(19) Japanese Patent Office (JP)			(12) Publication of Unexamined Patent Application (A)				(11) Disclosure Number: Hei 05-58800
(51) Int. Cl.5   C30B 33/02 C30B 15/00 H01L 21/02 H01L 21/208 H01L 21/304         10/00         10/00		Identification Code         311			Internal Agency Classification No. 7821-4G Z 9151-4G Z 8518-4M P 7353-4M B 8831-4M	(43) Date of Disclosure: 1993.03.09
	Examination Request Status: Not yet requested. No. of Claims: 5 (5 pages total)
				(21)   Filing Number: Hei 03-246938 (22)   Date of Application: 1991.08.30
(71)  Assignee:          000190149                                     Shin Etsu Handohtai Co., Ltd.                                     4-2 Marunouchi 1-chome                                     Chiyoda-ku, Tokyo-to (72)  Inventor:             Shuji YOKOTA                                     c/o Semiconductor Research Center                                     Shin Etsu Handohtai Co., Ltd.                                     2-13-1 Isobe                                     Annaka-shi, Gunma-ken (72)  Inventor:             Hirotoshi YAMAGISHI                                     c/o Semiconductor Research Center                                     Shin Etsu Handohtai Co., Ltd.                                     2-13-1 Isobe                                     Annaka-shi, Gunma-ken  (74)  Agent:               Shoji Ishihara, Attorney

 

Summary

 

[Title of the Invention]   Silicon Crystal Processing Method

 

[Goal]  Crystal is pulled from a silicon melt within a quartz crucible by the Czochralski method. Per the technique used for silicon crystal ingot processing, the occurrence of  OSFs in the main wafer surface is effectively controlled so as to be substantially zero.

 

[Content of the Invention]  An ingot is grown by the Czochralski method from a silicon melt contained within a quartz crucible. By storage of the crystal silicon ingot itself (or the trimmed ingot) at a low temperature, the occurrence of OSFs is effectively controlled or substantially eliminated in the front surface of the wafers manufactured from such an ingot.

 

[Scope of the Patent Claims]

[Claim 1]  A method for effectively controlling (or substantially eliminating) OSFs in the front surface of the wafers manufactured from an ingot, characterized in that the crystal silicon ingot, or the trimmed ingot thereof, is grown by the Czochralski method from a silicon melt within a quartz crucible and is stored at low temperature.

 

[Claim 2]  A silicon crystal treatment method as in Claim 1, characterized in that said low storage temperature is less than -10ºC.

 

[Claim 3]  A silicon crystal treatment method as in Claim 1, characterized in that said low storage temperature is less than -30ºC.

 

[Claim 4]  A silicon crystal treatment method for the treatment of wafers sliced from an ingot that has been produced by use of the Czochralski method to pull the ingot from a silicon melt contained within a quartz crucible, said method being characterized in that OSFs in the front surface of the wafers manufactured from said ingot are effectively controlled by slicing of said ingot into wafers of less than 2 mm in thickness within a certain number of days.

 

[Claim 5]  A silicon crystal treatment method as in Claim 4, characterized in that said ingot is sliced thinly within 10 days of ingot manufacture.

 

[Detailed Description of the Invention]

[0001]

[Industrial Field of Application]  This invention relates to a treatment method for silicon crystal ingot which effectively suppresses the occurrence of OSFs in the main surface of a polished silicon wafer (below simply referred to as a "wafer") manufactured in the normal process from such ingot, this crystal silicon ingot (below referred to simply as "crystal ingot") having been manufactured by the Czochralski method by pulling from a silicon melt contained within a quartz crucible.

 

[0002]

[Conventional Technology] Thermal oxidation processing is used to manufacture integrated circuit elements upon wafers, particularly for MOS-type integrated circuit elements. OSFs (Oxidation-induced Stacking Faults) arise during thermal oxidation processing, harming the electrical properties of these circuit elements. The occurrence of such OSFs has become an important problem.

 

[0003]  Specifically, stacking faults occur near the wafer surface when thermal oxidation is performed by treatment of the wafer at elevated temperature under an oxidizing atmosphere. These stacking faults may form leaks at pn junctions or may result in noise. Such stacking faults result in image defects within a CCD element.  Therefore it is extremely important to raise the manufacturing yield of integrated circuit elements made from wafers by the manufacture of such wafers without the formation of such OSFs.

 

[0004]  In general OSFs grow under an oxidizing atmosphere and shrink under a non-oxidizing atmosphere. The origins of OSFs have been studied extensively, and various mechanisms have been proposed: (a) mechanical damage during wafer processing, (b) metallic impurity contamination, (c) aggregation of point defects that arise during thermal processing, (d) ion implantation damage, (e) swirl or oxygen precipitation bulk defects.

 

[0005]  Among the above mechanisms (e), swirl or oxygen precipitation bulk defects, may be effectively prevented so as to be essentially absent within the wafer front active layer per various intrinsic gettering treatments at the start of integrated circuit manufacturing processing of the wafer.

 

[0006]  Furthermore, per modification of the crystal pulling process, technology such as that revealed in Unexamined Patent Application Sho 55-56098 suppresses oxygen-caused bulk defects during the Czochralski method so that the effects of thermal history during pulling are suppressed.  The major feature of this well-known technology is silicon crystal ingot growth in the temperature range of 900ºC to 500ºC for less than 4 hours, followed by cooling at a rate greater than 100ºC/hr.

 

[0007]  However until now there was no procedure to effectively, and almost completely, eliminate OSF generation. For example in the <100> orientation wafer surface it is not easy to reduce the front surface OSF density below 100 cm^-2 .

 

[0008]

[Problems Solved by the Invention]  This invention has the goal of providing a method for effective elimination and control of the occurrence of OSFs in the front surface of a wafer manufactured by processing crystal ingot.

 

[0009]

[Means of Solving the Problems] In order to solve the above mentioned problem the inventors investigated the occurrence of numerous OSFs in wafers manufactured from crystal ingots which, after pulling, had been immediately cut into various forms and that had been inspected for OSFs.

 

[0010]  It was previously thought that the occurrence of such OSFs could be prevented by avoiding OSF generation during the polished wafer manufacturing processes after the crystal ingot was grown.

 

[0011]  Various tests and observations were made to provide background for this problem.  A very interesting tendency was for wafer OSF occurrence to increase the longer such pulled ingot was stored as a crystal ingot or as a trimmed ingot. Moreover, there was an intimate relationship between the degree of OSF generation and the storage temperature. Particularly interesting was the trend for OSF formation to be suppressed when the ingot was processed into wafers by slicing / polishing immediately after crystal ingot pulling or after a relatively short period after crystal pulling. These observations form the basis of this invention.

 

[0012]  In other words per this invention, by storage at a low temperature of the crystal silicon ingot itself (or the trimmed ingot) previously grown by the Czochralski method from a silicon melt within a quartz crucible, the occurrence of OSFs is effectively controlled or substantially eliminated in the front surface of the wafers manufactured from the ingot.

 

[0013]  Polished wafers are manufactured from the crystal ingot by various processes, including cutting into thin sections perpendicularly to the growth axis (called slicing), lapping, etching, polishing, and cleaning.  These processes may require a total of one month or several months.

 

[0014]  However per this invention by storage at -30ºC, even as crystal ingot, OSF occurrence may be entirely prevented over several months, whether the crystal is n-type or p-type. It becomes possible to realize the goal of OSF prevention in p-type ingot, which does not readily generate OSFs, by storage at -10ºC.

 

[0015]  Also it is possible to effectively prevent such OSF occurrence in wafers, even when the pulled crystal ingot is stored at normal temperatures, by reducing the storage time, and then slicing the ingot into wafers as soon as possible. In this case it is desirable that the thickness of such slices be less than 2 mm.  It is desirable that the pulled crystal be sliced within 10 days.

 

[0016]  This may be done by further integration of manufacturing processes so as to reduce the crystal ingot storage period prior to wafer processing to less than 10 days. If the slices are less than 2 mm thick, it is possible to prevent further generation of the OSFs revealed by etching. In other words, effective prevention of OSF generation is possible whether or not surface damage results during wafer processing ...