JPS6178121A - Electron beam exposure - Google Patents

Abstract

PURPOSE:To improve the accuracy of pattern dimension by correcting any focussing error due to electron beam resist by a method wherein a focussing system is composed of a focus setting up device and a corrector shifting a focus to overfocus side. CONSTITUTION:Any reaction electrons and secondary discharge electrons from the surface of the wafer 2 are detected by an electron sensor 14 and then a processor 15 and a focus setting up device 12 are set up to adjust an objective lens 10 while electron beams EB are set up to be focussed on the surface of wafer 2 so that maximum electrons may be detected. At this time, a corrector 7 outputs any correctable value to be added to the value processed by the processor 15 transmitting it to the focus setting up device 12. Through these procedures, a focus may be adjusted to overfocus side to shift the focus of electron beams EB very little outside the surface of wafer 2. In such a status, a deflector 11 may be operated to scan the electron beams EB on the wafer 2 in X and Y directions so that the wafer 2 may be exposed to any specified pattern.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an electron beam exposure apparatus suitable for use in manufacturing semiconductor devices, and more particularly to an electron beam exposure lid with improved pattern dimensional accuracy.

[Background technology]

In recent years, electron beam exposure has been used to print patterns in photolithography technology, and with improvements in resolution, attempts have been made to miniaturize pattern dimensions and improve their dimensional accuracy. Incidentally, in this type of electron beam exposure apparatus as well as in a normal optical exposure apparatus, it is necessary to accurately focus the exposure beam (electron beam) onto the wafer surface (electron beam resist surface) that is the object to be exposed. For this reason, an electronic sensor facing the wafer surface is used as a focusing device to detect the amount of reflection of exposure electrons irradiated onto the wafer or the amount of secondary emitted electrons, and when the focal position relative to the wafer is changed. A method is adopted in which focusing is performed based on changes in the amount of detected electrons. In other words, the amount of reflected or secondary emitted electrons from the wafer surface is considered to reach its maximum value when the applied electron beam density is maximum, and therefore, when the amount of detected electrons is maximum, the electron beam flux is the highest. The diameter is small, and the electron beam is focused and focused on the wafer surface.

However, when the present inventor actually performed electron beam exposure on a wafer using all of the above-mentioned focusing devices, the pattern resolution was not so good, and therefore the dimensional accuracy of fine patterns was not as high as expected. It turned out that it was not possible.

The reason for this is that the electron content resist required for photolithography technology is coated on the wafer surface.
It is inferred that this resist film causes optical phenomena such as refraction and scattering of the electron beam, causing an error between the effect of the electron beam on the resist that forms the actual pattern and the aforementioned focusing effect. be done.

[Purpose of the invention]

An object of the present invention is to provide a focusing device capable of correcting the above-mentioned practical errors to find an optimal focal position, improving the accuracy of pattern dimensions based on this, and realizing the formation of fine patterns. An object of the present invention is to provide an electron beam exposure apparatus.

The above and other objects and novel features of the present invention include:
It will become clear from the description of this specification and the accompanying drawings.

[Summary of the invention]

A brief overview of typical inventions disclosed in this application is as follows.

That is, a focusing device is constituted by a setting section that detects the position of the object to be exposed and performs focusing based on this, and a correction section that shifts the focal position determined by the setting section to the overfocus side. Accordingly, it is possible to correct the focusing error caused by the electron beam resist and set the optimum focal position for the resist, thereby achieving an improvement in the accuracy of pattern dimensions.

〔Example〕

As a result of various experiments conducted by the present inventor to analyze the above-mentioned pattern accuracy problem, it was found that the focal position of the electron beam,
As a correlation with the dimensional accuracy of the pattern formed by the photolithography process, the relationship schematically shown in FIG. 3 was determined. That is, it can be seen from this that the pattern dimensional accuracy is slightly higher at the over-focus position than when the fish collection is correctly aligned with the surface of the exposed object (quafer).

Therefore, the pattern size at can be improved by exposing the object to be exposed in a slightly overfocused state in the electron beam exposure apparatus as well.

FIG. 1 shows an embodiment of an electron beam exposure apparatus constructed based on the above. This is a semiconductor wafer as a sample. Needless to say, the surface of the semiconductor wafer S2 is coated with an electron beam resist 4 which functions as a mask pattern for the photolithography process by electron beam irradiation and post-treatment.

The electron beam exposure apparatus 1 includes an exposure device 5, and a setting section 6 and a correction section 7 connected thereto.

The exposure device 5 includes an electron gun 8 that emits an electron beam, a condenser lens section 9 that once focuses the electron beam, an objective lens section 10 that focuses the electron beam on the wafer 2, and a condenser lens section 9 that focuses the electron beam on the wafer 2. Deflection unit 1 for scanning in the X and Y directions
In particular, the objective lens unit 10 is controlled by a focal position setting mechanism (circuit) 12 to change and adjust the imaging position (focal position) of the electron beam, and the deflection unit 11 is a pattern forming mechanism. (Circuit) 13 to change and adjust the X and Y positions of the electron beam onto the wafer 2.

The setting section 6 includes an electronic sensor 14 that is disposed opposite to the surface of the wafer 2 and detects electrons reflected or secondary emitted from the surface of the wafer 2, and determines the optimum focus based on the amount of electrons detected by the electronic sensor 14. It is provided with an arithmetic unit 15 that calculates the position and controls the focus position setting mechanism 12 based on the calculation result to perform focus control in the objective lens unit 10. Furthermore, the correction section 7 is connected to the calculation section 15, adds a correction amount to the calculated focal position, and changes the focal position t to the overfocus side, that is, to a position further forward than the optimum focal position. This amount of change is preset to a value obtained based on numerous experiments.

The setting unit 6 includes a laser irradiation source and a photoreceptor that receives the emitted light from the laser irradiation source, is emitted by the wafer, and calculates the optimal focal position based on the detection signal of the photoreceptor. Further, the amount of change in which the focal position f is changed from the optimum focal position to the overfocus side may be set within a value of approximately 100 μm. The reason is that focusing the electron beam and changing the size of the exposed dot is 0.2 to 0.
5μm to 4-6μm.

Therefore, (4-6 / 0.2-0.5)
It turns out that (510, 5)=100 should be used as the standard.

Furthermore, the reason for setting the amount of change of about 100 and the reason why optimum dimensional accuracy can be obtained by changing the focal position to the overfocus value are due to the action of the repulsive force of the Coulomb force of the electron beam. This takes into consideration that the focal position changes depending on the exposure thickness size.

According to the above configuration, in the exposure device 5, the electron beam emitted from the electron gun 8 is focused onto the wafer 2 by the condenser lens section 9 and the objective lens section 10, and is imaged onto the wafer 2.

At this time, the reflected electrons and secondary emitted electrons from the surface of the wafer 2 are detected by the electronic sensor 14, and the arithmetic unit 15 and the fish collecting position setting device $12 are connected to the objective lens unit in order to maximize the amount of detected electrons. Control 10. As a result, the electron beam EB is set to be imaged on the surface of the wafer (electron beam resist 4) 2, as shown in FIG. 2(4).

At the same time, the correction section 7 outputs a correction value to be added to the calculation result value of the calculation section 15 and sends it to the focus position setting mechanism 12. This is the focus position setting mechanism 12.
Then, the focal position is corrected to the overfocus side, and the imaging position of the electron beam EB is shifted outward by a minute dimension from the surface of the wafer (electron beam resist 4) 2, as shown in FIG.

In this state, if the deflection section 11' is operated, the electron beam E
B is scanned on the wafer 2 in the t-X and Y directions, and in combination with the opening and closing action of a shutter (not shown), exposure of the required pattern on the wafer 2 can be completed.

Therefore, according to this electron beam exposure, the wafer 2
The electron beam focused on the top is overfocused, so compared to the conventional method that focuses on the wafer surface, there are fewer errors in pattern dimensions after the completion of the 7th generation process, and pattern dimension accuracy is improved. It is possible to improve the

〔effect〕

(1) A correction unit is attached to the setting unit that sets the focal position of the electron beam, and the configuration is such that the focal point of the electron beam is over-focused with respect to the wafer, so the dimension n of the pattern formed on the wafer is You can improve your degree.

(2) Since a correction section is attached to an exposure apparatus having substantially the same configuration as the conventional one and the focus is set on the overfocus side, the same pattern accuracy as above can be achieved without requiring a major change in the structure.

Although the detailed explanation has been given above based on all the embodiments of the invention made by the present inventor, the invention r! 81f'i It is not to be said that the present invention is not limited to the above embodiments, and that various changes can be made without departing from the gist thereof. for example,
The configuration of the exposure device is not limited to that shown in the drawings, and the exposure device may have various configurations. Further, the correction section and the calculation section may be integrally configured as a control section.

[Application field]

The above explanation has mainly been about the application of the invention made by the present inventor to the field of application which is its background, which is electron beam exposure technology on the surface of a semiconductor wafer. It can be applied to all formation techniques and other fine pattern electron beam exposure techniques.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of an embodiment of the device of the present invention, Fig. 2
3 is a diagram showing the imaging state of the electron beam, and FIG. 3 is a diagram showing the relationship between the focal position and pattern dimensional accuracy. DESCRIPTION OF SYMBOLS 1... Electron beam exposure apparatus, 2... Sample (exposed object, wafer), 3... Stage, 4... Electron beam resist, 5... Exposure device, 6... Setting section, 7... Correction section, 8... Electron gun, 9... Condenser lens section, 1
0... Objective lens section, 11... Deflection section, 12...
Focus position setting mechanism, 14... Electronic sensor, 15...
Arithmetic unit, EB...electron beam. Figure 1 Figure 2 (A) (', 9) 3rd UA

Claims (1)

[Scope of Claims] 1. An apparatus for performing pattern exposure by irradiating an exposed object with a resist coated on its surface with an electron beam, comprising: a setting section for setting a focal position of the exposed object; and this setting section. An electron beam exposure apparatus comprising: a focusing device having a correction section for displacing the focal position determined by the above to the overfocus side of the electron beam. 2. The setting section includes an electronic sensor that detects electrons reflected or secondarily emitted from the exposed object, a calculation section that calculates the focal position based on the output of this electronic sensor, and a calculation section that calculates the focal position based on the output of this calculation section. 2. The electron beam exposure apparatus according to claim 1, further comprising a focus position setting mechanism for adjusting the focus position of the beam to the calculated position. 3. The setting section includes a laser irradiation source that irradiates the object to be exposed with laser light, a photoreceptor that receives the laser beam emitted from the object, and a calculation section that calculates the focal position based on the output of the photoreceptor. 2. The electron beam exposure apparatus according to claim 1, further comprising: a focal position setting mechanism for adjusting the focal position of the electron beam to a calculated position in accordance with the output of the calculation section. 4. A patent claim in which the correction unit corrects the focus position calculated by the calculation unit to the overfocus side, and displaces the focus position by the focus position setting mechanism in a direction behind the surface of the exposed object by a minute dimension. The electron beam exposure apparatus according to the range 1 or 2.