JPS63262516A - Positioning stage of sample - Google Patents

Abstract

PURPOSE:To simplify a vacuum vessel itself and to improve the efficiency and reliability of a test, by a construction wherein a movable stage having a tubular sample block put in with an O-ring interposed is disposed outside a space of the vacuum vessel. CONSTITUTION:A through hole in which a tubular sample block 3 is put is formed in the center of a base board 8 of a vacuum vessel 9, and an airtight sealing element of an O-ring 13 is formed between this through hole and the sample block 3. Outside a space of the vacuum vessel, a movable stage 6 having the tubular sample block 3 put in with an O-ring 4 interposed is disposed. The movable stage 6 constitutes a part of the base board 8 of the vacuum vessel 9, and a lubricating sealing surface 5 having a small sliding friction coefficient in relation to the O-ring 4 is formed on the periphery of the stage 6. A movable stage 15 in the direction Y is provided in relation to the movable stage 6 in the direction X, and these stages are driven by surbo motors.

Description

[Detailed Description of the Invention] [Summary] A sample to be inspected, such as an IC, is mounted on a sample stage that can freely move on an XV plane in a high vacuum.
Regarding the sample positioning mechanism of electron beam probing equipment for diagnostic testing of LSI etc., X
This simplifies the positioning of the sample in the Y plane and its driving mechanism, and improves the reliability of the test.

[Industrial application field]

The present invention relates to a sample positioning stage for inspecting samples such as ICs and LSIs in vacuum.

Recently, for example, in the testing of LSI devices, due to the increase in density, the line width of the pattern inside the chip device is 1 μm!
! i! Due to the ultra-fine dimensions of the device, probing using conventional mechanical probe methods cannot be used due to the risk of destroying the internal pattern of the device.
The intensity of secondary electrons generated by irradiation with an electron beam (electron beam) is measured to measure the potential distribution and its absolute value at a specific position of the ultrafine pattern of the element.

In electron beam probing, a sample is mounted on a stage in a high vacuum, and the mounted stage is freely stepped in the XY plane to determine its position.

The present invention presents a stage positioning mechanism that is useful when applied to diagnostic tests of LSIs and ICs, failure analysis, and the like.

[Conventional technology]

FIG. 4 is a side sectional view of a conventional sample positioning stage in a vacuum chamber. An overview of the stage configuration and test equipment will be explained using figures.

In the figure, a vacuum chamber 22 forming a vacuum space of about 10-6 Torr or more is assembled on a bottom plate 24 made of iron. A vacuum exhaust pipe 23 is connected to a part of the bottom plate 24, and the vacuum chamber 22 has an electron lens barrel 2 in its center.
5 is placed.

Although not shown in detail in the electron lens barrel 25, there are an electron beam generation source, a beam accelerator for the generation source, a beam deflection controller,
A secondary electron detector and a secondary electron energy analyzer from the sample 21 using the irradiation beam 26 (dotted line) are housed.

Next, a mechanism for positioning the movable stage 20 provided in the vacuum chamber and the sample 21 on the stay sheet will be explained.

The movable stage 20 includes two servo motors M arranged orthogonally to freely move the position of the sample 21 in the X and Y directions.

That is, the illustrated motor M moves the upper stage 31 in parallel along the X-direction arrow 30, and the lower stage 32 is moved in parallel by the V-direction motor provided on the back side of the drawing, so that the printed circuit board 9 is mounted. The sample 21 is positioned within the XV plane.

A connector 39 having a plurality of pin terminals is connected to the end of the printed circuit board 19, and power or various signals are inputted through the connector 39.

Each stage is moved by the aforementioned servo motor M (
The feed) is an axial feed screw 3 connected to the shaft of the motor M.
6, and a feeding mechanism consisting of the bearing portion 33 of the nephew 36. In the figure, 34 is a support shaft at the end of the shaft of the feeder 36, and 37 is a base stage that guides the movement of the lower stage 32 in parallel and supports the stage.

Various signals and drive power supplied to the sample 21 attached to the printed circuit board 19 inside the vacuum chamber, and drive power for the servo motor M for the stages 31 and 32 are supplied by cables from an electronic control circuit 40 provided outside the vacuum chamber. 41. For this purpose, a terminal board 42 for connecting the cable 41 is provided on the wall of the vacuum chamber 22.

[Problem that the invention seeks to solve]

However, since the conventional positioning stage has the movable stage 20 inside the vacuum chamber, the chamber itself becomes large, and the extra length of the cable 41 connecting the electronic control circuit 40 and the sample 21 to be inspected is long, especially inside the vacuum chamber. cable 41
Considering the movable range of the sample 21, a sufficient extra length is required. If the extra length of the cable 41 becomes longer than necessary,
As a result, there is a problem that the operating characteristics of the sample 21 cannot be measured correctly.

Furthermore, the cable 41 disposed within the vacuum chamber 22 releases organic gas, lowers the degree of vacuum within the chamber, and increases the pump load capacity of the vacuum evacuation system.

[Means for solving problems]

According to the present invention, a movable stage for mounting a sample provided in a vacuum chamber has a sliding surface with a small sliding friction coefficient between the vacuum chamber, a bottom plate having a window, and an O-ring connected on the back side of the bottom plate. a movable stage that is driven to be fed in the X and Y directions, and
A sample positioning stage comprising a cylindrical sample stand integrally connected to the movable stage and arranged to protrude from a window of a bottom plate, and for positioning a sample placed on the sample stand in a vacuum. That's what I did.

[For production]

As is clear from a comparison between FIG. 1 showing the sample positioning stage of the present invention and FIG. 4 showing the conventional stage, the stage was conventionally placed in a vacuum chamber, but the present invention A movable stage into which a cylindrical sample stage is fitted via an O-ring is placed outside the tank space.

The movable stage forms part of the bottom of the vacuum chamber,
A lubricating seal surface with a low sliding friction coefficient should be formed around the O-ring.

For this reason, a servo motor similar to the conventional one can be used to
Easy to feed in the Y plane. In addition, internal wiring such as a power cable for driving the stage feed and a signal cable for the sample is not required, the load on the vacuum pump is reduced, and at the same time, a predetermined degree of vacuum can be quickly obtained.

The cylindrical sample stage is convenient for storing the necessary signal and power cable lengths from the back side of the sample mounted on the front side in the shortest distance.

〔Example〕

FIG. 1 is a side sectional view showing the structure of the sample positioning stage of the vacuum chamber of the present invention. 2 is an enlarged sectional view of the vacuum seal portion A of the O-ring 4'' shown in FIG. 1, and FIG. 3 is a plan view of the stage taken along the index line BB in FIG. 1.

Although the embodiment drawings illustrate a vacuum chamber to which an electron lens barrel 25 is coupled as in the prior art, the sample positioning stage of the present invention is not limited to a vacuum chamber with an electron lens barrel 25.

The bottom plate 8 of the vacuum chamber 9 is made of iron or the like as a base material, for example.
A wide window 7 is punched out in the portion where the positioning stage is mounted, allowing the stage 6 to move in the X and Y directions. In addition, a groove 11 is formed on the back surface of the groove 11 for stably fixing the inserted rubber O-ring 4 for vacuum sealing.
figure).

The movable stage 6, which is in contact with the bottom plate 8 via an interposed O-ring 4 (diameter approximately 70 mm), is made of iron of an appropriate thickness to which a small amount of carbon is added.

A through hole into which the cylindrical sample stand 3 having a diameter of approximately 140 m is inserted is formed in the center of the bottom plate 8, and an airtight seal portion is formed between the through hole and the sample stand 3 by an O-ring 13.

The front and back peripheral surfaces of the stage 6 are formed into highly accurate flat surfaces by surface grinding. Note that the lower end of the cylindrical sample stage 3 extends to the base stage 16 side, and the lower end thereof extends to the base stage 16 side.
It protrudes into the window 17 of.

Further, the flat ground surface of the movable stage 6 forms a sliding surface 5 having a small sliding friction coefficient as shown in FIG.

The sliding surface 5 is obtained by forming a porous, for example, nickel plating layer 12 on the base layer, impregnating the surface with a 500 μm thick organic liquid resin, such as a fluorine-based resin, and firing the same.

If a movable stage 6 with such a sliding surface 5 is used, the coefficient of friction μ against the rubber O-ring 4 will be approximately 0.1.
The movement of the movable stage 6 in the XY plane becomes easy. However, the ratio of the static friction coefficient (μ0) to the dynamic friction coefficient (μS) of the sliding surface 5 is extremely small, that is, μ07μs.
A contact surface with good lubricity is formed for about a month.

The airtight sliding movement 5 caused by the O-ring 4 in FIG. 2 resists the compression reaction force caused by the O-ring 4, and a load of about 200 kg is applied upward. Therefore, the horizontal driving force in the XY plane for the movable stage 6 that contacts the O-ring 4 is approximately 20 kg.
becomes.

If the movable stage 6 is used as a feed stage in the X direction, a feed stage 15 for driving in the Y direction is provided outside of the movable stage 6. The Y-direction feed stage 15 guides the X-direction feed in parallel to the X-direction feed stage 6.

FIG. 3 is a plan view of a movable stage 6.15 that drives and feeds the cylindrical sample stage 3 within the XY plane. Although the figure shows a stage configuration in which a single stage is fed and driven in multiple directions on a flat surface, a stacked stage configuration may also be used.

A base stage 16 movable in the vertical (Z) direction is provided below the XY direction feeding stage 6.15.

The movable stage 6.15 is driven by a conventional servo motor (not shown). Reference numeral 18 in the figure is a control section of the motor.

As described above, according to the sample positioning stage of the present invention, the sample 1 is moved from the back side of the sample stage 3 on which the printed circuit board 2 is attached by using the movable stand connected to the back side of the vacuum chamber bottom plate 8.
The necessary signals and power for the base stage 16
Since the power is supplied from the internal electronic control circuit 40, the extra length of the connection cable, which has been a problem in the past, is also significantly reduced.

〔Effect of the invention〕

As described above, according to the sample positioning stage in vacuum of the present invention, since the stage is placed outside the vacuum chamber, the vacuum chamber itself can be simplified, and this can be used for diagnostic tests of LSIs and ICs. If applied to testing and failure analysis, it will have a remarkable effect of improving test efficiency and test reliability.

[Brief explanation of the drawing]

Fig. 1 is a side sectional view of the sample positioning stage of the vacuum chamber of the present invention, Fig. 2 is an enlarged sectional view of part A of the vacuum seal portion of the O-ring in Fig. 1, and Fig. 3 is the index line in Fig. 1. FIG. 4 is a side sectional view of a stage for positioning a sample in a conventional vacuum chamber. In the figure, 1 is a sample (for example, an IC chip), 2 is a printed circuit board, 3 is a sample stage, 4 is an O-ring, 5 is a sliding friction surface, 6 is a movable stage, 7 is a through hole in the bottom plate 8, and 8 is a vacuum chamber 9 is a vacuum chamber, 10 is a vacuum space from which the sample stage 3 protrudes,

Claims (1)

[Claims] A vacuum chamber (9), a bottom plate (8) having a window (7), and an O-ring (4) connected on the back side of the bottom plate (8).
A sliding surface (5) with a small sliding friction coefficient is formed.
The movable stage (6) or (1) is driven in the Y direction.
5); and a cylindrical sample stand (3) integrally connected to the stage (6) or (15) and arranged to protrude from the surface of the bottom plate (8). A sample positioning stage characterized in that a sample (1) placed on a sample is positioned in a vacuum (10).