JP2006171122A - Inspection method and exposure method for charged particle beam exposure mask - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inspection method for measuring mask distortion in a short time with high accuracy by using a conventional coordinates measuring device and an exposure device. <P>SOLUTION: An inspection method for a charge particle beam exposure mask is a method for inspecting a pattern position on a mask having a pattern surface, a support layer and a support substrate, and the method is characterized in that: while the mask is held on an opposite side of the support substrate to the face held by an exposure device and in a state of opposite direction of gravity to the mask in the exposure device, the position of the mask is measured to obtain a first position measurement data; while the mask is held on the face of the support substrate to be held by an exposure device and in a state with the same gravity direction as the mask in the exposure device, the position of the mask is measured to obtain second position measurement data; and a deformation amount at the pattern position of the mask is calculated by using the first position measurement data and the second position measurement data. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a charged particle beam exposure mask inspection method and exposure method. In particular, the present invention relates to a charged particle beam exposure mask inspection method capable of measuring mask distortion in a short time with high accuracy and a high accuracy exposure method in which the distortion is corrected.

  Semiconductor integrated circuits are increasingly miniaturized, and more and more advanced technology is required in the manufacturing process for realizing them. Among these, charged particle beam projection exposure, particularly electron beam projection exposure technology, has attracted attention as a technology that replaces the ultraviolet exposure technology.

  As an example of the electron beam projection exposure technique, a stencil mask is irradiated with an electron beam having a size of about 1 mm on a mask and subjected to reduced exposure to one-fourth, whereby a side of 250 μm (a region exposed simultaneously) Has been proposed (for example, Patent Document 1). The stencil mask used here is composed of a large number of divided patterns obtained by dividing the entire pattern of one chip, and collective electron beam exposure is performed on each divided pattern.

  In the above method, if the position of the image of each subfield shifts during exposure, the divided circuit pattern does not connect well on the wafer, resulting in a failure. One cause of the subfield misalignment is a subfield misalignment on the mask due to mask distortion or the like. Such a defect can be prevented by accurately grasping the positional deviation on the mask and correcting the mask stage position by the amount of the deviation. Alternatively, in the case of electron beam exposure, the image position can be finely adjusted by correcting the deflection of the electron beam in the projection optical system.

For example, by providing in advance a position mark for measuring the position of each subfield and an alignment mark detected by the exposure apparatus on the mask, and measuring these marks with a coordinate measuring apparatus (provided separately from the exposure apparatus) A method for correcting mask distortion (deformation amount) has been proposed (for example, Patent Document 2). There has also been proposed a method of correcting the linear distortion in the exposure apparatus using the alignment mark described above and correcting the nonlinear positional deviation of each subfield using the position mark (for example, Patent Document 3). Further, when measuring the above-mentioned position mark, the surface (where the mask is held by the coordinate measuring device) is made the same as the exposure device, so that the distortion (deformation amount) caused by the holding is the same as that of the exposure device (for example, patent Document 4) and a method of measuring mask distortion with high accuracy by measuring the amount of deviation in the height direction due to gravity or the like (for example, Patent Document 5) have been proposed.
JP-A-9-139344 JP 2000-124114 A JP 2002-319533 A Japanese Patent Laid-Open No. 2004-094068 JP 2004-165250 A

However, in the methods in Patent Documents 2 and 3, a correction error occurs when the subfield in which the alignment mark is arranged is distorted nonlinearly. In Patent Documents 4 and 5, a new coordinate measuring device is required.
Furthermore, in the method of Patent Document 4, there is a problem in the reproducibility of the mask holding method due to “bending” of the holder.

  SUMMARY OF THE INVENTION An object of the present invention is to use an existing coordinate measuring apparatus and exposure apparatus, and to inspect the charged particle beam exposure mask inspection method for measuring the distortion of the charged particle beam exposure mask in a short time and with high accuracy, and to correct the distortion. It is to provide an exposure method.

In order to achieve the above object, according to one aspect of the present invention, a circuit pattern to be exposed and transferred on a semiconductor substrate is divided into a plurality of batch exposure small regions, and the pattern surface is reinforced. And a support substrate portion provided around the support layer, and a method for inspecting a pattern position in a charged particle beam exposure mask comprising:
The support substrate unit is held on the opposite side of the surface held by the exposure apparatus, and the mask is held in a state in which the direction of gravity is opposite to that of the mask in the exposure apparatus to perform position measurement. 1 position measurement data is acquired,
A second position measurement is performed by holding the surface of the support substrate portion held by the exposure apparatus and measuring the position while holding the mask in a state where the direction of gravity is the same as that of the mask in the exposure apparatus. Get the data,
There is provided a mask inspection method for charged particle beam exposure, wherein a deformation amount of the pattern position of the mask is calculated using the first position measurement data and the second position measurement data.

  Here, the first and second position measurement data are set so that the distortion of the entire mask obtained from the first position measurement data is equal to the distortion of the entire mask obtained from the second position measurement data. Can be calculated to calculate the deformation amount of the pattern position of the mask.

  In addition, the first position measurement data and the second position measurement data can be acquired for the same batch exposure small region among the plurality of batch exposure small regions.

  In this case, a first mask deformation amount is obtained from the first position measurement data acquired for the same batch exposure subregion, and a second value is obtained from the second position measurement data acquired for the same batch exposure subregion. The amount of change in the pattern position of the mask can be calculated by obtaining the amount of deformation of the mask and associating the amount of deformation of the first mask and the amount of deformation of the second mask.

  On the other hand, according to another aspect of the present invention, distortion data relating to a variation of the pattern position of the mask calculated by the above-described mask inspection method for charged particle beam exposure is given to an exposure apparatus, and the pattern surface and the semiconductor An exposure method is provided in which exposure is performed while correcting the relative position to the substrate based on the distortion data.

    According to the present invention, it is possible to accurately inspect mask distortion in a state of being held in an exposure apparatus using an existing coordinate measuring apparatus. By providing this data to the exposure apparatus, an exposure method with excellent accuracy and throughput can be provided, and the industrial merit is great.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1 and 2 are schematic views for explaining an inspection method of a charged particle beam exposure mask (hereinafter simply referred to as “mask”) according to a specific example of the present invention.

  First, in FIG. 1, a charged particle beam exposure mask 20 to be inspected is fixed to a holding unit 22 of an existing coordinate measuring apparatus by, for example, a vacuum chuck. An electrostatic chuck may be used as a method for fixing the mask, but it should be taken into consideration that scratches are likely to occur in the atmosphere. The holding unit 22 is fixed on the XY stage 24. In FIG. 1, the pattern surface 20 a of the mask 20 faces vertically upward, and the support side of the support substrate portion 19 of the mask 20 is attracted to the holding portion 22. In a normal exposure apparatus, the pattern surface is vertically downward, and the pattern surface is adsorbed by the holding unit. Therefore, the masks in this measurement are in the opposite state.

  Next, the measurement procedure will be briefly described. Light emitted from a light source (not shown) such as a laser is focused on the pattern surface 20a of the mask by the lens 32. The reflected light from the pattern is reflected by the reflecting plate 34 (for example, a half mirror) and enters the detector 30. For example, a CCD camera or a photodiode is used as the detector.

Here, an example of a mask inspected by this inspection method will be described.
FIG. 3 is a schematic plan view of the charged particle beam exposure mask 20 as viewed from the pattern surface 20a. FIG. 4 is a perspective view of the mask 20 as viewed from the support side, and FIG. 5 is a cross-sectional view at a place where a pattern is arranged.

  As shown in FIG. 3, the position mark 10 is provided on the minor strut 18. Further, position marks 10 are also provided in some subfields (collective exposure small areas). On the other hand, the alignment mark 14 is provided in most of the outermost subfield and a plurality of inner subfields. However, since a circuit pattern is mainly provided on the inner side, it is difficult to allocate a large area for the alignment mark.

  As illustrated in FIGS. 4 and 5, the membrane film constituting the subfield 16 is a silicon thin film having a thickness of 0.1 to several micrometers, for example, and has insufficient strength. In order to reinforce this, a support body (that is, a beam portion) made of, for example, silicon is provided, and this is called a minor strut 18. This thickness is, for example, about 0.7 millimeters.

  Usually, in the exposure apparatus, the wafer is arranged vertically downward and the mask is arranged vertically upward. After the electron beam passes through the pattern surface 20a, the charged minor strut 18 causes beam deflection, and the image is distorted on the wafer. Therefore, it is desirable that the pattern surface 20a be disposed on the wafer side. In a normal exposure apparatus, since the wafer is disposed below, the pattern surface 20a is electrostatically attracted to the holding portion so as to face vertically downward.

  That is, in FIG. 1, the position mark position and the alignment mark position are measured by the coordinate measuring device 40 with the pattern surface 20a facing upward as opposed to in the exposure apparatus. The position mark on the minor strut 18 can be measured only on the pattern surface 20a side as shown in FIG. Further, since the position mark placed on the minor strut is not an area transferred onto the wafer by exposure, it can be placed between all subfields. On the other hand, the position of the alignment mark 14 arranged in the subfield can be measured by the coordinate measuring device 40 from above or below. The position can also be measured in the exposure apparatus by irradiating the reference mark with an electron beam. However, the index in this case is slow.

  In FIG. 1, the support side of the support substrate portion 19 of the mask 20 is attracted to the holding portion 22. Although this state is opposite to that of the exposure apparatus, the point that an existing measuring apparatus can be used is a great merit. Further, since there is a holding member that can hold the mask holding portion 22 with good reproducibility, the reproducibility in measurement is good. The position and number of marks to be measured can be selected according to the expected position accuracy of the mask. If the predicted position accuracy is high, the number of measurement marks can be reduced.

  Next, as illustrated in FIG. 2, the alignment mark position is measured from above with an existing coordinate measuring apparatus in a state where the pattern surface 20 a faces vertically downward and is attracted to the holding unit 22 on the pattern surface side. That is, the mask is arranged upside down from FIG. 2, the same elements as those shown in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted. In the measurement method shown in FIG. 2, the direction of gravity on the suction surface and the mask is the same as that of the exposure apparatus. As described above, the position mark 10 on the minor strut 18 cannot be detected. Although the position of the alignment mark 14 can be measured by the exposure apparatus, the coordinate measuring apparatus 40 can measure the position with higher accuracy and in a shorter time. Therefore, if the position of more alignment marks 14 is measured by the method of FIG. 2, the throughput in the exposure process can be improved.

  In particular, if the alignment marks 14 are not formed only in the outermost subfield of the mask but are also formed in the gaps of the circuit pattern as illustrated in FIG. Since it increases, it becomes more effective. In general, when a circuit pattern is formed on a semiconductor substrate, there is a scribe region that becomes a margin for cutting a chip (ie, a semiconductor element) from the semiconductor substrate (wafer), and various marks that are not circuit patterns are present in the scribe region. Since it is formed, it is sufficiently possible to form the alignment mark 14 here, that is, to form the alignment mark 14 in the subfield. Heretofore, a specific example has been described in which the alignment mark 14 is employed as a mark formed in the subfield 16 (on the membrane film), but not only the alignment mark 14 but also the position mark 10 or the like may be formed. .

  Since the mask holding state in FIG. 2 is the same as the actual exposure apparatus, if there is a coordinate measuring device that can irradiate light from below in this state, mask distortion (deformation due to holding, deflection due to gravity, distortion of the mask itself) Etc.) should be measured very accurately. However, in order to realize this, the optical system (consisting of a light source, a lens 32, a reflecting plate 34, a detector 30 and the like) and a drive system for the XY stage 24 must be arranged below the object to be measured. Design is extremely difficult. Therefore, such a measuring apparatus has not been put into practical use.

  With the configuration illustrated in FIGS. 1 and 2, each of the alignment marks 14 (position marks 10 can be provided) in the sub-field 16 in the same mask is measured from the top and bottom to measure each of the measurement marks from the pattern surface 20 a. The correlation between the detailed position of the subfield and the distortion (deformation amount) of the entire mask estimated from the coordinates of the alignment mark 14 measured from the support surface becomes clear.

  FIG. 6 is a flowchart showing the steps from obtaining the distortion of each subfield by the above inspection procedure to inputting this data to the exposure apparatus. Hereinafter, step 51 to step 55 will be described with reference to FIG.

1. Step 51 (S51)
The position of the position mark 10 and the alignment mark 14 is measured using the coordinate measuring device 40 in a state where the gravity direction and the suction surface are different from those of the exposure device (reverse direction). As a result, mask deformation data 1 is obtained.

2. Step 52 (S52)
The position of the alignment mark 14 is measured using the coordinate measuring device 40 in the same state as the exposure device in the direction of gravity and the suction surface. In this state, the deformation caused by holding the mask and the influence of gravity are included. As a result, mask deformation data 2 is obtained.
3. Step 53 (S53)
In S51 and S52, the entire mask distortion is calculated from the measurement position (plural places) of the same subfield.

4). Step 54 (S54)
Individual subfield coordinates are obtained from the position mark measurement values measured in S51 so that the total mask distortion in S51 is equal to the total mask distortion in S52.

5. Step 55 (S55)
The obtained subfield coordinates represent mask distortion, and this data is given to the exposure apparatus to perform correction at the time of exposure.

Next, a method for obtaining mask distortion data will be specifically described.
FIG. 7 shows the mask deformation data 1 measured in step S51. This data is obtained by measuring the position mark position and alignment mark position, and the position of all subfields can be measured as long as the measurement time is allowed.

  FIG. 8 shows the mask deformation data 2 measured in step S52. In step S53, the entire mask distortion is calculated for both the mask deformation data 1 and 2. Here, this distortion is expressed by a cubic function. When this mask is held in the exposure apparatus, the gravitational direction and the suction surface are the same as the state in which the mask deformation data 2 is measured. Therefore, the overall distortion of this mask deformation data 2 is the state held in the exposure apparatus. It is thought to reflect. However, since only marks formed in the subfield can be measured, the positions of all the subfields are unknown.

Therefore, the mask deformation data 1 and the mask deformation data 2 are divided into an overall distortion expressed by a cubic function and a residue from the function. Then, the total distortion (cubic function) of the mask deformation data 2 and the residue of the mask deformation data 1 are added to generate new mask deformation data. This process corresponds to step S54.
FIG. 9 illustrates the new mask deformation data obtained in this way.

In the mask inspection method, an existing coordinate measuring apparatus can be used, and distortion can be measured more accurately while being held in an actual exposure apparatus.
By providing the exposure apparatus with the distortion data obtained by this inspection method, the throughput can be improved by measuring as few marks as possible in the alignment mark detection by the exposure apparatus. Further, by using the mask distortion in step 55, the mask distortion can be corrected with high accuracy without detecting the alignment mark for a long time in the exposure apparatus.

The embodiments of the present invention have been described with reference to specific examples. However, the present invention is not limited to these specific examples.
That is, even if a person skilled in the art has changed the design of each step constituting the mask inspection method and the exposure method of the present invention and the apparatus, mask, wafer, etc. used therefor, it has the gist of the present invention. If any, they are included within the scope of the present invention.

It is a schematic diagram showing the mask inspection method concerning the example of this invention. It is a schematic diagram showing the mask inspection method concerning the example of this invention. It is a schematic plan view which shows an example of the pattern surface of the mask for charged particle beam exposure. It is the perspective view seen from the support body side which shows an example of the mask for charged particle beam exposure. It is a schematic cross section which shows an example of the mask for charged particle beam exposure. It is a flowchart showing the inspection method concerning the specific example of this invention. The mask deformation data 1 measured in step S51 is illustrated. The mask deformation data 2 measured in step S52 is illustrated. The newly generated mask deformation data is illustrated.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Position mark 14 Alignment mark 16 Subfield 18 Minor strut 19 Support board part 20 Mask for charged particle beam exposure 20a Pattern surface 22 Holding part 24 XY stage 30 Detector 32 Lens 34 Reflector
1 Coordinate measuring device

Claims (5)

A pattern surface formed by dividing a circuit pattern to be exposed and transferred onto a semiconductor substrate into a plurality of small exposure small regions, a support layer for reinforcing the pattern surface, and a support provided around the support layer A method of inspecting a pattern position in a charged particle beam exposure mask having a substrate part,
The support substrate unit is held on the opposite side of the surface held by the exposure apparatus, and the mask is held in a state in which the direction of gravity is opposite to that of the mask in the exposure apparatus to perform position measurement. 1 position measurement data is acquired,
A second position measurement is performed by holding the surface of the support substrate portion held by the exposure apparatus and measuring the position while holding the mask in a state where the direction of gravity is the same as that of the mask in the exposure apparatus. Get the data,
An inspection method for a charged particle beam exposure mask, wherein a deformation amount of a pattern position of the mask is calculated using the first position measurement data and the second position measurement data.   The first and second position measurement data are related so that the distortion of the entire mask obtained from the first position measurement data is equal to the distortion of the entire mask obtained from the second position measurement data. 2. The charged particle beam exposure mask inspection method according to claim 1, wherein the deformation amount of the pattern position of the mask is calculated.   3. The first position measurement data and the second position measurement data are acquired for the same batch exposure subregion among the plurality of batch exposure subregions. Inspection method for charged particle beam exposure mask.   A first mask deformation amount is obtained from the first position measurement data acquired for the same batch exposure subregion, and a second mask deformation is obtained from the second position measurement data acquired for the same batch exposure subregion. 4. The charged particle beam exposure apparatus according to claim 3, wherein a change amount of the pattern position of the mask is calculated by obtaining an amount and correlating the first mask deformation amount and the second mask deformation amount. Mask inspection method. 2. Distortion data relating to a variation of the pattern position of the charged particle beam exposure mask calculated by the charged particle beam exposure mask inspection method according to claim 1 is given to an exposure apparatus, and the relative relationship between the pattern surface and the semiconductor substrate is determined. An exposure method comprising exposing while correcting the position based on the distortion data.