JP2007027488A - Method for polishing semiconductor wafer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To remove the flaws and defects of a wafer surface, while improving the roughness of the wafer surface without deteriorating the productive efficiency of a silicon wafer, by removing silicon chips remaining on polishing cloth, without having to interrupt the polishing works of the silicon wafer. <P>SOLUTION: In a chemical polishing process, the silicon wafer is pushed against the polishing-cloth side, while a section between the silicon wafer and polishing cloth with a working liquid from a tank between a rough polishing process and a finishing polishing process is supplied, and the surface of the silicon wafer is polished. The chemical polishing process may be conducted by supplying the working liquid, in parallel with a water-polishing process, or in place of the supply of a rinsing liquid in the wafer-polishing process in the case of the carrying-out of a method for polishing the silicon wafer. The process may be transferred from the rough polishing process to the chemical polishing process, by changing over the liquid supplied between the silicon wafer, and polishing the cloth from slurry for a polishing to the working liquid in the case of the carrying-out of the method. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for polishing a surface of a semiconductor wafer such as a silicon wafer.

  One of the processes for manufacturing a silicon wafer is a polishing process for polishing the surface of the silicon wafer into a mirror surface.

  The polishing process includes a plurality of stages of rough polishing process and finish polishing process, and the surface of the silicon wafer is polished stepwise.

  The rough polishing process is performed in order to remove surface damage given to the silicon wafer by the previous lapping process or etching process and to increase the flatness. The final polishing step is performed in order to improve the roughness (roughness) of the wafer surface given by the previous steps (including the rough polishing step).

  In the polishing step, the surface of the silicon wafer is polished by pressing the silicon wafer against the polishing cloth while the polishing slurry is supplied between the silicon wafer and the polishing cloth.

  The polishing slurry used in the polishing process is a mixture of abrasive grains (colloidal silica) and processing liquid (alkaline aqueous solution), mechanically polished by the abrasive grains and polishing cloth, and chemically processed by the processing liquid. Polishing (etching) is performed. Thus, the polishing step is performed by mechanical chemical polishing.

  The polishing cloth deteriorates with increasing use time (number of batches). The deterioration of the polishing cloth is manifested by a phenomenon such as clogging. Silicon scraps and abrasive grains generated during polishing enter the holes of the polishing cloth and cause clogging. The clogging (unevenness) of the polishing cloth means that the surface of the polishing cloth is rough. When a silicon wafer is polished as it is, the surface roughness of the polishing cloth is transferred to the surface of the silicon wafer, The surface becomes rough, and scratches and defects occur.

  Therefore, dressing the surface of the polishing cloth (seasoning) to remove abrasive grains and silicon debris remaining on the polishing cloth and prevent the polishing cloth surface roughness from being transferred to the silicon wafer surface. ) Is performed at regular intervals. During the dressing operation, the polishing operation is temporarily interrupted.

  By grinding the surface of the polishing cloth by dressing, the clogging (unevenness) of the polishing cloth surface can be eliminated and the cloth surface can be cleaned and smoothed. It is possible to prevent the surface from becoming rough and from generating scratches and defects. As a method of dressing the polishing cloth, generally, a method of brushing the polishing cloth with a tool in which a plate electrodeposited with diamond or a ceramic surface is processed while flowing water through the polishing cloth is used. .

  In Patent Document 1 to be described later, when the rough polishing process is finished, the polishing cloth is supplied with an alkaline aqueous solution having a pH (pH = 8 or more) similar to that of the polishing slurry used in the next finishing polishing process. An invention is described in which after the brushing is finished and the brushing is finished, a finish polishing step is performed.

Further, in Patent Document 2 described later, in order to remove scratches observed on the surface of the silicon wafer after the finish polishing step, the surface of the silicon wafer is finish-polished only with a processing liquid (alkaline aqueous solution) that does not contain abrasive grains. The invention is described.
JP 2003-39310 A Japanese Patent No. 3202305

  When the invention described in Patent Document 1 is carried out, after the rough polishing process, it is necessary to interrupt the polishing operation and perform brushing. During the brushing, the polishing operation of the silicon wafer surface is not performed, so that the production efficiency of the wafer is lowered.

  On the other hand, when the invention described in Patent Document 2 is implemented, the scratches observed on the surface of the silicon wafer after the finish polishing process are reduced to some extent, but the roughness of the surface of the silicon wafer after the finish polishing process is reversed. In particular, haze (surface roughness with a small period) is deteriorated.

  The present invention has been made in view of such circumstances, and reduces the production efficiency of the wafer by removing the silicon waste remaining on the polishing cloth without interrupting the polishing operation of the silicon wafer. Therefore, it is an object of the present invention to eliminate the scratches and defects on the wafer surface and improve the roughness of the wafer surface.

The first invention is
The process of polishing the surface of the semiconductor wafer by pressing the semiconductor wafer against the polishing cloth while supplying the polishing slurry mixed with the abrasive grains and the processing liquid between the semiconductor wafer and the polishing cloth. A method for polishing a semiconductor wafer, which is performed in a process and a finish polishing process,
Chemical polishing that polishes the surface of the semiconductor wafer by pressing the semiconductor wafer against the polishing cloth while supplying the processing liquid between the semiconductor wafer and the polishing cloth between the rough polishing process and the final polishing process. It is characterized by carrying out the process.

The second invention is the first invention,
A polishing method in which, following the rough polishing process, a water polishing process is performed in which the surface of the semiconductor wafer is polished by pressing the semiconductor wafer against the polishing cloth while supplying a rinsing liquid between the semiconductor wafer and the polishing cloth. There,
In parallel with the water polishing process or instead of supplying the rinsing liquid in the water polishing process, the chemical polishing process is performed by supplying the processing liquid.

The third invention is the first invention,
The liquid supplied between the semiconductor wafer and the polishing cloth is switched from the polishing slurry to the processing liquid, thereby shifting from the rough polishing process to the chemical polishing process.

4th invention is 1st invention-3rd invention,
The processing liquid is an alkaline aqueous solution having a pH of 8 or more and 12 or less.

5th invention is 1st invention-3rd invention,
The chemical polishing step is performed within a time range of 5 seconds to 15 minutes.

  According to the present invention, the silicon wafer 6 is pushed toward the polishing cloth 2 while supplying the processing liquid 10b from the tank 11 between the silicon wafer 6 and the polishing cloth 2 between the rough polishing process and the final polishing process. The chemical polishing step of polishing the surface of the silicon wafer 6 is performed (first invention).

  In carrying out the present invention, the chemical polishing step may be performed by supplying the processing liquid 10b in parallel with the water polishing step or instead of supplying the rinse liquid in the water polishing step (first step). 2 invention).

  In carrying out the present invention, the liquid supplied between the silicon wafer 6 and the polishing cloth 2 is switched from the polishing slurry 10 to the processing liquid 10b by, for example, the switching valve 8 to change the chemical from the rough polishing step. It is also possible to shift to a mechanical polishing step (third invention; FIG. 1).

  The working fluid 10b used in the chemical polishing step is preferably an alkaline aqueous solution having a pH value of 8 or more and 12 or less (fourth invention). This is because the effect of improving the surface roughness by etching the surface of the silicon wafer 6 is obtained, and the surface roughness of the surface of the silicon wafer 6 does not become remarkable.

  The chemical polishing step is preferably performed within a time range of 5 seconds to 15 minutes (fifth invention). This is because it is necessary to adjust the time of the chemical polishing process according to the surface state of the wafer when chemical polishing is performed on the wafer surface and the surface state of the polishing cloth 2. For example, when rough polishing is performed at a low surface pressure, the mechanical polishing damage given to the surface of the silicon wafer 6 is small, so that the chemical polishing can remove the damage in a short time. The process time is set short. On the contrary, when rough polishing is performed at a high surface pressure, the mechanical polishing damage given to the surface of the silicon wafer 6 is large. Since it cannot be removed, the time for the chemical polishing step is set long.

  According to the present invention, the following effects can be obtained.

1) During the chemical polishing step, the silicon wafer 6 is polished without using the abrasive grains 10a, and silicon scraps that cause clogging of the polishing cloth 2 can be dissolved by the etching action of the processing liquid 10b. Therefore, the abrasive cloth 10 is not left with any abrasive grains 10a or silicon scraps, and is polished by the polishing cloth 2 without clogging, so that no new scratches are formed on the silicon wafer 6. The surface polishing scratches given to the silicon wafer 6 by the rough polishing in the previous process can be effectively removed, and the surface roughness can be improved. In this way, the finish polishing of the next process is performed in a state where the surface roughness of the silicon wafer 6 is improved, so that the surface roughness is further improved, and in particular, haze deterioration can be suppressed.

2) The surface of the silicon wafer 6 can be chemically polished while dissolving silicon scraps that cause clogging of the polishing cloth 2 by the etching action of the processing liquid 10b. For this reason, it is not necessary to interrupt the polishing operation and perform brushing, thereby improving the wafer production efficiency.

3) In particular, when rough polishing using the abrasive grains 10a and chemical polishing without using the abrasive grains 10a are performed with the same polishing apparatus, the abrasive used during the rough polishing by the etching action of the processing liquid 10b. The grains 10a, that is, the abrasive grains 10a that cause clogging of the polishing cloth 2 can be dissolved. Further, the agglomeration of the abrasive grains 10a can be prevented by the hydroxyl ions in the working liquid 10b (alkaline aqueous solution). Further, even the abrasive grains 10a once aggregated can be redispersed. For this reason, as in the above 1), since the wafer is polished by the polishing cloth 2 without clogging, it is possible to shift to the final polishing of the next process while the wafer surface is improved, and the surface roughness is further increased by the final polishing. By improving, haze deterioration can be suppressed. Similarly to the above 2), since the surface of the silicon wafer 6 can be chemically polished while dissolving silicon scraps and abrasive grains 10a that cause clogging of the polishing cloth 2, the polishing operation is temporarily interrupted. This eliminates the need for brushing and improves wafer production efficiency.

  Embodiments of a semiconductor wafer polishing method according to the present invention will be described below with reference to the drawings.

  FIG. 1 shows a configuration of a polishing apparatus used in the rough polishing process of the embodiment. In the embodiment, a single-side polishing apparatus that polishes one side (surface) of a silicon wafer is assumed. In the embodiment, a batch type polishing apparatus that simultaneously polishes a plurality of silicon wafers is assumed.

  As shown in FIG. 1, the rough polishing polishing apparatus is provided with a disk-shaped rotating surface plate 1 so as to be rotatable by a rotating shaft 1a. A polishing cloth 2 is adhered to the upper surface of the rotating surface plate 1 using, for example, a double-sided tape.

  An upper surface plate 3 is provided above the polishing cloth 2 so as to be movable in the vertical direction and to be rotatable.

  A polishing block 4 is positioned below the upper surface plate 3. A plurality of silicon wafers 6 are bonded to the polishing block 4 via wax 5. The silicon wafer 6 is attached to the polishing block 4 so that the polishing surface (front surface) of the silicon wafer 6 faces the polishing cloth 2.

  A supply nozzle 7 is provided above the polishing cloth 2 at a position where liquid can be supplied between the silicon wafer 6 and the polishing cloth 2.

  The supply nozzle 7 communicates with a tank 9 and a tank 11 via a switching valve 8. The tank 9 stores a polishing slurry 10 in which abrasive grains 10a (colloidal silica) and a processing liquid 10b (alkaline aqueous solution) are mixed. The tank 9 stores a processing liquid 10b obtained by removing the abrasive grains 10a from the polishing slurry 10.

  When the switching valve 8 is located at the switching position 8A, the polishing slurry 10 is sucked from the tank 9 and passes through the supply nozzle 7 to be between the silicon wafer 6 and the polishing cloth 2. Is supplied. On the other hand, when the switching valve 8 is located at the switching position 8B, the processing liquid 10b is sucked from the tank 11, passes through the supply nozzle 7, and between the silicon wafer 6 and the polishing cloth 2, the processing liquid 10b. Is supplied.

  When a command signal for performing a rough polishing operation is output from a controller (not shown), the upper surface plate 3 rotates while a load is applied to the upper surface plate 3 from above. Further, the rotating surface plate 1 rotates. As a result, the surface of the silicon wafer 6 travels on the polishing cloth 2 while being pressed against the surface of the polishing cloth 2, and the surface of the silicon wafer 6 is polished. Further, the switching valve 8 is positioned at the switching position 8A. As a result, the polishing slurry 10 is sucked from the tank 9, passes through the supply nozzle 7, and is supplied between the silicon wafer 6 and the polishing cloth 2.

  On the other hand, the polishing apparatus used in the finish polishing step of the embodiment has the same configuration as that shown in FIG. 1, and is prepared separately from the above-described rough polishing polishing apparatus.

  However, a polishing cloth 2 suitable for finish polishing is used. In the polishing apparatus for finish polishing, the rinsing liquid is stored in the tank 11 instead of the processing liquid 10b.

  Generally, since the rough polishing process is mainly aimed at improving the flatness of the silicon wafer 6, a hard pad is used as the polishing cloth 2 for rough polishing. On the other hand, since the final polishing process is mainly aimed at improving the surface roughness of the silicon wafer 6, a soft pad is used for the polishing cloth 2 for final polishing. In addition, the grain size and polishing time of the abrasive grains 10a may be different between the rough polishing process and the final polishing process.

  The polishing process of this embodiment includes a plurality of stages of rough polishing processes and finish polishing processes, and assumes a case where the surface of the silicon wafer 6 is polished stepwise.

  In the case of performing a multi-stage rough polishing process, a polishing apparatus having the configuration shown in FIG. 1 may be provided separately for each stage of the rough polishing process. You may implement.

  When a polishing apparatus is provided separately for each stage of rough polishing process, the processing liquid 10b is stored in the tank 11 of the polishing apparatus prepared for the final rough polishing process, and the previous stage of rough polishing is performed. A rinsing liquid is stored in the tank 11 of the polishing apparatus prepared for the process instead of the processing liquid 10b.

  The polishing block 4 to which the silicon wafer 6 is bonded via the wax 5 is common to each process and each polishing apparatus. The silicon wafer 6 is conveyed onto the rotating surface plate 1 (polishing cloth 2) of each process in a state where the silicon wafer 6 is adhered to the common polishing block 4. When the silicon wafer 6 is unloaded after the finish polishing process, the polishing block 4 is replaced with the polishing block 4 to which the unpolished silicon wafer 6 is adhered, and each polishing process is sequentially performed.

  Each example will be described below.

(First embodiment)
In this embodiment, it is assumed that a two-stage rough polishing process, that is, a first-stage rough polishing process and a second-stage rough polishing process are sequentially performed, and finally a final polishing process is performed. Then, the silicon wafer 6 is pushed toward the polishing cloth 2 while supplying the processing liquid 10b from the tank 11 between the silicon wafer 6 and the polishing cloth 2 between the rough polishing process at the second stage and the final polishing process. The chemical polishing step for polishing the surface of the silicon wafer 6 was performed.

  The processing liquid 10b used in the chemical polishing step was an alkaline aqueous solution having a pH value of 8 or more and 12 or less. The working liquid 10b used in the chemical polishing step is a pH value that can improve the surface roughness by etching the surface of the silicon wafer 6 and does not cause the surface roughness of the silicon wafer 6 to be remarkable. Good.

  As the processing liquid 10b, for example, a strongly basic alkaline aqueous solution such as KOH or NaOH can be used.

  The load applied to the upper surface plate 3 was adjusted so that the surface pressure of the wafer surface during chemical polishing was equivalent to that during rough polishing. When the surface pressure is lower than that during rough polishing, surface roughness is likely to occur on the wafer surface due to etching, and when the surface pressure is higher than during rough polishing, mechanical polishing damage received by the polishing cloth 2 on the wafer surface is increased. Because it grows.

  Further, the chemical polishing step was performed within a time range of 5 seconds to 15 minutes. The time for the chemical polishing process may be any time that can remove the silicon chips and the abrasive grains 10a remaining on the polishing cloth 2. Further, the time of the chemical polishing step is set according to the surface state of the wafer when chemical polishing is performed on the wafer surface and the surface state of the polishing cloth 2. For example, when rough polishing is performed at a low surface pressure, the mechanical polishing damage given to the surface of the silicon wafer 6 is small, so that the chemical polishing can remove the damage in a short time. The process time is set short. On the contrary, when rough polishing is performed at a high surface pressure, the mechanical polishing damage given to the surface of the silicon wafer 6 is large. Since it cannot be removed, the time for the chemical polishing step is set long.

  In this example, a polishing apparatus was provided separately for each of the first-stage rough polishing process and the second-stage rough polishing process. In the chemical polishing process, a polishing apparatus for rough polishing in the second stage was used.

  Hereinafter, the process performed in each process of a present Example is demonstrated.

(First stage rough polishing process)
While supplying the polishing slurry 10 from the tank 9 via the supply nozzle 7 between the silicon wafer 6 and the polishing cloth 2, the first-stage rough polishing of the silicon wafer 6 was performed for a predetermined time.

  Subsequently, the silicon wafer 6 was subjected to water polishing for a predetermined time while supplying the rinsing liquid from the tank 11 via the supply nozzle 7 between the silicon wafer 6 and the polishing cloth 2.

  Thereafter, the polishing block 4 to which the silicon wafer 6 was adhered was conveyed onto the rotating surface plate 1 (polishing cloth 2) of the next second stage rough polishing polishing apparatus.

(2nd rough polishing process)
While supplying the polishing slurry 10 from the tank 9 via the supply nozzle 7 between the silicon wafer 6 and the polishing cloth 2, the second stage rough polishing of the silicon wafer 6 was performed for a predetermined time.

(Chemical polishing process)
Subsequently, chemical polishing of the silicon wafer 6 was performed for a predetermined time while supplying the processing liquid 10b from the tank 11 through the supply nozzle 7 between the silicon wafer 6 and the polishing cloth 2.

  Thereafter, the polishing block 4 to which the silicon wafer 6 was adhered was conveyed onto the rotating surface plate 1 (polishing cloth 2) of the next polishing apparatus for final polishing.

(Finishing polishing process)
While the polishing slurry 10 was supplied from the tank 9 through the supply nozzle 7 between the silicon wafer 6 and the polishing cloth 2, the silicon wafer 6 was subjected to final polishing for a predetermined time.

  Subsequently, the silicon wafer 6 was subjected to water polishing for a predetermined time while supplying the rinsing liquid from the tank 11 via the supply nozzle 7 between the silicon wafer 6 and the polishing cloth 2.

(Second embodiment)
In this example, a polishing apparatus was prepared for each of the first-stage rough polishing process, the second-stage rough polishing process, and the chemical polishing process.

  The polishing apparatus for chemical polishing is the same as that shown in FIG. However, a switching configuration for switching and supplying the polishing slurry 10 and the machining liquid 10b is not necessary, and it is sufficient that the machining liquid 10b can be supplied.

  Hereinafter, the process performed in each process of a present Example is demonstrated.

(First stage rough polishing process)
While supplying the polishing slurry 10 from the tank 9 via the supply nozzle 7 between the silicon wafer 6 and the polishing cloth 2, the first-stage rough polishing of the silicon wafer 6 was performed for a predetermined time.

  Subsequently, the silicon wafer 6 was subjected to water polishing for a predetermined time while supplying the rinsing liquid from the tank 11 via the supply nozzle 7 between the silicon wafer 6 and the polishing cloth 2.

  Thereafter, the polishing block 4 to which the silicon wafer 6 was adhered was conveyed onto the rotating surface plate 1 (polishing cloth 2) of the next second stage rough polishing polishing apparatus.

(2nd rough polishing process)
While supplying the polishing slurry 10 from the tank 9 via the supply nozzle 7 between the silicon wafer 6 and the polishing cloth 2, the second stage rough polishing of the silicon wafer 6 was performed for a predetermined time.

  Subsequently, the silicon wafer 6 was subjected to water polishing for a predetermined time while supplying the rinsing liquid from the tank 11 via the supply nozzle 7 between the silicon wafer 6 and the polishing cloth 2.

  Thereafter, the polishing block 4 to which the silicon wafer 6 was adhered was conveyed onto the rotating surface plate 1 (polishing cloth 2) of the next chemical polishing polishing apparatus.

(Chemical polishing process)
The chemical polishing of the silicon wafer 6 was performed for a predetermined time while supplying the processing liquid 10b from the tank 11 via the supply nozzle 7 between the silicon wafer 6 and the polishing cloth 2.

  Thereafter, the polishing block 4 to which the silicon wafer 6 was adhered was conveyed onto the rotating surface plate 1 (polishing cloth 2) of the next polishing apparatus for final polishing.

(Finishing polishing process)
While the polishing slurry 10 was supplied from the tank 9 through the supply nozzle 7 between the silicon wafer 6 and the polishing cloth 2, the silicon wafer 6 was subjected to final polishing for a predetermined time.

  Subsequently, the silicon wafer 6 was subjected to water polishing for a predetermined time while supplying the rinsing liquid from the tank 11 via the supply nozzle 7 between the silicon wafer 6 and the polishing cloth 2.

(Third embodiment)
A common polishing apparatus may be used in the first-stage rough polishing process, the second-stage rough polishing process, and the chemical polishing process.

  In this case, the polishing apparatus requires a configuration in which the rinse liquid is switched and supplied in addition to the polishing slurry 10 and the processing liquid 10b, or the rinse liquid is supplied by a nozzle provided separately.

  Hereinafter, the process performed in each process of a present Example is demonstrated.

(First stage rough polishing process)
While supplying the polishing slurry 10 from the tank 9 via the supply nozzle 7 between the silicon wafer 6 and the polishing cloth 2, the first-stage rough polishing of the silicon wafer 6 was performed for a predetermined time.

  Subsequently, the silicon wafer 6 was subjected to water polishing for a predetermined time while supplying a rinsing liquid from another tank via the supply nozzle 7 between the silicon wafer 6 and the polishing cloth 2.

(2nd rough polishing process)
While supplying the polishing slurry 10 from the tank 9 via the supply nozzle 7 between the silicon wafer 6 and the polishing cloth 2, the second stage rough polishing of the silicon wafer 6 was performed for a predetermined time.

(Chemical polishing process)
Subsequently, chemical polishing of the silicon wafer 6 was performed for a predetermined time while supplying the processing liquid 10b from the tank 11 through the supply nozzle 7 between the silicon wafer 6 and the polishing cloth 2.

  Thereafter, the polishing block 4 to which the silicon wafer 6 was adhered was conveyed onto the rotating surface plate 1 (polishing cloth 2) of the next polishing apparatus for final polishing.

(Finishing polishing process)
While the polishing slurry 10 was supplied from the tank 9 through the supply nozzle 7 between the silicon wafer 6 and the polishing cloth 2, the silicon wafer 6 was subjected to final polishing for a predetermined time.

  Subsequently, the silicon wafer 6 was subjected to water polishing for a predetermined time while supplying the rinsing liquid from the tank 11 via the supply nozzle 7 between the silicon wafer 6 and the polishing cloth 2.

  As described above, according to this embodiment, the processing liquid 10b is supplied from the tank 11 between the silicon wafer 6 and the polishing cloth 2 between the second rough polishing process and the final polishing process. Since the chemical polishing process of polishing the surface of the silicon wafer 6 by pressing the silicon wafer 6 against the polishing cloth 2 side, the following effects can be obtained.

1) During the chemical polishing step, the silicon wafer 6 is polished without using the abrasive grains 10a, and silicon scraps that cause clogging of the polishing cloth 2 can be dissolved by the etching action of the processing liquid 10b. Therefore, the abrasive cloth 10 is not left with any abrasive grains 10a or silicon scraps, and is polished by the polishing cloth 2 without clogging, so that no new scratches are formed on the silicon wafer 6. The surface polishing scratches given to the silicon wafer 6 by the rough polishing in the previous process can be effectively removed, and the surface roughness can be improved. In this way, the finish polishing of the next process is performed in a state where the surface roughness of the silicon wafer 6 is improved, so that the surface roughness is further improved, and in particular, haze deterioration can be suppressed.

2) The surface of the silicon wafer 6 can be chemically polished while dissolving silicon scraps that cause clogging of the polishing cloth 2 by the etching action of the processing liquid 10b. For this reason, it is not necessary to interrupt the polishing operation and perform brushing, thereby improving the wafer production efficiency.

3) Especially when rough polishing using the abrasive grains 10a and chemical polishing without using the abrasive grains 10a are performed by the same polishing apparatus as in the first and third embodiments, the processing liquid By the etching action of 10b, the abrasive grains 10a used at the time of rough polishing, that is, the abrasive grains 10a causing clogging of the polishing cloth 2 can be dissolved. Further, the agglomeration of the abrasive grains 10a can be prevented by the hydroxyl ions in the working liquid 10b (alkaline aqueous solution). Further, even the abrasive grains 10a once aggregated can be redispersed. For this reason, as in the above 1), since the wafer is polished by the polishing cloth 2 without clogging, it is possible to shift to the final polishing of the next process while the wafer surface is improved, and the surface roughness is further increased by the final polishing. By improving, haze deterioration can be suppressed. Similarly to the above 2), since the surface of the silicon wafer 6 can be chemically polished while dissolving silicon scraps and abrasive grains 10a that cause clogging of the polishing cloth 2, the polishing operation is temporarily interrupted. This eliminates the need for brushing and improves wafer production efficiency.

  Further, in the polishing apparatus for the second-stage rough polishing of the first embodiment, instead of supplying the rinse liquid in the water polishing step, the processing liquid 10b from which the abrasive grains 10a are removed from the polishing slurry 10 is supplied, A chemical polishing process is performed. For this reason, the apparatus which can implement this invention can be constructed | assembled only by storing the processing liquid 10b instead of storing the rinse liquid in the tank 11 of the existing grinding | polishing apparatus, and apparatus cost falls significantly.

  In the first embodiment, the machining liquid 10b is supplied instead of the rinsing liquid, but the rinsing liquid and the machining liquid 10b may be supplied in parallel. However, if the rinsing liquid and the machining liquid 10b are supplied in parallel, the rinsing liquid and the machining liquid 10b may be mixed and the pH value may be lowered. Therefore, the pH value of the machining liquid 10b does not fall below 8 in advance. It is desirable to adjust.

  Further, in each of the above-described examples, it is assumed that a two-stage rough polishing process is performed, then a chemical polishing process is performed, and finally a final polishing process is performed. Next, a chemical polishing process may be performed, and a final polishing process may be performed at the end, or a rough polishing process of three or more stages may be performed, then a chemical polishing process may be performed, and a final polishing process may be performed last. May be.

  Next, the effects of this embodiment will be described with specific numerical values.

  The experiment was conducted under the following conditions in the second embodiment.

・ Silicon wafer 6 to be polished
Six 20 silicon wafers having a P-type crystal orientation <100> and a diameter of 200 mm manufactured by the CZ method were prepared as wafers to be polished.

・ Polishing cloth 2
As the polishing cloth 2 used in the chemical polishing process, a polishing cloth having a usage time of about 6000 minutes was used.

・ Working fluid 10b
A processing liquid 10b diluted with a high-concentration alkaline aqueous solution and adjusted to a pH value similar to that of the polishing slurry 10 used during rough polishing was used in the chemical polishing step.

・ Abrasive grain 10a
At the time of rough polishing and finish polishing, a polishing slurry 10 mixed with colloidal silica was used as the abrasive grains 10a.

  In the examples, a first rough polishing process, a second rough polishing process, a chemical polishing process, and a final polishing process were sequentially performed through a slicing process, a chamfering process, a lapping process, and an etching process. After the finish polishing process, the silicon wafer 6 was washed and dried. Chemical polishing was performed for 7 minutes. In contrast to this example, the above-described steps, in which only the chemical polishing step was not performed, were used as comparative examples. Similarly, after the finish polishing step, the silicon wafer 6 was washed and dried.

  For the silicon wafer 6 after drying, the number of particles (LPD number) on the wafer surface, the surface roughness of the long wavelength, and the surface roughness of the short wavelength were measured.

-Measurement of the number of particles The number of particles (LPD) on the surface of the silicon wafer 6 was measured using Surfscan SP1 manufactured by Tencor. Particles having a diameter of 0.085 nm or more were measured.

-Surface roughness measurement of long wavelength Using "New View200" made by ZYGO, the roughness of the long wavelength (several tens to several hundreds μm) of the surface of the silicon wafer 6 was measured. Measurements were taken with mean square surface roughness (RMS).

・ Surface Roughness Measurement of Short Wavelength Using a “TMS-3000W” manufactured by “Schnitt Measurement System, Inc”, the roughness of the short wavelength (several to several tens of nm) of the surface of the silicon wafer 6 was measured. Measurements were taken with mean square surface roughness (RMS).

  FIG. 2 shows the particle count measurement results, FIG. 3 shows the long-wavelength surface roughness measurement results, and FIG. 4 shows the short-wavelength surface roughness measurement results. 2, FIG. 3, and FIG. 4 show examples and comparative examples in comparison.

  As shown in FIG. 2, the number of particles on the surface of the silicon wafer 6 of the example is smaller than the number of particles on the surface of the silicon wafer 6 of the comparative example. It was confirmed that scratches and defects were reduced.

  As shown in FIGS. 3 and 4, the surface roughness of the silicon wafer 6 of the example is smaller than the surface roughness of the silicon wafer 6 of the comparative example for both the long wavelength and the short wavelength, According to the present invention, it was confirmed that the surface roughness of the silicon wafer 6 was improved and the haze level was lowered.

  In the above-described embodiment, the description has been made assuming a batch type polishing apparatus. However, a single wafer type in which one silicon wafer 6 is bonded to the polishing block 4 to polish the silicon wafer 6 one by one. The present invention may be applied to a polishing apparatus. Moreover, although the description has been made assuming a single-side polishing apparatus that polishes one side (front surface) of the silicon wafer 6, the present invention may be applied to a double-side polishing apparatus that simultaneously polishes both sides of the silicon wafer 6. The present invention can also be applied to polishing various semiconductor wafers such as gallium arsenide other than silicon.

FIG. 1 is a diagram illustrating a configuration of a polishing apparatus according to an embodiment. FIG. 2 is a diagram showing the particle number measurement results in comparison with Examples and Comparative Examples. FIG. 3 is a diagram showing the results of measuring the long-wavelength surface roughness in comparison with Examples and Comparative Examples. FIG. 4 is a diagram showing the results of long-wavelength surface roughness measurement in comparison with Examples and Comparative Examples.

Explanation of symbols

  2 Polishing cloth 6 Silicon wafer 10 Polishing slurry 10a Abrasive grains 10b Processing fluid

Claims (5)

The process of polishing the surface of the semiconductor wafer by pressing the semiconductor wafer against the polishing cloth while supplying the polishing slurry mixed with the abrasive grains and the processing liquid between the semiconductor wafer and the polishing cloth. A method for polishing a semiconductor wafer, which is performed in a process and a finish polishing process,
Chemical polishing that polishes the surface of the semiconductor wafer by pressing the semiconductor wafer against the polishing cloth while supplying the processing liquid between the semiconductor wafer and the polishing cloth between the rough polishing process and the final polishing process. A method for polishing a semiconductor wafer, comprising performing a step. A polishing method in which, following the rough polishing process, a water polishing process is performed in which the surface of the semiconductor wafer is polished by pressing the semiconductor wafer against the polishing cloth while supplying a rinsing liquid between the semiconductor wafer and the polishing cloth. There,
2. The semiconductor wafer according to claim 1, wherein the chemical polishing step is performed by supplying a processing liquid in parallel with the water polishing step or instead of supplying the rinse liquid in the water polishing step. Polishing method. 2. The semiconductor wafer according to claim 1, wherein the liquid supplied between the semiconductor wafer and the polishing cloth is shifted from the polishing slurry to the processing liquid to shift from the rough polishing process to the chemical polishing process. 3. Polishing method. The method of polishing a semiconductor wafer according to claim 1, wherein the processing liquid is an alkaline aqueous solution having a pH of 8 or more and 12 or less. The method for polishing a semiconductor wafer according to claim 1, wherein the chemical polishing step is performed within a time range of 5 seconds to 15 minutes.

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