DE1901752B2 - METHOD OF GROWING SILICON SINGLE CRYSTALS ON A SUBSTRATE - Google Patents

Description

20th

In the manufacture of integrated circuits with silicon, it is necessary because of the formation of the matrix, that the substrate consists of a single crystal. To do this, it is necessary to grow a single crystal wafer and then use special means to divide it into a number of single crystal substrates, which 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 waxes in a vapor-liquid-solid mechanism come about when a droplet of a saturated solution of a crystalline material plus an admixture of gold, ie a droplet 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 method 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 methods.

For a method for growing silicon single crystals on a substrate, wherein in cylindrical recesses of the substrate drops of metals, the with silicon to form alloys, 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 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 drop 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 In this case, single crystal substrate no longer exists in an advantageous manner. Also the use of special, electrically insulating integrated circuits are omitted in the invention, since the discrete single crystals Silicon are already separated from each other because of the special substrate material. This substrate material can be polycrystalline or amorphous.

The invention is explained in more detail below with reference to the schematic drawings for an exemplary embodiment.

F i g. 1 is a schematic representation of an apparatus for carrying out the method according to FIG Invention.

F i g. Figure 2 is a phase diagram of the gold-silicon system.

Fig. 3 is an enlarged sectional view of a portion 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 of which have the same plane as the upper surface of the non-monocrystalline substrate.

The in F i g. 1 shown apparatus for performing the method according to the invention contains a Reaction tube 10, which is preferably made of quartz. In the tube 10 is through the inlet tube 11 Introduced reaction mixture and discharged through the outlet pipe 12. The outlet pipe 12 is located on Closing part 14 which closes the open end of the tube 10

A non-monocrystalline substrate 15, which is located on a holder 16, is introduced into the interior of the tube 10 is located. The holder 16 is connected to a handle 17 which is led to the outside. The handle 17 is passed through the end member 14 so that the position of the substrate 15 within the tube 10 can adjust.

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 The block 18 consists of a material which chemically interacts with the through the pipe 10 flowing vapors does not react. The block 18 could be made of silicon or a suitably coated one Graphite, for example, are made of.

I.

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. B. 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, stronuum, barium, titanium and iron, 5 the flow of helium has been stopped and hydrogen is removed from the

iind be magnesium. Source 25 outflow at a predetermined speed

The substrate contains i5 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 which are taken to accommodate metallic balls 20 in order 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. Heating elements 21 and 22 are was about 1063 ° C; that is the melting point of

preferably separately from each other. Each of the called- gold,

th heating elements can be precisely controlled. , _S, the valve 28 was opened Thereafter, so that

About 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

It took thirty minutes for the gas and steam to flow through the 0.001 molar ratio.

Inlet pipe 11 into the interior of the pipe 10 is via. Thereafter, the temperature at the bottom of the

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

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 reaction 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 30 After this period of time the valve became 28

contain, including, for example, tetrachlorosilane (SiCl ₄ ) closed to the flow of tetrachlorosilane

heard. Stop the flow of gas or steam from the source 27 in. 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 ⁰ C until a point 31 is reached.

The flow of the inert gas from the source 29 into the. The point 3t indicates an alloy which has a

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 950 ° C.

The depressions 19 in the substrate 15 have when the temperature at the bottom of the spherical

Cylindrical shape with a diameter of twelve bodies 20 ^{has decreased to 950 0} C, takes 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

saturated substantially parallel to the surface of the substrate 50. A continuation of the introduction of silicon

S5, 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 an intermediate between the bottom of the body 20 and the substrate

Cooperation ensured between the wall 55 15 is the supersaturation, which is necessary for a Siliciumkeimbil-

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

any vapor flow between them to the bottom of the well. Solid silicon nuclei 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 65 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 U 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 contact angle created by the body 20 ensures that 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. to limit the carrier life.

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 on the gold body 20 must be greater than 50 ⁰ C per centimeter of vertical displacement. With this temperature gradient, the flow rate of the 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 shown. These crystals 35 have grown from the gold bodies 20. You have parts 36 in the upper area, which consist of a silicon-gold alloy. That Growing of the single crystal parts 35 therefore stops when the upper parts of the crystal parts 35 above the upper part of the substrate 15 are. At this time, it is necessary to remove the part 36 of each of the single crystal parts 35 with the silicon-gold alloy to remove. The removal of the silicon-gold alloy can be based on be done mechanically or with the aid of chemical means. In the case of mechanical means the method of rubbing could be used. With the use of chemical agents one could get mercury with which the gold reacts to form amalgam. If it is required that the upper Surface of the single crystal parts 35 in the same plane with the upper 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. This could be achieved, for example, 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 115 lies if one wanted to form integrated circuits there.

The substrate body 15 shown in Figure 5 contains single crystal parts 35, the protruding parts of which have been removed. In the embodiment according to FIG. 5, the single crystals 35 are produced only as silicon single crystals with a small amount of gold separated and form separate islands. Accordingly, the method of the invention provides a product in which monolithic integrated circuits can be formed in each of the single crystal members 35 which are isolated from each other in the substrate IS. That is, each of the single crystals 33 is capable of accommodating a monolithic integrated circuit. While in the example used the block 18 consists of silicon and is effective as heat extraction, it would also be possible that the silicon crystals can grow in the substrate 13 without the heat extraction element. Anyway, a larger amount of supplied heat from the heating element 23 is required in order to obtain the desired temperature gradient on the body 20. "" ■■■ · ^ ' ^! ί ^; , ^Vl . "v; ■ * ■ '■ <■ - ■■ ■ ü Instead of tetrachlorosllane, monosllane (SiHO are set, in which case the hydrogen from the source 25 would not be necessary. Instead of Helium gas from source 29 could be used as the carrier gas monosilane.

Comparative example I.

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

This auxiliary heating was located on the pipe directly above the point of the introduced substrate. The furnace was brought up to 800 ⁰ C. The auxiliary heating made it possible to regulate higher temperatures in the furnace.

The pipe had a simple gas-mixing manifold for introducing the desired gases into it the pipe. This branch pipe was in a line for the introduction of pure hydrogen or Heliums and in a second line for the introduction of the tetrachlorosilane in a saturation at about 24 ° C set up.

Before being deposited on the substrate, hydrogen was released at a rate of one liter passed per minute. The tube was with platinum and 10% rhodium coated one centimeter thick. The substrate consisted of a laminated polycrystalline material on a thick block of silicon was upset. The substrate was very close to and close to the top surface of the reactor tube

Auxiliary heater. The temperature gradient was using

controlled by two thermocouples. The substrate was put on a thick lump of silicon, which functioned as a heat drain.

The substrate, which consists of a mixed ceramic

See oxide was about 1 cm ² and about 1 mm thick. The substrate was specially provided with four cylindrical holes. The diameter of the holes was 0.30 mm. The depth of the hole was 0.125 mm to 0.25 mm. These holes were in near the center of the substrate.

The gold bodies, which were 0.25 mm in diameter, 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 in

heated to a flow of hydrogen at a rate of one liter per minute. Both heaters were used for heating, namely for one hour at a temperature of 95O ⁰ C. The thermocouples were located under the quartz holder of the substrate. Of the

The temperature gradient was 8 ^° C · cm- '.

Tetrachlorosilane was then introduced into the tube and held at 0.C3 mole percent for thirty minutes. The! Concentration of the TetraChlorosUah would? Da1 | '"- two ^ hours on H MolpfozenWerliöhtr" ¹ ^

the for

Reference temperature of 950 «? C would practice the building; \ Overall process kept. ■ ^ V " ^ m- ^ sW ^ mrS - < The resulting material was insoluble, high-polycrystalline silicon.""

Comparative _BelspleUl, all parameters from comparative example 1 were also adhered to here, but with the exception; that dl | Reference temperature to 105Ö ^e C and the Temperatiir ^ serves to 1 $ · G ;. cm- 'was set. DleftfriperÄ |

at the lower thermocouple was 1050 ° OT

In the case of the comparison game I, it was also St. "_" Material produced in all holes with high polycrystalline silicon. ™ ·. <■,.,.-.- ,,,,. ^.

(i

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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- '. Silicon single crystals became in three out of four holes bred. A three-grain silicon crystal had grown in the fourth hole.

example

Il

All parameters from the comparative example are taken over here, but with one exception Reference temperature was 1050 ° and the temperature was about 100 ° C · cm- '. The temperature on Thermocouple was 1050 ° C. Silicon single crystals grown in all four holes.

1 sheet of drawings

Claims (1)

19 Oi Claim: Method for growing silicon single crystals on a substrate, wherein in cylindrical S Depressions in the substrate melted drops of metals that form alloys with silicon and the vapor of a silicon compound, which reacts to form silicon at the melting temperature capable of being exposed, characterized in that the substrate (15) is ceramic materials and as alloy metal gold, tin, zinc or indium at temperatures above the eutectic point the silicon alloy and below the silicon melting point and at a temperature gradient on the alloy drop of> 50 ° C · cm-'.