DK177587B1

DK177587B1 - Method and apparatus for producing a single crystal of semiconductor material

Info

Publication number: DK177587B1
Application number: DKPA201100216A
Authority: DK
Inventors: Wilfried Von Ammon
Original assignee: Siltronic Ag
Priority date: 2003-01-24
Filing date: 2011-03-23
Publication date: 2013-11-04
Also published as: DK201100216A

Abstract

Opfindelsen angår en fremgangsmåde til fremstilling af en énkrystal af halvledermateriale, ved hvilken andele af en smeltemasse, der holdes flydende af en trækspole, størkner på en podekrystal under dannelse af den voksende énkrystal. og granulat smeltes induktivt og. fra oven for at vedligeholde væksten af énkrystallen, idet det smeltende granulat ledes forsinket til smeltemassen. Opfindelsen angår også et til gennemførelse at fremgangsmåden egnet apparat med en indretning, der forsinker blanding af det smeltede granulat og smeltemassen.The invention relates to a process for producing a single crystal of semiconductor material in which proportions of a melt held by a tensile coil solidify on a seed crystal to form the growing single crystal. and granules are inductively melted and. from above to maintain the growth of the single crystal as the melting granule is delayed to the melt. The invention also relates to a method suitable for carrying out the apparatus with a device which delays mixing of the molten granule and the melt mass.

Description

DK 177587 B1DK 177587 B1

Opfindelsen angår en fremgangsmåde til fremstilling af en énkrystal af halvledermateriale ved en fremgangsmåde, der i det væsentlige adskiller sig fra den kendte zonetrækning (Fz-fremgangsmåden) ved, at polykrystallinsk granulat i stedet for en polykrystallinsk forrådsstav leverer materialet til énkrystallens vækst. Opfindelsen 5 angår også et apparat, der er egnet til fremstilling af énkrystallen.The invention relates to a method for producing a single crystal of semiconductor material by a method substantially different from the known zone drawing (F 2 method) in that polycrystalline granules deliver the material to the growth of the single crystal instead of a polycrystalline stock. The invention also relates to an apparatus suitable for the preparation of the single crystal.

En fremgangsmåde af samme art er allerede kendt fra tysk offentliggørelsesskrift nr. 19.538.020. Granulat smeltes i en beholder og tilføres en smeltemasse, der befinder sig på den voksende énkrystal. Énkrystallens vækst opretholdes ved en ligevægt 10 mellem smeltet granulat, der tilføres smeltemassen, og størknende andele af smeltemassen.A method of the same kind is already known from German Publication No. 19,538,020. Granules are melted in a container and fed to a melting mass located on the growing single crystal. The growth of the single crystal is maintained at an equilibrium 10 between molten granules fed to the melt and solidifying proportions of the melt.

Den foreliggende opfindelses opgave består i at muliggøre fremstillingen af énkrystaller uden forskydninger, især med diametre på 200 mm og derover.The object of the present invention is to enable the production of single crystals without displacements, especially with diameters of 200 mm and above.

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Opfindelsen angår en fremgangsmåde til fremstilling af en énkrystal af halvledermateriale, ved hvilken andele af en smeltemasse, der holdes flydende af en oven for smeltemassen anbragt trækspole, størkner på en podekrystal under dannelse af den voksende énkrystal, og granulat smeltes for at vedligeholde énkrystallens vækst, og 20 som er ejendommelig ved, at granulatet smeltes induktivt ved hjælp af en opsmeltningsspole, der er anbragt oven for det smeltende granulat, og det smeltende granulat ledes forsinket til smeltemassen.BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to a process for producing a single crystal of semiconductor material in which proportions of a melt held by a tensile coil disposed above the melt, solidify on a seed crystal to form the growing single crystal, and granulate is melted to maintain the growth of the single crystal. and 20, characterized in that the granulate is inductively melted by means of a melting coil disposed above the melting granule and the melting granulate is delayed to the melting mass.

Opfindelsens genstand er også et apparat til fremstilling af en énkrystal med en over 25 den voksende énkrystal anbragt beholder og en transportindretning til tilførsel af granulat til beholderen og en opsmeltningsspole til smeltning af granulatet og en oven for smeltemassen anbragt trækspole til at holde en smeltemasse på den voksende énkrystal, idet det smeltende granulat gennem åbninger i beholderen og trækspolen kommer til smeltemassen under dannelse af en smeltehals, og størknende andele af 30 smeltemassen vedligeholder énkrystallens vækst, som er ejendommeligt ved, at opsmeltningsspolen er anbragt oven for det smeltende granulat, og beholderen har en indretning, som forhaler blanding af det smeltede granulat og smeltemassen.The object of the invention is also an apparatus for producing a single crystal having a container placed over 25 the growing single crystal and a transport device for supplying granules to the container and a melting coil for melting the granulate and a tensile coil disposed above the melting mass for holding it. growing single crystal, the melting granule coming through openings in the container and the draw coil to the melt to form a melt neck, and solidifying portions of the melt mass maintaining the single crystal growth which is peculiar to the melting coil being positioned above the melting granule and the container a device which retards mixing of the molten granule and the melt.

Den omhandlede fremgangsmåde tillader fremstilling af énkrystaller med zonesmeltet 35 materiales karakteristik til omkostninger, der ligger langt under de for Fz-materialet liggende omkostninger. Det polykrystallinske granulat, der udgør råstoffet til krystal- 2 DK 177587 B1 væksten, er betydelig billigere end de til Fz-fremgangsmåden nødvendige polykrystal-linske forrådsstave. Desuden kan der næppe tilvejebringes polykrystallinske forrådsstave i en kvalitet og størrelse til at kunne fremstille énkrystaller med diametre på 200 mm og derover. Selvom når dette lykkes, er trækprocessen for énkrystaller med 5 sådanne diametre vanskelig at styre på grund af de masser, der samtidig skal opsmel-tes og krystalliseres. Følgen er ringe udbytter af krystaller uden forskydninger, som ikke er økonomisk konkurrencedygtige.The present process permits the production of single crystals having the zone-melting material characteristics at costs well below the cost of the Fz material. The polycrystalline granules, which constitute the raw material for the crystal growth, are significantly cheaper than the polycrystalline stock poles required for the Fz process. In addition, polycrystalline stock rods of a quality and size can hardly be provided to produce single crystals having diameters of 200 mm or more. Although successful, the single crystallisation process with 5 such diameters is difficult to control due to the masses which must simultaneously be melted and crystallized. The result is poor yields of non-offset crystals that are not economically competitive.

Den i det nævnte tyske offenltiggørelsesskrift nr. 19.538.020 beskrevne fremgangs-10 måde undgår ganske vist de problemer, som fremstillingen og anvendelsen af polykrystallinske forrådsstave frembyder, men er dog ikke egnet til fremstilling af énkrystaller uden forskydninger, fordi fra granulatet stammende partikler alt for let kommer til grænsefladen mellem smeltemassen og den voksende énkrystal og kan bringe den forskydningsfrie vækst af énkrystallen til afslutning.The process disclosed in the German disclosure specification 19,538,020 avoids the problems presented by the manufacture and use of polycrystalline storage rods, but is not suitable for the production of single crystals without displacements, because particles from the granulate are too much easily reaches the interface between the melting mass and the growing single crystal and can bring to an end the shear-free growth of the single crystal.

15 Hér tager den foreliggende opfindelse udgangspunkt, idet det foreslås at forsinke tilførslen af granulatet til smeltemassen, således at granulatet så vidt muligt først kan komme til smeltemassen, når det er fuldstændig opsmeltet. Til dette formål træffes foranstaltninger, der forlænger det smeltende granulats vej til smeltemassen og/eller 20 udgør en barriere for endnu ikke fuldstændig opsmeltet granulat. Det smeltede granulat må fortrinsvis tilbagelægge en vejlængde på mindst 25 mm, især 50 mm, inden det når smeltemassen. Opfindelsen udmærker sig endvidere ved, at der foreslås foranstaltninger, ved hvilke ukontrolleret indbygning af oxygen i énkrystallen effektivt undgås. På den anden side kan der styret tilføres smeltemassen over den voksende 25 énkrystal oxygen, f.eks. ved at der på smeltemassen anbringes en ring af Si02. En egnet ring er eksempelvis beskrevet i USA-patentskrift nr. 5.089.082.Here, the present invention is based on the proposition that it is proposed to delay the delivery of the granulate to the melt, so that, as far as possible, the granulate can only reach the melt when fully melted. For this purpose, measures are taken that extend the path of the melting granule to the melting mass and / or 20 constitute a barrier to yet completely melted granulate. Preferably, the molten granule must provide a path length of at least 25 mm, especially 50 mm, before reaching the melt mass. The invention is further characterized by the fact that measures are proposed by which uncontrolled incorporation of oxygen into the single crystal is effectively avoided. On the other hand, the control may be applied to the melting mass over the growing single crystal oxygen, e.g. by applying a ring of SiO 2 to the melt. A suitable ring is disclosed, for example, in U.S. Patent No. 5,089,082.

Til smeltning af granulatet og til trækning af énkrystallen anvendes i begge tilfælde højfrekvensspoler. Det er særlig fordelagtigt, når trækspolen og opsmeltningsspolen er 30 induktivt afkoblet, dvs. at den af trækspolen tilvejebragte energi ganske vist anvendes til styring af énkrystallens vækst, men ikke til opsmeltning af granulat. En sådan afkobling kan allerede gennemføres ved tilstrækkelig afstand af trækspolen fra bunden af den beholder, som granulatet tilføres.In both cases, high frequency coils are used for melting the granulate and for drawing the single crystal. It is particularly advantageous when the tensile coil and melt coil are inductively decoupled, i.e. that the energy provided by the coil is admittedly used to control the growth of the single crystal, but not for the melting of granules. Such decoupling can already be carried out at a sufficient distance from the draw coil from the bottom of the container to which the granulate is supplied.

35 Ved fremgangsmådens begyndelse dannes en smeltemasse på en podekrystal på sammenlignelig måde, som dette også er sædvanligt ved Fz-fremgangsmåden. Rum- 3 DK 177587 B1 fanget af smeltemassen, som i begyndelsen kun består af én smeltedråbe, forøges ved smeltning af halvledermateriale. Parallelt dermed bringes andele af smeltemassen til at størkne under dannelse af en voksende énkrystal, idet podekrystallen langsomt sænkes under drejning. I en første fase lader man énkrystallen vokse til en konus.At the beginning of the process, a melting mass is formed on a seed crystal in a comparable manner, as is usual in the Fz process. Room 3 trapped by the melt, which initially consists of only one drop of melt, is increased by the melting of semiconductor material. Parallel to this, proportions of the melt mass are solidified to form a growing single crystal as the seed crystal is slowly lowered during rotation. In a first phase, one crystal is grown into a cone.

5 Senere holdes énkrystallens diameter konstant, hvorved den største del af énkrystallen får et cylindrisk udseende. Det til fremstilling af énkrystaller med diametre på 200 mm og derover nødvendige halvledermateriale leveres især ved trækningen af det cylinderformige afsnit i det væsentlige af polykrystallinske granulat, som smeltes ved hjælp af opsmeltespolen, idet det smeltende granulat tilføres smeltemassen med 10 forsinkelse. For at holde partikler på afstand fra den voksende énkrystal sørges der hensigtsmæssigt for, at rummet omkring beholderen er støvtæt adskilt fra rummet omkring den voksende énkrystal. Foruden konstruktionsforanstaltninger, der fremmer en sådan adskillelse, sendes hensigtsmæssigt under fremstillingen af énkrystallen en gasstrøm, der f.eks. består af indifferent gas, såsom argon, nedefra og opad gennem 15 trækspolen.Later, the diameter of the single crystal is kept constant, giving the largest part of the single crystal a cylindrical appearance. The semiconductor material required to produce single crystals having diameters of 200 mm and above is supplied, in particular, by the pulling of the cylindrical section, essentially of polycrystalline granules, which are melted by the melting coil, the melting granule being supplied with the melt mass with a delay. In order to keep particles away from the growing single crystal, it is convenient to make sure that the space around the container is dust tight separated from the space around the growing single crystal. In addition to structural measures that promote such separation, during the preparation of the single crystal, a gas stream which is e.g. consists of inert gas, such as argon, from below and upward through the 15 coil.

Opfindelsen beskrives i det følgende mere udførligt under henvisning til figurer. Ensartede kendetegn er forsynet med samme henvisningstal. Figur 1 til 4 viser foretrukne udførelsesformer for apparatet ifølge opfindelsen. Figur 5 viser en plantegning 20 af en opsmeltningsspole, som er særlig egnet til anvendelse i en indretning ifølge figur 4. I de andre udførelsesformer nævnes silicium som særlig foretrukket halvledermateriale.The invention is described in more detail below with reference to figures. Uniform characteristics are provided with the same reference numerals. Figures 1 to 4 show preferred embodiments of the apparatus according to the invention. Figure 5 shows a floor drawing 20 of a melting coil which is particularly suitable for use in a device according to Figure 4. In the other embodiments, silicon is mentioned as a particularly preferred semiconductor material.

I indretningen ifølge figur 1 befinder en pottelignende, drejelig og i aksial retning for-25 skydelig beholder 1 sig over en trækspole 2. Beholderen består af Si02, f.eks. kvarts, og har ligesom trækspolen en cirkulær åbning 3 i centrum. Dens indre rum er af koncentriske kvartsvægge 4 opdelt i flere, fortrinsvis mindst tre områder, der danner et kanalsystem. De enkelte områder er således forbundet med hinanden gennem åbninger 6, at vejen fra det ydre område til beholderens centrale åbning 3 bliver så 30 lang som muligt og eksempelvis er udformet mæanderformigt. I områderne befinder der sig enkelte eller flere parallelt koblede viklinger af en højfrekvensspole, der tjener til opsmeltning af granulatet og derfor betegnes opsmeltespole 5. I det ydre område, i hvilket granulatet 11 tilføres, er spoleviklingerne dækket med afdækninger 12 af kvarts for at undgå kontakt af granulatet med opsmeltespolens metalliske overflade. Kvarts-35 væggene 4 er således udformet i det ydre område, at det over en transportindretning 10 tilførte granulat 11 ikke kan drysses ind i de indre områder.In the device according to Figure 1, a pot-like, rotatable and axially displaceable container 1 is located above a pulling coil 2. The container consists of SiO 2, e.g. quartz, and like the draw coil has a circular aperture 3 in the center. Its interior space is of concentric quartz walls 4 divided into several, preferably at least, three areas forming a duct system. The individual regions are thus connected to each other through apertures 6 so that the path from the outer region to the central aperture 3 of the container becomes as long as possible and, for example, is shaped mutually. In the regions, there are single or more parallel coupled windings of a high frequency coil which serve to melt the granulate and therefore is called melt coil 5. In the outer area in which the granulate 11 is supplied, the coil windings are covered with covers 12 of quartz to avoid contact. of the granulate with the metallic surface of the melting coil. The quartz walls 4 are designed in the outer region so that the granules 11 supplied via a transport device 10 cannot be sprayed into the inner regions.

4 DK 177587 B1 I beholderens centrale åbning 3 stikker en stav 7 af silicium, på hvilken det flydende silicium kan løbe nedad til smeltemassen 8 på den voksende énkrystal 9 gennem det indre hul i trækspolen 2 under dannelse af en smeltehals 18. Staven er drejelig og 5 både aksialt og radialt forskydelig. Drejningsaksen af beholderen 1 er vippet en lille vinkel a, hvorved det sikres, at staven altid fugtes på samme sted i forhold til trækspolen 2. Ved radial forskydning af trækspolen kan strømmen af smelteflydende materiale fra en smeltesø 17 i beholderen 1 til smeltemassen 8 styres.4 DK 177587 B1 In the central opening 3 of the container, a rod 7 of silicon protrudes on which the liquid silicon can flow downward to the melting mass 8 of the growing single crystal 9 through the inner hole of the draw coil 2 to form a melt neck 18. The rod is rotatable and 5 both axially and radially displaceable. The axis of rotation of the container 1 is tilted a small angle a, thereby ensuring that the rod is always wetted at the same location with respect to the draw coil 2. By radial displacement of the draw coil, the flow of melt flowing material from a melting sea 17 in the container 1 to the melt mass 8 can be controlled.

10 For at forhindre, at støvpartikler kommer til smeltemassen 8, bør det rum, i hvilket énkrystallen trækkes, være så støvtæt som muligt adskilt fra det rum, i hvilket beholderen befinder sig. Det er derfor hensigtsmæssigt, at den seglformige spalte mellem staven 7 og randen af den centrale åbning 3 i beholderen er så snæver som muligt, og at en gasstrøm er rettet opad gennem spalten og forhindrer indtrængning af 15 støv i trækrummet.In order to prevent dust particles from reaching the melt 8, the space in which the single crystal is drawn should be as dust-proof as possible separated from the space in which the container is located. It is therefore desirable that the seal-shaped gap between the rod 7 and the rim of the central opening 3 in the container is as narrow as possible and that a gas flow is directed upwards through the slot and prevents the ingress of dust into the draft chamber.

Fremstillingen af en énkrystal begynder med, at der først i beholderen 1 opsmeltes en ringe mængde silicium og holdes flydende. Staven 7 har i denne fase endnu ingen berøring med den dannede smeltesø 17. Derefter køres staven nedad gennem den 20 centrale åbning 3 i beholderen og trækspolens indre hul, og på kendt måde påbegyndes podningstrækningen, idet der dannes en smeltedråbe på stavens nederste spids ved hjælp af trækspolen 2, og en podekrystal sættes på denne smeltedråbe. Staven har i dette øjeblik funktion som forrådsstaven ved Fz-fremgangs-måden. Ved videre opsmeltning af staven og begyndende sænkning af podekrystallen 25 dannes først en énkrystallinsk begyndelseskonus med en derpå liggende smeltemasse af tilstrækkeligt stort rumfang. Derpå forskydes staven synkront sammen med trækspolen, således at det i beholderen smeltede materiale kommer i kontakt med staven, og flydende silicium således kan komme langs staven til smeltehalsen 18 og derfra til smeltemassen 8 på den voksende énkrystal 9. Under fremgangsmådens 30 videre forløb tilføres granulat 11 beholderen efter behov og opsmeltes. Énkrystallens vækst vedligeholdes nu i det væsentlige med smeltet granulat.The preparation of a single crystal begins by first melting in the container 1 a small amount of silicon and keeping it liquid. The rod 7 has no contact with the formed melting sea 17 at this stage. The rod is then driven downwards through the central opening 3 in the container and the inner coil of the draw coil, and in a known way the grafting is started, forming a drop of melt on the lower tip of the rod. of the draw coil 2 and a seed crystal is applied to this drop of melt. The rod currently has the function of the storage rod in the Fz method. Upon further melting of the rod and initial lowering of the graft crystal 25, a single crystalline initial cone is first formed with a melting mass of sufficient volume thereon. Then, the rod is displaced synchronously with the tensile coil so that the material melted in the container contacts the rod and liquid silicon can thus come along the rod to the melt neck 18 and thence to the melt mass 8 on the growing single crystal 9. During the further process of the process 30, granules are added. 11 the container as needed and melted. The growth of the single crystal is now maintained substantially with molten granules.

Størrelsen af den aksiale forskydning af beholderen 1 i forhold til opsmeltningsspolen 5 regulerer graden af smeltet granulats kobling til denne spoles HF-felt. Dermed og 35 med valget af HF-effekten kan granulatets opsmeltning påvirkes. En forskydning af beholderen i forhold til trækspolen kan også være fordelagtig for reguleringen. Bliver 5 DK 177587 B1 afstanden til trækspolen stor, sker der ikke længere nogen indkobling af energi nedefra i smeltesøen af smeltet granulat, og silicium fryser ud på bunden af beholderen. Modificeres trækspolens form endvidere, således at der dannes en udbugtning opad på fugtningssiden, hvor trækspolen grænser op til den med flydende silicium 5 fugtede stav, udfryser der på dette sted intet silicium på beholderens bund på grund af den lokalt højere energiindkobling. Det smeltede granulat kan derfor som hidtil løbe uforstyrret til smeltemassen, medens det smeltede granulats direkte berøringsflade med den af Si02 bestående beholderbund samtidig minimeres af laget af frosset silicium. Derved kan indføring af oxygen i smeltemassen og dannelsen af SiO 10 nedsættes i betydelig grad.The magnitude of the axial displacement of the container 1 relative to the melt coil 5 controls the degree of coupling of molten granules to the HF field of this coil. Thus, and with the choice of HF effect, the granulation's melting can be affected. A displacement of the container relative to the draw coil may also be advantageous for the regulation. If the distance to the traction coil becomes large, no energy is reduced from below in the melting lake of molten granules and silicon freezes on the bottom of the container. Furthermore, if the shape of the draw coil is modified so that a bulge is formed upwards on the wetting side, where the draw coil adjoins the rod with liquid silicon 5, at this point no silicon freezes on the bottom of the container due to the locally higher energy engagement. Therefore, the molten granule can, as heretofore, run undisturbed to the melt, while the direct contact surface of the molten granule with the SiO2 container bottom is simultaneously minimized by the layer of frozen silicon. Thereby, the introduction of oxygen into the melt and the formation of SiO 10 can be significantly reduced.

I indretningen ifølge figur 2 består beholderen 1 af en plade af silicium, der i centrum har en rørformig åbning 3, som dannes af et nedad trukket rørstykke 13. Pladen er lejret drejeligt, fortrinsvis på tre hjul 14, der støtter pladen ved randen, og som også 15 tjener til at drive drejningen. Pladen 1 og det formede rørstykke 13 beskyttes mod direkte indkobling af HF-feltet fra trækspolen 2 fra neden henholdsvis fra siden af en køleindretning 15, f.eks. en vandkølet metalplade, således at opsmeltning af undersiden af pladen 1 og ydersiden af rørstykket gennem trækspolen forhindres. Desuden virker metalpladen som varmesænkning, som fører den af opsmeltespolen 5 i pladen 20 dannede varme bort. Opsmeltespolen er anbragt over pladen. Den centrale åbning 3 i pladen og indersiden af det formede rørstykke 13 opvarmes af en yderligere energikilde, f.eks. en som linse 16 forenklet vist strålingsopvarmning for at hindre frysning af det til smeltemassen strømmende, smeltede granulat og af smeltehalsen 18, som dannes. Den termiske gradient, der opbygges i pladen og det formede rørstykke, 25 sikrer, at der på pladens overflade dannes en stabil smeltesø 17, og indersiden af rørstykket forbliver smelteflydende, medens pladens bund og det formede rørstykkes yderside forbliver faste. Rørstykket 13 er nedad fuldstændig lukket af flydende silicium i smeltehalsen 18. I den ved begyndende smeltning af pladens overside og ved smeltning af granulat dannede smeltesø stikker koncentriske kvartsringe 4, der ligesom i 30 udførelsesformen ifølge figur 1 definerer områder, der er således indbyrdes forbundet gennem åbninger 6, at der dannes en mæanderformig vej, som det smeltede granulat må overvinde, inden det kan komme til smeltemassen 8. Tilførselsindretningen 10 og afdækningerne 12 har samme funktion som i udførelsesformen ifølge figur 1. Desuden overtager den inderste afdækning ved en tilsvarende konstruktiv udformning den 35 funktion at hindre tilført granulat i at komme direkte ind i pladens indre område.In the device of Figure 2, the container 1 consists of a plate of silicon having in the center a tubular aperture 3 formed by a downwardly drawn pipe piece 13. The plate is rotatably mounted, preferably on three wheels 14 supporting the plate at the rim, and which also serves 15 to power the turn. The plate 1 and the shaped pipe piece 13 are protected against direct engagement of the HF field from the pull coil 2 from below or from the side respectively of a cooling device 15, e.g. a water-cooled metal plate so that melting of the underside of plate 1 and the outside of the pipe piece through the tensioning coil is prevented. In addition, the metal plate acts as a heat sink which dissipates the heat generated by the melting coil 5 in the plate 20. The melting coil is placed over the plate. The central aperture 3 in the plate and the inside of the shaped pipe piece 13 is heated by an additional energy source, e.g. a radiant heating shown as lens 16 to prevent freezing of the molten granules flowing to the melt and of the melt throat 18 which is formed. The thermal gradient built up in the plate and the formed pipe piece 25 ensures that a stable melting sea 17 is formed on the surface of the plate and the inside of the pipe piece remains melt-flowing, while the bottom of the plate and the outside of the shaped pipe piece remain solid. The downpiece 13 is completely completely closed down by liquid silicon in the melt neck 18. In the initial melting of the top surface of the plate and melting of granules melting concentric quartz rings 4 which, like in the embodiment according to Figure 1, define areas which are thus interconnected through orifices 6 to form a meander path which the molten granule must overcome before it can reach the melting mass 8. The feed device 10 and the covers 12 have the same function as in the embodiment of Figure 1. In addition, the inner cover takes over by a similar constructive design. the function of preventing added granules from entering directly into the inner region of the plate.

6 DK 177587 B16 DK 177587 B1

Indretningen ifølge figur 2 har den fordel, at kontaktarealet med kvarts og dermed indføringen af oxygen i smeltemassen 8 er yderligere nedsat, og at opsmeltningen af granulatet 11 og trækningen af énkrystallen er fuldstændig elektromagnetisk afkoblet. Derved kan trækspolen 2 optimeres alene med hensyn til trækprocessen. Også 5 reguleringen bliver mere stabil. Den indre smelteoverflade af smeltehalsen 18 ved enden af rørstykket 13 virker derudover som en barriere for enkelte, endnu ikke fuldstændig opsmeltede granulatkorn, da disse driver på overfladen, indtil de er opsmeltet.The device of Figure 2 has the advantage that the contact area with quartz and thus the introduction of oxygen into the melt mass 8 is further reduced and that the melting of the granulate 11 and the drawing of the single crystal is completely electromagnetically decoupled. Thereby the pull coil 2 can be optimized solely with respect to the pulling process. The regulation also becomes more stable. In addition, the inner melt surface of the melt neck 18 at the end of the pipe piece 13 acts as a barrier to some, not yet fully melted, granular grains as they drift on the surface until melted.

Det er næsten udelukket, at sådanne partikler kan nå til énkrystallens vækstfront og fremkalde forskydninger i krystalgitteret. En anden fordel består i, at rummet med den 10 voksende énkrystal 9 kan tætnes særdeles godt støvtæt mod rummet med pladen 1, da de to rum kun er forbundet med en snæver ringspalte mellem metalpladen 15 og pladen 1. Den støvtætte adskillelse af rummene kan yderligere forstærkes af et beskyttelsesskjold 19.It is almost impossible for such particles to reach the single-crystal growth front and cause displacements in the crystal lattice. Another advantage is that the space with the 10 growing single crystal 9 can be sealed very well against the space with the plate 1, since the two spaces are only connected by a narrow ring gap between the metal plate 15 and the plate 1. The dust-tight separation of the spaces can further reinforced by a protective shield 19.

15 Fremstillingen af en énkrystal begynder med, at der først smeltes et stykke ved rørstykkets nederste ende, og en podekrystal påsættes på den allerede beskrevne måde og trækkes til en konus. Et i rørstykket indsat stykke silicium eller den efter trækning af en i forvejen fremstillet énkrystal størknede smeltehals kan tjene som plombe. Plomben overtager i denne henseende funktionen af staven 7 i figur 1. Samtidig eller 20 derefter opsmeltes oversiderne af pladen 1 og af plomben i den rørformige centrumsåbning ved hjælp af opsmeltespolen 5 og strålingsopvarmningen 16, og mere smeltet materiale tilføres den voksende énkrystal. Med tiltagende smeltebehov tilføres derpå yderligere granulat, således at der dannes en stabil smeltesø på pladens overflade, fra hvilken der foregår en kontinuerlig, styrbar smeltemassetilstrømning til smeltemassen 25 på den voksende énkrystal.The preparation of a single crystal begins by first melting a piece at the bottom end of the pipe piece and applying a seed crystal in the manner already described and drawing to a cone. A piece of silicon inserted in the tube or the melting neck of a pre-formed single crystal solidified after drawing can serve as a seal. In this regard, the seal assumes the function of the rod 7 of Figure 1. Simultaneously or thereafter, the upper sides of the plate 1 and of the seal are melted in the tubular center opening by the melt coil 5 and the radiant heating 16, and more molten material is supplied to the growing single crystal. With increasing melting requirements, additional granules are then added to form a stable melting lake on the surface of the plate, from which there is a continuous controllable melt flow to the melting mass 25 of the growing single crystal.

I indretningen ifølge figur 3, som ligner indretningen ifølge figur 2, er der helt givet afkald på kvartsvægge, som står i kontakt med smeltesøen, således at der ikke sker nogen oxygendotering af énkrystallen eller SiO-dannelse. I stedet er opsmeltespolen 5 30 således udformet i området over den rørformige åbnings rand, at der på overfladen af pladen 1 opstår en forhøjning 20, som danner en barriere. Føres opsmeltespolen nærmere til smeltesøen eller forøges HF-effekten, fortrænges smeltet materiale af den frastødende elektromagnetiske kraftvirkning og strømmer over barrieren ned i den rørformige åbning 3. Ved tilstrækkelig forhøjelse af barrieren kan granulatkorn, der endnu 35 ikke er helt smeltede, ikke overvinde barrieren på grund af tyngdekraftens virkning. Barrieren virker altså som et filter, der tilbageholder fast halvledermateriale. Opsmelte- 7 DK 177587 B1 spolen kan naturligvis være udformet således, at der dannes flere, efter hinanden stillede barrierer på pladen.In the device of Figure 3, which is similar to the device of Figure 2, quartz walls which are in contact with the melting lake are completely dispensed with so that no oxygen doping of the single crystal or SiO formation occurs. Instead, the melting coil 5 30 is formed in the region above the tubular opening rim so that on the surface of the plate 1 there is an elevation 20 which forms a barrier. As the melting coil is brought closer to the melting lake or the HF effect is increased, the molten material is displaced by the repulsive electromagnetic force effect and flows over the barrier into the tubular opening 3. By sufficiently raising the barrier, granules that are not yet fully melted cannot overcome the barrier of because of the effect of gravity. The barrier thus acts as a filter that retains solid semiconductor material. The molten coil may, of course, be designed so as to form multiple, barred, barriers on the plate.

Fremstillingen af en énkrystal sker analogt med den allerede for udførelsesformen 5 ifølge figur 2 beskrevne fremgangsmåde.The preparation of a single crystal takes place analogously to the method already described for the embodiment 5 according to Figure 2.

I indretningen ifølge figur 2 er de koncentriske kvartsvægge i indretningen ifølge figur 2 erstattet med faste mellemstykker 21 af silicium, som rager op fra overfladen af pladen 1. De enkelte viklinger på afsmeltespolen 5 er indadtil trukket forholdsvis langt fra 10 hinanden, således at pladen ikke smeltes op mellem viklingerne, og mellemstykkerne bliver tilbage. Dér, hvor opsmeltespolens viklinger er ført sammen med forbindelsesstykker, afsmeltes mellemstykkerne dog, således at åbningerne 6 mellem de af mellemstykkerne adskilte områder åbner en mæanderformig vej, som det smeltende granulat 11 må overvinde for at nå til smeltemassen 8 på den voksende énkrystal 9.In the device of Figure 2, the concentric quartz walls of the device of Figure 2 have been replaced by solid silicon spacers 21 which protrude from the surface of the plate 1. The individual windings on the melting coil 5 are drawn inward relatively far from each other, so that the plate does not fused up between the windings and the intermediate pieces remaining. However, where the coils of the melt coil are joined together with connecting pieces, the intermediates are melted, so that the openings 6 between the regions separated by the intermediate pieces open a meandering path which the melting granule 11 must overcome to reach the melting mass 8 on the growing single crystal 9.

15 Drejes pladen langsomt, smelter et mellemstykke af, så snart det kommer ind i et forbindelsesstykkes indflydelsesområde. Samtidig genopbygges mellemstykket igen dér, hvor smeltet materiale fjernes fra forbindelsesstykkets indflydelsesområde. I dette tilfælde krummer det smeltede materiale, som befinder sig på pladen mellem opsmeltespolens fra hinanden trukne viklinger, på grund af den dér forholdsvis svage 20 elektromagnetiske kraftvirkning opad og størkner endelig igen.15 Turn the plate slowly, melting a middle piece as soon as it enters the influence area of a connecting piece. At the same time, the spacer is rebuilt again where molten material is removed from the influence of the connector. In this case, the molten material which is on the plate between the coils of the melt coil curves due to the relatively weak electromagnetic force effect up there and finally solidifies again.

En hensigtsmæssigt udformet opsmeltespole er illustreret i figur 5. Den har flere koncentriske viklinger 22, idet afstandene mellem de indre viklinger er større end afstandene mellem de ydre viklinger. Viklingerne er forbundet med hinanden gennem 25 forbindelsesstykker 23. De skraverede arealer mellem de længere fra hinanden liggende viklinger antyder tilstedeværende mellemstykker 21.An appropriately designed melt coil is illustrated in Figure 5. It has several concentric windings 22, the distances between the inner windings being greater than the distances between the outer windings. The windings are connected to each other through 25 connecting pieces 23. The shaded areas between the further apart windings indicate the intermediate pieces 21 present.

Anvendelsen af en indretning ifølge figur 4 foretrækkes især, da enhver kontakt mellem smeltet materiale og kvartsdele undgås, og en lang mæanderformig vej kan 30 realiseres, som med sikkerhed hindrer indføring af endnu ikke fuldstændig smeltet granulat i smeltemassen på den voksende énkrystal. Opdeles opsmeltespolen i en spole til det ydre område, i hvilket granulat indføres, og en spole til udformning af den mæanderformige vej, så kan smeltestrømmen styres og reguleres uafhængigt af granulatets opsmeltning. Dette er særlig fordelagtigt ved den vanskelige trækfase 35 under opbygningen af konus.The use of a device according to Figure 4 is particularly preferred, as any contact between molten material and quartz parts is avoided and a long meandering path can be realized which certainly prevents the introduction of not yet fully molten granulate into the melt of the growing single crystal. If the melting coil is divided into a coil for the outer region into which granules are introduced and a coil for forming the meander path, the melt flow can be controlled and controlled independently of the melting of the granulate. This is particularly advantageous in the difficult tensile phase 35 during cone build-up.

8 DK 177587 B18 DK 177587 B1

Fremstillingen af en énkrystal sker analogt med den allerede for udførelsesformen ifølge figur 2 beskrevne fremgangsmåde.The preparation of a single crystal takes place analogously to the method already described for the embodiment of Figure 2.

Med den omhandlede fremgangsmåde fremstillede énkrystaller af silicium gør halv-5 lederskiver tilgængelige, hvis defektegenskaber er særlig fordelagtige. De indgroede defekter er selv ved oxygenkoncentrationer på 3-9*1017 cm'3, fortrinsvis 4-8,5*1017 cm 3 og især 4,5-8*1017 cm'3 mindre end 60 nm og derfor enkle at fjerne ved varmebehandlinger, i det mindste i de områder, hvor de kan forstyrre elektroniske konstruktionsdele. Til yderligere formindskelse af defekternes størrelse og til 10 stimulering af en oxygenfældning er det derudover fordelagtigt yderligere at dotere énkrystallen med nitrogen. En nitrogenkoncentration på 1*1013-6*1015, fortrinsvis 1*1014-4*1015, er hensigtsmæssig.The silicon single crystals produced by the process of the invention make half-conductor discs available, whose defect properties are particularly advantageous. The ingrown defects are even at oxygen concentrations of 3-9 * 1017 cm 3, preferably 4-8.5 * 1017 cm 3 and especially 4.5-8 * 1017 cm 3 less than 60 nm and therefore easy to remove by heat treatments , at least in the areas where they may interfere with electronic components. In addition, for further reducing the size of the defects and for stimulating an oxygen precipitation, it is advantageous to further dop the single crystal with nitrogen. A nitrogen concentration of 1 * 1013-6 * 1015, preferably 1 * 1014-4 * 1015, is appropriate.

Claims

A method of producing a single crystal of semiconductor material in which portions of a melt held by a tensile coil disposed above the melt are solidified on a seed crystal to form the growing single crystal and granulate is melted in a central opening container for maintaining the growth of the single crystal, characterized in that the granulate is inductively melted by a melting coil disposed above the melting granule and the melting granule is delayed to the melting mass.

Process according to claim 1, characterized in that the melting granulate is fed to the melting mass through a duct system.

Process according to claim 2, characterized in that the melting granulate is fed to the melting mass through a mean-shaped channel system.

Process according to one of claims 1 to 3, characterized in that the melting granule must overcome at least one barrier on the way to the melting mass.

Method according to one of Claims 1 to 4, characterized in that the melting granule must travel a distance of at least 25 mm before reaching the melting mass.

Process according to one of claims 1 to 5, characterized in that the granulate is completely melted to the melt.

Process according to one of Claims 1 to 6, characterized in that the melting of the granulate and the maintenance of the melting mass in liquid state take place by inductive energy supply, the two processes being inductively decoupled.

Process according to one of Claims 1 to 7, characterized in that the granulate is melted in an outer region of a container disposed over the growing single crystal and is led to a central opening in the container and thence to the melt.

An apparatus for producing a single crystal having a container placed above the growing single crystal and a transport device for supplying granules to the container and a melting coil for melting the granulate and a tensile coil disposed above the melting mass for holding a melting mass thereon. growing single crystal, the melting granule passing through openings in the container and the draw coil to the melt to form a melt neck, and solidifying portions of the melt maintaining the growth of the single crystal, characterized in that the melt coil is disposed above the melting granule and the container has a which delays the conduction of the melting granule to the melt.

9 DK 177587 B1

Apparatus according to claim 9, characterized by a protective shield, which dust-tightly separates a space around the container from a space around the growing single crystal.

Method according to Claim 9 or Claim 10, characterized by coverings placed over the melting coil and which the granulate strikes upon delivery to the container.

Apparatus according to one of claims 9 to 11, characterized by a device for cooling the container.

Apparatus according to claim 12, characterized by a water-cooled metal plate which is separated from the container by a narrow gap, thereby effecting radiation and convection cooling.

Apparatus according to claim 9, characterized in that the container is rotatably rotated about a axis of rotation and consists of quartz and has walls of quartz which divide the inner space of the container into concentric areas, these areas being interconnected and forming a duct system. which the melting granule must overcome before it can reach the melting mass between the opening in the container and a rod of semiconductor material protruding through the opening.

Apparatus according to claim 14, characterized in that the axis of rotation of the container is tilted at an angle a.

Apparatus according to claim 9, characterized in that the container consists of a plate of coolable semiconductor material and quartz walls which divide the inner space of the container into concentric areas, these areas being interconnected and forming a duct system. which the melting granule must overcome before it can reach the melting mass through the opening in the container which is designed as a pipe piece, and that there is a radiant heating for heating a surface of the melt neck and of semiconductor material flowing through the pipe piece.

Apparatus according to claim 9, characterized in that the container consists of a plate of semiconductor material which can be cooled and limited by an outer rim, and the opening of the container is formed as a downwardly directed pipe piece which is connected to the raised inner edge of the plate. the inner edge of the plate forming a barrier which the molten granule must overcome before it can reach the melt mass through the opening in the container and a radiant heating is present for heating a surface of the melt neck and of the semiconductor material flowing through the pipe piece.

Apparatus according to claim 9, characterized in that the container is rotatably rotated about an axis of rotation and consists of a plate of semiconductor material which can be cooled and has spacers still melting under the influence of the heating coil and the rotation of the container and divides the inner space of the container. areas, these areas being interconnected and forming a duct system which the melting granule must overcome before it can reach the melt through the aperture in the tubular-shaped container and radiant heating is present to heat a surface of the melt neck and of the semiconductor material flowing through the tube.