JP2003121988A - Method for modifying defective part of halftone phase shifting mask - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for modifying the surplus defective part of a halftone phase shifting mask by which the harmful effect of a glass part which remains under the surplus defective part without being etched can be eliminated by a relatively simple process. SOLUTION: The surplus defective part 6 of a translucent film in a halftone phase shifting mask is removed by modification, and only a part 7 of a transparent substrate situated under the modified part is etched simultaneously with the removal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a defect correcting method for a phase shift mask, which can improve the resolution of a transfer pattern by giving a phase difference between exposure lights passing through the mask. The present invention relates to a method of correcting defects of the phase shift mask blank, etc.

[0002]

2. Description of the Related Art A phase shift mask is known as one of photomasks which is a transfer mask used when a fine pattern such as a semiconductor LSI is transferred by a projection exposure apparatus. This phase shift mask is capable of improving the resolution of the transfer pattern by giving a phase difference between the exposure lights passing through the mask. As one of the phase shift masks, a mask particularly suitable for transferring an isolated hole or space pattern is disclosed in JP-A-4-1368.
The phase shift mask described in Japanese Patent No. 54 is known.
This phase shift mask forms a semi-transmissive film on a transparent substrate that transmits light having an intensity that does not substantially contribute to exposure and at the same time shifts the phase of light passing therethrough. By selectively removing (patterning),
A mask pattern composed of a light-transmitting portion that transmits light having an intensity that substantially contributes to exposure and a semi-light-transmitting portion that transmits light that does not substantially contribute to exposure is formed. The phase shift mask shifts the phase of light passing through the semi-transparent portion so that the phase of light passing through the semi-transparent portion is substantially inverted with respect to the phase of light passing through the transparent portion. By having such a relationship, the light passing through the vicinity of the boundary between the light-transmitting portion and the semi-light-transmitting portion and circulated by diffraction can cancel each other out so that the contrast of the boundary portion can be maintained well. And is commonly referred to as a halftone type phase shift mask. In this halftone type phase shift mask, when the wavelength of the exposure light is λ and the refractive index of the semitransparent film with respect to the exposure light is n, the value of the film thickness t of the semitransparent film is generally t = λ / It is usually set to a value that satisfies {2 (n-1)}, and is set so that the transmittance of the semitransparent film at the wavelength of the exposure light is about 1 to 50%. As described above, the halftone type phase shift mask has a semitransparent portion that has both a phase shift function and a light shielding function. That is, this semi-translucent portion functions as a phase shift layer at the boundary of the pattern and as a light shielding layer at other portions.
Therefore, a small amount of leaked light also occurs in a portion where it is ideal to completely block the exposure light. Normally,
The total exposure amount is adjusted so that even if the leaked light is present, the exposure is not substantially achieved.

In order to maximize the characteristics of the phase shift mask, it is ideal that the phase shift amount be 180 °, but in practical use it is desirable that it falls within the range of about 180 ° ± 3 °. Therefore, for example, a semi-transmissive film (halftone film) having a phase difference φ of 90 ° <φ <180 ° is formed in advance, the semi-transmissive film is etched and patterned, and then a semi-transmissive film pattern is formed. The exposed part (translucent part) of the transparent glass substrate which is not exposed is etched by a predetermined amount by wet etching with hydrofluoric acid or the like or dry etching with CF ₄ etc. Japanese Patent Application Laid-Open No. 7-152142 discloses a method in which the total phase difference is 180 °. Further, Japanese Patent Application Laid-Open No. 10-104815 discloses a method of adjusting the phase difference by etching the glass part with a hydrofluoric acid vapor or a vapor of a hydrofluoric acid solution. In these described methods, in the case of a halftone type phase shift mask having a semi-transparent film containing chromium as a main component, the semi-transparent film is formed by using hydrofluoric acid, a hydrofluoric acid buffer solution, a hydrofluoric acid vapor or a vapor of a hydrofluoric acid solution. This is a very simple and effective method because only the exposed portion (glass portion) of the transparent glass substrate on which the light film pattern is not formed is etched and the semi-transparent film containing chromium as a main component is not etched.

[0004]

By the way, in the method described in JP-A-7-152142, for example, in the case of a molybdenum silicide-based semi-transparent film containing molyfden, silicon, oxygen and nitrogen as main constituents, It is general to etch the semi-transparent film and then to dig the glass portion by etching to adjust the phase difference. This method has a great process merit because the semi-transparent film and the glass portion can be continuously etched. Then, a transmission type defect inspection is performed after the mask is completed, and if there is an extra defect in the semi-transparent film, the extra defect is removed by a repair device using a laser or FIB. When the glass portion to be etched is first etched for adjusting the phase difference, a surplus defect exists on the upper portion and remains without being etched.
Conventionally, this glass part may not have much digging amount of glass for adjusting the phase difference,
Since it had almost no effect in the transmission inspection and it was not a problem, and the laser repair device used to repair the semi-transparent film cannot remove the glass substrate, it is generally used as it is. It was However, there is a problem that the edge of the glass step may be detected and recognized as a defect depending on the sensitivity of the inspection device. In addition, for example, it is difficult to secure a phase shift amount of a halftone type phase shift mask having a high transmittance (for example, 9% or more) which has been required in recent years with a semitransparent film. If the amount of digging must be increased, the glass portion left unetched at the bottom of this surplus defect causes the phase difference of only the surplus defect repaired portion to deviate from other normal portions, resulting in the mask being removed. When the pattern is exposed and transferred onto the wafer by using it, the more the amount of the glass portion etched and the phase difference is adjusted, the more the unnecessary pattern is transferred onto the wafer in the worst case.

In the methods described in the above publications,
For example, in the case of a chrome-based semi-transparent film, after the semi-transparent film is etched and patterned, defect inspection is performed, and if there is an extra defect in the semi-transparent film, the surplus is removed by a correction device using a laser or FIB. It is possible to remove the defects and then etch the glass portion with a hydrofluoric acid solution or the like to adjust the phase difference. In this case, since the chromium-based semi-translucent film is not etched, no problem occurs. However, when this method is applied to a semi-transmissive film that is etched or damaged by the etching liquid or etching gas used when adjusting the phase difference by etching the glass part, the semi-transmissive film is Since it is etched or damaged, desired semi-transmissive film pattern accuracy and optical characteristics such as transmittance and phase shift amount cannot be obtained.

[0006]

In order to solve the above problems, the present invention has the following constitution.

(Structure 1) Half-tone type which has at least a semi-transparent film pattern on a transparent substrate, and is formed by etching a predetermined depth on an exposed portion of the transparent substrate on which the semi-transparent film pattern is not formed. A method of correcting defects in a phase shift mask, comprising: after removing at least the excess defects of the semi-transparent film, etching the transparent substrate located under the excess defect removal portion to a predetermined depth. Method for defect correction of die phase shift mask.

(Structure 2) In Structure 1, the halftone phase is characterized in that the excess defects of the semitransparent film are removed, and at the same time, the transparent substrate portion located below the excess defect removed portion is also etched. Shift mask defect correction method.

(Structure 3) In Structure 2, the excess defect of the semi-transparent film is removed by the repair device using the FIB, and at the same time, the portion of the transparent substrate located below the excess defect removed portion by the repair device using the FIB. A method of repairing defects in a halftone phase shift mask, characterized by continuously etching.

(Structure 4) Any one of the structures 1 to 3 characterized in that the portion of the transparent substrate located below the surplus defect removed portion is etched to a depth that does not affect pattern transfer and / or defect inspection. 5. A method of repairing a defect of a halftone type phase shift mask described in.

(Structure 5) The halftone phase according to Structure 4, wherein the portion of the transparent substrate located below the surplus defect removed portion is etched to the same depth as the surrounding transparent substrate portion. Shift mask defect correction method.

(Structure 6) In the halftone type phase shift mask, a step of sequentially forming a semitransparent film and a light-shielding film on a transparent substrate, and further forming a resist pattern on the light-shielding film, and the resist pattern as a mask. And a step of forming the light-shielding film pattern by etching the light-shielding film, and a step of forming the semi-light-transmitting film pattern by etching the semi-light-transmitting film using the light-shielding film pattern as a mask. A step of etching the transparent substrate, then a step of peeling the resist pattern, and then
A resist pattern is formed on the light-shielding film pattern, and the light-shielding film pattern is etched by using the resist pattern as a mask to form a final shape of the light-shielding film pattern. 6. A defect correction method for a halftone phase shift mask according to any one of Configurations 1 to 5 characterized.

[0013]

According to the above structure 1, after the excess defects of the semitransparent film are removed, only the portion of the transparent substrate located below the excess defect removed portion is etched. It is possible to reduce or avoid that the phase difference is shifted from other normal parts due to the remaining glass part. Moreover, this part (edge of glass step) is detected and recognized as a defect by the automatic mask defect inspection machine. It is possible to reduce or avoid such a situation. Incidentally, after removing the excess defects of the semi-transparent film, if the glass portion is entirely etched, the glass portion located under the excess defect removed portion can be removed, but other glass portions are also etched, The phase difference shifts. In the configuration 1, "at least the excess defect of the semi-translucent film is removed" means that when another film such as the light-shielding film is formed, the case of removing the excess defect of the light-shielding film or the like is included. Is. Usually, since a light-shielding film or the like is formed on the semi-translucent film, in this case, after removing the surplus defects of the light-shielding film or the like, the surplus defects of the semi-transmissive film located therebelow are removed. This also applies to the following configurations. In Configuration 1, the excess defect refers to a defect in which a film remains in a portion where the transparent substrate is to be exposed, and a defect that protrudes at an edge portion of a thin film pattern such as a semi-transparent film or a light shielding film, or a defect that connects thin film patterns ( Short circuit) and isolated defects that are not in contact with the thin film pattern are included. This also applies to the following configurations. If there is an isolated defect in the portion where the transparent substrate is to be exposed, and this isolated defect affects the phase shift near the edge of the semi-transparent film, the transparent defect located under the isolated defect is transparent. The part of the substrate needs to be removed. In this case, if the isolated defect is relatively large, it is necessary to remove only the part of the transparent substrate located under the isolated defect that is near the edge of the semitransparent film and affects the phase shift. The effect on the shift can be avoided. Further, when there is an isolated defect in the portion where the transparent substrate is to be exposed, and when this isolated defect does not exist near the edge of the semi-transparent film and does not affect the phase shift, only this isolated defect is removed, Even if the portion of the transparent substrate located under the isolated defect is not removed, it does not affect the pattern transfer accuracy. However, this portion (edge of glass step) is detected by the automatic mask defect inspection machine to detect the defect. In order to avoid the situation of recognizing, it is preferable to remove the portion of the transparent substrate located under the isolated defect.

According to the above configuration 2, the excess defects of the semi-transparent film are removed, and at the same time, the transparent substrate portion located below the excess defect removed portion is also continuously etched, which requires reduction and correction of steps. The time can be shortened.

According to the above configuration 3, FIB (focused io)
(n beam) is used to remove excess defects in the semi-transparent film, and at the same time, the repair device that uses FIB is also used to continuously etch the transparent substrate portion located below the excess defect removal portion. In addition to the effect of the configuration 2, both the excess defect portion of the semitransparent film and the transparent substrate portion located below the excess defect removed portion can be corrected with high accuracy. In addition, the defect can be accurately corrected by a relatively simple method. When a laser is used, the excess defect portion of the semi-transparent film can be repaired, but the transparent substrate portion located under the excess defect cannot be removed. In the above configuration 1, after removing the excess defects of the semi-transmissive film, the portion except the portion of the transparent substrate located under the excess defect removed portion is protected by a resist or the like, and then this portion is wet or A method of removing by dry etching is also included, but the process becomes more complicated than that of the above-described Configuration 3.

According to the above configuration 4, the portion of the transparent substrate located below the surplus defect removed portion is subjected to pattern transfer and / or pattern transfer.
Alternatively, by performing etching to a depth that does not affect the defect inspection, it is possible to transfer the pattern to the wafer with higher accuracy, and / or detect this portion (edge of glass step) in a mask automatic defect inspection machine to detect a defect. It is possible to reduce the situation of recognizing.

According to the above-mentioned structure 5, the portion of the transparent substrate located below the excess defect removed portion is etched to a depth equivalent to that of the peripheral transparent substrate etching portion, whereby the excess defect is etched to the lower portion. The remaining glass portion does not cause the phase difference to shift from other normal portions, and therefore, optical characteristics that do not change from normal portions at all even after correcting excess defects are obtained.
Moreover, it is possible to avoid erroneous defect detection by the automatic defect inspection apparatus. As a result, it is possible to transfer the pattern to the wafer with higher accuracy than that of the above-described configuration 4, and it is possible to reliably avoid the situation in which this portion is detected and recognized as a defect by the automatic mask defect inspection machine.

According to the above configuration 6, even if the semi-transmissive film is easily etched by the etching liquid or etching gas used when the transparent substrate is etched to adjust the phase difference, the resist and the light shield are provided. Since the transparent substrate is etched using the film pattern as a mask, the semitransparent film is not etched. Further, since the light-shielding film pattern having the final shape is formed by etching the light-shielding film pattern using the resist pattern as a mask, a halftone phase shift mask having the light-shielding film pattern can be manufactured without wasting steps.

[0019]

EXAMPLE 1 FIG. 1 is an explanatory diagram of a manufacturing process of a halftone type phase shift mask according to an example of the present invention. Hereinafter, this embodiment will be described with reference to the drawings. The transparent substrate 1 is a quartz glass substrate (size 6 inch square, thickness 0.25 inch) whose surface is mirror-polished and subjected to predetermined cleaning. First, a semi-transparent film 2 made of molyfden, silicon, and nitrogen is formed on the transparent substrate 1 with a film thickness of 90 nm by the spackling method, and then a light shielding film 3 made of chromium is formed with a film thickness of 100 nm.
Formed by. Next, a positive electron beam resist (ZEP7
000: manufactured by Zeon Corporation) 4 was applied by a spin coating method to a film thickness of 500 nm (FIG. 1 (a)). Next, a resist pattern 4 is formed by drawing a desired pattern with an electron beam and developing it.
a was formed ((b) of the same figure). Next, using the resist pattern 4a as a mask, the light-shielding film 3 is dry-etched with a mixed gas of chlorine and oxygen to form the first light-shielding film pattern 3.
a was formed ((c) in the figure). Next, after removing the resist pattern 4a and performing a predetermined cleaning ((d) in the same figure),
Using the first light-shielding film pattern 3a as a mask, the semi-translucent film 2 is mixed with CF ₄ / O ₂ mixed gas at a pressure of 0.4 Torr, R
The semi-transmissive film pattern 2a was formed by dry etching under the condition of F power of 100 W (FIG. 7E). At this time, it was previously known that the phase difference of the semi-transparent film alone was 165 °, so that the target value of 180 ° was 15 °.
Since there was not enough degree, the glass substrate was etched by about 20 nm so that the total was 180 degrees (FIG. 8E). After performing a predetermined cleaning, the photoresist (A
Z1350: manufactured by Clariant Co., Ltd.) 5 was applied by a spin coating method to a film thickness of 500 nm and baked (FIG. 6 (f)). Next, a desired pattern was exposed and developed to form a resist pattern 5a (FIG. 9 (g)). next,
Using the resist pattern 5a as a mask, the first light-shielding film pattern 3a was etched using an etching solution composed of cerium ammonium nitrate and perchloric acid to form a second light-shielding film pattern 3b (FIG. 2 (h)). . Finally, the resist pattern 5a was peeled off and predetermined cleaning was performed to obtain a halftone type phase shift mask ((i) in the figure).

When the halftone phase shift mask obtained through the above steps was subjected to a defect inspection by an automatic defect inspection apparatus, an excessive defect 6 in the semitransparent film was detected (FIG. 2).
(A)). Then, the excess defect 6 of the semi-transparent film is removed by etching with the FIB device (FIG. 7B), and the glass portion 7 located below the excess defect removed portion is continuously removed by 2
Etching was performed at a depth of 0 nm (FIG. 7C). After that, when the defect was inspected again by the automatic defect inspection apparatus, it was found that the above-mentioned surplus defect portion was not detected and was satisfactorily corrected.

Although the present invention has been described with reference to the preferred embodiments, the present invention is not limited to the above embodiments. For example,
Although the molybdenum silicide nitride film is taken as an example of the semi-transmissive film in the above-described embodiments, the present invention partially etches glass by FIB or the like to match the phase difference. The material forming the transparent film does not matter. That is, since only the surplus defect portion of the semi-transparent film and only the glass portion located below the surplus defect-removed portion are partially etched by FIB or the like, the material forming the semi-transparent film is glass. Even in the case of a semi-transparent film that is etched or damaged by the etching liquid or etching gas used for adjusting the phase difference by etching the portion, no problem occurs.

[0022]

As described above in detail, according to the surplus defect repairing method in the halftone type phase shift mask of the present invention, after the surplus defects of the semi-transparent film are removed, they are positioned below the surplus defect removed portion. Since only the portion of the transparent substrate to be etched is etched, it is possible to reduce or avoid that the phase difference is shifted from other normal portions due to the glass portion left unetched under the surplus defect. It is possible to reduce or avoid the situation in which the inspection machine detects this portion (edge of glass step) and recognizes it as a defect. In addition, the defect can be accurately corrected by a relatively simple method. As a result of these, the influence of defects disappears in actual wafer transfer, and a high quality halftone type phase shift mask can be obtained with a high yield.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view for explaining a manufacturing process of a halftone type phase shift mask according to an embodiment of the present invention.

FIG. 2 is a partial cross-sectional view for explaining a method of repairing a surplus defect of a halftone type phase shift mask according to an embodiment of the present invention.

[Explanation of symbols]

1 transparent substrate 2 Semi-transparent film 2a Semi-transparent film pattern 3 Light-shielding film 3a Light-shielding film pattern 4 resist 4a Resist pattern 5 resist 5a resist pattern 6 surplus defects 7 Glass part under the surplus defect

Claims (6)

[Claims] 1. A half-tone type phase shift having at least a semi-transmissive film pattern on a transparent substrate, wherein an exposed portion of the transparent substrate on which the semi-transmissive film pattern is not formed is etched to a predetermined depth. A method of repairing a defect of a mask, comprising: after removing at least the surplus defects of the semi-transparent film, etching a transparent substrate located under the surplus defect removal portion to a predetermined depth. Shift mask defect correction method. 2. The halftone phase shift according to claim 1, wherein the excess defects of the semi-transparent film are removed, and at the same time, the portion of the transparent substrate located under the excess defect removed portion is also etched. Mask defect repair method. 3. The repair device according to claim 2, wherein the repair device using the FIB removes the excess defects of the semi-transparent film, and at the same time, the repair device using the FIB also removes the portion of the transparent substrate located below the excess defect removal portion. A method of repairing defects in a halftone type phase shift mask, characterized by continuously etching. 4. The part of the transparent substrate located below the surplus defect removed part is etched to a depth that does not affect pattern transfer and / or defect inspection. A method for repairing a defect in a halftone phase shift mask as described. 5. The halftone phase shift according to claim 4, wherein a portion of the transparent substrate located under the excess defect removed portion is etched to a depth equivalent to that of the peripheral transparent substrate portion. Mask defect repair method. 6. A step of forming a semi-transmissive film and a light-shielding film on a transparent substrate in order for the halftone type phase shift mask, and further forming a resist pattern on the light-shielding film; and using the resist pattern as a mask. A step of etching the light-shielding film to form a light-shielding film pattern, a step of etching the semi-light-transmitting film using the light-shielding film pattern as a mask to form a semi-light-transmitting film pattern, and then a transparent substrate. And then removing the resist pattern, and then forming a resist pattern on the light-shielding film pattern, by etching the light-shielding film pattern using the resist pattern as a mask, the final shape 6. The process according to claim 1, wherein the light-shielding film pattern is formed. A method of repairing a defect in a halftone phase shift mask according to any one of the above.