Manufacturing method of high molecular weight modified siliconized polyurethane electrostatic chuckTechnical Field
The invention belongs to the field of semiconductor and flat panel display manufacturing, and particularly relates to a manufacturing method of a high molecular weight modified siliconized polyurethane electrostatic chuck.
Background
In semiconductor and flat panel display manufacturing process equipment, an electrostatic chuck is one of the key core components. In wafer processing equipment such as photolithography, plasma etching, ion implantation, vapor deposition, resist stripping, and vacuum ion beam testing. The type of equipment required for these processes includes various features disposed in a vacuum chamber having a plasma and a halogen. These features must be stable and reliable for thousands of cycles while maintaining complete functionality and cleanliness. Among them, electrostatic chucks are critical components that hold a semiconductor wafer or other workpiece in a vacuum chamber in a fixed position.
From the mechanical model, the existing mainstream ceramic electrostatic chucks are divided into coulomb force and very-back thermal (JR), and the electrostatic chuck in the cavity is connected with an electrostatic chuck power supply outside the cavity through a high-voltage connecting part arranged on the vacuum cavity. The wafer is held in a fixed position while the processing equipment is in operation, such as plasma etching, ion implantation, vapor deposition processes, by continued energization of an external high voltage dc power supply. The principles of electrostatic chuck generation are well known and will not be described in detail herein.
The ceramic electrostatic chuck is divided into two types, namely aluminum oxide ceramic and aluminum nitride ceramic, the aluminum oxide ceramic and the aluminum nitride ceramic are sintered together with metals such as tungsten or molybdenum arranged in a ceramic layer through procedures such as hot isostatic pressing, and ceramic composite sheets are processed and molded through a series of high-precision numerical control centers after sintering and molding. The manner of preparation of alumina ceramic electrostatic chucks and aluminum nitride ceramic electrostatic chucks is well known and will not be described in detail herein.
In addition, with the rapid development of semiconductor technology, integrated circuit chips are becoming thinner and thinner, and the difficulty of performing secondary thinning and removing particles and metal element residues is increasing for thin wafers due to the decrease of mechanical strength thereof. In order to solve the problems of metal element and particle pollution on the back surface of a wafer and the like caused by the ceramic electrostatic chuck in the long-term use process of the ceramic electrostatic chuck in a plasma gas environment, a DLC (diamond like carbon) coating and other processes are adopted on the surface of the ceramic electrostatic chuck. However, the diamond-like carbon surface coating is harder, so that secondary damage to the back surface of the thin wafer is easy to occur, and the risk of fragments and damage is high.
In addition, the high molecular weight modified siliconized polyurethane material prepared by the published patent (CN 202111552045.6) has strong initial viscosity, can not realize the rapid detachment of a wafer, and the indexes such as heat transmissibility, heat stability, mechanical strength, insulation resistance, dielectric constant and the like of the high molecular weight modified siliconized polyurethane material prepared by the method do not meet the use requirement of an electrostatic chuck.
Therefore, in order to conform to the more advanced development of integrated circuit technologies such as etching, ion implantation, etc., an electrostatic chuck structure having a high temperature difference tolerance, clean, flexible chucking function is necessary.
Disclosure of Invention
The invention provides a manufacturing method of a high molecular weight modified siliconized polyurethane electrostatic chuck, which aims to overcome the defects of the existing electrostatic chuck caused by uneven thermal expansion coefficient and precipitation of element substances, and the electrostatic chuck prepared by the manufacturing method has a high dielectric constant, a stable molecular structure and a thermal expansion coefficient similar to that of other component layers, can ensure that a heat conducting insulating layer has high mechanical strength, has high temperature difference tolerance, cleanliness and flexible clamping function, and enables the electrostatic chuck to have higher thermal stability and temperature region adaptation interval by combining key components by using the heat conducting insulating layer similar to the thermal expansion coefficient and Rockwell hardness of the dielectric layer.
The invention provides a manufacturing method of a high molecular weight modified siliconized polyurethane electrostatic chuck, which comprises the following steps:
step one, hyperbranched polyurethane (HBPU) solution with the hyperbranched degree of 0.6 is obtained by a known mode;
Step two, obtaining a hydroxyl end-capped hyperbranched organic silica gel solution in a known manner;
Preparing a high molecular weight modified siliconized polyurethane rubber primer solution;
Adopting a known mode, adopting a proper amount of silane coupling agent (KH 550) to respectively carry out surface modification treatment on the aluminum oxide nanometer powder, the aluminum nitride nanometer powder, the white carbon black nanometer powder and the diamond-like nanometer powder by a liquid phase modification method, and then obtaining a modified material by a spray drying method;
Preparing high molecular weight modified siliconized polyurethane primer solution;
Step six, preparing a high molecular weight modified siliconized polyurethane dielectric layer and an electrode layer;
Step seven, preparing a heat conduction insulating layer;
and step eight, patterning the electrode layer of the dielectric substrate B.
Preferably, the third step includes:
1) Adding proper amount of polydimethylsiloxane into the high molecular weight modified siliconized polyurethane synthesized after catalysis by lithium siloxide;
2) The addition of polydimethylsiloxane can reduce the surface tension and viscosity of the liquid state of the high molecular weight modified siliconized polyurethane.
Preferably, in the fourth step, a proper amount of silane coupling agent (KH 550) and white carbon black nanometer micropowder are used for carrying out surface grafting modification treatment, so that KH550@white carbon black (KH 550-SiO 2) with high crosslinking density, uniform filler dispersion, high wear resistance and strong thermal stability can be prepared.
Preferably, the fifth specific step is as follows:
1) Adding a proper amount of hyperbranched polyurethane (HBPU) solution and a hydroxyl end-capped hyperbranched organic silica gel solution into a beaker filled with nitrogen, stirring for a plurality of times, and carrying out polymerization reaction at normal temperature to obtain a high molecular weight modified siliconized polyurethane bottom layer solution A;
2) Adding one or more of KH550@white carbon black (KH 550-SiO2), KH550@alumina (KH 550-Al2O3), KH550@diamond-like carbon into a high molecular weight modified siliconized polyurethane bottom layer solution A, placing the mixed solution into a vacuum stirring and defoaming device for stirring and defoaming treatment for not less than 60 minutes, wherein the vacuum degree is not less than 2000Pa during defoaming;
3) The high molecular weight modified siliconized polyurethane bottom mixed solution which is synthesized by adding the modified nanometer micro powder, namely dielectric solution C;
4) The obtained dielectric solution C has the characteristics of higher compactness, wear resistance, thermal stability, dielectric constant and the like, and the dielectric constant is not lower than 10, so that the dielectric solution C is one of ideal electrostatic chuck dielectric materials.
Preferably, the specific steps of the step six are as follows:
1) Uniformly coating a dielectric solution C on the metal foil subjected to plasma modification in a known manner to prepare a dielectric substrate B, wherein the coating mode of the dielectric solution C and the metal foil can adopt roller coating, tape casting, spraying and the like;
2) Then, the dielectric substrate B is vulcanized at a high temperature in a vacuum atmosphere in a known manner, wherein the vulcanization temperature is not lower than 230 ℃;
3) The thickness of the dielectric layer of the prepared dielectric substrate B is not less than 0.1mm;
4) And (3) performing polydimethylsiloxane treatment on the dielectric substrate B electrically non-metal again to further reduce the non-metal surface tension of the dielectric substrate B.
Preferably, the specific steps of the step seven are as follows:
1) The high molecular weight modified siliconized polyurethane bottom mixed solution, namely the heat conducting and insulating solution D, is obtained by increasing or reducing the types or dosage of the modified nanometer micro powder in the high molecular weight modified siliconized polyurethane bottom solution;
2) Introducing the heat conduction insulating solution D into an unlabeled mold, suspending and paving an electronic glass fiber net layer in the mold, and performing vacuum defoaming, wherein the vacuum degree in the cavity is not lower than minus 3 times of 10;
3) The heat conduction insulating solution D fully dips the electronic glass fiber net layer, and the electronic glass fiber net layer is arranged in the middle of the heat conduction insulating layer after solidification.
Preferably, the specific steps of the step eight are as follows:
1) Forming a conductive line of a specific pattern on the metal side of the dielectric substrate B by known means, such as wet etching;
2) Vacuum bonding is carried out on a dielectric substrate B with an existing formed circuit structure and a heat-conducting insulating substrate B, after a crosslinking reaction, an electrode layer of the dielectric substrate B is completely wrapped by a heat-conducting insulating layer, and the dielectric substrate B has a compact structure, so that a composite material F is prepared;
3) Cutting the composite material F in a special shape structure;
4) And vacuum bonding the composite material F with the special shape structure and the metal base layer.
Preferably, the heat conducting insulating layer and the metal base are components with different thermal expansion coefficients, and have larger relative areas, so that bonding and adhesion at higher temperature are realized.
Preferably, the metal base is formed by machining a top layer from a plurality of pieces of aluminum in total, and then is assisted by one or more of a brazing process, friction stir welding and ion beam welding to realize the completion of the internal heat dissipation water channel.
The electrostatic chuck dielectric layer prepared by the invention has higher dielectric constant, stable molecular structure and thermal expansion coefficient similar to that of other component layers, can ensure that the heat conducting insulating layer has higher mechanical strength, has high temperature difference tolerance, cleanness and flexible clamping function, and combines key components by using the heat conducting insulating layer similar to the thermal expansion coefficient and Rockwell hardness of the dielectric layer, so that the electrostatic chuck has higher thermal stability and temperature region adaptation interval.
Drawings
FIG. 1 is a schematic cross-sectional view of an electrostatic chuck made in accordance with the present invention;
in the figure, a dielectric layer 100, an electrode layer 200, a heat conducting insulating layer 300, an electronic glass fiber net layer 400 and a metal base layer 500 are shown.
Detailed Description
The invention is described in further detail below by way of examples and figures, all of which are commercially available or can be prepared by known conventional methods.
Examples
A manufacturing method of a high molecular weight modified siliconized polyurethane electrostatic chuck comprises the following steps:
Step one, hyperbranched polyurethane (HBPU) solution with the hyperbranched degree of 0.6 is obtained by a known method.
And step two, obtaining the hydroxyl end-capped hyperbranched organic silica gel solution by a known mode.
And thirdly, preparing high molecular weight modified siliconized polyurethane rubber primer solution.
1) A suitable amount of polydimethylsiloxane is added to the high molecular weight modified siliconized polyurethane synthesized after lithium siloxide catalysis.
2) The addition of polydimethylsiloxane can reduce the surface tension and viscosity of the liquid state of the high molecular weight modified siliconized polyurethane.
And fourthly, adopting a known mode, carrying out surface modification treatment on the aluminum oxide nanometer powder, the aluminum nitride nanometer powder, the white carbon black nanometer powder and the diamond-like nanometer powder respectively by adopting a proper amount of silane coupling agent (KH 550) in a liquid phase modification method and other modes, and obtaining the modified material by a spray drying method.
In this embodiment, the white carbon black nano-micro powder is taken as an example. The KH550@white carbon black (KH 550-SiO 2) with high crosslinking density, uniform filler dispersion, high wear resistance and strong thermal stability can be prepared by carrying out surface grafting modification treatment on a proper amount of silane coupling agent (KH 550) and alumina nanometer micropowder.
Fifthly, the preparation method of the high molecular weight modified siliconized polyurethane primer solution comprises the following steps:
1) Adding a proper amount of hyperbranched polyurethane (HBPU) solution and a hydroxyl end-capped hyperbranched organic silica gel solution into a beaker filled with nitrogen, stirring for a plurality of times, and carrying out polymerization reaction at normal temperature to obtain a high molecular weight modified siliconized polyurethane bottom layer solution A.
2) Adding one or more of KH550@white carbon black (KH 550-SiO2), KH550@alumina (KH 550-Al2O3), KH550@diamond-like carbon into the high molecular weight modified siliconized polyurethane bottom layer solution A, placing the mixed solution into a vacuum stirring and defoaming device for stirring and defoaming for not less than 60 minutes, and removing bubbles at a vacuum degree of not less than 2000Pa.
3) And adding the high molecular weight modified siliconized polyurethane bottom mixed solution which is synthesized by the catalysis of the modified nanometer micro powder, namely a dielectric solution C.
4) The obtained dielectric solution C has the characteristics of higher compactness, wear resistance, thermal stability, dielectric constant and the like, and the dielectric constant is not lower than 10, so that the dielectric solution C is one of ideal electrostatic chuck dielectric materials. A
And step six, preparing the high molecular weight modified siliconized polyurethane dielectric layer 100 and the electrode layer 200.
1) Dielectric substrate B is prepared by uniformly coating dielectric solution C over a metal foil modified, such as by plasma, in a well-known manner. The dielectric solution C and the metal foil can be coated by roller coating, casting, spraying, etc. The metal foil in this embodiment is preferably an electrolytic copper foil of 50 μm thickness.
2) The dielectric substrate B is subjected to high-temperature vulcanization treatment in a vacuum atmosphere in a known manner, and the vulcanization temperature is not lower than 230 ℃.
3) The thickness of the dielectric layer of the prepared dielectric substrate B is not less than 0.1mm.
4) And (3) carrying out polydimethylsiloxane treatment on the dielectric substrate B electrically non-metal again to further reduce the non-metal surface tension of the dielectric substrate B.
Step seven, the heat conductive insulating layer 300.
1) The high molecular weight modified siliconized polyurethane bottom mixed solution, namely the heat conducting and insulating solution D, is obtained by increasing or decreasing the types or dosages of the modified nanometer micro powder in the high molecular weight modified siliconized polyurethane bottom solution.
2) And (3) introducing the heat conduction insulating solution D into an unlabeled mold, suspending and paving an electronic glass fiber net layer in the mold, and performing vacuum defoaming, wherein the vacuum degree in the cavity is not lower than minus 3 times of 10.
3) The heat conductive insulating solution D fully covers the electronic glass fiber net layer 400, and after curing, the electronic glass fiber net layer 400 is placed in the middle of the heat conductive insulating layer 300.
And step eight, patterning the dielectric substrate B electrode layer 200.
1) A specific pattern of conductive traces is created on the metal side of the dielectric substrate B by well known means, such as wet etching.
2) The dielectric substrate B with the formed circuit structure and the heat-conducting insulating substrate B are subjected to vacuum bonding, and after the crosslinking reaction, the heat-conducting insulating layer 300 completely wraps the electrode layer 200 of the dielectric substrate B, has a compact structure and is manufactured into the composite material F.
3) And cutting the composite material F in a special shape structure.
4) The composite material F having a specific shape structure is vacuum bonded to the metal base layer 500.
5) In the above embodiment, the heat conductive insulating layer 300 and the metal base 500 are components having different thermal expansion coefficients and have a relatively large area, and bonding and adhesion at a relatively high temperature are realized in this embodiment.
The metal base 500 is formed by machining a top layer of a plurality of pieces of aluminum together, and then performing one or more processes of brazing, friction stir welding and ion beam welding to complete the internal heat dissipation water channel.
In the above embodiment, the preparation of the main functional components of the electrostatic chuck is similar, and the thermal stability and the thermal linear expansion coefficient reach the best matching values. The thermal expansion coefficient is not limited to be similar to that of the existing electrostatic chuck, the thermal expansion coefficient is obviously improved in the heat transfer rate, the difference of the thermal expansion coefficients is reduced, the whole tolerance temperature interval of the electrostatic chuck is further improved, and the precipitation of contact surface elements and particulate matters in the plasma atmosphere is reduced.
Examples
Referring to fig. 1, the high molecular weight modified siliconized polyurethane electrostatic chuck prepared by the invention has an assembly structure in the form of a combination of multiple layers of functional components, and the main components of the high molecular weight modified siliconized polyurethane electrostatic chuck are high molecular weight modified siliconized polyurethane, alumina nanometer micropowder and the like. The functional component comprises a dielectric layer, an electrode layer, a heat conducting insulating layer and a mounting base layer. The dielectric layer is compounded by nonmetallic materials containing high molecular weight modified siliconized polyurethane, alumina nano micro powder, aluminum nitride nano micro powder, white carbon black nano micro powder, diamond-like nano micro powder and the like, and the material has higher dielectric constant and stable molecular structure and thermal expansion coefficient similar to that of other component layers, so that the defects of the traditional electrostatic chuck caused by uneven thermal expansion coefficient and precipitation of element substances are overcome.
In the embodiment, the heat conduction insulating layer is composed of a high molecular weight modified siliconized polyurethane layer with higher impedance and heat conduction performance and an electronic glass fiber net layer with a stable structure, wherein the electronic glass fiber net layer is arranged in the high molecular weight modified siliconized polyurethane layer, and the structure can ensure that the heat conduction insulating layer has higher mechanical strength.
In this embodiment, the main component of the heat conductive insulating layer is one or more of high molecular weight modified siliconized polyurethane, alumina nano micro powder, aluminum nitride nano micro powder, and the like, and the preparation method is similar to that of the dielectric layer. The electrostatic chuck has higher thermal stability and temperature zone adaptation interval by combining key components through the heat conducting insulating layer with the thermal expansion coefficient and Rockwell hardness similar to those of the dielectric layer.
Although particular embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations may be made therein without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.