An electrostatic chuck

Abstract

The present invention discloses an electrostatic adsorption chuck, which comprises a circular chuck formed by the cooperation of two aluminum semi-circular disk surfaces. There is a ceramic layer on the aluminum disk surface. C-shaped bosses are respectively arranged at the center positions of the two semi-circular disk surfaces. C-shaped grooves extending to the power supply are arranged on the C-shaped bosses. Titanium and titanium nitride coatings are arranged on the upper surface and the groove wall of the C-shaped bosses, so that the electrostatic voltage on the upper surface of the C-shaped boss can be directly connected to the power supply as a neutral ground. On the ceramic layer of the two semi-circular disk surfaces, a number of radially different flow guiding ring grooves diffusing outward from the center are provided. On the ceramic layer, a number of flow guiding wire grooves facing the periphery of the semi-circular disk surface are provided on the innermost flow guiding ring groove. A number of titanium small-area contact points are arranged on a number of ceramic surfaces formed by the common enclosure of the flow guiding ring grooves and the flow guiding wire grooves. A number of air outlet holes are arranged on the circumferential surface of the semi-circular disk surface near the outermost periphery, and a number of air inlet holes are arranged on the disk surface of the semi-circular disk surface near the C-shaped boss.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor packaging, and particularly to an electrostatic chuck. Background Art

[0002] There are many devices operating in a vacuum environment in the front-end FAB factories of the semiconductor industry, such as PVD and ETCH. When wafers are processed in these devices, it is necessary to cool the wafers. The electrostatic chuck for wafer adsorption is a device that meets this requirement. It uses the principle of electrostatic adsorption to form static electricity with different polarities on the surface of the chuck and the back of the wafer, thereby generating an adsorption effect. Then, argon gas flows in the gas grooves on the surface of the chuck to achieve the cooling effect. This is a high-end device, and many semiconductor equipment manufacturers have corresponding products.

[0003] The cold plate cooling method has the following defects:

[0004] 1. Currently, the disk surfaces of electrostatic chucks on the market all use ceramic material packaging technology to integrally package electrodes and other auxiliary parts in a ceramic package, and then process on the ceramic. The processing difficulty is high and the structure is complex, resulting in an expensive electrostatic chuck and an equally expensive refurbishment cost. FAB factories often complain that although the performance is good, it is too expensive to use.

[0005] 2. For electrostatic chucks on the market, generally, helium gas is used to flow on the back of the wafer on the surface of the chuck to cool the wafer. The current theory holds that the gas heat conduction efficiency is the highest when the helium gas pressure on the back of the wafer is 4 - 6 Torr. Therefore, during cooling, in order to maintain a high pressure, relatively shallow gas guiding grooves are used and the gas flow rate is also relatively small, at 3 - 5 sccm. However, if the electrostatic suction force decreases due to an increase in particulate matter on the surface of the chuck, the high pressure will cause the wafer to jump up, resulting in process failure. This is a persistent problem of electrostatic chucks on the market currently.

[0006] 3. Due to the existence of pressure, the gas grooves on the surface of the chuck are generally relatively shallow, which can only accommodate a small amount of gas, and the cooling effect is also relatively limited. Summary of the Invention

[0007] Object of the Invention: The object of the present invention is to solve the problems that the existing electrostatic chuck has a complex structure, high production difficulty resulting in high costs, inability to provide a large air flow, unsatisfactory cooling effect, and that providing too large an air flow will cause the wafer to jump up.

[0008] Technical Solution: To solve the above problems, the present invention provides the following technical solutions:

[0009] An electrostatic chuck includes a circular chuck composed of two aluminum semi-circular disk surfaces. An insulating layer is provided at the joint between the two aluminum semi-circular disk surfaces. There is a ceramic layer on the aluminum disk surface. C-shaped bosses are respectively provided at the center positions of the two semi-circular disk surfaces. C-shaped grooves extending to the power supply are provided on the C-shaped bosses. Continuous titanium and titanium nitride coatings are provided on the upper surface and the groove wall of the C-shaped bosses, so that the electrostatic voltage on the upper surface of the C-shaped boss can be directly connected to the power supply as a neutral ground. On the ceramic layer of the circular chuck, a number of diversion ring grooves with different radii diffusing outward from the center are formed. On the ceramic layer, a number of diversion wire grooves facing the periphery of the semi-circular disk surface are provided starting from the innermost diversion ring groove. A number of uniformly distributed air outlet holes are provided on the circumferential surface of the semi-circular disk surface near the outermost periphery. A number of uniformly distributed air inlet holes are provided on the disk surface of the semi-circular disk surface near the C-shaped boss. Three first thimble holes with an included angle of 120° to each other are uniformly distributed between the air inlet holes and the air outlet holes of the circular chuck formed by the two semi-circular disk surfaces. A deposition ring with the same height as the C-shaped boss is provided outside the air outlet holes of the circular chuck.

[0010] The existing electrostatic adsorption method of the electrostatic chuck is to form opposite electrodes on the chuck and the wafer respectively, and then perform electrostatic adsorption. However, it can be seen from the background technology that this technology has already had bottlenecks. One is the difficulty in manufacturing. Due to the limitation of the gas flow rate, the cooling effect is not obvious. At the same time, the limitation of the gas flow rate is reflected in the fine structure of the gas, making it difficult to manufacture.

[0011] At the same time, the present application finds that, when adopting the solution of the background technology, during the electrostatic adsorption process, due to the accumulation of induced charges, local unequal induced voltages will be generated on the basis of the power supply. Further, when increasing the electrostatic adsorption force between the wafer and the chuck, an uneven distribution will be formed, and further, it is impossible to accurately determine the required gas pressure.

[0012] During the electrostatic adsorption process, through the conductivity of the surface of the C-shaped groove, the voltage formed at the semi-circular chuck can be directly connected to the power supply. At the power supply, according to the voltage deviation, a corrected voltage after eliminating the deviation value can be further provided, so that the electrostatic adsorption force formed at the electrostatic chuck can be more uniform.

[0013] The reason for the design of two semi-circular chucks, one semi-circular chuck connected to the positive electrode and one semi-circular chuck connected to the negative electrode is that after the process is completed and the DC power supply is removed, the positive and negative charges on the back of the wafer can be neutralized, and there will be no residual charges. The positive and negative electrodes on the chuck are connected to the ground point while the DC power supply is removed, discharging the positive and negative static charges, so that the electrostatic adsorption force can be completely removed, and the wafer can be safely detached from the chuck and safely transmitted out of the reaction chamber by the robotic arm.

[0014] There is a ceramic layer between the aluminum electrode on the disk surface and the back of the wafer. The ceramic layer is a dielectric material, which is equivalent to having a capacitor between two flat plates. After applying a DC voltage to the electrode, opposite-polarity charges are induced on the other side of the capacitor (the back of the wafer), thereby forming an electric field between the electrode and the back of the wafer and generating an electrostatic attraction.

[0015] Furthermore, at least one positioning groove is provided on the outer wall of the deposition ring, and a positioning protrusion that cooperates with the positioning groove is provided on the inner wall of the deposition ring support outside the deposition ring for fixation.

[0016] Furthermore, a number of small titanium contact points are provided on several ceramic surfaces jointly surrounded by the diversion ring groove and the diversion wire groove, and a titanium nitride layer is coated on the outer surface of the small titanium contact points.

[0017] Titanium nitride has high hardness and wear resistance and is an excellent material for making contact points. However, the connection between titanium nitride and ceramic is not good, and a titanium layer needs to be added under the titanium nitride layer to improve the firmness of adhesion.

[0018] Furthermore, the insulating layer is a polystyrene cross-linked resin layer.

[0019] This makes the two semi-circular disk surfaces unable to conduct electricity, and the generated charges only exist on the current disk surface.

[0020] Furthermore, the air outlet is connected to a negative pressure generating device.

[0021] One of the core technical means of this application is not to provide air pressure at the air inlet to push the air flow, but to form a negative pressure at the air outlet and cool by "sucking" the cooling gas at the air inlet. Therefore, the function of the air inlet is only to provide the cooling gas that will be sucked later.

[0022] Since the gas is sucked and flows, it first has an adsorption effect on the wafer at the air outlet, and the adsorption pressure also determines the inlet pressure, so that the wafer will not jump up.

[0023] Gas can be supplied at the air inlet or not. If gas is supplied at the air inlet, due to the existence of negative pressure, the required inlet pressure can also be reduced, reducing the impact on the wafer and preventing the wafer from jumping up.

[0024] Furthermore, a thimble that can move up and down in the first thimble hole is provided in the first thimble hole.

[0025] Further, the deposition ring mounting support is arranged in the facility support plate. The facility support plate has a cavity for placing the deposition ring mounting support. At the corresponding position at the bottom of the cavity, there are cooling air holes for providing cooling gas to the air inlet holes, an air outlet channel capable of connecting to the air outlet hole and providing a negative pressure environment, a second thimble hole capable of cooperating with the first thimble hole and providing a thimble displacement space, a temperature sensor capable of detecting the temperature of the circular chuck surrounded by the deposition ring mounting support in real time, positive and negative terminals capable of providing positive and negative poles for the two semi-circular disk surfaces respectively, a floating neutral connection joint capable of floatingly connecting the C-shaped groove to the power supply, and a non-contact cooling water cavity formed at the bottom for cooling the circular chuck. The cooling water cavity is connected to the external cooling water.

[0026] The cooling gas enters the cooling air holes through the air pipes of the facility support plate, and then reaches the gas grooves on the disk surface through the air inlet holes at the bottom of the electrostatic disk surface. Two sealing rings can also be arranged around the cooling air holes to seal the gas in the ring formed by the cooling air holes, preventing leakage to other positions of the electrostatic chuck or the reaction chamber.

[0027] Further, the negative pressure generating device is a vacuum pump or a facility vacuum system.

[0028] Further, a notch is provided at the bottom of the circular chuck for the temperature sensor to penetrate and measure the temperature inside the chuck.

[0029] Further, the height of the C-shaped boss, the height of the deposition ring, and the height of the small-area contact point boss are the same.

[0030] By restricting the height of the small-area contact points, the small-area contact points protruding on the disk surface contact the back of the wafer, playing a role in supporting the wafer and at the same time forming an adsorption force.

[0031] The height of the area contact points is very small (micrometer level). The part of the chuck outside the small-area contact points does not contact the back of the wafer, and there are extremely small gaps. The tiny gaps form a dielectric (air) capacitance, which will form the Johnsen-Rahbek effect and can also enhance the attraction force.

[0032] Advantageous effects: Compared with the prior art, the present invention:

[0033] 1. By designing two independent semi-circular electrodes, the processing difficulty is reduced, thereby reducing the price of the electrostatic adsorption chuck.

[0034] 2. Through the setting of the vacuum pipeline, the flow of the cooling gas is strengthened, thereby reducing the cooling gas pressure and solving the stubborn problem of the wafer jumping up in the previous products.

[0035] 3. With this design, due to the increased adsorption force, a larger cooling gas guide groove can be designed. The expansion of the cooling gas guide groove can increase the cooling gas flow rate and also improve the ability of the chuck to cool the wafer.

[0036] 4. Different cooling effects can also be achieved by adjusting the flow rates of the cooling gas and the vacuum. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 is a top view structural schematic diagram of the electrostatic chuck of the present invention;

[0038] Figure 2 is a cross-sectional structural schematic diagram of the electrostatic chuck of the present invention;

[0039] Figure 3 is a schematic diagram of installing the electrostatic chuck on the facility support disk of the present invention;

[0040] Figure 4 is a schematic diagram of the principle of electrostatic adsorption of the present invention;

[0041] Figure 5 is a structural schematic diagram of the small-area contact points of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0042] The present invention will be further described below with reference to the drawings and embodiments.

[0043] Embodiment 1

[0044] As Figures 1 to 5 shown, an electrostatic adsorption chuck includes a circular chuck formed by the joint cooperation of two aluminum semi-circular disk surfaces 1. An insulating layer 2 is provided at the joint of the two aluminum semi-circular disk surfaces 1. A ceramic layer 3 is provided on the aluminum disk surface 1. C-shaped bosses 4 are respectively provided at the center positions of the two semi-circular disk surfaces. C-shaped grooves 5 extending to the power supply are provided on the C-shaped bosses 4. Continuous titanium and titanium nitride coatings 6 are provided on the upper surfaces and the groove walls of the C-shaped bosses 4, so that the electrostatic voltage on the upper surface of the C-shaped bosses 4 can be directly connected to the power supply (not shown, this power supply is an adjustable power supply and can be automatically controlled for output according to the neutral ground) as the neutral ground. On the ceramic layer 3 of the circular chuck, a number of diversion ring grooves 7 with different radii diffusing outward from the center are formed. On the ceramic layer 3, a number of diversion wire grooves 8 facing the periphery of the semi-circular disk surface are provided starting from the innermost diversion ring groove 7. A number of uniformly distributed air outlet holes 9 are provided on the circumferential surface of the semi-circular disk surface 1 near the outermost periphery. A number of uniformly distributed air inlet holes 10 are provided on the disk surface of the semi-circular disk surface 1 near the C-shaped boss 4. Three first thimble holes 11 with an included angle of 120° to each other are uniformly distributed between the air inlet holes 10 and the air outlet holes 9 of the circular chuck formed by the two semi-circular disk surfaces 1. A deposition ring 12 with the same height as the C-shaped boss 4 is provided outside the air outlet holes 9 of the circular chuck.

[0045] The existing electrostatic chuck uses an electrostatic adsorption method in which opposite electrodes are formed on the chuck and the wafer respectively, and then electrostatic adsorption is carried out. However, as can be seen from the background technology, this technology has reached a bottleneck. One is the difficulty in manufacturing. Due to the limitation of the gas flow rate, the cooling effect is not obvious. At the same time, the limitation of the gas flow rate is reflected in the fine structure of the gas, making it difficult to manufacture.

[0046] At the same time, the present application finds that, when adopting the solution of the background technology, during the electrostatic adsorption process, due to the aggregation of induced charges, local unequal induced voltages will be generated on the basis of the power supply. Further, increasing the electrostatic adsorption force between the wafer and the chuck will result in uneven distribution, and further make it impossible to accurately determine the required gas pressure.

[0047] During the electrostatic adsorption process, through the conductivity of the C-shaped groove surface, the voltage formed at the semi-circular chuck can be directly connected to the power supply. At the power supply, according to the voltage deviation, a corrected voltage after eliminating the deviation value can be further provided, so that the electrostatic adsorption force formed at the electrostatic chuck can be more uniform.

[0048] Through the design of two semi-circular chucks, one semi-circular chuck is connected to the positive electrode and the other semi-circular chuck is connected to the negative electrode. The reason is that after the process is completed and the DC power supply is removed, the positive and negative charges on the back of the wafer can be neutralized and there will be no residual charges. The positive and negative electrodes on the chuck are connected to the ground point while the DC power supply is removed, discharging the positive and negative static charges, so that the electrostatic adsorption force can be completely removed, and the wafer can be safely detached from the chuck and safely transmitted out of the reaction chamber by the robotic arm.

[0049] There is a ceramic layer between the aluminum electrode on the disk surface and the back of the wafer. The ceramic layer is a dielectric material (the thickness of the ceramic layer is greater than the depths of the diversion ring groove and the diversion wire groove formed on the ceramic layer), which is equivalent to having a capacitor between two flat plates. After applying a DC voltage to the electrode, opposite-polarity charges are induced on the other side (the back of the wafer) of the capacitor, thus forming an electric field between the electrode and the back of the wafer and generating an electrostatic attraction force.

[0050] At least one positioning groove 13 is provided on the outer wall of the deposition ring 12, and a positioning protrusion 15 that cooperates with the positioning groove 13 is provided on the inner wall of the deposition ring mounting support 14 provided outside the deposition ring 12.

[0051] For fixing.

[0052] A number of titanium small-area contact points 17 are provided on a number of ceramic surfaces 16 jointly surrounded by the diversion ring groove 7 and the diversion wire groove 8. The outer surface of the titanium small-area contact points 17 is coated with a titanium nitride layer 18.

[0053] Titanium nitride has high hardness and wear resistance and is an excellent material for making contact points. However, the connection between titanium nitride and ceramics is not good, and a titanium layer needs to be added under the titanium nitride layer to improve the bonding firmness.

[0054] The insulating layer 2 is a polystyrene cross-linked resin layer.

[0055] This makes the two semi-circular disk surfaces unable to conduct electricity, and the generated charges only exist on the current disk surface.

[0056] The air outlet hole 9 is connected to a negative pressure generating device.

[0057] One of the core technical means of this application is not to provide air pressure at the air inlet hole to push the air flow, but to form a negative pressure at the air outlet hole and cool by "sucking" the cooling gas at the air inlet hole. Therefore, the function of the air inlet hole is only to provide the cooling gas that will be sucked later.

[0058] Since the gas is sucked and flows, it first adsorbs the wafer at the air outlet hole, and the adsorption pressure also determines the intake pressure, so that the wafer will not jump up.

[0059] Gas can be supplied at the air inlet hole or not. If gas is supplied at the air inlet hole, due to the existence of negative pressure, the required intake pressure can also be reduced, reducing the impact on the wafer and preventing the wafer from jumping up.

[0060] A thimble (not shown) capable of moving up and down in the first thimble hole is provided in the first thimble hole 11.

[0061] The deposition ring 12 is installed and supported on the facility support disk. The facility support disk has a cavity capable of placing the deposition ring installation support 14. At the corresponding position at the bottom of the cavity, there are cooling air holes 19 capable of providing cooling gas to the air inlet hole 10, an air outlet channel 20 capable of connecting to the air outlet hole 9 and providing a negative pressure environment, a second thimble hole 21 capable of cooperating with the first thimble hole 11 and providing a thimble displacement space, a temperature sensor 22 capable of detecting the temperature of the circular chuck surrounded by the deposition ring installation support 14 in real time, positive and negative terminals 23 capable of providing positive and negative poles for the two semi-circular disk surfaces respectively, a floating neutral ground joint 24 capable of floatingly connecting the C-shaped groove to the power supply, and a non-contact cooling water cavity 25 formed at the bottom capable of cooling the circular chuck. The cooling water cavity is connected to the external cooling water.

[0062] The cooling gas enters the cooling air holes through the air pipes of the facility support disk, then reaches the gas grooves on the disk surface through the air inlet holes at the bottom of the electrostatic disk surface. Two sealing rings can also be provided around the cooling air holes to seal the gas in the ring formed by the cooling air holes, avoiding leakage to other positions of the electrostatic chuck or the reaction chamber.

[0063] The negative pressure generating device is a vacuum pump or a facility vacuum system.

[0064] A notch 26 is provided at the bottom of the circular chuck, which can allow a temperature sensor to penetrate and measure the temperature inside the chuck.

[0065] The height of the protrusion of the C-shaped boss 4, the height of the deposition ring 12, and the height of the protrusion of the small-area contact point 17 are the same.

[0066] By restricting the height of the small-area contact point, the small-area contact point protruding on the disk surface contacts the back surface of the wafer, playing a role in supporting the wafer and forming an adsorption force at the same time.

[0067] The height of the area contact point is very small (micrometer level). The chuck part outside the small-area contact point does not contact the back surface of the wafer, and there is a very small gap. The small gap forms a dielectric (air) capacitance, which will form the Johnsen-Rahbek effect and can also enhance the attraction.

Claims

1. An electrostatic chuck, characterized in that: It includes a circular chuck composed of two jointly cooperating semi-circular aluminum discs. An insulating layer is provided at the joint between the two semi-circular aluminum discs. A ceramic layer is provided on the aluminum disc surface. C-shaped bosses are respectively provided at the center positions of the two semi-circular discs. C-shaped grooves extending to the power supply are provided on the C-shaped bosses. Continuous titanium and titanium nitride coatings are provided on the upper surface and the groove wall of the C-shaped bosses, so that the static voltage on the upper surface of the C-shaped boss can be directly connected to the power supply as a neutral ground. On the ceramic layer of the circular chuck, a number of diversion ring grooves with different radii diffusing outward from the center are formed. On the ceramic layer, a number of diversion wire grooves facing the periphery of the semi-circular disc are provided starting from the innermost diversion ring groove. A number of uniformly distributed air outlet holes are provided on the circumferential surface of the semi-circular disc near the outermost periphery. A number of uniformly distributed air inlet holes are provided on the disc surface of the semi-circular disc near the C-shaped boss. Three first thimble holes with an included angle of 120° to each other are uniformly distributed between the air inlet holes and the air outlet holes of the circular chuck formed by the two semi-circular discs. A deposition ring with the same height as the C-shaped boss is provided outside the air outlet holes of the circular chuck; The air outlet holes are connected to a negative pressure generating device; At least one positioning groove is provided on the outer wall of the deposition ring. A positioning protrusion cooperating with the positioning groove is provided on the inner wall of the deposition ring installation support provided outside the deposition ring.

2. The electrostatic chuck according to claim 1, characterized in that: A number of titanium small-area contact points are provided on a number of ceramic surfaces formed by jointly surrounding the diversion ring grooves and the diversion wire grooves. The outer surface of the titanium small-area contact points is coated with a titanium nitride layer.

3. The electrostatic chuck according to claim 1, characterized in that: The insulating layer is a polystyrene cross-linked resin layer.

4. The electrostatic chuck according to claim 1, characterized in that: A thimble capable of moving up and down in the first thimble hole is provided in the first thimble hole.

5. The electrostatic chuck according to claim 1, characterized in that: The deposition ring installation support is arranged in the facility support plate. The facility support plate has a cavity capable of placing the deposition ring installation support. Cooling air holes capable of providing cooling gas to the air inlet holes are provided at the corresponding positions at the bottom of the cavity. An air outlet channel capable of connecting to the air outlet holes and providing a negative pressure environment. A second thimble hole capable of cooperating with the first thimble hole and providing a thimble displacement space. A temperature sensor capable of real-time detecting the temperature of the circular chuck surrounded by the deposition ring installation support. Positive and negative terminals capable of respectively providing positive and negative electrodes for the two semi-circular discs. A floating neutral ground joint capable of connecting the floating neutral ground of the C-shaped groove to the power supply. And a non-contact cooling water cavity formed at the bottom capable of cooling the circular chuck. The cooling water cavity is connected to the external cooling water.

6. The electrostatic chuck according to claim 1, characterized in that: The negative pressure generating device is a vacuum pump or a facility vacuum system.

7. The electrostatic chuck according to claim 5, characterized in that: A notch capable of allowing the temperature sensor to penetrate and measure the temperature inside the chuck is provided at the bottom of the circular chuck.

8. The electrostatic chuck according to claim 1 or 2, characterized in that: The height of the protrusion of the C-shaped boss, the height of the deposition ring, and the height of the protrusion of the small-area contact point are the same.

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