JPH01136334A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To perform lithography simply and to make it possible to perform highly accurate position alignment without special steps, by performing the detection of a position aligning mark by using an electron beam, which is emitted from the same particle beam source as an ion beam. CONSTITUTION:A positive potential is applied to the lead-out electrode of a liquid metal particle beam source, and electrons are taken out 1. The electrons are scanned with a particle beam optical system, and a position aligning mark is detected 2. Thus a region for lithography and exposure of an ion beams is determined. The side of a lead-out electrode is made to be a negative potential, and positive ions are taken out 3. At the same time the polarity of the optical system is changed 4, and the condensed ion beam is formed. In this way, the path of an electron beam system and the path of the condensed ion beam in the electrostatic optical become substantially the same, and the scanning regions become equal. Thus the lithography and the exposure can be performed 5 with the condensed ion beam in the region, where the position alignment is performed with the electron beam. Said two operations are repeated, the position alignment is performed with the electron beam and, at the same time, the lithography can be performed with the condensed ion beam.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for manufacturing a semiconductor device using lithography using focused ion beams.

[Conventional technology]

Regarding changes in secondary electron emission patterns due to lithography using focused ion beams and alteration of resist, see Section 34.
It is described in the Proceedings of the United Conference on Applied Physics (Spring 1987), pp. 407. This article describes that with respect to negative resist CMS, the secondary electron emission pattern changes due to carbonization of the resist, making detection difficult.

[Problem that the invention seeks to solve]

The above conventional technology detects marks using a focused ion beam, and does not take into account the detection of marks using an electron beam probe, resulting in a decrease in alignment accuracy due to alteration of the resist by the ion beam. There have been problems such as the need to remove the resist near the marks in order to improve the alignment accuracy.

An object of the present invention is to provide a method for performing highly accurate alignment without requiring special steps in ion beam lithography.

[Means for solving problems]

The above object is achieved by performing alignment mark detection using, instead of a focused ion beam, an electron beam drawn from the same liquid metal particle source with a reverse bias.

The specific method is shown in the flowchart of Figure 1. first.

A positive potential is applied to the extraction electrode of the liquid metal particle source relative to the chip to extract electrons, which are scanned by a particle beam optical system to detect alignment marks.

Thereby, the drawing and exposure area of the ion beam can be determined.The extraction electrode side of the primary electrode is set to a negative potential to draw out positive ions, and at the same time, the polarity of the optical system is also changed to form a focused ion beam. In this way, the paths of the electron beam and the focused ion beam within the electrostatic optical system become substantially the same, and the scanning areas become equal. Thereby, the area aligned by the electron beam can be drawn and exposed by the focused ion beam. By repeating the above two operations, it is possible to perform lithography using a focused ion beam in which positioning is performed using an electron beam.

FIG. 2 shows an example of the device configuration during electron beam extraction. The ion beam can be extracted by switching the power supplies of the acceleration system and optical system in opposite directions.

[Effect]

The distance that an electron beam can reach in a resist is larger than that of an ion beam, and if an acceleration energy of about 20 keV is applied,
It passes through a normal resist of up to about 2 μm to reach the substrate. Therefore, compared to the case of ion beams, secondary electron emission occurs from interaction with the substrate, and is less susceptible to deterioration and carbonization of the resist film.As a result, the secondary electron emission pattern faithfully follows the irregularities of the substrate. ”, the alignment marks can be detected with high sensitivity, making it possible to perform highly accurate alignment.

In addition, since both electrons and ions are emitted from the same particle beam source, the particle beam can be formed using the same optical system, and there is no need for mechanical sample movement. It can be easily performed by only replacing , and is highly accurate.

〔Example〕

Hereinafter, an example will be described in which a gate electrode of an MO8 field effect transistor is formed by focused ion beam lithography using the method of the present invention. FIG. 3 shows an outline of the manufacturing process of a transistor using this method. 10Ω・(!
After forming concave alignment marks for focused ion beam direct writing on an I(100)P type substrate by dry etching, an active region is formed by LOGO3 oxidation, and a gate oxide film is formed by dry oxidation at 950°C for 30 minutes. It was formed to have a thickness of about 20 nm. After implanting boron ions into the channel,
Deposit polycrystalline silicon to a thickness of 300 nm using the CVD method.
A 0MS resist was spin-coated thereon to a thickness of 0.6 μm.

The wafer was transferred to a focused ion beam lithography system, and after the system was evacuated (~10-'Torr) L/L, a positive voltage of 5 kV was applied to the extraction side of the liquid metal particle source to emit an electron beam. After gradually increasing the accelerating voltage and setting it at 300 keV, the current was measured using a Faraday cup on the sample stage, and it was confirmed that the electron beam was stably emitted. This electron beam is gradually moved from the edge of the wafer, scanning a small area, detecting the first alignment mark, and rotating the sample stage to change the scanning direction of the beam in the width direction of the gate (perpendicular to the straight line connecting the source and drain). direction), and also.

The pattern dimensions of the active region were measured from the secondary electron intensity peak obtained from the cross mark and using the moving distance of the sample stage.

After this, reverse the polarity of the extraction voltage of the liquid metal particle source, the acceleration voltage, and the voltage for scanning the beam.

A focused monovalent gallium ion beam of 300 kaV was formed. At this time, measurements using a Faraday cup revealed that the ion current was 30 pA, and the resolution of the secondary electron image revealed that the beam diameter was ~0.1 μmφ. Based on the data obtained from dimension measurement using the focused ion beam and electron beam scanning, direct writing was performed while moving the sample stage to expose the entire gate pattern on the wafer.

After a normal development process, a polycrystalline silicon gate was formed using dry etching. The source and drain were formed by implanting arsenic 5×10''3-2 at an accelerating voltage of 40 keV. After the PSGS film was deposited, contact holes were formed, and wiring was performed by aluminum evaporation and dry etching.

The characteristics of the MO8 type field effect transistor produced were as shown in FIG. SEMWl of device cross section! From S, the gate length was about 0.3 μm.

In order to investigate the change in the bright spot position of the conger beam and the ion beam, we first drew 20 straight lines at 0.5 μm intervals on the resist using an electron beam, then reversed the polarity to form a focused ion beam, and completely An experiment was conducted in which the same pattern was drawn on top of this, but no pattern deviation was observed, and the drawn patterns matched within an error (line width) of 0.05 μm. From this experiment, it was found that the shift in the bright spot positions of the electron beam and ion beam due to bias reversal is extremely small, and the error does not pose a problem when used for five-position alignment.

Furthermore, when seven marks were detected using a focused ion beam, carbonization of the resist occurred, making it impossible to detect alignment marks.

According to this embodiment, alignment marks under a thick resist film can be detected, which has the effect of enabling microfabrication using focused ion beam lithography.

〔Effect of the invention〕

According to the present invention, in focused ion beam lithography, it is possible to increase mark detection sensitivity and alignment accuracy, so that 10-
Since alignment on the order of 2 μm can be performed on any resist regardless of film thickness, it is possible to omit processes such as exposing one alignment mark in the manufacture of semiconductor devices with fine patterns, and to perform lithography easily. In addition, it is possible to eliminate the problem of small stoppages caused by a decrease in alignment accuracy.

[Brief explanation of the drawing]

FIG. 1 is a flowchart showing the basic operation of the present invention, FIG. 2 is a vertical sectional view showing the basic configuration of an apparatus suitable for carrying out the present invention, and FIG. 3 is a MO8 type FET in one embodiment of the present invention.
FIG. 4 is a schematic flowchart of the manufacturing process for manufacturing the MOSFET, and FIG. 4 is a diagram showing the operating characteristics of the MOSFET manufactured in the above embodiment. 1...Liquid metal particle source emitter, 2...Liquid metal,
3... Power supply for extraction/acceleration, 4... Lens system for convergence, 5... Power supply for optical system, 6... Sample stage, 7... Sample wafer.

Claims (1)

[Claims] 1. Includes the step of exposing the resist film at a specific position on the substrate by scanning a fine ion beam on a resist film coated on a semiconductor substrate with convex or concave alignment marks. 1. A method of manufacturing a semiconductor device, characterized in that, in a processing step, alignment marks are detected using an electron beam emitted from the same particle beam source as the ion beam.