JPS6011843A - Reticle protecting device - Google Patents

Abstract

PURPOSE:To use stably a titled device without causing a drop of intensity of illumination and unevenness of the intensity of illumination even against plural monochromatic lights by setting the thickness of a protecting film to a value of the least common multiple or a value of its integer hold of the value of a half-wavelength in a protecting film medium of each wavelength light. CONSTITUTION:A frame member 2 is provided on a reticle 1, and the pattern surface of the reticle 1 supported by this frame member 2 is protected by a protecting film 3 supported at a height (h). In that case, a film thickness of this protecting film 3 is set to the least common multiple of a value of a half-wavelength in a protecting film medium of the first wavelength light and a value of a half-wavelength in a protecting film medium of the second wavelength light, or a value almost equal to an integer fold or the least common multiple. That is to say, with respect to both wavelengths of the first wavelength lambda1 and the second wavelength lambda2 being different from said wavelength, lambda1' and lambda2' in the medium of the protecting film are shown by the expression I and an expression II when refractive indexes of the protecting film against each wavelength are denoted by n1 and n2, and when m1 and m2 are made natural numbers, the thickness (d) of the protecting film is selected so as to satisfy a condition of the expression III, by which it can be used in common for both the wavelengths.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to a reticle protection device, and more particularly to a pellicle membrane for reticle protection.

(Background of the Invention) A reduction projection exposure apparatus (hereinafter referred to as a stepper) has been widely used in the semiconductor manufacturing process in recent years because it can reduce and project the pattern of a reticle as an original onto a wafer and obtain a fine pattern of high quality. It has contributed greatly to the production of S.

If dust adheres to the reticle, this dust will be transferred to the wafer and cause defects in the pattern, so an extremely thin pellicle H'A -(: (' A method has been proposed for protecting the reticle.For example, as shown in the perspective view of FIG. Support 1 at a predetermined height 11
．． A pellicle film (3) is formed and the reticle (1
) This prevents dirt and dust from accumulating on the upper pattern surface. Here, the height h of the pellicle film (3) from the reticle surface is selected to be such that there is no substantial problem even if dirt or dust adheres to the pellicle pattern (3).

This film needs to be thin in order not to degrade the stepper's performance, but since the light used in the stepper is monochromatic, if the film is not thick enough, interference effects in the film may occur. Therefore, the illuminance obtained at the wafer surface decreases.

(2) This causes the second problem of uneven illuminance within the exposed area. Problem (2) needs to be solved because the exposure time increases, which leads to a decrease in the throughput (wafer processing capacity within unit time) of the manufacturing equipment. On the other hand, (2) means that there are places where the appropriate exposure amount can be obtained and places where it is not within the exposure area, so the pattern line width cannot be controlled in device creation (this is a serious drawback. If the thickness of the pellicle film is changed for each different wavelength used, the optimum conditions can be obtained for each. However, this increases the number of types of pellicle film that require strict control of film thickness, which increases manufacturing costs and increases usage. In this case, it is necessary to replace the pellicle film every time the wavelength changes, which is unavoidable.Also, when using multiple different wavelengths at the same time to increase the exposure amount, the illumination Decrease in illumination and uneven illumination cannot be avoided, and there is a risk that it will not have any negative effects.

(Objective of the Invention) An object of the present invention is to provide a reticle protection device that can be used stably even with a plurality of different types of monochromatic light without causing a decrease in illuminance or unevenness in illuminance.

(Summary of the Invention) The present invention provides a reticle protection device having a frame part provided on a reticle and a protective film supported by the frame member and provided to cover the pattern surface of the reticle at a predetermined height. Odor −ζ, ]I+ J8r of the protective film is the value of the half wavelength of the first wavelength light that falls into the protective film medium, and the value of the second wavelength light that is different from this.
It is characterized in that the wavelength of light is the least common multiple of the value of a half wavelength in τ in the protective film medium, or a value that is approximately equal to an integral multiple of the least common multiple. That is, the first wavelength λ1
and a second wavelength λ2 different from this, the wavelengths λ1'' and 22'' in the medium of the pellicle film are λ, where the refractive index of the pellicle film for each wavelength is nl and n2.
It is expressed as 1゛-λ1/nl, λ2゛-λ2/n2, and ml
, When m2 is a natural number, the thickness d of the pellicle film is d = ml ・λ1'/2 = m2 ・λ2゛/2
By selecting a wavelength that satisfies the following conditions, it becomes possible to engrave both wavelengths and use them in common.

FIG. 2 shows an example of the relationship between the thickness d of the pellicle film and the transmittance 1'' for the monochromatic light of the first wavelength i'λ1 and the monochromatic light of the second wavelength λ2.

In the characteristics shown in the figure, for the first wavelength λ1,
All film thicknesses of dla, dlb, ・+, and did satisfy the condition d = ml ・λ1 / (2・nl>, while for the second wavelength λ2, d2a, d2b, ・−
, d=m2・λ2/ for each film thickness of d2d.
The condition of (2・n2) is satisfied. Therefore, for example the thickness dla
With the pellicle film, there is no problem with the light of the first wavelength λ1, but the transmittance of the light with the second wavelength λ2 decreases considerably, as well as unevenness in the film thickness and uneven illuminance due to obliquely incident light. It becomes noticeable. However, when the film thickness is made equal to the least common multiple of the half-wavelength value of the first wavelength light in the pellicle IIQ medium and the half-wavelength value of the second wavelength light in the pellicle film medium, ml · λ1゛/2 and m2・λ2゛/2 become equal. That is, if the reflective thickness of the pellicle film for each wavelength is, then the refractive index of the pellicle film for each wavelength is nl, n2
As, dlc=m'iλ1/(2・nl).

It is expressed as d2c=m2·λ2/(2×12), and these two are substantially equal.

Therefore, in the case of a film thickness of dlc (-d2c), the thickness is appropriate for both wavelengths, the transmittance does not decrease for each wavelength, and uneven illumination is less likely to occur.

(Example) A specific example will be explained below. The back of the emission spectrum of the 'Ii pressurized water tank lamp, the first wavelength λ1 is 436 mm, the 26th Jj is 365 mj as the length λ2
When using n, the least common 3 number of the value of 1/2 of each wavelength in the pellicle IiA medium is expressed as mlλ1'/2=m2·λ21/2. Further, in this case, the refractive index for each wavelength can be considered to be approximately the same value n. Therefore, from ml/m2=365/436'-5/6,
When ml-5, m2=6, the required optical film 1and is 5÷2×436=1090 nm or 6÷2×365=
The wavelength may be 1095 nm, and the thickness may be approximately 1.09 μm. Further, the optical film thickness can be an integral multiple of this.

On the other hand, when using 405 nm as the first wavelength λ1 and 365 nm as the second wavelength λ2, the optical thickness required for the pellicle film is similarly calculated from the least common multiple of each half-wavelength value in the pellicle film medium. , m1=10. or m2=il
is given. That is, 22O25n or 2007.
5 nm, and it is desirable that the optical film thickness be approximately 2.02 μm, which is the intermediate value between the two.

(Effects of the Invention) As described above, according to the present invention, reticles provided with the same protective film can be used for steppers with different wavelengths. In this way, when the pellicle membranes are made common, there is no need to develop pellicle membranes of different thicknesses, and the production volume of the same type increases, so production costs are reduced and inexpensive pellicle membranes can be obtained. It is also advantageous for management and storage as there are fewer varieties. In addition, a reticle with a pellicle film can be shared by steppers with different wavelengths, which saves the number of reticles and significantly increases VL.
This leads to SI cost reduction. Note that the wavelength used is λ1. λ
The pellicle membrane according to the present invention is not limited to the case where a plurality of steppers different from λ1. It is clear that steppers providing exposure at wavelengths of λ2 would also be highly effective when developed. In addition, in the above explanation, there are two types of wavelengths used: λ1. λ2, but three or more wavelengths λ1. λ2. λ3. . . . The present invention similarly applies, and it goes without saying that in this case, the required thickness of the pellicle film may be the least common multiple of the light of each wavelength in the pellicle film medium or an integral multiple thereof. .

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an example of a reticle protection device. FIG. 2 is a diagram showing the relationship between film thickness and transmittance in the present invention. [Explanation of symbols of main parts] ■... Reticle, 2... Frame member 3... Pellicle membrane Applicant: Takao Watanabe, Agent, Nippon Kogaku Kogyo Co., Ltd.

Claims (1)

[Claims] It has a frame member provided on the reticle and a protective film supported by the frame member and provided to cover the pattern surface of the reticle, and is used for first and second lights of different wavelengths. In the reticle protection device obtained, the thickness of the protective film is equal to the value of the half wavelength of the first wavelength light in the medium of the protective film and the value of the half wavelength of the second wavelength light in the medium of the protective film. A reticle protection device that uses the least common multiple of or an integral multiple of the least common multiple.