JP3264548B2 - Exposure mask and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure mask substrate used for a photolithography technique in a semiconductor manufacturing process, and more particularly to an exposure mask having a phase shift region provided in a part of a transparent region and a method of manufacturing the same.

[0002]

2. Description of the Related Art In recent years, in semiconductor integration technology, the integration of elements and wirings constituting a circuit has been advanced. Along with that, the necessity of pattern miniaturization has become increasingly higher,
There is a demand for miniaturization and high precision of integrated circuit patterns that can be transferred onto a wafer.

Recently, as one of the methods, a phase shifter for shifting the phase of exposure light is provided in a part of an opening region of an exposure mask substrate, so that an optically illuminated portion and a non-illuminated portion on a wafer are optically exposed. A phase shift mask that improves contrast has been proposed.

As a method of manufacturing a phase shift mask, for example, a light-shielding film pattern made of a metal or a metal oxide is formed on a transparent substrate, a resist film is applied, and then a second method for forming a phase change region is performed. Is transferred by, for example, an electron beam drawing apparatus, and then the transparent substrate body is dry-etched to form a phase shifter.

In this dry etching step, for example, R
CF ₄ + H by IE (Reactive Ion Etching)
13.56 MHz from the lower electrode using _two gases
Directional etching by applying a high frequency voltage (RF bias). It is a well-known fact that the etching shape changes depending on the temperature of the object to be etched.
As in the RIE apparatus having the configuration shown in FIG. 5, a mechanism for maintaining the transparent substrate at a constant temperature during etching is provided. That is, while the stage is cooled by the refrigerant,
₂ or He gas flows between the transparent substrate 64 and the stage 62, and the pressure between them is maintained at several to several tens Torr. Since the inside of the reaction chamber is at 10 ⁻⁴ to 10 ⁻² Torr, a force for pushing up the mask substrate from below acts on the mask substrate, but the mask substrate 64 is pressed and fixed by the clamp 63.

As described above, since the temperature adjusting gases 66 and 67 flow from the back surface of the transparent substrate, a load of 50 kgf is applied to the contact portion of the clamp end with the transparent substrate. In order to suppress the deflection of the clamp 63 and secure the positional accuracy of the substrate during etching, the clamp 63 needs to be made of a material having sufficient rigidity and strength such as a metal such as aluminum.

However, when the clamp material is made of metal, the RF bias 69 applied from the stage is directly applied to the light shielding film 25 shown in FIG. 6 not through the transparent substrate but through the clamp. Applied. This allows
The potential of the insulating substrate surface of the portion 23 adjacent to the light-shielding film 25 of the substrate outer peripheral portion 22 becomes larger than that of the substrate surface of the distant portion 24, so that ions contributing to etching are easily attracted. Energy increases. Therefore, a difference occurs in the etching rate between the opening pattern adjacent to the light-shielding film on the outer periphery of the substrate and the opening pattern located at the center of the substrate and not adjacent to the light-shielding film on the outer periphery, and it is possible to appropriately control both phase shift amounts. It becomes difficult. For example, the substrate body is etched and the depth d = λ / 2
(N-1), (where λ: wavelength of exposure light, n: refractive index of the shifter (substrate body)), when forming a concave shifter, as shown in FIG. A difference occurs in the etching rate between the portion 23 adjacent to the light shielding film pattern and the portion 24 not adjacent to the light shielding film pattern. This is shown in FIG.
As shown in FIG. 7, the depth is different between a fine pattern located at a position close to the outer light-shielding film pattern and a fine pattern located at a position distant from the light-shielding film pattern. Therefore, if one of them is adjusted to the optimum value of the depth d = λ / 2 (n−1), the other does not become the optimum value, and the performance of the shifter cannot be sufficiently brought out. In other words, looking at the exposure state of the pattern when this substrate is exposed, the focus margins in the two parts are different, and in the case of a pattern of fine dimensions near the resolution limit, the resolution is achieved in the part adjusted to the optimum value. However, there is a problem that the other does not resolve.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problem, and has as its object the difference in etching rate between an opening pattern adjacent to a light-shielding film on the outer periphery of a substrate and an opening pattern located at a distance therefrom. It is an object of the present invention to provide a mask and a method for manufacturing the mask, which do not cause the exposure and have the same exposure performance.

[0009]

An exposure mask according to the present invention comprises:
An opening groove is provided around the exposure area to be transferred onto the wafer, and the RF bias applied via the clamp is cut off so as not to affect the exposure area. For the purpose of blocking the influence of the RF bias applied directly to the substrate surface via the clamp and making the width of the opening groove the same or less than the effect of the RF bias applied via the substrate body from the back surface of the substrate, It is desirable to have a width greater than the thickness of the substrate.

By providing the opening groove, the etching rate can be made the same in the part adjacent to the outer peripheral light-shielding part and in the part distant from it, and the phase shift amounts of the shifter patterns located in both parts can be made equal.

The step of forming an opening groove on the exposure substrate does not need to be specially added. If the pattern data of the opening groove is input to the pattern data for forming the light shielding film pattern, the step of forming the opening groove at the same time as forming the light shielding film pattern is performed. It is possible.

[0012]

According to the present invention, an opening groove having a width greater than the thickness of the transparent substrate is provided so as to surround the exposure area transferred onto the wafer. Since the transparent substrate body is made of an insulating material such as quartz, the RF bias applied to the outer peripheral light-shielding film via the clamp is insulated by the opening groove, and the R bias applied via the substrate body is
It is possible to attenuate the influence of the F bias or less to make the etching amount uniform.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to the illustrated embodiments. FIG. 1A shows a top view of an exposure mask substrate according to an embodiment of the present invention. That is, an opening groove 13 is provided around the exposure area 11 (within the dotted line) to be transferred onto the wafer, so that the RF bias applied via the clamp does not affect the exposure area. For the purpose of blocking the influence of the RF bias applied directly to the substrate surface via the clamp and making the width of the opening groove the same or less than the effect of the RF bias applied via the substrate body from the back surface of the substrate, It is desirable to have a width greater than the thickness of the substrate.

By providing the opening groove 13, FIG.
As shown in (b), the etching rate in the part adjacent to the outer peripheral light-shielding part and the part apart therefrom can be made the same, and the phase shift amounts of the shifter patterns located in both parts can be made equal.

The step of forming the opening groove 13 on the exposure substrate does not need to be specially added. If the pattern data of the opening groove is input to the pattern data for forming the light shielding film pattern, the step of forming the light shielding film pattern can be performed simultaneously. It can be formed.

Next, an example of a manufacturing process of an i-line exposure mask according to the present invention will be described with reference to FIG. 2, and the effect of the exposure mask of the present invention will also be described. Another example of the manufacturing process will be described with reference to FIG.

FIGS. 2A to 2E are cross-sectional views of main parts of the mask in each manufacturing process. First, a substrate main body serving as a main part of an exposure substrate for forming a phase change region was formed (FIG. 2A). That is, on a transparent substrate made of synthetic quartz glass 41 having a thickness of 2.3 nm, for example, C
A resist film is applied on the substrate covered with the light-shielding film 42 on which rOx is laminated, and the first drawing is performed by an electron beam drawing apparatus. Here, the pattern data of the first drawing includes the data in the exposure area, the data of the alignment mark for the second drawing for forming the phase shifter region to be performed in a later step, and the opening groove formed to surround the exposure area. At least is included. The width of the opening groove surrounding the exposure area is at least 2. to cut off the RF bias applied to the outer periphery.
It is desirable that it is 3 mm or more. Next, the light-shielding film is etched using the resist pattern 43 as a mask to form a light-shielding pattern, and then the resist is removed.

Next, after a resist 46 is applied again on the substrate, a second drawing and development are performed by an electron beam drawing apparatus to expose the phase shift region. The substrate body in that region is dug by RIE (reactive ion etching) with CF ₄ + H ₂ gas to form a concave shifter. In this step, the phase shift amount is set to 18 in consideration of the refractive index of the substrate body at the i-line exposure wavelength.
It is desirable to adjust so as to be near 0 °. For example, when the refractive index is 1.48, the etching amount is about 3900 angstroms.

Finally, the resist film is removed. Next, FIG.
As another embodiment of the present invention shown in (a) to (e), a manufacturing process of an exposure substrate will be described.

That is, a film 52 made of silicon or silicon nitride is formed on a transparent substrate made of synthetic quartz glass 51 by, for example, a CVD method. When etching the shifter film in a later step, the film 52 serves as an etching stopper by etching under a condition having a selectivity with respect to the shifter film. Next, for example, the Si
The O ₂ film 53 is provided with a predetermined thickness d = λ / 2 (n−
1) Forming by controlling in the vicinity. Next, Cr on the Cr layer
A light-shielding film 54 formed by laminating Ox is coated on the substrate, a resist film is further applied, and first drawing is performed by an electron beam drawing apparatus. Here, similarly to the first embodiment, the pattern data of the first drawing includes the data in the exposure area, the data of the alignment mark for the second drawing for forming the phase shifter region to be performed in a later process, and the exposure area. At least includes data of an opening groove to be formed. Next, the light-shielding film is wet-etched using a solution containing a ceric ammonium nitrate solution using the resist pattern as a mask to form a light-shielding pattern in a state where the film 52 is not removed, and then the resist is removed. Next, after a resist is applied again, a second drawing is performed and developed to expose the phase shift region, and then the SiO ₂ film is directionally etched by an RIE apparatus to form a shifter pattern.

Here, if an opening groove is not provided, a difference occurs in the etching amount. Even if the shift pattern is located away from the outer peripheral light-shielding film and stopped at the etching stopper film 52, the etching speed is high in the adjacent pattern, so that the stopper film is high. 52 is slightly etched. As a result, the adjacent shifter patterns have a higher transmittance and a larger phase shift amount, causing problems such as a difference in the pattern size after transfer corresponding to both positions. Therefore, this problem is avoided by providing an opening groove also in this manufacturing process.
Finally, an exposure mask is manufactured by removing the resist.

[0022]

The effect of the present invention will be described. In the present invention, an opening groove for blocking an RF bias is provided so as to surround an exposure area. As a result, although a transient region of the etching amount exists in the opening groove, it does not affect the inside of the exposure area.

There is no difference in the etching amount between the shifter pattern adjacent to the outer peripheral light-shielding portion in the exposure area and the shifter pattern located apart from the shifter pattern, and it is possible to control the etching amount near both the optimum values in both cases.

In the case of a pattern arrangement as shown in FIG.
In the opening pattern existing in the large light-shielding portion 70 such as the portion A, there is no difference in the etching amount because the potential on the surrounding light-shielding film is uniform. However, when the pattern existing in the large opening such as the part A and the part B coexists,
Since a large potential is applied to the surrounding light-shielding film in the pattern in the portion A, the etching amount is larger than that of the pattern in the portion B that is farther from the outer peripheral light-shielding film. In this case as well, the opening groove 71 indicated by a dotted line surrounds the portions A and B.
Is provided, the etching amount can be made equal.

[Brief description of the drawings]

FIG. 1 is a top view of an exposure mask substrate according to the present invention.

FIG. 2 is a process cross-sectional view showing a process of manufacturing an exposure mask according to the present invention.

FIG. 3 is a process sectional view of a manufacturing process of an exposure mask shown as another embodiment of the present invention.

FIG. 4 is a plan view of an exposure mask according to another embodiment of the present invention.

FIG. 5 is a cross-sectional view illustrating a configuration example of a dry etching apparatus used in a manufacturing process of an exposure substrate.

FIG. 6 is a view for explaining a conventional exposure mask.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 11 ... Exposure area 45 ... Opening groove 12 ... Peripheral light shielding film 46 ... Resist film 13 ... Opening groove 47 ... Phase shifter 14 ... Light shielding film 51 ... Transparent substrate 15 ... Transparent substrate 52 ... Etching stopper film 21 ... Exposure area 53 ... Shifter film Reference numeral 22: outer peripheral light-shielding area 54 ... light-shielding film 23 ... adjacent area 55 ... resist film 24 ... non-adjacent area 56 ... resist film 25 ... light-shielding film 61 ... upper electrode 26 ... transparent substrate 62 ... lower electrode (stage) 31 ... outer peripheral light-shielding part 63 ... Clamp 32 ... Opening 64 ... Exposure mask 41 ... Transparent substrate 65 ... Reaction chamber outer wall 42 ... Light shielding film 66 ... Stage cooling refrigerant inlet 43 ... Resist film 67 ... Substrate temperature adjusting gas inlet 44 ... Exposure area 68 ... Reaction gas inlet

Claims (2)

(57) [Claims] An outer peripheral light-shielding film is formed on a transparent insulating substrate,
An exposure mask comprising a light-shielding film pattern made of a metal or metal oxide or a dielectric film in an exposure area transferred onto a wafer and a shift pattern for shifting a phase with respect to light transmitted through the transparent insulating substrate , Said
The outer peripheral light shielding film is disposed so as to surround the exposure area.
Said transparent shield to block the effect of RF bias applied to
An exposure mask , wherein an opening groove having a width equal to or greater than the thickness of the edge substrate is provided . 2. A method according to claim 1, wherein the first light-shielding film is coated on a transparent insulating substrate.
After the resist film is formed and patterned, the light-shielding film is removed by etching using the resist film as a mask, and the thickness of the light-shielding film pattern in the exposure area and the thickness of the transparent insulating substrate arranged so as to surround it are not less than the thickness. A step of forming an opening groove having a width, a step of removing the resist pattern, and a step of forming and patterning a second resist film to expose a phase shifter forming portion on the substrate; A method for manufacturing an exposure mask, comprising a step of forming a shifter by dry-etching a shifter film or a transparent substrate body at the shifter portion.