Plasma current monitoring device for semiconductor plasma etching cavity

Abstract

The invention provides a plasma current monitoring device for a semiconductor plasma etching cavity, and relates to the field of monitoring of a semiconductor plasma etching process. The plasma flow in the cavity can be measured in real time under the condition that the environment of the cavity is not interfered. The device is composed of a main body substrate, an upper surface sensing layer, a lower surface integration layer and an electromagnetic shielding film covering the surface of the substrate. The upper surface sensing layer comprises a non-contact magneto-impedance effect current sensor network which is arranged in an annular array; the lower surface integration layer comprises a master control acquisition microcontroller circuit, a power supply circuit, a thin film battery, a charging circuit, a real-time communication circuit and a storage module. The device adopts a structure, a size and an impedance design similar to those of an actual process wafer, can simulate a real state of the wafer in a plasma etching process, and acquires a magnetic signal of the substrate in real time in an etching process. The collected magnetic signals are processed and stored under the control of the microcontroller, and are transmitted to an external reading device through the real-time communication circuit. The method has wide applicability, can be compatible with various semiconductor process equipment, and provides a reliable technical means for real-time monitoring and optimization of the plasma etching process.

Description

Technical Field

[0001] The present invention relates to the field of monitoring of semiconductor plasma etching processes, and particularly to a plasma current monitoring device for a semiconductor plasma etching chamber, which can simulate the real state of a wafer in a plasma etching process and collect substrate magnetic signals in real time during the etching process. Background Art

[0002] After the progress of semiconductor manufacturing technology, plasma processes are widely used in the production of semiconductors, displays, and electronic devices. Plasma has anisotropic characteristics, which helps to form narrow and deep patterns. Plasma etching that can achieve anisotropic etching has become an irreplaceable technology for continuously reducing the device feature size. Since the 1970s, plasma etching has been widely used to etch high-resolution patterns and is still popular in the etching of today's 55nm to 10nm process nodes. In the etching process, the plasma spatial distribution directly determines the etching uniformity, and the ion flux and energy determine the etching rate and morphology quality. How to accurately measure and predict the key plasma parameters has become a key factor restricting the research and development of new equipment and the optimization of process conditions, which requires effective monitoring of the characteristics and distribution of electrons and ions in the plasma during the etching process, such as the uniformity of the plasma current. If the plasma is spatially non-uniform, defects will be generated on the wafer surface, resulting in different etching rates and deposition rates. Therefore, in order to control the spatial plasma uniformity, it is very important to detect the changes in plasma parameters. On the other hand, plasma damage caused by high-energy ion bombardment may cause substrate damage. This damage will reduce the reliability and life of the equipment. The traditional method for measuring plasma current parameters is mainly to insert a Langmuir probe into the conductive electrode in the plasma and provide a bias voltage for the probe through an external power supply to generate a potential value of the probe voltage relative to the plasma potential. The I-V characteristic curve formed by the probe bias voltage and the collected current can be used to calculate the plasma parameter information at the location of the probe. Its main advantages are simple and economical experimental equipment. The disadvantages are that it will cause certain interference to the measured plasma itself, reducing the accuracy of the experiment, and in semiconductor processes, it is necessary to modify the leads for a specific chamber to insert the Langmuir probe into the chamber for measurement, which often destroys the original process environment, introduces unpredictable contamination, and different processes and different chambers often cannot be adapted. At the same time, the processing and modification costs are relatively high, which also increases the cost of chamber modification. Summary of the Invention

[0003] Based on this, the present invention provides a plasma current monitoring device for a semiconductor plasma etching chamber, which has a structure, size, and impedance design similar to that of an actual process wafer, can simulate the real state of a wafer in a plasma etching process, and realizes non-invasive plasma current monitoring.

[0004] A plasma current monitoring device for a semiconductor plasma etching cavity of the present invention includes: a circular main substrate, a sensing layer disposed on the upper surface of the main substrate, an integrated layer disposed on the lower surface of the main substrate, an upper electromagnetic shielding film covering the upper surface of the sensing layer, and a lower electromagnetic shielding film covering the lower surface of the integrated layer; the sensing layer is an array of current sensors, distributed in a multi-layer annular manner on the upper surface of the main body with the center of the main substrate as the center; the integrated layer includes: a main control acquisition microcontroller circuit, a power supply circuit and a thin-film battery, a charging circuit, a real-time communication circuit, a storage module, and a transmission antenna; the integrated layer circuit modules are mounted on the substrate through surface mount technology via dispensing, mounting, curing, and soldering; the main control acquisition microcontroller circuit is the core of the entire integrated layer, controlling the acquisition mode, acquisition frequency of the current sensors, and the processing of the acquired data; the power supply circuit and the thin-film battery supply power to the main control acquisition microcontroller circuit, the real-time communication circuit, the storage module, and the current sensors, and the storage circuit is used to temporarily store the sensor data acquired; the real-time communication circuit is used to transmit the real-time data or the data stored in the storage circuit to a device outside the monitoring device through the transmission antenna; the transmission antenna is printed on the main substrate, and a curved streamline antenna is adopted and bent, which can effectively radiate the electrical signal and receive external signals; the various circuit modules of the integrated layer are connected by printed copper wires; an antenna clearance area is provided below the antenna to ensure that the metal object maintains a sufficient distance from the antenna body, and the antenna and the various circuit modules of the integrated layer are isolated by metal wires. By adjusting the size of the clearance area, the resonance frequency of the antenna is changed to optimize its performance and the grounding plane extension design.

[0005] Further, the material of the main substrate is one of FR-4, aluminum substrate, polyimide laminate, and ceramic substrate.

[0006] Further, the real-time communication circuit uses any single or combined technical solution of the following wireless transmission protocols: ZigBee protocol, IEEE 802.11 standard wireless local area network, low-power Bluetooth, and radio frequency identification system.

[0007] Further, the size of the current sensor is 3.50mm x 3.50mm, the thickness does not exceed 1mm, the thickness of each circuit element of the integrated layer does not exceed 800μm, and the thickness of the entire device after encapsulation does not exceed 2mm.

[0008] Further, the position of the upper electromagnetic shielding film corresponding to the current sensor is hollowed out, and the upper surface of the current sensor is coated with gold material.

[0009] Furthermore, the current sensor array is connected to the main substrate using a surface mount process, with an installation positioning accuracy of less than 0.05 mm. The current sensor transmits data to the integrated layer via an integrated circuit bus, and different current sensors are distinguished by different bus addresses.

[0010] Step 1: Make a groove at the installation location of the current sensor on the main substrate;

[0011] Step 2: The current sensor is glued to the slot with epoxy resin. The data line of the current sensor passes directly through the main substrate and connects to the microcontroller circuit on the other side of the main substrate.

[0012] Step 3: Perform vacuum reflow soldering on the main substrate with the current sensor attached;

[0013] Step 4: Apply conformal coating to the current sensor.

[0014] Step 5: Pass the aging test.

[0015] After adopting the above technical solution, the present invention has the following significant effects:

[0016] Compared with the existing Langmuir probe solution, the present invention realizes wireless data transmission without introducing wired circuits and is compatible with complex process environments including high-density plasma etching (ICP) and reactive ion etching (RIE).

[0017] The present invention uses a method of replacing wafers with special substrates, which can greatly reduce the difficulty of measuring actual wafer process parameters and has the characteristics of low cost, simple operation and strong scalability.

[0018] The sensor network part of the present invention adopts a bus design, driving multiple hardware devices through a small number of IO ports, greatly reducing the power consumption and circuit complexity of the processor, and having the ability to connect more sensors.

[0019] The device of the present invention is light and thin, with a total thickness of no more than 4 mm, and can be applied to most semiconductor chip manufacturing process environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is an overall schematic diagram of a plasma current monitoring device for a semiconductor plasma etching chamber according to the present invention.

[0021] Figure 2 It is a schematic diagram of the lower surface integration layer of the present invention.

[0022] Figure 3 Schematic diagram of the upper surface sensing layer of the present invention.

[0023] Figure 4This is the schematic diagram of the measurement working principle of the present invention.

[0024] Description of the reference numerals in the drawings: 1. Upper surface sensing layer; 2. Main body substrate; 3. Lower surface integrated layer; 4. Electromagnetic shielding film covered by the upper surface sensing layer; 5. Electromagnetic shielding film covered by the lower surface integrated layer; 6. Main control acquisition microcontroller circuit; 7. Power supply circuit; 8. Thin film battery; 9. Charging circuit; 10. Real-time communication circuit; 11. Storage module; 12. Signal transmission antenna; 13. Current sensor array network. Detailed implementation manners

[0025] The following will describe in detail the detailed implementation manners of the present invention with reference to the drawings.

[0026] The electronic modules on the main body substrate, the upper surface sensing layer, and the lower surface integrated layer include: a main control acquisition microcontroller circuit, a power supply circuit, a thin film battery, a charging circuit, a real-time communication circuit, a storage module, and a non-contact magneto-impedance effect current sensor network arranged in a circular array. The circuit modules distributed on the lower surface integrated layer charge the thin film battery through the charging circuit, and the power supply circuit supplies power to other circuit modules. During the operation of the device, the main control acquisition microcontroller circuit controls the sensor network to write the collected data into the storage module and send it to other reading devices through the real-time communication circuit for data storage and analysis.

[0027] The charging circuit provides voltage to the power supply circuit and the thin-film battery to make them reach the normal operating voltage of each circuit, and can be charged by one of wireless charging and wired charging; the power supply circuit and the thin-film battery are used to supply power to the main control acquisition microcontroller circuit, the real-time communication circuit, the storage module and all sensors to ensure the normal operation of the device. The main control acquisition microcontroller circuit realizes the setting of the acquisition time and acquisition frequency of the current sensor and the data processing of the acquired data, and can draw the plasma current density and distribution based on the measured current data, and can display the current density and distribution at each position in digital or image form. In addition, the main control acquisition microcontroller circuit can control the charging circuit, the real-time communication circuit, and the storage module to perform various functions. The storage module is used to store the acquired sensing data outside the chip, and the real-time communication circuit is used to transmit the real-time data or the data stored in the storage module to other reading devices, and can also receive the instructions conveyed by other reading devices to set the acquisition command. The upper surface sensing layer is provided with a non-contact magneto-impedance effect current sensor network arranged in a ring array, and the number and position of the sensors are optimized according to the measurement requirements. The surface of the sensor is subjected to an immersion gold process to prevent corrosion and enhance conductivity; the sensor is calibrated to ensure the accuracy of the measurement results. The main body substrate plate is made of polyimide laminate, which has high thermal stability, low dielectric loss, high mechanical strength, and optimized layout and wiring to achieve the effects of heat dissipation and power consumption reduction. The real-time communication circuit uses low-power Bluetooth (BLE) and is equipped with an on-board radio frequency antenna to realize communication with external reading devices. The current sensor has a size of 3.50 mm x 3.50 mm and a thickness of no more than 1 mm, and the thickness of each module on the upper surface of the main body substrate does not exceed 800 μm. The electromagnetic shielding film covering the substrate surface is hollowed out at the position where the sensors on the upper surface sensing layer are located to avoid damage to the substrate surface caused by high-energy plasma bombardment, and at the same time expose the sensors to collect data more stably and accurately.

[0028] In the electronic module, the selected current sensor has a small size and thickness, with a size not exceeding 3.50 mm x 3.50 mm and a thickness not exceeding 1 mm, so as to reduce the direct contact area with the plasma; the main control acquisition microcontroller circuit, the power supply circuit, the thin-film battery, the charging circuit, the real-time communication circuit, and the storage module can have relatively large sizes and thicknesses, and devices with high temperature resistance and electromagnetic interference resistance are selected. At the same time, the layout and wiring are optimized and heat insulation design is carried out to ensure the robustness and stable operation of the device.

[0029] To avoid strong electromagnetic interference in the plasma chamber, the surface of the main substrate is covered with an electromagnetic shielding film, which protects the data transmission between circuits without affecting real-time communication. At the same time, the electromagnetic shielding film covering the upper surface sensing layer has a hollowed-out position where the sensor is located, ensuring that the current generated by the plasma on the substrate surface is accurately collected, while also protecting other components. The power supply circuit of the system can use either wireless or wired charging methods, but it will not be charged during actual operation, so no additional leads will be introduced into the chamber, thus keeping the interior of the chamber clean.

[0030] The main substrate can be selected from FR-4, aluminum substrate, polyimide laminate, and ceramic substrate, with the same size, shape, and thickness as the actual processed wafer. The main substrate has good electrical insulation performance and mechanical strength, and at the same time has excellent heat resistance and flexibility, can accurately simulate the process on the wafer surface, measure the plasma current, and is suitable for on-line non-invasive plasma diagnosis of processes such as semiconductor etching and PVD coating.

[0031] As Figure 1 As shown in the overall structural schematic diagram of the present invention, a plasma current monitoring device 1 for a semiconductor plasma etching chamber of the present invention includes an upper surface sensing layer 2, a main substrate 3, a lower surface integrated layer 4, an electromagnetic shielding film covering the upper surface sensing layer 5, and an electromagnetic shielding film covering the lower surface integrated layer 5. Specifically, the size of the main substrate can meet the sizes of different wafers, such as two-inch, four-inch, six-inch, eight-inch, and twelve-inch. The devices and functions of the lower surface integrated layer can change the size layout for protection and heat insulation. The device packaging can select QFP, that is, small square flat package, PLCC, that is, plastic package J-lead chip package, BGA, that is, ball grid array package, and comprehensively consider chip devices with smaller volume, better heat dissipation performance, and electrical performance. The upper surface sensing layer and the lower surface integrated layer can be directly designed as a complete path or separately designed, and electrical interconnection is achieved through welding. Preferably, they are more densely distributed at the center and edge of the main substrate to achieve uniform measurement of physical quantities on the wafer surface, but the number of sensor networks can also be 8, 16, or more, which is determined by the actual physical quantity measurement position, measurement density, and measurement accuracy requirements.

[0032] Figure 2It is a schematic diagram of the principle of the lower surface integrated layer 3 of the present invention. The electronic modules distributed on the process monitoring module include: a main control acquisition microcontroller circuit 6, a power supply circuit 7, a thin-film battery 8, a charging circuit 9, a real-time communication circuit 10, a storage module 11, and a signal transmission antenna 12. The lower surface integrated layer communicates with other external reading devices through the real-time communication circuit to achieve real-time data transmission and processing. At the same time, the thin-film battery is charged through the charging circuit, without the support of an external power supply and data cable, ensuring the mobility and independence of the system. The structural layout of the lower surface integrated layer of the intermediate layer can interconnect the circuits completely, and isolate the plasma and heat in the process environment by covering an electromagnetic shielding film. The main control acquisition microcontroller circuit, the power supply circuit, the thin-film battery, the charging circuit, the real-time communication circuit, and the storage module comprehensively control the acquisition work of the upper surface sensing layer. The current data on the main body substrate is measured by a total of 19 sensors placed at different positions. When the sensors are working, the collected data is stored in the storage module. After receiving the control instructions from other reading devices, the 19-channel data is sequentially sent to the upper computer at the PC end for temperature field restoration. The signals collected by the sensors are transmitted through the bus and sent to the main control acquisition microcontroller circuit, avoiding the problems of high power consumption and high resource occupancy caused by connecting each sensor to the IO port of the processor chip.

[0033] As Figure 3 Shown is the current sensor array network 13 of the upper surface sensing layer 1 of the present invention, which includes a non-contact magneto-impedance effect current sensor network arranged in a circular array. These sensing units are electrically connected to other electronic modules through metal wires on the main body substrate 2, thereby realizing the acquisition, processing, storage, and transmission of physical quantity signals in the process environment. The non-contact magneto-impedance effect current sensor uses a magneto-impedance element with high sensitivity and low consumption current, realizing non-contact detection (without wiring in the current sensor), and at the same time achieving an extremely small size of 3.5mm * 3.5mm and an ultra-low consumption current of 0.07mA during operation. In addition, it also has a function of eliminating interference magnetic fields with anti-noise, and can be installed on the main body substrate without shielding measures. Moreover, the built-in A / D converter uses digital output, which can reduce the burden on the microcontroller, and can more easily monitor the current, and perform current detection for various applications with high reliability and ease. In addition, the sensor network arranged on the upper surface sensing layer 1 includes, but is not limited to, a gaussmeter, a Hall sensor, a magnetoresistive sensor, a magneto-impedance sensor, etc.

[0034] As Figure 4The following is the working principle diagram of the present invention. The charging circuit provides voltage to the thin-film battery to make it reach the normal discharge voltage of the lithium battery, which is 3.8V - 4.2V. The voltage of the thin-film battery is converted into the 3.3V voltage for the normal operation of the main control acquisition microcontroller circuit, communication circuit, storage module and all sensors through the voltage conversion of the power supply circuit, ensuring the normal operation of the device. The main control acquisition microcontroller circuit can control the charging circuit, real-time communication circuit and storage module to execute various functions. The storage module is used to store the sensed data collected outside the chip, and the real-time communication circuit is used to transmit the real-time data or the data stored in the storage module to other reading devices, and can also receive the instructions conveyed by other reading devices to set the acquisition command.

Claims

1. A plasma current monitoring device for a semiconductor plasma etching chamber, the device comprising: a circular main substrate, a sensing layer disposed on the upper surface of the main substrate, an integrated layer disposed on the lower surface of the main substrate, an upper electromagnetic shielding film covering the upper surface of the sensing layer, and a lower electromagnetic shielding film covering the lower surface of the integrated layer; the sensing layer is an array of current sensors, and is distributed on the upper surface of the main body in a multi-layer annular manner with the center of the main substrate as the center; the integrated layer includes: Main control acquisition microcontroller circuit, power supply circuit and thin film battery, charging circuit, real-time communication circuit, storage module, transmission antenna; The integrated layer circuit module is glued, mounted, cured, and welded on the substrate using surface mount technology. The main control acquisition microcontroller circuit is the core of the entire integrated layer, controlling the current sensor's acquisition mode, acquisition frequency, and processing of the acquired data. The power supply circuit and the thin film battery provide power for the main control acquisition microcontroller circuit, the real-time communication circuit, the storage module, and the current sensor. The storage circuit is used to temporarily store the collected sensor data. The real-time communication circuit is used to transmit real-time data or data stored in the storage circuit to equipment outside the monitoring device through the transmission antenna; the transmission antenna is printed on the main substrate, adopts a meander line antenna and is bent, which can effectively radiate electrical signals and receive external signals; the various circuit modules of the integrated layer are connected by printed copper wires; an antenna clearance area is set under the antenna to ensure that metal objects maintain a sufficient distance from the antenna body, and the antenna and the various circuit modules of the integrated layer are separated by metal wires. By adjusting the size of the clearance area, the resonant frequency of the antenna is changed, and its performance ground plane extension design is optimized.

2. The plasma current monitoring device for a semiconductor plasma etching chamber according to claim 1, characterized in that, The main substrate plate is one of FR-4, aluminum substrate, polyimide laminate, and ceramic substrate.

3. The plasma current monitoring device for a semiconductor plasma etching chamber according to claim 1, characterized in that, The real-time communication circuit uses any single or combined technical solution of the following wireless transmission protocols: ZigBee protocol, IEEE 802.11 standard wireless local area network, low-power Bluetooth, and radio frequency identification system.

4. The plasma current monitoring device for a semiconductor plasma etching chamber according to claim 1, characterized in that The current sensor has a size of 3.50mm x 3.50mm and a thickness of no more than 1mm. The thickness of each circuit element in the integrated layer does not exceed 800μm. After packaging, the thickness of the entire device does not exceed 2mm.

5. The plasma current monitoring device for a semiconductor plasma etching chamber according to claim 1, characterized in that, The position of the upper electromagnetic shielding film corresponding to the current sensor is hollowed out, and the upper surface of the current sensor is plated with gold material.

6. The plasma current monitoring device for a semiconductor plasma etching chamber according to claim 1, wherein The current sensor array is connected to the main substrate using a surface mount process, with an installation positioning accuracy of less than 0.05 mm. The current sensor transmits data to the integrated layer via an integrated circuit bus, and different current sensors are distinguished by different bus addresses. Step 1: Make a groove at the installation location of the current sensor on the main substrate; Step 2: The current sensor is glued to the slot with epoxy resin. The data line of the current sensor passes directly through the main substrate and connects to the microcontroller circuit on the other side of the main substrate. Step 3: Perform vacuum reflow soldering on the main substrate with the current sensor attached; Step 4: Apply conformal coating to the current sensor. Step 5: Pass the aging test.

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