Abstract:
A photo-assisted atomic layer deposition method includes the following steps: preparing a processing system having a processing chamber and a first gas input channel connecting the processing chamber, and the first gas input channel having a pre-chamber with a transparent side wall; introducing a first gas into the pre-chamber; illuminating the interior space of the pre-chamber by ultraviolet light via the transparent side wall; and injecting the first gas illuminated by the ultraviolet light into the processing chamber. The reactivity of the first gas can be promoted by the illumination of the ultraviolet light in the pre-chamber, so that the first gas illuminated by the ultraviolet light becomes more active to react completely in the process of film depositions, with reduced ligand residues in the deposited films.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a photo-assisted atomic layer deposition method, and more particularly, the present invention relates to a photo-assisted atomic layer deposition method capable of increasing reaction rate in the process of film depositions, reducing ligands in the deposited films and optimizing the atomic layer deposition. 
         [0003]    2. Description of the Prior Art 
         [0004]    Atomic layer deposition is a method to form a single atomic layer from the adsorbed molecule on the surface of the substrate. The atomic layer deposition is similar to the chemical vapor deposition (CVD), but every new atomic layer is relevant to the last atomic layer in the atomic layer deposition. Therefore, there is only one layer of molecules after every reaction. The atomic layer deposition is able to obtain a uniform thickness of layer deposited and an exact control of thickness by self-controlling and uniformly covering. Generally, two different kinds of gas reactants are introduced into the processing chamber in turn to deposit on the substrate in the atomic layer deposition. These gas reactants are called precursors. 
         [0005]    Take Al 2 O 3  deposition on a silicon substrate as an example. Firstly, the surface of the silicon which is predetermined to be deposited by Al 2 O 3  is processed to absorb hydroxyls. Then, the precursor, Al(CH 3 ) 3 , is introduced into the processing chamber. As Al(CH 3 ) 3  reacts with hydroxyls, a chemical bond is formed between aluminum and oxygen. CH 4  is generated in the reaction and leaves the surface under the vacuum conditions. When the hydroxyl groups are completely reacted, Al(CH 3 ) 3  can no longer adsorb on the silicon surface, limiting the surface reaction to a single molecule scale. Then, residual Al(CH 3 ) 3  is removed, and water is introduced into the processing chamber. Water molecules react with methyl groups (CH 3 ) to form the new hydroxyl groups atop of the alumina. The other two methyl groups react with water molecules to form oxygen bonds between two adjacent aluminum atoms through a dehydration reaction. A single atomic layer is formed after the processes mentioned above. The processes are repeated to form a plurality of atomic layers. 
         [0006]    The atomic layer deposition is able to obtain a uniform thickness of layers deposited, an exact control of thickness, and a high aspect ratio. However, the deposition process is often limited by the choice of precursors which are required to possess high reactivity at a reaction temperature between 100 to 300° C. In addition, ligand residuals in the deposited films play a central role in the quality of deposited film. In the prior arts, plasma has been used to assist the complete decomposition of precursor involved in the reaction and to increase the deposition rate. 
         [0007]    In the prior art, photo-assisted reaction is applied in a CVD system, wherein a transparent conduit is connected between a plasma generator and a CVD chamber, and an ultraviolet (UV) light illuminating the transparent conduit is provided to maintain the activation of the active species from the plasma generator. The disadvantages of the process in the prior art are as follows: (1) The temperature of the precursor illuminated by the UV light cannot be controlled independently, neither to the illumination time. (2) The long conduit is generally made of quartz or glass. A large portion of UV light is significantly adsorbed when the UV light passes through the long conduit, leading to a remarkable reduction of UV intensity and an ineffective illumination accordingly. (3) To provide the UV light with enough intensity, the power of the UV light should be enlarged, increasing the cost of facility. (4) Since the conduit is not spatially separated from the reaction chamber, there might be a plurality of films deposited on the inner wall of the long conduit, leading to the reduction of the transparence of the conduit quartz or glass. 
         [0008]    As mentioned above, it is essential to provide a new photo-assisted atomic layer deposition method that are able to improve the reactivity of the precursor efficiently, to improve the growth rate, and to reduce the residuals of the ligand functional groups in the deposited films. 
       SUMMARY OF THE INVENTION 
       [0009]    One scope of the present invention is providing a photo-assisted atomic layer deposition which comprises the following steps: preparing a processing system including a processing chamber and a plurality of gas input channels, wherein the processing chamber is used for containing a substrate and connected to a first gas input channel of the plurality of gas input channels, the first gas input channel includes a pre-chamber and a heating device, the pre-chamber includes a transparent side wall and is separated from the processing chamber by a first valve; starting the heating device to raise the temperature of the pre-chamber to a predetermined temperature; closing the first valve and introducing a first gas into the pre-chamber of the first gas input channel; illuminating the interior space of the pre-chamber by an ultraviolet light via the transparent side wall for a predetermined duration; and, opening the first valve to input the first gas illuminated by the ultraviolet light into the processing chamber to form atomic layers on the substrate. 
         [0010]    Because the first gas is illuminated by the ultraviolet light in the pre-chamber of the first gas input channel, the reactivity of the first gas in the processing chamber is raised to form an atomic layer on the substrate efficiently. Besides, in the design of the pre-chamber, the planar transparent side wall is able to be made of the material with low absorption coefficient like MgF 2 , outperforming the prior art with the smaller illumination area and the less illumination intensity of the ultraviolet light. 
         [0011]    The pre-chamber of the first gas input channel and the processing chamber are separable via a vacuum valve, so that the duration of illuminating the ultraviolet light is controllable separately. The temperature of the precursor illuminated by the ultraviolet light can also be controlled separately, so as to reduce the ligand residues of the precursor. 
         [0012]    The pre-chamber of the first gas input channel and the processing chamber is separable via a vacuum valve to block any deposition occurred on the transparent side wall of the pre-chamber, so as not to degrade the illumination intensity of the ultraviolet light in the atomic layer deposition and the CVD process. 
         [0013]    Another scope of the present invention is providing a photo-assisted atomic layer deposition method; according to another embodiment, the photo-assisted atomic layer deposition method further comprises the following step of: heating the pre-chamber to keep the temperature of the pre-chamber in a temperature range from 25° C. to 400° C. 
         [0014]    Another scope of the present invention is providing a photo-assisted atomic layer deposition method; according to another embodiment, the thickness of the atomic layer in every single deposition process is less than 1 nm. 
         [0015]    Another scope of the present invention is providing a photo-assisted atomic layer deposition method; according to another embodiment, in the deposition process of atomic layer in the embodiment mentioned above, the predetermined duration of ultraviolet light illumination is in a range from 0.1s to 10s. 
         [0016]    Another scope of the present invention is providing photo-assisted atomic layer deposition method; according to another embodiment, the wavelength of the ultraviolet light in the embodiment mentioned above is in a range from 160 nm to 360 nm, and the power is in a range from 100 Watts to 500 Watts. The temperature of the substrate heated by the processing chamber is in a range from 25° C. to 800° C. The flow rate of the react gas is in a range from 20 sccm to 5000 sccm. 
         [0017]    Another scope of the present invention is providing a photo-assisted atomic layer deposition method; according to another embodiment, the reacting gas in the embodiment mentioned above comprises at least one of Ti, Zr, Hf, Nb, Ta, Cr, Mo, W, Re, Fe, Co, Ni, Si, Ge, In, Sn and Ga compounds. The second gas comprises at least one of oxygen, water, hydrogen and nitrogen. 
         [0018]    Another scope of the present invention is providing a photo-assisted atomic layer deposition method; according to another embodiment, the transparent side wall of the pre-chamber in the embodiment mentioned above is made of one of magnesium fluoride, quartz and glass with high penetrability of the ultraviolet light. 
         [0019]    Another scope of the present invention is providing a photo-assisted atomic layer deposition method; according to another embodiment, the photo-assisted atomic layer deposition method further comprises the following steps of: closing the first valve between the first gas input channel and the processing chamber to keep the first gas in the pre-chamber when the first gas is introduced into the pre-chamber. 
         [0020]    Another scope of the present invention is providing a photo-assisted atomic layer deposition method; according to another embodiment, the photo-assisted atomic layer deposition method further comprises the following steps of: opening the first valve to input the first gas illuminated by the ultraviolet light into the processing chamber when the first gas has been illuminated by the ultraviolet light for a predetermined duration in the pre-chamber. 
         [0021]    Another scope of the present invention is providing a photo-assisted atomic layer deposition method; according to another embodiment, the photo-assisted atomic layer deposition method further comprises the following steps of: introducing the second gas into the pre-chamber of the first gas input channel via a second gas input channel. 
         [0022]    Another scope of the present invention is providing a photo-assisted atomic layer deposition method; according to another embodiment, the photo-assisted atomic layer deposition method further comprises the following steps of: introducing the second gas and the first gas from the pre-chamber into the processing chamber to form the atomic layer on the substrate. 
         [0023]    Another scope of the present invention is providing a photo-assisted atomic layer deposition method; according to another embodiment, the photo-assisted atomic layer deposition method further comprises the following steps of: introducing the second gas into the processing chamber via the second gas input channel to form the atomic layer on the substrate. 
         [0024]    Another scope of the present invention is providing a photo-assisted atomic layer deposition method; according to another embodiment, the photo-assisted atomic layer deposition method further comprises following steps of: introducing the third gas into the processing chamber via a third gas input channel. 
         [0025]    Another scope of the present invention is providing a photo-assisted atomic layer deposition method; according to another embodiment, the third gas introduced into the processing chamber via the third gas input channel is plasma gas or an inert gas, wherein the inert gas comprises nitrogen and argon. 
         [0026]    Another scope of the present invention is providing a photo-assisted atomic layer deposition method; according to another embodiment, the photo-assisted atomic layer deposition method further comprises the following steps of: alternatively opening and closing the first valve and a second valve which connects the second gas input channel to the processing chamber in turns, so as to introduce the first gas and the second gas into the processing chamber in turns to form the atomic layers on the substrate. 
         [0027]    The advantages and spirits of the invention may be understood by the following recitations together with the appended drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE APPENDED DRAWINGS 
         [0028]    Some of the embodiments will be described in detail, with reference to the following figures, wherein like designations denote like members, wherein: 
           [0029]      FIG. 1A  shows the flow chart of the photo-assisted atomic layer deposition method according to an embodiment of the present invention. 
           [0030]      FIG. 1B  shows the diagram of a processing system applying the photo-assisted atomic layer deposition method of  FIG. 1A . 
           [0031]      FIG. 2  shows the flow chart of a photo-assisted atomic layer deposition method according to another embodiment of the present invention. 
           [0032]      FIG. 3  shows the flow chart of a photo-assisted atomic layer deposition method according to another embodiment of the present invention. 
           [0033]      FIG. 4A  shows the flow chart of a photo-assisted atomic layer deposition method according to another embodiment of the present invention. 
           [0034]      FIG. 4B  shows the diagram of the processing system applying the photo-assisted atomic layer deposition method of  FIG. 4A . 
           [0035]      FIG. 4C  shows the flow chart of a photo-assisted atomic layer deposition method according to another embodiment of the present invention. 
           [0036]      FIG. 5A  shows the flow chart of a photo-assisted atomic layer deposition method according to another embodiment of the present invention. 
           [0037]      FIG. 5B  shows the diagram of the processing system applying the photo-assisted atomic layer deposition method of  FIG. 5A . 
           [0038]      FIG. 5C  shows the flow chart of a photo-assisted atomic layer deposition method according to another embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0039]    Please refer to  FIG. 1A  and  FIG. 1B .  FIG. 1A  shows flow chart of the photo-assisted atomic layer deposition method according to an embodiment of the present invention.  FIG. 1B  shows the diagram of a processing system applying the photo-assisted atomic layer deposition method of  FIG. 1A . A processing system  2  used in a photo-assisted atomic layer deposition method in the embodiments comprises a processing chamber  20  and a first gas input channel  22  connected to the processing chamber  20 , wherein the processing chamber  20  is used for placing the substrate S therein, and a processing gas used in the photo-assisted atomic layer deposition method is introduced into the processing chamber  20  to form an atomic layer on the substrate S. Besides, the first gas input channel  22  further comprises a pre-chamber  220  and a first valve  222 . One of the side walls of the pre-chamber  220  is a transparent side wall  2200 . The light illuminates the interior space of the pre-chamber  220  via the transparent side wall  2200 . The transparent side wall is made of one among magnesium fluoride, quartz and glass with high penetrability of the ultraviolet light. The first valve  222  connects the first gas input channel  22  and the processing chamber  20 . The gas from the first input channel  22  is able to flow into the processing chamber  20  or is blocked by closing the first valve  222 . The left outlet of the processing chamber  20  is able to be connected to an exhausting apparatus which is not shown in the figure to input or output the process gas or the other gas in or out of the processing chamber  20 , and to maintain the pressure in the processing chamber  20 . Besides, the pre-chamber  220  is connected to the heating device  224 , and the temperature of the pre-chamber  220  heated by the heating device  224  is in a range from 25° C. to 400° C. 
         [0040]    As shown in  FIG. 1A  and  FIG. 1B , the photo-assisted atomic layer deposition method comprises the following steps of: in the step S 10 , preparing a processing system  2  in  FIG. 1B ; in the step S 12 , introducing a first gas G 1  into the pre-chamber  220  of the first gas input channel  22 ; in the step S 14 , illuminating the interior space of the pre-chamber  220  via the transparent side wall  2200  by the ultraviolet light; and in the step S 16 , introducing the first gas G 1  illuminated by the ultraviolet light into the processing chamber  20  to form the atomic layer on the substrate S. 
         [0041]    In the step S 10 , the structures of the processing chamber  20  and the first gas input channel  22  of the processing system  2  were mentioned on the above paragraph. In practice, the processing chamber  20  and the first gas input channel  22  are able to be connected to different objects to achieve the process of the photo-assisted atomic layer deposition method. For example, the processing chamber  20  is able to be connected to an exhausting apparatus and another heating device to make suitable process conditions in the processing chamber. In another example, the first gas input channel  22  is able to be connected to a storage tank of the first gas G 1 . In practice, the processing chamber  20  is connected to another heating device to heat the substrate S in the processing chamber  20  to make the temperature in a range from 25° C. to 800° C. for the atomic layer deposition. 
         [0042]    In step S 12 , the first gas G 1  is introduced into the pre-chamber  220  of the first gas input channel  22 . As mentioned above, the first gas input channel  22  is able to be connected to the storage tank of the first gas G 1 , so the first gas G 1  is able to be introduced into the pre-chamber  220  from the storage tank. In step S 14 , the ultraviolet light is provided from an ultraviolet light generator. Please refer to  FIG. 1A . Because the pre-chamber  220  is extended perpendicularly to the first gas input channel  22 , and the transparent side wall  2200  faces to the extending direction of the pre-chamber  220 , so the ultraviolet light can readily illuminate all space of the pre-chamber. The first gas G 1  can be illuminated efficiently without enlarging the exposure area of the ultraviolet light. In step  16 , the first gas G 1  has higher chemical reactivity after being illuminated by the ultraviolet light to form an atomic layer on the substrate. 
         [0043]    In the embodiment, because of the design of the pre-chamber  220  and the transparent side wall  2200 , the first gas G 1  can be effectively illuminated by sufficient ultraviolet light in the pre-chamber  220  to reduce the reaction time for each cycle. To make sure enough illumination on the first gas G 1  by the ultraviolet light, the first gas G 1  is able to stay in the pre-chamber  220  for a longer duration before getting into the processing chamber  20 . 
         [0044]    Please refer to  FIG. 2  and  FIG. 1B .  FIG. 2  shows the flow chart of a photo-assisted atomic layer deposition method according to another embodiment of the present invention. The difference between the embodiment shown in  FIG. 2  and the last embodiment is that the photo-assisted atomic layer deposition method in this embodiment further comprises step S 12 ′ and step S 16 ′. The other steps of the photo-assisted atomic layer deposition method are the same as the corresponding steps of the photo-assisted atomic layer deposition method in the last embodiment. 
         [0045]    In step S 12 ′, the first valve is closed when the first gas G 1  is introduced into the pre-chamber  220  to keep the first gas G 1  in the pre-chamber  220 , so that the molecules of the first gas G 1  can be illuminated by enough ultraviolet light in the follow-on steps. In step S 16 ′, when the first gas G 1  has been illuminated by the ultraviolet light provided by the step S 14  for a predetermined duration, the first valve  222  is opened to introduce the first gas G 1  into the processing chamber  20 . The predetermined duration is determined by the parameters of the process and the system setup such as the kinds of the first gas G 1  (precursor), the size of the processing chamber  20 , and the kinds and the size of the substrate S. The first gas can be illuminated by enough ultraviolet light in the pre-chamber  220  by controlling the first valve  222 . 
         [0046]    In the atomic layer deposition, there are two kinds of process gases (precursors) which are introduced into the processing chamber in turns to form the atomic layers on the substrate; for example, trimethylaluminum and water are introduced into the processing chamber to form aluminium oxides on the substrate. Please refer to  FIG. 3  and  FIG. 1B .  FIG. 3  shows the flow chart of a photo-assisted atomic layer deposition method according to another embodiment of the present invention. The processing system  2  of  FIG. 1B  further comprises a second gas input channel  24  and a second valve  240  connecting the second gas input channel  24  and processing chamber  20 . Besides, the second gas input channel  24  can be connected to the storage tank of the second gas G 2  to receive the second gas G 2  from the storage tank. As shown in  FIG. 3 , the difference between the embodiment and the last embodiment is that the present embodiment further comprises steps S 12 ″ and S 16 ″, and other steps in the present embodiment are the same as the steps of the last embodiment. 
         [0047]    In the step S 12 ″ in the embodiment, when the first gas G 1  is introduced into the pre-chamber  220 , the first valve  222  is closed to keep the first gas G 1  in the pre-chamber  220 , and the second valve  240  is opened to input the second gas G 2  into the processing chamber  20 . Therefore, in the step S 14 , the first gas G 1  is blocked in the pre-chamber  220  to be illuminated by the ultraviolet light. In the step S 16 ″, as the first gas G 1  is illuminated by the ultraviolet light for the predetermined duration, the first valve is opened to introduced the first gas G 1  into the processing chamber, and the second valve  240  is closed to block the second gas G 2  from entering the processing chamber  20 . One atomic layer is formed after one cycle of the steps S 12 ″ to S 16 ″, and it moves forward to the step S 12 ″ of the next cycle to form another atomic layer, as shown in  FIG. 3 . That is to say, the first valve  222  and the second valve  240  are opened and closed alternatively to input the first gas G 1  illuminated by the ultraviolet light and the second gas G 2  to stack the plurality of atomic layers on the surface of the substrate S. It should be noted that the first precursor in the first cycle of the process could be the first gas G 1 , instead of the gas G 2 . Therefore, even though the second valve is opened in the step S 12 ″, the second gas is not able to be introduced to affect the surface condition of the substrate S. 
         [0048]    In practice, the first gas input channel  22  of the processing system  2  shown in  FIG. 1B  is able to comprise a third valve connecting the first gas input channel  22  and the storage tank of the first gas G 1 , and the third valve and the second valve are able to be opened and closed at the same time. That is to say, when the second valve  240  and the third valve are opened and the first valve  222  is closed, the second gas G 2  is able to be introduced into the processing chamber to form the atomic layer on the substrate S, and the first gas G 1  is introduced into the pre-chamber  220  but blocked from the processing chamber  20  to be illuminated by the ultraviolet light. When the first valve  222  is opened, the second valve  240  and the third valve are closed, so as to input the first gas G 1  illuminated by enough ultraviolet light into the processing chamber  20  and to block the second gas G 2 . The third valve is closed when the first valve  222  is opened to make sure that the first gas G 1  introduced into the processing chamber  20  has been illuminated by enough ultraviolet light. 
         [0049]    In addition to the first gas G 1  and the second gas G 2 , the photo-assisted atomic layer deposition method of the present invention is able to utilize a third gas to assist the process. Please refer to  FIG. 4A  and  FIG. 4B .  FIG. 4A  shows the flow chart of a photo-assisted atomic layer deposition method according to another embodiment of the present invention.  FIG. 4B  shows the diagram of the processing system applying the photo-assisted atomic layer deposition method of  FIG. 4A . The difference between the processing system  4  shown in  FIG. 4B  and the processing system  2  shown in the embodiments mentioned above is that the processing system  4  further comprises a third gas input channel  46  connected to the processing chamber  40 . The third gas input channel  46  is able to be connected to the storage tank of the third gas G 3  which is not shown in the figure to input the third gas G 3  into the processing chamber  40  from the storage tank. 
         [0050]    As shown in  FIG. 4A , the photo-assisted atomic layer deposition method in the present embodiment further comprises the following step of: in the step  31 , introducing the third gas G 3  into the processing chamber  40  via the third gas input channel  46 . In the embodiments, the third gas G 3  is able to be an inert gas like Ar or N 2  to maintain the stable circumstance in the processing chamber  40 . Besides, the step S 31  is able to be carried out once a reaction of a ALD process is completed, so as to bring the previous residual reaction gas out by the inert gas. 
         [0051]    Please refer to  FIG. 4C  and  FIG. 4B .  FIG. 4C  shows the flow chart of a photo-assisted atomic layer deposition method according to another embodiment of the present invention. As shown in  FIG. 4C , the difference between the present embodiment and the last embodiment is that the step S 31 ′ of the photo-assisted atomic layer deposition method is continually introducing the third gas G 3  into the processing chamber  40 . In the embodiment, the third gas G 3  is a plasma gas. After the third gas is introduced into the processing chamber  40 , the plasma is ignited by an electrical field. Therefore, the photo-assisted atomic layer deposition method in the embodiment is able to utilize the plasma to facilitate the atomic layer deposition and accelerate the growth rate of each atomic layer. 
         [0052]    The processing chamber of the photo-assisted atomic layer deposition method of the present invention is able to maintain a process temperature to keep the process fluent. Besides, according to another embodiment, the photo-assisted atomic layer deposition method further comprises the following step of heating the pre-chamber  420  by the heating device  424  to make the temperature of the pre-chamber  420  in a temperature range from 25° C. to 400° C. Therefore, the first gas G 1  achieves a higher reactivity to make the deposition rate faster and the required illuminating duration shorter. 
         [0053]    Please refer to  FIG. 5A  and  FIG. 5B .  FIG. 5A  shows the flow chart of a photo-assisted atomic layer deposition method according to another embodiment of the present invention.  FIG. 5B  shows the diagram of the processing system applying the photo-assisted atomic layer deposition method of  FIG. 5A . The difference between the processing system  6  shown in  FIG. 5B  and the processing chamber of the other embodiments mentioned above is that the processing system  6  further comprises the second gas input channel  64 ′ connected to the pre-chamber  620  of the first gas input channel  62 . The other elements of the processing chamber  6  are the same as the processing chambers of the embodiments mentioned above. 
         [0054]    As shown in  FIG. 5A , the photo-assisted atomic layer deposition method in the embodiment comprises the following steps of: in the step S 50 , preparing the processing system  6  as shown in  FIG. 5B ; in the step S 52 , introducing the first gas G 1  into the pre-chamber  620  of the first gas input channel  62  and blocking the second gas G 2 ; in the step S 54 , illuminating the first gas G 1  in the pre-chamber  620  by the ultraviolet light; in the step S 56 , introducing the first gas G 1  illuminated by the ultraviolet light into the processing chamber  60  to form the atomic layer on the substrate S; and in the step S 58 , blocking the first gas G 1  and introducing the second gas G 2  into the pre-chamber  620  via the second gas input channel  64 ′. After finishing the step S 58 , restart the step S 52  to repeat the cycles. 
         [0055]    In the embodiments, the second gas G 2  can work as a precursor and be introduced into the processing chamber  60  from the pre-chamber  620 . When the second gas G 2  is a precursor, the first gas G 1  and the second gas G 2  can be introduced into the pre-chamber  620  and the processing chamber  60  in turns to form the atomic layers one by one. Please refer to  FIG. 5C  and  FIG. 5B .  FIG. 5C  shows the flow chart of a photo-assisted atomic layer deposition method according to another embodiment of the present invention. The difference between this embodiment and the last embodiment is that the method of the embodiment further comprises the steps S 55 ′ and S 56 ′. In step S 55 ′, the second gas G 2  is introduced, and the second gas G 2  can be an inert gas or other assisting gas. When the second gas G 2  is an inert gas or other assisting gas, in the step S 56 ′, the second gas G 2  can be introduced into the processing chamber  60  with the first gas G 1  to form the atomic layers. 
         [0056]    In the embodiments of  FIG. 5A  to  FIG. 5C ; the processing system  6  further comprises the third gas input channel  66  which can be connected to the processing chamber  60 . In the step S 58  of the  FIG. 5A , the second gas G 2  introduced via the second gas input channel  64 ′ is a process gas, so that the assisting gas such as the inert gas and the plasma gas can be introduced via the third gas input channel  66 . Oppositely, in the step S 55 ′ of  FIG. 5C , the second gas G 2  introduced via the second gas channel  64 ′ is an inert gas, so that the process gas can be introduced via the third gas input channel  66 . It should be noted that the valves configured on each of the gas input channels in  FIG. 5  are used to control the flow and the duration of different gases injecting into the processing chamber and the pre-chamber. 
         [0057]    The photo-assisted atomic layer deposition method of the present invention utilizes the design of the pre-chamber in the gas input channel to enhance the reactivity of precursor molecules through an effective illumination of ultraviolet light. Therefore, the present invention provides a photo-assisted atomic layer deposition method utilizing the design of a pre-chamber through which the temperature of precursor molecules and the illumination of ultraviolet light can be well controlled, improving the reactivity, deposition rate and reducing the residues of the ligand functional groups of the precursor. 
         [0058]    With the examples and explanations mentioned above, the features and spirits of the invention are well described. More importantly, the present invention is not limited to the embodiment described herein. Those skilled in the art will readily observe that numerous modifications and alterations of the device may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.