JPS5999732A - Measuring device for potential distribution of electronic device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Techniques of the Invention] □ The present invention relates to a potential distribution measuring device for an electronic device, which measures the potential distribution of an electronic device, particularly a semiconductor sample, in a non-contact manner using an electron beam.

[Departure] Technical background and its problems]

BACKGROUND ART Recently, research and development has been conducted on a sample potential measuring device that measures the potential of a sample surface in a non-contact manner by irradiating an electron beam onto a semiconductor sample such as an IC or LSI and detecting secondary electrons emitted from the sample. This device applies the 19 principle that when an electron beam is irradiated onto a specimen in an operating state with a drive signal of 1", information about the potential at the beam irradiation point is stored in the secondary electrons emitted from the specimen. It is.

Therefore, in the device described in 2 above, the sample potential can be reduced by extracting the secondary 'FL' emitted from the sample using an appropriate detector when the sample is irradiated with an electron beam. Cedar in contact
Furthermore, by pulsing the electron beam, ejecting the pulsed beam onto the sample only at a specific phase of the sampling operation, and detecting the secondary electrons, it is also possible to observe the state of signal transmission. Therefore, it is extremely effective for observing high-speed operation in semiconductor testing.

By the way, when a semiconductor sample in an operating state is irradiated with an electron beam, the secondary electrons emitted from the sample not only contain information on the potential at the beam irradiation point, but also information on the composition of the sample at the beam irradiation point. It also includes a mixture of information regarding. For example, if a drive signal is applied to a sample having regions 1, 2, and 3 with different compositions as shown in FIG. 1(a), and the beam is scanned in the direction of the arrow in the figure, the detected secondary electron The flow differs from the same figure (b) depending on the difference in composition.
). This is because the number of p1 emitted secondary electrons with an i:p secondary electron emission rate changes depending on the underlying composition at the beam irradiation position. Note that 4 in the figure indicates a deflection plate for beam scanning.

Because the number of secondary electrons differs depending on the composition, in order to accurately measure the potential at the beam irradiation point of a sample in an operating state, information about the composition must be removed from the detected secondary electron signal. There is a must-breathe. Conventionally, the following procedure has been used to correct level fluctuations in detected secondary electron signals caused by differences in underlying composition. That is, as shown in FIG. 2, first, the application of the drive signal to the sample is stopped, the electron beam is scanned over the sample surface, and the detected secondary electron signals for all pixels in the measurement area are appropriately stored as non-application data 5. Store in the device. Next, while applying a drive signal to the sample, an electron beam is scanned over the sample surface, and the detected secondary electron signals for all pixels in the same measurement area as when obtaining the non-application data 5 are appropriately set as the application data 6. Store it in a suitable storage device. Then, a subtracter 7 extracts the above data 5 and 6 from the respective storage devices and calculates the difference between the two. Since the application data 6 includes information regarding the potential and composition,
From now on, non-applied data 5 that includes only information about the composition.
By subtracting , correction data 8 containing only potential information can be obtained.

However, this type of conventional method has the following problems. That is, the troublesome operation of switching the driving signal of the semiconductor sample to the applied state and then to the non-applied state becomes a nuisance. However, it takes about 100 seconds to obtain the applied data 6, depending on the device and the pixel density, and it takes twice as long to measure the non-applied data 5 and calculate the composition information. , which is unfavorable in terms of measurement efficiency. Furthermore, since the beam irradiation dose is applied to the sample at a dose twice as high as that for normal measurement, this is not desirable from the viewpoint of protecting the sample from damage to the beam.

[Purpose of the invention]

The purpose of the present invention is to remove information about the composition from the detected secondary electronic code, to improve the potential measurement of electronic devices, especially semiconductor samples, and to prevent beam damage during testing. An object of the present invention is to provide a potential distribution measuring device for an electronic device that can be made extremely small.

[Summary of the Invention] The gist of the present invention is to create non-applied data (background data) without irradiating an electronic device with an electron beam, and to subtract this packed ground data from a detected secondary electron signal.

That is, the TEPCO device of the present invention applies a drive signal to a semiconductor sample, scans the sample with an electron beam using a predetermined scanning signal, and at this time, the electron beam is emitted from the sample.
In a trial potential measuring device that detects secondary electrons to measure the potential distribution on a sample surface, pattern data of an element to be realized on the sample is stored in advance with information on the type of substrate added to the data, and Nokunk ground data, which is a detected secondary electron signal when the drive number 4N is not applied to the base glaze, is stored in the base glaze, and the irradiation position of the electron beam is verified from the scanning signal of the electron beam. The type fA of the bottom and ground formed at the beam irradiation position is determined based on the detected base data and the stored pattern data, and the stored pack ground data is determined based on the determined base data. Pack ground data configured at the selected beam irradiation position is determined, and the determined /4 square ground data is subtracted from the detected secondary electron signal with a drive signal applied to the sample. □
[Effect of explanation] According to the present invention, the beam irradiation position is detected from the scanning signal of the electron beam, and the duck ground data belonging to the beam irradiation position is obtained from the detected position data. By subtracting the value of this pack ground wave from the detected secondary signal, the level fluctuation of the detected secondary 1.1 signal caused by the difference in the underlying composition can be automatically compensated for. 7 things to add? ;Te, I can. Therefore, it is possible to measure the potential distribution of an electronic device using high-speed fabric. In addition, since it takes a lot of time to irradiate the beam to obtain the bank ground data, it has the effect of causing damage to electronic equipment with the beam.

[Embodiments of the invention]

FIG. 3 is a schematic diagram showing an embodiment of the present invention. In the figure, reference numeral 11 denotes a T-element gun.a) The electron beam emitted from this negative four-element gun 11 is converted into a beam by a deflection plate J2 for a beam navigator and a chopper dryer A13. The pulsed beam is passed through a beam scanning deflection coil 14 and
The semiconductor sample 1 is deflected by the dry nozzle 15.
6 and scanned two-dimensionally. The sample 16 is placed on a sample stage Noah that is movable in a direction perpendicular to the irradiation direction of the beam, and a drive signal is applied to the sample 16 from a drive signal generator 18.

:' 2 emitted from the sample 16 by the beam irradiation
The secondary electrons are detected by a secondary electron detector 19, and this detected secondary 1st pulse is amplified via an amplifier 20 and then sent to an A/D converter 21. Here □, the detected secondary i,
In order to increase the S/N ratio of the child signal, it takes 2 to obtain one piece of data.
If the electron detector 19 performs sampling a plurality of times, in this case an analog integrator may be provided in the A/D converter 21. The A/D converter 21 performs the above detection 2.
Next voice: The child signal is digitized, and this r digital number is 1
! The output leaks to the 1% unit 22.

□ - 10,000, the scanning signals from the deflection dry noses 15 are supplied to the position calculation section 23. Position calculation unit 23: Calculates the beam irradiation point position on the sample 16 from the above scanning G and the coordinate values in the X and T directions to the deflection center in the chip coordinate system input from the outside. be done. This situation will be explained with reference to FIG. When the chip area P and the deflection area Q have the relationship as shown in the figure with respect to the chip f reference system shown in Figure 4, the coordinate (X0+7.) is input from the outside at the center of the deflection area, that is, the deflection center point. be done. This value is, for example, C
j, trial stage position all needles 811] is read by the length measuring system force and inputted by the operator. Coordinates (Xd,
y6) is the deflection center force/distance to the radius beam irradiation point R, and is the deflection □ driver 15 or I]/
When the A converter and amplifier are connected, the input signal of the D/A converter is sent from the deflection driver 15 as a scanning signal to the position calculation section 23, and the position meter section 2 calculates the gain of the amplifier. (X6°yd) can be calculated from y*jH, : based on information such as the beam polarization Mt jG' degrees and the like. □Furthermore, the coordinates of the beam irradiation point R in the chip coordinate system (
40X, 1 * 3'c+)'6) 7>'' is determined and sent to the base determining unit 25 connected to the house coordinate information @-pattern data memory 24.

The pattern data memory 24 stores nof-turn data created by a CAD system corresponding to IC+LSI etc. that has been prepared on the sample 16 and subjected to the following pre-processing. First, the coordinate origin of the pattern data is moved so that it coincides with the coordinate origin when calculating the beam irradiation point position in the position calculation unit 23, that is, the coordinate origin of the Tesozo coordinate system. Next, the coordinate units are converted to match the scale of the pattern data or the scale of the IC, LSI, etc. on the sample 16. Finally, base information, such as UAt or SiO2 information, is added to the pattern data. After these pre-processes, the pattern data is stored in the pattern data memory 24. The base determining unit 25 receives the position coordinates of the beam irradiation point from the position meter part 23, searches the pattern data in the turn data memory 24 based on these coordinates, and determines the base at the position of the beam irradiation point. The type is determined. For example, the fourth
The beam irradiation point position t(xc+xd+yo”d shown in the figure)
) is determined to be on the At wiring from the search of the pattern data memory 24, the type of base is determined to be At. This background data is then sent to a background compensation data determining section 27 to which the background compensation data memory 26 is connected.

The base compensation data memory 26 stores secondary electrons emitted from the sample 16 when the pulse beam is irradiated onto the base region without applying a drive signal to the sample 16.
9, and data (background 9 data) obtained by converting this detected secondary electron signal into an A/D converter 2 via an amplifier 2o is stored.

The measurement conditions at this time, such as the beam acceleration voltage, beam current, beam diameter, beam pulse width, and number of samplings, are the conditions for actual measurement, and the conditions for the multi-sample 16
It is best to set the conditions to be the same as when measuring by applying a drive signal to. When changing measurement conditions midway through, sample 16
It is better to remeasure the data in the underlying area without applying a drive signal to the area. However, if there is an item for which the measurement conditions change frequently during measurement, the base data is collected without applying the drive signal over the expected range in advance and stored in the base compensation data memory 26. It is also possible to store the background data and then retrieve it with matching conditions when selecting background data from the background compensation data memory 26 later. For example, set the beam pulse width to 0.5 n
If you wish to perform measurements under three different conditions: S*1nS r 2nS, you can collect data in advance under these three conditions with no drive signal applied and store it in the base compensation data memory 26. Note that in order to obtain compensation data when no voltage is applied, instead of actually irradiating the sample 16 with the beam, various types of bases are placed at the sample position, and secondary electrons caused by the beam irradiation are detected in this state. Desired. The base compensation data determining unit 27 selects base compensation data from the base compensation data memory 26 based on the base data determined by the base determining unit 25, and thereby sets the base pack to be configured at the position where the beam is irradiated. Grand data is determined. This pack ground bias is then sent to the subtracter 22.

The digital data from the A/D converter 21 is input to the subtracter 22 together with the background data, and the background data is subtracted from the digital data. In other words, bank ground data containing only information on the base composition is subtracted from digital data containing information on the sample potential and information on the base composition, and the output data of the subtracter 22 is often mixed with base composition information. The data is based only on potential information. Then, data based only on this potential information is sent to the display 28, and the potential contrast image and potential waveform of the sample 16 are displayed on the display 28.

In this manner, the present apparatus automatically corrects the level fluctuation of the extracted secondary electron signal based on the underlying composition at any position on the semiconductor sample 16. For this reason, the semiconductor test f-q, 160
Measurement accuracy can be significantly improved. In addition, since it is necessary to irradiate the sample 16 with an electron beam when creating bank ground data, there are advantages such as minimizing beam damage to the sample 16 and shortening measurement time. be.

Next, other embodiments of the present invention will be described.

This embodiment differs from the previously described embodiments in that it is equipped with a length measurement system consisting of a position detector 3 for measuring the position of the sample stage 17 and a table position length measurement section 32. The received signal (coordinates) is sent to the position calculation unit 2.
I decided to answer question 3 directly. Fifth. X shown in the figure.

If Y is the sample coordinate system and the chip arrangement in the coordinate system is as shown in the figure, then the coordinate value from the sample coordinate system origin O is (
Xt, Y) are sent to the position calculation section 32 as the output of the table position measurement section 32.

The position calculation unit 23 calculates the pitch Px of the chip arrangement in the X direction,
The coordinates (Xc, yc) in the chip coordinate system are determined from the pitch Py in the Y direction and, if necessary, the chin 1 playout.

If the Chigg layout is as shown in Figure 5, it can be found using the following simple formula. However, in the above formula, [ ] is a Gauss symbol. From this point on, the deviation (y, y, 1) from the deflection center to the beam irradiation point is calculated as in the previous example.
, will be done.

With this configuration, it is possible to obtain the same seedlings as in the previous example, but it is also possible to measure the electric potential at any arbitrary point on large samples such as semiconductor wafers. 1m1M
What can you do?

Note that although the present invention is limited to each of the above-mentioned embodiments, 0. ′
``1'' may be modified and implemented in various ways without departing from its spirit.

[Brief explanation of drawings]

Figure 1 (a) and (b) are not intended to explain the level fluctuation of the extracted secondary electron signal due to the underlying composition. □8.5 A schematic diagram for explaining the conventional method for correcting fluctuations, FIG. 3 is a schematic diagram showing an embodiment of the present invention, and FIG. 4 shows the operation of the above embodiment. FIG. 5 is a schematic diagram for explaining the operation of another embodiment. 1 No... Electron gun, 12... Deflection plate for beam chop, 13... Chopper driver, 14... Deflection coil for beam scanning, 15... Deflection driver, 16... Semiconductor sample, 17 ...Sample stay 2.18 River drive signal generator, 19...Secondary cloth, child detector, 2o...Amplifier, 2no...A/D converter, 22...Driving force, Instrument 1, Chi 3...Position meter Takeshibe, 24...Linin day) Memo 0
．． 25... Base determining unit, 26... Base compensation data memory, 27... Base compensation data determining unit, 28... Display digit, 31... Position detector, 32... Table position measurement Nagabe.

Claims (2)

[Claims] (1) At the same time as applying a drive signal to the electronic device, the electron beam is scanned over the sample using a predetermined scanning signal, and the secondary electrons emitted from the electronic device at this time are detected to determine the potential of the beam irradiated surface. 4. In a potential distribution measuring device of an electronic device to be measured, pattern data of an element realized on the electronic device is stored with information on the type of underlying layer added to the data.
turn data storage means; beam irradiation position detection means for detecting the irradiation position of the beam from the scanning signal of the electron beam; and position data detected by this means and pattern data from the turn data storage means. a base determining means for determining the type of base configured at the position to be irradiated with the beam based on the background data, which is a secondary electronic signal for detection in a state where no drive signal is applied to the electronic device; background data storage means for storing each background data, and the background data determined by the background determination means;
background data determining means for selecting and determining background data of a base formed at the position to be irradiated with the beam from the background data storage means based on the f-event; 1. A potential distribution measuring device for an electronic device, comprising: subtracting means for subtracting the ground data determined by the background data determining means from the detected secondary electron signal. (2) The child device is moved in a certain direction perpendicular to the electron beam irradiation direction and is placed on a harsh specimen stage.
So, based on the position information of the beam irradiation position detecting means (I) and the above-mentioned communication, I determined the position of the beam irradiation position detection means (I). The % distribution illumination device for the electronic device according to claim 1, which is a device that uses a black irradiation device.