KR20080040901A - Method for inspecting psm - Google Patents

Abstract

A method for inspecting a phase-shift mask is provided to prevent an unnecessary subsequent process by determining whether a waste mask is disposed just after etching a chrome light shielding layer. A phase-shift layer(130) and a light shielding layer are formed on a mask substrate(110). The light shielding layer is patterned to form a light shielding pattern(150). An inspecting light is irradiated onto the light shielding pattern and an exposed section of the phase-shift layer to detect light transmission. The light transmission of the exposed section of the phase-shift layer is compared with that of the light shielding layer on the basis of the light transmission of the exposed section to detect a defect of the light shielding pattern. The light shielding layer includes a chrome layer. The phase-shift layer includes a MoSi layer. The light transmission of the exposed section of the phase-shift layer is less than 100 % and light reflectance thereof is greater than 0 %.

Description

Phase reversal mask inspection method {Method for inspecting PSM}

1 is a view illustrating a phase inversion mask (PSM) inspection method according to an embodiment of the present invention.

2 is a flowchart illustrating a phase inversion mask (PSM) inspection method according to an embodiment of the present invention.

3 is a view showing a light calibration setting of the inspection apparatus used in the phase inversion mask (PSM) inspection method according to an embodiment of the present invention.

4 and 5 are diagrams for explaining the optical calibration results used in the phase inversion mask (PSM) inspection method according to an embodiment of the present invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to semiconductor device manufacturing, and more particularly, to a method of inspecting a phase shift mask (PSM).

As a design rule of an integrated circuit device or a semiconductor device is rapidly reduced, an ArF light source having a shorter wavelength band is introduced as a light source used in an exposure process for transferring a device pattern onto a wafer. Accordingly, the structure of the attenuated PSM is also newly configured to be suitable for the ArF light source. For example, the thicknesses of the molybdenum-silicon (MoSi) -based phase inversion layer and the chromium (Cr) -based light shielding layer constituting the PSM for ArF light source are the same as those of the PSM structure used in the KrF light source, which is an exposure source of longer wavelength range. It is set differently. In addition, mask patterns constituting the PSM for ArF light source are also formed in a fine pattern having a smaller size.

As the structure and configuration of the ArF light source PSM are different from those of the KrF light source PSM, it is difficult to use an apparatus for inspecting the KrF light source PSM when inspecting the mask pattern of the ArF light source PSM. Substantially, in the case of the PSM for ArF light sources, it is known that the inspection of the PSM for ArF light sources is possible with an expensive inspection apparatus using a deep ultra violet (DUV) light source having a wavelength of approximately 258 nm as an inspection light source.

In the case of the DUV inspection apparatus, the transmittance of the Cr / MoSi layer is 0%, the transmittance of the quartz substrate as the mask substrate is set to substantially 100%, and the phase shift layer pattern as the mask pattern is inspected. In contrast, the height of the Cr / MoSi layer of the ArF PSM is different from that of the KrF PSM, so it is difficult to directly inspect the ArF PSM using a wavelength band longer than that of the DUV. However, since the DUV inspection apparatus is quite expensive and the DUV inspection apparatus must be newly introduced, the development of a method for inspecting the ArF PSM using a longer wavelength band is required.

An object of the present invention is to provide a method for inspecting a phase inversion mask.

One aspect of the present invention for the technical problem, forming a phase inversion layer and a light shielding layer on a mask substrate, forming a light shielding layer pattern by patterning the light shielding layer, the light shielding layer pattern and the exposed phase Irradiating inspection light to the inversion layer portion to detect light transmittances, and comparing the light transmittance of the light shielding layer pattern to the light transmittance of the phase inversion layer portion based on the light transmittance of the phase shift layer portion; A phase inversion mask inspection method comprising detecting a defect in a light blocking layer pattern is provided.

The inspection light may use light having a wavelength longer than the wavelength range of 248 nm.

The inspection light may be light of a wavelength of 365 nm.

The light shielding layer includes a chromium (Cr) layer, and the phase shifting layer includes a molybdenum-silicon alloy (MoSi) layer to detect the phase shifting layer portion by the inspection light. The light transmittance can be detected less than 100% and the light reflectance is greater than 0%.

Applying light calibration settings based on light transmittance and light reflectance for the phase shift layer and detecting the light transmittances for the light shielding layer pattern and the exposed portion of the phase shift layer together with light reflectances, and the The method may further include detecting whether the light blocking layer pattern is defective from the detected light blocking layer pattern and the light calibrated light transmittances and light reflectances of the phase reversal.

Detecting whether the light shielding layer pattern is defective may further include detecting data of the light transmittances and the light reflectances by comparing a data of a reference mask layout to be implemented on the mask substrate by a die to dei method. It may include.

The inspection light may be light of a wavelength range of 248 nm.

Detecting the light transmittances of the light shielding layer pattern and the exposed portion of the phase shifting layer together with light reflectances, and from the data of the detected light shielding layer pattern and the light transmission of the phase shift and the light reflectances The method may include detecting whether the light shielding layer pattern is defective.

In an embodiment of the present invention, a method capable of inspecting a phase inversion mask for an ArF light source using an inspection light source in a wavelength range longer than approximately 238 nm wavelength band, for example, an approximately 365 nm wavelength range, is provided. In an embodiment of the present invention, for example, inspection is performed on, for example, a chromium light shielding layer pattern patterned on the phase inversion layer before patterning the phase inversion layer of the molybdenum-silicon alloy layer.

Since the phase inversion layer of the lower molybdenum-silicon alloy layer is patterned using the chromium light shield layer pattern as an etch mask, the phase inversion layer pattern is formed in a shape depending on the profile of the light shield layer pattern. Will be. Therefore, a defect in the chromium light shielding layer pattern is transferred to the phase inversion layer pattern. In an embodiment of the present invention, by detecting whether a defect is detected in the chromium light shielding layer pattern, the defect to be caused in the phase shift layer pattern is controlled in advance, or the process is not further progressed when detecting a large defect that may greatly affect the pattern. It is possible to determine in advance whether or not to discard the mask itself.

In the embodiment of the present invention, in order to detect whether there is a defect in the light shielding layer pattern, the transmittance of the inspection light and the transmittance of the lower phase inversion layer with respect to the light shielding layer pattern are used as a detection value measured during inspection. In this case, the inspection light transmittance of the light shielding layer pattern may be detected as 0%, but the transmittance of the phase inversion layer may be obtained to some extent other than 0%.

Since the phase inversion layer is not substantially a transparent layer such as a quartz substrate which is a mask substrate, it exhibits a low transmittance of less than 100%. In fact, for the inspection light of a long wavelength range of 365 nm, the MoSi phase inversion layer applied to the ArF PSM mask is measured to exhibit a transmittance of about 54%. Therefore, the Cr shading layer pattern and the MoSi phase inversion layer may be set to show transmittances of 0% and 54%, respectively, which are different from the 0% and 100% transmittances recognized by the inspection apparatus when detecting the inspection light. have.

Substantially, the light calibration set in the inspection apparatus is set such that the detection transmittance is positioned in the range of 0% transmittance and 100% transmittance. In the case of the PSM inspection apparatus for KrF light source, the optical calibration set value is set in the inspection apparatus so that the transmittance of Cr as a measurement target is 0% and the transmittance of the quartz substrate is set to 100%. Accordingly, when using the existing optical calibration settings as it is, it is difficult to directly compare and contrast the detected data by including the data in the pattern layout to be implemented on the actual PSM mask and the reference mask data to be compared. Therefore, in order to be recognized by the inspection apparatus, the optical calibration is reset to compensate for this in consideration of the transmittance difference. That is, the light calibration setting is changed so that the inspection device recognizes that the 54% transmittance is 100% transmittance.

Considering the light reflectance detection, the reflectance of the MoSi phase inversion layer is detected with a reflectance of approximately 46%, so that a wavelength of approximately 365 nm is longer than that of a DUV light source such as an inspection apparatus such as the KLA5 series inspection apparatus. The optical calibration setting value of the inspection execution parameters of the KrF PSM inspection apparatus using the light source is reset so that the reflectance of 46% is recognized as the reflectance of 0%. Accordingly, PSM inspection for ArF light source can be enabled in the KrF PSM inspection apparatus.

Substantially, in an inspection apparatus using a laser inspection light source having a wavelength of approximately 365 nm, the transmittance of Cr in an ArF Half Tone (HT) PSM is 0% and the MoSi transmittance of ArF HT is measured to be about 54%. . The inspection apparatus considers the transmittance of Cr as 0% and the transmittance of quartz as 100%, and applies the optical calibration to the value measured by dividing the optical calibration range by 256 equal parts. Therefore, in the ArF HT PSM, since the transmittance of Cr is 0% and the transmittance of MoSi is 54% and the transmittance difference is about 54%, the value is set by dividing the optical calibration range by approximately 138 to set the calibration range. The detected results can be applied to the light calibration. That is, 54% of the MoSi transmittance may be recognized as 100% transmittance so that light calibration of the inspection result may be performed. Accordingly, the mask pattern can be inspected even in an inspection apparatus using a wavelength longer than the DUV wavelength after Cr etching.

1 is a view illustrating a phase inversion mask (PSM) inspection method according to an embodiment of the present invention. 2 is a flowchart illustrating a phase inversion mask (PSM) inspection method according to an embodiment of the present invention. FIG. 3 is a diagram showing an optical calibration setting of an inspection apparatus used in a phase inversion mask (PSM) inspection method according to an embodiment of the present invention. 4 and 5 are diagrams for explaining the light calibration results used in the phase inversion mask (PSM) inspection method according to an embodiment of the present invention.

1 and 2, the phase reversal mask inspection method according to an embodiment of the present invention performs the inspection using an inspection light source having a wavelength band longer than that of the DUV for the ArF light source reversal mask. Specifically, a halftone phase inversion layer 130, such as a molybdenum-silicon (MoSi) alloy layer, is formed on a substantially transparent mask substrate 110, such as a quartz substrate. A light blocking layer such as a chromium layer is formed on the phase inversion layer 130 (210 of FIG. 2). The light blocking layer is selectively etched along the designed mask layout to form the light blocking layer pattern 150 (220 of FIG. 2).

Before etching the portion of the phase shifting layer 130 exposed to the shielding layer pattern 150, pattern defect inspection is performed on the portion of the shielding layer pattern 150 and the phase shifting layer 130 (240 of FIG. 2). . At this time, the process of resetting the optical calibration setting value of the inspection apparatus is first performed so that the detected data meet the changed criteria (230 of FIG. 2).

In the pattern defect inspection, the mask substrate 110 is mounted to be aligned with an inspection unit (170 of FIG. 1) in an inspection apparatus using an inspection light source having a longer wavelength band than a DUV light source having a wavelength of 248 nm, and the inspection light includes a light shielding layer pattern ( 150 and irradiated to the phase inversion layer 130 exposed to the transmission light of the inspection light to measure the transmittance and reflectance. This inspection device is a die to die method for comparing and inspecting the shape or layout of the light shielding layer pattern 150 on the mask substrate 110 fabricated with respect to the reference mask pattern on the reference mask. It can be performed as.

The inspection object mask in the embodiment of the present invention may be a halftone PSM for an ArF light source, and the inspection device for inspecting the light shielding layer pattern 150 may use an inspection device for a mask for KrF light source. The inspection apparatus for KrF mask can use the inspection light source of the wavelength band of about 365 nm which is longer wavelength compared with DUV inspection orchard. In this case, the light transmittance and the light reflectance of the light shielding layer pattern 150 and the phase inversion layer 130 exposed thereto are preferably compared to the light shielding layer pattern 150 of the chromium layer. Substantially 0% transmittance and 100% light reflectance can be detected.

In contrast, the light shielding layer pattern 150, which is a standard for inspection, may be detected with a transmittance of 54% and a reflectance of 46%. However, since data for the reference mask is based on 0% reflectivity and 100% transmittance with respect to the quartz mask substrate, it is difficult to perform defect inspection with the original data detected by the inspection apparatus. In order to solve this problem, in the embodiment of the present invention, the optical calibration setting is first performed to apply the detected measurement value (230 of FIG. 2). At this time, the light calibration setting value is set to recognize the light transmittance and the light reflectance of the portion of the phase inversion layer 130 as 100% transmittance and 0% reflectance, respectively.

In more detail, during the inspection of the die-to-die method, the input value in the light calibration step is changed and applied using the light transmittance. Accordingly, the pattern inspection after the etching of the chromium layer is possible. After attaching the mask substrate to an inspection apparatus using an inspection light source having a wavelength of 365 nm, which is longer than the DUV wavelength, and seeing an optical calibration step at the time of setting for inspection, as shown in the table of FIG. A value for the transmitted light, a value for the white transmitted light, a value for the black reflected light and a value for the back reflected light are input to the control panel of the inspection apparatus. These values represent the transmittance of the chromium (Cr) light shielding layer, the transmittance of the quartz (Qz) substrate, the reflectance of the quartz substrate, and the reflectance of the chromium light shielding layer, respectively.

In the exemplary embodiment of the present invention, the black transmitted light value corresponding to the light transmittance of the chromium light shielding layer pattern 150 and the white reflected light value corresponding to the reflectance of the chromium light shielding layer pattern 150 are set to be maintained at their default values, and the MoSi phase shift layer The white transmitted light value corresponding to the transmittance of 130 and the black reflected light value corresponding to the reflectance of the MoSi phase inversion layer 130 are calculated and applied as follows.

Since the transmittance of MoSi is approximately 54%, a value of 54% of the numerical value 256 set by the inspection apparatus is calculated and applied as a default when 100% transmittance is used as in the case of a quartz substrate. That is, since 256 X 0.54 ≒ 138, and hexadecimal is used to input a value, 8a, which is a hexadecimal value of 138, may be a back-transmitted light value. Since the reflectivity of MoSi is approximately 46%, when the value is calculated to be 46% of 256 which is set as a default value based on 100%, 73 may be a black reflected light value. When the calculated values are summarized and input as shown in the setting value 300 on the setting panel screen of the inspection apparatus of FIG. 3, the optical calibration setting may be performed. In this case, the measurement 320 may be performed on the light transmittance, and the inspection may be performed by the die-to-die method 330. Changing the light calibration setting can be understood to induce detection data to be calibrated to values within a range based on the transmittance and reflectances of Cr and MoSi.

The measured measurement transmittance data accompanying this optical calibration is calibrated with data comparable with the reference mask data. In the case of ArF PSM, the reference mask data is 100% light transmittance of the quartz substrate and 0% light transmittance of the mask patterns of the Cr layer and the MoSi layer, so that the MoSi phase inversion layer 130 and the chromium light shielding layer pattern It cannot be directly contrasted or contrasted with the test results according to the embodiment of the present invention based on 150.

Nevertheless, by the light calibration, the inspection result according to the embodiment of the present invention is also calibrated to normalize to numerical data in the same range as the reference mask data. Thus, the post-calibration inspection result data can be directly contrasted with the reference mask data in a die-to-die manner. Accordingly, the pattern inspection after the Cr etching in the ArF attenuated PSM is possible. Thereafter, defect detection on the light shielding layer pattern 150 is performed by the inspection apparatus (250).

Referring to FIG. 4, the basic optical calibration value 410 before the change provided by the inspection apparatus and the post-change optical calibration input values 420 calculated for the post-etch inspection of the Cr shading layer pattern 150 of the ArF attenuated PSM are shown. , Hexadecimal values (decimal values in parentheses) may actually be presented in the numerical values shown in FIG. 4.

On the other hand, the inspection method according to an embodiment of the present invention can be applied to the case of using the inspection light source of the DUV wavelength band without using a KrF PSM inspection apparatus using a longer wavelength band than the DUV. At this time, pattern inspection is possible without changing the optical calibration setting set in the inspection apparatus. For example, as shown in FIG. 5, the pattern inspection may be performed using only black transmitted light and white transmitted light values. In this case, it may be understood that the black transmitted light value represents the transmittance of chromium and the white transmitted light value represents the transmittance of MoSi. As shown in FIG. 5, it can be understood that there is no major change between the input value 510 before completing the optical calibration and the adjusted value 520 after the completion of the optical calibration. Accordingly, when the inspection apparatus using the DUV wavelength band inspection light source is used, the pattern inspection may be performed using the optical calibration set in the apparatus. In this case, the determination of whether the pattern is defective may be performed using transmittance data of the chromium light shielding layer pattern (150 of FIG. 1) and the MoSi phase inversion layer 130.

According to the present invention described above, in addition to the expensive inspection apparatus for inspecting using the DUV wavelength band, a pattern inspection of the ArF attenuated PSM is possible even in a relatively inexpensive inspection apparatus longer than the DUV wavelength. Thereby, it can contribute to the increase in the production efficiency of an inspection apparatus. In addition, when detecting defects that greatly affect the mask pattern, it is determined immediately after etching the chrome shading layer to prevent unnecessary subsequent processes in advance, thereby effectively preventing mask manufacturing turnaround time (TAT). It can be shortened.

As mentioned above, although this invention was demonstrated in detail through the specific Example, it is not preferable that this invention is interpreted as limited to this. Embodiments of the invention are preferably to be interpreted as being provided to those skilled in the art to more fully describe the invention. In addition, it can be understood that the present invention can be modified or improved by those skilled in the art within the technical idea of the present invention.

Claims (8)

Forming a phase inversion layer and a light shielding layer on the mask substrate; Patterning the light blocking layer to form a light blocking layer pattern; Irradiating inspection light on the light shielding layer pattern and the exposed portion of the phase shifting layer to detect light transmittances; And Comparing the light transmittance of the light shielding layer pattern with respect to the light transmittance of the phase shifting layer portion based on the light transmittance of the phase shifting layer portion to detect whether the light shielding layer pattern is defective. . The method of claim 1 The inspection light is light of a wavelength band longer than the wavelength range of 248 nm. The method of claim 2 The inspection light is a phase inversion mask inspection method of the 365nm wavelength band. The method of claim 2 The light blocking layer is formed to include a chromium (Cr) layer The phase inversion layer is formed to include a molybdenum-silicon alloy (MoSi) layer And the light transmittance detected by the inspection light with respect to the phase inversion layer portion is less than 100% and the light reflectance is greater than 0%. The method of claim 2 Applying a light calibration setting based on light transmittance and light reflectance for the phase shift layer and detecting the light transmittances for the light shielding layer pattern and the exposed portion of the phase shift layer together with light reflectances; And And detecting whether the light blocking layer pattern is defective from the detected light blocking layer pattern and the light-calibrated light transmittances and light reflectances of the phase inversion. The method of claim 1 Detecting whether the light shielding layer pattern is defective And comparing the data of the light transmittances and the light reflectances with data for a reference mask layout to be implemented on the mask substrate by using a die to dei method. The method of claim 1 The inspection light is a phase inversion mask inspection method of the light of 248nm wavelength band. The method of claim 7, Detecting the light transmittances for the light shielding layer pattern and the exposed portion of the phase shifting layer together with light reflectances; And And detecting whether the light shielding layer pattern is defective from the detected light shielding layer pattern and the data of the light transmittances and the light reflectances of the phase inversion.

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