JPS61165608A - Film thickness measuring 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 [Technical Field] The present invention relates to a film thickness measuring device, and more particularly to a film thickness measuring device capable of simultaneously measuring multiple points within a member to be measured (for example, a semiconductor wafer).

[Cost technology]

Conventionally, there are optical types of film thickness measurement devices for semiconductor wafers, etc., especially non-destructive film thickness measurement devices.Among these, the optical type that can perform multi-point measurements on the film to be measured is mainly used for measuring reflectance. Various methods have been developed, including those that use wavelength dependence to calculate and measure film thickness, and those that use polarized light to measure film thickness.

However, all of these optical multi-point non-destructive film thickness measuring devices take a long time to measure one point. For example, methods that calculate film thickness using the wavelength dependence of reflectance are said to require relatively short measurement times;
It takes about 15 seconds to measure black light. For this reason, for example, 10
It takes too much time to measure at multiple points, such as 0 points or more, 700 points, or 800 points, and it is therefore difficult to incorporate the film thickness measuring device into the production line.

Further, a stage for multi-point measurement is required, and in particular, an automatic stage for multi-point measurement is expensive, making the device expensive.

In addition, DENK etal, Proc, Mi
croelectr.

Sem1nar, P P 28-34 (1976
) describes a film thickness measuring device for multi-point measurements.

[Purpose of the invention]

An object of the present invention is to provide a film thickness measuring device that can be incorporated into a manufacturing line by extremely shortening the time required for simultaneous multi-point measurement.

Another object of the present invention is to provide an inexpensive film thickness measuring device that does not require a stage for measuring other points.

The above and other objects and novel features of the present invention include:
It will become clear from the description of this specification and the accompanying drawings.

[Summary of the invention]

A brief overview of typical inventions disclosed in this application is as follows.

In other words, the light from the light source is separated by a spectrometer, and the resulting light is sequentially changed in wavelength and is spread over a plurality of measurement positions (measurement points) of the film to be measured. The incident light from the spectroscope is made to simultaneously irradiate a plurality of measurement positions of the film to be measured, and the reflected light is transmitted to a plurality of photosensors arranged corresponding to the plurality of measurement positions. The light is transmitted through a second optical fiber provided corresponding to each measurement position, and the reflected light at each measurement position is converted into a reflected light intensity signal by the plurality of photosensors, and the reflected light for each wavelength is sequentially detected. This product provides a film thickness measuring device that sends light intensity signal data to a data processing device and calculates the film thickness at multiple measurement positions on the film to be measured.It enables simultaneous measurement of other points on the film to be measured, reducing measurement time. This is an epoch-making shortening, which makes it possible to incorporate this device into a production line, and also eliminates the need for a multi-point measurement stage, resulting in an inexpensive device.

〔Example〕

FIG. 1 shows an embodiment of a film thickness measuring device according to the present invention. In addition, in the illustration, for convenience of explanation, there are three measurement positions (measurement points) on the film to be measured. FIG. 2 shows the data of the reflected light intensity signal versus the wavelength of the incident light at a certain measurement position (measurement point).

The present invention will be explained below using FIGS. 1 and 2.

Now, a semiconductor wafer 1 as a measurement target is placed at a predetermined position, and a plurality of measurement positions (for example, a resist film) 2 formed on the wafer 1 are set.
One end of the optical fiber 3 is placed at each of the points to be measured. Here, three optical fibers 3 are shown for convenience in order to explain the present invention in an easy-to-understand manner, but in reality, the number of measured positions (measured points) may be 100 (points) or 700 (points), depending on the need. Accordingly, a large number of measured positions (measured points) are set, and correspondingly, the number of fibers 3 is the same or more (in case the same measured position is irradiated with multiple optical fibers) ). In order to make the measurement position accurate, it is necessary to set one end of each optical fiber 3 on a predetermined measurement position, or move the wafer side so that each optical fiber 3 is positioned on a predetermined measurement position. 30 as the alignment time to
It takes about seconds.

On the other hand, 4 is a light source that outputs white light, and this light f1
The light from 4 is separated into spectra by a spectrometer 5. The chopper 6 sequentially changes the wavelength of the incident light from the spectroscope 5 and sends it to the other end of each optical fiber 3, one end of which extends above each measured position,
The incident light is transmitted through each optical fiber 3 and irradiated perpendicularly from the one end of each optical fiber 3 to each measured position of the measured film 2 at the same time. Then, the reflected light is sent to each photosensor 8 via an optical fiber 7 paired with the optical fiber 3, respectively. Each photosensor 8 converts the reflected light from each measured position into a reflected light intensity signal, sequentially sends the reflected light intensity signal data for each wavelength to the data buffer 9a of the data processing device 9, and temporarily stores it in the memory. Ru. The data processing device 9 uses a data buffer 9a to process the film at each measured position of the film to be measured 2 based on the measurement data from the data buffer 9a (characteristic data as shown in the second section at each measured position). Calculation device 9 that calculates the thickness using predetermined calculations.
It consists of b. Note that the chopper 6 sequentially sends the incident light from the spectrometer 5 to each optical fiber 3 at a predetermined timing, but the chopper 6 synchronizes with the data buffer 9a and transfers measurement data (for example) from each photosensor 8 to the data buffer 9a. The timing when the reflected light intensity data (with respect to wavelength) is input is matched with the predetermined timing of the chopper 6. Therefore, when reflected light intensity data for incident light of a certain wavelength is input to the data buffer 9a, the chopper 6 sends light of a different wavelength out of the output light of the spectrometer 5 to each optical fiber 3.

Thereafter, the wavelength of the incident light from the spectrometer 5 is sequentially changed by the chopper 6, and the reflected light for each wavelength of the incident light at each measured position is sequentially converted into a reflected light intensity signal for each wavelength by each photo sensor 8. The data (reflected light intensity data for each wavelength of incident light) is temporarily stored in the data buffer 9a. Next, using the data stored in the data buffer 9a, the film thickness at each measurement position (measurement point) can be determined using the following equation (2) using the calculation device 9b that constitutes the data processing device 9.

That is, for example, each wavelength light (
If the reflected light intensity data for the incident light from the spectrometer 5 is obtained as shown in FIG. ), the film thickness of the film to be measured 2 at the certain measurement position is d,
The wavelength that gives the mth maximum value is λ3, (m+1)
If the wavelength that gives the th maximum value is λ2, then the following equation holds true depending on the interference conditions.

2n+ ct,=mλl=(m+1) λ,・(
1) m: Natural number From this, m = λ2/(λ1 - λ2), so 2n+
We obtain d+ = λ1 λ2/(λ, -λ2) - (2). Therefore, in this equation (2), n+, λ1,
By substituting the value of λ2, the film thickness d at the certain measurement position is
, can be found. The arithmetic unit 9b calculates λ from the data as shown in FIG. 2 stored in the data buffer 9a.
1. The value of λ2 is determined, and d is calculated from this value and nl of the weight using equation (2).

As described above, the calculation device 9b can instantaneously calculate the film thickness at each measurement position, display the calculated film thickness on a display device (not shown), or store it as needed. Storage on the device takes place.

For calculation of equations (1) and (2), 0°S,
HEAVENS,'0PTICAL PROPERT
IES OF THIN 5OUNDF I L
MS″DOUVER PUBLICALATIONS, INC.
, New York (1965), p. 115.

In this way, the film thickness at each measurement position (measurement point) is instantaneously calculated by the data processing device 9, and its value can be known over time through the display device.

Therefore, by monitoring and controlling the film thickness at each measurement position of the film to be measured 2 with a monitor having a display device, it is possible to adjust, for example, the resist film thickness to be constant everywhere. Therefore, size distribution is particularly problematic for MOS memories, but the present invention is effective for MOS memories because the resist film thickness can be made constant on the wafer and the size distribution is significantly improved. Also, if the diameter of the wafer 1 is large, the measurement position (measurement point)
If the number of optical fibers 3 and 7 is increased accordingly, the film thickness can be made constant everywhere regardless of the diameter of the wafer 1. As the number of measurement positions increases in this way, monitoring control can be performed so that a nearly constant film thickness distribution can be obtained everywhere.

In principle, if the cross-sectional area of the optical fiber 3.7 per measurement point is S, it is possible to simultaneously measure measurement points up to the wafer area/S, and the film thickness distribution can be highly accurate over the entire area. It can be monitored and controlled so that it remains constant.

Next, the total measurement time is 45 seconds, which is the sum of the alignment time of 30 seconds for the measurement position of the film 2 to be measured and the actual measurement time of 15 seconds, and how many measurement positions (measurement points) are there? Since the measurement time does not change even if the number of measurement points increases, the effect increases as the number of measurement points increases. For example, if conventionally it took 15 seconds to measure one black light, in the present invention, it takes 15 seconds to measure one black light, but in the present invention, it takes 30 seconds for alignment time, that is, 4 seconds.
It is possible to measure as many points as possible (100 points, 800 points, etc.) in 5 seconds. Since the total time required for one measurement is thus 45 seconds, the present device can be incorporated into a production line (cycle time approximately 1 minute).

Furthermore, since multiple points are measured simultaneously, a stage for multiple points measurement is not required, and therefore an automatic stage for multiple points measurements, which was conventionally particularly expensive and had an effect on the cost increase of the device, is no longer necessary, and an inexpensive device can be obtained.

〔effect〕

(1) Simultaneous measurement of multiple points (many measured positions (measured points)) on the film to be measured is possible, and the time for multi-point measurement can be extremely shortened. Moreover, since the measurement time does not change even if the number of points to be measured increases, the effect becomes greater as the number of points to be measured increases.

(2) The total time for multi-point measurement can be extremely shortened and can be applied to production lines.

(3) It is possible to eliminate the need for the conventional stage for multi-point measurement, and therefore also to eliminate the need for an expensive automatic stage for multi-point measurement, making it possible to provide an inexpensive apparatus.

(4) By enabling simultaneous measurement at multiple points, in-line monitor control becomes possible, film thickness can be controlled, and film thickness distribution can be improved.

(5) (4) improves the size distribution of the MOS memory.

(6) Even if the surface area of the film to be measured is large, the number of points to be measured can be increased as much as possible, so simultaneous measurement at multiple points can be handled regardless of the surface area.

Although the invention made by the present inventor has been specifically explained above based on examples, the present invention is not limited to the above-mentioned examples (although it is possible to make various changes without departing from the gist of the invention). For example, in Fig. 1, optical fibers 3 and 7 are used, but from the viewpoint of efficiency, the number of optical fibers 3 and 7 for each measured point is not limited to one each, but various combinations may be used. For example, as shown in FIG. 3(a) at each point to be measured, a plurality of optical fibers 7 that receive reflected light are arranged around one optical fiber 3, and
These plurality of optical fibers 7 may be connected to corresponding photosensors a, and the reflected lights may be sent to the photosensors 8 through these optical fibers 7, and the total intensity signal of the reflected lights may be extracted here. Alternatively, as shown in FIG. 3(b), a plurality of optical fibers 3 and 7 may be used and these optical fibers 3 and 7 may be arranged alternately.

Furthermore, although the chopper 6 is used, it is also possible to make the spectroscope 5 also have the same function and sequentially send light of different wavelengths from the spectrometer 5 to each optical fiber 3 at the same predetermined timing as described above.

[Application field]

In the above explanation, the invention made by the present inventor is mainly applied to the field of application which is the background of the invention, such as measuring the resist film thickness of semiconductor wafers, but the invention is not limited to this, for example, coloring It can be applied not only to the thickness of semiconductor devices but also to all kinds of film thickness measurements, such as measuring the thickness of stainless steel films and measuring the thickness of thin films (such as oxide films) on metal surfaces.

[Brief explanation of drawings]

Fig. 1 is a simplified system configuration diagram showing one embodiment of the film thickness measuring device according to the present invention, Fig. 2 is a characteristic diagram showing data of reflected light intensity signal versus wavelength at a certain measurement point, and Fig. 3 (a) ) and (b) are end views showing the arrangement of optical fibers at the measurement position of the film to be measured, respectively. 1... Wafer, 2... Film to be measured (resist film),
3.7... Optical fiber, 4... Light source, 5... Spectrometer, 6... Chopper, 8... Photo sensor, 9...
Data processing equipment.

Claims (1)

[Scope of Claims] 1. A light source, a spectrometer that spectrally separates the light from the light source, each disposed corresponding to a plurality of measurement positions set on the film to be measured,
and a plurality of photosensors that detect the reflected light from each measurement position, convert it into a reflected light intensity signal, and output it, and transmit the incident light from the spectrometer to simultaneously irradiate the plurality of measurement positions, or a plurality of optical fibers for transmitting reflected light to each of the photo sensors arranged corresponding to the plurality of measurement positions; A film thickness measuring device characterized by comprising a data processing device that calculates the film thickness at a measurement position. 2. The plurality of optical fibers include a plurality of first optical fibers for transmitting the incident light from the spectrometer and simultaneously irradiating the plurality of measurement positions set on the film to be measured; and a plurality of second optical fibers each receiving and transmitting reflected light at a plurality of measurement positions of the film to be measured by irradiating the incident light from the optical fiber. film thickness measuring device.