CN102354084A - Flow field pressure transducer of immersion lithography machine based on PVDF (polyvinylidene fluoride) - Google Patents

Abstract

The invention discloses a PVDF-based flow field pressure sensor for an immersion photolithography machine. It includes a PVDF pressure sensing element with a shielding film, and a signal processing device composed of a voltage amplifying circuit, a charge amplifying circuit and a filter circuit. The charge signal generated by the PVDF pressure sensing element with shielding film is connected to the input terminal of the voltage amplifier through the output terminal of the charge amplifier, and the output terminal of the voltage amplifier is connected to the input terminal of the filter circuit. BNC interface connection for PVDF pressure sensing element. The PVDF pressure sensing element containing the shielding film of the invention has the characteristics of high sensitivity, low impedance, good flexibility, etc., is convenient and simple to install, and has little interference to the flow field. The signal processing device adjusts the charge signal output by the PVDF pressure sensing element into a -5~5V voltage signal that can be collected, and effectively suppresses zero drift and noise interference.

Description

Flow field pressure sensor of immersion lithography machine based on PVDF

technical field

The invention relates to a flow field pressure sensor in an immersion lithography (Immersion Lithography) system, in particular to a flow field pressure sensor based on PVDF (polyvinylidene fluoride) for an immersion lithography machine.

Background technique

Modern dry lithography machines use the optical system to accurately project and expose the pattern on the mask on the silicon wafer coated with photoresist, while immersion lithography uses the optical system between the lens group and the silicon wafer on the dry lithography system. A layer of immersion liquid that meets the requirements of optical characteristics is filled in the gap between them, and the refractive index of light waves in this layer of space is increased to increase the numerical aperture of the projection objective lens and the focal depth of the system, thereby achieving the purpose of obtaining a smaller line width.

Immersion lithography technology improves the resolution and depth of focus of the exposure system, making it possible to etch lines with a feature size of 65 to 22nm. , the height change of the flow field caused by the adjustment of the vertical position of the silicon wafer, and the generation and collapse of bubbles in the immersion flow field. It affects the exposure accuracy of the system. Therefore, it is of great significance to study the dynamic pressure of the immersion flow field to optimize the structure and working parameters of the immersion system.

At present, the commonly used pressure detection method in the micro-slit flow field is the small-hole pressure introduction method or the micro-diffusion silicon piezoresistive sensor. The small hole pressure introduction method refers to opening a small hole in the measurement area and connecting it to the pressure sensor through a section of conduit. The function of the conduit is to transmit the pressure. The length of the conduit depends on the installation requirements. It is often used for pressure distribution on curved surfaces or in narrow areas. Measurement. The diffused silicon piezoresistive pressure sensor is made by doping boron impurities into the silicon wafer to form a pressure-sensitive bridge using the diffusion process of the integrated circuit. Its measurement principle is based on the piezoresistive effect of the semiconductor strain gauge.

These pressure measurement methods have their own shortcomings.

1) For small hole pressure introduction method:

a) It is difficult to exhaust the air bubbles in the pressure induction tube. When the air bubbles are compressed, the measured value will be much larger than the actual value;

b) The pressure fluctuation of the submerged flow field is small, and the error caused by the damping effect of the impulse tube cannot be ignored;

c) Since the placement of ordinary pressure sensors still requires a large space, the density of measurement points will be limited.

2) For diffused silicon piezoresistive sensors

a) The manufacturing process of the diffused silicon piezoresistive sensor is complex and expensive (10,000 RMB/piece). When there are many measurement points, the cost of the sensor is high;

b) Although diffused silicon piezoresistive sensors are easy to miniaturize, the two indicators of sensor volume and sensitivity still restrict each other: when the sensitivity is high and the range is small, the sensor volume is still large and it is difficult to meet the installation requirements; and when the sensor volume is small , and its measuring range is much larger than the pressure fluctuation range of the submerged flow field. Therefore, it is difficult to find a diffused silicon piezoresistive sensor that meets the requirements in volume and range.

Contents of the invention

The purpose of the present invention is to provide a PVDF-based flow field pressure sensor for an immersion lithography machine, which is used to detect the dynamic pressure distribution of the flow field of an immersion lithography machine.

In order to achieve the above object, the technology adopted in the present invention is as follows:

The present invention is a flow field pressure sensor attached to the lower surface of a projection lens model and immersed in a liquid film; the flow field pressure sensor includes a PVDF pressure sensing element containing a shielding film and a signal processing device; wherein:

1) PVDF pressure sensing element with shielding film:

The two sides of one end of the PVDF film of the PVDF pressure sensing element have symmetrically distributed pressure measurement areas. The two pressure measurement areas are respectively equipped with an aluminum electrode arranged in the same direction, and the two aluminum electrodes are opposite to each other along the center line of the respective pressure measurement area. , Symmetrical distribution; the aluminum electrode on one side is in contact with one end of the wire core of the low-noise shielded wire and fixedly connected with the first rivet, and then the entire PVDF pressure sensing element is covered with an insulating layer, and the aluminum electrode on the other side scrapes off part of the insulating layer , in contact with one end of the shielding layer of the low-noise shielding wire and fixedly connected with the second rivet, the entire PVDF pressure sensing element, insulating layer, first rivet and second rivet are completely covered with the aluminum shielding film and connected with the low-noise shielding The shielding layer of the wire is fixedly connected with the third rivet; the other end composed of the wire core and the shielding layer is connected to the BNC interface;

2) Signal processing device: including voltage amplifying circuit, charge amplifying circuit and filter circuit; the voltage amplifying circuit is built with low power consumption and high-precision amplifier AD627; the charge amplifying circuit includes a low-noise high-speed FET input amplifier The DC feedback network built by AD745 and high-speed BiFET operational amplifier AD711; the filter circuit is built by the eighth-order elliptic filter MAX293; the charge signal is connected to the input terminal of the voltage amplifier through the output terminal of the charge amplifier, and the output terminal of the voltage amplifier is connected to the input terminal of the filter circuit. The input end of the charge amplification circuit has a matching BNC interface and is connected to the BNC interface of the PVDF pressure sensing element with shielding film. The 9V battery voltage is converted into +5V and -5V through the micropower low dropout voltage regulator LT1121 and the reverse charge pump MAX1697 DC voltage provides power to the above circuits.

The beneficial effects that the present invention has are;

1) PVDF film has the characteristics of low density and high sensitivity (more than 10 times higher than piezoelectric ceramics),

And the impedance is low, as a sensor, it can more effectively transmit tiny signals to the signal detection device. Compared with piezoelectric ceramics, PVDF film also has high elastic flexibility and can be directly pasted on the surface of objects without affecting its mechanical movement. The thickness of the PVDF pressure sensing element used in the present invention is only about 200 μm, and it can be pasted on the lower surface of the projection lens model with ordinary adhesive, which is convenient and simple to install, takes up little space, and has little interference to the flow field.

2) A low-noise high-speed FET input amplifier circuit AD745 is selected to build a charge amplifier circuit. Its high input impedance can effectively improve the signal-to-noise ratio of PVDF pressure sensing elements. The relationship between the output voltage and the input charge is,

　　　　　　　　(a)

(a)

为电路输出端电压，

为PVDF压力传感元件产生的电荷，为跨接在放大器输入端与输入端之间的反馈电容。以高速BiFET运算放大器AD711为核心的直流反馈电路能有效地降低零漂和噪声干扰，电荷放大电路输出零漂信号为

，经放大电路后输出的零漂信号为

，满足精度要求，引入直流反馈网络后，信号处理电路的零漂会在大概30s内归零，归零后信号稳定，不再发生漂移。将系统简化及等效处理后可知，传感器的低频的幅值误差和截止频率只取决于反馈电路的

和等效的。其中，

还决定了前置放大器输出电压的大小。

is the output voltage of the circuit,

The charge generated for the PVDF pressure sensing element, is the feedback capacitor connected across the input terminal of the amplifier. The DC feedback circuit with the high-speed BiFET operational amplifier AD711 as the core can effectively reduce zero drift and noise interference, and the output zero drift signal of the charge amplifier circuit is

, the zero-drift signal output by the amplifying circuit is

, to meet the accuracy requirements, after introducing the DC feedback network, the zero drift of the signal processing circuit will return to zero within about 30s, and the signal will be stable after zeroing, and no drift will occur. After simplification and equivalent treatment of the system, it can be seen that the low-frequency amplitude error and cut-off frequency of the sensor only depend on the feedback circuit

and the equivalent . in,

It also determines the size of the output voltage of the preamplifier.

3) A low-power, high-precision instrument amplifier AD627 is selected to build a voltage amplification circuit. The amplification factor is determined by the measurement point area of the PVDF pressure sensor, the actual detected pressure range, and the voltage range of the signal acquisition system. If the magnification is too small, the measurement accuracy will decrease; if the magnification is too large, the noise and zero drift will also be amplified. Satisfy the following relationship,

　　　　　　　　(b)

(b)

When the magnification is 105, the output sensitivity of the sensor is 1.32mv/Pa. If MSP430 is used for data acquisition, the acquisition voltage range is 0-2.5V, and the range of the sensor is about -1KPa-1KPa, which is in good agreement with the actual pressure fluctuation range. .

4) The signal shielding process is effectively carried out to ensure that the acquisition and output signals are not distorted to the greatest extent. First of all, the shielding film of PVDF pressure sensor is a method to isolate electromagnetic interference from the source; secondly, because the actual measured pressure signal is a low-frequency signal, a simple RC low-pass filter is connected before each amplifier stage, and the effective attenuation has entered the sensor High-frequency interference; Finally, the last stage of the signal processing circuit is designed as a low-pass filter with steep attenuation characteristics to minimize the interference in the output signal.

Description of drawings

Fig. 1 is a schematic diagram of the assembly of the present invention and a projection lens model.

Fig. 2 is a top view of the PVDF pressure sensing element of the present invention.

Fig. 3 is a front view of the PVDF pressure sensing element of the present invention.

4 is a cross-sectional view P-P of a top view of a PVDF pressure sensing element of the present invention.

Fig. 5 is a schematic diagram of a PVDF pressure sensing element containing a shielding film of the present invention.

Fig. 6 is a voltage amplifying circuit diagram of the present invention.

Fig. 7 is a circuit diagram of the charge amplifier of the present invention.

Fig. 8 is a filter circuit diagram of the present invention.

In the figure: 1. Projection lens model, 2. Flow field pressure detection sensor, 3. Liquid film, A. PVDF pressure sensing element with shielding film, B. Signal processing device, A01, PVDF film, A02, aluminum electrode, A03, aluminum electrode, A0, PVDF pressure sensing element, A1, wire core, A2, insulating layer, A3, shielding layer, A4, shielding film, A5, first rivet, A6, second rivet, A7, third rivet .

Detailed ways

The specific implementation process of the present invention will be described in detail below in conjunction with the accompanying drawings and examples.

As shown in Figure 1, the present invention is a flow field pressure sensor 2 attached to the lower surface of the projection lens model 1 and immersed in the liquid film 3; the flow field pressure sensor 2 includes a PVDF pressure sensing element containing a shielding film A and signal processing device B; the present invention can be applied in lithographic equipment such as step-and-repeat or step-and-scan, when in use, the projection lens model 1 does not move, and the PVDF pressure sensing element A containing the shielding film accepts the liquid film 3 The pressure fluctuations are excited to generate a pressure signal, which is output to the signal processing device B, and finally output to a monitoring device such as an oscilloscope.

As shown in Fig. 2, Fig. 3, Fig. 4, Fig. 5, have represented the PVDF pressure sensing element A that contains shielding membrane of the embodiment of the present invention, utilize photoetching electrode method to make required electrode pattern on a piece of PVDF thin film; Both sides of one end of PVDF film A01 have symmetrically distributed pressure measurement areas. The two pressure measurement areas have an aluminum electrode A02 and A03 arranged in the same direction respectively, and the two aluminum electrodes A02 and A03 are along the centerline of the respective pressure measurement area. On the contrary, it is distributed symmetrically; the aluminum electrode A02 on one side is in contact with one end of the wire core A1 of the low-noise shielding wire and fixedly connected with the first rivet A5, and then the entire PVDF pressure sensing element A0 is covered with an insulating layer A2, and the aluminum electrode on the other side is Electrode A03 scrapes off part of the insulating layer, contacts one end of the shielding layer A3 of the low-noise shielding wire and fixes it with the second rivet A6, and uses the aluminum shielding film A4 to connect the entire PVDF pressure sensing element A0, insulating layer A2, and the first rivet A5 and the second rivet A6 are completely covered and fixedly connected with the shielding layer A3 of the low-noise shielding wire with the third rivet A7; the other end composed of the wire core A1 and the shielding layer A3 is connected to the BNC interface. the

As shown in Fig. 6, Fig. 7, Fig. 8, represented the signal processing device B of the embodiment of the present invention to comprise voltage amplifying circuit, electric charge amplifying circuit and filter circuit; Voltage amplifying circuit is the amplifier AD627 that low power consumption, high-precision instrument Built; the charge amplification circuit includes a low-noise high-speed FET input amplifier AD745 and a DC feedback network built by a high-speed BiFET operational amplifier AD711; the filter circuit is built with an eighth-order elliptic filter MAX293; the charge signal is output through the charge amplifier The terminal is connected to the input terminal of the voltage amplifier, the output terminal of the voltage amplifier is connected to the input terminal of the filter circuit, the input terminal of the charge amplification circuit has a matching BNC interface and is connected to the BNC interface of the PVDF pressure sensing element A with a shielding film, and the 9V battery voltage passes through the micropower low voltage The differential voltage regulator LT1121 and the inverting charge pump MAX1697 convert +5V and -5V DC voltages to provide power for the above circuits.

Choose AD745 to build the charge amplifier circuit, choose AD711 to build the DC feedback network, connect the input terminal and output terminal of the amplifier circuit, the output voltage is linearly proportional to the input charge signal.

The AD627 is used to build a voltage amplification circuit. The gain adjustment range is 5 to 1000 times. If the amplification factor is too large, the noise and zero drift will increase. If the amplification factor is too small, the sensitivity will be seriously affected. The selected amplification factor is 105 times through experiments.

MAX293 was chosen to build a low-pass filter circuit to filter out high-frequency noise signals.

The 9V battery voltage is converted into +5V and -5V DC voltages through the micro-power low-dropout voltage regulator LT1121 and the reverse charge pump MAX1697, and provided to each circuit.

Connect the low-noise shielded wire drawn from the PVDF pressure sensing element A with shielding film to the input interface of signal processing device B, connect the low-noise shielded wire of the detection device such as an oscilloscope to the output port of signal processing device B, and switch the control signal The processing device is powered on and off, and the device is powered by a 9V battery (under normal circumstances, it can be used continuously for 4 days).

The shielding film A03 of the PVDF pressure sensing element A with the shielding film shares the ground with the aluminum box of the signal processing device B and the detection instrument.

(1) PVDF pressure sensing element A0 uses the photolithography electrode method to etch the required electrode pattern. The photolithography technology uses the method of photocopying to accurately copy the pattern on the mask on the metal coated with photoresist. On the evaporation layer, and then use the protective effect of the photoresist to selectively chemically etch the metal layer to obtain a pattern corresponding to the mask on the metal layer. In the present invention, after the steps of cleaning-fixing-film-spinning-pre-baking-exposure-development-post-baking-etching-removing photoresist, the desired single-point or multi-point PVDF pressure sensing element can be obtained A0.

(2) The core components of the signal processing device B include a charge amplifier circuit, a voltage amplifier circuit and a filter circuit. The composition relationship is to convert the 9V battery voltage into +5V and - 5V DC voltage is provided to each circuit. The PVDF pressure sensing element A containing the shielding film is excited by dynamic pressure to generate a charge signal and then input to the charge amplifier circuit. The output alternating voltage signal is amplified by the voltage amplifier and further input to the filter Filtering is performed in the circuit, and finally a voltage signal with an amplitude of -3 to +3V is output by the filter circuit. The signal on the PVDF pressure sensing element A containing the shielding film is introduced into the input BNC interface on the signal processing device B, which is connected to the input end of the charge amplification circuit; the final output voltage signal of the filter circuit is passed through the signal processing device B The output on the BNC interface is output to each monitoring instrument, and the on-off switch controls the work of the signal processing device B.

Claims (1)

1. A PVDF-based immersion photolithography flow field pressure sensor, characterized in that it is a flow field pressure sensor (2) attached to the lower surface of the projection lens model (1) and immersed in the liquid film (3) ); the flow field pressure sensor (2) includes a PVDF pressure sensing element (A) containing a shielding film and a signal processing device (B); wherein: 1) PVDF pressure sensing element with shielding film (A): The PVDF film (A01) of the PVDF pressure sensing element (A0) has symmetrically distributed pressure measurement areas on both sides of one end. The two pressure measurement areas are respectively equipped with an aluminum electrode (A02, A03) arranged in the same direction, and two aluminum electrodes. The electrodes (A02, A03) are opposite and symmetrically distributed along the center line of the respective pressure measurement area; the aluminum electrode (A02) on one side is in contact with one end of the conductor core (A1) of the low-noise shielding line and fixed with the first rivet (A5) Connect, and then cover the entire PVDF pressure sensing element (A0) with an insulating layer (A2), scrape off part of the insulating layer with the aluminum electrode (A03) on the other side, contact with one end of the shielding layer (A3) of the low-noise shielding wire and use The second rivet (A6) is fixedly connected, and the entire PVDF pressure sensing element (A0), insulating layer (A2), first rivet (A5) and second rivet (A6) are completely covered with an aluminum shielding film (A4) And connect with the shielding layer (A3) of the low-noise shielding wire with the third rivet (A7); the other end composed of the wire core (A1) and the shielding layer (A3) is connected to the BNC interface; 2) Signal processing device (B): including a voltage amplifier circuit, a charge amplifier circuit and a filter circuit; the voltage amplifier circuit is built with a low-power, high-precision instrument amplifier AD627; the charge amplifier circuit includes a low-noise high-speed field effect transistor The DC feedback network built by the input amplifier AD745 and the high-speed BiFET operational amplifier AD711; the filter circuit is built by the eighth-order elliptic filter MAX293; the charge signal is connected to the input terminal of the voltage amplifier through the output terminal of the charge amplifier, and the output terminal of the voltage amplifier is connected to the filter circuit Input terminal, the input terminal of the charge amplification circuit has a matching BNC interface and is connected to the BNC interface of the PVDF pressure sensing element (A) with shielding film, and the 9V battery voltage is transformed by the micropower low dropout voltage regulator LT1121 and the reverse charge pump MAX1697 Provide power to the above circuits for +5V and -5V DC voltage.

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