Thin semiconductor die, approximately 0.004 to 0.007 inches thick, are positioned substantially on the neutral plane of a smart card, the neutral plane defined as the plane of substantially no mechanical strain during flexure of the smart card, thereby providing smart cards having improved resistance to mechanical flexure, and/or smart cards having improved rf performance.
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1. A semiconductor die for use in a smart card, characterized in that the semiconductor die is less than 0.008 between 0.004 and 0.007 inches thick.
3. A smart card including:
(a) a memory device, and/or (b) a processing device, wherein the memory device and the processing device are fabricated using a semiconductor die having a thickness of 0.008 inches or less between 0.004 and 0.007 inches.
2. A semiconductor die for use in a smart card, characterized in that:
(a) the semiconductor die is less than 0.008 between 0.004 and 0.007 inches thick; and (b) the semiconductor die includes an active device equipped to operate at an rf frequency greater than 20 Khz.
4. A smart card including:
(a) a memory device, and/or (b) a processing device, wherein the memory device and the processing device are fabricated using a semiconductor die having a thickness of 0.008 inches or less between 0.004 and 0.007 inches, and wherein the processing device operates at a speed greater than or equal to 4.0 Mhz.
5. A semiconductor die for use in a smart card package having a neutral plane defined as the plane of substantially zero mechanical strain during mechanical flexure of the smart card package, characterized in that:
(a) the semiconductor die is less than 0.008 between 0.004 and 0.007 inches thick, and (b) at least a portion of the semiconductor die is positioned within the neutral plane of the smart card package.
6. A semiconductor die as set forth in
7. A semiconductor die as set forth in
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Related subject matter is disclosed in the co-pending, commonly assigned U.S. patent application of E. Suhir--1, Ser. No. 08/551,241, filed on Oct. 31, 1995, entitled "Data Carriers Having An Integrated Circuit Unit", in the co-pending, commonly-assigned U.S. patent application of Clifton-Flynn-Verdi 4-6-15, Ser. No. 08/558,579, filed on Oct. 31, 1995, entitled, "Smart Card Having a Thin Die", and in U.S. Pat. No. 5,480,842 issued on Jan. 2, 1996 to Clifton, Flynn, and Verdi.
1. Field of the Invention
This invention relates generally to semiconductor devices, and more particularly to semiconductor die that are used in the manufacture of smart cards.
2. Background Art
Existing smart cards may fail when, due to applied mechanical stress, the semiconductor die of the smart card breaks. Mechanical stress is inherent in typical smart card operational environments, such as point-of-sale terminals, electronic cash machines, credit card reading devices, wallets, pockets, and purses. Semiconductor die strength is a significant factor in determining the overall durability and reliability of a smart card. Die thickness affects the ability of a semiconductor die to withstand flexure and applied mechanical force.
In the field of semiconductor fabrication, skilled artisans attempt to use the thickest semiconductor die that will fit within a smart card package. This approach is based upon an assumption that die strength is proportional to die thickness. Since existing smart card packages are approximately 0.030 inches thick, this dimension places a constraint on the maximum thickness of the semiconductor die which will fit within the package. To this end, note that it is not feasible to use semiconductor die that are about 0.030 inches thick. In addition to the die itself, the space within the smart card package is also occupied by lead terminations, structures that protect the die and/or the leads, labeling, magnetic striping, and discrete circuit components. Therefore, die thickness on the order of 0.011 inches are employed, representing the maximum die thickness that can easily fit within a smart card package. Semiconductor die thinner than 0.011 inches are typically not used in smart cards, as such die have traditionally been difficult to handle during the manufacturing process, and the resulting manufacturing expenses are relatively high. Furthermore, conventional wisdom dictates that, as the thickness of a die is decreased, the die become increasingly vulnerable to mechanical failure.
A shortcoming of existing 0.011-inch die is that the die do not provide sufficient immunity to mechanical flexure. When such die are used to fabricate smart cards, breakage and card failure may result if the smart card user bends or flexes the card. Accordingly, flexure is an especially important physical property to consider for smart card applications. In order to improve performance in this area, existing approaches have focused on strengthening the 0.011-inch die through the optimization of specific individual design parameters, such as grinding parameters, dicing parameters, and others. As opposed to integrating these design parameters into a broad-based design solution, typical approaches have adopted a piecemeal approach by considering the effects of only one or two design parameters on flexure resistance. For example, in material systems having high thermal coefficients of expansion, design parameters have been optimized for the purpose of increasing die tolerance to severe thermal transient conditions.
Another shortcoming of existing smart card semiconductor die designs is that little, if any, consideration is given to RF (radio frequency) performance issues. For example, one presently-available smart card requires direct mechanical and electrical contact during use, whereas another type of smart card uses signals in the extremely-low-frequency (ELF) area of the RF spectrum, in the range of 300 to 20,000 Hz, with existing industry-standard UART protocols of 2400, 4800, 9600, and/or 19,200 band. Existing smart cards do not operate at frequencies above the ELF region. Although transponder devices and pagers have been developed for use at higher frequencies, such devices occupy a much larger physical volume than is available within the confines of a smart card. Meanwhile, in relatively recent times, high-speed microprocessors operating at speeds of around 100 Mhz have been developed, and radio frequencies in the 800 and 900-Mhz regions of the frequency spectrum are now enjoying widespread use.
Consider a two-inch lead used in an existing smart card package. This lead provides negligible inductive reactance at 1 Khz, on the order of a fraction of an ohm. That same lead, used at 500 Mhz, provides an inductive reactance of several hundred ohms, which may severely disrupt desired circuit operations at higher frequencies. Moreover, when an existing semiconductor dice having a thickness of 0.011 inches is used to fabricate active semiconductor device, these devices provide electron transit times on the order of several tenths of microseconds, effectively limiting device operation to frequencies less than about 10 Mhz.
Existing field-effect transistors for use in the UHF and microwave regions of the RF spectrum use die thicknesses in the order of 0.00236 inches, so as to provide a relatively short electron transit time. These short electron transit times provide increased high-frequency performance. One technique for fabricating these field-effect transistors is described in U.S. Pat. No. 5,163,728 issued to Miller and entitled, "Tweezer Semiconductor Die Attach Method and Apparatus". Unfortunately, the methods and systems described in the Miller patent are only practical when used to construct discrete transistor devices. The use of tweezer-based devices to construct smart cards is impractical because it would be much too labor-intensive, time-consuming, and expensive. What is needed is an improved technique for constructing a smart card that has enhanced RF (radio frequency) properties.
Smart card packages are about 0.030 inches thick, thereby providing a package that is very similar in dimensions to that of a conventional credit card. Note that existing smart card packaging techniques place the semiconductor die near the surface of the card, due to tight packaging and interconnect requirements, and also because the thickness of the die represents a substantial portion of the thickness of the actual smart card package. Therefore, if a user bends a smart card back and forth, the semiconductor die, being situated near the surface of the card, is subjected to relatively high levels of mechanical stress.
RF coupling, as opposed to direct physical contact, is a more advantageous technique for sending and receiving data to and from a smart card, in terms of user convenience and smart card reliability. However, semiconductor die material functions as a lossy dielectric, attenuating RF signals that are incident thereupon, including the signals that are used to couple data to and from the smart card. This attenuation limits the maximum coupling distance between a smart card and a smart card reader, and also restricts the position in which a smart card must be held relative to a smart card reader/writer, in order to successfully read and write data from and to the smart card. The attenuation is substantially proportional to the thickness of the semiconductor die used to fabricate the smart card, inasmuch as the smart card packaging material is a nonconductive plastic encapsulant offering very minimal RF attenuation, and the conductive leads to and from the semiconductor die occupy an inconsequential portion of the smart card package.
Improved smart card semiconductor die are provided that have a thickness of approximately 0.004 to 0.007 inches. These die are positioned at or near the neutral plane (i.e., plane of substantially zero mechanical strain during flexure) of a smart card, thereby providing smart cards having improved resistance to mechanical flexure and/or enhanced performance at RF frequencies.
FIG. 6 and
Existing die strength improvement techniques have not adequately addressed applications involving mechanical die flexure. In the context of smart card semiconductor die, during mechanical flexure, the mechanical stresses are greatest near the card surface, and are at a minimum value along a neutral plane within the body of the smart card. The neutral plane of the smart card may be defined as the plane of no strain during mechanical flexure of the smart card. If it is assumed that the smart card package is of a substantially uniform composition throughout, with no internal cavities, this neutral plane is at a depth approximately equal to half the thickness of the smart card, i.e., the "mid-plane" of the smart card. However, as a practical matter, the smart card package must contain a cavity for accommodating the semiconductor die. Additionally, stickers, laminates, and/or other types of dressing materials may be applied to the surface of the smart card for identification or ornamentation. These cavities, laminates, and/or stickers may shift the location of the neutral plane to a location that is not approximately equal to half the thickness of the smart card. However, the location of the neutral plane may be determined empirically, and/or with resort to mathematical calculations well-known to those skilled in the art.
Since the mechanical stresses are substantially zero at any point on the neutral plane, it would be desirable to position the semiconductor die at or near the neutral plane. However, even if an existing 0.011 inch die is centered along the neutral plane, the sheer thickness of the die itself results in portions of the die being located in higher stress regions near the surface of the card. Note that the thickness of a smart card must be limited to about 0.030 inches if the smart card is to physically resemble a conventional credit card. In order to provide physical space within the 0.030-inch-thick smart card package for electrical connections to a semiconductor die that is 0.011 inches thick, the semiconductor die must be mounted relatively close to a surface of the smart card.
It is generally difficult or impossible to situate a conventional 0.011-inch-thick semiconductor die on or near the neutral plane (i.e., within a few thousandths of an inch), even if the location of the neutral plane is shifted from a mid-plane location through the use of cavities in the smart card package, non-uniform smart card package composition, and/or the application of stickers or laminates to the smart card package. What is needed is a thinner die, such that the entire die can be situated at or near the neutral plane.
One advantage of using a thin semiconductor dice is that a smart card having enhanced RF performance is provided. For example, when an existing semiconductor dice having a thickness of 0.011 inches is used to fabricate active devices for use in a smart card, these active devices often provide electron transit times on the order of several tenths of microseconds, effectively limiting device operation to frequencies less than about 4 MHz. To this end, note that existing RF transistors for use at VHF and UHF frequencies generally use die much thinner than 0.011 inches, and typically in the range of 0.004 to 0.007 inches. By using a thin dice having a thickness in the range of from 0.004 to 0.007 inches in a smart card, relatively short electron transit times are provided, enabling active device operation in the MF, HF, VHF, UHF, and/or microwave frequency ranges.
Device operation at higher frequencies is advantageous in that a smart card is no longer limited to using industry-standard UART protocols, the fastest of which operates at 19,200 baud. (Note that other standard UART protocols used by existing smart cards operate at 2400 baud and/or 4800 baud.) In addition to being adapted for use with these conventional UART protocols, the thin smart card semiconductor die disclosed herein are also adapted for use with faster data transfer protocols and modulation schemes that operate at higher speeds than conventional UART protocols. These faster data transfer protocols and modulation schemes may be associated with higher-frequency RF carriers above 20 Khz, such as, for example, in the HV, VHF, UHF, and/or microwave regions of the RF spectrum. Such high-frequency RF carriers may be employed in conjunction with known RF modulation schemes as for example, QAM (quadrature amplitude modulation), PCM (pulse-coded modulation), FM (frequency modulation), SSB (single-sideband modulation), and others.
If a smart card uses RF encoding, as opposed to direct physical contact, for sending and receiving data, the use of a thin semiconductor dice provides another advantage. As discussed above, semiconductor die material functions as a lossy dielectric, attenuating RF signals that are incident thereupon. Since this attenuation is roughly proportional to the thickness of the die, the use of a thin die reduces the extent to which RF signals are attenuated by the smart card. This reduced attenuation, in turn, increases the maximum allowable coupling distance between a smart card and a smart card reader/writer, and also increases the number of locations in which a smart card can be held relative to a smart card reader/writer, in order to successfully read and write data from and to the smart card.
Although the semiconductor die 201 of
A plan view of the smart card 500 described in
A more detailed cross-sectional view of the smart card 500 of
When the smart card 500 is bent, the resulting mechanical strains are shown as vectors 520 in FIG. 5. At a given distance from the neutral plane of the smart card, these strains are lowest in relatively stiff smart card structural components and greatest in relatively flexible smart card structural components. With respect to
In order to mathematically calculate the amount of strain on semiconductor die 301 when this die is packaged into a smart card 500, and to calculate the location of the neutral plane within the smart card 500, the entire smart card structure of
Reducing H10 reduces the amount of stress on the smart card die 301. This reduction in H10 is achieved by using as thin a die as is practicable for semiconductor die 301. Further improvements are achieved by constructing smart card 500 such that the most fragile portion of the semiconductor die 301 is at or near the neutral plane. This portion is typically the location at which active devices, such as transistors and diodes, are situated within the semiconductor die 301. More specifically, the interface between the conducting (metal-doped) portion of the die and the semiconducting (i.e., N- or P-doped silicon body) of the remainder of the die is the most fragile portion of semiconductor die 301. This interface is approximated by the active surface defined above. Locating this interface at the neutral plane further protects the semiconductor die 301 from mechanical strain, resulting in a smart card 500 with improved reliability. polyvinyl chloride (PVC) labels 402 and 403. The strains are
Traditional smart card packaging techniques place the die near the surface of the card due to stringent packaging and interconnect requirements. However, according to an embodiment disclosed herein, semiconductor die 301 are situated as close as possible to the neutral plane, e-e', of smart card 500. In this manner, the effective level of mechanical stress transmitted to the semiconductor die 301 by the smart card package 303 during mechanical flexure is substantially reduced. The smart card package 303 thus affords extra protection to the semiconductor die 301 by reducing the mechanical stresses realized upon the die.
Various techniques may be employed to fabricate the relatively thin semiconductor die 201 (
When these existing techniques are applied to fabricate thin die of 0.008 inches or less, the thinner die are more fragile during the handling and fabrication process than conventional 0.011-inch smart card semiconductor die. Substantially improved yields of thin semiconductor die may be obtained if special die fabrication techniques are applied to the semiconductor wafer from which the thin semiconductor die are made. These fabrication techniques include taping the semiconductor wafer with conventional UV dicing tape and then immersing the wafer into an acid bath. The acid bath, which may include nitric acid, hydrofluoric acid, and acetic acid in relative proportions of 7:2:1, provides chemical stress relief for the semiconductor wafer. Additionally, the semiconductor wafer may be diced using a dicing saw, soft rubber or plastic die pickup heads, non-piercing ejector pins, and servo or programmable dynamic ejector pins to reduce or eliminate die damage. Moreover, the die may be ejected from the dicing tape using velocity-controlled or programmable servo-controlled, non-piercing ejector pins. Suitable techniques for manufacturing smart card semiconductor die are set forth in greater detail in U.S. Pat. No. 5,480,842 entitled, "Method for Fabricating Thin, Strong and Flexible Die for Smart Cards".
Verdi, Fred William, Clifton, Mark Bradford, Flynn, Richard Michael
Patent | Priority | Assignee | Title |
10192801, | Dec 08 2008 | STATS CHIPPAC PTE LTE | Semiconductor device and method of forming vertical interconnect structure in substrate for IPD and baseband circuit separated by high-resistivity molding compound |
7138295, | Apr 04 1997 | Elm Technology Corporation; ELM 3DS INNOVATONS, LLC | Method of information processing using three dimensional integrated circuits |
7176545, | Apr 08 1992 | TAIWAN SEMICONDUCTOR MANUFACTURING CO , LTD | Apparatus and methods for maskless pattern generation |
7193239, | Apr 04 1997 | Elm Technology Corporation; ELM 3DS INNOVATONS, LLC | Three dimensional structure integrated circuit |
7223696, | Apr 08 1992 | TAIWAN SEMICONDUCTOR MANUFACTURING CO , LTD | Methods for maskless lithography |
7242012, | Apr 08 1992 | TAIWAN SEMICONDUCTOR MANUFACTURING CO , LTD | Lithography device for semiconductor circuit pattern generator |
7307020, | Apr 08 1992 | TAIWAN SEMICONDUCTOR MANUFACTURING CO , LTD | Membrane 3D IC fabrication |
7344087, | Nov 05 2003 | Samsung Electronics Co., Ltd. | IC card, IC card processor and IC card system to improve data transmission speed |
7385280, | Nov 11 2004 | Seiko Epson Corporation | Electronic device package and electronic equipment |
7385835, | Apr 08 1992 | TAIWAN SEMICONDUCTOR MANUFACTURING CO , LTD | Membrane 3D IC fabrication |
7474004, | Apr 04 1997 | Elm Technology Corporation; ELM 3DS INNOVATONS, LLC | Three dimensional structure memory |
7479694, | Apr 08 1992 | TAIWAN SEMICONDUCTOR MANUFACTURING CO , LTD | Membrane 3D IC fabrication |
7485571, | Apr 08 1992 | TAIWAN SEMICONDUCTOR MANUFACTURING CO , LTD | Method of making an integrated circuit |
7504732, | Apr 04 1997 | Elm Technology Corporation; ELM 3DS INNOVATONS, LLC | Three dimensional structure memory |
7550805, | Apr 08 1992 | TAIWAN SEMICONDUCTOR MANUFACTURING CO , LTD | Stress-controlled dielectric integrated circuit |
7615837, | Apr 08 1992 | TAIWAN SEMICONDUCTOR MANUFACTURING CO , LTD | Lithography device for semiconductor circuit pattern generation |
7670893, | Apr 08 1992 | TAIWAN SEMICONDUCTOR MANUFACTURING CO , LTD | Membrane IC fabrication |
7705466, | Apr 04 1997 | ELM 3DS INNOVATONS, LLC | Three dimensional multi layer memory and control logic integrated circuit structure |
7763948, | Apr 08 1992 | TAIWAN SEMICONDUCTOR MANUFACTURING CO , LTD | Flexible and elastic dielectric integrated circuit |
7786562, | Nov 11 1997 | NYTELL SOFTWARE LLC | Stackable semiconductor chip layer comprising prefabricated trench interconnect vias |
7820469, | Apr 08 1992 | TAIWAN SEMICONDUCTOR MANUFACTURING CO , LTD | Stress-controlled dielectric integrated circuit |
7911012, | Apr 08 1992 | TAIWAN SEMICONDUCTOR MANUFACTURING CO , LTD | Flexible and elastic dielectric integrated circuit |
8035233, | Apr 04 1997 | Elm Technology Corporation; ELM 3DS INNOVATONS, LLC | Adjacent substantially flexible substrates having integrated circuits that are bonded together by non-polymeric layer |
8080442, | Aug 08 2002 | Elm Technology Corporation | Vertical system integration |
8168470, | Dec 08 2008 | STATS CHIPPAC PTE LTE ; STATS CHIPPAC PTE LTD | Semiconductor device and method of forming vertical interconnect structure in substrate for IPD and baseband circuit separated by high-resistivity molding compound |
8269327, | Aug 08 2002 | Vertical system integration | |
8288206, | Apr 04 1997 | Elm Technology Corporation; ELM 3DS INNOVATONS, LLC | Three dimensional structure memory |
8318538, | Apr 04 1997 | Elm Technology Corporation; ELM 3DS INNOVATONS, LLC | Three dimensional structure memory |
8410617, | Apr 04 1997 | Elm Technology Corporation; ELM 3DS INNOVATONS, LLC | Three dimensional structure memory |
8587102, | Aug 08 2002 | Vertical system integration | |
8629542, | Apr 04 1997 | Elm Technology Corporation; ELM 3DS INNOVATONS, LLC | Three dimensional structure memory |
8791581, | Apr 04 1997 | Elm Technology Corporation; ELM 3DS INNOVATONS, LLC | Three dimensional structure memory |
8796862, | Apr 04 1997 | Elm Technology Corporation; ELM 3DS INNOVATONS, LLC | Three dimensional memory structure |
8824159, | Apr 04 1997 | Elm Technology Corporation; ELM 3DS INNOVATONS, LLC | Three dimensional structure memory |
8841778, | Apr 04 1997 | Elm Technology Corporation; ELM 3DS INNOVATONS, LLC | Three dimensional memory structure |
8907499, | Apr 04 1997 | Elm Technology Corporation; ELM 3DS INNOVATONS, LLC | Three dimensional structure memory |
8928119, | Apr 04 1997 | Elm Technology Corporation; ELM 3DS INNOVATONS, LLC | Three dimensional structure memory |
8933570, | Apr 04 1997 | Elm Technology Corporation; ELM 3DS INNOVATONS, LLC | Three dimensional structure memory |
9087556, | Apr 04 1997 | Elm Technology Corporation; ELM 3DS INNOVATONS, LLC | Three dimension structure memory |
9401183, | Apr 04 1997 | Elm Technology Corporation; ELM 3DS INNOVATONS, LLC | Stacked integrated memory device |
Patent | Priority | Assignee | Title |
4962415, | Dec 15 1986 | Hitachi Maxell, Ltd. | IC card |
5163728, | Nov 15 1990 | Tweezer semiconductor die attach method and apparatus | |
5480842, | Apr 11 1994 | AT&T Corp | Method for fabricating thin, strong, and flexible die for smart cards |
5489637, | May 28 1992 | Henkel Corporation | Low temperature flexible die attach adhesive and articles using same |
5546275, | Sep 23 1994 | Motorola, Inc. | Electrical module mounting apparatus |
5561328, | Jun 24 1991 | HEWLETT-PACKARD DEVELOPMENT COMPANY, L P | Photo-definable template for semiconductor chip alignment |
5619165, | Apr 30 1992 | SGS-Thomson Microelectronics, S.A. | Voltage threshold detection circuit with very low consumption |
5719437, | Apr 19 1996 | THE CHASE MANHATTAN BANK, AS COLLATERAL AGENT | Smart cards having thin die |
6051877, | Aug 04 1993 | Renesas Electronics Corporation | Semiconductor device and fabrication method |
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