A method and system for measuring metal work function using Kelvin probe

Abstract

The present invention provides a method and system for measuring the work function of a metal using a Kelvin probe, comprising: providing a substrate, the surface of the substrate having a metal film to be measured; grounding the metal film; applying a changing voltage to a vibrating probe of a Kelvin probe device using a voltage applying device; monitoring the current change between the probe and the metal film to be measured using a current monitoring device in real time, stopping the application of the voltage when the current value is 0, and obtaining the current applied voltage value; the work function of the metal film to be measured is the sum of the voltage applied when the current value is 0 and the work function of the probe metal. The present invention can accurately obtain the work function of the metal film.

Description

Technical Field

[0001] The present invention relates to the field of wafer detection, and in particular to a method and system for measuring metal work function using a Kelvin probe. Background Art

[0002] Metal gate work function refers to the minimum energy required for electrons in metal gate materials to escape from the surface. In semiconductor devices, metal gate work function has an important impact on device performance. A suitable metal gate work function can optimize key parameters such as transistor threshold voltage and carrier mobility, thereby improving the electrical performance of the device, such as switching speed and power consumption. Different metal materials have different work function values. In semiconductor processes, it is necessary to select suitable metal gate materials based on specific design requirements and performance goals.

[0003] The metal gate work function is one of the key parameters when the size of the metal-oxide-semiconductor transistor (MOSFET) is reduced to 45nm and 32nm technology nodes, and the new generation of metal / high-k dielectric structure replaces the traditional polysilicon / SiO2 structure. It affects the flat band voltage of the device, determines the threshold voltage of the MOSFET device, and thus determines the driving performance of the device. In the high-k metal gate process, the realization of the metal gate work function is difficult. The main reasons include the following: Influence of interface characteristics: The interface characteristics between the metal gate and the high-k dielectric have an important influence on the work function. The interface chemical composition, interface atomic bonding structure, interface defects, crystal orientation of metal polycrystalline nanoparticles, etc. may cause changes in the work function, so the interface needs to be precisely controlled and optimized. Process complexity: The high-k metal gate process usually involves complex process steps such as deposition, annealing and patterning, which may affect the metal gate work function. For example, high temperature processing may cause the drift of the work function, and the etching and cleaning steps in the patterning process may also introduce interface defects. Material selection and compatibility: Selecting suitable metal gate materials and high-k dielectric materials and ensuring their compatibility are the key to achieving the required work function. The work functions of different materials may affect each other, and certain material combinations may have stability issues.

[0004] Therefore, how to obtain an accurate work function of a metal layer is the focus of those skilled in the art. Summary of the invention

[0005] The purpose of the present invention is to provide a method and system for measuring the work function of a metal using a Kelvin probe, which can obtain an accurate work function of a metal layer.

[0006] In order to achieve the above object, the present invention provides a method for measuring metal work function using a Kelvin probe, comprising:

[0007] Providing a substrate, wherein the surface of the substrate has a metal film to be tested;

[0008] grounding the metal film;

[0009] applying a varying voltage to a vibrating probe of the Kelvin probe device using a voltage applying device;

[0010] Using a current monitoring device to monitor the current change between the probe and the metal film to be tested in real time, when the monitored current value is 0, stop applying the voltage and obtain the current applied voltage value;

[0011] The work function of the metal film to be measured is the sum of the voltage applied when the current value is 0 and the work function of the probe metal.

[0012] In an optional solution, the metal film to be tested is controlled to be grounded through a relay switch.

[0013] In an optional solution, the vibration of the probe of the Kelvin probe device and the on and off of the relay switch are controlled by a host computer.

[0014] In an optional solution, the voltage applying device is controlled by the host computer to apply a variable voltage to the probe;

[0015] The host computer displays the voltage data of the voltage applying device and the current data of the current monitoring device.

[0016] In an optional solution, the substrate includes a semiconductor substrate and a dielectric layer located on the semiconductor substrate, and the metal film to be tested is located above the dielectric layer.

[0017] In an optional solution, the semiconductor substrate is a silicon substrate, and the dielectric layer is silicon dioxide or a high-K dielectric.

[0018] The present invention also provides a system for measuring metal work function using a Kelvin probe, comprising:

[0019] A Kelvin probe device having a vibrating probe head;

[0020] A voltage applying device, used for applying a varying voltage to the probe;

[0021] A current monitoring device, used for real-time monitoring of the current change between the probe and the metal film to be measured;

[0022] A grounding device, used for grounding the metal film to be tested;

[0023] When the current value is detected to be 0, the test value of the probe is obtained;

[0024] The work function of the metal film is the sum of the test value of the probe and the work function of the probe metal.

[0025] In an optional solution, the grounding device includes a relay switch.

[0026] In an optional solution, the system includes a host computer, and the host computer is used to:

[0027] controlling the vibration of the probe;

[0028] Controlling the on and off of the relay switch;

[0029] Controlling the voltage applying device to apply a varying voltage to the probe of the Kelvin probe device;

[0030] The voltage data of the voltage applying device and the current data of the current monitoring device are displayed.

[0031] The beneficial effects of the present invention are:

[0032] The present invention can accurately obtain the work function of the metal film. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] 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.

[0034] Figure 1 FIG. 4 is a schematic diagram of measuring the work function of a metal layer using a Kelvin probe method in an example.

[0035] Figure 2 FIG. 4 is a schematic diagram of a system for measuring metal work function using a Kelvin probe according to an embodiment of the present invention. DETAILED DESCRIPTION

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] In order to ensure the realization and stability of the metal gate work function, monitoring is usually required in process control. The Kelvin probe method can be used to measure the metal gate work function. The Kelvin probe method is a non-contact, non-destructive gas-phase environment metal surface potential measurement technology based on vibrating capacitance. It uses a movable probe and a fixed sample metal electrode (the sample metal electrode is the metal film to be measured, and the ambient air is between the probe and the metal electrode, similar to the simplest plate capacitor model). The surface potential of the sample is determined by the capacitance change generated when the probe vibrates on the sample surface. The change in real capacitance is difficult to characterize, but the current between the plate capacitors can be cleverly applied to measure the sample surface potential. The specific method is to apply a variable voltage to the Kelvin probe. When the current between the plate capacitors is detected to be zero, the variable voltage applied to the surface is the measured sample surface potential, which greatly simplifies operability and provides measurement accuracy.

[0041] Reference Figure 1 , the formula for measuring metal work function by Kelvin probe method is as follows: V KP =V Si +V ox +V id +V sd +WF,V Si : The potential in the silicon substrate due to band bending, V ox : Potential caused by the charge in the oxide layer, V id : Due to the potential generated by the interface state, V sd : The potential generated by the AMC on the sample surface, WF: The work function difference between the surface metal and the Kelvin probe, that is, WF = WF metal surface -WF probe surface VKP; the voltage value measured by the metal probe. Therefore, the work function WF of the surface metal metal surface =V KP +WF probe surface -V Si -V ox -V id -V sd . Since V Si 、V ox 、V id 、V sd The values ​​of are relatively small and difficult to measure. The current practice is to ignore these four values ​​and consider WF metal surface =V KP +WF probe surfaceObviously, such a result is inaccurate. However, those skilled in the art have not yet come up with a good solution.

[0042] Example 1

[0043] Reference Figure 2 , this embodiment provides a method for measuring metal work function using a Kelvin probe, comprising: providing a substrate, wherein a surface of the substrate has a metal film to be measured;

[0044] grounding the metal film;

[0045] applying a varying voltage to a vibrating probe of the Kelvin probe device using a voltage applying device;

[0046] Using a current monitoring device to monitor the current change between the probe and the metal film to be tested in real time, when the monitored current value is 0, stop applying the voltage and obtain the current applied voltage value;

[0047] The work function of the metal film to be measured is the sum of the voltage applied when the current value is 0 and the work function of the probe metal.

[0048] Specifically, in this embodiment, the substrate includes a semiconductor substrate and a dielectric layer located on the semiconductor substrate, and the metal film to be measured is located above the dielectric layer. More specifically, the semiconductor substrate is a silicon substrate, and the dielectric layer is silicon dioxide or a high-K dielectric. At the beginning of the measurement, the vibration component 2 of the Kelvin probe device is controlled by the host computer to vibrate (the Kelvin probe device has a vibration component 2, and the vibration component 2 is connected to the probe 1, so that the probe 1 vibrates), and the relay switch K1 is controlled to be closed to ground the metal film to be measured.

[0049] The host computer controls the voltage application device to apply a changing voltage to the probe 1; the current monitoring device monitors the current change between the probe 1 and the metal film to be tested in real time, and when the current value is 0, the voltage application is stopped and the current applied voltage value is obtained. The host computer displays the voltage data of the voltage application device and the current data of the current monitoring device.

[0050] In this embodiment, since the metal film to be tested is grounded, the potential influence of the middle layer of the substrate is removed, that is, V Si +V ox +V id +V sd = 0, so that WF metal surface =V KP +WF probe surfaceThe Kelvin probe is made of metal material, which determines the value of its work function. For example, when the probe metal is gold (Au), its work function is 5.1eV, that is, WF probe surface =5.1eV. WF metal surface =V KP (voltage applied when current value is 0) + 5.1 eV. This embodiment cleverly grounds the metal to be tested, i.e., V Si +V ox +V id +V sd =0, the accurate work function of the metal layer can be obtained.

[0051] Example 2

[0052] Reference Figure 2 This embodiment provides a system for measuring metal work function using a Kelvin probe, comprising:

[0053] A Kelvin probe device having a vibrating probe head;

[0054] A voltage applying device 31, used for applying a variable voltage to the probe 1;

[0055] A current monitoring device 32, used for real-time monitoring of the current change between the probe 1 and the metal film to be measured;

[0056] A grounding device, used for grounding the metal film to be tested;

[0057] When the current value is detected to be 0, the test value of the probe is obtained;

[0058] The work function of the metal film is the sum of the test value of the probe and the work function of the probe metal.

[0059] Specifically, the Kelvin probe device has a vibrating component 2, and the vibrating component 2 is connected to the probe 1, so that the probe 1 vibrates. The grounding device includes a relay switch. The vibration of the vibrating component 2 is controlled by the host computer; the on and off of the relay switch K1 is controlled; the voltage applying device is controlled to apply a changing voltage to the probe of the Kelvin probe device; and the voltage data of the voltage applying device and the current data of the current monitoring device are displayed. The work function of the metal film to be measured is the sum of the voltage applied when the current value is 0 and the work function of the probe metal.

[0060] 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 method for measuring metal work function using a Kelvin probe, characterized in that: include: Providing a substrate, wherein the surface of the substrate has a metal film to be tested; grounding the metal film; applying a varying voltage to a vibrating probe of the Kelvin probe device using a voltage applying device; Using a current monitoring device to monitor the current change between the probe and the metal film to be tested in real time, when the monitored current value is 0, stop applying the voltage and obtain the current applied voltage value; The work function of the metal film to be measured is the sum of the voltage applied when the current value is 0 and the work function of the probe metal.

2. The method for measuring metal work function using a Kelvin probe as claimed in claim 1, characterized in that: The metal film to be tested is controlled to be grounded through a relay switch.

3. The method for measuring metal work function using a Kelvin probe as claimed in claim 2, characterized in that: The vibration of the probe of the Kelvin probe device is controlled by the host computer, and the on and off of the relay switch is controlled.

4. The method for measuring metal work function using a Kelvin probe as claimed in claim 3, characterized in that: Controlling the voltage applying device to apply a variable voltage to the probe through the host computer; The host computer displays the voltage data of the voltage applying device and the current data of the current monitoring device.

5. The method for measuring metal work function using a Kelvin probe as claimed in claim 1, characterized in that: The base plate comprises a semiconductor substrate and a dielectric layer located on the semiconductor substrate, and the metal film to be tested is located above the dielectric layer.

6. The method for measuring metal work function using a Kelvin probe as claimed in claim 5, characterized in that: The semiconductor substrate is a silicon substrate, and the dielectric layer is silicon dioxide or a high-K dielectric.

7. A system for measuring metal work function using a Kelvin probe, characterized in that: include: A Kelvin probe device having a vibrating probe head; A voltage applying device, used for applying a varying voltage to the probe; A current monitoring device, used for real-time monitoring of the current change between the probe and the metal film to be measured; A grounding device, used for grounding the metal film to be tested; When the current value is detected to be 0, the test value of the probe is obtained; The work function of the metal film is the sum of the test value of the probe and the work function of the probe metal.

8. The system for measuring metal work function using a Kelvin probe as claimed in claim 7, characterized in that: The grounding device includes a relay switch.

9. The system for measuring metal work function using a Kelvin probe as claimed in claim 8, characterized in that: The system includes a host computer, which is used for: controlling the vibration of the probe; Controlling the on and off of the relay switch; Controlling the voltage applying device to apply a varying voltage to the probe of the Kelvin probe device; The voltage data of the voltage applying device and the current data of the current monitoring device are displayed.

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