JPS60250640A - Temperature measuring device by fluorescent light - Google Patents

Abstract

PURPOSE:To measure temperature distribution in high resolution and sensitivity without contact by emitting a laser light to a photoresist coated thinly on an IC, and corresponding the variation in the fluorescent light intensity from the resist itself to the variation in the temperature. CONSTITUTION:A laser light 11 generated from a generator 1 is enlarged via 2 to a thick laser light, an optical path is bent by a mirror 3 for reflecting the laser wavelength, the light is focused by a lens 4 at a focal position to approx. mum degree to emit a sample 5. The fluorescent light 13 emitted from the sample and the laser reflected light are formed through the lens 4 to parallel light beam, separated by the mirror 3, the passed light is led through a fluorescent filter 7 and a condensing lens 8 to a detector 9, and analyzed by a signal processor 10. When a portion locally heated is presented on a photoresist on the substrate, the fluorescent light intensity decreases near the portion. With this configuration, since the photoresist is used, influence of impurity diffusion can be eliminated, and the position resolution of temperature distribution can be set to 1mum or lower by selecting the laser light. Since the photoresist stores the information corresponding to the received temperature, it can be analyzed later.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to the measurement of temperature distribution on the surface of a sample, and is particularly suitable for measuring the temperature of an integrated circuit pattern after coating a photoresist film in the process of manufacturing a semiconductor integrated circuit. This article relates to a non-contact measurement device using a fluorescence method.

[Background of the invention]

In the conventional temperature measurement method using the fluorescence method, a fluorescent substance is added to a photoresist thin film applied to the measurement substance, and the fluorescence intensity is made to correspond to the temperature (P, Kolde et al.
r and J, A, Tyson; Appl, Ph
ysi.

Lett, 42 (1), 117 (1983)
). However, in this method, it is necessary to add a fluorescent substance to the photoresist material, and there are problems such as an adverse effect on the semiconductor surface due to diffusion of the added fluorescent substance into the measurement sample.

[Purpose of the invention]

An object of the present invention is to provide a device that detects the temperature distribution of a semiconductor circuit pattern in a non-contact manner, with high resolution, and with high sensitivity.

[Summary of the invention]

The present invention utilizes photoresists commonly used in semiconductor etching as is. That is, a method was used in which, when photoresist thinly applied on a semiconductor integrated circuit is irradiated with laser light, changes in fluorescence intensity from the photoresist itself are correlated with changes in temperature.

As an example of photoresist, AZ1350J (product name=S
A case in which the software (Hippley, Inc.) is used will be specifically explained. A photoresist AZ1350J (hereinafter referred to as sample) coated with a constant film thickness on a Sl wafer was coated with a wavelength of 48
When 8.0 nm Ar laser light is irradiated, fluorescence having a spectrum as shown in FIG. 1 (measured values, but no corrections were made by the optical system or light receiving system) is generated. It was found that this fluorescence intensity was reduced by heating the sample. Figure 2 shows this situation. Figure 0 shows the fluorescence intensity of the sample at each temperature when the sample was heated from room temperature (25℃) to about 100℃. It is observed that the fluorescence intensity decreases. This means that changes in sample temperature can be interpreted as changes in fluorescence intensity. The temperature range that can be measured here is determined by the heat resistance of the sample, and in this example is up to approximately 100°C.

The temperature change in the fluorescence intensity of the sample is an irreversible change, and this situation is shown in Figure 3. Figure 3(a) shows the change in the temperature of the sample. The temperature is set to T at t. Next, consider the case where the temperature is returned to the original temperature T at time t3 after cooling.

The change in fluorescence intensity of the sample at this time is shown in the same figure (b).

At time t, the fluorescence intensity was T, but when the temperature became T due to heating, according to Fig. 2,
When the fluorescence intensity reaches I2, the fluorescence intensity decreases to I2 according to FIG.

Next, when the temperature is lowered and returned to its original state (time ta, temperature T1
), the fluorescence intensity is I, but it is an LSI, and the sample retains the received thermal information.

This retention rate is called the temperature information retention rate and is (I+-In
)/(it-Ii). Figure 4 shows the change in temperature information retention rate with respect to the sample temperature difference (I2-TI). In Figure 4, the reference temperature (T,) is room temperature (25
℃). By calibrating with this diagram, it becomes possible to track the thermal information received by the sample later.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be explained with reference to FIG. 5. This embodiment includes a laser beam irradiation system and a sample holding system.

It consists of a fluorescence signal detection and processing system. The laser light irradiation system is a laser light generator! The laser beam 11 emitted by the
and a dichroic mirror 3 that reflects the laser wavelength.
The optical path of the laser beam 12 is bent by 90 degrees, and then the laser beam diameter at the focal position is focused to about μm using the condenser lens 4, and the sample 5 is irradiated with the laser beam.

The sample holding system fixes the sample 5 to the sample moving table 6. The sample moving stage 6 is designed to be able to move three-dimensionally, and is designed to hold the sample 5 at a position where the laser beam is minimized.

The fluorescence signal detection/processing system collects the fluorescence 13 emitted from the sample and the reflected light of the laser beam again using a condensing lens 4 into parallel light, separates the fluorescence and the reflected laser light using a dichroic mirror 3, and filters the transmitted fluorescence through a fluorescence filter 7 and The light is guided to a photodetector 9 by a condensing lens 8 for detection, and can be analyzed by a signal processing device 10.

Here, by moving the sample 5 two-dimensionally in the direction perpendicular to the optical axis using the sample moving table 6, the temperature distribution of the sample 5 can be easily measured. Consider the sample. Consider a sample in which a photoresist 15 is coated on a substrate 14 of a semiconductor integrated circuit, and assume that there is a locally heated region 16 around point B. Points 0 A, B,
When the fluorescence intensity distribution on the line passing through C was measured using the apparatus shown in Figure 5, the fluorescence intensity decreased in the vicinity of 0 point B as shown in Figure 6(b), indicating that the temperature had increased. It shows. By using the measurement results of the fluorescence intensity and FIGS. 2 and 4, it is possible to know the temperature experienced by the region 16.

As described above, according to this embodiment, the temperature distribution on the sample surface can be measured without contact.
is moved using the sample moving stage 6, but the same effect can be obtained by fixing the sample and moving the laser light irradiation system and fluorescence signal detection/processing system.

〔Effect of the invention〕

According to the present invention, since a photoresist that is commonly used in the etching process of semiconductors is used, there is little influence of impurity diffusion into the semiconductor. Furthermore, the positional resolution of the temperature distribution can be easily reduced to 1 μm or less by selecting the laser beam to be used, and the measurable temperature range is wide from room temperature to about 100° C.

Furthermore, since photoresist stores information corresponding to the temperature it receives, it has the novel effect of allowing the temperature to be analyzed later even if it cannot be measured in real time.

[Brief explanation of drawings]

Figure 1 is an example of the fluorescence spectrum of photoresist, Figure 2 is a measurement diagram showing the temperature dependence of fluorescence intensity, Figure 3 is an explanatory diagram showing the information retention characteristics of the temperature applied to the photoresist, and Figure 4 is a diagram showing the temperature dependence of the fluorescence intensity.
The figure is a measurement diagram of temperature information retention characteristics, and FIG. 5 is a block diagram showing the basic configuration of a temperature measuring device according to an embodiment of the present invention.
FIG. 6 is a schematic diagram showing one embodiment of the present invention. 1... Laser light generator, 2... Luminous flux expander, 3
...Dichroic mirror, 4...Condensing lens, 5
... Sample, 6... Sample moving stage, 7... Filter, 8... Condensing lens, 9... Photodetector, 10...
Signal processing device. 11.12...Laser light, 13...Fluorescence, 14.
...Substrate, 15...Photoresist, 16...Heated liquid length C) 6th country inclusion #Rohi's phrase 11

Claims (1)

[Claims] A sample stage on which a semiconductor sample whose surface is coated with a photoresist film is movable in two dimensions; a light source that generates a light beam for inducing fluorescence from the photoresist film on the surface of the semiconductor sample; means for focusing a light beam on a minute area on the surface of the semiconductor sample; means for transmitting only the fluorescence generated from the photoresist film on the surface of the semiconductor sample by irradiation with the light beam; and detection for generating an electrical signal corresponding to the intensity of the fluorescence. 1. A temperature measuring device using fluorescence, comprising: means.