KR19990004380A - Mask for forming diffraction grating and method for forming diffraction grating using same - Google Patents

Abstract

The present invention discloses a mask for a diffraction grating and a method for forming the diffraction grating using the same.

The present invention discloses a method of forming a resist film on a compound semiconductor substrate structure, exposing the resist film to light by irradiating the resist film, developing the exposed resist film, and using the developed resist film. A method of forming a diffraction grating comprising etching a substrate structure by a predetermined depth to form a diffraction grating. In the exposing process, a mask pattern is attached to expose a predetermined period scheduled portion of the compound substrate structure. Characterized in that.

Description

Mask for diffraction grating and method for forming diffraction grating using same

The present invention relates to a compound semiconductor device and a method for forming the same, and more particularly, to a mask for a diffraction grating and a method for forming a diffraction grating using the same.

In general, WDM optical communication technology is attracting attention as a next-generation core technology capable of transmitting a large amount of data at high speed. As a key element used as a light source in a WDM system, it is very important to fabricate a multi-period diffraction grating array on one substrate in order to make an integrated multi-wavelength distributed feedback laser that can dramatically reduce package cost.

Here, the diffraction grating is formed on the compound semiconductor structure by using an electron beam lithography or holography method, which will be described with reference to FIG. 1, where the diffraction grating is to be formed. The compound substrate structure 2 coated with the film 3 is placed on the wafer support 1. Subsequently, the laser beams L1 and L2 divided into multiples are applied, and a path difference Δ of a predetermined interval is generated between the laser beams L1 and L2 to cause constructive or extinction interference. Therefore, exposure is performed to the portion where constructive interference occurs, and exposure is not generated to the portion where extinction interference occurs, so that the resist film 3 is exposed in the form of an interference fringe. Thereafter, the exposed portion is developed, and the compound substrate structure 2 is etched by a predetermined depth using the remaining resist film as a mask to form a diffraction grating (not shown).

However, according to the above-described prior art, the following problems arise.

First, when the multiple diffraction grating layer is formed by electron beam lithography, the gap and depth of the diffraction gratings are etched relatively accurately, while the process must be performed for a long time and expensive equipment must be used. The unit price increases.

In addition, when the multi-period diffraction grating layer is formed using the holographic system, the manufacturing cost is low, but the diffraction grating layer has difficulty in controlling the depth, and thus it is difficult to form a high quality diffraction grating layer.

Accordingly, an object of the present invention is to solve the above-mentioned conventional problems, and to provide a diffraction grating forming method capable of uniformly controlling the width and depth between diffraction gratings in a multi-period diffraction grating arrangement while having low manufacturing cost. To provide.

Moreover, this invention provides the mask for a diffraction grating which can form a diffraction grating as mentioned above.

1 is a cross-sectional view for explaining a conventional method for forming a diffraction grating.

2 is a view for explaining a method for forming a diffraction grating of a laser diode according to the present invention.

3 is a plan view of a mask used in the present invention.

4A to 4C are cross-sectional views of masks taken along the line IV-IV 'of FIG. 3.

5 is a perspective view of a wafer on which a diffraction grating is formed in accordance with the present invention;

Explanation of symbols for the main parts of the drawings

11 compound semiconductor substrate structure 12 resist film

13: mask 14: mask holder

100: wafer resulting diffraction grating

101: diffraction grating

In order to achieve the above object of the present invention, the present invention provides a method for forming a resist film on a compound semiconductor substrate structure, exposing the resist film to light by irradiating the resist film, and developing the exposed resist film. And etching the substrate structure by a predetermined depth by using the developed resist film to form a diffraction grating, wherein in the exposing step, the same cycle scheduled portion of the compound substrate structure The mask pattern is attached so as to be exposed, and then exposed.

In addition, the present invention is a mask used in the exposure process of the resist film for forming a diffraction grating, characterized in that the mask is provided with a slit-shaped opening so that the diffraction grating portions having the same period are exposed.

According to the present invention, during exposure to form a diffraction grating having multiple periods, a mask is provided so that a portion having the same period is exposed, and then a laser beam divided into two is applied as a light source, thereby specifying a specific area within a certain area. It is possible to form a diffraction grating having a period.

In addition, the position of the mask and the position of the wafer may be adjusted to form a diffraction grating in a desired area, and the reflection angle of the laser beam may be adjusted to form a plurality of diffraction gratings having different periods.

EXAMPLE

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

2 is a view for explaining a method for forming an alignment of a multi-period diffraction grating according to the present invention, FIG. 3 is a plan view of a mask used in the present invention, and FIGS. 4A to 4C show FIG. It is sectional drawing of the mask cut | disconnected by the IV-IV 'line | wire.

In this embodiment, a mask is attached on a wafer and then exposed by a laser beam to form a plurality of diffraction gratings having a specific period at a specific position by a simple process.

First, referring to FIG. 2, a resist film 12 having a thickness of 200 to 500 kPa is applied onto the compound semiconductor substrate structure 11, and then the wafer 11 is a wafer support 10 so that an exposure process proceeds. It is put on the table. Subsequently, the mask 13 supported by the mask holder 14 has a predetermined distance from the wafer 11 and is disposed on the wafer 11. Here, the wafer 11 and the mask 13 are preferably installed to be spaced apart by a slight distance within a few mm. Here, the mask 13 is opened in the form of a diffraction grating region having a single period so that the diffraction grating region having a single period can be exposed.

Thereafter, the photoresist 12 exposed by the mask 13 is exposed by the laser beam. At this time, two laser beams L1 and L2 are applied to the laser beam as an exposure source, and a path difference Δ of a predetermined interval is generated between the laser beams L1 and L2, thereby preventing constructive or extinction interference. Will be raised. Therefore, exposure is performed at the portion where constructive interference occurs, and exposure is not generated at the portion where extinction interference occurs, so that the resist film 12 is exposed in the form of an interference fringe. As a result, the region in which the interference fringe is formed in one exposure process is limited, so that a diffraction grating is partially formed.

In addition, in order to form diffraction gratings having different periods in each portion of the wafer by the laser beam exposure method as described above, first, a first diffraction grating having a predetermined period is formed in the above manner. Subsequently, the mask 13 is fixed during exposure, and while the wafer holder 10 is moved up and down, left and right at regular intervals, the neighboring portions of the first diffraction grating are adjusted by adjusting the reflection angles θ1 and θ2 of the incident laser beam. A second diffraction grating is formed at.

Alternatively, the wafer holder 10 is fixed, and the reflection angles θ1 and θ2 of the incident laser beam are adjusted to be moved to the neighboring portions of the first diffraction gap while the position of the mask holder 14 is moved up and down and left and right. Can form another diffraction grating.

Here, a mask structure according to the present invention is shown in FIG.

As shown in FIG. 3, the mask 13 has light transmission regions x spaced apart at regular intervals. Here, the space between the light transmissive regions x becomes one unit cell.

To explain in more detail, for example, suppose that eight diffraction gratings having different periods are formed in one unit cell portion. At this time, if one diffraction grating width A is 200 mu m, the width of the transmission region x is 200 mu m, and the width B of the blocking region y is 1400 mu m.

In other words, if a diffraction grating having eight periods is formed, the width of the region where the entire diffraction grating is to be formed is 1600 mu m. At this time, if the first diffraction grating is formed, the transmission region of the mask 13 is positioned so that only the portion (width = 200 μm) on which the first diffraction grating is to be formed is positioned, and the remaining second, third, ... eighth diffraction The portion to be a grating (width = 1400 mu m) is blocked by the blocking region y of the mask. Then, a diffraction grating having a first period is formed by the laser beam exposure method, and then the mask pattern is moved so that the second diffraction grating portion (width = 200 mu m) is opened. At this time as well, the third, fourth, ..., eighth, first diffraction grating portions (width = 1400 占 퐉) are covered by the blocking region y of the mask 13. This process is repeated to form several diffraction gratings with different periods.

4A to 4C are cross-sectional views taken along the line IV-IV 'of FIG. 3, and the mask is used in a structure in which a chromium pattern 13b is disposed on the transparent glass 13a as shown in FIG. 4A. As shown in FIG. 4B, a structure for stacking and forming the silicon pattern 13c and the metal pattern 13d such that the side surfaces are anisotropic may be used. In addition, as shown in FIG. 4C, the silicon pattern 13c and the silicon nitride film pattern 13e may be used in various forms, such as a structure in which a side surface of the silicon pattern 13c is wet formed to have a mesa shape, that is, a (111) direction.

FIG. 5 is a perspective view in which the diffraction gratings 101a, 101b, 101c, 101d, 101e, 101f, 101g, and 101h having different periods are formed on the wafer resultant 100 on which the laser diode is to be formed as an exposure source. . As shown in the drawing, the diffraction gratings 101a, 101b, 101c, 101d, 101e, 101f, 101g, and 101h are sequentially formed while the mask is sequentially moved or the position of the wafer is sequentially moved. To form a diffraction grating having In addition, the period can be changed by adjusting the incident angle of the laser beam.

In this embodiment, when the Ar laser in the ultraviolet region is used as the laser beam, for example, its wavelength is 3511 GHz or 3638 GHz, and the width of the transmissive region of the mask is several hundred 占 퐉, for example, 200 占 퐉. However, interference and diffraction due to the mask do not occur.

In addition, in the present embodiment, the description of the development and etching steps after the exposure step is omitted, but the diffraction grating described above includes a series of diffraction grating layers, resist film coating, exposure, development, and etching of the diffraction grating layer. It is formed by the process.

As described in detail above, according to the present invention, in the exposure for forming a diffraction grating having multiple periods, after installing a mask so that the portions having the same periods are exposed, the laser beam divided into two as a light source is By being applied, it is possible to form a diffraction grating having a specific period within a certain area.

In addition, the position of the mask and the position of the wafer may be adjusted to form a diffraction grating in a desired area, and the reflection angle of the laser beam may be adjusted to form a plurality of diffraction gratings having different periods.

Therefore, the manufacturing cost is lowered, and an alignment of a high quality multi-period diffraction grating can be obtained.

In addition, this invention can be implemented in various changes within the range which does not deviate from the summary.

Claims (10)

Forming a resist film on a compound semiconductor substrate structure, exposing the resist film by irradiating the resist film with light, developing the exposed resist film, and preforming the substrate structure using the developed resist film. A method of forming a diffraction grating comprising etching a depth to form a diffraction grating, wherein the exposing of the mask pattern is performed by exposing the mask pattern to expose the predetermined period of the compound substrate structure during the exposing process. A method of forming a diffraction grating. The method of claim 1, wherein the light is a laser beam divided into two and having a predetermined path difference. The method of claim 1, wherein in the exposing step, the mask is repeatedly exposed by moving a predetermined interval. The method of claim 1, wherein, in the exposing step, the compound semiconductor substrate structure is repeatedly exposed by moving at a predetermined interval. The method of forming a diffraction grating according to claim 1 or 2, wherein the exposure is performed while adjusting the reflection angle of the laser beam during the exposing step. The method of forming a diffraction grating according to claim 1, wherein the resist film and the mask on the wafer are placed at intervals within several mm. A mask for use in the exposure process of a resist film for forming a diffraction grating, wherein the mask has a slit-shaped opening to expose a portion of the diffraction grating having the same period, the mask for forming a diffraction grating. 8. The mask for forming a diffraction grating according to claim 7, wherein the mask comprises an opaque metal film spaced at regular intervals on a transparent glass substrate. The mask for forming a diffraction grating according to claim 7, wherein the mask is a double pattern of a silicon pattern and a metal pattern, or a double pattern of a silicon pattern and a nitride film pattern. The mask for forming a diffraction grating according to claim 9, wherein the sidewall portion of the mask is anisotropic or mesa in a (100) direction.