DE1901752C3 - Process for growing silicon single crystals on a substrate - Google Patents

Description

In the fabrication of integrated circuits with silicon it is because of the formation of the matrix It is necessary that the substrate consists of a single crystal. For this it is necessary to use a single crystal plate to grow and then to divide this into a number of single crystal substrates by special means, what It is a relatively expensive method, but it provides a »single crystal substrate

However, since only a small part of the total area of the substrate is used for integrated circuits can, the growth of a single crystal substrate leads to a significantly larger consumption of silicon than actually needed to form the integrated circuit.

In addition, in forming various integrated circuits in the substrate, it is necessary that these circuits are also electrically isolated from one another. This happens e.g. B. also with the help of PN junctions or by using dielectric materials.

To resolve the existing difficulties in order to achieve a substantial reduction in manufacturing costs and in order to achieve a considerable saving in unused silicon in integrated semiconductor circuits arrive, is the underlying task of the invention.

From an article titled "New Mechanism Used to Grow Crystals" in the journal Chem. And Engng. News 42 (1964), No. 11, pp. 48 and 49, has become known that crystal growth in a vapor-liquid-solid mechanism occurs when a droplet of a saturated solution of a crystalline material plus an admixture of gold, ie a Droplets of a liquid Au-Si alloy, silicon atoms from a silicon tetrachloride vapor and if these atoms can be deposited between said liquid droplets from a crystalline silicon substrate. According to the publication mentioned, the droplet is possibly a catalyst for the reaction. The known process is used to produce almost perfect silicon crystals at temperatures which are considerably lower than the growth temperatures of around 1200 ^° C. of the conventional processes.

For a method for growing silicon single crystals on a substrate, wherein in cylindrical recesses of the substrate drops of metals, the Form alloys with silicon, melted and the vapor of a silicon compound, which at the melting temperature capable of reacting to silicon, is exposed to the solution of those discussed above

S problems with the invention are that the substrate is ceramic and the alloy metal is gold, tin, zinc or indium at temperatures above the eutectic point of the silicon alloy and below the Silicon melting point and with a temperature gradient at the alloy plug of > 50 ° C · cm ~ 'can be used.

This method leads to a selective growth of discrete single crystals of dielectric Material. The requirement of breeding a

Is single crystal substrate consists in advantageous Orphan no more. There is also no need to use special, electrically insulating integrated circuits in the invention, because the discrete single crystals of silicon because of the special substrate material are separated from each other. This substrate material can be polycrystalline or amorphous.

The invention is hereinafter based on the schematic Drawings for an example embodiment explained in more detail

Fig. 1 is a schematic representation of an apparatus for performing the method according to Invention.

Fig. 2 is a phase diagram of the gold-silicon system.

Fig. 3 is an enlarged sectional view of a Part of a non-monocrystalline substrate with in Depressions inlaid gold balls.

Figure 4 is an enlarged cross-sectional view of a portion of the non-monocrystalline substrate of Figure 4. 3, single crystal parts have grown.

F i g. 5 is a perspective view, partly in section, of the non-monocrystalline substrate of FIG 3 and 4 with silicon crystal parts, the upper Surface parts have this plane like the upper surface of the non-monocrystalline substrate.

The in Fi g. 1 shown device for implementation of the method according to the invention contains a reaction tube 10, which is preferably made of quartz. In the pipe 10 is through the inlet pipe U that

Reaction mixture introduced and through the outlet pipe

12 discharged The outlet pipe 12 is located on

End part 14, which is the open end of the tube 10

closes

Inside the tube 10 is a non-monocrystalline

so substrate 15 is introduced, which is on a holder 16 The holder 16 is connected to a handle 17 that extends outwards. The handle 17 is passed through the end member 14 so that the position of the substrate 15 within the tube 10

ss can set.

The holder 16 and the handle 17 are made of a material which is chemically with all elements inside the tube 10 and does not react with the gases and vapors flowing through the holder 16 and the handle 17 can, for. B. made of quartz, aluminum or a suitable coated graphite. The substrate body 15 carried by the holder 16 rests advantageously on a block 18, which has the effect of a Has thermal conductor. The block 18 consists of a material which chemically interacts with the through the pipe 10 flowing vapors does not respond. The block 18 could be made of silicon or a suitably coated one Graphite, for example, are made of.

3 4

The substrate 15 is made of ceramic material, outlet pipe 12 flow out and when passing through the

e.g. aluminum oxide and silicon dioxide, also clean the system,

the substrate could be a mixed oxide ceramic, e.g. After the cleaning process with helium, that became

a mixture of oxides of aluminum, silicon valve 30 closed and valve 26 opened so that

Zirconium, calcium, strontium, barium, titanium and iron, 5 the flow of helium has been stopped and hydrogen is removed from the

and be magnesium. Source 25 outflow at a predetermined speed

The substrate 15 contains according to FIG. 3 could be a number of men. Depressions 19 formed in a surface of 15 Then the heating elements 21 to 23 were in operation

are and soft to accommodate metallic balls 20 taken to create a temperature gradient on the spherical

to serve. They are made of gold, tin, zinc or indium. io gene body 20 to produce. This gradient runs in

The tube 10 includes on its upper surface a substantially perpendicular to the surface of the substrate Heating element 21 and on its lower surface a 15. The temperature at the bottom of the spherical body 20 Heating element 22. The heating elements 21 and 22 are measured at about 1063 ^° C .; that is the melting point of

preferably separately from each other. Each of the named- gold

th heating elements can be precisely controlled. 15 Then the valve 28 was opened so that

Above the heating element 21 is also a separate tetrachlorosilane in the manifold 24 with the Heating element 23 arranged. The heating element 23 can flow in hydrogen from the source 25. the

an infrared heater or other radiant heater Valves 26 and 28 were adjusted so that the

be. The heating elements 23 can also be used as the electrical molar ratio of the tetrachlorosilane to the hydrogen

Wires wound around a semi-cylindrical tube. 20 was 0.001. The flow of gases with the The flow of gas and steam through the 0.001 molar ratio took 30 minutes. Einiaßrofir 11 into the interior of the tube 10 takes place above. Thereafter, the temperature was? Bottom of

a Ansauge-manifold 24. This Ansauge- spherical body 20 is reduced to 950 ⁰ C, and the

Manifold 24 is connected to a source 25 for molar ratio by regulating the accordingly Hydrogen connected via valve 26. With the 25 valves 26 and 28 increased to 0.02 this response was At valve 26 the flow of hydrogen from source 25 is continued for about an hour and a half Manifold 24 adjustable. During this time, a silicon single crystal was from The suction manifold 24 is also connected to a lower portion of each of the gold bodies 20 through the body Source 27 connected. This supplies the vapor of the 20 and is bred out to the top Silicon compound. The source 27 can e.g. B. a silane 3 ° After this period of time the valve became 28

contain, including, for example, tetrachlorosilane (SiCU) closed to the soot of the tetrachlorosilane

The gas or steam flow from the source 27 in stopping. The flow of hydrogen was however for

manifold 24 is continued through valve 28 for a sufficient period of time to allow the

adjustable. Clean system. Then the electric

The hydrogen serves both as a carrier for the heating elements 21 to 23 switched off and the substrate 15 Tetrachlorosilane as well as a reactant therefor. removed from the tube 10 The intake manifold 24 is also provided with an according to FIG. 2 the reaction will be at temperature Source 29 of an inert gas, e.g. B. helium connected. continued from 1063 ° C until a point 31 is reached

The flow of the inert gas from the source 29 into the. The point 31 indicates an alloy that iinen Pipe branch 24 can be regulated by a valve 30. 40 has a greater silicon percentage than in the point

The inert gas acts like a cleaning agent for the 32nd at point 32 is the composition of the silicon Inside the tube 10. at a temperature of 95O ⁰ C. The depressions 19 in the substrate 15 have when the temperature at the bottom of the spherical The cylindrical shape with a diameter of twelve bodies 20 ^{has decreased to 95O 0} C, the Thousands and a depth of five to ten 45 percent silicon in the gold body 20 to Thousands of a meter. The balls 20 are in execution points 33 to. At this point the temperature becomes

example made of gold and had a diameter of 950 ^° C. at the bottom of the spherical body 20

ten thousandths of a meter. The spherical bodies 20 are when the silicon concentration in the body 20 den

flattened on its upper surface and reached at point 34, the body 20 is made of silicon substantially parallel with the surface of the substrate so saturated a continuation of the introduction of silicon

15, in which the recesses 19 are formed. You in the body 20 from the vapor phase leads to a

can extend outward beyond the surface with supersaturation of the body 20 with silicon, so that the

extend a distance which is not greater than the condition for nucleation of silicon is created

Radius of the spherical body 20. This is between the bottom of the body 20 and the substrate interaction ensured between the wall 5 $ 15 is the supersaturation for a Siliciumkeimbil-

the recess 19 and the spherical body 20, so that manure is necessary, significantly lower than that for

any vapor flow therebetween to the bottom of the well nucleation of solid silicon by nucleation in the

19 is limited. Body 20 required.

In one experimental design, the block 18 consisted of once nucleation has taken place becomes silicon, while the holder 16 and its handle 17 were made of quartz through the growth of the crystal from the vapor phase. The diameter in the liquid solution with the help of the temperature inside the tube was about 25 mm. Controlled according to the gradient. Of course, it is necessary that the introduction of the substrate 15 into the tube 10 and after the lowest temperature of the body 20 is greater than the closing of the open end 14 of the tube 10, due to the eutectic temperature (about 300 ⁰ C) of the interconnection of the substrate 15 was introduced, the 6j composition.

Valve 30 opened so that the inert gas helium from the ways of the high contact angle between the Source 29 into the interior of the tube 10 via the body 20 and the bottom of the recess 19 Inlet pipe 11 flowed in. The gas could also localize the nucleation and thus the

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Number of nuclei that form on substrate 15 want reduced. The high created by the body 20; Contact angle ensures nucleation takes place on the lower part of the body 20.

The final crystal of silicon has about 0.0001 percent gold under the above conditions. This Gold content may be desirable, e.g. B. the carrier lifetime to limit.

The temperature at the lower part of the gold body 20 could be any value above the eutectic temperature of the gold-silicon alloy and below the melting point of silicon, e.g. B. between 600 ⁰ C and 1200 ⁰ C. Furthermore, the temperature gradient! ^{be greater than 50 0} C per centimeter of vertical displacement on the gold body 20. With this temperature gradient, the flow rate of hydrogen through the tube 10 in front of the substrate 15 is about one liter per minute.

In Fig. 4 is the substrate 15 with silicon single crystals 35 These crises 35 are from the Guiukürpci i'i 20 grown. You have parts 36 in the upper area, which consist of a silicon-gold alloy. That Growing of the Eink / istallteile 35 therefore stops when the upper parts of the crystal parts 35 are above the upper part of the substrate 15. At this point it is required to remove the part 36 from each of the single crystal parts 35 with the silicon-gold alloy. the The silicon-gold alloy can be removed mechanically or with the aid of chemicals Means done. In the case of mechanical means, the abrasion method could be used. at Chemical agents could use mercury, with which the gold is formed Amalgam reacts. When the upper surface of the single crystal pieces 35 is required to be in the same plane with the top surface of the substrate, as in Fig.5 As shown, it would be necessary to place all of the silicon over the top surface of the substrate 15 to remove. You could do this e.g. B. can be achieved by polishing. It is of course not necessary that the upper surface of the single crystal parts 35 in the same plane with the upper surface of the substrate 15 lies if one wanted to form integrated circuits there.

The substrate body 15 shown in Figure 5 contains Single crystal parts 35 whose protruding parts are removed. The single crystals 35 are in the embodiment according to FIG. 5 produced only as silicon single crystals with a small amount of gold. With the top Surface of each of the elements 35 in the same plane with the upper surface of the substrate 15 are the various members 35 are electrically isolated from one another in the substrate 15 and form separate islands. Accordingly the method according to the invention provides a product in which monolithic integrated circuits in each of the single crystal members 35 isolated from each other in the substrate 15 are formed can. That is, each of the single crystals 35 is able to to include a monolithic integrated circuit.

While in the example used, the block 18 consists of silicon and is effective for extracting heat, it would also be possible for the silicon crystals to grow in the substrate 15 without the heat extraction member can. However, a larger amount of supplied tub from the heating element 23 is required to the to achieve the desired temperature gradient on the body 20.

Instead of tetrachlorosilane, monosilane (SiH ₄ ) can be used

are set, in which case the hydrogen from the source 25 would not be necessary. Instead of before Helium gas from source 29 could be used as the carrier gas monosilane.

Comparative example 1

A tube made of quartz with a diameter of 25 millimeters! was placed in an oven. Around 72 mm long semi-cylindrical tube was wound on a heating coil

jo This auxiliary heater was located directly on the pipe over the place of the introduced substrate. The oven could be brought to 800 ° C. Through the Auxiliary heating could be adjusted to higher temperatures in the furnace.

The pipe had a simple gas-mixing pipe branch for the introduction of the desired gases ir the pipe. This branch pipe was in a line for the introduction of the pure hydrogen odei Heliums and in a second line for the introduction

UCS ι cn aniline uaiitliia in ciuci tjamguiig uci civra at ν.

set up.

Before being deposited on the substrate, hydrogen was passed through at a rate of one liter per minute. The tube was with platinum unc ₂ j 10% Rhodium thickness of one centimeter coated, the substrate consisted of a lameliierten polykristal linem material because: s on a thick Siliciumklot; was upset. The substrate was very close to the upper one. Surface of the reactor tube and dense type auxiliary heater. The temperature gradient was controlled with the aid of two thermocouples. The substrate was placed on a thick lump of silicon which acted as a heat sink.

The substrate, which consists of a mixed ceramic

See oxide was about 1 cm in size and about 1 mm thick. The substrate was specially mi four-cylindrical holes provided. The diameter!

the holes was 0.30 mm. The depth of the hole differs 0.125 mm to 0.25 mm. These holes were located near the center of the substrate.

The gold corpse, which has a diameter in front 0.25 mm were placed in each of the holes. The bodies were made of 99.99% pure gold.

The substrate with the four gold balls was then ii

a hydrogen flow of one liter per minute

Speed heated. When heating were both Heater used for an hour at one Temperature of 950 ⁰ C. The thermocouples were located

under the quartz holder of the substrate. De

jo temperature gradient was 8 ⁰ C · cm- '.

Tetrachlorosilane was then introduced into the tube and increased to 0.05 mole percent over thirty minutes The concentration of the tetrachlorosilane was then increased to 2 mole percent for two hours Reference temperature of 950 ° C was maintained over the duration of the entire process.

The resulting material in this example was high polycrystalline silicon.

. Comparative example II

All parameters from Comparative Example I were also used here, with the exception that the reference temperature was set at 1050 ° C and the temperature gradient was set at 16 ° C · cm- '. The temperature at the lower thermocouple was 1050 ^° C. As in the case of Comparative Example I, here too the material produced in all holes was highly polycrystalline: silicon.

752

example

Il

19 Ol

Example I.

All parameters of Comparative Example I were adhered to here, too, with the exception that the temperature gradient was about 100 ° C · cm- '. In

three out of four holes were silicon ^{single crystals 5 about 100 0} C · cm-'. The temperature at the bottom bred. In the fourth hole was a three-grain one
Silicon crystal grown.

All parameters from Comparative Example I have been adopted here, with the exception that the Reference temperature 1050 ° and the temperature gradient

Thermocouple was 1050 ° C. Silicon single crystals were grown in all four holes.

1 sheet of drawings

Claims (1)

Claim; Process for growing silicon single crystals on a substrate, with drops of metals in cylindrical recesses of the substrate, which form alloys with silicon, melted and the vapor of a silicon compound which at capable of reacting to the melting temperature to form silicon, characterized in that, that as substrate (15) ceramic materials and as alloy metal gold, tin, zinc or indium at temperatures above the eutectic point of the silicon alloy and below the Silicon melting point and at a temperature gradient on the alloy drop of> 50 ° C · cm-'.