CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority from Japanese Patent Applications No. 2019-084353, filed on Apr. 25, 2019, the entire contents of which are incorporated herein by reference.

FIELD OF THE INVENTION

Embodiments relate to a multi charged particle beam writing apparatus.

BACKGROUND OF THE INVENTION

With high integration of semiconductor devices, circuit patterns of semiconductor devices have become fine. In realizing a fine circuit pattern, a lithography technique for forming a circuit pattern on a semiconductor substrate becomes important. In order to form a fine circuit pattern by using a lithography technique, an original image pattern (also referred to as a reticle or a mask) with high accuracy is required. Electron beam writing inherently has excellent resolution, and thus, is used for manufacturing an original image pattern with high accuracy.

For example, there is a writing apparatus using multiple beams. Compared to pattern drawing with one electron beam, a target object can be irradiated with many electron beams at once by using the multiple beams. Therefore, it is possible to greatly improve the throughput of the pattern drawing.

In a writing apparatus using multiple beams, the multiple beams are formed by allowing an electron beam emitted from an electron gun assembly to pass through a shaping aperture array having a plurality of openings. Each beam of the multiple beams is independently deflected by a blanking aperture array substrate.

The blanking aperture array substrate has a plurality of openings through which each beam of the multiple beams passes and an electrode pair provided in each of the openings. By controlling the voltage applied to the electrode pair, each beam of the multiple beams is deflected. The beam deflected by the electrode pair is shielded, and the target object is irradiated with the beam that is not deflected, so that the pattern drawing is performed.

The temperature of the shaping aperture array substrate rises due to the irradiation with the electron beam. If the temperature of the shaping aperture array substrate rises, the pitch of the openings changes due to thermal expansion. If the pitch of the openings deviates from a predetermined range, for example, each beam of the multiple beams cannot pass through the desired openings of the blanking aperture array, and thus, there is a problem that the electron beam with which the target object is irradiated is lost.

For this reason, for example, the pitch of the openings of the shaping aperture array is designed in consideration of a change due to a rise in temperature of the shaping aperture array substrate in advance. During the time of pattern drawing, the temperature of the shaping aperture array substrate is maintained in a predetermined range, so that the pitch of the openings falls within a predetermined range.

In order to prevent the temperature of the shaping aperture array substrate from rising, for example, it is considered that a restriction aperture that restricts the amount of the electron beam with which the shaping aperture array substrate is irradiated is provided. The restriction aperture is provided between the electron gun assembly and the shaping aperture array substrate and shields a portion of the electron beam to restrict the amount of the electron beam with which the shaping aperture array substrate is irradiated.

On the other hand, if the shaping aperture temperature is suppressed to be too low, there is a problem in that the growth of dirt (mainly hydrocarbon) in the holes of the shaping aperture is facilitated. If dirt grows in the holes of the shaping aperture, there occur problems in pattern drawing accuracy such as a deterioration in beam shape accuracy and a deterioration in beam position accuracy. For this reason, it is necessary to replace the shaping aperture, but since it is necessary to stop the apparatus and perform the replacement operation, there is a problem in that the operating rate of the apparatus significantly decreases. Thus, in order to suppress a change in pitch of the shaping aperture openings due to a temperature rise, it is better to lower the temperature, but if the temperature is too low, there occur problems such as a deterioration in accuracy due to the growth of dirt on the shaping aperture and a decrease in operating rate.

SUMMARY OF THE INVENTION

A multi charged particle beam writing apparatus according to one embodiment includes: an emission unit emitting a charged particle beam; a restriction aperture unit having a first opening having a variable opening area, the restriction aperture unit shielding a portion of the charged particle beam; a shaping aperture array substrate having a plurality of second openings, the shaping aperture array substrate forming multiple beams by allowing the shaping aperture array substrate to be irradiated with the charged particle beam passing through the first opening and allowing a portion of the charged particle beam to pass through the plurality of second openings; and a blanking aperture array substrate having a plurality of third openings, each beam of the multiple beams passing through the plurality of third openings, the blanking aperture array substrate being capable of independently deflecting each beam of the multiple beams.

