Optical Sensor System

Abstract

The present invention relates to a thin optical sensor for measuring distance, comprising a light emitter and a light detector. More specifically, the optical sensor includes a focusing film with a series of blinds to filter diffusely reflected light without the need for a focusing lens. The optical sensor can be used in a variety of applications, including measuring the thickness of an object using two sensors or determining the angle between two surfaces using three sensors. The present invention also relates to a calibration sensor and a calibration method for leveling a showerhead and chuck in a semiconductor deposition tool using three or more optical sensors.

Description

[Technical field]

[0001] The following relates generally to optical sensors and systems for measuring distances between two points, and more particularly to low profile optical sensors and the use of multiple sensors to level two plates. Additionally, the following relates to the use of multiple sensors to calibrate semiconductor deposition equipment. [Background technology]

[0002] Optical sensors, particularly laser optical sensors, exist in the art. This type of sensor works by emitting a beam of light from a laser, which passes through a focusing lens before reaching a target point. The light is diffusely reflected back through a second focusing lens, which focuses the reflected light to a spot on a photodetector. The position of the light on the photodetector is then processed and used to determine the distance between the laser and the target point. This method of optically measuring distance is useful in many applications, but the sensor, particularly the focusing lens, requires an adequate amount of space to function effectively.

[0003] Without a focusing lens, the diffused light hits a wider area of ​​the photodetector, which often cannot provide an accurate position reading. Thus, optical sensors, especially laser optical sensors, have proven ineffective for applications in tight spaces that require a thin sensor.

[0004] In semiconductor deposition equipment, for example, a fairly accurate alignment between the chuck and the showerhead is required to obtain a uniform film across the wafer. Typically, because the spacing between the chuck and the showerhead is limited, a low-profile wafer capacitive gap sensor has been used. A series of three capacitive gap sensors are used to measure the gap between the chuck, on which the sensors sit during calibration, and the showerhead. The relative position of the chuck and showerhead is adjusted until all three sensors measure the same gap, and the chuck and showerhead are thus parallel to each other.

[0005] Capacitance is an electrical property of two conductive plates, e.g., a sensor and a showerhead, separated by an insulator, in this case air or vacuum, between them. It is proportional to the area of ​​the plates and the dielectric constant of the insulator separating them, and inversely proportional to the gap separating the plates, as shown by the following equation:

[0006]

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[0007] Capacitive gap sensors are limited in that their accuracy depends on the conductivity of the target material. Such sensors do not allow for a high level of reference distance between the sensor and the target, limiting them to a small range of applications. They can be highly sensitive to unwanted tilt, spacing, electrical noise, as well as temperature, humidity and overall noise. Each sensor is fairly large, typically 12-60 mm in diameter, limiting their use to small applications. There remains a need for an accurate and reliable thin sensor for measuring distances or leveling plates. Summary of the Invention

[0008] A low-profile optical sensor is provided that includes a light emitter and a light detector to measure distance. More specifically, the optical sensor includes a focusing film that has a series of blinds to filter diffuse reflected light without the need for a focusing lens. The optical sensor can be used in a variety of applications, including measuring the thickness of an object using two sensors or determining the angle between two surfaces using three or more sensors. The following further describes a calibration sensor and a calibration method using three or more optical sensors to level a showerhead and chuck in a semiconductor deposition apparatus.

[0009] This description is given by way of example only with reference to the accompanying drawings, in which: [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram of a light sensor and the light pattern emanating therefrom. [Figure 2A] FIG. 2A is a schematic diagram showing the optical path of the optical sensor when the target point is at its maximum distance. [Figure 2B] FIG. 2B is a schematic diagram showing the optical path of the optical sensor when the target point is at a minimum distance. [Diagram 3] FIG. 3 shows the reflected light path and the photodetector. [Figure 4A] FIG. 4A is a side view of a first embodiment of the focus film. [Figure 4B] FIG. 4B is a side view of a second embodiment of the focus film. [Diagram 5] FIG. 5 is a schematic diagram of two optical sensors used to determine the thickness of an object. [Figure 6] FIG. 6 is a schematic diagram of three optical sensors used to determine whether the two plates are level. [Figure 7] FIG. 7 is a schematic diagram illustrating the use of a calibration sensor in a semiconductor deposition tool. [Figure 8] FIG. 8 is a top view of the calibration sensor. [Figure 9] FIG. 9 is a partially exploded perspective view of the calibration sensor. [Figure 10] FIG. 10 is a flow chart illustrating the interaction of the components of the calibration sensor during use. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] FIG. 1 shows an optical sensor 2 having a light emitter 4, preferably a laser, and a light detector 6, preferably a charge-coupled device (CCD). These elements are preferably contained in a housing (not shown). In use, the light emitter emits a light beam 8 towards a target point 10 on a surface 12. The emitted light beam 8 reaches the target point 10 and is reflected / scattered from the surface 12 to the detector 6 as reflected / scattered light 14. The reflected / scattered light 14 strikes the photodetector 6. The angle at which the light is reflected / scattered from the surface 12 is determined by the distance of the target point from the photodetector 6. The reflected / scattered light 14 strikes the photodetector 6 and the location at which it strikes the photodetector is used to determine the distance from the photodetector 6 to the target point 10. For example, if the target point 10 is far away (e.g., at a certain maximum range), as depicted in FIG. 2A, the reflected light 14 will strike the end of the photodetector 6 that is furthest from the light emitter 4. Alternatively, as shown in Figure 2B, if the target point 10 is at its closest location (e.g., at a certain minimum range), the reflected light 14 will land on the opposite end of the photodetector 6 closest to the laser emitter 4. The range of distances that any particular sensor can measure is determined in part by the size of the photodetector, as well as the characteristics of the target surface and the emitter. The received light 14 is processed and analyzed by a signal processor 16 to determine the distance to the target point 10 based on principles of optical triangulation known to those skilled in the art.

[0012] As shown in Figures 1 and 3, the reflected light 14 reflects diffusely from the target point 10. Unless it is first filtered or focused in some way, the reflected light will strike a large area of ​​the photodetector 6, resulting in an inaccurate measurement of the distance to the target point 10. To address this, a focusing film 18 is placed between the reflecting surface 12 and the photodetector 6. The focusing film 18 is preferably placed adjacent to the light receiving surface 20 of the photodetector 6. In an alternative embodiment, the focusing film is spaced from the photodetector 6, but configured so as not to interfere with the light emitter. As shown in Figure 4A, the focusing film 18 includes a plurality of blinds 22 that extend outwardly from a transparent base surface 24 to create a plurality of windows 26 between each adjacent pair of blinds. The blinds preferably extend generally perpendicular to the surface of the photodetector 6 for increased accuracy and reduced light loss. A transparent top surface 28 is included in the preferred embodiment to maintain the position of the blinds. Optionally, as shown in Figure 4B, focus film 18b eliminates the top surface and has blinds 22 protrude outward from base 24. Preferably, blinds 22 are evenly spaced apart, although depending on the application, the spacing between blinds can be customized.

[0013] Referring again to FIG. 3, when the reflected light 14 is diffusely reflected from the target point 10, it passes through the focusing film 18 before striking the photodetector 6. The focusing film 18 acts to block some of the diffuse reflected light 14 from striking the photodetector 6, thereby reducing the area over which the photodetector 6 operates and increasing the accuracy of the measurement. In many applications, there is no focusing film or focusing lens, and the sensor is illuminated equally along its length and cannot be determined in the measurement. For illustrative purposes, the diffuse reflected light 14 is shown in FIG. 3 as a series of dashed lines 14a-14i, each of which represents a portion of the diffuse light. Portions of light 14d, 14e, 14f, and 14g that are located within the diffusion pattern strike the focusing film 18 at angles that allow the light to pass through windows 26a, 26b, 26c, and 26d, respectively. This portion of light strikes the photodetector 6, and its position is used to determine the distance of the target point 10. However, the portion of the light outside the diffusion pattern, including 14a, 14b, 14c, 14h, and 14i, is transmitted through the focusing film 18 at an angle where the light strikes the blinds 22a, 22b, 22c, 22d, and 22e, respectively. This prevents this portion of the reflected light 14 from contacting the photodetector 6. Because only a portion of the diffuse reflected light 14 is transmitted through the focusing film 18, the area of ​​the photodetector activated by the light is reduced. The overall effect of the focusing film is that the reflected light 14 is filtered, reducing the area of ​​light on the photodetector and eliminating the need for a focusing lens.

[0014] By itself, the optical sensor of the present invention can be used to measure the distance or presence of an object. By adjusting various features such as the robustness of the housing, the size of the photodetector, the spacing and size of the blinds in the focusing film or the characteristics of the light emitter, the optical sensor can be adapted for use in a wide variety of applications and environments, from small spaces to outdoors or in industrial applications. Common applications include, but are not limited to, quality control, error prevention and positioning applications.

[0015] With a height of at least 8 mm, the lensless design is particularly advantageous for applications in tight spaces. Moreover, the optical sensor is robust and can be used under a wide variety of conditions, including temperatures ranging from 20° C. to 65° C., a wide range of humidities, and pressures, including vacuum.

[0016] Optical sensors can also be used in pairs: as shown in Figure 5, sensors 27 and 29 can be placed on opposite sides of an object 30 to determine the distance from respective sensors 32 and 34 to the object 30. This information can then be used to determine the thickness t of the object 30.

[0017] Three optical sensors can be used in combination to determine if the two plates are horizontal or parallel. As shown in FIG. 6, three optical sensors 34, 36 and 38 are configured on a first plate 40 and positioned to emit light to various target points 42, 44 and 46, respectively, on a second plate 48. The first optical sensor determines the distance d1 to the first target point 42, the second optical sensor determines the distance d2 to the second target point 44, and the third optical sensor determines the distance d3 to the third target point 46. When d1, d2 and d3 are all equal, the plates are horizontal and aligned parallel to each other. All three sensors are preferably fixed to a common base 50 for ease of use and to maintain their relative positions. Using the three known distances, the angle of one plate relative to the other can also be calculated. Thus, this type of sensor can be used to calibrate or set the two plates at any relative angle. It should be appreciated that a minimum of three sensors is required to determine the angle between the two plates, but more sensors can be used.

[0018] In a preferred embodiment, the sensors 60 include a communication transmitter, preferably wireless or Bluetooth, to transmit measurements in real time. In a further embodiment, a high precision accelerometer is included in one or more of the sensors to measure the inclination of the sensor relative to the ground. The sensors can also be configured to operate remotely.

[0019] This design is particularly useful in calibration procedures for semiconductor deposition equipment. FIG. 7 shows a simplified semiconductor deposition equipment 52 with a showerhead 54 and a chuck 56 disposed within a lower housing 58. For simplicity, the chamber surrounding the chuck and showerhead, as well as other components found in this type of equipment, are omitted. To produce a wafer product with a uniform thickness, it is important that the showerhead 54 and the chuck 56 are level. Therefore, before producing the product, the semiconductor deposition equipment is calibrated. A calibration sensor 60, which includes at least three optical sensors, is disposed on the chuck and operates to determine at least three distances between the chuck and the showerhead. The chuck and / or showerhead are then adjusted until all three measured distances are equal. By allowing the calibration sensor to be remotely operated, there is no time limit in aligning the chuck with respect to the showerhead.

[0020] FIG. 8 shows a preferred design of a wafer-like calibration sensor 62 incorporating three optical sensors 64, 66 and 68 disposed and fixed on a base 70. Although a variety of materials can be used to fabricate the base, preferred embodiments for use in semiconductor potential base materials include, but are not limited to, Meldin®, Celazole®, Torlon®, PEEK®, Vespel®, anodized aluminum and ceramic, fused quartz, silicon or sapphire. The base is preferably rigid to prevent relative movement between the sensors. The rigidity of the base ensures that the distance from the base to the light emitter remains constant, since the distance is typically measured from the sensor location to the target point. The base is preferably designed such that the properties of the base change significantly (e.g., expand or contract) under various temperature or pressure conditions. Each optical sensor has a light emitter 72, 74 and 76 disposed next to a light detector 78, 80 and 82, respectively. As can be seen in FIG. 9, which shows a close-up of the light sensor 66, the light detector 80 has a focus film 84 attached to its top, which is consistent with each sensor. A top cover 86 is provided to protect the working components of the calibration sensor 62. A first set of slots 88 are provided to allow the respective light emitters 72, 74 and 76 to emit light, and a second set of slots 90 are provided in the top cover 86 to expose the light detectors 78, 80 and 82. The top cover may be monolithically formed or comprised of multiple covers, each protecting a particular aspect of the calibration sensor. The top cover may be removably secured to the base in any manner known to those skilled in the art. In the preferred embodiment shown in the figures, screws are used.

[0021] In the preferred embodiment shown, the calibration sensor is circular with light sensors 64, 66 and 68 located near the edge of the base and evenly spaced around the periphery. By spacing the sensors as far apart as the base will allow, the measured distance between the three target points is maximized. This results in a more accurate level than if the three points were closer together.

[0022] The center of the base can be used to house other operating components, such as a transmitter, preferably wireless or Bluetooth, to transmit measurements to an external transceiver. With this design, the measurements can be used as input to calibration software that can automatically adjust the position of the chuck and / or showerhead in response to real-time measurements. Additionally, the center of the base can be utilized to house a power supply 92 to power the three optical sensors. The power supply is preferably a battery, although other power supplies may be known to those skilled in the art, allowing for an entirely wireless calibration sensor. Since the preferred embodiment includes the ability to operate the sensor wirelessly, one advantage of the design is that the sensor can be used remotely without releasing the vacuum within the semiconductor housing.

[0023] The flow chart in Figure 10 shows the overall interaction of the components of the calibration system. First, at 100, the calibration sensor is activated by a magnetic switch. The voltage from the battery is regulated by a switching regulator 102. Next, a microcontroller unit (MCU) is powered on and a software algorithm 104 is started. The data from the CCD photodetectors is processed 106 and the final distance value calculated from each photodetector is sent to the PC 108 by the MCU sending a wireless signal 110 on a wireless channel which is received by the PC. One advantage of the magnetic switch is that a robot can activate the sensor by moving it to the side of the magnet, so no human intervention is required.

[0024] In use, the calibration system is activated using a magnetic switch and control options are built into the corresponding software. The calibration sensor is placed inside an enclosed semiconductor deposition chamber with no personnel access during calibration. A light emitter enables real-time transmission of three distance measurements. The corresponding software compares the distances and determines optimal adjustments to the chuck and / or showerhead position.

[0025] Although a wide range of powers has been found to be acceptable and is known to those skilled in the art, the preferred embodiment includes a laser emitter emitting a maximum power of 0.67 mW at 100 mm, which is considered safe for the unprotected human eye. Other light sources are known to those skilled in the art, including but not limited to LED or incandescent sources. The shape or wavelength of the beam may also vary from ultraviolet to infrared. However, the preferred embodiment of the calibration sensor further includes an emitter having an operating wavelength of 850 nm. Although other photodetectors are operable and known, a linear CCD sensor with a pixel size of <10 μm is preferred. The smaller the pixel size, the greater the measurement accuracy, and in the preferred embodiment, a CCD photodetector with a pixel size of 8 μm is used. For this preferred configuration, the target point is located 120 mm ± 5 mm from the center of the sensor with a measurement range of 15 mm ± 5 mm.

[0026] The scope of the claims should not be limited to the preferred embodiments set forth in the examples, but should be accorded the broadest interpretation consistent with the entire description.

Claims

1. a plurality of light emitters configured on the first plate, each of the light emitters emitting a light beam toward a corresponding target point on the second plate; a plurality of photodetectors configured on the first plate, each photodetector including a plurality of pixels, the plurality of photodetectors configured to receive diffusely reflected light from the corresponding target points; a plurality of blinds disposed over at least a portion of each of the plurality of light detectors; A signal processor; Equipped with The plurality of blinds include: (i) forming a plurality of windows, each disposed over a portion of the plurality of pixels; (ii) limiting the diffusely reflected light detected by each portion of the plurality of pixels to diffusely reflected light normal or substantially normal to the first plate. It is configured as follows: the signal processor is configured to process the diffusely reflected light received by the plurality of light detectors to determine a distance from each of the plurality of light emitters to the corresponding target point on the second plate. Optical sensor system.

2. The optical sensor system of claim 1 , wherein the plurality of blinds comprises two or more blinds.

3. The optical sensor system of claim 2 , wherein the plurality of blinds comprises a string of blinds.

4. The optical sensor system of claim 3 , wherein said plurality of blinds are disposed generally perpendicular to each of said plurality of optical detectors.

5. The optical sensor system of claim 4 , wherein said plurality of blinds are disposed adjacent to each of said plurality of optical detectors.

6. The optical sensor system of claim 1 further comprising a communication transmitter for communicating information to a receiving device.

7. The optical sensor system of claim 6 , wherein the communication transmitter is wireless.

8. 8. The optical sensor system of claim 7, wherein the communication transmitter functions using Bluetooth technology.

9. The optical sensor system of claim 1 further comprising means for remotely activating the optical detector.

10. The optical sensor system of claim 1 further comprising a high precision accelerometer.

11. The optical sensor system of claim 1 , further comprising a housing device configured to maintain relative positions of each of the plurality of light emitters, each of the plurality of light detectors, and each of the plurality of blinds.

12. The optical sensor system of claim 6 , wherein the communication transmitter transmits information in real time.

13. The optical sensor system of claim 1 , wherein each of said plurality of photodetectors is a charge-coupled device.

14. said optical sensor system being circular; each of the plurality of light detectors is disposed near an edge of the light sensor system and is equally spaced around a periphery of the light sensor system; The optical sensor system of claim 1 .

15. the signal processor is configured to perform processing to determine whether the first plate and the second plate are parallel based on a distance between each of the plurality of light emitters and the corresponding target point. The optical sensor system of claim 1 .

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