JPS60136278A - Pattern formation - Google Patents

Abstract

PURPOSE:To optimize the processing time without taking out a processed semiconductor substrate from developer so often by a method wherein a pattern is formed by selectively removing a resist film while the shape of the pattern is monitored with diffraction light of light flux. CONSTITUTION:The semiconductor substrate 11 is coated with resist, which is passed through processes by the conventional technique, and the exposure of the stripe pattern is performed with the two-flux interference method using a light flux of He-Cd laser. For the purpose of developing this resist film 12, the substrate is dipped in the developer 14 by the conventional technique. The light flux of He-Ne laser is made incident to the resist film 12 being under development, and the strength of its primary diffraction light shown by broken lines is monitored. As the development advances, the diffraction light is detected with the gradual increase in strength. At the point of maximum, the substrate 11 is taken out of the developer 14 and rinsed by the usual method, and then the substrate is etched by using the pattern-formed resist film as a mask.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field of the Invention The present invention relates to a pattern forming method, and particularly to a forming method capable of forming a resist mask with a fine periodic pattern in the best condition.

(b) Background of the technology As the technology for using optical communication systems as a medium for information signals is developed and progresses, these systems are becoming more and more popular. A semiconductor laser is a typical example of this device development.

In a semiconductor laser, the source is amplified by guided emission and oscillated by an optical resonator.

A 77 Brie-Perot type resonator, which has a structure in which a pair of mirrors face each other in parallel, is often used as this optical resonator, but semiconductor lasers with this structure have extremely difficult control of the axial mode, and temperature changes The oscillation wavelength changes due to a change in the energy bandgap of the half 44B, and cannot be stably controlled.

These characteristics can be greatly improved by a distributed feedback laser in which resonator feedback is selectively performed by a diffraction grating provided at the interface of the optical waveguide. However, it is not easy to form the diffraction grating with good reproducibility.

(C), Prior art and problems Figure 1 (a) and (b) are cross-sectional views showing an example of a distributed feedback laser.
b) shows a cross section perpendicular to the resonator.

In the figure, 1 is an n-type indium phosphorus (InP) substrate;
2 is an n-type InP confinement layer, 3 is an n-type indium-gallium-arsenic-phosphorus (InGaAaP) guide layer, and 4 is an InP confinement layer.
GaAaP active layer, 5 is p-type InP confinement layer, 6 is p
m I n P layer, 7 is n-type InP layer, 8 is p-type In
The GaAsP layers 9 and 10 are electrodes, and as shown in the figure, the n-type InP confinement layer 2 and the InGaAsP guide layer 3
A diffraction grating is formed at the interface.

That is, in the above example, the upper surface of the n-type InP confinement layer 2 is selectively etched to provide striped periodic unevenness, and InGaAaP, which has a refractive index different from InP, is epitaxially grown on this surface to form a diffraction grating. is formed.

The period A of this diffraction grating needs to be as follows, where the wavelength in vacuum is the source of the oscillation and the effective refractive index of the optical waveguide is n. However, in formula (1), t is a positive integer (1, 2, 3,...), and ideally t = 1 is desirable, but it is selected in consideration of manufacturing issues. Ru. In the above example, for example, small=i, 55(μ
m), n=1-3.26, A'-p475 as t-2
(nm).

The uneven pattern on the surface of a semiconductor substrate is generally created by forming a resist pattern using the phosphorography method, in which a resist film is formed on the substrate and then exposed and developed, and the substrate is selectively etched using this resist pattern as a mask. It is formed. However, in the exposure process of the Mi+ diffraction grating pattern where the period A of the pattern is minute and a degree of freedom is required to select and control its value, as in the above example, the phosphorography method using the element is usually used. Since it is extremely difficult to use a mask that does not require the use of a mask, exposure is usually performed by binary flux interferometry. 2
The beam interferometry is a method in which a single wavelength laser source is split into two beams and interference fringes are formed by the optical path difference between the two beams.The period of the interference fringes can be easily adjusted by changing the angle. can.

The development process for the resist after this exposure is carried out in advance by performing a preliminary development process, measuring the diffraction efficiency, and determining the development conditions such as the optimum value of the development time that yields the maximum efficiency, and then following these development conditions. is managed. However, the optimum development time is greatly affected by exposure conditions, fA image temperature, developer concentration fluctuations, etc., and it is difficult to ensure the best development results. I have taken it out and processed it many times.

Further, unnecessary resist often remains after the development process is completed, and plasma ashing is sometimes performed to remove this unnecessary and harmful resist. In this case as well, the processing time is set experimentally in advance and the processing is performed accordingly, but it is even more difficult to perform the optimal processing due to fluctuations in the remaining state.

(d) Purpose of the Invention The invention is to deal with the above-mentioned situation and to prepare lettuce leaves on a substrate.
In the development process for forming a striped periodic pattern using a film, the semiconductor substrate to be processed is not taken out from the front of the image. The purpose is to provide a forming method.

(e) Structure of the Invention The object of the present invention is to prevent the exposure of a striped periodic pattern on a resist film provided on a substrate due to interference between energy beams.
After that, a light beam that does not expose the resist film is irradiated onto the resist film, and while monitoring the shape of the shadow of the pattern by the diffracted light of the light beam, the resist film is selectively removed to expose the pattern. It is quickly formed by the process of forming.

(f) Embodiments of the Invention The present invention will be specifically described below with reference to the drawings.

FIG. 2 is a schematic diagram showing a state in which the present invention is implemented when the original resist film is immersed in a developer and developed. In the figure, 11 is a semiconductor substrate, 12 is a resist film under development, 13 is a container, and 14 is a developer.

In this embodiment, a resist (for example, Sibley's Az1350) is applied to a thickness of about 250 [nm] on the semiconductor substrate 11 as described above, and helium-cadmium (He- Cd) Exposure of a striped pattern with a period A=467 Cnm, for example, is performed by a binary beam interferometry using a laser beam having a wavelength of 441.6 (nm).

In order to develop the resist film 12 according to the processing method of the present invention, the resist film 12 is immersed as shown in the figure using, for example, Sibley's MF312: water = 4:5 dilution solution as the developer 14 according to the prior art. do.

In this example, a helium-neon (He-Ne) laser with a wavelength of 632.8 C was applied to the resist film 12 during development.
A light beam of nm: ] is made incident as shown by the solid line in the figure, and the intensity of its primary diffraction source shown by the broken line is monitored. As the development progresses, diffracted light is detected and its intensity gradually increases, but at the point when the diffracted light becomes extremely thick, the semiconductor substrate 11 is removed from the developer 1.
4 and rinsed in the usual manner. After that, the semiconductor substrate is etched using the patterned resist film as a mask.

According to the present invention, the light flux with which the resist 12 is irradiated during development processing needs to have a wavelength that does not expose the resist 12 to light. In addition, in order to monitor using the first-order diffraction source as in this embodiment, the wavelength of the light beam must be 2 times the period A of the diffraction grating.
It is necessary that the amount is less than twice that.

Further, FIG. 3 is a schematic diagram showing an embodiment of the present invention in which unnecessary and harmful resist remaining after development processing is removed by a plasma Angling method. In the figure, reference numeral 21 indicates four semiconductor plates, 22 indicates a resist necessary for pattern formation, and 23 indicates an unnecessary and harmful resist to be removed.

In this embodiment, the resist 23 remaining in the process of the previous embodiment is removed, but plasma is generated using the conventional technique, for example, oxygen (0,) is turned into plasma at a pressure of about 1 Torr. During this plasma ashing or etching, for example, He-N
By directing e-laser light onto the resists 22 and 23, detecting the intensity of the diffracted light, and terminating the process when the intensity of the diffracted light becomes extremely thick, the harmful resist 23 can be effectively removed. At this time, the resist 22 necessary for pattern formation is also etched and deformed as illustrated by the broken line in the figure, but the amount of deformation is minute and causes no particular problem.

Although the embodiments described above are directed to development by immersion and removal of unstable resists by plasma, the present invention can also be applied to JA, image, or dry development using spray methods. Furthermore, the present invention can be applied not only to the formation of a diffraction grating for a distributed feedback laser, but also to the formation of similar periodic structures, and similar effects can be obtained.

In this embodiment, the surface of the semiconductor substrate was etched using the resist film formed in striped form by the above method as a mask, but it may also be used as a mask for ion implantation, etc.

(g) As described in detail, according to the present invention, a resist mask for forming a periodic structure in the form of fine stripes can be easily and reliably formed in the best condition. , it is possible to form diffraction gratings and the like with good reproducibility and high efficiency, which has a great effect on the development of systems to which 9 is applied.

[Brief explanation of the drawing]

FIGS. 1(a) and 3(b) are plan views showing an example of a distributed feedback laser, and FIGS. 2 and 3 are schematic views showing embodiments of the present invention. 21 is a substrate, 12 and 22 are resists, 13 is a container, 14 is a developer, and 23 is a resist to be removed.

Claims (1)

[Claims] A resist film provided on a substrate is exposed to a striped periodic pattern by interference between energy beams, and then a source that does not expose the resist film to light is irradiated onto the resist film, and the diffracted light of the light beam is A pattern forming method comprising the step of selectively removing the resist film to form the pattern while monitoring the shape of the pattern.