JPH10186635A - Production of photomask - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten the time for defect inspection of a photomask by relatively parallel moving the coordinates of the forming data of a pattern forming device with respect to the coordinates on a blank mask so as to prevent all pinhole defects from overlapping on the mask patterns of the forming data of the pattern forming device. SOLUTION: The pinhole defects existing at a chromium film 2 formed with the mask patterns after formation of the blank mask are inspected to be found out by using an optical inspection apparatus. The positions and sizes of the pinhole defects are recorded as defect coordinate data in the inspection apparatus. The real pattern coordinate data of the mask recorded in a CAD is collated with this defect coordinate data. The defect coordinate data is recognized as A=1 unless all the defect coordinate data overlap on the real pattern coordinate data. The blank mask is set and when the recognition number of A=1 is not imparted in a recognition stage, a stage is moved parallel on a plane by a distance (a) in the relative coordinates taking an offset into consideration and the patterns are formed by an electron beam.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of forming a mask pattern having no defect in a pattern forming film such as a light-shielding film, a semi-transparent film or a phase shift film of a photomask, particularly a blank mask.

[0002]

2. Description of the Related Art Quartz is mainly used for a transparent substrate material used for a photomask, and chromium is mainly used for a light shielding film material for forming a pattern. The chromium film thickness of the blank mask before forming the photomask is about 11
0 nm, and formed by a vacuum evaporation method or a sputtering method. In addition, a translucent film, which is a kind of pattern forming film, or a laminated film of an oxynitride film of MoSi and a chromium film as a phase shift film, or another metal film (alloy film) may be formed by sputtering.

An EB (Electron Beam) resist is mainly used as a protective film material necessary for processing a photomask. The thickness of the EB resist is about 300 to 50
0 nm and applied by a spin-on method. This EB resist is patterned by EB drawing and development. The light-shielding film, the translucent film, the phase shift film, and the like on the transparent substrate are patterned by a wet etching method or a dry etching method. This patterned mask is used as a photomask in a photolithography process such as processing of a semiconductor device.

As a specific example, a manufacturing process of a photomask having only a light-shielding film made of chromium will be described.

[0005] First, a blank mask in which a chromium film of about 110 nm is formed on a transparent substrate by sputtering, vacuum evaporation, or the like is manufactured. Subsequently, a resist is applied to a thickness of about 500 nm. In addition, when etching the chrome film as a resist,
It must be excellent in etching resistance. EB
In the drawing step, the light-shielding area is set to a non-drawn state, and the transmissive area is set to a necessary charge amount capable of completely removing the resist, and irradiated with an electron beam. There are two types of resists, negative and positive.If a positive resist is used, the part that has not been exposed to the electron beam will remain as a resist pattern in the next development step, and the part that has been exposed to the electron beam will be exposed to the developer. Dissolve,
The chromium film is partially exposed.

After development, the exposed chromium film is dry-etched. The resist functions as a protective film against etching, and only the chromium film in the portion not covered with the resist is removed, and the transparent substrate is partially exposed. When a chlorine-based gas is used for dry etching of the chromium film, the dry etching resistance of the resist is sufficient. After etching the chromium film, the entire surface of the resist is removed. For removing the resist, a chemical solution such as acetone or sulfuric acid / hydrogen peroxide is used.
In this case, the resistance of the transparent substrate and the chromium film to the chemical is sufficient.

[0007] Generally known photomask defects include black defects such as etching residue of a pattern forming film and foreign substances on the exposed transparent surface of quartz which is etched and has no mask pattern, and the inside of the mask pattern. There is a white defect such as a pinhole due to any of the above, or whether the pinhole of the upper resist is transferred to the lower pattern forming film by etching and formed. As a method of inspecting a pinhole of the photomask, a method of inspecting optically is known. As a method for correcting these defects after the defect inspection, the former black defect is focused ion beam method (FIB: Focused).
There is known a method of removing etching residue or foreign matter by using an ion beam or a laser, and a method of filling the pinhole by attaching carbon to a pattern for the latter white defect is known.

The defect relating to the present invention is the latter white defect (hereinafter referred to as "pinhole"). If the formed light-shielding mask pattern has a pinhole, a problem occurs in that a desired pattern is defective when used for photolithography on a semiconductor device, printing, or the like. Therefore, as a generally known effective method, a pinhole filling method using FIB will be described with reference to FIGS. 4 (a) to 4 (e).

First, as shown in FIG. 4A, a blank mask with a resist before forming a photomask already has a pinhole, albeit at a low frequency. The configuration of the blank mask with resist is such that a light shielding film 22 is formed on a transparent substrate 21,
There is an EB resist on it, and EB (short for electron beam)
As a result, an exposed region 24 and an unexposed region 23 remaining as a pattern are formed.

Next, as shown in FIG. 4B, after the resist is developed, a resist pattern 25 remains. At this stage, a region where a pinhole exists in the resist may be removed. In some cases, the pinhole 26 remains in the resist pattern. Therefore, FIG.
As shown in FIG. 5, a pinhole 26 appears in the light-shielding pattern of the photomask etched by the resist pattern, and a pinhole of the light-shielding film 22 covered with the original resist pattern 25 also exists. It is difficult to prevent pinholes from being generated in the mask forming process.

Therefore, as shown in FIG. 4D, the nozzle 2 is aimed at a pattern having a pinhole defect on the mask.
By spraying the carbon-based gas 29 from 8 and simultaneously irradiating the FIB 30 with focusing on the pinhole defect portion of the pattern, the carbon 31 enters and is embedded in the pinhole as shown in FIG.

Since the carbon 31 acts to prevent light from transmitting, like the chromium, the pinhole is closed by the light shielding portion. In particular, this method is effective for fine pinhole defects. In addition, as described in JP-A-6-75363, a large missing portion of a wide light-shielding pattern is
However, there is a problem that it takes too much time or cannot be completely filled with carbon only by carbon filling, and carbon is peeled off by cleaning the mask. Therefore, after forming a carbon film pattern with a gap in the missing portion by FIB, further laser There is disclosed a method in which chromium is vapor-deposited on a missing portion by an irradiation method to completely cover the missing portion and shield light. This method is effective for shading large missing portions.

[0013]

However, white defects such as pinholes in the mask pattern after the photomask is manufactured,
Optical means after the mask pattern is formed is difficult to distinguish from the mask pattern and hard to find. For this reason, not only takes time for the inspection, but also it is no longer possible to reliably pick up white defects. In addition, since the process of attaching carbon using FIB is included in the correction of the white defect, there is a problem that the cost of the correction process is increased.

[0014]

According to a first aspect of the present invention, there is provided a method of manufacturing a photomask, comprising applying a resist to a blank mask having a pattern forming film deposited on a transparent substrate, and then applying the resist to the blank mask. A first step of detecting a pinhole defect to be detected and a pinhole defect existing in the pattern forming film of the transparent substrate; and all the pinholes on a blank mask having the resist detected in the first step. A second step of recording the coordinates of the position and the size of the defect, and the coordinates of the position and the size of the pinhole defect recorded in the second step are used to calculate the position and the size of the mask pattern of the drawing data of the pattern drawing apparatus. 3rd to match with coordinates
And moving the coordinates of the drawing data of the pattern writing apparatus relative to the coordinates on the blank mask so that all the pinhole defects do not overlap the mask pattern of the writing data of the pattern writing apparatus at all. Four steps, a blank mask is set in a drawing apparatus while maintaining the state of the parallel movement, the resist is drawn, the resist is patterned, and the resist pattern is used as a mask to form the pattern forming film on a transparent substrate. And a fifth step of forming a mask pattern by etching.

More specifically, first, a resist is applied to a blank mask having a pattern forming film on a transparent substrate, and then a pinhole defect existing in the resist is determined by optical inspection of the blank mask having the resist. Then, a pinhole defect existing in the pattern forming film of the transparent substrate is detected. For example, a pinhole defect existing in the resist is detected from reflected light, and a pinhole defect existing in the pattern forming film is detected from transmitted light.

Next, the position and size coordinates of all the pinhole defects on the blank mask having the resist are recorded in an inspection device, and the position and size coordinates of the pinhole defects are recorded in a pattern drawing device. Drawing data, for example, EB
The position and the size of the mask pattern to be originally formed on the drawing CAD data of the drawing apparatus are compared with the coordinates.

Next, as a result of the collation, if all the pinhole defects do not overlap, a mask patterning forming step (a resist pattern formation by EB drawing and development, and etching using the resist pattern as a mask to form a pattern forming film). If at least one pinhole of a problem size overlaps, the coordinates on the blank mask are compared with the coordinates on the blank mask until none of the pinholes of a problem size overlap. Is relatively translated (CA of the EB drawing apparatus)
Offsets are provided for all coordinates on D data), while keeping this state, a blank mask is set in the drawing apparatus, the resist is patterned, and the pattern forming film on the transparent substrate is etched with the resist mask. And patterning.

Regarding the method of setting the offset, whether the pin pattern is randomly or finely changed in sequence, if all the pinholes are overlapped with the mask pattern position data on the CAD data of the EB drawing apparatus in the collation processing, It is desirable to repeat the processing until it disappears.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, based on one embodiment,
The present invention will be described in detail.

FIG. 1 is a diagram showing a follow chart of a photomask manufacturing process according to an embodiment of the present invention, and FIG.
FIG. 3 is a manufacturing process diagram of a photomask according to an embodiment of the present invention, and FIG. 3 is a plan view of a photomask formed according to the present invention. 1 to 3, 1 and 11 are transparent substrates, 2 is a chromium film, 3 is an EB resist, 4 is a defect detection light, 5 is a reflection light of a pinhole defect in the resist by the defect detection light, and 6 and 13 are 7 is a pinhole defect, and 7 is the transmitted light of the pinhole defect in the pattern forming film by the defect detection light.
8 is a resist drawing area, 9 is a resist pattern, 1
0 and 12 indicate light shielding film patterns, and a indicates an offset amount.

Hereinafter, a manufacturing process of a photomask according to one embodiment of the present invention will be described with reference to FIG.

First, a blank mask in which a chromium film 2 having a thickness of about 110 nm is formed on a transparent substrate 1 by sputtering, vacuum deposition, or the like. Subsequently, the EB resist 3 is applied for about 500
nm. As the EB resist, a commercially available EB resist having excellent etching resistance when etching a chromium film was used.

In the EB drawing process, the light-shielding region is set to a non-drawn state, and the transmission region is set to a necessary charge amount capable of completely removing the resist, and irradiated with an electron beam. The EB resist is classified into a negative type and a positive type. In the present embodiment, the positive type is used, and a portion not irradiated with the electron beam remains as a resist pattern 9 in the next developing step, and a portion 8 irradiated with the electron beam. Is dissolved, and the chromium film 2 is partially exposed.

After the development, the exposed chromium film 2 is dry-etched. The resist pattern 9 functions as a protective film against etching, and only a portion of the chromium film not covered with the resist is removed, and a chlorine-based gas is used for dry etching of the chromium film 2 where the transparent substrate 1 is partially exposed. In addition, the dry etching resistance of the resist is sufficient. After etching the chromium film 2, the entire resist pattern 9 is removed. For removing the resist, a chemical solution such as acetone or sulfuric acid-hydrogen peroxide is used. In this case, the resistance of the transparent substrate and the chromium film to the chemical is sufficient.

Next, referring to FIG. 1, a description will be given of a defect correcting step in a photomask manufacturing step according to an embodiment of the present invention.

First, after the above-mentioned blank mask is formed (S1), a defect inspection is performed (S2). Mainly, a pinhole defect existing in a chromium film on which a mask pattern is formed is inspected and found using an optical inspection device.
Specifically, a pinhole defect existing in the EB resist is detected from the reflected light 5, and a pinhole defect existing in the pattern forming film is detected from the transmitted light 7. If there is no pinhole,
With no defect, a recognition number of A = 1 is given and the process goes to blank setting (S7). Here, this is the step of setting a blank mask in the drawing apparatus. Since this mask is A = 1, drawing is performed without moving the stage (S9), and the manufacturing process continues.

When a pinhole defect is found,
The position and size are recorded as defect coordinate data in the inspection device (S5). Recorded in the CAD attached to the EB exposure apparatus connected to the defect inspection apparatus of the present invention,
The actual pattern coordinate data of the mask created in advance is read out (S3) and collated with the defect coordinate data (S3).
6).

In this case, if all the defect coordinate data do not overlap the actual pattern coordinate data, it is recognized that A = 1, and the process goes to blank setting (S7).

However, as shown in FIG. 3 (a), when at least one piece of defect coordinate data overlaps with the actual pattern coordinate data, the relative coordinates are used until all the defect coordinate data no longer overlaps with the actual coordinate data. By shifting the position, a solution of an offset that does not overlap any time is obtained (offset characteristic).

In principle, if the position data is regularly shifted at the minimum pitch, the positions will not overlap any more. However, in this embodiment, the maximum size of the pinhole defect is extracted.
Based on this, it is set so that a pitch of a larger offset value is always provided, and a trial and error process is repeated by randomizing the way of giving the X and Y coordinate values of the offset so as to satisfy this condition. Data is collated by program.

Originally, the solution of the offset obtained in the present embodiment is not unique and may exist in a large number, and the content of the above-mentioned collation program itself in the present embodiment is the only one that solves the problem. Not a means. This offset is set so as not to exceed the mask size.
This offset is set to all the mask data coordinates of the CAD of the corresponding drawing apparatus.

Next, a blank mask is set,
Next, in the identification step of whether A = 1 or not, when the identification number of A = 1 is not given, the distance of the symbol a in FIG. 2C or FIG. The stage is moved in parallel only on the plane, and drawing is performed with an electron beam. In this case, the stages of the defect inspection apparatus and the drawing apparatus need to be shared.

Further, it is desirable that the defect inspection apparatus and the drawing apparatus are integrated and that there is no transfer by the stage, because the drawing alignment deviation of the mask due to the movement of the stage hardly occurs.

The manufacturing process of the photomask after the above defect correction will be described below.

FIG. 2C shows a pattern obtained by performing the above-described EB drawing. The drawing area 8 includes all pinholes in the resist. Therefore, in the developing process, FIG.
As shown in (d), all the pinholes in the resist are removed together with the unnecessary resist. Further, by etching using the resist pattern 9 having no pinhole as a mask, the region having the pinhole 6 of the chromium film 2 on the transparent substrate 1 is removed as shown in FIG. A photomask having no defects was obtained.

[0036]

As described above in detail, by using the present invention, a defect inspection of a photomask can be performed in a short time, a conventional mask defect correction can be omitted, and a special correction method (such as FIB) can be used. Without using, a white defect such as a pinhole can be picked up and removed with high accuracy, and a photomask having no pinhole defect can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing a flowchart relating to a defect repair method in a photomask manufacturing process according to an embodiment of the present invention.

FIG. 2 is a manufacturing process diagram of a photomask according to one embodiment of the present invention.

FIG. 3 is a partial process diagram related to a defect correction method in a photomask manufacturing process according to one embodiment of the present invention.

FIG. 4 is a manufacturing process diagram of a conventional photomask.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1, 11 Transparent substrate 2 Chromium film 3 EB resist 4 Defect detection light 5 Reflection light of pinhole defect in resist by defect detection light 6, 13 Pinhole defect 7 Defect of pinhole defect in pattern formation film by defect detection light Transmitted light 8 Resist drawing area 9 Resist pattern 10, 12 Light shielding film pattern a Offset amount

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI H01L 21/30 502V 502W

Claims (2)

[Claims] After applying a resist to a blank mask in which a pattern forming film is deposited on a transparent substrate, a pinhole defect existing in the resist and a pinhole defect existing in the pattern forming film of the transparent substrate are provided. A second step of recording the coordinates of the positions and sizes of all the pinhole defects on the blank mask having the resist detected in the first step; and A third step of comparing the position and size coordinates of the pinhole defect recorded in the process with the position and size coordinates of the mask pattern of the drawing data of the pattern drawing apparatus; and Make the coordinates of the drawing data of the pattern writing device relative to the coordinates on the blank mask so that they do not overlap the mask pattern of the writing data of the device at all. A fourth step of performing a parallel movement; placing a blank mask in a drawing apparatus while maintaining the state of the parallel movement, drawing the resist, patterning the resist, and using the resist pattern as a mask, Etch the pattern forming film,
And a fifth step of forming a mask pattern. 2. A pinhole defect existing in the resist is detected by the defect detection light reflected from the pattern forming film, and the pinhole defect present in the pattern forming film on the transparent substrate is detected by the defect detection light. 2. The method for manufacturing a photomask according to claim 1, wherein the photomask is optically detected by transmitting through a back surface of the transparent substrate of the blank mask having the resist.