JPH0213463B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a semiconductor device evaluation method for performing a non-contact functional test of elements on a semiconductor wafer or semiconductor chip using a charged beam.

(Prior Art) As an example of a conventional non-contact evaluation device, there is one shown in FIG. 8, for example. The main part of this device is a charged beam (the electron beam will be described below).
an optical column 1 for generating and irradiating a predetermined position on a sample surface; a sample chamber 2 equipped with a sample, a sample stage (not shown) on which the sample is placed, and a secondary beam energy discriminator; It is configured. Inside the optical barrel 1, an electron gun 3, a beam interrupter 4, a deflection coil 5, and an electron beam focusing lens system (not shown) are provided. 6 is an energy discriminator constructed by stacking a plurality of hemispherical meshes (usually four layers), and 7 is a sample.

FIG. 2 is an explanatory diagram of the energy discriminator 6. Four concentric hemisphere meshes 9, 10, 11,
12 are assembled so as to be insulated from each other by an insulating intermediate 13, and a hole is provided at the apex of each mesh to introduce the incident primary beam 8, and the inner wall is at the same potential as the mesh 9. A cylinder 14 is fitted.

The mesh 9 with radius R (for example, 40 mm) is used to make the electric field near the sample 7 as uniform as possible.
It is kept at a potential close to 0V, which is almost the same as sample 7. The mesh 10 with radius R+△R is a deceleration grit for decelerating the secondary beam, and the mesh 11 with radius R+2△R is a collector electrode, and the mesh 11 with radius R+3△R (for example,
The mesh 12 (42 mm) detects the low energy component (the part of the true secondary electron distribution in Figure 5) of the secondary beam that has passed through the collector electrode (mesh 11).
is repelled by a reverse electric field and collected again at the collector electrode 11, and high-energy components are dissipated to the outside. The energy of the secondary beam passing toward the outside (collector electrode 11 side) changes depending on the potential of the mesh 10, and the total sum of the secondary beams collected on the collector electrode 11 is determined. ) can be analyzed. Further, since noise components due to high-energy electrons such as reflected electrons that are emitted almost regardless of the potential of the sample surface can be removed, the surface potential can be accurately converted from the energy distribution of the secondary beam.

When the potential is high, the distribution shifts to the lower energy side in the graph, and the amount of emitted electrons in the area above the threshold value decreases. Furthermore, when the potential is low, the distribution shifts to the high energy side and the amount of emitted electrons increases. Figure 6 shows this situation; when collecting the right side of straight line a (threshold) parallel to the y-axis,
The potential at the measurement point can be determined without contact by the amount on the right side. An energy discriminator (energy filter) is used to pass higher energy components than straight line a and remove lower energy components.
6 is used.

(Problems to be Solved by the Invention) The conventional non-contact evaluation method using a device equipped with the energy discriminator 6 has excellent energy resolution (surface potential resolution). However, from the output value obtained by amplifying the secondary beam collected by the collector electrode (mesh 11), it is possible to know the total sum of the secondary beam emitted from the surface of the sample 7 and its energy distribution. It is not possible to know the directional distribution.

The present invention attempts to measure the surface potential Vs by simultaneously measuring the emission ratio δ and the directional distribution h of the secondary beam.

(Means for Solving the Problems) In the present invention, the secondary beam detection section is configured by a combination of an energy discriminator and a multiplier, and the secondary beam multiplied by the multiplier is independently transmitted for each direction. The directional distribution of the emitted secondary beam can be measured by using a collector divided into multiple pieces.

(Function) FIG. 9 is an enlarged view showing an example of sample 7,
A is an elevational view, and b is a plan view. Semiconductor substrate 15
The upper insulating layer 16 is covered, and a metal 17 is further deposited thereon. As shown in figure a,
The directional distribution and amount of emitted secondary beams change depending on whether the incident primary beam 8 is incident on the center of the metal 17 or when the incident primary beam 8' is incident on the stepped portion of the metal 17. Even if the second
Even if the mesh 9 in the figure works to homogenize its internal electric field, if various potentials are applied to the metal 17 or if the surface of the insulating layer 16 becomes abnormally potential due to charging, the incident primary beam 8 will move near the sample 7. The electromagnetic coil (or electrostatic deflection plate) that deflects the incident primary beam 8 is bent by the abnormal electric field and the incident position shifts like the incident primary beam 8'.
The incident primary beam only from the supply current (voltage) to 8
It is no longer possible to determine the incident position of the ion beam, and it is also no longer possible to know the surface potential. That is,
The emission ratio δ and directional distribution h of the secondary beam are expressed by the following equations using the incident angle θ of the primary beam and the surface potential Vs of the sample material Z.

δ=f ₁ (θ, Vs, Z) ………(1) h=h ₂ (θ) ………(2) However, when the primary beam 8 is bent like 8′ due to the abnormal electric field, As the incident angle θ changes, the emission ratio δ and the directional distribution h change. Therefore, for a certain sample material Z, it is impossible to know Vs only by measuring δ, but by measuring h at the same time, θ can be found and Vs can be found.

(Examples) Hereinafter, the present invention will be explained in detail by way of examples.

Figures 1a and 1b are diagrams showing a first embodiment of the present invention, in which figure a is a configuration diagram showing the main parts of the device used in the present invention, and figure b is an enlarged view of the secondary beam detection section 18. be. In the figures, the same reference numerals as the previous ones indicate the same.

As is clear from the figure, the structural feature of the apparatus used in the present invention is that the secondary beam detection section 18 is equipped with the hemispherical mesh shown in FIG. 2, and is configured to be able to observe the low energy component of the secondary beam. Energy discriminator 6, multipliers 19, 19', and collector 20
It is made up of. Multiplier 19,1
9' was constructed using a multi-channel plate (hereinafter abbreviated as MCP) as shown in an enlarged view in FIG. Note that a in FIG. 3 is a plan view and b is a cross-sectional view, and the disk has an opening 21 in the center thereof through which the primary beam 8 passes.

MCP has a large number of glass capillaries ( ^channels ) (for example, 100
10,000 pieces) in parallel and glued plate shape (for example, 3 pieces thick)
It is a secondary electron multiplier with a diameter of about 1.0 mm), and its geometrical shape can be changed flexibly depending on the method of bonding. The reason why two MCPs are stacked and used in this embodiment is to increase the multiplication factor.
As shown in FIG. 4, the collector 20 is composed of electrodes 201, 203, 203, and 204 divided into four parts, each having an independent terminal, and is arranged above the MCP (on the electron gun side).

FIG. 5 shows the relationship between the region of "true secondary electrons" and the entire spectrum of secondary electrons. A hemispherical energy analyzer has high resolution for true secondary electrons in this region. The hemispherical energy analyzer eliminates high-energy electrons, including reflected electrons, because they not only do not contain surface potential information, but also generate secondary electrons that become noise components on the sample chamber wall. Equipped with a mechanism. The energy discriminator 6 described above can be used in this way.

In the device used in the present invention, the energy discriminator 6 may be provided with the same operations and functions as conventional ones, if necessary, but rather the main focus is on the energy discrimination function.

Now, in FIG. 1b, secondary beam distribution peaks with different directional distributions are represented by arrows 22 and 23. Furthermore, if the potential of the collector electrode 11 is appropriately applied, the charged secondary beam will reach the collector electrode 11.
The energy can pass through the mesh 12 and be guided to the outside of the energy discriminator 6 without being trapped. If the potential difference between the mesh 12 and the MCP 19 is appropriate, the secondary electrons reach the collector 20 through an electron multiplication process by the MCPs 19 and 19'. Assuming that the cross sections of the electrodes 201 and 202 are visible in the collector 20 shown in FIG. The secondary beam in the peak direction shown by is the opposite. Here, the effect of dividing the collector 20 into four electrodes as shown in FIG. 4 will be described. Temporarily, electrode 201 and electrode 202
Assuming that the outputs are the same, the emission peaks of the secondary beams will be directionally distributed on the central plane in which the electrodes 201 and 202 are viewed symmetrically. Similarly, if electrode 203 and electrode 204 have the same output,
The direction distribution is on the central plane of the electrodes 203 and 204, and when considering the logical sum of the two, it can be seen that the secondary beam is emitted with a peak in the vertical direction. That is, the electrodes 201, 202, 20
By performing calculations on the respective outputs of 3 and 204, it is possible to estimate the direction cosine of the secondary beam that forms the axis of the incident primary beam 8. Note that the estimation of the direction cosine requires the presence of at least three electrodes.

The energy in FIG. 6 is the collected secondary electron energy, and is a distribution diagram of electrons that usually have an energy of about 0 eV to 50 eV. During measurement, Vs is directly read using the configuration shown in FIG. (FIG. 6 is an enlarged view of the true secondary electron part in FIG. 5.) The secondary beam taken out from the mesh 12 is multiplied by MCPs 19 and 19', and the electrode 201 and
After performing calculations on the output values of 202, 203, and 204 to determine the incident position of the primary beam 8, the total sum of the output values of the respective electrodes is determined, and the sample surface potential is determined in inverse proportion to the sum of the output values of the respective electrodes. In this case, the noise of high-energy components such as reflected electrons is superimposed, so the
Although the signal-to-noise ratio cannot be expected, high-speed measurement of the sample surface potential is possible by taking advantage of the fast response speed of the secondary electron multiplier. Therefore, a rough evaluation can be performed over the entire surface of the sample 7 at high speed, and then a precise evaluation measurement can be performed at a low speed on a problematic location. That is, as shown in FIG. 7, a potential for decelerating secondary electrons is applied to the deceleration grid 10, and the deceleration grid potential Vs' is set such that the number of electrons collected at the collector electrode 11 is 0 or a constant value. Find Vs′=Vs
By configuring the feedback amplification system so that +C (C=Const.), it is possible to perform low-speed but highly accurate measurement.

In general, it is impossible to compare design data or perform evaluation while operating the sample 7 during the manufacturing of a semiconductor device without proper information on the incident position of the primary beam 8. Incident primary beam 8 to sample 7
Since it is assumed that the pattern of the sample 7 itself cannot be trusted when moving on the plane of the sample and attempting to irradiate it in the desired case, a pattern check is necessary to check the electrical characteristics at the wafer stage. It is included. A feature of the present invention is that the incident primary beam 8 can be moved and stopped at a target position while performing a pattern check, and the potential at that location can be precisely measured, and directional distribution can be detected as in the embodiment shown in FIG. This can be done by the secondary beam detection section 18.

(Effects of the Invention) As described above, according to the present invention, the directional distribution of the emitted secondary beam can be known, and this can be used for positioning the incident beam. Furthermore, it becomes possible to perform high-speed measurement of the sample surface potential by taking advantage of the high response speed of the secondary electron multiplier.

[Brief explanation of drawings]

FIG. 1 shows the first embodiment of the present invention, and FIG. 1A is a schematic diagram of the device, FIG.
Fig. 3 is an explanatory diagram of a multiplier (multi-channel plate), a is a plan view, b is a sectional view, Fig. 4 is an explanatory diagram showing an example of a collector used in the present invention, and Fig. 5 is an explanatory diagram of a true double Figure 6 shows how the amount of emitted secondary beam changes depending on the sample surface potential. Figure 7 shows the feedback amplification system. Figure 8 shows the conventional evaluation method. FIG. 9 is an enlarged view of the sample, where a is an elevational view and b is a plan view. 1... Optical lens barrel, 2... Sample chamber, 3... Electron gun, 4... Beam intermittent device, 5... Deflection coil,
6...Energy discriminator, 7...Sample, 8...Primary beam (electron beam), 9...Mesh, 10...
Mesh (deceleration grid), 11... Mesh (collector electrode), 12... Mesh, 13... Insulating intermediate inclusion, 14... Cylinder, 15... Semiconductor substrate, 16... Insulating layer, 17... Metal , 18...
Secondary beam detection unit, 19, 19'... Multiplier (MCP), 20... Collector (electrodes 201, 20
2,203,204), 21... open hole, 22,2
3...Arrow (secondary beam distribution peak).

Claims (1)

[Claims] 1. Irradiating the surface of a semiconductor sample with a charged primary beam,
In the non-contact evaluation method for a semiconductor device, which evaluates a semiconductor by detecting a secondary beam emitted from the sample surface, one or more energy components having a predetermined value or less among the low energy components of the secondary beam are detected. is removed using an energy discriminator, and a secondary beam consisting of an energy component equal to or higher than the predetermined value extracted from the energy discriminator is multiplied by a multiplier, and a plurality of secondary beams are separated according to the emission direction of the secondary beam. generates a detection signal, determines the emission peak angle of the secondary beam from the difference between the plurality of detection signals, obtains information on the sample incident position of the charged primary beam based on this, and detects the plurality of detection signals. The method is characterized in that the electrical characteristics of the semiconductor sample are evaluated by determining the amount of secondary beam emission in the energy region equal to or higher than the predetermined value from the sum of the signals and determining the surface potential of the semiconductor sample based on this. A non-contact evaluation method for the semiconductor device.