JP5184498B2 - Deposition method - Google Patents

Description

  The present invention relates to a film forming method on a substrate, and more particularly to a film forming method for forming an oxide film on a substrate having a hydrophobic surface by using an atomic layer deposition method.

  The Atomic Layer Deposition (ALD) method is a film formation method in which an atomic layer is digitally grown one by one using an organometallic compound called a precursor and its oxidizing agent (mainly water). It is. The reason why each atomic layer can be grown is to utilize the self-inhibiting mechanism of the precursor, that is, the property that when the atomic layer is adsorbed on the surface, the thickness does not increase beyond that. The ALD method is a kind of chemical vapor deposition (CVD) method, but differs from the normal CVD method in that the atomic layer is grown by a self-suppression mechanism by surface adsorption.

  Since the ALD method uses the surface adsorption of the substrate, the surface condition of the substrate greatly affects the growth conditions beyond the substrate temperature and substrate material which are important in thin film growth. Substrates such as silicon (Si) and gallium arsenide (GaAs) have hydrophilic properties due to the presence of hydroxyl groups (OH groups) on the substrate surface, and can be uniformly deposited without any problem by the ALD method. It is. However, graphite and its one atomic layer film, graphene, have honeycomb structure crystals, and only pi electrons exist on the surface. For this reason, the substrate surface exhibits inert hydrophobicity, and it is difficult to grow a uniform film by the ALD method.

For this reason, as a method of forming an oxide film on a hydrophobic substrate such as graphite or graphene, a method of growing a uniform oxide film by providing a buffer layer between the oxide film and the substrate has been proposed. ing. For example, a method of growing the aluminum oxide (Al ₂ O ₃ ) film on the surface with nitrogen dioxide as a buffer layer, a thin metal thin film (aluminum (Al) film, titanium (Ti) film, etc.) on the substrate A method of depositing and growing an oxide film on the metal thin film, a method of using strong oxidizing power ozone or nitrogen oxide (NO ₂ ), and the like have been proposed (for example, see Non-Patent Documents 1 to 4).

J.R.Williams, L.DiCarlo, C.M.Marcus, “Quantum Hall Effect in a Gate-Controlled p-n Junction of Graphene,” 2007, Science, vol 317, p.638-640 Seyoung Kim, Junghyo Nah, Insun Jo, Davood Shahrierdi, Luigi Colombo, Zhen Yao, Emanuel Tutuc, and Sanjay K. Banerjee, “Realization of a high mobility dual-gated graphene field-effect transistor with Al2O3 dielectric,” 2009, Applied Physics Letters 94, 062107 WHWang, W. Han, K. Pi, KMMcCreary, F. Miao, W. Bao, CNLau, and RKKawakami, “Growth of atomically smooth MgO films on graphene by molecular beam epitaxy,” 2008, Applied Physics Letters 93 , 183107 Bongki Lee, Seong-Yong Park, Hyun-Chul Kim, KyeongJae Cho, Eric M. Vogel, Moon J. Kim, Robert M. Wallace, and Jiyoung Kim, “Conformal Al2O3 dleccctr deposited by atomic layer deposition for graphene-based nanoelectronics, ”2008, Applied Physics Letters 92, 203102

However, in the methods using these buffer layers, there are problems such as changes in the interface state due to secular change and increases in interface states due to the presence of the buffer layer. For example, when an Al ₂ O ₃ film deposited by the ALD method is used as a gate insulating film of a transistor, a metal film that is essentially unnecessary for forming a transistor at the interface between the gate insulating film and the substrate, A semiconductor oxide film, a semiconductor nitride film, etc. remain as a buffer layer. For this reason, a problem may occur with respect to controllability of the gate voltage and withstand voltage due to charge accumulation at the interface. In particular, when the substrate is a compound semiconductor, the effect of this interfacial charge is significant and is a big problem.

  In view of the above problems, an object of the present invention is to provide a film forming method for forming a good oxide film on a hydrophobic substrate.

According to one aspect of the present invention, (a) an atomic layer deposition method for forming a base oxide film on a substrate surface of a hydrophobic substrate that is supersaturated with water at a first substrate temperature that is not less than room temperature and less than the boiling point of water. And (b) forming an upper oxide film on the base oxide film by using an atomic layer deposition method at a second substrate temperature, and forming the base oxide film, Supplying water to the substrate to bring the substrate surface into a supersaturated state of the substrate; a precursor having a vapor pressure sufficient to form a film by an atomic layer deposition method at a first substrate temperature; A film forming method including performing a low temperature cycle a plurality of times including a step of alternately supplying the substrate to a substrate in which the substrate surface is supersaturated with water is provided.

  ADVANTAGE OF THE INVENTION According to this invention, the film-forming method which forms a favorable oxide film on a hydrophobic substrate can be provided.

It is typical sectional drawing which shows the example of the semiconductor device manufactured using the film-forming method which concerns on embodiment of this invention. It is a schematic diagram which shows the example of the manufacturing apparatus used for the film-forming method which concerns on embodiment of this invention. It is a process step for demonstrating the film-forming method which concerns on embodiment of this invention. It is a process step for demonstrating the method to supply water to a board | substrate in the film-forming method which concerns on embodiment of this invention. It is a schematic diagram which shows the example of the water adhering on a hydrophobic substrate.

  Next, an embodiment of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, the embodiment described below exemplifies an apparatus and a method for embodying the technical idea of the present invention, and the embodiment of the present invention is the material, shape, structure, arrangement, etc. of the component parts. Is not specified as follows. The embodiment of the present invention can be variously modified within the scope of the claims.

  FIG. 1 shows an example of a semiconductor device 10 manufactured using a film forming method according to an embodiment of the present invention. In the semiconductor device 10 shown in FIG. 1, a base oxide film 12 and an upper oxide film 13 are sequentially stacked on a substrate surface 110 of a hydrophobic substrate 11. In the following, the film forming method according to the embodiment of the present invention will be described by taking as an example the case of manufacturing the semiconductor device 10 shown in FIG.

  In the film forming method according to the embodiment of the present invention, the base oxide film 12 is formed on the substrate surface 110 of the hydrophobic substrate 11 that is supersaturated with water at the first substrate temperature T1 that is at least room temperature and less than the boiling point of water. A step of forming using an atomic layer deposition method, and a step of forming the upper oxide film 13 on the base oxide film 12 using the atomic layer deposition method at a second substrate temperature T2.

The reason why the first substrate temperature T1 is set to a temperature higher than room temperature (for example, about 25 ° C.) and lower than the boiling point of water (100 ° C.) is to supply water (H ₂ O) to the substrate 11 as will be described later. This is to make the substrate surface 110 of the hydrophobic substrate 11 into a supersaturated state of water, that is, a sufficiently hydrophilic surface state. A base oxide film 12 is formed on the substrate surface 110 in a supersaturated state of water.

For this reason, a material that can obtain a vapor pressure sufficient to form a film using the ALD method at the first substrate temperature T1 is selected as a precursor used to form the base oxide film 12. Generally, the vapor pressure of the precursor in the ALD method is about 5 to 10 hectopascals (hPa). For example, when the base oxide film 12 is an aluminum oxide (Al ₂ O ₃ ) film, trimethylaluminum (TMA) is an organometallic compound that can be used as a precursor. TMA has a sufficient vapor pressure even at the first substrate temperature T1 in the range from room temperature to less than 100 ° C.

The second substrate temperature T2 is set to a temperature at which the precursor can obtain a sufficient vapor pressure for forming the upper oxide film 13 by the ALD method. When the upper oxide film 13 is an Al ₂ O ₃ film, TMA can be adopted as a precursor. Alternatively, when the upper oxide film 13 is a hafnium oxide (HfO ₂ ) film, tetrakisethylmethylaminohafnium (TEMAH) can be used as a precursor.

The film forming method according to the embodiment of the present invention is executed using, for example, an atomic layer deposition apparatus 100 as shown in FIG. In the atomic layer deposition apparatus 100 shown in FIG. 2, the carrier gas 101 used for transporting the precursor 102 and the oxidant 103 flows into the reaction chamber 104 in which the substrate 11 is stored via the gas line 108. Nitrogen (N ₂ ) gas, helium (He) gas, or the like can be used as the carrier gas 101.

  The precursor 102 is introduced into the gas line 108 by opening the pulsing valve 106, and is transferred to the reaction chamber 104 by the carrier gas 101. The oxidant 103 is introduced into the gas line 108 by opening the pulsing valve 107 and is transported to the reaction chamber 104 by the carrier gas 101. Further, the dry pump 105 discharges reaction gas, excess precursor 102, and the like to the outside of the reaction chamber 104.

  The carrier gas 101 is introduced into the gas line 108 at a pressure of about 3 to 6 hPa. For this reason, in order to introduce the precursor 102 into the gas line 108, the vapor pressure of the precursor 102 at the film forming temperature needs to be 5 hPa or more, preferably about 8 to 10 hPa.

Hereinafter, a case where the base oxide film 12 and the upper oxide film 13 are formed on the substrate 11 as illustrated in FIG. 1 using the atomic layer deposition apparatus 100 illustrated in FIG. 2 will be described as an example. Here, it is assumed that the precursor 102 used for forming the base oxide film 12 is TMA, and the base oxide film 12 is an Al ₂ O ₃ film.

  In addition, the precursor 102, the oxidizing agent 103, and the like are supplied in a pulsed manner to the reaction chamber 104 by pulse supply. In the following, “pulse time” is used to supply the precursor 102, the oxidizing agent 103, and the like to the reaction chamber 104. The pulsing valve 106 and the pulsing valve 107 are opened, and the “purge time” is the time when the pulsing valve 106 and the pulsing valve 107 are closed in order to supply only the carrier gas 101 to the reaction chamber 104. It's time. Usually, the purge time is a time for discharging TMA adsorbed excessively on the substrate surface 110, reaction products, surplus water molecules, and the like to the outside of the reaction chamber 104.

Below, the film-forming method which concerns on embodiment of this invention is demonstrated with reference to FIG. The vertical axis of the graph in FIG. 3 represents the substrate temperature of the substrate 11 and the pressure in the reaction chamber 104. Note that the oxidizing agent 103 is H ₂ O, and the water supplied to the substrate 11 is introduced into the reaction chamber 104 via the gas line 108 by opening the pulsing valve 107.

  (A) After storing the hydrophobic substrate 11 in the reaction chamber 104, the temperature in the reaction chamber 104 is set, and the substrate temperature of the substrate 11 is within the range of room temperature to less than the boiling point of water (100 ° C.). 1 substrate temperature T1. Since TMA has a sufficient vapor pressure even at room temperature, it can be used as the precursor 102 in a range from room temperature to less than 100 ° C. Note that, when the precursor 102 is TMA, it has been experimentally obtained that the optimum first substrate temperature T1 is about 80 ° C.

(B) During the period tw of the period t _T1 shown in FIG. 3, water is supplied to the substrate 11 to bring the substrate surface 110 of the substrate 11 into a supersaturated state of water. For example, as shown in FIG. 4, a pulse supply cycle comprising a pulse time t _PLW when the pulsing valve 107 is open and a purge time t _PGW when the pulsing valve 107 is closed to supply only the carrier gas 101 ( Hereinafter, it is referred to as “water supply cycle”.) Cw is repeated to supply water to the substrate 11. However, the purge time t _PGW is set so that water is always supplied to the substrate 11. Specifically, the purge time t _PGW is made shorter than the passage time t _PASS required for water to pass from the pulsing valve 107 to the reaction chamber 104. For example, when the passage time t _PASS is 2.5 seconds, the purge time t _PGW is shorter than 2.5 seconds. The passage time t _PASS depends on the structure of the atomic layer deposition apparatus 100.

(C) In the period tm following the period tw, the substrate surface 110 is in a supersaturated state of water by the pulse supply consisting of the pulse time t _{PLM for} opening only the pulsing valve 106 and the purge time t _PGM for closing the pulsing valves 106 and 107. TMA is supplied to the substrate 11 once. Specifically, TMA is gasified as the precursor 102, the pulsing valve 106 is opened for a pulse time t _PLM = 0.1 second, and TMA is placed on the carrier gas 101 and introduced into the reaction chamber 104. During this time, the pulsing valve 107 is closed. As a result, the precursor 102 reacts with the substrate surface 110 of the substrate 11 placed in the reaction chamber 104, and only one atomic layer is adsorbed on the substrate surface 110. At this time, since water adheres to the entire surface of the substrate surface 110, the precursor 102 is adsorbed to the entire surface of the substrate surface 110.

(D) After the precursor 102 is adsorbed on the substrate surface 110, the pulsing valves 106 and 107 are closed for the purge time t _PGM = 2.5 seconds, and only the carrier gas 101 is introduced into the reaction chamber 104. The purge time t _PGM is a time required to remove TMA adsorbed excessively on the substrate surface 110. The purge time t _PGM can be set in the range of 2.5 to 120 seconds according to the temperature in the reaction chamber 104 (first substrate temperature T1).

(E) Next, in the period tm, the oxidant 103 of the precursor 102 is supplied to the substrate 11 by the pulse supply consisting of the pulse time t _{PLO for} opening only the pulsing valve 107 and the purge time t _PGO for closing the pulsing valves 106 and 107. To do. For example, the pulsing valve 107 is opened for a pulse time t _PLO = 0.1 second, and the oxidizing agent 103 is placed on the carrier gas 101 and introduced into the reaction chamber 104. As a result, a lowermost layer corresponding to one atomic layer of the base oxide film 12 in contact with the substrate surface 110 is formed. Next, during the purge time t _PGO = 4.0 seconds, the pulsing valves 106 and 107 are closed, and only the carrier gas 101 is introduced into the reaction chamber 104. Thereby, reaction products and excess water molecules are discharged to the outside of the reaction chamber 104.

(F) Thereafter, the base oxide film is formed at the first substrate temperature T1 by an ALD process in which the step of supplying the precursor 102 to the substrate 11 and the step of supplying the oxidizing agent 103 of the precursor 102 to the substrate 11 are repeated. 12 is formed. That is,
(A) During the pulse time t1 _PLM , the pulsing valve 107 is closed, the pulsing valve 106 is opened, and the precursor 102 is supplied to the substrate 11;
(B) During the purge time t1 _PGM , the pulsing valves 106 and 107 are closed and only the carrier gas 101 is supplied to the substrate 11;
(C) During the pulse time t1 _PLO , the pulsing valve 106 is closed, the pulsing valve 107 is opened, and the oxidant 103 of the precursor 102 is supplied to the substrate 11;
(D) During the purge time t1 _PGO , the pulsing valves 106 and 107 are closed and only the carrier gas 101 is supplied to the substrate 11.
As a cycle (hereinafter referred to as a “low temperature cycle”) C1, the low temperature cycle C1 is repeatedly executed a plurality of times at the first substrate temperature T1. For example, TMA is supplied to the substrate 11 as the precursor 102 at a pulse time t1 _PLM = 0.1 second and a purge time t1 _PGM = 4.0 second, and a pulse time t1 _PLO = 0.1 second and a purge time t1 _PGO = 4. In 0 second, H ₂ O is supplied to the substrate 11 as the oxidizing agent 103. Also in this case, the purge time t1 _PGM may be increased to about 120 seconds depending on the temperature in the reaction chamber 104 (first substrate temperature T1). In the period tw, the period tm, and the period t _T1 including a plurality of low temperature cycles C1, the base oxide film 12 is formed on the substrate 11.

(G) After the formation of the base oxide film 12, the temperature in the reaction chamber 104 is set, and the substrate temperature of the substrate 11 is set to the second substrate temperature T2. The second substrate temperature T2 is a general film formation temperature in the ALD method. For example, when the precursor 102 is TMA, the second substrate temperature T2 is about 140 ° C. to 350 ° C. After the substrate temperature of the substrate 11 reaches the second substrate temperature T2, the upper oxide film 13 is formed by a normal process in the ALD method in the period t _T2 shown in FIG. That is,
(A) During the pulse time t2 _PLM , the pulsing valve 106 is opened and the pulsing valve 107 is closed to supply the precursor 102 to the substrate 11;
(B) During the purge time t2 _PGM , the pulsing valves 106 and 107 are closed and only the carrier gas 101 is supplied to the substrate 11;
(C) During the pulse time t2 _PLO , the pulsing valve 106 is closed and the pulsing valve 107 is opened to supply the oxidant 103 of the precursor 102 to the substrate 11;
(D) During the purge time t2 _PGO , the pulsing valves 106 and 107 are closed and only the carrier gas 101 is supplied to the substrate 11.
The upper oxide film 13 having a desired film thickness is obtained by repeatedly executing the normal cycle C2 a plurality of times at the second substrate temperature T2 as one cycle (hereinafter referred to as “normal cycle”) C2. Form. Thus, the semiconductor device 10 shown in FIG. 1 is completed.

  The number of repetitions of the water supply cycle Cw in the period tw is preferably an even number (for example, 2, 4, 6, 8, etc.). This is because, since water molecules have a very large dipole moment, it is preferable to form an electric double layer for water to stably exist on the substrate surface 110. When the water layer is thick, the reaction with TMA is not uniform, and there is a concern about the influence on the subsequent growth of the oxide film. For this reason, it is preferable that the water supply cycle Cw is limited to about 8 cycles. Since a water film having a film thickness of about 0.2 nm is formed in one water supply cycle Cw, for example, when the water supply cycle Cw is set to 8 cycles, a film thickness of about 1.6 nm is formed on the substrate surface 110. A water film is formed.

The pulse times t1 _PLO , t1 _PLM , t2 _PLO , t2 _PLM , and the purge times t1 _PGO , t1 _PGM , t2 _PGO , t2 _PGM are values that depend on the structure of the atomic layer deposition apparatus 100, but are general values. In the atomic layer deposition apparatus 100, for example, as described above, t1 _PLO = t1 _PLM = t2 _PLO = t2 _PLM = 0.1 second and t1 _PGO = t1 _PGM = t2 _PGO = t2 _PGM = 4.0 seconds are typical. Value.

However, when the first oxide layer of one atomic layer is formed on the substrate surface 110, it is necessary to always supply water to the substrate 11. For this reason, as described above, the purge time t _PGW needs to be shorter than the passage time t _PASS , for example, the purge time t _PGW is 2.5 seconds.

After the first monolayer oxide film is formed on the substrate surface 110, for example, the pulse time t1 _PLO = 0.1 second, the purge time t1 _PGO = 4.0 second, the pulse time t1 _PLM = 0.1 second, The base oxide film 12 is grown by repeating the low temperature cycle C1 consisting of the purge time t1 _PGM = 4.0 seconds for 20 cycles or more (typically about 50 cycles). Although depending on the growth conditions, the film thickness of the Al ₂ O ₃ film formed by one low-temperature cycle C1 is about 0.1 nm. When the number of repetitions of the low temperature cycle C1 is less than 20 cycles, the substrate surface 110 cannot be uniformly covered with the Al ₂ O ₃ film, which may result in incomplete film growth. On the other hand, if the underlying oxide film 12 is thick, it is disadvantageous in terms of breakdown voltage and the like because it is formed by low-temperature growth. Therefore, the base oxide film 12 is formed by repeating the low temperature cycle C1 for about 50 cycles. At this time, the thickness of the base oxide film 12 is about 5 nm.

In the formation of the upper oxide film 13, for example, the precursor 102 made gaseous is put on the carrier gas 101 and introduced into the reaction chamber 104 for a pulse time t 2 _PLM = 0.1 second, and the precursor is formed on the base oxide film 12. The body 102 is adsorbed only by one atomic layer. Next, only the carrier gas 101 is introduced into the reaction chamber 104 for a purge time t2 _PGM = 4.0 seconds, and the product generated by the surface adsorption reaction and the excess precursor 102 are removed from the reaction chamber 104 by the dry pump 105. To discharge. Thereafter, an oxidant 103 (mainly water) that reacts with the precursor 102 is introduced into the reaction chamber 104 for a pulse time t2 _PLO = 0.1 second to oxidize the metal molecules adsorbed on the surface of the base oxide film 12. A single atomic layer oxide film is formed. Next, the carrier gas 101 is introduced into the reaction chamber 104 for a purge time t2 _PGO = 4.0 seconds, and reaction products and excess water molecules are discharged to the outside of the reaction chamber 104. Thus, the normal cycle C2 for growing the upper oxide film 13 by one atomic layer at the second substrate temperature T2 is completed.

Then, by repeating the normal cycle C2 a plurality of times, the upper oxide film 13 having a desired film thickness is formed. The purge time t2 _PGM can be in the range of 4 to 120 seconds depending on the temperature in the reaction chamber 104 (second substrate temperature T2).

In the above description, the precursor used for forming the base oxide film 12 is TMA, and the base oxide film 12 is an Al ₂ O ₃ film. However, as long as the precursor has a sufficient vapor pressure even at a temperature lower than the boiling point of water, it is a matter of course that the precursor used for forming the base oxide film 12 may be other than TMA. Further, an oxide film other than the Al ₂ O ₃ film may be used for the base oxide film 12.

However, materials that require film formation at 100 ° C. or higher, such as TEMAH that requires film formation at 125 ° C. or higher, cannot be used as the precursor used for forming the base oxide film 12. This is because these materials condense during transportation at a temperature lower than the boiling point of water. However, if a material that can be used for film formation at a temperature lower than the boiling point of water other than TEMAH is found as the precursor 102 for forming the HfO ₂ film, the material is used as the base oxide film 12 in the same manner as TMA. It is also possible to use the base oxide film 12 as an HfO ₂ film for the formation.

As the precursor 102 used for forming the upper oxide film 13, TMA, TEMAH, or the like can be adopted. As described above, when TMA is used for the precursor 102, the upper oxide film 13 is an Al ₂ O ₃ film. When TEMAH is used for the precursor 102, the upper oxide film 13 is an HfO ₂ film.

Further, as the upper oxide film 13, an oxide film other than the Al ₂ O ₃ film and the HfO ₂ film, for example, a titanium oxide (TiO ₂ ) film, a silicon oxide (SiO ₂ ) film, a zinc oxide (ZnO) film, and a zirconia (ZrO) film. A tin oxide (SnO ₂ ) film or the like can be grown. In forming the TiO ₂ film, titanium chloride (TiCl ₄ ) is used as the precursor 102, and H ₂ O is used as the oxidant 103. For the formation of the SiO ₂ film, bisdiethylamidosilane (Bis (diethylamido) silane: 2DEAS) is used as the precursor 102, and H ₂ O is used as the oxidizing agent 103. In forming the ZnO film, zinc chloride (ZnCl ₂ ) is used as the precursor 102 and H ₂ O is used as the oxidizing agent 103. For the formation of the ZrO film, tetrakisethylmethylamidozirconium (Tetrakis (ethylmethylamido) zirconium) is used as the precursor 102 and H ₂ O is used as the oxidizing agent 103. For the formation of the SnO ₂ film, tin chloride (SnCl ₄ ) is used as the precursor 102 and H ₂ O is used as the oxidizing agent 103.

ZnCl ₂ has a vapor pressure sufficient to form a film by the ALD method at room temperature to 100 ° C. Therefore, the base oxide film 12 can be made a ZnO film by using ZnCl ₂ as a precursor.

  The film formation method according to the embodiment of the present invention is similar to the normal ALD method, (1) the film can be digitally grown by one atomic layer, and (2) the film can be uniformly formed on any shape of material. Therefore, it is possible to form a film with a complicated three-dimensional structure, and (3) a dense amorphous film is formed because of low temperature growth as compared with the CVD method.

  The deposition conditions include selection of the precursor 102 and the oxidant 103, the temperature in the reaction chamber 104 (substrate temperature), the flow rate of the carrier gas 101, the opening and closing time of the pulsing valves 106 and 107, and the carrier gas 101 alone. 11 has a supply time (barge time). As already described, since the ALD method uses surface adsorption of the substrate, the surface state of the substrate greatly affects the growth conditions.

  Therefore, in order to form a uniform oxide film on the hydrophobic substrate, the point of the film forming method according to the embodiment of the present invention is that water is supplied to the substrate 11 and the substrate surface 110 is supersaturated with water. Then, the formation of the base oxide film 12 is started.

After the formation of the base oxide film 12, the upper oxide film 13 can be formed as a good oxide film by a normal process. For example, in the semiconductor device 10 shown in FIG. 1, the base oxide film 12 (Al ₂ O ₃ film) is grown on the substrate 11 at a low temperature (room temperature to less than 100 ° C.), and the ALD method is formed on the base oxide film 12. The upper oxide film 13 (Al ₂ O ₃ film, HfO ₂ film, etc.) can be grown at a general film formation temperature.

  On the other hand, when the base oxide film 12 is formed, if water is not always supplied to the substrate 11, a part of the water on the substrate surface 110 is removed by the carrier gas 101 during the purge time, etc. The entire surface 110 cannot be covered with water. For this reason, for example, as shown in FIG. 5, water separates and adheres to several regions on the substrate surface 110. As a result, the base oxide film 12 is formed separately on the area where water adheres, and a uniform oxide film cannot be formed on the substrate surface 110.

  In the above description, it is assumed that the hydrophobic substrate 11 is graphite or graphene. However, it is possible to grow an oxide film on a hydrophobic organic molecular film or a protein film by a similar method. Since organic molecules and proteins are vulnerable to heat, it is desired to grow an oxide film at a relatively low temperature. In the case of such a heat-sensitive film, a method of forming the upper oxide film 13 without increasing the substrate temperature after the formation of the base oxide film 12 is applied. At this time, the first substrate temperature T1 and the second substrate temperature T2 are, for example, the same. The low-temperature growth of the base oxide film 12 can be performed by a general ALD apparatus up to a substrate temperature of about 65 ° C. Therefore, it is possible to grow an oxide film without damaging or denaturing the organic molecular film or protein film, and application to organic molecular devices and biological devices is also expected.

  As described above, in the film forming method according to the embodiment of the present invention, the surface of a hydrophobic substrate such as graphite, graphene, a hydrophobic organic molecular film, or a protein film is set to a sufficiently hydrophilic surface state. Start the ALD process. Thereby, a uniform oxide film can be formed on the hydrophobic substrate without forming a buffer layer. For this reason, it is possible to eliminate adverse effects such as changes in the interface state due to aging and increases in the interface state due to the presence of the buffer layer. Therefore, according to the film forming method according to the embodiment of the present invention, it is possible to provide a film forming method for forming a good oxide film on a hydrophobic substrate.

(Other embodiments)
As mentioned above, although this invention was described by embodiment, it should not be understood that the description and drawing which form a part of this indication limit this invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

In the description of the above-described embodiment, an example in which water is supplied to the substrate 11 by pulse supply in order to make the substrate surface 110 supersaturated with water has been described. However, water is continuously supplied to the substrate 11 instead of pulse supply. You may supply. Further, as the oxidizing agent 103, a material other than H ₂ O, for example, ozone may be used.

  As described above, the present invention naturally includes various embodiments not described herein. Therefore, the technical scope of the present invention is defined only by the invention specifying matters according to the scope of claims reasonable from the above description.

  The film forming method of the present invention can be used for a semiconductor device having an oxide film, an organic molecular device, a biological device, and the like.

DESCRIPTION OF SYMBOLS 10 ... Semiconductor device 11 ... Substrate 12 ... Base oxide film 13 ... Upper oxide film 100 ... Atomic layer deposition apparatus 101 ... Carrier gas 102 ... Precursor 103 ... Oxidant 104 ... Reaction chamber 105 ... Dry pump 106 ... Pulsing valve 107 ... Pulsing valve 108 ... Gas line 110 ... Substrate surface

Claims (6)

Forming a base oxide film on a substrate surface of a hydrophobic substrate supersaturated with water at a first substrate temperature not less than room temperature and less than the boiling point of water using an atomic layer deposition method;
Forming an upper oxide film on the underlying oxide film at a second substrate temperature using an atomic layer deposition method;
And forming the base oxide film comprises:
Supplying water to the substrate to bring the substrate surface into a supersaturated state of water;
A precursor having a vapor pressure sufficient to form a film by an atomic layer deposition method at the first substrate temperature and an oxidant of the precursor are alternately applied to the substrate in which the substrate surface is supersaturated with water. A film forming method comprising performing a low temperature cycle including a supplying step a plurality of times . The film formation method according to claim 1 , wherein the lowermost layer of the base oxide film in contact with the substrate surface is formed by supplying the precursor to the substrate while always supplying water. A pulse that opens the valve using an atomic layer deposition apparatus that includes a gas line that supplies water and a carrier gas to a reaction chamber that houses the substrate, and a valve that is opened and closed to introduce water into the gas line. Water is supplied to the substrate by a pulse supply in which a time and a purge time for closing the valve are set, and the purge time is made shorter than the time required for water to pass from the valve to the reaction chamber. The film forming method according to claim 2 , wherein water is always supplied to the substrate. In the low-temperature cycle, after it said precursor supplying to said substrate, and said oxidizing agent after the step of supplying to said substrate, 1 to claim and supplying only the carrier gas to the substrate the film deposition method according to any one of 3. The underlying oxide film, film forming method according to any one of claims 1 to 4, characterized in that trimethyl aluminum is aluminum oxide film formed by using the precursor. The film deposition method according to any one of claims 1 to 5 wherein the second substrate temperature is equal to or higher than the first substrate temperature.

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