JPH07135244A - Method and apparatus for detecting and correcting photomask pattern defect - Google Patents

Abstract

PURPOSE:To detect and correct photomask pattern defects depending on their type and locations. CONSTITUTION:A method is provided for detecting and/or correcting defects of a pattern formed on a photomask, wherein a distance (if necessary, size of fault, Cr defect or shifter defect,) from the edge 41 of a pattern 4 to a defect is detected by the use of differential waveforms 6 (6a to 6d) or the like, and the distance concerned is taken into consideration. A device for detecting and correcting photomask pattern defects is equipped with an image recognition means which recognizes the image of a photomask, a differentiating circuit which produces differential waveforms of the intensity of light transmitted through the photomask, and a comparative discriminating circuit which discriminates faults.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pattern defect inspection / repair method and a pattern defect inspection / repair device for inspecting a pattern defect of a photomask on which a pattern is formed and / or correcting the pattern defect. INDUSTRIAL APPLICABILITY The present invention can be used as a defect inspection method and an apparatus for inspecting a pattern transfer photomask used in a manufacturing process of a semiconductor device, for example, a phase shift mask having a phase shift portion.

[0002]

2. Description of the Related Art A photomask used in a semiconductor device manufacturing process has a structure in which a light-shielding film is formed on a transparent member such as a quartz or glass substrate, and the semiconductor is manufactured by projecting and exposing the photomask. Created by. Therefore, the defect of the photomask is directly linked to the defect of the semiconductor product. Photomask defects include isolated defects,
There are defects such as edge defects of patterns and corner defects of patterns, which are caused by defect generation positions, and defects in which an unnecessary light-shielding film is attached to a glass substrate, so-called Cr residual defects, and defects in which holes are formed in the light-shielding film, There are various types such as so-called pinhole defects.

Further, recently, a so-called phase shift mask having a phase difference has been spotlighted in the light transmitting portion of the photomask. In the phase shift mask, so-called shifter defects in the phase shift portion must be newly considered in addition to the above-mentioned defects, and the number of defect types to be detected in the photomask defect inspection step is increasing. is there.

[0004]

However, even if the defect size is the same, Cr defects (in this specification, defects due to excessive adhesion of the light shielding material are collectively referred to as "Cr defects"). Since the influence of the shifter defect after the photomask projection exposure is different, it is necessary to change the defect detection sensitivity for each defect type. Further, the influence after projection exposure is different even for a defect isolated from the mask pattern, a defect occurring inside the contact hole pattern and a defect having no pattern in the periphery. In a conventional defect inspection apparatus, for example, a defect detection algorithm has a defect position such as one for detecting an isolated defect and one for detecting a pattern edge defect as parameters.
Defect detection sensitivity was determined only by adjusting the inspection sensitivity balance by one algorithm. Therefore, it is impossible to determine whether the guaranteed defects are Cr defects or shifter defects,
For example, there was no choice but to guarantee on the basis of a shifter defect that has a large influence after projection exposure. As a result, even if the defect size is the same, it is possible to detect, for example, an isolated Cr defect or a pinhole defect having no mask pattern in the periphery, which lowers the throughput of photomask creation. I was supposed to. In particular, when a photomask is formed using a negative resist, since there are many light transmitting parts with respect to the light shielding part, minute Cr defects and the like are likely to occur, and conventional devices detect all of them as defects. Was.

Therefore, the present invention provides a defect inspection / repair method and device for the defect inspection / repair method and device of the photomask, which can detect defects according to the location and type of defect. The purpose is to

[0006]

The invention according to claim 1 of the present application provides a pattern defect inspection / repair method for inspecting a pattern defect of a photomask on which a pattern is formed and / or correcting the pattern defect. A method for inspecting / defecting a pattern defect of a photomask, which is characterized by considering a distance from an edge to a defect, which achieves the above object.

The invention of claim 2 of the present application considers the distance from the edge of the pattern to the defect and also considers the size of the defect. Defect repair method,
This achieves the above object.

According to the invention of claim 3 of the present application, the distance and / or the size of the defect is detected by using a differential waveform of the transmitted light intensity, and the pattern of the photomask according to claim 1 or 2. Defect inspection / defect correction method,
This achieves the above object.

The invention of claim 4 of the present application is characterized by detecting whether the defect is a defect of a light transmitting part or a defect of a light shielding part (including a halftone part) by using a differential waveform of transmitted light intensity. A method of inspecting and correcting a pattern defect of a photomask according to any one of claims 1 to 3, which achieves the above object.

According to a fifth aspect of the present invention, in a pattern defect inspection / repair method for inspecting a pattern defect of a photomask on which a pattern is formed and / or repairing the pattern defect, the distance from the edge of the pattern to the defect. When,
Defect inspection / defect correction method for photomask, characterized in that the size of the defect, whether the defect is a defect in a light transmitting part or a light shielding part (including a halftone part), and the size of the pattern are taken into consideration. Therefore, the above object is achieved thereby.

According to a sixth aspect of the present invention, in a pattern defect inspection / repair device for inspecting a pattern defect of a photomask on which a pattern is formed and / or correcting the pattern defect, an image for recognizing an image of the photomask is obtained. A pattern defect inspection / defect correction device for a photomask, comprising: a recognition unit, a differentiation circuit that obtains a differential waveform of the transmitted light intensity of the photomask, and a comparison / determination circuit that determines a defect. This achieves the above object.

[0012]

According to the present invention, photomask defect inspection and / or
Or, in the repair, after capturing the pattern image by the transmitted light, for example, by considering the change point of the transmitted light intensity, by considering the distance from the pattern edge to the defect, it is possible to determine whether or not the defect requires correction. Alternatively, it is possible to determine whether the defect is a Cr defect or a shifter defect.

For example, in the present invention, by using, for example, a differential waveform with respect to the light intensity signal of the transmitted light obtained when the photomask defect inspection apparatus detects a defect,
It is possible to measure the distance from the pattern edge and distinguish between Cr defects and shifter defects. As a result, only the minimum defects that should be guaranteed in the photomask are detected,
The throughput of the photomask making process can be significantly improved.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. However, it should be understood that the present invention is not limited to the embodiments.

Prior to the description of a specific embodiment, typical types of defects occurring in a photomask will be described with reference to FIG.

FIG. 5 shows an example of a halftone type phase shift mask (the same applies to other mask structures, and there is no problem at all). Figure 5 (a)
Indicates a pinhole defect when a contact hole pattern or the like is not present in the vicinity. In the figure, reference numeral 1 is a halftone Cr portion, 2 is a defect portion, 3 is a transparent substrate, and 4 is a phase shift portion. 5 (b) is a pinhole defect near the contact hole pattern, FIG. 5 (c) is a Cr defect near the contact hole pattern, FIG. 5 (d).
5 (e) shows a shifter defect near the contact hole pattern, FIG. 5 (e) shows a Cr defect at the center of the contact hole pattern, and FIG. 5 (f) shows a shifter defect at the center of the contact hole pattern.

When the inventors of the present invention confirmed the influence of these various defects after projection exposure, the defect shown in FIG. 5 (f) had an effect on the contact hole width even though the defect size was exactly the same. It was confirmed to be the largest. The confirmation method was obtained as the rate of change of the contact hole diameter when there is a defect with respect to the contact hole diameter when there is no defect. In the case of this evaluation, the allowable change rate of the contact hole diameter was defined as within ± 10%. An example of the experiment will be described.

A photomask having a defect type as shown in FIG. 5 was prepared, and KrF 248 nm, NA = 0.45, σ
A reduction projection exposure was attempted under the condition of 0.3. As a result,
In the case of the defect shown in FIG. 5F, it is necessary to guarantee a defect of 0.3 μm □ on the photomask which is five times larger than that of the defect shown in FIG. 5A. It turns out that defect guarantee is also good.

Further, the influence of various photomask defects on the contact hole pattern was evaluated by using light intensity simulation. In FIG. 6, the horizontal axis shows the defect size on the 5 × photomask, and the vertical axis shows the change rate of the contact hole diameter. From FIG. 6, it can be seen that there is a large difference in the rate of change even for photomask defects of the same size. In particular, it can be seen that the defect is large in the defect of FIG. 5F shown in FIG.

Example 1 A schematic diagram illustrating this example is shown in FIGS. 1 and 2.

FIG. 2 (a) shows an isolated defect when there is no pattern in the surroundings, and FIG. 2 (b) shows a pattern for comparison inspection. FIG. 2B may be a so-called database inspection image created by data conversion or an image obtained from an actual photomask pattern. Further, reference numeral 5 in FIG. 2 indicates the light intensity obtained from the transmitted light of the photomask inspection apparatus, and 6 indicates the differential waveform obtained by differentiating the original signal.

FIG. 2A shows an isolated defect generated near the center of the contact hole pattern. In the case of the conventional device, the defects of FIGS. 1 and 2 are detected as defects of the same size. On the other hand, in this embodiment, when a defect is detected, 1, m in FIG. 3, that is, the distance between the defect and a pattern in the vicinity thereof is considered. It goes without saying that 1 and m also change depending on the photomask method and the optical data of the projection exposure apparatus in which the photomask is used. When there is no 1, m within a certain range when a defect is detected, for example, a defect of 1 μm or more is detected,
Further, when there is any one of 1 and m, it is possible to detect only the required defect by detecting the defect corresponding to the value. Further, considering the defect size s, the data is used to decide whether or not the defect needs to be corrected. 1, m,
The value of s can be obtained from the signals 6a to 6d of the differential waveform 6.

Example 2 A schematic diagram of this example is shown in FIG. FIG. 3A shows a case where a Cr residual defect occurs near the center of the contact hole pattern when the halftone phase shift mask is applied to the contact hole pattern, and FIG. 3B shows the defect. Shows the case where the shifter residual defect is present. Reference numeral 5 in FIG. 3 indicates the light intensity obtained from the transmitted light of the photomask inspection apparatus, and reference numeral 6 indicates the waveform obtained by differentiating the original signal. The defect information obtained from the differential waveform 6 in FIG. 3 makes it possible to distinguish between a Cr defect and a shifter defect, and it becomes possible to detect only the required defect. This is because in the case of a Cr defect, there are two differential waveforms 6c and 6d indicating the defect, whereas in the case of a shifter defect, four differential waveforms 6g to 6j appear.

This method can be used not only for the shifter defect but also for distinguishing the uneven defect on the light transmitting portion from the Cr defect.

Embodiment 3 This embodiment is embodied as a photomask pattern defect inspection / correction apparatus. The apparatus of this example is shown in a block diagram in FIG.

In FIG. 4, reference numeral 11 is a network, 12 is a pattern generator, 13 is a comparison / determination circuit for determining the position / size and type of the defect, 14 is a differentiation circuit, 15 is an image recognition, 16
Is auto focus, 17 is lens, 18 is mask, 19 is X / Y stage, 20 is illumination, 21 is Y motor, 22 is X motor, 23 is laser interferometer, 24 is stage controller, 25 is microprocessor, 26 Is a display, 27 is a disk, and 28 is a printer.

This embodiment will be described below with reference to FIG. The mask 18 is illuminated from below by the illumination 20, and the image of the mask 18 is captured by the image recognition unit 15 through the lens 17 focused by the automatic focus control mechanism 16 and converted into a signal, which is captured by the differentiating circuit 14. And is used as a differential waveform signal of the light intensity distribution. This differential waveform signal is taken into the comparison / determination circuit 13, where the distance between the defect and the pattern edge, the defect size, the size of the pattern, and whether the defect is a light shielding part (Cr) defect or a transmissive part (shifter etc.) defect. Then, a defect inspection is performed. Since the pattern generator 12 is supposed to perform a database inspection in this system, the pattern signal stored in the database is used by the pattern generator 12.
It is provided in order to make it possible for the comparison decision circuit 13 to compare it with the actual pattern signal.

If necessary, the inspection signal taken into the network 11 can be used to issue a correction signal.

Reference numeral 23 is a laser interferometer for detecting the position of the stage, which controls the position of the mask 18.

The mask 18 is placed on the X / Y stage and controlled by the stage controller 24.
The mask image is recognized by driving the stage by 21 and 22. Driving of each mechanism is controlled by a signal from the microprocessor 25.

The display 26 allows an image of the defect to be displayed for actual visual confirmation of the defect. Also,
The display 26 can be configured to display a differential waveform and a light intensity distribution map.

The disk 27 stores defects such as
Store various data. The printer 28 can print out data on the structure of defects.

[0033]

As described above, according to the present invention, in a conventional photomask defect inspection apparatus, a defect which has detected a defect of a certain size or more irrespective of the kind of the defect is influenced by the photomask projection exposure. It is possible to selectively detect the considered defects. By using the photomask inspection method according to the present invention, it is possible to improve the yield in producing a photomask, reduce the cost, and significantly improve the throughput.

[Brief description of drawings]

FIG. 1 is a diagram schematically illustrating a first embodiment.

FIG. 2 is a diagram schematically illustrating a first embodiment.

FIG. 3 is a diagram schematically illustrating a second embodiment.

FIG. 4 is a block diagram showing an apparatus of Example 3.

FIG. 5 is a diagram illustrating a typical defect example occurring in a photomask.

FIG. 6 is a diagram showing transferability of photomask defects by light intensity simulation.

[Explanation of symbols]

 1 Light-shielding part 2 Defect part 3 Transparent substrate 4 Phase shift part 5 Transmitted light intensity 6 Differentiated waveform of transmitted light intensity

[Procedure amendment]

[Submission date] September 10, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0003

[Correction method] Change

[Correction content]

Further, recently, a so-called phase shift mask having a phase difference has been spotlighted in the light transmitting portion of the photomask. In the phase shift mask, so-called shifter defects in the phase shift portion must be newly considered in addition to the above-mentioned defects, and the number of defect types to be detected in the photomask defect inspection step is increasing .

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0018

[Correction method] Change

[Correction content]

A photomask having a defect species as shown in FIG. 5 was prepared, and KrF excimer laser light, wavelength 248 was used.
A reduction projection exposure was attempted under the conditions of nm, NA = 0.45, σ = 0.3. As a result, in the case of the defect as shown in FIG. 5F, it is necessary to guarantee the defect of 0.3 μm □ on the photomask 5 times as large as that of the defect as shown in FIG. It was found that the defect guarantee of 0 μm □ is also good.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0021

[Correction method] Change

[Correction content]

FIG. 2 (a) shows an isolated defect when there is no pattern in the surroundings, and FIG. 2 (b) shows a pattern for comparison inspection. FIG. 2B may be a so-called database inspection image created by data conversion or an image obtained from an actual photomask pattern. Further, reference numeral 5 in FIG. 2 indicates a light intensity obtained from the transmitted light of the photomask inspection apparatus, and 6 indicates a differential waveform (absolute value waveform: hereinafter, obtained by differentiating the original signal).
In the text, the differential waveform refers to this waveform) .

[Procedure amendment 4]

[Document name to be amended] Statement

[Name of item to be corrected] 0022

[Correction method] Change

[Correction content]

[0022] FIG. 1 (a) shows a defect of the isolated occurring near the center of the contact hole pattern. In the case of the conventional device, the defects of FIGS. 1 and 2 are detected as defects of the same size. On the other hand, in this embodiment, when a defect is detected, l and m in FIG. 1 , that is, the distance between the defect and a pattern in the vicinity thereof is considered. It goes without saying that l and m vary depending on the photomask method and the optical data of the projection exposure apparatus in which the photomask is used. Upon detection of defects, if there is no pattern within a certain range l, m, for example, to detect the above defects 1 [mu] m, also, if there is a pattern l, in any range of m is, the By detecting the defect according to the value, it becomes possible to detect only the required defect. Further, considering the defect size s, the data is used to decide whether or not the defect needs to be corrected. The values of l, m, and s are the signals 6a to 6 of the differential waveform 6.
This can be obtained from 6d.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Name of item to be corrected] 0023

[Correction method] Change

[Correction content]

Example 2 A schematic diagram of this example is shown in FIG. FIG. 3A shows a case where a Cr residual defect occurs near the center of the contact hole pattern when the halftone phase shift mask is applied to the contact hole pattern, and FIG. 3B shows the defect. Shows the case where the shifter residual defect is present. Reference numeral 5 in FIG. 3 indicates the light intensity obtained from the transmitted light of the photomask inspection apparatus, and reference numeral 6 indicates the waveform obtained by differentiating the original signal. The defect information obtained from the differential waveform 6 in FIG. 3 makes it possible to distinguish between a Cr defect and a shifter defect, and it becomes possible to detect only the required defect. This is because, in the case of a Cr defect, there are two peaks of the differential waveform indicating defects, 6c and 6d, whereas in the case of a shifter defect, four peaks of 6g to 6j appear.

[Procedure correction 6]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 2

[Correction method] Change

[Correction content]

[Fig. 2]

[Procedure Amendment 7]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 6

[Correction method] Change

[Correction content]

[Figure 6]

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location H01L 21/027

Claims (6)

[Claims] 1. A pattern defect inspection / repair method for inspecting a pattern defect of a photomask on which a pattern is formed and / or correcting the pattern defect, wherein the distance from the edge of the pattern to the defect is considered. Photomask pattern defect inspection / defect correction method. 2. The pattern defect inspection / defect correction method for a photomask according to claim 1, wherein the defect size is taken into consideration while considering the distance from the edge of the pattern to the defect. 3. The pattern defect inspection / defect correction method for a photomask according to claim 1, wherein the distance and / or size of the defect is detected by using a differential waveform of transmitted light intensity. 4. The photomask according to claim 1, wherein whether the defect is a defect in a light transmitting part or a defect in a light shielding part is detected by using a differential waveform of transmitted light intensity. Pattern defect inspection and defect repair method. 5. A pattern defect inspection / repair method for inspecting a pattern defect of a photomask on which a pattern is formed and / or repairing the pattern defect, the distance from the edge of the pattern to the defect, the size of the defect, and the defect. A method for inspecting and repairing defects in a photomask, characterized in that whether the defect is a defect in the light transmitting part or the defect in the light shielding part and the size of the pattern are taken into consideration. 6. A pattern defect inspection / repair device for inspecting a pattern defect of a photomask on which a pattern is formed and / or correcting the pattern defect, and an image recognition means for recognizing an image of the photomask and a transmission of the photomask. A pattern defect inspection / defect repair device for a photomask, comprising: a differentiation circuit for obtaining a differential waveform of light intensity; and a comparison / judgment circuit for judging a defect.