FR2820825A1 - Probe card used for semiconductor device manufacturing, separates dielectric of substrate main casing and support dielectric supporting external connecting terminal by conductive materials - Google Patents

Abstract

An external connecting terminal (1) is placed on a substrate. The conductive materials (3,4) attached to the substrate, enclose the external connecting terminal. A dielectric of substrate main casing and a support dielectric supporting external connecting terminal are separated by conductive materials.

Description

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 The present invention relates to a probe card for connection to a wafer which is to be measured with a measuring device in a semiconductor wafer testing device.

 Significant progress has been observed in recent semiconductor manufacturing technology, including advancement in the fine processing technology required for high density integration. For a high density implementation as well as for the suppression of the generation of heat and for the reduction of each element, the current and the voltage necessary for the operation in semiconductor devices are reduced from year to year. Thus, the importance of measuring microcurrents has been recognized and higher accuracy in measuring microcurrent is required in probe cards to connect measuring devices and wafers.

 Such a requirement is also present in the wafer processing control test. As a conventional test method for treatment control, measurement chips known as TEGs (Test Element Group) are formed at the same time as ordinary chips are formed on the wafers for characteristic measurement purposes. . In such measurements, a probe card is used as an interface card between a measuring device and a wafer probe device for moving and positioning a wafer to be measured, and is provided around its circular hole with a plurality of wafer contact needles also called contact blades

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 so as to establish contacts with the measurement terminals of the wafer.

 In FIG. 10, a probe card is generally a circular disc 100 having a diameter of approximately 20 to 30 cm, with its central part provided with an opening 102 through which the contact needles or the blades (not shown) can extend for contact with measurement terminals on a semiconductor wafer placed to be measured just under the probe card. Each wire 103 extends from each needle or blade positioned at its internal periphery towards the external periphery where it is connected to a measuring device or the like. That is to say, a signal taken from each terminal of a semiconductor wafer which is to be measured is introduced into the external periphery of the probe card via each needle or blade and is then sent to a measuring device from an external connection terminal 104 positioned on the external periphery of the probe card. At this time, the wires for the connection of the semiconductor wafer which is to be measured to the measuring device are a few tens and are placed mutually adjacent. Guard patterns 105 formed with a conductor are positioned around the corresponding external connection terminals 104. In the example shown in the drawings, the number of terminals or pins for external connection is forty-eight (48). Such a probe card is also known as a personality card or an interface card. See the provisional publication of the Japanese utility model (JP-A) no Showa 64-47042 and the provisional publication of the Japanese patent (JP-A) no Heisei 8-330369.

 In general, such a probe card has external contact terminals 104 at its external periphery for connection to a measurement device. Each

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 contact terminal 104 is composed of a planar conductor disposed on a surface of a substrate of a probe card on which, for example, a conductive contact needle, such as a contact pin element which comprises a conductive rod with a circular cross section provided with a spring at its base and surrounded by a cylindrical element so that on application of the appropriate force, the rod is retracted and stressed by a reaction force so as to establish the electrical contact by pushing the tip of the rod against a surface of the conductor, with a mechanism to ensure secure electrical contact is pushed against the planar conductive surface of the probe card for thereby connection to an external device, such as a measuring device. In addition, each external contact terminal 104 has a pattern extension portion 106 near its internal periphery, and a corresponding planar conductor on the surface of the probe card extends inward. At the pattern extension portion, one end of a coaxial cable 103 is connected and the other end of the coaxial cable is connected to a base end of a contact needle which is in the shape of a needle or d 'a blade as described above. That is, the coaxial cable 103 extends in the air between the pattern extension portion and the contact needle. The needle or the blade is fixed to the internal periphery of the probe card and extends from it towards the inside. In addition, the tip of the inwardly extending needle or blade is connected to a predetermined terminal on a semiconductor wafer to be tested.

 As previously mentioned, in the field of semiconductor element testing, test devices which can measure microcurrents smaller than the level usually used are necessary. Similarly, the measurement accuracy of the order of femoamps is re-

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 required for interface cards used for wafer testing devices. Major problems relating to the development of test devices with such high performance include the leakage current between the adjoining electrical wires for connection of a test device and a semiconductor to be measured and the dielectric absorption occurring between these wires and the dielectrics in a substrate of the probe card.

 For example, the problem of dielectric absorption occurs due to the dielectric absorption properties (absorption current) of the dielectric used as the substrate of the probe card. In general, insulating materials exhibit dielectric polarization when a voltage applied across two electrodes changes and gradually absorbs current until polarization processing is completed. As a result, even if a predetermined voltage is applied to a semiconductor wafer for current measurement, the current measurement cannot be performed correctly for a certain time and a waiting time is necessary until the current flow becomes stabilized. A waiting time is also necessary when the voltage supply is stopped because a discharge current flows gradually. For conventional interface cards, for wafer measuring devices, it is not unusual for such a waiting time for the measurement to last a few tens of seconds until the dielectric absorption current is reduced on the order of the femtoampere. This is one of the important problems in the case of reducing the time required for the measurement of microcurrents.

 Since measurement accuracy on the order of femampamp is now required, the leakage current

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 circulating in a dielectric material between two adjoining wires has also become important.

 Among the components on the probe card as previously mentioned, the parts of the external contact terminal and the pattern extension part tend to be influenced by dielectric absorption and current leakage. The coaxial cable extending from each pattern extension portion is in the air so that it is little influenced by dielectric absorption or current leakage. As the needle part, for example, a highly insulating coaxial needle can be used and a sheathing wire surrounding the core wire of this needle can be connected to a guard. In addition, the insulation between adjoining needles having a part of the needle thread not covered with the protective thread is good because it is obtained by air which has the same dielectric constant approximately as that of vacuum. . Likewise, the response time of the dielectric bias is not a problem.

 To address these problems caused by the external contact terminal, conventionally, a plurality of through holes are formed from the electrodes on the surface through the substrate of the probe card so that the periphery of the electrodes can be defined. An example of one of these technologies is described in Japanese provisional patent publication Heisei 8-335754.

 A problem in such a method is that deformation tends to occur in the probe card as the number of through holes is increased and the physical strength of the card deteriorates in or near the region of the holes. through. Even if the number of through holes is increased without taking into account the manufacturing difficulties and the rising cost, some

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 leakage current through the dielectric between these through holes still remains a problem and dielectric loss cannot be reduced to a desired level as a higher level of measurement accuracy is required.

 It should be noted that there are variations in the dielectric and leakage current properties of each wire for each probe card. Therefore, even if the control of the manufacturing process is sufficiently improved, such variations in the dielectric and current leakage properties of each wire for each probe board should limit the accuracy of current measurements. For example, in the case of a probe card currently used with 48 pins, after applying a voltage of approximately 10 volts, the leakage current 10 seconds after this voltage application on most of the pins is approximately 0.3 x 10-13 A. However, such a leakage current from other specific pins becomes approximately 1 to 2 x 10 '"A.

 It is an object of the present invention to reduce the waiting time for the measurement which results from the dielectric absorption and to reduce the leakage current under normal conditions so as to improve the accuracy of the measurement of the microcurrents or of the fluctuations. of these. It is another object of the present invention to reduce variations in the properties of each pin or each probe card.

 In view of the above-described problems of the prior art, the present invention relates to a structure in which an external connection terminal for use in a probe card is surrounded by conductors.

 The present invention provides a probe card comprising a substrate and an external connection terminal placed on a dielectric support material disposed in the

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 substrate, the external connection terminal is surrounded by a conductor disposed between the substrate and the dielectric support material and a dielectric material of the substrate body and the dielectric support material for supporting the external connection terminal are separated one on the other via the driver.

 Advantageously, the probe card has at least one of the following characteristics: - the conductor comprises at least one lower conductor disposed on a bottom of a recess formed in the substrate to receive the dielectric support material and a lateral conductor disposed on the faces lateral of the recess and a space or gap is disposed between said dielectric support material and the lateral conductor; - the air gap or space is sealed with a dielectric material from the outside of the substrate; the probe card comprises two or more external connection terminals and the electrical connection between these external connection terminals is ensured by the electrical connection disposed inside the substrate; - Said conductor comprises meshed parts or cut parts; - Said external terminal is placed at a lower level over a predetermined distance than the surface of the body of the substrate; - said conductor is connected to a guard terminal; and, - said guard terminal is provided with an active guard.

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 The conductors surrounding the external connection terminal in the present invention are preferably connected to a guard terminal, more preferably to an active guard terminal.

 The conductor attached to the substrate surrounds the external connection terminal in the substrate. Assuming that the conductor has a box-like configuration, the underside of the conductor is positioned below the external terminal in the substrate and the four side faces are positioned in the substrate and surround the external connection terminal from the four sides. The term "in the substrate" does not necessarily mean that the conductor is embedded in the substrate. That is, at least part of each conductor should appear from and may protrude from the surface of the substrate. In addition, when the surface of the substrate is hollowed out or notched, the conductor can be exposed in the hollowed out or notched parts of the substrate or protruded into the air.

 In such a construction of the present invention, the properties of microcurrents in the order of femtoampere can be enhanced so that the accuracy of the measurement can be improved. The waiting time which results from the instability of the current resulting from the dielectric absorption can also be reduced. In addition, the substrate may include other electrical networks which may not be included in the substrate because they may deteriorate the properties of the microcurrents. Since the probe card of the present invention can generally be made up of a planar structure (although one can have three-dimensional structures), it can be easily manipulated and reduce the cost for the stock-

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 age or transportation. In addition, the present invention is compatible with the probe cards currently found on the market.

 The substrate may have a monolayer structure but preferably has a multilayer structure. In a preferred embodiment, for example, the conductive wires can be arranged among the layers and through-holes or through holes can be formed in a multilayer substrate by one of the technologies currently known for manufacturing multilayer substrates.

 The probe card of the present invention can be manufactured in accordance with the following procedure, although it is not limited to any manufacturing process. The external connection terminal surrounded by the conductor can be produced, for example, by forming a recess in a substrate, by disposing a box-type external connection terminal part in which an external connection terminal is formed on the upper surface and a conductive material is disposed on the side surfaces by electrodeposition or the like and by fitting the box type external connection terminal portion in the recess. As a variant, the external connection terminal can be produced by forming a recess in a substrate, by placing a conductive material in the part hollowed out by electrodeposition or the like, and by adjusting or causing an element consisting of a dielectric to adhere to it of the box type and of an external connection terminal arranged thereon. Otherwise, in the case of a multilayer substrate, the external connection terminal surrounded by the conductors can be produced by placing a conductive pattern on an internal layer positioned below the external connection terminal, by cutting a pattern surrounding the terminal and by reaching the inner layer

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 after laminating and applying a conductive material in the cut pattern.

 Figure 1 is a perspective view of a basic embodiment of the present invention, parts of the substrate around the side and bottom conductors being removed.

 Figure 2 is a sectional view along line A-A of Figure 1.

 Figure 3 is a sectional view corresponding to Figure 2 showing another embodiment of the present invention.

 Figure 4 is a simplified diagram for roughly determining the capacitance between an external connection terminal and each side surface of an embodiment of the present invention.

 FIG. 5 is a perspective view of another embodiment of the present invention with the substrate parts around the lateral and bottom conductors being eliminated, as shown in FIG. 1.

 Figure 6 is a perspective view corresponding to Figure 5 showing yet another embodiment of the present invention.

 Figure 7 is a perspective view showing yet another embodiment of the present invention.

 Figure 8 is a sectional view of an embodiment in which spaces are provided inside a substrate of the present invention.

 Figure 9 is a sectional view of another embodiment in which spaces are provided inside a substrate of the present invention.

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Figure 10 is a top view of a probe card showing its entire construction.

 Several embodiments of the present invention will be described with reference to Figures 1 to 9. Figure 1 shows a basic embodiment of the present invention. In the same drawing, parts surrounding the substrate are removed to show the external connection terminal 1 and a conductive material 2, 3, 4 placed around it. The conductive material 2, 3, 4 is electrically connected and these are equipotential to each other. On the substrate, the external connection terminal 1 and the upper guard pattern 2 surrounding the terminal 1 can be seen, both being composed of a conductor. On the external connection terminal 1 and on the upper guard pattern 2, three contact pin elements 20, 21, 22 projecting from a test head of a semiconductor measuring device are positioned so as to be in contact with their corresponding targets. In this embodiment, the contact pin element 20 is a so-called "force" terminal for applying a voltage and measuring a current, the contact pin element 21 is a "detection" terminal "to take a voltage to be measured. These force and detection terminals provide a Kelvin connection. The contact pin element 22 is a guard pin for applying voltage to the upper guard pattern 2. The guard pin element 22 acts as a guard terminal in an active guard device in which it is held equipotential to force and detection terminals to block external influences above the external connection terminal or in a passive guard mechanism in which it is connected to a fixed voltage. The present invention is applicable to both guard mechanisms, whether active or passive. In FIG. 1, these force and detection terminals are placed on the same terminal

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 external connection 1. However, two external connection terminals can be provided separately for the detection and force terminals and each external connection terminal can be connected to a probe needle using a separate coaxial cable.

 FIG. 1 represents the external connection terminal 1 surrounded by the lateral conductors 3 and the bottom conductor 4. The lateral conductors 3 and the bottom conductor 4 are electrically connected to each other and also connected to the upper guard pattern 2. Ideally, the external connection terminal 1 is electromagnetically separated from a dielectric constituting the external substrate via the lateral conductors 3 and the bottom conductor 4. However, as will be described below, complete electromagnetic separation is not not required for certain specific embodiments of the present invention. A core wire of the coaxial cable 8 for connection with a probe needle is connected to an external connection terminal 1 and the other external conductor of the coaxial cable 8 is connected to the conductor 2.

 Figure 2 shows a sectional view along line A-A showing a sectional view of the substrate 10. As can be seen in Figure 2, the substrate consists of two layers. The surface of the first layer 5 defines the surface of the substrate 10 and the lower conductor 4 is disposed between the first layer 5 and the second layer 6.

This structure can be fabricated by providing the conductor 4 using plating or the like on the bottom of the first layer 5 or on the top of the second layer 6. The side conductor 3 can be formed using the plating or the like on faces created by cutting out part of the first layer 5. As a variant, the conductor can be formed by electrodeposition or the like on the lateral and lower faces

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 dielectric 7 to fit in the surface cut in the first layer 5.

 Examples of the materials which can be used to make substrate 10 include synthetic resins commonly used for electrical circuit substrates, for example, glass fiber reinforced polycarbonates, polyimides, epoxy glass resins and other products such as ceramics . Examples of the materials used for the dielectric to be placed in the substrate 10 to support the external connection terminal 1 thereon include synthetic resins similar to those used for the substrate 10 as well as materials having excellent insulating properties and dielectrics, such as PTFE. It is also possible to fabricate fine structures using materials other than those described above by applying fabrication technologies to produce integrated circuits and micromachining technologies.

 FIG. 3 represents another embodiment having a cross section different from that of FIG. 2. In this embodiment, air gaps 9 are arranged between the first layer 5 and the dielectric 7 supporting on it the connection terminal external 1.

These air gaps can greatly reduce the capacity between the external connection terminal 1 and the conductors 3,4.

In the configuration of Figure 2, assuming that the capacitance values Cl and C3, as shown in Figure 4 (A) between the external connection terminal 1 and the conductor 3 on its right and left sides are 10 pF, respectively, and assuming that the capacitance C2 between terminal 1 and the bottom conductor 4 is 10 pF, the total capacitance becomes 30 pF as the sum of these.

In the case where the air gaps 9 are provided, as shown in FIG. 4 (B), the capacitance values C12 and

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C32 corresponding to these air gaps 9 can be considered to be around 1 pF, respectively. Thus, for example, the capacitance Cl 'between the conductor on the left side 3 and the external connection terminal 1 is 0.9 pF as obtained by the following equation: Cl' = C12 * Cl / (C12 + Cl) = 0.9 pF
Consequently, the total capacity is approximately 11.8 pF as obtained by Cl '+ C2 + C3' (C3 is the capacity between the conductor on the right side 3 and the external connection terminal 1), thereby reducing significantly total capacity.

 In the structures shown in FIGS. 1 to 3, each lateral conductor 3 can protrude from the surface of the substrate (not specifically shown). In such a structure, when the contact pin elements 20, 21, 22 contact the surface of the substrate, these pin elements may not be seen from the outside and an electromagnetic protection may be provided between these contact pin elements. .

 FIG. 5 shows another embodiment in which the external connection terminals 31, 32 can only be in areas where the contact pin elements 20, 21 for connection to an external measurement device will be in contact with the latter . The connection between these terminals 31, 32 is provided by a conduction path 35 formed in the substrate. Terminal 33 can connect to a probe needle via a coaxial cable. In this embodiment, higher shielding properties can be obtained by forming a conductive pattern 34 which serves as an upper guard just near the periphery of the external connection terminals 31, 32, 33.

Thus, the contact pin element 22 for measuring a guard potential can contact an upper shield 34.

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In addition, the connection to a probe needle via a coaxial cable 8 can be replaced by a shielded conductive path formed in the substrate.

 A partially or fully meshed part, cut parts 41 and notched parts 42 in the lateral conductor 3 are shown in Figures 6 (A) to 6 (C), respectively. The conductive path 35 inside the substrate, as shown in FIG. 5, can be arranged through the cut parts 41 or the notched parts 42 from the outside of the support structure of the connection terminal external 1. In another embodiment of the present invention, one of the lateral surfaces corresponding to the lateral conductors 3 of the dielectric supporting the external connection terminal 1 thereon can be opened at a location covering all the surfaces including the underside with the driver. Such a structure is preferred for ease of manufacture and flexibility of design.

 In Figures 1 to 3, substrates 10 with two-layer structures are shown as examples. Substrates having structures of three or more layers, however, can also be applied to the present invention and it is possible to use more complex structures using substrates with a number of layers. In a first example of these cases, it is possible to propose a structure in which the external connection terminal 1 is positioned lower than the surface of the substrate 10, as shown in FIG. 7. In FIG. 7, four faces sides of the substrate 10 are removed leaving the guard pattern 2. The level of the external connection terminal 1 is lowered, while the lateral conductor 3 on the wall surfaces of the substrate 10 around the external connection terminal 1 exceeds it. So when the contact pin elements

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 20, 21 touch terminal 1, the lateral conductors 3 serve as electromagnetic shielding for the contact pin elements 20,21 to prevent dielectric absorption resulting from potential differences between the components of the adjoining external connection terminals and the brooch.

 As described with reference to Figures 3 and 4, by providing air gaps around the dielectric supporting the external connection terminal thereon, the capacity between the external connection terminal and the surrounding conductor can be significantly reduced. The effects of dust fixation on the air gap and moisture surfaces and the like can cause deterioration of the insulating resistance and dielectric absorption properties. To prevent such unwanted effects, the air gaps or spaces can be sealed. Figures 8 and 9 show sectional views of these structures, respectively. In the structures of FIGS. 8 and 9, an external connection terminal 51 extends upwards to the interior of the substrate 10. The external connection terminal 51 is supported by a support dielectric 52 embedded in the substrate 10 Spaces or air gaps 54 are sealed by dielectric layers 53, respectively. In the air gaps or sealed spaces 54, dry air or an inert gas is placed. The external connection terminal 51 is exposed on the surface of the substrate and the upper guard conductor patterns 55 are formed surrounding the exposed part. In FIG. 8, the support dielectric 52 is in contact with the lateral and lower conductors 56, 57. In FIG. 9, the support dielectric 52 is in contact with the lower conductor 57 but is not in contact with the lateral conductor 56. The structure as shown in FIGS. 8 and 9, is generally similar to the structure or principle of shielded wires. Consequently, using such a structure to

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 the place of connection via coaxial cables or shielded cables means that it is also possible to connect the external connection terminal 51 with a probe needle.

 The present invention has been described with reference to a number of embodiments above. It is also possible, in specific applications, to replace the coaxial cable with a single core cable with a highly insulating coating typically represented by PTFE (Teflon @) or the like which must be used for connection to a probe needle.

 The probe card of the present invention as described above can reduce the waiting time resulting from the dielectric absorption occurring between the different electrical potentials and reduce the leakage current under normal conditions to a negligible level. In addition, since the insulating body placed between the different potentials can be protected by conductors, variations in the micro-current properties for each probe card or each contact pin element due to the inherent nature of the insulating body or methods of non-regular manufacturing can be prevented.

 Reference may be made to the entire description of Japanese patent application no. 2000-36626 filed on February 15, 2000 including the specification, the claims, the drawings and the summary.

Claims (8)

 CLAIMS 1. Probe card comprising a substrate (10) and an external connection terminal (1) placed on a dielectric support material disposed in the substrate (10), characterized in that the external connection terminal (1) is surrounded by a conductor (3,4) disposed between the substrate (10) and the dielectric support material and a dielectric material of the substrate body and the dielectric support material for supporting the external connection terminal (1) are separated l 'from each other via the conductor (3,4). 2. Probe card according to claim 1, characterized in that the conductor (3,4) comprises at least one lower conductor arranged on a bottom of a recess formed in the substrate to receive the dielectric support material and a lateral conductor disposed on the lateral faces of the recess and a space or gap (9) is disposed between said dielectric support material and the lateral conductor. 3. Probe card according to claim 2, characterized in that the air gap or space (9) is sealed with a dielectric material from the outside of the substrate (10). 4. probe card according to claim 1, characterized in that the probe card comprises two or more external connection terminals (31,32) and the electrical connection between these external connection terminals (31,32) is ensured by the electrical connection arranged inside the substrate (10). <Desc / Clms Page number 19>  5. Probe card according to claim 1, characterized in that said conductor (3, 4) comprises meshed parts or cut parts. 6. Probe card according to claim 1, characterized in that said external terminal is placed at a lower level over a predetermined distance than the surface of the body of the substrate (10). 7. Probe card according to claim 6, characterized in that said conductor is connected to a guard terminal. 8. Probe card according to claim 7, characterized in that said guard terminal is provided with an active guard.