JPH0283914A - Electron beam exposure device - Google Patents

Abstract

PURPOSE:To easily discover pattern anomality due to insufficient exposure by integrating reflected electrons of an electron beam applied to a wafer for every fixed time while one of results of the integration is taken as a reference value and compared with the other values, sending out an alarm signal in case of their difference being above a fixed value. CONSTITUTION:A detector 12 detects reflection electrons 5 of an electron beam 4 applied to a wafer 1 while changing them into an electric signal to output it to an integrator 13. The integrator 13 integrates an output signal of the detector 12 for every fixed time for being outputted. A judge instrument 14 makes one of a plurality of output of an integrator 13 a reference signal to compare the other output as a signal to be judged. Then, when a difference above fixed value is detected between both signals, an anomality judgement signal is outputted to an alarm device 11. The alarm device 11 outputs an alarm signal basing thereon.

Description

[Detailed Description of the Invention] [Summary] Regarding an electron beam exposure device that uses an electron beam to draw a desired pattern on a resist coated on a wafer, an insufficient amount of exposure occurs to the extent that it causes pattern abnormalities due to fluctuations in the electron beam, etc. The purpose of the present invention is to provide an electron beam exposure system that automatically issues a warning when a pattern abnormality occurs, making it possible to easily and reliably detect pattern abnormalities. A detector that outputs an electrical signal as an electric signal, an integrator that integrates the output signal of the detector for a certain period of time and outputs it, and one of the multiple output signals of the integrator as a reference signal and a A judge that compares the same reference signal and the signal to be judged, using the output signal as the signal to be judged, and outputs an abnormality judgment signal when a difference of more than a certain value is detected between the two signals, and a judge that outputs an abnormality judgment signal based on the output signal of the judge. It consists of a warning device that outputs a warning signal.

[Industrial Field of Application] The present invention relates to an electron beam exposure apparatus that uses an electron beam to draw a desired pattern on a resist coated on a wafer in the manufacturing process of semiconductor devices.

In recent years, with the demand for higher integration of semiconductor devices, electron beam exposure equipment has been used in patterning T to make the line width of circuit patterns smaller and thinner.

[Prior art 1] Conventionally, in pattern abnormality detection using electron beam exposure, when forming a pattern 21 as shown in FIG.
By sequentially moving this irradiation position and repeatedly irradiating the electron beam, a desired pattern is drawn on the surface of IC.

In such an electron beam exposure apparatus, dirt such as dust accumulates inside the lens barrel during operation, and the dirt becomes electrically charged.

When the charged dirt momentarily discharges, the beam axis may become unstable, or noise entering the electromagnetic lens may cause the beam axis to become unstable, resulting in localized damage due to insufficient exposure. Pattern abnormalities may occur.

Such pattern abnormalities result in various pattern states as shown in FIGS. 4(E) to 4(d), for example, depending on the degree of fluctuation of the electron beam.

[Problems to be Solved by the Invention] The abnormal pattern 23 shown in FIG. 4(b) is relatively mild and poses no particular problem in terms of reliability, and the chip having the abnormal pattern 25 shown in FIG. 4(d) Screening ensures removal. However, in the case of the abnormal pattern 24 shown in FIG. 4(G), the conduction state is secured for the time being, so it cannot be removed by screening, and chips with such an abnormal pattern may be damaged by stress during actual use. There is a risk of exposure causing malfunction. Therefore, in order to prevent failures due to such abnormal patterns and improve the reliability of semiconductor devices, it is necessary for operators to visually inspect the patterns of all chips after exposure with an electron beam. The problem was that the work was extremely analogous. The purpose of this invention is to easily and reliably correct pattern abnormalities by automatically issuing a warning when there is a shortage of exposure holes to the extent that causes pattern abnormalities due to electron beam fluctuation etc. during the electron beam exposure process. An object of the present invention is to provide an electron beam exposure device that enables discovery.

[Means for Solving the Problem 1] Fig. 1 is a diagram showing the principle of the present invention. That is, the detector 12 detects the reflected electrons 5 of the electron beam 4 irradiated onto the detector 1 and outputs it as an electric signal to the integrator 13, and the integrator 13 converts the output signal of the detector 12 for a certain period of time. Integrate and output each step. The determiner 14 uses one of the plurality of output signals of the integrator 13 as a reference signal, uses the other output signals as a determined signal, compares the reference signal with the determined signal, and sets a constant value for both signals. When the above difference is detected, abnormality determination No. 13 is output to the warning device 11, and the warning device 11 outputs a warning signal based on the output signal of the determiner.

[Operation J] During the process of electron beam exposure on a wafer, anti-tJ4 electrons reflected from the wafer are detected, and the reflected electron group is converted into multiple electrical signals integrated at fixed time intervals by an integrator. One of the plurality of electrical signals is used as a reference signal, and the other electrical signals are sequentially compared with the reference signal as signals to be determined, and if a difference of more than a certain value is detected between the two signals, a warning signal is issued from the warning device. Output.

[Example 1] Hereinafter, an example embodying this invention is shown in Figs. 2 and 3.
To explain with reference to the drawings, the same predetermined pattern is sequentially drawn on each of a large number of chips 2 formed on a wafer 1 shown in FIG. 3 using an electron beam exposure device. As shown in FIG. 2, a backscattered electron detection element 3 is provided within the lens barrel of the electron beam exposure apparatus. In the electron beam exposure apparatus, an electron beam 4 is irradiated onto the wafer 1 from an electron gun, and anti-OA electrons 5, secondary electrons, or 111 waves are reflected from the upper surface of the wafer 1 based on the irradiation. The backscattered electron detection element 3 is normally used for detecting the position of a wafer, and detects backscattered electrons 5 reflected from the upper surface of the wafer 1, and converts the detection R into an electrical signal and outputs it.

The backscattered electron detection element 3 is connected to an amplifier circuit 6, which amplifies the output signal of the anti-fj4 electron detection element 3 and outputs it to an integration circuit 7. A detector 12 is constituted by the backscattered electron detection element 3 and the amplifier circuit 6. Integrating circuit 7 integrates the output signal of amplifier circuit 6, and level holding circuit 8
Output to. A level holding signal SG1 is outputted to the level holding circuit 8 from the control device (not shown) of this electron beam exposure apparatus every time exposure of one chip is completed, and based on the level holding signal SG1, the level holding circuit 8 is outputted to the integrating circuit 7. The potential of the output signal is held and outputted. An integrator 13 is constituted by the integrating circuit 7 and the level holding circuit 8.

The output signal of the level holding circuit 8 is outputted to a reference potential holding circuit 9 and a comparison circuit 10 that constitute the determiner 14. The reference potential holding circuit 9 receives the reference potential setting signal SG2 from the control I device, and holds the output signal of the level holding circuit 8 as a reference potential based on the reference potential setting signal @SG2. The base setting signal SG2 is outputted, for example, when the exposure of the first exposed chip 2a on the wafer 1 shown in FIG. It has become so.

The output signal of the base rP-potential holding circuit 9 is output to the comparison circuit 10. The comparison circuit 10 is a reference potential holding circuit 9.
The output signal of the level holding circuit 8 is compared as a signal to be judged with respect to the reference potential output from the circuit, and if the potential difference is greater than a certain value, an abnormality judgment signal is output to the warning device 11, and the warning device 11 detects the abnormality. Based on the signal, for example, it sounds like a warning sound.

Next, the operation of the electron beam exposure apparatus configured as described above will be explained.

Now, when exposing the wafer 1 with this electron beam exposure apparatus, a predetermined pattern is first exposed on the first depth 2a based on the UJ operation of the control IO apparatus.

Then, the backscattered electrons reflected from the wafer 1 during the exposure are detected by the backscattered electron detection probe 3, converted into an electrical signal and output, and the output signal is amplified by the amplifier circuit 6 and then sent to the integration circuit 7. is integrated and output to the level holding circuit 8. Then, at the same time as the exposure of the chip 2a is completed, the
The level holding signal SG1 is sent from the ll device to the level holding circuit 8.
When the same level is outputted, the same level holding circuit 8 holds the potential integrated by the integrating circuit 8, that is, the potential corresponding to the total exposure amount of the depth 2a, and outputs it to the comparison circuit 10 and the reference potential holding circuit 9. Here, the reference potential holding circuit 9 holds the output signal of the level holding circuit 9 as a reference potential by the reference potential holding signal SG2 from the control I device, and the comparison circuit 10
Output to. The comparison circuit 10 then compares the reference potential with the output signal of the level holding circuit 8, but since the two are equal for the first chip 2a, no abnormality determination signal is output.

Subsequently, when the second depth 2b is exposed, the backscattered electrons reflected from the wafer 1 are detected by the backscattered electron detection probe 3, and the output signal is amplified by the amplifier circuit 6, and then sent to the integrator circuit. 7 and output to the level holding circuit 8. When the level holding signal SGI is output from the control m+ device to the level holding circuit 8 at the same time as the end of exposure of the chip 2b, the same level holding circuit 8 holds the potential corresponding to the total exposure amount of the chip 2b, and the comparison circuit 10 and the reference potential holding circuit 9. The comparison (b) path 10 corresponds to the reference potential and level holding circuit 8 which corresponds to the exposure amount of the chip 2a.
Compare with the output signal of Here, if the pattern of chip 2a is normally exposed and the pattern in depth 2b contains an abnormal pattern as shown in FIG. 4(C), l), the total exposure amount of chip 2b is Since the exposure amount is smaller than the exposure amount of the chip 2a, a potential difference of a certain value or more is generated between the exposure potential and the reference potential. Therefore, the comparator circuit 10 outputs an abnormality determination signal Δ, and a warning sound is emitted from the warning 1ffi11.

Also, chip 2a1. : An abnormal pattern occurs and the reference potential based on the exposure amount increases by +1! Since a similar potential difference occurs when the potential holding circuit 9 is set and the subsequent chip 2b is normally exposed, a warning sound is emitted from the warning position 11.

On the other hand, if the output voltage of the level holding circuit 8 and the reference potential are within a certain value, the comparator circuit 10 will not output an abnormal signal, and each chip 2 on the wafer 1 will be sequentially exposed.

As described above, this electron beam exposure apparatus C has two
The voltage signals based on the exposure amount of other depths 2 of the same wafer 1 are sequentially compared with the reference potential set based on all the exposure companies of the chip 2a exposed first in the exposure operation, and If the potential difference exceeds a certain threshold, a warning sound is emitted. Then, in order to compare the exposure amount of other chips 2 on the same wafer 1 using the exposure amount of the first chip 2a of each wafer 1 as a reference, the threshold value in the comparison circuit 10 is set as ! ! Even if the sensitivity is increased by approximating the quasi-potential, no warning sound is emitted due to changes in the beam irradiation amount from the electron gun due to long-term changes, and each chip on the same wafer 1 When the exposure amount changes in step 2, that is, when an abnormal pattern occurs, a warning sound is reliably emitted. Therefore, a wafer with an abnormal pattern can be found extremely easily without visual inspection, and the reliability of each chip can also be improved.

[Effects of the Invention J As detailed above, the present invention automatically issues a warning when an insufficient amount of exposure occurs to the extent that it causes pattern abnormalities due to fluctuation of the electron beam during the electron beam exposure process. Therefore, it is possible to provide an electron beam exposure apparatus that allows pattern abnormalities to be easily and reliably discovered by emitting electron beams.

[Brief explanation of the drawing]

FIG. 1 is a diagram explaining the principle of this invention, FIG. 2 is a block diagram showing an embodiment of this invention, FIG. 3 is a front view of a wafer related to this invention, and FIGS. 4(a), (b), (C) ( d) is an explanatory diagram showing a pattern drawn by an electron beam exposure device. In the figure, 1 is a wafer, 4 is an electron beam, 5 is a reflected electron, 1
7 is a warning device, 12 is a detector, 13 is a cusp divider, and 14 is a judge. Figure 3 Front view of sea urchin)) Figure 4 Exposure J1 turn illustration (b) (C) (d)

Claims (1)

[Claims] 1. A detector (12) that detects reflected electrons (5) of an electron beam (4) irradiated onto a wafer (1) and outputs the detected electrons as an electrical signal; an integrator (13) that integrates the output signal of the integrator (13) for a certain period of time and outputs the integrated signal, one of the plurality of output signals of the integrator (13) is used as a reference signal, and the other output signals are used as the signals to be determined. A determiner (14) that compares the reference signal and the determined signal and outputs an abnormality determination signal when a difference of more than a certain value is detected between the two signals, and outputs a warning signal based on the output signal of the determiner. An electron beam exposure apparatus comprising: a warning device (11) for causing a warning;