Patent Publication Number: US-2017369990-A1

Title: Reactive heat treatment apparatus

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a reactive heat treatment apparatus, and more particularly to a reactive heat treatment apparatus used for treating a thin-film device. The reactive heat treatment apparatus has a sunken portion to prevent liquid selenium which is condensed from a gas containing selenium from flowing back. 
     Description of Related Art 
     Solar power is renewable and environmentally friendly for the generation of electricity, which does not produce carbon dioxide or other greenhouse gases during the process of solar power generation. These days, people pay attention to environmental protection, so solar power systems are widely applied to residential buildings, public facilities, installation art, and transportation. For converting sunlight into electricity, a solar cell is required to store the electricity converted from sunlight. There are various types of solar cells on the markets. CIGS (copper indium gallium selenide) solar cells have the advantages of better conversion efficiency, good stability, and good low light characteristic. Therefore, CIGS solar cells become one of the mainstream solar cells on the markets. In general, conventional CIGS solar cells are manufactured by sputtering. After Ga/Cu/In and other elements are sputtered on a Mo metal substrate, a selenization furnace is used for selenization reaction at a high temperature of 450˜550° C.  FIG. 1  is a schematic view of a conventional selenization process. Referring to  FIG. 1 , in a selenization furnace  10 , the temperature of a low-temperature portion  12  near the mouth of the furnace must be maintained below 250° C., avoiding the degradation of an O-shaped ring to cause an air leak. However, when the gas  14  containing selenium approaches the low-temperature portion  12 , the gas  14  containing selenium will be condensed into liquid selenium to flow downward along the furnace wall of the low-temperature portion  12  and flow back to a high-temperature portion  11  along the bottom of the furnace wall. The condensed liquid selenium flowing back to the high-temperature portion  11  is gasified again to be mixed with the gas in the high-temperature portion  11 . As a result, the concentration of the gas  14  containing selenium is changed, which influences the stability of the manufacturing process. It is worth for the person skilled in the art to consider how to stabilize the process for manufacturing CIGS solar cells. Accordingly, the inventor of the present invention has devoted himself based on his many years of practical experiences to solve these problems. 
     SUMMARY OF THE INVENTION 
     Based on the above reasons, the present invention is to provide a reactive heat treatment apparatus which can prevent condensed liquid selenium from flowing back to a high-temperature portion so as to keep the stability of selenization reaction and to improve the yield for processing thin-film devices. 
     According to a first aspect of the present invention, a reactive heat treatment apparatus is provided. The reactive heat treatment apparatus is configured to treat a thin-film device. The reactive heat treatment apparatus comprises a furnace pipe. The furnace pipe extends in a direction and has a first end and a second end. The furnace pipe further includes a high-temperature portion, a low-temperature portion, and a furnace door. The high-temperature portion is disposed close to the second end and configured to receive the thin-film device. The low-temperature portion is disposed close to the first end and provided with an airtight configuration. The furnace door is disposed close to the first end. An inner side wall of the low-temperature portion has a sunken portion, and a height differential is formed between the sunken portion and an inner side wall of the high-temperature portion. 
     In one embodiment of the present invention, the inner side wall of the low-temperature portion, except the sunken portion, is level with the inner side wall of the high-temperature portion. 
     In one embodiment of the present invention, the sunken portion extends throughout the low-temperature portion. 
     In one embodiment of the present invention, the high-temperature portion and the low-temperature portion are made of an identical material. 
     In one embodiment of the present invention, the high-temperature portion and the low-temperature portion are made of quartz. 
     In one embodiment of the present invention, the high-temperature portion and the low-temperature portion are parts of a monolithic structure. 
     In one embodiment of the present invention, the high-temperature portion and the low-temperature portion are made of different materials. 
     In one embodiment of the present invention, the low-temperature portion is made of stainless steel. The reactive heat treatment apparatus further comprises a container mated with the sunken portion. 
     In one embodiment of the present invention, the high-temperature portion has a length greater than that of the low-temperature portion. 
     According to a second aspect of the present invention, a method to manufacture a reactive heat treatment apparatus is provided. The method comprises the steps of: providing a furnace pipe, the furnace pipe extending in a direction, the furnace pipe having a first end and a second end, the furnace pipe including a high-temperature portion and a low-temperature portion, the high-temperature portion being disposed close to the second end and configured to receive a thin-film device, the low-temperature portion being disposed close to the first end and provided with an airtight configuration; and forming a sunken portion on an inner side wall of the low-temperature portion, a height differential being formed between the sunken portion and an inner side wall of the high-temperature portion. 
     In one embodiment of the present invention, the method further comprises the step of providing a container mated with the sunken portion. 
     In one embodiment of the present invention, the high-temperature portion has a length greater than that of the low-temperature portion. 
     In one embodiment of the present invention, the high-temperature portion and the low-temperature portion are made of an identical material. 
     In one embodiment of the present invention, the high-temperature portion and the low-temperature portion are made of different materials. 
     In one embodiment of the present invention, the low-temperature portion is made of stainless steel. 
     According to a third aspect of the present invention, a method to manufacture a reactive heat treatment apparatus is provided. The method comprises the steps of: providing a first furnace pipe; providing a second furnace pipe, the second furnace pipe being provided with an airtight configuration, the first furnace pipe having a length greater than that of the second furnace pipe, the second furnace pipe having a cross-section greater than that of the first furnace pipe; and connecting the first furnace pipe with the second furnace pipe, a height differential being formed at a junction of the first furnace pipe and the second furnace pipe. 
     In one embodiment of the present invention, the first furnace pipe and the second furnace pipe are made of a stainless steel material. 
     In one embodiment of the present invention, the first furnace pipe and the second furnace pipe are made of a quartz material. 
     In one embodiment of the present invention, the first furnace pipe is made of quartz, and the second furnace pipe is made of stainless steel. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view of a conventional selenization process; 
         FIG. 2A  is a schematic view of a reactive heat treatment apparatus in accordance with a first embodiment of the present invention; 
         FIG. 2B  is a schematic view of a reactive heat treatment apparatus in accordance with another embodiment of the present invention; 
         FIG. 3A  and  FIG. 3B  are schematic views of a reactive heat treatment apparatus in accordance with a further embodiment of the present invention; 
         FIG. 4  is a schematic view of a reactive heat treatment apparatus in accordance with a yet further embodiment of the present invention; 
         FIG. 5  is a flow chart of a method to manufacture the reactive heat treatment apparatus; and 
         FIG. 6  is a flow chart of a method to manufacture the reactive heat treatment apparatus of another embodiment. 
     
    
    
     DESCRIPTION OF THE INVENTION 
       FIG. 2A  is a schematic view of a reactive heat treatment apparatus  200  in accordance with a first embodiment of the present invention. The reactive heat treatment apparatus  200  of the present invention is configured to treat a thin-film device  211 . The thin-film device  211  in this embodiment is a CIGS (copper indium gallium diselenide) thin-film solar cell. The thin-film device  211  is placed in the reactive heat treatment apparatus  200  to be processed by sputtering. At high temperatures, selenium is deposited on the surface of the thin-film device  211  for selenization reaction. 
     The reactive heat treatment apparatus  200  comprises a furnace pipe  201 . The furnace pipe  201  extends in a direction. The furnace pipe  201  has a first end  202  and a second end  203 . The second end  203  is opposite the first end  202 . The second end  203  and the first end  202  are disposed at two ends of the furnace pipe  201 , respectively. The furnace pipe  201  further includes a high-temperature portion  210  and a low-temperature portion  220 . In this embodiment, the high-temperature portion  210  has a length greater than that of the low-temperature portion  220 . 
     The high-temperature portion  210  is disposed close to the second end  203 . The high-temperature portion  210  is the area configured to treat the thin-film device  211 , so the thin-film device  211  is placed in the high-temperature portion  210 . The temperature of the high-temperature portion  210  during processing can be up to 450-550 degrees centigrade, subjecting the thin-film device  211  to selenization reaction in the high-temperature portion  210 . During selenization reaction, the gas  14  containing selenium in the furnace pipe  201  flows toward the low-temperature portion  220 . The gas  14  containing selenium is a fluid that is a noble gas, such as nitrogen or argon, mixed with a certain proportion of gaseous selenium or selenium compound. 
     The low-temperature portion  220  is disposed close to the first end  202 . The low-temperature portion  220  includes a sunken portion  221 , an airtight configuration  222 , and a furnace door  223 . In this embodiment, the airtight configuration  222  is an O-shaped ring. The low-temperature portion  220  is able to lower the temperature of the gas  14  containing selenium in the furnace pipe  201  to about 250 degrees centigrade or a lower temperature. This can avoid the degradation of the airtight configuration  222  to cause an air leak due to a high temperature. Thus, the low-temperature portion  220  is capable of protecting the airtight configuration  222 . The pipe wall or the outer side of the pipe wall of the low-temperature portion  220  may be provided with a cooling device, such as a cooling pipe, to accommodate a cooling fluid for lowering and/or keeping the temperature of the low-temperature portion  220 . The sunken portion  221  is disposed on the inner side wall of the low-temperature portion  220 . A height differential D is formed between the inner side wall of the sunken portion  221  of the low-temperature portion  220  and the inner side wall of the high-temperature portion  210 . When the gas  14  containing selenium flows from the high-temperature portion  210  to the low-temperature portion  220  due to a temperature difference, the gas  14  containing selenium will be condensed because the temperate drops. The condensed selenium flows downward along the pipe wall of the low-temperature portion  220  and accumulates at the bottom of the pipe wall of the low-temperature portion  220  to enter the sunken portion  221 .  FIG. 2B  is a schematic view of a reactive heat treatment apparatus  200  in accordance with another embodiment of the present invention. In this embodiment, the sunken portion  221  is provided with a container  224  mated with the sunken portion  221 . The container  224  can be a crucible for storing the liquid selenium condensed from the gas  14  containing selenium. After finishing selenization reaction, the condensed selenium accumulated in the container  224  can be cleaned regularly. The container can be taken out from the sunken portion if necessary, so that the accumulated condensed selenium can be cleaned conveniently. 
     In this embodiment, the inner side wall of the low-temperature portion  220 , except the sunken portion  221 , is level with the inner side wall of the high-temperature portion  210 . Besides, the high-temperature portion  210  and the low-temperature portion  220  are parts of a monolithic structure. Therefore, the high-temperature portion  210  and the low-temperature portion  220  are made of an identical material and formed in one piece. For example, the furnace pipe  201  of the high-temperature portion  210  and the low-temperature portion  220  is a quartz pipe in one piece. The high-temperature portion  210  and the low-temperature portion  220  can be made of different materials and are connected with each other. For example, the high-temperature portion  210  is a quartz pipe and the low-temperature portion  220  is made of a stainless steel material. In addition, the sunken portion  221  is formed on the inner side of the low-temperature portion  220 , so the outer diameter of the furnace pipe  201  doesn&#39;t be changed.  FIG. 3A  and  FIG. 3B  are schematic views of a reactive heat treatment apparatus  200  in accordance with a further embodiment of the present invention. In the embodiment of  FIG. 3A , the sunken portion  221  protrudes out of the furnace pipe  201 . In the embodiment of  FIG. 3B , the container  224  is disposed beneath the sunken portion  221  and mated with the sunken portion  221 . The sunken portion  221  can be a closed part, as shown in  FIG. 3A , or the sunken portion  221  has an opening, as shown in  FIG. 3B , to mate with the container  224 . 
     When the gas  14  containing selenium flows from the high-temperature portion  210  to the low-temperature portion  220  due to a temperature difference, the gas  14  containing selenium will be condensed because the temperate drops. The condensed selenium flows downward along the pipe wall of the low-temperature portion  220  and accumulates at the bottom of the pipe wall of the low-temperature portion  220  to enter the sunken portion  221 . That is to say, the gas  14  containing selenium is condensed into liquid selenium and stored in the sunken portion  221  due to cooling, preventing the condensed liquid selenium from flowing back along the bottom of the furnace pipe  201  to the high-temperature portion  210  to be gasified again and change the concentration of the selenium contained in the gas  14  containing selenium in the furnace pipe  201 . Therefore, the concentration of the gas  14  containing selenium in the high-temperature portion  210  can be kept constant rendering stable process for treating the thin-film device  211  because the condensed liquid selenium won&#39;t flow back to the high-temperature portion  210 . 
       FIG. 4  is a schematic view of a reactive heat treatment apparatus  300  in accordance with a yet further embodiment of the present invention. The reactive heat treatment apparatus  300  of this embodiment comprises a first furnace pipe  312  and a second furnace pipe  324  connected with the first furnace pipe  312 . The second furnace pipe  324  has a cross-section greater than that of the first furnace pipe  312 . The inside of the second furnace pipe  324  is defined as a low-temperature portion  320 . The inside of the first furnace pipe  312  is defined as a high-temperature portion  310 . The functions of the high-temperature portion  310  and the low-temperature portion  320  are similar to those of the aforesaid embodiments and won&#39;t be described again. The diameter of the first furnace pipe  312  is greater than that of the second furnace pipe  324 . After the first furnace pipe  312  and the second furnace pipe  324  are connected together, a sunken portion  321  is formed at the junction of the first furnace pipe  312  and the second furnace pipe  324  because of the diameter difference between the first furnace pipe  312  and the second furnace pipe  324 . The sunken portion  321  extends throughout the low-temperature portion  320 . The sunken portion  321  is adapted to store the condensed liquid selenium flowing downward along the pipe wall of the low-temperature portion  320 , preventing the condensed liquid selenium from flowing back to the high-temperature portion  310 . In this embodiment, the first furnace pipe  312  and the second furnace pipe  324  are made of an identical material, such as quartz pipes or stainless steel pipes to be connected together. The first furnace pipe  312  and the second furnace pipe  324  can be made of different materials. For instance, the first furnace pipe  312  is made of quartz and the second furnace pipe  324  is made of stainless steel. In some embodiments, the first furnace pipe  312  is made of stainless steel and the second furnace pipe  324  is made of quartz. 
       FIG. 5  is a flow chart of a method to manufacture the reactive heat treatment apparatus  200  of  FIG. 2A  and  FIG. 2B . Referring to  FIG. 5 ,  FIG. 2A  and  FIG. 2B , a furnace pipe  201  is provided (step A 10 ). The furnace pipe  201  extends in a direction. The furnace pipe  201  has a first end  202  and a second end  203 . The furnace pipe  201  further includes a high-temperature portion  210  and a low-temperature portion  220 . The high-temperature portion  210  is disposed close to the second end  203  and configured to receive a thin-film device  211 . The low-temperature portion  220  is disposed close to the first end  202 . The low-temperature portion  220  is further provided with an airtight configuration  222 . In some embodiments, the high-temperature portion  210  has a length greater than that of the low-temperature portion  220 . A sunken portion  221  is formed on the inner side wall of the low-temperature portion  220  (step A 20 ). A height differential is formed between the sunken portion  221  and the inner side wall of the high-temperature portion  210 . In some embodiments, the sunken portion  221  is provided with a container  224  mated with the sunken portion  221 . The container  224  can be a crucible for storing the condensed selenium dropped in the low-temperature portion  220 . Besides, in this embodiment, the low-temperature portion  220  is made of stainless steel. In different embodiments, the low-temperature portion  220  and the high-temperature portion  210  are made of an identical material, or they can be made of different materials. 
       FIG. 6  is a flow chart of a method to manufacture the reactive heat treatment apparatus  300  of  FIG. 4 . Referring to  FIG. 6  and  FIG. 4 , a first furnace pipe  312  is provided (step B 10 ). The first furnace pipe  312  is configured to form a high-temperature portion  310  and adapted to treat a thin-film device  311 . A second furnace pipe  324  is provided (step B 20 ). The second furnace pipe  324  is further provided with an airtight configuration  322 . The second furnace pipe  324  is configured to form a low-temperature portion  320 . The low-temperature portion  320  is capable of protecting the airtight configuration  322 . The first furnace pipe  312  has a length greater than that of the second furnace pipe  324 . The second furnace pipe  324  has a cross-section greater than that of the first furnace pipe  312 . The step B 10  can be interchanged with the step B 20 . 
     After that, the first furnace pipe  312  and the second furnace pipe  324  are connected together (step B 30 ). For example, they are connected by sintering. Because the cross-section of the second furnace pipe  324  is greater than that of the first furnace pipe  312 , a height differential D (as shown in  FIG. 4 ) is formed at the junction of the first furnace pipe  312  and the second furnace pipe  324 . The height differential D is to form a sunken portion  321 . The sunken portion  321  is adapted to store the condensed liquid selenium of the low-temperature portion  320 . The height differential D can block the condensed liquid selenium from flowing back to the high-temperature portion  310 . Therefore, the concentration of the gas in the high-temperature portion  310  can be kept constant for processing selenization reaction stably. 
     In this embodiment, the reactive heat treatment apparatus  300  is formed by connecting the first furnace pipe  312  with the second furnace pipe  324 . The first furnace pipe  312  and the second furnace pipe  324  can be made of an identical material or different materials. For instance, the first furnace pipe  312  is made of a quartz material and the second furnace pipe  324  is made of a stainless steel material. In another embodiment, both the first furnace pipe  312  and the second furnace pipe  324  are made of a stainless steel material. In a further embodiment, both the first furnace pipe  312  and the second furnace pipe  324  are made of a quartz material. A person skilled in this field can know that the materials of the first furnace pipe  312  and the second furnace pipe  324  can be changed according to the design of the reactive heat treatment apparatus  300 . 
     The low-temperature portion  220 ,  320  of the reactive heat treatment apparatus  200 ,  300  of the present invention is provided with the sunken portion  221 ,  321 . When the gas  14  containing selenium flows from the high-temperature portion  210 ,  310  to the low-temperature portion  220 ,  320  due to a temperature difference, the gas  14  containing selenium will be condensed because the temperate drops. The condensed selenium flows downward along the pipe wall of the low-temperature portion  220  and accumulates at the bottom of the pipe wall of the low-temperature portion  220  to enter the sunken portion  221 ,  321 . The condensed liquid selenium won&#39;t flow back along the furnace pipe  203 ,  303  to the high-temperature portion  210 ,  310 . Therefore, the concentration of the gas  14  containing selenium in the high-temperature portion  210 ,  310  can be kept constant. The arrangement of the sunken portion  221 ,  321  can greatly enhance the stability for treating the thin-film device. 
     Although particular embodiments of the present invention have been described in detail for purposes of illustration, various modifications and enhancements may be made without departing from the spirit and scope of the present invention. Accordingly, the present invention is not to be limited except as by the appended claims.