JPS62176129A - Exposure apparatus - Google Patents

Abstract

PURPOSE:To supply the adequate amount of exposing light on the surface of a wafer all the time in a simple structure, by providing an intermittent emission type light source for exposing a wafer through a mask pattern, and providing a light detecting means, which detects the peak value of light that is proportional to the amount of the light of the light source. CONSTITUTION:When a mask pattern is projected on a wafer and the wafer is exposed, at first a shutter 6 is closed. One or several light pulses are outputted from an excimer laser 1. The output energy of the pulse light at this time is detected by a detecting means 5. Thus, the degree of the deterioration of mixed gas sealed in the excimer laser 1 is found. Based on the output signal from the detecting means 5, the amount of the light projected on the surface of a mask 8 is controlled by a control means 14. When the specified amount of the light is detected by the detecting means 5, the detecting means 5 is removed from a light path. The shutter 6 is opened with a solenoid 13. The pulse light from the excimer laser 1 is projected on the mask pattern. The mask pattern is projected on the surface of the wafer 10 through a projecting system by the adequate amount of the exposing light and the exposure is carried out.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application) The present invention provides a method for transferring a mask pattern on a wafer surface onto a wafer surface using an intermittent light source as a light source. The present invention relates to an exposure apparatus that can always supply an appropriate amount of exposure onto a surface.

(Conventional technology) Recent semiconductor manufacturing technology includes high integration of electronic circuits.
There is a need for phosphorography technology that can form high-density circuit patterns.

Generally, when a circuit pattern on a mask or reticle surface is transferred onto a wafer surface via a projection optical system, the resolved line width of the circuit pattern transferred onto the wafer surface is proportional to the wavelength of the light source. In addition, in the case of the so-called contact proximity method in which a mask and a square are transferred in close contact or overlappingly with a distance of several to several tens of microns, the resolution is proportional to the square root of the wavelength. For this purpose, for example, a high-pressure mercury lamp, a xenon mercury lamp, or the like, which oscillates a short wavelength of far ultraviolet (deep UV region) with a wavelength of 200 to 300 rv, is used. However, these light sources have low brightness and lack directivity, and the photoresist coated on the wafer surface has low photosensitivity, resulting in a long exposure time and a reduction in throughput.

On the other hand, recently, intermittent light sources such as excimer
A light source called a mer) laser having an oscillation wavelength in the deep UV region has been developed, and various reports have been made that it is effective as a phosphorography technique due to its high brightness, monochromaticity, directivity, etc.

Many excimer lasers currently on the market use a mixed gas for laser oscillation sealed in a gas chamber, circulated, and discarded after use.

As the mixed gas, a highly corrosive halogen gas such as F2 or HCJ2 is used. For this reason, with the addition of the influence of discharge during excitation, the halogen-based gas reacts with the inner wall of the laser discharge tube and the discharge electrode to form impurities, causing the laser output to deteriorate over time. This reaction of halogen molecules always occurs even when laser light is not oscillated.

For this reason, especially when the laser beam is oscillated after the laser oscillation has been stopped for a long time, the laser beam oscillates with an uncertain output energy that is unrelated to the previous laser output.

Therefore, when using excimer lasers in exposure equipment for semiconductor manufacturing, it is necessary to constantly monitor changes in laser output because it is necessary to strictly control the amount of exposure to the surface as circuit patterns become finer. be.

(Object of the present invention) The present invention provides an exposure apparatus for semiconductor manufacturing that can always supply an appropriate amount of exposure to the eight surfaces of the sea urchin when a light source with unstable output is used as a light source. Particularly, it is an object of the present invention to provide an exposure apparatus in which the output of an intermittent light source cannot be monitored by using a light detection means, such as a silicon photodiode, which has a simple configuration, for example, does not require an integrating circuit. .

(Example) FIG. 1 is a schematic diagram of an example of an exposure apparatus of the present invention, in which 1 is an intermittent light source, for example, an excimer laser, 2 is a switchable ND filter whose optical density can be switched to several levels, and 3 is a variable aperture member whose aperture diameter can be arbitrarily changed;
4 is a reflecting mirror, and 5 is a detection means arranged in a part of the optical path to detect the amount of light, preferably a photoelectric conversion element made of a general silicon photodiode, for example. 6 is a shutter; 7 is an illumination system that illuminates the reticle and mask 8 with the light beam output from the excimer laser 1; 9 is a projection system for projecting the mask pattern on the mask 8 onto the wafer 10; 11 is the wafer 1o is mounted on an XY stage which can be driven by a drive means (not shown); 12 is a surface plate; 13 is a solenoid for driving the shutter 6; and 14 is a control means.

In this embodiment, an alignment optical system for adjusting the relative relationship between the mask 8 and the wafer 1o is provided, but it is omitted in the figure.

In this embodiment, when projecting and exposing a mask pattern onto the convex surface of a sea urchin, the shutter 6 is first closed, one or several pulsed lights are output from the excimer laser 1, and the output energy of the pulsed light at that time is detected by the detection means 5. Detect with. This makes it possible to know the degree of deterioration of the mixed gas sealed in the excimer laser 1. and detection means 5
The control means 14 controls the mask 8 based on the output signal from the
Controls the amount of light irradiated onto the surface. Control at this time is performed by using a voltage adjusting means (not shown) that varies the discharge voltage of the excimer laser 1, by changing the optical density by using the switching type ND filter 2, by changing the aperture diameter of the variable aperture member 3, or by using each of these elements. This is performed by an exposure amount control means that performs the following operations in duplicate. When the detection means 5 detects a predetermined amount of light, the detection means 5 is moved out of the optical path, the shutter 6 is opened by the solenoid 13 as shown in FIG. 2, and the mask pattern is irradiated with pulsed light from the excimer laser 1. A mask pattern is projected and exposed onto the surface of the wafer 10 at an appropriate exposure amount using a projection system.

In this embodiment, the object of the present invention can be achieved even if the switchable ND filter 2, the detection means 5, the shutter 6, etc. are placed at any position in the optical path from the excimer laser 1 to the wafer 10. . Further, the object of the present invention can be achieved even if the variable aperture member 3 is placed at any position as long as it is located at the pupil position of the wafer or at its optical conjugate surface.

Further, the detection means 5 may be arranged at the position 5' by using 4 as a half mirror. At this time, you can monitor even during exposure.

In this embodiment, the shutter 6 does not need to be provided. However, in this case, it is necessary to remove the wafer 10 from the XY stage and set it aside when outputting the excimer laser l.

When an excimer laser is used as a light source as in this embodiment and exposure is repeatedly performed by the so-called step-and-rebead method, the output pulse time of the excimer laser is, for example, 10
By taking advantage of the short length of ~20 n5ec, it is possible to perform transfer exposure while continuously feeding the XY stage without stopping it. In such cases, high throughput can be easily achieved by performing one exposure with one pulse of light. In such a case, the present invention accurately controls one pulse-like output for exposure, so that accurate exposure can be performed.

The present invention can also be applied to a so-called contact method in which a mask and a wafer are brought into close contact with each other, or a proximity method in which a mask and a wafer are placed apart from each other by a small space of several to several tens of microns. Alternatively, a solid-state laser device using a slab glass may be used.

FIG. 2 is a timing chart for explaining the operation of FIG. 1. In the example (A), the power is turned on after a long-term stop, and a plurality of output laser pulses, for example, four, are used for exposure detection.

During these four pulse output periods, the shutter 6 is closed, and the computer in the control means 14 calculates the average value of the four pulses, adjusts the laser output as described above, and starts from the fifth output. Start exposure.

Example (B) shows a case where the number of this monitoring pulse is one. As a specific example of the detection means 5, a silicon photodiode is preferably used as described above. Because P I N (Pos
tive (intrinsic)
If the element has a fast response speed, such as a photodiode, the output current will be approximately the same as the excimer laser pulse shown in FIG. 3(A), as shown in FIG. 3(C). Here, if the waveform shape of the laser pulse (A) is always constant, (C)
Since the peak value of is almost proportional to the area of (A), (C)
The peak value of can be regarded as the energy of (A). However, in the case of an excimer laser, its output waveform is generally unstable, so an integrating circuit is required to detect a value proportional to the area of (A). However, as shown in (B), since the response speed of the silicon photodiode is slow, it has an integral effect. Therefore, the peak value S of 2 is proportional to the area of (A), and this S can be Once detected, the laser output energy can be measured without using an integrating circuit. Figure 4 shows each n optical area CI, C2-- on the wafer.
- An example is shown in which the laser is output only at one time and the wafer is exposed while continuously moving.

That is, first, the first exposure area C1 is exposed with a laser beam. Next, the second exposure area c2 is moved to position 01, and a second exposure is performed. During this movement, the output of the laser 1 is of course stopped.

Furthermore, during the second exposure, the wafer 10 is not stopped but is exposed while it is moving. Thereafter, the wafer 10 is continuously moved to the exposure area C5 and exposed at C3, C4°C5. When this is completed, the wafer 10 is sent upward by one row, and exposure is performed while continuously moving through the next rows 06 to C12.

The following processing is performed in the same manner. Since the wafer is exposed continuously in this way, throughput is improved.

(Effects) As described above, the present invention makes it impossible to monitor the exposure amount with an extremely simple circuit configuration, and can greatly contribute to miniaturization and cost reduction.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an example of the present invention, and FIGS. 2 to 4 are timing charts for explaining the operation. 1-111 excimer laser source

Claims (2)

[Claims] (1) An exposure apparatus comprising an intermittent light source for exposing a pattern of a mask onto a wafer and a light detection means for detecting a peak value proportional to the amount of light from the light source. (2) The exposure apparatus according to item (1), wherein the light source includes an ultraviolet laser source, and the photodetector includes a silicon photodiode.