Patent Application
20100078814
The present invention relates to the field of semiconductors. More particularly, the present invention relates to a system and method for utilizing porous films as Inter Layer Dielectric materials.
Electronic systems and circuits have made a significant contribution towards the advancement of modern society and are utilized in a number of applications to achieve advantageous results. Electronic technologies such as digital computers, calculators, audio devices, video equipment, and telephone systems have facilitated increased productivity and reduced costs in analyzing and communicating data, ideas and trends in most areas of business, science, education and entertainment. Correspondingly, as technology has advanced, electronic technologies are increasingly shrinking in size. As electronic components shrink, electrical interference and other negative effects on electrical components, such as wires, have an increasingly large impact. The tiny widths and close proximity of adjacent lines introduces resistance and capacitance delays that can hinder chip performance.
One particular such problem is that the RC (resistive-capacitive) delay on interconnects increases as devices are made smaller. The capacitance may be expressed by the equation:
Where A is the area, D is the thickness, K is the dielectric constant of the material, and ∈0 is the permittivity of free space. The area (A) and thickness (D) are governed by the microelectronic chip size.
Accordingly, conventional solutions have been focused on using materials which have a low dielectric constant, such as, porous materials. Unfortunately, porous materials are not able to withstand the mechanical stresses during semiconductor manufacturing, such as, the Chemical Mechanical Polish (CMP) step in damascene processes.
Additionally, the porous nature of the material makes copper deposition problematic as the copper diffuses into the pores of the porous material. One such solution to this problem has been to put an additional layer on top of the porous material. The additional layer provides a sufficient barrier to prevent copper from diffusing into the pores, however, the additional layer increases the dielectric constant. Further, the additional layer requires an additional step in the manufacturing process, as well as, increasing the thickness.
Accordingly, what is needed is a way to manufacture a semiconductor using a material with an appropriate dielectric constant with sufficient mechanical strength for further semiconductor processing and manufacture.
A system and method for manufacturing a semiconductor device including a low dielectric constant porous material layer. Ions are implanted into the low dielectric constant porous material layer which thereby provides the porous material layer with sufficient mechanical strength for withstanding semiconductor manufacturing processes. The ions implanted in the porous material layer further facilitate disposition of a conductive layer on the porous material layer.
The system and method of the present invention facilitates use of low dielectric constant porous materials in semiconductor devices. Ions implanted in the porous material provide mechanical strength to the porous material to withstand subsequent semiconductor manufacturing steps or processes with minimal change in chemical properties of the porous material. The implanted ions further facilitate adhesion of a conductive material layer (e.g., copper) and prevent diffusion of the conductive layer into the pores of the porous material. In addition, the implanted ions results in the porous material layer being hydrophobic. Moreover, the implanted ions avoid increases in thickness caused by a capping layer and thereby facilitate reduced fabrication times and reduce costs. The ions provide the aforementioned advantageous properties with relatively small change in to the dielectric constant of the porous material.
Reference will now be made in detail to the preferred embodiments of the invention, a semiconductor isolation material deposition system and method, examples of which are illustrated in the accompanying drawings. While the invention will be described in conjunction with the preferred embodiments, it will be understood that they are not intended to limit the invention to these embodiments. On the contrary, the invention is intended to cover alternatives, modifications and equivalents, which may be included within the spirit and scope of the invention as defined by the appended claims. Furthermore, in the following detailed description of the present invention, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be obvious to one ordinarily skilled in the art that the present invention may be practiced without these specific details. In other instances, well known methods, procedures, components, and circuits have not been described in detail as not to unnecessarily obscure aspects of the current invention.
Some portions of the detailed descriptions which follow are presented in terms of procedures, logic blocks, processing, and other symbolic representations of operations on data bits within a computer memory. These descriptions and representations are the means generally used by those skilled in data processing arts to effectively convey the substance of their work to others skilled in the art. A procedure, logic block, process, etc., is here, and generally, conceived to be a self-consistent sequence of steps or instructions leading to a desired result. The steps include physical manipulations of physical quantities. Usually, though not necessarily, these quantities take the form of electrical, magnetic, optical, or quantum signals capable of being stored, transferred, combined, compared, and otherwise manipulated in a computer system. It has proven convenient at times, principally for reasons of common usage, to refer to these signals as bits, values, elements, symbols, characters, terms, numbers, or the like.
It should be borne in mind, however, that all of these and similar terms are associated with the appropriate physical quantities and are merely convenient labels applied to these quantities. Unless specifically stated otherwise as apparent from the following discussions, it is appreciated that throughout the present application, discussions utilizing terms such as “processing”, “computing”, “calculating”, “determining”, “displaying” or the like, refer to the action and processes of a computer system, or similar processing device (e.g., an electrical, optical, or quantum, computing device), that manipulates and transforms data represented as physical (e.g., electronic) quantities. The terms refer to actions and processes of the processing devices that manipulate or transform physical quantities within a computer system's component (e.g., registers, memories, other such information storage, transmission or display devices, etc.) into other data similarly represented as physical quantities within other components.
At block 110, a semiconductor substrate layer is deposited. At block 120, an inert gas layer is deposited on the substrate layer. In one embodiment, the inert gas layer comprises Argon.
At block 130, a porous material layer or film is deposited above the substrate layer. The porous material may be selected based on a relatively low dielectric constant (e.g., 1.5-2.5). The porous material may be a variety of materials including, but not limited to, an oxide material (e.g., SiO2), polyarylene ether, Polytetrafluoroethylene (PTFE), methyl silsequioxane (MSSQ), hydrogen silsequioxane (HSSQ), Chemat porous films, Parylene, templated silica, or SiLK by Dow Chemical Company of Midland Mich.
At block 140, ions are implanted in the porous material layer. It is appreciated that the dose, energy, and type of ions can be varied or selected according to the application being used or semiconductor device being made. In one embodiment, the dose, energy, and ions use may be selected based on amount of change of the dielectric constant, strength of the porous material layer after implantation, level of diffusion into the pores of the porous material, the hydrophobic nature of the resulting implanted material, thickness, and adhesiveness. To the extent possible the dose, energy, and type of ions are selected so the dielectric constant of the porous material layer (with implanted ions) remains substantially unchanged after implantation of the ions. It is further appreciated that implanting may beneficially facilitate surface cleaning of the porous material layer (e.g., removal of organic contamination from the surface).
The ions and associated implantation properties may further be selected so as to harden the surface of the porous material layer. For example, the ions may be selected to provide sufficient strength to the porous material layer to withstand mechanical stresses of semiconductor manufacturing (e.g., Chemical Mechanical Polish (CMP) step in damascene processes). The implantation may thus be performed so as to balance between hardening the porous material layer and changing the dielectric constant of the porous layer material with implanted ions.
The ions may further be selected based on the hydrophobic nature of the resulting implanted surface of the porous material layer. For example, pores of the porous material layer may normally absorb moisture and the ion implantation results in a surface chemical modification making the porous material layer (or films) hydrophobic.
In one exemplarily embodiment, multiple implants may be done to the extent necessary to achieve the desired properties while avoiding significant changes in dielectric constant. Correspondingly, the integrity of the porous material layer may be checked after each ion implantation. The ions may be implanted by indenting with a needle on the surface of the porous material layer.
In one embodiment, the ions are noble gas ions and may be selected from the group consisting of Argon, Helium, Xenon, Neon, and Helium. In addition, other ions may be used including, but not limited to Nitrogen and Carbon. In one exemplary embodiment, a porous film of 0.5 to 1 μm is implanted with ions via a dose of 2×1015 or 1×1016 Ar ions/cm2, with energy of 50, 75, 100 and 150 keV, and a thermal treatment of annealed in inert ambient at 450° C. for 1 hour. In another exemplary embodiment, Argon ions are implanted with an energy of 20 keV, a dose of 1×1016 ions/cm2, and a thermal treatment in an inert ambient environment for 1 hour.
Embodiments may further be used in Silicon on Glass (SOG) applications. The role of metastable Ar (Ar*) ions may play an important role in improving the SOG film and further the SOG film may be more relaxed by the energy released from the conversion of Ar* to Ar.
At block 150, copper is deposited on the porous material layer. It is appreciated that any conductive material may be used. The ions implanted within the porous material layer prevents diffusion of the copper into the pores of porous material layer. For example, the modified surface of the porous material layer prevents chemical penetration of gases into the low dielectric constant (K) porous material during chemical vapor deposition (CVD) (e.g., Cu deposition). In one exemplary embodiment, NAND back end of line (BEOL) interconnections can be made with materials having less than a 2.5 dielectric constant to insulate copper lines or wires.
The ions implanted further facilitate adhesion of the copper to the porous material layer. Ion implantation results in increased adhesive properties so conductive lines (e.g., copper lines or wires) adhere to the surface (e.g., able to pass the scotch tape test). For example, the copper may adhere better because of the increased surface area of the porous material. It is appreciated that embodiments may facilitate adhesion of other metals including, but not limited to, Ta, TaN, Ti, and TiN. It is further appreciated that embodiments may provide sufficient adhesive properties with or without thermal treatment after the ion implantation. In one exemplary embodiment, the implanted low dielectric constant materials are shown to be efficient solutions for high quality inter layer dielectric (ILD) films.
In one embodiment, the inert gas layer 204 is deposited on substrate layer 202 and porous material layer 206 is deposited on inert gas layer 204. Inert gas layer 204 may include Argon. The material of porous material layer 206 may be selected based on having a relatively low dielectric constant of 1.5-2.5 and may be suited for manufacturing of 90 mm or less semiconductor device.
As described herein the plurality of ion 208 may be selected and implanted based on a plurality of properties of the resulting implanted layer including, but not limited to, strength, hydrophobic nature, adhesive properties, and diffusion of subsequent layers or films into the pores of porous material layer 206.
Plurality of ions 208 prevents diffusion of copper layer 210 into the pores of porous material layer 206. Further, the implantation of plurality of ions 208 facilitates adhesion of copper layer 210 to porous material layer 206. In one embodiment, plurality of ions 208 are a noble gas (e.g., Argon, Helium, and Xenon). The dielectric constant of porous material layer remains substantially unchanged after implantation of plurality of ions 208.
The implantation of plurality of ions 208 provides sufficient strength to porous material layer 206 to withstand mechanical stresses of subsequent semiconductor manufacturing processes (e.g., Chemical Mechanical Polish). Implantation of plurality of ions 208 further results in the implanted portion of porous material layer 206 being advantageously hydrophobic as described herein.
In one embodiment, semiconductor device 200 may be a variety of devices including, but not limited to, gates (e.g., NAND gates) or a memory device (e.g., NAND based flash). A memory device in accordance with an embodiment of the present invention may include a semiconductor substrate (e.g., substrate layer 202), a plurality of wires (e.g., copper layer 210) disposed above the semiconductor substrate, and a porous material layer (e.g., porous material layer 206) disposed between the semiconductor layer and the plurality of wires. The porous material layer of an exemplary memory device, in accordance with an embodiment, includes a plurality of ions which fill a portion of the porous material layer.
The plurality of ions facilitates adhesion of the plurality of wires to the porous material layer. Further, the plurality of ions advantageously allow use of the porous material layer without requiring an increase in thickness below the plurality of wires (e.g., an additional layer or capping layer). Thus, embodiments of the present invention provide a solution of zero thickness or no increase in thickness.
Thus, a system and method of the present invention facilitates use of low dielectric constant porous materials in semiconductor devices. Ions implanted in the porous material provide mechanical strength to the porous material to withstand subsequent semiconductor manufacturing steps or processes with minimal change in chemical properties of the porous material. The implanted ions further facilitate adhesion of a conductive material layer (e.g., copper) and prevent diffusion of the conductive layer into the pores of the porous material. In addition, the implanted ions results in the porous material layer being hydrophobic. Moreover, the implanted ions avoid increases in thickness caused by a capping layer and thereby facilitate reduced fabrication times and reduce costs. The ions provide the aforementioned advantageous properties with relatively small change in to the dielectric constant of the porous material.
The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and its practical application, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the Claims appended hereto and their equivalents.
