JP3325695B2 - Charged particle beam exposure method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charged particle beam exposure method using a so-called charged particle beam such as an ion beam or an electron beam, and more particularly to a charged particle beam using a transmission mask plate (hereinafter referred to as a block mask). BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charged particle beam exposure method in which the time required for cleaning is shortened by limiting a place where a charge-up is caused in an exposure apparatus, a decrease in throughput of the apparatus is suppressed, and a pattern accuracy is improved.

In recent years, as the density of integrated circuits has increased, photolithography, which has been the mainstream for forming fine patterns for many years, has been replaced by exposure using a charged particle beam, for example, an electron beam or ion beam, or a new exposure method using X-rays. Are being studied and realized.

[0003] Among them, in the electron beam exposure for forming a pattern using an electron beam, since the beam itself can be reduced to several [数], a fine pattern of 1 [μm] or less can be formed. Has a great feature.

However, since electron beam exposure is a so-called "one-stroke" drawing method, as the pattern becomes finer, it must be exposed with a smaller beam, and the exposure time becomes enormously long. To solve this problem, a block exposure method has been devised.

[0005]

2. Description of the Related Art First, a block exposure method will be described. FIG. 5 is a configuration diagram of a general charged particle beam exposure apparatus capable of performing exposure by a block exposure method.

In FIG. 1, the charged particle beam exposure apparatus is divided into an exposure unit 10 and a control unit 50. The exposure unit 10
Cathode electrode 11, grid electrode 12, and anode 13
, A first slit 15 for shaping a charged particle beam (hereinafter abbreviated as a beam) into, for example, a rectangular shape, a first electron lens 16 for converging the shaped beam, and a deflection. A slit deflector 17 for deflecting a position at which the beam shaped according to the signal HS ₁ is irradiated onto the block mask 20, second and third lenses 18 and 19 provided opposite to each other, and a block mask 20 which is movably mounted in the horizontal direction between the third lens, the second and third lens according to each position information PS ₁ ~PS ₄ are arranged in the vertical direction of the block mask 20 18 And 19, which deflects the beam between the two and selects one of a plurality of transmission holes on the block mask 20.
To a fourth mask deflector 21 to 24, a blanking 25 for blocking or passing a beam according to a blanking signal, a fourth lens 26, and an aperture 27.
And a refocus coil 28, a fifth lens 29,
The dynamic focus coil 30, a dynamic stigmatic coil 31, the lens 32 of the sixth, the main differential coils 33 to the beam positioning on the wafer in accordance with an exposure position determination signals S ₂ and S ₃ and sub-deflector 34
And a stage 35 on which a wafer is mounted and movable in the XY directions, and first to fourth alignment coils.

On the other hand, the control unit 50 includes a storage medium 51 storing design data of the position of the integrated circuit, a CPU 52 for controlling the entire beam, and, for example, drawing information taken by the CPU 52 and a wafer W on which the pattern is to be drawn. An interface 53 for transferring various information such as the above-described drawing position information and mask information of the block mask 20, a data memory 54 for storing the drawing pattern information and mask information transferred from the interface 53, and the drawing pattern information and mask information For example, one of the transmission holes of the block mask 20 is designated, mask irradiation position data PS _{1 to} PS ₄ indicating the position of the designated transmission hole on the block mask 20 are generated, and the pattern is exposed. the wafer exposure position data S ₃ indicating the position on the wafer W to be generated,且A designating unit for performing various processes including a process of calculating a correction value H according to a shape difference between a pattern shape to be drawn and a designated transmission hole shape, a holding unit, a calculating unit,
And a pattern generation unit 55 as an output unit, and a correction value H
Amplifier unit for generating a correction deflection signals HS ₁ from (DAC /
AMP) 56, a mask moving mechanism 58 for moving the block mask 20 as necessary, and a system lock and a blanking clock that receive the exposure time / exposure wait time from the pattern generation unit 55 and operate the entire exposure apparatus. a clock control circuit 59 for generating a blanking control circuit 60 for generating a blanking timing in response to an output of the clock control circuit 59, a blanking signal S _B
(DAC / AMP) 61 that generates the main differential deflection information based on the exposure start / end information transferred from the interface 53 to the data memory 54 via the pattern generator. Also, it instructs the stage control unit to move to a desired stage position, controls the stage correction unit to correct the difference between the stage movement position and the main differential deflection, and instructs the clock control unit. , A sequence controller 62 that controls the general sequence of exposure processing, such as instructing generation / stop of a pattern, and a data memory 54.
Differential deflection signal S based on the main differential deflection information from
2. A deflection control circuit 63 that generates
And an amplifier unit (DAC / AMP) for generating exposure position determination signals S2 and S3 based on the output from the deflection control circuit 63.
64 and 65, a stage control mechanism 66 for moving a stage as necessary, a laser interferometer 67 for detecting a stage position, a main differential deflection amount from a deflection control circuit, and a stage movement position from a stage control unit. received,
Stage correction unit 68 for correcting the difference from the main differential deflection
And

[0008] The charged particle beam exposure apparatus having such a configuration operates as follows. First, the beam emitted from the electron gun is shaped into a rectangular shape by the first slit 15, then focused by the first and second lenses 16 and 18, and irradiated onto the block mask 20.

The deflection of the block mask 20 within a relatively large range (within about 5 mm) is performed by the first to fourth mask deflectors 21 to 24.
4 after a relatively small range of deflections (about 500
[Μm] is performed by the slit deflector 17.
In the case of variable rectangular exposure, the slit deflector 1
7 to shape into an arbitrary shape size (for example, an arbitrary rectangular size of 3 [μm □] or less).

The beam that has passed through the block mask 20 is
It passes through blanking 25. Then, the image is reduced by the fourth lens 26, and thereafter, 100
It is deflected in a small deflection area of about [μm]. The sub-deflector deflection area is 2 [m
[m].

The data to be exposed is read from the storage medium 51 by the CPU 52 and stored in the data memory 54. When exposure is started by a signal to the sequence controller 62, first, the stored main differential deflection position is sent to the deflection control circuit 63 to output deflection amount data S2, which is output to the main differential coil 33 via the DAC / AMP 64. Is done.

After the output value is stabilized, the sequence controller instructs the clock control circuit 59 to generate a system clock. As a result, the data memory 54 sends the stored pattern data to the pattern generation unit. Send out.

The pattern generator 55 generates the read pattern data. When this shot data is specifically shown, a signal PS indicating the beam irradiation position on the mask
_{1 to} PS ₄ , a signal H indicating the amount of deflection of the beam irradiation position on the mask, a signal S ₃ for deflecting the beam shaped by transmitting the beam through these masks to a desired position on the wafer, a shot time Data and shot waiting time data indicating how long it is necessary to wait until the electrostatic deflector / electromagnetic deflector settles when these signals are applied.

After these signals are generated by the pattern generator 55, they enter the pattern corrector. The pattern correction unit corrects wafer rotation and the like that occur when the exposure sample W is set on the stage 35. The output signals for shot generation are input to DACs, respectively, and converted into analog signals.
Is applied to the electrodes / coils.

In the charged particle beam exposure apparatus having such a configuration and operation, as a method of shaping a beam using the block pattern on the block mask 20, the entire surface of the block pattern formed on the block mask 20 is formed. Irradiation method and the block pattern 20
There is a method of irradiating a part of the image. In particular, when performing variable rectangular exposure with a block exposure apparatus, the latter method will be adopted.

Usually, in the exposure of the repetitive portion, a beam is formed by irradiating the entire block pattern, and in the exposure of the peripheral portion, both beam forming methods are performed in the same manner. Used for exposure of the wafer W.

In a standby state in which exposure, adjustment, or exposure using a variable beam is not performed (a transition state between the adjustment state and the exposure state, which corresponds to wafer exchange, etc.), the beam irradiated to the block mask 20 is changed. The amount increases, and inevitably the amount of reflected electrons also increases. If the second mask deflector 22 closest to the block mask 20 is contaminated, the reflected electrons are accumulated and cause charge-up drift.

If there is dirt on the exit side of the block mask 20, electrons are accumulated due to the scattering of the beam transmitted through the block mask 20, causing charge-up drift. When such a charge-up drift occurs, the lens barrel needs to be cleaned.

[0019]

In the conventional charged particle beam exposure apparatus, all portions where the inside of the lens barrel is likely to be contaminated are cleaned. This is because it was not possible to limit the dirty portion, and it was necessary to clean even unnecessary portions. As a result, there was a problem that the time for stopping the exposure was prolonged and the throughput of the apparatus was reduced. Was.

The present invention solves the above problems,
It is an object of the present invention to provide a charged particle beam exposure method capable of shortening a time required for cleaning by limiting a place where charge-up is caused, suppressing a decrease in throughput of the apparatus, and improving pattern accuracy. I do.

[0021]

FIG. 1 is a diagram illustrating the principle of the present invention. In order to solve the above-mentioned problem, the present invention relates to FIG.
In the charged particle beam exposure method of transmitting a charged particle beam through the transmission mask plate 20 and the small hole 27 to measure the current value of the charged particle beam transmitted through the small hole 27, as shown in FIG. A step of blocking the charged particle beam by the transmission mask plate 20 for a certain period of time; and a part of the transmission hole pattern so that an edge of the charged particle beam appears at a position on the transmission mask plate 20 different from the blocking step. And the time change I (t) of the current value
, A step of determining whether or not a charge-up exists based on the time change I (t) of the current value, and a step of determining if a charge-up exists in the determination step. Irradiating a part of the transmission hole pattern so that an edge of the charged particle beam is projected to a different position on the transmission mask plate 20, and measuring a second time change I2 (t) of the current value; The time change I (t) of the current value and the second time change I2 of the current value
A step of determining whether charge-up has occurred on the incident side or the exit side of the transmission mask plate 20 based on (t).

[0022]

According to the present invention, as shown in FIG. 1, a lens barrel managing means G for limiting a place where a charge-up is caused.
First, a first step of interrupting the charged particle beam by the transmission mask plate 20 for a certain period of time by M is performed.
A part of the transmission hole pattern is irradiated to a position on the transmission mask plate 20 different from the process so that the edge of the charged particle beam appears, and the time change I (t) of the current value is measured by the measuring means FC.
Is performed, and then the time change I of the current value is measured.
Based on (t), a third step of determining whether a charge-up exists is performed, and if it is determined in the third step that a charge-up exists, a transmission different from that of the second step is performed. A portion of the transmission hole pattern is irradiated onto a position on the mask plate 20 so that the edge of the charged particle beam appears, and the second time change I2 of the current value is measured by the measuring means FC.
A fourth step of measuring (t) is performed. Further, based on the time change I (t) of the current value and the second time change I2 (t) of the current value, the incident side or the exit side of the transmission mask plate 20 is measured. A fifth step of determining which of the charge-ups is occurring is executed to limit a portion of the lens barrel to be cleaned.

As described above, in the charged particle beam exposure method of the present invention, the presence or absence of charge-up is inspected by changing the beam irradiation position on the transmission mask plate 20, and the incident side of the transmission mask plate 20 is inspected. By determining on which side of the emission side, the location causing the charge-up is limited, so that the location to be cleaned is limited, so that the time required for cleaning can be reduced, and as a result, the throughput of the device is reduced. And the pattern accuracy can be improved.

[0024]

Next, an embodiment according to the present invention will be described with reference to the drawings. FIG. 1 shows a basic configuration diagram of a charged particle beam exposure apparatus for carrying out the present invention. The charged particle beam exposure apparatus of the present embodiment is applied to a charged particle beam exposure apparatus or method (FIG. 5) having a general configuration capable of performing exposure by the block exposure method described in the background art. is there.

In FIG. 1, a polygon forming plate (first slit) 15 for forming a beam at a position where a charged particle beam (hereinafter, referred to as a beam) transmits, and a transmission mask having at least one transmission hole pattern formed therein. A plate (hereinafter, referred to as a block mask) 20 and a selecting means for selecting a desired transmission hole pattern (hereinafter, referred to as first to fourth mask deflectors)
21 to 24, a small hole (hereinafter, referred to as an aperture) 27 provided at a position where a beam formed by the selected transmission hole pattern reaches, and a measurement for measuring a current value of a charged particle beam transmitted through the aperture 27 A means (hereinafter, referred to as a Faraday cup; on-sample current detector) FC and a lens barrel management means GM for limiting a location causing charge-up.

The lens barrel management means GM is included in the control unit 50 in the configuration example of FIG.
Is realized by the program processing in. FIG.
FIGS. 2A and 2B are diagrams illustrating charge-up and charge-up drift. FIG. 2A is a diagram illustrating a state in which charge-up occurs in a second mask deflector 22, and FIG. FIG.

In FIG. 2A, when the second mask deflector 22 is dirty, electrons reflected by the block mask 20 accumulate in the second mask deflector 22 and charge-up occurs.

When the deflector 2i (i = 1 to 4) charged up as described above is present, the beam drifts due to the charge-up of the deflector 2i as shown in FIG. 2B. Originally, the condition is set by the control unit 50 so that the beam completely passes through the aperture 27. However, due to the drift of the beam, a part of the beam is cut off by the aperture 27.
The current value on the sample W decreases.

By measuring this with the Faraday cup FC, the occurrence of charge-up drift can be confirmed. The occurrence of the charge-up drift is confirmed by changing the irradiation position on the clean block mask 20 every several tens of seconds and measuring the behavior of the current value in the sample W.

Next, the processing for limiting the location causing the charge-up by the lens barrel management means GM will be described.
This will be described with reference to the flowchart shown in FIG. Also,
FIG. 4A is an explanatory diagram of a beam position in the following processing.
(B) and (c).

The processing of the lens barrel management means GM is large, and the processing for confirming the presence or absence of charge-up drift (steps S1 to S
4) and the process of limiting the position of the incident side or the outgoing side with respect to the block mask 20 when the presence is confirmed (Step S)
5 to S9). (1) Confirmation Process of Presence or Absence of Charge-Up Drift First, in step S1, the beam (B1) is applied to the block mask 2 using the non-opening portion of the block mask 20 in FIG.
By 0, the cutoff is performed for a fixed time (for example, for 30 [sec]).

Next, in step S2, the beam (B2) is transmitted through a part of the rectangular opening PO (FIG. 4).
(In (a), the hatched portion is a portion through which the electron beam B2 passes.) In this state, the behavior (time change) of the sample current value is measured by the Faraday cup FC (step S).
3). If charge-up has occurred, it is determined that it takes several [seconds] to settle the sample current value (step S4).

That is, if steps S1 to S4 are repeatedly performed, and it does not take several seconds for the setting of the sample current value, no charge-up occurs. In this case, beam exposure (step S11) is performed without cleaning.

When the presence of the charge-up is confirmed, the process proceeds to the following processing. (2) Limiting process of the position on the incident side or the exit side with respect to the block mask 20 First, in step S5, as shown in FIG. Size x
L1 in the direction and L2 in the y direction (L1> L2).
In this state, the behavior of the sample current value is measured for 30 seconds.

Next, in step S6, as shown in FIG. 4C, the size of the transmission portion of the beam B4 is formed to L2 in the x direction and L1 in the y direction using the rectangular aperture portion PO.
In this state, the behavior of the sample current value is measured for 30 seconds.

In step S7, steps S5 and S6
In the repetition of the above, if there is no change in the current value (unless the setting of the sample current value takes several [seconds]), it is determined that no charge-up has occurred on the incident side of the block mask 20, and it is determined that the charge exists on the emission side. Is determined (step S
9).

That is, since the areas of the transmission portions in steps S5 and S6 are the same, the amount of transmission current is constant. In this case, no charge-up occurs on the emission side. On the other hand, on the incident side, the position at which the reflected electrons are emitted changes, and the direction in which the reflected electrons are taken into the second mask deflector 22 is different. Therefore, if the second mask deflector 22 is dirty, charge-up occurs.

Therefore, if steps S5 and S6 are repeated and it takes several [seconds] to settle the sample current value,
This means that charge-up has occurred on the incident side (step S8).

The processing of steps S1 to S9 is performed by the CPU.
When the charge-up drift is present, a warning or the like to the user is displayed on the screen of the operation terminal together with the specified position or range to the user.

As described above, in the charged particle beam exposure apparatus of this embodiment, the presence or absence of charge-up is checked by changing the beam irradiation position on the block mask 20, and the incident side or the exit side of the block mask 20 is checked. In this case, it is possible to identify the place to be cleaned, to shorten the interruption time of the beam exposure, and greatly contribute to the charged particle beam exposure method.

[0041]

As described above, according to the present invention,
The lens barrel management means changes the beam irradiation position on the transmission mask plate to check for the presence of charge-up, and
By judging which of the incident side and the outgoing side of the transmission mask plate is occurring, the place where the charge-up is caused is limited, so that the place to be cleaned is limited and the time required for cleaning can be reduced. As a result, it is possible to suppress a decrease in the throughput of the device and improve the pattern accuracy.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the principle of the present invention.

FIG. 2 is an explanatory diagram of charge-up and charge-up drift, and FIG. 2 (a) shows a second mask deflector 2
2 is an explanatory diagram of the occurrence of charge-up, and FIG. 2B is an explanatory diagram of an operation for confirming the occurrence of charge-up drift.

FIG. 3 is a flowchart of a process in a lens barrel management unit of the embodiment.

4A and 4B are explanatory diagrams of a beam position in a process of a lens barrel management unit. FIG. 4A is an explanatory diagram of a beam position in a process of confirming the presence or absence of a charge-up drift, and FIGS. It is explanatory drawing of the beam position in the confirmation processing of an up position.

FIG. 5 is a configuration diagram of a general charged particle beam exposure apparatus using a block exposure method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Exposure part 11 ... Cathode electrode 12 ... Grid electrode 13 ... Anode 14 ... Charged particle beam generation source 15 ... 1st slit (polygon formed plate) 16 ... 1st electron lens 17 ... Slit deflector 18 ... 2nd lens 19 third lens 20 block mask (transmission mask plate) 21-24 first to fourth mask deflector (selection means) 25 blanking 26 fourth lens 27 aperture (small hole) 28 Refocus coil 29 ... Fifth lens 30 ... Dynamic focus coil 31 ... Dynamic stig coil 32 ... Sixth lens 33 ... Main differential coil 34 ... Sub deflector 35 ... Stage 50 ... Control unit 51 ... Storage medium 52 ... CPU 53 ... Interface 54 Data memory 55 Pattern generator 56 61 61 Reference numeral 65: Amplifier unit (DAC / AMP) 58: Mask moving mechanism 59: Clock control circuit 60: Blanking control circuit 62: Sequence controller 63: Deflection control circuit 66: Stage control mechanism 67: Laser interferometer 68: Stage correction unit 2i: charged deflectors B1 to B4 (charged particle) beams FC: Faraday cup; current detector on sample (measuring means) GM: lens barrel management means H: correction value HS ₁ ... deflection signal S _B : blanking signal S _2, S ₃ ... exposure position determination signals P ₁ to P ₄ ... position information PS ₁ ~PS ₄ ... mask irradiation position data PO ... rectangular openings W ... sample (wafer)

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-6-275502 (JP, A) JP-A-7-74071 (JP, A) JP-A-59-143321 (JP, A) JP-A-3-3 76211 (JP, A) JP-A-55-78451 (JP, A) JP-A-5-211113 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/027 G03F 7 / 20

Claims (1)

(57) [Claims] 1. A transmission mask plate (20) and a small hole (2).
7) a charged particle beam exposure method for irradiating a charged particle beam by transmitting the charged particle beam; and measuring a current value of the charged particle beam transmitted through the small hole (27); A step of blocking by a mask plate (20); and irradiating a part of the transmission hole pattern to a position on the transmission mask plate (20) different from the blocking step so that an edge of the charged particle beam comes out. Value change over time I (t)
And determining whether or not a charge-up exists based on the time change I (t) of the current value; and determining that the charge-up exists in the determination step; A step of irradiating a part of the transmission hole pattern so that an edge of the charged particle beam appears at a position on a different transmission mask plate (20), and measuring a second time change I2 (t) of the current value. And the second time change I2 (t) of the current value and the time change I (t) of the current value.
0) a step of determining whether charge-up has occurred on the incident side or the emission side of the charged particle beam exposure method.