JPS61111529A - Exposure amount controller - Google Patents

Abstract

PURPOSE:To yield the titled device capable of controlling the effective exposure amount to a photosensitive material at suitable values for a long time, by using an excimer laser of injection locking type which can vary the wavelength and control the spread angle and the line width of beams. CONSTITUTION:If the wavelength of the excimer laser 1 is varied by producing control signals transmitted to a wavelength-variable mechanism 2 by mans of a comparator and microprocessor 10 in such a manner that the amount of light coming into a photo receptor 8 with a wavelength of oscillation efficiency other than the maximum becomes constant, the stabilization of output energy is enabled for a long period. Such a variation in oscillation wavelength a very small range of wavelength at 1nm or less can largely vary the oscillation efficiency of laser and vary the laser output in proportion to this. As a result, it is made possible to arbitrarily control exposure energy to the wafer surface 6.

Description

[Detailed description of the invention] The present invention relates to an exposure control device, and particularly to an IC.

When projecting and exposing the single-child circuit pattern 7 of a semiconductor such as an LSI onto the wafer surface, the exposure lid on the wafer surface must be properly maintained.
cRegarding the exposure amount control deviceO Recent semiconductor technology is progressing toward higher integration and miniaturization of Nariko circuits, and the field of optical exposure methods is also expanding further with the development of high-resolution lenses, etc. be. In such exposure equipment for semiconductor manufacturing, when transferring and printing the circuit pattern of a mask or reticle onto the wafer surface,
The resolution line width of the circuit pattern printed on the surface is proportional to the wavelength of the light source.
Short wavelength light sources in the UV) region are used.

Conventional deep ultraviolet light sources of this type include deuterium lamps and Xs
-Hg lamps were known.

Generally, in semiconductor manufacturing, a circuit pattern is projected and exposed onto the wafer surface repeatedly, so the effective amount of exposure onto the wafer surface must always be maintained at an appropriate value for each process. Here, the effective exposure amount is defined as the energy of the exposure light and the sensitivity of the photosensitive resin to be printed, integrated over all wavelengths.

Conventionally, a light receiving means is placed in the optical path of the illumination optical system so that the illuminance on the wafer surface is constant, and the input low pressure to the light source is controlled or the exposure time is controlled so that the output from the light receiving means is constant. A friend who is in control and careful.

On the other hand, in recent years, excimer lasers and light sources with output wavelengths all in the a-ultraviolet region have been used in various fields. This excimer laser has Takakura F-degree properties.
Due to its monochromatic nature and short coherence distance, the exposure system is very effective for producing semi-cotton bodies.

The excitation method of this excimer laser is the 11 electric excitation method, so the excimer laser is used as the light source of the illumination optical system for exposing the circuit pattern, and in order to maintain the exposure energy on the eight faces of the sea urchin at a predetermined vL. It is conceivable that this could be done by controlling the discharge excitation voltage. However, if the excitation voltage becomes too large, the laser or excitation circuit will be destroyed, and conversely, if the excitation voltage becomes too small, the laser will no longer oscillate, so it is generally very difficult to control the excitation voltage and greatly change the output energy. .

′! The 92 xima laser is the 9th type of high-power pulse oscillation.
Normally, the necessary exposure energy can be obtained with one to several pulses, and the pulse emission time is 410 to 20 nSe.
It is difficult to precisely control the exposure energy by controlling the exposure time, which requires a very short time of about C and an ultra-high speed shutter.

The present invention is characterized by providing an exposure amount control device which can control the effective exposure amount to a photosensitive material to an appropriate value in a stable state at all times and over a period of time. An object of the present invention is to provide an effective exposure amount control device suitable for projecting and exposing a circuit pattern onto a photosensitive material such as a photoresist on a /S surface.

The main feature of the lightless control device for achieving the object of the present invention is that the oscillation wavelength is variable and the output energy varies depending on the oscillation wavelength. When emitting light, a light receiving means is disposed in the optical path of the light beam or an optical path branched from the light path, and an output signal from the light receiving means is used so that the effective exposure amount to the photosensitive material becomes a predetermined value. The method is to change the oscillation wavelength of the light source.

Next, one embodiment of the present invention will be described with reference to each drawing.

FIG. 1 is a schematic diagram of an embodiment of the present invention. This is an injection locking type excimer laser that can fully control the square and line widths.

The excimer laser used in this example uses a technique called Kanagamachi-hen injection locking, in which two lasers are connected in series, and one of the two resonators is used for oscillation, and the other is used for amplification. use,
By arranging prisms, gratings, etalons, etc. in the oscillation laser, the oscillation wavelength width can be narrowed and the oscillation wavelength can be changed.

Reference numeral 2 denotes a wavelength variable mechanism for the excimer laser (c), which is comprised of, for example, a step motor for tilting the prism angle. 3 is a nine laser beam emitted from the excimer laser 1, 4 is an illumination optical system for converting the laser beam 3 into a desired irradiation beam, 5 is an irradiation beam, and 6 is a Ueno beam.
Circuit patterns such as mask patterns and reticles are projected on the surface. 7 is a mirror for taking in a part of the irradiation beam 5, 8 is a light receiver, 9 is an integrating circuit, and 10 is a comparison circuit and a microprocessor.

At this time, due to the properties of the rare gas halide that is the laser medium of the excimer laser, for example in the case of KrF, the oscillation efficiency changes due to the difference in wavelength K as shown in Figure 2, so the quality of the oscillation output changes accordingly. It's turning into something.

Since the wavelength change range at this time is very narrow, approximately 1n1rL, it is relatively easy to almost eliminate the influence of chromatic aberration of the optical system.

As described above, in this embodiment, if the oscillation wavelength is changed within a very narrow range of wavelength change of 1n1rL or less, the oscillation efficiency of the laser can be greatly changed, and the laser output f: can be changed in proportion to the oscillation efficiency. can. As a result, it becomes possible to arbitrarily control the exposure energy onto the Uninow surface.

In this implementation, in the initial stage, wavelengths other than the maximum value of oscillation efficiency are used, and the wavelength variable mechanism 2 is controlled by the comparison circuit and the microprocessor 10 so that the amount of light incident on the light receiver 8 is constant.
By creating all the control signals sent to the excimer laser 1 and changing the wavelength of the excimer laser 1, it becomes possible to stabilize the output energy over a long period of time.

Note that the integration circuit 9 of this embodiment has a short-term paralysis in the energy of each pulse of the excimer laser 1, so its influence j#
It is for removing gold.

Instead of the nine wavelength tunable indiexicon locking type excimer laser used in this implementation, a nine dye laser excited with the fourth harmonic of an excimer laser, N2 laser, or YAG laser or its second harmonic is used. The oscillation wavelength may also be changed by using f, t', etc. In this case, the amount of change in the oscillation wavelength is increased to maintain a constant effective exposure amount depending on the difference in spectral sensitivity of photosensitive materials such as photoresists.

For example, Figure 3 shows the product name RD200O manufactured by Hitachi Chemical Co., Ltd.
This is a spectral sensitivity curve of a photoresist named N. In general, the sensitivity change of a photoresist due to wavelength is much gentler than the change due to wavelength of the oscillation output of the injection locking type excimer laser mentioned above. For this reason, when all dye lasers are used, the oscillation wavelength of the laser is changed greatly to an extent corresponding to the spectral sensitivity distribution of the photosensitive material, so that the effective exposure amount is maintained constant.

As described above, according to the present invention, by utilizing the wavelength dependence of the output energy of the light source and the wavelength dependence of the sensitivity of the photosensitive material, the amount of exposure to the photosensitive material is determined by changing the oscillation wavelength from the light source. It is possible to achieve the next layer light amount control device ifk by controlling it so that the value is the same.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an embodiment of the present invention, and FIG. 2 is an explanatory diagram of emission efficiency according to wavelength of an excimer laser according to the present invention.
Figure 3 shows the spectral sensitivity of photoresist as a photosensitive material [
It's song i. In the figure, 1 is an excimer laser, 12 is a wavelength variable mechanism, 4 is an illumination optical system, 6 is a surface to be irradiated, 7Fi<ra, 8σ light receiving G,
9 is an integrating circuit, lO is a comparison circuit and a microprocessor.

Claims (1)

[Claims] (1) When exposing a photosensitive material through an illumination optical system with a light beam emitted from a light source whose oscillation wavelength is variable and whose output energy differs depending on the oscillation wavelength, an optical path in the exposure optical path or branched from the exposure optical path A light receiving means is placed inside,
An exposure amount control device characterized in that the oscillation wavelength of the light source is changed using an output signal from the light receiving means so that the effective amount of exposure to the photosensitive material becomes a predetermined value.