JPS62132318A - Exposing apparatus - Google Patents

Abstract

PURPOSE:To obtain a uniform pattern by detecting in advance the thickness and the refractive index of a photosensitizer layer of an element to be exposed before exposing, calculating an emitting exposure amount for maintaining an effective exposure amount constant on the basis of the detected results, and controlling the emitting exposure amount to the element to be exposed. CONSTITUTION:When an element 1 to be exposed is emitted by an incident polarized light 12 of linear polarized light at an incident angle theta, the light 12 is reflected on the surface of the element 1 to be exposed to cause the polarized state to alter. The light is incident as reflected polarized light 13 to a polarization measuring unit 4. Phase difference delta and reflection counting ratio angle psi of the measured results of the unit 4 are fed to a refractive index film thickness calculating mechanism 5, which are used together with a wavelength lambda, the incident angle theta and refractive indexes n0, n1 of a medium 14 and the element 1 to be exposed, input in advance to calculate the refractive index (n) and the thickness (d) of a photosensitizer layer 11. Data of the refractive index (n) and the thickness (d) calculated by the mechanism 5 are fed to an emitting exposure amount calculating and controlling mechanism 6, which calculates an emitting exposure amount that the effective exposure amount becomes constant.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to an exposure apparatus, and more particularly to an exposure apparatus that controls the amount of exposure fl and l so that the pattern obtained by exposure is uniform.

[Prior Art] Recent advances in LSI manufacturing technology have been remarkable, and IC circuit patterns are becoming increasingly finer due to higher integration. For this reason, exposure equipment that transfers IC circuit patterns onto wafers also
The conventional contact method and proximity method have been replaced by a projection method, and even in the projection method, there has been a shift from a mirror optical system to an exposure apparatus having a lens projection optical system that can reduce the pattern and transfer it with high precision.

In an exposure apparatus having this lens projection optical system, the aberration of the optical system is minimized only for a single wavelength in order to maximize resolution performance. In other words, the wavelength of light that can be used for exposure is a single line, for example, Q line (wavelength 436 nm) or i
The irises have only lines (wavelength 365 nm).

However, in the process of coating an exposed object with a photosensitizer such as photoresist, the thickness and refractive index of the photosensitizer layer are affected by the viscosity of the photosensitizer, the content of the solvent, and the temperature of the hot water.
Obtaining a uniform photosensitive agent layer is extremely difficult. For this reason, especially in single-line exposure equipment, the amount of light irradiated to the exposed object (
Even if the irradiation exposure amount is constant, if the photosensitive agent layer is not uniform, there is a drawback that the pattern shape obtained is unstable due to standing waves generated in the photosensitive agent layer.

In other words, the energy of light that effectively acts on the photosensitizer (effective exposure amount) varies depending on the thickness and refractive index of the photosensitizer layer.
It is not possible to keep the effective exposure m constant just by keeping the irradiation exposure constant as with conventional exposure equipment, and therefore the width of the pattern 1q produced as a result of exposure changes, causing problems in the manufacture of IC circuits. It became.

In addition, the reflectance of the exposed object is measured using light at the wavelength used for exposure, and in order to keep the shape of the pattern constant despite variations in the thickness of the photosensitive agent layer (that is, to keep the effective exposure amount constant). ) Exposure apparatuses have been proposed that have means for calculating the irradiation exposure amount. However, even with this device, the wavelength of the light used for reflectance measurement is the same as the exposure wavelength, so it is not possible to measure the portion of the pattern that is actually exposed. In addition, if the thickness of the photosensitive agent layer varies greatly by more than λ/4n, where the wavelength of the measurement light is λ and the refractive index of the photosensitive agent is n, the optimum irradiation exposure amount may not be determined. However, this method has the disadvantage that it cannot detect step breaks in the photosensitive material at the step portion of the exposed object, and cannot solve important problems in IC circuit manufacturing.

[Object of the Invention] The object of the present invention has been made in view of the above-mentioned drawbacks of the conventional exposure apparatus. An object of the present invention is to provide an exposure apparatus that calculates an irradiation exposure amount that makes the effective exposure amount constant based on the result, controls the irradiation exposure amount to the exposed object, and makes it possible to obtain a uniform pattern.

In addition, the present invention also provides for avoiding unnecessary work by skipping exposure work on objects to be exposed that pose problems in IC circuit manufacturing, such as large variations in the thickness of the photosensitive agent layer, without exposing them to light. A further object is to make it possible to improve throughput (yield).

Examples] Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic diagram of an exposure apparatus according to an embodiment of the present invention. In the figure, 1 is an exposed object coated with a photosensitizer, 2 is an exposed object suction chip that adsorbs and holds the exposed object 1, and 3 is an exposed object with light of an arbitrary wavelength in an arbitrary polarization state. A light leakage light source capable of irradiating the body 1; 4 a polarization measuring device for measuring the polarization state of light reflected from the subject 1; A refractive index/thickness calculation mechanism 6 calculates the refractive index and film thickness, and 6 is an irradiation unit whose effective exposure amount is constant for the refractive index and film thickness of the photosensitive material layer calculated by the refractive index/thickness calculation mechanism 5. The irradiation exposure calculation/control mechanism 7 calculates the exposure amount and controls the irradiation exposure amount to the exposed object. 8 is a reticle or mask on which the IC circuit pattern to be transferred is drawn; 9 is a projection optical system that transfers the IC circuit pattern on the reticle 8 to the object to be exposed; 10 is the object to be exposed 1 The photosensitive agent layer can be moved from the position where the refractive index and film thickness of the photosensitive agent layer is measured to the exposure position, or the exposed object 1 can be moved in steps to repeatedly expose that portion, or the photosensitive agent layer can be measured at multiple positions on the exposed object 1. The refractive index of
It is an XYZ stage that can drive the exposed object 1 so that film thickness can be measured.

FIG. 2 is a diagram illustrating the principle of measuring the refractive index and film thickness of a photosensitive agent layer on the surface of an exposed object. In the figure, 11 is a photosensitive agent layer coated on the surface of the exposed object 1, 12 is the incident polarized light that enters the exposed object 1 at an incident angle θ, 13 is the reflected polarized light reflected from the exposed object, and 14 is the polarized light that is reflected from the exposed object. medium (usually air). Further, λ is the wavelength of the incident polarized light 12, n and d are the refractive index and thickness of the photosensitive layer 11, no is the refractive index of the medium 14, and nl is the refractive index of the exposed object 1. In the example shown in FIG. 2(a), the incident polarized light 12 is linearly polarized light in the S direction, and the reflected polarized light 13 is elliptically polarized light.

FIG. 3 illustrates the relationship between the film thickness d of a photosensitive layer having a refractive index n and the irradiation exposure amount for obtaining a uniform pattern (effective exposure amount is constant).

Next, the operation of the exposure apparatus having the configuration shown in FIG. 1 will be explained with reference to FIGS. 2 and 3.

The object to be exposed 1 is first set on the object suction chuck 2, and the refractive index and thickness in m of the photosensitive agent layer 11 on the xYZ stage 10 are measured by a drive mechanism (not shown).

Here, as shown in FIG. 2(a), the incident angle θ is
When incident polarized light 12 whose polarization state is linearly polarized light is irradiated, the incident polarized light 12 changes its polarization state by being reflected on the surface of the object 1 to be exposed, becomes reflected polarized light 13, and enters the polarization measuring device 4. In general, reflected polarized light 13 from the exposed object 1
becomes reflected polarized light 13 of elliptically polarized light. This change can be described by the following two parameters. One is P of reflected polarization 13
, the phase difference δ between the S component waves, and the other is the reflection count ratio angle ψ between the P and S component waves. These two parameters δ and ψ are measured by a polarimeter 4. δ, Φ are the second
The wavelength λ of the incident polarized light 12 shown in FIG.
From the film thickness d, the phase difference δ9 reflection count ratio angle ψ obtained from the measurement result of the polarization meter 4 is sent to the refractive index/film thickness calculation mechanism 5, where the wavelength input in advance is λ, incident angle θ, medium 14, exposed object 1
Together with the values of the refractive index no and nl, it is used to determine the refractive index n and film thickness d of the photosensitive agent layer 11. Data on the refractive index n 33 and film thickness d calculated by the refractive index/thickness calculation mechanism 5 are sent to the irradiation exposure amount calculation/control mechanism 6, where the third
Irradiation exposure m at which the effective frost level is constant due to the relationship shown in the figure
is calculated.

Thereafter, the object 1 to be exposed is carried by the XYz stage 10 to below the projection optical system 9. Then, the reticle 8 is illuminated by the illumination system 7 controlled by the irradiation, exposure, and control device 4M6.
The IC circuit pattern is projected onto the exposed object 1 through the projection optical system 9.
The irradiation exposure amount is such that the effective exposure amount is constant.

[Modified example] In the above embodiment, polarized light is used to measure the refractive index n and film thickness d of the photosensitive agent layer 11, but if the refractive index n is known and the variation in the film thickness d is small, The refractive index is set in advance, and a mechanism that simply measures the reflectance of the exposed object is used instead of the film thickness and refractive index measuring means consisting of the polarized light source and polarization measuring device 4, and the film thickness d is determined by this value. It may be regarded as a function of reflectance.

Furthermore, even if the configuration is such that the incident polarized light is emitted so that the reflected polarized light becomes linearly polarized light, and the polarization state of the incident polarized light is measured, the refractive index n of the photosensitive agent layer can be determined using the same method.

The film thickness d can be measured.

[Effects of the Invention] As explained above, according to the present invention, when the refractive index and film thickness of the photosensitive agent layer of the exposed object vary and a uniform pattern shape cannot be obtained simply by keeping the irradiation exposure constant. However, the irradiation exposure amount can be changed so as to keep the effective exposure amount constant, and a uniform pattern shape can be obtained.

Further, according to the present invention, when measuring the refractive index and film thickness of the photosensitive agent layer, measurements are performed at multiple wavelengths other than the exposure wavelength so as not to damage the photosensitive agent layer, and the exposure light is measured based on the dispersion relationship between the refractive index and the wavelength. It is also possible to determine the refractive index of the photosensitive layer at different wavelengths, and in this case, the refractive index and film thickness of the photosensitive layer at the portion where the 10 circuit pattern is actually printed can be measured.

Furthermore, if the refractive index and film thickness of the photosensitive agent layer are measured at multiple locations on the surface of the exposed object, it is possible to It is also possible to vary the irradiation exposure amount so that the effective exposure amount is constant for each portion. In this case, even if there is a film thickness distribution of the photosensitive agent layer on the surface of the exposed object, the effective exposure amount can be made constant over the entire surface of the exposed object.

In addition, if upper and lower limits are set for the thickness of the photosensitive agent layer, it is possible to check the thickness of the exposed object before exposure if the thickness varies enough to cause problems in the later IC circuit manufacturing process. Since it is possible to avoid unnecessary exposure, it is possible to improve throughput (yield).

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of an exposure apparatus according to an embodiment of the present invention; FIG. 2 is a diagram for explaining the principle of measuring the refractive index and film thickness of a photosensitive agent layer on the surface of an exposed object; FIG. 3 is a diagram showing the relationship between the irradiation exposure amount and the thickness of the photosensitive agent layer with the refractive index n (effective exposure 0 is constant for obtaining a uniform pattern). 1: Exposed object, 2: Exposed object adsorption chuck, 3: Q-direction light source, 4: Polarization meter, 5: Refractive index/film thickness calculation mechanism, 6: Irradiation exposure amount calculation/control mechanism, 7: Illumination system , 8 reticle or mask, 9: projection optical system, 10: XYZ stage, 11: photosensitive layer,
12: incident polarized light, 13: reflected polarized light.

Claims (1)

[Scope of Claims] 1. A projection optical system that projects an image of an original plate onto an exposed object using light irradiated from an illumination system, and a refractor that sets the refractive index and film thickness of a photosensitive agent layer of the exposed object. an irradiation exposure amount calculation means for calculating an appropriate irradiation exposure amount based on the set refractive index and film thickness; and an irradiation exposure amount calculation means for calculating an appropriate irradiation exposure amount based on the calculation result 1. An exposure apparatus comprising: irradiation exposure amount control means for controlling irradiation exposure amount. 2. The refractive index/film thickness setting means includes a polarized light source that irradiates the exposed object with polarized light, and a phase difference between orthogonal component waves of the reflected polarized light that is received by the polarized light that is irradiated onto the surface of the exposed object. and a refractive index/thickness calculation mechanism that calculates the refractive index and film thickness of the photosensitive agent layer from the phase difference and the reflection coefficient ratio angle. An exposure apparatus according to claim 1. 3. comprising means for measuring the reflectance of the surface of the exposed object;
The refractive index/film thickness setting means sets the refractive index by manually inputting the measured reflectance value as a function of the film thickness when the refractive index is known and the variation in film thickness is small. An exposure apparatus according to claim 1.