JPH07253435A - Manufacture of probe - Google Patents

Abstract

PURPOSE:To manufacture a probe of a structure in which a chip surface of a packaged semiconductor integrated circuit can be inspected in the probe of a scanning tunneling microscope, an interatomic force microscope or an apparatus using them. CONSTITUTION:A probe has a tip 3 formed of a silicon structure 1 cut from a silicon substrate 2 and of a protrusion having a sharp end at an end of a cantilever 4. The structure 1 is so manufactured that an axial direction of the tip 3 is perpendicular to an orientation of the substrate 2, and then the end of the tip 2 is sharpened.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a probe for a scanning tunneling microscope, an atomic force microscope, or an apparatus using them, and more particularly to a probe suitable for measuring a chip surface of a packaged semiconductor integrated circuit. And a manufacturing method thereof.

[0002]

2. Description of the Related Art FIG. 6 is an explanatory view of a conventional example. In the figure, 3 is a tip, 4 is a cantilever, 5 is a probe substrate, 12 is a package, 13 is an IC chip, and 14 is a convex portion on the IC surface, for example, wiring.

A scanning tunneling microscope (STM) invented by G. Binnig et al.
, For example, U.S. Pat. No. 4,343,993), Atomic Force Microscope (AFM: Atomic Force Microscope, for example, U.S. Pat. No. 4,724,318, or G. Binnig, CFQuate, C. Gerber:
Phys.Rev.Lett.56, P930, 1986) is capable of measuring physical and physical properties of a sample surface with ultra-high spatial resolution of atomic order, and many applications have been tried.

One of the important applications is the field of semiconductor integrated circuits. By using the AFM, the unevenness on the surface of the semiconductor integrated circuit can be measured with high resolution, which is useful for process evaluation, failure analysis, and the like.

Further, recently, application to measurement of an internal signal voltage of a semiconductor integrated circuit in operation has been considered. In developing and manufacturing a semiconductor integrated circuit, it is indispensable to test the element to find out the cause when there is a malfunction (fault analysis). In recent years, high integration of LSI and increase of I / O pins As a result, it has become difficult to perform accurate design verification and failure analysis only by measuring the signals of I / O pins of LSI testers and the like.

Therefore, the voltage of fine wiring in the device is measured. A device using an electron beam is known as a device suitable for measuring a voltage of a fine wiring inside a semiconductor integrated circuit chip. However, as a semiconductor integrated circuit is highly integrated and speeded up, measurement speed and time resolution are improved. It is becoming insufficient. Technologies using light beams (eg JA
Valdmanis; Electron.Lett.23,1308-1310,1987), but the spatial resolution determined by the wavelength limitation is insufficient.
Not applicable to LSI.

The inventor of the present invention has applied the AFM technique and has proposed a voltage measuring device with a high spatial resolution by means of a light beam, which has the functions of the wiring search and the probe positioning by the conductive fine probe. (JP-A-5-251524: Probe device and integrated circuit inspection device) Further, a method of measuring a wiring voltage by sampling an electrostatic force acting between a conductive microprobe and a wiring with an AFM cantilever (for example,
ASHou et al; Ultrafast Elrctronics & Optoelectro
nics (Jan. 1993), WA4) is also proposed. These methods have higher sensitivity and faster LS than conventional electron beam testers.
I is expected to become an internal diagnosis technology.

There are many methods for manufacturing a probe for the above-mentioned scanning tunneling microscope, atomic force microscope, and devices to which these are applied. According to the method of manufacturing the probe made of all silicon from the silicon wafer by using the semiconductor process, it is possible to manufacture a large number of probes with good reproducibility.

[0009]

For example, as shown in FIG. 6 (c), the AFM probe base 5 is generally provided with a microneedle (tip) 3 having a height of several μm and a tip diameter of about 0.1 μm. To prepare for, for example, a spring constant of 0.1-10N /
It has a structure in which a cantilever (cantilever) 4 having a length of m and a length of several hundred μm is attached to a probe base 5. Probe base 5
The length is a few mm.

As shown in FIG. 6 (a), the probe is used by tilting it at a certain angle (for example, 10 °). This allows
If the sample surface is flat (for example, a silicon wafer on which a circuit is formed), only the tip 3 at the tip of the probe base 5 contacts the IC chip 13 that is the sample. However,
When the IC chip 13 fixed to the package 12 is measured, if the IC chip 13 is at a position deeper than the surface of the package 12 (for example, 1 mm lower side), the probe base 5,
Alternatively, since the bottom surface of the probe holder is in contact with the surface of the package 12, the tip 3 of the tip of the probe base 5 cannot be in contact with the surface of the IC chip 13, that is, there is an unobservable region. In addition, IC chip 13
When is deep inside the package 12, no observation is possible. In this way, the package 12 of the IC chip 13
An unobservable region occurs on the surface of the IC chip 13 depending on the internal depth and the chip area.

Although it is considered that this problem can be alleviated by increasing the inclination of the probe, another problem as shown in FIG. 6B occurs. That is, depending on the tilt of the probe,
Since the tape 3 also tilts with respect to the surface of the IC chip 13, the IC chip 13 can be used when measuring the image or line profile.
There is a problem that the observed image is distorted because the force acts between the wall surface of the convex portion such as the surface pad and the wiring 14 and the wall surface of the tape 3, that is, the spatial resolution is lowered. Become.

It is an object of the present invention to provide a method for manufacturing a probe that does not have the above problems.

[0013]

FIG. 1 is a diagram for explaining the principle of the present invention. In the figure, 1 is a silicon structure, 3 is a tip, 4 is a cantilever, 5 is a probe base, and 6 is a parallel leaf spring.

FIG. 1 (a) shows an example of the AFM probe shape suitable for measuring a sample having large irregularities such as observing an IC chip fixed to a package. The tip 3, which is a microprobe, is installed almost vertically to the sample surface, the width of the probe in the direction perpendicular to the tip 3 is short, and the entire probe is held by the upper part of the probe base 5 (the end opposite to the tip). Is desirable. When the cantilever 4 is formed in a direction substantially perpendicular to the tip 3 (parallel to the horizontal surface of the sample),
It is desirable to provide the tip 3 having a length such that the cantilever 4 does not come into contact with the sample. If the length of the tip 3 is too long to be ignored compared to the cantilever 4, the cantilever 4 is likely to be twisted. If this becomes a problem, it is desirable to use two parallel leaf springs 6 instead of the cantilever as shown in FIG.

Conventionally, when manufacturing an all-silicon probe, as shown in FIG. 6C of the conventional example, etching is performed so that the axis of the tip 3 is formed perpendicular to the surface of the silicon substrate 2. Has been processed. in this way,
For example, it is extremely difficult to manufacture the tip 3 having a long length of 100 μm. Further, it is almost impossible to manufacture the parallel leaf spring 6 as shown in FIG.

[0016]

According to the present invention, as shown in FIG. 2 (d), the axial direction of the projection which is the base of the tip is orthogonal to the plane direction of the silicon substrate (the tip axis direction is parallel to the silicon substrate surface). Silicon structure, and then
The step of sharpening the tip of the protrusion is provided, and an axial cross section of the tip is formed on the silicon substrate surface.

Therefore, a large number of tips having a long shaft can be precisely manufactured.

[0018]

2 to 5 are explanatory views of the first to third embodiments of the present invention. In the figure, 1 is a silicon structure, 2 is a silicon substrate, 3 is a tip, 4 is a cantilever, 5
Is a probe substrate, 6 is a parallel leaf spring, 7 is a leaf spring, 8 is a mask, 9 is a milling ion, 10 is an impurity doped layer, and 11 is an electrode.

A first embodiment of the probe manufacturing method of the present invention will be described with reference to FIGS. 2A to 2C are sectional views of a part of the silicon substrate 2, FIG. 2D is a perspective view of the structure, and FIG. 3 is a sectional view of the probe 5.

As shown in FIG. 2A, the first step of manufacturing a silicon structure is, for example, using a silicon substrate (wafer) 2 having a (110) orientation, and using a silicon substrate as shown in FIG. After forming the mask 8 corresponding to the cross-sectional shape of the probe structure on the substrate 2, anisotropic etching is performed with a KOH solution or a mixed solution of ethylenediamine: pyrocatechol: water to a depth corresponding to a desired thickness of the probe. Thereby, the silicon structure 1 perpendicular to the surface of the silicon substrate 2 is formed.

After that, as shown in FIG. 2C, the silicon substrate 2 is polished from the back surface by combined use of lapping, polishing and etching on the entire surface to form the silicon structure 1 as shown in FIG.
Then, as shown in a perspective view in (d), the protrusion that is the base of the probe is separated so as to be exposed.

As shown in FIG. 1 (a), in the method of the present invention, the length of the tip 3 of the silicon structure 1 is at least 50 μm or more, and the length of the probe base 5 including the tip 3 is also at least. It can be 500 μm or more.

The step of manufacturing the tip 3 by sharpening the tips of the protrusions in the second step is performed by ion milling, as shown in FIG. For example, using argon ions as the milling ions 9 and utilizing the property that the etching rate depends on the tip angle of the tip 3, the tip of the tip 3 of the probe substrate 5 can be sharpened as shown in FIG.
Furthermore, it is possible to manufacture the tip 3 having a sharpened tip by removing the tip of the protrusion after thermal oxidation or thermal nitriding.

The method of forming the silicon structure 1 in the first step is not limited to the above. For example, general (100)
Even on the surface silicon substrate 2, by devising the mask orientation, etc.
It is possible to form a silicon structure 1 whose major plane, ie the axis of the tip 3, is parallel to the plane of the silicon substrate 2. In addition to the wet etching described above, anisotropic dry etching by RIE may be used.

According to the present invention, in addition to the probe having the cantilever 4 as shown in FIG. 3, a probe having a structure in which the parallel leaf spring 6 forming a bridge supports the tip 3 as shown in FIG. 4 can be manufactured. There is also a structure in which the tip 3 is supported by one leaf spring 7 forming a bridge as shown in FIG. In these cases, the central part of the bridge moves in the vertical direction by the movement of the tip 3
The tip displacement measurement by an optical lever such as FM has low measurement sensitivity.

In FIG. 4, the silicon substrate 2 is not doped with impurities, and an impurity-doped layer 10 in which impurities are selectively doped is formed on only one of the parallel leaf springs 6 forming a bridge. By forming the pattern 11 and connecting it to the impurity-doped layer 10, a strain gauge utilizing the piezoresistive effect and shape change of silicon can be formed. Then, the probe displacement can be measured by measuring the change in the resistance value of this portion with, for example, a bridge circuit.

Further, the cantilever 4 shown in FIG. 3 and FIG.
Similarly, in the leaf spring 7 shown in FIG. 5, the deep needle displacement can be measured by utilizing the resistance change due to the deformation of the semiconductor caused by the shape change and the sum of the piezoresistive effects due to the introduction of impurities.

According to the present invention, as described in the embodiment,
By cutting out the silicon structure parallel to the silicon substrate surface, a probe with a long tip can be formed, and various types of spring elements can be attached to the probe, so it is possible to detect the displacement of the probe with high sensitivity. Can be done.

The probe manufactured by the method of manufacturing a probe according to the present invention can be applied to an STM or an apparatus to which the STM is applied.

[0030]

Industrial Applicability Since a probe with a long tip capable of measuring a sample such as an IC chip having a large unevenness such as an LSI mounted in a package can be manufactured, a scanning tunneling microscope, an atomic force microscope, and these are applied. The probe of the present invention can be used in a device, and can greatly contribute to and contribute to quality control and improvement in reliability of semiconductor devices such as LSIs.

[Brief description of drawings]

FIG. 1 is an explanatory view of the principle of the present invention.

FIG. 2 is an explanatory diagram of the first embodiment of the present invention (No. 1)

FIG. 3 is an explanatory diagram of the first embodiment of the present invention (part 2).

FIG. 4 is an explanatory diagram of a second embodiment of the present invention.

FIG. 5 is an explanatory diagram of a third embodiment of the present invention.

FIG. 6 is an explanatory diagram of a conventional example.

[Explanation of symbols]

 1 Silicon Structure 2 Silicon Substrate 3 Tips 4 Cantilever 5 Probe Base 6 Parallel Leaf Spring 7 Leaf Spring 8 Mask 9 Milling Ion 10 Impurity Doped Layer 11 Electrode

Claims (1)

[Claims] 1. A tip (3) formed of a silicon structure (1) cut out from a silicon substrate (2) and having a pointed tip is provided at the tip of a cantilever (4). In the probe, the silicon structure (1) is manufactured so that the axial direction of the tip (3) is orthogonal to the plane orientation of the silicon substrate (2), and then the tip of the tip (3) is sharpened. A method of manufacturing a probe, which comprises: