Glass Articles for Use in Manufacturing Silicon Crystals
Publication Date: 2005-Sep-26
The IP.com Prior Art Database
A glass article for use in the manufacturing of silicon crystals, i.e., pulling silicon single crystal, wherein the article has an inner wall with an optimized curvature for the ratio of the melt contact area to the free surface area of the silicon crystal to have a value ranging from 0.8 to 1.2.
Quartz Crucible for Manufacturing Silicon
CROSS-REFERENCE TO RELATED APPLICATIONS
FIELD OF THE INVENTION
 This invention relates to a crucible for the manufacture of silicon single crystals according to the Czochralski (“CZ”) method.
BACKGROUND OF THE INVENTION
 Silicon single crystals have been conventionally manufactured according to the Czochralski (“CZ”) method. In this method as illustrated in Figures 1a – 1c, a seed crystal which is a silicon single crystal is brought into contact with silicon melt, and is then slowly pulled while being rotated to grow a silicon single crystal ingot. In the CZ process, crystals several feet in length and several inches in diameter are routinely grown.
 Oxygen in the semiconductor crystal is essential for internal gettering of impurities upon precipitation (e.g., SiO2) during device processing. The source of the oxygen is the fused silica crucible used to contain the silicon melt in the Czochralski process. Different levels of oxygen concentrations are required for different device processing, depending on the nature of the particular device fabrication process. For example, bipolar processing requires higher oxygen concentrations than MOS processing. In one application using the ASTM-80 standard, the amount of oxygen incorporation is in the range of 12-18 ppma with the bulk of the crystal ingot grown in the 12-16 ppma range. However, if the oxygen level is too high, the crystal may have undesirable oxygen induced defects such as stacking faults or point defects due to oxygen clusters. Therefore uniform oxygen level in the crystal and minimizing variation of oxygen concentration along the axis of the crystal is an important requirement independently from what absolute level is desired. The reason for variation in oxygen level along the length of the crystal is that the inflow of oxygen, proportional to the crucible crystal contact surface area decreases as the crystal is pulled, but the outflow, proportional to the free melt surface remains relatively unchanged between the parallel walls of the crucible for a substantial portion of the crystal.
 Accelerated and decelerated crucible rotation is one approach used in the prior art to enhance oxygen incorporation in many cases. Japanese Patent Publication No. 63-112488 discloses a method wherein the crucible dissolution is controlled by the crucible rotation rate, thus controlling the oxygen level in the melt. US Statutory Invention Registration (Reg No. H520) describes methods to increase the crucible-silicon interface for elevated oxygen concentration in the melt by increasing the contact surface area through incorporation of extra silicon material such as ribs, corrugations, etc. Japanese Publication No. 09-235176 teaches a crucible equipped with a spiral staircase-shaped fin on the inner sidewall to regulate the rising of the thermal convection in the silicon melt, thus control...