Abstract:
Modular chemical delivery substrate blocks which have both directional and transverse flow direction capabilities united in a single modular substrate block and which utilize localized fastener substrate joining techniques unique to such a design. The design, which incorporates current semiconductor industry standards (such as SEMI 2787.1), dictates specific mechanical dimensional constraints and bolt joining localities that are also presented herein. Likewise, the mechanical features and constraints specific to attaching other direct chemical process flow substrate blocks to such unified multidirectional flow blocks are described. Use of this united multi-flow block design results in fewer seals and fasteners required to provide multi-directional flow regimes, reduces the total chemical wetted volume of the chemical delivery streams, minimizes modular chemical delivery system stacking height, and reduces system weight.

Description:
FIELD OF THE INVENTION 
     This invention pertains to semiconductor modular chemical distribution substrate block design and, more particularly, to the &#34;unified&#34; multi-directional flow (direct and transverse flows in combination) in a single substrate block, the specific mechanical dimension requirements of such a substrate unified multi-directional flow block design, and subsequent mechanical features of mating single directional flow blocks to such a unified multi-directional flow block design. 
     BACKGROUND OF THE INVENTION 
     In the semiconductor industry as well as in other industries, there is need for &#34;united&#34; or combined flow regimes in a single modular chemical delivery substrate block. For example, as shown in FIGS. 1A, 2A, 3A and 4A, some designs for modular chemical delivery blocks (4,8) have typically achieved process chemical flows for both directional flow along line (6) (south to north, or north to south when viewed from the top) and transverse flow along line (14) (cast to west, or west to east when viewed from the top) by combining a top layer block (4) to provide directional process flow (6) with a bottom layer block (8) to provide a transverse directional process flow (14). As shown in FIGS. 1A and 2A, this is typically accomplished by using fasteners (12) (usually threaded bolts and/or nuts) to attach the multiple layer blocks (4,8) together. Although this prior art multi-block multi-layer approach satisfies the requirement for having both directional and transverse process (and/or purge) chemical flows, several limitations to utilizing modular chemical delivery substrates result. 
     First, in a multi-block multi-layer design, the center height (18) measured from the top of the process stream line (20) to the bottom of the block assembly (24) is effectively much higher than that in a design using a single block (28) of the present invention as shown in FIG. 1B which can provide the same chemical flow regimes. Because each chemical flow direction is achieved with two or more individual blocks (4,8) for multi-layer substrate block assemblies, the typical total stacking height (32) of 1.054&#34; (26.8 mm) increases linearly in proportion to the substrate thicknesses of each block in a dual stack design. This contributes to both excessive system weight and the total height of the resulting system. Secondly, when compared to a single block design, prior art multi-block multi-layer modular chemical delivery systems on average have a higher mass of material (usually machined or cast from stainless steel) and thus tend to be heavy and bulky in a completed modular system assembly. For many applications, excess system size and weight present extreme disadvantages for the user who wishes to use traditional modular chemical substrate delivery systems. 
     Multi-layer blocks that are stacked together via a fastened interface also require at least one additional seal (36) per layer and additional fasteners (40) in order to provide a leak-proof system for potentially corrosive or hazardous chemical transport through the system. Although prior art multi-layer block designs provide directional and transverse chemical flow regimes, the additional joining fasteners (40) and seals (36) required also increases total costs. Therefore, modular chemical delivery blocks which can provide both directional and transverse chemical flows independently and which are integrated into a single substrate block design with united flows are desired and needed. 
     Furthermore, as shown in FIGS. 3A and 3B, multi-layer stacked blocks having multi-directional flow capabilities increase the total chemical wetted volume of the bore (52) inside each substrate assembly system as compared to the bore (53) in the unified design of the present invention. This increase can reduce the dry down times when an inert gas carrier is used to dry out the moisture content of the chemical system. Per the industry standard SEMI 2787.1, the internal diameter of both bores (52,53) must be a minimum of 0.18&#34; (4.57 mm). Thus the volume (V) of wetted area V=A×L (where A=IID 2  /4 and L=length of wetted bore) increases with the stacking heights and corresponding increase in the length of the bore. In FIG. 3A, the length L of the bore (54) for a multi-layer assembly is almost twice that of the unified single layer block bore length (55) shown in FIG. 3B. Clearly, a method and system for providing multiple flow regimes (directional and/or transverse flow) in a single, united chemical distribution block overcomes many disadvantages of the prior art. Additionally, certain mechanical features and constraints specific to this design are presented for achieving such a multidirectional flow in a unified block substrate. 
     SUMMARY OF THE INVENTION 
     Modular chemical delivery substrate blocks which have both directional and transverse flow direction capabilities united in a single modular substrate block and which utilize localized fastener substrate joining techniques unique to such a design are described. The design, which incorporates current semiconductor industry standards (such as SEMI 2787.1), dictates specific mechanical dimensional constraints and bolt joining localities. Use of this united multi-flow block technique results in fewer seals and fasteners required to provide multi-directional flow regimes, reduces the total chemical wetted volume of the chemical delivery streams, minimizes modular chemical delivery system stacking height, and reduces system weight. The mechanical features and constraints specific to accomplishing such a unified multi-directional chemical distribution substrate block design are also presented herein. Likewise, the mechanical features and constraints specific to attaching other direct chemical process flow substrate blocks to such unified multi-directional flow blocks are described. Additional objects and advantages of the invention will also become apparent from a consideration of the drawings and ensuing description. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1A is a perspective view of a multi-layer multi-directional chemical delivery block assembly. 
     FIG. 1B is a perspective view of a unified multi-directional chemical delivery block assembly of the present invention. 
     FIG. 2A is an exploded perspective view of the prior art block assembly shown in FIG. 1A. 
     FIG. 2B is an exploded perspective view of the unified block assembly of the present invention. 
     FIG. 3A is a cutaway cross-sectional view of a prior art multi-layer block assembly system. 
     FIG. 3B is a cutaway cross-sectional view of a unified multi-directional flow assembly of the present invention. 
     FIG. 4A is a perspective view of a multi-layer block assembly with both directional and transverse directional flow regimes. 
     FIG. 4B is a perspective view of a unified multi-directional flow regime assembly which depicts the potential stacking height and weight reduction achieved by utilizing the design of the present invention. 
     FIG. 5 is a perspective view of a unified multi-directional chemical delivery block of the present invention depicting certain mechanical constraints of the design. 
     FIG. 6 is a perspective view of a single directional chemical delivery flow block capable of being attached to a multi-directional unified chemical delivery block of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     SEMI standard 2787.1 sets forth the industry standard for the mechanical interface for modular chemical delivery surface mount components. Referring to FIGS. 2A and 2B, such chemical delivery surface mount controls (56) attach directly to the top block (61) of a modular chemical delivery substrate and control the flow of chemicals to the desired destination. SEMI standard 2787.1 dictates the top mechanical chemical gas delivery mounting hole locations (57) (four holes each at 1.188&#34; centers), the gas path bore centerline locations (58), and the gas seal porting locations (59). Based on these industry standard requirements and dictated procedures, the following method and apparatus to provide multi-directional chemical flow, both direct and transverse directional flows, in a single unified substrate block shall be described herein. 
     Providing multi-directional flow in a unified substrate block requires several mechanical features and flow path constraints when conforming to SEMI 2787.1 standards. FIG. 2A depicts a multi-layer modular substrate block assembly whereby the top block (61) (responsible for the direct flow process stream) is attached via intermediate (top to bottom) fasteners (40) and one or more intermediate seals (36) to a lower layer block (64) (commonly referred to as a manifold layer, header, or transverse directional flow). The lower layer block (64), when combined with other lower layer blocks, provides the user a greater number of common chemical delivery process streams due to its ability to supply chemical flow in a direction perpendicular to that provided by the top block (61). Referring to FIG. 2B, a unified multi-directional flow substrate block (60) can be used to provide the same flow regimes as the previously described multi-layer substrate assembly while eliminating the need for intermediate fasteners (40) and intermediate seals (36) required by the multi-layer assembly technique of FIG. 2A. This is accomplished by machining the required multi-directional flow regimes into a single substrate block with the specific dimensions as further described herein. 
     FIGS. 3A and 3B illustrate the realized reduction in chemical delivery flow path length and corresponding wetted volume between the typical multi-layer substrate assembly shown in FIG. 3A and a unified substrate block assembly of the present invention shown in FIG. 3B. Because multi-layer substrate assemblies require additional intermediate fastener hardware (74) and intermediate seals (80) to mate the two layers together, the proper fastener clearances (75) (typically 0.300&#34; to 0.330&#34; with two to four each per assembly) for the top surface blocks to mate to a lower layer block require additional depth to the flow paths. This increases the total wetted flow path (54) and the corresponding flow path volume of the prior art system. With a unified substrate block assembly design of the present invention, however, the multiple layer fastener hardware (74) and associated sealing methodology (80) is eliminated, thus dramatically reducing the length (55) of wetted chemical delivery flow paths in the vertical flow directions. 
     FIG. 4A is a perspective view of a multi-layer block assembly (140) with both directional and transverse directional flow regimes. FIG. 4B shows the unified multidirectional flow regime assembly (148) of the present invention. A comparison of FIG. 4A with FIG. 4B illustrates the difference in the potential stacking height (108) of a multi-layer substrate assembly (140) and a unified multi-directional chemical distribution substrate block regime (148) with lower stacking height (109). Since the weight of these assemblies (140,148) is in direct proportion to the sum total mass of their respective components, any reduction in mass such as that achieved in the unified multi-directional flow substrate block (148) will likewise reduce the total weight of the given system assembly in which the unified block (148) is used. 
     Because both the multi-layer multi-directional flow assembly (140) and the unified multi-directional flow assembly (148) must provide top and lower level axial seal locations (116) to mate one block to another block in a full system assembly, each block must have a minimum depth to provide proper screw clearances for the top layer blocks in order to accommodate the fastener locations (154) and depths for mounting surface mount components as required by SEMI 2787.1. This minimal depth is typically 0.3&#34; to 0.33&#34; and must exist at four fastener locations (154) on each block. Likewise, the blocks must have a minimum depth to provide enough surface area to the top axial seal locations (125,126) without violating industry compliance standards for minimal wall thickness of the flow paths per ASTM specifications A-269, A-270, and A-632 (0.035&#34; wall thickness) as applicable. Based on a minimal top block depth (127) of 0.5&#34;, it becomes evident that the same constraints would hold true in calculating the lower layer block depths (138) of 0.55&#34;. 
     In summary, in order to provide multi-directional flow regimes in a multiple stack configuration, the total stacking height (108) of a multi-directional, multi-layer system (140) must be increased substantially over the height (109) required for a unified multidirectional flow design. Utilizing a unified multi-directional flow substrate block (148) eliminates the need for a secondary layer (144) to provide transverse flow, and thus the total stacking height (109) of the unified multi-directional flow substrate block (148) is reduced significantly. Since most modular chemical delivery substrate blocks are machined out of high purity stainless steel materials, a completely assembled modular chemical delivery system&#39;s weight is dependent upon the total mass weight of the blocks making up the assembly. The elimination of a secondary layer in a multiple layer, multidirectional modular chemical delivery system through utilization of a unified multidirectional flow block configuration can significantly reduce the overall weight of the system. 
     In accordance with SEMI 2787.1, and referring to FIG. 5, it is clear that no mechanical interference with regard to the placement of the fastener locations (154) and seal cavity areas (180) is permitted. Additionally, as shown in FIG. 5, four surface mount component fastener locations (154) are required with typical mechanically threaded (tapped) hole depths at no less than 0.30&#34;-0.33&#34; for safety reasons (so as not to over-travel the fasteners into the block). Likewise, because SEMI 2787.1 constrains the length and width of the modular substrate blocks to a maximum of 1.547&#34; (39.3 mm), the following mechanical features for providing multi-directional chemical flow regimes in the unified singular block configuration of the present invention can be realized. Specifically, SEMI Standard 2787.1 requires a 0.29&#34; (7.36 mm) sealing interface diameter (159) on the top surface of all such substrate designs. Likewise, the unified multi-directional flow block design described herein utilizes the same 0.29&#34; (7.36 mm) sealing interface for the top layer axial connection (160) and the lower axial sealing pin (164). 
     FIG. 5 illustrates the design of the present invention that results from complying with SEMI 2787.1. In particular, the depth of the block permits machining of four top surface mount component fastener holes (154) having depths of 0.30&#34; to 0.33&#34; at 1.188&#34; (top surface) centers (170) while allowing for a 0.29&#34; (7.36 mm) sealing interface for the top axial connection (160) and maintaining safe chemical path wall thickness per ASTM specifications A-269, A-270, and A-632. The minimum mechanical interface depth (184) of the top axial connection (160) is 0.5&#34; (12.7 mm). In order to also maintain safe chemical path wall thickness per ASTM specifications, to provide a minimal depth of 0.305&#34; (7.747 mm) to accommodate lower axial (transverse axial) fasteners (192) from the bottom of the block to the bottom wall thickness of the top directional chemical flow path (194), while still allowing for a 0.29&#34; (7.36 mm) sealing interface for the lower axial (transverse axial) connection (196), a total minimum depth (200) of 0.63&#34; (16 mm) from the bottom of the transverse side of the unified multi-directional chemical flow block to the top of the unified multi-directional chemical flow block is required. Because both the top axial seal and lower axial (transverse axial) connection (60,164) require a 0.29&#34; (7.36 mm) sealing diameter interface, while maintaining a 0.18&#34; (4.572 mm) chemical wetted bore internal diameter (196) and a safe chemical path wall thickness per ASTM specifications, the minimum center-to-center spacing (208) of the axial fastener locations is 0.62&#34; (15.748 mm) for the top axial connections, and the minimum center-to-center spacing (209) is 0.62&#34; (15.748 mm) for t he bottom axial connections. 
     Referring now to FIG. 6, the interface between a typical single directional chemical flow substrate block (211) and a unified multi-directional chemical flow substrate block (212) is described along with the associated mechanical features of such a block (211). FIG. 6 depicts a typical direct (singular) chemical flow path block substrate (211) which must mate at the top axial connection locations with a unified multi-directional chemical flow substrate block (212). First, it should be pointed out that the unified multidirectional flow block design described herein utilizes the same 0.29&#34; (7.36 mm) sealing interface (213) with a 0.18&#34; diameter wetted chemical path bore (214) for t he top axial connection to properly connect to the top axial singular (direct flow) connection (215). The design also uses the corresponding 0.29&#34; (7.36 mm) sealing interfaces (216) and 0.18&#34; diameter wetted chemical path bores (220) for the singular (direct) chemical flow path block substrates (211). As stated previously, SEMI 2787.1 requirements for a typical singular or multiple chemical flow rate block should maintain a block depth which can accept the 0.30&#34;-0.33&#34; four top surface mount component fastener holes (223) at 1.188&#34; (top surface) centers (224), allow for a 0.29&#34; (7.36 mm) sealing interface for the top sealing interface connections (228), and maintain safe chemical path wall thickness (232) per ASTM specifications. Thus, another mechanical requirement for mating singular chemical flow path blocks to either another singular chemical flow path block or a multidirectional unified chemical flow path block is a minimum mechanical interface depth (236) for the top axial mating interface of at least 0.5&#34; (12.7 mm). As stated previously in conjunction with the description of the unified multi-directional chemical flow path block (212), because both the top axial seal (label) and lower axial (transverse axial) connection interfaces (label) require a 0.29&#34; (7.36 mm) sealing diameter interface, while maintaining the 0.18&#34; (4.572 mm) chemical wetted bore internal diameter and the safe chemical path wall thickness per ASTM specifications, the minimum center-to-center spacing of the top axial fastener locations are 0.62&#34; (15.748 mm) for the singular (direct) flow mating substrate blocks (211). By adhering to the dimensions set out above, a single directional flow substrate block (211) can be properly mated with a unified block (212) of the present invention. 
     While this invention has been described with an emphasis upon certain preferred embodiments, variations in the preferred method and apparatus may be used and the embodiments may be practiced otherwise than as specifically described herein. Accordingly, the invention as defined by the following claims includes all modifications encompassed within the spirit and scope thereof.