JP4498368B2 - Micro contact type prober - Google Patents

Description

  The present invention relates to a probe of a contact-type circuit test prober, position control of the probe, and pushing force control.

As a conventional technique, a probe of a contact type circuit test prober has a probe-like contact [113] attached to the tip of a metal elastic cantilever [112] as shown in FIG. In order to align the probe with an arbitrary measurement point of the LSI circuit, the probe has a moving mechanism [111] such as an XYZ stage at the base of the probe. In order to measure multiple points simultaneously, a plurality of electrical signals are obtained from measurement terminals arranged in an array at regular intervals as shown in FIG. As an alignment method, the measurement terminal of the subject and the probe are placed in the same field of view of the long-focus objective lens [115], and the measurement terminal of the subject or the probe is moved by a moving mechanism such as a stage. The probe was pressed against the measurement terminal to perform electrical measurement.
Japanese Patent Laid-Open No. 10-27832

  When the circuit of the subject is miniaturized and the cell size of the memory to be inspected becomes 1 μm × 1 μm or less, it becomes difficult to process the cantilever and the contact with the metal cantilever. It was. In the case of inspection of memory cells in which the cells are arranged at equal intervals of 2 to 5 μm, it is difficult to arrange a plurality of metal probes next to each other.

  Further, in the probe currently used, the pressing pressure on the subject surface becomes sharp unless the pressing force is controlled because the probe becomes sharp due to the miniaturization of the cell. For example, in the case of a memory cell made by depositing a ferroelectric thin film under an electrode like FeRAM, or in a structure in which an organic thin film is arranged under an electrode like TFT liquid crystal, The possibility of damaging the thin film increases, and it is necessary to control the minute pressing force. Also, when multiple probes are arranged next to each other, if the tips of the contacts are not aligned, the probe pressing depth will vary, and the pressing force of each probe will vary, resulting in poor contact due to insufficient pressing. , Film damage due to excessive pressing occurs.

  Further, when the cell size is reduced to 0.5 μm × 0.5 μm or less, the current optical microscope has insufficient resolution and alignment becomes difficult.

  In order to solve the above-mentioned problems, the present invention uses a micro probe based on silicon based on a microfabrication process used in an atomic force microscope (AFM) and the like, instead of a conventional metal probe. . This probe (cantilever part) has a measuring cantilever in which a plurality of contacts are made on one cantilever for simultaneous measurement of a plurality of object measuring terminals, and an object measuring terminal on both sides of the cantilever. The structure has a long cantilever for controlling the Z distance between the surface and the contact.

  The Z distance control cantilever was used to control the moving speed of the contact to the subject measurement terminal, and the pressing force control was performed so that the amount of deflection of the measurement cantilever was constant.

  To align the contact with the measurement terminal, create an alignment mark on the measurement cantilever, and align the mark with an optical microscope so that each contact is directly above the measurement terminal. Arranged a relationship.

  Furthermore, in order to align with a resolution higher than that of an optical microscope, the Z-distance control cantilever at one end is operated in the same manner as the AFM probe to measure the cell shape and confirm the cell position. Since the positional relationship between the probe and the contact of the cantilever for measurement is known, the contact can be positioned directly above the cell.

  Next, in order to perform reliable contact, a plurality of forested carbon nanotubes were employed as contacts.

  The Z distance control cantilever has conductivity and is longer than the measurement cantilever. For example, as shown in FIG. 1, a plurality of cantilevers are formed on the same chip. The displacement detection of these cantilevers may be a self-displacement type using piezoresistive resistance as described in the paper of M. Tortonese, RC Barrett, CF Quate Appl. Phys. Lett. 62 (8) 1993, 834, Alternatively, an external displacement detector such as an optical lever detector may be used.

  These cantilevers are initially several millimeters away from the subject measurement terminal. These cantilevers are brought close to the subject measurement terminal surface at high speed. First, the long Z-distance control cantilever comes into contact with the subject measurement terminal surface, and generates a deflection signal. The feed speed of Z coarse movement is switched to a low speed by this deflection signal. Next, a measurement cantilever with a contact is brought into contact with the subject measurement terminal surface, and then low-speed feeding is performed until the pushing force enters the set amount range. Here, the contact between the contact and the measurement terminal is electrically confirmed, and the operation of each subject is confirmed. The present invention will be described in more detail below.

  Embodiments of the present invention will be described below with reference to the drawings with reference to FIGS. 3, 4, 9 and 10. FIG. 3 is a schematic diagram of a probe (cantilever part) portion of a micro prober. FIG. 5 is a schematic diagram of detailed description of the probe, and FIG. 9 is a schematic diagram of the probe of the micro prober device, its position control mechanism (XYZ scanning scanner), and its control system. FIG. 10 is an operation time cheat.

<Configuration of cantilever part>
The structure of the cantilever part shown in FIGS. 1, 2, 3, 4, 5, 6, 7, and 8 will be described. FIGS. 1 and 2 show a cantilever part that uses an external lever detector, for example, to detect the displacement of the cantilever. FIG. 3 shows the outer shape of the cantilever as in FIG. 1, but the displacement detection is embedded inside the cantilever. It is another embodiment using the self-detection cantilever performed by the piezoresistor [72]. A constant current is passed through the piezoresistor [72], distortion due to displacement of the cantilever is captured as a change in piezoresistance, and is detected as a current change by a bridge circuit. FIG. 4 shows another embodiment of a cantilever portion having three or more cantilevers. The distance control cantilevers are provided at both ends, and a plurality of measurement cantilevers are provided at the center, and each measurement cantilever has a plurality of contacts.

  The distance between the contacts on the adjacent cantilevers is arranged to be an integral multiple of the cell distance to be measured. Also, the reason why the measuring cantilever is composed of a plurality is that the spring constant of the cantilever is reduced, and when the cantilever part is tilted with respect to the cell to be measured, the pushing amount is adjusted with each cantilever and the pushing force is adjusted. Because.

  This will be described below with reference to FIGS. The cantilever part has a long cantilever [c1] (length 11: 400 to 1000 μm) for Z distance control and a short measurement cantilever [c2] (length l2: 100 to 500 μm) with a contact. ) Are arranged next to each other (the distance between the cantilever probe [40] and the contact [3] is an integral multiple of the cell pitch). The Z-distance control cantilever is coated with a conductive metal such as gold to the tip of the needle to provide conductivity.

  When the cantilever is viewed from the side as shown in FIG. 2, when the cantilever [c1] for Z distance control is in contact with the sample surface, the cantilever for measurement [c2] c1] sample surface by height h <100 to 300 μm (h = (l1-l2) sin θ; l1: length of cantilever for Z distance control, l2: cantilever length for measurement, θ: cantilever mounting angle) The structure is more floating. The cantilever [c1] for Z distance control has a tip radius of about 100 to 200 nm and a spring constant of 0.01 to 0.1 N / m. Since the spring constant is soft, even if the Z-distance control cantilever is brought into contact with the sample surface at high speed, the cantilever is hardly damaged or damaged.

  Next, details of the measurement cantilever including the arrangement and configuration of the contact shown in FIG. 5 will be described. The contact [3] is a protrusion having a height of about 10 μm, the tip radius is 100 to 200 nm, and the metal coating [31] is applied only to this protrusion. This metal coating is wired [50] to the cantilever base [70] and is connected to the connecting pad [60] at the base. An external electrical tester (FIG. 9 [12]) is connected to the pad, and various test signals can be applied between the contact and the measurement terminal. Also, as shown in the plan view of FIG. 6, the insulation [75] between the contacts is separated by silicon oxide. Further, the surface of the contact and the surface on the opposite side of the contact are separated by a silicon oxide film [75] as shown in the sectional view of FIG. 7, and the cantilever surface on the opposite side of the contact is coated with metal [76. It can be connected to ground potential and can serve as a shield electrode.

  The interval between adjacent contacts is made equal to the cell pitch to be inspected or an integer multiple of the pitch.

  FIG. 8 shows another embodiment in which a plurality of carbon nanotubes [33] are formed as a contact. In this case, the contactor is made by patterning a 1-3 μm square iron-based catalyst on the base [71] of the silicon cantilever [32] and vapor-growing at 700 to 1000 ° C. in a hydrocarbon atmosphere such as ethane. A large number of carbon nanotubes having a uniform length perpendicular to the substrate grow from the patterning with the iron-based catalyst. The carbon nanotubes are conductive, and the iron-based catalyst at the base and the cantilever base [70] may be wired with a thin metal wire [50], and the insulation [75] between the contacts may be separated by silicon oxide. When carbon nanotubes are used as contacts, a voltage can be applied stably without the coating material popping out by field evaporation compared to a metal-coated contact. In addition, the carbon nanotubes themselves are elastic and robust so that they can withstand multiple contact.

<Main equipment configuration>
The configuration of the main part of the apparatus will be described with reference to FIG. An XYZ scanning scanner [2] is fixed to a moving mechanism (Z coarse movement mechanism) [1] for bringing the cantilever close to the sample, and a cantilever base [70] is attached to the tip thereof. Further, the subject [6] is electrically connected to the sample stage [5] by the sample stage contact [4], and is arranged to face the cantilever portion. In FIG. 9, cantilevers [c1] and [c2] are depicted as self-detecting cantilevers. The displacement signal of the measurement cantilever [c2] shown in FIG. 9 is amplified by the preamplifier [7] and input to the Z servo system [8]. The output signal is amplified by the Z scanning controller [11]. As a result, the Z axis of the XYZ scanning scanner [2] expands and contracts, and the amount of deflection of the measuring cantilever becomes constant, between the contact [3] and the measuring terminal. The distance of [6] is controlled. On the other hand, the signal from the Z distance control cantilever [c1] shown in FIG. 9 is similarly amplified by the preamplifier [7] and input to [9] to the Z coarse motion controller, as a control signal for the Z coarse motion mechanism [1]. It is used. The Z coarse movement mechanism is mainly composed of a mechanical system such as a differential screw and a reduction lever, and can move about mm in steps of 0.1 to 0.05 μm. Here, from a few mm to 0.1 to 0.3 mm on the measurement terminal surface, the Z coarse movement mechanism [1] is controlled to send at high speed, and the remaining 0.1 to 0.3 mm or less is controlled to be sent at low speed.

<Distance control operation and contact pushing force adjustment>
Next, the operation of the Z coarse movement will be described with reference to the time charts of FIGS. Initially, the cantilever part is several mm away from the sample surface. When the Z coarse motion system mechanism [1] is moved at high speed and the Z distance control cantilever [c1] is in contact with the sample surface as shown in FIG. 1 [FIG. 10: t0], the Z distance control cantilever is the measurement terminal. The displacement signal of the cantilever changes due to the force from the surface. This signal is input to the Z coarse motion controller [9], and the Z coarse motion system mechanism [1] is switched to the low speed feed. At this time [FIG. 10: t0], the measurement cantilever [c2] floats from the sample surface by approximately h. Next, the measurement cantilever [c2] is pushed in at a low speed by approximately h> 100 to 300 μm (h: difference in height between the Z-distance control cantilever and the measurement cantilever from the subject surface). [FIG. 10: t1] Thereafter, the contactor is pushed into the object measurement terminal surface by Δh [FIG. 10: t2]. At this time, the measurement cantilever receives a force from the measurement terminal surface, and the displacement signal of the cantilever changes. The pressing force is obtained by multiplying the spring constant of the measuring cantilever by Δh (cantilever pressing depth), and this amount can be controlled by a pressing force setting signal indicated by asterisks in FIG.

  Finally, when using the cantilever portion having a plurality of measurement cantilevers shown in FIG. 4, if the OR signals of the Z distance control cantilevers [c1] and [c1 ′] at both ends are taken, the cantilever base tilts. The Z distance control cantilever signal closer to the sample surface may be used as the signal for the Z coarse motion controller [9].

  After contact with the measurement terminal of the subject and adjustment of the pressing force (after t2), various test signals are applied between the contact and the measurement terminal from the external electrical tester [12] to perform electrical evaluation of the subject. .

<Alignment with measurement cell>
Here, the description will be made on the assumption that the subject is a two-dimensional array of spatially similar shapes such as memory cells.

  The dimensions of each part of the cantilever for cell measurement are made as follows. The contacts on the measurement cantilever are arranged at equal intervals with the cell pitch or an integer multiple of the pitch, and the distance between the needle tip of the cantilever for Z distance control and the contact is an integer multiple of the cell. Include. In addition, an alignment mark [Fig. 6: 76] (size: 1 μm × 1 μm or more) having a fixed positional relationship with the contact is created on the back surface or side surface of the measurement cantilever and used as a guide for alignment in a microscope. use.

  For fine alignment with the cell, fine adjustment of the XY position is performed by applying a voltage to the XY axes of the XYZ scanning scanner while observing with an optical microscope so that the contact on the measurement cantilever is directly above the cell. . If the cell is too small to be seen with an optical microscope, the Z distance control cantilever is scanned in XY, the Z scanner is controlled so that the displacement of this cantilever is constant, and the cell operates in the same way as the AFM. Can be obtained. Based on the shape of the cell, the positional relationship between the contact and the cell is obtained, and alignment is possible.

  According to the present invention, electrical evaluation can be performed by directly contacting each miniaturized cell using the micro probe as described above. In addition, since the pressing force is controlled, electrical evaluation can be performed without causing contact failure due to insufficient pressing or damage to the thin film of the cell due to excessive pressing.

  Further, when the resolution of the optical microscope is insufficient, the cell shape can be obtained by the same operation as that of the AFM, and the contact can be accurately positioned on the cell.

It is a perspective view of the probe (cantilever part) for external detectors. It is a side view of the probe (cantilever part) for external detectors. (A) is a perspective view of a probe using a self-detecting cantilever, and (b) is a cross-sectional view taken along line A-A ′ in (a). It is a model drawing of a probe having three or more cantilevers. (A) is a perspective view of a measurement cantilever, (b) is a view seen from the A direction in (a). It is a top view of a measurement cantilever. It is sectional drawing of the measurement cantilever. (A) is a perspective view of a measurement cantilever using a carbon nanotube as a contact, and (b) is a view as seen from the A direction in (a). It is a schematic diagram of the prober apparatus of this invention. Time cheat when the probe is close. It is a schematic diagram of the probe of the conventional prober. It is the schematic diagram of the prober which has arranged the probe in the conventional array type.

Explanation of symbols

1 Z coarse movement mechanism 2 XYZ fine movement scanner 3 Probe (cantilever part)
4 Contact of Sample Table 5 Sample Table 6 Subject 7 Preamplifier 8 Z Servo System 9 Z Coarse Motion Controller 10 XY Scan Controller 11 Z Scan Controller 12 External Electric Circuit 20 Control Computer ☆ Marking Force Setting Signal

Claims (10)

A cantilever base,
One or a plurality of measurements for supporting an electrical test using the plurality of contacts supported by the cantilever base and having a tip radius of 100 to 200 nm and wired so that signal transmission is possible. For cantilevers,
An arm that is supported by the cantilever base and has a longer arm than the measurement cantilever, and is provided on both sides of the one or more measurement cantilevers to acquire information in the height direction with respect to the subject measurement terminal surface. Two Z-distance control cantilevers;
A Z coarse movement mechanism that enables movement of the cantilever in the Z-axis direction ,
Of the two Z distance control cantilever earliest said by Z distance control cantilever which has reached the object measurement terminal surface to obtain information in the height direction of the subject measured terminal surface, based on the information and have Dzu, the cantilever is brought into contact with contacts provided in the measuring cantilever by controlling movement by the Z coarse adjustment mechanism in the subject measurement terminal surface, to perform the electrical test by the measurement cantilever in this state A micro-contact prober featuring Wherein the Z distance control cantilever is brought close to the object measurement terminal surface at high speed, when the Z distance system cantilever comes into contact with the object measurement terminal surface, to generate a more deflection signals to the information from the object measurement terminal surface , and the deflection signal to trigger switching access to the object measurement terminal surface to the low speed,
The measurement cantilever is brought close to the subject measurement terminal surface at a low speed, the subject measurement terminal surface is brought into contact with the contact,
2. The microcontact prober according to claim 1, wherein when the pushing force of the contact to the subject measurement terminal surface reaches a predetermined value, the contact between the contact and the measurement terminal is electrically confirmed. 3. The microcontact prober according to claim 1, wherein each contact provided on the measurement cantilever is insulated from each other, including wiring connected thereto. 4. The microcontact prober according to any one of claims 1 to 3, wherein insulation between the contacts is made by a silicon oxide layer of an SOI substrate. The microcontact prober according to any one of claims 1 to 4, wherein the measurement cantilever has contacts arranged at an interval substantially equal to an arrangement interval of each cell to be measured or an integer multiple thereof. The microcontact prober according to any one of claims 1 to 5 , wherein the contact is made of carbon nanotubes. The microcontact prober according to claim 6, wherein the contact is composed of a plurality of forested carbon nanotubes. The micro contact prober according to any one of claims 1 to 7, wherein the measurement cantilever has a surface on which a contact is provided and a back surface insulated from each other, and the back surface is coated with a metal film. The measurement cantilever has a guide mark for controlling the position of the measurement cantilever with respect to the subject measurement terminal surface using an optical microscope on at least one of the side surface and the back surface of the surface provided with the contact. The microcontact type prober according to any one of claims 1 to 8 . 10. The microcontact prober according to claim 1 , comprising at least one of a piezo scanner operating in the XY direction and a piezo scanner operating in the Z direction for controlling the micro position of the measurement cantilever. .

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