JPH04317317A - Apparatus and method for pattern transfer - Google Patents

Abstract

PURPOSE:To provide an improved throughput by use of a mask along with high accuracy in a transfer pattern with regard to a pattern transfer technique used with a charged particle beam through the mask. CONSTITUTION:In a secondary mask 10 used for a mask-type pattern transfer apparatus with a charged particle beam, a plurality of isolated patterns i1 and i2 are formed into part of a plurality of transfer patterns A-I, which constitute an opening pattern 10a. Then, an electron beam is transmitted through the isolated patterns i1 and i2 so that a sample for a second mask 10 can be aligned, and an operational compensation in an electron-optical system can be performed.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pattern transfer technique, and more particularly to a technique effective when applied to a pattern transfer technique in which a pattern is transferred by irradiation with a charged particle beam such as an electron beam.

0002

[Background Art] In the manufacturing process of semiconductor integrated circuit devices, an integrated circuit pattern is drawn on a photomask (reticle) or a semiconductor wafer using an electron beam or a laser beam.
Various microfabrication techniques for integrated circuit patterns using focused beams have been put into practical use, such as repairing defective parts of integrated circuit patterns using focused ion beams.

Among the above-mentioned focused beam processing techniques, the electron beam direct writing technique, in which an integrated circuit pattern is directly drawn (exposed) on the wafer by irradiating an electron beam onto a wafer coated with an electron beam-sensitive resist, is used to form an integrated circuit pattern on a photomask. This method has attracted particular attention in recent years because it can form finer integrated circuit patterns than conventional light exposure techniques that transfer integrated circuit patterns onto wafers.

[0004] In the above-mentioned focused beam processing technology, highly accurate microfabrication is achieved by controlling the focused beam by computer based on the design data of the integrated circuit and accurately aligning the beam and the sample. .

In addition, the semiconductor substrate on which the pattern is written has distortions and surface steps that occur during the repetition of many processes, and in response to this, it is necessary to correct the exposed pattern drawn by the electron beam. This is essential to maintain the overlay accuracy and dimensional accuracy of exposed figures.For this reason, the control computer applies prescribed corrections to the drawing data for each unit exposure area, and then The signal is sent to the control circuit.

Furthermore, in the exposure method using a charged particle beam, the throughput becomes a problem because the pattern is generally filled in using a very finely focused beam. Therefore, as a countermeasure to this problem, a technique for transferring a mask image in the same way as in the case of light exposure is available, for example, Press Journal Co., Ltd., June 20, 1999, "Semiconductor World", July 1990 issue, P170- It is described in documents such as P175. That is, by forming an aperture pattern of a specific shape in a small region of a mask by selectively transmitting a beam having a relatively large diameter, a relatively large pattern can be transferred in one irradiation.

[0007]

[Problems to be Solved by the Invention] The conventional mask image transfer technology using a charged particle beam as described above has been proposed as an effective means of improving throughput, but it has the following problems. Discovered by the present inventor.

In order to transfer a mask image using a charged particle beam, it is necessary to reduce alignment errors between the transfer mask and the workpiece. In particular, when applied to a semiconductor integrated circuit device, it is necessary to switch between multiple types of transfer masks for each process.

At this time, it is essential that alignment errors of the transfer mask can be easily corrected.

In particular, among alignment errors, the position of the mask,
Although the magnification can be corrected in the beam control system, there is a problem in that it is difficult to correct the rotation of the mask because the error cannot be easily measured.

Furthermore, pattern defects and adhering foreign matter on the transfer mask are transferred in the same way as with the optical mask and become defects in the semiconductor integrated circuit device, so there is a problem as to how to check them. Furthermore, when selecting and transferring from a plurality of masks, it is not possible to directly see the mask pattern, which causes mask selection errors, and eliminating this is an important issue.

[0012] An object of the present invention is to provide a pattern transfer technique that can both improve throughput by using a mask and improve pattern transfer accuracy in pattern transfer using a charged particle beam shaped by a mask. It's about providing.

Another object of the present invention is to provide a pattern transfer technique that allows accurate verification of a plurality of masks and opening patterns formed in the masks.

Still another object of the present invention is to provide a pattern transfer technique that enables quick replacement of multiple types of masks.

Still another object of the present invention is to provide a pattern transfer technique that can prevent errors caused by distortion of the vacuum load lock mechanism.

The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

[0017]

[Means for Solving the Problems] Among the inventions disclosed in this application, a brief overview of typical inventions will be as follows:
It is as follows.

That is, the pattern transfer method of the present invention is as follows:
A first mask and a second mask each having a first and second aperture pattern of a desired shape are interposed in order in the path of the charged particle beam from the beam source to the sample, and the charged particle beam is deflected by controlling the deflection of the charged particle beam. A pattern transfer method for irradiating a desired position on a sample with a charged particle beam formed by selecting a combination of a first aperture pattern and a second aperture pattern through which the particle beam passes, the charged particle beam on a second mask Alignment aperture patterns are formed in at least two locations within the deflection region of the sample, and a plurality of charged particle beams passing through each of these alignment aperture patterns target the sample or a specific location on the stage on which the sample is mounted. By scanning, the relative positions of the plurality of charged particle beams are detected, and at least one of the rotation error and the magnification error of the second mask is corrected.

The pattern transfer device of the present invention includes a beam source that emits a charged particle beam to a sample, and a pattern transfer device that is interposed in the path of the charged particle beam from the beam source to the sample, each of which has a desired shape. a beam control means for controlling the path and magnification of a charged particle beam passing through the first and second masks and reaching a sample; A pattern transfer device that irradiates a sample with a charged particle beam in a desired shape by appropriately controlling a combination of first and second aperture patterns through which the beam passes, the device comprising: a second mask relative to a beam control means; The second mask has at least two alignment opening patterns in addition to the second opening pattern.

The pattern transfer device of the present invention includes a beam source that emits a charged particle beam to a sample, and a pattern transfer device that is interposed in the path of the charged particle beam from the beam source to the sample, each of which has a desired shape. a beam control means for controlling the path and magnification of a charged particle beam passing through the first and second masks and reaching a sample; A pattern transfer device that irradiates a sample with a charged particle beam in a desired shape by appropriately controlling the combination of first and second aperture patterns through which the beam passes, and in which a charged particle beam is provided near the second mask. The device includes a charged particle detector that detects charged particles generated when the charged particle beam passes through the second mask or when the second mask is scanned by the charged particle beam.

The pattern transfer device of the present invention uses previously known reference data or the design of the second aperture pattern to determine the characteristics of the charged particles detected by the charged particle detector for each second mask or for each second aperture pattern. The second mask or the second opening pattern is verified by comparing it with the data.

The pattern transfer apparatus of the present invention includes a first vacuum load-lock chamber for exchanging the second mask in a part of the lens barrel to which the second mask is attached.

The pattern transfer device of the present invention has a part of the second vacuum load-lock chamber in which samples are exchanged without impairing the degree of vacuum in the pattern transfer device. It is equipped with a deformation absorption mechanism that absorbs deformation.

[0024]

[Operation] According to the pattern transfer technology of the present invention described above,
Within the beam deflection area, at least two isolated positioning aperture patterns can be used to correct the transfer position of the aperture pattern on the mask onto the sample, which eliminates magnification and rotation errors. Therefore, pattern transfer can be performed with high precision by irradiation with a charged particle beam that selectively passes through the opening pattern of the second mask. That is, it is possible to achieve both improvement in throughput and improvement in pattern transfer accuracy using the mask method.

[0025] Also, based on the state of generation of charged particles from the second mask when the charged particle beam passes through the second mask, the individual second masks, the aperture patterns, and the shapes can be confirmed. , etc. can be verified accurately.

Furthermore, by exchanging the second mask through the first vacuum load-lock chamber provided in the lens barrel, the mask can be quickly exchanged without damaging the degree of vacuum within the lens barrel. This is effective in improving throughput in the transfer process.

In addition, the deformation absorbing mechanism provided in the second vacuum load-lock chamber in which samples are exchanged prevents distortions caused by changes in atmospheric pressure in the second vacuum load-lock chamber from affecting the pattern transfer device, such as the lens barrel. This prevents the spread to the main body side, and improves pattern transfer accuracy.

[0028]

Embodiment 1 FIG. 1 is a perspective view showing the main parts of a pattern transfer device which is an embodiment of the present invention. A semiconductor wafer 1, which is a sample, is mounted on an X
It is mounted on stage 2, which consists of the Y stage and others. The surface of the semiconductor wafer 1 is coated with, for example, an electron beam sensitive resist. An electron gun 3 is provided above the stage 2, and emits an electron beam 4 toward the semiconductor wafer 1.
is configured so that it is emitted.

The path of the electron beam 4 from the electron gun 3 to the stage 2 includes a blanking electrode 5 for controlling whether or not the electron beam 4 is emitted, an irradiation lens 6 for converging the electron beam 4, and the irradiation lens 6. A first mask 7 formed with, for example, a rectangular aperture pattern 7a through which the electron beam 4 focused by passes, a deflector 8, a beam shaping lens 9,
A second mask 10 in which a plurality of desired aperture patterns 10a as described below are formed, a reduction lens 11 that reduces the cross-sectional shape of the electron beam 4 that has passed through the second mask 10, and a direction around the optical axis of the electron beam 4. An electron optical system consisting of a rotating lens 11a that performs rotation correction, etc., a projection lens 12 that performs focusing of the electron beam 4 on the semiconductor wafer 1, a position deflector 13 that controls the irradiation position of the electron beam 4 on the semiconductor wafer 1, etc. is provided.

FIG. 2 is an explanatory diagram showing an example of the structure and function of the second mask 10.

As shown in FIG. 2(a), the second mask 10 has a range in which the electron beam 4 can be deflected by the deflector 8 located between the second mask 10 and the preceding first mask 7. A plurality of aperture patterns 10a having a size that can fit within the size of the aperture pattern 10a are arranged in a grid pattern, and each aperture pattern 10a includes, for example, a plurality of independent types of transfer patterns A to I.

In this case, a pair of isolated patterns i1 and i2 that can be simultaneously selected by the electron beam 4 that has passed through the first mask 7 is provided in some of the transfer patterns A to I, for example, at both corners in the diagonal direction. is formed.

When each of the transfer patterns A to I is collectively transferred onto the semiconductor wafer 1, the positional deviation of the second mask 10 is corrected by appropriately using these isolated patterns i1 and i2.

That is, using two isolated patterns i1 and i2 that can be selected simultaneously by the electron beam 4,
Correction can be made by measuring in advance the relationship between the excitation current and magnification of the reduction lens 11 that constitutes the electron optical system after the second mask 10, and the relationship between the rotary lens 11a and the rotation angle. However, in the case of isolated patterns i1 and i2 provided within a region that can be selected at once by the electron beam 4,
Since the distance between them is small, it is necessary to increase the detection accuracy of the beam position. Therefore, in the case of this embodiment, a Faraday cup portion (not shown) having a knife edge provided on the stage 2 on which the semiconductor wafer is mounted is scanned multiple times in both the X-axis and Y-axis directions to determine the beam position. Improve detection conditions. The method of detecting reflected electrons by scanning a step mark on a semiconductor wafer has poor detection accuracy.

It is also conceivable to form isolated patterns c and g, which have a larger distance between them than the isolated patterns i1 and i2, at both corners of the opening pattern 10a. However, in this case, individual isolated patterns c and g cannot be selected at once, so it is necessary to adjust the beam deflection to select both individually and the beam swing back after selection, making the correction work slightly complicated. Become.

FIG. 2(b) schematically shows the detection signal waveforms for each of the X-direction scan and Y-direction scan when the Faraday cup portion (not shown) is scanned by the electron beam 4 that has passed through the isolated patterns i1 and i2. This is shown in . The distances lx and ly are determined from the peak position of the detected waveform in each scanning direction, and the magnification error M and rotational error of the transfer patterns A to I can be measured using equations (1) and (2), and based on these measured values. 2nd mask 1
The relationship between the excitation current and magnification of the reduction lens 11 constituting the electron optical system after 0 is corrected, the relationship between the rotary lens 11a and the rotation angle, and the scanning direction and scanning width of the electron beam 4 are corrected. In addition, in the case of this embodiment, the isolated patterns i1,
Since the positional relationship of i2 is set in the diagonal direction of the transfer patterns A to I, when two electron beams 4 that have passed through the individual isolated patterns i1 and i2 are used, the XY two-axis scanning of the electron beam 4 is It becomes easier to measure.

An example of the operation of the pattern transfer device of this embodiment will be explained below.

First, the mask drive mechanism 14 causes the second
A target opening pattern 10a in the mask 10 is positioned on the optical axis of the electron optical system.

Next, the electron beam 4 that has passed through the first mask 7 is deflected by the deflector 8 to an isolated pattern formed in one of the transfer patterns A to I (I in this case) included in the aperture pattern 10a. i1 and i2, pass through the isolated patterns i1 and i2, and irradiate the stage 2 side as two electron beams 4. And the stage 2
By scanning a Faraday cup (not shown) provided in the image forming apparatus, transfer errors such as rotational deviations and magnification errors of the isolated patterns i1 and i2 around the optical axis are measured and stored.

After that, the opening pattern 7a of the first mask 7 is
The electron beam 4 that has passed through is guided by the deflector 8 to the target transfer patterns A to I of the aperture pattern 10a to shape the cross-sectional shape of the electron beam 4, and the shaped electron beam 4 is subjected to the above-mentioned measurement. The reduction lens 11 and the rotary lens 11 whose operation is corrected by the correction value obtained by
a. By controlling via the projection lens 12, position deflector 13, etc., the transferred patterns A to 1 are placed at a desired position on the semiconductor wafer 1 placed on the stage 2 in a desired size.
The electron beam is irradiated in the shape of I to expose the electron beam resist on the surface of the semiconductor wafer 1.

As described above, according to the pattern transfer apparatus of this embodiment, the target transfer patterns A to I are collectively formed by the irradiation of the electron beam 4 formed by the combination of the first mask 7 and the second mask 10. It is possible to achieve both an improvement in throughput due to transfer and an improvement in transfer accuracy.

[0042]

Embodiment 2 FIG. 3 is an explanatory diagram showing the main part of the structure of a pattern transfer device according to another embodiment of the present invention. In the case of this second embodiment, the beam shaping lens 9 and the second mask 10
A sensor 20 for detecting the amount of charged particles such as reflected electrons and secondary electrons generated when the second mask 10 is scanned by the electron beam 4 is arranged between the second mask 10 and the second mask 10 .

The output of the sensor 20 becomes one input of a comparator 23 via an amplifier 21 and a changeover switch 22. Further, at the other input of the comparator 23, a memory 24 for storing measurement data via the changeover switch 22 is connected.
They are connected via a changeover switch 25. Furthermore, a memory 26 in which design data 27 of transfer patterns A to I in the second mask 10 is stored is also connected to the changeover switch 25 .

Then, the electron beam 4 passing through the first mask 7 is scanned over the aperture pattern 10a of the second mask 10 under the control of the deflector 8 and beam shaping lens 9, and the charged particles obtained at this time are The detection signal is stored in the memory 24, and when later selecting a part of the plurality of opening patterns 10a on the second mask 10, the selected one is compared with the detection signal held in the memory 24. The shapes and types of transfer patterns A to I are verified. In addition, the detection signal during the transfer operation and the second mask 1
It is also possible to compare the design data 27 of transfer patterns A to I of 0. However, since the detection signal of the actual pattern of the second mask 10 and the signal obtained from the design data differ, for example, in the roundness of the pattern corner, data processing corresponding to this difference is performed as necessary.

In this way, in the case of the second embodiment, the second
The shape and type of the aperture pattern 10a of the mask 10 can be verified, and for example, transfer errors due to foreign matter adhering to the second mask 10, incorrect loading of the second mask 10, and incorrect selection of the aperture pattern 10a can be verified. It is possible to reliably prevent mistakes in transcription work due to such reasons. This means that many second
This is particularly effective in maintaining and improving the reliability of pattern transfer work in mass production processes using the mask 10.

[0046]

Embodiment 3 FIG. 4 is a schematic cross-sectional view showing an example of the configuration of a pattern transfer device according to another embodiment of the present invention.

A lens barrel 40 housing an electron optical system having a structure as illustrated in FIG. 1 in the first embodiment described above is connected to a housing 30 housing a stage 2 consisting of an X-Y table or the like. .

The interiors of the housing 30 and the lens barrel 40 are evacuated to a desired degree of vacuum by a vacuum pump 31. In addition, a part of the housing 30 is provided with a stage drive unit 32 that drives the stage 2, a laser length measuring device 33 that precisely measures the amount of displacement of the stage 2, and the like. The structure is such that any part of the semiconductor wafer 1 can be positioned on the optical axis of the electron optical system provided in the lens barrel 40.

Further, a part of the casing 30 is provided with a well-known vacuum load that allows the semiconductor wafer 1 placed on the stage 2 to be taken in and out of the outside without impairing the degree of vacuum within the casing 30. A lock chamber 34 is connected via a gate valve 35.

In this case, a deformation absorbing mechanism 36 made of, for example, a bellows is provided on a part of the wall surface of the vacuum load-lock chamber 34. This prevents the vacuum load-lock chamber 34 from being generated due to changes in internal pressure when the vacuum load-lock chamber 34 is evacuated or returned to atmospheric pressure.
The mechanical deformation and distortion of the deformation absorption mechanism 36 itself is absorbed by the deformation of the deformation absorbing mechanism 36 itself, and serves to prevent the mechanical deformation and distortion from spreading to the housing 30 and lens barrel 40 side.

Furthermore, in the case of the present embodiment, a vacuum load lock chamber 42 is connected to the loading portion of the lens barrel 40 for the second mask 10 via a gate valve 41, and the loading area of the lens barrel 40 and the housing 30 is without compromising the internal vacuum.
The structure is such that the mask 10 can be replaced at any time.

In this way, in the case of the third embodiment, the pattern transfer operation using the electron optical system provided in the lens barrel 40 and the loading and unloading of the semiconductor wafer 1 through the vacuum load lock chamber 34 are performed simultaneously. In this case, distortion due to internal pressure fluctuations in the vacuum load-lock chamber 34 does not spread to the housing 30 or the lens barrel 40, and the electron beam 4 controlled by the electron optical system can be used to precisely target the semiconductor wafer 1. can perform pattern transfer work.

In addition, the second mask 10 can be easily and quickly replaced via the vacuum load lock chamber 42 provided in the lens barrel 40 without damaging the degree of vacuum inside the lens barrel 40 or the housing 30. This improves the operating rate of the pattern transfer device.

[0054] Although the invention made by the present inventor has been specifically explained based on examples, the present invention is not limited to the above-mentioned examples, and can be modified in various ways without departing from the gist thereof. Needless to say.

For example, the structure of the electron optical system is not limited to that exemplified in each of the above-described embodiments, and other structures may be used.

As an example of pattern transfer, the case where it is applied to the exposure process of semiconductor wafers has been described, but it goes without saying that it may be applied to general processing techniques that use a charged particle beam shaped by a mask.

[0057]

[Effects of the Invention] Among the inventions disclosed in this application, the effects obtained by the typical inventions are briefly explained as follows.
It is as follows.

That is, according to the pattern transfer method and apparatus of the present invention, in pattern transfer using a charged particle beam using a mask method, it is possible to simultaneously improve throughput by using a mask and improve pattern transfer accuracy. You can get the effect that you can.

Furthermore, according to the pattern transfer method and apparatus of the present invention, it is possible to accurately verify a plurality of masks and the opening patterns formed in the masks.

Further, according to the pattern transfer apparatus of the present invention, it is possible to easily and quickly replace a plurality of types of masks.

Further, according to the pattern transfer device of the present invention, it is possible to prevent errors in the transferred pattern due to distortion in the vacuum load lock mechanism spreading to the housing, lens barrel, etc. It will be done.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing a main part of a pattern transfer device which is an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing an example of the configuration and operation of a mask used in a pattern transfer device that is an embodiment of the present invention.

FIG. 3 is an explanatory diagram showing a main part of the configuration of a pattern transfer device according to another embodiment of the present invention.

FIG. 4 is a schematic cross-sectional view showing an example of the configuration of a pattern transfer device according to another embodiment of the present invention.

[Explanation of symbols]

i1 Isolated pattern i2 Isolated pattern c Isolated pattern g Isolated pattern 1 Semiconductor wafer 2 Stage 3 Electron gun 4 Electron beam 5 Blanking electrode 6 Irradiation lens 7 First mask 7a Aperture pattern 8 Deflector 9 Beam shaping lens 10 Second mask 10a Aperture Pattern 11 Reduction lens 11a Rotating lens 12 Projection lens 13 Position deflector 14 Mask drive mechanism 20 Sensor 21 Amplifier 22 Changeover switch 23 Comparator 24 Memory 25 Changeover switch 26 Memory 27 Design data 30 Housing 31 Vacuum pump 32 Stage drive unit 33 Laser Length measuring device 34 Vacuum load lock chamber (second vacuum load lock chamber) 35 Gate valve 36 Deformation absorption mechanism 40 Lens barrel 41 Gate valve

Claims (6)

[Claims] 1. A first mask and a second mask each having a first and second opening pattern of a desired shape,
shaping by selecting a combination of the first aperture pattern and the second aperture pattern through which the charged particle beam passes by sequentially intervening in the path of the charged particle beam from the beam source to the sample and controlling the deflection of the charged particle beam; A pattern transfer method for irradiating the charged particle beam onto a desired position of the sample, the method comprising: forming alignment aperture patterns at at least two locations on the second mask within a deflection area of the charged particle beam; , the relative positions of the plurality of charged particle beams are determined by scanning the sample or a specific part on the stage on which the sample is mounted with the plurality of charged particle beams that have passed through each of these positioning aperture patterns. A pattern transfer method comprising detecting and correcting at least one of a rotation error and a magnification error of the second mask. 2. A beam source that emits a charged particle beam toward a sample; and a first and second beam source disposed in a path of the charged particle beam from the beam source to the sample, each having a desired shape; comprising first and second masks having aperture patterns, and beam control means for controlling the path and magnification of the charged particle beam that passes through the first and second masks and reaches the sample; A pattern transfer device that irradiates the sample with the charged particle beam in a desired shape by appropriately controlling a combination of the first and second aperture patterns through which the charged particle beam passes,
a mask moving mechanism for controlling a relative position of the second mask with respect to the beam control means; the second mask has at least two alignment aperture patterns in addition to the second aperture pattern; A pattern transfer device characterized by: 3. A beam source that emits a charged particle beam toward a sample; and a first and second beam source disposed in a path of the charged particle beam from the beam source to the sample, each having a desired shape; comprising first and second masks having aperture patterns, and beam control means for controlling the path and magnification of the charged particle beam that passes through the first and second masks and reaches the sample; A pattern transfer device that irradiates the sample with the charged particle beam in a desired shape by appropriately controlling a combination of the first and second aperture patterns through which the charged particle beam passes,
A charged particle detector is disposed near the second mask to detect charged particles generated when the charged particle beam passes through the second mask or when the second mask is scanned by the charged particle beam. A pattern transfer device characterized by: 4. In the charged particle detector, the second
By comparing the characteristics of the charged particles detected for each mask or each second aperture pattern with pre-known reference data or design data of the second aperture pattern, the second mask or the second aperture pattern is detected. 4. The pattern transfer apparatus according to claim 3, wherein the pattern transfer apparatus performs pattern verification. 5. A first vacuum load lock chamber for exchanging the second mask is provided in a part of the lens barrel to which the second mask is attached.
Or the pattern transfer device according to 4. 6. A part of the second vacuum load-lock chamber, in which the sample is exchanged without impairing the degree of vacuum in the pattern transfer device, absorbs deformation due to pressure fluctuations in the second vacuum load-lock chamber. 6. The pattern transfer device according to claim 2, further comprising a deformation absorbing mechanism.