JPH08119616A - Formation of silicon carbide thin-film - Google Patents

Abstract

PURPOSE: To prepare a high-quality silicon carbide thin-film of an arbitrary shape by applying a polysilane polymer contg. silicon atoms on a thin film of a metal having dehydrogenation action and carrying out firing. CONSTITUTION: The surface of a silicon wafer 1 is coated with an oxidized film 2, a palladium thin film 3 is vapor-deposited on the oxidized film 2 and a polysilane polymer [Ib] layer 4 is formed on the palladium film 3. After drying, a palladium thin film 5 is further vapor-deposited on the polysilane polymer [Ib] layer 4 and they are fired at 400 deg.C to obtain the objective polycrystalline film 6 of silicon carbide.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a silicon carbide thin film which can be used as a protective film for semiconductor elements, a resistor and a diode.

[0002]

2. Description of the Related Art Silicon carbide is originally produced by heating coke and silica sand in an electric furnace at 1800 to 1900 ° C. Silicon carbide has a high melting point of 2700 ° C. or higher, does not react with other elements even at high temperatures, and is a stable substance that is not attacked by acid at all. Not only is it used as an abrasive because it has extremely high hardness and is close to diamond, it is also used for refractories and resistors. On the other hand, not only the above-mentioned conventional applications, but recently, attention has been paid to it as a semiconductor material replacing silicon. The reason is that the bandgap is about three times wider than that of silicon, the maximum electric field strength effective for avalanche resistance is about eight times larger, and the mobility of the drift region is smaller, but the conductivity of the drift region is 90 times larger. Promising as a next-generation material for devices.

In order to utilize such characteristics of silicon carbide in a semiconductor device, thin film formation is indispensable (it is currently difficult to increase the diameter like a silicon wafer). Conventionally, silicon carbide thin films are produced by sputtering or vapor deposition (for example, J. Electrochem. Soc., Vol.140, No.6 (1993), pp1756.
-1762, etc.) or CVD (eg J.
Electrochem.Soc., Vol.140, No.3 (1993), pp851-854, etc.) is generally used for the formation.

[0004]

However, the conventional forming method has the following drawbacks. 1 Since it is formed on the entire surface of the substrate, subsequent processing into a predetermined shape by photoetching is indispensable, but silicon carbide is chemically stable and it is difficult to apply conventional etching techniques. For example, even if the reactive ion etching method is used, the etching rate is too slow and there is no selectivity, and there are many practical problems.

2 At least 700 ° C. in case of CVD
The above high temperature treatment is required, and composition control is difficult in the case of heating vapor deposition or sputtering. Further, in the case of heating vapor deposition, the number of sheets to be processed is limited and mass productivity is poor. 3 High temperature treatment (annealing) of 1250 ° C. or higher is required to form a single crystal, but cracks occur during the heat treatment, and it is difficult to form a large area single crystal.

The present invention provides a method for forming a silicon carbide thin film which eliminates the above-mentioned drawbacks, obtains a good film quality by low temperature treatment, and can be processed into a predetermined shape.

[0007]

The present invention has the above objects.
In order to achieve, a metal thin film with dehydrogenation effect on the substrate
After being laminated with the organic polymer layer containing silicon atoms, the
Of hydrogen in organic polymer layer reacts with dehydrogenating metal thin film
Bake at the desired temperature. In addition, this substrate is a semiconductor substrate or
As an insulating substrate, a thin metal film with a dehydrogenation effect is on the substrate.
After being formed, a silicon source is formed on the substrate and the metal thin film.
Apply a liquid in which an organic polymer containing particles is dissolved and fire.
Or an organic polymer containing silicon atoms on the substrate
After applying the dissolved liquid and solidifying, dehydrogenate on the coating film
Forming and baking a thin metal film that works
A metal thin film having a dehydrogenation effect is formed on the substrate of
Organic compounds containing silicon atoms on the plate and on the metal thin film
After applying the liquid in which the child is dissolved and solidifying it, on the coating film,
A metal having a dehydrogenation action corresponding to the metal thin film.
It is effective to form a thin film and fire it. Also on the board
A metal thin film with dehydrogenation effect on part or all of the
Or organic polymer containing silicon atoms on the substrate
On the coating film after the liquid that has been dissolved is applied and solidified
Form a metal thin film with dehydrogenation effect on part or all of the surface
Or dehydrogenation of part or all of the substrate
After a certain metal thin film is formed, on the substrate and the metal thin film
A liquid in which an organic polymer containing silicon atoms is dissolved
After coating and solidifying, a part of the metal thin film on the coating film
Or, to support the entire surface, a thin metal film with dehydrogenation
It is effective to form a film and bake it. Also semiconductor base
An insulating layer may be formed on the plate, or a semi-insulating layer may be formed on the insulating substrate.
Form a conductor thin film layer or stack a semiconductor thin film and an insulating film
May be. Organic polymer containing silicon atoms is polysila
It is a polymer and has a firing temperature of 300 ° C to 700 ° C.
Setting C is effective. In addition, thin metal with dehydrogenation action
The film is a palladium thin film of dehydrogenation catalytic metal or dehydrogenation storage
Alloy Ni _FiveOf intermetallic compounds including stoichiometric composition of
It is effective to use a thin film. Silicon carbide thin film
Selectively formed or at least partly made into single crystal
Can be Liquid of organic polymer containing silicon atom
It is advisable to apply the above method by spin coating.

[0008]

[Function] Polydiene is used as a starting material for forming a silicon carbide thin film.
Methylsilylene and its cyclic compounds are known (Che
m.Lett., (1975) 931, ibid., (1975) 1209, J.Mat.Sci.,Fifteen
(1980) 720, J. Organometallic Chem.,300, p327-346, (1
986) etc.). When heating this polydimethylsilylene,
It is known that β-type silicon carbide can be formed. I
Stake, baking in a conventional vacuum or in an inert gas atmosphere
At low temperature of 400 ℃ or less, it becomes powdery
1 to obtain amorphous and polycrystalline thin films
Firing at a high temperature of 000 ° C or higher is required. For low temperature firing
To realize polycrystalline and single crystal thin films of silicon carbide
Therefore, it is necessary to borrow the power of the catalyst as in this invention.
It will be important.

Polysilane polymer (polysilane polymer)
Since a reaction to form a polycrystalline or single-crystal thin film of silicon carbide from an organic polymer containing silicon atoms such as is a dehydrogenation chain reaction, it has a metal thin film such as palladium as a dehydrogenation coupling catalyst and a hydrogen abstraction effect. If a thin film of a polysilane polymer and a high molecular polymer component is fired in a vacuum or in an inert gas atmosphere in the presence of a hydrogen storage alloy thin film, a polycrystal or single crystal of silicon carbide can be formed even at a low temperature treatment of about 400 ° C. . Further, whether it becomes a polycrystal or a single crystal depends on the film thickness of the silicon carbide thin film, and if the film thickness is made as thin as 0.2 μm or less, it is found as a result of X-ray diffraction that it becomes a single crystal. ing.

[0010]

EXAMPLES The polysilane polymer used in the present invention has the synthesis method of Yajima et al. Which has been already disclosed. The outline thereof will be described below. Polymers such as photoresists
A coating method typified by coating and a silicon carbide thin film forming method by subsequent heat treatment were adopted, and attention was paid to polysilane polymer as a coating material at that time. For example, polydimethylsilylene or its cyclic compound is known as a starting material for forming a silicon carbide thin film (Chem. Lett., (1975) 93.
1, ibid., (1975) 1209, J.Mat.Sci., 15 (1980) 720, J.Organ
ometallic Chem., 300 , p327-346, (1986)). It is known that when polydimethylsilylene is heated, β-type silicon carbide is generally formed according to the following reaction formula.

[0011]

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As an example, Yajima et al. (Chem. Lett., (1975) 9
The process synthesized by 31) is shown below. Dimethyldichlorosilane becomes dodecamethylcyclohexane according to the reaction formula in a tetrahydrofuran solvent in which Li metal pieces are present.

[0013]

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Next, the obtained dodecamethylcyclohexasilane was heated to 400 in a high pressure kettle filled with Ar gas for 48 hours.
When heated to 0 ° C., the following ring-opening reaction and subsequent polymerization reaction occur to produce a polymer.

[0015]

Embedded image

When the produced polymer is dissolved in diethyl ether, the low molecular weight polymer component (component having an extremely small value of n) of the polymer is evaporated together with the diethyl ether, and only the high molecular weight polymer component remains. When this residue is dissolved in a mixed solvent of normal hexane and acetone, among the high molecular polymer components, the high molecular polymer component having a large n value is dissolved in normal hexane and the high polymer component having a small n value is dissolved in acetone. To do. Therefore, by taking out a high molecular weight polymer component having a large n value dissolved in normal hexane, a high molecular weight polymer component having a uniform molecular weight can be obtained. Here, the left side of the reaction formula of (1) is the polysilane polymer [I], and the high molecular polymer component of the right side of the reaction formula of (3) is a polysilane polymer [I].
A polymer component having a large value of a] and n (here, n = 25) is defined as a polysilane polymer [Ib].

Polysilane polymer [I] dissolved in a solvent or polysilane polymer [Ib], which is a high molecular polymer component dissolved in normal hexane, is spin-coated on a wafer like a usual photoresist coating, and then,
By firing, a material containing β-SiC as a main component is obtained. Since the production reaction for obtaining a polycrystalline or single-crystal thin film of silicon carbide from this polysilane polymer [I] or polysilane polymer [Ib] is a dehydrogenation chain reaction, a metal thin film such as palladium or a hydrogen abstraction that serves as a dehydrogenation coupling catalyst. Use an effective hydrogen storage alloy thin film. In the synthesized polysilane polymer [Ib], n = 25 in the polymer of the reaction formula (3) is a polymer in which most of the high molecular weight polymer is dissolved in normal hexane, and the polysilane polymer [Ib] is used. An example of a method of forming a silicon carbide thin film by the following will be described below.

FIG. 1 is a process flow chart of the first embodiment.
An oxide film 2 having a thickness of about 1 μm is deposited on the surface of a 4-inch φ silicon wafer 1 (FIG. 3A). Next, palladium is vapor-deposited to a thickness of about 0.5 μm by a normal sputtering method to form a palladium thin film 3 (FIG. 2B). Then, a solution containing the polysilane polymer [Ib] is dropped onto the palladium thin film 3 and spin-coated at 500 rpm to form a liquid polysilane polymer [Ib] layer having a uniform thickness on the palladium thin film 3. Then, the wafer is baked and dried in a clean oven at 100 ° C. for about 1 hour. In this process, the solvent normal n-hexane was evaporated to solidify the polysilane polymer [Ib] layer 4
Are formed ((c) in the figure). After that, palladium is vapor-deposited on the solidified polysilane polymer [Ib] layer 4 to a thickness of about 0.5 μm to form a palladium thin film 5 (FIG. 3D). Next, this wafer is fired at 400 ° C. in an electric furnace in a vacuum state for 3 hours to obtain a polycrystalline silicon carbide thin film 6 (thickness: about 0.5 μm) ((e) in the same figure).

FIG. 2 shows the results of evaluation by X-ray diffraction of the crystallinity of the silicon carbide thin film when the coating rotation speed was changed and the film thickness of the polysilane polymer [Ib] layer was changed in the first embodiment. (1) in the figure is an X-ray diffraction pattern when the film thickness is 0.5 and 0.3 μm. Both show the same pattern, and although a peak due to the substrate silicon can be seen, The resulting peak is hidden by noise and cannot be clearly confirmed. (2) in the figure shows the case where the film thickness is 0.2 and 0.1 μm, and the peak of β-SiC having a diffraction angle of 35.5 ° is conspicuously observed. From this X-ray diffraction intensity, polysilane polymer [Ib]
It can be seen that when the layer is sandwiched by palladium layers from both sides, a single crystal of silicon carbide can be obtained by setting the film thickness of the polysilane polymer [Ib] to 0.2 μm or less.

FIG. 3 shows a process flow chart of the second embodiment.
Similar to FIG. 1, palladium is vapor-deposited to a thickness of about 0.5 μm on the oxide film 2 of a silicon wafer 1 of 4 inches φ whose surface is oxidized to a thickness of about 1 μm by a normal sputtering method to form a palladium thin film 3. It is formed ((a) in the same figure). This palladium thin film 3 is processed by ordinary photolithography using a photomask so that a predetermined portion remains (FIG. 2B). Although wet etching using a mixed acid (hydrochloric acid: nitric acid: acetic acid = 1: 10: 10) is adopted as the etching at the time of this processing, dry etching such as plasma etching is also possible. Then, similarly to FIG. 1, polysilane polymer [Ib] is dropped on the oxide film 2 of the silicon wafer, spin-coated and dried to form a polysilane polymer [Ib] layer 4 (FIG. 1C). After that, the palladium thin film 5 vapor-deposited to a thickness of about 0.5 μm is processed again by using the same photomask as that used previously (the same figure (d)). In this state, if the polysilane polymer [Ib] layer sandwiched between the upper and lower palladium thin films 3 and 5 is fired under the same conditions as in FIG.
μm), but the other portion becomes a powdery layer 7 containing silicon carbide as a main component (FIG. 7E). In this state, ultrasonic washing with water removes the powdery layer 7 and selectively forms the polycrystalline silicon carbide thin film 6 sandwiched between the palladium thin films 3 and 5 ((f) in the same figure). From this, it is understood that the processing of the silicon carbide thin film can be processed into a transferred form by interposing the processing of the palladium thin film which can be easily performed by the conventional technique.

FIG. 4 shows a process flow chart of the third embodiment.
The processed palladium thin film 3 is a polysilane polymer [I
b] It is formed under the layer 4 ((a) in the same figure). The thickness of the polysilane polymer [Ib] layer 4 was set to about 1 μm in consideration of the fact that the palladium thin film 3 is a single layer and the catalytic effect is weakened. In the subsequent heat treatment, only the portion in contact with the palladium thin film is formed as the silicon carbide single crystal thin film 8, and the other portion is a powdery layer 7 containing silicon carbide as a main component.
Is formed as shown in FIG. Next, the powdery layer 7 is removed by ultrasonic water washing, and a single crystal thin film 8 of silicon carbide is selectively formed only on the portion where the palladium thin film 3 is adhered (FIG. 7C).

FIG. 5 is a process flow chart of the fourth embodiment.
The processed palladium thin film is a polysilane polymer [I
b] It is formed on the layer 4 ((a) of the same figure). In the subsequent heat treatment, only the portion in contact with the palladium thin film 4 is formed as the silicon carbide crystal thin film 8, and the other portion is formed as the powdery layer 7 containing silicon carbide as the main component ((b) in the figure). ). Next, the powdery layer 7 is removed by ultrasonic water washing, and a single crystal thin film 8 of silicon carbide is selectively formed only on the portion where the palladium thin film 5 is adhered (FIG. 2C).

Although the above-mentioned embodiments are shown independently of each other, by arbitrarily combining these embodiments, a resistor of a silicon carbide thin film, a silicon substrate and an insulating film formed on the silicon substrate can be formed. In this way, a composite semiconductor device can be manufactured. In addition, polysilane polymer [Ib]
A polysilane thin film or a single crystal of silicon carbide can be obtained by the same treatment as above with polysilane polymer [I] instead of. Also, instead of the palladium thin film, a thin film containing an intermetallic compound containing a stoichiometric composition of Ni ₅ which is a dehydrogenation storage alloy as a main component can be used to obtain a polycrystalline silicon carbide film or a single crystal thin film of silicon carbide by the same treatment as described above. To be Also, instead of the silicon substrate, an insulating plate made of glass or the like, a plate having a silicon thin film formed on the insulating plate, or a plate having an insulating film such as a silicon thin film and an oxide film formed on the insulating plate may be used as the substrate. The result is obtained.

[0024]

According to the present invention, since it can be formed more simply and at a lower temperature than the conventional thin film forming method, it can be combined with a conventional silicon semiconductor. Further, since the layer can be formed in the coating step, the mass productivity is excellent and the cost can be reduced as compared with the conventional thin film forming method. Furthermore, since selective formation is possible, a thin film processing step is unnecessary, which produces a further cost reduction effect. An even greater effect is
Since a single crystal of silicon carbide can be obtained in a thin film at a low temperature, there is an advantage that a resistor, a diode and the like can be compositely formed on a silicon semiconductor wafer. It can also be used as an extremely stable semiconductor surface protective film.

[Brief description of drawings]

FIG. 1 is a process flow chart of a first embodiment, in which FIG. 1 (a) to FIG.

FIG. 2 is a diagram showing the results of evaluation of the crystallinity of a silicon carbide thin film by X-ray diffraction when the coating speed was changed and the film thickness of the high molecular polymer component [Ib] layer was changed in the first example.

FIG. 3 is a process flow chart of the second embodiment, wherein FIGS. 3A to 3F are process diagrams shown in the order of formation;

FIG. 4 is a process flow chart of the third embodiment, and FIGS. 4A to 4C are process diagrams shown in the order of formation;

5A to 5C are process flow charts of a fourth embodiment, and FIGS. 5A to 5C are process diagrams shown in the order of formation.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Silicon wafer 2 Oxide film 3 Palladium thin film 4 Polysilane polymer [Ib] layer 5 Palladium thin film 6 Polycrystalline thin film of silicon carbide 7 Powdery layer 8 Single crystal thin film of silicon carbide

Claims (16)

[Claims] 1. A temperature at which hydrogen in an organic polymer layer reacts with a dehydrogenating metal thin film after a metal thin film having a dehydrogenating action and an organic polymer layer containing silicon atoms are laminated on a substrate. A method for forming a silicon carbide thin film, which comprises firing at. 2. A metal thin film having a dehydrogenation effect is formed on a substrate, and then a liquid in which an organic polymer containing silicon atoms is dissolved is applied onto the substrate and the metal thin film and baked. The method for forming a silicon carbide thin film according to claim 1, wherein: 3. A liquid in which an organic polymer containing silicon atoms is dissolved is applied onto a substrate and solidified, and then a metal thin film having a dehydrogenation action is formed on the applied film and baked. The method for forming a silicon carbide thin film according to claim 1. 4. A metal thin film having a dehydrogenating action is formed on a substrate, and a liquid in which an organic polymer containing silicon atoms is dissolved is applied onto the substrate and the metal thin film, and after solidification, application. The method for forming a silicon carbide thin film according to claim 1, wherein a metal thin film having a dehydrogenation action is formed on the film so as to correspond to the metal thin film, and is baked. 5. The method for forming a silicon carbide thin film according to claim 1, wherein a metal thin film having a dehydrogenation action is formed on a part or the whole surface of the substrate. 6. A metal thin film having a dehydrogenation effect is formed on a part or the whole surface of a coated film after a liquid in which an organic polymer containing silicon atoms is dissolved is applied and solidified on a substrate. The method for forming a silicon carbide thin film according to claim 2, wherein 7. A liquid in which an organic polymer containing silicon atoms is dissolved is formed on the semiconductor substrate and on the metal thin film after a metal thin film having a dehydrogenation action is formed on a part or the whole surface of the substrate. 4. The metal thin film having a dehydrogenation effect is formed on the coated film so as to correspond to a part or the whole surface of the metal thin film after coating and solidifying, and then baked. Method for forming silicon carbide thin film. 8. The method for forming a silicon carbide thin film according to claim 1, wherein the substrate is made of a semiconductor or an insulator. 9. The method for forming a silicon carbide thin film according to claim 8, wherein an insulating layer is formed on the semiconductor substrate. 10. The method for forming a silicon carbide thin film according to claim 8, wherein a semiconductor thin film layer is formed on the insulating substrate. 11. The method for forming a silicon carbide thin film according to claim 1, wherein a semiconductor thin film and an insulating film are laminated and formed on an insulating substrate. 12. The organic polymer containing silicon atoms is a polysilane polymer, and the firing temperature is 300 ° C. to 700 ° C.
The method for forming a silicon carbide thin film according to claim 1, wherein the temperature is ° C. 13. A metal thin film having a dehydrogenation action is a palladium thin film of a dehydrogenation catalyst metal or a thin film mainly composed of an intermetallic compound containing a stoichiometric composition of Ni ₅ of a dehydrogenation storage alloy. The method for forming a silicon carbide thin film according to claim 1. 14. The method for forming a silicon carbide thin film according to claim 1, wherein the silicon carbide thin film is selectively formed. 15. The method for forming a silicon carbide thin film according to claim 1, wherein at least a part of the silicon carbide thin film is a single crystal. 16. The method for forming a silicon carbide thin film according to claim 2, wherein the coating of the organic polymer liquid containing silicon atoms is spin coating.