WO2007026556A1

WO2007026556A1 - Method and system for mirror-polishing semiconductor wafer

Info

Publication number: WO2007026556A1
Application number: PCT/JP2006/316301
Authority: WO
Inventors: Hiromasa Hashimoto; Hisashi Masumura; Kouzi Kitagawa
Original assignee: Shin-Etsu Handotai Co., Ltd.
Priority date: 2005-08-31
Filing date: 2006-08-21
Publication date: 2007-03-08
Also published as: JP2007067179A

Abstract

A method and a system for mirror-polishing a semiconductor wafer by applying multiple stages of polishing to the surface of the semiconductor wafer. The system (1) for mirror-polishing the semiconductor wafer is characterized by comprising at least a rough polishing device (10) for rough-polishing the surface of the wafer and a finish polishing device (20) for mirror-polishing the surface of the wafer after the rough polishing formed separately from the rough polishing device. As a result, a high quality mirror-finished wafer reduced in haze and particles can be manufactured at low cost and with high productivity.

Description

Semiconductor wafer mirror polishing method and mirror polishing system Technical Field

The present invention relates to a mirror polishing method and a mirror polishing system used when manufacturing a semiconductor wafer such as a silicon wafer. Background art

[0002] When manufacturing a semiconductor wafer, for example, a silicon single crystal ingot is grown by the Chiyoklarsky method, the ingot is sliced and processed into a thin disk, and then chamfering, wrapping, etching, polishing, etc. Through various processes, it is finished into a mirror-like wafer (mirror wafer).

In the silicon wafer polishing process, polishing is usually performed through a plurality of stages from rough polishing to final polishing (see JP-A-9-38849). For example, after the lapping process or the etching process, primary polishing is performed with a polishing allowance of about several x m in order to remove distortion on the surface of the wafer 8 and flatten it. Next, in order to remove scratches and the like generated in the primary polishing and improve the surface roughness, the secondary polishing is performed with a polishing margin of about l z m. Furthermore, in order to obtain a haze-free surface, finish polishing is performed with a polishing allowance of less than l x m. In this way, the surface of the wafer is mirror-finished through rough polishing (primary polishing and secondary polishing) and finish polishing.

[0003] When performing stepwise polishing as described above, the type of polishing cloth and polishing slurry used in each polishing step is different. Polishing is performed using. For example, in the polishing apparatus 81 shown in FIG. 10, three polishing surface plates 83, 84, and 85 to which a polishing cloth used in each polishing process is attached are arranged concentrically at intervals of 90 °. Yes. In addition, two eight polishing heads 82 for holding wafers are arranged concentrically at intervals of 90 °, and are configured to be rotated 90 ° counterclockwise by the head moving mechanism. . As the polishing head 82, for example, one having a ring 92 surrounding the wafer W as shown in FIG. 12 is used. If such a ring 92 is provided, the wafer W can be prevented from coming off during polishing. In addition, by pressing the polishing cloth 93 around the wafer W, it is possible to prevent the outer periphery of the wafer W from being excessively polished.

[0004] In such a polishing apparatus 81, the wafer transported to the load section 86 is held by the polishing head 82, and is sequentially transported between the surface plates with a fixed tact time, and the first surface plate 83 performs the primary polishing. The second surface plate 84 is subjected to secondary polishing, and the final surface plate 85 is subjected to final polishing. The wafer that has been mirror-polished through the rough polishing (primary polishing and secondary polishing) and the final polishing is carried out to the unloader section 87.

As shown in the polishing apparatus 91 shown in FIG. 11, after the first surface plate 88 performs rough polishing that serves both as primary polishing and secondary polishing, the other two surface plates 89 and 90 perform final polishing. Sometimes it is done.

[0005] In this way, a polishing apparatus that performs a series of polishing using the polishing apparatuses 81 and 91 having a plurality of surface plates, from rough polishing to finish polishing while holding the wafer by the same polishing head 82 with one apparatus. It is said that wafers can be mirrored efficiently because they can be performed sequentially.

However, in order to sequentially perform the wafer polishing from the final polishing to the final polishing with a single polishing apparatus as described above, it is necessary to perform polishing with different properties with the same tact time. Therefore, in a polishing process that is not rate-limiting, the polishing load is intentionally set to be low or the polishing speed is reduced by reducing the number of rotations, etc., for adjusting the time, and polishing is performed with the same tact. Therefore, such a mirror polishing system is not necessarily good in terms of productivity and cost.

[0007] On the other hand, recently, the degree of integration of electronic devices has progressed further, and the particle size of particles that obstruct device manufacture has become smaller, and there has been a demand for a reduction in the number of particles on the wafer. Therefore, the demand for reducing the haze level, which is an obstacle to particle detection, has become more severe.

However, in the polishing apparatuses 81 and 91 as described above, the polishing slurry having a strong etching action used in the rough polishing process adheres to the polishing head 82 and mixes into the final polishing process, so that the polishing cost in the final polishing is not much. Since it is very small, there is a risk that the haze level is deteriorated by an unintended etching action. In addition, foreign matter such as particles generated before final polishing may adhere to the polishing head and remain on the wafer surface after final polishing. is there. Disclosure of the invention

[0008] In view of the above problems, the present invention provides a mirror polishing method and a mirror surface of a semiconductor wafer that can manufacture a high-quality mirror surface wafer with reduced haze and particles at low cost and high productivity. An object is to provide a polishing system.

[0009] In order to achieve the above object, according to the present invention, in a method of polishing a surface of a semiconductor wafer in a plurality of stages to make a mirror surface, the surface of the wafer is roughened with a polishing apparatus for rough polishing. After polishing, there is provided a method for mirror polishing of a semiconductor wafer, characterized in that it is mirror-finished by finishing polishing with a polishing apparatus for finishing polishing separately from the polishing apparatus for rough polishing.

[0010] After rough polishing with a polishing apparatus for rough polishing, finish polishing with a polishing apparatus for final polishing separately prepared to make a mirror surface, it is not necessary to match the tact in rough polishing and final polishing. Polishing can be independently performed by each apparatus according to the tact. Therefore, a series of polishing steps can be performed efficiently, productivity can be improved as a whole, and cost can be reduced. In addition, since the polishing slurry and particles in the rough polishing process can be prevented from being mixed into the final polishing process, the haze level can be prevented from deteriorating and particles can be prevented from sticking, and a high-quality mirror surface wafer can be finished.

[0011] Of the polishing apparatus for rough polishing and the polishing apparatus for final polishing, at least as a polishing apparatus for rough polishing, a plurality of polishing heads for holding a wafer, and a plurality of polishing pads attached It is preferable to perform the rough polishing using a polishing plate having a polishing platen. Since the rough polishing process has a larger polishing allowance than the final polishing process, the tact is likely to be relatively long, but if rough polishing is performed using a polishing apparatus having a plurality of polishing heads and a plurality of polishing surface plates, The throughput in the rough polishing process and the finish polishing process are equal, and productivity can be further improved.

[0012] In this case, after performing primary polishing on a part of the plurality of polishing surface plates in the polishing apparatus for rough polishing, secondary polishing can be performed on another surface plate.

If primary polishing and secondary polishing are performed with a rough polishing machine equipped with multiple surface plates, It is possible to reduce the strikes and to achieve higher productivity and lower cost.

[0013] The rough polishing may be divided into primary polishing and secondary polishing, and the primary polishing and secondary polishing may be sequentially performed using different polishing apparatuses.

In addition to performing final polishing with a separate device from rough polishing, if the rough polishing is divided into primary polishing and secondary polishing, and polishing is performed with dedicated polishing devices, productivity will be further improved, especially in mass production. It becomes possible to improve.

[0014] Before the rough polishing, the back surface and / or both surfaces of the wafer can be polished by using a polishing device different from the polishing device for rough polishing and the polishing device for final polishing.

When polishing the backside or both sides of the wafer, it is possible to finish the backside or both sides with a different polishing device in advance, so that a higher quality mirror surface wafer can be produced while maintaining high productivity.

[0015] It is preferable to carry the wafer while holding the back surface or the chamfered portion of the wafer from the force at the end of rough polishing to the end of finish polishing.

In the present invention, the polishing apparatus for rough polishing and the polishing apparatus for final polishing are separate apparatuses. Therefore, the force required to transport the wafer is held between the polishing apparatus and the back surface or chamfered portion of the wafer after rough polishing. If it is conveyed, the surface after polishing can be prevented from being scratched, and a high-quality wafer can be finished more reliably.

In addition, when performing final polishing of the wafer, polishing is performed using a polishing head without a ring for pressing a polishing cloth around the wafer, or a polishing head having the ring. However, it is preferable to perform polishing so that the ring does not press the polishing cloth. In order to prevent excessive polishing at the outer periphery of the wafer 8, a force that may cause polishing with a polishing head equipped with a ring that presses the polishing cloth around the wafer may cause this ring force partition. However, in the present invention, since the final polishing is performed by an apparatus for final polishing separately from the apparatus for rough polishing, a higher quality mirror surface can be obtained by preventing the occurrence of a partition due to the ring during final polishing. Can be finished in woofer.

[0017] In addition, it is preferable that after the rough polishing of the wafer 8 is performed, the wafer is placed in storage water and then the final polishing is performed. If the wafer after rough polishing is put in storage water, the polishing slurry for rough polishing adhering to the surface of the wafer 8 can be surely removed to prevent the influence on the final polishing. In addition, it is possible to prevent the wafer from being contaminated by the polishing slurry remaining in the waiting time until it is transferred to another apparatus, which is a final polishing apparatus. Can be finished.

In this case, it is preferable to use a neutral or acidic aqueous solution to which a surfactant is added as the storage water.

By using such water for storage, the water repellency of the surface of the wafer after rough polishing is maintained, so that the polishing allowance of the final polishing becomes more uniform within the wafer surface. Adhesion is reduced. In addition, by making the storage water neutral or acidic, it is possible to prevent etching of the wafer surface by the alkali component of the polishing slurry.

[0019] Further, it is preferable that the wafer is washed by a pure water shower after the rough polishing of the wafer and before the final polishing.

If the wafer is washed by such a pure water shower, the polishing slurry can be removed more reliably, and the rough polishing slurry can be prevented from being mixed in the final polishing process.

[0020] Further, according to the present invention, there is provided a polishing system for applying a plurality of stages of polishing to the surface of a semiconductor wafer to make a mirror surface, at least for rough polishing of the surface of the wafer 8. A polishing apparatus for rough polishing and a polishing apparatus for final polishing for mirror-finishing the surface of the wafer after the rough polishing are provided separately from the polishing apparatus for rough polishing and the polishing apparatus for rough polishing A semiconductor wafer mirror polishing system is provided.

[0021] With such a mirror polishing system, it is not necessary to match the tact time between rough polishing and finish polishing, and each apparatus can proceed with polishing independently according to the tact of each polishing process. High productivity and low cost can be achieved. In addition, polishing slurry and particles in the rough polishing process can be prevented from entering the final polishing process, so haze level deterioration and particle adhesion can be reduced, resulting in a high-quality mirror finish. Mirror polishing system. [0022] Of the polishing apparatus for rough polishing and the polishing apparatus for final polishing, at least a polishing apparatus for rough polishing includes a plurality of polishing heads for holding a wafer, and a plurality of polishing cloths attached thereto. A polishing platen may be provided.

If the polishing apparatus for rough polishing has a plurality of polishing heads and a plurality of polishing surface plates, rough polishing that tends to be relatively long and finish polishing that has a short tact can be performed at an equivalent throughput. Thus, a mirror polishing system capable of further improving productivity is provided.

[0023] In this case, the polishing apparatus for rough polishing performs primary polishing on a part of the plurality of polishing surface plates as the rough polishing of the wafer, and then performs secondary polishing on another surface plate. It is possible to perform polishing.

If you have a polishing device for rough polishing with multiple surface plates, you can perform rough polishing by dividing it into primary polishing and secondary polishing even with a single machine, further improving productivity and low cost. This is a mirror polishing system that can

In this case, as the polishing apparatus for rough polishing, a polishing apparatus for primary polishing for performing primary polishing, and a secondary polishing for performing secondary polishing after the primary polishing. A polishing apparatus can be provided independently.

If each of them is equipped with a polishing machine that performs primary polishing and secondary polishing, respectively, it becomes a mirror polishing system that can further improve productivity, especially in mass production.

[0025] A polishing apparatus for the back surface for polishing the back surface of the wafer 8 before the rough polishing can be provided.

If a backside polishing device is also provided, even if the backside of the wafer is polished, it will be a mirror polishing system that can produce a higher quality mirror surface while maintaining high productivity.

[0026] Preferably, the wafer is provided with a conveying means for holding and conveying the back surface or the chamfered portion of the wafer until at least the finish power of the rough polishing is finished.

With such a transport means, it is possible to prevent scratches on the surface of the wafer 8 after rough polishing in transport between the polishing apparatus for rough polishing and the polishing apparatus for final polishing, thereby ensuring more reliability. It becomes a mirror-polishing system that can finish high quality UA-8.

[0027] A polishing head of the polishing apparatus for finish polishing removes a polishing cloth around the wafer. It is preferable that polishing is performed so that there is no ring for pressing or the ring does not press the polishing cloth.

If the polishing machine for finish polishing is equipped with a polishing head as described above, the generation of particles due to the ring that presses the polishing cloth around the wafer can be prevented, and a higher quality mirror surface can be finished. Mirror polishing system.

[0028] It is preferable that a water tank is provided between the polishing apparatus for rough polishing and the polishing apparatus for finishing to store the wafer after the rough polishing.

If the water tank as described above is provided, the wafer after rough polishing can be stored in storage water in the water tank before final polishing. Therefore, it is possible to finish polishing after reliably removing the polishing slurry and particles for rough polishing adhering to the surface of the wafer, and a mirror polishing system that can finish to a high-quality mirror surface more reliably. Become.

[0029] In this case, a means for supplying a surfactant to the storage water in the water tank and a means for adjusting the pH of the storage water can be provided.

If such a surfactant supply means and a pH adjustment means are provided, the wafer surface can be etched by the alkali component of the polishing slurry by maintaining the water repellency of the stored wafer after rough polishing. This is a mirror polishing system that can prevent and achieve a higher quality mirror wafer.

[0030] Further, it is preferable that a pure water shower tank is provided between the polishing apparatus for rough polishing and the polishing apparatus for finishing to clean the wafer after the rough polishing with pure water. If equipped with a pure water shower tank, the polishing slurry and particles for rough polishing adhering to the surface of the wafer 8 can be more reliably removed by the pure water shower, and the coarse polishing slurry is mixed into the final polishing process. This is a mirror polishing system that can perform finish polishing while preventing this.

[0031] According to the present invention, when the surface of the semiconductor wafer is polished to have a mirror surface, the polishing apparatus for rough polishing and the polishing apparatus for final polishing different from the polishing apparatus for rough polishing are used. Since the polishing equipment performs rough polishing to final polishing, it is not necessary to match the tact between rough polishing and final polishing. Can. Therefore, productivity is improved and low cost can be achieved. In addition, since the polishing slurry and particles in the rough polishing process can be prevented from entering the final polishing process, the haze level is deteriorated and the adhesion of particles is reduced, and a high-quality mirror surface wafer can be finished. Brief Description of Drawings

FIG. 1 is a schematic configuration diagram showing an example of a semiconductor wafer mirror polishing system according to the present invention (when loaded).

FIG. 2 is a schematic configuration diagram showing an example of a semiconductor wafer mirror polishing system according to the present invention (when unloaded).

FIG. 3 is a schematic view showing a state in which a wafer held by a polishing head is polished.

FIG. 4 is a schematic view showing an example of a polishing head used in finish polishing.

5 is an enlarged schematic view of the periphery of the ring of the polishing head shown in FIG.

FIG. 6 is a schematic configuration diagram showing another example of a semiconductor wafer mirror polishing system according to the present invention.

₇ is a schematic configuration diagram showing still another example of mirror polishing system for semiconductor Ueha according to the present invention.

FIG. 8 is a view showing the surface state of a wafer measured after finish polishing. (A) Example 1 (B) Example 2

FIG. 9 is a diagram showing the surface state of a wafer measured after finish polishing. (A) Comparative example 1 (B) Comparative example 2

FIG. 10 is a schematic configuration diagram showing an example of a conventional polishing apparatus.

FIG. 11 is a schematic configuration diagram showing another example of a conventional polishing apparatus.

FIG. 12 is a schematic configuration diagram of a polishing head provided with a pressing ring.

BEST MODE FOR CARRYING OUT THE INVENTION

The semiconductor wafer mirror polishing method and mirror polishing system according to the present invention will be specifically described below with reference to the accompanying drawings.

FIG. 1 schematically shows an example of the configuration of a semiconductor wafer mirror polishing system according to the present invention. Show. The mirror polishing system 1 is used to mirror the surface of the wafer after rough polishing separately from the polishing apparatus 10 for rough polishing for rough polishing the surface of the wafer and the polishing apparatus 10 for rough polishing. A polishing apparatus 20 for final polishing is provided. Both polishing apparatuses 10 and 20 are arranged via a transfer unit 30. The transfer unit 30 is provided with a transfer robot 31 for transferring wafers, a water tank 32 for storing the wafers after rough polishing, a shower tank 33, a pH adjuster tank 34, and a surfactant tank 35. ing.

The polishing apparatus 10 for rough polishing includes eight polishing heads 14 and three polishing surface plates 11, 12, and 13. The eight polishing heads 14 are arranged concentrically and are indexed by two at intervals of 90 °. Three polishing surface plates 11, 12, 13 are also arranged concentrically at intervals of 90 °. The first and second surface plates 11 and 12 are used for primary polishing, and each has a polishing cloth for primary polishing. The third surface plate 13 is used for secondary polishing, and a polishing cloth for secondary polishing is attached. In addition, robot arms 3a and 3b for conveying wafers, a wafer positioning unit 4 for positioning wafers, and an unload tray 5 for unloading the polished wafers are provided.

On the other hand, the polishing apparatus 20 for final polishing also includes eight polishing heads 24 and three polishing surface plates 21, 22, and 23. Each of the polishing surface plates 21, 22, and 23 is provided for final polishing. Abrasive cloth is stuck. In addition, as with the polishing apparatus 10 for rough polishing, robot arms 6a and 6b for transferring wafers, a wafer positioning unit 7 and an unload tray 8 are also provided.

A method of polishing the semiconductor wafer in stages by using such a mirror polishing system 1 to make a mirror surface will be described.

First, a container containing wafers is transported to the loader section 2 of the polishing apparatus 10 for rough polishing. The robot arm 3a takes out the wafer from the wafer storage container, and sets it to the wafer positioning unit 4 so as to support the chamfered portion of the wafer. After two wafers are set in the wafer positioning unit 4, the back surface of the wafer is sucked and held by the two polishing heads 14 located at the top of the positioning unit 4.

The two polishing heads 14 holding the wafer are rotated 90 ° counterclockwise by the head moving means 15 and moved onto the first primary polishing surface plate 11. Then, as shown in FIG. 3, each polishing head 14 and the surface plate 11 are rotated at a predetermined number of rotations, respectively. The polishing slurry 38 is supplied from the polishing slurry supply means 37 onto the polishing cloth 11a attached to the wafer, and the wafer W held by the polishing head 14 is brought into sliding contact with the polishing cloth 11a with a predetermined polishing pressure.

As described above, while the first polishing is performed on the first surface plate 11, the next two wafers are set in the wafer positioning unit 4 in the same manner as described above, and are held by the next two polishing heads 14. .

[0038] After the primary polishing is performed on the first surface plate 11 for a predetermined time, each polishing head is rotated 90 ° by the head moving means 15 by the same procedure as described above, and polishing on the surface plate. Repeat the holding of the wafer. As a result, each wafer is subjected to primary polishing on the two surface plates 11 and 12 and then to secondary polishing on the third surface plate 13. For example, when the primary polishing tact time is twice as long as the secondary polishing tact time, the rough polishing apparatus 10 can proceed with the rough polishing step without delay. The surface plate for primary polishing and the surface plate for secondary polishing should be determined according to the takt time in each polishing process.For example, the takt time for secondary polishing is twice the takt time for primary polishing. In this case, it is sufficient to perform rough polishing by setting one surface plate for primary polishing and two surface plates for secondary polishing. However, since the primary polishing usually requires more machining allowance, it takes more time, and it is preferable to increase the number of primary polishing surface plates.

[0039] After the secondary polishing, the unload tray 5 is moved to the polishing head 14 which is returned to the original position by 90 ° rotation as shown in FIG. 2, and the wafer separated from the polishing head 14 is chamfered. It is placed on the unload tray 5 in such a way that the part is supported. Next, the wafer is held from the unload tray 5 by the robot arm 3b so as to support the back surface or the chamfered portion of the wafer, and is poured into the storage water in the water tank 32 in the transfer section 30. In the storage water, a surfactant is added as a non-etching chemical solution from the surfactant tank 35 in order to keep the water repellency of the wafer surface immediately after rough polishing uniform. In addition, in order to protect the surface of u18 from the etching by the alkali component of the polishing slurry remaining on the surface of the u8, the pH adjuster tank 34 is maintained so that the water for storage is kept neutral or acidic. Acid solution is dripped from.

[0040] By throwing the wafer after rough polishing into the storage water as described above before final polishing, the wafer having a uniform water-repellent surface can be reliably polished with a final polishing apparatus. And become possible. Since the polishing allowance for final polishing is very small, the quality of the wafer surface before final polishing greatly affects the quality after final polishing, but if the wafer has a uniform water-repellent surface as described above, final polishing The polishing allowance becomes uniform in the wafer surface, and the haze level on the surface of the wafer and the number of particles can be reduced. After immersing the wafer in storage water for a predetermined time, the wafer is transferred from the water tank 32 to the shower tank 33 by the transfer robot 31 and subjected to a pure water shower.

After removing polishing slurry and storage water on the wafer surface by a pure water shower, the wafer is set on the wafer positioning unit 7 by the robot arm 6a of the polishing apparatus 20 for final polishing. The wafer is held by the polishing head 24, and finish polishing is performed on each of the surface plates 21, 22, 23.

FIG. 4 shows an example of the polishing head 24 used in finish polishing. In this polishing head 24, a holding plate 46 is connected to a head main body 41 via a rubber diaphragm 40. The holding plate 46 is formed with a number of through holes 47 for vacuum suction of the wafer W. A backing pad 45 is affixed to the side that adsorbs wafer W, and a back plate 43 is provided on the back side. Further, a ring 44 is provided so as to surround the holding plate. The wafer can be adsorbed and separated by adjusting the pressure in the space between the holding plate 46 and the back plate 43 through the wafer adsorption control passage 49. Further, the pressure of the wafer W against the polishing pad 21 a can be adjusted by adjusting the pressure in the space between the back plate 43 and the head body 41 through the wafer pressing passage 48.

If polishing is performed while holding the wafer W with the polishing head 24 having such a ring 44, the wafer W can be prevented from coming off the holding plate 46 during polishing. However, if polishing is performed with the ring 44 pressing the polishing cloth, the ring itself may cause generation of particles.

Therefore, in the finish polishing, the polishing can be performed so that the ring 44 does not press the polishing cloth 2 la as shown in FIG. For example, the position of the ring 44 is set so that the surface of the wafer W (surface to be polished) protrudes 0.20 to 0.35 mm from the lower surface of the ring 44. This prevents the wafer W from being detached during polishing, and enables the ring 44 to perform polishing without pressing the polishing cloth 21a, thereby preventing particles from being generated from the ring 44. Can do. In addition, since the polishing allowance is extremely small in the final polishing compared with the rough polishing, even if the polishing is performed without pressing the polishing cloth 21a around the wafer W, it is excessive on the outer periphery of the wafer W. Polishing does not occur.

[0044] Thus, in the mirror polishing system 1 according to the present invention, the polishing apparatus 20 for finish polishing is provided in addition to the polishing apparatus 10 for rough polishing. The final polishing can be performed by holding the wafer W with another polishing head 24 for final polishing. Therefore, it is possible to prevent the generation of particles due to the ring 44 in the finish polishing. In finish polishing, a polishing head without a ring that presses the polishing cloth around wafer W can be used.

The wafers W held by the respective polishing heads 24 are subjected to final polishing on the respective surface plates 21 to 23 of the polishing apparatus 20 for final polishing. At this time, similarly to the polishing apparatus 10 for rough polishing, the two polishing heads 24 can be rotated 90 ° at a time so that the final polishing can be performed in three times, or six wafers can be formed with three sets of polishing heads 24. After holding W, finish polishing can be performed simultaneously on each of the surface plates 21, 22, 2 3 as well.

[0046] The finished polished wafer is carried out to the unload section 9 by the unload tray 8 and the robot arm 6b. Even in the polishing apparatus 20 for final polishing, the wafer is transferred by the robot arms 6a and 6b, the wafer positioning unit 7 and the unload tray 8, but these transfer means are the same as those of the polishing apparatus 10 for rough polishing. Hold the backside or chamfer of the wafer. Accordingly, the force at the end of rough polishing can be carried while holding the back surface or chamfered portion of the wafer until the end of finish polishing, and the surface after polishing can be prevented from being scratched.

[0047] After performing rough polishing with the polishing apparatus 10 for rough polishing as described above, by performing final polishing with the polishing apparatus 20 for final polishing, polishing is efficiently performed according to the takt time of each polishing step. In addition, it is possible to obtain a high-quality specular wafer with good haze level and low particle adhesion.

In addition, the mirror polishing system according to the present invention is used for finishing polishing to mirror the surface of the wafer 8 after rough polishing, separately from the polishing apparatus for rough polishing for rough polishing the surface of the wafer. The number of polishing heads and surface plates of each device is good if it has a polishing device. What is necessary is just to set according to the tact time in each grinding | polishing process.

FIG. 6 shows another example of the mirror polishing system according to the present invention. This mirror polishing system 50 includes a polishing apparatus 51 for primary polishing for performing primary rough polishing with a polishing apparatus 53 for final polishing, and a polishing apparatus 51 for performing secondary rough polishing after the primary polishing. A polishing apparatus 52 for the next polishing is provided independently. Each of the polishing apparatuses 51, 52, 53 includes eight polishing heads 55 and three surface plates 54. The polishing device 51 for primary polishing and the polishing device 52 for secondary polishing are transferred by way of the transfer unit 57, and the polishing device 52 for secondary polishing and the polishing device 53 for final polishing are transferred by the transfer unit 58. Will pass the wafer. The wafers transported to the loader unit 56 are sequentially polished into primary polishing, secondary polishing, and finish polishing in the polishing devices 51, 52, and 53, respectively, are mirror-finished, and are transported to the unloader unit 59. It is. Such a mirror polishing system 50 can perform each polishing process independently without delay regardless of the tact times of, for example, primary polishing, secondary polishing, and finish polishing.

FIG. 7 shows still another example of the mirror polishing system according to the present invention. The mirror polishing system 61 further includes a polishing apparatus 62 for the back surface in addition to the mirror polishing system shown in FIG. Each polishing apparatus 62, 63, 64 is provided with eight polishing heads 70 and three surface plates 69. The polishing device 62 for the back surface and the polishing device 63 for rough polishing are transferred by the transfer unit 66, and the polishing device 63 for rough polishing and the polishing device 64 for final polishing are transferred by the transfer unit 67. Delivered.

[0050] The back surface of the wafer transferred to the loader unit 65 is polished by the back surface polishing device 62. After the back surface polishing, the wafer is transferred to a polishing device 63 for rough polishing, and primary polishing and secondary polishing are performed in the same manner as the mirror polishing system 1 shown in FIG. Further, it is conveyed to a polishing apparatus 64 for final polishing, and after being subjected to final polishing, it becomes a mirror wafer, and is then carried out to the unloader section 68.

In this way, the mirror surface polishing system 61 that also includes the back surface polishing device 62 can polish the back surface of the wafer before rough polishing, which is particularly efficient when the back surface is also polished.

[0051] As described above, the mirror polishing system for a semiconductor wafer according to the present invention is a polishing tool for rough polishing. A polishing device for finish polishing is provided separately from the polishing device, so that it is not necessary to match the tact for rough polishing and finish polishing, and each device can proceed with polishing independently according to the tact of each polishing step. it can. Therefore, productivity is improved and low cost can be achieved. In addition, since the polishing slurry used in the rough polishing process can be prevented from entering the final polishing process, it is possible to prevent deterioration of haze level and adhesion of particles, and finish to a high-quality mirror surface. . Furthermore, there is no need to forcibly match the tact time in each process. As a result, optimum conditions for quality can be adopted in each process, and there is an advantage that wafers can be polished to a higher quality.

Hereinafter, examples and comparative examples of the present invention will be described.

A thin disc-shaped wafer was obtained by slicing a single crystal silicon ingot of P-type, 100>, resistance 8 to: 12 Q cm, pulled up by the Chiyoklarsky method. In order to prevent cracking and chipping of wafers, the outer edge was chamfered, and then lapping caloe was performed to planarize the wafers. Next, an etching process was performed to remove the processing strain remaining on the surface of the wafer after lapping. In addition, both sides of the wafer were polished, and the chamfered portion was also polished.

The wafer thus obtained was divided into two gnoles, and primary, secondary and finish polishing processes were performed under the conditions of the following examples and comparative examples, respectively.

[0053] (Example)

A mirror polishing system as shown in Fig. 1 was constructed, and the above-mentioned mirror polishing was performed. The polishing conditions are as follows.

A polyester nonwoven fabric impregnated urethane resin impregnated product (Asker C hardness 88 °) was used as the polishing cloth, and a pHl 1 alkaline solution containing colloidal silica was used as the polishing slurry. The polishing head used was equipped with a pressure ring that can adjust the pressure against the polishing cloth around the wafer.

The polishing head and polishing platen are rotated at 30 rpm each, and wafer polishing pressure is 30k. The primary polishing was performed with Pa and the pressure of the pressure ring set to 35 kPa.

[0054] <Secondary rough polishing>

A polyester nonwoven fabric urethane resin impregnated product (Asker C hardness 76 °) was used as the polishing cloth, and an alkaline solution of ρ 溶液 5 containing colloidal silica was used as the polishing slurry.

The polishing head and polishing platen were each rotated at 30 rpm, the polishing pressure of the wafer was set to 30 kPa, and the pressure of the pressure ring was set to 32 kPa to perform secondary polishing.

[0055] <Transfer unit>

To the storage tank of the transfer section, 10% citrate is added dropwise so that the pH of the storage water is maintained at 3-7, and the surfactant (polyoxyethylene alkyl ether) is added at a concentration of 0.0. It was dripped so that it might be kept at 1% or more.

After the secondary polishing, the wafer was stored in the above storage water for 1 minute or more and then moved to a shower tank.

[0056] <Finishing polishing>

A suede-type polishing cloth (Ciegal 7355 manufactured by Toray Coating Co., Ltd., Asker C hardness 73 °) was used, and the polishing slurry contained an alkaline solution of pH 9.5 containing colloidal silica with a particle size of 60 to 100 nm (silica concentration: 0.5% by weight) was used. The polishing head shown in Fig. 4 was used.

The polishing head and the polishing platen were each rotated at 20 rpm, the polishing pressure of the wafer was set to 10 kPa, and polishing was performed with the ring retracted from the polishing cloth.

[0057] (Comparative example)

Using two polishing machines as shown in Fig. 10, mirror polishing of silicon wafer 8 was performed. Each of the eight polishing heads is equipped with a pressing ring that presses the polishing cloth around the wafer, and the polishing cloth, polishing slurry, polishing pressure, etc. on each surface plate are shown in the examples. And so on. However, in the secondary polishing, the rotation speed of the polishing head and the polishing platen was set to 15 rpm respectively to match the tact time of the primary polishing.

[0058] <Productivity comparison> In the comparative example, primary polishing, secondary polishing, and finish polishing are performed by each device. Therefore, the tact times of the secondary polishing and finish polishing must be adjusted to the primary polishing with a large machining allowance. It was.

In the example, on the other hand, in the polishing apparatus for rough polishing, the primary polishing was performed on two surface plates, and the secondary polishing was performed on one surface plate, so the rough polishing was efficiently performed without matching the tact time. I was able to. Also, in finish polishing, it was necessary to carry the wafer after the secondary polishing to the polishing machine for finish polishing, but it was possible to perform finish polishing with the original tact time. The time required was equivalent to that of the comparative example.

As a result, the total polishing time per wafer was about two-thirds of that of the comparative example.

In the comparative example, the number of rotations was increased or the pressure was increased, but the flatness of the wafer deteriorated and the polishing time could not be shortened.

[0059] <Particle measurement result>

The silicon wafer was mirror-polished under the polishing conditions of the example and the comparative example, and then SC-1 cleaning was performed. After cleaning, two particles and two hazes were evaluated using a particle counter (“Surfscan SP-1 TBI” manufactured by KLA Tencor). In addition, in order to evaluate crystal defects (LPD-N) and particles (LPD) separately, particles of 0.065 xm or more were detected by performing measurement under high resolution conditions using an oblique incident beam. . The haze was measured at the same time as the particle measurement, and the haze value in the wide-angle wide-angle incidence channel (DWO) was used.

FIGS. 8A and 8B show a wafer polished using the mirror polishing system of the example, and FIGS. 9A and 9B show a wafer polished by the comparative example. This shows a mirror-polished wafer. Table 1 shows the evaluation results for particles and haze.

[0061] [Table 1] Number of particles D W O Haze

(Particle size 0.0 6 5 μm or less)

Example 1 1 4 0 0.0 3 6 p p m

Example 2 1 4 0 0.0 3 5 p p m

Comparative Example 1 4 0 0 0.0 3 9 p p m

Comparative Example 2 4 2 0 0.0 4 0 ppm [0062] From Fig. 8 and Fig. 9 and Table 1, it can be seen that a high-quality mirror wafer having smaller values for both the particles and haze in Examples 1 and 2 was obtained.

Note that the present invention is not limited to the above-described embodiment. The above-described embodiments are merely examples, and those having substantially the same configuration as the technical idea described in the claims of the present invention and exhibiting the same functions and effects will be recognized. However, it is included in the technical scope of the present invention.

For example, in the embodiment, the polishing apparatus for rough polishing and the polishing apparatus for finish polishing have been described with respect to a mirror polishing system having eight polishing heads and three surface plates, respectively. In the mirror polishing system, the number of polishing heads and the number of surface plates are not particularly limited, and can be configured according to the takt time in each polishing step. For example, if the tact time of final polishing is about one-third of the tact time of rough polishing, you can perform final polishing using a polishing machine for finishing polishing with one surface plate.

Further, the rough polishing may be performed once as both primary polishing and secondary polishing.

Claims

The scope of the claims

[1] A method of polishing the surface of a semiconductor wafer in a plurality of stages to form a mirror surface, and after roughly polishing the surface of the wafer with a polishing apparatus for rough polishing, A method for mirror polishing of semiconductor wafers, characterized in that it is mirror-finished by finishing with a polishing machine for final polishing prepared separately from the equipment.

[2] Of the polishing apparatus for rough polishing and the polishing apparatus for final polishing, at least as a polishing apparatus for rough polishing, a plurality of polishing heads for holding a wafer and a plurality of polishing cloths attached thereto 2. The method of polishing a semiconductor wafer according to claim 1, wherein the rough polishing is performed using a polishing plate having a polishing platen.

[3] The first polishing is performed on a part of the plurality of polishing surface plates in the polishing apparatus for rough polishing, and then the second polishing is performed on another surface plate. 2. A method for mirror polishing a semiconductor wafer according to 1.

[4] The rough polishing is divided into primary polishing and secondary polishing, and the primary polishing and secondary polishing are sequentially performed using different polishing apparatuses, respectively. A method for polishing a semiconductor wafer as described.

[5] Before performing the rough polishing, the back surface and / or both surfaces of the wafer are polished using a polishing device different from the polishing device for rough polishing and the polishing device for final polishing. The method for mirror polishing a semiconductor wafer according to claim 1.

[6] The force at the end of rough polishing of the wafer is carried while holding the back surface or chamfered portion of the wafer until the end of finish polishing. A method for mirror polishing a semiconductor wafer as described.

[7] When performing final polishing of the wafer, polishing is performed using a polishing head without a ring for pressing a polishing cloth around the wafer, or even a polishing head including the ring 7. The semiconductor wafer mirror polishing method according to claim 1, wherein the polishing is performed so that the ring does not press the polishing cloth.

[8] After the rough polishing of the wafer 8, the wafer is put in storage water, and then the final polishing is performed. The method of polishing a semiconductor wafer according to Item.

9. The semiconductor wafer mirror polishing method according to claim 8, wherein a neutral or acidic aqueous solution to which a surfactant is added is used as the storage water.

[10] The semiconductor according to any one of [1] to [9], wherein the wafer is cleaned by a pure water shower after the rough polishing of the wafer and before the final polishing. Wafer mirror polishing method.

[11] A polishing system for polishing the surface of a semiconductor wafer in a plurality of stages to make a mirror surface, and at least a polishing apparatus for rough polishing for rough polishing the surface of the wafer 8; A semiconductor wafer mirror polishing system comprising: a polishing apparatus for finish polishing for mirror-finishing the surface of the wafer after the rough polishing, separately from the polishing apparatus for rough polishing.

[12] Of the polishing apparatus for rough polishing and the polishing apparatus for finish polishing, at least a polishing apparatus for rough polishing includes a plurality of polishing heads for holding a wafer, and a plurality of polishing cloths attached thereto. 12. The semiconductor wafer eight mirror polishing system according to claim 11, comprising a polishing platen.

[13] The polishing apparatus for rough polishing includes the plurality of polishing surface plates as rough polishing of the wafer. 13. The semiconductor wafer mirror polishing system according to claim 12, wherein primary polishing is performed on a part of the surface plate, and then secondary polishing is performed on another surface plate.

[14] As the polishing apparatus for rough polishing, a polishing apparatus for primary polishing for performing primary polishing, and a polishing apparatus for secondary polishing for performing secondary polishing after the primary polishing, respectively. 13. The semiconductor wafer mirror polishing system according to claim 11, wherein the mirror polishing system is provided independently.

[15] The semiconductor wafer according to any one of [11] to [14], further comprising a back surface polishing device for polishing the back surface of the wafer before the rough polishing. Mirror polishing system.

[16] The conveyor as claimed in claim 11, further comprising conveying means for conveying the wafer while holding at least the back surface or the chamfered portion of the wafer from the force at the end of rough polishing to the end of finish polishing. Item 15. The semiconductor wafer mirror polishing system according to Item 15, wherein the deviation is one.

[17] The polishing head of the polishing apparatus for finishing does not have a ring for pressing the polishing cloth around the wafer, or performs polishing so that the ring does not press the polishing cloth. The semiconductor wafer mirror polishing system according to claim 11, wherein the semiconductor wafer mirror polishing system according to claim 11.

18. A water tank for storing the wafer after the rough polishing is provided between the polishing apparatus for rough polishing and the polishing apparatus for finishing. 18. The semiconductor wafer mirror polishing system according to claim 17, wherein the semiconductor wafer is mirror-polished.

19. The semiconductor wafer eight mirror polishing system according to claim 18, comprising means for supplying a surfactant to the storage water in the water tank and means for adjusting the pH of the storage water. 12. A pure water shower tank for cleaning the wafer after the rough polishing with pure water shower is provided between the polishing apparatus for rough polishing and the polishing apparatus for finishing. 20. The mirror polishing system for semiconductor wafers according to claim 19, wherein the mirror is polished.