TWI727610B - Electrostatic chuck and its plasma processing device - Google Patents

Abstract

The invention discloses an electrostatic chuck and a plasma processing device where the electrostatic chuck is located. The electrostatic chuck of the invention includes a base and an electrostatic interlayer arranged above the base, and a plurality of lifting thimble assemblies are arranged through the electrostatic chuck, The assembly includes a lifting thimble, a thimble clamping piece and a lifting thimble channel. The thimble clamping piece is arranged at the end of the lifting thimble channel away from the substrate, and is used to drive the lifting thimble to move up and down in the channel and in the process of moving up and down. Always under the base. In order to reduce the arc discharge phenomenon inside the channel containing the lifting pin that may be caused by high power, the present invention arranges the ejector pin holder outside the channel of the lifting pin, so that only the lifting pin is contained in the channel of the lifting pin, further reducing Lift the size of the thimble channel to maximize the working temperature adaptability of the electrostatic chuck without causing ignition.

Description

Electrostatic chuck and its plasma processing device

The present invention relates to the technical field of plasma etching, and particularly relates to the technical field of plasma processing that prevents arcs from being generated in an electrostatic chuck under high radio frequency power.

The micromachining of semiconductor substrates or substrates is a well-known technique that can be used to manufacture, for example, semiconductors, flat panel displays, light emitting diodes (LEDs), solar cells, etc. An important step of micro-processing manufacturing is the plasma treatment process step. The process step is performed inside a reaction chamber, and the process gas is input into the reaction chamber. The radio frequency source is inductively and/or capacitively coupled to the inside of the reaction chamber to excite the process gas to form and maintain plasma. Inside the reaction chamber, the exposed substrate is supported by the electrostatic chuck ESC and fixed in a fixed position by a certain clamping force to ensure the safety of the substrate during the process and the high yield rate of processing.

In order to meet the requirements of the manufacturing process, it is not only necessary to strictly control the operation process, but also involves the loading and de-clamping of the semiconductor substrate. The loading and de-clamping of semiconductor substrates is a key step in the processing of semiconductor substrates. By setting up a number of lifting thimble components inside the electrostatic chuck, when the process is completed, the supporting force of the lifting thimble is used to realize the substrate and electrostatic clamping When the disc is separated and pushed up, the manipulator located outside the reaction chamber penetrates between the substrate and the electrostatic chuck to realize the unloading of the substrate.

In the process of processing the substrate, the electrostatic chuck is not only used to support and fix the substrate, but also to control the temperature of the substrate. As the processing accuracy of the substrate becomes higher and higher, the temperature of the electrostatic chuck is uniform Sexual control requirements are getting higher and higher. With the development of 3D storage technology, the etching process requires higher Wafer temperature and higher RF power. High temperature and high power can easily cause arcing inside the lifting thimble assembly. Serious arcing can induce arc damage and even cause permanent damage to the electrostatic chuck.

Therefore, there is an urgent need to provide a lifting thimble assembly to meet the requirements of the continuously increasing temperature and radio frequency power in the reaction chamber and the uniformity of substrate processing.

In order to solve the above technical problems, the present invention provides an electrostatic chuck, which includes a base and an electrostatic interlayer disposed above the base. The electrostatic chuck is used to support and fix the substrate during the manufacturing process and is arranged through the electrostatic chuck. Plural lifting thimble assembly, the assembly includes a lifting thimble, a thimble clamping member and a lifting thimble channel. The thimble clamping member is arranged at the end of the lifting thimble channel away from the substrate, and is used to drive the lifting thimble in the lifting thimble channel Move up and down, and always stay under the base during the up and down movement.

Further, the lifting thimble assembly includes a thimble protective sleeve, and the thimble protective sleeve is arranged on the inner wall of the lifting thimble channel.

Further, during the up and down movement of the lifting thimble, the distance between the side wall of the lifting thimble and the thimble protective cover is greater than or equal to 0.01 mm.

Further, the working temperature difference of the electrostatic chuck is greater than 20°C.

Further, the working temperature difference of the electrostatic chuck is greater than 50°C.

Further, the electrostatic chuck includes a center, and the distance between the lifting thimble assembly and the center is less than or equal to a first distance, and the first distance is inversely proportional to the thermal expansion coefficient of the electrostatic chuck and the working temperature difference of the electrostatic chuck.

Further, the distance from the lifted thimble assembly to the center of the electrostatic chuck is less than or equal to 50 mm.

Further, the distance from the lifted thimble assembly to the center of the electrostatic chuck is less than or equal to 30 mm.

Further, the lifting thimble channel includes a channel corresponding to the electrostatic interlayer and a channel corresponding to the base, and the thimble protective sleeve is arranged on the inner wall of the channel corresponding to the base.

Further, the opening size of the channel corresponding to the electrostatic interlayer is larger than the inner diameter of the thimble protective sleeve and smaller than the outer diameter of the thimble protective sleeve.

Further, an insulating ring is provided on the outer side of one end of the thimble protective sleeve close to the electrostatic interlayer.

Further, the present invention also discloses a plasma processing device, which includes a reaction chamber, and an electrostatic chuck is arranged in the reaction chamber.

100: reaction chamber

110: Lifting thimble assembly

112: Thimble protective sleeve

114: thimble clamp

115: lift thimble

116: Lifting thimble channel

120: Gas injection device

130: Electrostatic chuck

132: Electrostatic interlayer

134: Pedestal

140: Cooling gas channel

150: substrate

155: Outer Wall

160: RF power source

170: Vacuum pump

212: Thimble protective sleeve

213: Insulating ring

214: thimble clamp

215: Lifting thimble

216,217: Lifting thimble channel

232: electrostatic interlayer

233: Adhesive Layer

234: Pedestal

250: substrate

A1, A2, A3, A4, B1, B2, B3, B4, C1, C2, C3, C4: lift the thimble position

O: Center

△Z: The size of the thimble protection sleeve when the electrostatic chuck is heated and expanded

In order to more clearly describe the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the drawings in the following description are merely These are some embodiments of the present invention. For those with ordinary knowledge in the field, other embodiments can be obtained based on these drawings without creative work.

Figure 1 shows a schematic structural diagram of a plasma processing device; Figures 2 and 3 show a schematic structural diagram of an electrostatic chuck; Figure 4 shows a schematic structural diagram of an electrostatic chuck after thermal displacement; Figure 5 It shows a schematic top view of the lifting thimble assembly at different positions on the electrostatic chuck; FIG. 6 shows a schematic structural diagram of another embodiment of the electrostatic chuck.

In order to make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments These are a part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work shall fall within the protection scope of the present invention.

FIG. 1 shows a plasma processing device, which includes a reaction chamber 100 surrounded by an outer wall 155 that can be evacuated. The reaction chamber 100 is used for processing substrates. An electrostatic chuck (ESC) 130 is provided at the bottom of the reaction chamber for supporting and fixing the substrate 150. A gas injection device 120 injects the reaction gas into the reaction chamber 100, and the reaction gas is dissociated into plasma under the excitation of the radio frequency power source 160 and maintained, thereby realizing the plasma processing of the substrate. The vacuum pump 170 can vacuum the reaction chamber to ensure that the plasma processes the substrate in a vacuum environment.

In the process of processing the substrate, the bombardment of the plasma on the substrate will cause the substrate to heat up and the temperature will rise. In order to ensure the uniformity of the temperature in different areas of the substrate and the stability of the process, it is necessary to set up on the electrostatic chuck The design of uniform cooling of the substrate temperature is currently a conventional method in the industry to deliver a cooling gas, such as helium gas, to the back of the substrate, and uniform diffusion of the cooling gas on the back of the substrate is used to achieve a uniform cooling of the substrate. The cooling gas is mainly transported through the cooling gas channel 140 provided in the electrostatic chuck. After reaching the back of the substrate, the cooling gas diffuses between the substrate and the electrostatic interlayer to achieve uniform cooling of the substrate. In addition, the cooling gas is also transported by lifting the ejector pin assembly 110.

Figures 2 and 3 show schematic diagrams of the structure of the electrostatic chuck of the present invention, and describe the structure of the lifting pin assembly 110 in detail. The lift thimble assembly 110 includes a lift thimble 115 and a lift thimble channel 116. The end of the lift thimble channel 116 away from the substrate is provided with a thimble clamping member 114. The thimble clamping member 114 is used to clamp the lift thimble 115 and The driving device drives the lifting thimble to move up and down. The inner wall of the lifting thimble channel 116 is provided with a thimble protective sleeve 112 for realizing effective isolation between the lifting thimble 115 and the base 134. As shown in Figure 3, the function of the lift pin is to use the lift of the lift pin to separate the substrate 150 from the electrostatic chuck 130 after the substrate manufacturing process is completed, and to push the substrate 150 to a certain height Then, the robot arm outside the reaction chamber takes over the substrate to realize the unloading of the substrate from the reaction chamber.

With the continuous development of the integrated circuit industry, the accuracy requirements for semiconductor substrate processing are getting higher and higher. In order to improve the processing accuracy, the power of the radio frequency power source applied to the reaction cavity is continuously increasing. In order to ensure the cooling effect on the substrate, the lifting thimble channel must convey a certain pressure of cooling gas, and with the application As the RF power added to the reaction chamber increases, the risk that the cooling gas in the lifting thimble channel is ignited into plasma will increase, and the phenomenon that the cooling gas is ignited into plasma becomes an arc discharge phenomenon. The arc discharge of the cooling gas in the lifting thimble channel will damage the components in the reaction chamber and cause a series of dangerous consequences, so it must be absolutely avoided.

The lifting thimble needs to have a certain degree of mechanical strength and stability in order to realize the lifting of the substrate. Therefore, the lifting thimble should not be too thin, and a certain gap must be ensured between the thimble protective sleeve 112, which leads to the lifting thimble channel 116 size cannot be too small. Studies have found that the arc discharge phenomenon of the cooling gas is related to the size of the container where the cooling gas is located and the gas pressure in the container. The larger the container size or the greater the gas pressure in the container, the more likely the gas to arc discharge. In order to avoid the occurrence of arc discharge, the size of the lifting pin channel 116 should be controlled as much as possible.

In the schematic diagram of the electrostatic chuck structure disclosed in FIG. 2, the ejector pin holder 114 is arranged at the end of the lifting ejector channel 116 away from the substrate, and is located below the base 134. When the ejector pin 115 is driven to move up and down, the ejector pin 114 The clamping member 114 is always located outside the lifting thimble channel 116 and moves below the lower surface of the base. In the present invention, the thimble clamping member is arranged outside the lift thimble channel 116, so that only the lift thimble 115 needs to be accommodated in the lift thimble channel 116, which can further reduce the opening size of the lift thimble channel 116. However, since the temperature of the electrostatic chuck changes greatly during the working process, as the temperature of the electrostatic chuck changes, the thermal expansion of the base will cause the lifting pin channel 116 to move outward in the radial direction, and the lifting pin itself As part of the electrostatic chuck thermal contact is still in a low temperature state, the position of the thimble remains unchanged. This will cause the phenomenon shown in Figure 4 to occur. The distance between the thimble protection sleeve on the edge of the electrostatic chuck in the lift pin channel 116 and the lift pin is greater than the lift protection on the side close to the center of the electrostatic chuck. The distance between the sleeve and the lifting thimble. The increase in the distance between the thimble protection sleeve on the side of the edge of the electrostatic chuck and the lifting thimble will greatly reduce the pressure application range of the cooling gas. In addition, when the temperature difference of the electrostatic chuck exceeds a certain value, the outer lateral displacement of the thimble protective sleeve is too large, and the fitting extrusion with the lifting thimble will occur, making the lifting thimble unable to move up and down smoothly, causing the parts to malfunction.

In order to solve the above problems, the present invention designs to move the lifting thimble assembly to the center of the electrostatic chuck. In this embodiment, the material of the base 134 is aluminum, and the coefficient of thermal expansion is -23.6*10-6/°C, and the material of the electrostatic interlayer 132 is ceramic, and the coefficient of thermal expansion is -7.9*10-6/°C. In this embodiment, the diameter of the thimble is 2.2 millimeters (mm), and the outer diameter of the thimble is 2.0 millimeters (mm). Figure 5 shows a schematic diagram of gradually moving the lifting thimble assembly to the center O of the electrostatic chuck. Table 1 shows that when the lifting thimble assembly is in the different positions shown in Figure 5, the lifting thimble channel 116 is at different temperatures △Z is the size of the thimble protection sleeve deviating outward when the electrostatic chuck is heated and expanded. “Dimensions on both sides of the channel” means that the thimble protection sleeve is moved outwards and the thimble channel 116 is lifted close to the electrostatic chuck The distance between the thimble protection sleeve on the edge side and the lifting thimble and the distance between the lifting protection sleeve on the side close to the center of the electrostatic chuck and the lifting thimble.

It can be seen from Table 1 that when the temperature of the electrostatic chuck is at a normal temperature of 20°C, no matter where the lifted thimble is located on the electrostatic chuck, the thimble protective sleeve will not deviate outward. However, when the temperature is 80℃, the lifting thimble cannot be used due to the excessively large offset size of the thimble protective sleeve at 90mm and 70mm from the center of the electrostatic chuck (A1, B1, C1) (A2, B2, C2). occur. According to the data in Table 1 It can be seen from the law that the closer the lift pin assembly is to the center of the electrostatic chuck, the smaller the effect of thermal expansion on the offset of the lift pin channel 116 is, and the better the lift pin assembly can adapt to higher temperature electrostatic chuck working conditions.

The inventor found that △Z is proportional to the thermal expansion coefficient of the electrostatic chuck, the distance from the thimble channel to the center of the electrostatic chuck, and the working temperature difference of the electrostatic chuck. When the thermal expansion coefficient of the electrostatic chuck is constant, in order to adapt to the ever-increasing temperature of the electrostatic chuck, it is necessary to reduce the distance from the thimble channel to the center of the electrostatic chuck. In actual work, when the distance between the lifting thimble and the thimble protective sleeve is less than 0.01mm, the lifting thimble will face the danger of being squeezed and not working properly, so the distance between the lifting thimble and the thimble protective sleeve needs to be greater than Equal to 0.01mm.

When designing the distance from the lift pin assembly to the center of the electrostatic chuck, consider the maximum temperature that the electrostatic chuck may require. For the electrostatic chuck that needs to cope with higher operating temperatures, the lift pin assembly needs to be set away from the center of the electrostatic chuck. Closer location.

According to the formula for calculating the channel offset △Z, △Z=β*Z*(TT ₀ )

0.01 Among them, β is the thermal expansion coefficient of the electrostatic chuck, Z is the distance from the lift pin assembly to the center of the electrostatic chuck, T is the working temperature _{of the electrostatic chuck, and T 0} is the normal temperature of the electrostatic chuck. When the working temperature of the electrostatic chuck is higher than the normal temperature, the electrostatic chuck has a tendency to expand outward, and the lift pin channel is inclined outward at this time; when the working temperature of the electrostatic chuck is lower than the normal temperature, the electrostatic chuck has The trend of shrinking inward, at this time the lifting thimble channel tilts inward. When determining the value of Z, first determine the size b of the lifting thimble and the size a of the channel that accommodates the lifting thimble. In order to meet the requirement that the distance between the lifting thimble and the thimble protective sleeve is greater than or equal to 0.01mm, |½(ab)-△ Z|

0.01

Then determine the value of Z according to _{the value of TT 0.}

The electrostatic chuck disclosed in the present invention is particularly suitable for use in a plasma processing device that needs to work at a higher temperature and apply a higher power. In order to reduce the high power that may be caused by accommodating the lifting pin in the channel In the present invention, the ejector pin holder is arranged outside the lift pin channel 116, so that only the lift pin is contained in the lift pin channel, which further reduces the size of the lift pin channel. At the same time, in order to meet the requirement of large working temperature difference of the electrostatic chuck, the present invention moves the plural lifting thimble assembly to the center of the electrostatic chuck as a whole to reduce the distance between the lifting thimble channel and the center of the electrostatic chuck, so as to prevent ignition. Under the premise of improving the working temperature adaptability of the electrostatic chuck as much as possible.

Figure 6 shows a schematic diagram of another embodiment of the electrostatic chuck. In this embodiment, the lift thimble assembly includes a lift thimble 215 and lift thimble channels 216 and 217, wherein the base 234 corresponds to the lift thimble channel 216, and the electrostatic interlayer 232 corresponds to the lift thimble channel 217. An end of the lifting thimble channel 216 away from the substrate is provided with a thimble clamping member 214. The thimble clamping member 214 is used to clamp the lift thimble 215 and drive the lift thimble to move up and down under the driving of the driving device. The inner wall of the lifting thimble channel 216 is provided with a thimble protective sleeve 212 for realizing effective isolation between the lifting thimble 215 and the base 234. Since the electrostatic interlayer is an insulating material, there is no need to provide a thimble protective sleeve inside the lifting thimble channel 217. Since there is plasma for cleaning in the reaction chamber 100 after the substrate is removed, in order to prevent the plasma from contacting the metal in the base, in this embodiment, an insulating ring is provided on the outside of the end of the thimble protective sleeve 212 near the electrostatic interlayer 232 213. The opening of the lifting thimble channel 216 is smaller than the opening of the thimble protective sleeve 212, so that the electrostatic interlayer 232 partially covers the upper end surface of the thimble protective sleeve 212 to prevent the cleaning plasma from contacting the metal in the base. An adhesive layer 233 is also provided between the electrostatic interlayer 232 and the base 234.

The embodiment shown in Figure 6 has the lifting thimble channel arranged in two parts, wherein the thimble protective sleeve 212 is provided on the side wall of the lifting thimble channel corresponding to the base 234, and the side wall of the lifting thimble channel corresponding to the electrostatic interlayer is not provided The thimble protective sleeve avoids the difference in thermal expansion coefficient due to the different materials of the base and the electrostatic interlayer. When the temperature of the electrostatic chuck increases, the horizontal stress on the thimble protective cover corresponding to the base and the electrostatic interlayer is different, which may Induced damage to the thimble shield.

Although the content of the present invention has been described in detail through the above preferred embodiments, it should be understood that the above description should not be regarded as limiting the present invention. Those with general knowledge in the field After reading the above content, various modifications and alternatives to the present invention will be obvious. Therefore, the scope of protection of the present invention should be limited by the scope of the attached patent application.

A1, A2, A3, A4, B1, B2, B3, B4, C1, C2, C3, C4: lift the thimble position

O: Center

Claims (11)

An electrostatic chuck includes a base and an electrostatic interlayer disposed above the base. The electrostatic chuck is used to support and fix a substrate during the manufacturing process, wherein: a plurality of lifts are arranged through the electrostatic chuck Lifting thimble assembly, the lifting thimble assembly includes a lifting thimble, a thimble clamping member and a lifting thimble channel, the thimble clamping member is arranged at the end of the lifting thimble channel away from the substrate, for driving the The lifting thimble moves up and down in the lifting thimble channel, and is always located under the base during the up and down movement; wherein: the electrostatic chuck includes a center, and the distance between the lifting thimble assembly and the center is less than or equal to A first distance, the first distance is inversely proportional to the thermal expansion coefficient of the electrostatic chuck and the working temperature difference of the electrostatic chuck. The electrostatic chuck according to claim 1, wherein: the lifting thimble assembly includes a thimble protective sleeve, and the thimble protective sleeve is arranged on the inner wall of the lifting thimble channel. The electrostatic chuck according to claim 2, wherein: during the up and down movement of the lifting thimble, the distance between the side wall of the lifting thimble and the thimble protective cover is greater than or equal to 0.01 mm. The electrostatic chuck according to claim 1, wherein: the working temperature difference of the electrostatic chuck is greater than 20°C. The electrostatic chuck according to claim 1, wherein: the operating temperature difference of the electrostatic chuck is greater than 50°C. The electrostatic chuck according to claim 5, wherein: the distance from the lift pin assembly to the center of the electrostatic chuck is less than or equal to 50 mm. The electrostatic chuck according to claim 5, wherein: the distance from the lift pin assembly to the center of the electrostatic chuck is less than or equal to 30 mm. The electrostatic chuck according to claim 2, wherein the lifting thimble channel includes a channel corresponding to the electrostatic interlayer and a channel corresponding to the base, and the thimble protective sleeve is disposed on the inner wall of the channel corresponding to the base. The electrostatic chuck according to claim 8, wherein: the opening size of the channel corresponding to the electrostatic interlayer is larger than the inner diameter of the thimble protective sleeve and smaller than the outer diameter of the thimble protective sleeve. The electrostatic chuck according to claim 8, wherein: an insulating ring is provided on the outer side of one end of the thimble protective sleeve close to the electrostatic interlayer. A plasma processing device, which includes a reaction chamber, and the electrostatic chuck according to any one of claims 1-10 is arranged in the reaction chamber.

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