JPS60224230A - Semiconductor surface protective film and manufacture thereof - Google Patents

Abstract

PURPOSE:To form an insulating film having preferable bondability on III-V group compound semiconductor by using a protective film which mainly contains polyphosphonitrile chloride. CONSTITUTION:A semiconductor surface protective film which mainly contains polyphosphonitrile chloride is used. Phosphonitrile chloride having 6-member annular structure as shown is opened at the ring and polymerized to form a polyphosphonitrile chloride thin film. For example, GaAs wafer 2 of III-V group compound semiconductor is placed on a carbon susceptor 3 in a quartz reaction tube 1, the tube 1 is evacuated by a pressure reduction rotary pump 4. Then, phosphonitrile chloride diluted with N2 gas is fed from a stainless steel tube 5, the susceptor is heated at 300 deg.C by a high frequency induction heating method with a high frequency power source 6 and a high frequency coil 8 to open the ring and polymerize the phosphonitrile, and to bond the polyphosphonitrile chloride film on the surface of the wafer 2.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical Field The present invention relates to a thin film formed on the surface of a l-V group compound semiconductor and a method for forming this thin film.

(2) Conventional techniques and problems The technique of forming a protective film of an insulating film on the semiconductor surface is a technique for stabilizing the semiconductor surface and for metal-insulator-semiconductor (Metal-
It is necessary to realize an Insulator-8 semiconductor (hereinafter abbreviated as MI8) structure transistor. However, for IV group compound semiconductors, a thin film formation method that can control the physical properties of the interface between the insulating film formed on the semiconductor and the semiconductor has not yet been established. A wide variety of insulating film types have been attempted, but the most promising example is a phosphorous nitride layer made of molecules with the structure shown in Figure 1. Hirota et al. When the interface unit of the MI8 interface was evaluated on an indium substrate, it was reported that a low interface state density on the order of 10"I:!II-" was obtained, indicating a good interface. (Hirota et al., Showa Kaku Spring Proceedings of the Society of Applied Physics, p584). In group IV compound semiconductors, group V elements tend to dissociate because of their high vapor pressure. Therefore, the surface of the IV group compound semiconductor is deficient in group V elements, and the group I elements have dangling bonds. By forming an A phosphorus nitride layer made of a group (Ⅰ) compound on this surface, the above-mentioned unpaired bonds can be closed. For this reason, it is believed that the phosphorus nitride layer/IV group compound semiconductor interface becomes good.

As mentioned above, the phosphorus nitride layer is a promising insulating film for IV group compound semiconductors, but the characteristics of the MI8 interface vary depending on subtle differences in the film fabrication conditions, and it is difficult to obtain one with good reproducibility. The current situation is that this is not the case.

As already mentioned, in group IV compound semiconductors, group V elements are likely to dissociate and thermal deterioration is likely to occur.

Such thermal deterioration is considered to be one of the reasons why the insulating film/IV group compound semiconductor interface cannot be controlled. Therefore, when an insulating film is formed on the semiconductor, thermal deterioration of the semiconductor surface must be minimized by doing so at a low temperature. However, the Journal of Applied Fixtures (Y, Hirota et al., J.
, Appl Phys, 53 (1982) 41)
As described in , the phosphorus nitride layer that has been attempted in the past requires a high gas reaction temperature of about 900° C. in order to cause ammonia and phosphine to react, resulting in thermal deterioration of the semiconductor surface. Furthermore, it is known that IV group compound semiconductors are extremely easily oxidized, and for this reason, natural oxides of IV group compounds are often formed at the interface between the insulating film and the semiconductor. This native oxide is thermodynamically unstable. Therefore, Aiiii Transaction Electrodevice 7, (B, Bayr
actaroglu, IEBB, Trans.

As stated in ED-26 (1979) 1854), in order to obtain a good insulating film/IV group compound, it is important to reduce the oxygen concentration in the insulating film and suppress the formation of a native oxide film. It is. However, in the conventional phosphorus nitride layer, a large amount of oxygen is taken in during the film formation process.

(3) Purpose of the Invention The purpose of the present invention is to provide an insulating film whose characteristics are not affected by manufacturing conditions as a protective film formed on an IV group compound semiconductor, and a method for manufacturing the same.

(4) Structure of the Invention The protective film of the present invention has polychlorinated phosphonitrile as its main component, and its manufacturing method consists in forming it by ring-opening polymerization of chlorinated phosphonitrile having a six-membered ring structure.

(5) Detailed explanation of configuration and examples Hereinafter, this invention will be explained in detail based on examples.

Figure 2 shows the molecular structure of phosphonitrile chloride.
It has been reported that this molecule can be obtained by dissolving phosphorus pentachloride in tetrachloroethane, adding ammonium chloride, and heating it (for example, Otsu et al., experimental method for polymer synthesis,
9285 Kagaku Dojin (1976) λ Phosphonitrile chloride undergoes ring-opening polymerization at a temperature of 300°C under a nitrogen stream to form rubber-like polyphosphonitrile chloride (Fig. 3) in 4 to 6 hours. In the formation process of this polymer compound, if a substrate is prepared, the polymer compound is deposited on the substrate. In the example of the present invention, a method was adopted in which phosphoryl chloride (IJ) was introduced into a reduced pressure CVD apparatus as shown in FIG. 3 and thermally decomposed.

Figure 4 shows a state in which a group IV compound semiconductor, such as a GaAs wafer 2, is placed on a carbon susceptor 3 in a quartz reaction tube 1.The inside of the quartz reaction tube 1 is equipped with a rotary pump 4 for evacuation. Perform vacuum evacuation. For the deposition of the IJ film, a phosphoryl chloride IJ film diluted with N and gas was introduced into the stainless steel tube 5, and the carbon susceptor was heated to 300°C by high-frequency induction heating using a high-frequency power supply 6 and a high-frequency coil 8. The mixture is heated to cause a ring-opening polymerization reaction of the phosphoniol. In the example, the outer wall of the reaction tube 1 had a double structure and was cooled by flowing water 7 therein to prevent the polychlorinated phosphonitrile film from adhering to the outer wall. N containing phosphonitrile chloride with the substrate heated.

A polychlorinated phosphonitrile film was attached to the surface of the I-Ⅰ group compound semiconductor GaAs wafer 2 by flowing gas and thermal decomposition.

(6) Effects In the conventional method of forming a protective film, two gases, phosphine and ammonia, were introduced into the reaction system. At this time, a chemical reaction progresses in which phosphorus (hereinafter referred to as P) and nitrogen (hereinafter referred to as N) are liberated from phosphine and ammonia to form PN. Therefore, if there is residual oxygen or moisture, N and P combine with oxygen, etc., and oxygen is taken into the PN film.

However, in the decomposition of the phosphonichloride (IJ) of the present invention, one point of the six-membered ring dissociates, the generated radical reacts, and pentapolymerization proceeds. Therefore, the number of radicals reacted to obtain molecules with the same degree of polymerization is reduced to one-sixth of the conventional method, and the probability that oxygen is incorporated into the molecules during the polymerization reaction process can be reduced.

Furthermore, polychlorinated phosphoryl (IJ) has an unsaturated double bond, as shown in FIG. 2, and therefore has a large degree of sway in one molecular chain. Therefore, the above-mentioned molecules easily approach the active sites on the solid surface, and when attached to the surface of the IV group compound semiconductor, have the effect of closing the dangling bonds. Furthermore, due to the sway of the molecular chains, internal strain in the polychlorinated phosphonitrile film is alleviated. Therefore, peeling from the solid surface due to internal strain can be prevented, and adhesion to the solid surface can be improved.

Furthermore, polychlorinated phosphozetatolyl has polar molecules because P and N, which have significantly different electron affinities, are adjacent to each other in the molecular chain. Generally, polar molecules exhibit good adhesion to metal surfaces. It is known that this means that free electrons in metals
This is because the polar molecules move in a direction that cancels out the electrostatic field due to the dipoles in the polar molecules that are close to the metal surface, resulting in the formation of dipoles in the opposite direction, which creates an attractive force between the polar molecules and the metal surface. Therefore, the polychlorinated phosphonitrile of the present invention also has I-
When approaching the surface of the group V compound, dipoles are induced on the surface of the group IV compound, resulting in good adhesion.

As explained above, according to the present invention, an insulating film with good adhesion can be formed on the Otori-V group compound semiconductor, and the evaluation result of the interface state at the MI8 interface is about 10HcIIL-'' can be obtained with good reproducibility. .

[Brief explanation of drawings]

Figure 1 is a diagram showing the molecular structure of phosphorus nitride that has been attempted in the past.
The gz diagram is a diagram showing the molecular structure of phosphonitrile chloride used when forming the membrane of the present invention, and FIG. 3 is a diagram showing the molecular structure of polychlorinated phosphonitrile. Figure 4 shows the decomposition of phosphonitrile chloride used in the examples.
FIG. 2 is a schematic diagram of an apparatus for forming a polychlorinated phosphonitrile film on the surface of a -V compound. In Fig. 4, 1 is a quartz reaction tube, 2 is a GaAs wafer, and 3 is a quartz reaction tube.
is a carbon susceptor, 4 is a rotary pump, 5 is a stainless steel tube for introducing phosphonitrile chloride, 6 is a high frequency power supply,
7 is cooling water, and 8 is a high frequency coil. Figure 1 1←P-N← 7?2 Figure ct cQ \ / ri \ N j −+ P = N ← l Procedural amendment (mackerel) Commissioner of the Japan Patent Office 1, Indication of case 1982 Patent application No. 079495 No. 2, Title of the invention: Semiconductor surface protective film and method for manufacturing the same 3
, Relationship to the case of the person making the amendment Applicant: 4, 5-33-1 Shiba, Minato-ku, Tokyo, Agent 5, Detailed explanation of the invention in the specification subject to amendment 6, Contents of the amendment (1) From line 16 to line 18 on page 3 of the specification, it says “Journal Op Applied Fixtures (Y,
Hirots et ml Jemu ppl Phya,
53 (1982) No. 1) J and a certain note - ``Proceedings of the Japan Society of Applied Physics (Hirota et al., Spring 1982 Proceedings of the Japan Society of Applied Physics, P2S5) J'' amended.

Claims (1)

[Claims] 1) A semiconductor surface protective film characterized in that its main component is polychlorinated phosphonitrile. 2) A method for producing a semiconductor surface protective film, which comprises forming a polychlorinated phosphonitrile thin film by ring-opening polymerization of chlorinated phosphonitrile having a six-membered ring structure.