JPH05102031A - Sensitivity measurement of photosensitive film, and formation of corrosion-resistant film - Google Patents

Abstract

PURPOSE:To provide a method of forming etching-resistant photosensitive film, including coating, exposure, and development; and a quick and accurate method of measuring the sensitivity of photosensitive film, thereby improving the lithographic process for semiconductor manufacture. CONSTITUTION:A plurality of areas 21-28 of a photosensitive film on a substrate are exposed to light in different quantities P1-P8. After the film is developed, the film thicknesses 31-38 of the areas are converted to image data consisting of position and brightness signals. The image data and the exposure data are processed to automatically measure the sensitivity Eth corresponding to the quantity of exposure that makes the photosensitive film completely resolvable. The sensitivity is used to automatically control the speed of a spin coater. Abnormal conditions of development are detected by processing image signals.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a process of coating, exposing and developing a photosensitive film (photoresist) in a photolithography process for manufacturing a semiconductor device, and particularly to a method for measuring the sensitivity of the photosensitive film and a corrosion-resistant mask. Regarding formation method. In recent years, with the miniaturization of semiconductor devices, the control of the coating thickness of the photosensitive coating applied on the substrate, the effective development time of the photosensitive coating on the same substrate, or the uniformity of the developing speed (uniformity). It is important to control the thickness of the photosensitive film. Therefore, a highly accurate measurement technique is required to measure the film thickness of the photosensitive film. The proper film thickness setting based on the measurement results, variations in the characteristics of the photosensitive film, etc. There is a need for a quick and accurate means of correcting the coating conditions for.

[0002]

2. Description of the Related Art The sensitivity of a photosensitive film is represented by the amount of energy required to insolubilize the photosensitive film (in the case of a negative resist) or solubilize it (in the case of a positive resist).
After exposing different areas of the photosensitive coating applied with a uniform thickness on the substrate with different exposure doses, developing under specified conditions, measuring the remaining film thickness of the photosensitive coating after development, and measuring the exposure energy The sensitivity of the photosensitive film was measured by preparing a characteristic diagram showing the relationship of the remaining film thickness, and the exposure amount in the manufacturing process was determined based on the value obtained by multiplying the measured sensitivity by a predetermined coefficient.

Further, the measurement and control of the film thickness of the photosensitive film is performed by using the correlation diagram of the film thickness and the sensitivity obtained by the above-mentioned method for each film thickness of the photosensitive film, by the ellipsometry method, the interferometry method, etc. It was based on the film thickness measured by the optical film thickness measurement method.

[0004]

However, in the above conventional technique, the film thickness of the photosensitive film after development is measured by an optical measurement method such as ellipsometry and interferometry, and the measured value is used as a basis. Since the film thickness of the photosensitive film was controlled in
The work was easily affected by the accuracy of the sensitivity measurement, and required a lot of manpower and time.

Further, in measuring the effective developing time of the photosensitive film in the developing step or the in-plane uniformity of the developing speed, the photosensitive film having the film thickness obtained from the correlation diagram between the sensitivity and the coating film thickness is used. After uniformly forming on the substrate, the sample exposed to a plurality of areas with a uniform exposure amount was developed, and the state of the remaining film thickness of the photosensitive film after development was observed. The sensitivity of the coating is fundamental, and it is directly affected by the measurement accuracy of the film thickness, which requires a huge amount of work.

Therefore, there is a problem that the width of the wiring pattern of the photosensitive film after development cannot be as designed, or the width of the wiring pattern varies within the substrate surface. It was a cause of different defective products.

It is an object of the present invention to provide a rapid and accurate method for measuring the sensitivity of a photosensitive film, and as a result, improve the photolithography process in manufacturing a semiconductor device and save labor.

[0008]

In the method for measuring the sensitivity of a photosensitive film according to the present invention, in order to achieve the above object, a plurality of regions of the photosensitive film formed on a substrate are exposed at different exposure doses. The exposed photosensitive film is exposed and developed, the state of the remaining film thickness of the developed photosensitive film is converted into image data consisting of a position and a luminance signal, and this image data and exposure amount data are processed. Adopted the configuration.

[0009]

According to the present invention, the state of the remaining film thickness of the photosensitive film after coating the photosensitive film on the substrate, exposing a plurality of regions of the photosensitive film with different exposure amounts, and developing under the specified conditions Is image-processed into image data composed of a luminance signal, and the image data and the exposure amount data are processed as information, so that the sensitivity of the photosensitive film can be automatically and accurately measured.

Further, according to the sensitivity thus obtained,
The number of revolutions of the spin coater (spin coater) for obtaining an appropriate film thickness of the photosensitive film, the exposure amount, etc. can be automatically determined without measuring the film thickness itself of the photosensitive film.

Further, it is possible to correct the optimum number of revolutions of the spin coater according to the characteristics of the photosensitive coating material and to detect an abnormality in the developing process, and thus to stabilize the pattern width of the photosensitive film after development. It is possible to prevent the occurrence of defective products in the manufacturing process.

[0012]

EXAMPLES Examples of the present invention will be described below. First Example [Method for Measuring Sensitivity of Photosensitive Coating] FIGS. 1A to 1C are explanatory views of the method for measuring sensitivity of a photosensitive coating according to the first example of the present invention. In this figure, 1 is a substrate on which a photosensitive film is formed, 2 ₁ , 2 ₂ , 2 ₃ , 2 ₄ , 2 ₅ , 2 ₆ , 2 ₇ , 2 ₈
Is the exposure area, 3 ₁ , 3 ₂ , 3 ₃ , 3 ₄ , 3 ₅ , 3 ₆ , 3
_7, 3 ₈ corrosion-resistant coating, 4 denotes an image data formation region.

A method of measuring the sensitivity of the photosensitive film of this embodiment will be described with reference to FIGS. Procedure 1 A positive photosensitive paint is applied onto a substrate 1 such as a semiconductor wafer by a spin coater to form a thin photosensitive film having a uniform thickness.

Procedure 2 Different exposure areas 2 of the formed photosensitive coating₁Two₂,
Two₃Two_FourTwo_FiveTwo ₆Two₇Two₈To step throw
By changing the exposure amount for each shot by the shadow exposure device,
Exposure amount P₁, P₂, P₃, P_Four, P_Five, P₆,
P₇, P₈Exposure is performed (see FIG. 1A). In this figure
In particular, the higher the horizontal line density, the smaller the exposure amount (dark
The lower the horizontal line density, the larger the exposure amount (bright).
It is shown that.

Step 3 The exposed photosensitive film is developed under specified conditions and baked, and the corrosion-resistant films 3 ₁ , 3 ₂ , 3 ₃ , 3 ₄ , 3 ₅ , having different residual film thicknesses depending on the exposure amount, 3 ₆ , 3 ₇ , and 3 ₈ are formed (see FIG. 1B). In this figure, the higher the horizontal line density, the thicker the residual film thickness, and the lower the horizontal line density, the thinner the residual film thickness.

[0016] Procedure obtain image data read by the CCD image pickup device brightness of the image data forming region 4 containing 4 corrosion resistant coating 3 ₁ to 3 ₈ was developed as a result remains. The image data corrosion coatings 3 ₁ to 3 ₈ pattern recognition to determine the brightness of the corrosion-resistant coating 3 ₁ to 3 ₈ corresponding to the exposure amount. The brightness signal of each exposure region sequentially changes from the smaller exposure amount to the larger exposure amount, and converges to a constant level at a certain exposure amount or more.

More specifically, when a positive type photosensitive film is used and a silicon substrate is used, the brightness signal which is the image data of each exposure area is directed from the smaller exposure amount to the larger exposure amount. (In FIG. 1 (B), it increases from left to right) sequentially, and above a certain exposure amount, the photosensitive film in the exposed region is completely dissolved by the development, and the surface of the substrate having a high light reflection coefficient is Because of the exposure, the brightness signal in the exposure area converges at the highest constant level.

When the light reflection coefficient of the substrate is lower than that of the photosensitive film, contrary to this explanation, the luminance signal of each exposure area is
It gradually decreases as the exposure amount increases, and the lowest level converges when the exposure amount exceeds a certain value. When a negative type photosensitive coating is used, the explanation is the reverse of that of the positive type.

Step 5 The image data is processed to determine the sensitivity of the photosensitive coating. FIG. 1C is a characteristic diagram showing the relationship between the exposure amount and the luminance signal. As can be seen in this figure, as the exposure amount increases from P _{1 to} P ₄ , the luminance increases sequentially, and P _{4 and} above converge to the highest constant level. The exposure amount at the point where the luminance tends to increase and then converges is defined as the sensitivity (Eth) of the photosensitive film. This sensitivity can be automatically determined by information processing comparing the signal intensities before and after the luminance signal that changes as the exposure amount increases.

(Second Embodiment) [Method for Measuring Sensitivity of Photosensitive Coating] FIGS. 2A and 2B are explanatory views of the method for measuring sensitivity of a photosensitive coating according to the second embodiment of the present invention. In this figure, 5 is the exposure area for position mark, and 6 is
1 is the same as that described with the same reference numerals in FIG. 1 except that it is a position mark.

In this embodiment, it is formed on the substrate 1.
Exposure areas 2 of the positive-working photosensitive coating₁,
Two₂Two₃Two_FourTwo_FiveTwo₆Two₇Two₈Differently
Exposure P₁, P₂, P₃, P_Four, P_Five, P₆, P₇,
P₈When exposing with P ₁~ P₈Exposure area of
Fixed to the position mark exposure area 5 having a fixed positional relationship
The shape position mark is exposed (see FIG. 2A). That
After development, corrosion resistance is based on this position mark 6
Film 3₁~ 3₈The brightness of the image with a CCD imager
Converted into image data (see FIG. 2A).

The pattern for obtaining According to this embodiment, since it is possible to detect the intensity of the corrosion-resistant coating 3 ₁ to 3 ₈ based on the position mark 6, the position information of the corrosion-resistant coating 3 ₁ to 3 ₈ Corrosion-resistant coating 3 without the need for recognition
It is possible to convert the brightness of _{1 to} 3 ₈ into read image data.

(Third Embodiment) [Exposure Method for Photosensitive Coating] In this embodiment, the sensitivity measured in the first embodiment or the second embodiment is multiplied by a predetermined coefficient to determine the exposure in the manufacturing process. It is a method of exposing the coating film properly.

This coefficient is
A numerical value of about 2 is usually used within a range in which a pattern having a predetermined line width can be formed accurately and stably, and a numerical value that is almost invariable even if the sensitivity (Eth) is different is used.

The sensitivity of the photosensitive film is measured by measuring the residual film thickness after development, and exposure with an exposure amount based on the value obtained by multiplying the coefficient by the above coefficient is conventionally performed manually. According to the present invention, however, the exposure amount can be automatically set and exposure can be performed by inputting this coefficient in advance to the control device of the exposure apparatus.

(Fourth Embodiment) [Exposure Method for Photosensitive Coating] Since the light source of the exposure apparatus currently used is monochromatic light, an interference effect due to the exposure light is produced in the corrosion-resistant coating which is the resist film.

FIG. 3 is an illustration of the interference effect of the exposure light on the photosensitive film. In this figure, A ₁ , A ₂ , A ₃
Is the maximum point of sensitivity, B ₁ , B ₂ and B ₃ are minimum points, and T is the period.

As shown in this figure, when the film thickness of the photosensitive film is increased, it is natural from the definition that the sensitivity tends to simply increase. The period T is (exposure light wavelength λ) / 2 /
The periodic fluctuation of (refractive index n of the photosensitive film) is used as a bias.

In this figure, the maximum value is the photosensitive coating.
The traveling wave and the reflected wave of light cancel each other most strongly in the film
A₁, A₂, A₃Of the film thickness and the progressive wave and the reflected wave strengthen each other
Minimum point B ₁, B₂, B₃Film in the sloping region between the film thickness of
If you set the thickness, even if the thickness fluctuates even slightly, the sensitivity
Changes significantly, so the width of the corrosion-resistant coating after exposure and development
Changes significantly, and a wiring layer is formed by this corrosion-resistant coating
If the width of the corrosion-resistant coating is reduced, the width of the wiring layer
Becomes narrower to increase the resistance, or conversely, the wiring layer
There is a great risk that the width will become wider and a short circuit between wiring layers will occur.
Yes.

Therefore, the maximum points A ₁ , A ₂ , A
It is desirable to set the film thickness of the photosensitive film at _three points, or at the minimum points B ₁ , B ₂ , and B ₃ . Therefore, consider the interests when the maximum point is selected as the film thickness and when the minimum point is selected as the film thickness.

1. Interests when film thickness is selected at point A a. If the film thickness deviates from this value, the exposure will be overexposed. Therefore, if the photosensitive film is positive, the corrosion-resistant film does not remain after exposure and development even if the film thickness is changed to some extent. Therefore, when the wiring layer is formed by etching using the corrosion-resistant coating as a mask, the wiring pattern is not short-circuited even if it is mistaken, and therefore the sequence test is passed.

If a short circuit does not occur in a part of the wiring pattern, even if the width of a part of the wiring pattern becomes narrow, it does not cause a fatal failure in the circuit, and other normal circuits can be used. There are cases. b. Even if there is some variation in the film thickness of the photosensitive film, the sensitivity does not greatly deviate from the center value because the left and right of the maximum value are almost flat.

2. Interests when film thickness is selected at point B a. If it deviates from this point, the amount of exposure is likely to be underexposure, resulting in insufficient exposure, leaving more residue, and increasing the risk of short-circuiting between wiring layers. b. If a short circuit occurs between wiring layers, the entire circuit cannot be evaluated, depending on the location of the circuit, but the location of the short circuit cannot be identified, and it is difficult to find the cause of it. Use a normal circuit. Also can not be. After all, it can be concluded that it is more advantageous to choose point A.

According to the present invention, the sensitivity corresponding to the film thickness at the point A is automatically determined by inputting the influence of such coherence as data to the spin coater, and the exposure of the optimum thickness is performed. A protective coating can be applied.

(Fifth Embodiment) [Photosensitive film coating method] When a photosensitive film is coated on a substrate, a spin coating device is usually used. The thickness is determined by the properties of the applied paint and the rotation speed of the rotating substrate.

FIG. 4 is an explanatory diagram of the relationship between the number of revolutions of the spin coater and the film thickness of the coating film. That is, as shown by the solid line in this figure, for example, there is a constant relationship between the rotational speed of the spin coater and the film thickness of the coating film, but the film thickness has a constant relationship with the sensitivity of the photosensitive film. Therefore, it is not necessary to calculate the film thickness itself of the coating film, and it is only necessary to directly control the rotation speed of the spin coating device for obtaining the desired sensitivity of the photosensitive film.

Since various characteristics of the photosensitive coating vary depending on the product lot at the time of manufacturing, the relationship between the number of revolutions of the spin coater and the film thickness is delicate for each lot as shown by a or b in FIG. You cannot avoid shifting.

Therefore, the relationship between the number of revolutions and the film thickness is periodically measured for each lot, and this data is input to the spin coater to automatically rotate the spin coater at an appropriate number of revolutions. You can

(Sixth Embodiment) [Method of measuring in-plane non-uniformity of development of photosensitive film] Even if the photosensitive film is applied in a uniform thickness and is uniformly exposed,
Since the developing conditions such as the supply method of the developing solution and the nonuniformity of the temperature are not appropriate for some reason, the photosensitive film may be uneven in the residual state after exposure and development.
The present embodiment relates to a method for measuring the in-plane non-uniformity of such developing conditions.

FIG. 5 is an explanatory view of a method for measuring in-plane non-uniformity of developing conditions of the photosensitive film. In this figure, 7 is a substrate, and 8 is a photosensitive film after development.

In this method, first, a photosensitive film is applied to the test substrate 7 with a uniform film thickness, and a plurality of regions on the photosensitive film are applied with the same exposure amount by a step type projection exposure apparatus (stepper). Prepare an exposed sample, insert it in the manufacturing process at appropriate intervals and develop it,
The state of the remaining film thickness of the photosensitive film is converted into image data, and the unevenness of the development conditions is detected from the brightness level of each exposure area and its distribution, and the semiconductor device manufactured by this development process is detected. When the occurrence of unacceptable development unevenness is detected, an alarm may be issued, or the operation of the developing device may be stopped to perform maintenance and inspection.

According to this method, the remaining state of the photosensitive film on the test substrate 7 after exposure and development is converted into image data by a CCD or the like, and the obtained luminance signals of the respective areas are compared to develop the image data. Since it is possible to detect the range of variation in conditions without human intervention, when development unevenness exceeding the allowable limit occurs, the appropriate countermeasures described above can be taken promptly and automatically. Occurrence can be suppressed to a minimum.

In the above description, the test substrate was used to detect the occurrence of uneven development conditions. However, the test film was not used, and the state of the photosensitive film remaining on the semiconductor substrate during manufacture was not detected. It is also possible to detect unevenness in the developing conditions by converting the image data into image data and averaging the brightness in each area.

(Seventh Embodiment) [Measurement Method of Variation of Development Condition of Photosensitive Coating] FIG. 6 is an explanatory view of a measurement method of variation of development condition of the photosensitive coating. In this figure, 9, 11, 13, and 15 are test substrates, 1
0, 12, 14, and 16 are the remaining photosensitive films.

Photosensitive coatings of the same thickness are applied to a plurality of test substrates.
A film is formed and multiple regions of these photosensitive coatings are
0.9E_th, 1.0E_th, 1.1E_th, 1.3E_thFeeling
Degree E _thOf uniform exposure with an exposure amount obtained by multiplying
Prepared, insert it into the manufacturing process and develop
After that, the state of the remaining film thickness of the photosensitive film is converted into image data.
And the amount of exposure at which a part of the photosensitive film in multiple areas begins to come off
(In this example, the exposure amount is 0.9E_thIn the case of, exposure of two areas
The protective film is missing. ) And all photosensitive coatings are completely
Exposed exposure amount (in this example, exposure amount 1.3E_thWhen everything
The photosensitive film of is missing. ) Width (this example
Then 1.3E_th-0.9E_th= 0.4E_thIs. ).

As described above, the cause of the uneven development or the temporal change regardless of the uniform film thickness of the photosensitive film and the uniform exposure amount of each substrate is that the uneven development is effective. Variations in the line width of the wiring pattern can be estimated from the non-uniformity of the development time or the development speed and their fluctuations, and the width of the exposure amount from the first removal of the photosensitive film to the complete removal thereof. ..

Therefore, it is judged whether or not the developing condition is within the allowable range for the semiconductor device being manufactured. If it is within the allowable range, the developing device is stopped and the developing condition is checked. By making the correction, it is possible to suppress the generation of defective products thereafter. In this case, the exposure,
Since the remaining state of the photosensitive film after development is performed by using the brightness signal by image processing, it can be executed quickly and easily without human intervention.

In this embodiment, the exposure is carried out by using the step-type projection exposure apparatus having a square exposure area in order to facilitate pattern recognition by the edge of the exposure area when converting into image data. Specifically,
It is also possible to perform blank exposure with a uniform exposure amount on the entire substrate,
In this case, the same measurement as described above can be performed by calculating the area of the portion where the photosensitive film has fallen out.

In the above description, the test sample was used to detect the occurrence of uneven development conditions. However, the test sample was not used, and the state of the photosensitive film remaining on the semiconductor substrate during manufacture remained. Can be converted into image data, and the luminance in each area can be averaged to detect variations in the developing conditions.

[0050]

As described above, according to the present invention,
The sensitivity of the photosensitive film is automatically measured by performing image processing on the state of the remaining film thickness after development of the photosensitive film, and based on this value, appropriate coating and exposure of the photosensitive film in the manufacturing process. , It becomes possible to develop, and by processing the remaining state of the photosensitive film after development, it is possible to automatically measure the fluctuation of development conditions and the degree of unevenness. It is possible to prevent the occurrence of defective products and suppress the generation of defective products in the manufacturing process.

[Brief description of drawings]

1A to 1C are explanatory views of a sensitivity measuring method of a photosensitive coating according to a first embodiment of the present invention.

2 (A) and 2 (B) are explanatory views of a sensitivity measuring method for a photosensitive coating of a second embodiment of the present invention.

FIG. 3 is an explanatory diagram of an interference effect due to exposure light of a photosensitive film.

FIG. 4 is an explanatory diagram of the relationship between the number of rotations of a spin coating device and the film thickness of a coating film.

FIG. 5 is an explanatory diagram of a method for measuring in-plane non-uniformity of developing conditions of a photosensitive film.

FIG. 6 is an explanatory diagram of a method for measuring fluctuations in developing conditions of a photosensitive film.

[Explanation of symbols]

1 Substrates on which a photosensitive film is formed 2 ₁ , 2 ₂ , 2 ₃ , 2 ₄ , 2 ₅ , 2 ₆ , 2 ₇ , 2 ₈ exposure areas 3 ₁ , 3 ₂ , 3 ₃ , 3 ₄ , 3 ₅ , 3 ₆ , 3 ₇ , 3 ₈ Corrosion resistant coating 4 Image data forming area

Claims (7)

[Claims] 1. A method of exposing a plurality of regions of a photosensitive coating formed on a substrate with different exposure amounts, developing the exposed photosensitive coating, and a state of residual film thickness of the developed photosensitive coating. Is a method for measuring the sensitivity of a photosensitive film, which comprises converting image data consisting of a position and a luminance signal and processing the image data and the exposure amount data. 2. A residual film thickness of a photosensitive film developed by exposing a position detection mark at a position having a specific relationship with the plurality of regions when exposing the plurality of regions of the photosensitive film with different exposure amounts. 2. The method for measuring the sensitivity of a photosensitive film according to claim 1, wherein said state is converted into image data based on this position detection mark. 3. A state of remaining film thickness of the developed photosensitive film by exposing a plurality of regions of the photosensitive film formed on a substrate with different exposure doses, developing the exposed photosensitive film, and developing the exposed photosensitive film. Is converted into image data consisting of position and brightness signals, and the sensitivity of the photosensitive film is measured by processing this image data and exposure amount data, and the sensitivity is multiplied by a predetermined coefficient to produce the exposure amount. A method for forming a corrosion resistant coating, which comprises exposing a photosensitive coating on a substrate in a step. 4. A plurality of substrates are uniformly coated with photosensitive coatings having different film thicknesses, and a plurality of photosensitive coatings coated on the substrates are provided for the respective substrate thicknesses. Areas are exposed with different exposure doses and the exposed photosensitive coating is developed,
The sensitivity of each photosensitive film is measured by converting the state of the remaining film thickness of the developed photosensitive film into image data consisting of position and brightness signals, and processing this image data and exposure amount data to determine the sensitivity of each photosensitive film. A method for measuring the film thickness of a photosensitive film from the correlation between film thickness and sensitivity. 5. A plurality of substrates are uniformly coated with photosensitive coatings having different film thicknesses between the substrates, and a plurality of photosensitive coatings coated on the substrates are provided for the respective substrate thicknesses. Areas are exposed with different exposure doses and the exposed photosensitive coating is developed,
The sensitivity of the photosensitive film was measured by converting the state of the residual film thickness of the developed photosensitive film into image data consisting of the position and the luminance signal, and processing this image data and exposure amount data. A method for correcting the coating film thickness of a photosensitive film based on the interference effect of the photosensitive film. 6. A different area of a photosensitive film coated on a substrate is exposed with the same exposure amount, the state of the remaining film thickness of the photosensitive film after development is converted into image data, and the development is performed from this image data. A method for measuring the effective development time or the uniformity of the development speed of the photosensitive film in the process. 7. A plurality of regions of a photosensitive film uniformly applied on a plurality of substrates with the same thickness are uniformly exposed with different exposure amounts for each substrate, and the photosensitive film remains after development. The state of the film thickness is converted into image data, and from this image data, the exposure amount at which a part of the photosensitive film begins to dissolve and the exposure amount at which all the photosensitive film dissolves are detected, and development is performed from the difference in the exposure amount. A method for measuring the fluctuation state of the effective developing time or developing speed of the photosensitive film in the process.