JPH027173B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electron beam exposure apparatus, and more particularly to an electron beam exposure apparatus that can automatically control a sample current.

When performing electron beam exposure on a sample such as a semiconductor substrate or a mask substrate that has an electron resist film on its surface, the sample current (electron beam amount) reaching the sample surface is adjusted before exposure depending on the sensitivity of the electron resist used. It must be controlled to a desired value in advance.

To adjust the sample current as described above in a conventional electron beam exposure system, while watching the sample ammeter connected to the Faraday cage attached to the stage on which the sample is placed, select two electron beams for adjusting the sample current. This was done by manually selecting the excitation current for the lens. That is, the strength of the electronic lens was adjusted manually. Therefore, not only does it take a long time to adjust the sample current, but also the imaging position of the crossover (minimum cross-section) image of the electron beam does not always match the position of the main surface of the blanking deflector. If these two do not match, the position of the electron beam shifts on the sample surface during blanking. This shift speed is very fast, so there is almost no problem when using a low-sensitivity electron resist, but when using a high-sensitivity electron resist, the trajectory portion where the electron beam has shifted is exposed. This may cause pattern disturbance. Therefore, when adjusting the sample current, trying to match the imaging position of the crossover image with the position of the main surface of the blanking deflector takes a longer time, and the operation is not easy.

An object of the present invention is to provide an electron beam exposure apparatus that can automatically control a sample current.

The object of the present invention is to provide first and second electron lenses for controlling the sample current reaching the sample surface, a Faraday cage for detecting the sample current, and a blanking deflector for blanking the electron beam. an electron beam exposure apparatus comprising: means for specifying a desired sample current value; and a comparison for calculating the difference between the sample current detected by the Faraday cage and the current value specified by the sample current value specifying means. a drive current controller that controls the excitation currents of the first and second electron lenses in response to the calculation results of the comparator, and a deflector that blanks the crossover image of the electron beam at a predetermined sample current value. the first image formed at the position of the main surface;
intensity control means for the first and second electron lenses including at least a storage device storing data regarding the intensity of the second electron lens, the intensity control means for controlling the intensity of the first and second electron lenses; This can be achieved by providing an electron beam exposure apparatus in which the intensities of the first and second electron lenses are controlled based on data from a storage device.

EMBODIMENT OF THE INVENTION Below, the electron beam exposure apparatus of the present invention will be specifically explained using examples.

FIG. 1 is a block diagram showing the main parts of a system configuration of a first embodiment of an electron beam exposure apparatus according to the present invention. In the figure, 1 is an electron gun, 2 is an electron beam, 3 and 4 are first and second electron lenses that control the sample current reaching the sample surface 5, and 6 and 7 are the first and second electron lenses, respectively. Lens drive power supply, 8
9 is a blanking deflector, 9 is a crossover image of the electron beam, 10 is an objective lens for forming an image of the electron beam 2 on the sample surface, and 11 is provided on a stage (not shown) in alignment with the position of the sample surface 5. Detector 1
This is a Faraday cage for detecting the sample current reaching the sample surface 5 through the sample surface 5. The above configuration is no different from a conventional electron beam exposure apparatus.

In this embodiment, in addition to this, a sample current setting device 13 for setting a desired value of the sample current and an intensity control device 14 for the first and second electron lenses are provided. The intensity control device 14 can be composed of, for example, a comparator 15 and a drive power supply control circuit 16.

Next, the operation of the electron beam exposure apparatus configured as described above when adjusting the sample current will be explained.

When it is necessary to adjust the sample current, such as when starting exposure work, changing the type of electronic resist, or replacing the filament of the electron gun, first move the stage (not shown) and adjust the Faraday cage 11. at the electron beam irradiation position, and set the desired sample current value I to the sample current setting device 13.
Set.

Next, the electron beam exposure device is activated, and the electron beam that has reached the sample surface is exposed to the Faraday cage 11.
The sample current i is detected by the receiving detector 12.
The comparator 15 compares the above i and I and calculates the difference △ between the two.
Calculate I. The drive power supply control circuit 16
Based on this, the drive power supplies 6 and 7 are controlled, and the excitation currents C ₁ and C ₂ of the first and second electron lenses 3 and 4 are selected so that ΔI becomes zero.

Curve group I in FIG. 2 is a curve showing the relationship between excitation currents C ₁ and C ₂ that provide a predetermined sample current I, and
For example, to set the desired value of the sample current as I _{0 ,} C ₁ and C ₂ should be selected so as to satisfy the curve I ₀ in the figure.
Therefore, when selecting the excitation currents C ₁ and C ₂ , C ₁ and C ₂
There is no need to change both C ₁ (or
C ₂ ) is fixed, C ₂ (or C ₁ ) is changed and △
Find the point where I becomes zero. If you cannot find a point where △I becomes zero within the variable range of C ₂ , set C ₁ (or C ₂ ) to a different value than before and change C ₂ again.
Find the point where I becomes zero. All of these operations are performed by commands from the drive current control circuit 16.

In this way, the sample current i reaching the sample surface could be set to a desired value. All that is left to do is to perform electron beam exposure while keeping the excitation currents of the two electron lenses fixed.

Figure 3 is a rewrite of Figure 2, where the horizontal axis shows the sample current I, the vertical axis shows the exciting current _C1 , and the curve group _C2 shows the exciting current _C2 as _C20 , _C21 , _C22, respectively. The relationship between I and C ₁ is shown below.

In the example shown in Fig. 2, the excitation currents C ₁ and C ₂ of the two electron lenses 3 and 4 are used to adjust the sample current to the desired value.
It is necessary to find a combination that makes ΔI zero by varying ΔI over a wide range. Therefore, the variable range of the sample current is divided into several regions, for example, I ₀ ±a, as shown in FIG.
It is divided into three regions, I ₁ ±a and I ₂ ±a, and the excitation current C ₂ of the electron lens 3 is set to C 20 , C ₂₀ ,
Choose C ₂₁ and C ₂₂ . As shown in FIG. 1, a storage device 17 is attached to the electron lens intensity control device 14 of the electron beam exposure apparatus used in the first embodiment, and a storage device 17 is attached to the electron lens intensity control device 14 of the electron beam exposure apparatus used in the first embodiment. to remember.

With such a system configuration, a desired sample current value, for example, I ₁ ', can be set using the sample current setting device 1.
3, the signal I ₁ ' is sent to the storage device 17, and the storage device 17 receives this and, since I ₁ ' is within the area of I ₁ ±a, a signal corresponding to that area is sent to the storage device 17. A signal is sent specifying the excitation current C ₂ as C ₂₁ .
In response to this, the drive power supply control circuit 16 first fixes the excitation current C ₂ to C ₂₁ and then changes the excitation current C ₁ to find a value C ₁₁ at which ΔI=0.

According to this embodiment, since the excitation current C ₂ is specified in advance according to the desired sample current value I, the excitation current C ₁ that satisfies ΔI=0 can be easily determined.

Next, a second embodiment of the present invention will be described using FIGS. 1 and 4.

As mentioned above, if the position of the main surface of the blanking deflector 8 and the position of the crossover image do not match (9' in Figure 1), there is a problem that the electron beam shifts on the sample surface during blanking. There is. When using a highly sensitive electronic resist, it is necessary to eliminate this shift as much as possible, and for this purpose, the crossover image must be aligned with the main surface of the blanking deflector 8, as shown at 9 in FIG. The third embodiment has an additional function of controlling the position of the crossover image, that is, controlling the shift amount of the electron beam.

FIG. 4 is a diagram in which a group of curves S showing the shift amount of the electron beam on the sample surface is added to FIG. Curve S ₀ ,
S ₁ and S ₂ correspond to the curves of sample currents I ₀ , I ₁ , and I ₂ , respectively. For example, when C ₁ and C ₂ are changed and the sample current I is set to I ₀ , the shift amount S changes as shown by the curve S ₀ . Note that these two curves are drawn so that each point on the same C ₁ corresponds.

As seen in the figure, there is an optimum value for the combination of excitation currents C ₁ and C ₂ that minimizes the shift amount S with respect to the value of the sample current I. A curve Q connects the points representing this optimal combination.

The system configuration of this embodiment is the same as that of the second embodiment described above, but the storage device 17 stores the curve Q
The difference is that data indicating . Therefore, in this embodiment, the storage device 17 receives a desired value of the sample current, for example I ₀ , and specifies the combination C ₁₀ and C ₂₁ of the excitation currents C ₁ and C ₂ that minimizes the shift amount S. In response to this, the drive power supply control circuit 16 controls the drive power supply C ₁ ,
Let C ₂ be C ₁₀ and C ₁₁ respectively. As a result, the sample current i
is almost the desired value I ₀ , so fine adjustment is made to C ₁ or C ₂ so that the error becomes ΔI=O.

As described above, in the third embodiment, the control of the sample current and the shift amount, that is, the position control of the crossover image can be performed easily and with good reproducibility.

As explained above, according to the present invention, the exciting current
Since the sample current is controlled by automatically controlling C ₁ and C ₂ and adjusting the intensities of the first and second electron lenses 3 and 4, the sample current can be adjusted easily and accurately in a short time. becomes possible. Furthermore, by storing data on the combination of electron lens strengths that minimize the amount of shift in the attached storage device,
The position of the crossover image can always be made substantially coincident with the main surface of the blanking deflector.

[Brief explanation of drawings]

FIG. 1 is a main block diagram showing the system configuration of the first to third embodiments of the present invention, FIG.
4 are curve diagrams for explaining the first to third embodiments, respectively. 1...electron gun, 2...electron beam, 3...first
electron lens, 4... second electron lens, 5...
Sample surface, 6, 7... Drive power supply, 8... Blanking deflector, 9, 9'... Crossover image, 11...
... Faraday cage, 12... detector, 13...
Sample current setting device, 14...Electronic lens intensity control device, 15...Comparator, 16...Drive power supply control circuit, 17...Storage device.

Claims (1)

[Claims] 1. First and second electron lenses for controlling the sample current reaching the sample surface, a Faraday cage for detecting the sample current, and a blanking deflection for blanking the electron beam. an electron beam exposure apparatus comprising: means for specifying a desired sample current value; and calculating a difference between a sample current detected by the Faraday cage and a current value specified by the sample current value specifying means. a comparator; a drive current controller that controls excitation currents of the first and second electron lenses in response to calculation results of the comparator; and a blanking deflection of a crossover image of the electron beam at a predetermined sample current value. intensity control means for the first and second electron lenses, comprising at least a storage device storing data regarding the intensities of the first and second electron lenses that form an image at the position of the main surface of the device;
An electron beam exposure apparatus characterized in that the intensities of the first and second electron lenses are controlled based on data read from a storage device in response to the specified sample current value.