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A RECHARGING METHOD IN CRYSTAL GROWTH

IP.com Disclosure Number: IPCOM000007334D
Original Publication Date: 1995-Mar-01
Included in the Prior Art Database: 2002-Mar-15
Document File: 4 page(s) / 132K

Publishing Venue

Motorola

Related People

Herng-Der Chiou: AUTHOR

Abstract

The feed stock used for a conventional recharging process in Czochralski (Cz) silicon crystal growth process is Siemens Chunk polysilicon or Ethyl par- ticulate polysilicon. The conventional recharging method requires an internal or external feed tube or hopper to feed the poly (silicon) into the remaining melt aher pulling a single crystal out. This article describes a new method which using a poly (crys- talline) crystal attached to a single crystal seed as a feed stock. Therefore, no internal or external feed tube or hopper is required in performing the recharging process.

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M-LA Technical Developments Volume 24 March 1995

A RECHARGING Ml3HOD IN CRYSTAL GROWTH

by Herng-Der Chiou

  The feed stock used for a conventional recharging process in Czochralski (Cz) silicon crystal growth process is Siemens Chunk polysilicon or Ethyl par- ticulate polysilicon. The conventional recharging method requires an internal or external feed tube or hopper to feed the poly (silicon) into the remaining melt aher pulling a single crystal out. This article describes a new method which using a poly (crys- talline) crystal attached to a single crystal seed as a feed stock. Therefore, no internal or external feed tube or hopper is required in performing the recharging process.

  The poly crystal can be produced from a remaining melt atIer grown a zero dislocation (ZD) single crystal within a resistivity specification. Take out the ZD single crystal with the seed, install a new seed and then grow a poly crystal out of the remaining melt.

  It is more economical to grow a n-type poly crys- tal after a n-type remaining melt than to grow a p-type poly crystal from a p-type remaining melt. Since the segregation coefficients of n-type dopants are much lower than the p-type boron dopant, the axial resistivity variation in n-type crystals is much bigger than in p-type crystals. For the same resistiv- ity specification range, there will be a longer por- tion of a p-type crystal within the specification than a n-type crystal. Therefore, in our experiment, we obtained the poly crystals from n-type remaining melts after growing n-type single crystals. The poly crystals were used in the recharging process ofgrow- ing heavily doped n+ crystals.

  In producing W55 single crystals, clOO> orien- tation 100 mm diameter, phosphorus-doped with resistivity specification of 8 to 12 ohm-cm, a charge weight of 28 Kg virgin Siemens chunk polysilicon were used. The resistivity distribution of a full length crystal is shown in Figure 1. Only about first 50% of the crystal will be...