Abstract:
An interlocking lid which is suitable for a wet bench tank used in the processing of semiconductor wafer substrates. The interlocking lid includes a pair of lid panels typically provided with a clasp having elements for engaging and interlocking with each other when the lid panels are in a closed position. At least one of the lids may further include a beveled lid shoulder which facilitates runoff of liquids from and hinders pooling of liquids on the exterior surface of the lid.

Description:
FIELD OF THE INVENTION 
   The present invention relates to processes and equipment for removing potential circuit-contaminating particles from WIP (work-in-process) semiconductor wafers in the semiconductor fabrication industry. More particularly, the present invention relates to a novel interlocking lid having a pair of interlocking lid panels for a wet bench, at least one of which lid panels has a bevel-shaped exterior flow surface to facilitate the sweeping of residual cleaning fluid therefrom during opening of the panels. 
   BACKGROUND OF THE INVENTION 
   Generally, the process for manufacturing integrated circuits on a silicon wafer substrate typically involves deposition of a thin dielectric or conductive film on the wafer using oxidation or any of a variety of chemical vapor deposition processes; formation of a circuit pattern on a layer of photoresist material by photolithography; placing a photoresist mask layer corresponding to the circuit pattern on the wafer; etching of the circuit pattern in the conductive layer on the wafer; and stripping of the photoresist mask layer from the wafer. Each of these steps, particularly the photoresist stripping step, provides abundant opportunity for organic, metal and other potential circuit-contaminating particles to accumulate on the wafer surface. 
   In the semiconductor fabrication industry, minimization of particle contamination on semiconductor wafers increases in importance as the integrated circuit devices on the wafers decrease in size. With the reduced size of the devices, a contaminant having a particular size occupies a relatively larger percentage of the available space for circuit elements on the wafer as compared to wafers containing the larger devices of the past. Moreover, the presence of particles in the integrated circuits compromises the functional integrity of the devices in the finished electronic product. 
   Currently, mini-environment based IC manufacturing facilities are equipped to control airborne particles much smaller than 1.0 μm, as surface contamination continues to be of high priority to semiconductor manufacturers. To achieve an ultraclean wafer surface, particles must be removed from the wafer, and particle-removing methods are therefore of utmost importance in the fabrication of semiconductors. 
   The most common system for cleaning semiconductor wafers during wafer processing includes a series of tanks which contain the necessary cleaning solutions and are positioned in a “wet bench” in a clean room. Batches of wafers are moved in sequence through the tanks, typically by operation of a computer-controlled automated apparatus. Currently, semiconductor manufacturers use wet cleaning processes which may use cleaning agents such as deionized water and/or surfactants. 
   Other wafer-cleaning processes utilize solvents, dry cleaning using high-velocity gas jets, and a megasonic cleaning process, in which very high-frequency sound waves are used to dislodge particles from the wafer surface. Cleaning systems which use deionized (DI) water currently are widely used in the industry because the systems are effective in removing particles from the wafers and are relatively cost-efficient. Approximately 4.5 tons of water are used for the production of each 200-mm, 16-Mbit, DRAM wafer. 
   A conventional wet bench system  8  is shown schematically in  FIG. 1 . The system  8  includes wet bench tanks  10   a,    10   b,    10   c.  The first tank  10   a  and second tank  10   b  each typically contains a basic ACT organic solvent solution (not shown) in which multiple wafers  16  are immersed for the stripping of photoresist from each of the wafers  16 . In the third wet bench tank  10   c , the wafers  16  are typically rinsed with an aqueous acidic NOE solution, which removes photoresist residues and particles from the wafers  16  after the wafers  16  are immersed in the basic ACT solutions in the first tank  10   a  and second tank  10   b , for example. Typical other uses for the system  8  include SPM cleaning, APM cleaning and M 2  etch/cleaning, for example. 
   Each tank  10   a ,  10   b,    10   c  includes tank walls  12  that define a tank interior  14  which receives the multiple wafers  16 . As shown in  FIG. 2 , the first tank  10   a , as well as the second tank  10   b  and third tank  10   c,  typically includes a top opening  15  which is reversibly closed by a pair of half-lid panels  18  hingedly attached to respective opposing tank walls  12 . When closed, the half-lid panels  18  are separated by a lid gap  20 . In another design, shown in  FIG. 3 , each wet bench cleaning tank  22  includes a full-lid panel  24  which is hingedly attached to one of the tank walls  12  to reversibly close the top opening  15 . 
   In operation of the system  8 , a wafer boat or other wafer support (not illustrated), which typically holds up to fifty of the semiconductor wafers  16  in horizontally-adjacent relationship to each other, is sequentially placed in the tank interiors  14  of the wet bench tanks  10   a ,  10   b,    10   c , respectively. The wafers  16  are initially immersed in the basic first ACT solution (not shown) contained in the first tank  10   a  for the stripping of photoresist from the wafers  16  after a photolithography process is carried out on the wafers  16 . 
   Next, a wafer transfer robot  26  transfers the wafers  16  from the first tank  10   a  to the second tank  10   b.  In the second tank  10   b , the wafers  16  are immersed in a second ACT solution, which removes residual photoresist from the wafers  16 . Finally, the robot  26  transfers the wafers  16  from the second tank  10   b  to the third tank  10   c , where the wafers  16  are rinsed with the acidic NOE solution, which removes additional residual particles from the wafers  16  prior to further processing. 
   After the wafers  16  are placed in the third tank  10   c , the robot  26  typically returns to the load position adjacent to the first tank  10   a  to receive an additional lot of wafers and place the wafers in the first tank  10   a . However, during transit of the robot  26 , residual aqueous acid solution  28  which remains on the robot  26  has a tendency to drip from the robot  26  and fall into the ACT solution in the first tank  10   a  and second tank  10   b , through the lid gap  20 . Some of the residual aqueous acid solution  28  drips onto the half-lid panels  18  and flows into the tank  10   a  or  10   b  through the lid gap  20 . 
   While the NOE solution used to rinse the wafers in the third tank  10   c  typically contains about 5% water, the ACT organic solvents in the first tank  10   a  and second tank  10   b  typically contain monoethanolamine (C 2 OHNH 2 ), without water. In the event that residual aqueous acid NOE solution  28  falls into the ACT organic solvent, the amino group on the monoethanolamine reacts with the water in the NOE solution to form hydroxide ion, according to the following equation:
 
R−NH 2 +H 2 O-----&gt;OH − +R−NH 3   + 
 
   The resulting hydroxide ion reacts with and damages aluminum layers and interconnects previously fabricated on the wafers  16 . In severe cases, aluminum damage is manifested by peeling of the aluminum layers or interconnects from the wafer  16 . Accordingly, a novel interlocking lid for a wet bench is needed to prevent aqueous acid solution from inadvertently dripping from a transfer robot into a basic ACT solution used in the stripping of photoresist from wafers. 
   Accordingly, an object of the present invention is to provide a novel interlocking lid which is suitable for a wet bench tank. 
   Another object of the present invention is to provide a novel interlocking lid which substantially prevents a liquid from inadvertently falling into a wet bench tank. 
   Still another object of the present invention is to provide an interlocking lid which substantially prevents contamination of a liquid in a wet bench tank. 
   Yet another object of the present invention is to provide a novel interlocking lid which may prevent water-induced damage to metal structures on semiconductor wafers processed in a wet bench tank. 
   A still further object of the present invention is to provide a novel interlocking lid suitable for a wet bench tank, which interlocking lid may include features that facilitate runoff and prevent or hinder pooling of liquids that fall on the exterior of the lid. 
   Yet another object of the present invention is to provide a novel interlocking lid which may include a pair of lid panels provided with a clasp for interlocking each other when in a closed position on a wet bench tank. 
   SUMMARY OF THE INVENTION 
   In accordance with these and other objects and advantages, the present invention generally relates to a novel interlocking lid which is suitable for a wet bench tank used in the processing of semiconductor wafer substrates. The interlocking lid includes a pair of lid panels typically provided with a clasp having elements for engaging and interlocking with each other when the lid panels are in a closed position. At least one of the lid panels may further include features which facilitate runoff of liquids from and hinder pooling of liquids on the exterior surface of the lid. 
   In a typical embodiment, the interlocking lid of the present invention includes a base lid panel and a cover lid panel which are hingedly attached to opposite side panels of the wet bench tank. The adjacent inner edges of the base lid panel and cover lid panel, respectively, are shaped to define clasp members which removably engage each other to seal the interior of the wet bench tank. Accordingly, the clasp members provide a seal between the base lid panel and the cover lid panel to prevent the inadvertent flow or dripping of water or other liquid into the wet bench tank between the base lid panel and cover lid panel. 
   At least one of the base lid panel and cover lid panel may be provided with a feature or features which facilitate the runoff and prevent the pooling or accumulation of water or other liquids on the exterior of the lid panel. One of the features may include a beveled lid shoulder which is shaped in the exterior surface of the lid panel and extends from the front end to the rear end of the panel. The lid shoulder has a beveled configuration which defines a slanted runoff surface when the lid panel is in the open position. This facilitates the runoff of liquids from the exterior surface of the lid upon opening of the lid panel. 
   A shoulder slope may be provided in one end of the beveled lid shoulder to further facilitate or expedite runoff of liquids from the exterior surface of the lid panel as the lid panel is raised from the closed to the open configuration. The shoulder slope is typically provided in the discharge end of the beveled lid shoulder. The beveled lid shoulder and shoulder slope, in combination with the clasp on the base lid panel and cover lid panel, ensure that water or other liquids pooled on the exterior surface of the lid panel are substantially incapable of inadvertently falling into the wet bench tank to contaminate or react with processing liquids therein. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will now be described, by way of example, with reference to the accompanying drawings, in which: 
       FIG. 1  is a schematic of a typical conventional wet bench system for the sequential processing of semiconductor wafers in multiple wet bench tanks; 
       FIG. 2  is a schematic of a conventional wet bench tank having a pair of half-lid panels; 
       FIG. 3  is a schematic of a conventional wet bench tank having a full-lid panel; 
       FIG. 4  is a front end view of a wet bench tank fitted with an interlocking lid of the present invention, with the interlocking lid shown in the closed position; 
       FIG. 4A  is an enlarged sectional view, taken along section line  4 A in  FIG. 4 ; 
       FIG. 5  is a transverse cross-section of a base lid panel element of the interlocking lid of the present invention, taken along section line  5 — 5  in  FIG. 7 ; 
       FIG. 6  is a transverse cross-section of a cover lid panel element of the interlocking lid of the present invention, taken along section line  6 — 6  in  FIG. 8 ; 
       FIG. 7  is a top view of a base lid panel element of the interlocking lid of the present invention; 
       FIG. 8  is a top view of a cover lid panel element of the interlocking lid; 
       FIG. 9  is a front end view of a wet bench tank fitted with the interlocking lid of the present invention, illustrating opening of the interlocking lid and runoff of liquid from the exterior surface of the base lid panel; and 
       FIG. 10  is an exterior view of the base lid panel, illustrating runoff of liquid from the exterior surface of the base lid panel upon opening of the interlocking lid. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The present invention has particularly beneficial utility in the sealing of a wet bench tank to prevent the inadvertent contamination of a processing liquid, such as an ACT photoresist stripping solution, in the tank during a PRS (photoresist stripping) process in the fabrication of integrated circuits on semiconductor wafer substrates. However, the invention is not so limited in application, and while references may be made to such wet bench tank, the present invention is more generally applicable to preventing or minimizing liquid or other contamination of tanks in other semiconductor processes as well as other industrial applications outside semiconductor fabrication. 
   Referring initially to  FIGS. 4–8 , a wet bench tank  32  which is provided with an interlocking lid  42  according to the present invention, is shown in  FIG. 4 . The wet bench tank  32  includes a typically elongated, rectangular tank body  34 , which is shown in front end view in  FIG. 4 . The tank body  34  typically includes a pair of side walls  36  and a pair of spaced-apart end walls  37  (one of which is shown). The side walls  36 , end walls  37  and a tank bottom  38  define a tank interior  40 , within which semiconductor wafers (not shown) are subjected to photoresist stripping or other semiconductor processing. 
   Briefly, the interlocking lid  42  of the present invention includes a base lid panel  44  and a cover lid panel  60  which are hingedly connected to the tank body  34 , as hereinafter further described. The base lid panel  44  and cover lid panel  60  are together provided with a lid clasp  49  by which the base lid panel  44  and cover lid panel  60  sealingly engage each other when in the closed position. Accordingly, the closed and sealed interlocking lid  42  prevents the inadvertent entry of potential contaminating liquids or other foreign substances into the tank interior  40  during or prior to processing of wafers therein, as hereinafter further described. The base lid panel  44  and cover lid panel  60  of the interlocking lid  42  may be polytetrafluoroethylene (TEFLON) or other inert material. 
   The base lid panel  44  of the interlocking lid  42  is shown in  FIGS. 5 and 7  and includes a generally elongated, rectangular panel body  48 . As shown in  FIG. 7 , the panel body  48  includes a front edge  48   a  and a rear edge  48   b . An elongated panel hinge  46  is attached to the exterior longitudinal edge  48   c  of the panel body  48  for hingedly attaching the panel body  48  to one of the longitudinal side walls  36  or other element of the tank body  34 , typically as shown in  FIG. 4  and according to the knowledge of those skilled in the art. An elongated panel extension  50  extends from the opposite, interior longitudinal edge (which is defined by a beveled lid shoulder  56 , hereinafter described) of the panel body  48 . An elongated interlock flange  52  protrudes upwardly from and extends along the extending longitudinal edge of the panel extension  50 . 
   A beveled lid shoulder  56  is provided in the panel body  48  and extends from the front edge  48   a  to the rear edge  48   b  of the panel body  48 . As shown in  FIG. 7 , the beveled lid shoulder  56  typically defines the interior longitudinal edge of the panel body  48 , which is opposite the exterior longitudinal edge  48   c  to which the panel hinge  46  is attached. Accordingly, as shown in  FIG. 5 , the panel extension  50  extends between the beveled lid shoulder  56  and the interlock flange  52 . An interlock groove  53  of the lid clasp  49  is defined by the beveled lid shoulder  56 , the panel extension  50  and the interlock flange  52 . 
   As further shown in  FIG. 7 , the beveled lid shoulder  56  angles away from the interlock flange  52  from the front edge  48   a  to the rear edge  48   b  of the panel body  48 . The beveled lid shoulder  56  includes a front segment  56   a , which extends rearwardly from the front edge  48   a  of the panel body  48 ; and a rear segment  56   b , which extends rearwardly from the front segment  56   a  to the rear edge  48   b  of the panel body  48 . 
   A shoulder slope  58  may be shaped typically in the rear segment  56   b  of the beveled lid shoulder  56 , and terminates at the rear edge  48   b  of the panel body  48 . Alternatively, the shoulder slope  58  may be provided in both the front segment  56   a  and rear segment  56   b , in which case the shoulder slope  58  may extend along a portion or the entire length of the beveled lid shoulder  56 . One or multiple vent openings  54  may extend through the panel body  48 , typically adjacent to the front edge  48   a  and rear edge  48   b , respectively, to vent gas pressures from the tank interior  40  of the wet bench tank  32 . 
   The cover lid panel  60  of the interlocking lid  42  is shown in  FIGS. 6 and 8  and includes a generally elongated, rectangular panel body  64 . As shown in  FIG. 8 , the panel body  64  includes a front edge  64   a , a rear edge  64   b , an exterior longitudinal edge  64   c  and an interior longitudinal edge  64   d . An elongated panel hinge  62  is attached to the exterior longitudinal edge  64   c  of the panel body  64  for hingedly attaching the panel body  64  to a longitudinal side wall  36  or other element of the tank body  34 , typically as shown in  FIG. 4  and according to the knowledge of those skilled in the art. An elongated panel extension  66  extends from the opposite, interior longitudinal edge  64   d  of the panel body  64 . An elongated interlock flange  68  protrudes downwardly from and extends along the extending longitudinal edge of the panel extension  66 . Accordingly, an interlock groove  69  of the lid clasp  49  is defined by the interlock flange  68 , the panel extension  66  and the interior longitudinal edge  64   d  of the panel body  64 . One or multiple vent openings  70  may extend through the panel body  64 , typically adjacent to the front edge  64   a  and rear edge  64   b , respectively. 
   In wet bench tank applications, both the base lid panel  44  and the cover lid panel  60  may have a length of typically about 50 cm, a width of typically about 20 cm and a thickness of typically about 1.5˜2 cm. However, it is understood that these dimension may vary among wet bench applications as well as among other applications of the interlocking lid  42 . 
   As shown in  FIG. 4 , the panel hinge  46  of the base lid panel  44  and the panel hinge  62  of the cover lid panel  60  hingedly mount the base lid panel  44  and the cover lid panel  60  to opposite side walls  36 , or to alternative elements, of the wet bench tank  32 . A lid panel actuation piston  74 , which is extendible from a pneumatic or hydraulic cylinder  72 , may be operably connected to the base lid panel  44  and the cover lid panel  60 , respectively, to actuate automatic opening and closing of the interlocking lid  42 , as hereinafter described. Alternatively, it is understood that a motor (not shown) or any other suitable mechanism known by those skilled in the art may operably engage the base lid panel  44  and cover lid panel  60  for the automated opening and closing of the interlocking lid  42 . 
   Referring next to  FIGS. 4 and 4A , wherein the interlocking lid  42  is shown in the closed position. Accordingly, the base lid panel  44  and the cover lid panel  60  are disposed in a generally horizontal position on the tank body  34 , with the interlocking lid  42  sealing the tank interior  40 . The lid clasp  49  seals the junction between the base lid panel  44  and the cover lid panel  60 . As particularly shown in  FIG. 4A , the panel extension  50  of the base lid panel  44  extends parallel to and beneath the panel extension  66  of the cover lid panel  60 ; the interlock flange  52  of the base lid panel  44  is seated in the interlock groove  69  of the cover lid panel  60 ; and the interlock flange  68  of the cover lid panel  60  is seated in the interlock groove  53  of the base lid panel  44 . 
   During a PRS (photoresist stripping) or other semiconductor processing operation, liquids (not shown) may inadvertently drip from a wafer transfer robot (not shown), for example, onto the exterior surfaces of the base lid panel  44  and/or cover lid panel  60 . Some of these liquids may otherwise react with a processing liquid (not shown) contained in the tank interior  40  of the tank body  34  to form by-products which are corrosive or damaging to metal layers formed on wafers to be processed in the tank interior  40 , if not prevented from entering the tank interior  40 . Accordingly, the lid clasp  49  of the interlocking lid  42  seals the junction between the base lid panel  44  and cover lid panel  60  and prevents liquids and other contaminants from inadvertently falling into the tank interior  40 , between the base lid panel  44  and the cover lid panel  60 . 
   Referring next to  FIG. 9 , wherein the interlocking lid  42  is shown in the open position, and  FIG. 10 , wherein a top view of the base lid panel  44  in the open position is shown. In the side view of  FIG. 9  and the top view of  FIG. 10 , a liquid  76 , such as a residual aqueous acid solution, for example, has previously inadvertently dripped from a wafer transfer robot (not shown), for example, onto the exterior surface of the base lid panel  44 , the cover lid panel  60 , or both, when the interlocking lid  42  was in the closed position of  FIG. 4 . As the interlocking lid  42  is opened, typically by actuation of the cylinders  72  ( FIG. 4 ) or other mechanism, the base lid panel  44  and cover lid panel  60  are gradually opened from the horizontal, closed position of  FIG. 4  to the sloped position of  FIG. 9 . Accordingly, the liquid  76  rolls off the upper surface of the base lid panel  44  and/or cover lid panel  60  without entering the tank interior  40  between the base lid panel  44  and cover lid panel  60 . 
   As shown in  FIG. 10 , as the interlocking lid  42  is opened from the closed position to the open position, the beveled lid shoulder  56  gradually assumes a downwardly-sloped configuration from the front edge  48   a  to the rear edge  48   b  of the panel body  48  of the base lid panel  44 . In the event that liquid  76  inadvertently falls onto the exterior surface of the base lid panel  44 , particularly onto the exterior or upper surface of the panel extension  50 , the beveled lid shoulder  56  defines a downwardly-sloped liquid runoff surface along which the liquid  76  flows from the base lid panel  44 . The shoulder slope  58  provided in the beveled lid shoulder  56  further facilitates runoff of the liquid  76  from the base lid panel  44 , as shown in  FIG. 9 . Consequently, the liquid  76  is substantially incapable of flowing from the panel extension  50  and into the tank interior  40 , between the base lid panel  44  and the cover lid panel  60 , upon opening of the interlocking lid  42 . 
   In the embodiment of the interlocking lid  42  described herein above and shown with respect to  FIGS. 4–9 , the beveled lid shoulder  56 , alone or in combination with the shoulder slope  58 , is provided in the base lid panel  44  rather than in the cover lid panel  60 . However, it is understood that the beveled lid shoulder  56 , alone or in combination with the shoulder slope  58 , may be provided in the base lid panel  44  alone, the cover lid panel  60  alone, or in both the base lid panel  44  and the cover lid panel  60 . 
   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.