GB2244349A

GB2244349A - Method for manufacturing a mask

Info

Publication number: GB2244349A
Application number: GB9021149A
Authority: GB
Inventors: Yong-Hyeon Kim
Original assignee: Samsung Electronics Co Ltd
Current assignee: Samsung Electronics Co Ltd
Priority date: 1990-05-25
Filing date: 1990-09-28
Publication date: 1991-11-27
Also published as: FR2662518A1; JPH0431858A; IT9021589A0; DE4031413A1; KR910020802A; KR920009369B1; IT9021589A1; GB9021149D0

Abstract

A method for manufacturing a mask having a phase shift region useful for producing printed circuits comprises the steps of: coating an opaque mask plate (13) and a photosensitive film (15) on a surface of a transparent substrate (11); exposing a predetermined part of the mask plate (13); exposing a predetermined part of the substrate (11) by etching an exposed part of the mask plate (13); forming a pattern region (17) by etching the substrate (11) to a predetermined thickness (d) forming a phase shift region (19) of width (W) by horizontally etching the side of the mask plate (13); and removing the remaining photosensitive film (15). In the method, the thickness difference between the phase shift region (19) and the pattern region (17) can be exactly controlled by the etch to shift the phase of light passing through the pattern region (17) and the phase shift region (19) respectively. The phase shift region (19) is formed as a part of the substrate (11). Accordingly, a long lifetime mask can be easily manufactured. <IMAGE>

Description

1 METHOD FOR MANUFACTURING A MASK The present invention relates to a

method for manufacturing a mask, and particularly to a method for manufacturing a mask having a phase shift region which can improve pattern resolution.

Generally, in a manufacturing method for a semiconductor device, a pattern of an integrated circuit is formed on the surface of a wafer by using a photo lithography method. The photo lithography method includes an exposure process that selectively copies a desired pattern on the photoresist coated on the wafer by irradiation with an ultraviolet light (hereinafter referred to as UV), etc. There are, as exposing methods, a contact method, a proximity method and a projection method. However, according to the trends in achieving ultra very large integrated semiconductor devices, the line width of a circuit becomes finer, so that the use of the above methods has limitations. on the other hand, there is another exposing method, referred to as a wafer stepping method. The wafer stepping method can give a finer line width in such a manner that a mask which is 5 to 10 times as large as a chip pattern is used and the exposure is carried out by a step and repeat method.

However, in the wafer stepping method, when irradiated U-V is passing through the mask pattern, it is diffracted and as the result, the resolution of the pattern copied on the photosensitive film is deteriorated. Thus, it is impossible to 2 apply the method to manufacturing a semiconductor device having an integration of 16M DRAM or more.

Thus, another method is suggested wherein, when the mask is irradiated with light which passes through the predetermined pattern, the phase of the light passing through the neighbouring pattern is shifted by 1801 to prevent the diffraction of the light, resulting in improvement in the resolution of the pattern. That is, in the mask having the phase shift layer or region, the phase of the light irradiated on the portion other than the predetermined pattern is shifted by 1800, so that a point where light intensity is zero can be obtained.

FIGS. 1A to ID of the accompanying drawings illustrate a conventional manufacturing process of a mask having a phase shift layer.

Referring to FIG. 1A, a mask plate 3 and a photosensitive film 5 are sequentially formed on the glass substrate 1. The mask plate 3 is formed with Cr, emulsion, or ferric oxide.

Referring to FIG. 1B, the pattern of a reticle is exposed to light on the photosensitive film 5 by using UV. Thereafter, the photosensitive film 5 is developed, so that the exposed part of the photosensitive film 5 is removed. Then, the exposed part of the mask plate 3 is etched by using the resultant photosensitive film 5 as an etching mask, and the pattern is 3 formed.

Referring to FIG. 1C, after the mask plate 3 is exposed by removing the photosensitive film 5, the mask plate 3 formed on the glass substrate is inspected and defects are repaired. Next, the photosensitive film 7 is coated on the exposed part of the glass substrate 1 and the surface of the mask plate 3.

Referring to FIG. 1D, UV is radiated through the lower surface of the glass substrate 1 without using any reticle. At this time, since the mask plate 3 is opaque, only the photosensitive film 7 formed on the surface of the glass substrate 1 is exposed. Next, the photosensitive film 7 is developed and then the exposed portion is removed. Thereafter, the mask plate 3 is horizontally overetched by using the photosensitive film 7 as an etching mask. Said photosensitive film 7 is not removed, but is used as a phase shift layer of the mask.

In the mask manufactured by the aforesaid method, the thickness of the photosensitive film used as the phase shift layer is very important, and this thickness of the photosensitive film is controlled by the viscosity of the photosensitive solution and the rotation velocity of the sputtering apparatus when the photosensitive solution is coated by a sputtering method. In the photomask process of the semiconductor element, the thickness of the photosensitive film to shift the phase of the irradiated light by 180' is given by 4 A d, = -------------- 2 ( n, - 1) where, d, is the thickness of photosensitive film, x is the wavelength of the irradiated light, and n, is the refractive index of the photosensitive film. Accordingly, if the thickness of the photosensitive film used as the phase shift layer satisfies the above equation, the phase of the light irradiated on the surface of the photosensitive film is shifted to obtain the zero point of the light intensity, so that the resolution of the pattern is improved.

However, in the conventional method for manufacturing a mask, after inspection and repair, the photomasking and the overetching of the mask plate are carried out again, so that the process is very complicated. In addition, the thickness of the phase shift layer, which varies in dependence upon the viscosity of the photosensitive solution and the rotation velocity during coating the photosensitive solution, can not be easily controlled, and a step exists between the glass substrate and the mask plate, so that the topography of the photosensitive film becomes worse and the thickness of the phase shift layer is not uniform. Also, since the phase shift layer is formed with the photosensitive f ilm, the mask is easily damaged, and when the mask is damaged, the phase shift layer can not be f ormed and used again.

Accordingly, it is an object of the present invention to provide a method for manufacturing a mask having phase shift region through a simple process.

It is another object of the present invention to provide a method for manufacturing a mask having a semi-permanent phase shift region.

According to the present invention there is provided a method for manufacturing a mask having a phase shift region according to the present invention comprising the steps of:

coating an opaque, mask plate and a photosensitive film on a surface of a transparent substrate; exposing a predetermined part of the mask plate by exposing and developing a predetermined part of the photosensitive film; exposing a predetermined part of the substrate by etching an exposed part of the mask plate; forming a pattern region by etching the substrate to a predetermined thickness; forming a phase shift region by horizontally etching the side of the mask plate; and removing the photosensitive film.

Embodiments of the present invention will now be described, by way of example with reference to the accompanying drawings, in which:

FIGS. 1A to 1D illustrate a conventional manufacturing method of a mask; 6 FIGS. 2A to 2D illustrate a manufacturing method of a mask according to an embodiment of the present invention; FIG. 3 and FIG. 4 illustrate states of the light after passing through the mask when irradiated with light; and FIG. 5 illustrates an example of an application for the mask manufactured according to an embodiment of the present invention, namely in a manufacturing process of a semiconductor device.

FIGS. 2A to 2D illustrate a preferred embodiment of the method for manufacturing a mask according to the present invention.

Referring to FIG. 2A, a mask plate 13 and a photosensitive film 15 are sequentially formed on the surface of substrate consisting of usual glass. The mask plate 13 is formed with Cr, ferric oxide, or emulsion, having a thickness of about 1000A.

Referring to FIG. 2B, the photosensitive film 15 is exposed by, for example, UV, etc. to form a pattern of reticle. Next, the exposed part of the photosensitive film 15 is developed and then the predetermined part of the mask plate 13 is exposed. By using the unremoved part of the photosensitive film 15 as an etching mask, the exposed part of the mask plate 13 is then etched. When the mask plate 13 is formed with Cr, hydrochloric acid or acetic acid is used as an etching solution. Also, since the thickness of the mask plate 13 is as thin as about 1000A, 7 the horizontal etching of the side can be ignored.

Referring to FIG. 2C, using the photosensitive film 15 as an etching mask, the exposed part of the substrate 11 is etched to a predetermined depth by, for example, a glass etchant, etc. The thickness difference d between the etched part and the non-etched part of the substrate 11 should satisfy the equation given by 2 ( n - 1) ( n: a refractive index).

Referring to FIG. 2D, using the photosensitive film 15 as an etching mask, the side of the mask plate 13 is horizontally etched by hydrochloric acid or acetic acid. The exposed part of the substrate 11 becomes a phase shift region 19, and at this time the width W of the phase shift region 19 is preferably in the range of 0.2 to 0.3 gm. Also, the etched part of the substrate 11 becomes a pattern region 17. Next, the photosensitive film 15 is removed and then the mask is completed.

FIG. 3 and FIG. 4 illustrate respectively the phase state and intensity of the light passing through the patter= region 17 and the phase shift region 19 when the mask is irradiated with light such as, for example, UV. In FIG.3, the parabola (a) shows the phase of light passing through a pattern region 17 and the parabola (b) shows the phase of light passing through a phase shift region 19. The phase of the light passing through the phase shift region 19 is shifted by 180' to the light 8 passing through the pattern region 17. Also, in FIG. 4, the parabola (a') shows intensities of 1 ight passing through a pattern region 17, and the parabola (bl) shows intensities of light passing through a phase shift region 19. In the figure, the parabolas (a') and (bl) join each other at the zero point of the light intensity. That is, there is a zero point of the light intensity between the pattern region 17 and the phase shift region 19.

FIG. 5 shows an example of the application of the mask manufactured by the method of the present invention to the manufacturing process of a semiconductor device wherein reference numeral 21 designates a semiconductor substrate, the reference numeral 23 indicates a photosensitive film.

the and The reference numeral 25 designates a part which is exposed and developed by the light passed through the phase shift region 19. In addition, the reference numeral 27 indicates a corresponding point to the zero point of the light intensity between the pattern region 17 and phase shift region 19 during exposure process and its sharpness indicates that the resolution of pattern of the photosensitive film 23 is excellent.

As described above, since the pattern region and the phase shift region are formed by using the same photosensitive film as an etching mask, the thickness difference between the pattern region and the phase shift region can be easily controlled.

9 Thus, in the present invention, the thickness difference between the phase shift region and the pattern region can be exactly controlled by the etching, and the phase shift region is formed as a part of the substrate, so that a long lifetime mask can be easily manufactured.

Claims

CLAIMS:

1. A method for manufacturing a mask having a phase shift region comprising the steps of: coating an opaque mask plate and a photosensitive film; on a surface of a transparent substrate; exposing a predetermined part of said mask plate by exposing and developing a predetermined part of the photosensitive film; exposing a predetermined part of the substrate by etching an exposed part of the mask plate; forming a pattern region by etching said substrate to a predetermined thickness; forming a phase shift region by horizontally etching the side of said mask plate; and removing said photosensitive film.

2. A method as claimed in claim 1, wherein in said process of forming a pattern region, the etch is carried out to shift the phases of the light passing through the pattern region and the phase shift region respectively.

3. A method as claimed in any preceding claim wherein the phase of the light passing through the phase shift region is shifted by 1800 with respect to the light passing through the pattern region.

A method as claimed in any preceding claim, wherein 11 said phase shift region is formed with a width of 0.2 to 0.3 pm.

5. A method as claimed in any preceding claim wherein the mask plate is formed with a thickness of about 1000A.

6. A method for manufacturing a mask substantially as herein described with reference to Figure 2A to 2D and Figure 5 of the accompanying drawings.

claim.

A mask manufactured by the method of any preceding Published 1991 at The Patent Office, Concept House, Cardiff Road. Newport. Gwent NP9 1RH. Further copies may be obtained from Sales Branch. Unit 6. Nine Mile Point. Cwmfelinfach, Cross Keys. Newport, NPI. 7RZ. Printed by Multiplex techniques lid, St Mary Cray. Kent.