JPS6067932A - Exposing device - Google Patents

Abstract

PURPOSE:To perform high-precision positioning in atmosphere by arranging a diffraction grating on a sample nearly in parallel to interference fringes obtained by the interference between two pieces of luminous flux, and photodetecting plural diffracted light beams as return light by a photodetecting element. CONSTITUTION:Coherent light R from a laser generator 10 is guided to a pinhole 14 arranged near the focus position of a diffusion optical system 13, and the light passed through the pinhole 14 is passed through the hole (e) of the photodetecting element 18 and then split by amplitude through a two-luminous-flux splitting optical system 17 into reflected light beams R1 and R2, which are allowed to interfere with each other on the sample W such as a semiconductor wafer through reflecting mirrors M1 and M2, forming interference fringes. The diffraction grating G is arranged on the surface of the sample W nearly in parallel to the interference fringes, and plural diffracted light beams from the diffraction grating G are returned through said optical system and detected as return light by a photodetection part provided at the circumference of the hole (e) of the photodetection element 18 to generate an electric signal, thereby making an adjustment so that the pitch of the diffraction grating G on the sample W is nearly equal to the pitch of the interference fringes.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention is particularly applicable to high-density semiconductor devices (hereinafter referred to as LSI).
The present invention relates to an exposure apparatus for forming fine patterns such as the above.

Conventional Structures and Problems LSIs have recently become more and more densely packed, and the dimensions of the fine patterns of each element have reached 1 micron or less. FIG. 1 shows a diagram of the principle of a conventional exposure apparatus. Photomask 1
and St Ueno-2 are aligned, and light is irradiated from the light source 3 for exposure.

・To align the position at this time, use the alignment mark provided on the Si Ueno rod 2, rotate the stage 4 on which the St Ueno 2 is attached, and move it parallel to the 2 axes (-, 'y). This was done by overlapping the mark on Mask 1 and the mark on Si Unino 2, but
The alignment accuracy is about ±0.3 microns, and when forming submicron elements, the alignment accuracy is poor and it is not practical.

Further, FIG. 2 shows a principle diagram of a projection exposure apparatus, which is the mainstream of recent exposure apparatuses. A reduced image of the pattern on the mask 6 is formed on the Si wafer 7 through the reduction lens 6 to perform exposure. At this time, the resolving power δ and the depth of focus Δ when the aberration-free optical system is completely focused on the Si wafer 7 are determined by diffraction and are given by the following equation.

・・・・・・・・・・・・・・・(1) However, NA is the numerical aperture, α is half of the angle from the focal point of the objective lens to the lens, N is the magnification of the objective lens system, and F is the lens. The focal length f and the diameter are given by F=f/D.

From equation (1), in projection exposure, by increasing the NA, it is possible to obtain resolution close to the wavelength of the light source.

However, when the NA is increased, the field area becomes smaller and the number of pixels per field also decreases.

For exposure lenses, due to chip size requirements, 10 to 16
A simple field is required, which limits the resolution to around 1 μm. Therefore, there are practical problems in forming elements that require alignment of submicrons or less.

Purpose of the Invention In view of such conventional problems, the present invention has been developed to
Another object of the present invention is to provide an exposure apparatus that can perform highly accurate positioning with a simple configuration and is suitable for forming fine patterns.

, Structure of the Invention The present invention detects the return position of the returned light through a diffusion optical system such as a lens for diffusing a coherent light beam, near the position where the light beam is focused by the diffusion optical system. In addition, a light-receiving element having a microhole for passing the light flux is installed, and the light flux passing through the microhole is passed through a parallel optical system such as a collimator lens provided so as to become a parallel light flux. A famous beam splitter that splits the amplitude of a parallel beam into two beams 1. The beam is passed through a two-beam splitting optical system such as a mirror or a parabolic mirror, and the two amplitude-split beams are overlapped and interfered with, for example, two reflecting mirrors. By placing a sample having a diffraction grating arranged substantially parallel to the interference fringes obtained by the two light beams in the optical path of the two light beams, the two light beams are diffracted. The diffracted light becomes return light and returns to the light receiving element through the two reflecting mirrors, the two-beam splitting optical system and the parallel optical system. Based on the position information obtained from the light receiving element, the By rotating two reflectors, two
By adjusting the angle of incidence of the light beam on the diffraction grating and making the 1° interference between the two light beams and the pitch of the diffracted photons approximately equal, an exposure apparatus is realized that can enable alignment for forming a sisap micron pattern. It is something to do.

DESCRIPTION OF THE EMBODIMENTS FIG. 3 shows an overall configuration diagram of the positioning mechanism portion of an exposure apparatus in an embodiment of the present invention.

Coheren from laser generator 10!・The light R is generated, and this light R is guided to the diffusion optical system 13 for diffusing the light R by the reflecting mirror 11.12, and then the diffusion optical system 1
3 into a pinhole 14 placed near the focal point of
Furthermore, the light R that has passed through the pinhole 14 is converted into parallel light beams by a parallel optical system 15 such as a collimator lens so that the light R has a parallel light velocity, and is then passed through a reflecting mirror 16 to a two-beam splitting optical system such as a beam splitter. 17, and the amplitude is divided into reflected light R1 and transmitted light R2 having approximately the same intensity. The amplitude-divided reflected light R1 and transmitted light R2 enter the reflecting mirror M1 and the reflecting mirror M2, respectively, and are arranged so that they are incident on the surface of the semiconductor sea urchin fermentation sample W at approximately equal angles φ1° and φ2.
Light beam splitting optical system 17, reflecting mirror M1. M2, place the sample W.

As shown in Fig. 4, on the surface of the sample W, a diffraction grating G with a pitch PCII of 1 μm is placed in a non-pattern forming area (scratch) so that the diffraction grating G is approximately parallel to the interference fringes formed by the interference of the two beams R1 and R2. line, etc.) are formed. The diffracted lights R3 and R4 diffracted by the diffraction grating G are detected by the photodetector D1.
．． It enters D2.

Further, the reflected light R1 is diffracted by the diffraction grating G of the sample W, and a plurality of diffracted lights are generated. Now, if we consider that counterclockwise rotation is a positive direction with respect to the traveling direction of the diffracted light, among the plurality of diffracted lights, as shown in Fig. 6, the 0th order new light R1o and the 11st order diffracted light R11 are reflected by the reflecting mirror M2 and The light beam passes through Ml, passes through the two-beam splitting optical system 17, the reflecting mirror 16, and the parallel optical system 15, and returns toward the laser source. Similarly, the transmitted light R2 is also diffracted by the diffraction grating G of the sample W, producing a plurality of diffracted lights. Among the plurality of diffracted lights, as shown in Fig. 6, the 0th-order diffracted light R20 and the +1st-order diffracted light R21 pass through the reflecting mirrors M1 and M2, respectively, the two-beam splitting optical system 17, the reflecting mirror 16, and the parallel optical system 16 to generate a laser. Return to the source direction.

18 is a light receiving element for detecting the position of each returning diffracted light R10, R11, R20°R21, and is installed near the pinhole 14, as shown in FIG.
For example, the light receiving part 8 is divided into four parts, a part, b part, 0 part, and d part.The received light is used as an electric signal to connect each lead wire a.
', part b.

It can be extracted from c' and d'. In addition, the light receiving element 18
A hole e is provided in the center of the hole e through which the light R that has passed through the pinhole 14 passes. Hole e is on the optical axis.

The reflecting mirrors M1 and M2 have variable angles φ1 and φ2, as shown in FIGS. 8 and 9, respectively. When the optical axis direction is two axes, the X-axis rotation is α rotation, the y-axis rotation is If the rotation of the shaft is β, it has means for rotating in the α and β directions.

19 is a movable frame for fixing the reflecting mirror, 20 is a protrusion 20
The support plate 21 and 22 having a micrometer head 21 and 22 are fixed to the movable frame 19, and the tips 21 and 22 of the micrometer head 21 and 22 are fixed to the movable frame 19 by forming two parts. pushes the support plate 2o, and rotates in the α and β directions about the protrusion 20-a of the support plate 20 as a rotation center against the tensile force of the tension springs 23 and 24.

When the wavelength of the laser is λ and the pitch of the diffraction grating G on the wafer W is P, the reflected light R1 is reflected by the diffraction grating G,
The diffraction angle φd1 at the time of diffraction is P(sinφd, -5Inφ1)=mλ ・・・・・・
......It is expressed as (4). (However, m
=o, 1, 2.3...Positive integer) m:= O
The diffraction angle φd1° of the 0th-order diffracted light R10 is P(sinφd10−sinφ1)=o −=2.
......(6), φd1o=φ1, 0th order diffracted light R10 is equal to the incident angle φ1 of reflected light R1, reflecting mirror M2゜2 beam splitting optical system 17, reflecting mirror flow, parallel optics It passes through the system 16 and returns toward the laser source. m
= 1, that is, the diffraction angle φd11 of the first-order diffracted light R11 is P
(sinφd, 1Sillφ1)=λ ・・・・・・・・・
......(6). It is now φ1;-φd11.

Also, when the transmitted light R2 is diffracted by the diffracted photon G, the diffraction angle φd2 is P(sinφd2 510φ2)=mλ based on the same Bragg diffraction condition.
......It is expressed in pieces. (However, m=o
, 1, 2...positive integer) m-0, that is, the diffraction angle φd20 of the 0th order diffracted light R20 is P(sinφd2o31+1φ2)20...
・・・・・・・・・It becomes the chest and becomes φd20”φ1,
The 0th new party R2° is equal to the incident angle φ2 of the transmitted light R2,
At the same time, the light becomes light in the opposite direction, passes through the reflecting mirror M1.2, the beam splitting optical system 17, the reflecting mirror 16, and the parallel optical system 16, and returns to the direction of the laser source.

m-1, that is, the diffraction angle φd21 of the first-order diffracted light R21 is P(sinφd21-51nφ2)=λ...
・・・・・・・・・It will be 9Q. Now φd21=-φ2
It will be when.

Here, as shown in Figure 10, φ1N (-φ2), φ1ki (
-φd1), φ2ki (-φd21), each diffracted light R
10, R11, R20, and R21 pass through the parallel optical system 16, but do not pass through the hole e of the light-receiving element 18, and the light-receiving portion of the light-receiving element 18, a, as shown by the dotted line in FIG.

Return to position b, c, or d. The tip metal intensity received at each light receiving surface is converted into an electrical signal, which is extracted as position information, and the rotating mechanisms of reflectors M1 and M2 are operated to transmit diffracted light to each light receiving section a, b, c, and d. When not incident, each diffracted light passes through the hole e (on the optical axis) of the pick light receiving element 17, so that φ1 (-φ2) ≠ (-φd1) (10φ
d21)...It can be set to θo.

Further, if the pitch of interference fringes formed by interference between reflected light R1 and transmitted light R2 is 4, it is expressed as follows. At this time, from equation (6), equation 03 becomes,
Furthermore, the ω formula, 904 formula is 71 =−−21−= p ・・・・・・・・・・・・
...Ran2 Slnφd11 , and the pitch A of the interference fringes created by the interference of the two beams of reflected light R1 and transmitted light R2 and the pitch P of the diffraction grating G on the sample W.
can be made approximately equal to

In this way, by making the pitch P of the interference fringes of the two light beams approximately equal to the pitch P of the diffraction grating G on the sample W, the interference fringes of the two light beams R1 and R2 can be output from the diffraction grating G on the wavefront. Light R diffracted by the dividing diffraction grating G
s and R4 are obtained, and the photodetectors D1 and D2 obtain a light intensity indicating a positional relationship with very good resolution between the interference fringes of the two beams and the grating G. Using the light intensity indicating this positional relationship, the positional relationship between the interference fringes of the two light beams and the sample W is detected, and the position of the sample W (direction perpendicular to the interference fringe and rotation around the optical axis) is corrected. Interference fringes of light beams R1 and R2 and sample W
Perform alignment. In other words, as a laser beam,
By using a He-Cd laser with a wavelength of 4416 people, it is possible to form interference fringes with a pitch of 1 μm.
For example, a sample W such as a semiconductor wafer can be aligned with high accuracy of several hundred angstroms or less with respect to the interference fringes by using the diffraction grating G with a pitch of m.

Thereafter, exposure may be performed by exposing the pattern forming part (semiconductor element forming part) of the sample W, that is, the semiconductor wafer. It should be noted that this pattern exposure can be carried out using an exposure device that has an exposure function capable of realizing the method proposed by the applicant using two-beam interference of a laser, as well as the positioning mechanism described above, to perform accurate pattern exposure. can. Further, after performing the above-described 61 alignment method according to the present invention, it is also possible to perform fine pattern exposure using an exposure apparatus such as a projection exposure apparatus.

As a second embodiment, the light receiving section is 4" in the first embodiment, and 4" in the first embodiment.
Although a divided light receiving element 18 was used, a similar effect can be obtained by using a light receiving element unit in which four light receiving elements are fixed on an easy-to-process substrate that has a hole in the center for allowing light to pass through. .

In addition, as a third embodiment, each diffracted light R10°R11,
By arranging a light-receiving element in the vicinity of the pinhole 14, which has a matrix of light-receiving surfaces that receive the returned light from R20 and R21 and has a microhole in the center that allows the light to pass through, each Since the return position of the diffracted light can be obtained as two-dimensional position information, it becomes easier to match the pitch of the interference fringes to the pitch P of the diffraction grating G.

In addition, by arranging the light receiving element 18 near the focal point of the diffusing optical system 13, each diffracted light R10, R11,
Since the beams of R20 and R21 are returned to the light-receiving surface of the light-receiving surface of the light-receiving element 18 as reflected light when the beam diameters of R20 and R21 are narrowed down to the maximum, the pitch of the interference fringes can be more accurately matched to the pitch P of the diffraction grating G.

By arranging the pinhole 14 and the light receiving element 18 near the focal point of the diffusing optical system 13, the harmful diffracted light y, (
mlfrL and the pitch of the interference fringes can be precisely matched to the pitch P of the diffraction grating G.

Effects of the Invention As described above, according to the present invention, the diffraction grating on the sample is arranged approximately parallel to the interference fringes obtained by the interference fringes of the binary bundle, and the plurality of diffracted lights diffracted by the diffraction grating are The returned light is received by a light receiving element, extracted as position information, and then, for example, two reflecting mirrors are rotated.The incident angle of the two light beams to the diffraction grating is adjusted, and the pitch of the interference fringes of the two light beams and the pitch of the interference fringe of the two light beams are adjusted. By making the pitch of the diffraction grating substantially equal, it is possible to detect the relative positional relationship between the interference fringes of the two light beams and the sample with a high accuracy of several hundred eights or less9.
With a simple configuration, it is possible to realize an exposure apparatus that has a large throughput I and is capable of forming submicron patterns.

[Brief explanation of the drawing]

FIG. 1 is a principle diagram of a conventional exposure apparatus, FIG. 2 is a principle diagram of a conventional projection exposure apparatus, FIG. 3 is an overall configuration diagram of an exposure apparatus according to an embodiment of the present invention, and FIG. 4 is a diagram of the same apparatus. FIG. 5 is a plan view of a sample W having a diffraction grating G used for this purpose. FIG. A diagram showing the optical path of light when diffracted by the diffraction grating G (FIG. 7 is a plan view of the light receiving element 18 used in the device, FIG. 8 is a front view of the reflecting mirrors M1 and M2 used in the device, Fig. 9 is a side view of reflecting mirrors M1 and M2 used in the same device, and Fig. 10 shows that each diffracted light R10, R11, R20°R21 of the same device is φ1+(
-φ2), ψ1'=(-ψd1), φ2N(-ψd21
) is a diagram showing the optical path when 1o... Laser generator, 14... Pinhole, 15... Parallel optical system, 17...
2-beam splitting optical system, 18... Light receiving element, Ml,
N2...Reflector, R1...Reflected light, R
2...Transmitted light, W...sample, G...
Diffraction grating, R10...0th order diffracted light, R11...
...4th order diffraction light, R2Q...0th order diffraction light, R2
1...+1st order diffracted light. Name of agent: Patent attorney Toshio Nakao and 1 other person N1
Figure 2 Figure 4 p Figure 5 2 Figure 8 2 to Figure 10

Claims (4)

[Claims] (1) Place the light receiving element near the coherent light beam,
A diffraction grating formed in space and arranged substantially parallel to the interference fringes is disposed in the optical path of the two beams, and the light diffracted by the diffraction grating is further returned through the optical system to receive the light. By measuring the intensity of the returned light at the element,
An exposure apparatus characterized in that the pitch of the interference fringes is adjusted to be approximately equal to the pitch of the diffraction grating. (2) A light-receiving element is disposed in the vicinity of a position where the light flux is narrowed down by the diffusion optical system through a diffusion optical system for diffusing coherent light speed. Exposure equipment. (3) A coherent light beam is passed through a diffusing optical system to diffuse it, a pinhole is arranged near the position where the light beam is focused by the diffusing optical system, and a light receiving element is placed near the light beam that has passed through the pinhole. and further includes an optical system that divides the amplitude of the light beam and overlaps it to cause interference, and forms interference fringes in space by interfering with the two amplitude-divided light beams, and is arranged substantially parallel to the interference fringes. The above-mentioned 2 diffraction gratings
The pitch of the interference fringes is made approximately equal to the pitch of the diffraction grating by placing the light in the optical path of the light beam, returning the light diffracted by the diffraction grating through the optical system, and measuring the intensity of the returned light at the light receiving element. An exposure device characterized by adjusting the exposure device so that (4) The exposure apparatus according to claim 3, wherein the light receiving element is a light receiving element whose light receiving portion is divided into four parts and has a microhole for passing a light beam.