JP2007273536A - Thin film forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To further improve a film forming speed in forming a thin film using an atomic layer growing method. <P>SOLUTION: Introduction of a material gas 121 into a film forming chamber is stopped after an absorbing process, and the inside of the film forming chamber is degassed by a degassing means (vacuum pump), thereby forming a state that an excessive gas other than the gas (aminosilane molecular layer 102) absorbed on a silicon substrate 101 is removed from the film forming chamber with one part left. For example, an inert gas such as a nitrogen gas is introduced into the film forming chamber degassed by the vacuum pump to purge the inside of the film forming chamber, thereby forming a state where the material gas 121 is removed with one part left in the inside of the film forming chamber. In other words, the purge process is completed without forming a state that the material gas 121 is completely removed from the inside of the film forming chamber. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a thin film forming method for forming a thin film in units of molecular layers, for example, by supplying a source gas onto a substrate heated in a gas phase.

  An atomic layer deposition method has been developed as a technique that enables a very thin film to be formed with good uniformity while having excellent step coverage (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. According to the atomic layer growth method, it has high shape adaptability and film thickness controllability as well as general CVD (Chemical Vapor Deposition) method. It is expected that it will be put to practical use. In addition, since an insulating film can be formed at a low temperature of about 300 ° C., application to the formation of a thin film transistor of a display device using a glass substrate is also expected.

JP-A-1-179423 JP-A-5-160152

  By the way, in the atomic layer growth method, for example, when forming a metal oxide film, since two kinds of gases, ie, a metal source gas and an oxidizing gas are used alternately, gas introduction and exhaust are repeated. For this reason, compared with a general CVD method in which a film is deposited by continuously introducing a gas, the atomic layer growth method has a smaller film thickness formed per unit time, in other words, a film formation rate. There is a problem that is slow.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to further improve the deposition rate in forming a thin film by an atomic layer growth method.

  In the thin film forming method according to the present invention, a source gas composed of a metal compound containing silicon or the like is supplied to the heated substrate surface inside the film forming chamber, and the metal compound is adsorbed on the surface of the substrate. A first step in which the adsorption layer is formed, and a first step of removing the source gas from the inside of the deposition chamber so that a part of the source gas remains inside the deposition chamber after the supply of the source gas is stopped. By introducing an oxidizing gas into the film forming chamber in which the source gas remains in two steps, the adsorption layer is oxidized to form an adsorption oxide layer made of a metal oxide on the substrate, And at least a third step in which a deposited oxide layer deposited by reacting the introduced oxidizing gas with a part of the source gas remaining in the film forming chamber is formed on the adsorption oxide layer. It is a thing.

  In the thin film forming method, after the supply of the oxidizing gas is stopped, the fourth step of removing the oxidizing gas from the inside of the film forming chamber so that a part of the oxidizing gas remains inside the film forming chamber, and the oxidizing gas is a residue And a fifth step of introducing the source gas into the film forming chamber.

  In addition, another thin film forming method according to the present invention is a method in which a source gas composed of a metal compound is supplied to a heated substrate surface inside the film forming chamber, and the metal compound is adsorbed on the substrate surface. 1st process in which 1 adsorption layer is formed, 2nd process of removing source gas from the inside of the film forming chamber after supply of the source gas is stopped, and introducing an oxidizing gas into the inside of the film forming chamber Then, after the first adsorption layer is oxidized and the first adsorption oxide layer made of metal oxide is formed on the substrate, the third step, and after the supply of the oxidizing gas is stopped, A fourth step of removing the oxidizing gas from the inside of the film forming chamber so that a part of the oxidizing gas remains inside the film forming chamber, and introducing the source gas into the film forming chamber in which the oxidizing gas remains, Deposited oxidation deposited by reaction of the introduced source gas with some oxidizing gas remaining in the deposition chamber Is formed on the first adsorbed oxide layer, and a second step is formed in which the second adsorbed layer in which the metal compound is adsorbed on the surface of the deposited oxide layer is formed, and the inside of the film forming chamber And at least a sixth step of oxidizing the second adsorption layer to form a second adsorption oxide layer composed of a metal oxide on the deposited oxide layer by introducing an oxidizing gas into It is what I did.

  As described above, according to the present invention, when the source gas and the oxidizing gas supplied to the inside of the film forming chamber are exhausted, some of these remain in the film forming chamber. In addition to the adsorption layer, a layer by deposition is also formed, so that the film formation rate can be further improved in the formation of thin films by the atomic layer growth method. Is obtained.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a process diagram for explaining an example of a thin film forming method according to an embodiment of the present invention. In the following description, aminosilane is taken as an example of the metal compound. First, the silicon substrate 101 is fixed inside the film formation chamber of a predetermined atomic layer growth apparatus, the pressure in the film formation chamber is set to about 2 to 3 Pa by a predetermined exhaust mechanism, and the silicon substrate 101 is heated to about 400 ° C. It is assumed that The state where the silicon substrate 101 is heated is continued until a series of thin film formation is completed. In this state, a source gas 121 made of aminosilane is introduced into the film forming chamber, and the source gas 121 is supplied onto the silicon substrate 101 as shown in FIG. The source gas 121 is supplied for about 2 seconds, for example. As a result, an aminosilane molecular layer (adsorption layer) 102 in which aminosilane molecules as a raw material are adsorbed is formed on the silicon substrate 101.

  Next, the introduction of the source gas 121 into the film formation chamber is stopped, and the inside of the film formation chamber is evacuated by an evacuation means (vacuum pump), so that other than those adsorbed on the silicon substrate 101 (aminosilane molecular layer 102). It is assumed that the surplus gas is removed from the film forming chamber, leaving a part. For example, an inert gas such as nitrogen gas is introduced into the film formation chamber evacuated by a vacuum pump to purge the film formation chamber, and the source gas 121 is removed while leaving a part in the film formation chamber. State. In other words, the purge process is terminated without setting the source gas 121 completely removed from the film forming chamber.

  As described above, the thin film forming method is characterized in that a part of the source gas remains in the purge process subsequent to the adsorption process in which the source gas 121 is introduced and adsorbed to shorten the purge process. is there. Here, the amount of the source gas remaining in the purge process can be controlled, for example, by controlling the pressure of the exhaust gas using a vacuum pump. For example, by setting the exhaust ultimate pressure in the film formation chamber in the purge process to 100 Pa, a part of the source gas can be left in the film formation chamber. Further, the amount of the raw material gas remaining in the purge process can also be controlled by controlling the supply amount of the inert gas introduced in the purge process. Moreover, you may combine these.

  Next, as shown in FIG. 1B, an oxidizing gas 122 such as ozone is introduced into the film forming chamber, and the oxidizing gas 122 is supplied to the surface of the aminosilane molecular layer 102. The supply of the oxidizing gas 122 is performed for about 2 seconds. As a result, molecules (aminosilane molecular layer 102) adsorbed on the surface of the silicon substrate 101 are oxidized, and as shown in FIG. 1B, the adsorbed 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. Further, in this oxidation process, the source gas left in the purge process reacts with the introduced oxidizing gas 122, and the deposited silicon oxide layer 104 is formed on the adsorbed silicon oxide layer 103.

  Next, introduction of the oxidizing gas 122 into the deposition chamber is stopped, and the oxidizing gas 122 inside the deposition chamber is exhausted. For example, an inert gas such as nitrogen gas is introduced into the film formation chamber evacuated by a vacuum pump to purge the film formation chamber, and the oxidizing gas 122 is removed from the film formation chamber. This purging process is performed, for example, for about 5 seconds.

  Next, as shown in FIG. 1C, a source gas 121 made of aminosilane is supplied onto the silicon substrate 101 so that a new aminosilane molecular layer 105 is formed on the deposited silicon oxide layer 104. . This is the same as the adsorption process described with reference to FIG.

  Next, the introduction of the source gas 121 into the deposition chamber is stopped, the source gas 121 inside the deposition chamber is exhausted, and a surplus gas other than the adsorbed aminosilane molecular layer 105 leaves a part of the deposition chamber. Removed. In other words, the purge process is terminated without setting the source gas 121 completely removed from the film forming chamber.

  Next, as illustrated in FIG. 1D, the oxidizing gas 122 is introduced into the film formation chamber so that the oxidizing gas 122 is supplied to the surface of the aminosilane molecular layer 105. The supply of the oxidizing gas 122 is performed for about 2 seconds. As a result, the aminosilane molecular layer 105 is oxidized and the adsorbed silicon oxide layer 106 is formed. Further, in this oxidation process, the source gas left in the purge process reacts with the introduced oxidizing gas 122, and the deposited silicon oxide layer 107 is formed on the adsorbed silicon oxide layer 106. This is the same as the oxidation process described with reference to FIG.

  As described above, the silicon oxide layer formed by adsorption on the silicon substrate 101 by the series of basic steps of adsorption → partial purge → oxidation → purge from FIG. 1 (a) to FIG. 1 (b). And a silicon oxide layer formed by deposition. FIG. 1 shows a case where the basic process is repeated twice. As described above, according to the thin film forming method illustrated in FIG. 1, the silicon oxide layer can be formed thicker than the adsorbed layer in one basic process. Further, as described above, according to the thin film forming method illustrated in FIG. 1, the time for the purging process subsequent to the adsorption process is shortened. Thus, according to the thin film formation method shown in FIG. 1, a thick silicon oxide layer can be formed in a shorter time than the conventional atomic layer growth method.

  Next, another thin film forming method according to the present invention will be described. FIG. 2 is a process diagram for explaining the thin film forming method according to the embodiment of the present invention. First, the silicon substrate 201 is fixed inside the film forming chamber of a predetermined atomic layer growth apparatus, the pressure in the film forming chamber is set to about 2 to 3 Pa by a predetermined exhaust mechanism, and the silicon substrate 201 is heated to about 400 ° C. It is assumed that Note that the heated state of the silicon substrate 201 is continued until a series of thin film formation is completed. In this state, a source gas 221 made of aminosilane is introduced into the film formation chamber, and the source gas 221 is supplied onto the silicon substrate 201 as shown in FIG. The source gas 221 is supplied for about 2 seconds, for example. As a result, an aminosilane molecular layer (adsorption layer) 202 in which aminosilane molecules as raw materials are adsorbed is formed on the silicon substrate 201.

  Next, the introduction of the source gas 221 into the film formation chamber is stopped, and the inside of the film formation chamber is evacuated by an evacuation means (vacuum pump), so that other than those adsorbed on the silicon substrate 201 (aminosilane molecular layer 202) The surplus gas is removed from the film formation chamber. For example, an inert gas such as nitrogen gas is introduced into the film formation chamber evacuated by a vacuum pump to purge the film formation chamber, and the source gas 221 is removed from the film formation chamber.

  Next, as shown in FIG. 2B, an oxidizing gas 222 such as ozone is introduced into the film forming chamber so that the oxidizing gas 222 is supplied to the surface of the aminosilane molecular layer 202. The supply of the oxidizing gas 222 is performed for about 2 seconds. As a result, molecules adsorbed on the surface of the silicon substrate 201 (aminosilane molecular layer 202) are oxidized, and as shown in FIG. 2B, adsorbed silicon oxide for one atomic layer of silicon is formed on the surface of the silicon substrate 201. The layer 203 is formed.

  Next, the introduction of the oxidizing gas 222 into the film forming chamber is stopped, and the inside of the film forming chamber is evacuated by a vacuum pump, so that the oxidizing gas 222 is removed from the film forming chamber while leaving a part. . For example, an inert gas such as nitrogen gas is introduced into the film formation chamber evacuated by a vacuum pump to purge the film formation chamber, and the oxidizing gas 222 is removed while leaving a part in the film formation chamber. State. In other words, the purge process is completed without completely removing the oxidizing gas 222 from the inside of the film forming chamber.

  As described above, in this thin film forming method, in the purging process subsequent to the oxidizing process for introducing the oxidizing gas 222 and oxidizing the adsorbed layer, a part of the oxidizing gas remains, and the purging process is performed. It is characterized by shortening. Here, the amount of oxidizing gas left in the purge process can be controlled by, for example, pressure control of exhaust gas by a vacuum pump. In addition, the amount of oxidizing gas remaining in the purge process can also be controlled by controlling the supply amount of the inert gas introduced in the purge process. Moreover, you may combine these.

  Next, a source gas 221 made of aminosilane is supplied onto the silicon substrate 201. Here, as described above, since the oxidizing gas used in the previous oxidation process remains, in this adsorption process, the oxidizing gas remaining in the initial stage reacts with the supplied raw material gas 221, and FIG. As shown in FIG. 2C, a deposited silicon oxide layer 204 is formed on the adsorbed silicon oxide layer 203. After this initial stage, the introduced source gas 221 is adsorbed on the surface of the deposited silicon oxide layer 204, and a new aminosilane molecular layer 205 is formed.

  Next, the introduction of the source gas 221 into the film formation chamber is stopped, and the inside of the film formation chamber is evacuated by a vacuum pump so that surplus gas other than the aminosilane molecular layer 205 is removed from the film formation chamber. To do. For example, an inert gas such as nitrogen gas is introduced into the film formation chamber evacuated by a vacuum pump to purge the film formation chamber, and the source gas 221 is removed from the film formation chamber.

  Next, as illustrated in FIG. 2D, the oxidizing gas 222 is introduced into the film formation chamber, and the oxidizing gas 222 is supplied to the surface of the aminosilane molecular layer 205. The supply of the oxidizing gas 222 is performed for about 2 seconds, for example. As a result, the aminosilane molecular layer 205 is oxidized and the adsorbed silicon oxide layer 206 is formed.

  As described above, after the initial adsorption process from FIG. 2A to FIG. 2B, adsorption is performed on the silicon substrate 201 through a series of basic steps of purge → oxidation → partial purge → adsorption. Thus, a silicon oxide layer formed by deposition and a silicon oxide layer formed by deposition are formed. FIG. 2 shows a case where the basic process is performed once and subsequently the next basic oxidation process is performed. As described above, according to the thin film formation method illustrated in FIG. 2, the silicon oxide layer can be formed thicker than the adsorbed layer in one basic process. Further, as described above, according to the thin film formation method illustrated in FIG. 2, the time for the purging process subsequent to the oxidation process is shortened. As described above, according to the thin film forming method shown in FIG. 2, a thick silicon oxide layer can be formed in a shorter time than the conventional atomic layer growth method.

  By the way, a part of the source gas may be left in the purging process subsequent to the adsorption process, and a part of the oxidizing gas may be left in the purging process subsequent to the oxidation process. By combining in this way, a thicker film can be formed in a shorter time.

  In the above description, the formation of the silicon oxide film using aminosilane as the source gas has been described as an example. However, the present invention is not limited to this, and the present invention is not limited to this. Even in the case of a layer, the same applies. The present invention is also applicable to the formation of a metal oxide film using another organometallic material as a source gas.

It is process drawing for demonstrating the example of the thin film formation method which concerns on embodiment of this invention. It is process drawing for demonstrating the example of another thin film formation method which concerns on embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 101 ... Silicon substrate, 102, 105 ... Aminosilane molecular layer (adsorption layer), 103, 106 ... Adsorption silicon oxide layer, 104, 107 ... Deposition silicon oxide layer, 121 ... Source gas, 122 ... Oxidation gas, 201 ... Silicon substrate, 202, 205 ... aminosilane molecular layer (adsorption layer), 203, 206 ... adsorption silicon oxide layer, 221 ... source gas, 222 ... oxidation gas.

Claims (3)

A source gas composed of a metal compound is supplied to the surface of the heated substrate inside the film forming chamber, so that an adsorption layer in which the metal compound is adsorbed on the surface of the substrate is formed. Process,
A second step of removing the source gas from the inside of the film forming chamber so that a part of the source gas remains inside the film forming chamber after stopping the supply of the source gas;
By introducing an oxidizing gas into the film forming chamber in which the source gas remains, the adsorption layer is oxidized to form an adsorption oxide layer made of the metal oxide on the substrate. A third step in which a deposited oxide layer deposited by a reaction between the introduced oxidizing gas and a part of the source gas remaining in the film forming chamber is formed on the adsorption oxide layer; A thin film forming method comprising: The thin film forming method according to claim 1,
A fourth step of removing the oxidizing gas from the inside of the film forming chamber so that a part of the oxidizing gas remains inside the film forming chamber after stopping the supply of the oxidizing gas;
And a fifth step of introducing the source gas into the film forming chamber in which the oxidizing gas remains. In the film forming chamber, a source gas composed of a metal compound is supplied to the surface of the heated substrate to form a first adsorption layer in which the metal compound is adsorbed on the surface of the substrate. 1 process,
A second step of removing the source gas from the inside of the film forming chamber after stopping the supply of the source gas;
By introducing an oxidizing gas into the film formation chamber, the first adsorption layer is oxidized to form a first adsorption oxide layer made of the metal oxide on the substrate. A third step;
A fourth step of removing the oxidizing gas from the inside of the film forming chamber so that a part of the oxidizing gas remains inside the film forming chamber after stopping the supply of the oxidizing gas;
By introducing the raw material gas into the film forming chamber where the oxidizing gas remains, the introduced raw material gas and a part of the oxidizing gas remaining in the film forming chamber are reacted and deposited. A fifth step in which a deposited oxide layer is formed on the first adsorbed oxide layer, and a second adsorbed layer in which the metal compound is adsorbed on the surface of the deposited oxide layer is formed; ,
A state in which the second adsorption layer composed of the metal oxide is formed on the deposited oxide layer by oxidizing the second adsorption layer by introducing an oxidizing gas into the film forming chamber. A thin film forming method comprising: at least a sixth step.

Images