Abstract:
The linear controlling of the pressure of a vacuum chamber, such as a plasma etch chamber used in semiconductor processing, is disclosed. A plasma etch chamber pressure control mechanism includes an aperture diaphragm and a number of aperture blades rotatably mounted on the aperture diaphragm. The diaphragm defines a contractible and expandable aperture for controlling the pressure of the chamber. Rotation of the aperture blades in a first direction contracts the aperture by causing movement of the blades towards the aperture, increasing the pressure of the chamber. Rotation of the aperture blades in a second direction opposite to the first direction expands the aperture by causing movement of the blades away from the aperture, decreasing the pressure of the chamber.

Description:
FIELD OF THE INVENTION  
         [0001]    This invention relates generally to vacuum chambers, such as dry etch plasma chambers used in semiconductor processing, and particularly to controlling the pressure of such chambers.  
         BACKGROUND OF THE INVENTION  
         [0002]    There are four basic operations in semiconductor processing, layering, patterning, doping, and heat treatments. Layering is the operation used to add thin layers to the surface of a semiconductor wafer. Patterning is the series of steps that results in the removal of selected portions of the layers added in layering. Doping is the process that puts specific amounts of dopants in the wafer surface through openings in the surface layers. Finally, heat treatments are the operations in which the wafer is heated and cooled to achieve specific results, where no additional material is added or removed from the wafer.  
           [0003]    Of these four basic operations, patterning is typically the most critical. The patterning operation creates the surface parts of the devices that make up a circuit on the semiconductor wafer. The operation sets the critical dimensions of these devices. Errors during patterning can cause distorted or misplaced defects that result in changes in the electrical function of the device, as well as device defects.  
           [0004]    The patterning process is also known by the terms photomasking, masking, photolithography, and microlithography. The process is a multi-step process similar to photography or stenciling. The required pattern is first formed in photomasks and transferred into the surface layers of the semiconductor wafer. This is shown by reference to FIGS. 1A and 1B. In FIG. 1A, the wafer  100  has an oxide layer  102  and a photoresist layer  104 . A mask  106  is precisely aligned over the wafer  100 , and the photoresist  104  is exposed, as indicated by the arrows  108 . This causes the exposure of the photoresist layer  104 , except for the part  110  that was masked by the part  112  of the mask  106 . In FIG. 1B, the unexposed part  110  of the photoresist layer  104  is removed, creating a hole  114  in the photoresist layer  104 .  
           [0005]    Next, a second transfer takes place from the photoresist layer  104  into the oxide layer  102 . This is shown in FIG. 1C, where the hole  114  extends through both the photoresist layer  104  and the oxide layer  102 . The transfer occurs when etchants remove the portion of the wafer&#39;s top layer that is not covered by photoresist. The chemistry of photoresists is such that they do not dissolve, or dissolve very slowly, in the chemical etching solutions. Finally, the photoresist layer  104  is removed, as shown in FIG. 1D, such that only the wafer  100  and the oxide layer  102  with the hole  114  remains.  
           [0006]    The removal of the photoresist layer can be accomplished by either wet or dry etching. Wet etching refers to the use of wet chemical processing to remove the photoresist. The chemicals are placed on the surface of the wafer, or the wafer itself is submerged in the chemicals. Dry etching refers to the use of plasma stripping, using a gas such as oxygen (O 2 ), C 2 F 6  and O 2 , or another gas. Whereas wet etching is a low-temperature process, dry etching is typically a high-temperature process.  
           [0007]    One type of dry etching process is shown in FIG. 2. Within the chamber  200 , a semiconductor wafer  202  sits on a number of pins  208 ,  210 , and  212 , such that the wafer rests against a heater block  216 . This position of the wafer  202  resting against the block  216  is referred to as the pin down position. Gas is introduced at insertion point  206 , where the showerhead  204  sprays the gas onto the plasma  218 , which is situated within the grounded grid  214 . The plasma  218  energizes the gas to a high-energy state, which in turn oxidizes the resist components to gases that are removed from the chamber  200  by a vacuum pump (not shown in FIG. 2). Dry etching is advantageous to wet etching for resist stripping because it eliminates the use of wet hoods and the handling of chemicals.  
           [0008]    For the dry etch process to work properly, the pressure within the chamber must be able to be controlled in a precise manner. However, existing pressure control mechanisms are less than desirable. They make it difficult to control chamber pressure in a linear manner. Furthermore, their machine parts are heavy, taking up great amounts of space, and move slowly, rendering pressure control a slow process, particularly to stabilize the pressure at a desired level.  
           [0009]    [0009]FIG. 3 shows one type of existing plasma chamber pressure control mechanism  300 , which utilizes a throttle valve design. The pressure chamber  304  opens to a cavity  302  through an opening  314 , in which a tapered valve  306  is situated. The tapered valve  306  is connected to a rod  308 . Vertical movement of the rod  308 , as indicated by the arrow  310 , is possible through a controller  312 . Such vertical movement causes the valve  306  to expose more or less of the opening  314 , allowing control of the pressure in the chamber  304 .  
           [0010]    For example, where the valve  306  is positioned higher within the chamber  304 , more of the opening  314  is exposed, causing lower chamber pressure. This is shown in the vertical view of FIG. 4A, where the valve  306  occupies less of the opening  314 , exposing a larger part of the opening  314 , as indicated by the reference number  402 . However, where the valve  306  is positioned lower within the chamber  304 , less of the opening  314  is exposed, causing higher chamber pressure. This is shown in the vertical view of FIG. 4B, where the valve  306  occupies more of the opening  314 , exposing a smaller part of the opening  314 , as indicated by the reference number  404 .  
           [0011]    [0011]FIG. 5 shows another type of existing plasma chamber pressure control mechanism  500 , which also utilizes a throttle valve design. The pressure chamber  504  opens to a cavity  502  through an opening defined between the spacers  508  and  510 , in which a valve  506  is situated. Vertical movement of the valve  506  causes the valve  506  to expose more or less of the opening defined between the spacers  508  and  510 , allowing control of the pressure in the chamber  504 .  
           [0012]    For example, where the valve  506  is positioned higher within the cavity  502 , more of the opening is exposed, causing lower chamber pressure. This is shown in the vertical view of FIG. 6A, where a relatively large part of the opening, indicated by the reference numbers  602  and  604 , is exposed. However, where the valve  506  is positioned lower within the cavity  502 , less of the opening is exposed, causing higher chamber pressure. This is shown in the vertical view of FIG. 6B, where a relatively small part of the opening, indicated by the reference numbers  606  and  608 , is exposed.  
           [0013]    [0013]FIG. 7 shows an exploded view of a final type of existing plasma chamber pressure control mechanism  700 , which utilizes a pendular valve design. The pressure chamber  712  has an opening  714 , which is concentrically positioned along the vertical axis  702  over the opening  706  of the top flange  704 . The pendular valve  708  has an opening  710  that allows access of the opening  714  of the chamber  712  to the opening  706  of the flange  704  when the opening  710  is concentrically aligned over the openings  714  and  706 . However, the valve  708  is rotatable along the vertical axis  718 , as indicated by the arrow  716 , such that more or less of the opening  710  can be exposed, meaning that more or less of the opening  714  of the chamber  712  is allowed access to the opening  706  of the top flange  704 .  
           [0014]    For example, where the opening  710  of the valve  708  is positioned relatively more concentrically over the opening  714  of the chamber  712 , more of the opening  706  of the flange  704  is exposed, causing lower chamber pressure. This is shown in the vertical view of FIG. 8A, where the opening  710  is relatively more concentrically positioned over the opening  714 , causing a relatively large access area  802  to the opening  706  (not shown in FIG. 8A), for lower chamber pressure. The large access area  802  is the area of overlap, or intersection, between the openings  710  and  714 .  
           [0015]    However, where the opening  710  of the valve  708  is positioned relatively less concentrically over the opening  714  of the chamber  712 , less of the opening  706  of the flange  704  is exposed, causing higher chamber pressure. This is shown in the vertical view of FIG. 8B, where the opening  710  is relatively less concentrically positioned over the opening  714 , causing a relative small access area  804  to the opening  706  (not shown in FIG. 8A), for higher chamber pressure. The small access area  804  is the area of overlap, or intersection, between the openings  710  and  714 .  
           [0016]    The plasma chamber pressure control mechanisms of FIGS. 3, 5, and  7  that have been described exhibit the mentioned disadvantages of existing chamber pressure control mechanisms. Therefore, there is a need to control chamber pressure in a linear manner. There is also a need for a pressure control mechanism that does not require a heavy valve and associated machinery, such that the mechanism does not use a large amount of space. Finally, there is a need for a pressure control mechanism that moves relatively quickly, rendering pressure control a faster process, particularly to stabilize the pressure at a desired level. For these and other reasons, there is a need for the present invention.  
         SUMMARY OF THE INVENTION  
         [0017]    Linearly controlling the pressure of a vacuum chamber, such as a plasma etch chamber used in semiconductor processing, is disclosed. A plasma etch chamber pressure control mechanism of the invention includes an aperture diaphragm and a number of aperture blades rotatably mounted on the aperture diaphragm. The diaphragm defines a contractible and expandable aperture for controlling the pressure of the chamber. Rotation of the aperture blades in a first direction, such as counter-clockwise, contracts the aperture, increasing the pressure of the chamber. Rotation of the aperture blades in a second direction opposite to the first direction, such as clockwise, expands the aperture, decreasing the pressure of the chamber.  
           [0018]    The mechanism can also include two rotatable circular frames. The first frame is around the aperture diaphragm and has a number of inward facing gear teeth. Gear teeth of circular gears corresponding to the aperture blades, and rotatably mounting the blades to the diaphragm, interlock with the inward-facing gear teeth of the first frame. Rotation of the frame in the first direction causes the rotation of the blades in the first direction, and vice-versa. The first frame preferably insulates the aperture diaphragm and the aperture blades in an airtight manner.  
           [0019]    The second frame is around the first frame, and interacts with the first frame to cause the rotation of the first frame indirectly in the direction that the second frame is directly rotated. Both frames may include magnets substantially equally spaced around them, where each magnet of the second frame has a polarity opposite to that of a corresponding magnet of the first frame. Directly rotating the second frame causes indirect rotation of the first frame through interaction among the magnets of the second frame with magnets of the first frame. A motor may be used to directly rotate the second frame.  
           [0020]    The invention provides for advantages not found within the prior art. Plasma chamber pressure may be controlled linearly, because the aperture may be expanded and contracted linearly. In the embodiment where there are two frames, the outer frame is directly controlled with a motor, such that the motor and the frames do not require a large amount of space. The aperture may also be quickly contracted and expanded, stabilizing the chamber pressure at a desired level faster than in the prior art. Still other advantages, aspects, and embodiments of the invention will become apparent by reading the detailed description that follows, and by referencing the attached drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0021]    [0021]FIGS. 1A, 1B,  1 C, and  1 D are diagrams illustrating the general patterning process performed in semiconductor manufacture.  
         [0022]    [0022]FIG. 2 is a diagram of a typical plasma etch chamber.  
         [0023]    [0023]FIG. 3 is a diagram of an existing plasma chamber pressure control mechanism, utilizing a throttle valve design.  
         [0024]    [0024]FIGS. 4A and 4B are diagrams showing how the pressure of the chamber of FIG. 3 is changed by controlling the opening between the chamber and a cavity.  
         [0025]    [0025]FIG. 5 is a diagram of another existing plasma chamber pressure control mechanism, also utilizing a throttle valve design.  
         [0026]    [0026]FIGS. 6A and 6B are diagrams showing how the pressure of the chamber of FIG. 5 is changed by controlling the opening between the chamber and a cavity.  
         [0027]    [0027]FIG. 7 is a diagram of another existing plasma chamber pressure control mechanism, utilizing a pendular valve design.  
         [0028]    [0028]FIGS. 8A and 8B are diagrams showing how the pressure of the chamber of FIG. 7 is changed by controlling the opening to the chamber.  
         [0029]    [0029]FIG. 9 is a diagram of a simplified plasma etch system, shown only as an example of an etch system that can be used in conjunction with the invention.  
         [0030]    [0030]FIGS. 10A and 10B are diagrams showing how the pressure of the chamber of FIG. 9 is changed by controlling the opening to the chamber via aperture blades.  
         [0031]    [0031]FIG. 11 is a diagram showing a specific embodiment of a plasma etch chamber pressure control mechanism, without the aperture blades for illustrative clarity.  
         [0032]    [0032]FIG. 12 is a diagram showing the magnets of the outer frame of the mechanism of FIG. 11 interact with the magnets of the inner frame of the mechanism of FIG. 11, such that direct rotation of the former frame indirectly causes rotation of the latter frame in the same direction.  
         [0033]    [0033]FIG. 13 is a diagram showing how rotation of the inner frame of the mechanism of FIG. 11 causes rotation of the aperture blades, via interlocking gear teeth of the former and the latter, such that the aperture is expanded and contracted. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0034]    In the following detailed description of exemplary embodiments of the invention, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration specific exemplary embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. Other embodiments may be utilized, and logical, mechanical, and other changes may be made without departing from the spirit or scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only by the appended claims.  
         [0035]    [0035]FIG. 9 shows a simplified plasma etch system  900 , only as an example of an etch system that can be used in conjunction with the invention. Other types of etch systems are also amenable to the invention, however. Semiconductor wafers are placed in the plasma chamber  904 , for etching purposes. A mechanism  902  separates the chamber  904  from a cavity  906 . The mechanism  902  is for linearly controlling the pressure within the plasma chamber  904 , as may be required for proper etching. The mechanism  902  in particular has a changeable opening there within for controlling the access of the chamber  904  to the cavity  906 , which governs the pressure within the chamber  904 . The cavity  906  is optional, however, and not required.  
         [0036]    The mechanism  902  in the invention includes an aperture diaphragm and a number of aperture blades. The aperture blades are rotatable, so that the aperture defined by the diaphragm is expandable and contractible, to lower and raise, respectively, the pressure of the chamber  904 . FIG. 10A shows the aperture  1004  of the mechanism  902  in a fully expanded position. There are a number of aperture blades, such as the aperture blade  1002 , rotatably mounted to the aperture diaphragm  1006  via members, such as the member  1008 . Each blade is rotatable in a counter-clockwise direction to reduce, or contract, the size of the aperture  1004 , and a clockwise direction to enlarge, or expand, the size of the aperture  1006 . FIG. 10B, by comparison, shows the aperture  1004  of the mechanism  902  in a more contracted position.  
         [0037]    Thus, by rotating the blades in either a clockwise or a counter-clockwise direction, the pressure of the chamber  904  (not shown in FIGS. 10A and 10B) is decreased or increased, respectively. There may be more or less aperture blades than shown in FIGS. 10A and 10B. The blades are also quickly and easily moved (rotated), and allow for precise control of the size of the aperture  1004 . This in turn allows precise control of the pressure of the chamber  904 .  
         [0038]    [0038]FIG. 11 shows a specific embodiment of the mechanism  902 . The aperture blades are not shown in FIG. 11 for purposes of illustrative clarity only. The aperture diaphragm  1006  surrounds the aperture  1004 , and has immovably mounted thereto the members by which the aperture blades are rotatably mounted to the diaphragm  1006 , such as the member  1008 . An inner rotatable circular frame  1102  surrounds the diaphragm  1006 . The frame  1102  has two purposes. First, it seals the diaphragm  1006  and the aperture blades in an airtight manner, so that the pressure within the chamber  904  (not shown in FIG. 11) can be stabilized. Second, the frame  1102 , by its own rotation, causes the aperture blades to rotate, as will be shown and described.  
         [0039]    The inner frame  1102  has a number of magnets, such as the magnet  1106 , situated there around in a substantially equally spaced configuration. An outer rotatable circular frame  1104  surrounds the inner frame  1102 . The outer frame  1104  also has a number of magnets, such as the magnet  1108 , situated there around in a substantially equally spaced configuration. There are preferably the same number of magnets in the outer frame  1104  as there are in the inner frame  1102 , and each magnet in the former frame corresponds to a magnet in the latter frame. For instance, the magnet  1108  of the outer frame  1104  corresponds to the magnet  1106  of the inner frame  1102 . There may be more or less magnets than the number shown in FIG. 11.  
         [0040]    Rotation of the outer frame  1104  causes rotation of the inner frame  1102 , due to the interaction of the former with the latter. More specifically, the magnets of the outer frame  1104  interact with the magnets of the inner frame  1102  for rotation of the former frame to cause rotation of the latter frame. This is done by oppositely configuring corresponding magnets of the frames  1102  and  1104  so that the north pole of each magnet in the outer frame  1104  aligns with the south pole of its corresponding magnet in the inner frame  1102 , and vice-versa. In this way, rotation of the outer frame  1104  causes rotation of the inner frame  1102  in the same direction, because the magnets of the former frame are magnetically locked to the corresponding magnets of the latter frame.  
         [0041]    This is shown in more detail in FIG. 12. The magnet  1108  of the outer frame  1104  has its north pole directly aligned with the south pole of the magnet  1106  of the inner frame  1102 , as indicated by the line  1202 . Similarly, the south pole of the magnet  1108  is directly aligned with the north pole of the magnet  1106 , as indicated by the line  1204 . Direct rotation, or movement, of the outer frame  1104  thus indirectly causes corresponding rotation, or movement, of the inner frame  1102 . Rotation of the outer frame  1104  may be by a motor, not shown in FIG. 12. The motor, along with the mechanism  902  itself (not shown in FIG. 12), take up substantially less space than the plasma chamber pressure control mechanisms of the prior art.  
         [0042]    The manner by which the rotation of the inner frame  1102 , resulting from the direct rotation of the outer frame  1104 , causes rotation of the aperture blades is shown in FIG. 13. The inner frame  1102  has a number of inward facing gear teeth, such as the inward facing gear teeth  1306  and  1308 . The members of the aperture blades, such as the member  1008  for the aperture blade  1002 , are gears in the embodiment of FIG. 13, having gear teeth, such as the gear teeth  1302  and  1034 . The gear teeth of the blade members interlock with the inward facing gear teeth of the inner frame  1102 . Therefore, when the inner frame  1102  is rotated in one direction, the blade members and the aperture blades rotate in the same direction.  
         [0043]    For instance, when the inner frame  1102  rotates clockwise, because of the inward facing gear teeth of the frame  1102  interlocking with the gear teeth of the member  1008 , the member  1008  also rotates clockwise. Because the aperture blade  1002  is mounted to the member  1008 , it, too, rotates clockwise. Similarly, when the inner frame  1102  rotates counter-clockwise, the aperture blade  1002  rotates counter-clockwise. The aperture blade  1002  is immovably part of or affixed to the member  1008 , whereas the member  1008  rotatably mounts the blade  1002  to the aperture diaphragm  1006 .  
         [0044]    It is noted that, although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that any arrangement is calculated to achieve the same purpose may be substituted for the specific embodiments shown. This application is intended to cover any adaptations or variations of the present invention. For instance, the invention is applicable to vacuum chambers other than plasma etch chambers. Therefore, it is manifestly intended that this invention be limited only by the claims and equivalents thereof.