JPH05160394A - Mis type semiconductor device and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain an excellent surface stabilizing effect, and to a fine thin film without a pin hole and increase productivity, by making a thin film on a III-V compound semiconductor substrate out of a sulfur-containing organic compound having long-chain hydrocarbon radicals, and forming a metal layer the thin film. CONSTITUTION:A sulfer-containing organic compound having long-chain hydrocarbon radicals is a thiol compound, is a carboxylic compound represented by one of equations I, II, and III, is a carboxylic acid ester represented by one of equations IV, V, and VI, is a sulfide compound R-S-R, and a disulfide compound R-S-S-R. A thin film is made out of a compound on the surface of a III-V compound semiconductor substrate by dipping the substrate in a solution of a sulfur-containing organic compound having long-chain hydrocarbon radicals, and a film of a metal layer is formed on this thin film after that. Incidentally, the metallic layer is usually formed by an vacuum evaporation method, etc.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a MIS (metal-oxide-semiconductor) formed by laminating an insulating layer and a metal layer on a III-V group compound semiconductor substrate such as GaAs (gallium arsenide).
Type semiconductor device and its manufacturing method.

[0002]

2. Description of the Related Art The surface of a compound semiconductor such as GaAs has a peculiar instability due to the surface state. For example, a Schottky barrier having a desired barrier height or a Schottky barrier having a small reverse current is formed with good reproducibility. It's difficult. Therefore, MIS is formed on the compound semiconductor.
It is a big obstacle in constructing the type structure.

Under these circumstances, various attempts have been made to stabilize the surface of the compound semiconductor. For example, Naminichi and others are Japanese journals of applied physics vos (JAPANESE JOURNAL OF APPLIED PHYSICS VO
L.27, No.12, 1988), it is reported that when the GaAs surface is treated with an ammonium sulfide solution, a monoatomic layer-level S (sulfur) layer is formed and good MIS characteristics are obtained.

However, since the S layer formed by treatment with the ammonium sulfide solution has an ultimate thickness of about a monoatomic layer or a diatomic layer, an insulating layer or a metal layer is formed on this S layer. There is a risk of dissociation from the GaAs surface during the step of doing so, impairing its surface stabilizing effect. Therefore, Nannica et al.
Japanese Patent No. 41 discloses a technique of forming a coating layer while cooling a GaAs substrate.

However, this method also basically forms an insulating layer and a metal layer on the S layer formed by treating with an ammonium sulfide solution, and sufficiently suppresses dissociation of the S layer. It's difficult. Further, not only is a treatment operation with an ammonium sulfide solution added, but also the formation of the insulating layer is complicated and the number of steps is large, which is disadvantageous in mass production.

On the other hand, it has been attempted to use an organic thin film as an insulating layer for a compound semiconductor to reduce the interface density of the MIS type device. For example, JP-A-62-65
In Japanese Patent No. 471,471, the LB film (Langmuir-Blodgett film) of a hydrazone compound is used as an insulating layer, and
Is disclosed. However, when the insulating layer is formed of the LB film, some pinholes cannot be avoided and the desired characteristics cannot be obtained. Further, the LB film is difficult to form and is not suitable for mass production.

[0007]

As described above, dissociation of the S layer becomes a problem when attempting to stabilize the GaAs surface in the S layer at the monoatomic layer level, and the L of the hydrazone compound becomes a problem.
When the insulating layer is formed of the B film, deterioration of characteristics due to pinholes becomes a problem. Further, in any case, mass productivity is extremely poor, which hinders practical application.

Therefore, the present invention has been proposed in view of such conventional circumstances, and provides a surface stabilizing layer which is excellent in the surface stabilizing effect of a compound semiconductor and which also functions as an insulating layer. M with good MIS characteristics
An object is to provide an IS type semiconductor device and a manufacturing method thereof. A further object of the present invention is to provide a MIS type semiconductor device excellent in mass productivity and a manufacturing method thereof.

The present inventors have conducted extensive research over a long period of time to achieve the above object. As a result, it has been found that the sulfur-containing organic compound having a long-chain hydrocarbon group exerts an excellent surface stabilizing effect and also functions as a good insulating layer due to the self-organization property of the hydrocarbon chain. The present invention has been proposed on the basis of such knowledge, and a thin layer made of a sulfur-containing organic compound having a long-chain hydrocarbon group is formed on a III-V group compound semiconductor substrate, and the thin layer is formed on the thin layer. It is characterized in that a metal layer is formed on.

Further, in the manufacturing method of the present invention, after a III-V compound semiconductor substrate is immersed in a solution of a sulfur-containing organic compound having a long-chain hydrocarbon group, a thin layer of the compound is formed on the surface. The metal layer is formed on the thin layer, and the metal layer is formed while the III-V compound semiconductor substrate is cooled.

As shown in FIG. 1, the MIS type semiconductor device of the present invention comprises a III-V group compound semiconductor substrate 1 such as GaAs.
A thin layer 2 made of a sulfur-containing organic compound having a long-chain hydrocarbon group is formed thereon, and a metal film 3 is formed on the thin layer 2.

Here, as the sulfur-containing organic compound having a long chain hydrocarbon group used for forming the thin layer 2, a thiol compound represented by the general formula (1), chemical formula 7, chemical formula 8 and chemical formula 9 ( However, each R in the formula is a long-chain hydrocarbon group.)
0, Chemical formula 11, Chemical formula 12 (wherein R ¹ and R ² in the formula are both long-chain hydrocarbon groups), a sulfide compound represented by the general formula (2) Of the compounds, the disulfide compound represented by the general formula (3), and the compound represented by the general formula (4), a trithiophosphorous acid long-chain ester compound represented by the general formula (5) and the general formula (6) are particularly shown. Examples thereof include compounds such as trithioarsenous acid long-chain ester compounds and trithioammonous acid long-chain ester compounds represented by the general formula (7), all of which contain a sulfur atom in the molecular chain and are further bound to this sulfur atom. It has a hydrocarbon chain.

R-SH (1) (wherein R is a long-chain hydrocarbon group)

[0014]

[Chemical 7]

[0015]

[Chemical 8]

[0016]

[Chemical 9]

[0017]

[Chemical 10]

[0018]

[Chemical 11]

[0019]

[Chemical 12]

R-S-R (2) (wherein R is a long-chain hydrocarbon group)

R-S-S-R (3) (wherein R is a long-chain hydrocarbon group)

(RS) ₃ Q ... (4) (wherein R represents a long-chain hydrocarbon group and Q represents a Va group element).

(RS) ₃ P ... (5)

(RS) ₃ As (6)

(RS) ₃ Sb (7)

When the III-V group compound semiconductor substrate 1 is treated with the sulfur-containing organic compound having these long-chain hydrocarbon groups, the compound molecules are adsorbed on the surface thereof,
A dense film is formed as the thin layer 2 by so-called self-assembly. At this time, the sulfur atom in the sulfur-containing organic compound molecule having a long-chain hydrocarbon group is adsorbed on the surface of the III-V compound semiconductor substrate 1, and the surface of the compound semiconductor is stabilized. At the same time, due to the self-assembly, an insulating layer made of a hydrocarbon chain is formed on the surface, which can be directly used for the MIS structure.

In the above-mentioned sulfur-containing organic compound having a long-chain hydrocarbon group, the number of carbon atoms of the hydrocarbon chain bonded to the sulfur atom is arbitrary, but the number of carbon atoms is required to make the thin layer 2 function as an insulating layer. It is preferably 10 or more. The upper limit is not particularly limited, but the limit is about 30 for this type of compound, and even if it is more than this, the substantial merit is small.

The hydrocarbon chain may contain a branch, an alicyclic ring, a double bond, an aromatic ring or the like, but a straight chain hydrocarbon is preferable. Therefore, as the sulfur-containing organic compound having a long chain hydrocarbon group, a compound having an alkyl group having 10 or more carbon atoms is suitable.

The thickness of the thin layer 2 should be 30 nm or less, preferably 10 nm or less. If the thickness of the thin layer 2 is too large, the barrier height becomes too high, and good MIS characteristics cannot be obtained. The lower limit is not particularly specified, but it is difficult to provide a sufficient function as an insulating layer unless there is at least a thickness corresponding to one molecule of the sulfur-containing organic compound having a long chain hydrocarbon group.

To form the thin layer 2 composed of the sulfur-containing organic compound having a long-chain hydrocarbon group on the surface of the III-V compound semiconductor substrate 1, the compound is immersed in a solution prepared by dissolving the compound in a suitable solvent. Then, pull up slowly. As a result, the sulfur-containing organic compound having a long-chain hydrocarbon group in the solution is adsorbed on the surface of the compound semiconductor substrate 1 to form the thin layer 2. At this time, the sulfur atom in the compound is changed to GaAs or the like on the surface of the substrate 1. Therefore, the molecules are lined up in order to form a so-called self-assembled film, and a pinhole-free dense film is very easily formed.

After the thin layer 2 (insulating layer) made of a sulfur-containing organic compound having a long-chain hydrocarbon group is formed as described above,
A metal layer is formed on this, and the metal layer may be formed by a normal vacuum deposition method or the like. In this case, since the surface of the compound semiconductor substrate 1 is covered with the thin layer 2 made of a sulfur-containing organic compound having a long-chain hydrocarbon group, the sulfur atom is not dissociated, but the surface stabilization by the sulfur atom is surely performed. In order to maintain the effect, it is preferable to cool the compound semiconductor substrate 1 using a cooler or the like when forming the metal layer.

The cooling temperature is preferably as low as possible, but for example, when a metal layer is vapor-deposited, it is preferable that the temperature of the substrate 1 is kept at room temperature or lower during vapor deposition. It should be noted that the temperature of the substrate 1 must be suppressed to a temperature below the decomposition temperature of the sulfur-containing organic compound having a long-chain hydrocarbon group used, however high.

[0033]

The sulfur-containing organic compound having a long-chain hydrocarbon group is adsorbed on the surface of the III-V group compound semiconductor to form a self-assembled film. At this time, the sulfur atom in the sulfur-containing organic compound molecule having a long-chain hydrocarbon group is bonded to the III-V group compound semiconductor surface, and surface stabilization is performed as in the case where the S thin layer is formed by ammonium sulfide or the like. Planned.

On the other hand, the hydrocarbon chain in the sulfur-containing organic compound molecule having a long-chain hydrocarbon group functions as an insulating layer, the compound semiconductor region is surely covered with an insulator, and the S from the surface of the compound semiconductor region is surely covered. Dissociation of atoms is suppressed.

[0035]

EXAMPLES Specific examples to which the present invention is applied will be described below. Example 1 In this example, a case where a thiol compound is used as a sulfur-containing organic compound having a long-chain hydrocarbon group will be described.

First, a compound semiconductor substrate made of GaAs and having an n-type semiconductor region on its surface was prepared. Also, as an etching solution, KOH (potassium hydroxide) -H ₂ O is used.
_A solution of ₂ (hydrogen peroxide) -H ₂ O (water) was further prepared as a thiol compound solution, and an octadecanethiol (C ₁₈ H ₃₇ SH) alcohol solution having a concentration of 1 mm was prepared.

Next, the surface of the n-type semiconductor region was etched and cleaned with the above etching solution for about 1 minute. Subsequently, the cleaned compound semiconductor substrate was immersed in the octadecanethiol solution. Although the immersion time is 1 hour here, it can be widely selected from several seconds to several days.

The compound semiconductor substrate was slowly pulled up from the octadecanethiol solution, washed with alcohol, and further dried by blowing nitrogen gas onto the surface of the n-type semiconductor region. As a result, the surface of the n-type semiconductor region had a layer of S atoms in a state of being bonded to Ga and As, and was covered with an insulating layer of about 3 nm formed by an alkyl group that was organically bonded to the S atoms. In fact, when observed by XPS (X-ray photoelectron spectroscopy), it was confirmed from the chemical shift that the S atom of octadecanethiol was adsorbed on the GaAs surface.

Next, a 0.2 μm thick metal layer of Au was formed on the upper surface of this insulating layer by a well-known vacuum deposition method. During the vapor deposition of the metal layer, the compound semiconductor substrate was cooled to −100 ° C. or lower (in this example, −150 ° C.).

Although the case where octadecanethiol was used as the thiol compound has been described here, it has been confirmed that each compound shown in Table 1 below has the same effect.

[0041]

[Table 1]

Example 2 In this example, the case where a carboxylic acid compound is used as the sulfur-containing organic compound having a long-chain hydrocarbon group will be described. First, as in Example 1, a compound semiconductor substrate made of GaAs and having an n-type semiconductor region on the surface was etched. Next, Example 1 was applied to a dithiooctadecanoic acid (C ₁₇ H ₃₅ CSSH) alcohol solution having a concentration of 1 mm, which was prepared as a carboxylic acid compound solution and kept at room temperature.
It was dipped in the same manner as above and dried to form an insulating layer. At this time,
The surface of the n-type semiconductor region is Ga and As as in the first embodiment.
It has an S atom layer in a bonded state with and is covered with an insulating layer of about 3 nm by an alkyl group which is intercalated from this S atom by an organic bond, and when observed by XPS (X-ray photoelectron spectroscopy), From the chemical shift, it was confirmed that the S atom of dithiooctadecanoic acid was adsorbed on the GaAs surface.

Further, a metal layer of Au having a thickness of 0.2 μm was formed on the upper surface of the insulating layer in the same manner as in Example 1.

Although the case of using dithiooctadecanoic acid as the carboxylic acid compound has been described here,
It has been confirmed that each compound shown in Table 2 below has a similar effect.

[0045]

[Table 2]

Example 3 In this example, the case where a carboxylic acid ester compound is used as the sulfur-containing organic compound having a long-chain hydrocarbon group will be described. First, as in the first embodiment, GaAs
A compound semiconductor substrate made of and having an n-type semiconductor region on its surface was etched. Next, dithiooctadecanoic acid ethyl ester (C ₁₇ H ₃₅ CS) prepared as a carboxylic acid ester compound solution and kept at room temperature with a concentration of 1 mm
It was dipped in an SC ₂ H ₅ ) alcohol solution in the same manner as in Example 1 and dried to form an insulating layer. At this time, the surface of the n-type semiconductor region has an S atom layer in a bonded state with Ga and As as in Example 1, and an insulating layer of about 3 nm formed by an alkyl group that is organically bonded from the S atom. When observed by XPS (X-ray photoelectron spectroscopy), the chemical shift confirmed that the S atom of dithiooctadecanoic acid ethyl ester was adsorbed on the GaAs surface.

Further, on the upper surface of this insulating layer, a metal layer of Au having a thickness of 0.2 μm was formed in the same manner as in Example 1.

Although the case of using dithiooctadecanoic acid ethyl ester as the carboxylic acid ester compound has been described here, it has been confirmed that each compound shown in Table 3 below has the same effect.

[0049]

[Table 3]

Example 4 In this example, a case where a sulfide compound is used as the sulfur-containing organic compound having a long-chain hydrocarbon group will be described. First, as in Example 1, a compound semiconductor substrate made of GaAs and having an n-type semiconductor region on the surface was etched. Then, the insulating layer was immersed in a dioctadecyl sulfide [(C ₁₈ H ₃₇ ) ₂ S)] alcohol solution having a concentration of 1 mm, which was prepared as a sulfide compound solution and was kept at room temperature, and dried to form an insulating layer. Formed. At this time, the surface of the n-type semiconductor region has an S atom layer in a bonded state with Ga and As as in Example 1, and an insulating layer of about 3 nm formed by an alkyl group that is organically bonded from the S atom. When observed by XPS (X-ray photoelectron spectroscopy), it was confirmed from the chemical shift that the S atom of dioctadecyl sulfide was adsorbed on the GaAs surface.

Further, a 0.2 μm-thick metal layer made of Au was formed on the upper surface of the insulating layer in the same manner as in Example 1.

Although the case where dioctadecyl sulfide is used as the sulfide compound has been described here, it has been confirmed that each compound shown in Table 4 below has a similar effect.

[0053]

[Table 4]

Example 5 In this example, a case where a disulfide compound is used as the sulfur-containing organic compound having a long-chain hydrocarbon group will be described. First, as in Example 1, a compound semiconductor substrate made of GaAs and having an n-type semiconductor region on the surface was etched. Next, in the same manner as in Example 1, a dioctadecyl disulfide (C ₁₈ H ₃₇ SSC ₁₈ H ₃₇ ) alcohol solution having a concentration of 1 mm and prepared as a disulfide compound solution and kept at room temperature was dipped and dried to form an insulating layer. did. At this time, the surface of the n-type semiconductor region has an S atom layer in a bonded state with Ga and As as in Example 1, and an insulating layer of about 3 nm formed by an alkyl group that is organically bonded from the S atom. When observed by XPS (X-ray photoelectron spectroscopy), it was confirmed from the chemical shift that the S atom of dioctadecyl disulfide was adsorbed on the GaAs surface.

Further, a 0.2 μm thick metal layer made of Au was formed on the upper surface of this insulating layer in the same manner as in Example 1.

Although the case where dioctadecyl disulfide is used as the disulfide compound has been described here, it has been confirmed that each compound shown in Table 5 below has a similar effect.

[0057]

[Table 5]

Example 6 In this example, as a sulfur-containing organic compound having a long-chain hydrocarbon group, a compound represented by the general formula (RS) ₃ Q (wherein R represents a long-chain hydrocarbon group and Q represents a Va group element) is used. The case of using a compound represented by First, as in Example 1, a compound semiconductor substrate made of GaAs and having an n-type semiconductor region on the surface was etched. next,
In the same manner as in Example 1, the prepared trioctadecyltrithiophosphite [(C ₁₈ H ₃₇ S) ₃ P] alcohol solution kept at room temperature and having a concentration of 1 mm was immersed and dried to form an insulating layer. At this time, the surface of the n-type semiconductor region has an S atom layer in a bonded state with Ga and As as in Example 1, and an insulating layer of about 3 nm formed by an alkyl group that is organically bonded from the S atom. Coated with XPS (X
As a result of the chemical shift, it was confirmed that the S atom of trioctadecyltrithiophosphite was adsorbed on the GaAs surface.

Further, a metal layer of Au having a thickness of 0.2 μm was formed on the upper surface of the insulating layer in the same manner as in Example 1.

When trioctadecyl trithiophosphite is used as the compound represented by the general formula (RS) ₃ Q (wherein R represents a long chain hydrocarbon group and Q represents a Va group element). However, it has been confirmed that each compound shown in Table 6 below has the same effect.

[0061]

[Table 6]

In the MIS structure formed as in Example 1, Example 2, Example 3, Example 4, Example 5, and Example 6, a sulfur-containing organic compound having a long-chain hydrocarbon group was used. Therefore, dissociation of S atom from the compound semiconductor region could be minimized. Moreover, the insulating layer formed by the self-organizing property of the alkyl chain and the metal layer formed by vapor deposition satisfactorily maintain the surface stabilizing effect of S, and extremely good MIS characteristics were obtained.

[0063]

As is clear from the above description, in the present invention, since the surface of the compound semiconductor is coated with the sulfur-containing organic compound having a long chain hydrocarbon group, a good surface stabilizing effect is obtained. The surface stabilizing effect is not impaired by the coating of the metal layer or the like. Furthermore, this thin layer of a sulfur-containing organic compound having a long-chain hydrocarbon group also exhibits an excellent function as an insulating layer.

Therefore, according to the present invention, a good MI is obtained.
It is possible to provide a MIS semiconductor device having S characteristics.

Further, the thin layer of the sulfur-containing organic compound having a long-chain hydrocarbon group can be formed by simply immersing the compound semiconductor substrate in the compound solution, and is free from pinholes due to its self-organizing property. A dense thin layer can be formed. Therefore, it is very advantageous in terms of productivity.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of an essential part showing an example of a MIS type semiconductor device to which the present invention is applied.

[Explanation of symbols]

1 ... Compound semiconductor substrate 2 ... Sulfur-containing organic compound thin layer having long-chain hydrocarbon group 3 ... Metal layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (31) Priority claim number Japanese Patent Application No. 3-292559 (32) Priority date Hei 3 (1991) October 12 (33) Priority claiming country Japan (JP) (31) Priority Claim No. Japanese Patent Application No. 3-292560 (32) Priority Day No. 3 (1991) October 12, (33) Country of priority claim Japan (JP) (31) Priority claim number Japanese Patent Application No. 3-292561 (32) Priority Hihei 3 (1991) October 12 (33) Priority claiming country Japan (JP)

Claims (11)

[Claims] 1. A MIS type semiconductor device comprising a III-V compound semiconductor substrate on which a thin layer of a sulfur-containing organic compound having a long-chain hydrocarbon group is formed, and a metal layer is formed on the thin layer. 2. The MIS type semiconductor device according to claim 1, wherein the sulfur-containing organic compound having a long chain hydrocarbon group is a thiol compound represented by the following general formula. R-SH (provided that R is a long-chain hydrocarbon group) 3. The sulfur-containing organic compound having a long-chain hydrocarbon group is a carboxylic acid compound represented by any of the following chemical formula 1, chemical formula 2, and chemical formula 3 below.
IS type semiconductor device. [Chemical 1] [Chemical 2] [Chemical 3] (However, R is a long-chain hydrocarbon group.) 4. The sulfur-containing organic compound having a long-chain hydrocarbon group is a carboxylic acid ester compound represented by any one of the following chemical formulas 4, 5, and 6.
The MIS type semiconductor device described. [Chemical 4] [Chemical 5] [Chemical 6] (However, R ¹ and R ² are both long-chain hydrocarbon groups.) 5. The MIS type semiconductor device according to claim 1, wherein the sulfur-containing organic compound having a long chain hydrocarbon group is a sulfide compound represented by the following general formula. R-S-R (however, R is a hydrocarbon group.) 6. The MIS type semiconductor device according to claim 1, wherein the sulfur-containing organic compound having a long chain hydrocarbon group is a disulfide compound represented by the following general formula. R-S-S-R (however, R is a hydrocarbon group.) 7. The MIS type semiconductor device according to claim 1, wherein the sulfur-containing organic compound having a long chain hydrocarbon group is a compound represented by the following general formula. (RS) ₃ Q (wherein R represents a long-chain hydrocarbon group and Q represents a Va group element). 8. The MIS type semiconductor device according to claim 1, wherein the long-chain hydrocarbon group is an alkyl group having 10 or more carbon atoms. 9. The MIS type semiconductor device according to claim 1, wherein the thin layer made of a sulfur-containing organic compound having a long-chain hydrocarbon group has a thickness of 10 nm or less. 10. A sulfur having a long-chain hydrocarbon group on the III-V compound semiconductor substrate by immersing a III-V compound semiconductor substrate in a solution of a sulfur-containing organic compound having a long-chain hydrocarbon group. A method of manufacturing a MIS type semiconductor device, comprising forming a thin layer made of a contained organic compound and then forming a metal layer on the thin layer. 11. The method of manufacturing a MIS type semiconductor device according to claim 10, wherein the metal layer is formed while cooling the III-V compound semiconductor substrate.