JP2869849B2 - Integrated circuit manufacturing method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the integration of ICs, LSIs and the like.
The present invention relates to a circuit manufacturing method , and more particularly to an integrated circuit manufacturing method using excimer laser light . 2. Description of the Related Art Conventionally, a projection exposure apparatus has been used to manufacture an integrated circuit by printing a pattern of an integrated circuit such as an IC or an LSI on a wafer. Most of the projection exposure apparatuses of this kind perform printing by irradiating light of a central wavelength of 436 nm or 365 nm from a mercury lamp onto a pattern of an integrated circuit, and projecting the pattern of the integrated circuit onto a wafer by a projection lens system. . [0003] However, the center wavelength 43
Since light of 6 nm or 365 nm has low intensity and requires a long time for printing, there has been a demand for a light source for exposure that emits light of higher intensity than these lights. In response to this demand, Japanese Patent Application Laid-Open No. 57-1986
Japanese Patent Publication No. 31 proposes to use a laser that emits light in an ultraviolet region having a relatively large intensity as a light source for exposure. The projection exposure apparatus disclosed in this publication uses a laser beam from an excimer laser when projecting and exposing a mask pattern on a wafer, thereby shortening the printing time and improving the throughput of the apparatus. SUMMARY OF THE INVENTION However, the present inventor has studied and found that when an integrated circuit pattern having a submicron line width such as 0.5 micron is printed on a wafer, the projection exposure apparatus disclosed in the above publication is required. Just irradiating a laser beam from an excimer laser to a mask,
It has been found that a clear integrated circuit pattern cannot be printed on a wafer due to the influence of chromatic aberration generated in the projection lens system. SUMMARY OF THE INVENTION The present invention has been made in view of such a problem, and provides a projection exposure apparatus for manufacturing an integrated circuit capable of printing a clear integrated circuit pattern on a wafer using an ultraviolet laser as a light source. Aim. In order to achieve this object, the present invention illuminates an integrated circuit pattern with laser light from an excimer laser and projects the integrated circuit pattern onto a wafer by a projection lens system. In the integrated circuit manufacturing method described above, the projection lens system controls
Compensate for the difference and narrow the bandwidth such as injection locking
By means, the emission spectrum of the excimer laser is
The projection by having a very narrow emission spectrum
The chromatic aberration of the lens system is suppressed . [0008] The present invention relates to an injector.
The excimer is narrowed by band narrowing means such as
Very narrow emission spectrum of laser
By doing so, the chromatic aberration of the projection lens system can be suppressed , so that even an integrated circuit pattern having a submicron line width can be printed clearly on a wafer. . DESCRIPTION OF THE PREFERRED EMBODIMENTS As described above, the present invention relates to the above-described excimer laser.
The emission spectrum of
It is characterized by having a band narrowing means such as injection locking , and other configurations are described in, for example, the above-mentioned Japanese Patent Application Laid-Open No. 57-198631, so that illustration and description are omitted here. . In this embodiment, the wavelength is 248.5 nm.
Is used for projection exposure using an excimer laser having a main emission spectrum, and a laser beam whose wavelength width is narrowed by means such as injection locking (band narrowing means). As will be described later, the projection lens system includes:
It was composed of a single glass material (SiO ₂ ). The single material can be used because laser light having a very narrow emission spectrum can be used without having to consider chromatic aberration. Therefore, the apparatus of this embodiment is equipped with an extremely novel projection lens system, which could not be considered in a conventional projection exposure apparatus for circuit manufacturing. If such a projection lens system can be composed of a single material, the projection lens system can be composed only of a material that has the best transmittance for laser light used for projection exposure and has excellent lens processing accuracy. This can greatly improve the performance of the apparatus. The projection lens system according to the present embodiment will be described. Each of the embodiments of the projection lens system described below is made of a single glass material made of only fused silica, and has a design wavelength of 24.
8.5 nm. However, if it is a material through which light having a wavelength of 248.5 nm is transmitted, even if it is not fused quartz, for example, CaF
₂ , MgF ₂ may be used. The main features of the projection lens system of this embodiment are as follows.
The first, second, and third lens groups are composed of a first, second, and third lens groups having positive, negative, and positive refractive power in order from the object side, and each of the first, second, and third lens groups is a single glass material And the first, second and third lenses.
Each focal length of the lens unit f _1, 0.8 ≦ when the _{f 2, f 3 | f 1} / f 2 | ≦ 3.8 ... (1) 1.1 ≦ | f 1 / f 3 | ≦ 4 (2) The following condition must be satisfied. As described above, the projection lens system has three lens groups, and the second lens having a negative refractive power is provided at the center of the lens system.
It is composed of a lens system and a reduction system in which first and third lens units having a positive refractive power are arranged on both sides of the lens system. By setting the above-mentioned conditional expressions (1) and (2), good aberration correction can be achieved. Have achieved. Conditions (1) and (2) are conditions for properly correcting the curvature of field by appropriately setting the refractive power of each lens group as one of the basics of the lens performance. When the Petzval sum becomes large, the field curvature becomes insufficiently corrected. When the upper limit is exceeded, the field curvature becomes excessively corrected, and it becomes difficult to satisfactorily correct the aberration of the entire screen. Further, in order to achieve better aberration correction, the first lens unit is composed of _two lens units I ₁ and I ₂ having negative and positive refractive power in order from the object side. I ₂ is a lens system having at least one each of a biconvex lens I ₂₁ having both convex lens surfaces and a lens I ₂₂ having a positive refractive power, and the second lens group is composed of a convex surface on the object side and a convex surface on the image surface side. And a focal length of the lens group I ₂ is f ₁₂ , and a focal length of the second lens group is f _2. Outside 1) What is necessary is to satisfy the following conditions. [0018] The lens I ₂₂ is the projection lens system reduction ratio of the time on the order of 1 / 3-1 / 7 is composed of a meniscus-shaped lens with a convex surface facing the object side, the reduction magnification of the projection lens system 1 When the distance is about / 7 to 1/12, the lens is composed of a biconvex lens. With such a constitution, aberration can be corrected well. In order to maintain good imaging performance as a projection lens system over the entire screen, in addition to correcting the curvature of field, coma is corrected to almost zero over the entire screen, and then spherical aberration and off-axis are further corrected. Must be corrected. For this purpose, in an optical system satisfying the conditions (1) and (2), a meniscus lens having a negative refractive power and a convex surface is provided on each of the object side and the image plane side of the second lens group. preferable. In this projection lens system, the spherical aberration is corrected mainly by appropriately setting the radius of curvature of the lens surface of the second lens unit. At this time, the coma is also corrected simultaneously with the spherical aberration. For this purpose, it is preferable that the second lens group is constituted by at least two meniscus lenses having a negative refractive power. One is with the convex surface facing the object side,
The other one is to form a lens shape with the convex surface facing the image plane. This is because the entire lens system is composed of three positive, negative, and positive lens groups, so that the second lens group has an action of correcting insufficient correction of spherical aberration generated in the first and third lens groups. is there. By arranging at least two meniscus lenses having a negative refractive power in the second lens group as described above, correction of coma aberration, that is, balance between a light beam portion above the off-axis ray and a light beam portion below the off-axis ray is achieved. Has taken. That is, the lower light beam portion is formed by a meniscus lens having a convex surface facing the object side disposed on the object side, and the upper light beam portion is formed by a negative meniscus lens having a convex surface directed to the image surface side disposed on the image side. Thus, the aberration of the off-axis light beam can be corrected in a well-balanced manner, and the off-axis coma can be satisfactorily corrected. Moreover, since the principal ray of the off-axis light beam passes near the optical axis of the second lens group, the configuration (shape) itself of the second lens group does not significantly affect distortion and astigmatism.
By configuring the refracting system as a three-part system and keeping the conditions (1) and (2), the second lens group can favorably correct spherical aberration and coma. In particular, coma can be corrected by appropriately disposing the negative meniscus lens. Further, it is preferable to satisfy the condition (3) in order to favorably correct off-axis meridional and sagittal halo. In a lens system composed of three partial systems, the biconvex lens and the positive lens of the first lens unit on the object side have a combined refractive power of a meniscus-shaped lens and the refractive power of the second lens unit which is a second partial system. If the spherical aberration and coma are corrected too much, high order halo aberration occurs in the first lens group, and correction over the entire screen is performed. If aberrations are corrected using the difference or using glass materials having a high refractive index and a low refractive index, high-order aberrations will occur and it will be difficult to achieve good correction. Therefore, it is preferable that the conditions (1) and (2) are satisfied and the condition (3) is satisfied, especially when designing a projection lens system made of a single glass material. Examples (1), (3), (6), (7), (8), which will be described later,
(9) satisfies the condition (3), and the embodiment (2),
(4) indicates that the value is close to the limit. The conditions (1), (2), and (3) are conditions for satisfying the imaging performance (resolution, contrast ratio) required as a projection lens system for printing an integrated circuit. An important performance condition required for a type of projection lens system is distortion. In the manufacture of ICs and LSIs, it is necessary to perform alignment for each printing step since the printing step is performed many times on the wafer, and each printing step is performed by a different projection exposure apparatus. Sometimes. Therefore, in order to accurately align the patterns in each process, the distortion of the projection lens system must be almost zero. In particular, a reduction projection lens system that uses a single glass material to reduce distortion to almost zero is composed of three lens units having positive, negative, and positive refractive powers. Two lens groups I ₁ having negative and positive refractive power in order from the side,
Configure than I _2, [0024] [circumflex] When the lens group I _1, each f ₁₁ the focal length of I _2, f _12, the focal length of the first lens group and f ₁ It is preferable to configure so as to satisfy the following conditions. This projection lens system is designed as a reduction system, and the first lens group is divided into _two lens groups I ₁ and I ₂ having negative and positive refractive power as viewed from the object side.
₁ corrects distortion. [0026] Particularly, to constitute a lens group I ₁ at least two or more negative with the convex surface facing the object side of the refractive power and a meniscus-shaped lens is preferred to favorably correct distortion. In addition, it is preferable to use three or more lenses, since the sharing of the refractive power of each lens is reduced and the influence of other aberrations is reduced. Since the lens I ₂ is made of a lens having a positive refractive power and at least two lenses having a positive refractive power, the position where the off-axis principal ray passes is near the optical axis. Correction of aberration and astigmatism and off-axis coma,
Halo is corrected well. When the value exceeds the upper limit of the condition (4) or the lower limit of the condition (5), a large amount of negative distortion occurs, which is not preferable. In addition, the lower limit of the condition (4) or the upper limit of the condition (5) is not satisfied. If it exceeds, positive distortion is generated and the amount of other aberrations is increased, which is not preferable. Next, Numerical Examples 1 to 10 of the present projection lens system
Are shown. In the numerical examples, Ri is the radius of curvature of the i-th lens surface in order from the object side, Di is the i-th axial lens thickness and axial air gap in order from the object side, and Ni is the i-th lens thickness in order from the object side. It is the refractive index of the glass of the lens. The SiO ₂ of the glass material is fused quartz and has a wavelength of 2
The refractive index at 48.5 nm is 1.521130. In Numerical Examples 1 to 5, magnification 1/5 and NA =
0.3, a projection lens system with a screen size of 14 × 14 mm,
Numerical Examples 6 to 10 are magnifications 1/10, NA = 0.35,
A projection lens system having a screen size of 10 × 10 mm is shown. [Outer 3] [Outside 4] [Outside 5] [Ex. 6] [Outside 7] [Ex. 8] [Formula 9] [Outer 10] [Expression 11] [Outer 12] The relationship between Numerical Examples 1 to 10 and the above-described conditional expressions is as follows. [Table 1] FIGS. 1 and 2 are sectional views of a projection lens system according to Numerical Embodiments 1 and 6 of the present invention, respectively. FIGS. 3 to 12 show aberration diagrams of Numerical Examples 1 to 10, respectively. The projection lens system according to the numerical example (1) is shown in FIG.
As shown by the aberration curve in FIG. The projection lens system of Numerical Example (2) satisfies the condition (1),
In the example in which the value near the lower limit of (2) is taken, when the aberration curve shown in FIG. 4 is compared with the aberration curve shown in FIG. 3 of the numerical example (1), the lower limits of the conditions (1) and (2) are compared. By approaching the value, the refractive power of the lens group with negative refractive power decreases,
Therefore, the Petzval sum becomes large positively, and the field curvature correction is not so successful. That is, condition (1),
If the lower limit of (2) is exceeded, the field curvature will be under, and
It is difficult to satisfy an important requirement of the projection lens, that is, a condition of high resolution uniform over the entire screen. Numerical example (2) is given as an example of the lower limit side of conditions (1) and (2) and compared with numerical example (1). Numerical example (3) is close to the intermediate example. is there.
The aberration curve of the embodiment (3) is shown in FIG. 5, which satisfies the conditions (1) and (2), and the field curvature is good. The numerical embodiment (4) is an example in which the spherical aberration of the projection lens system of the numerical embodiment (2) is further corrected. The projection lens system of the numerical example (6) has a magnification of 1
FIG. 8 shows a reduction system having a specification of / 10, has an aberration curve as shown in FIG. 8, and has satisfactory performance by satisfying the conditions (1) and (2). The projection lens system of Numerical Embodiment (7) is an example in the vicinity of the upper limit of the conditions (1) and (2), as shown in the aberration curve of FIG. And the refractive power of the second lens group is weakened because the configuration of the lens system approaches the upper limit of the conditions (1) and (2).
The tzval sum becomes small and the field curvature becomes overcorrected,
The performance required as a projection lens is approaching the limit of the condition that the entire screen has a uniform high resolution. Numerical example (7) is given as the upper limit of the conditions (1) and (2) and compared with numerical example (6). Numerical example (8) is in between. Numerical Example (8)
FIG. 10 shows the aberration curve of the projection lens system of FIG. This projection lens system satisfies the conditions (1) and (2), and the field curvature is well corrected. The numerical example (9) is an example in which the spherical aberration of the projection lens system of the numerical example (8) is slightly overcorrected. Numerical example (5) shows a projection lens system having a configuration near the upper limit value of condition (4) and the lower limit value of condition (5). As shown in FIG. 7, distortion is negative (insufficient correction). , Which is approaching the required performance limit. Numerical example (10) shows the lower limit of condition (4) and condition (5).
Shows a projection lens system having a configuration in the vicinity of the upper limit of, wherein distortion is positive and overcorrected, and the required performance is approaching the limit. In the projection lens system of the projection exposure apparatus, the first lens group is divided into _two lens groups I ₁ and I ₂ as shown in FIGS. 1 and 2, and the lens configuration of each lens group is considered. The specified aberrations are corrected by specifying them. As shown in the embodiment of FIGS. 1 and 2, the second lens group is provided with a lens having an intermediate negative refractive power to satisfactorily correct spherical aberration. If the meniscus lens having negative refracting power on the object side and the image plane side is responsible for correcting spherical aberration, this lens need not be particularly used. In the projection lens system of the projection exposure apparatus, the third lens group includes, in order from the object side, a meniscus lens having a convex surface facing the image surface side, a biconvex lens, and a positive lens having a convex surface facing the object side. It is preferable to arrange two meniscus lenses with a refractive power of 4 and configure a total of four lenses. This is effective in achieving good aberration correction over the entire screen. It is to be noted that, for example, two or more biconvex lenses may be divided into two or more lenses, and a total of five lenses may be formed. As described above, according to the present invention, the excimer
Very narrow emission spectrum of Shima laser
With torr, it is an integrated circuit pattern having a line width of submicron, on the wafer, it is possible to clearly baking.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a lens sectional view of Numerical Example 1 of a lens system used in the present invention. FIG. 2 is a lens cross-sectional view of Numerical Example 6 of the lens system used in the present invention. FIG. 3 is a diagram illustrating various aberrations of Numerical Example 1 of the lens system used in the present invention. FIG. 4 is a diagram illustrating various aberrations of Numerical Example 2 of the lens system used in the present invention. FIG. 5 is a diagram illustrating various aberrations of Numerical Example 3 of the lens system used in the present invention. FIG. 6 is a diagram illustrating various aberrations of Numerical Example 4 of the lens system used in the present invention. FIG. 7 is a diagram illustrating various aberrations of Numerical Example 5 of the lens system used in the present invention. FIG. 8 is a diagram illustrating various aberrations of Numerical Example 6 of the lens system used in the present invention. FIG. 9 is a diagram illustrating various aberrations of a numerical example 7 of the lens system used in the present invention; FIG. 10 is a diagram illustrating various aberrations of Numerical Example 8 of the lens system used in the present invention. FIG. 11 is a diagram illustrating various aberrations of a numerical example 9 of the lens system used in the present invention. FIG. 12 is a diagram illustrating various aberrations of Numerical Example 10 of the lens system used in the present invention; [Description of Signs] I First lens group II Second lens group III Third lens group Y Image height M Meridional image plane S Sagittal image plane

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI H01L 21/30 529 (56) References JP-A-56-80043 (JP, A) JP-A-54-80739 (JP, A) JP-A-60-140310 (JP, A) JP-A-3-34308 (JP, A) JP-B-4-74855 (JP, B2) US Patent 3,573,456 (US, A) “Laser Handbook” edited by Laser Society of Japan (published by Ahm Corporation on December 15, 1982), pp. 90, 216-220, 229, 346-347, 368-369, 470, etc. B. Biai Shimazu, "Laser and its Applications" (published on August 25, 1978, the eighth edition of Sanho Publishing Co., Ltd.), pages 53-55, 61-62, 75-76, 125-126. Etc. C. (Electronic Communication Glossary) edited by the Institute of Electronics and Communication Engineers (published by Corona Co., Ltd. on November 30, 1984), page 475, right column, “monochromatic light” column (58) Field surveyed (Int. Cl. ⁶⁾ , DB name) H01L 21/027 G03B 27/32 G03F 7/20 505 G03F 7/20 521

Claims (1)

(57) [Claims] In integrated circuit manufacturing method of projecting the integrated circuit pattern on the wafer by the projection lens system to illuminate the integrated circuit pattern with a laser beam from an excimer laser, before
The projection lens system corrects aberrations other than chromatic aberration
And by means of band narrowing such as injection locking.
The emission spectrum of the excimer laser is very narrow.
The projection lens system
Integrated circuit manufacturing method characterized by suppressing chromatic aberration of light
Law. 2. The aberration other than the chromatic aberration includes a field curvature.
2. The integrated circuit manufacturing method according to claim 1, wherein: 3. The magnification of the projection lens system is a reduction magnification.
The method for manufacturing an integrated circuit according to claim 1, wherein: 4. The magnification of the projection lens system ranges from 1/3 to 1/12.
4. The integrated circuit according to claim 3, wherein:
Production method. 5. The magnification of the projection lens system ranges from 1/3 to 1/7
5. The integrated circuit according to claim 4, wherein
Construction method. 6. The projection lens system has a positive refractive power from the object side to the image side.
It has folding power, negative refractive power, and positive refractive power.
The method for manufacturing an integrated circuit according to claim 1. 7. The projection lens system has a negative bending from the object side to the image side.
Folding power, positive refracting power, negative refracting power, and positive refracting power
The method according to claim 1, wherein: 8. There are multiple printing steps by the projection, each printing step
The alignment is performed every time.
2. The integrated circuit manufacturing method according to 1.