JPS6370522A - Ultraviolet ray exposure method - Google Patents

Abstract

PURPOSE:To superpose patterns in a highly accurate manner even when a wafer is expanded or contracted by a method wherein the wavelength of the source of light is controlled based on the amount of expansion and contraction of the wafer. CONSTITUTION:A control device system is composed of a CPU 20, a rotating stage control circuit 21, a mark detecting device 22 with which the mark to be used for detection of the amount of expansion and contraction is detected, a mark detecting signal processing circuit 23, an X-Y-Z stage control circuit 24, an X-Y control circuit 25, an X-Y direction shifting mechanism 26, a Z-control part 27, and a Z-direction shifting mechanism 28. The position of chip marks 33 and 34 is detected, and the size of the chip is computed from the result of said detection. After the amount of expansion and correction of the chip has been computed from the chip size, the magnification of the projection lens is worked out, the center wavelength of the laser is computed for the purpose of correcting said amount of expansion and contraction, the position of image formation is set, and the height of the wafer is adjusted using the X-Y-Z stage. On the other hand, when the center wavelength of the laser is computed, the angle of rotation of an etalon is set, and the etalon is rotated by the rotating stage. At this point, all preparations are arranged, and the pattern is exposed on the chip.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ultraviolet exposure method used for pattern formation of semiconductor integrated circuits and the like.

[Conventional technology]

Generally, when manufacturing semiconductor integrated circuits, an ultraviolet exposure apparatus using a laser as a light source is used.

For example, Microcircuit Engineer 83
ing83), pp. 73-78 (Authors G, M, Dub
roeucq.

As disclosed in D., Zahorsky) i, an excimer laser is used as a light source, the light generated from it is diffused, and then the diffused light is irradiated onto a reticle, which is an object surface, through an illumination lens, and the reticle is The transmitted light is focused onto the surface of the sample by a projection lens. In this case, the ultraviolet rays (wavelength 435
When using one line (wavelength: 365 nm) or one line (wavelength: 365 nm), it is possible to form battens with a minimum line width of 0.5 μm and 8 lines.

[Problem that the invention seeks to solve]

However, when manufacturing semiconductor integrated circuits, wafers undergo expansion and contraction through various processes, so when overlapping patterns, it is difficult to ensure pattern overlay accuracy before and after the wafer expands and contracts. I had a problem.

[Means for solving problems]

In order to solve such problems, the present invention detects the stretched weight of the sample and controls the wavelength of the light source based on the detection result.

[For production]

By controlling the wavelength, the enlargement rate of the pattern is controlled.

〔Example〕

FIG. 1 is a block diagram showing an embodiment of an exposure apparatus constructed to which the present invention is applied. In the figure, 1 is an excimer laser, 1a and 1b are resonators, 1c is an etalon, 1d is a holding frame for the etalon 1c, 1e is a rotating stage, 1f is a discharge tube, 1F and 1h are windows, 2 is a reflection burner, and 3 is a diffuser plate, 4a,
4b is an illumination lens, 5 is an aperture, 6 is a reticle, T is a projection lens, 8 is a wafer, and 9 is an xYz stage. The resonator 18 to the window 1h constitute the excimer laser 1. In addition, the etalon 1c is rotated by the rotation stage 1e, which allows the wavelength of the light generated from the excimer laser 1 to vary from 248.94 to 248.94, as will be described later.
It is designed to be able to vary within a range of about 249.06 nm. The projection lens γ is made of quartz glass and has a focal length of 8
0 mf? 1% The distance a between the surface of the reticle 6 and the rear principal surface of the projection lens 7 is 480 mm. When the s wavelength is 249 nm, the distance a between the front principal surface of the projection lens 7 and the surface of the wafer 8 that becomes the image plane is 96 mm. mm.

The magnification, or b/a, is 115.

Since the projection lens 7 uses quartz glass, its focal length has a large dependence on wavelength, and as shown in FIG.
When changing from 8.5 nm to 249.5 am, the focal length changes from 79.985 mm to 80.015 mmK. Further, when the wavelength changes, the distance changes as shown in FIG. 3, and therefore the imaging position changes. When the distance changes, the magnification represented by b/& changes, and FIG. 4 shows the change in the magnification of the projection lens 7 depending on the wavelength.

The amount of expansion and contraction of a wafer in the manufacturing process of semiconductor integrated circuits and the like is approximately ±0.14 μm in a 10 mm span. As shown in FIG. 4, in order to generate an expansion/contraction amount of ±0.14 μm for a 10 mm span on the image plane, the wavelength is changed from 248.97 nm to 249. Since it is understood that it is sufficient to change the wavelength up to 03 nm, it is sufficient to completely change the wavelength within this range in response to expansion and contraction of the wafer.

Next, the wavelength of the excimer laser 1 is controlled by changing the rotation angle of the etalon 1c. If the interval between the reflective surfaces of the etalon 1c is d, the angle of inclination of the reflective surfaces with respect to the plane orthogonal to the optical axis is θ, and the refractive index of air is n, then the center wavelength λ0 of the light passing through the etalon 1c is expressed as follows. It will be done.

nd λ0=−μsθ ・・Fist・(1) Here, m is an integer and (2nd/m) is a constant, so the wavelength λ0 changes according to the value of −θ. FIG. 5 shows the relationship between the inclination angle θ of the etalon 1c and the center wavelength λ0.

In order to correct the expansion/contraction amount of ±0.14 μm for a 10 mm span on the image plane, it is sufficient to perform the correction in units of about 0.02 μm. In other words, it is sufficient to change the center wavelength in units of 0.004 nm. The rotation angle of the etalon 1c required to change the center wavelength by 0.004 nm is 1 mrad as shown in FIG. 5, and the change in the imaging position at that time is 0.2 μm as shown in FIG.

A rotation angle control accuracy of 1 mraciLv and a two-direction position control accuracy of 0.2 μm can be sufficiently achieved using known techniques.

FIG. 6 shows a control device system in this embodiment, 20 is a CPU, 21 is a rotation stage control circuit, 22 is a mark detection device for detecting a mark for detecting the amount of expansion and contraction attached on a wafer, which will be described later, and 23 is a Mark detection signal processing circuit, 24 is an XYz stage control circuit, 25 is an XY control section, 26 is an x
21 is a y-direction moving mechanism, 21 is a 2-control unit, and 28 is a 2-direction moving mechanism. FIG. 7 shows details of the wafer 8, 30 is a chip such as a semiconductor integrated circuit, 31.32 is a wafer mark,
33.34 are step marks.

Diagram N8 shows the exposure procedure when applying Kg light to such a curved surface. First, as shown in step S1, step mark 3
3. Detect the position of 34, and determine the dimensions of the chip from this detection result. From this chip dimension, the amount of expansion and contraction of the chip is calculated as shown in step S2, and then the magnification of the projection lens is calculated as shown in step s3.In order to correct this amount of expansion W3, the amount of expansion and contraction of the chip is calculated as shown in step S4. The center wavelength is calculated, the imaging position is set as shown in step S5, and the height vI& of the wafer is adjusted using the XYZ stage as shown in step S6. On the other hand, when the center wavelength of the laser is determined in step S4, the rotation angle of the etalon is set in step s7, and step S
As shown in 8, the etalon is rotated by the rotation stage. Now that everything is ready, step S
At step 9, the chip is exposed to light.

In the above embodiments, the angle of the etalon is controlled to change the center wavelength of light, but this method is disclosed in Utility Model Application No. 982222.
As shown in Figure 1, the etalon may be placed in a closed container and the pressure within the container may be varied. The center wavelength λ0 changes depending on the change in the refractive index n.
This means that it is changing. FIG. 1O shows the change in the center wavelength when the pressure inside the closed container is changed within the range of 760 to 1520 mmHP. If the pressure inside the sealed container of the etalon is automatically adjusted, an etalon housed in a sealed container can be used instead of the etalon with a rotating stage shown in the embodiment.

Furthermore, although the above explanation has been given for the case where the light source is an excimer laser with a wavelength of 249 nm, it can also be applied to an exposure apparatus whose light source is a laser that generates light of other wavelengths, and the etalon is placed outside the laser cavity. Alternatively, the wavelength of the laser beam incident on the projection lens may be adjusted by installing the laser beam so that the light generated from the laser passes through the etalon.

〔Effect of the invention〕

As explained above, this invention controls the wavelength of the light source based on the amount of expansion and contraction of the wafer, so even if the wafer expands and contracts, it is possible to overlap patterns with high precision and expose each chip. have an effect.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the constituent countries of an embodiment of the present invention, and FIGS. 2, 3, and 4 are graphs showing wavelength vs. focal length characteristics, wavelength vs. imaging position characteristics, and wavelength vs. magnification characteristics of the projection lens. , Figure 5 is a graph showing the etalon rotation angle versus center wavelength characteristics, Figure 6 is a graph showing the etalon rotation angle versus center wavelength characteristics.
The figure is a block diagram of the control system, W, 7 is a plan view of the wafer,
FIG. 8 is a flowchart showing the exposure procedure, and FIG. 9 is a graph showing the relationship between the enclosed air pressure and the center wavelength of the laser beam passing through the etalon when the etalon is sealed in the airtight container. 1 race/war/excimer laser, 1c... etalon,
16e fist... rotating stage, 6 fist... Renacle, TΦ
...-projection lens, 8...wafer, 9 e * @
*XYZ Stage 1.

Claims (1)

[Claims] An ultraviolet exposure method in which a sample is exposed to light using a laser as a light source, the ultraviolet exposure method being characterized by detecting the amount of expansion and contraction of the sample and controlling the wavelength of light emitted from the light source based on this detection result.