KR19980068792A - Method of forming chrome blind halftone phase shift mask - Google Patents

Abstract

A method of forming a chrome blind halftone phase shift mask (HT PSM) is disclosed. This method is characterized by covering the edge portion of the light shielding layer pattern by flowing a photoresist pattern formed on the light shielding layer pattern before the etching process for removing the light shielding layer pattern in the region where the phase shift layer pattern is formed. Accordingly, the edge portion of the region where the phase shift layer pattern is formed is cleanly formed, thereby reducing the occurrence of defects in the PSM.

Description

Method of forming chrome blind halftone phase shift mask

The present invention relates to a method of manufacturing a phase shift mask, and more particularly, to a method of forming a chrome blind halftone phase shift mask (HT PSM).

As the size of the semiconductor device is reduced, the required pattern size is also reduced, leading to a stage in which a sufficient resolution cannot be obtained with a conventional chromium (Cr) mask. In order to obtain higher resolution, there is a method of exposing to shorter wavelengths of light or using an exposure apparatus having a larger numerical aperture (NA), but these are very difficult and require a lot of time and high cost. Therefore, a phase shifting mask (Phse Shifting Mask), which can increase the resolution while maintaining the current exposure equipment, has attracted attention, and a double halftone phase shifting mask (hereinafter referred to as HT PSM) has been manufactured. There has been much research due to the ease of design and design.

One of the disadvantages of the HT PSM is that light is slightly transmitted even in a portion without a pattern, so that photoresist loss may occur due to the chromium. A chrome blind structure has been proposed that prevents this. In order to manufacture the chrome blind HT PSM, there is a process of stripping the chromium from the patterned part.In this case, if chromium is left, the HT PSM cannot be obtained and the effect is the same as that of the chrome mask. There is a significant over process. At this time, since the interface of chromium is over etched, it becomes a cause of defects in the inspection and becomes difficult to inspect.

1 to 3 are process flowcharts for explaining a method of forming a conventional chrome blind HT PSM.

Referring to FIG. 1, first, a light shielding layer made of a phase inversion layer and chromium is sequentially formed on a quartz substrate 10, and a first photoresist pattern is formed on the light shielding layer in order to apply a conventional photolithography process. And a pattern of the light shielding layer and the phase shifting layer by applying the first photoresist pattern to form the phase shift layer pattern 12 and the light shielding layer pattern 14 to form the first photoresist. The resist pattern is stripped to form the pattern 16. Subsequently, after applying the photoresist for the second exposure, the pattern region 30 is exposed and developed to form the photoresist pattern 20.

Referring to FIG. 2, a wet etching process is performed on the light shielding layer pattern formed in the pattern region 30, that is, chromium. In this case, if chromium remains in the pattern region 30, the etch process acts as a defect so that a considerable overprocess is performed. . The result is over etched chrome resulting in an under cut (40).

Referring to FIG. 3, the chrome blind HT PSM is completed by stripping the second photoresist pattern after the process of FIG. 2.

According to the conventional method of forming the HT PSM as described above, if the light shielding layer pattern, ie, chromium remains in the pattern region, acts as a defect in the mask, the chromium is over-etched as a result. Resulting in undercuts, and when the second photoresist pattern is stripped to complete the chrome blind HT PSM, the changed pattern region 30 'is not clearly defined and the edge 31 of the pattern region is rough. Lose. This rough edge 31 has no problem at all in wafer exposure, but causes a defect to be caught as a defect during mask inspection. Since this defect appears over the entire edge 31 of the changed pattern region 30 ', the number of defects is so great that it is difficult to classify the actual defect even if the inspection cannot be performed or the inspection is performed.

The technical problem to be achieved by the present invention is to cover the edge portion of the chromium with a photoresist before etching etching to remove the chromium in the pattern region by forming a clean pattern region of the edge of the chrome blind HT PSM to prevent defects It is to provide a manufacturing method.

1 to 3 are process flowcharts for explaining a method of forming a conventional chrome blind HT PSM.

4 to 7 are process flowcharts for explaining a method for forming a chrome blind HT PSM according to the present invention.

Explanation of symbols for the main parts of the drawings

10 ... Quartz substrate 12 ... Phase inversion layer pattern

14 ... light shield layer pattern 20 ... second photoresist pattern

30,30 ', 33 ... pattern area 40 ... undercut

50 ... chrome defect

In order to achieve the above object, the method of the present invention, in the method of forming the chrome blind HT PSM, before the etching process for removing the light shielding layer pattern of the region where the phase shift layer pattern is formed, Flowing to cover the edge portion of the light shielding layer pattern.

Hereinafter, with reference to the accompanying drawings will be described the present invention.

4 to 7 are process flowcharts for explaining a method for forming a chrome blind HT PSM according to the present invention.

Referring to FIG. 4, first, a light shielding layer made of a phase inversion layer and chromium is sequentially formed on a quartz substrate 10, and a first photoresist pattern is formed on the light shielding layer in order to apply a conventional photolithography process. And a pattern of the light shielding layer and the phase shifting layer by applying the first photoresist pattern to form the phase shift layer pattern 12 and the light shielding layer pattern 14 to form the first photoresist. The resist pattern is stripped to form the pattern 16. Subsequently, after applying the photoresist for the second exposure, the pattern region 30 is exposed and developed to form the photoresist pattern 20.

5 and 6, a wet etching process is performed on the light shielding layer pattern formed in the pattern region 30, that is, chromium, in which the present invention performs negligible over-etching so that there is no undercut ( 40 ') state. At this time, since no over-etching is performed, defects 50 in which chromium remains inside the pattern region 30 may occur due to non-uniformity of particles or chromium thickness. Before performing chromium over-etching to remove this chromium defect 50, the mask is heated to flow the first photoresist pattern 20 to cover the edges of the pattern region 30 with PR.

Referring to FIG. 7, after removing the chromium defect by repeating chrome over-etching and physical cleaning after the process of FIG. 6, stripping the PR opens the pattern region 33 having the clean edge 32 ′. can do.

Since the chrome blind HT PSM according to the present invention manufactured as described above does not generate defects due to rough edges during the inspection, it is possible to shorten the manufacturing time and improve the yield of the chrome blind HT PSM.

Claims (1)

In the method of forming a chrome blind halftone phase shift mask, A chrome blind halftone phase characterized by covering an edge portion of the light shielding layer pattern by flowing a photoresist pattern formed on the light shielding layer pattern before the etching process for removing the light shielding layer pattern in the region where the phase shift layer pattern is formed. Formation method of the inversion mask.