JP2005259966A - Method of forming thin film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form a film consisting of metal oxide and metal nitride more quickly, while retaining high-quality characteristics, generated by atomic layer growing method, as they are. <P>SOLUTION: After an SiCl<SB>4</SB>molecular layer (adsorption layer) 102 is formed, oxidizing gas 113, such as H<SB>2</SB>O, is introduced into a reaction vessel to obtain a condition such that the oxidizing gas 113 is supplied on the surface of the silicon substrate, whereby a molecule (SiCl<SB>4</SB>molecular layer 102), adhered to the surface of the silicon substrate 101, is oxidized; and turns into the condition where silicon oxide layer 103 of one silicon molecular layer is formed on the surface of the silicon substrate 101. Thereafter, the inside of the reaction vessel is purged by an inert gas 112 heated to 700°C to obtain a condition that the inert gas 112 is supplied on the silicon substrate 101 and the oxidizing gas is removed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a thin film forming method for forming a metal oxide film or a metal nitride film by an atomic layer growth method.

  In a liquid crystal display device, a display device using an organic EL, or the like, a thin film transistor (hereinafter referred to as “TFT”) formed on a glass substrate is used as a switching element. Since this TFT is formed on a glass substrate having low heat resistance, the gate insulating film is formed by a plasma CVD (Chemical Vapor Deposition) method in which high-temperature treatment is not performed. Further, in recent years, development of a gate insulating film made of a material having a higher dielectric constant has been promoted as higher density integration is required as LSI density increases. It has been studied to form such an insulating material having a high dielectric constant by an atomic layer growth method.

  However, a film formed by the plasma CVD method includes many crystal defects in the film, and is not very reliable, such as insufficient denseness. In addition, there is a problem that the interface between the semiconductor and the insulating film is damaged due to the influence of charged particles in the plasma when the film is formed. For example, when the interface is damaged by plasma, a trap is formed, which greatly reduces the performance. As described above, the field effect transistor has a problem that the characteristics of the transistor are not so good when the gate insulating film is formed by the CVD method.

  In order to solve the above-described problem, a technique for forming a gate insulating film by an atomic layer growth method has been proposed (see Patent Documents 1 and 2). The atomic layer growth method is a technique for forming a thin film in units of atomic layers by alternately supplying a raw material of each element constituting a film to be formed to a substrate.

In the atomic layer growth method, only one layer or n layer is adsorbed on the surface while the raw materials for each element are being supplied, so that excess raw materials do not contribute to the growth. This is called self-stopping action of growth. Since the atomic layer growth method does not use plasma, a high-quality film can be formed.
According to the atomic layer growth method having such characteristics, it has both high shape adaptability and film thickness controllability, as in general CVD, and forms an insulating film called a capacitor of a memory element or a high-k gate. It is expected to be put to practical use.

The applicant has not yet found prior art documents related to the present invention by the time of filing other than the prior art documents specified by the prior art document information described in this specification.
JP-A-1-179423 JP-A-5-160152

However, in the atomic layer growth method, for example, in the formation of a film made of a metal oxide, when the metal adsorbed on the surface of the substrate reacts with the oxidant introduced to oxidize the metal reacts on the surface of the substrate. Increased speed and complete reaction without residue are required. The same applies to the formation of a nitride film. For this reason, the film forming speed (film forming speed) is not so high, and the film formation may not be completed within a desired time. In order to improve the deposition rate, use of highly reactive ozone (O ₃ ) or the like has been attempted in the formation of an oxide film, but a sufficient deposition rate has not been obtained.

  The present invention has been made to solve the above-described problems, and a film made of metal oxide or metal nitride can be formed more quickly while maintaining high quality characteristics by atomic layer growth. The purpose is to be able to.

In the thin film forming method according to the present invention, a source gas composed of a metal compound is supplied to a surface of a substrate heated to a first temperature inside a reaction vessel depressurized to a predetermined pressure. A first step in which an adsorption layer adsorbed on the surface of the substrate is formed; a second step of supplying and purging an inert gas to the surface of the substrate after stopping the supply of the source gas; and an inert gas A third step of supplying an oxidizing gas to the surface of the substrate to oxidize the adsorption layer and forming a metal oxide layer composed of a metal oxide on the substrate; And a fourth step of supplying and purging an inert gas to the surface of the substrate after stopping the supply, and at least one of the inert gas and the oxidizing gas is a second temperature not lower than the first temperature, for example, 500 ° C. So that it is heated and supplied to the surface of the substrate. It is intended.
According to this method, when the source gas is not supplied, the substrate is heated to the substrate heating temperature or higher by the supplied inert gas or oxidizing gas.

In another thin film forming method according to the present invention, a source gas composed of a metal compound is supplied to a surface of a substrate heated to a first temperature inside a reaction vessel depressurized to a predetermined pressure. A first step in which an adsorption layer in which a compound is adsorbed on the surface of the substrate is formed; a second step of purging by supplying an inert gas to the surface of the substrate after the supply of the source gas is stopped; After the supply of the active gas is stopped, a nitriding gas is supplied to the surface of the substrate to nitride the adsorption layer, and a metal nitride layer composed of a metal nitride is formed on the substrate; A fourth step of supplying and purging the surface of the substrate with an inert gas after stopping the supply of the gas, and at least one of the inert gas and the nitriding gas has a second temperature equal to or higher than the first temperature, for example, Supply to the surface of the substrate by heating to 500 ° C or higher One in which the.
According to this method, when the source gas is not supplied, the substrate is heated to a temperature higher than the substrate heating temperature by the supplied inert gas or nitriding gas.

  As described above, in the present invention, since the substrate is heated by the supplied gas in the absence of the source gas, the reaction of the layer already formed on the surface of the substrate is further improved. Proceeds quickly. As a result, according to the present invention, it is possible to obtain an excellent effect that a film made of a metal oxide or a metal nitride can be formed more rapidly while maintaining high quality characteristics by the atomic layer growth method.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a process diagram for explaining a thin film forming method according to an embodiment of the present invention.
First, as shown in FIG. 1A, a silicon substrate 101 is fixed inside a predetermined reaction vessel, and the pressure in the reaction vessel is set to about 2 to 3 Pa by a predetermined exhaust mechanism. The main surface of the silicon substrate 101 has a plane orientation of (100).

Next, the substrate temperature is set to 400 ° C., the source gas 111 made of SiCl ₄ is introduced into the reaction vessel, and the source gas 111 is supplied onto the silicon substrate 101. The source gas 111 is supplied for about 30 seconds. As a result, a SiCl ₄ molecular layer (adsorption layer) 102 in which SiCl ₄ molecules as raw materials are adsorbed is formed on the silicon substrate 101.

Next, the introduction of the source gas 111 into the reaction vessel is stopped, and as shown in FIG. 1B, an inert gas 112 such as nitrogen gas is heated to 700 ° C. and introduced into the reaction vessel. Then, the inside of the reaction vessel is purged with an inert gas 112 heated to a high temperature, and surplus gases other than those adsorbed on the silicon substrate 101 (SiCl ₄ molecular layer 102) are removed from the reaction vessel. The purge is performed for about 30 seconds. Further, the inert gas 112 is supplied vertically from directly above the substrate 101. At this time, the silicon substrate 101 is heated to a high temperature of 300 ° C. or higher without the source gas 111.

Next, as shown in FIG. 1C, an oxidizing gas 113 such as H ₂ O is introduced into the reaction vessel, and the oxidizing gas 113 is supplied to the surface of the silicon substrate. The supply of the oxidizing gas 113 is performed for about 30 seconds. As a result, molecules (SiCl ₄ molecular layer 102) adsorbed on the surface of the silicon substrate 101 are oxidized, and as shown in FIG. 1C, silicon oxide for one atomic layer of silicon is formed on the surface of the silicon substrate 101. It is assumed that the layer 103 is formed. Here, the introduced oxidizing gas 113 may be heated to about 700 ° C.

  Next, the inside of the reaction vessel is purged with an inert gas 112 heated to 700 ° C., and the inert gas 112 is supplied onto the silicon substrate 101 as shown in FIG. Is removed from the silicon substrate 101. The purge is performed for about 30 seconds. At this time, the silicon substrate 101 and the silicon oxide layer 103 are heated to a high temperature of 300 ° C. or higher without the source gas 111.

Next, as shown in FIG. 1E, a source gas 111 made of SiCl ₄ is supplied onto the silicon substrate 101, and a new SiCl ₄ molecular layer 104 is formed on the silicon oxide layer 103. To do.
Thereafter, the process described with reference to FIGS. 1B to 1E is repeated 20 times, for example, so that a silicon oxide film having a thickness of about 2 nm is formed.

Next, the effect of purging with the heated inert gas 112 by the above-described atomic layer growth method will be described.
As a comparison object, first, the substrate temperature was set to 300 ° C., the sample A in which the silicon oxide film was formed by the above-described atomic layer growth method by purging using an inert gas without heating, and the substrate temperature was set to 400 ° C. By purging using an inert gas without heating, sample B in which the silicon oxide film was formed by the above-described atomic layer growth method, and purging using a substrate temperature of 500 ° C. without heating the inert gas, A sample C on which a silicon oxide film is formed by the atomic layer growth method described above is manufactured.

When the sample D created by the manufacturing method in the present embodiment shown in FIG. 1 is compared with the samples A, B, and C described above, the film formation rate per cycle is shown in the comparison result of FIG. However, the sample D according to the present embodiment has a higher film formation speed than many samples. Note that the interface state densities of Sample D and Sample A are both 6 × 10 ¹⁰ / cm ² eV.

  In the above description, the formation of the silicon oxide film has been described as an example. However, the present invention is not limited to this. By using another metal source gas as the source gas, it can be applied to the formation of other metal oxide films (metal oxide layers). Further, the present invention can be applied to the case where a metal nitride film (metal nitride layer) is formed by using a nitriding gas instead of an oxidizing gas. In the above description, the gas is heated to 700 ° C. and supplied. However, the present invention is not limited to this, and the temperature may be higher than the substrate temperature in the atomic layer growth method. In the formation of the metal oxide film or metal nitride film by the atomic layer growth method, the substrate temperature is about 500 ° C. at the maximum, so the gas temperature may be heated to 500 ° C. or higher for supply.

  The manufacturing method of the present embodiment is an atomic layer growth method in which at least one of an inert gas and an oxidizing gas for purging is heated to be supplied at a temperature higher than the substrate heating temperature. Further, in the atomic layer growth method, at least one of an inert gas and a nitriding gas for purging is heated to a temperature equal to or higher than the substrate heating temperature and supplied.

It is process drawing for demonstrating the thin film formation method in embodiment of this invention. It is explanatory drawing which shows the comparison result with the sample produced with the prior art.

Explanation of symbols

101 ... silicon substrate, 102 ... SiCl ₄ molecules layer (adsorption layer), 103 ... silicon oxide layer, 111 ... source gas, 112 ... inert gas, 113 ... oxidizing gas.

Claims (3)

In the reaction vessel depressurized to a predetermined pressure, a source gas composed of a metal compound is supplied to the surface of the substrate heated to the first temperature, and the metal compound is adsorbed on the surface of the substrate. A first step in which a layer is formed;
A second step of purging by supplying an inert gas to the surface of the substrate after stopping the supply of the source gas;
After the supply of the inert gas is stopped, an oxidizing gas is supplied to the surface of the substrate to oxidize the adsorption layer, and a metal oxide layer composed of the metal oxide is formed on the substrate. A third step;
And at least a fourth step of purging by supplying an inert gas to the surface of the substrate after stopping the supply of the oxidizing gas,
At least one of the inert gas and the oxidizing gas is heated to a second temperature not lower than the first temperature and supplied to the surface of the substrate. In the reaction vessel depressurized to a predetermined pressure, a source gas composed of a metal compound is supplied to the surface of the substrate heated to the first temperature, and the metal compound is adsorbed on the surface of the substrate. A first step in which a layer is formed;
A second step of purging by supplying an inert gas to the surface of the substrate after stopping the supply of the source gas;
After the supply of the inert gas is stopped, a nitriding gas is supplied to the surface of the substrate to nitride the adsorption layer, and a metal nitride layer composed of the metal nitride is formed on the substrate. A third step;
A fourth step of supplying and purging an inert gas on the surface of the substrate after stopping the supply of the nitriding gas,
At least one of the inert gas and the nitriding gas is heated to a second temperature not lower than the first temperature and supplied to the surface of the substrate. In the thin film formation method of Claim 1 or 2,
The method for forming a thin film, wherein the second temperature is 500 ° C. or higher.

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