Abstract:
An apparatus and method for visualization of process conditions in a process chamber or chambers, particularly during the fabrication of integrated circuits on substrates in the process chambers. The apparatus includes an inspection chamber which is installed adjacent to a process chamber. A camera provided in the inspection chamber is used to view the interior of the process chamber as the etching, chemical vapor deposition or other process is carried out in the process chamber. A video monitor is typically connected to the camera for viewing images from the camera. In the event that a defect-precipitating event occurs in the process chamber, such as a mechanical malfunction or accumulation of excessive levels of polymer deposition on the chamber walls, the event is displayed on the monitor in real-time.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to process chambers used in the fabrication of integrated circuits on semiconductor wafer substrates. More particularly, the present invention relates to an apparatus which facilitates real-time visualization and monitoring of conditions inside a process chamber as a process is carried out in the chamber.  
       BACKGROUND OF THE INVENTION  
       [0002]     In the semiconductor production industry, various processing steps are used to fabricate integrated circuits on a semiconductor wafer. These steps include the deposition of layers of different materials including metallization layers, passivation layers and insulation layers on the wafer substrate, as well as photoresist stripping and sidewall passivation polymer layer removal. In modern memory devices, for example, multiple layers of metal conductors are required for providing a multi-layer metal interconnection structure in defining a circuit on the wafer. Chemical vapor deposition (CVD) processes are widely used to form layers of materials on a semiconductor wafer. Other processing steps in the fabrication of the circuits include formation of a photoresist or other mask such as titanium oxide or silicon oxide, in the form of the desired metal interconnection pattern, using standard lithographic techniques; subjecting the wafer substrate to a dry etching process to remove the conducting layer from the areas not covered by the mask, thereby leaving the metal layer in the form of the masked pattern; removing the mask layer using reactive plasma and chlorine gas, thereby exposing the top surface of the metal interconnect layer; cooling and drying the wafer substrate by applying water and nitrogen gas to the wafer substrate; and removing or stripping polymer residues from the wafer substrate.  
         [0003]     CVD processes include thermal deposition processes, in which a gas is reacted with the heated surface of a semiconductor wafer substrate, as well as plasma-enhanced CVD processes, in which a gas is subjected to electromagnetic energy in order to transform the gas into a more reactive plasma. Forming a plasma can lower the temperature required to deposit a layer on the wafer substrate, to increase the rate of layer deposition, or both. However, in plasma process chambers used to carry out these various CVD processes, materials such as polymers are coated onto the chamber walls and other interior chamber components and surfaces during the processes. These polymer coatings frequently generate particles which inadvertently become dislodged from the surfaces and contaminate the wafers.  
         [0004]     The chemical vapor deposition, etching and other processes used in the formation of integrated circuits on the wafer substrate are carried out in multiple process chambers. The process chambers are typically arranged in the form of an integrated cluster tool, in which multiple process chambers are disposed around a central transfer chamber equipped with a wafer transport system for transporting the wafers among the multiple process chambers. By eliminating the need to transport the wafers large distances from one chamber to another, cluster tools facilitate integration of the multiple process steps and improve wafer manufacturing throughput.  
         [0005]     A typical conventional integrated cluster tool is generally indicated by reference numeral  10  in  FIG. 1 . An integrated cluster tool  10  such as a Centura HP 5200 tool sold by the Applied Materials Corp. of Santa Clara, Calif., includes one or a pair of adjacent loadlock chambers  12 , each of which receives a wafer cassette or holder  13  holding multiple semiconductor wafers  28 . The loadlock chambers  12  are flanked by an orientation chamber  14  and a cooldown chamber  16 . Multiple process chambers  18  for carrying out various processes in the fabrication of integrated circuits on the wafers  28  are positioned with the orientation chamber  14 , the cooldown chamber  16  and the loadlock chambers  12  around a central transfer chamber  20 . A transfer robot  22  in the transfer chamber  20  is fitted with a transfer blade  24  which receives and supports the individual wafers  28  from the wafer cassette or holder  13  in the loadlock chamber  12 . The transfer robot  22  is capable of rotating the transfer blade  24  in the clockwise or counterclockwise direction in the transfer chamber  20 , and the transfer blade  24  can extend or retract to facilitate placement and removal of the wafers  28  in and from the load lock chambers  12 , the orientation chamber  14 , the cooldown chamber  16  and the process chambers  18 .  
         [0006]     In operation, the transfer blade  24  initially removes a wafer  28  from the wafer cassette  13  and then inserts the wafer  28  in the orientation chamber  14 . The transfer robot  22  then transfers the wafer  28  from the orientation chamber  14  to one or more of the process chambers  18 , where the wafer  28  is subjected to a chemical vapor deposition or other process. From the process chamber  18 , the transfer robot  22  transfers the wafer  28  to the cooldown chamber  16 , and ultimately, back to the wafer cassette or holder  13  in the loadlock chamber  12 .  
         [0007]     After they are processed in the various process chambers of the cluster tool, some of the wafers are sampled for inspection, with the sampling rate and selection method based on the process involved. Typically, the sampled wafers are transported from the cluster tool to an inspection station and inspected for surface defects, line width, electrical functions and the like. U.S. Pat. No. 6,424,733, details an apparatus which is incorporated into a cluster tool for the inspection of wafers.  
         [0008]     It is known that some of the processes utilized in the integrated circuit fabrication process differ from each other in stability. The processes which are deemed most stable do not exhibit large variations in the process parameters over time after the parameters are initially adjusted to within the inspection criteria. Thus, the process chambers in which these processes are carried out may be able to operate for days at a time without the need for adjustments and fine-tuning to return the process parameters to within the predetermined specifications. Consequently, these stable processes do not require a high sampling rate for inspection. On the other hand, less stable processes are more likely to veer from within the predetermined specifications and thus, require frequent sampling in order for corrective measures to the processes to be taken.  
         [0009]     Wafers are generally processed in lots each having from 20 to 25 wafers. If the sampling rate for a given process is low, the process may inadvertently veer from the preset specifications unbeknownst to the equipment operating personnel, in which case a large number of wafers having defects may complete processing. These defects may be caused by mechanical failures such as a blown o-ring or adverse processing phenomena such as electrical arcing, for example.  
         [0010]     Another common cause of process-related defects induced in substrates includes the dislodging of etchant or deposition polymer material from the walls of the chamber onto the substrate. If this occurs early in the first lot or shortly after a sampling, for example, the defect-causing event may be eventually ascertained by facility personnel only after a large number of defect-laden substrates have been processed. While a higher sampling rate would enable personnel to discover the cause for the defects earlier in the process, sampling tends to inhibit productivity, and thus, is best avoided when possible.  
         [0011]     Due to the ever-decreasing size of device features in fabricated integrated circuits, IC manufacturers are required to detect defects of corresponding reduced size. The defect detection equipment used for this purpose, however, is typically expensive and occupies an inordinately large footprint space. Moreover, transfer of the substrates from the process tool to an inspection station requires handling equipment which occupies additional footprint space and the operation of which may introduce additional contaminants onto the devices on the substrates. Accordingly, an apparatus is needed for the real-time visualization of operating conditions inside process chambers to enable personnel to take corrective action in the event that defect-precipitating events occur in the chamber during semiconductor processing.  
         [0012]     An object of the present invention is to provide a novel apparatus for visualization of conditions inside a process chamber.  
         [0013]     Another object of the present invention is to provide a novel apparatus which may be adapted to record real-time images of conditions inside a process chamber.  
         [0014]     Still another object of the present invention is to provide a novel apparatus which may be adapted to visualize or monitor conditions inside multiple process chambers.  
         [0015]     Yet another object of the present invention is to provide a novel apparatus which may be adapted to enable semiconductor fabrication facility personnel to troubleshoot various process conditions during the fabrication of semiconductor integrated circuits.  
         [0016]     A still further object of the present invention is to provide a novel apparatus which may reduce the frequency of periodic maintenance for process chambers.  
         [0017]     Still another object of the present invention is to provide a novel apparatus including an inspection chamber which may be installed adjacent to a process chamber and a camera provided in the inspection chamber for viewing process conditions in the process chamber.  
       SUMMARY OF THE INVENTION  
       [0018]     In accordance with these and other objects and advantages, the present invention is generally directed to a novel apparatus for visualization of process conditions in a process chamber or chambers, particularly during the fabrication of integrated circuits on substrates in the process chambers. The apparatus includes an inspection chamber which is installed adjacent to a process chamber. A camera provided in the inspection chamber is used to view the interior of the process chamber as the etching, chemical vapor deposition or other process is carried out in the process chamber. A video monitor is typically connected to the camera for viewing images from the camera. In the event that a defect-precipitating event occurs in t h e process chamber, such as a mechanical malfunction or accumulation of excessive levels of polymer deposition on the chamber walls, the event is displayed on the monitor in real-time. Accordingly, personnel operating the process tool can take appropriate corrective or preventative measures to reduce or prevent the inducement of defects in the devices being fabricated on the substrate or substrates in the process chamber.  
         [0019]     The apparatus of the present invention may further be used in conjunction with a cluster tool for the sequential processing of semiconductor wafer substrates. Accordingly, an inspection chamber is attached typically to the transfer chamber or buffer chamber of the cluster tool and a camera is provided in the inspection chamber. The camera is preferably a panaramic camera such as a charged-coupled device (CCD) which facilitates simultaneous viewing of multiple process chambers in the cluster tool. Accordingly, the camera views the interior of each process chamber typically through a wafer transfer slot provided in each chamber, from inside the transfer chamber or buffer chamber. These images are typically transmitted to a monitor for real-time viewing by tool operating personnel.  
         [0020]     The apparatus of the present invention may be further provided with a motion actuating mechanism which is operably connected to the camera. The motion actuating mechanism may be actuated to advance the camera from the inspection chamber into the transfer chamber or buffer chamber. The camera may be fitted with a zoom lens for zooming in on the process chamber, or a selected one of the multiple process chambers in the case of a cluster tool, for detailed visualization of processing conditions inside the selected chamber.  
         [0021]     The apparatus may further be provided with a catch head including an electrostatic chuck head and adhesive tape on the camera. The catch head may be used to remove foreign powders or particles from the bottom of the inspection chamber during use. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0022]     The invention will now be described, by way of example, with reference to the accompanying drawings, in which:  
         [0023]      FIG. 1  is a top view of a typical conventional cluster tool for the sequential processing of semiconductor wafer substrates;  
         [0024]      FIG. 2  is a top view of a cluster tool in implementation of the present invention;  
         [0025]      FIG. 3  is a cross-sectional view, taken along section lines  3 - 3  in  FIG. 2 ; and  
         [0026]      FIG. 4  is a schematic view illustrating typical operational components for the apparatus of the present invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0027]     The present invention has particularly beneficial utility in the viewing of process conditions inside process chambers used in the fabrication of integrated circuits on substrates. However, the invention is not so limited in application, and while references may be made to such process chambers for processing of semiconductor integrated circuits, the invention may be more generally applicable to viewing of process conditions inside process chambers in a variety of industrial and mechanical applications.  
         [0028]     Referring to  FIGS. 2-4 , an integrated cluster tool  30  which includes an illustrative embodiment of the apparatus for visualization of process chamber conditions of the present invention may include one or a pair of adjacent loadlock chambers  32 , each of which receives a wafer cassette or holder  33  containing multiple semiconductor wafers  48 . An orientation chamber  34  and a cooldown chamber  36  are typically provided on opposite sides of the loadlock chambers  32 . Multiple process chambers  38  are positioned around a central transfer chamber  40  with the orientation chamber  34 , the cooldown chamber  36  and the loadlock chambers  32 . The process chambers  38  may include an etch chamber, a chemical vapor deposition (CVD) chamber, a physical vapor deposition (PVD) chamber, or other type of chamber used to carry out a process in the fabrication of integrated circuits on the wafers  48 . A transfer robot  42  in the transfer chamber  40  has multiple transfer blades  44 , each of which receives and supports an individual wafer  48  from the wafer cassette or holder  33  in the loadlock chamber  32 . The transfer robot  42  is capable of rotating each transfer blade  44  in the clockwise or counterclockwise direction in the transfer chamber  40 , and each transfer blade  44  can extend or retract to facilitate placement and removal of the wafers  48  in and from the load lock chambers  32 , the orientation chamber  34 , the cooldown chamber  36  and the process chambers  38 . As shown in  FIG. 3 , each process chamber  38  includes an inner wall  39  that faces the interior of the transfer chamber  40 . An elongated wafer slot  39   a  is provided in the inner wall  39 , through which wafer slot  39   a  the transfer robot  42  inserts each wafer  48  into and removes each wafer  48  from the corresponding process chamber  38 . It is understood that the integrated cluster tool  30  heretofore described serves as just one example of a cluster tool which is suitable for implementation of the present invention, and the invention may be equally appllicable to cluster tools having alternative characteristics and features which differ from those heretofore described.  
         [0029]     In accordance with the present invention, an inspection station  52  is typically attached to the transfer chamber  40  of the integrated cluster tool  30 . As shown in  FIG. 3 , the inspection chamber  52  includes a chamber wall  53  which defines a chamber interior  54  and is attached to the chamber wall  41  of the transfer chamber  40 . The chamber interior  54  typically communicates with the interior of the transfer chamber  40  through a chamber opening  55 . As shown in  FIG. 2 , the inspection chamber  52  may be provided between the orientation chamber  34  and one of the process chambers  38  or in any other location which facilitates optimum viewing of the interiors of the process chambers  38  through the respective wafer slots  39   a  ( FIG. 3 ) thereof, as hereinafter described.  
         [0030]     As shown in  FIG. 3 , a camera assembly  56  is provided in the chamber interior  54  and typically includes an elongated, horizontal camera support  58  which may be engaged by a motion actuating mechanism  74  through a support arm  76 . The motion actuating mechanism  74  is provided in the bottom of the chamber interior  54  and may be a stepper motor, for example, or any other mechanism which is capable of moving the camera support  58  in a bidirectional horizontal motion in the chamber interior  54 , as indicated by the arrows and in the manner hereinafter described. As shown in  FIG. 4 , the motion actuating mechanism  74  is electrically connected, through wiring  75 , to a motion controller  78  which controls the forward and reverse motions of the camera support  58  in the chamber interior  54 .  
         [0031]     A camera  62 , having a light  64 , is provided on the forward end of the camera support  58 . In a preferred embodiment, the camera  62  is a panoramic charge coupled device (CCD) which is well known in the art. The camera  62  is connected, through a camera cable  63 , to a video monitor  82 , as shown in  FIG. 4 , which video monitor  82  displays images illuminated by the light  64  and viewed by the camera  62 . As further shown in  FIG. 4 , a recording device  84  may be connected to the video monitor  82 , typically through a cable  85 , for recording of the images on a video cassette recorder (VCR) tape, a digital video disk (DVD), or other recording media.  
         [0032]     As further shown in  FIGS. 3 and 4 , a catch head  66  may be provided on the front end of the camera support  58  for purposes which will be hereinafter described. The catch head  66  includes an electrostatic chuck head  68  which is mounted on the camera support  58 , typically beneath the camera  62 . The chuck head  68  is provided in electrical contact with an electrically-conductive metal strip  60  provided typically on the bottom surface of the camera support  58 . The conductive metal strip  60  is electrically connected through wiring  81  to a voltage source  80 . Adhesive tape  70  may be provided on the bottom surface of the chuck head  68 . Accordingly, by application of an electrostatic voltage to the chuck head  68  through the conductive strip  60  and the voltage source  80 , particles  72  which may flow by air turbulence from the process chambers  38  into the chamber interior  54  may be electrostatically removed from the bottom of the inspection chamber  52  and cling to the adhestive tape  70  of the catch head  66  for subsequent removal therefrom, during operation of the camera assembly  56  as hereinafter further described.  
         [0033]     In operation, the integrated cluster tool  30  is used to sequentially process each of multiple wafers  48  during the fabrication of integrated circuits on each wafer  48 . The process sequence begins as one of the transfer blades  44  of the transfer robot  42  initially removes a wafer  48  from the wafer cassette  33  and then inserts the wafer  48  in the orientation chamber  34 . The transfer robot  42  then transfers the wafer  48  from the orientation chamber  34  sequentially to the respective process chambers  38 , where the wafer  48  is sequentially subjected typically to CVD, PVD, etching or other processes. From the last process chamber  38  in the sequence, the transfer robot  42  transfers the wafer  48  to the cooldown chamber  36 , and ultimately, back to the wafer cassette or holder  33  in the loadlock chamber  32 .  
         [0034]     Throughout sequential processing of each wafer  48  in the integrated cluster tool  30 , polymer residues (not shown) tend to gradually accumulate in one or more of the process chambers  38 . Moreover, mechanical breakdown may also occur in one or more of the process chambers  38 . These events potentially induce large or small defects in the wafers  48  being processed therein. Thus, the factors which contribute to these events must be continually monitored to enable facility personnel to take corrective and/or preventative measures and prevent or reduce the number of defects induced in the devices being fabricated on the wafers  48 . Accordingly, the camera assembly  56  inside the inspection chamber  52  enables facility personnel to continually visually monitor the interiors of the respective process chambers  38  through the wafer slot  39   a  ( FIG. 3 ) of each, as follows.  
         [0035]     As each of the wafers  48  in a lot is sequentially processed in the respective process chambers  38  in the manner heretofore described, the light  64  on the camera  62  illuminates the interior of the transfer chamber  40 , as well as the interiors of the respective process chambers  38  through the wafer slot  39   a  of each. Accordingly, the camera support  58  is typically advanced from the retracted configuration indicated by the solid lines to the extended configuration indicated by the phantom lines in  FIG. 3 , wherein the camera support  58  extends through the chamber opening  55  and the camera  62  is positioned in the interior of the transfer chamber  40 , to facilitate optimum viewing of the chamber interiors of the respective process chambers  38  in the integrated cluster tool  30 . The camera  62  generates images of the interiors of the process chambers  38  and transmits these images to the video monitor  82 . Facility personnel visually observing the images on the video monitor  82  can then readily ascertain the excessive accumulation of polymer residues in the interior of each process chamber  38 , as well as mechanical breakdown or failure of operational or structural components or abnormal process conditions in the process chambers  38 . This enables the personnel to terminate operation of the affected process chamber or chambers  38  and make repairs or take other corrective measures to prevent defects from being induced in the wafers  48  during processing. The images displayed on the video monitor  82  may be simtaneously recorded on the VCR, DVD or other recording medium in the recording device  84 . It will be appreciated by those skilled in the art that the typically panoramic viewing capability of the camera  62  facilitates simultaneous visual monitoring of the process conditions inside all of the process chambers  38  in the integrated cluster tool  30 . It is understood that the camera  62  may be fitted with a zoom lens or lenses (not shown), as desired, to facilitate close-up viewing of the interior of any one of the process chambers  38 , as needed.  
         [0036]     As further shown in  FIG. 3 , it will be appreciated by those skilled in the art that the catch head  66  on the camera assembly  56  may be operated to remove particles  72  which might tend to drift from the process chambers  38 , through the transfer chamber  40  and into the chamber interior  54  of the transfer chamber  40 . This is accomplished by applying an electrostatic voltage to the conductive strip  60  and electrostatic chuck head  68  by operation of the voltage source  80 . Accordingly, the chuck head  68  electrostatically attracts the particles  72 , which are lifted from the bottom of the inspection chamber  52  and adhere to the adhesive tape  70 . This maintains a substantially particle-free environment inside the chamber interior  54  for optimum operation of the camera  62 . The adhesive tape  70  is periodically replaced on the chuck head  68  to remove the particles  72  from the catch head  66 .  
         [0037]     While the preferred embodiments of the invention have been described above, it will be recognized and understood that various modifications can be made in the invention and the appended claims are intended to cover all such modifications which may fall within the spirit and scope of the invention.