Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L28/00—Passive two-terminal components without a potential-jump or surface barrier for integrated circuits; Details thereof; Multistep manufacturing processes therefor
  • H01L28/20—Resistors
  • H01L28/24—Resistors with an active material comprising a refractory, transition or noble metal, metal compound or metal alloy, e.g. silicides, oxides, nitrides
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L23/00—Details of semiconductor or other solid state devices
  • H01L23/52—Arrangements for conducting electric current within the device in operation from one component to another, i.e. interconnections, e.g. wires, lead frames
  • H01L23/522—Arrangements for conducting electric current within the device in operation from one component to another, i.e. interconnections, e.g. wires, lead frames including external interconnections consisting of a multilayer structure of conductive and insulating layers inseparably formed on the semiconductor body
  • H01L23/5228—Resistive arrangements or effects of, or between, wiring layers
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
  • H01L21/70—Manufacture or treatment of devices consisting of a plurality of solid state components formed in or on a common substrate or of parts thereof; Manufacture of integrated circuit devices or of parts thereof
  • H01L21/71—Manufacture of specific parts of devices defined in group H01L21/70
  • H01L21/768—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics
  • H01L21/76838—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics characterised by the formation and the after-treatment of the conductors
  • H01L21/76885—By forming conductive members before deposition of protective insulating material, e.g. pillars, studs

Definitions

• TFRs thin-film resistors
• IC integrated circuit
• IC Semiconductor integrated circuits
• interconnect or back end of line (BEOL) elements.
• BEOL back end of line
• Copper is often preferred over aluminum due to its lower resistivity and higher electromigration resistance. Electrical resistance is generally referred to herein as “resistance” for convenience. Copper interconnect, however, is typically difficult to manufacture with traditional photoresist masking and plasma etching used for aluminum interconnect.
• a so-called damascene process may include patterning dielectric materials, such as silicon dioxide, or fluorosilicate glass (FSG), or organo-silicate glass (OSG) with open trenches where the copper or other metal conductors should be.
• a copper diffusion barrier layer typically Ta, TaN, or a bi-layer of both is deposited, followed by a deposited copper seed layer, followed by a bulk Copper fill, e.g., using an electro-chemical plating process.
• a chemical-mechanical planarization (CMP) process may then be used to remove any excessive copper and barrier, and may thus be referred to as a copper CMP process.
• the copper remaining in the trench functions as a conductor.
• a dielectric barrier layer e.g., SiN or SiC, is then typically deposited over the wafer to prevent copper corrosion and improve device reliability.
• a similar damascene process can be used to form integrated TFR modules.
• TFRs Thin-Film Resistors
• TFRs are typically formed from SiCr (siliconchromium), SiCCr (silicon-silicon carbide-chromium), TaN (tantalum nitride), NiCr (nickelchromium), AlNiCr (aluminum-doped nickel-chromium), or TiNiCr (titanium-nickel- chromium), for example.
• FIGs 1A and IB show cross-sectional views of two example TFR devices 10A and 10B, respectively, implemented using conventional processes. Fabrication of conventional TFR devices 10A and 10B typically requires three added mask layers. A first added mask layer is used to create the TFR heads 12A and 12B. A second added mask layer is used to create TFR elements 14A and 14B in respective contact with TFR heads 12A and 12B. A third added mask layer is used to create TFR vias 16A and 16B in contact with TFR heads 12A and 12B. As shown, TFR elements 14A and 14B are formed across the top and bottom of TFR heads 12A and 12B, respectively, but in each case three added mask layers are typically required.
• FIGS 1 A and IB also indicate the areas at which TFR elements 14A and 14B contact the respective TFR heads 12A and 12B.
• TFR element 14A contacts top surfaces of TFR heads 12A and 12B
• TFR element 14B contacts bottom surfaces of TFR heads 12A and 12B.
• Electrical resistance at these TFR contact areas referred to herein as “contact resistance,” provides a component of the overall TFR device resistance.
• Low contact resistance is generally desired in TFR design, so that the overall TFR device resistance is dominated by the shape of TFR element.
• the TFR contact areas in the conventional TFR devices 10A and 10B often provide a relatively high and/or unreliable contact resistance.
• the TFR contact area with each TFR head 12A and 12B may be relatively small.
• a TFR element may comprise an SiCr, SiCCr, NiCr, or TaN film having a thickness of less than 100A for a sheet resistance of about IKQ/square (IKQ/n).
• IKQ/n IKQ/square
• FIG. 2 shows a representation of an example TFR device 200 to illustrate various resistance calculations.
• the view of example TFR device 200 shown in Figure 2 may represent a top-down view of the TFR device 10A shown in Figure 1 A or a bottom-up view of the TFR device 10B shown in Figure IB.
• TFR device 200 includes a TFR element 202 (e.g., TFR film) extending from a first end 204 in contact with a first TFR head 210 at a first TFR contact area 220, and a second end 206 in contact with a second TFR head 212 at a second TFR contact area 222.
• TFR element 202 e.g., TFR film
• First and second ends 204 and 206 of the TFR element 202 may be in contact with top or bottom surfaces of TFR heads 210 and 212, respectively, depending on whether TFR device 200 corresponds with the configuration of TFR device 10A shown in Figure 1 A or TFR device 10B shown in Figure IB.
• the TFR element 202 has a length L extending between TFR heads 210 and 212, and a width W.
• the length L is illustrated as being made up of a number of divisions, with each division having a length equal to W, thus forming a number of WxW squares.
• the resistance of the TFR element 202, RTFR element can be expressed by Equation (1):
• RTFR element Rs * L/W (1)
• the TFR element resistance RTFR element is proportional to the number of WxW squares along the length L of the TFR element 202.
• a total resistance RTFR device for the TFR device 200 includes the TFR element resistance RTFR element in series with a contact resistance at each TFR contact area 220, 222.
• the total TFR device resistance RTFR device can be expressed by Equation (2):
• RTFR device RTFR element + RTFR_contact_area_220 + RTFR_contact_area_222 (2)
• TFR contact resistance such as the resistance at each TFR contact area 220, 222 (RTFR contact_area_220 and RTFR _contact_area_222), may vary significantly as a function of manufacturing process variations, providing an unpredictable resistance.
• the temperature coefficient of resistance (TCR) at each TFR contact area 220, 222 is typically uncontrollable. Accordingly, it would typically be desirable, from a design perspective, to minimize or reduce the TFR contact resistance, such that the TFR device performance (resistance and TCR) is dominated by well -characterized properties of the TFR element itself.
• TFR modules integrated TFR devices
• TFR modules having improved contact between the TFR element and TFR heads, to provide lower and more reliable contact resistance.
• TFR modules with a sheet resistance of about IkQ/square and a low temperature coefficient of resistance (TCR) (e.g., absolute value close to 0), which enables improved designs of integrated circuits, particularly with analog components.
• TCR temperature coefficient of resistance
• Embodiments of the present disclosure provide improved thin-film resistors (TFRs), which may be integrated in IC devices in a modular manner and thus referred to herein as “TFR modules.” More particularly, embodiments of the present disclosure provide TFR modules including a TFR element extending laterally between two vertically-extending TFR side contacts (e.g., elongated vias) that are each contacted by a respective TFR head, wherein the TFR element includes TFR element end flanges in contact with the vertically-extending TFR side contacts.
• the TFR element includes a first TFR element end flange at one lateral end of the TFR element and a second TFR element end flange at an opposite lateral end of the TFR element.
• the first TFR element end flange extends parallel to, and is in contact, with one of the vertically-extending TFR side contacts
• the second TFR element end flange extends parallel to, and is in contact with, the other vertically-extending TFR side contact.
• the contact between the respective TFR element end flanges and vertically-extending TFR side contacts may provide an increased contact area for the TFR element, which may reduce contact resistance and improve contact reliability between the TFR element and the TFR heads.
• the TFR module may be formed such that a distal end of each TFR element end flange directly contacts a bottom surface of a respective TFR head, to thereby provide two contacts between each TFR element end flange and a respective TFR head: (1) contact between the TFR element end flange and a vertically-extending TFR side contact in contact with the respective TFR head and (b) direct contact between the distal end of the TFR element end flange and the respective TFR head.
• This dual contact design may define two parallel resistance paths between the TFR element and each TFR head, which may further reduce contact resistance and improve contact reliability, as a failure of either one of the two contacts will not cause a TFR module failure.
• such TFR modules with reduced contact resistance may be formed in damascene structures of an IC device.
• some embodiments provide methods of forming TFR modules using damascene techniques including only one added mask layer to the background fabrication process for the IC device.
• the TFR modules can be formed at any level of interconnect (e.g., at any metal layer) in the IC device.
• such TFR modules are formed with a sheet resistance of about IkQ/square and a low temperature coefficient of resistance (TCR) (e.g., absolute value close to 0).
• TCR temperature coefficient of resistance
• One aspect of the invention provides a method of forming a thin film resistor (TFR) module in an integrated circuit (IC) structure.
• TFR thin film resistor
• IC integrated circuit
• First and second vertically-extending TFR side contacts are formed spaced apart from each other.
• a TFR element is formed between the first and second vertically-extending TFR side contacts.
• the TFR element includes (a) a laterally- extending TFR element base extending from a first end proximate the first vertically-extending TFR side contact to a second end proximate the second vertically-extending TFR side contact, (b) a first TFR element end flange projecting vertically from the first end of the TFR element base, the first TFR element end flange extending parallel to, and in contact with, the first vertically-extending TFR side contact, and (c) a second TFR element end flange projecting vertically from the second end of the TFR element base, the second TFR element end flange extending parallel to, and in contact with, the second vertically-extending TFR side contact.
• a first TFR head is formed in contact with the first vertically-extending TFR side contact
• a second TFR head is formed in contact with the second vertically-extending TFR side contact.
• the TFR element comprises SiCr, SiCCr, NiCr, or TaN.
• the method includes forming the first TFR head such that a bottom surface of the first TFR head is in contact with the first TFR element end flange; and forming the second TFR head such that a bottom surface of the second TFR head is in contact with the second TFR element end flange.
• the method includes forming the first TFR head such that a bottom surface of the first TFR head is in contact with both (a) the first vertically-extending TFR side contact and (b) the first TFR element end flange; and forming the second TFR head such that a bottom surface of the second TFR head is in contact with both (a) the second vertically- extending TFR side contact and (b) the second TFR element end flange.
• the TFR element also includes TFR element side flanges projecting vertically from the TFR element base and extending between the first and second TFR element end flanges, and the method includes removing at least a partial height of each TFR element side flange. In one embodiment, the method includes performing a metal etch to both (a) define the first and second TFR heads and (b) remove the at least partial height of each TFR element side flanges.
• forming the first and second vertically-extending TFR side contacts includes forming first and second elongated via openings, and filling the first and second elongated via openings with metal.
• forming the TFR element includes (a) removing a partial thickness of a non-conductive region between the first and second vertically-extending TFR side contacts to define a TFR opening exposing a first sidewall of the first vertically-extending TFR side contact and a second sidewall of the second vertically-extending TFR side contact, and (b) depositing a TFR film in the TFR opening, the deposited TFR film including (i) a first TFR film portion covering a top surface of the non-conductive region between the first and second vertically-extending TFR side contacts, the first TFR film portion defining the laterally- extending TFR element base, (ii) a second TFR film portion covering the exposed first sidewall of the first vertically-extending TFR side contact, the second TFR film portion defining the first TFR element end flange, and (iii) a third TFR film portion covering the exposed second sidewall of the second vertically-extending TFR side contact, the third TFR film portion defining the second TFR element end f
• the TFR module includes a first and second vertically-extending TFR side contacts spaced apart from each other, a TFR element, and first and second TFR heads.
• the TFR element includes (a) a laterally-extending TFR element base extending from a first end proximate the first vertically-extending TFR side contact to a second end proximate the second vertically-extending TFR side contact, (b) a first TFR element end flange projecting vertically from the first end of the TFR element base, the first TFR element end flange extending parallel and in contact with the first vertically-extending TFR side contact, and (c) a second TFR element end flange projecting vertically from the second end of the TFR element base, the second TFR element end flange extending parallel and in contact with the second vertically- extending TFR side contact.
• the first TFR head is in contact with the first vertically-extending TFR side contact
• the second TFR head is in contact with the first vertically-extending TFR side contact
• the TFR element comprises SiCr, SiCCr, NiCr, or TaN.
• a bottom surface of the first TFR head is in contact with the first TFR element end flange, and a bottom surface of the second TFR head is in contact with the second TFR element end flange.
• a bottom surface of the first TFR head is in contact with both (a) the first vertically-extending TFR side contact and (b) the first TFR element end flange
• a bottom surface of the second TFR head is in contact with both (a) the second vertically- extending TFR side contact and (b) the second TFR element end flange.
• the TFR element also includes TFR element side flanges projecting vertically from the TFR element base and extending between the first and second TFR element end flanges, wherein a vertical height of each TFR element side flange is less than a vertical height of each of the first and the second TFR element end flanges.
• each of the first and second vertically-extending TFR side contacts comprises an elongated metal via.
• Another aspect of the invention provides a method of forming an IC device including a TFR module and an interconnect structure.
• the method includes concurrently forming (a) a via and (b) first and second vertically-extending TFR side contacts.
• the method further includes forming a TFR element between the first and second vertically-extending TFR side contacts, the TFR element including (a) a laterally-extending TFR element base extending from a first end proximate the first vertically-extending TFR side contact to a second end proximate the second vertically-extending TFR side contact, and (b) a first TFR element end flange projecting vertically from the first end of the TFR element base, the first TFR element end flange extending parallel and in contact with the first vertically-extending TFR side contact, and (c) a second TFR element end flange projecting vertically from the second end of the TFR element base, the second TFR element end flange extending parallel and in contact with the second vertically-extending TFR
• the method further includes concurrently forming (a) a metal line in contact with the via, (b) a first TFR head in contact with the first vertically-extending TFR side contact, and (c) a second TFR head in contact with the second vertically-extending TFR side contact.
• each of the first and second vertically-extending TFR side contacts comprises an elongated metal via.
• each of the first and second vertically-extending TFR side contacts has a TFR side contact width in a first lateral direction equal to a width of the via, and a TFR side contact length in a second lateral direction at least twice as large as the TFR side contact width.
• the method includes forming the first TFR head such that a bottom surface of the first TFR head is in contact with the first TFR element end flange, and forming the second TFR head such that a bottom surface of the second TFR head is in contact with the second TFR element end flange.
• forming the TFR element further includes forming TFR element side flanges projecting vertically from the TFR element base and extending between the first and second TFR element end flanges, and removing at least a partial height of the TFR element side flanges.
• a metal etch is performed to (a) form the metal line in contact with the via, (b) form the first and second TFR heads and (c) remove the at least partial height of the TFR element side flanges.
• FIGS. 1 A and IB are a cross-sectional views of two example thin-film resistor (TFR) devices implemented using known processes;
• Figure 2 is a cross-sectional view of a known integrated circuit (IC) structure including an example TFR formed according to known techniques;
• IC integrated circuit
• Figure 3 A is a cross-sectional side view of an IC device structure including an example TFR module formed near a typical metal interconnect structure, according to one embodiment of the present invention
• Figure 3B is an enlarged view of one end of the TFR module shown in Figure 3A, showing two parallel conductive paths between one end of the TFR element and a respective TFR head, according to one embodiment of the present invention
• Figures 4A-10C illustrate an example process for forming an IC device structure including an example TFR module and metal interconnect structure, according to one embodiment of the invention
• Figure 11 is a cross-sectional side view showing a patterned mask opening well-aligned in the x-direction relative to underlying TFR side contacts, according to one example implementation
• Figures 12A-12B are cross-sectional side views showing an example misalignment of a patterned mask opening for forming a TFR trench ( Figure 12 A), and showing the absence of a negative effect of such misalignment on the resulting TFR element ( Figure 12B), according to another example implementation.
• Figure 13 shows a cross-sectional side view of an example IC device structure including a TFR module and interconnect structure formed between a polysilicon layer and a metal layer, according to one example embodiment.
• Embodiments of the present invention provide a TFR module formed in an IC device, and methods of forming such a TFR module.
• the TFR module includes a TFR element connected between first and second vertically-extending TFR side contacts.
• the TFR element may include a laterally-extending base portion extending between the vertically-extending TFR side contacts, and first and second vertically-extending flanges projecting vertically (e.g., upwardly) from opposing ends of the base portion.
• the first vertically-extending flange may be formed on a sidewall of the first vertically-extending TFR side contact, and the second vertically-extending flange may be formed on a sidewall of the second vertically-extending TFR side contact.
• a first TFR head may be formed in contact with the first TFR side contact and a top end of the first TFR element vertical flange, and a second TFR head may be formed in contact with the second TFR side contact and a top end of the second TFR element vertical flange, thus defining two parallel conductive paths between the TFR element and each TFR head, which may reduce contact resistance and improve contact reliability.
• Figure 3A is a cross-sectional side view of an IC device structure 300 including a TFR module 302 having a TFR element 320 formed near a metal interconnect structure 304, according to one embodiment of the present invention.
• Figure 3B is an enlarged view of one end of TFR module 302, showing two parallel conductive paths between one end of the TFR element 320 and a respective TFR head 322b.
• TFR module 302 and metal interconnect structure 304 are formed in common layers of the IC device structure 300, including a first metal layer 310, a second metal layer 312, and a dielectric region 314 (e.g., comprising one or more oxide layers).
• TFR module 302 may be formed concurrently with metal interconnect structure 304 and other structures of IC device structure 300.
• TFR module 302 may be formed at any depth in IC device structure 300, i.e. between any two metal layers.
• the example metal interconnect structure 304 may comprise a via contact including a via 350 connecting a metal line 352 formed in the second metal layer 312 with a metal line 354 formed in the underlying first metal layer 310.
• the TFR module 302 may include a TFR element 320 formed between a pair of TFR heads 322a and 322b, and a pair of vertically-extending TFR side contacts 326a and 326b connecting the respective TFR heads 322a and 322b to underlying metal lines 328a and 328b, which underlying metal lines 328a, 328b are formed in the underlying first metal layer 310.
• TFR heads 322a and 322b are formed in the second metal layer 312.
• Each vertically-extending TFR side contact 326a and 326b may be elongated in a direction into the page, e.g., in the form of a widened or “slotted” via, as discussed below with reference to Figures 4A and 4B.
• TFR element 320 may be formed using a damascene process including a chemical mechanical planarization (CMP) process.
• CMP chemical mechanical planarization
• Elements 326a and 326b are referred to as “vertically-extending TFR side contacts” because vertically-extending flanges of the TFR element 320 contact sidewalls of vertically-extending TFR side contacts 326a and 326b, as discussed below.
• the TFR element 320 includes (a) a laterally-extending TFR element base 330 extending from a first end 330a proximate a first vertically-extending TFR side contact 326a to a second end 330b proximate a second vertically-extending TFR side contact 326b and (b) TFR element end flanges 332a and 332b each projecting vertically from the first end 330a and second end 330b, respectively of the TFR element base 330.
• First TFR element end flange 332a is formed on a sidewall 336a of vertically-extending TFR side contact 326a
• the TFR element end flange 332b is formed on a sidewall 336b of vertically- extending TFR side contact 326b.
• the TFR element 320 may comprise a conductive film, e.g., formed from SiCCr, SiCr, NiCr, TaN, or other suitable TFR material.
• a protective cap 338 e.g., comprising SiN or SiO2, may be formed over the TFR element 320, as discussed below in more detail.
• the TFR module 302 may be formed such that a top (distal) end 340a of the TFR element end flange 332a is in contact with a bottom surface 366a of TFR head 322a, and a top (distal) end 340b of the TFR element end flange 332b is in contact with a bottom surface 366b of TFR head 322b.
• each TFR element end flange 332a, 332b contacts an associated TFR head 322a, 322b through two parallel conductive paths: (1) a first (direct) conductive contact path through direct contact between the respective top (distal) end 340a, 340b of each TFR element end flange 322a, 322b and associated TFR head 322a, 322b, and (2) a second (indirect) conductive contact path between each TFR element end flange 322a, 322b and associated TFR head 322a, 322b via the associated vertically-extending TFR side contacts 326a, 326b.
• FIG. 3B provides a more detailed view of the two conductive contact paths between TFR element end flange 332b and TFR head 322b. As shown, the top end 340b of TFR element end flange 332b is in direct contact with the bottom surface 366b of TFR head 322b, and a sidewall 364 of TFR element end flange 332b is in contact with sidewall 336b of vertically- extending TFR side contact 326b.
• This configuration defines (a) a first (direct) conductive path 360 between the top end 340b of TFR element end flange 332b and bottom surface 366b of TFR head 322b and (b) a second (indirect) conductive path 362 extending from TFR element end flange 332b, through the interface between sidewall 364 of TFR element end flange 332b and sidewall 336b of vertically-extending TFR side contact 326b, and through vertically- extending TFR side contact 326b to TFR head 322b.
• Conductive paths 360 and 362 are electrically in parallel.
• conductive paths 360 and 362 define two parallel contact resistances between the TFR element 320 and TFR head 322b: (1) a first resistance, RTFR flange top-TFR head, associated with the first (direct) conductive contact path 360 and (2) a second resistance, RTFR fian e-TFR side contact-TFR head, associated with the second (indirect) conductive contact path 362. Similar parallel conductive paths and parallel contact resistances are defined between the TFR element end flange 332a and TFR head 322a.
• the parallel conductive paths may reduce the contact resistance (RcontactTFR eiement-TFR head) at each end of the TFR element 320, as the contact resistance (RcontactTFR eiement-TFR head) is lower than each of the two parallel resistance components (RTFR flange top-TFR head and RTFR fiange-TFR side contact-TFR head) individually.
• the parallel conductive contact paths may improve the contact reliability for the TFR module 302, as the TFR module 320 may continue to operate even with a failure of one of conductive paths 360 and 362 between the TFR element 320 and a TFR head 322a or 322b.
• Figures 4A-10C illustrate an example process for forming an example IC device structure 400 including an example TFR module and metal interconnect structure, which may correspond with the example TFR module 302 and metal interconnect structure 304 shown in Figures 3A-3B, according to one embodiment of the invention.
• the figures are arranged in groups of three ( Figures 4A-4C, Figures 5A-5C, etc.), with each group of three figures including (a) a top view (e.g., Figure 4A, Figure 5A, etc.), (b) a first cross-sectional side view (e.g., Figure 4B, Figure 5B, etc.), and (c) a second cross-sectional side view (e.g., Figure 4C, Figure 5C, etc.).
• Figure 4A shows a top view
• Figure 4B shows a first cross-sectional side through cut line 4B-4B shown in Figure 4A
• Figure 4C shows a second cross-sectional side view through cut line 4C-4C shown in Figure 4A.
• the process may start by forming a metal layer 402 including metal lines 404a, 404b and 404c, and forming a via 406 and vertically-extending TFR side contacts 408a and 408b over and in contact with respective metal lines 404a-404c.
• Metal layer 402 may be any metal layer (e.g., interconnect layer) at any depth in the IC device structure 400 being formed.
• Via 406 and TFR side contacts 408a, 408b may be formed in a dielectric region 410 including one or more oxide layers and/or other dielectric layer(s).
• Via 406 may comprise a conventional via formed using conventional techniques.
• Each vertically-extending TFR side contact 408a, 408b may be elongated in a lateral direction, in this example the y-direction, to provide a continuous structure for contacting a vertically- extending flange of a subsequently formed TFR element, as discussed below with reference to Figures 10A-10B.
• each vertically-extending TFR side contact 408a, 408b may have a width WTFR contact in the x-direction, and an elongated length LTFR contact in the y-direction that is at least 2 times, at least 4 times, at least 6 times, at least 8 times, or at least 10 times the width WTFR contact.
• each vertically-extending TFR side contact 408a, 408b may have a width WTFR contact in the range of 0.1-0.5 pm, and length LTFR contact in the range of 1-100 pm.
• Via 406 and vertically-extending TFR side contacts 408a, 408b may be formed simultaneously, by forming respective openings in the dielectric region 410, filling the openings with tungsten or other suitable metal, and performing a CMP to arrive at the structure shown in Figures 4A-4C.
• each vertically-extending TFR side contacts 408a, 408b may be formed by forming an elongated via opening (elongated in the y-direction), using the same via mask as the conventional via opening for via 406, and simultaneously filling the elongated and conventional via openings.
• the process may continue by depositing a photoresist 420 and patterning a mask opening 422 for extending in the x-direction from vertically- extending TFR side contact 408a to vertically-extending TFR side contact 408b and extending in the y-direction across the full or partial width (in the y-direction) of vertically-extending TFR side contacts 408a, 408b.
• the mask opening 422 is aligned such that the lateral ends of the mask opening 422 in the x-direction are aligned directly over vertically-extending TFR side contacts 408a and 408b.
• each lateral edge 422a, 422b of the mask opening 422 may be aligned in the x-direction anywhere over the respective vertically-extending TFR side contact 408a, 408b, or even beyond the respective vertically-extending TFR side contact 408a, 408b in the direction away from the other vertically-extending TFR side contact 408a, 408b, without negatively effecting the subsequently formed TFR element 460.
• a trench etch is performed through the mask opening 422 shown in Figure 5B to form a TFR trench 430 between vertically-extending TFR side contacts 408a and 408b.
• a plasma etch or alternatively a wet etch, may be used.
• a resist strip and clean process may be performed, resulting in the structure shown in Figure 6A-6C.
• the TFR trench 430 exposes a sidewall 474a of vertically-extending TFR side contact 408a, and a sidewall 474b of vertically-extending TFR side contact 408b.
• a subsequently formed TFR element may include flanges formed in contact with these exposed sidewalls 474a and 474b.
• the TFR trench 430 has an x-direction trench length LTFR trench defined by the distance between vertically-extending TFR side contacts 408a and 408b, a y-direction trench width WTFR trench defined by the y-direction width of the mask opening 422, and a z-direction trench depth DTFR trench defined by the relevant etch parameters (e.g., etch chemistry, time, without limitation).
• the trench width WTFR trench and trench depth DTFR trench may define a contact area between vertically-extending flanges of a subsequently formed TFR element and each vertically-extending TFR side contact 408a, 408b, as shown in Figures 10A and 10B discussed below.
• This contact area may influence the contact resistance (RTFR fiange-TFR side contact-TFR head discussed above) between the TFR element and each vertically-extending TFR side contact 408a, 408b, which may influence the overall resistance (RcontactTFR eiement-TFR head discussed above) of the resulting TFR module.
• the trench length LTFR trench, trench width WTFR trench, and trench depth DTFR trench define the dimensions, and thus the performance, of the TFR element to be formed in the TFR trench 430.
• the trench length LTFR trench, trench width WTFR trench, and trench depth DTFR trench may be selected to provide desired performance characteristics of the resulting TFR module.
• the trench length LTFR trench may be selected by selecting or adjusting the x-direction distance between vertically-extending TFR side contacts 408a and 408b.
• the trench width WTFR trench may be selected by selecting or adjusting the y-direction width of the mask opening 422.
• the trench depth DTFR trench may be selected by selecting or adjusting the relevant etch parameters (e.g., etch chemistry, time, without limitation).
• a TFR film 440 is deposited over the structure and extending down into the TFR trench 430, e.g., by a physical vapor deposition (PVD) process.
• the TFR film 440 may comprise SiCCr, SiCr, NiCr, TaN, or any other suitable TFR element material, and may have a thickness of less than lOOA (1 pm), e.g., in the range of 0.01-0.1 pm.
• a TFR cap 450 may be deposited over the TFR film 440 and extending into the TFR trench 430.
• the TFR cap 450 may comprise a nitride or oxide, for example, SiN or SiCh, and may have a thickness in the range of 0.01-0.1 pm.
• a CMP may be performed to remove portions of the TFR cap 450 and TFR film 440 outside the TFR trench 430 and above the dielectric region 410.
• the remaining portions of the TFR film 440 define a TFR element 460, which includes:
• a laterally-extending TFR element base 462 extending from a first end 464a proximate first vertically-extending TFR side contact 408a to a second end 464b proximate the second vertically-extending TFR side contact 408b;
• vertically-extending TFR element end flanges 466a and 466b projecting vertically (upwardly) from the first and second ends 464a and 464b, respectively, of the TFR element base 462, and
• TFR element side flanges 468a and 468b projecting vertically (upwardly) from opposing sides of the TFR element base 462.
• the vertically-extending TFR element end flange 466a is formed on sidewall 474a of vertically-extending TFR side contact 408a
• the vertically-extending TFR element end flange 466b is formed on sidewall 474b of vertically-extending TFR side contact 408b.
• the TFR element side flanges 468a and 468b may create unwanted TCR effects for the TFR module, for example a TCR dependence on the TFR trench width (WTFR trench), as described in U.S. Patent 10,818,748, the entire contents of which are hereby incorporated by reference for all purposes.
• WTFR trench TFR trench
• at least a portion of the TFR element side flanges 468a and 468b may be removed, to thereby reduce the TFR module’s TCR dependence on the TFR trench width.
• a metal layer 480 is deposited, patterned, and etched using metal deposition, patterning, and metal etch techniques to form TFR heads 482a and 482b and metal line 482c, thereby completing the formation of the TFR module and interconnect structure, indicated respectively at 490 and 492.
• TFR cap 450 (for example, comprising SiN or SiCh) protects the underlying TFR element base 462 from the metal etch.
• Metal layer 480 may be any metal layer (e.g., interconnect layer) at any depth in the IC device structure being formed.
• TFR head 482a is formed with a bottom surface 484a in contact with (a) first vertically-extending TFR side contact 408a and (b) a top (distal) end 470a of vertically- extending TFR element end flange 466a.
• TFR head 482b is formed with a bottom surface 484b in contact with (a) second vertically-extending TFR side contact 408b and (b) a top (distal) end 470b of vertically-extending TFR element end flange 466b.
• TFR element side flanges 468a and 468b ( Figures 9A - 9C) of the TFR element 460 may create unwanted TCR effects for the TFR module.
• the metal etch used to form TFR heads 482a and 482b and metal line 482c may be used to remove a full or partial vertical height (z-direction) of the TFR element side flanges 468a and 468b outside the footprint of TFR heads 482a and 482b.
• Figure 10C shows openings 486a and 486b formed by the etching of the full height of TFR element side flanges 468a and 468b.
• the metal etch may remove a partial vertical height (z-direction) of the TFR element side flanges 468a and 468b outside the footprint of TFR heads 482a and 482b, such that the remaining (post-etch) TFR element side flanges 468a and 468b extend upwardly from the TFR element base 462, but to a lower height then the TFR element end flanges 466a and 466b.
• the portions of the TFR element side flanges 468a and 468b in these overlap regions may be protected from the metal etch (by an overlying mask, as known in the art) and thus not removed.
• These protected, non-etched portions of TFR element side flanges 468a and 468b are shown in Figure 10A at 468a’, 468a”, 468b’, and 468b”.
• the TFR element end flanges 466a and 466b provide dual conductive paths between the TFR element 460 and TFR heads 482a and 482b, as discussed herein (e.g., above with respect to Figures 3A-3B).
• the metal etch may extend down into the dielectric (e.g., oxide) region 410, as indicated at 488.
• the disclosed process may provide an alignment margin (in the x-direction) for the alignment of mask opening 422 patterned in photoresist 420, without negatively effecting the resulting TFR element 460.
• Figures 11 and Figures 12A-12B discussed below illustrate this concept.
• Figure 11 is a cross-sectional side view corresponding with Figure 5B, showing a patterned mask opening 422 well-aligned in the x-direction relative to vertically-extending TFR side contacts 408a and 408b.
• the x-direction length of the TFR trench 430, LTFR trench, in which the TFR film 440 is deposited to form the TFR element 460 is defined by the distance between TFR side contacts 408a and 408b.
• the x-direction length of the patterned mask opening 422, Lmask opening may be significantly longer than the TFR trench length LTFR trench without affecting the resulting TFR trench 430 and subsequently formed TFR element 460, as any portions of the TFR film 440 deposited outside the TFR trench 430 are removed as shown in Figures 9A-9C (or physically disconnected from the TFR film 440 within the TFR trench 430, as shown in Figure 12B, discussed below), and thus do not affect the resulting TFR element 460.
• Using a patterned mask opening length Lmask opening longer than the TFR trench length LTFR trench provides an alignment margin for the alignment of the patterned mask opening 422 relative to vertically-extending TFR side contacts 408a and 408b, thus allowing a degree of misalignment of the patterned mask opening 422 (e.g., caused by misalignment of a photomask overlay, as known in the art).
• Figures 12A-12B illustrate an example misalignment of the patterned mask opening 422, and absence of effect of such misalignment on the resulting TFR element 460, according to one example implementation.
• the patterned mask opening 422, having the same x-direction length Lmask opening as the well-aligned implementation shown in Figure 11, is poorly aligned in the x-direction as indicated by the “misalignment” arrow.
• Figure 12A is a cross-sectional side view showing the misaligned mask opening 422 and resulting TFR trench 430 formed by the TFR etch through the misaligned mask opening 422.
• the lateral edge 422a of the misaligned mask opening 422 is aligned beyond the TFR side contact 408a in the x-direction away, which results in an additional trench 1202 formed beyond the TFR side contact 408a during the TFR trench etch.
• Figure 12B is a cross-sectional side view showing the resulting TFR element 460 formed in the TFR trench 430, after depositing a TFR film 440, depositing a TFR cap 450, and performing a CMP to remove portions of TFR film 440 and TFR cap 450 above the dielectric region 410, e.g., according to the process steps shown in Figs. 7A-7C through 9A-9C.
• an additional region of TFR film material indicated at 1204, extends down into the additional trench 1202 during deposition of the TFR film 440.
• TFR film region 1204 is physically detached from the TFR element 460 in the TFR trench 430, and thus does not affect the performance of the resulting TFR module.
• a TFR module according to the present invention may be formed at any depth in the relevant IC device structure.
• the TFR module may be formed between any two metal layers in the relevant IC device structure, e.g., metal layers 310 and 312 shown in Figure 3 A, or metal layers 402 and 480 shown in Figure 10B.
• the TFR module may be formed between a silicided polysilicon layer and a metal layer (e.g., metal- 1 layer) in an IC device structure.
• Figure 13 shows a cross-sectional side view of an example IC device structure 1300 including a TFR module 1302 and interconnect structure 1304 formed between a poly silicon layer 1306 and a metal layer 480 (e.g., metal- 1 layer), according to one example embodiment.
• IC device structure 1300 is similar to IC device structure 400 shown in Figure 10B, except the lower metal lines 404a-404c of IC device structure 400 are replaced by respective silicided poly silicon elements 1310a-1310c.
• Each poly silicon element 1310a- 1310c includes a respective poly silicon element 1312a- 1312c formed in polysilicon layer 1306, and silicided to form a silicide region 1314a-1314c on the top of each respective poly silicon element 1312a- 1312c.
• Silicide regions 1314a-1314c may comprise of Titanium Silicide, Cobalt Silicide, or Nickel Silicide.
• Silicide regions 1314a and 1314b define conductive contacts for vertically- extending TFR side contacts 408a and 408b, respectively, and silicide region 1314c defines a conductive contact for via 406 of interconnect structure 1304.

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• 2021
  • 2021-06-29 WO PCT/US2021/039563 patent/WO2022146486A1/en active Application Filing
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