RU2126188C1 - Ion-beam microprojector and its adjustment process - Google Patents

Abstract

FIELD: electronic engineering; large-capacity integrated circuits manufactured by lithographic method. SUBSTANCE: divergence of ion beam produced by ion-beam generator is varied during microprojector adjustment in metrological template plane by varying supply voltage across electrostatic lens of illuminating device incorporated in optical system of microprojector; in the process, circumferential distortion is measured on working field of target incorporated in receiving unit; when circumference with zero- distortion radius is detected, distortion on circumference with r_m = 3/5 radius is measured and measurement results are used to determine adjustment of microprojector with respect to permissible distortion. EFFECT: improved quality of image due to reduced aberrations brought in by illuminating device. 2 cl, 8 dwg

Description

 The present invention relates to the field of electronic technology and can find application in the manufacture of integrated circuits with a large information capacity by the method of lithography, as well as in other processes of precision surface treatment of materials with an ion beam, for example, drawing on a substrate with changes in the surface properties of materials in it, in particular , a change in the type of conductivity in semiconductor materials as a result of the introduction of doping ions, a change in other physical properties of the material due to the introduction of I have the same name and foreign ions, the creation of new layers on the surface as a result of the deposition of atoms of matter from the surrounding cloud vapor under the influence of incident ions, the removal of matter from the surface of the substrate as a result of its sputtering.

 An ion-projection device is known that contains an ion source sequentially and coaxially, a mass filter, a template, immersion and reducing lenses, a multipole element with a solenoid, an Enzel lens, an alignment system, and a receiving unit consisting of a coordinate table with a processing object fixed on it (see Springer Series in Solid-State Sciences Vol. 83: Physics and Technology of Submicron Structures, c. 56-61, Fig. 1, Springer-Verlag Berlin Heidelberg, 1988).

 A known method of tuning an ionic microprojector based on the extraction of support sub-beams from the ion beam using the holes in the template, combining the position of the support sub-beams with registration marks at the processing object by changing the potentials of lenses and multipole elements (see J. Vac.Sci.Technol.B, Vol. 4, 1, 1986, 194-200).

 The disadvantages of the known device and method are the low quality of the optical image due to excessive aberrations of the optical system. This applies to distortion, which characterizes the distortion of the shape of the pattern, and scattering, which determines the optical resolution.

 Known ion-projection lithographic equipment containing placed in a vacuum chamber sequentially and coaxially arranged device for creating an ion beam, a lighting device consisting of a filtering magnetic lens, a template, an optical column (projector), consisting of the first and second lenses, the first and second multipole elements located respectively behind the first and second lenses, a metrological unit, a receiving unit consisting of a target and a coordinate table, and the information output of the metrological about the unit is connected to the information input of the control unit, the control outputs of which are connected respectively to the control inputs of the first and second power supplies, the outputs of the first and second power supplies are connected respectively to the power buses of the first and second lenses of the optical column, as well as the third power supply, the outputs of which are connected to an ion beam generating device (see patent 4985634, CL H 01 J 37/30, 1991).

 A known method of tuning the ion-projection lithographic equipment, including the formation of a collimated ion beam, extracting reference beams from it using the holes in the template, measuring the dimensions and coordinates of the centers of the reference beams in the target plane by alternately changing one of the adjustable parameters of the ion-projection equipment with the constancy of the other parameters, comparing the obtained values with the corresponding values in the plane of the template, taking into account the reduction coefficient of the equipment, with a difference t using the method of linear optimization correction value to the parameter, adjustable ion projection lithography apparatus and change the size and central position of the supporting beams by setting a proximate value, adjustable parameter (ibid.).

 A disadvantage of the known devices and method is the inability to obtain an optimum quality image over the entire working field of the target for a given reduction scale and an acceptable level of distortion due to the influence of aberrations of the lighting device and the lack of necessary means for controlling the divergence of the ion beam in the plane of the template.

 A disadvantage of the known device is the appearance of anisotropic aberrations associated with oblique rays resulting from the residual rotation of the ion beam in the filtering magnetic lens, even when using compensation methods.

 A disadvantage of the known device is the scattering in the image due to the low speed of ions in the beam in the crossover region, causing increased repulsion of ions in the crossover.

 The technical result of the invention is to improve image quality by reducing aberrations introduced by the lighting device.

 The technical result is achieved by the fact that in an ionic microprojector containing an ion beam creating device arranged sequentially and coaxially inside the vacuum chamber, a lighting device consisting of a mass filter, a template, a projector consisting of the first and second lenses and the first and second multipole elements, coaxially arranged respectively, behind the first and second lenses, the metrological unit and the receiving unit containing the coordinate table with the processing object located in it, as well as the first and second power supplies and the unit board, the first information input of which is connected to the information output of the metrological unit, its first and second control outputs are connected respectively to the control inputs of the first and second power supplies, the first output of the first power supply is connected to the internal electrode of the first lens of the projector, the second output of the first and first output of the second power supplies combined, introduced the third and fourth power supplies, the first and second reference power sources, in the lighting device electrostatic collimating l a probe mounted coaxially behind the mass filter into the projector an immersion lens mounted coaxially in front of the first lens, the first electrode of the electrostatic collimating lens of the lighting device is connected to the first output of the third power supply, the control input of which is connected to the third control output of the control unit, its second output and the power input of the ion beam making device is connected to the first output of the second reference power source, the second output of which is connected to a common bus to which it is connected the housing of the vacuum chamber, the external electrodes of the first and second lenses of the projector and the first output of the first reference power source, the second output of which is connected to the combined outputs of the first and second power supplies, the second output of the second power supply is connected to the internal electrode of the second lens of the projector, while the first electrode is immersion the projector’s lens is connected to the second electrode of the electrostatic collimating lens of the lighting device and through the fourth power supply to the first output of the second reference power source Ia, the latter electrode immersion lens is connected to a common bus.

, где r₀ - радиус окружности с нулевым значением дисторсии, сравнивают измеренную величину дисторсии с допустимым значением, при отличии повторяют указанные выше операции до тех пор, пока на радиусе r_m, соответствующем вновь полученному радиусу r₀, абсолютное значение измеренной величины дисторсии не достигнет допустимого значения дисторсии, или пока вновь полученный радиус r₀ не достигнет заданного размера рабочего поля, даже если абсолютное значение величины дисторсии на соответствующем радиусе r_m меньше допустимого значения дисторсии.The technical result is achieved by the fact that in the method of tuning an ionic microprojector, including pre-setting its projector by determining the adjusted values of the adjustable parameters of the ionic microprojector based on the measurement results on the target of the sizes and coordinates of the centers of the reference beams extracted using the metrological template from the collimated ion beam, make a change the divergence of the ion beam in the plane of the metrological template and the measurement around the circumference of the distortion at work than the target field, when a circle with a zero distortion value is detected, the divergence of the ion beam is recorded and the radius of the circle on which zero distortion is detected is measured, and the distortion value is measured on a circle with a radius

, where r ₀ is the radius of a circle with a zero distortion value, compare the measured distortion value with an acceptable value, with the difference, repeat the above operations until, at a radius r _m corresponding to the newly obtained radius r ₀ , the absolute value of the measured distortion value reaches permissible distortion value, or until the newly obtained radius r ₀ reaches the specified size of the working field, even if the absolute value of the distortion value at the corresponding radius r _{m is} less than the permissible distortion value and.

In FIG. 1 is a structural diagram of an ionic microprojector (IM) that implements a method for tuning it; FIG. 2a — standard paths characterizing the tuning of the optical system of the MI, in FIG. 2b is an optical circuit of the MI, in FIG. 3 is a graph of the dependence of the third-order distortion coefficient on the parameter θ characterizing the divergence of the ion beam in the plane of the template, FIG. 4 is a graph of a fifth-order distortion coefficient versus θ, FIG. 5 - the possibility of reconfiguring the optical system of the MI relative to the distortion distribution function (Δw _d ) with the help of a lighting device at a constant value of the image reduction scale, in FIG. 6 shows the results of calculating the dependence of the size of the working field at a given level of distortion on parameter θ, obtained in three different ways, and FIG. 7 is an example of an optimally tuned optical system (the dependence of the absolute value of distortion on the radius of the working field), FIG. 8 - algorithm of the control unit in the setting mode.

 The ion microprojector (Fig. 1) contains an ion beam generating device 2 located in a vacuum chamber 1 sequentially on one straight axis, an illumination device consisting of a mass filter 3 and an electrostatic collimating lens 4, template 5, and a projector consisting of an immersion lens 6, the first a lens 7, a first multipole element 8, a second lens 9, a second multipole element 10, a receiving unit 11 with a processing object and a smart device placed therein, as well as a metrological unit 12, the information output of the block 12 and information This output of the smart device is connected to the information inputs of the control unit 13, the first, second and third control outputs of which are connected respectively to the control inputs of the first 14, second 15 and third 16 power supplies, the first output of the first 14 and second output of the second 15 power supplies are connected respectively to the internal electrodes of the first 7 and second 9 lenses of the projector, the second output of the first 14 and the first output of the second 15 power supplies are combined and connected through a first reference power source 17 to a common bus, the first output of the third 1 6, the power supply is connected to the first electrode of the electrostatic lens 4, its second output is connected to the first output of the second 18 reference power supply, to which the power input of the device 2 is connected, and through the fourth power supply 19, the first electrode of the immersion lens 6 of the projector is connected to which the second the lens electrode 4, the last electrode of the lens 6 is connected to a common bus, to which the external electrodes of the lenses 7 and 9 are connected, the second output of the second 18 power source and the housing of the vacuum chamber 1.

 The ion beam generating device 2 contains a plasma-type ion source 20 that draws 21 and suppresses 22 electrodes, as well as the first 23 and second 24 power supplies, with the source 20 through the first 23 power supply, the suppressing 22 electrode through the second 24 power supply connected to the input power supply of the device 2, to which the pulling electrode 21 is connected. Device 2 is capable of creating an ion beam with high brightness due to the small size of the virtual source having a diameter of about 10 μm and provides an initial ion energy of 5 keV to 10 keV.

 The lighting device comprises a 3 mass filter and an electrostatic collimating lens 4. The 3 mass filter can be implemented as a Wien filter containing crossed electric and magnetic fields configured to transmit only one type of ion without deviation.

 The template 5 is replaceable, for which it is mounted in a special drum having thermal stabilization and a control system for changing templates (not shown in Fig. 1). There are two types of templates: working and metrological. The working template has holes to create the desired pattern and additional holes that play the role of alignment marks. The metrological template has many metrological holes that allow you to determine the various parameters of the MI, similar to how it is done in the known device. The metrological template for measuring distortion should contain many identical holes arranged in rows and columns with the same pitch in the X, Y plane and cover a space slightly exceeding the permissible size of the working field. The shape of the holes can be round or square, the size is chosen so that the projected image of one hole can fit into one square pixel of the detector with a size of 10 μm x 10 μm.

 The immersion lens 6 of the projector contains a series of accelerating electrodes separated by dielectrics, with potential evenly distributed across the electrodes coming from the power supply unit 19. Connecting the first electrode of lens 6 to the second electrode of lens 4 of the lighting device includes lenses 4 and 6 in a single system that provides ions with final energy before they reach a crossover located between the first 7 and second 9 lenses of the projector. In this case, the repulsion of ions among themselves in the crossover will be minimal, which helps to reduce the total scattering. In addition, most of the device is under the ground potential.

 The first lens 7 of the projector is an accelerating ensel lens that collects the ion beam into a crossover and is intended primarily for smoothly changing the reduction ratio.

 Each multipole element 8 and 10 contains 16 electrodes forming a hole of a cylindrical shape, which are used to control the displacement of the optical axis, correct differences in the scale of reduction along the X, Y axes, and correct quadrupole and other multipole effects resulting from random axial symmetry violations.

 The second lens 9 of the projector is an enzel lens, which provides final focusing and is adjusted so that the resolution at the edges of the working field is the same as at the center point of the optical axis. The energy of ions incident on the target is in the range from 50 to 200 keV.

 The receiving unit 11 contains a processing object connected to a common IM bus (not shown in FIG. 1) and a smart device mounted on a coordinate table, which are used alternately as a target. The movements of the coordinate table are controlled using a laser interferometer. The distortion is measured by registering on the target using a smart device the coordinates of the centers of the reference beams extracted from the ion beam using the template 5. The output signal of the smart device is connected to the control unit 13 at the time of MI tuning. The smart device includes a detector and several integrated circuits that digitally process the detector signals, which is manufactured by Irvin Sensors, USA (see Laser Focus World, july 1966, pp. 113-115).

 The metrological unit 12 is a series of detectors installed in predetermined places on a precision metrological table in front of the target, which is mounted on the coordinate table of block 11. The detectors are designed to register the registration alignment beams generated during the passage of the ion beam through special holes on working template 5 (similar to metrological unit of a known device).

 The control unit 13 may be performed on a Pentium microprocessor or on a personal computer of the IBM PC type containing it. The operation algorithm of block 13 in the tuning mode of the electrostatic collimating lens 4 is shown in Fig. 8.

 Power units 14, 15 and 16 are configured to adjust the output voltage.

 The first reference power source 17 creates a common potential bias on the inner electrodes of the first 7 and second 9 lenses of the projector relative to the housing of the vacuum chamber 1, which is under the ground potential.

 The second reference power source 18 provides a total potential bias on the device 2, the collimating lens 4, the target, the immersion lens 6 relative to the housing of the vacuum chamber 1.

 All listed power sources contain primary autonomous power sources. The use of reference sources 17 and 18 allows the power supply units 14, 15 and 16 to be made in the MI with finer adjustment of the output voltage.

 The practical work is preceded by a metrological cycle of measuring the modes and parameters of the optical system of the IM and setting it to a state that provides the IM with the required mode of image reduction with an acceptable level of image aberration.

 It is generally accepted that the highest quality image corresponds to the normal incidence of the collimated ion beam on pattern 5, i.e. when the main rays emanating from each image point of the template are strictly orthogonal to the surface of the template, and the further course of the main rays in the projector is subject to confocal conditions. The usual distortion analysis scheme in this case is based on taking into account third-order aberrations, according to which the distribution function distortion along the working field continuously increases as a cubic parabola as the image point moves from the center of the picture to its periphery, and it is assumed that the fifth-order distortion being significantly smaller in magnitude does not introduce significant differences in the nature of the specified distribution. Due to the fact that the third-order distortion coefficient has the property of vanishing, the fifth-order distortion, which is sensitive to aberrations of the lighting system, qualitatively changes the picture of the distortion distribution.

 For a better understanding of the invention we give a number of definitions that are further used in the description of the invention.

 Definition 1. Image distortion is the aberration of the main rays in the image plane.

 Definition 2. The main beam is a trajectory connecting the center of the ion source with the studied point in the plane of the template and is its continuation in the projector.

Definition 3. The non-cathode optical system, hereinafter referred to simply as the optical system, contains the lighting and projector parts, considered as a whole, in which the beginning is a virtual source (coordinate z _v in figa), and the end of the system is a target (z _i ), while the beginning and end of the system are not optically conjugated, as in the case of an optical column of a known device corresponding to the projection part of the proposed system with optically conjugated planes of the template (z _m ) and target (z _i ).

 Definition 4. An optical system is called paraxial if the distortion and scattering aberrations in the entire given image field are limited to certain specified limits that satisfy the conditions of the problem being solved.

 Definition 5. An optical system is called optimally tuned for distortion if it has the maximum possible working field satisfying the paraxiality condition, and the corresponding picture of the distortion distribution in this case is called a fine structure.

 Adjustable MI parameters are parameters that change their values during the setup process. These include potentials mounted on the lenses 7 and 9 of the projector and multipole elements 8 and 10.

Based on the results of our studies, we affirm that each optical system is characterized by its optimal tuning and the corresponding fine distortion structure, by its optimal value of the parameter θ characterizing the divergence of the ion beam. Such an optimal value of θ depends on the value of the permissible distortion level ε, on the geometric design parameters, the internal configuration of the lens electrodes and the shell of the vacuum chamber 1, affecting the structure of the electric field, characterized by the distribution function of the potential along the optical axis and its derivatives in the z direction, which up to fourth order inclusively have a significant impact on the nature of the distribution of distortion within the working field. Such an optimal value is in the vicinity of the value θ ₀ = 0 and requires special fine tuning.

Theoretical studies of distortion show that each optical system can be tuned at an acceptable level of ε distortion using the lens of a lighting device in such a way that it will have the maximum possible size of the image working field, bounded by a circle with a radius r ₀ , where there is zero distortion. On this circle, the condition of equality of the third and fifth order distortion terms in magnitude and opposite in sign is satisfied, as a result of which they are compensated. This position can be regulated and shifted in any direction, however, a shift in the direction of increasing the radius entails an increase in the maximum absolute value of distortion in the inner region. Fulfillment of the requirement of equality of the maximum absolute value of distortion inside the specified circle to the permissible level ε determines the maximum possible acceptable value r ₀ . In this state, which is called a fine structure according to Definition 5, the fifth-order distortion term plays the main role.

где θ - параметр, характеризующий расходимость ионного пучка в плоскости шаблона 5 и играющий главную роль в поиске оптимального режима работы.The traditional approach to the study of distortion is to consider the projector (fig.2b) in the range from z _m to z _i , where z _m and z _i respectively the coordinates of the template 5 and the target located in the receiving unit 11 on the optical axis. When describing the ion trajectory, the standard trajectories T ₁ (z), S ₁ (z) and V ₁ (z) (Fig. 2a) are used, which are found from the solution of the homogeneous differential equation of the Guass approximation trajectories according to their initial conditions in the plane of the template 5:

where θ is a parameter characterizing the divergence of the ion beam in the plane of template 5 and playing a major role in the search for the optimal operating mode.

и означает место расположения кроссовера в зависимости от параметра θ.The trajectory S ₁ (z) corresponds to the case of a strictly collimated ion beam, i.e., to the normal incidence of the main rays on the template, which is a special case, but usually implied as an ideal case. In the general case, it is replaced by the trajectory V ₁ (z), between which there is the following connection
V ₁ (z) = S ₁ (z) + θT ₁ (z). (4)
The intersection of each of the trajectories S ₁ (z) and V ₁ (z) of the optical axis is marked by points z _p and

and means the location of the crossover depending on the parameter θ.

 There is a correlation between the location of the crossover and the type of distortion (pillow-shaped or barrel-shaped); it is generally accepted that the type of distortion is determined by the sign of the third-order distortion coefficient, and a change in its sign entails a change in the type of distortion. This statement is true in cases where the absolute value of the third-order distortion at all points of the working field significantly exceeds the same value of the fifth order. However, there is a transition region where the last condition is violated and where fifth-order distortion comes first in value. This region occupies a narrow range in θ and is of main interest, since it contains a fine distortion structure. The fine structure of distortion is achieved by adjusting the divergence of the ion beam in the plane of the template 5, carried out by an electrostatic collimating lens 4.

.Standard trajectories make it possible to represent a linear approximation of the general solution of the trajectory equation of the main ray, expressed in terms of the initial conditions in the plane of template 5 in the form of an equation
w (z) = w _m V ₁ (z) + w ' _m T ₁ (z), (5)
where wm = w (z _m ),

.

In the general case, θ ≠ 0, and the particular case (used in the known device) θ = 0 corresponds to the equation
w (z) = w _m S ₁ (z) + w ' _m T ₁ (z). (6)
By tradition, it is such a condition that is considered to be ideal.

Дисторсия Δw(z_i) в плоскости изображения, соответствующая традиционному подходу, равна

где K_6v, L_12v - коэффициенты дисторсии соответственно третьего и пятого порядков с индексом "v", указывающим на зависимость от стандартной траектории V₁, учитывающей влияние параметра θ.Note another important value shown in FIG. 2a, is the coefficient of increase V, which is calculated using the formula
S ₁ (z _i ) = V ₁ (z _i ) = V. (7)
In MI, instead of the increase coefficient V, the decrease scale M is used, which is the reciprocal of the absolute value of the increase coefficient

The distortion Δw (z _i ) in the image plane corresponding to the traditional approach is

where K _6v , L _12v are the distortion coefficients of the third and fifth orders, respectively, with the index "v" indicating the dependence on the standard path V ₁ , taking into account the influence of the parameter θ.

где R - расстояние от точки исхождения луча в плоскости шаблона 5 до оптической оси,
i - мнимая единица,
φ - азимутальный угол этой точки в полярной системе координат.The initial position w _{m of the} ion trajectory in the plane of template 5 is set using small complex parameters

where R is the distance from the point of origin of the beam in the plane of the pattern 5 to the optical axis,
i is the imaginary unit
φ is the azimuthal angle of this point in the polar coordinate system.

The distortion coefficients are included in the corresponding sets of third and fifth order aberration coefficients under the indicated serial numbers and are calculated as integral functionals depending on the field functions on the axis of the optical system and their derivatives with respect to z, and also depend on the indicated standard trajectories. The coefficient L _12v , in addition, depends on the function K ₁ (z) characterizing the third-order aberration.

Equation (9) expresses distortion in the classical style, but, as theoretical studies show, it has a significant drawback in that it does not take into account the effect of aberrations in the (z _v , z _m ) region (Fig. 2a), which affect the deviation of the true slopes of rays in the plane of pattern 5 from slopes characterized by divergence of the first (Gaussian) order. The special calculation of these aberrations (first stage) and taking into account their influence on distortion in the traditional way (second stage) leads to complex calculations that require taking into account all third-order aberration coefficients. The result of this two-step calculation is reduced to the addition of Δ ₃ = F ₃ (K ₁ , ..., K ₅ ), the effect of which is shown in Fig. 6 in the form of curve 2.

Настройка оптической системы и поиск оптимального состояния производится при фиксированном М и варьируемом θ. В этом случае траектории главных лучей определяются в соответствии с определением 2 и имеют вид

где

верхняя черта обозначает комплексное сопряжение, функциональные коэффициенты К₁(z), L₁(z) являются решениями соответствующих им нелинейных дифференциальных уравнений.Faster and more accurate accounting is performed as a result of a new method developed by us, namely, when considering the entire optical system (z _v , z _i ) as a whole (Fig. 2a), described using one new standard trajectory T (z) taking the beginning in position z _v (figb) and determined by the initial conditions
T (z _v ) = 0, T '(z _v ) = 1, (11)
where the prime denotes the derivative with respect to z. The parameter θ is found from the condition

The tuning of the optical system and the search for the optimal state are performed for a fixed M and a variable θ. In this case, the trajectories of the main rays are determined in accordance with Definition 2 and have the form

Where

the upper line denotes complex conjugation, the functional coefficients K ₁ (z), L ₁ (z) are solutions of the corresponding nonlinear differential equations.

где

Результат учета новым методом влияния указанных аберраций на размер рабочего поля показан также на фиг.6 в виде кривой 3.The desired distortion Δw _{D /} image of the point w _m on the target, according to Definition 1, is represented by the expression

Where

The result of taking into account the influence of these aberrations on the size of the working field by a new method is also shown in Fig. 6 in the form of curve 3.

зависимы между собой. Из графика видно, что в некотором положении θ₀, которого можно достичь с помощью изменения расходимости ионного пучка, функция K_6v(θ) принимает значение нуль. Это положение θ₀ не обязательно совпадает с нулевым значением величины θ, которое характеризует строго коллимированный ионный пучок в плоскости шаблона 5. Однако такое отклонение обычно мало, но имеет существенное значение при настройке, несмотря на его малость.The main feature of electrostatic systems is related to the possibility of vanishing of the third-order distortion coefficient K _6v (θ), which is shown in FIG. 3. Functions

are interdependent. The graph shows that at a certain position θ ₀ , which can be achieved by changing the divergence of the ion beam, the function K _6v (θ) takes the value zero. This position θ ₀ does not necessarily coincide with the zero value of θ, which characterizes a strictly collimated ion beam in the plane of template 5. However, such a deviation is usually small, but it is significant when tuning, despite its smallness.

, которое соответствует обращению суммарной дисторсии в ноль на некотором радиусе r₀ в плоскости изображения, связанного с радиусом R₀ в плоскости шаблона 5 соотношением r₀ = VR₀. Диапазон по

и возможно несколько дальше имеет отличительную особенность, заключающуюся в существовании на изображении окружности с нулевой дисторсией при радиусе R₀, которым мы можем управлять с помощью электростатической линзы 4.In FIG. Figure 4 shows the function L _12v (θ) correlated with K _6v (θ), which determines the fifth-order distortion. On both mentioned figures the value is highlighted

, which corresponds to the reversal of the total distortion to zero at a certain radius r ₀ in the plane of the image associated with a radius R ₀ in the plane of pattern 5 by the ratio r ₀ = VR ₀ . Range by

and perhaps a little further has a distinctive feature, which consists in the existence in the image of a circle with zero distortion at a radius R ₀ , which we can control using an electrostatic lens 4.

где

Тогда получим

Пользуясь выражениями (19), можно написать

Таким образом, распределение дисторсии по радиусу мы представили как функцию коэффициента пятого порядка и значения малого параметра, соответствующего месту обращения в нуль дисторсии.Figure 5 shows graphs of the distribution of distortion along the radius R for two cases of tuning the lens 4 to two close values of the parameter θ, characterized respectively by different levels of distortion ε ₁ , ε ₂ . The graph shows that the shift of the point R ₀ in the direction of increase entails an increase in the absolute value of distortion in the inner region. In the region R <R _0, third-order distortion prevails over fifth-order distortion, but is comparable in magnitude with it. In the region R> R ₀ , fifth-order distortion becomes dominant and up to the value of R _{max, the} absolute value does not exceed the permissible value of ε, which limits the distortion in the inner region. It is reasonable to take R ₀ as a measure of the working field
We write a condition that determines the existence of a circle with radius R ₀ (based on expressions 9 and 10):
K _6v R $\genfrac{}{}{0ex}{}{\text{3}}{\text{0}}$ + L _12v R $\genfrac{}{}{0ex}{}{\text{5}}{\text{0}}$ = 0 (16)
and similar to it in the new proposed method (from expression 14)

Where

Then we get

Using expressions (19), we can write

Thus, we presented the distribution of distortion along the radius as a function of the fifth-order coefficient and the value of a small parameter corresponding to the place where the distortion vanishes.

или с учетом того, что r = RV, в плоскости мишени

которому соответствует значение абсолютной дисторсии, равное

Уравнение (24) может быть использовано для вычисления коэффициента L_12v.A study of expression (20) for an extremum in the inner region shows the existence of a maximum value of the distortion modulus on a circle with a radius corresponding to the plane of template 5:

or taking into account that r = RV, in the target plane

which corresponds to the value of absolute distortion equal to

Equation (24) can be used to calculate the coefficient L _12v .

 FIG. 5 is a qualitative illustration of the nature of the change in distortion near the axis of the system and is intended to give an idea of the possibilities of tuning the optical system in a certain transition region with respect to θ, in which fifth-order distortion plays a decisive role. The extent of this region is limited by the region of applicability of the decomposition used. However, the very existence of the region is undeniable. The practical detection of this region is a subtle experimental problem that can be solved with the use of sufficiently sensitive instruments for measuring distortion and tuning the collimating lens 4.

 The method of tuning the ion microprojector is implemented as follows.

 In the initial state, a smart device is installed as a target in the receiving unit 11, the vacuum chamber is evacuated, voltages are supplied to the lens power supply units 14, 15, 16 and 19 to ensure their normal functioning. The reference sources 17 and 18 provide the corresponding voltage displacements, in the first case on the internal electrodes of the lenses 7 and 9 of the projector, in the second case on the device 2 for creating an ion beam, a collimating lens 4 of the lighting device and an immersion lens 6. A number of metrological and working patterns are installed in the special drum 5. It is assumed that the ion beam generating device 2, the mass filter 3, and the collimating lens 4 of the lighting device are in some tuned state that provides uniform illumination the collimated ion beam of the location of the working position of the template 5. The receiving unit 11 is also loaded with the processing object. A metrological template 5 is installed in the working position, with the help of which the image is sharpened, the projector is adjusted to the desired image scale and then adjusted for distortion. It is carried out as follows. The potential determining the final ion energy is fixed on the immersion lens 6. The first 7 and second 9 lenses of the projector are supplied with some estimated voltage values from blocks 14 and 15. From the ion beam that has passed through pattern 5, the control tuning beams (KLN) are targeted. Then, by a series of sequentially alternating operations, the voltage value supplied by block 15 is refined, while the KLN measurements are made in order to detect their smallest sizes and coordinates of the centers.

 The measurement process is carried out using a smart device in a position centered with respect to the ion beam and mechanical scanning carried out by the coordinate table under the control of a laser interferometer. Scanning is carried out to a limited extent, depending on the size of the check marks. Simultaneously with focusing, a resolution of the image is measured based on measurements of the front width of the measured signal profiles. The first stage of tuning is terminated when the size of the specified KLN is reached. In the case of differences in the size of the CLI located at the vertices of the square of the working field and the distances between them, they are aligned using the multipole element 9. From the calculation of the ratio for a number of CLI between the measured distances and the corresponding distances on the template, the image reduction scale is determined. If the reduction scale so determined does not correspond to the required value, the voltage on the first lens 7 is corrected using block 14, and the above adjustment cycle is repeated until the desired reduction scale is reached. The next step is to adjust the distortion.

 Distortion adjustment is performed on the same metrological template using the full set of reference beams, uniformly filling the entire working field. First, the coordinates of the centers of all the reference beams are recorded and analyzed for correspondence to circular symmetry. If this is absent, distortion correction is achieved using the multipole element 10 and measurements and coordinate analysis are performed again until symmetry is reached, after which the last stage of image fine-tuning begins.

и измеряется дисторсия для опорных пучков, расположенных на окружности, имеющей радиус r_m. Измеренную величину дисторсии сравнивают с допустимым ее значением ε. В случае когда r₀ меньше желаемого значения рабочего поля, существуют две следующих возможности: измеренное значение дисторсии на окружности с радиусом r_m меньше или больше величины ε. В зависимости от этого результата изменяют расходимость ионного пучка до тех пор, пока на каждом вновь полученном расстоянии r_m абсолютное значение дисторсии не достигнет заданного значения ε или пока при меньшем, чем ε, абсолютном значении дисторсии радиус r₀ окружности с нулевой дисторсией не достигнет заданного размера рабочего поля. Дополнительные сведения о тонкой настройке дисторсии содержатся в описании алгоритма настройки.The data characterizing the distortion are found as the differences between the measured coordinates of the centers of the reference rays and calculated taking into account the scale of reduction of the coordinates of the "correct" position of these rays. Based on these data, distortion coefficients are calculated and the type of distortion state is determined: 1) the third-order coefficient is positive, the third-order terms everywhere significantly exceed the values of the fifth-order terms, 2) the absolute values of the third-order terms become comparable with the absolute values of the fifth-order terms for a certain group of reference beams, 3) the third-order coefficient takes a negative value, there is a group of reference beams for which the absolute value of the total distortion is less certain threshold smallness, 4) of the third order coefficient is negative, the absolute value of the third order terms throughout exceed the absolute value of the fifth order terms. Depending on the result of the analysis, a decision is made to change the voltage on the collimating lens 4, which controls the parameter θ of the divergence of the ion beam on the template 5. When a clearly defined third type of distortion is detected, it is possible to determine a circle with a certain radius r ₀ with zero distortion. Then the value is calculated

and measured distortion for reference beams located on a circle having a radius r _m . The measured distortion value is compared with its permissible value ε. In the case where r _{0 is} less than the desired value of the working field, there are two of the following possibilities: the measured value of distortion on a circle with a radius r _{m is} less than or greater than ε. Depending on this result, the divergence of the ion beam is changed until, at each newly obtained distance r _{m, the} absolute value of distortion reaches a predetermined value ε or until, at a value smaller than ε, the absolute value of distortion, the radius r _{0 of a} circle with zero distortion reaches a predetermined value the size of the working field. For more information on fine tuning the distortion, see the tuning algorithm.

После указанной настройки ионный пучок в области рабочего поля перекрывается механическим затвором, и ионный микропроектор готов к работе с рабочим шаблоном 5 и рабочей мишенью. После установки рабочего шаблона 5 в положение, совпадающее с оптической осью, производится процесс совмещения проектируемого изображения с рисунком на рабочей мишени. Для этого используются контрольные лучи совмещения (КЛС), образующиеся в результате прохождения ионов через специальные отверстия в рабочем шаблоне, находящиеся вне поля проецируемого рисунка, но в непосредственной близости к вершинам квадрата (прямоугольника), образующего рабочее поле. Процесс совмещения достигается с использованием метрологического блока 12 и меток совмещения, расположенных на мишени. Для этого КЛС поочередно электрически сканируются по соответствующим меткам совмещения, и по сигналу рассеяния производится с помощью мультипольного устройства 10 соответствующая коррекция координат Х и Y центра рабочего поля. После этой операции производится открытие механического затвора и экспонирование мишени.In FIG. Figure 8 shows a block diagram of the algorithm for tuning the MI to the optimal mode of operation, taking into account the fine structure of distortion. The tuning is based on the standard cycle of measuring the coordinates of the centers of the reference beams on the target. The cycle begins with the movement of the coordinate table (CS) in the process of mechanical scanning, which is carried out in order to determine the profiles of all reference beams in sections X and Y. For this, a control pulse is received from the general process control program at which its coordinates are fixed, all pixels are initialized detector matrix and the measurement process begins, which consists in the accumulation of charges delivered by the incident ion stream for each pixel for a given time interval. At the end of this time interval, the smart device digitally processes the signals of each pixel and stores this data in the form of a card. Then such a card is read by the memory circuit, and the indicated period of the measurement cycle after the next movement of the CS is repeated a predetermined number of times. As a result of the full measurement cycle, a sequential series of cards corresponding to the temporary execution of the cycle are placed in the indicated memory. In those pixels to which the reference beams fell, time-consistent data form cross-sectional profiles of the corresponding reference beams with known coordinates determined by the positions of these pixels in the matrix of the smart device. At the end of this cycle, the data obtained is processed, which consists in first determining the position of the centers of the signal fronts at the level of 0.5 of its maximum signal value of each reference beam. The coordinate of the center of the reference beam is found as the arithmetic mean of its coordinates of the left and right fronts. The repetition of the cycle by displacing the CS in another mutually perpendicular direction makes it possible to determine both coordinates of the center for each reference beam. The next processing step is to calculate the magnitude of the reduction scale M necessary to determine the distortion of each reference beam. To do this, a comparison is made of the distances between the selected tuning control beams (KLN) on the target and their known distances on the template. Such highlighted VLFs should be located close enough to the center of the image to be slightly susceptible to distortion and at the same time sufficiently far from it so that the measurement error is small. Finally, linear components characterizing the ideal position of the reference beams are subtracted from these coordinate centers, and the resulting coordinate differences characterize distortion data ((Δx _ij , Δy _ij )), from which, based on the position of the image center, the distortion matrix r _ij is calculated with the number of terms equal to the number of reference beams. This matrix serves as a source of information for further analysis and logical tuning operations. The sets of values of this matrix are divided into subsets characterizing distortion in the radial directions, i.e. related to reference beams lying on lines passing through the center of the image. These data are approximated in one case using the Kr ³ cubic parabola, and in the other case using the Kr ³ + Lr ⁵ sum, where r is the radial distance between the image center and the correct position of the current measured reference beam, K and L are experimentally determined values, respectively third and fifth order distortion coefficients, for which statistical processing methods are used with the dispersion calculation and the corresponding standard errors, based on which the reliability of the calculated values is estimated th. Then begins the logical part of the setup, in which first sequentially determined third-order coefficients K _i , K _{i-1 are} compared. Among the adjustable parameters, we add the potential at the first electrode of the collimating lens 4 of the lighting system. The subsequent potential U _{i + 1} on this lens behind the potential U _i is determined according to the scheme shown in Fig. 8, where ΔU _{i /} is the increment used in the i-th measurement step. The logical branch of the setting changes direction after the sign of the justified presence of the fifth-order distortion coefficient L and the confident difference in the signs of the third and fifth-order distortion coefficients begins to be executed. From the data of the distortion matrix, subsets related to concentric circles are selected, and data is analyzed for the existence of a circle with zero distortion. A sign of the existence of such a circle is a sign change in the distortion members r _ij related to consecutive subsets of concentric circles. The position of the circle with zero distortion, and the value of its radius r _{0 is} calculated by approximating the distortion data related to the subsets of the radial directions. After that, using the formula (23), the radius r _{m of the} connected circle is calculated on which the absolute value of the distortion inside the circle with radius r ₀ should be maximum. Based on the experimental distortion data, the distortion value Δ (r _m ) is determined for a circle with a calculated radius. Further tuning operations are performed in accordance with the logical results shown in FIG. 8, where ε is the permissible value of distortion, r _k is the specified value of the working field on the target, and δ is the accuracy of determining the final result from distortion. The tuning process ends when one of two possible cases is fulfilled: 1) if the distortion value Δ (r _m ) reaches its permissible value or 2) the radius r ₀ reaches the specified value of the working field with a smaller value Δ (r _m ) of its permissible value. At the end of the tuning process, a certain distortion value Δ (r _m ) is assigned the designation y _m , the experimental values of the distortion coefficients are calculated based on the formulas

After this adjustment, the ion beam in the area of the working field is blocked by a mechanical shutter, and the ion microprojector is ready to work with working template 5 and a working target. After setting the working template 5 to the position coinciding with the optical axis, the process of combining the projected image with the pattern on the working target is performed. To do this, control alignment beams (CLS) are used, which are formed as a result of the passage of ions through special holes in the working pattern that are outside the field of the projected pattern, but in close proximity to the vertices of the square (rectangle) that forms the working field. The alignment process is achieved using the metrological unit 12 and alignment marks located on the target. For this, the CLSs are alternately electrically scanned according to the corresponding alignment marks, and the corresponding correction of the X and Y coordinates of the center of the working field is made using the scattering signal 10 using the multipole device. After this operation, the mechanical shutter is opened and the target is exposed.

 The total length of the optical system from the ion source to the target surface of the proposed ion microprojector is 180 cm. The size of the working field on the template 5 fits into a square with a side of 75 mm. The reduction scale can be from 5 to 2.5. The magnitude of the distortion depends on the scale of the decrease and in the optimal state is no more than 0.1 microns inside the working field. The optimal state for each reduction scale requires an individual adjustment of the internal geometry of the location of the lenses inside the projector.

Claims (2)

 1. An ionic microprojector containing an ion beam generator arranged in series and coaxially in a vacuum chamber, a lighting device consisting of a mass filter, a template, a projector consisting of the first and second lenses, the first and second multipole elements, coaxially located respectively behind the first and second lenses, the metrological unit and the receiving unit with the processing object located in it, as well as the first and second power supplies and the control unit, the first information input of which is connected to the information output a metrological unit, its first and second control outputs are connected respectively to the control inputs of the first and second power supplies, the first output of the first power supply is connected to the internal electrode of the first lens of the projector, the second output of the first and first output of the second power supply are combined, characterized in that the third and fourth power supplies, the first and second reference power sources, in the lighting device - electrostatic - collimating lens mounted coaxially behind the mass filter, in the projector - an immersion lens mounted coaxially in front of the first lens, the first electrode of the electrostatic collimating lens of the lighting device is connected to the first output of the third power supply, the control input of which is connected to the third control output of the control unit, its second output and the power input of the ion beam making device are connected to the first output the second reference power source, the second output of which is connected to a common bus to which the casing of the vacuum chamber is connected, the external electrodes of the first and second the projector’s lens and the first output of the first reference power supply, the second output of which is connected to the combined outputs of the first and second power supplies, the second output of the second power supply is connected to the internal electrode of the second projector lens, while the first electrode of the projector’s immersion lens is connected to the second electrostatic collimating electrode lenses of the lighting device and through the fourth power supply to the first output of the second reference power source, the last electrode of the immersion lens is connected to bschey bus. 2. A method for tuning an ionic microprojector, including presetting its projector by determining the adjusted values of the adjustable parameters of the ionic microprojector on the basis of measurements on the target of the sizes and coordinates of the centers of the reference beams extracted using a metrological template from a collimated ion beam, characterized in that they produce a divergence change ion beam in the plane of the metrological template and circumferential measurement of the distortion value on the working field of the target, at aruzhenii circumference with zero distortion fixed divergence of the ion beam and measure the radius of the circle on which the detected zero distortion, the distortion measure value for the circle with a radius

where r ₀ is the radius of the circle with a zero distortion value, the measured distortion value is compared with an acceptable value, with the difference, the above operations are repeated until, at a radius r _m corresponding to the newly obtained radius r ₀ , the absolute value of the measured distortion value reaches an acceptable distortion values or until the newly obtained radius r ₀ reaches the specified size of the working field, even if the absolute value of the distortion value at the corresponding radius r _{m is} less than the permissible distortion value.

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