JP2000348662A - Charged particle beam irradiating system, charged particle beam exposure device and manufacture of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a charged particle beam irradiating system capable of completely removing charged particles around the optical axis having no contribution to image formation. SOLUTION: This irradiating system is equipped with a light source 9 to radiate a charged particle, an extraction electrode 12 and an acceleration electrode 11. It is also equipped with a trim aperture 13 to shield an outer peripheral part comparatively away from the optical axis of the flux of the charged corpuscular ray which has not been accelerated yet and a mechanism 10 to adjust the position of the trim aperture 13 in the vertical surface of the optical axis.

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 irradiation system represented by an electron gun provided in an electron beam exposure apparatus used for lithography of semiconductor integrated circuits and the like.
In particular, the present invention relates to an electron gun improved so that charged particles around the optical axis that do not contribute to imaging can be more completely removed before high acceleration. Further, the present invention relates to a method for manufacturing a semiconductor device with high accuracy using such a charged particle beam exposure apparatus.

[0002]

2. Description of the Related Art In a conventional electron gun, electrons are emitted not only from the optical axis direction of a chip (cathode) as a light source but also from the side surface thereof. Such charged particles not only result in wasted currents that do not affect imaging, but also accelerate off the optical axis after being accelerated at high speed by the accelerating electrode and collide with structures inside the electron gun, particularly hitting insulators. Charged particles stay there,
Exceeding a certain amount causes a discharge phenomenon. This adversely affects the degree of vacuum inside the electron gun, the stability of the current, the operation circuit of the electron gun, and the like.

In order to prevent this, an aperture (trim aperture) having a diameter approximately equal to the crossover diameter is placed at a point where the effective beam connects the crossover on the extraction electrode, and this is connected to the extraction electrode. Off-axis charged particles were prevented from being accelerated at high speed.

[0004]

The trim aperture is positioned by mechanical fitting with respect to the casing of the electron gun. Therefore, the center of the trim aperture may not coincide with the center line (optical axis) of the electron gun, which is a line connecting the center of the light source (cathode) and the center of the acceleration electrode (aperture). In that case, a wasteful electron beam that does not contribute to image formation may be emitted from the electron gun, causing the same problem as described above.

[0005] Alternatively, if the position of the light source or the accelerating electrode is to be adjusted to the center of the trim aperture, the degree of freedom in adjusting the optical axis of the electron gun and the optical axis of the optical system (illumination optical system, etc.) after the electron gun decreases. There is also. The present invention has been made in view of such a problem, and a charged particle beam irradiation system improved so that charged particles around the optical axis that do not contribute to image formation can be more completely removed before being highly accelerated. The purpose is to provide. Still another object is to provide a method for manufacturing a semiconductor device with high accuracy by using an exposure apparatus having such a charged particle beam irradiation system.

[0006]

In order to solve the above problems, a charged particle beam irradiation system according to the present invention comprises a light source for emitting charged particles, an extraction electrode, an acceleration electrode, and an optical axis of an unaccelerated charged particle beam. A charged particle beam irradiation system provided with a trim aperture for blocking a relatively distant outer peripheral portion, further comprising a mechanism for adjusting a position of the trim aperture in a plane perpendicular to an optical axis. A charged particle beam exposure apparatus according to the present invention includes the above charged particle beam irradiation system.

In the present invention, the mechanism for removing charged particles that are off the optical axis and do not contribute to image formation before being accelerated by an aperture provided on the extraction electrode is made movable. The center of the trim aperture can be easily adjusted. Therefore, charged particles around the optical axis that do not contribute to image formation can be more completely removed before high acceleration, and charge-up of equipment harmful to stable operation of the charged particle beam irradiation system can be suppressed.

[0008] A semiconductor device manufacturing method according to the present invention is characterized in that exposure in a lithography step is performed using a charged particle beam exposure apparatus.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. First, a configuration example of an entire exposure apparatus using an electron beam, which is a kind of charged particle beam, will be described. FIG. 3 is a diagram illustrating an example of the image forming relationship and the configuration of a control system in the entire optical system of the electron beam projection exposure apparatus of the division transfer system. The electron gun 41 arranged at the uppermost stream of the optical system emits an electron beam downward. Below the electron gun 41, two stages of condenser lenses 42 and 43 are provided. The electron beam is converged by these condenser lenses 42 and 43 and forms a crossover CO on a blanking aperture 47.

Below the condenser lens 43, a rectangular opening 44 is provided. The rectangular aperture (illumination beam shaping aperture) 44 allows only an illumination beam that illuminates one subfield (unit exposure pattern area) of the mask (reticle) 110 to pass. Specifically, the opening 44 forms the illumination beam into a square having a dimension of slightly more than 1 mm square in mask size conversion. The image of the opening 44 is formed on the mask 110 by the lens 49.

A blanking deflector 45 is disposed below the beam forming opening 44. The deflector 45 deflects the illumination beam so that the beam falls on the non-opening portion of the blanking opening 47 so that the beam does not hit the mask 110. Below the blanking opening 47, an illumination beam deflector 48 is arranged. The deflector 48 mainly scans the illumination beam sequentially in the horizontal direction in FIG. 3 to illuminate each subfield of the mask 110 within the field of view of the illumination optical system. A condenser lens 49 is arranged below the deflector 48. The condenser lens 49 converts the electron beam into a parallel beam, impinges the beam on the mask 110, and forms an image of the beam forming aperture 44 on the mask 110.

Although only one subfield on the optical axis is shown in FIG. 3, the mask 110 actually extends in a plane perpendicular to the optical axis (XY plane) and has many subfields. On the mask 110, a pattern (chip pattern) forming one semiconductor device chip as a whole is formed.

To illuminate each subfield within the field of view of the illumination optical system, the electron beam can be deflected by the deflector 48 as described above. In order to illuminate each subfield beyond the field of view of the illumination optical system, the mask 110 is mounted on a mask stage 111 movable in the X and Y directions.

A projection lens 112 is provided below the mask 110.
And 114 and a deflector 113 are provided. Then, an illumination beam is applied to a certain subfield of the mask 110, and the electron beam passing through the pattern portion of the mask 110 is reduced by the projection lenses 112 and 114, and deflected by the lenses and the deflector 113 to be deflected by the wafer 115. An image is formed at a predetermined position above. An appropriate resist is applied on the wafer 115, and the resist is given a dose of an electron beam, so that the pattern on the mask is reduced and transferred onto the wafer 115.

A crossover CO is formed at a point where the space between the mask 110 and the wafer 115 is internally divided at a reduction ratio, and a contrast aperture 118 is formed at the crossover position.
Is provided. The opening 118 blocks the electron beam scattered by the non-pattern portion of the mask 110 from reaching the wafer 115.

Below the second projection lens 114, secondary electron detectors 119 and 131 are arranged. The secondary electron detector detects secondary electrons generated from the wafer 115.
The position of the mark on the wafer 115 or the wafer stage 117 can be known from the detected secondary electron signal, and basic information on alignment between the wafer and the optical system or the mask can be obtained.

The wafer 115 is placed on a wafer stage 117 that can move in the X and Y directions via an electrostatic chuck 116. By synchronously scanning the mask stage 111 and the wafer stage 117 in directions opposite to each other, it is possible to sequentially expose a number of subfields arranged in a chip pattern. In addition, both stages 1
11 and 117 are equipped with an accurate position measuring system using a laser interferometer, and the stage position is accurately measured, and the beam position is controlled based on the result.

Each of the lenses 42, 43, 49, 112,
114 and the deflectors 45, 48, 113 are controlled by the control unit 121 via the respective coil power supplies 42a, 43a, 49a, 112a, 114a and 45a, 48a, 113a. Further, the mask stage 111 and the wafer stage 117 are also controlled by the control unit 121 via the stage drive motor control units 111a and 117a. The electrostatic chuck 116 is controlled by the main controller 121 via an electrostatic chuck control unit 116a. By controlling the accurate stage position and the optical system, the mask 110
The reduced images of the upper subfield are accurately joined, and the entire chip pattern on the mask is transferred onto the wafer.

FIG. 1 is a sectional view schematically showing the structure of a charged particle beam irradiation system according to one embodiment of the present invention. An extraction electrode 12 and an acceleration electrode 11 are disposed downstream of the light source 9. The extraction electrode 12 and the acceleration electrode 11 are
At 6a, it is fixed to the outer wall 5 in an electrically independent state. At the center of the extraction electrode 12, an aperture 13 is provided.
Is installed so as to contact the electrode 12 and move in a direction perpendicular to the optical axis direction (details will be described later). A negative voltage of −95 KV is applied to the extraction electrode 12 from the extraction electrode terminal 1. The electrode terminal 1 is fixed to the outer wall 5 via an insulator 16b. The acceleration electrode 11 is grounded.

The light source 9 comprises a cathode portion, a heating electrode 7 which holds the cathode portion, and a Wehnelt electrode 8. The cathode unit consists of a single crystal LaB ₆ and W, a negative voltage of -100kV is applied. The Wehnelt electrode 8 has a ring shape and is made of Mo, W, or stainless steel, and a negative voltage of several tens of volts is applied slightly lower than the cathode portion. The central portions of the heating electrode 7 and the Wehnelt electrode 8 are fixed to an insulator 16c. On the other hand, the heating electrode terminal 3 at the end of the heating electrode 7 and the Wehnelt electrode terminal 2 at the end of the Wehnelt electrode 8 are held movably in a direction perpendicular to the optical axis while contacting the insulator 16d. Insulator 16d
Are fixed to the outer wall 5.

The charged particles are extracted from the lower end surface or side surface of the cathode portion, pass through the aperture 13, and are accelerated by the potential difference (about 100 kV) between the extraction electrode 12 and the acceleration electrode 11. The charged particle beam accelerated in this manner is emitted downward from the central hole 11 a of the acceleration electrode 11. The Wehnelt electrode 8 acts to prevent the charged particles drawn from the cathode portion from spreading. In addition, each part of the light source 9 and the periphery of each electrode are maintained in a discharge preventing gas atmosphere 15 and a high vacuum atmosphere 14.

The tip position adjusting knob 6 is attached to the insulator 16c which fixes the center of the heating electrode 7 and the center of the Wehnelt electrode 8. Two chip position adjustment knobs 6 are arranged on a plane perpendicular to the optical axis (Z axis) so as to be orthogonal to the X axis direction and the Y axis direction, but only one is shown in the figure. The tip position adjusting knob 6 is like a micrometer. When the knob 6 is rotated, the insulator 16c moves in the X-axis direction and the Y-axis direction.

The outer cylinder 6a of the tip position adjusting knob 6 is an insulator and is fixed to the outer wall 5 at right angles. Further, the flange 6b of the knob 6 is fixed to the upper part of the extraction electrode 12 via the bellows tube 4a. The bellows tube 4a is made of an alloy of stainless steel or berylim and copper,
It expands and contracts according to the rotation of the knob 6. The tip of the tip position adjustment knob 6 is in sliding contact with the side surface of the insulator 16c. That is, when one of the tip position adjusting knobs 6 in the axial direction is rotated, the insulator 16c moves in the coaxial direction, and during this, the other tip position adjusting knob 6 in the axial direction is moved.
Has slid on the side surface of the insulator 16c in contact therewith.
Therefore, the insulator 16c moves in the XY plane perpendicular to the optical axis. Further, the insulator 16c is made of an insulator 16e.
From the bellows tube 4b. These bellows tubes 4a and 4b serve to isolate the gas atmosphere 15 from the high vacuum atmosphere 14.

An aperture position adjusting knob 10 is also attached to the aperture 13. Two aperture position adjustment knobs 10 are arranged on a plane perpendicular to the optical axis (Z axis) so as to be orthogonal to the X axis direction and the Y axis direction, but only one is shown in the figure. The aperture position adjusting knob 10 is like a micrometer, and the knob 10
Is rotated, the aperture 13 moves in the X-axis direction and the Y-axis direction.

The aperture position adjusting knob 10 has the same structure and operation as the tip position adjusting knob 6.
That is, the outer cylinder 10a of the aperture position adjustment knob 10
Is an insulator fixed to the outer wall 5 at right angles.
Further, the flange 10b of the knob 10 is
Is fixed to the lower part of the extraction electrode 12 through the intervening electrode.
The bellows tube 17 expands and contracts as the knob 10 rotates. The tip of the aperture position adjusting knob 10 is in contact with the side surface of the aperture 13 so as to slide. That is, when one of the aperture position adjustment knobs 10 in the axial direction is rotated, the aperture 13 moves in the coaxial direction. During this time, the tip of the aperture position adjustment knob 10 in the other axial direction slides on the side surface of the contacting aperture 13. Moving. Therefore, the insulator aperture 13 moves in the XY plane perpendicular to the optical axis.

The micrometer used for the tip position adjustment knob 6 and the aperture position adjustment knob 10 preferably has a movable range of 1 mm and a positioning accuracy of about 10 μm.

FIG. 2 is an enlarged sectional view showing the vicinity of the aperture of the charged particle beam irradiation system in FIG. This figure shows a state where the aperture is at an appropriate position with respect to the optical axis. As described above, a charged particle beam is emitted from the cathode portion of the light source 9 by the extraction electrode 12. The aperture 13 is provided at a position where the effective charged particle beam on the extraction electrode 12 connects the crossover. That is, the charged particle beam 31 emitted from the lower surface of the cathode portion 31
Pass through the crossover 35 in the plane of the opening of the aperture 13 on the optical axis. However, the charged particle beam 33 emitted from the side surface of the cathode part moves outside the optical axis and is blocked around the opening of the aperture 13.

Since the aperture 13 can be moved in the XY plane, the opening of the aperture 13 can be accurately adjusted to the position of the crossover 35.

The charged particle beam irradiation system of this example is installed above an illumination optical system having a lens and an aperture as an electron gun. In order to match the optical axes of the electron gun, first, the light source 9 is positioned on a line connecting the extraction electrode 12 and the acceleration electrode 11. Next, the two aperture position adjustment knobs 10 are operated to align the center of the electron gun with the center of the aperture 13. This line becomes the center line (optical axis) of the electron gun. If the optical axis of the electron gun does not coincide with the optical axis of the illumination optical system, the two chip position adjustment knobs 6 and the two aperture position adjustment knobs 10 are operated again, and the light emitted from the electron gun and the illumination optical system is operated. Align the axes.

Next, an example of a mode of use of the exposure apparatus of the present invention will be described. FIG. 4 is a flowchart showing an example of the semiconductor device manufacturing method of the present invention. This manufacturing process includes the following main steps. Wafer manufacturing process for manufacturing a wafer (or wafer preparing process for preparing a wafer) Mask manufacturing process for manufacturing a mask to be used for exposure (or mask preparing process for preparing a mask) Wafer processing process for performing necessary processing on a wafer Wafer Chip assembling step of cutting out the chips formed on the chip one by one to make it operable Chip inspecting step of inspecting the resulting chips Each of the steps further includes several sub-steps.

Among these main steps, the main step that has a decisive effect on the performance of the semiconductor device is the wafer processing step. In this step, designed circuit patterns are sequentially stacked on a wafer, and a number of chips that operate as memories and MPUs are formed. This wafer processing step includes the following steps. A thin film forming step of forming a dielectric thin film to be an insulating layer, a wiring portion, or a metal thin film forming an electrode portion (using CVD or sputtering, etc.) An oxidation step of oxidizing the thin film layer or the wafer substrate Thin film layer or wafer substrate A lithography process of forming a resist pattern using a mask (reticle) in order to selectively process etc. An etching process of processing a thin film layer or a substrate according to a resist pattern (for example, using a dry etching technology) An ion / impurity implantation diffusion process Resist stripping step Inspection step for inspecting the processed wafer Further, the wafer processing step is repeated by a necessary number of layers to manufacture a semiconductor device that operates as designed.

FIG. 5 is a flowchart showing a lithography step which is the core of the wafer processing step shown in FIG. This lithography step includes the following steps. A resist coating step of coating a resist on a wafer on which a circuit pattern has been formed in the preceding step An exposing step of exposing the resist A developing step of developing the exposed resist to obtain a resist pattern Stabilizing the developed resist pattern Annealing Step for Using the exposure apparatus of the present invention in the above-mentioned exposure step, the accuracy of pattern formation in the lithography step is greatly improved.
In particular, the process related to realizing the required minimum line width and the overlay accuracy corresponding thereto is a lithography process, in particular, an exposure process including alignment control, and it has been difficult until now by applying the present invention. Semiconductor devices can be manufactured.

[0033]

As is apparent from the above description, according to the present invention, charged particles that are off the optical axis and do not contribute to imaging are
Since the mechanism for removing before high acceleration by the aperture provided on the extraction electrode is made movable, the center of the trim aperture can be easily adjusted to the optical axis of the charged particle beam irradiation system. Therefore, charged particles around the optical axis that do not contribute to image formation can be more completely removed before high acceleration, and charge-up of equipment harmful to stable operation of the charged particle beam irradiation system can be suppressed. Further, a charged particle beam exposure apparatus and a semiconductor device manufacturing method capable of forming a pattern with high precision can be provided.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing the structure of a charged particle beam irradiation system according to one embodiment of the present invention.

FIG. 2 is an enlarged sectional view showing the vicinity of an aperture of the charged particle beam irradiation system in FIG. 1;

FIG. 3 is a diagram illustrating an example of a configuration of an imaging relationship and a control system in the entire optical system of the electron beam projection exposure apparatus of the division transfer system.

FIG. 4 is a flowchart illustrating an example of a semiconductor device manufacturing method according to the present invention.

FIG. 5 is a flowchart showing a lithography step which is the core of the wafer processing step shown in FIG. 4;

[Explanation of symbols]

REFERENCE SIGNS LIST 1 extraction electrode terminal 2 Wehnelt electrode terminal 3 chip heating electrode terminal 4, 17 bellows tube 5 outer wall 6 chip position adjustment knob 7 chip heating electrode 8 Wehnelt electrode 9 light source 10 aperture position adjustment knob 11 acceleration electrode 12 extraction electrode 13 aperture 14 high vacuum Atmosphere 15 Discharge prevention gas atmosphere 16 Insulator 31 Charged particle beam on optical axis 33 Charged particle beam off optical axis 35 Crossover

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 21/027 H01L 21/30 541B

Claims (3)

[Claims] 1. A charged particle beam irradiation system comprising: a light source that emits charged particles; an extraction electrode; an acceleration electrode; and a trim aperture that blocks an outer portion relatively far from an optical axis of an unaccelerated charged particle beam flux. A charged particle beam irradiation system further comprising a mechanism for adjusting the position of the trim aperture in a plane perpendicular to the optical axis. 2. A charged particle beam exposure apparatus having the charged particle beam irradiation system according to claim 1. 3. A method for manufacturing a semiconductor device, comprising performing exposure in a lithography step using the charged particle beam exposure apparatus according to claim 2.