US20200144942A1

US20200144942A1 - Micro device electrostatic chuck

Info

Publication number: US20200144942A1
Application number: US16/181,365
Authority: US
Inventors: Li-Yi Chen
Original assignee: Mikro Mesa Technology Co Ltd
Current assignee: Shenzhen Mikro Quintessence Optoelectronics Co Ltd
Priority date: 2018-11-06
Filing date: 2018-11-06
Publication date: 2020-05-07
Also published as: US10665493B1; CN111146974B; CN111146974A

Abstract

An electrostatic chuck including a body, an electrode, at least one dielectric layer, and a composite dielectric layer is provided. The electrode is present on the body. The dielectric layer is present on and covers the electrode. The composite dielectric layer is present on the dielectric layer. The composite dielectric layer includes a polymer layer and a plurality of inorganic dielectric particles. The inorganic dielectric particles are distributed within the polymer layer, and a permittivity of the inorganic dielectric particles is greater than a permittivity of the polymer layer. A resistivity of the dielectric layer is greater than a resistivity of the composite dielectric layer.

Description

BACKGROUND

Field of Invention

The present disclosure relates to an electrostatic chuck for picking up a micro device through an electrostatic pressure.

Description of Related Art

The statements in this section merely provide background information related to the present disclosure and do not necessarily constitute prior art.
In recent years, micro devices have become popular in various applications. Among all technical aspects of micro devices, transfer process is one of the most challenging tasks for micro devices to be commercialized. One of the important issues of the transfer process is the design of electrostatic chucks.

SUMMARY

According to some embodiments of the present disclosure, an electrostatic chuck including a body, an electrode, at least one dielectric layer, and a composite dielectric layer is provided. The electrode is present on the body. The dielectric layer is present on and covers the electrode. The composite dielectric layer is present on the dielectric layer. The composite dielectric layer includes a polymer layer and a plurality of inorganic dielectric particles. The inorganic dielectric particles are distributed within the polymer layer, and a permittivity of the inorganic dielectric particles is greater than a permittivity of the polymer layer. A resistivity of the dielectric layer is greater than a resistivity of the composite dielectric layer.
It is to be understood that both the foregoing general description and the following detailed description are by examples, and are intended to provide further explanation of the disclosure as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure can be more fully understood by reading the following detailed description of the embodiment, with reference made to the accompanying drawings as follows:

FIG. 1A is a cross-sectional view of an electrostatic chuck according to some embodiments of the present disclosure;

FIG. 1B is an enlarged cross-sectional view of a portion of a composite dielectric layer according to some embodiments of the present disclosure;

FIG. 2 is a cross-sectional view of an electrostatic chuck according to some embodiments of the present disclosure;

FIG. 3 is a cross-sectional view of an electrostatic chuck according to some embodiments of the present disclosure; and

FIG. 4 is a cross-sectional view of an electrostatic chuck according to some embodiments of the present disclosure.

DETAILED DESCRIPTION

Reference will now be made in detail to the present embodiments of the disclosure, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts.
In various embodiments, description is made with reference to figures. However, certain embodiments may be practiced without one or more of these specific details, or in combination with other known methods and configurations. In the following description, numerous specific details are set forth, such as specific configurations, dimensions and processes, etc., in order to provide a thorough understanding of the present disclosure. In other instances, well-known semiconductor processes and manufacturing techniques have not been described in particular detail in order to not unnecessarily obscure the present disclosure. Reference throughout this specification to “one embodiment,” “an embodiment”, “some embodiments” or the like means that a particular feature, structure, configuration, or characteristic described in connection with the embodiment is included in at least one embodiment of the disclosure. Thus, the appearances of the phrase “in one embodiment,” “in an embodiment”, “in some embodiments” or the like in various places throughout this specification are not necessarily referring to the same embodiment of the disclosure. Furthermore, the particular features, structures, configurations, or characteristics may be combined in any suitable manner in one or more embodiments.
The terms “over,” “to,” “between” and “on” as used herein may refer to a relative position of one layer with respect to other layers. One layer “over” or “on” another layer or bonded “to” another layer may be directly in contact with the other layer or may have one or more intervening layers. One layer “between” layers may be directly in contact with the layers or may have one or more intervening layers.
References are made to FIGS. 1A and 1B. FIG. 1A is a cross-sectional view of an electrostatic chuck 100 a according to some embodiments of the present disclosure. FIG. 1B is an enlarged cross-sectional view of a portion of a composite dielectric layer 140 a according to some embodiments of the present disclosure. In some embodiments, an electrostatic chuck 100 a including a body 110, an electrode 120 a, a dielectric layer 130 a, and a composite dielectric layer 140 a is provided. Although most of terms described in the following disclosure use singular nouns, said terms may also be plural in accordance with figures or practical applications.
The electrode 120 a is present on the body 110. The body 110 may include a variety of materials such as silicon, ceramic, glass, or quartz, which are capable of providing structural support. The dielectric layer 130 a is present on and covers the electrode 120 a. The composite dielectric layer 140 a is present on the dielectric layer 130 a. In some embodiments, the dielectric layer 130 a can be formed by atomic layer deposition (ALD), thermal deposition, sputtering, chemical vapor deposition (CVD), or physical vapor deposition (PVD). The composite dielectric layer 140 a includes a polymer layer 142 a and a plurality of inorganic dielectric particles 144 a, as shown in FIG. 1B which is an enlarged view of the portion E in FIG. 1A. The inorganic dielectric particles 144 a are distributed within the polymer layer 142 a. Specifically, the polymer layer 142 a can be a polymer matrix which can be made by crosslinking polymers, and the inorganic dielectric particles 144 a are embedded in the polymer matrix. The volume ratio of the polymer layer 142 a and the inorganic dielectric particles 144 a of the composite dielectric layer 140 a shown FIG. 1B is only schematic. The polymer layer 142 a can be polymethyl methacrylate (PMMA), polydimethylsiloxane (PDMS), or epoxy, but should not be limited thereto. The inorganic dielectric particles 144 a can include titanium dioxide (TiO₂), barium titanate (BaTiO₃), zirconium dioxide (ZrO₂), or combinations thereof. In some embodiments, the composite dielectric layer 140 a is made by first mixing the inorganic dielectric particles 144 a into the polymer layer 142 a, and then using a process such as spin-coating, slit-coating, or inkjet printing to form the composite dielectric layer 140 a on the dielectric layer 130 a.
In some embodiments, each of the inorganic dielectric particles 144 a is coated with a metal thereon, and is wrapped by said metal, so as to enhance dipole moments of each of the inorganic dielectric particles 144 a, and hence the electrostatic pressure exerted by the electrostatic chuck 100 a to the micro device to be picked up can be further enhanced. In some embodiments, an average diameter of the inorganic dielectric particles 144 a is smaller than a size of a micro device to be picked up by the electrostatic chuck 100 a, such as equal to or smaller than 100 nanometers, so as to provide a substantially uniform electrostatic pressure to said micro device.
In some embodiments, a thickness of the composite dielectric layer 140 a is greater than a thickness of the dielectric layer 130 a, so as to increase a breakdown voltage of the electrostatic chuck 100 a. Besides, the thicker composite dielectric layer 140 a can be less sensitive to an air gap between the composited dielectric layer 140 a and the micro device to be picked up when the applied voltage increases. Furthermore, the thicker dielectric layer 140 a can prevent the dielectric layer 130 a from scratching. In some embodiments, a thickness of the composite dielectric layer 140 a ranges from about 0.2 μm to about 100 μm. In some embodiments, a thickness of the composite dielectric layer 140 a ranges from about 1 μm to about 10 μm.
In some embodiments, a permittivity of the inorganic dielectric particles 144 a is greater than a permittivity of the polymer layer 142 a, such that an equivalent permittivity of the composite dielectric layer 140 a can be enhanced compared to a permittivity of the composite dielectric layer 140 a without the inorganic dielectric particles 144 a (i.e., compared to the case with only the polymer layer 142 a constituting the composite dielectric layer 140 a). In some embodiments, a material of the polymer layer 142 a has a permittivity about 1.4 to 1.5 times the vacuum permittivity (i.e., a dielectric constant of the polymer layer 142 a is about 1.4 to 1.5). In some embodiments, a material of the inorganic dielectric particles 144 a has a permittivity more than two decades of the vacuum permittivity (i.e., a dielectric constant of the inorganic dielectric particles 144 a is more than 20). In some embodiments, an equivalent permittivity of the composite dielectric layer 140 a is greater than 6 times of the vacuum permittivity by tuning a ratio of the total volume of the polymer layer 142 a to the total volume of the inorganic dielectric particles 144 a. As such, the composite dielectric layer 140 a not only can prevent the electrostatic chuck 100 a from scratches when picking up a micro device due to its pliable surface formed by the polymer layer 142 a (i.e., a hardness of the dielectric layer 130 a is greater than a hardness of the composite dielectric layer 140 a), but also have a sufficiently high permittivity to exert an electrostatic pressure which is high enough to stably transfer a micro device.
In some embodiments, a resistivity of the dielectric layer 130 a is greater than a resistivity of the composite dielectric layer 140 a, so as to prevent a possible current leakage from the electrode 120 a to a contact surface between the composite dielectric layer 140 a and the micro device to be picked up.
In some embodiments, the dielectric layer 130 a includes teflon, epoxy, or combinations thereof. In some embodiments, the dielectric layer 130 a includes an inorganic material, such as silicon nitride (SiN_x), hafnium oxide (HfO₂), silicon dioxide (SiO₂), or combinations thereof.
With the above configuration, a combination of the dielectric layer 130 a and the composite dielectric layer 140 a can have several benefits. First, since the polymer layer 142 a of the composite dielectric layer 140 a is generally pliable (e.g., PMMA) compared to a micro device to be picked up, the polymer layer 142 a can prevent the electrostatic chuck 100 a from scratches, thus preventing failure of picking up. The polymer layer 142 a also reveals better contact with the micro device to be picked up. However, soft materials often have lower permittivities, and thus an electrostatic pressure exerted by the electrostatic chuck with a soft material thereon (e.g. said polymer layer 142 a) to the micro device is also lower compared to dielectric materials having greater hardness (e.g., silicon nitride). In order to enhance the electrostatic pressure while keeping a pliable contact between the electrostatic chuck 100 a and the micro device, the inorganic dielectric particles 144 a having a higher permittivity compared to the polymer layer 142 a are introduced and mixed in the polymer layer 142 a to enhance the equivalent permittivity of the composite dielectric layer 140 a. However, the introduction of the inorganic dielectric particles 144 a tends to increase the occurrence of local charge accumulations, such charge accumulations may cause the inorganic dielectric particles 144 a to form channels and cause current leakages. Therefore, the dielectric layer 130 a with a higher resistivity compared to the composite dielectric layer 140 a is present to solve the current leakage phenomenon of the channels formed by the inorganic dielectric particles 144 a.
Reference is made to FIG. 2. FIG. 2 is a cross-sectional view of an electrostatic chuck 100 b according to some embodiments of the present disclosure. Differences between the electrostatic chuck 100 b and the electrostatic chuck 100 a are that, the dielectric layer 130 b has a substantially flat surface facing away from the electrode 120 b as shown in FIG. 2, while a surface of the dielectric layer 130 a facing away from the electrode 120 a has a raised platform above the electrode 120 a as shown in FIG. 1A. Similarly, the composite dielectric layer 140 b has a substantially flat surface facing away from the electrode 120 b, while a surface of the composite dielectric layer 140 a facing away from the electrode 120 a has a raised platform above the electrode 120 a. The above differences may come from different thicknesses between the electrode 120 a and the electrode 120 b, but should not be limited thereto.
Reference is made to FIG. 3. FIG. 3 is a cross-sectional view of an electrostatic chuck 100 c according to some embodiments of the present disclosure. In some embodiments, a number of the dielectric layer 130 c is plural. For example, in FIG. 3 the dielectric layer 130 c includes a first dielectric layer 1302 c and a second dielectric layer 1304 c. The first dielectric layer 1302 c is present on and in contact with the electrode 120 a. The second dielectric layer 1304 c is present and stacked on the first dielectric layer 1302 c. The first and second dielectric layers 1302 c, 1304 c may include two of the materials selected from silicon nitride (SiN_x), dioxohafnium (HfO₂), Silicon dioxide (SiO₂), tantalum pentoxide (Ta₂O₅), titanium dioxide (TiO₂), zirconium dioxide (ZrO₂), aluminium oxide (Al₂O₃), teflon, and epoxy respectively, but should not be limited thereto. Although in FIG. 3 the dielectric layer 130 c has a raised platform, in some other embodiments, such as embodiments with thinner electrode 120 a (e.g., replacing the electrode 120 a with the electrode 120 b, similar to the embodiments illustrated by FIG. 2), the dielectric layer 130 c can also have a substantially flat surface facing away from the electrode 120 a (or 120 b).
Reference is made to FIG. 4. FIG. 4 is a cross-sectional view of an electrostatic chuck 100 d according to some embodiments of the present disclosure. In some embodiments, the electrostatic chuck 100 d can include two electrodes (e.g., a first electrode 1202 b and a second electrode 1204 b) present between the dielectric layer 130 b and the body 110. The second electrode 1204 b is adjacent to and electrically isolated from the electrode 1202 b. In some embodiments, the electrodes 1202 b and 1204 b can be bipolar electrodes. That is, different voltages are respectively applied to the electrodes 1202 b and 1204 b for picking up the micro device. In some embodiments, voltages applied to the electrodes 1202 b and 1204 b can be a positive voltage and a negative voltage respectively to enhance and stabilize the electrostatic pressure for picking up the micro device. Besides, the bipolar electrodes can have two-phase and multi-phase when alternating currents is applied to the electrodes 1202 b and 1204 b. Specifically, bipolar electrodes are more capable of picking up an insulator or an ungrounded object (or an electrostatically floated object).
In summary, embodiments of the present disclosure provide an electrostatic chuck for picking up a micro device through an electrostatic pressure. A dielectric layer with high resistivity is present between a composite dielectric layer with low resistivity and an electrode. As such, when a transferring process is conducted, a current leakage caused by charge accumulations of the electrostatic chuck can be prevented, while an electrostatic pressure can be stable and kept high enough.
Although the present disclosure has been described in considerable detail with reference to certain embodiments thereof, other embodiments are possible. Therefore, the spirit and scope of the appended claims should not be limited to the description of the embodiments contained herein.
It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present disclosure without departing from the scope or spirit of the disclosure. In view of the foregoing, it is intended that the present disclosure cover modifications and variations of this disclosure provided they fall within the scope of the following claims.

Claims

What is claimed is:

1. An electrostatic chuck, comprising:

a body;

an electrode present on the body;

at least one dielectric layer present on and covering the electrode; and

a composite dielectric layer present on the at least one dielectric layer, comprising:

a polymer layer; and

a plurality of inorganic dielectric particles distributed within the polymer layer, a permittivity of the inorganic dielectric particles being greater than a permittivity of the polymer layer,

wherein a resistivity of the at least one dielectric layer is greater than a resistivity of the composite dielectric layer.

2. The electrostatic chuck of claim 1, wherein a hardness of the at least one dielectric layer is greater than a hardness of the composite dielectric layer.

3. The electrostatic chuck of claim 1, wherein the at least one dielectric layer comprises an inorganic material.

4. The electrostatic chuck of claim 1, wherein the at least one dielectric layer comprises silicon nitride (SiN_x), dioxohafnium (HfO₂), silicon dioxide (SiO₂), or combinations thereof.

5. The electrostatic chuck of claim 1, wherein the at least dielectric layer comprises teflon, epoxy, or combinations thereof.

6. The electrostatic chuck of claim 1, wherein a number of the at least one dielectric layer is plural.

7. The electrostatic chuck of claim 1, wherein the inorganic dielectric particles comprise titanium dioxide (TiO₂) or barium titanate (BaTiO₃).

8. The electrostatic chuck of claim 1, wherein each of the inorganic dielectric particles is coated with a metal thereon, and is wrapped by the metal.

9. The electrostatic chuck of claim 1, wherein a thickness of the composite dielectric layer is greater than a thickness of the at least one dielectric layer.

10. The electrostatic chuck of claim 1, further comprising a second electrode present between the at least one dielectric layer and the body, wherein the second electrode is adjacent to and electrically isolated from the electrode.