Patent Application
20070224827
1. Field of the Invention
The present invention generally relates to semiconductor processing technologies and, more specifically, to methods for etching a bottom anti-reflective coating (BARC) layer in a dual damascene etching processing.
2. Description of the Related Art
Integrated circuits have evolved into complex devices that can include millions of components (e.g., transistors, capacitors and resistors) on a single chip. The evolution of chip designs continually requires faster circuitry and greater circuit density. The demands for greater circuit density necessitate a reduction in the dimensions of the integrated circuit components.
As the dimensions of the integrated circuit components are reduced (e.g. sub-micron dimensions), the materials used to fabricate such components contribute to their electrical performance. For example, metal interconnects with low resistance (e.g., copper and aluminum) provide conductive paths between the components on integrated circuits.
Typically, the metal interconnects are electrically isolated from each other by a dielectric bulk insulating material. When the distance between adjacent metal interconnects and/or the thickness of the dielectric bulk insulating material has sub-micron dimensions, capacitive coupling potentially occurs between such interconnects. Capacitive coupling between adjacent metal interconnects may cause cross talk and/or resistance-capacitance (RC) delay which degrades the overall performance of the integrated circuit.
Some integrated circuit components include multilevel interconnect structures (e.g., dual damascene structures). Typically, dual damascene structures have dielectric bulk insulating layers and conductive layers, such as copper, stacked on top of one another. Vias and/or trenches are etched into the dielectric bulk insulating layer and copper conductive layers are subsequently filled into the vias and/or trenches and polished back using a process such as chemical mechanical planarization (CMP), so the conducting materials are only left in the vias and/or trenches. In the dual damascene approach, both vias and trenches are patterned into a layer of dielectric material or a stack of different dielectric materials before copper.
Different processing sequences of etching vias and/or trenches in dielectric materials can be used in a dual damascene process. As an exemplary embodiment shown in
A bottom anti-reflective coating (BARC) layer 112 is spin-applied to fill the vias 128, 130 and cover the dielectric stack 132 before trench lithography. A hard mask layer 134 is deposited over the BARC layer 112 to serve as an etch mask layer. A hard mask etching process is performed to expose the underlying BARC layer 112 using a patterned photoresist layer 114. After the exposed hard mask layer 134 defined by the photoresist layer 114 has been etched away, a BARC etching process is performed to clear away a portion of the BARC layer 112 over the via opening 128, 130 by the hard mask layer 134 before etching the trenches. The spin-applied BARC layer 112, however, does not fill dense vias 128 and isolated vias 130 in a same manner. Typically, isolated vias 130 are filled more easily than dense vias 128, resulting in large variation in the BARC thickness between the first and second regions 116, 118 on top of the dielectric stack 132. As the BARC layer 112 at the via openings is etched away, portions of the underlying polish stop layer 110 defined by the hard mask layer 134 in dielectric stack 132 are exposed during the BARC etching process, as shown in
Therefore, there is a need for a method of uniformly etching a BARC layer to form a desired dimension and profile of structures.
Methods for two step etching of a BARC layer in a dual damascene structure are provided. In one embodiment, a method for etching a BARC layer in a dual damascene structure includes providing a substrate having vias filled with a BARC layer disposed on the substrate in an etch reactor, supplying a first gas mixture into the reactor to etch a first portion of the BARC layer filling in the vias, and supplying a second gas mixture comprising NH3 gas into the reactor to etch a second portion of the BARC layer disposed in the vias.
In another embodiment, a method for etching a BARC layer in a dual damascene structure includes providing a substrate having a vias formed in a dielectric bulk insulating layer and filled with a BARC layer in an etch reactor, supplying a first gas mixture having N2 and H2 gas into the reactor to etch a portion of the BARC layer filling in the vias, and supplying a second gas mixture comprising NH3, CO and O2 gas into the reactor to etch the remaining portion of the BARC layer disposed in the vias to a predetermined depth.
In yet another embodiment, a method for etching a BARC layer in a dual damascene structure includes providing a substrate having vias formed in a dielectric bulk insulating layer and filled with a BARC layer in an etch reactor, wherein the BARC layer has a hard mask layer disposed thereover, supplying a gas mixture having a fluorine containing gas into the reactor to etch the hard mask layer using a patterned photoresist layer to expose a surface of the BARC layer, supplying a first gas mixture having N2 and H2 gas into the reactor to etch a portion of the BARC layer filling in the vias, and supplying a second gas mixture comprising NH3, CO and O2 gas, into the reactor to etch the remaining portion of the BARC layer in the vias to a predetermined depth.
So that the manner in which the above recited features of the present invention are attained and can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to the embodiments thereof which are illustrated in the appended drawings.
To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.
It is to be noted, however, that the appended drawings illustrate only exemplary embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.
Embodiments of the present invention include two step methods for etching a BARC layer in a dual damascene structure. The methods facilitate the profile and dimension of a BARC layer during a etching process, thereby enhancing the accuracy of trench formation in a dual damascene structure. The two step etching method includes supplying two different gas mixtures into an etch reactor to etch a BARC layer with good sidewall and/or surface protection, thereby minimizing profile variation associated with etching trenches having different pattern density.
In one embodiment, the reactor 302 includes a process chamber 310 having a conductive chamber wall 330. The temperature of the chamber wall 330 is controlled using liquid-containing conduits (not shown) that are located in and/or around the wall 330.
The chamber 310 is a high vacuum vessel that is coupled through a throttle valve 327 to a vacuum pump 336. The chamber wall 330 is connected to an electrical ground 334. A liner 331 is disposed in the chamber 310 to cover the interior surfaces of the walls 330. The liner 331 facilitates the cleaning capabilities of the chamber 310.
The process chamber 310 also includes a support pedestal 316 and a showerhead 332. The support pedestal 316 supports a substrate 300 below the showerhead 332 in a spaced-apart relation during processing. The support pedestal 316 may include an electrostatic chuck 326 for retaining the substrate 300. Power to the electrostatic chuck 326 is controlled by a DC power supply 320.
The support pedestal 316 is coupled to a radio frequency (RF) bias power source 322 through a matching network 324. The bias power source 322 is generally capable of producing an RF signal having a tunable frequency of from about 50 kHz to about 60 MHz and a bias power of about 0 to 5,000 Watts. Optionally, the bias power source 322 may be a DC or pulsed DC source.
The temperature of the substrate 300 supported on the support pedestal 316 is at least partially controlled by regulating the temperature of the support pedestal 316. In one embodiment, the support pedestal 316 includes a cooling plate (not shown) having channels formed therein for flowing a coolant. In addition, a backside gas, such as helium (He) gas from a gas source 348, is provided into channels disposed between the back side of the substrate 300 and grooves (not shown) formed in the surface of the electrostatic chuck 326. The backside He gas provides efficient heat transfer between the pedestal 316 and the substrate 300. The electrostatic chuck 326 may also include a resistive heater (not shown) within the chuck body to heat the chuck 326. In one embodiment, the substrate 300 is maintained at a temperature of between about 10 to about 500 degrees Celsius.
The showerhead 332 is mounted to a lid 313 of the processing chamber 310. A gas panel 338 is fluidly coupled to a plenum (not shown) defined between the showerhead 332 and the lid 313. The showerhead 332 includes a plurality of holes to allow gases, provided to the plenum from the gas panel 338, to enter the process chamber 310. The holes in the showerhead 332 may be arranged in different zones such that various gases can be released into the chamber 310 with different volumetric flow rates.
The showerhead 332 and/or an upper electrode 328 positioned proximate thereto is coupled to an RF source power 318 through an impedance transformer 319 (e.g., a quarter wavelength matching stub). The RF source power 318 is generally capable of producing an RF signal having a tunable frequency of about 160 MHz and a source power of about 0 to 5,000 Watts.
The reactor 302 may also include one or more coil segments or magnets 312 positioned exterior to the chamber wall 330, near the chamber lid 313. Power to the coil segment(s) 312 is controlled by a DC power source or a low-frequency AC power source 354.
During processing, gas pressure within the interior of the chamber 310 is controlled using the gas panel 338 and the throttle valve 327. In one embodiment, the gas pressure within the interior of the chamber 310 is maintained at about 0.1 to 999 mTorr.
A controller 340, including a central processing unit (CPU) 344, a memory 342, and support circuits 346, is coupled to the various components of the reactor 302 to facilitate control of the processes of the present invention. The memory 342 can be any computer-readable medium, such as random access memory (RAM), read only memory (ROM), floppy disk, hard disk, or any other form of digital storage, local or remote to the reactor 302 or CPU 344. The support circuits 346 are coupled to the CPU 344 for supporting the CPU in a conventional manner. These circuits include cache, power supplies, clock circuits, input/output circuitry and subsystems, and the like. A software routine or a series of program instructions stored in the memory 342, when executed by the CPU 344, causes the reactor 302 to perform processes of the present invention.
The process 400 begins at step 402 by providing a substrate having a dual damascene structure in the reactor 302.
A BARC layer 514 fills the vias 516 and covers the dielectric stack 518. The BARC layer 514 is used to control reflections from the underlying dielectric layer and/or stack during lithography. The BARC layer 514 may comprise, for example, organic materials such as polyamides and polysulfones typically having hydrogen and carbon containing elements, or inorganic materials such as silicon nitride, silicon oxynitride, silicon carbide, and the like. In the embodiment depicted in
A hard mask layer 530 may be disposed over the BARC layer 514 to serve as a etch mask during trench etching. In one embodiment, the polish stop layer 512 is a dielectric layer, such as SiO2, SiON, SiN, SiOCN, SiCN, or the like. In the embodiment depicted in
The polish stop layer 512 may be disposed over the dielectric bulk insulating layer 510. In one embodiment, the hard mask layer 512 is a dielectric layer, such as SiO2, SiON, SiN, SiOCN, SiCN, or the like. In embodiments that the polish stop layer 512 is not present, the BARC layer 514 may directly dispose on and cover a portion 524 (e.g. a surface) of the dielectric bulk insulating layer 510.
The optional dielectric barrier layer 508 is selected from a material having a dielectric constant of about 5.5 or less. In one embodiment, the dielectric barrier layer 406 is a carbon containing silicon layer (SiC), a nitrogen doped carbon containing silicon layer (SiCN), or the like.
A photoresist layer 506 is disposed on the hard mask layer 530 to transfer a predetermined pattern and/or feature into the dielectric stack 518 through an etching process. The patterned photoresist layer 506 may comprise a conventional carbon-based, organic or polymeric materials used to pattern integrated circuit. In the embodiment depicted in
At step 404, a hard mask etching process is performed to etch the hard mask layer 530 exposed in the opening 520. During etching, the hard mask layer 530 in the opening 520 may be removed until an upper surface of the underlying BARC layer 514 is exposed, as shown in
In one embodiment, the hard mask layer 530 may be etched using a plasma formed from a fluorine containing gas mixture. Examples of suitable fluorine containing gases include, but not limited to, CF4, CHF3, C2F6, C3F8, CF6, C4F8,C5F8, C4F6, NF3, SF6 and the like. In another embodiment, the hard mask layer 530 is etched using a plasma formed from a fluorine containing gas mixture that includes at least one of O2, N2, Ar, He, an insert gas, and the like. The hard mask layer 530 may be etched in an etch chamber, such as the reactor 302 described in
In one embodiment, the hard mask etch process may be performed by supplying a gas mixture of fluorine containing gas, such as CF4 and CHF3, into the etch reactor, applying a power between about 300 Watt to about 2000 Watt, maintaining a temperature between about 0 degrees Celsius to about 60 degrees Celsius, and controlling process pressure between about 10 to about 300 mTorr into the reactor. The CF4 gas may be supplied at a flow rate between about 5 sccm to about 300 sccm. The CHF3 gas may be supplied at a flow rate between about 5 sccm to about 300 sccm. In another embodiment, at least one insert gas, such as O2, may also be supplied with the fluorine containing gas mixture into the reactor. The O2 gas may be supplied at a flow rate between about 0 to about 100 sccm.
At step 406, a first BARC etching step is performed to initially etch a portion of the BARC layer 514 filling the via 516 by supplying a first gas mixture in the reactor 302. In one embodiment, the first gas mixture supplied into the reactor 302 contains hydrogen gas (H2) and nitrogen gas (N2). The first gas mixture is also used to purge and flush out the residual gas, e.g, fluorine containing gas, from the previous step 404 remaining in the reactor 302, thereby preventing defect generation or chemical reaction with residual fluorine chemistry in the following etching steps.
In one embodiment, the BARC layer 514 is first etched by forming a plasma from the first gas mixture containing H2 gas and N2 gas. The BARC layer 514 may be etched in an etch chamber, such as the reactor 302 described in
Several process parameters are regulated at step 406 while the first gas mixture is supplied into the reactor 302. In one embodiment, a pressure of the gas mixture in the etch reactor is regulated between about 5 mTorr to about 200 mTorr, and the substrate temperature is maintained between about 0 degrees Celsius and about 60 degrees Celsius. RF source power may be applied at a power of about 300 Watts to about 2000 Watts. The H2 gas may be flowed at a flow rate between about 5 sccm to about 200 sccm. The N2 gas may be flowed at a flow rate between about 5 sccm to about 200 sccm.
In one embodiment, the first BARC etching step may be terminated by expiration of a predefined time period. For example, the first BARC etching step is terminated by processing between about 5 second to about 50 second. In another embodiment, the first BARC etching step may be terminated by other suitable method including monitoring optical emission or by another indicator.
At step 408, a second BARC etching step is performed to etch the remaining portion of the BARC layer 514 filling the via 516 into a predetermined depth, as shown in
In one embodiment, the BARC layer 514 is etched by forming a plasma from the second gas mixture containing NH3 gas and an oxygen containing gas, such as CO and/or O2. In another embodiment, the BARC layer 514 is etched by forming a plasma from the second gas mixture containing NH3, CO and O2. The BARC layer 514 may be etched in an etch chamber, such as the reactor 302 described in
Several process parameters are regulated at step 408 while the second gas mixture is supplied into the reactor 302. In one embodiment, a pressure of the gas mixture in the etch reactor is regulated between about 5 mTorr to about 200 mTorr, and the substrate temperature is maintained between about 0 degrees Celsius and about 60 degrees Celsius. RF source power may be applied at a power of about 300 Watts to about 2000 Watts. The NH3 gas may be flowed at a flow rate between about 5 sccm to about 300 sccm. The O2 gas may be flowed at a flow rate between about 5 sccm to about 200 sccm. The CO gas may be flowed at a flow rate between about 5 sccm to about 500 sccm. The etching time may be processed at between about 20 seconds to about 100 seconds.
During the second BARC etching step, the NH3 gas supplied with the second gas mixture reacts with the BARC layer 514, forming a protective polymer on the surface and/or sidewall of the BARC layer 514. As the BARC layer 514 in the dense vias is etched faster relative to the BARC layer 514 in isolated vias, a relatively higher amount of the protective polymer may be accumulated over the BARC layers 514 in dense vias than in the isolated vias. The accumulated protective polymer in dense vias prevents the BARC layer 514 from etched while the BARC layer 514 in isolated vias remains sequentially etched until a predetermined depth is reached. The differential etch rate associated with the pattern density of the substrate is minimized by the different amount of accumulated protective polymer in dense and isolated vias. As such, a substantially uniform etching profile can be achieved in both regions having isolated and dense vias, thereby preventing the defects, e.g. fence or BARC layer concave, associated with via pattern density variation in conventional etch processes.
Subsequently, several etching process including etching the polish stop layer 512, dielectric insulating layer 510 from the opening surface 524 to the predetermined depth 526 may be performed to form a trench 528 as needed. After the trenches are formed, the remaining BARC layer 514, or the hard mask layer 530 may be stripped or removed from the substrate by any suitable method to form a dual damascene structure, as shown in
Thus, the present invention provides a two step etching method for etching a BARC layer with a uniform etching profile. The method advantageously facilitates the profile and dimension of trenches and/or vias in both the isolated and dense vias in a dual damascene structure by supplying different gas mixtures to two step etch the BARC layer with sufficient sidewall and/or surface protection.
While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.
