阅读说明：本技术 电流源装置和方法 (Current source apparatus and method ) 是由 王義向 王燕秋 何晓东 叶国凡 于 2020-04-03 设计创作，主要内容包括：在其他方面中公开了一种诸如可以用在带电粒子检查系统中的电源。该电源包括直流源,诸如连接到受控电压源的可编程线性电流源,其中用于受控电压源的控制信号从跨直流源测量的电压降被导出。(In other aspects, a power supply such as may be used in a charged particle inspection system is disclosed. The power supply comprises a direct current source, such as a programmable linear current source connected to a controlled voltage source, wherein a control signal for the controlled voltage source is derived from a voltage drop measured across the direct current source.)

1. A power supply unit comprising:

a controlled voltage source arranged to receive a voltage control input signal and adapted to provide a controlled voltage at a controlled voltage output based at least in part on the voltage control input signal; and

a direct current source having a current source input and a current source output, the current source input arranged to receive the controlled voltage output.

2. The power supply unit of claim 1, wherein the direct current source comprises a programmable linear current source.

3. A power supply unit according to claim 1, wherein the direct current source is arranged to supply current to a load in a charged particle manipulator.

4. A power supply unit according to claim 3, wherein the load in a charged particle manipulator comprises a lens coil.

5. The power supply unit of claim 1, further comprising circuitry arranged to: sensing a magnitude of a voltage drop across the direct current source and adapted to generate the voltage control input signal based at least in part on the magnitude of the voltage drop.

6. The power supply unit of claim 1, wherein

The direct current source comprises a programmable linear current source output and is arranged to supply a current to a load in a charged particle manipulator, an

The voltage control input signal has a value indicative of a magnitude of a voltage drop across the programmable linear current source, and wherein

The controlled voltage source is controlled such that a voltage drop across the programmable linear current source remains within an operating range.

7. The power supply unit of claim 6, wherein the operating range is a programmable range.

8. The power supply unit of claim 6, wherein the operating range is a pre-settable range.

9. The power supply unit of claim 6, wherein the operating range is a predetermined range.

10. The power supply unit according to claim 6, wherein the load in a charged particle manipulator comprises a lens coil.

11. A method of supplying power to a current source load, the method comprising the steps of:

generating a controlled voltage based at least in part on the voltage control input signal;

supplying the controlled voltage to a direct current source;

generating a drive current using the direct current source; and

supplying the drive current to the current source load.

12. The method of claim 11, further comprising the steps of:

sensing a voltage drop across the direct current source; and

generating the voltage control input signal based at least in part on the voltage drop.

13. The method of claim 11, wherein the direct current source comprises a programmable linear current source.

14. The method of claim 13, further comprising the steps of:

sensing a voltage drop across the programmable linear current source; and

generating the voltage control input signal based at least in part on the voltage drop.

15. The method of claim 11, wherein the step of generating the voltage control input signal based at least in part on a voltage drop across the direct current source, such as a programmable linear current source, is performed such that the voltage drop across the direct current source, such as a programmable linear current source, remains within an operating range.

Technical Field

Embodiments provided herein relate to a current source, such as a current source that may be used to supply current to a load, such as a lens, in a charged particle manipulator using one or more charged particle beams (e.g., an electron microscopy device using one or more electron beams).

Background

Integrated circuits are made by creating a pattern on a wafer (also referred to as a substrate). The wafer is supported on a wafer stage in an apparatus for creating a pattern. One part of the process for manufacturing integrated circuits involves viewing or "inspecting" various portions of the wafer. This may be done using a charged particle manipulator such as a scanning electron microscope or SEM.

Optical microscopes use visible light and transparent lens (es) or mirror(s) to visualize objects as small as about one micron. The resolving power of an optical microscope is limited by the wavelength of the light used for illumination. Charged particle manipulators use a beam of charged particles instead of light and use electromagnetic or electromagnetic/electric lenses to focus the particles. They can make visible features as small as a tenth of a nanometer.

The charged particle manipulator comprises a column with elements similar to those of an optical microscope. The light source of the optical microscope is replaced by a charged particle source, which is built into the column. The charged particle manipulator has an electromagnetic or electromagnetic/electric lens instead of a glass lens. The performance (focal length) of these lenses can be varied by varying the current through the lens coils. There is a need for an improved current driver for supplying current to the lens coil.

Disclosure of Invention

The following presents a simplified summary of one or more embodiments in order to provide a basic understanding of such embodiments. This summary is not an extensive overview of all contemplated embodiments, and is intended to neither identify key or critical elements of all embodiments nor delineate the scope of any or all embodiments. Its sole purpose is to present some concepts of one or more embodiments in a simplified form as a prelude to the more detailed description that is presented later.

According to an aspect of the embodiments, a power supply unit is disclosed, the power supply unit comprising a controlled voltage source arranged to receive a voltage control input signal and adapted to provide a controlled voltage at a controlled voltage output based at least partly on the voltage control input signal, and a direct current source (such as a programmable linear current source) having a current source input and a current source output, the current source input being arranged to receive the controlled voltage output. The current source output may be arranged to supply a current to a load, which may be a lens in a charged particle manipulator. The power supply unit may further comprise a circuit arranged to sense a magnitude of a voltage drop across the direct current source and adapted to generate the voltage control input signal based at least in part on the magnitude of the voltage drop. The controlled voltage source may be controlled such that the voltage drop across the dc source remains within a programmable range, a pre-settable range, or a predetermined range.

According to another aspect of the embodiments, a lens in a charged particle manipulator system is disclosed, the system comprising a controlled voltage source arranged to receive a voltage control input signal and adapted to provide a controlled voltage at a controlled voltage output based at least in part on the voltage control input signal, a direct current source, such as a programmable linear current source, arranged to receive a controlled voltage output and adapted to supply a controlled current, a load, such as a lens coil, arranged to receive the controlled current, and a circuit arranged to sense a magnitude of a voltage drop across the direct current source, such as the programmable linear current source, and adapted to generate the voltage control input signal based at least in part on the magnitude of the voltage drop. The controlled voltage source may be controlled such that the voltage drop across the direct current source (such as a programmable linear current source) remains within a programmable range, a pre-settable range, or a predetermined range.

According to another aspect of the embodiments, a method of supplying power to a load (such as a lens coil) in a charged particle manipulator is disclosed, the method comprising: generating a controlled voltage based at least in part on the voltage control input signal; supplying a controlled voltage to a direct current source (such as a programmable linear current source); generating a drive current using a direct current source; and supplying a drive current to a load in the charged particle manipulator. The method may further comprise: sensing a voltage drop across a direct current source (such as a programmable linear current source); and generating a voltage control input signal based at least in part on the voltage drop. The step of generating the voltage control input signal based at least in part on a voltage drop across a direct current source (such as a programmable linear current source) may be performed such that the voltage drop across the direct current source (such as a programmable linear current source) remains within a programmable range, a pre-settable range, or a predetermined range.

Further features and advantages of the invention, as well as the structure and operation of various embodiments of the invention, are described in detail below with reference to the accompanying drawings. It is noted that the present invention is not limited to the specific embodiments described herein. Such embodiments are presented herein for illustrative purposes only. Other embodiments will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein.

Drawings

The accompanying drawings, which are incorporated herein and form a part of the specification, illustrate the present invention and, together with the description, further serve to explain the principles of the invention and to enable a person skilled in the pertinent art to make and use the invention.

FIG. 1 is a diagram illustrating an exemplary charged particle beam inspection system consistent with embodiments of the present disclosure.

Fig. 2 is a schematic diagram illustrating a power control circuit in accordance with an aspect of an embodiment.

Fig. 3 is a flow diagram illustrating exemplary steps in a method of supplying current to a load (such as a lens) in accordance with an aspect of an embodiment.

Detailed Description

Reference will now be made in detail to exemplary embodiments, examples of which are illustrated in the accompanying drawings. The following description refers to the accompanying drawings, in which like references indicate the same or similar elements in different drawings, unless otherwise indicated. The implementations set forth in the following description of exemplary embodiments do not represent all implementations consistent with the invention. Rather, they are merely examples of systems, apparatus and methods consistent with aspects related to the invention as set forth in the claims below. The relative dimensions of the components in the figures may be exaggerated for clarity.

Electronic devices are made up of circuits formed on a silicon wafer called a substrate. Many circuits may be formed together on the same piece of silicon and are referred to as an integrated circuit or IC. The size of these circuits has been significantly reduced so that more circuits can be mounted on the substrate. For example, an IC chip in a smart phone may be as small as the thumb, but may contain over 20 billion transistors, each of which is less than 1/1000 of human hair.

Manufacturing these extremely small ICs is a complex, time consuming and expensive process, typically involving hundreds of individual steps. Even if an error occurs in one step, it may cause defects in the finished IC, rendering it unusable. Therefore, one goal of the fabrication process is to avoid such defects to maximize the number of functional ICs fabricated in the process, i.e., to improve the overall yield of the process.

One component that improves yield is monitoring the chip fabrication process to ensure that it produces a sufficient number of functional integrated circuits. One way of monitoring the process is to inspect the chip circuit structure at various stages of its formation. The inspection may be performed using a charged particle manipulator. The charged particle manipulator may be used to image these very small structures, in effect taking a "picture" of the structure. This image can be used to determine whether the structure was formed correctly and whether it was formed in the correct location. If the structure is defective, the process can be adjusted so that the defect is less likely to reoccur.

As the name implies, charged particle manipulators use a charged particle beam, since such a beam can be used to observe structures that are too small to be seen by an optical microscope (i.e., a microscope using light). The charged particle manipulator comprises a column comprising elements that contribute to shaping and focusing the charged particle beam. These elements are called lenses because they perform functions similar to those performed by lenses in optical microscopes. Such lenses and other loads that require current from a current source in a charged particle manipulator are herein referred to as loads in a charged particle manipulator. But these lenses do not manipulate light but use magnetic or electric fields or a combination of magnetic and electric fields to manipulate the charged particle beam. The performance of these lenses is controlled by controlling the amount of current supplied to the lenses by the lens current drivers.

Typically, a lens current driver uses a fixed voltage power supply to power a dc source to enable the dc source to provide current to drive the lens. With this configuration, the lens current driver is set to maintain the current flowing through the lens coil. One disadvantage of this configuration is that the sum of the voltage measured between one end of the coil and the other plus the voltage drop across the current source remains the same value, resulting in a relatively high amount of power being dissipated even if the current source only supplies a small amount of current to the lens.

There is a need to reduce power consumption and avoid the need to dissipate excess heat resulting from excessive power consumption. According to an aspect of the embodiments, these needs are addressed by providing an arrangement with reduced power consumption. This saves operating costs. Further, when the load receives less current, less heat is dissipated, which results in greater stability and less expansion of the assembly, thereby improving accuracy (e.g., less wafer expansion, less stage expansion, etc.), resulting in less movement and less corresponding error due to position changes.

This arrangement reduces power consumption by placing a controlled voltage source in series with a direct current source, such as a programmable linear current source. In such an arrangement, when the load requires less current, so that the voltage drop across the load will be smaller, the current source does not take up the remainder of the fixed total voltage drop. Conversely, the total voltage is reduced and the current source takes less, which means that the current source does not need to use as much power and generates less heat.

Newer designs require more powerful magnetic lenses due to the need for focusing, collimation, and generally steer beams with higher landing energies. This means that the lens coil typically has more turns and therefore exhibits higher resistance. Driving these lenses requires new designs for higher voltage power supplies and higher currents. Furthermore, as the resistance increases, the amount of heat generated by the voltage source also increases. Handling this heat presents significant design challenges. For example, excessive thermal loading can negatively impact current output stability. Of course, this is merely a general description and the actual details are set forth more fully and accurately below.

Without limiting the scope of the present disclosure, the description and drawings of the embodiments may exemplarily be referred to as using a charged particle beam. However, the embodiments are not intended to limit the invention to certain charged particles, such as electrons. For example, the systems and methods for beam forming can be applied to photons, x-rays, ions, and the like. Further, the term "beam" may refer to a primary charged particle beam, a primary charged particle beam wave, a secondary charged particle beam wave, or the like.

As used herein, unless otherwise specifically stated, the term "or" encompasses all possible combinations, unless otherwise not feasible. For example, if a component is stated to include a or B, the component may include a or B, or both a and B, unless explicitly stated otherwise or otherwise not possible. As a second example, if it is stated that a component can include A, B or C, the component can include a, or B, or C, or a and B, or a and C, or B and C, or a and B and C, unless explicitly stated otherwise or not possible.

In the description and claims, the terms "upper", "lower", "top", "bottom", "vertical", "horizontal", and the like may be used. Unless otherwise specified, these terms are intended to refer only to a relative orientation and not to any absolute orientation, such as an orientation relative to gravity. Similarly, terms such as left, right, front, rear, and the like are intended to give relative orientations only.

Referring to fig. 1, in one embodiment, an SEM-based charged particle beam manipulator 100 is provided for defect inspection. The charged particle beam manipulator 100 comprises in sequence a charged particle tip 110, an anode 112, an electrode 114, a plate 116, a condenser lens 120, and a plate 130. The charged particle tip 110 is for emitting a primary charged particle beam 101, the anode 112 is for extracting charged particles from the tip 110, the electrode 114 has an aperture for selecting charged particles in a suitable solid angle in the primary beam 101, the plate 116, such as a coulomb plate, has apertures for adjusting the primary charged particle beam 101 to reduce field effects, the condenser lens 120 is for converging the primary charged particle beam 101, the plate 130 has apertures for further adjusting the primary beam 10 to control the beam current of the primary charged particle beam 101. In the following discussion, embodiments will be described primarily using a particular type of charged particle manipulator, SEM, and a particular type of charged particle, electron, but it should be understood that the teachings provided herein are equally applicable to other systems using other types of charged particles.

The tool shown in fig. 1 further comprises a detector 140 for receiving SE (secondary electrons) and BSE (back scattered electrons) emanating from the sample 10, a deflector unit 150 for scanning the primary electron beam 101, a magnetic objective lens 160 for focusing the primary electron beam 101 onto the sample 10, and electrodes 170 for providing a drag to the primary electron beam 101 such that the landing energy of the primary electron beam 101 can be reduced. The pole pieces of the objective lens 160, the electrodes 170 and the specimen 10 supported by the stage may constitute an electric lens which is combined with a magnetic lens to form an EM (electromagnetic) compound objective lens.

Existing lens drivers for any of the lenses in such systems are typically implemented as a fixed voltage power supply and a direct current source. Voltage drop V across the current source_CSWith voltage drop V across the load (e.g. lens coil)_LThere will always be a total of a fixed voltage V generated by the voltage source. When the current of the DC source is at the lower end of its operating range, then the voltage drop across the load V_LWill be relatively low. Therefore, a larger voltage drop, i.e., V, must occur across the current source_CSWill be higher. This requires the current source to dissipate more power with attendant heat dissipation and current stability issues.

A circuit for supplying current to a lens according to one aspect of an embodiment is shown in fig. 2. The current I is supplied to the lens coil 160 by a direct current source 200, such as a programmable linear current source. The controlled voltage source 210 supplies a voltage to the direct current source 200. The closed loop feedback circuit 220 supplies a control signal to the controlled voltage source 210 based on the magnitude of the voltage drop across the direct current source 200.

In the arrangement shown in fig. 2, the voltage generated by the controlled voltage source is no longer fixed. The total voltage drop is still the sum of the voltage drops across the current source and the load. However, when the current I is at the lower limit of its operating range, then the voltage drop across the current source is sensed and the controlled voltage of the controlled voltage source is reduced to in turn reduce the voltage drop across the current source. This results in a reduction in the amount of power consumed by the combination of the voltage source and the current source. In particular, the voltage source may be controlled such that the voltage drop across the current source remains within a programmable range or a presettable range or a predetermined range. Generally, the voltage V from the voltage source 210₂₁₀Will be the voltage drop V across the current source₂₀₀And the voltage drop V across the lens coil 160₁₆₀And (4) summing. Preferably, V₂₀₀Less than or equal to V₁₆₀I.e. V₂₀₀Is minimized.

According to another aspect of the embodiments, a method of supplying current to a current load, such as a lens coil in a charged particle manipulator, is disclosed. Referring to fig. 3, in a first step S10, a direct current source, such as a programmable linear current source, is used to generate the drive current. Then, in step S20, a voltage drop across a direct current source, such as a programmable linear current source, is sensed. In step S30, the sensed voltage drop across the current source is used to generate a control signal input to control the voltage source to generate a voltage for the current source. In step S40, the voltage source adjusts its voltage according to the control signal input. For example, the control input signal controls the voltage source to decrease the voltage of the voltage source when the sensed voltage drop across the current source increases, and controls the voltage source to increase the voltage of the voltage source when the sensed voltage drop across the current source decreases. It should be understood that some combination of these steps, including all of these steps, may occur substantially simultaneously.

The embodiments may be further described using the following clauses:

1. a power supply unit comprising:

a controlled voltage source arranged to receive a voltage control input signal and adapted to provide a controlled voltage at a controlled voltage output based at least in part on the voltage control input signal; and

a direct current source having a current source input and a current source output, the current source input arranged to receive the controlled voltage output.

2. The power supply unit of clause 1, wherein the direct current source comprises a programmable linear current source.

3. The power supply unit according to clause 1 or 2, wherein the direct current source is arranged to supply current to a load in a charged particle manipulator.

4. The power supply unit according to clause 3, wherein the load in the charged particle manipulator comprises a lens coil.

5. The power supply unit of any one of clauses 1 to 4, further comprising a circuit arranged to: sensing a magnitude of a voltage drop across the direct current source and adapted to generate the voltage control input signal based at least in part on the magnitude of the voltage drop.

6. The power supply unit according to clause 1, wherein

The direct current source comprises a programmable linear current source output and is arranged to supply a current to a load in a charged particle manipulator, an

The voltage control input signal has a value indicative of a magnitude of a voltage drop across the programmable linear current source, and wherein

The controlled voltage source is controlled such that a voltage drop across the programmable linear current source remains within an operating range.

7. The power supply unit of clause 6, wherein the operating range is a programmable range.

8. The power supply unit of clause 6, wherein the operating range is a pre-settable range.

9. The power supply unit of clause 6, wherein the operating range is a predetermined range.

10. The power supply unit of clause 6, wherein the load in the charged particle manipulator comprises a lens coil.

11. A current source load system comprising:

a controlled voltage source arranged to receive a voltage control input signal and adapted to provide a controlled voltage at a controlled voltage output based at least in part on the voltage control input signal;

a direct current source arranged to receive the controlled voltage output and adapted to supply a current;

a current source load arranged to receive the current; and

circuitry arranged to sense a magnitude of a voltage drop across the direct current source and adapted to generate the voltage control input signal based at least in part on the magnitude of the voltage drop.

12. The current source load system of clause 11, wherein the direct current source comprises a programmable linear current source.

13. The current source load system according to clause 11 or 12, wherein the controlled voltage source is controlled such that a voltage drop across the direct current source, such as a programmable linear current source, remains within an operating range.

14. The current source load system of clause 13, wherein the operating range is a programmable range.

15. The current source load system of clause 13, wherein the operating range is a pre-settable range.

16. The current source load system of clause 13, wherein the operating range is a predetermined range.

17. The current source load system of any of clauses 11-16, wherein the current source load comprises a lens in a charged particle manipulator system.

18. A method of supplying power to a current source load, the method comprising the steps of:

generating a controlled voltage based at least in part on the voltage control input signal;

supplying the controlled voltage to a direct current source;

generating a drive current using the direct current source; and

supplying the drive current to the current source load.

19. The method of clause 18, further comprising the steps of:

sensing a voltage drop across the direct current source; and

generating the voltage control input signal based at least in part on the voltage drop.

20. The method of clause 18, wherein the direct current source comprises a programmable linear current source.

21. The method of clause 20, further comprising the steps of:

sensing a voltage drop across the direct current source; and

generating the voltage control input signal based at least in part on the voltage drop.

22. The method of any of clauses 18 to 21, wherein the step of generating the voltage control input signal based at least in part on a voltage drop across the direct current source, such as a programmable linear current source, is performed such that the voltage drop across the direct current source, such as a programmable linear current source, remains within an operating range.

23. The method of any of clauses 18-21, wherein the operating range is a programmable range.

24. The method of any of clauses 18-21, wherein the operating range is a pre-settable range.

25. The method of any of clauses 18-21, wherein the operating range is a predetermined range.

Although the foregoing description is in relation to the current supply to a lens in a charged particle imaging system, it will be appreciated that the current supply may be advantageously employed to supply current in other applications.

The foregoing description of the specific embodiments will so fully reveal the general nature of the invention that others can, by applying knowledge within the skill of the art, readily modify and/or adapt for various applications such specific embodiments, without undue experimentation, without departing from the general concept of the present invention. Therefore, such modifications and adaptations are intended to be within the meaning and range of equivalents of the disclosed embodiments, based on the teaching and guidance presented herein. It is to be understood that the phraseology or terminology herein is for the purpose of description and not of limitation, such that the terminology or phraseology of the present specification is to be interpreted by the skilled artisan in light of the teachings and guidance.