JP2001349816A - Method and apparatus for evaluating thin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To evaluate the developing characteristics of a resist by measuring the dissolving speed of the resist at a high speed in the development. SOLUTION: A quartz vibrator 1, having a plurality of electrodes 2 each having a resist membrane 3 formed thereon, is connected to a resonance circuit 4, and the resonance frequencies of the respective electrodes are measured by a frequency mater 6 to be fetched in a calculator 7. The quartz vibrator is dipped in the developing liquid in a developing liquid tank 5, and the developing speeds of the resist in the respective electrode regions are measured from a change in the resonance frequencies which corresponds to the development of the resist at the respective electrode ports to evaluate the developing characteristics of the resist.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film evaluation technique, and more particularly to a method and an apparatus for evaluating resist characteristics in a lithography process.

[0002]

2. Description of the Related Art As LSIs become more highly integrated, devices are becoming finer and approaching the limit of the exposure wavelength. In a lithography process that supports this miniaturization, process conditions are optimized so that a resist, which is a key material, achieves high resolution. During this optimization,
Important factors to consider include development characteristics such as resist development speed.

Hitherto, the evaluation of the development characteristics of a resist has been performed by a microbalance method using an optical means or a quartz oscillator. For example, in an optical method, a resist thin film is irradiated with light, and a change in film thickness during development is measured using thin film interference. However, recently, there is an essential problem that the thickness of the resist thin film becomes shorter than the wavelength of the light source, and it is difficult to measure a change in the film thickness with sufficient accuracy. On the other hand, the microbalance method has high sensitivity that can measure even a film thickness of several nanometers, but since it can measure only one type of exposure condition with one crystal oscillator, it is necessary to examine the development characteristics of resist. In practice, the resist on each crystal unit must be irradiated with 10 or more different exposure doses, and the dissolution rate must be measured. Since the measurement is repeated for the number of different exposure doses, the processing speed is slow. Above, there is a big problem.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for measuring the development characteristics of a resist at a high speed to evaluate the development characteristics of the resist, and a measuring apparatus based on the method.

In order to solve the above-mentioned problems, a resist film is applied on a quartz oscillator using a microbalance composed of a quartz oscillator having a plurality of electrodes, and various resists on the plurality of electrode regions are formed. And the developing speed of the resist during development is measured for each electrode. The microbalance method is a mass measurement method utilizing a fact that a change in mass of a substance on an electrode of a quartz oscillator is proportional to a change in a resonance frequency, and is also known as a microbalance.

[0006]

According to the thin film evaluation method of the present invention, a thin film to be measured is formed on a surface electrode of a quartz oscillator, immersed in a solvent, and a change in weight of the thin film is measured. In the microbalance method, a plurality of surface electrodes of the crystal unit are provided separately from each other, and a change in weight of the thin film to be measured on each surface electrode is measured.

The thin film evaluation method according to the second aspect of the present invention
2. The method according to claim 1, wherein the plurality of surface electrodes are provided on a surface of the crystal unit in a region of equal sensitivity by a microbalance method.

According to a third aspect of the present invention, there is provided a thin film evaluation method comprising:
3. The method according to claim 1, wherein the thin film to be measured is formed on a surface of a quartz oscillator, exposed to a predetermined light, and then immersed in the solvent.

A thin film evaluation method according to a fourth aspect of the present invention
4. The method according to claim 3, wherein in each of the plurality of surface electrodes, the thin film to be measured formed thereon is exposed at an individually controlled exposure amount. Things.

According to a fifth aspect of the present invention, there is provided a thin film evaluation method comprising:
5. The method according to claim 3, wherein the plurality of surface electrodes are formed relatively large in an area where the weight change of the thin film to be measured by the exposure is small, and relatively small in an area where the weight change is large. 6. It is characterized by the following.

[0011] The thin film evaluation method according to the invention of claim 6 comprises:
The method according to claim 3, wherein the exposing is:
Exposure with a small change in weight of the thin film to be measured is performed in a relatively sensitive region of the crystal unit, and exposure with a large change in weight is performed in a relatively low sensitivity region of the crystal unit. Is what you do.

According to a seventh aspect of the present invention, there is provided a thin film evaluation apparatus comprising:
The thin film to be measured formed on the surface electrode of the crystal unit is immersed in a solvent, and the surface electrodes of the crystal unit are separated from each other in a thin film evaluation device (micro balance device) for measuring the weight change of the thin film. It is characterized in that a plurality are provided.

[0013] The thin film evaluation method according to the invention of claim 8 comprises:
8. The device according to claim 7, wherein the plurality of surface electrodes are provided on a surface of the crystal unit in a region of equal sensitivity by a microbalance method.

According to a ninth aspect of the present invention, there is provided a thin film evaluation apparatus comprising:
8. The device according to claim 7, wherein the plurality of surface electrodes are formed relatively small in a high-sensitivity region of the microbalance method on the surface of the crystal unit and relatively large in a low-sensitivity region. It is characterized by the following.

According to a tenth aspect of the present invention, in the thin film evaluation apparatus according to any one of the seventh to ninth aspects, the plurality of surface electrode regions are exposed with individually controlled exposure amounts. The exposure means is provided.

According to an eleventh aspect of the present invention, in the thin film evaluation apparatus according to the tenth aspect, the exposure means includes at least one of a light source, an electron beam, an X-ray, and an ion beam as an exposure light source. It is characterized by the following.

According to a twelfth aspect of the present invention, in the thin film evaluation apparatus according to the tenth or eleventh aspect, the plurality of surface electrodes are made relatively small in a region where the amount of exposure to the thin film to be measured is large. It is characterized in that it is formed relatively large in a region where the exposure amount is small.

According to a thirteenth aspect of the present invention, in the thin film evaluation apparatus according to any one of the seventh to twelfth aspects,
A resonance circuit to which the plurality of surface electrodes are individually connected, and a frequency meter for detecting a resonance frequency of the resonance circuit; It is characterized in that the weight change of each of the measurement thin films is measured.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 are diagrams for explaining a thin film evaluation device (microbalance device) and a thin film evaluation method according to one embodiment of the present invention. FIG. 1 is a plan view showing a quartz oscillator for applying a resist thin film as a sample to be measured. 1 is a quartz oscillator, and 2 is a plurality of surface electrodes formed separately on the surface of the quartz oscillator 1. Show. In this example, twelve surface electrodes 2 are formed on the same circumference of the crystal unit 1.

A resist thin film 3 whose characteristics are to be evaluated is applied to the surface of the crystal unit 1 including the electrodes 2.
As a method for applying the resist thin film 3, means such as spin coating, casting, vacuum deposition, and electrolytic polymerization can be used. The back surface of the quartz crystal unit 1 on which the resist is not applied may be provided with a waterproof member by using a protective member so as not to come into contact with the resist developing solution.

FIG. 2 is a diagram showing a schematic configuration of the thin film evaluation apparatus. In FIG. 2, reference numeral 1 denotes a crystal oscillator, and reference numeral 3 denotes a resist thin film to be evaluated applied to the surface of the crystal oscillator 1, all of which are cross-sectional views (the electrode 2 is not shown because it is thin). ). 4 is a developer tank, 5 is a resonance circuit, 6 is a frequency meter, and 7 is a control computer. A detection unit composed of the quartz oscillator 1 coated with the resist thin film 3 is immersed in a developing solution in a developing solution tank 4, and a change in weight of the resist thin film 3 during development is measured. Of course, the measurement may be performed while the developer tank 4 is a flow cell and the developer is supplied.

Each electrode 2 of the crystal unit 1 is connected to an oscillation circuit 4 by a lead wire. By the oscillation circuit 4, a resonance frequency corresponding to the sum of the masses of the resist thin film 3 on the electrode 2 and the quartz oscillator is obtained. That is, when the amount of mass Δm of the resist thin film 3 is added, the resonance frequency of the crystal oscillator at the electrode portion changes by Δω. The relationship between the weight of the resist and the resonance frequency of the crystal unit is given by the following equation (1).

[0023]

(Equation 1)

Where ω is the resonance frequency, N is the frequency constant,
A is the surface area of the electrode on the crystal unit, and ρ is the density of the crystal unit 1. Accordingly, information on the thickness of the resist thin film 3 can be obtained from the weight (mass) or the change in weight of the resist thin film 3. For example, the diameter of a 9-MHz crystal unit 1 is 10 mm.
When the thickness of the resist thin film 3 on the electrode changes by 1 nm, 1
Hz. As described above, the film thickness can be measured with high accuracy on the order of nm. This resonance frequency is measured with a frequency meter 6
And save the data in the control computer 7. Such a circuit is provided for each electrode 2 and a plurality of electrodes 2 are formed by one development.
The development speed of the upper resist thin film 3 can be measured independently and simultaneously.

By irradiating the resist thin film 3 on each electrode 2 with different exposure amounts, information on the development speed corresponding to a plurality of exposure amounts can be obtained by one development, and the development characteristics of the resist can be easily and quickly increased. Can be evaluated. As a means of exposing a plurality of regions of the resist thin film 3 on one crystal unit 1 as a feature of the present invention, a known exposure apparatus can be used. For example, a reduction projection exposure apparatus for semiconductors, an electron beam exposure apparatus, an X-ray exposure apparatus, a laser light source equipped with a galvanomirror, a light source equipped with a step tablet, and the like can be used.

The area of the electrode 2 can be anywhere on the crystal unit 1, but there is an optimum location setting depending on the purpose. In the case of measuring a circular quartz oscillator with reference oscillation, the center of the circle has the highest sensitivity, and the sensitivity decreases toward the periphery. Therefore, if the developing speeds under a plurality of exposure conditions are measured with the same accuracy, an exposure area having an equal area on the circumference equidistant from the center of the circular crystal oscillator may be set as shown in FIG. .

Since the signal intensity is proportional to the electrode area, changing the electrode area is also an effective means. By changing the area, equal sensitivity measurement can be performed for all electrodes. FIG. 3 is one such example. The electrode 11 on the center of the circle, which has the highest sensitivity of the crystal unit 1, has a small area and the lowest sensitivity.
The electrode 12 on the periphery has a large area. In this way, measurement can be performed with the same sensitivity on any electrode.

It is also an effective measuring method to change the measuring sensitivity according to the change in the developing speed. For example, when measuring a positive resist, since the development speed is low in the low exposure area, the change in the signal intensity of the micro balance is small, and it is necessary to measure the dissolution speed with higher accuracy. Therefore, in order to accurately measure this low exposure condition,
What is necessary is just to set a low exposure amount area | region at the center of the circular crystal resonator 1. FIG. 4 shows a quartz oscillator 1 having electrodes with different measurement sensitivities.
This is an example. Since the electrode 21 is located at the center of the crystal unit 1, the measurement sensitivity is highest. Conversely, when the exposure amount is large and the change in the dissolution rate is large, the measurement sensitivity may be low. In this way, it is possible to measure with high accuracy at any dissolution rate.

When a resist thin film 3 in which a plurality of areas on one crystal unit 1 are exposed at different exposure amounts is developed at a time, and a change in resonance frequency at each electrode portion of the crystal unit is measured. It is preferable that each resonance frequency measurement be independent so as not to interfere with each other. Of course, one frequency measurement circuit and one computer may be used as needed. In that case, a timing circuit for sequentially detecting the signal of each electrode may be provided, and the resonance frequency of each electrode may be measured in order. The exposure amount on each electrode can be set to the same exposure amount to check reproducibility or increase the data amount to improve the measurement accuracy. Of course, it is also possible to measure the removal and deposition of the film other than the resist without the exposure step.

The electrodes may be provided with a plurality of similar electrode structures on both sides of the crystal unit, or a plurality of electrode structures may be provided on only one of the electrodes. If only one has a plurality of electrode structures, the other acts as one large common electrode. In this case, when the resist is applied to the common electrode side, the application is performed by spin coating on a flat substrate, so that there is an advantage that a coating film having good flatness can be obtained. When a plurality of electrodes are provided on both surfaces, there is an advantage that the independence of each vibration is high.
In the case of a common electrode, it is needless to say that the interval between the plurality of electrodes on the opposite surface is wider than the thickness of the crystal unit in order to maintain the independence of each vibration.

In the apparatus and method of the present invention described above, since there are a plurality of exposure regions on the resist thin film 3, which is a sample to be measured, applied on one crystal unit 1, a single measurement can be performed. Data of multiple exposure conditions can be measured,
Short measurement time. Further, in the present invention, the sensitivity of each electrode can be changed, so that measurement can be performed under the optimum conditions according to the sample to be measured. Further, in the method of the present invention, a resist thin film 3 as a sample to be measured is applied on the quartz oscillator 1, and SiO ₂ , SiN _x , TiO ₂ is applied on the quartz oscillator 1.
By depositing such as, or electrodepositing Al, Pt, Cu, or the like, the characteristics of the resist on various base materials can be easily evaluated.

Further, the resist thin film on the quartz oscillator is subjected to pattern exposure, and the development process in which patterning is formed can be directly measured. That is, in the case of a positive resist in which the exposed area becomes soluble in an aqueous alkaline solution, the resonance frequency increases if the exposed area is dissolved, and the resonance frequency decreases if the exposed area swells. Dissolution characteristics can be evaluated.

[0033]

EXAMPLES (Example 1) As an example, the development process of a positive resist was measured. The gold electrode 2 is provided by the vapor deposition method in the arrangement shown in FIG.
A cut crystal resonator 1 was used. On this crystal oscillator 1,
Spin-coat positive resist, heat dry, thickness 500
A resist thin film 3 of nm was formed. The resist thin film 3 on the crystal unit 1 is formed by using an ArF excimer laser.
Exposure was performed at a dose of 0.1 to 100 mJ / cm ² .

A lead wire is connected to the electrode 2 of the crystal unit 1 and the back surface of the crystal unit 1 on which the resist is not applied and the lead line are protected from touching the developing solution. Connected to circuit 5. The resonance frequency of the circuit 5 was measured by a frequency meter 6 having a frequency resolution of 1 Hz, and the measured value was stored in a control computer 7. In addition to data acquisition, the control computer 7 also performs timing control for starting measurement before the crystal unit 1 is immersed in the developing solution, and temperature control for keeping the temperature of the detecting unit including the crystal unit 1 and the developing solution constant. Done.

When this crystal resonator 1 was immersed in an alkaline developer at 20 ° C., a change in the resist film thickness over time as shown in FIG. 5 was obtained. The frequency on the vertical axis in FIG. 5 is converted into the thickness of the resist thin film using Equation 1. 0.
At an irradiation dose of 1 mJ / cm ² , the film thickness is constant and does not change with time, but as the exposure dose increases, the development time change of the film thickness increases, and at an irradiation dose of 100 mJ / cm ² , the resist thin film 3 dissolves in a few seconds. You can see that it is doing. Thus, it can be seen that the change in the development time of the film thickness depends on the exposure amount. FIG.
The development speed can be easily obtained from the above, and the development characteristics of the resist can be evaluated. As described above, the development characteristics of the resist can be evaluated by one-time development even if the microbalance method is used, which is made possible only by using the electrode configuration of the present invention.

(Embodiment 2) The gold electrode 1 in the arrangement shown in FIG.
The same operation as in Example 1 was repeated, except that 1, 12 were provided. As a result, a measurement result similar to that of FIG. 5 of Example 1 is obtained, and measurement can be performed with equal sensitivity by using the electrode structure of FIG.

Example 3 Next, an example in which the developing speed was measured at different measurement sensitivities using a negative resist will be described.
In the arrangement shown in FIG. 4, gold electrodes 21 and 22 are provided by a vapor deposition method, and an AT-cut crystal resonator 1 having a fundamental resonance frequency of 5 MHz is provided.
Was used. A negative resist was spin-coated on the quartz oscillator 1 and dried by heating to form a resist thin film 3 having a thickness of 300 nm. The resist on the crystal unit 1 is removed using an ArF excimer laser by 0.1 to 500 mJ / cm ^2.
Exposure. However, the electrode closer to the center was exposed at a higher irradiation dose.

A lead wire is connected to the electrodes 21 and 22 of the quartz oscillator 1 to protect the back surface of the quartz oscillator 1 on which the resist is not applied and the lead wire so as not to come into contact with the developing solution. It was connected to the resonance circuit 5. The resonance frequency of this circuit 5 is measured by a frequency meter 6 having a frequency resolution of 1 Hz,
The measured values were stored in the control computer 7. In addition to data acquisition, the control computer also performed timing control to start measurement before immersing the crystal unit 1 in the developing solution, and temperature control for keeping the temperature of the detecting unit composed of the crystal unit and the developing solution constant. .

When this crystal oscillator was immersed in an alkali developing solution at 20 ° C., the resist was insolubilized at a high irradiation dose, and it was possible to measure with good signal intensity even at the electrode portion where the dissolution rate was reduced. Was. Such measurement of the resist development characteristics with a minute change in film thickness is only possible with the electrode configuration of the present invention.

Example 4 The same operation as in Example 1 was carried out except that the resist was changed to an electron beam resist and exposed to 0.1 to 100 μC / cm ² using an electron beam instead of exposing with an ArF excimer laser. Was repeated. As a result, the development characteristics of the electron beam resist were successfully measured.

[0041]

As described above, the method of the present invention has an advantage that the developing characteristics of a resist can be evaluated by quantitatively measuring the dissolution rate of a resist having a plurality of exposure amounts in a single development in real time. There is. In the present invention, since the mass on the quartz oscillator is measured, there is an advantage that the measurement can be similarly performed not only on the resist thin film but also on an inorganic vapor deposition film or the like.

[Brief description of the drawings]

FIG. 1 is a diagram of a crystal resonator having a plurality of electrodes according to the present invention.

FIG. 2 is a diagram showing a schematic configuration of a thin film evaluation apparatus of the present invention.

FIG. 3 is a diagram of a crystal resonator having electrodes of equal sensitivity according to the present invention.

FIG. 4 is a diagram of a quartz resonator having electrodes of different sensitivities according to the present invention.

FIG. 5 is a diagram illustrating a change in development time of the film thickness of a positive resist.

[Explanation of symbols]

 1 crystal oscillator, 2 electrodes, 3 resist thin film, 4 developer tank, 5 resonance circuit, 6 frequency meter, 7 control computer.

Claims (13)

[Claims] In a microbalance method for forming a thin film to be measured on a surface electrode of a quartz oscillator and immersing the thin film in a solvent, and measuring a weight change of the thin film, the surface electrodes of the quartz oscillator are separated from each other. A thin film evaluation method comprising: measuring a weight change of the thin film to be measured on each surface electrode; 2. The thin-film evaluation method according to claim 1, wherein the plurality of surface electrodes are provided on a surface of the crystal unit at a region of equal sensitivity by a microbalance method. 3. The method for evaluating a thin film according to claim 1, wherein the thin film to be measured is formed on the surface of a quartz oscillator, exposed to a predetermined light, and then immersed in the solvent. 4. In each region of the plurality of surface electrodes, the measured thin film formed thereon is
4. The thin film evaluation method according to claim 3, wherein the exposure is performed at an individually controlled exposure amount. 5. The method according to claim 1, wherein the plurality of surface electrodes are formed relatively large in a region where the weight change of the thin film to be measured due to the exposure is small, and relatively small in a region where the weight change is large. Item 5. The method for evaluating a thin film according to item 3 or 4. 6. The exposure is performed in an area where the weight change of the thin film to be measured is small in a relatively sensitive region of the quartz oscillator, and an exposure in which the weight change is large is relatively sensitive to the quartz oscillator. 4. The method according to claim 3, wherein the step is performed in an area where the temperature is low.
Or the thin-film evaluation method according to 4. 7. A thin film evaluation apparatus for immersing a thin film to be measured formed on a surface electrode of a quartz oscillator in a solvent and measuring a weight change of the thin film, separating the surface electrodes of the quartz oscillator from each other. A thin-film evaluation device, wherein a plurality of thin-film evaluation devices are provided. 8. The thin-film evaluation apparatus according to claim 7, wherein the plurality of surface electrodes are provided on a surface of the crystal unit in a region of equal sensitivity by a microbalance method. 9. The method according to claim 1, wherein the plurality of surface electrodes are formed relatively small in a high sensitivity region of the microbalance method on the surface of the crystal unit, and formed relatively large in a low sensitivity region. The thin-film evaluation device according to claim 7. 10. The method according to claim 10, wherein:
The thin film evaluation apparatus according to claim 7, further comprising an exposure unit configured to perform exposure with an individually controlled exposure amount. 11. The exposure means comprises: light as an exposure light source;
The thin-film evaluation apparatus according to claim 10, further comprising a light source of at least one of an electron beam, an X-ray, and an ion beam. 12. The device according to claim 10, wherein the plurality of surface electrodes are formed relatively small in a region where the exposure amount of the thin film to be measured is large and relatively large in a region where the exposure amount is small. Or the thin-film evaluation device according to 11. 13. A resonance circuit to which the plurality of surface electrodes are individually connected, and a frequency meter for detecting a resonance frequency of the resonance circuit, wherein a change in the resonance frequency causes a change in the resonance frequency on the plurality of surface electrodes. 13. The thin film evaluation apparatus according to claim 7, wherein a change in weight of each of the thin films to be measured is measured.