CA1250511A - Technique for the growth of epitaxial compound semiconductor films - Google Patents

Technique for the growth of epitaxial compound semiconductor films

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Publication number
CA1250511A
CA1250511A CA000478159A CA478159A CA1250511A CA 1250511 A CA1250511 A CA 1250511A CA 000478159 A CA000478159 A CA 000478159A CA 478159 A CA478159 A CA 478159A CA 1250511 A CA1250511 A CA 1250511A
Authority
CA
Canada
Prior art keywords
gallium
compound
growth
vapor stream
arsenic
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
CA000478159A
Other languages
French (fr)
Inventor
Rajaram Bhat
Herbert M. Cox
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Iconectiv LLC
Original Assignee
Bell Communications Research Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Bell Communications Research Inc filed Critical Bell Communications Research Inc
Application granted granted Critical
Publication of CA1250511A publication Critical patent/CA1250511A/en
Expired legal-status Critical Current

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Classifications

    • CCHEMISTRY; METALLURGY
    • C30CRYSTAL GROWTH
    • C30BSINGLE-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
    • C30B25/00Single-crystal growth by chemical reaction of reactive gases, e.g. chemical vapour-deposition growth
    • C30B25/02Epitaxial-layer growth
    • CCHEMISTRY; METALLURGY
    • C30CRYSTAL GROWTH
    • C30BSINGLE-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
    • C30B29/00Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
    • C30B29/10Inorganic compounds or compositions
    • C30B29/40AIIIBV compounds wherein A is B, Al, Ga, In or Tl and B is N, P, As, Sb or Bi

Abstract

Abstract of the Disclosure A technique is described for the deposition of group III-V
compound semiconductor films in epitaxial form wherein the group V source material employed is in solid elemental or compound form. The prime advantage of such technique resides in the elimination of the need for the highly toxic arsine gas for this purpose while permitting the preparation of a product essentially free of contamination.

Description

~2SO~;ll This invention relates to -the growth of epitaxial films comprising Groups III-V semiconduc-tor compounds. More particularly, the present invention relates to a method for the deposition of epitaxial layers of gallium arsenide and gallium aluminum arsenide by means of an organometallic chemical vapor deposition process.
Gallium arsenide and gallium aluminum arsenide are well-known compound semiconductor materials in the Group III-V system which have been widely used commercially in numerous applications. Prior to applicants' entry into -the field, it was common practice -to prepare these materlals by the well-known organometallic chemical vapor deposition process in which a hydride is employed as the source of the Group V element. Thus, in the preparation of gallium arsenide or gallium aluminum arsenide, arsenic trihydride (AsH3) was employed as the arsenic source material, either alone or in combination with other hydride and organometallic compounds.
Although this procedure had been used by workers in the art for several years with a modicum of success, the total exploitation of -the process was inhibited by -the high risk of exposure to harmful Ievels of toxicity of -the arsenic trihydride which is commonly known as arsine.
Furthermore, -the use of hydrides was plagued by a contamina-tion problem created by -the presence of both oxygen and water vapGr therein. Applicants focused -their atten-tion upon obviating these known prior art limi-tations and, much to their surprise, discovered a method which completely eliminated the need for hydrides as the source of the Group V element.
This end was successfully attained in a process in which the arsenic source material, in elemental or compound form, is maintained in a first conduit separa-te and apart from a second condui-t which contains vapors of either an organometallic gallium compound or an organometallic gallium aluminum compound. The arsenic source material is -then vaporized and upon confluence of vapors from the firs-t and ~ ~f~, ~LZ5~)5~L~

second condui-ts, -the arsenic vapors are diluted with hydrogen, so precluding condensation of the arsenic as it travels to the next stage of the reaction. It is this unique processing sequence which applicants believe to be the situs of invention. In other words, applicants made a surprising departure from the prior art practice of using a hydride of arsenic as an arsenic source. They eliminated the need for the hydrlde by using elemental arsenic or arsenic in compound form as the arsenic source, a concept not previously contemplated by workers in the ar-t since it was widely recognized that vapors of the Group V elemen-ts, such as arsenic, could not be transported in a compatible fashion with vapors of the Group III organometallic compounds which decompose at vaporization temperatures of arsenic. Thus, applicants departure from the prior art practice is even more surprising. In essence, they discovered that vapors of arsenic could, indeed, be transported compatibly with vapors of a Group III
organometallic compound by diluting the arsenic vapors with hydrogen as the arsenic vapors join the Group III
organometallic compound vapors.
The prime advantage of the described process resides in the elimination of the use of the highly toxic arsine gas. However, ancillary benefits include the elimination of parasitic reactions between the arsenic source and the organometallic compounds which lead to contamination of the desired epitaxial film.
Our invention will be more readily understood by reference to the accompanying drawing the single Figure of which is a fron-t elevational view, in cross-section, of an apparatus suitable for use in the practice of the present invention.
With reference now more particularly to the drawing, there is shown a conventional cold wall reactor 11 having disposed therein a quar-tz block 12, a susceptor 13 which serves as a support for a substrate wafer 31, and a quartz support member 30 for susceptor 13. Reactor 11 is ,, A

iZ5~

- 2a -adapted with an inlet conduit 14, an exhaus-t condui-t 15 and a cap member 16 which serves as a seal at the exit end of reactor 11. Rf coil 17 is provided around the midsection of reactor 11 for the purpose of heating the susceptor during the reaction. A heating tape 18 is also provided around the inlet end of the reactor for the purpose of obviating the likelihood of the group V element condensing during the course of the reaction but it does not heat this region sufficiently to cause parasitic reactions between the group III organometallic compound and the vapors of -the group V
element. The -tempera-ture in this region is within the range of 200-300C. Also included as par-t of -the apparatus used in the practice of the invention is a vaporizing furnace 19 for vaporization of the group V source material, furnace 19 having disposed -therein boat 20 for containing the source material, boat 20 being coupled with quartz tube 21 having a soft iron bar 22 sealed therein. A hook means 23 connected to tube 21 permits the magnetic movement of the boat during ~l~S~J~

the processing sequence. Eurnace 19 also includes inlet conduit 24, a cap 25 to seal the inlet end and e~it conduit 26 which is connected to inlet conduit 1~ of cold wall reactor 11. ~leating of the source material exitlng Erom furnace 19 is effected hy means of a heating tape 27 wrapped around exit conduit 26. Also shown connected to conduits 26 and 14 is conduit 2~ for introduction of organometallic compounds and hydrogen to reactor 11.
A brief description of the procedure followed in the practice of our invention will now be given.
Initially, a substrate member is selected upon which deposition of the desired epitaxial films will be effected. Substrates suitable for this purpose may be conductive or insulating in nature, ultimate selection being dependent upon the type of device contemplated.
Typical materials found suitable for this purpose are gallium arsenide, indium phosphide and the like. These substrates may conveniently be obtained from commercial sources.
Prior to insertion of the substrate wafer 31 upon the surface of susceptor 13, the substrate is subjected to a conventional degreasing and etching sequence, thereby assuring the presence of a clean surface for deposition. A typical cleansing sequence would involve degreasing with trichloroethylene, acetone and methyl alcohol followed by etching with a 3:1:1 mixture of sulfuric acid, hydrogen peroxide and water. Etching is continued for a time period sufficient to remove approximately 2 microns from the surface of the substrate.
The degreased, etched substrate 31 is then placed upon susceptor 13 in cold wall reactor 11.
In accordance with an aspect of our invention, a group V source material in solid, elemental or compound form of high purity is selected. For -this purpose, it is desirable to employ the material in a form of the highest purity available, typically 99.9999+% purity. ~rsenic, gallium arsenide polycrystals, indium arsenide ~Z~)Sl~

polycrystals, indium phosphide polycrystals, and phosphorous are the materials most commonly employed for this purpose. The source material so selected is then placed in boat 20 in vaporizing furnace 19. The weight of the source material is not considered critical, the only requirement being that sufficient material be present to obtain the desired III-V compound. The source selected may be obtained in solid form from known commercial sourc~:i or it may be generated in situ by cracking halides such as arsenic trichloride or phosphorous trichloride and condensing the arsenic or phosphorous vapors prior to a deposition run. In this latter case, the furnace 19 is made movable and the movable boat eliminated.
In the operation of the process, the source material in boat 20 is heated with hydrogen flowing into the furnace via inlet 24. Heating is effected at a temperature sufficient to vaporize the solid source, the hydrogen serving as a means for transporting the vaporized source to reactor 11. The amount of vapor which is transported determines the carrier type and concentration level, the morphology of the deposited layer and the growth rate. These parameters must be determined experimentally for each system, such being dependent upon considerations relating to the intended use of the deposited film. Heating tape 27 is heated to a temperature equal to that of furnace 19, thereby assuring that source vapors leaving furnace 19 will not condense in the conduit leading to cold walled reactor 11.
Simultaneous with heating of the source material, hydrogen is bubbled through a liquid organometallic compound of a group III element at a temperature a few degrees lower than room temperature or lower depending on the vapor pressure of the group III
organometallic compound, so resulting in vapors of the organometallic compound being transported via conduit 28 past the region 33 of confluence with the vapor from solid source 20 and through conduit 14 into the growth region in ~;2S~)Sl:l reactor 11. Transport of the organome-tallic compound may be regulated by controlling the rate at which hydrogen is bubbled through the organometallic compound. The hydrogen introduced through conduit 28 serves to dilute the group V
vapors in the region 33. I-t will be understood by those skilled in the art that during the growth sequence it is feasible to alter the source of the group III compound and/or add suitable dopants to the system such as hydrogen selenide, silane, diethylzinc and the like.
The substrate material 31 contained in the cold wall reactor 11 is heated to a temperature sufficient to permit growth of the desired compound semi-conductor. In general this temperature may range from 475-750C with a general preference being found for a range of 600-750C, such range being dictated by considerations relating to layer quality.
Epitaxial films prepared in accordance with the described procedure may be used in a wide variety of device applications which will be readily appreciated by those skilled in the art. Typical of such devices are field effect transistors, light emitting diodes, lasers, etc.
An example of the practice of the present invention is set forth below. It will be understood that this example is solely for purposes of exposition and is not to be construed as limiting.
This example describes the growth of a gallium arsenide epitaxial film utilizing an apparatus of the type shown in the Figure. The substrate employed was a semi-insulating chromium doped gallium arsenide wafer oriented six (6) degrees off the (100) crystalline surface toward the (111)~ surface. The source material chosen was 99.9999% purity elemental arsenic, obtained Erom commercial sources.
The arsenic source material was placed in the boat of the vaporizing furnace and heated to a temperature of approximately 450C. The susceptor in the cold wall ~ZS~

reactor was then heated using radio frequency induction toa temperature of 650C, the susceptor being heated without substantially heating the quartz reactor tube above the wafer of gallium arsenide. High purity hydrogen was then passed through the vaporizing furnace at a flow rate of 6 liters per minute, so resulting in a flow velocity of about 25 cm./sec. at the leading edge of the susceptor.
The amount of arsenic transported to the deposition region ranged from 0.025 grams/min to 0.125 grams/min corresponding to an arsenic source temperature of ~25-470C. ~Iydrogen was then bubbled through trimethyl gallium and trimethyl aluminum and the resultant vapors transported to the cold wall reactor. ~t the deposition site, a trimethyl gallium partial pressure of lxlO 4 was established to commence growth. Growth was initiated at a rate of approximately 0.125 ,um/min. The resultant grown - layer was p-type and had a carrier concentration of approximately 2X10l5 cm~3.
Studies of the reaction described in that foregoing example revealed that deposition was dominated by the decomposition reaction of the As~ molecule produced by heating solid arsenic. This was found to result in deposition characteristics markedly different from those observed with the commonly used arsine. This conclusion is supported by the fact that a (100) facet was observed on an epitaxial layer deposited on a 6 off (100) toward (lll)A substrate, the layer being of p-type when using a solid arsenic source. However, when arsine is used, no (lO0) facet is observed and the resultant layers are under similar growth conditions generally of n-type.
As indicated above, the prime advantage of the described process resides in the elimination of the use of the highly toxic arsine gas. However, ancillary benefits include the elimination of parasitic reactions between the group V source and the organometallic compounds, such reactions being of particular concern with indium containing organometallics.

~25~51~

Lastly, it will be appreciated that optimigation of the deposition parameters permits deposition of any of the group III-V compounds or their alloys.

Claims (3)

WHAT IS CLAIMED IS:
1. A method for the growth of epitaxial gallium arsenide or gallium aluminum arsenide upon a substrate which comprises forming a first vapor stream from an arsenic source in elemental or compound solid form, introducing to said first vapor stream a second vapor stream comprising an organometallic compound selected from the group consisting of a gallium compound and a gallium and aluminum compound, and upon the confluence of said first and second vapor streams diluting said first vapor stream with hydrogen to prevent condensation thereof as the temperature is lowered to a temperature compatible with said second vapor stream, and transporting the combined streams to the growth region containing the substrate where growth is initiated.
2. A method in accordance with claim 1 wherein said substrate is a gallium arsenide wafer, said arsenic source is elemental arsenic and the gallium compound is trimethyl gallium.
3. A method for the growth of epitaxial gallium arsenide or gallium aluminum arsenide upon a substrate which comprises forming a first vapor stream from an arsenic source in elemental or compound solid form, joining with said first vapor stream a second vapor stream comprising an organometallic compound selected from the group consisting of a gallium compound and a gallium and aluminum compound and hydrogen, the hydrogen diluting the first vapor stream and preventing condensation thereof as the temperature is lowered to a temperature compatible with the gallium or gallium and aluminum compound vapor, and exposing the substrate to the joined vapor streams, so resulting in deposition from the vapor streams upon the substrate.

- Page 1 of Claims -
CA000478159A 1984-10-31 1985-04-02 Technique for the growth of epitaxial compound semiconductor films Expired CA1250511A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US66683184A 1984-10-31 1984-10-31
US666,831 1984-10-31

Publications (1)

Publication Number Publication Date
CA1250511A true CA1250511A (en) 1989-02-28

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Family Applications (1)

Application Number Title Priority Date Filing Date
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Country Status (5)

Country Link
EP (1) EP0199736A1 (en)
JP (1) JPS62500695A (en)
CA (1) CA1250511A (en)
ES (1) ES8606523A1 (en)
WO (1) WO1986002776A1 (en)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4740606A (en) * 1986-07-01 1988-04-26 Morton Thiokol, Inc. Gallium hydride/trialkylamine adducts, and their use in deposition of III-V compound films
US4792467A (en) * 1987-08-17 1988-12-20 Morton Thiokol, Inc. Method for vapor phase deposition of gallium nitride film

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2075325A5 (en) * 1970-01-09 1971-10-08 Hitachi Ltd

Also Published As

Publication number Publication date
JPS62500695A (en) 1987-03-19
WO1986002776A1 (en) 1986-05-09
EP0199736A1 (en) 1986-11-05
ES548358A0 (en) 1986-04-16
ES8606523A1 (en) 1986-04-16

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