JPH0533496B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for correcting deflection distortion of an ion beam used in a maskless implantation apparatus, etc., and a deflection distortion detection element used in this method. (Prior Art) In recent years, maskless ion implantation equipment has been developed and used for manufacturing semiconductor devices. In this maskless ion implantation equipment, ions are implanted onto a semiconductor substrate by deflecting an ion beam. Beam lithography is used. In order to perform this ion beam drawing with high precision,
It is necessary to reduce the ion beam diameter and eliminate deflection distortion of the ion beam. (Problem to be Solved by the Invention) However, an electrostatic deflection system is normally used to deflect an ion beam, and the electric field distortion of this electrostatic deflection system causes deflection distortion such as pincushion distortion in the deflection field. This inevitably occurs, and therefore there is a limit to the accuracy of ion beam drawing using conventional ion implanters. An object of the present invention is to propose a method for correcting deflection distortion in an ion beam that enables highly accurate ion beam drawing. Another object of the present invention is to propose a deflection distortion detection element for use in the above method, which can accurately detect deflection distortion of an ion beam. (Means for Solving the Problems) In order to solve the above problems, in the present invention, striped regions with different emission levels of secondary electrons emitted by ion beam irradiation are made of AlAs.
A deflection strain detecting element is formed periodically from GaAs and has the cleaved cross section as its surface, and is arranged at an angle with respect to the X-Y axis. The ion beam deflection distortion is measured from the asymmetry, and the ion beam scanning sweep signal is corrected based on the measured value to correct the ion beam deflection distortion. Here, the deflection strain detection element is made by cleaving a stacked body in which films of materials having different emission levels of secondary electrons emitted by ion beam irradiation are cleaved, and periodically providing striped regions. For example, a striped region having a heteroperiodic structure of GaAs/AlAs and a region width of 0.1 μm or less is used. (Function) That is, as in the present invention, the deflection strain detection element surface is periodically provided with regions where the emission level of secondary electrons emitted by ion beam irradiation is different, and is used in a maskless ion implantation device or the like. When the ion beam is scanned, different levels of secondary electron signals are obtained each time the ion beam traverses the region of the deflection strain sensing surface. At this time, the surface of the deflection strain detection element is formed periodically by AlAs and GaAs, and the cleavage cross section is used as the surface, so the surface of the deflection strain detection element is completely flat, and the secondary electron emission characteristics are , accurate characteristics can be obtained regardless of the surface condition. If the ion beam has deflection distortion, the amplitude, period, etc. of this secondary electron signal change depending on the deflection distortion, and asymmetry etc. are detected. Therefore, in the present invention, the deflection distortion of the ion beam is measured by detecting changes in the amplitude, period, etc., or asymmetry, etc. of the secondary electron signal, and based on this measurement value, the scanning sweep signal of the ion beam, etc. to correct the deflection distortion of the ion beam. As a deflection distortion detection element for correcting the deflection distortion of an ion beam used in a maskless ion implantation device, striped regions with different emission levels of secondary electrons emitted by ion beam irradiation are periodically provided. For example, if the striped region is GaAs/
It is a heteroperiodic structure of AlAs, and its region width is
Although a thickness of 0.1 μm or less is preferable, it is extremely difficult to form a striped GaAs/AlAs heteroperiodic structure with such a narrow region width over the entire deflection field of the ion beam. Therefore, in such cases, a deflection strain detection element with a GaAs/Als heteroperiodic structure with a stripe region width of 0.1 μm or less is used in the X-Y direction where the ion beam is scanned.
The deflection distortion detection element is placed at an inclination angle of 45° to the axis, and while maintaining this area angle, the deflection distortion detection element is moved across the entire ion beam deflection field, and the ion beam is scanned on the surface of this deflection distortion detection element at the required location. What is necessary is to obtain a secondary electron signal by doing so. (Embodiments) Hereinafter, the present invention will be explained based on the illustrated embodiments. Reference numeral 1 indicates a deflection distortion detection element according to the present invention. In this embodiment, the deflection strain detection element 1 has a thickness of
It is formed by cleaving a laminate of 3 to 5 layers of 300 Å AlAs and GaAs semiconductors with a length of about 2 mm, and the cleaved cross section has a striped AlAs semiconductor region 2 and a striped GaAs semiconductor region 3. are formed periodically, and this cleaved cross section is the surface of the deflection strain detection element 1. On the other hand, 4 is a precision stage for fixing the deflection strain detection element 1 on its surface, and the precision stage 4 has a pulse motor 5a on its side for moving the precision stage 4 in the X-axis direction and a pulse motor 5a for moving the precision stage 4 in the Y-axis direction. The deflection strain detection element 1 is located at the center of the surface of the precision stage 4 in an X-Y direction.
It is placed at an angle of inclination of 45° to the axis. Next, a method for correcting deflection distortion of an ion beam using the deflection distortion detection element 1 configured as described above will be described. As shown in Figure 2, the shape of the deflection field usually deviates from the ideal shape (square PQRS) due to electric field distortion in the electrostatic deflection system, resulting in so-called pincushion distortion such as P′Q′R′S′. arise. Therefore, when high-precision drawing such as ion beam drawing is performed, drawing is performed at coordinates different from the originally intended position, resulting in inaccurate drawing, and it is therefore necessary to correct the deflection distortion of the ion beam. be. Therefore, in this embodiment, first, the deflection distortion detection element 1 is
is located on the diagonal line QS of the ideal deflection field PQRS, and the deflection field PQRS without deflection distortion is
The focused ion beam a is scanned so that the focused ion beam a passes through the center O of the deflection distortion detection element 1 at an angle of 45°. In this case, the focused ion beam a is applied to the surfaces A, B, and
C and D, and at this time, secondary electrons are emitted from the striped AlAs semiconductor region 2, the striped GaAs semiconductor region 2, and the striped GaAs semiconductor region 3. Since the secondary electron emission rates are different and the secondary electron emission rate of AlAs is greater than the secondary electron emission rate of GaAs, a secondary electron signal like the signal shown in FIG. 4 is obtained. In this case, the signal is a symmetrical signal with amplitude h and period w, AB=CD. This is the secondary electron signal when there is no deflection distortion. Next, the precision stage 4 is moved in the A direction with an accuracy of, for example, about 1 μm by the pulse motors 5a and 5b, and the deflection strain detection element 1 is moved to a position as shown in FIG. Here, the focused ion beam a
is scanned along the PS line of the deflection field PQRS so as to cross the deflection distortion detection element 1. In this case, assuming that there is no deflection distortion in the focused ion beam a, the focused ion beam a crosses the deflection distortion detection element 1 at an angle of 45°, and a secondary electron signal identical to the signal is obtained. However, there is a deflection distortion in the actual scanning shape of the focused ion beam a, and in this case, the focused ion beam a does not cross the deflection distortion detection element 1 and has an angular distortion of θ with respect to the PS line.
The line A'B'C'D' crosses the deflection strain detection element 1. As a result, the resulting signal becomes an asymmetric secondary electron signal with amplitude h' and period ω', where A'B'≠C'D', as shown in FIG. The degree of deflection distortion of the focused ion beam a can be measured by comparing the amplitude, period, symmetry, etc. of the signal with those of a signal without deflection distortion. For example, the relationship between periods ω', ω and angular distortion (θ) is shown in the table below.

[Table] Therefore, the angular distortion (θ) is measured from the periods ω' and ω, and from the angular distortion (θ) and AB, A'B',
The Y-coordinate deviations ΔX' and ΔY' are obtained from the following formulas. △X′=AB−A′B′cosθ △Y′=A′B′sinθ Specifically, as shown in FIG. The secondary electrons are received by the secondary electron multiplier 6, and then the A/D
The signal obtained through the converter 7 is guided to the computer 8 to calculate the above-mentioned measurement value. Further, the calculated deflection distortion is introduced to the ion beam scanning sweep signal corrector 9 to correct the deflection distortion of the focused ion beam a. The above operation is performed by moving the deflection distortion detection element 1 in the A direction and then in the B direction by, for example, 1 μm, measuring the deviation between PQRS and P′Q′R′S′ around the entire circumference of the deflection field, and correcting it. That's what I'm going to do. (Effects of the Invention) In summary, according to the present invention, distortion of ion beam deflection, which is a problem in devices using focused ion beams such as maskless ion beam devices, and the accompanying positional changes in the ion beam diameter can be accurately corrected. Since the deflection distortion of the ion beam can be corrected based on the accurate measurement, it is possible to perform high-precision, high-quality writing using the ion beam.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an embodiment of the present invention;
Figure 2 is a plan view showing the movement range of the deflection strain detection element in the same embodiment as above, Figure 3 is a partially enlarged view of the same, and Figure 4 is a relationship curve between secondary electron signal intensity and ion beam scanning distance. In the figures, FIG. 4a shows the case without distortion, and FIG. 4b shows the case with distortion. In the figure, 1 is a deflection strain detection element, 2 is a striped AlAs semiconductor region, and 3 is a striped GaAs semiconductor region.

Claims (1)

[Claims] 1. Striped areas having different emission levels of secondary electrons emitted by ion beam irradiation.
The amplitude of the secondary electron signal detected by scanning the ion beam by arranging a deflection strain detecting element periodically formed of AlAs and GaAs and having the cleaved cross section as the surface is arranged at an angle with respect to the X-Y axis. Correction of deflection distortion in an ion beam, characterized in that the deflection distortion of the ion beam is corrected by measuring the deflection distortion of the ion beam from periodicity and asymmetry, and correcting the scanning sweep signal of the ion beam based on the measured value. Method. 2 Deflection strain in an ion beam characterized by periodically providing striped regions by cleaving a stacked body in which films of materials having different emission levels of secondary electrons emitted by ion beam irradiation are cleaved. Deflection distortion detection element used in the correction method. 3. The deflection strain detection element according to claim 2, wherein the striped region has a heteroperiodic structure of GaAs/AlAs. 4. The deflection strain detection element according to claim 2, wherein the width of the striped region is 0.1 μm or less.