

Abstract

To provide a double-side processing method and a double-side processing apparatus for a wafer, capable of reliably removing a process-damaged layer (damage) or the like of the wafer, reducing work and time such as wafer transportation and cleaning or the like between steps, improving productivity, preventing clogging in double-side polishing, lowering of a polishing rate, roughening of a wafer surface, and generation of particles and defects, and processing the wafer into a wafer having a high front and back surface quality and stable quality.SOLUTION: The present invention relates to a double-side processing method of a wafer using double-side processing apparatus having an upper and lower surface plates to which polishing cloth is attached, in which the wafer is held in a holding hole of a carrier disposed between the upper and lower surface plates, an etching liquid is supplied to perform an etching processing on the wafer, and then a slurry containing an abrasive grain is supplied to the same double-side processing apparatus to perform double-side polishing processing on the wafer using the polishing cloth.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method and an apparatus for processing both sides of a wafer. [Background technology]

[0002] The manufacturing process for silicon wafers for semiconductor devices consists of a single crystal manufacturing process in which a single crystal ingot is grown using the Czochralski (CZ) method or other methods, and a wafer processing process in which this single crystal ingot is sliced ​​and processed to a mirror finish.To add further value, the process may also include an annealing process in which heat treatment is performed and an epitaxial growth process in which an epitaxial layer is formed.

[0003] In the wafer processing process, wafers sliced ​​from a single crystal ingot are turned into products through multiple processes, such as chamfering, lapping or grinding, hard laser marking, etching, double-sided polishing, mirror chamfering, and CMP (chemical mechanical polishing), as shown in the flow chart in Figure 6.

[0004] This involves processing using grinding mechanisms (machining) such as slicing and lapping, and the main role of these processes is to shape the wafer, including warpage and thickness, but they also leave cracks and scratches on the bare silicon wafer, leaving a processing-affected layer (hereinafter sometimes referred to as damage) in which stress from the processing remains.

[0005] These process-affected layers are then removed by etching or polishing.

[0006] Etching processes include acid etching using a mixed acid of hydrogen fluoride, nitric acid, acetic acid, etc., and alkaline etching using an alkali such as sodium hydroxide or potassium hydroxide.

[0007] Acid etching has the advantage that the etching rate and surface condition can be easily controlled, but has the disadvantage that the high etching rate deteriorates the flatness of the wafer that has been improved by lapping and double-side grinding.

[0008] On the other hand, alkaline etching has the advantage that the etching rate is small, making it possible to maintain the flatness of the wafer, and thus to obtain a wafer with good flatness after etching.

[0009] In order to perform etching uniformly, the etching apparatus rotates or swings the wafer immersed in the etching solution to ensure uniform etching across the surface.

[0010] Because wafer processing processes are diverse, different equipment is used for each process, and productivity is reduced due to the time it takes to transport wafers to the equipment for each process, as well as the time lost due to cleaning and conditioning.

[0011] For example, Patent Document 1 discloses a technology that addresses the problem of wafers being damaged when they are handled to another device by changing backgrinding to etching so that handling is not required, and by allowing the wafer to continue to be chucked while moving on to the polishing process. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-86481 Summary of the Invention [Problem to be solved by the invention]

[0013] In the processing of silicon wafers, etching is sometimes performed before the double-side polishing process to remove scratches and altered layers (damage) caused by processing using grinding mechanisms such as slicing and lapping (or surface grinding).

[0014] These processes all involve processing wafers in separate processes and equipment, and therefore require time and cost for transporting and cleaning wafers between processes.

[0015] Furthermore, in recent years, a trend has been to demand not only high-precision planarization, as has been conventionally required, but also high quality on both the front and back surfaces in order to improve the yield of semiconductor devices.

[0016] Double-sided polishing polishes both the front and back sides of a silicon wafer simultaneously, making it possible to efficiently produce high-quality surfaces. However, the polishing cloths used in double-sided polishing are mainly made of foamed urethane, and repeated wafer processing can cause abrasive grains and silica debris from the slurry to get into the foamed areas, causing clogging. This can lead to variations in quality, such as a decrease in the polishing rate, roughening of the wafer surface, and the generation of particles and defects.

[0017] In particular, due to the life of the polishing cloth, changes in the compressibility of the polishing cloth and clogging etc. have an effect, and as the frequency of use increases, the shape of the wafer changes, and the outer periphery of the wafer is polished excessively, making it more likely that so-called outer periphery sagging will occur.

[0018] If no measures are taken to prevent clogging, the surface quality will tend to deteriorate, so regular conditioning of the polishing cloth, such as dressing, is necessary.

[0019] To explain dressing in more detail, a diamond dresser equipped with a diamond or other grinding wheel is sandwiched between the upper and lower plates, and the device is operated in the same manner as in normal polishing, dressing both the upper and lower polishing cloths simultaneously. This scrapes off the surface of the polishing cloth, improving slurry retention and maintaining polishing performance. This type of dressing maintains the surface condition of the polishing cloth in good condition, allowing for the stable production of highly flat wafers, but it also causes a decrease in productivity because wafers cannot be polished during dressing.

[0020] The present invention has been made to solve the above problems, and aims to provide a double-sided wafer processing method and apparatus that can reliably remove processing-affected layers (damage) from wafers, reduce the work and time required for wafer transport and cleaning between processes, improve productivity, and prevent clogging during double-sided polishing, a decrease in the polishing rate, roughening of the wafer surface, and the generation of particles and defects, thereby producing wafers with high and stable quality on both the front and back surfaces. [Means for solving the problem]

[0021] In order to solve the above problems, the double-sided processing method of the present invention is a method for processing double-sided wafers using a double-sided processing device having upper and lower surface plates with abrasive cloths attached, in which the wafer is held in a holding hole of a carrier arranged between the upper and lower surface plates, an etching liquid is supplied to perform etching on the wafer, and then a slurry containing abrasive grains is supplied to the same double-sided processing device, and the wafer is double-sided polished using the abrasive cloths.

[0022] This double-sided wafer processing method first performs etching and double-sided polishing, thereby reliably removing the wafer's processing-induced layers (damage). Second, because etching and double-sided polishing are performed using the same double-sided processing equipment, the labor and time required for wafer transport and cleaning between processes can be reduced, improving productivity. Furthermore, because etching is performed first, silica debris and other substances that cause clogging of the polishing cloth can be dissolved and removed by etching, preventing clogging in the subsequent double-sided polishing process, a decrease in the polishing rate, roughening of the wafer surface, and the generation of particles and defects. This allows for the production of wafers with high, consistent quality on both sides.

[0023] It is also preferable to use a urethane foam-based polishing cloth as the polishing cloth.

[0024] With such a urethane foam-based polishing cloth, even if abrasive grains in the slurry or silica debris get into the foamed portion of the polishing cloth during repeated double-side polishing of wafers, causing clogging, the silica debris and the like can be reliably dissolved and removed by etching. Therefore, even without conditioning such as dressing, clogging in the next double-side polishing process, a decrease in the polishing rate, roughening of the wafer surface, and the generation of particles and defects can be prevented, and wafers with high and stable quality on both sides can be processed.

[0025] The etching solution is preferably an alkaline etching solution.

[0026] Such an alkaline etching solution can dissolve and remove silica debris and the like that has become clogged in a urethane foam-based polishing cloth, in particular. This prevents clogging in the subsequent double-side polishing process, a decrease in the polishing rate, roughening of the wafer surface, and the generation of particles and defects, even without conditioning such as dressing, and allows wafers to be processed into wafers with high and stable quality on both sides.

[0027] It is also preferable that the removal amount in the etching process be 10 μm or more.

[0028] If the removal amount is 10 μm or more, it is possible to sufficiently remove the process-affected layer (damage) of the wafer.

[0029] It is also preferable that the load during the etching process be smaller than the load during the double-side polishing process.

[0030] During etching, it is sufficient to dissolve and remove silica debris and other debris that cause clogging of the polishing cloth, so it is not necessary to apply as much load as during double-sided polishing. Therefore, it is preferable to apply a load during etching that is smaller than that during double-sided polishing. A smaller load does not compress the polishing cloth, ensuring gaps in the foamed areas, allowing the etching solution to easily penetrate and directly reach the silica debris and other debris that cause clogging. As a result, silica debris and other debris can be more reliably dissolved and removed, preventing clogging in the subsequent double-sided polishing process, a decrease in the polishing rate, roughening of the wafer surface, and the generation of particles and defects, and enabling the processing of wafers with high, stable quality on both sides.

[0031] In addition, the wafer double-side processing device of the present invention has upper and lower surface plates on which abrasive cloths are attached, a carrier arranged between the upper and lower surface plates and having holding holes formed therein for holding the wafer, a first tank holding an etching solution that does not contain abrasive grains, a second tank holding a slurry that contains abrasive grains, and a switching means for switching between the supply of the etching solution from the first tank and the supply of the slurry from the second tank.

[0032] This double-sided wafer processing device can first etch wafers when an etching solution is supplied from the first tank, and can double-sided polish wafers when a slurry is supplied from the second tank, both of which can remove damage from the wafer. Second, by switching between the supply of etching solution and the supply of slurry using a switching device, the same double-sided processing device can switch between etching and double-sided polishing, thereby reducing the time and effort required for wafer transport and cleaning between processes and improving productivity. Furthermore, etching can dissolve and remove silica debris and other substances that cause clogging of the polishing cloth, preventing clogging, reduced polishing rate, roughening of the wafer surface, and the generation of particles and defects during double-sided polishing, resulting in wafers with high, consistent quality on both sides.

[0033] The polishing cloth is preferably a urethane foam polishing cloth.

[0034] With such a urethane foam polishing cloth, even if abrasive grains in the slurry or silica debris get into the foamed portion of the polishing cloth during repeated double-side polishing of wafers, causing clogging, the silica debris and the like can be reliably dissolved and removed by etching. Therefore, even without conditioning such as dressing, clogging in the next double-side polishing process, a decrease in the polishing rate, roughening of the wafer surface, and the generation of particles and defects can be prevented, and wafers with high and stable quality on both sides can be processed. [Effects of the Invention]

[0035] As described above, the double-side wafer processing method of the present invention first performs etching and double-side polishing, thereby reliably removing the process-induced layers (damage) of the wafer. Second, since etching and double-side polishing are performed consecutively using the same double-side processing equipment, the labor and time required for wafer transport and cleaning between processes can be reduced, improving productivity. Furthermore, since etching is performed first, silica debris and other substances that cause clogging of the polishing cloth can be dissolved and removed by etching, preventing clogging in the subsequent double-side polishing process, a decrease in the polishing rate, roughening of the wafer surface, and the generation of particles and defects. This allows for the processing of wafers with high, stable quality on both sides.

[0036] Furthermore, with the double-sided wafer processing apparatus of the present invention, first, etching can be performed when an etching solution is supplied from the first tank, and double-sided polishing can be performed when a slurry is supplied from the second tank, both of which can remove processing-induced layers (damage) from the wafer. Second, by switching between the supply of etching solution and the supply of slurry using a switching device, the same double-sided processing apparatus can switch between etching and double-sided polishing, thereby reducing the work and time required for wafer transport and cleaning between processes and improving productivity. Furthermore, etching can dissolve and remove silica debris and other substances that cause clogging of the polishing cloth, preventing clogging, a decrease in the polishing rate, roughening of the wafer surface, and the generation of particles and defects during double-sided polishing, thereby enabling the processing of wafers with high, stable quality on both sides.

[0037] Furthermore, to address clogging of the polishing cloth that can occur during double-sided polishing, etching wafers using the same double-sided processing equipment can dissolve and remove silica debris, which causes clogging. This means that even if continuous processing is performed without conditioning such as polishing cloth dressing, it is possible to achieve surface quality equivalent to that achieved immediately after conditioning. This also improves quality variations due to the life of the polishing cloth. [Brief explanation of the drawings]

[0038] [Figure 1] 1 is a flow chart showing an example of a method for processing both sides of a wafer according to the present invention. [Figure 2] 1 is a schematic diagram showing an example of a double-side processing apparatus for a wafer according to the present invention; [Figure 3] FIG. 2 is a plan view showing an example of the arrangement of carriers and wafers used in the double-side processing device. [Figure 4] FIG. 10 is a diagram showing the measurement results of the number of defects in an example and a comparative example. [Figure 5] FIG. 10 is a diagram showing the results of measuring roughness in an example and a comparative example. [Figure 6] FIG. 1 is a flow chart showing an example of a conventional double-side processing method for a wafer. [Figure 7] FIG. 10 is a flow chart showing another example of a conventional method for processing both sides of a wafer. DETAILED DESCRIPTION OF THE INVENTION

[0039] The present invention will be described in detail below, but the present invention is not limited thereto.

[0040] As described above, there has been a demand for a double-sided wafer processing method and apparatus that can reliably remove processing-affected layers (damage) from wafers, reduce the work and time required for transporting and cleaning wafers between processes, improve productivity, and prevent clogging during double-sided polishing, a decrease in the polishing rate, roughening of the wafer surface, and the generation of particles and defects, thereby producing wafers with high and stable quality on both sides.

[0041] As a result of extensive research into the above-mentioned problems, the inventors have found that the problems can be solved by performing wafer etching and double-side polishing in the same apparatus, which have conventionally been performed in separate apparatuses, by first supplying an etching solution to perform the etching, and then supplying a slurry containing abrasive grains to perform the double-side polishing, and have thus completed the present invention.

[0042] In other words, the present invention is a double-sided processing method for wafers using a double-sided processing device having upper and lower surface plates with abrasive cloths attached, characterized in that the wafer is held in a holding hole of a carrier arranged between the upper and lower surface plates, an etching liquid is supplied to perform etching on the wafer, and then a slurry containing abrasive grains is supplied to the same double-sided processing device, and double-sided polishing of the wafer is performed using the abrasive cloth.

[0043] The present invention also provides a double-sided wafer processing device, characterized by having upper and lower surface plates on which abrasive cloths are attached, a carrier arranged between the upper and lower surface plates and having holding holes formed therein for holding wafers, a first tank holding an etching solution that does not contain abrasive grains, a second tank holding a slurry that contains abrasive grains, and a switching means for switching between the supply of the etching solution from the first tank and the supply of the slurry from the second tank.

[0044] By performing etching and double-sided polishing in the same equipment, wafers can be transported from the etching process to the double-sided polishing process, and cleaning and other processes can be omitted, improving wafer productivity. Furthermore, etching also conditions the polishing cloth, improving quality variations due to the life of the polishing cloth.

[0045] The equipment used in this invention (wafer double-sided processing equipment) can be an equipment with the same mechanism as conventional double-sided polishing. It is preferable that the components used in the equipment be highly chemical-resistant to alkalis such as KOH and NaOH, and that two chemical tanks be provided: one for etching that supplies alkalis such as KOH and NaOH, and the other for supplying a slurry containing abrasive grains used in conventional double-sided polishing. By switching between these tanks, etching and double-sided polishing can be performed within the same equipment. This allows each process to be performed simply by switching tanks, without the need for wafer cleaning or transportation.

[0046] An embodiment of the present invention will now be described in detail with reference to the drawings.

[0047] Fig. 7 is a flow chart showing another example of a conventional double-sided processing method for wafers. As shown in Fig. 7, the processing of semiconductor wafers such as silicon wafers includes, for example, a process of etching and double-sided polishing the wafers that have been processed in a previous process (often double-sided polishing is followed by finish polishing).

[0048] Here, the pre-processing refers to a processing step in which damage may occur due to mechanical processing such as lapping or grinding.

[0049] Conventionally, damaged wafers are etched using an etching device dedicated to the etching process to remove the damage from the wafer surface, then cleaned and dried (not shown), and transported to a double-sided polishing device dedicated to the next process, the double-sided polishing process, where both sides are polished, and then cleaned and transported again for finish polishing.

[0050] 1 is a flow chart showing an example of a double-side processing method for wafers according to the present invention. In one embodiment of the present invention, as shown in FIG. 1, a wafer processed in a pre-processing step is subjected to etching and double-side polishing in the same process (using the same processing equipment), and then the wafer is transported to perform post-processing such as cleaning and finish polishing.

[0051] In one embodiment of the present invention, the transport from etching to double-side polishing can be omitted.

[0052] A specific double-sided wafer processing apparatus for sequentially performing etching and double-sided polishing in the same apparatus is shown in Figure 2. This double-sided wafer processing apparatus 1 can be configured similarly to a conventional double-sided polishing apparatus, except for the first tank 2 containing an etching solution that does not contain abrasive grains, the second tank 3 containing a slurry that contains abrasive grains, and the switching means 4 that switches between the supply of etching solution from the first tank 2 and the supply of slurry from the second tank 3. For example, a four-way double-sided processing apparatus that is generally used in double-sided polishing processes can be used.

[0053] The wafer double-sided processing device 1 using the 4-way system is equipped with a lower surface plate 5 and an upper surface plate 6 arranged opposite each other at the top and bottom, and abrasive cloths (not shown) are attached to the opposing surfaces of the upper and lower surface plates 5 and 6, respectively.

[0054] In addition, a supply mechanism (including a supply nozzle 7 and a through-hole in the upper platen 6) is provided above the upper platen 6 to supply chemical liquid between the upper platen 6 and the lower platen 5, thereby supplying the chemical liquid to the wafer W. It is preferable that this supply mechanism be made of a material that is highly resistant to chemicals even at high temperatures.

[0055] This apparatus has at least two tanks, the first tank 2 containing, but not limited to, an alkaline chemical solution for etching that does not contain abrasive grains, and the second tank 3 containing a slurry containing abrasive grains for double-sided polishing. The apparatus has a mechanism that can supply either the alkaline chemical solution or the slurry containing abrasive grains into the apparatus via a supply nozzle 7 by switching using a switching means 4 such as a three-way valve.

[0056] It is preferable to use an alkaline chemical solution containing either NaOH or KOH as the alkaline component in the first tank 2 for the alkaline chemical solution used for etching. By supplying these chemical solutions at a concentration of, for example, about 10% to 55% and at a chemical solution temperature of 70±10°C, damage can be efficiently removed within this processing equipment.

[0057] The second tank 3 for the abrasive slurry for double-side polishing is not particularly limited, but for example, a KOH-based abrasive slurry with an average silica abrasive grain size of about 25 to 35 nm, an abrasive grain concentration of 1.0 to 1.5 wt%, and a pH of about 10 to 11 can be prepared. Additives may also be added.

[0058] Although not shown in Fig. 2, wafers (semiconductor silicon wafers) W are held in holding holes of a carrier arranged between upper and lower surface plates 5 and 6. This is shown in Fig. 3. Fig. 3 is a plan view looking downward from the upper surface plate 6 side of Fig. 2, and shows a configuration in which five carriers 9 are arranged on a polishing cloth 8 attached to the lower surface plate 5, and five wafers W are arranged so that they fit into respective holding holes 10 of the carriers 9, thereby holding the wafers W.

[0059] A sun gear 11 is provided in the center between the upper surface plate 6 and the lower surface plate 5, and an internal gear 12 is provided on the periphery, making it possible for the device to operate in a planetary gear system.

[0060] When an alkaline chemical solution or the like is used for etching, the carrier 9 for the double-side processing device is preferably chemical-resistant (alkali-resistant), and may be made of either metal or resin as long as it is chemical-resistant. For example, the carrier 9 may be made of metal. Furthermore, although not shown, a ring-shaped resin insert may be provided on the inner peripheral surface of the holding hole 10 of the carrier 9 that contacts the peripheral edge of the wafer W to be held.

[0061] As the polishing cloth 8, for example, a urethane foam-based polishing cloth can be used, and it is preferable that the Shore A hardness thereof is 70 or more. In particular, by using a polyurethane foam pad having a Shore A hardness of 70 to 90, double-side polished silicon wafers having a stable high surface quality can be obtained.

[0062] The outer teeth of the carrier 9 mesh with the teeth of the sun gear 11 and the internal gear 12, and as the upper surface plate 6 and the lower surface plate 5 are rotated by a drive source (not shown), the carrier 9 revolves around the sun gear 11 while rotating on its axis. At this time, the semiconductor silicon wafer W is held in the holding hole 10 of the carrier 9, and both sides are simultaneously processed by the upper and lower polishing cloths 8 while a load is applied. During etching, an etching solution is supplied from the supply nozzle 7 through the through-holes in the upper surface plate 6, and during double-side polishing, a slurry containing abrasive grains is supplied from the supply nozzle 7 through the through-holes in the upper surface plate 6.

[0063] When etching is performed with such an apparatus, the wafer W is held and rotated while also revolving, and centrifugal force causes the chemical solution to flow down without stagnating, resulting in uniform etching across the surface of the wafer W, allowing for efficient and accurate removal of damage, etc. Furthermore, by using an alkaline solution without abrasive grains, silicon debris stuck in the urethane foam polishing cloth 8 can also be dissolved and removed.

[0064] The double-side processing device according to the present invention is not limited to such a planetary gear system (four-way system), and may also be of an oscillating system.

[0065] Furthermore, although not particularly limited, it is preferable to coat the surface of metal parts inside the device, such as the surface plate, with a resin. For example, when etching is performed at high temperatures using an alkaline etching solution, this is preferable from the standpoint of durability, as it can prevent contamination and corrosion of the device.

[0066] Next, an embodiment of the double-side processing method for a wafer according to the present invention will be described.

[0067] Referring to FIG. 1, first, in a pre-process, a wafer is prepared that has scratches or a process-induced layer (damage) caused by processing using a mechanical grinding mechanism such as slicing or lapping (or surface grinding).

[0068] In this embodiment, such damaged wafers are subjected to etching and double-sided polishing using the same double-sided processing apparatus as shown in FIG.

[0069] First, etching is performed using a double-sided processing device. A damaged wafer is loaded into the carrier of the double-sided processing device, and while the wafer is held in the carrier's holding holes, an alkaline etching solution is supplied to the rotating platen, and the wafer is etched while being lightly supported by the upper and lower polishing cloths while being loaded.

[0070] The load at this time is not particularly limited, but it is preferable to set it to be smaller than that of normal double-side polishing, for example, 30 to 45 gf / cm 2 A smaller load does not compress the polishing cloth, so gaps in the foamed area can be secured, allowing the etching solution to penetrate more easily and reach silica debris and other particles that cause clogging. As a result, silica debris and other particles can be dissolved and removed more reliably.

[0071] Furthermore, the removal amount in the etching process is set to a removal amount that allows damage to be removed. Although not particularly limited, for example, if the removal amount is 10 μm or more, it is possible to sufficiently remove the process-affected layer (damage) of the wafer. More preferably, if the removal amount is 20 μm or more, it is possible to more reliably remove damage. Furthermore, although not particularly limited, the upper limit of the removal amount can be set to 30 μm or less.

[0072] The treatment time is not particularly limited, but for example, etching may be carried out in a high-temperature alkaline chemical solution at 70±10° C. for 5 minutes or more.

[0073] The removal amount and wafer thickness can be controlled by controlling the processing time, etc., but a sizing device may be installed in this double-sided processing device, and a processing mechanism may be provided to monitor the wafer thickness during processing.

[0074] Then, once a predetermined amount of removal is removed by etching (when the wafer reaches a predetermined thickness), the etching process is terminated, and in the present invention, the process proceeds to double-side polishing of the wafer using the same double-side processing device.

[0075] Before switching the tanks, the platen may be rotated at 10 rpm for at least one minute to shake off the chemical solution used in etching from the platen, and the polishing cloth may then be washed with a water jet.

[0076] Thereafter, the first tank containing an etching solution without containing abrasive grains for etching is switched to a second tank containing a slurry containing abrasive grains for double-side polishing.

[0077] It is preferable to change the processing conditions (platen rotation speed and load) to those suitable for double-side polishing. For example, but not limited to, a platen rotation speed of 10 to 20 rpm and a load of 100 to 150 gf / cm 2 It can be said that:

[0078] Then, once the predetermined amount of removal is removed by double-sided polishing (when the wafer reaches a predetermined thickness), the double-sided polishing is completed.

[0079] After that, the product is washed and moved to a subsequent process (for example, a finish polishing process).

[0080] According to the above-described double-sided wafer processing method, etching and double-sided polishing can be performed using the same double-sided wafer processing apparatus. [Example]

[0081] The present invention will be specifically explained below with reference to examples, but the present invention is not limited to these examples.

[0082] [Example] The equipment used in this invention is a four-way double-sided processing equipment as shown in Figure 2. This processing equipment is equipped with a tank for alkaline chemicals for etching and a tank for slurry containing abrasive grains for double-sided polishing.

[0083] A urethane foam pad (urethane foam pad with a Shore A hardness of 90) was used as the polishing cloth, and conditioning was performed using a diamond dresser before processing the first batch.

[0084] An alkaline chemical solution containing 48% NaOH at a temperature of 70±10°C was prepared in the etching tank.

[0085] A KOH-based abrasive slurry containing silica abrasive grains, with an average grain size of 35 nm, an abrasive grain concentration of 1.0 wt %, a pH of 10.5, was prepared in the double-side polishing tank.

[0086] The wafers used were P-type silicon wafers with a diameter of 300 mm. Ten batches of five lapped wafers were subjected to double-sided processing (etching + double-sided polishing) using the same polishing cloth without conditioning using the processing method of the present invention.

[0087] Specifically, a wafer is placed in a double-sided processing device, and an alkaline chemical solution is first supplied at a flow rate of 8 L / min, and the rotation speed of the surface plate is 5 rpm and the load is 30 gf / cm. 2 The machining time was set to 5 minutes, and the removal rate was 20 μm.

[0088] Next, the slurry was changed to abrasive grains for double-sided polishing, and the rotation speed of the surface plate was 15 rpm and the load was 100 gf / cm 2 and processed for 30 minutes.

[0089] After processing, SC-1 cleaning is performed on wafers under the following conditions: NH4OH:H2O2:H2O=1:1:15 So I went.

[0090] The quality of the wafers was then checked, and the number of surface defects and roughness were evaluated.

[0091] The number of surface defects was measured on the cleaned wafer using an SP5 manufactured by KLA Tencor. The roughness was measured in a 2 μm square area using an AFM Park manufactured by Park Systems.

[0092] [Comparative Example] As a comparative example, etching and double-side polishing were carried out in separate steps and with separate equipment, as in the conventional case.

[0093] First, a P-type silicon wafer having a diameter of 300 mm was prepared as in the example, and the wafer was lapped.

[0094] Next, in the etching process, unlike in the example, the wafer was immersed in an alkaline bath containing 48% NaOH at a chemical temperature of 70±10° C. using an immersion etching device, and etching was performed. At this time, etching was performed while controlling the removal amount to be the same as in the example (20 μm).

[0095] After that, it was washed, dried, stored in a box, and then transported to the next process, double-sided polishing.

[0096] In the double-side polishing process, a four-way double-side processing device was used as shown in Figure 2. However, unlike the example, no tank for alkaline chemical solution for etching was used, and only a tank for slurry containing abrasive grains for double-side polishing was used.

[0097] The polishing cloth used was a foamed urethane pad (a foamed urethane pad with a Shore A hardness of 90) similar to that used in the example, and conditioning was carried out with a dresser before processing the first batch.

[0098] In the double-side polishing tank, a KOH-based abrasive slurry containing silica abrasive grains, an average grain size of 35 nm, an abrasive grain concentration of 1.0 wt %, a pH of 10.5, was prepared, as in the example.

[0099] In double-sided polishing, 10 batches of five etched wafers were subjected to conventional double-sided processing (double-sided polishing) without conditioning using the same polishing cloth.

[0100] At this time, the rotation speed of the surface plate was 15 rpm and the load was 100 gf / cm 2 and processed for 30 minutes.

[0101] After processing, SC-1 cleaning is performed on wafers under the following conditions: NH4OH:H2O2:H2O=1:1:15 So I went.

[0102] Thereafter, the quality of the wafer was checked in the same manner as in Example 1. The wafer quality was evaluated by the number of surface defects and roughness.

[0103] The number of surface defects was measured on the cleaned wafer using an SP5 manufactured by KLA Tencor. The roughness was measured in a 2 μm square area using an AFM Park manufactured by Park Systems.

[0104] The measurement results are shown in Figures 4 and 5.

[0105] First, using a conventional double-sided processing method (the etching process and double-sided polishing process are separate processes, each performed using separate equipment), the first batch was processed using a polishing cloth after conditioning in the double-sided polishing process, and the tenth batch was used continuously without conditioning, and was designated Comparative Example 2.

[0106] On the other hand, the first batch (processed using the double-sided processing method of the present invention (etching and double-sided polishing are performed in the same process and with the same equipment)) was processed using a polishing cloth that had been conditioned on both sides, and the tenth batch (processed using the same method but without conditioning) was used in succession as Example 2.

[0107] Regarding the surface quality of the processed wafers, such as the roughness and the number of scratches and defects, we first calculated the number of surface defects (unit: pieces) per wafer (Fig. 4). The wafers with the most surface defects were ranked in descending order (worst order): Comparative Example 2 >> Comparative Example 1 ≒ Example 1 ≒ Example 2 The order was as follows.

[0108] From these results, it can be seen that in the initial stage of conditioning (first batch), Example 1 of the present invention had fewer surface defects and maintained equal or better quality than Comparative Example 1 of the conventional method. Furthermore, in the 10th batch, when the life of the polishing cloth had progressed, Comparative Example 2 of the conventional method showed an increase in the number of surface defects and a deterioration in quality, but Example 2 of the present invention remained stable and equal to the initial stage of conditioning (first batch).

[0109] Next, the roughness of the wafer after processing was determined as the arithmetic roughness Sa (unit: nm) per 2 μm square (Figure 5). Even when etching and double-sided polishing were performed using the same equipment as in the present invention, no particular abnormalities were observed, and in the initial stage of conditioning (first batch), Example 1 of the present invention was able to maintain a roughness equivalent to that of Comparative Example 1 using the conventional method. Furthermore, in the 10th batch, when the polishing pad life had progressed, a deterioration in roughness was observed in Comparative Example 2 using the conventional method, but Example 2 of the present invention remained stable and equivalent to that in the initial stage of conditioning (first batch).

[0110] If double-sided polishing is performed in the immediately preceding batch, pad clogging due to silica debris occurs. However, in the examples of the present invention, etching is performed in the same equipment, which dissolves and removes the silica debris that causes clogging. This is thought to be why good surface quality was achieved without conditioning even after polishing 10 or more batches.

[0111] Furthermore, when the processing method of the embodiment of the present invention is used, the time from etching to double-sided polishing is 30% shorter than the conventional method. This is because the transport from etching to double-sided polishing, the drying time required for transport, and the time required for setting up the equipment, which are required in the conventional method, can be omitted. Furthermore, with regard to equipment costs, a significant cost reduction is expected because the present invention does not require the installation of a separate etching device.

[0112] The present specification includes the following aspects. [1]: A method for double-sided processing of wafers using a double-sided processing device having upper and lower surface plates with abrasive cloths attached, characterized in that the wafer is held in a holding hole of a carrier arranged between the upper and lower surface plates, an etching solution is supplied to etch the wafer, and then a slurry containing abrasive grains is supplied to the same double-sided processing device, and the wafer is double-sided polished using the abrasive cloths. [2]: The method for double-side processing of a wafer according to the above [1], characterized in that a urethane foam-based polishing cloth is used as the polishing cloth. [3]: The method for processing both sides of a wafer according to [1] or [2] above, characterized in that the etching solution is an alkaline etching solution. [4]: The method for double-side processing of a wafer according to any one of [1] to [3] above, characterized in that the removal amount in the etching process is 10 μm or more. [5]: A method for double-side processing of a wafer according to any one of [1] to [4] above, characterized in that the load during the etching process is smaller than the load during the double-side polishing process. [6]: A double-sided wafer processing device comprising: upper and lower surface plates on which abrasive cloths are attached; a carrier disposed between the upper and lower surface plates and having holding holes formed therein for holding wafers; a first tank holding an etching solution that does not contain abrasive grains; a second tank holding a slurry that contains abrasive grains; and a switching means for switching between supplying the etching solution from the first tank and supplying the slurry from the second tank. [7]: The double-side processing apparatus for wafers according to the above [6], characterized in that the polishing cloth is a urethane foam-based polishing cloth.

[0113] The present invention is not limited to the above-described embodiments. The above-described embodiments are merely examples, and anything that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits similar effects is included within the technical scope of the present invention. [Explanation of symbols]

[0114] 1...wafer double-sided processing device; 2...first tank; 3...second tank; 4...switching means, 5...lower surface plate, 6...upper surface plate, 7...supply nozzle, 8...abrasive cloth, 9...carrier, 10...retaining hole, 11...sun gear, 12...internal gear. W...wafer.

Claims

1. A double-sided processing method for a wafer using a double-sided processing apparatus having upper and lower surface plates to which abrasive cloths are attached, The wafer is held in a holding hole of a carrier disposed between the upper and lower surface plates; supplying an etching solution to etch the wafer; Thereafter, a slurry containing abrasive grains is supplied to the same double-side processing device, and the wafer is subjected to double-side polishing processing using the polishing cloth.

2. 2. The method for processing both sides of a wafer according to claim 1, wherein the polishing cloth is a urethane foam polishing cloth.

3. 2. The method for processing both sides of a wafer according to claim 1, wherein the etching solution is an alkaline etching solution.

4. 2. The method for processing both sides of a wafer according to claim 1, wherein the etching is performed with a removal amount of 10 μm or more.

5. 5. The method for double-side processing of a wafer according to claim 1, wherein a load during the etching process is set to be smaller than a load during the double-side polishing process.

6. Upper and lower surface plates with abrasive cloths attached thereto; a carrier disposed between the upper and lower surface plates and having a holding hole formed therein for holding a wafer; a first tank containing an abrasive-free etching solution; a second tank containing an abrasive slurry; 10. A wafer double-side processing apparatus comprising: a switching means for switching between supplying the etching liquid from the first tank and supplying the slurry from the second tank.

7. 7. The apparatus for processing both sides of a wafer according to claim 6, wherein the polishing cloth is a urethane foam polishing cloth.

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