System for forming uniform charge density on surface of wafer

Abstract

The invention provides a system for forming uniform charge density on the surface of a wafer. The system comprises a spray point; the first high-voltage module is used for applying voltage to the spray point; the electric field modules are arranged in sections, and each section of the electric field module is used for forming an electric field with set size and polarity; the tip of the spray point enables air to be ionized to generate charges under high voltage; an electric field formed by the electric field module controls the speed and the motion path of charges, so that the charges are scattered on the wafer to be tested along the vertical direction as much as possible; and the control unit is used for controlling the first high-voltage module and the electric field module, and adjusting the output voltage of the first high-voltage module according to the number of charges needing to be scattered on the to-be-tested wafer and the number of charges actually scattered on the to-be-tested wafer. According to the system, uniform controllable quantity of charges can be scattered to the surface of the wafer, and the measurement precision of electrical parameters is improved.

Description

Technical Field

[0001] The invention relates to the technical field of wafer measurement, and in particular to a system for forming uniform charge density on a wafer surface. Background Art

[0002] In the chip manufacturing process, electrical parameter testing is a key link to ensure device performance, yield and functional integrity. Electrical parameter testing is involved in multiple process stages of chip manufacturing (lithography, doping, metallization, packaging).

[0003] Uneven charge distribution on the wafer surface due to metal contamination or surface roughness directly affects the test accuracy of electrical parameters (such as leakage current and breakdown voltage).

[0004] Therefore, how to make the charge on the wafer surface in the test area uniformly distributed before testing is the focus of those skilled in the art. Summary of the invention

[0005] The object of the present invention is to provide a system for forming a uniform charge density on the surface of a wafer, which can spread a uniform and controllable amount of charge on the surface of the wafer.

[0006] In order to achieve the above object, the present invention provides a system for forming a uniform charge density on a wafer surface, comprising: Discharge needle; A first high voltage module, used for applying voltage to the discharge needle; Electric field modules are arranged in sections, each section of the electric field module is used to form an electric field of set magnitude and polarity; The tip of the discharge needle ionizes the air under high voltage to generate electric charges; the electric field formed by the electric field module controls the speed and movement path of the electric charges so that the electric charges are spread on the wafer to be tested in a vertical direction as much as possible; The control unit is used to control the first high-voltage module and the electric field module, and adjust the output voltage of the first high-voltage module according to the amount of charge to be sprinkled on the wafer to be tested and the amount of charge actually sprinkled on the wafer to be tested.

[0007] In an optional solution, the electric field module includes: a first cover wall surrounding the outer periphery and the lower area of ​​the discharge needle, and the lower end of the first cover wall is open; A second cover wall, located below the first cover wall and insulated from the lower end of the first cover wall; a second high-voltage module, used for applying voltage to the first cover wall to form an electric field in the first cover wall; a third high-voltage module, used for applying voltage to the second cover wall to form an electric field in the second cover wall; The fourth high-voltage module is used to apply voltage at the outlet of the lower end of the second cover wall to form an electric field at the outlet of the lower end of the second cover wall.

[0008] In an optional solution, the overall profile of the first cover wall and the second cover wall is wider at the top and narrower at the bottom.

[0009] In an optional solution, the lower end of the first cover wall and the upper end of the second cover wall are connected by an insulating material.

[0010] In an optional solution, outer walls of the first cover wall and the second cover wall are coated with an insulating layer.

[0011] In an optional solution, the control unit includes a current monitoring module, a host computer, a signal generator, an analog-to-digital converter, a high-voltage amplifier and a servo circuit; The signal generator sends a pulse signal to the servo circuit according to the instruction of the host computer to enable the charge to be spread; The current monitoring module is used to monitor the amount of charge spread on the wafer, and convert the charge into a current signal, and then convert the current signal into a voltage signal, which is transmitted to the servo circuit as negative feedback; The host computer is used to set the required amount of charge in the configuration file, and send control instructions to the analog-to-digital converter and the signal generator; The analog-to-digital converter outputs an analog voltage to the servo circuit according to the digital instruction of the host computer; The servo circuit makes a difference between the output voltage of the analog-to-digital converter and the voltage signal fed back by the current monitoring module, and outputs a voltage signal to the high-voltage amplifier according to the difference; The high-voltage amplifier controls the positive and negative voltages applied by the first high-voltage module and the electric field module through high and low levels, amplifies the voltage signal of the servo circuit, and outputs it to the first high-voltage module, thereby controlling the output voltage of the first high-voltage module.

[0012] In an optional solution, the system further includes a motion module for driving the discharge needle and the electric field module to move synchronously.

[0013] In an optional solution, the output voltages of the second high-voltage module, the third high-voltage module and the fourth high-voltage module are fixed and are set by a manual knob.

[0014] The beneficial effects of the present invention are: The present invention can spread a uniform and controllable amount of electric charges on the surface of the wafer, thereby improving the measurement accuracy of electrical parameters. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The above and other objects, features and advantages of the present invention will become more apparent through a more detailed description of exemplary embodiments of the present invention in conjunction with the accompanying drawings, in which like reference numerals generally represent like components.

[0016] Figure 1 Schematic diagram of the structure of a system for forming a uniform charge density on a wafer surface according to an embodiment of the present invention.

[0017] Figure 2 This is a simulation diagram of the electric field distribution in one embodiment of the present invention.

[0018] Figure 3 2 is a simulated diagram of the distribution of the amount of charge (positive charge) emitted in one embodiment of the present invention.

[0019] Figure 4 4 is a simulated diagram of the distribution of the amount of charge (negative charge) emitted in one embodiment of the present invention.

[0020] Figure Number: 1-first high-voltage module; 2-second high-voltage module; 3-third high-voltage module; 4-fourth high-voltage module; 5-first cover wall; 6-second cover wall; 7-high-voltage amplifier; 8-analog-to-digital converter; 9-servo circuit; 10-signal generator; 11-host computer; 12-current monitoring module; 13-discharge needle; 14-wafer. DETAILED DESCRIPTION

[0021] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. According to the following description and drawings, the advantages and features of the present invention will become clearer. However, it should be noted that the concept of the technical solution of the present invention can be implemented in a variety of different forms and is not limited to the specific embodiments described herein. The drawings are all in a very simplified form and are not in precise proportions, and are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention.

[0022] It should be understood that when an element or layer is referred to as being "on, adjacent to, connected to or coupled to other elements or layers, it may be directly on, adjacent to, connected to or coupled to other elements or layers, or there may be intervening elements or layers. In contrast, when an element is referred to as being "directly on, directly adjacent to, directly connected to or directly coupled to other elements or layers, there may be no intervening elements or layers. It should be understood that, although the terms first, second, third, etc. may be used to describe various elements, components, regions, layers and / or parts, these elements, components, regions, layers and / or parts should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or part from another element, component, region, layer or part. Therefore, without departing from the teachings of the present invention, the first element, component, region, layer or part discussed below may be represented as a second element, component, region, layer or part.

[0023] Spatially relative terms such as "under," "below," "below," "under," "above," "above," etc., may be used herein for ease of description to describe the relationship of an element or feature shown in the figures to other elements or features. It should be understood that in addition to the orientations shown in the figures, the spatially relative terms are intended to include different orientations of the device in use and operation. For example, if the device in the accompanying drawings is flipped, then the elements or features described as "under other elements" or "under" or "under" will be oriented as "on" the other elements or features. Therefore, the exemplary terms "under" and "under" may include both upper and lower orientations. The device may be oriented otherwise (rotated 90 degrees or other orientations) and the spatial descriptors used herein are interpreted accordingly.

[0024] The purpose of the terms used herein is only to describe specific embodiments and is not intended to be limiting of the present invention. When used herein, the singular forms "one", "an" and "said / the" are also intended to include plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "consisting of" and / or "comprising", when used in this specification, determine the presence of the features, integers, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, parts and / or groups. When used herein, the term "and / or" includes any and all combinations of the relevant listed items.

[0025] Example 1 Reference Figure 1 , this embodiment provides a system for forming a uniform charge density on a wafer surface, comprising: Discharge needle 13; A first high voltage module 1, used for applying voltage to the discharge needle 13; Electric field modules are arranged in sections, each section of the electric field module is used to form an electric field of set magnitude and polarity; The tip of the discharge needle 13 ionizes the air under high voltage to generate electric charges; the electric field formed by the electric field module controls the speed and movement path of the electric charges so that the electric charges are spread on the wafer 14 to be tested in a vertical direction as much as possible; The control unit is used to control the first high-voltage module 1 and the electric field module, and adjust the output voltage of the first high-voltage module 1 according to the amount of charge to be sprinkled on the wafer 14 to be tested and the amount of charge actually sprinkled on the wafer 14 to be tested.

[0026] Specifically, the electric field module in this embodiment is divided into three sections, including: a first cover wall 5, surrounding the periphery and lower area of ​​the discharge needle 13, and the lower end of the first cover wall 5 is open; a second cover wall 6, located below the first cover wall 5 and insulated from the lower end of the first cover wall 5; a second high-voltage module 2, used to apply voltage to the first cover wall 5 to form an electric field in the first cover wall 5; a third high-voltage module 3, used to apply voltage to the second cover wall 6 to form an electric field in the second cover wall 6; a fourth high-voltage module 4, used to apply voltage at the outlet of the lower end of the second cover wall 6 to form an electric field at the outlet of the lower end of the second cover wall 6.

[0027] In this embodiment, the first cover wall is cylindrical, and the second cover wall is a rounded pyramid shape that is wide at the top and narrow at the bottom. In other embodiments, the first cover wall and the second cover wall can be spherical or semicircular as a whole. It should be noted that the overall contours of the first cover wall and the second cover wall are not limited, as long as the movement path of the charge can be controlled so that the charge is spread on the wafer to be tested as vertically as possible. In general, the overall contours of the first cover wall and the second cover wall are wide at the top and narrow at the bottom.

[0028] The discharge needle, the first cover wall 5 and the second cover wall 6 are all made of metal. The discharge needle is made of a non-shedding (non-consumable) metal material, and the needle tip surface is smooth and relatively sharp, such as platinum. The first cover wall 5 and the second cover wall 6 can be made of ordinary metal materials, such as copper and aluminum. The lower end of the first cover wall 5 and the upper end of the second cover wall 6 are connected by an insulating material to form two independent electric fields. The outer walls of the first cover wall 5 and the second cover wall 6 are coated with an insulating layer.

[0029] In this embodiment, the control unit includes a current monitoring module 12, a host computer 11, a signal generator 10, an analog-to-digital converter 8, a high-voltage amplifier 7 and a servo circuit 9; the signal generator 10 sends a pulse signal to the servo circuit 9 according to the instruction of the host computer 11 to enable spreading charge (also known as ionized deposition charge); the current monitoring module 12 is used to monitor the amount of charge spread on the wafer 14, and convert the charge into a current signal, and then convert the current signal into a voltage signal, which is transmitted to the servo circuit 9 as negative feedback; the host computer 11 is used to set the required amount of spreading charge in the configuration file, and send control instructions to the analog-to-digital converter 8 and the signal generator 10; the analog-to-digital converter 8 outputs an analog voltage according to the digital instruction of the host computer 11 (the conversion relationship between voltage and charge in this embodiment is 3.27E-7C / V, This value is determined by the circuit design, and the amount of charge is set artificially, so we can know how large the analog voltage is) to the servo circuit 9; the servo circuit 9 makes a difference between the output voltage of the analog-to-digital converter 8 and the voltage signal fed back by the current monitoring module 12, and outputs a voltage signal to the high-voltage amplifier 7 according to the difference; the high-voltage amplifier 7 controls the positive and negative voltage applied by the first high-voltage module 1 and the electric field module (the second high-voltage module 2, the third high-voltage module 3, and the fourth high-voltage module 4) through high and low levels, and amplifies the voltage signal of the servo circuit 9, and then outputs it to the first high-voltage module 1, thereby controlling the output voltage of the first high-voltage module 1.

[0030] At the beginning, the amount of charges scattered is small, and the servo circuit outputs a relatively large high voltage to the high-voltage amplifier. As the amount of charges scattered increases, the voltage output by the servo circuit will gradually decrease. When the target charge amount is equal to the amount of charges scattered, the servo circuit does not output, and the entire working process ends. During the charge spreading process, the output voltage of the first high-voltage module 1 is variable and is controlled by the high-voltage amplifier 7. The output voltages of the second high-voltage module 2, the third high-voltage module 3, and the fourth high-voltage module 4 are fixed and are set by manual knobs.

[0031] Reference Figure 2 , when spreading positive charge, the discharge needle is added with 10000V, the first cover wall is added with 2000V, the second cover wall is added with 400V, and the outlet at the lower end of the second cover wall is added with 100V. If negative charge needs to be spread, all are changed to negative voltage accordingly.

[0032] Reference Figure 3 and Figure 4 , Figure 3 This is a simulated diagram of the distribution of the amount of charge (positive charge) released. Figure 4 A simulated diagram of the distribution of the amount of charge (positive charge) released. Figure 3 and Figure 4 The X-axis and Y-axis coordinates are the size (mm), and the Z-axis coordinate is the charge. Ideally, the charge deposition shape is a standard cylinder. Since the direction of charge movement is difficult to ensure vertical downward, Figure 3 and Figure 4 The charge deposition is approximately cylindrical.

[0033] The system can be used before testing to spread charge at a single point, or can be used with a mobile bracket to spread charge at multiple points or on the entire wafer surface. In one embodiment, the system also includes a motion module for driving the discharge needle and the electric field module to move synchronously.

[0034] The system of this embodiment can spread a uniform and controllable amount of charge onto the surface of the wafer, thereby improving the measurement accuracy of electrical parameters.

[0035] The above description is only a description of the preferred embodiments of the present invention, and is not intended to limit the scope of the present invention. Any changes or modifications made by a person skilled in the art in the field of the present invention based on the above disclosure shall fall within the scope of protection of the claims.

Claims

1. A system for forming a uniform charge density on a wafer surface, characterized in that: include: Discharge needle; A first high voltage module, used for applying voltage to the discharge needle; Electric field modules are arranged in sections, each section of the electric field module is used to form an electric field of set magnitude and polarity; The tip of the discharge needle ionizes the air to generate electric charge under high voltage; The electric field formed by the electric field module controls the speed and movement path of the charge so that the charge is spread vertically on the wafer to be tested as much as possible; The control unit is used to control the first high-voltage module and the electric field module, and adjust the output voltage of the first high-voltage module according to the amount of charge to be sprinkled on the wafer to be tested and the amount of charge actually sprinkled on the wafer to be tested.

2. The system for forming a uniform charge density on a wafer surface as claimed in claim 1, characterized in that: The electric field module comprises: A first cover wall surrounds the outer periphery and lower area of ​​the discharge needle, and the lower end of the first cover wall is open; A second cover wall, located below the first cover wall and insulated from the lower end of the first cover wall; a second high-voltage module, used for applying voltage to the first cover wall to form an electric field in the first cover wall; a third high-voltage module, used for applying voltage to the second cover wall to form an electric field in the second cover wall; The fourth high-voltage module is used to apply voltage at the outlet of the lower end of the second cover wall to form an electric field at the outlet of the lower end of the second cover wall.

3. The system for forming a uniform charge density on a wafer surface as claimed in claim 2, characterized in that: The overall profile of the first cover wall and the second cover wall is wide at the top and narrow at the bottom.

4. The system for forming a uniform charge density on a wafer surface as claimed in claim 2, characterized in that: The lower end of the first cover wall and the upper end of the second cover wall are connected by an insulating material.

5. The system for forming a uniform charge density on a wafer surface as claimed in claim 2, characterized in that: The outer walls of the first cover wall and the second cover wall are coated with an insulating layer.

6. The system for forming a uniform charge density on a wafer surface as claimed in claim 1, characterized in that: The control unit includes a current monitoring module, a host computer, a signal generator, an analog-to-digital converter, a high-voltage amplifier and a servo circuit; The signal generator sends a pulse signal to the servo circuit according to the instruction of the host computer to enable the charge to be spread; The current monitoring module is used to monitor the amount of charge spread on the wafer, and convert the charge into a current signal, and then convert the current signal into a voltage signal, which is transmitted to the servo circuit as negative feedback; The host computer is used to set the required amount of charge in the configuration file, and send control instructions to the analog-to-digital converter and the signal generator; The analog-to-digital converter outputs an analog voltage to the servo circuit according to the digital instruction of the host computer; The servo circuit makes a difference between the output voltage of the analog-to-digital converter and the voltage signal fed back by the current monitoring module, and outputs a voltage signal to the high-voltage amplifier according to the difference; The high-voltage amplifier controls the positive and negative voltages applied by the first high-voltage module and the electric field module through high and low levels, amplifies the voltage signal of the servo circuit, and outputs it to the first high-voltage module, thereby controlling the output voltage of the first high-voltage module.

7. The system for forming a uniform charge density on a wafer surface as claimed in claim 1, characterized in that: The system further comprises a motion module, which is used for driving the discharge needle and the electric field module to move synchronously.

8. The system for forming a uniform charge density on a wafer surface as claimed in claim 2, characterized in that: The output voltages of the second high-voltage module, the third high-voltage module and the fourth high-voltage module are fixed and are set by a manual knob.

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