DEPOSITING A MATERIAL OF CONTROLLED, VARIABLE THICKNESS ACROSS A SURFACE FOR PLANARIZATION OF THAT SURFACE

Abstract: A method is provided for obtaining a topography with a substantially planar upper surface. The profile of the upper surface of the semiconductor topography is first detected by a profile detection tool, such as a stylus profilometer. The profile detection tool creates a database to quantify the elevational variations across the upper surface of the semiconductor topography. The database is then provided to a control system of a deposition tool. The control system controls the deposition of a profile layer upon the upper surface of the semiconductor topography such that a thickness of the profile layer is a function of the elevation of the surface. In one embodiment, the control system controls a potential gradient across the semiconductor topography so as to cause more reactant species to be directed toward the more recessed regions of the topography. In another embodiment, the control system controls the opening and closing of valves disposed within a shower head above the semiconductor topography. More reactant species are allowed to pass from those valves positioned directly above the more recessed regions of the topography. The resulting upper surface of the semiconductor topography is thus planar.

Description: TITLE : DEPOSITING A MATERIAL OF CONTROLLED, VARIABLE THICKNESS ACROSS A SURFACE FOR PLANARIZATION OF THAT SURFACE BACKGROUND OF THE INVENTION 1 Field of the Invention This invention relates to the field of semiconductor processmg and, more particularly, to an integrated circuit and method of making the same in which a layer of varying thickness is deposited upon a topographical surface of a semiconductor topography to compensate for elevational variations across the surface. 2 Description of Relevant Art An integrated circuit consists of electronic devices electrically coupled by conductive trace elements, i.e., interconnect Interconnect are patterned from conductive layers formed above the surface of a semiconductor substrate in which impurity regions have been formed. An mtegrated circuit can compnse multiple levels of interconnect spaced from each other by mterlevel dielectπc layers and electrically linked by contact structures extending through the mterlevel dielectπc layers. The use of multiple levels of interconnect within an mtegrated circuit mcreases the density of active devices placed upon a smgle monolithic substrate. In addition to added process complexity, an increase m the number of interconnect levels leads to a corresponding mcrease in the elevational disparity of the resulting surface (l e., an mcrease m the difference between the peaks and valleys of the resultmg upper surface). For example, when a dielectπc layer is chermcally- vapor deposited across interconnect lines laterally spaced from each other within a smgle horizontal plane, numerous peaks and valleys may result m the upper surface of the dielectπc layer The chemical- vapor deposition ("CVD") process produces a relatively conformal dielectπc layer across the semiconductor topography comprismg the interconnect lmes. In this manner, the dielectric layer climbs to a higher elevation when it crosses over an interconnect line and falls to a lower elevation m between interconnect lmes. Unfortunately, elevation disparity across the upper surface of an ensumg mtegrated circuit can lead to many problems. Exemplary problems mclude strmgers arising from mcomplete etchmg over severe steps, failure to open vias due to mterlevel dielectπc thickness disparity, and poor adhesion to underlymg mateπals. Elevation dispaπty also causes step coverage problems of, e.g., interconnect placed over an mterlevel dielectπc peak and valley area as well depth-to-focus problems when patterning, e.g., interconnect upon an mterlevel dielectπc. Many manufacturers have undergone extensive research m methods for planaπzmg topographical surfaces m order to avoid the above problems Chemical-mechanical polishing ("CMP") is a well known technique used to planaπze the surfaces of layers formed durmg integrated circuit fabncation. A typical CMP process involves placmg a semiconductor wafer face-down on a polishing pad which is fixedly attached to a rotatable table or platen Elevationally extending portions of the downward-directed wafer surface contact with the rotatmg pad. A fluid-based chemical, often referred to as a "slurry" is deposited upon the pad possibly through a nozzle such that the slurry becomes disposed at the interface between the pad and the wafer surface. The slurry initiates the polishing process by chemically reacting with the surface mateπal bemg polished. The polishing process is facilitated by the rotational movement of the pad relative to the wafer (or vice versa) to remove material catalyzed by the slurry Unfortunately, if the reaction rate of the slurry with the surface mateπal varies across the surface, certain areas of the wafer may be removed more quickly than others Further, a CMP polishing pad which conforms to underlying surfaces, or bows in an arcuate pattern m response to force applied thereto, may undesirably remove some portions of the wafer while leaving others behmd Thus, reaction rate variation and or pad pressure variation can lead to the formation of recesses m the topographical surfaces bemg "planaπzed" by CMP It would therefore be desirable to develop a process for substantially planaπzing the upper surface of a semiconductor topography Particularly, a process is needed which would rmnrrnize the surface dispanty across a layer formed during the fabncation of an mtegrated circuit A planarization process which does not result m the formation of recesses in the topographical surfaces bemg planaπzed would be beneficial Such a process could be used as a replacement of a CMP planarization step, or in some cases as a back-up planarization step m addition to CMP SUMMARY OF THE INVENTION The problems identified above are, in large part, addressed by an improved method for substantially planaπzmg a surface havmg surface dispanty The profile of the upper surface of a semiconductor topography is detected m order to quantify the elevational vaπations across the surface and store the elevational vaπations in a database A deposition tool is then used to deposit a profile layer of varying thickness across the topographical surface, wherem the thickness of the profile layer is controlled as a function of the elevation of the topographical surface, as mdicated by the database In this manner, the thickness of the profile layer is made thicker upon the more recessed regions of the topographical surface than upon the more elevated regions of the topographical surface Thus, the profile layer compensates for elevational vanations, resultmg m a substantially planar upper surface Advantageously, the present planarization method may be used to replace CMP planarization techniques or to compensate for recesses formed in a surface as a result of CMP In one embodiment, a profile detection tool (e g , a stylus profilometer, an mterferometer, a scanning capacitance microscope, or a Thermowave™ microscope) is used to detect the elevational variations across a topographical surface A database is created to quantify the elevational vaπations across the topographical surface The database comprises a plurality of x, y, and z coordmates, wherem the x and y coordmates mdicate a location across the surface of the wafer, and wherem the z coordmate mdicates the elevation of the upper surface of the wafer at that location The database is provided to a control system of a deposition tool, e g , a plasma- enhanced CVD ("PECVD") deposition tool A semiconductor topography compnsmg the topographical surface is positioned withm a chamber of the deposition tool A potential gradient representative of the elevational variations of the topographical surface, as indicated by the control system, is formed across the surface A profile layer is then deposited upon the topographical surface The potential present at a particular location on the surface dictates the amount of material deposited at that position Thus, the potential gradient causes a varying thickness of the profile layer to be deposited across the topographical surface For example, the potential gradient may be used to control where excited atoms sourced from a plasma become adsorbed upon the surface during PECVD In this manner, more excited atoms can be adsorbed upon the valleys of the topographical surface than upon the peaks The excited atoms thus react to form a material that is thicker over the more recessed regions of the topographical surface than over the more elevated regions of the topographical surface. The upper surface of the resultmg semiconductor topography is thus substantially free of surface dispanty. In another embodiment, elevational variations across a topographical surface are used to dictate the openmg and closmg of piezo valves disposed within a conduit leadmg to shower head openmgs. The piezo valves control the flow of reactant species through the openmgs mto a PECVD chamber in which the semiconductor topography comprising the topographical surface is placed. A database created from measurements taken by a profile detection tool of the topographical surface is provided to a control system which regulates the piezo valves A larger quantity of reactant species is allowed to pass from those openmgs positioned directly above the more recessed regions of the topographical surface. Smce a larger quantity of reactant species is directed toward the valleys of the topographical surface, more mateπal becomes deposited there than upon the peaks of the surface. In this manner, a profile layer is deposited across the topographical surface whose thickness is controlled as a function of the elevation of the surface. Thus, vanations m the thickness of the profile layer deposited across the topographical surface are used to compensate for elevational dispanty across the surface. The upper surface of the resultmg semiconductor topography is thus substantially planar. BRIEF DESCRIPTION OF THE DRAWINGS Other objects and advantages of the mvention will become apparent upon readmg the following detailed description and upon reference to the accompanying drawings m which: Fig. 1 is a flow chart descnbmg a method for plananzing an upper surface of a semiconductor topography; Fig. 2 is a partial cross-sectional view of a semiconductor topography showing a recess formed m the upper surface of the semiconductor topography Fig. 3 is a side plan view of a stylus profilometer used to detect a profile of the upper surface of the semiconductor topography; Fig. 4 is a table havmg an exemplary list of locations on the upper surface of the semiconductor topography and the corresponding elevation of the upper surface at each location; Fig. 5 is a side plan view of the PECVD tool used to deposit a profile layer upon the upper surface of the semiconductor topography, Fig. 6 is a plan view of the base of a shower head from which reactant species pass into a chamber of the PECVD tool; and Fig. 7 is a partial cross-sectional view of a semiconductor topography showmg a deposited profile layer of varying thickness arranged upon the upper surface of the semiconductor topography, wherem the surface of the resultmg semiconductor topography is substantially planar While the mvention is susceptible to vaπous modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herem be described m detail. It should be understood, however, that the drawings and detailed descπption thereto are not mtended to limit the invention to the particular form disclosed, but on the contrary, the intention is to cover all modifications, equivalents and alternatives falling withm the spirit and scope of the present mvention as defined by the appended claims. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Turning now to the figures, Fig 1 shows a flowchart descnbmg a process for obtaining a semiconductor topography with a substantially planar upper surface. As shown m block 10, a semiconductor topography is first provided with an upper surface having elevational variations Thereafter, as shown m block 20, a profile of the upper surface of the semiconductor topography is detected usmg a tool that can trace the elevational changes of the upper surface Turning to block 30, a database is then created to quantify these elevational vaπations across the upper surface of the semiconductor topography as a function of location. As shown m block 40, the created database is then provided to a deposition tool, e g., a PECVD tool Turning to block 50, the deposition tool is programmed to deposit a profile layer upon the upper surface of the semiconductor topography, wherem a thickness of the profile layer is a function of the elevation of the topography. After deposition, an upper surface of the resulting topography is substantially planar. Turning now to Fig 2, a cross-sectional view of semiconductor topography 100 is shown. Upper surface 110 of semiconductor topography 100 is shown to have elevational variations. Upper surface 110 is recessed as a result of, e.g., usmg the CMP process to plananze the surface. In alternative embodiments, upper surface 110 may also have other types of elevational vanations. Fig. 3 depicts a stylus profilometer which may be used to detect the profile (elevational vanations) of upper surface 110 of semiconductor topography 100. The stylus profilometer includes a profilometer tip 120 attached to supporting base 130, the supporting base being attached to supporting structure 140. Profilometer tip 120 is free to move m the vertical direction, enablmg it to detect elevational changes The elevational changes are recorded by electronic control unit 150 which is attached to supporting structure 140. Electronic control unit 150 is also connected to positioning unit 160. Positioning unit 160 is able to control the motion of stage 170 m the x-y plane. Semiconductor topography 100 may be placed upon stage 170, and as positioning unit 160 moves stage 170 m the horizontal plane, profilometer tip 120 detects the elevational variations m the upper surface 110 of topography 100 The elevational vanations detected by profilometer tip 120 are recorded by electronic control unit 150 as a function of the horizontal position of stage 170. The location of stage 170 is given m x and y coordmates. It is to be understood that other profile detection tools, e.g., an mterferometer, a scanning capacitance microscope, and a Thermowave™ microscope, may be used as well Turning now to Fig. 4, a table of exemplary data collected by electronic control unit 150 is illustrated The elevation (z) detected by profilometer tip 120 is shown m the second column of the table. The location of positioning unit 160 corresponding to each vertical position of profilometer tip 120 is recorded by control unit 150. The location of positioning unit 160 is shown in x and y coordmates in the first column of the table Turning now to Fig 5, a PECVD deposition tool is shown Prior to the deposition of a profile layer across the upper surface of semiconductor topography 100, the topography is positioned withm a reaction chamber 180 Vapor phase compounds that contam the required reactant species to form the desired matenal across topography 100 are passed mto reaction chamber 180 An rf power 190 with a frequency of approximately 40 kHz to 40 MHz is applied to water-cooled rf electrode 200 while electrode 210 is mamtamed at ground The applied rf power establishes a plasma m gas chamber 180 The establishment of a plasma enables the chemical- vapor deposition to be performed at lower than typical deposition temperatures (approximately 200° C to 400° C) During the deposition, heater 220 mamtams reaction chamber 180 and the reactant species at a constant temperature According to one embodiment, a voltage bias film 230 is placed against the backside of semiconductor topography 100 Voltage bias film 230 is connected to electronic control unit 250 which controls the voltage bias across the surface of film 230 Electronic control unit 250 receives mput from electronic control unit 150 (see Fig 4) that controls the profilometer tool A database created from the elevational vanations detected by the profilometer tool are exchanged between the two electronic control units The resultant voltage bias across the surface of voltage bias film 230 controls where upon the surface of topography 100 the reactant species accumulate Specifically, film 230 can be biased at dissimilar magnitudes withm corresponding distinct regions upon the film For example, a relatively small first region (less than, e g , several microns) can be positively biased more so than another small, second region laterally adjacent the first region The amount of biasing dictates the quantity of ions directed upon the frontside surface of topography 100 from chamber 180 Thus, the bias at isolated regions of film 230 translates from the backside surface to the frontside surface m a direction substantially perpendicular to that surface This ensures the localized, biased areas of film 230 align with topography 100 In this manner, the amount of mateπal directionally introduced upon topography 100 can vary dependmg on where on the underlymg film bias is applied, and the amount of that bias The the thickness of the profile layer deposited across the surface of topography 100 can therefore be controlled based on that bias location and amount so as to compensate for elevational vanations upon topography 100 The end result is a planar upper surface for semiconductor topography 100 Fig 6 depicts a plan view of a shower head 270 which may be used for the deposition of a profile layer across a non-planar surface of a semiconductor topography, accordmg to another embodiment Shower head 270 may be positioned above the semiconductor topography withm a reaction chamber of a PECVD tool similar to the one shown m Fig 5 Shower head 270 mcludes a plurality of piezo valves 280 through which the gas compnsmg the reactant species may pass into the reaction chamber Each of the piezo valves 280 communicates with an electronic control unit 290 Electronic control unit 290 receives mput from electronic control unit 150 (see Fig 4) that controls the profilometer tool Based on the x, y, and z coordmates of the database stored by electronic control unit 150, electronic control unit 290 determines which piezo valves 280 to open and which to close Each piezo valve 280 is positioned at an x and y coordmate corresponding to an x and y coordmate of the semiconductor topography disposed below shower head 270 Electronic control unit 290 controls the openmg and closmg of piezo valves 280 by adjustmg the electronic voltage applied to each valve Specifically, control unit 290 controls which valve withm the array of valves is to be opened Also it determines the amount by which a selected valve is opened In order to control the thickness of the profile layer deposited across the semiconductor topography, electronic control unit 290 causes those valves positioned directly above the more recessed regions of the topography to be m the open position for the longest duration of time. In this manner, more reactant species are permitted to pass mto the reaction chamber through those valves Because the pressure of the PECVD chamber is relatively low, the reactant species experience relatively few collisions, and follow straight lme trajectories directly from shower head 270 and to the underlying semiconductor topography. In this manner, the openmg and closmg of valves can control localized areas of deposition by virtue of material flowing through those values or absence thereof. For example, valves can remam open more so directly above recessed regions of the semiconductor topography to fill those regions A resultmg surface of the profile layer topography can therefore be made substantially planar. Turning now to Fig. 7, semiconductor topography 100 is shown with deposited profile layer 300 formed accordmg to either of the previously descnbed embodiments. Profile layer 300 has a vanable thickness across the surface 110 of semiconductor topography 100 m which the thickness is thinner over higher elevations of surface 110 and thicker over lower elevations of surface 110. The thickness of profile layer 300 therefore compensates for elevational vanations across surface 110 of semiconductor topography 100. As a result, upper surface 310 of profile layer 300 is substantially planar. It will be appreciated to those skilled m the art havmg the benefit of this disclosure that this mvention is believed to be capable of producmg a semiconductor topography with a substantially upper surface. Furthermore, it is also to be understood that the form of the mvention shown and descnbed is to be taken as exemplary, presently preferred embodiments. Vaπous modifications and changes may be made without departing from the spurt and scope of the mvention as set forth m the claims. It is mtended that the followmg claims be mterpreted to embrace all such modifications and changes.

Claims: WHAT IS CLAIMED IS: 1 A process for forming a substantially planar upper surface of a semiconductor topography, compnsmg detectmg a profile of a surface of said semiconductor topography compnsmg elevational vanations, and depositing a profile layer of varying thickness across said surface, wherein said thickness of said profile layer is controlled as a function of the elevational variations such that a resultmg new upper surface of said semiconductor topography is substantially planar 2 The process as recited in claim 1, further compnsmg creatmg a database from said profile to quantify said elevational vaπations subsequent to said detectmg the profile 3 The process as recited m claim 2, further compnsmg providmg said database to a control system configured to receive said database prior to said depositmg 4 The process as recited m claim 1 , wherem said detecting a profile comprises usmg a profile detection tool selected from the group consistmg of a profilometer, an mterferometer, and a scanning capacitance microscope 5 The process as recited m claim 3, wherem said database compnses a plurality of x, y, and z coordmates, and wherem said x and said y coordmates represents various locations upon said surface of said semiconductor topography, and wherem said z coordmate represents corresponding elevations of said varying locations 6 The process as recited m claim 1 , wherein said profile layer is deposited usmg a PECVD tool 7 The process as recited m claim 6, wherem said control system causes a potential gradient representative of said elevational variations to form across said surface of said semiconductor topography during said deposition, thereby controlling where reactant species generated by said PECVD tool are directed onto said surface 8 The process as recited in claim 7, wherem said control system regulates openmg and closmg of valves through which reactant species pass mto a chamber of said PECVD tool via a shower head, thereby controlling where said reactant species are directed onto said surface 9 The process as recited in claim 1, wherem said surface compnses a recess formed while providmg a chemical-mechanical polish to said surface 10 A system for forming a planar upper surface of a semiconductor topography, compnsmg a profile detection tool for detectmg a profile of a topographical surface of a semiconductor topography, wherein said topographical surface comprises elevational variations, and wherem said profile detection tool is configured to create a database which quantifies said elevational variations across said upper surface of said semiconductor topography; and a deposition tool configured to receive said database, wherein said deposition tool is further configured to deposit a varying thickness of a profile layer across said topographical surface of said semiconductor topography as a function of an elevation of said surface. 11. The system of claim 10, wherein said profile detection tool comprises a tool selected from the group consisting of a profilometer, an interferometer, a scanning capacitance microscope, and a Thermowave™ microscope. 12. The system of claim 10, wherein said database comprises a plurality of x, y, and z coordinates, and wherein said x and said y coordinates represent various locations upon said topographical surface of said semiconductor topography, and wherein said z coordinate represents conesponding elevations of said various locations. 13. The system of claim 10, wherein said deposition tool comprises a PECVD tool. 14. The system of claim 13, wherein said PECVD tool comprises a control system for receiving said database. 15. The system of claim 14, wherein said PECVD tool comprises a chamber, and wherein said semiconductor topography is positioned within said chamber of said PECVD tool. 16. The system of claim 15, wherein said PECVD tool further comprises a conductive tape arranged adjacent said topographical surface of said semiconductor topography. 17. The system of claim 16, wherein said control system is configured to form a potential gradient representative of said elevational variations of said topographical surface across said conductive tape to control where reactant species generated by said PECVD tool are directed onto said topographical surface. 18. The system of claim 15, wherein said PECVD tool further comprises a shower head positioned above said semiconductor topography, said shower head comprising piezo valves through which reactant species pass into said chamber, and wherein said control system is configured to regulate opening and closing of said valves to control where said reactant species are directed onto said topographical surface.

Inventors: DAWSON ROBERT, MAY CHARLES E, DAWSON, ROBERT, MAY, CHARLES, E.
Applicants: ADVANCED MICRO DEVICES INC, ADVANCED MICRO DEVICES, INC.
Application year: 1998
Main classification: H01L21
IPC codes: H01L21