JPH04318406A - Measuring device using light - Google Patents

Abstract

PURPOSE:To predict a failure and to find a point of the failure early by provid ing a circuit for monitoring the state of an illuminating part and a detecting part, and always monitoring the change of the state of a light emitting element and the change of the intensity of the detecting light. CONSTITUTION:The light from an illuminating part 211 comprised of a laser diode, a lens and the like is cast onto an object 203 to be measured as an illuminating light 207 through an optical path 212. A reflecting light 208 is, through an optical path 214, guided to a detecting part 215. A detecting diode of the detecting part 215 detects the position of the reflecting light 208. A monitoring circuit 220 has two inputs, one being the emitting intensity S1 of the laser diode obtained from a monitoring signal of the laser diode, and the other being a signal S2 obtained by the detecting part 215 which indicates the intensity of the reflecting light. The circuit 220 obtains both signals S1, S2 and the ratio R=S2/S1, and records in a recording circuit 221 built therein. The circuit 221 records also the change immediately after the signals S1, S2 and R are adjusted.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a measuring device using light, which includes an irradiating section and a detecting section. In particular, it relates to a position measuring device used in an electron beam lithography device or the like.

0002

2. Description of the Related Art As a measuring device using light, a conventional technique will be explained by taking a height detector in an electron beam lithography device as an example. FIG. 2 shows a schematic configuration of an electron beam lithography apparatus. An electron beam 201 emitted from an electron gun 200 is focused by an electron lens (not shown) provided in an electron optical column, and is focused on a wafer 20 mounted on a sample stage 202.
3. The control computer 204 sends pattern data for drawing a desired pattern on the wafer to the control circuit 205, and the control circuit deflects the electron beam using the electron beam deflector 206 to draw the desired pattern on the wafer. do. If the height of the wafer (in the z direction in the figure) changes during drawing, the beam irradiation position on the wafer changes for the same deflection signal, making it impossible to draw a pattern with high precision. For this reason, a height detector is provided to measure changes in the wafer in the z direction.

An example of the principle of height measurement will be explained with reference to the same figure. Light from an irradiation unit 211 consisting of a laser diode, an optical lens, etc. is irradiated onto the wafer as irradiation light 207 through an optical path unit 212 consisting of a plurality of reflecting mirrors, and the reflected light 208 by the wafer is directed to the optical path. Section 214
It leads to the detection unit 215 through. The detection section is provided with a position detector diode for detecting the position of the reflected light. Since the position of the wafer in the z direction corresponds to the position of the reflected light on the position detector, the position of the reflected light is determined by the processing circuit 2.
By processing according to 10, the wafer height can be determined. The control computer 204 controls the deflection circuit based on this height information, and adjusts the deflection amount of the electron beam to an appropriate amount commensurate with the wafer height.

0004

SUMMARY OF THE INVENTION In such an electron beam lithography system, maintaining the reliability of the system has been a major problem. That is, electron beam lithography equipment, which is a semiconductor manufacturing equipment, is required to operate continuously day and night. Therefore, highly reliable components are used in the control circuit, such as the height detector, and an abnormality detection function is also provided. However, sudden failures during drawing can lead to defects in semiconductor products, and
Partly because no preparations had been made for repairs in the event of an accident, it took a great deal of time to recover. Accidents at night, in particular, caused large losses, partly because the vehicles were unmanned. Furthermore, in the height detector in the electron beam lithography system, some of its components are located in the sample chamber, which is a vacuum container, so it takes time to take measures to recover after an accident occurs.

[0005] An object of the present invention is to prevent large losses due to such accidents.

[0006]

[Means for solving the problem] In order to prevent the above problem,
In a height detector, a means is provided that enables failure prediction, especially for a laser diode that is likely to cause failure. Furthermore, even in the unlikely event that an accident occurs, a function is provided to determine which part of the height detector, which consists of the irradiation section, optical path section, and detection section, is abnormal. To achieve this, a function is provided to constantly monitor the laser diode of the irradiation section and the position detection sensor of the detection section.

[0007]

[Operation] By constantly monitoring the characteristics of the laser diode, it is possible to know the changes in the characteristics over time, and it is possible to predict the life of the diode in advance. Therefore, it is possible to deal with accidents before they occur, and it is possible to prevent large losses. In addition, since the status of the irradiation unit and detector are monitored, even if an accident occurs, it is possible to know in a short time which part of the failure has occurred, and maintenance can be carried out. This will reduce the time required.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described below, taking a height detector in an electron beam lithography apparatus as an example. Figure 1 shows
1 is a schematic configuration diagram of an electron beam lithography apparatus equipped with a height detection device based on the present invention. The device is equipped with a circuit 220 for monitoring the height detector.

The function of the circuit will be explained below. The monitoring circuit has two inputs. One is the emission intensity S1 of the laser diode. The intensity S1 can be obtained from the laser diode monitor signal. Another input is the detection intensity signal S2 from the position detection sensor. This indicates the detected reflected light intensity. The monitoring circuit 220 monitors both signals S1 and S2 and their ratio R=S
2/S1 is determined and recorded in the built-in recording circuit 221. Furthermore, the same circuit also has a function of recording changes in S1, S2, and R immediately after adjustment. For example, for the light emission intensity signal S1, if the intensity immediately after adjustment is S10 and the intensity after a certain period of time is S11, then the parameter S1R indicating the change over time is expressed by the following equation.

S1R=S11/S10 Similarly, the change in detected light intensity over time is S2R=S21
/S20 Regarding the change over time of the intensity ratio R, the ratio R immediately after adjustment is expressed as R0.
, if the intensity ratio after a certain elapsed time is R1, then RR=R1
/R0. The monitoring circuit 220 periodically monitors these values indicating changes over time. Furthermore, the tolerance value C for the same circuit is
It is given in advance by the control computer. The tolerance value C is
These are parameters for determining whether the values of S1R, S2R, and RR are abnormal. That is, S1R, S2R, RR
When the value of C becomes smaller than C, it is determined that there is an abnormality. In addition, this device includes a display unit 230,
Changes in the values can be displayed on the device. From preliminary studies, we confirmed that this height measuring device can be used normally up to R = 0.4, and the value of C is 0.
．． 7 was set.

When an electron beam lithography system having the above-mentioned system configuration was used, a situation as shown in FIG. 3 occurred. That is, over time, the relative luminescence intensity S1R becomes
On the other hand, the relative change value RR of the ratio between the emission intensity S1 and the detected light intensity S2 remained constant. This was determined to mean that the laser diode had deteriorated, and the laser diode in the detection unit 211 was replaced using a short time between drawing operations. As a result, the emission intensity S1 is again
The original strength has been restored and the device can now be used.

FIG. 4 shows another example. In this case,
Although the relative luminescence intensity S1R was constant, the relative intensity ratio R
The R value has become smaller. Considering that the cause was deterioration of the position detection sensor, the sensor was replaced, but the result was not improved. Therefore, the cause is due to dirt in the optical path.
It was determined that the signal was degraded. Since the optical path sections 212 and 214 are located in the vacuum sample chamber 209, their replacement is a large-scale task that involves disassembling the electron optical column. Therefore, the usable period was predicted from the slope of RR. As a result, we found that it could be used until the next periodic inspection, so we continued the drawing process. The optical path section was then replaced during regular inspections. If the monitoring circuit based on the present invention were not prepared, the optical path section would not be replaced during periodic inspection. As a result, immediately after regular inspection, R
<0.4, a height measurement failure occurred due to contamination of the optical path section, and the device had to be disassembled and repaired again.

[0013]

[Effects of the Invention] As explained in the embodiments, by providing the monitoring function based on the present invention, it is possible to predict accidents, and therefore, sudden equipment failures can be prevented, thereby preventing large losses. I can do it. Moreover, high operating rate of the device can be achieved.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of an electron beam lithography apparatus equipped with a height measuring device according to the present invention.

FIG. 2 is a schematic configuration diagram of an electron beam lithography apparatus equipped with a height measuring device based on a conventional method.

FIG. 3 shows an example of the output results of the height measuring device monitoring circuit based on the present invention.

FIG. 4 shows an example of the output results of the height measuring device monitoring circuit based on the present invention.

[Explanation of symbols]

200... Electron gun, 201... Electron beam, 202... Sample stage, 2
03... Wafer, 204... Control computer, 205... Control circuit, 206... Electron beam deflector, 207... Irradiation light, 208...
Reflected light, 209 sample chamber, 210... processing circuit, 211... irradiation section, 212... optical path section, 214... optical path section, 215... detection section, 220... monitoring circuit, 221... storage circuit, 230... display section.

Claims (11)

[Claims] Claim 1: An irradiation unit for irradiating a predetermined light onto an object to be measured, and optical information such as the position of reflected light, scattered light, or transmitted light from the object, or the intensity of the light. A measuring device that processes the information obtained by the detection system to obtain the position of the object to be measured or physical constants, etc. and a means for measuring optical information such as reflected light or scattered light at the detection section, and means for grasping the operating state of the measuring device based on the optical information of both of them. A measuring device that uses light. 2. The measuring device according to claim 1, further comprising means for grasping the operating state of the measuring device based on optical information from the irradiating section and the detecting section, and means for displaying the information. A measuring device characterized by: 3. The measuring device according to claim 1, further comprising means for grasping the operating state of the measuring device based on optical information from the irradiating section and the detecting section, and transmitting the information to the measuring device.
A measuring device characterized by comprising a correction means for feeding back to a control circuit of the measuring device and adjusting the operation of the device to a predetermined value. 4. The measuring device according to claim 1, wherein the measuring device measures the height of an object to be measured. 5. The measuring device according to claim 1, wherein a laser beam is used as the measuring light. 6. The measuring device according to claim 1, wherein a laser beam from a semiconductor laser is used as the measuring light. 7. The measuring device according to claim 1, wherein the detection section includes a one-dimensional or two-dimensional position detector. 8. The measuring device according to claim 1, wherein the detection section includes an image sensor. 9. A semiconductor manufacturing or inspection device comprising the measuring device according to claim 1. 10. A particle beam apparatus comprising the measuring device according to claim 1. 11. An electron beam lithography apparatus comprising the measuring device according to claim 1.