KR102236013B1 - A apparatus for depositing the atomic layer - Google Patents

Abstract

The present invention relates to an atomic layer deposition apparatus capable of performing a uniform thin film formation process on a plurality of substrates arranged in a plurality of rows while having a single chamber structure instead of a double chamber, the atomic layer deposition apparatus according to the present invention , A process chamber having an opening formed at one side and having a constant internal space to perform an atomic layer deposition process; A plurality of substrates are stacked in parallel so that the gap between each substrate is a layered flow gap, and the plurality of substrates are loaded inside the process chamber to proceed with the atomic layer deposition process and unloading to the outside after completion of the process A plurality of process cassettes; It is installed at the opening side of the process chamber and supplies gas to the front end of the substrate in a direction parallel to the arrangement direction of the substrates so that layered flow occurs in the space between the substrates with respect to all substrates loaded in the cassette. Gas supply means; An exhaust side laminar flow forming unit installed on the opposite side of the opening in the process chamber and maintaining a laminar flow of the process gas injected by the gas supply means to a rear end of the substrate; An exhaust means installed at a rear side of the exhaust side laminar flow forming part among the process chambers and sucks and exhausts gas inside the process chamber; A heating means provided on the outside of the process chamber in a manner surrounding the outer surface of the process chamber, and heating the process chamber; And a door opening and closing the opening.

Description

Atomic layer deposition apparatus {A APPARATUS FOR DEPOSITING THE ATOMIC LAYER}

The present invention relates to an atomic layer deposition apparatus, and more particularly, to an atomic layer deposition apparatus capable of performing a uniform thin film formation process on a plurality of substrates arranged in multiple rows while having a single chamber structure instead of a double chamber. About.

In general, in manufacturing a semiconductor device or a flat panel display device, various manufacturing processes are performed. Among them, a process of depositing a predetermined thin film on a wafer or glass (hereinafter, referred to as a “substrate”) is essentially performed. Such thin film deposition processes include sputtering, chemical vapor deposition (CVD), atomic layer deposition (ALD), and the like.

First, in the sputtering method, an inert gas such as argon is injected into a process chamber while a high voltage is applied to a target to generate argon ions in a plasma state. At this time, argon ions are sputtered on the surface of the target, and atoms of the target are separated from the surface of the target and deposited on the substrate.

A high-purity thin film having excellent adhesion to the substrate can be formed by such sputtering, but when a highly integrated thin film having a process difference is deposited by sputtering, it is very difficult to ensure uniformity of the entire thin film. Therefore, there is a limit to the application of the sputtering method for a fine pattern formation process.

Next, the chemical vapor deposition method is the most widely used deposition technique, and is a method of depositing a thin film having a required thickness on a substrate using a reaction gas and a decomposition gas. For example, in the chemical vapor deposition method, various gases are first injected into a reaction chamber, and a thin film having a required thickness is deposited on a substrate by chemically reacting gases induced by high energy such as heat, light, or plasma.

In addition, in the chemical vapor deposition method, the deposition rate is increased by controlling the reaction conditions through the ratio and amount of plasma or gases applied as much as the reaction energy.

However, in the chemical vapor deposition method, since reactions are fast, it is very difficult to control the thermodynamic stability of atoms, and there is a problem of deteriorating the physical and chemical electrical properties of the thin film.

Finally, in the atomic layer deposition (ALD: Atomic Layer Deposition), two or more reactants are sequentially introduced into a reaction chamber to form a thin film, and the thin film is deposited into an atomic layer by decomposition and adsorption of each reactant. It is a method of depositing in units. That is, after the first reaction gas is supplied by a pulsing method and chemically deposited on the lower film inside the chamber, the remaining first reaction gas physically bound is removed by a purge method. Subsequently, a desired thin film is deposited on the substrate while part of the second reaction gas is chemically bonded to the first reaction gas (first reactant) through pulsing and purge processes. In the above-described atomic layer deposition process, the time during which each reaction gas is subjected to one pulsing and purge is referred to as a cycle. Typical thin films that can be formed by the atomic layer deposition method include Al ₂ O ₃ , HfO ₂ , ZrO ₂ , TiO ₂ and ZnO.

Since the atomic layer deposition can form a thin film with excellent step coverage even at a low temperature of 60°C or less, it is a process that is expected to be widely used in the process of manufacturing next-generation semiconductor devices, displays, solar cells, etc. It's technology.

In order for such atomic layer deposition technology to be expanded and used not only in the semiconductor field, but also in the fields of displays and solar cells, it is necessary to obtain a uniform thin film for a large-area substrate. Sufficient productivity must be secured.

However, the conventional atomic layer deposition apparatus has a dual-chamber structure of an inner chamber and an outer chamber, so that the structure of the equipment is complex and manufacturing and maintenance are difficult, and a plurality of substrates are loaded in order to process a plurality of substrates in one process. When performing the atomic layer deposition process in a state in which a plurality of cassettes are loaded for a long time, the period through which the process gas passes is lengthened, so that the process time is lengthened, and it is difficult to form a uniform thin film on a plurality of substrates.

Accordingly, there is an urgent need to develop an atomic layer deposition apparatus that has a simple structure and can perform a uniform process on all substrates within a short process time in a state in which a plurality of rows of cassettes are loaded.

The technical problem to be solved by the present invention is to provide an atomic layer deposition apparatus capable of performing a uniform thin film formation process on a plurality of substrates arranged in a plurality of rows while having a single chamber structure instead of a double chamber.

An atomic layer deposition apparatus according to the present invention for solving the above-described technical problem includes: a process chamber having an opening formed at one side and a constant internal space to perform an atomic layer deposition process; A plurality of substrates arranged in a plurality of rows are loaded in parallel so that the distance between each substrate becomes a layered flow distance, and the atomic layer deposition process proceeds and the process is completed by being loaded into the process chamber while the plurality of substrates are loaded. A plurality of process cassettes unloaded to the outside after; It is installed on the opening side of the process chamber and supplies gas to the front end of the substrate in a direction parallel to the arrangement direction of the substrates so that layered flow occurs in the space between the substrates for all substrates loaded in the cassette Gas supply means; An exhaust side laminar flow forming unit installed on the opposite side of the opening in the process chamber and maintaining the laminar flow of the process gas injected by the gas supply means to the rear end of the substrate; An exhaust means installed at a rear side of the exhaust side laminar flow forming part of the process chamber, and sucks and exhausts gas inside the process chamber; A heating means provided on the outside of the process chamber in a manner surrounding the outer surface of the process chamber, and heating the process chamber; And a door for opening and closing the opening.

And in the present invention, the heating means is preferably a plurality of jacket heaters surrounding the process chamber.

In addition, it is preferable that the atomic layer deposition apparatus according to the present invention further includes front heating means capable of heating the front portion of the process chamber outside or inside the door.

In addition, in the present invention, the gas supply means is preferably a plurality of gas supply ports formed through sidewalls or corners adjacent to the opening of the process chamber, and uniformly diffuse and supply gas over the entire width of the opening.

In addition, in the present invention, the plurality of gas supply ports are formed at corners of the process chamber adjacent to the openings, and pipes are connected so that source gas and purging gas are supplied to the first corner and the second corner in the diagonal direction thereof. , It is preferable that a pipe is connected and installed so that a reaction gas and a purging gas are supplied to a third corner adjacent to the first corner and a fourth corner in a diagonal direction thereto.

In addition, in the atomic layer deposition apparatus according to the present invention, a gas which is provided at a front end of a substrate loaded in the cassette in the process chamber and induces a layered flow of the process gas injected by the gas supply means before reaching the substrate. It is preferable that the laminar flow forming part is further provided.

In addition, in the present invention, the process cassette is preferably provided with either or both of an exhaust side laminar flow forming part formed at the rear end of the process cassette or a gas laminar flow forming part formed at the front end of the process cassette. .

In addition, the atomic layer deposition apparatus according to the present invention includes an additional gas supply means installed at a point between a specific substrate and a substrate among a plurality of substrates charged into the process chamber among sidewalls or corners of the process chamber to supply process gas. It is preferable to be further provided.

In addition, in the atomic layer deposition apparatus according to the present invention, it is preferable that two or more of the process chambers are provided in an up-down direction or a left-right direction.

In addition, in the atomic layer deposition apparatus according to the present invention, it is preferable that two or more rows of the process cassettes are mounted in the process chamber in the vertical direction or the left and right directions.

In addition, in the atomic layer deposition apparatus according to the present invention, it is preferable that a plurality of sealing members are further provided between the opening of the process chamber and the door.

In addition, in the atomic layer deposition apparatus according to the present invention, it is preferable that a cooling means is further provided at the sealing member installation portion.

In addition, in the atomic layer deposition apparatus, it is preferable that a space is formed between the upper end of the substrate loaded in the process cassette and the inner wall of the process chamber, and between the lower end of the substrate and the inner wall of the process chamber while the process cassette is loaded.

In addition, in the present invention, the gas supply means may include a gas supply port installed in the door to supply a process gas into the door; It is preferable to include a distribution plate in which the process gas supplied through the gas supply port is uniformly diffused in the direction of the substrate while being heated by a front heating unit installed inside the door.

In addition, it is preferable that the atomic layer deposition apparatus according to the present invention further includes a cassette mounting portion installed below the inside of the process chamber and supporting a lower portion of the cassette mounted at the bottom of the plurality of cassettes.

In addition, in the present invention, it is preferable that the process cassette has an open bottom surface.

Meanwhile, in the atomic layer deposition apparatus according to the present invention, it is preferable that two substrates are loaded in a back to back form in one slot of the process cassette.

According to the atomic layer deposition apparatus of the present invention, there is an advantage that a uniform thin film formation process can be performed with excellent throughput and process efficiency for a plurality of substrates arranged in a plurality of rows while having a single chamber structure instead of a double chamber.

1 is a cross-sectional view showing the structure of an atomic layer deposition apparatus according to an embodiment of the present invention.
2 is a view showing the structure of a gas supply means according to an embodiment of the present invention.
3 is a diagram showing the structure of a process cassette according to an embodiment of the present invention.
4 is a diagram showing the structure of a process cassette according to another embodiment of the present invention.
5 is a view showing a state in which process cassettes are inserted into a process chamber according to an embodiment of the present invention.
6 is a view showing a state in which process cassettes are inserted into a process chamber according to another embodiment of the present invention.
7 is a diagram illustrating a state in which process chambers according to an embodiment of the present invention are disposed.
8 is a diagram illustrating a state in which process chambers according to another embodiment of the present invention are disposed.
9 is a view showing the structure of a door according to an embodiment of the present invention.
10 is a view showing a state in which a process cassette is inserted in a process chamber according to an embodiment of the present invention.
11 and 12 are views showing the structure of a door and a gas supply means according to another embodiment of the present invention.

Hereinafter, specific embodiments of the present invention will be described in detail with reference to the accompanying drawings.

<Example 1>

As shown in FIG. 1, the atomic layer deposition apparatus 100 according to the present embodiment includes a process chamber 110, a process cassette 120, a gas supply means 130, and an exhaust side layered flow forming unit 140. , Exhaust means 150, heating means 160, and comprises a door 170.

First, as shown in FIG. 1, the process chamber 110 is a component capable of performing an atomic layer deposition process by having an opening 111 formed at one side and a constant internal space. For example, the process chamber 110 may have an elongated rectangular cylindrical shape.

In addition, it is preferable that a gas laminar flow forming unit 180 is further provided at the front end of the process chamber 110 according to the present embodiment. As shown in FIG. 1, the gas laminar flow forming unit 180 is provided at a front end of the substrate S loaded on the cassette 120 of the process chamber 110 to the gas supply means 130. It is a component that induces a layered flow of the process gas injected by the substrate before it reaches the substrate.

In this way, when the layered flow of gas is smoothly formed from the front end of the substrate S by the gas layered flow forming unit 180, there is an advantage that a uniform thin film can be formed on all areas of all substrates.

Meanwhile, for the efficiency of the process in the atomic layer deposition apparatus 100 according to the present embodiment, as shown in FIGS. 7 and 8, two or more of the process chambers 110 are arranged in the vertical direction or 2 are arranged in the left and right directions. It may have a structure in which more than one is arranged or four or more are provided in the vertical, left and right directions.

Next, the process cassette 120 has a structure with an open bottom surface as shown in FIG. 1 and is a component that loads a plurality of substrates S in parallel so that the gap between the substrates becomes a layered flow gap. . The process cassette 120 is loaded into the process chamber 110 while the plurality of substrates S are loaded, and the atomic layer deposition process proceeds, and after the process is completed, the process is unloaded to the outside. do.

At this time, as shown in FIG. 10 with the process cassette 120 loaded, between the top of the substrate S loaded on the process cassette 120 and the inner wall of the process chamber 110, and the substrate S ) It is preferable that the spaces 101 and 102 are formed between the lower end and the inner wall of the process chamber 110 to maintain a uniform gas flow in the space in which the substrates are arranged.

Meanwhile, in the present embodiment, two substrates may be loaded in one slot of the process cassette in a back-to-back form. Here, the term'back-to-back type' refers to a state in which the rear surfaces of two substrates are in close contact with each other, and the rear surface of the substrate is a surface that does not need to be subjected to an atomic layer deposition process. If two substrates are stacked in a back-to-back form in one slot, there is an advantage in that the process can be performed while more substrates are loaded in one cassette.

Therefore, it is preferable that a cassette mounting part 190 is further provided inside the process chamber. As shown in FIG. 10, the cassette mounting part 190 is installed in the form of a plurality of installation bars on the inner lower side of the process chamber 110, and the lower portion of the cassette mounted on the lowermost side of the plurality of cassettes 120 Is a component that supports to be spaced apart from the lower surface of the process chamber 110 by a predetermined distance.

In the loading/unloading process of the process cassette 120 by the cassette mounting part 190, a moving space of the cassette moving means (not shown in the drawing) is secured, and the lower end of the substrate S and the process chamber 110 ) A space 101 between the inner walls can also be secured.

In this embodiment, the process cassette 120 has a plurality of substrates (S) arranged in a plurality of rows, as shown in FIG. 3, and the substrates disposed in each row maintain the same position and spacing so that the gas supply means The gas supplied from 130 has a structure capable of passing through a space between a plurality of rows of substrates S while maintaining a layered flow while maintaining a substantially linear path.

Meanwhile, in the process cassette 120 according to the present embodiment, as shown in FIG. 4, either or both of the exhaust side laminar flow forming unit 122 or the gas laminar flow forming unit 124 are formed. Can be. The exhaust side laminar flow forming part 122 is formed at the rear end of the process cassette 120, and the gas laminar flow forming part 124 is formed at the front end of the process cassette 120, For the plurality of rows of substrates S loaded on the process cassette 120, a uniform thin film is formed over all areas of all substrates.

In addition, in the atomic layer deposition apparatus 100 according to the present embodiment, as shown in FIGS. 5 and 6 in order to shorten the process time and process efficiency, the process cassette 120 is disposed inside one process chamber 110. It may have a structure in which two or more rows are seated in the vertical direction or the left and right directions.

Next, the gas supply means 130 is installed on the side of the opening 111 of the process chamber 110, as shown in FIG. 1, with respect to all the substrates S loaded in the cassette 120. It is a component that supplies gas to the front end of the substrate S in a direction parallel to the arrangement direction of the substrate S so that a layered flow occurs in the space between the substrates. That is, the gas supply means 130 forms a layered flow of the raw material gas, the reaction gas, and the purging gas so that the atomic layer deposition process proceeds with respect to all the substrates S charged into the process chamber 110. ) To move to the space between.

In this embodiment, the gas supply means 130 is formed through a sidewall or a corner adjacent to the opening 111 of the process chamber 110, as specifically shown in FIGS. 1 and 2, and the opening ( 111) It may be composed of a plurality of gas supply ports (130a ~ 130d) for supplying by uniformly spreading the gas over the entire width.

At this time, the same gas may be supplied to the plurality of gas supply ports 130a to 130d in the same manner at the same time period, or different gases may be supplied in different manners at different time periods. For example, as shown in Figure 2, the plurality of gas supply ports (130a ~ 130d) are each connected to two pipes, one pipe (134a ~ 134d) supply the same purging gas, the other The pipes 132a to 132d of the source gas or reaction gas may be supplied the same or differently.

In particular, the gas supply ports 130a and 130c formed at a corner of the process chamber 110 adjacent to the opening 111 and installed at a first corner and a second corner in a diagonal direction thereof are supplied with the same raw material gas. Pipes 132a and 132c and pipes 134a and 134c for supplying purging gas are connected and installed, and a gas supply port 130b is installed at a third corner adjacent to the first corner and a fourth corner in a diagonal direction thereto. In the same manner, the pipes 132b and 132d supplied with the reactive gas and the pipes 134b and 134d supplied with the purging gas are connected and installed in the 130d) for uniform and rapid diffusion of the gas.

Meanwhile, an additional gas supply means 136 may be further provided in the atomic layer deposition apparatus according to the present embodiment. As shown in FIG. 1, the additional gas supply means 136 is between a specific substrate and a substrate among a plurality of substrates S charged into the process chamber 110 among sidewalls or corners of the process chamber 110. It is a component that additionally supplies raw material gas and process gas by being installed at the branch of

When a very large number of substrates are charged in one process chamber 110, the gas flow may be weakened or changed at the rear end, unlike the front end of the chamber, so that gas is additionally supplied by the additional gas supply means 136.

Next, the exhaust side laminar flow forming unit 140 is installed on the opposite side of the opening 111 of the process chamber 110, and is injected by the gas supply means 130, as shown in FIG. It is a component that maintains the layered flow of the process gas to the rear end of the substrate (S). That is, the exhaust side laminar flow forming unit 140 performs the same function as the exhaust side laminar flow forming unit 122 installed in the process cassette 120.

Next, the exhaust means 150 is installed at the rear of the exhaust side laminar flow forming unit 140 of the process chamber 110, as shown in FIG. 1, and sucks the gas inside the process chamber 110. It is a component that is exhausted. The exhaust means 150 sucks and exhausts the gas supplied by the gas supply means 130 as well as the gas existing in the process chamber 110. To this end, in this embodiment, the exhaust means 150 may specifically include a gas collection discharge unit 152 and an exhaust pump 154 as shown in FIG. 1.

In addition, in the exhaust means 150 according to the present embodiment, the powder trap (not shown in the drawing) is installed between the vowel discharge unit 152 and the discharge pump unit 154 to perform a function.

Next, the heating means 160 is provided on the outside of the process chamber 110 in a manner that surrounds the outer surface of the process chamber 110, as shown in FIGS. It is a heating component. In this embodiment, the heating means 160 heats the process chamber 110 to maintain the temperature inside the process chamber 110 at a temperature suitable for an atomic layer deposition process. ) Is preferably a plurality of jacket heaters surrounding the outside.

Next, the door 170 is a component that opens and closes the opened opening 111 of the process chamber 110 as shown in FIG. 1. The opening 111 must be completely closed during the process and must be opened while loading or unloading the process cassette 120, which opens and closes the opening 111 in accordance with the process in which the door 170 is proceeding. .

Accordingly, a sealing member 174 is provided along the inner edge of the door 170 to maintain airtightness in a state in close contact with the process chamber 110. In this case, as shown in FIG. 9, it is preferable that a plurality of the sealing members 174 are provided in duplicate, since it is possible to reliably maintain the airtightness of the inside of the process chamber 110.

In addition, as shown in FIG. 9, a cooling means 176 is further provided at a portion of the door 170 where the sealing member 174 is installed, so that the sealing member 174 is damaged by heat during operation of the equipment. It is preferable because it can be prevented.

Meanwhile, in the present embodiment, a front heating means 172 capable of heating the front portion of the process chamber 110 may be further provided outside or inside the door 170. The front heating means 172 heats the front portion of the process chamber 110 that cannot be heated by the heating means 160 to maintain a uniform temperature inside the process chamber 110.

<Example 2>

In this embodiment, the remaining components except for the gas supply means 230 and the door 270 are substantially the same as those of the first embodiment, so a repeated description thereof will be omitted and the gas supply means 230 and the door 270 It will only be explained. The gas supply means 230 according to this embodiment is not installed on the sidewall of the process chamber as in the first embodiment, but is installed on the door 270. Accordingly, the gas supply means 230 includes a gas supply port 232 and a distribution plate 234 as shown in FIGS. 11 and 12.

First, the gas supply port 232 is a component installed in the door 270 to supply a process gas into the door, and the distribution plate 234 is a process gas supplied through the gas supply port 232. It is a component that diffuses and distributes so as to be sprayed in a state uniformly diffused in the direction of the substrate. In addition, a front heating unit 272 is installed inside the door 270, and the gas supplied through the gas supply port 232 is heated by the front heating unit 272, and the distribution plate 234 is It is supplied to the inside of the process chamber through.

100: atomic layer deposition apparatus according to an embodiment of the present invention
110: process chamber 120: process cassette
130: gas supply means 140: exhaust side laminar flow forming unit
150: exhaust means 160: heating means
170: door S: substrate

Claims (17)

A process chamber having an opening formed at one side and having a constant internal space to perform an atomic layer deposition process;
A plurality of substrates arranged in a plurality of rows are loaded in parallel so that the distance between each substrate becomes a layered flow distance, and the atomic layer deposition process proceeds and the process is completed by being loaded into the process chamber while the plurality of substrates are loaded. A plurality of process cassettes that are then unloaded to the outside;
It is installed at the opening side of the process chamber and supplies gas to the front end of the substrate in a direction parallel to the arrangement direction of the substrates so that layered flow occurs in the space between the substrates with respect to all substrates loaded in the cassette. Gas supply means;
An exhaust side laminar flow forming unit installed on the opposite side of the opening in the process chamber and maintaining a laminar flow of the process gas injected by the gas supply means to a rear end of the substrate;
An exhaust means installed at a rear side of the exhaust side laminar flow forming part of the process chamber, and sucks and exhausts gas inside the process chamber;
A heating means provided on the outside of the process chamber in a manner surrounding the outer surface of the process chamber, and heating the process chamber;
A door opening and closing the opening; And
Includes; a front heating means installed outside or inside the door and capable of heating the front portion of the process chamber,
An atomic layer deposition apparatus, characterized in that a space is formed between an upper end of a substrate loaded in the process cassette and an inner wall of the process chamber, and between a lower end of the substrate and an inner wall of the process chamber while the process cassette is loaded. The method of claim 1, wherein the heating means,
Atomic layer deposition apparatus, characterized in that the plurality of jacket heaters surrounding the process chamber. delete The method of claim 1, wherein the gas supply means,
An atomic layer deposition apparatus comprising a plurality of gas supply ports formed through sidewalls or corners adjacent to the opening of the process chamber, and uniformly diffuses and supplies gas over the entire width of the opening. The method of claim 4, wherein the plurality of gas supply ports,
It is formed at a corner of the process chamber adjacent to the opening, and a pipe is connected and installed so that a source gas and a purging gas are supplied at a first corner and a second corner in a diagonal direction thereto, and a third corner adjacent to the first corner and Accordingly, an atomic layer deposition apparatus, characterized in that pipes are connected and installed at the fourth corner in the diagonal direction to supply the reaction gas and the purging gas. The method of claim 1,
A gas laminar flow forming unit provided at a front end of the substrate mounted on the cassette of the process chamber and inducing a laminar flow of the process gas injected by the gas supply means before reaching the substrate is further provided. Atomic layer deposition apparatus. The method of claim 1, wherein the process cassette,
An atomic layer deposition apparatus comprising either one or both of an exhaust side laminar flow forming portion formed at a rear end of the process cassette or a gas laminar flow forming portion formed at a front end of the process cassette. The method of claim 1,
An atomic layer deposition apparatus, characterized in that further comprising an additional gas supply means for supplying a process gas by being installed at a point between a specific substrate and a substrate among a plurality of substrates charged into the process chamber among sidewalls or corners of the process chamber. . The method of claim 1,
An atomic layer deposition apparatus, characterized in that two or more of the process chambers are provided in an up-down direction or a left-right direction. The method of claim 1,
An atomic layer deposition apparatus, characterized in that two or more rows of the process cassettes are mounted in the process chamber in an up-down direction or a left-right direction. The method of claim 1,
An atomic layer deposition apparatus, characterized in that a plurality of sealing members are further provided between the opening of the process chamber and the door. The method of claim 11,
An atomic layer deposition apparatus, characterized in that a cooling means is further provided at the sealing member installation portion. delete The method of claim 1, wherein the gas supply means,
A gas supply port installed in the door to supply a process gas into the door;
And a distribution plate in which the process gas supplied through the gas supply port is uniformly diffused in the direction of the substrate while being heated by a front heating unit installed inside the door. Layer deposition equipment. The method of claim 1,
An atomic layer deposition apparatus, further comprising a cassette mounting unit installed below the inside of the process chamber and supporting a lower portion of the cassette mounted at the lowermost side of the plurality of cassettes. The method of claim 1, wherein the process cassette,
An atomic layer deposition apparatus, characterized in that the lower surface is an open structure. The method of claim 1,
An atomic layer deposition apparatus, characterized in that two substrates are loaded back to back in one slot of the process cassette.

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