JP2003297721A - Electron beam exposure apparatus and reticle for the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electron beam exposure apparatus capable of calibrating an electron-optical system by the use of a reticle by deflecting an electron beam so as to be in the same state as that of normal continuous exposure. <P>SOLUTION: A batch exposed region is arranged at a position corresponding to the deflected state of the electron beam when a reticle stage (RS) and a wafer stage move successively. Reticle alignment marks 55 are arranged respectively at top and bottom ends of small field (SF) rows of a stripe 21 and the alignment of the reticle is carried out on the reference electron beam trajectory in a state in which RS is kept stationary. When the electron beam trajectory rises toward the right, the alignment is carried out with SF marks of SF no.1 to SF no.10 and parameters such as the position and rotation of the reticle required for the reticle alignment are calculated from these results. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lithography technique using an electron beam.

[0002]

2. Description of the Related Art In recent years, there have been increasing demands for semiconductor exposure apparatuses for higher resolution and large exposure field. An exposure apparatus using an electron beam has been attracting attention as a measure to meet the demand for higher resolution.

When a semiconductor device is formed on a wafer by using an electron beam exposure apparatus, this design pattern is divided into small pattern areas, and a transmission hole for forming an electron beam in each divided pattern shape of the small pattern areas is formed. A reticle composed of a stencil film and a strut that supports it is placed in the electron optical system to deflect the electron beam or move the position of the reticle, and the small area on these divided reticles. The wafer is irradiated with an electron beam, and the small area patterns are collectively and sequentially transferred to the wafer. These small area (hereinafter referred to as SF) patterns are sequentially exposed adjacent to each other on the wafer by deflecting the projection beam or moving the wafer to form the original design pattern on the wafer.

In order to realize a high throughput in an exposure apparatus using an electron beam, a reticle stage (hereinafter, RS) / wafer stage (hereinafter, WS) is continuously moved, and an electron beam is followed at a high speed in the vertical direction. The method of large deflection is used. At this time, the electron beam shows a locus as shown in the example of FIG. 3 due to the direction of following the stage and the large deflection perpendicular thereto (details will be described later). The electron beam exposure apparatus is required to have electron optical performance such as aberration, beam blur, and current amount and accurate deflection position accuracy for such electron beam deflection trajectory. Therefore, device calibration at each deflection position is important.

This calibration is performed by irradiating an electron beam on a reticle having slits or lattice-shaped openings and a structure having a membrane called a fiducial mark, and then irradiating the corresponding concave and convex marks on the wafer stage. Position error, blurring, etc. are measured from the signal obtained by scanning and are calibrated. The current amount is measured by a Faraday cup or the like on the wafer stage, with an opening corresponding to the collective exposure range provided on the reticle stage.

On the other hand, the reticle stage, the wafer stage, and the projection lens must be aligned with high precision in order to connect the divided SFs onto the wafer with high precision. Further, similarly, a high position measurement technique is required to accurately overlay the lower layer pattern already formed on the wafer. The minute alignment error that occurs at this time causes a minute change in the shape of the pattern formed on the wafer. This shape change becomes a very serious obstacle especially for a fine pattern such as a gate portion of a transistor circuit.

The reticle mounted on the electron beam exposure apparatus is accurately aligned with the apparatus by using the exposure electron beam. At this time, the electron beam is applied to the alignment mark such as the slit shape on the reticle in the same state as the exposure,
Scanning is performed on the concave-convex mark provided on the wafer stage, and the alignment is performed based on the reflected electron signal obtained at this time.

[0008]

The electron beam draws a deflection locus corresponding to the exposure state, that is, the continuous movement of the reticle stage and the wafer stage, whereas the ordinary reticle has a batch exposure area on a grid. Since they are arranged in the shape of an eye, it is impossible to irradiate the collective exposure range with the electron beam along the deflection trajectory while each stage is stationary.

[0009]

A batch exposure range on a reticle is arranged according to a deflection locus of an exposure apparatus. In order to calibrate the electron optical system of the apparatus using this reticle, the electron beam large deflection is in the normal exposure state, the reticle stage is stationary, and the apparatus is controlled so that mark detection and current detection can be performed. The membrane of the reticle alignment mark is enlarged so that the reticle alignment can be performed while the deflection path of the electron beam remains unchanged. With the stage stationary,
Control is performed so that the electron beam can be deflected for normal exposure and mark detection can be performed.

[0010]

The function can be calibrated by using the reticle when the electron beam is normally exposed. The reticle alignment can be performed with the electron beam exposed normally.

[0011]

DETAILED DESCRIPTION OF THE INVENTION A description will be given below with reference to the drawings. FIG. 1 is a diagram showing an example of a general EB reticle, FIG. 1 (A) is a plan view, and FIG. 1 (B) is an enlarged perspective view showing a part of the reticle. Reticle 10 is φ200
And a batch exposure area called a subfield 11 (hereinafter referred to as SF) is arranged in a grid pattern. As shown in FIG. 1 (B), this SF 11 is provided in a silicon membrane 13 having a thickness of 2 μm with a pattern as an opening 15. Each SF membrane 13 is supported by a beam called a minor strut 17 having a width of 170 μm. Moreover, there is a non-patterned portion called a skirt at the edge of each SF. The membrane 13 is illuminated with an electron beam 19 having a size of about 1 mm, and the electron beam passing through the pattern aperture 15 is imaged on the wafer. The SF area on the reticle is divided into areas each having a lateral width of 20 SF called a stripe 21. The stripe 21 corresponds to the maximum deflection range of the electron beam during pattern exposure.

FIG. 2 is a perspective view schematically showing the exposure method of the electron beam exposure apparatus. FIG. 3 is a diagram showing an example of the trajectory of the electron beam when the stage continuously moves. The EB stepper draws by the operation as shown in FIG. The reticle stage 31 (RS) has two reticles (reticle 1 and reticle 2) 3 corresponding to complementary exposure.
3, 35 are mounted. The RS31 and the wafer stage 37 (WS) have their respective positions determined by the interferometric measurement length system 3
Continuously move while monitoring the position with 9, 41. In the figure, reference numeral 49 is an illumination electron optical system, reference numeral 47 is a projection electron optical system, reference numeral 51 is an RS reference mark, and reference numeral 53 is W.
The S reference mark is shown.

The electron beam 43 draws a locus that follows the movement of each stage in a direction parallel to the direction in which it is largely deflected in a direction perpendicular to the direction in which the stage is continuously moved. Therefore, this electron beam 43
Is stationary relative to the SF on the reticles 33 and 35 and the exposure position on the wafer 45 for the exposure time. This is schematically shown in FIG. 3 for RS31. This electron orbit shows a large deflection from left to right, but when it is largely deflected from right to left, it is to this left and right object, and when the moving direction of the stage is from the top to the bottom of the paper, it is to the upper and lower mirror image objects respectively. Become. In addition, WS draws a deflection orbit by packing the reticle's minor struts and skirt. Such a series of electron beam trajectories will be referred to as a reference electron beam trajectory.

FIG. 4 is a diagram for explaining the linear component of the distortion of the projected SF. The electro-optical performance such as the aberration of the EB stepper and the distortion of the exposure SF greatly depends on the large deflection position. SF distortion is an isotropic magnification error as shown in FIG.
(A)), rotation error (FIG. 4B), orthogonality error (FIG. 4C), anisotropic magnification error (FIG. 4D),
It is decomposed into 5 linear errors of position error (Fig. 4 (E)),
It is corrected by the projection optical system 47 (see FIG. 2). These five error components depend on the large deflection position of the electron beam. On the other hand, the optical aberration mainly related to the blur of the image also largely depends on this large deflection position.

FIG. 5 is a plan view showing an example of the SF distortion measuring reticle pattern. The means for measuring / correcting the linear error component of SF distortion projects a slit mark as shown in FIG. 5 (A) onto the mark detector on WS for mark detection. Alternatively, it can be obtained by exposing the wafer with a pattern as shown in FIG. 5B and measuring the dimensions with a coordinate measuring device or the like. With respect to the aberration associated with blurring, a fine pattern for resolution evaluation is exposed and correction is performed based on the resolution.

As described above, the mark detection / exposure for such correction must be performed on the reference electron beam trajectory. Also, although some objects such as the mark detection slit pattern are included in the reference mark 51 (FIG. 2) on the RS 31, the resolution evaluation pattern and the like are formed on the reticle having a high degree of freedom in pattern design. It is advantageous to do so. Further, when evaluating the performance of the electro-optical performance alone, it is desirable that the WS / RS be performed in a stationary state in order to reduce error factors such as device vibration due to continuous movement of the stage.

FIG. 6 shows S adjusted to the deflection of the reference electron beam.
It is a top view showing the arrangement of F. From this, it is desirable that the reticle for calibrating the electron optical system has SF11 obliquely arranged as shown in FIG. By doing so, mark detection or exposure can be performed in a state where each stage is stationary on the reference electron beam trajectory. Here, the follow-up deflection in the continuous movement direction of the stage is as small as about 13 μm on the wafer and can be ignored.

FIG. 7 is a plan view showing a reticle alignment mark SF according to another embodiment. Note that FIG.
Indicates only the alignment mark at the bottom of the stripe.
Further, the alignment of the reticle is performed on the reference electron beam trajectory with the RS kept stationary. Now, consider a case where the reticle alignment marks 55 are arranged in the SF rows at the upper and lower ends of the stripe 21. SF57 for reticle alignment
Are expanded in the direction of continuous movement of the stage to absorb the vertical deflection of the electron beam (FIG. 7). The portion surrounded by the diagonal lines in the figure shows the electron beam irradiation portion.

When the electron beam orbit (indicated by an arrow in the drawing) goes up to the right, alignment is performed with SF marks of SF numbers # 1 to # 10, and up to the left with # 11 to # 20 marks. From these results, the parameters required for reticle alignment such as reticle position and rotation are calculated.

Here, when the electron beam orbit rises to the right,
Regarding the deflection positions of SF # 11 to # 20, only the deflector of the electron optical system operates normally, and the electron beam is not illuminated by a blanker (not shown) provided below the electron gun (in the figure). Shown with dashed arrows). This is to prevent the heat caused by the electron beam irradiation to the portion other than the membrane from causing the deformation of the reticle. Further, mark detection used for reticle alignment is obtained by scanning a beamlet made of an alignment mark (slit-like opening) on SF on a corresponding mark (WS reference mark etc.) on a wafer. It is calculated from the reflected electron signal.

This reticle alignment mark row can be arranged at the upper end of the stripe or in the stripe other than that shown in FIG.

[0022]

As is apparent from the above description, according to the present invention, the electron beam can be deflected in the same state as in normal continuous exposure, and the electron optical system can be calibrated using the reticle. Furthermore, reticle alignment can be performed in this electron beam deflection state.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a general EB reticle, FIG. 1 (A) is a plan view, and FIG. 1 (B) is an enlarged perspective view showing a part of the reticle.

FIG. 2 is a perspective view schematically showing an exposure method of an electron beam exposure apparatus.

FIG. 3 is a diagram showing an example of a trajectory of an electron beam during continuous movement of a stage.

FIG. 4 is a diagram illustrating a linear component of a projected SF distortion.

FIG. 5 is a plan view showing an example of a SF distortion measurement reticle pattern.

FIG. 6 is a plan view showing an array of SFs according to a reference electron beam deflection.

FIG. 7 is a plan view showing a reticle alignment mark SF.

[Explanation of symbols]

10 reticle 11 subfield (SF) 13 membrane 15 aperture 17 strut 19 electron beam 21 stripe 31 reticle stage (RS) 33, 35 reticle 37 wafer stage (RS) 39, 41 interferometry system 43 electron beam 45 wafer 47 projection electron Optical system 49 Illumination electron optical system 51 Reticle stage reference mark 53 Wafer stage reference mark 55 Reticle alignment mark 57 Reticle alignment SF

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H01J 37/20 H01J 37/305 B 5F056 37/305 H01L 21/30 541S 541J 541K F term (reference) 2H095 BA08 2H097 AB09 BB03 CA16 KA03 KA28 LA10 5C001 AA01 CC06 5C033 BB02 5C034 BB04 BB05 BB06 5F056 AA06 AA20 AA22 BA08 BD06 CB11 CB21 CC01 CC09 EA06 EA14 FA05

Claims (4)

[Claims] 1. An electron gun unit for generating and accelerating an electron beam, an electron optical system for illuminating the accelerated electron to a desired position on a reticle, and an electron beam irradiated in a collective exposure area on the reticle. Electron beam limiting aperture that limits the reticle, a stage that supports the reticle in which the desired pattern is divided into batch exposure areas, and projection optics that accurately forms and transfers the pattern on this reticle onto a sample such as a wafer. A reticle of an electron beam exposure apparatus, which has a system and a stage for holding a sample, and performs drawing by deflecting an electron beam by continuously moving a reticle stage and a wafer stage. A reticle for an electron beam exposure apparatus, in which a collective exposure area is arranged at a position corresponding to a deflection state when the wafer stage is continuously moved. 2. An electron gun unit for generating and accelerating an electron beam, an electron optical system for illuminating the accelerated electron to a desired position on the reticle, and an electron beam irradiated within a collective exposure area on the reticle. Electron beam limiting aperture that limits the reticle, a stage that supports the reticle in which the desired pattern is divided into batch exposure areas, and projection optics that accurately forms and transfers the pattern on this reticle onto a sample such as a wafer. An electron beam exposure apparatus, which has a system and a stage for holding a sample, and performs drawing by deflecting an electron beam by continuously moving a reticle stage and a wafer stage. An electron beam exposure apparatus, which is capable of performing exposure and electron beam mark detection by irradiating an exposure area with an electron beam. 3. An electron gun unit for generating and accelerating an electron beam, an electron optical system for illuminating the accelerated electron to a desired position on the reticle, and an electron beam irradiated within a collective exposure area on the reticle. Electron beam limiting aperture that limits the reticle, a stage that supports the reticle in which the desired pattern is divided into batch exposure areas, and projection optics that accurately forms and transfers the pattern on this reticle onto a sample such as a wafer. An electron beam exposure apparatus, which has a system and a stage for holding a sample, and performs drawing by deflecting an electron beam by continuously moving a reticle stage and a wafer stage. While the stage is continuously moving, the reticle stage and wafer stage are held stationary while the exposure is performed by the electron beam and the electron beam mark is detected. Electron beam exposure apparatus for reticle enlarged shot exposure region, characterized in that arranged on a part of. 4. An electron gun unit for generating and accelerating an electron beam, an electron optical system for illuminating the accelerated electron to a desired position on a reticle, and an electron beam irradiated within a collective exposure area on the reticle. Electron beam limiting aperture that limits the reticle, a stage that supports the reticle in which the desired pattern is divided into batch exposure areas, and projection optics that accurately forms and transfers the pattern on this reticle onto a sample such as a wafer. An electron beam exposure apparatus, which has a system and a stage for holding a sample, and performs drawing by deflecting an electron beam by continuously moving a reticle stage and a wafer stage. While the stage is continuously moving, the reticle stage and wafer stage are kept stationary in the deflected state to perform electron beam exposure and electron beam mark detection. Electron beam exposure apparatus according to claim.