US8816489
(Abstract)
"Methods for fabricating integrated circuit devices on an acceptor substrate devoid of (無い、有さない)circuitry are disclosed. Integrated circuit devices are formed by sequentially disposing(配設)one or more levels of semiconductor material on an acceptor substrate, and fabricating(作製)circuitry on each level of semiconductor material before disposition(配設)of a next-higher level. After encapsulation of the circuitry, the acceptor substrate is removed and semiconductor dice are singulated(単一化、個片化). Integrated circuit devices formed by the methods are also disclosed."
"Conventionally(通常), three-dimensional (3D) integrated circuit (IC) devices have been fabricated to improve chip density, by initially forming individual circuit devices and subsequently stacking(重ね、積層)and bonding(貼り合わせ)the chips together to form a multi-level chip stack or assembly. Consequently, the time, materials and process acts expended(要する)in carrying out individual chip fabrication, forming an assembly and electrically connecting the chips results in undesirably high cost. Moreover, stacking and electrical connection of the individually fabricated chips may lead to increased resistance and signal delay in the overall circuit due to undesirably long signal paths. Further, transmission of signals through wiring of one layer of the assembly may electrically interfere with(干渉)wiring on other layers, e.g., cross-talk.
Another technique that has been suggested to increase chip density, for minimization of design dimension(設計寸法), is a so-called “bottom-up” approach. In this approach, circuits are fabricated conventionally on a base substrate, such as a silicon-on-insulator (SOI) wafer, followed by growth of successive layers of silicon on the wafer to provide an active surface and fabrication of additional circuit levels on each successive silicon layer prior to growth of the next-higher level. The process is repeated to create a device having a desired number of layers. One of the difficulties of this approach is that each circuit level, other than the last fabricated, is exposed to multiple thermal cycles as subsequent levels are formed. Further, due to the thermal cycling required by a bottom-up approach, suitable material choices for circuit structures are limited. Additionally, this approach requires an excessive amount of time as a consequence of growing each new layer of silicon on the base substrate.
Further, the foregoing(上記)approaches to multi-level circuit fabrication each require the use, and consumption, of a silicon wafer or other bulk substrate, which bulk substrate comprises(構成、成す、占める)a significant portion of the total cost of the fabrication process, on the order of twenty to thirty percent.
Accordingly, there are needs for processes to make 3D integrated circuits more efficiently and with reduced expense, while facilitating(容易化)minimization of the overall dimensions of the device."
"An embodiment of a process for fabricating a multi-level integrated circuit according to the present invention is described. In FIG. 1A, a sacrificial material 102 is formed on a base substrate(基板), which may also be characterized as an acceptor substrate 100. A passivation material 104 is then formed on sacrificial material 102, followed by another, dielectric material 106. Acceptor substrate 100 may comprise(成る、構成される、含む), by way of non-limiting example, monocrystalline silicon, and may comprise a new wafer or a reject wafer on which defective semiconductor devices have been fabricated. Acceptor substrate 100 may also comprise a substrate of another material, such as a ceramic, having a coefficient of thermal expansion (CTE) similar to that of a semiconductor material of a donor substrate to be bonded thereto as described below, to which sacrificial material 102 may bond, and highly resistant to an etchant for sacrificial material 102. In any case, acceptor substrate 100 may be of sufficient thickness and structural integrity to withstand mechanical stresses thereon without detectable deformation during handling and processing. Sacrificial material 102 may comprise a material which may be etched selective to silicon such as, by way of example, a silicon oxide (SiOx, e.g., SiO or SiO2), and may comprise(有する)a thickness of, for example, between about 2000 Å and 2 μm.
As shown in FIG. 1Band independent of the foregoing process described in association with FIG. 1A, a donor substrate 200 is processed. The donor substrate 200 may comprise any structure that includes a layer of semiconductor type material including, for example, silicon, germanium, gallium arsenide, indium phosphide, and other III-V or II-VI type semiconductor materials. By way of non-limiting example(非限定の例), the donor substrate 200 may comprise silicon. The donor substrate 200 will be used to dispose a semiconductor foundation material over acceptor substrate 100, as described in further detail below.
As a non-limiting example, the foundation semiconductor material may be placed on acceptor substrate 100 by a process described herein using a modification of so-called SMART-CUT® technology.
However, other processes suitable for fabricating a semiconductor material on the surface of acceptor substrate 100 may also be used, if sufficiently low processes temperatures are maintained. In conventional implementation(実施態様)of SMART-CUT® technology, donor and acceptor wafers are bonded together using a high temperature anneal, on the order of about 1000° C. to about 1300° C. Such temperatures are unacceptable for use when a substrate already bears(有する)circuitry fabricated thereon. For example, processing temperatures should not exceed about 800° C. when flash memory(*無冠詞)is fabricated. However, an additional plasma activation act may be integrated into(一体化)a conventional SMART-CUT® technology fabrication process to lower a required substrate bonding temperature, as described in detail below.
In an embodiment, a plurality of(複数の)ions of rare gases (e.g., neon, argon, krypton, or xenon), hydrogen, or helium may be implanted into the donor substrate 200 to form an implanted region 202. As represented by directional arrows(矢印で示す)204, a conventional ion source (not shown) may be used to implant the plurality of ions into the donor substrate 200 in a direction substantially perpendicular to a major surface(主表面)206 of the donor substrate 200 to create the implanted region 202, which may also be characterized as a transfer region, the inner boundary 208 of which is shown in the donor substrate 200 in broken lines(破線). As known in the art, the depth to which the ions are implanted into the donor substrate 200 is at least partially a function of the energy with which the ions are implanted. Generally, ions implanted with less energy will be implanted at relatively lesser depths, while ions implanted with higher energy will be implanted at relatively greater depths. The inner boundary 208 of implanted region 202 lies(ある、位置する)substantially parallel to the major surface 206 of the donor substrate 200 and is at a preselected depth which is dependent on selected parameters of the atomic species implant process, as is well known to one of ordinary skill in the art. As a non-limiting example, hydrogen ions may be implanted into the donor substrate with an energy selected to form the inner boundary 208 at a depth D of between about eighty nanometers (80 nm) and about five hundred nanometers (500 nm) (about 800 Å to about 5000 Å), and more particularly, of about two hundred nanometers (200 nm) (about 2000 Å) within the donor substrate 200.
The inner boundary 208 of implanted region 202 comprises a layer of microbubbles or microcavities (not shown) comprising the implanted ion species, and provides a weakened structure within donor substrate 200(*無冠詞). The donor substrate 200 may then be thermally treated at a temperature above that at which ion implantation is effected(実施、行う), in accordance with the disclosures of the patent documents in the preceding paragraph, to effect(引き起こす、生ぜしめる)crystalline rearrangement in the semiconductor material of the donor substrate 200 and coalescence of the microbubbles or microcavities.
An attachment surface 210 to be bonded to dielectric material 106 on acceptor substrate 100 (FIG. 1A) may be formed on donor substrate 200 by exposing the major surface 206 of the donor substrate 200 to a reactive ion etching (RIE) plasma including hydrogen or an inert gas (e.g., argon, oxygen, or nitrogen) to form a plasma-activated major surface 206′. The plasma-activated major surface 206′ increases the kinetics(動特性、速度)of a subsequent bonding act in the form of an oxide reaction with an adjacent surface of the dielectric material 106 overlying the acceptor substrate 100 due to the increased mobility and reactivity of the ionic species (e.g., hydrogen) created on attachment surface 210. By utilizing a plasma-activated material, the wafer bonding process may be performed at temperatures of less than about four hundred degrees Celsius (400° C.). Plasma-activated bonding is described in U.S. Pat. No. 6,180,496 to Farrens et al., assigned to Silicon Genesis Corporation.
As shown in FIG. 1C, the donor substrate 200 is disposed on the dielectric material 106 carried by acceptor substrate 100 and may be bonded to the dielectric material 106 using an annealing process. The plasma-activated major surface 206′ enables annealing at a substantially reduced temperature, as noted above, in comparison to those employed in conventional wafer bonding techniques. Further, the hydrogen or other ions implanted in ion implanted region 202 to the depth of inner boundary 208 makes the silicon in the thermally treated donor substrate 200 susceptible to (易く、しやすく)breakage substantially along inner boundary 208 when a shear force is applied substantially parallel to the major plane(主平面)of the donor substrate 200. After attaching the donor substrate 200 to the dielectric material 106 on acceptor substrate 100, the portion of the donor substrate 200 on the side of(側)the inner boundary 208 opposing(対向、対面)the dielectric material 106 may be cleaved or fractured by applying a shearing force to the donor substrate 200. The portion of the donor substrate 200 below the inner boundary 208, of a thickness, for example, of between about eighty nanometers (80 nm) (about 800 Å) and about four hundred nanometers (400 nm) (about 4000 Å), for example, about two hundred nanometers (200 nm) (about 2000 Å), is detached from the remainder of donor substrate 200 and remains bonded to the acceptor substrate 100 through dielectric material 106, passivation material 104 and sacrificial material 102 to form a foundation material 212, as shown inFIG. 1D.
US8765578
"A method of edge protecting bonded(貼り合わせ)semiconductor wafers.(*体言止め)A second semiconductor wafer and a first semiconductor wafer are attached(貼付け、取付)by a bonding layer/interface and the second semiconductor wafer undergoes(受ける、経る、される)a thinning process(薄膜化?). As a part of the thinning process, a first protective layer is applied to(付ける、塗布?)the edges of the second and first semiconductor wafers. A third semiconductor wafer is attached to the second semiconductor wafer by a bonding layer/interface and the third semiconductor wafer undergoes a thinning process. As a part of the thinning process, a second protective layer is applied to the edges of the third semiconductor wafer and over the first protective layer. The first, second and third semiconductor wafers form a wafer stack. The wafer stack is diced into a plurality of 3D chips while maintaining the first and second protective layers."
ウェーハー貼り合わせ: wafer bonding;ASCIIデジタル「半導体プロセスまるわかり」
Silion on insulator; Wikipedia
"Wafer bonding[14][15] – the insulating layer is formed by directly bonding oxidized silicon with a second substrate. The majority of the second substrate is subsequently removed, the remnants(残り)forming the topmost Si layer.
One prominent(よく知られた、代表的)example of a wafer bonding process is the Smart Cut method developed by the French firm Soitec which uses ion implantation followed by controlled exfoliation to determine the thickness of the uppermost silicon layer."