JP2005135936A - Wafer-chamfering method and wafer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wafer-chamfering method which is capable of chamfering the wafer stably, without causing stains or clouding to the wafer, when the wafer is subjected to a chamfering process, obtaining the wafers of high quality with a high yield, and obtaining the wafers where no chamfer stains or no mark is found when the chamfered parts of the wafer are checked. <P>SOLUTION: The wafer-chamfering method comprises processes of bringing the peripheral part of the wafer 4 into contact with a polishing cloth 3 making it slide on the cloth 3, and separating the wafer 4 from the polishing cloth 3 while both the wafer 4 and the polishing cloth are kept rotating, after the chamfering operation of the wafer 4 is finished. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a wafer chamfering method for chamfering a wafer in the manufacture of a wafer such as a silicon wafer.

  Conventionally, a semiconductor wafer manufacturing method generally includes a slicing step of cutting a wafer from a single crystal rod grown by the Czochralski method, a rough chamfering step of chamfering the outer peripheral portion of the obtained wafer, and flattening the wafer. Lapping process to eliminate thickness variation, etching process to remove processing distortion and contaminants, mirror chamfering process to polish the outer periphery of the etched wafer to be mirrored, and finish the main surface of the wafer to a mirror surface It consists of a mirror polishing process, a cleaning process for removing abrasives and foreign substances adhering to the wafer, and the like.

  Usually, in a wafer manufacturing process, a chamfering process with different surface finishes such as a rough chamfering process and a mirror chamfering process is performed according to the purpose. In these chamfering steps, for example, as shown in FIG. 1, the outer peripheral portion of the wafer 4 rotatably held by the lower chuck 5 is pressed against the cylindrical drum 2 to which the polishing cloth 3 for processing is stuck, and the nozzle 6 While supplying the abrasive 7, the polishing cloth 3 is rotated, the wafer 4 is rotated 360 ° to perform mechanochemical polishing on the outer periphery of the wafer, and then the rotation of the wafer 4 and the polishing cloth 3 is stopped. The wafer is chamfered by pulling the wafer 4 away from the processing polishing cloth 3.

  In this case, for example, in the above rough chamfering step, the outer peripheral portion of the wafer can be processed into a predetermined shape and size by using a tape-type polishing cloth with abrasive grains carried on the surface as the processing polishing cloth. Thereby, cracking and chipping of the wafer can be prevented in the subsequent wafer manufacturing process. In addition, the mirror chamfering process can smooth the outer peripheral part of the roughly chamfered wafer into a mirror surface, so that dust generation from the wafer chamfering part can be prevented in subsequent processes such as the device manufacturing process, and the wafer polishing scratches can be prevented. Effects such as prevention and reduction in the amount of particles generated can be obtained.

  Such a chamfering process of a wafer has become an indispensable process for increasing the cleanliness of the wafer surface and preventing fine scratches on the wafer surface in accordance with the recent miniaturization and high integration of semiconductor devices. . Therefore, recently, the processing state of the wafer chamfered part has become an important item as one of the wafer qualities, and it is required to inspect the chamfered part with high accuracy.

  In general, the chamfered portion of a wafer is inspected, for example, by directly observing a chamfered portion formed by chamfering with an optical microscope or by performing alkali etching on a chamfered wafer as described in Patent Document 1. A method of observing the chamfered portion with a microscope is used.

  However, when the chamfered portion of the wafer is actually observed with a microscope and the processing state is inspected as described above, dirt 8 or spiders are generated on the outer peripheral portion of the wafer W as shown in FIG. There were many. Dirt and spiders occurring in such a chamfered part were not a major problem until the chamfered part was inspected, but the processing state of the chamfered part was also emphasized as described above. When chamfered parts are inspected with high accuracy, a wafer with dirt or spiders on the chamfered part is judged as a defective wafer with chamfered dirt or scratches when a pass / fail judgment is made during the inspection. Therefore, it has become one of the factors that cause a decrease in yield in the chamfering process.

JP-A-11-330042

  Therefore, the present invention has been made in view of the above problems, and the object of the present invention is to stably form a chamfered portion without generating dirt or spiders when chamfering a wafer. It is an object of the present invention to provide a chamfering method for a wafer which can be performed and can obtain a high quality wafer with a high yield, in which chamfering dirt and scratches are not detected in a chamfered portion inspection.

  In order to achieve the above object, according to the present invention, in a method for chamfering a wafer by sliding the outer peripheral portion of the wafer on a polishing cloth for processing, the wafer and the processing material are processed at the end of the chamfering of the wafer. A method for chamfering a wafer is provided, wherein the wafer is pulled away from the processing polishing cloth while rotating the polishing cloth.

  In this way, in the chamfering process of the wafer, when the wafer and the polishing cloth are rotated while the chamfering process is finished, the wafer is pulled away from the processing polishing cloth, thereby causing excessive etching or overpolishing that causes dirt or spiders. Since the chamfered portion of the wafer can be stably formed by preventing the wafer from occurring on the outer peripheral portion of the wafer, it is possible to obtain a high-quality wafer with high yield that does not detect chamfered dirt or scratches during inspection. .

At this time, at the end of the chamfering process of the wafer, it is preferable that the wafer is pulled away from the processing polishing cloth while the wafer is rotating within a range of 1 to 20 ° after chamfering around the outer periphery of the wafer. 2).
Thus, at the end of chamfering of the wafer, while the wafer is rotating in the range of 1 to 20 ° after chamfering around the outer periphery of the wafer, the wafer is being rotated, particularly when the wafer is rotated about 10 °. By pulling away from the polishing cloth for processing, the wafer can be efficiently chamfered without causing unshaving at the outer periphery of the wafer.

Further, as the chamfering process, it is preferable to perform a mirror chamfering process.
The wafer chamfering method of the present invention is very effective when mirror chamfering is performed on the wafer. Thus, by performing the mirror chamfering processing on the wafer by the chamfering processing method of the present invention, the chamfered portion of the wafer is formed. It can be processed into an extremely high quality wafer that is mirror-finished and does not detect dirt or scratches.

In the present invention, when the chamfering is performed, the wafer can be chamfered while supplying an abrasive.
In the present invention, when chamfering is performed, the wafer can be chamfered while supplying an abrasive, whereby the outer peripheral portion of the wafer can be chamfered uniformly and very stably.

In this case, the wafer to be chamfered can be a silicon wafer.
The wafer chamfering method of the present invention can be suitably used when chamfering a silicon wafer. By processing the silicon wafer by the chamfering method of the present invention, dirt or spiders are generated in the chamfered portion. Unprecedented quality silicon wafers can be stably obtained with high yield.

And according to this invention, the wafer processed by the wafer chamfering method of the said invention can be provided (Claim 6).
If the wafer is processed by the chamfering method according to the present invention, the chamfered portion is free from dirt, spiders, etc., and the chamfering inspection does not detect chamfered dirt, scratches, etc. It can be a quality wafer.

  As described above, according to the chamfering method for a wafer of the present invention, the wafer is generated on the outer periphery of the wafer by pulling the wafer away from the processing polishing cloth while rotating the wafer and the processing polishing cloth at the end of the chamfering process of the wafer. It is possible to stably form a chamfered portion by preventing partial over-etching and over-polishing, so that it is possible to obtain a high-quality wafer with high yield that does not detect chamfering dirt or scratches during inspection. it can.

Hereinafter, although an embodiment is described about the present invention, the present invention is not limited to these.
The present inventors investigated the cause of the occurrence of dirt, spiders, etc. in the chamfered portion of the chamfered wafer. In conventional chamfering, the chamfering of the wafer is performed when the chamfering of the wafer is completed or the wafer is processed. Since both rotations of the polishing cloth are stopped, the portion of the wafer that is pressed against the polishing cloth is excessively etched with an alkaline abrasive, and further, the rotation stops and polishing is performed during chamfering. It has been clarified that the processing heat accumulated in the cloth concentrates on the portion of the wafer that is in contact with the polishing cloth, so that overetching is promoted and overpolishing occurs at the chamfered portion of the wafer. Therefore, in the conventional chamfering process, such overetching and overpolishing occur in the chamfered part, so that the wafer after processing is contaminated and spoiled in the chamfered part, resulting in a decrease in yield. I understood.

  Accordingly, the present inventors have intensively studied and studied a method for preventing excessive etching and overpolishing that cause dirt and spiders generated in the chamfered portion in such chamfering. As a result, in chamfering of the wafer, when the wafer is chamfered, the wafer is pulled away from the processing polishing cloth while rotating the wafer and the processing polishing cloth, so that the wafer is not chamfered without excessive etching or overpolishing. Has been found to be stably formed, and the present invention has been completed.

Hereinafter, the method for chamfering a wafer according to the present invention will be described in detail, but the present invention is not limited thereto.
The chamfering apparatus used in the chamfering method of the present invention is not particularly limited, and a conventionally used processing apparatus can be used. In the following description, a case where mirror chamfering is performed on a silicon wafer using a processing apparatus having the configuration shown in FIG. 1 will be described as an example.

  A chamfering apparatus 1 shown in FIG. 1 includes at least a cylindrical drum 2 to which a polishing cloth 3 for processing is attached, a lower chuck 5 that holds a silicon wafer 4, and a nozzle 6 that supplies an abrasive 7. After the silicon wafer 4 to be chamfered is held by the lower chuck 5, the drum 2 is rotated and the wafer 4 is brought into sliding contact with the polishing cloth 3, so that, for example, an alkaline abrasive 7 is supplied from the nozzle 6. By rotating the wafer 4 360 ° or more from the chamfering start position while supplying, the wafer outer peripheral portion can be mechanochemically polished to mirror chamfer the edge portion of the wafer. At this time, the wafer 4 may be slidably contacted with the processing polishing cloth 3 and rotated 360 ° a plurality of times, and by performing chamfering in this way, a uniform chamfered portion is formed on the outer peripheral portion of the wafer. Can be formed.

  When the silicon wafer is rotated 360 ° and mirror chamfering is performed on the outer periphery of the wafer, the wafer 4 is rotated while the silicon wafer 4 and the polishing pad 3 are rotated without stopping at the end of the wafer chamfering. Pull away from the polishing cloth 3 for processing.

  At this time, while the silicon wafer is rotating in the range of 1 to 20 ° after chamfering around the outer periphery of the wafer, especially when the wafer is rotated approximately 10 ° after chamfering, the silicon wafer is rotated while being processed. It is preferable to pull it away from the polishing cloth. For example, if the wafer is pulled away when the silicon wafer is rotated at less than 1 ° after chamfering, chamfering may result in unsharpening due to the difference in polishing rate that varies depending on the polishing cloth life. On the other hand, when the wafer is pulled apart, if the wafer is chamfered and rotated by more than 20 °, the wafer is chamfered more than necessary, which may affect the productivity.

  Therefore, as described above, while the silicon wafer is rotated in the range of 1 to 20 ° after the chamfered circumference of the outer periphery of the wafer, particularly when the wafer is rotated by 10 ° after the chamfered circumference, the wafer is rotated and processed. By separating from the polishing cloth, it is possible to efficiently chamfer the wafer without causing unshaving at the outer periphery of the wafer and without affecting the productivity.

  In this way, in chamfering of the wafer, when the wafer and the polishing cloth are rotated at the end of the chamfering process, the wafer is separated from the processing polishing cloth, thereby preventing the wafer outer peripheral portion from being partially etched excessively. In addition, since the processing heat generated in the polishing cloth can be prevented from concentrating on a part of the wafer, the chamfered portion can be stably mirror-finished without causing excessive polishing on the outer peripheral portion of the wafer. Therefore, the wafer processed by the chamfering method of the present invention can be a high-quality wafer in which chamfered portions are free from dirt and spiders and chamfered dirt and scratches are not detected in the chamfer inspection. An improvement in yield in the process can be achieved.

  At the end of the chamfering process, if the wafer is removed from the polishing cloth after stopping the rotation of the wafer, excessive etching or overpolishing occurs because of the surface finish such as rough chamfering process or mirror chamfering process. It is common to any different chamfering steps, and the chamfering method of the present invention can be applied to any of such chamfering steps. As a result, it is possible to suppress the yield reduction in the chamfering process, which has been regarded as a problem in the past, and to perform chamfering of the wafer stably at a high yield.

EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated more concretely, this invention is not limited to these.
(Example)
Two hundred 200 mm diameter silicon wafers having a mirror polished surface were prepared on the wafer main surface, and a mirror chamfering process was performed using an EP-IV type processing apparatus manufactured by Speedfam as a chamfering processing apparatus. At this time, a buff whose lifetime was shortened by use was used as a processing polishing cloth to be affixed to the drum, and an alkaline aqueous solution of SiO ₂ was used as an abrasive.

  First, 100 of the prepared silicon wafers are sequentially held by the lower chuck, and the wafer is rotated 360 ° while supplying the alkaline abrasive from the nozzle by sliding the outer periphery of the silicon wafer into contact with the polishing cloth for processing. As a result, mechanochemical polishing was performed on the outer periphery of the wafer. Then, after the wafer was rotated 360 °, the silicon wafer and the processing polishing cloth were rotated without being stopped, and after the wafer was chamfered, the wafer was pulled away from the processing polishing cloth when the wafer was further rotated 10 °.

  Next, the chamfered portion of the obtained silicon wafer was observed with an optical microscope, and the chamfered portion was inspected. As a result, as shown in FIG. 2, no chamfering dirt or scratches were observed on the chamfered portion of the wafer W in any silicon wafer that had been chamfered, and it was confirmed that the wafer was a high-quality wafer.

(Comparative example)
As a comparative example, the remaining 100 of the silicon wafers prepared above are sequentially held by the lower chuck as in the above embodiment, and the outer peripheral portion of the silicon wafer is slidably contacted with the polishing cloth for the nozzle. Then, mechanochemical polishing was performed on the outer periphery of the wafer by rotating the wafer 360 ° while supplying an alkaline abrasive. Thereafter, when the wafer was rotated 360 °, the rotation of the silicon wafer and the polishing cloth for processing were stopped, and then the wafer was separated from the polishing cloth for processing.

  Next, the chamfered portion of the obtained silicon wafer was observed with an optical microscope, and the chamfered portion was inspected. As a result, chamfering dirt 8 was observed on the outer peripheral portion (chamfered portion) of the wafer W as shown in FIG. 3 in about half of the silicon wafers, and was judged to be defective. In addition, chamfering contamination may or may not occur on the outer peripheral portion of the chamfered wafer as described above due to variations in the processing conditions such as the life of the polishing cloth and the pH value, temperature, and flow rate of the polishing agent. it is conceivable that.

  The present invention is not limited to the above embodiment. The above embodiment is merely an example, and the present invention has the same configuration as that of the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.

  For example, in the above description, the case where chamfering is performed on a silicon wafer has been described as an example. However, the present invention is not limited to this, and the present invention is not limited to this. The same applies to chamfering. Also, the diameter of the wafer to be processed is not particularly limited. In addition to the wafer having a diameter of 200 mm shown in the above embodiment, the wafer having a large diameter of 300 mm or more, or conversely, a wafer having a diameter of 150 mm or less. The same effect can be obtained for this. Furthermore, in the present invention, as a wafer to be chamfered, it is possible to use a prime wafer produced from a single crystal rod or the like, for example, a recycled wafer that has been recycled after being used in a device manufacturing process or the like. The same can be applied to chamfering.

It is a schematic block diagram which shows roughly an example of the chamfering processing apparatus used by the chamfering process of a wafer. It is a schematic diagram showing roughly the wafer processed by the chamfering processing method of the present invention. It is a schematic diagram which shows schematically the wafer processed with the conventional chamfering processing method.

Explanation of symbols

1 ... chamfering device, 2 ... drum,
3 ... polishing cloth for processing, 4 ... wafer (silicon wafer),
5 ... Lower chuck, 6 ... Nozzle, 7 ... Abrasive,
8 ... dirt, W ... wafer.

Claims (6)

  In the method of chamfering a wafer by sliding the outer peripheral portion of the wafer on the processing polishing cloth, the wafer is removed from the processing polishing cloth while rotating the wafer and the processing polishing cloth at the end of the chamfering of the wafer. A method for chamfering a wafer, characterized by separating the wafers.   2. The wafer according to claim 1, wherein at the end of the chamfering process of the wafer, the wafer is pulled away from the polishing cloth while the wafer is rotating within a range of 1 to 20 ° after chamfering the outer periphery of the wafer. The wafer chamfering method described.   3. The wafer chamfering method according to claim 1, wherein a mirror chamfering process is performed as the chamfering process.   The wafer chamfering method according to any one of claims 1 to 3, wherein the wafer is chamfered while supplying an abrasive when the chamfering is performed.   The wafer chamfering method according to claim 1, wherein the wafer to be chamfered is a silicon wafer.   A wafer processed by the wafer chamfering method according to any one of claims 1 to 5.

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