JP2737693B2 - Dissolution rate measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for measuring a dissolution rate, and more particularly, to an apparatus for accurately and efficiently measuring a dissolution rate of a photoresist used in a lithography process in a semiconductor device manufacturing process.

[0002]

2. Description of the Related Art Conventionally, this type of photoresist dissolution rate measuring apparatus is shown on pages 562 to 570 of the Institute of Electronics, Information and Communication Engineers (August 1993, Vol. J76-C-2II, No. 8). As described above, the interference effect by monochromatic light is used. FIG. 3A shows a conventional dissolution rate measuring device. A conventional dissolution rate measuring device includes a developing container 1, a developing solution 2, a substrate supporting jig 3, a silicon substrate 4,
Developing part 7 consisting of photoresist 5 and quartz glass window 6
A light source unit 10 including a lamp light source 8 and a convex lens 9;
Irradiation unit composed of optical fiber 11, convex lens 12, signal detection unit 1 composed of monochromatic filter 13 'and detector 14'
5, and a signal processing unit 16 for processing the detected signal.

Next, the operation of a conventional dissolution rate measuring device will be described. A silicon substrate 4 in which a developing container 1 is filled with an alkali developing solution (tetramethylammonium hydroxide 2.38% by weight) 2 and a photoresist (PFI-26 manufactured by Sumitomo Chemical Co., Ltd.) 5 is coated on a substrate supporting jig 3 is fixed. I do. The light emitted from the mercury lamp light source 8 is applied to the sample through the optical fiber, and the reflected light is guided to the detection unit through the optical fiber, passes through the monochromatic filter 13 ', and is converted into an interference signal by the detector 14'. The measured value is compared with the calculated value by the signal processing unit 16 and converted into a resist film thickness.

[0004]

The above-mentioned conventional photoresist dissolution rate measuring apparatus has various problems. For example, the detection signal of the actual dissolution rate measuring device includes:
Various noise components are superimposed due to vibration during measurement or disturbance such as external light. FIG. 3B shows an example of an interference waveform of a resist measured by a conventional measurement method. It can be seen that a sinusoidal waveform is obtained relatively well, but with noise. Therefore, the resist film thickness calculated from the detection signal also includes many errors, and it is difficult to measure the dissolution rate with high accuracy. Further, since the light quantity of the mercury lamp as the light source decreases with the passage of time, the obtained interference waveform also attenuates with the passage of time, so that it has been difficult to perform stable measurement over a long period of time.

[0005] Further, in the conventional dissolution rate measuring device, since the area irradiated with light is large, it is difficult to dissolve the photoresist.
When there is considerable non-uniformity, coherence is reduced, and there is a fatal defect that an interference waveform cannot be obtained. In recent years, the degree of deterioration of the interference waveform due to the non-uniform dissolution tends to be remarkable in recent years, particularly in resists having good resolution and large dissolution contrast.

[0006] In order to solve such a disadvantage, Japanese Patent Laid-Open Publication No.
JP-A-38822 proposes a method for calculating the dissolution rate when the interference waveform is deteriorated, but has the drawback that the calculation is complicated and the dissolution rate cannot be uniquely determined. .

Further, in the conventional dissolution rate measuring device, basically, the dissolution rate needs to include at least two maximum values or minimum values since it is calculated based on the interval between the maximum values or the minimum values of the interference waveform. is there. Therefore, when the dissolution rate is low, there is a drawback that it takes a long time until a maximum value or a minimum value appears in the interference waveform. For example,
When a monochromatic light of 650 nm is used as the light source, the interval between the maximum value or the minimum value of the interference waveform is about 0.1 μm (≡λ / 4n).
It is. Here, λ is the wavelength of the measurement light, and n is the refractive index of the resist. The actual photoresist dissolution rate is 1 (μm
/ S) to about 1E-5 (μm / s). When measuring a dissolution rate of about 1E-5 (μm / s), at least 1E4 is required to obtain a maximum or minimum value. A development time of at least seconds (2.8 hours) is required. In this case, the measurement efficiency is low, and it is necessary to measure the reflected signal stably over a long period of time. Therefore, accurate measurement was impossible with the conventional apparatus.

An object of the present invention is to provide an apparatus capable of accurately and efficiently measuring the dissolution rate of a resist which is not affected by external noise and has poor dissolution uniformity.

[0009]

In the dissolution rate measuring apparatus of the present invention, at least a developing section for developing a resist, a light source section, a signal detecting section for detecting light reflected from the resist,
A signal processing unit that processes a detection signal obtained from a signal detection unit, wherein the signal detection unit has means for measuring a spectral spectrum of reflected light, and the signal processing unit calculates a resist film thickness from the spectral spectrum. It is characterized by having a means for obtaining and a means for measuring the dissolution rate of the resist from the temporal change of the calculated resist film thickness. Here, the means for measuring the spectral spectrum of the signal detecting section comprises a multi-channel spectroscope, and the signal processing section includes means for sequentially performing a Fourier transform of the detected spectral spectrum, and a means for obtaining the obtained Fourier transform spectrum. A particularly desirable dissolution rate measuring apparatus can be obtained by having a means for calculating the resist film thickness from the above, and a means for calculating the dissolution rate from the temporal change of the calculated resist film thickness.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings.

(Embodiment 1) FIG. 1A shows an embodiment of the present invention. The dissolution rate measuring apparatus of the present invention is different from the conventional apparatus of FIG. 3 in that the inside of the light source section 10 is constituted only by the lamp light source 8 and the convex lens 9 and that the signal detecting section 15 includes the diffraction grating 13 Channel detector 1
It consists of four.

The operation of the dissolution rate measuring device according to the present invention will be described. A developing container 1 is filled with an alkali developing solution (tetramethylammonium hydroxide 2.38% by weight) 2, and a silicon substrate 4 on which a resist to be measured (PFI-26 manufactured by Sumitomo Chemical Co., Ltd.) 5 is applied to a substrate supporting jig 3 Fix it. The light emitted from the mercury lamp light source 8 is applied to the sample through the optical fiber, and the reflected light is guided to the spectrometer through the optical fiber, and the spectrum is measured.
The measured spectrum is compared with the spectrum of the mercury lamp measured in advance by the signal processing unit 16, and the spectrum of reflectance is calculated. FIG. 1B shows an example of the measured spectral spectrum waveform. Generally, in the measurement of the spectrum of a thin film, the wavelength giving the maximum value and the minimum value of the reflectance is given by the following equation.

Λ _max = 4nd / (2k−1) λ _min = 4nd / 2k where n is the refractive index of the resist, d is the thickness of the resist at the time of measurement, and k is a positive integer. The measurement example of FIG.
Since 1.65 and d = 733 nm, λ _{max in the} visible light amount region
And λ _min are respectively λ _max = 691 nm, 539 nm, 440 nm, 3272 nm and λ _min = 806 nm, 605 nm, 484 nm, 403 nm. Accordingly, conversely, the film thickness d can be obtained from λ _max and λ _min of the obtained spectral spectrum using the following equation.

D = λ _max (2k−1) / 4n d = λ _min (2k) / 4n The measurement of the resist film thickness by this method is performed, for example, for 50 msec.
The measurement is performed at c intervals, and the dissolution rate is calculated from the following equation. Dissolution rate R = {resist film thickness d (t1) -resist film thickness d (t2)} / (t2-t1) where t2 and t1 are the measurement times of the resist, respectively.

In the above description, the resist film thickness can be more accurately calculated by Fourier-transforming the spectral spectrum especially when obtaining the resist film thickness from the spectral spectrum.

Generally, the reflectance R of a single-layer thin film at normal incidence is represented by the following equation.

R2 = f (sin2 (δ / 2)) where f is an arbitrary function δ = 4πnd / λ.

That is, the reflectance R2 is δ, that is, 1 /
Since it is a periodic function of λ, the distribution of the film thickness d can be obtained by Fourier-expanding the spectral spectrum by 1 / λ.
When this Fourier transform is used, the resist film thickness distribution is output as information, so that the dissolution rate can be measured accurately even when the dissolution reaction of the resist occurs unevenly.

According to this embodiment, since the resist film thickness can be measured without directly depending on the intensity of the detection signal, accurate measurement can be performed without being affected by disturbance, and the resist is not uniformly dissolved. Even in this case, accurate measurement is possible. Further, even when the temporal change of the resist film thickness is very small, the resist film thickness can be measured instantaneously. Therefore, particularly when the dissolution speed is low, the accurate dissolution rate can be measured in a short time.

(Embodiment 2) A second embodiment of the present invention will be described with reference to FIG. In the embodiment shown in FIG. 2, the developer 2 is dropped on the photoresist 5 on the silicon substrate 4, the optical fiber 11 is inserted into the developer 2, the light from the light source unit 10 is irradiated, and the reflected light is converted into the optical fiber 11. The light is then introduced into the spectrometer and the spectrum is measured. The measured spectrum is compared with the spectrum of the mercury lamp measured in advance by the signal processing unit 16, the spectrum of reflectance is calculated, and the resist film thickness is calculated based on the spectrum.

In the second embodiment, since it can be easily introduced into a wafer processing step in a normal semiconductor device manufacturing process, it can be used not only for measuring the dissolution rate but also as an in-situ monitor for a developing process. it can.

Although the apparatus for measuring the dissolution rate of a resist has been described above, the present invention is not limited to the dissolution rate at the time of development of the resist, but also changes in the resist film thickness at the time of heat treatment after exposure of the chemically amplified resist, It is apparent that the present invention can be applied to control of the amount of oxidation, measurement of a change in the thickness of an object to be etched in an etching step, and the like.

[0023]

As described above, according to the dissolution rate measuring apparatus of the present invention, the spectroscope is included in the detection unit, and the dissolution rate can be measured stably and accurately by measuring the spectrum of the reflected signal. Further, by using a multi-channel spectrometer for the spectroscope of the detection unit, a spectrum can be easily obtained at a high speed. Furthermore, by sequentially performing the Fourier transform of the detected spectral spectrum and calculating the resist film thickness from the obtained Fourier transform spectrum, the resist film thickness can be accurately measured even when the dissolution reaction is uneven. Therefore, the dissolution rate can be measured accurately.

[Brief description of the drawings]

FIG. 1A is a diagram showing a first embodiment of the present invention. (B) An example of a spectrum measured according to the present invention.

FIG. 2 is a diagram showing a second embodiment of the present invention.

FIG. 3 (a) is a view showing a conventional dissolution rate measuring method. (B) is an example of an interference waveform measured by a conventional measurement method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Developing container 2 Developing liquid 3 Substrate support jig 4 Silicon substrate 5 Photoresist 6 Quartz glass window 7 Developing part 8 Lamp light source 9 Convex lens 10 Light source part 11 Optical fiber 12 Convex lens 13 Diffraction grating 13 'Monochromatic filter 14 Multi-channel detector 14 ′ Detector 15 Signal detector 16 Signal processor

──────────────────────────────────────────────────の Continuation of the front page (51) Int.Cl. ⁶ Identification symbol FI H01L 21/30 569Z (56) References JP-A-5-34114 (JP, A) JP-A-61-217705 (JP, A) JP-A-63-302307 (JP, A) JP-A-6-89855 (JP, A) JP-A-5-209724 (JP, A)

Claims (2)

(57) [Claims] 1. A developing unit for developing at least a resist, a light source unit, an irradiating unit for irradiating light from a light source, a signal detecting unit for detecting reflected light from the resist, and a detection obtained by the signal detecting unit. in dissolution rate measuring apparatus <br/> resist and a signal processing unit for processing a signal, the signal detection unit comprises means for measuring the spectrum of the reflected light, the signal processing unit, the resist from the spectrum and means for determining the thickness, and means for calculating the dissolution rate of the resist from the time variation of the calculated thickness of the resist film, means for measuring the spectrum of the signal detection unit circle
A channel thickness spectrometer , and obtains a resist film thickness from a spectrum of the signal processing unit.
Means for performing a Fourier transform of the detected spectrum.
And the obtained Fourier transform spectrum
A means for calculating a resist film thickness from the solution. 2. Irradiation for irradiating a resist with light from a light source.
The unit radiates light from the light source onto the resist through an optical fiber.
2. The dissolution rate measuring device according to claim 1 , further comprising means for guiding the developer into the dropped developer .