Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
• • C—CHEMISTRY; METALLURGY
  • C30—CRYSTAL GROWTH
  • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
  • C30B13/00—Single-crystal growth by zone-melting; Refining by zone-melting
• • C—CHEMISTRY; METALLURGY
  • C30—CRYSTAL GROWTH
  • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
  • C30B15/00—Single-crystal growth by pulling from a melt, e.g. Czochralski method
• • C—CHEMISTRY; METALLURGY
  • C30—CRYSTAL GROWTH
  • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
  • C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
  • C30B29/02—Elements
  • C30B29/08—Germanium
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S420/00—Alloys or metallic compositions
  • Y10S420/903—Semiconductive
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S438/00—Semiconductor device manufacturing: process
  • Y10S438/914—Doping
  • Y10S438/925—Fluid growth doping control, e.g. delta doping

Definitions

• This invention relates to methods for producing bodies of extrlnsic semiconductive material manifesting substantlally uniform conductivity characteristics within substanconstant conductivity level. Since conductivity level in extrinsic semiconductive materials such as silicon, gercompensates for the changing example, United States Patent 2,768,914. Other methods of compensating for such varying concentration within the melt include various mechanisms by which the material with respect to which the melt is depleted is gradually added in such amount as to exactly compensate for the amount removed through crystallization.
• a second approach utilizes a melt of constant volume and of constant composition which is maintained by producing a second solid-liquid interface which advances into solid material of substantially uniform concentration at the identical rate of the freezing interface at which the crystalline body is being produced.
• zone leveling One method of crystallizing from such a constant volume, constant composition melt, sometimes referred to as zone leveling, is described in United States Patent 2,739,088.
• the degree of success obtained in the production of a crystalline body manifesting uniform resistivity along the growth axis in any one of the above processes and in any other process utilizing a freezing solid-liquid interface is dependent upon the precision with which growth condi tions may be controlled.
• This diffusion layer of a thickness in the growth direction to which the symbol A is here ascribed, is the material from which the crystalline material is actually solidified, so that the concentration of any ingredient in the solidifying material is related through the distribution coeflicient not to the average melt concentration but rather to the concentration of the melt adjacent to the interface within the diffusion layer.
• the thickness of the diffusion layer A is in turn dependent upon various factors, all of which are affected by conditions of growth. Such factors include the diffusion rate of the ingredient of concern within the, liquid material which varies with temperature, the rate of movement of the freezing interface, and the degree of stirring within the melt whether by natural or artificial means.
• the concentration of the body of the melt varies more or less from the concentration at the interface, depending upon growth conditions, the concentration realized in the crystallizing material is not that dictated by the equilibrium distribution coeflicient in terms of body concentration. This has given rise to use of so-called effective distribution coeificients which are empirically determined and which invariably compare with the equilibrium coeff cient in that they are numerically closer to 1.
• the methods herein are directed to eliminating overall microscopic non-uniformity of resistivity.
• Such microscale fluctuations of resistivity are a serious problem, especially in transistors and diodes made by the diffusion technique, for in such cases, very irregular p-n junctions result from microscale resistivity variations in the base material.
• the processes of this invention attain the objective of uniform resistivity and uniformity of other conductivity characteristics by including in the melt from which material is being crystallized both a first significant impurity imparting the desired conductivity characteristics and a second significant impurity imparting either the same or the opposite conductivity characteristics, the second impurity being of such character and being included in such amount that random variations in growth conditions produce a variation in concentration level of both impurities so that the excess amount of impurities imparting the desired conductivity characteristics remain substantially constant in the crystallizing material.
• the second impurity is such as imparts the desired conductivity type or the opposite conductivity type
• the excess impurity in the crystallized product in the first instance being equal to the sum concentration of the two impurities and in the second instance being equal to the difference concentration of the first impurity less the second.
• the uniformity of resistivity of the final product may be improved several orders of magnitude over the same growth conditions as applied to a semiconductive material containing only the one impurity imparting desired conductivity type.
• the processes of this invention are referred to herein as compensation methods.
• the usual system discussed herein comprises, as the major ingredient, a fusible semiconductive material such as germanium or silicon, a significant impurity imparting the desired conductivity type referred to herein as the first significant impurity, or first solute and a second significant impurity or second solute compensating for concentration variations in the excess significant impurity, referred to herein as the second significant impurity or second solute.
• the invention is described in terms of such simple ternary systems, it is to be recognized that the invention is not so limited and may contain both types of second impurities and/or any number of additional ingredients which may contribute to the desideratum of uniform resistivity or which may serve any other function.
• Equation 6 R* can be expressed as:
• k C is less than k C (Z being considered to be positive), and 8* is numerically less than 1. It is generally-prefera'ble in the processes herein to maintain the fraction compensated, 8*, small. Thi requires that the fractional change of k with f or A, be relatively large compared with that of k In the processes of this invention it is preferred that the concentrations and characteristics of solutes be such as to result in the critical ratio, R*.
• Equation 13 It can be seen from Equation 13, that for any value of R from to 2R*/(1S), the presence of solute 2 decreases the effect of fluctuations in f or A on the resistivity.
• small S is favored where a low fraction compensated and a low sensitivity to the critical ratio are desired.
• Equation 12 eifect of the deviation, 7, of R from R* produced by the change (ff-'f) in growth rate
• Equation the right side of Equation is equal to unity.
• the quantity (fiZ/fif) is quite insensitive to growth rate where the distribution coefiicients of both impurities is equal to or less than 0.1.
• This approximation applies, for example, to a germanium system containing gallium and antimony as excess and compensating impurities. This approximation has been experimentally substantiated.
• Donort t Equations defining the requirements of solute material are derived above in terms of solutes of opposite con- Since in reality the difference concentration Z in Equation 1 has reference to the excess majority significant solute which, as is well known in the art, is a measure of the total amount of significant impurity imparting conductivity characteristics to the semiconductive material, Z, may with equal validity be considered to define the total concentration of all significant impurities of a given type where opposite conductivity type imparting solutes are not of concern in the system. Since this condition applies to the processes of this invention in which the compensating solute 2 is of the same type as solute 1, that is, for either of instances 1 or 2 in the above table,
• Z is the difference concentration and continues to represent the ditierence between concentrations of opposite type solutes, one of which is not of concern here, and in which the other symbols are as defined above.
• Example 1 is illustrative of the method of determining the proper amount of compensating solute to offset variations in growth conditions in a typical semiconductive system.
• Example 1 From experimental data of Bridgers (Journal of Applied Physics, volume 27, pages 746-751 (1956)) for the system germanium plus antimony (a donor, or n-type, impurity) plus gallium (an acceptor, orp-type impurity), it is found that the critical ratio R* has the value 0.14 at a growth rate of 0.0025 centimeter per second in av pulled crystal rotated at 144 R. P. M. Thus, the ratio of melt concentrations of antimony to gallium, C /C where 2 denotes antimony, is
• gallium and antimony in the melt are those determined by the critical ratio R in accordance with the equations.
• the growth rate of the growing crystal is increased 50 percent. Under these conditions the variation in difference concentration in the growing crystal is less than 1 percent. The percentage deviation in conductivity is also less than 1 percent.
• solutes 1 and 2 in accordance with this invention may be determined from the aseroos discussion and equations. By way of illustration, several suitable combinations are listed below:
• the compensating solute or solute 2 is that which has the greatest variation in k with variation in growth conditio
• the crystallizing material may be either solute l or solute 2 as desired and may in fact vary from one to the other in the solid under certain conditions. Where both solutes are either acceptors or donors this is of no consequence since the solute concentration of concern in the crystallizing material is the sum concentration.
• Crystals prepared in accordance with this invention may contain additional solutes. Such solutes may contribute to the compensation of this invention as in the instance of a solvent material containing a first significant impurity and two additional significant impurities, one of which is of opposite conductivity type and one of Which is of the same conductivity type as solute 1. Additional ingredients may also be included for any of the reasons known to the art as, for example, for the purpose of controlling lifetimes.
• a process of crystallizing semiconductive material evidencing uniform electrical conductivity characteristics from a body of liquid comprising as a major ingredient a. fusible extrinsic semiconductive material, and as minor ingredients, two significant solutes, such that one of the characteristics, (a) the conductivity imparting type, and (b) the sign of the quantity (lk), is opposite for the two solutes, and the other is the same for the tWo solutes, in which the ratio of the concentration of solute 2 in the liquid to that of solute 1 is from 0.8 to 1.2 times the absolute value of R* where 11* is the ratio of the growth rate coefiicient of the distribution coefficient of solute l to that of solute 2 and in which it is the eifective distribution coefiicient.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Crystallography & Structural Chemistry (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Physics & Mathematics (AREA)
• Condensed Matter Physics & Semiconductors (AREA)
• General Physics & Mathematics (AREA)
• Manufacturing & Machinery (AREA)
• Computer Hardware Design (AREA)
• Microelectronics & Electronic Packaging (AREA)
• Power Engineering (AREA)
• Crystals, And After-Treatments Of Crystals (AREA)
• Liquid Deposition Of Substances Of Which Semiconductor Devices Are Composed (AREA)

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  • BE BE567569D patent/BE567569A/xx unknown
  • NL NL112556D patent/NL112556C/xx active
  • NL NL229017D patent/NL229017A/xx unknown
• 1957
  • 1957-06-25 US US667956A patent/US2861905A/en not_active Expired - Lifetime
• 1958
  • 1958-05-08 DE DEW23291A patent/DE1215658B/de active Pending
  • 1958-06-03 FR FR1208294D patent/FR1208294A/fr not_active Expired
  • 1958-06-24 GB GB20207/58A patent/GB871839A/en not_active Expired
  • 1958-06-25 CH CH6104158A patent/CH402425A/fr unknown

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