WO2023178719A1

WO2023178719A1 - Optical measuring apparatus and method

Info

Publication number: WO2023178719A1
Application number: PCT/CN2022/084020
Authority: WO
Inventors: 兰艳平; 孙刚
Original assignee: 上海御微半导体技术有限公司
Priority date: 2022-03-22
Filing date: 2022-03-30
Publication date: 2023-09-28
Also published as: CN116819892A

Abstract

An optical measuring apparatus and method. The optical measuring apparatus comprises an object table (05) used to carry an object to be measured (4); an illumination system (01) used to emit a detection light beam, the illumination system (01) comprising an imaging light source (103) and an imaging light path, and the imaging light source (103) being a pulse light source; a focusing system (02), which is used record, by means of the optical assembly, the detection light beam to the object to be measured (4) and a reference focal plane (7), respectively, and converge to the spectrum detector (10) by means of an optical assembly; an imaging system (03), which is used to acquire an imaging light beam reflected from the detection light beam by the object to be measured (4); a data processing system (04), used to acquire information of an interference light beam from the spectrum detector (10), perform focal plane measurement on the object to be measured (4) according to the information of the interference light beam, acquire image information formed by the imaging light beam from the imaging system (03), and perform overlay measurement of the object to be measured (4) according to the image information. The optical measuring apparatus and method may improve detection accuracy and detection efficiency.

Description

An optical measurement device and method

cross reference

This application claims priority from the Chinese patent application with application number 2022102845740 filed on March 22, 2022. The contents of the above application are incorporated herein by reference.

Technical field

The present invention relates to the field of optical detection technology, and in particular, to an optical measurement device and method.

technical background

With the rapid development of the semiconductor industry in recent years, the requirements for the entire production yield have become higher and higher. This requires more accurate detection and measurement equipment to be applied to the semiconductor manufacturing process, rather than just being limited to the final product. product testing. Overlay accuracy is one of the core indicators in the photolithography process, which directly affects the final product yield. At present, overlay measurement equipment has been widely used to measure the overlay accuracy, and the measurement results are used as compensation values to compensate for the overlay process, which can greatly improve product yields.

However, as photolithography process nodes continue to advance, the number of photolithography process layers is also increasing, so the number of layers that need to be measured will also increase, and the process will become more complex. Therefore, higher requirements are put forward for the productivity and process adaptability of measuring equipment.

On existing equipment, the most critical factors currently limiting the overall measurement efficiency include camera integration time and system vibration requirements. Due to the continuous light devices currently used, and due to the movement of some mechanical shutters, the sampling time is long and the structure is slow to stabilize. And due to the use of continuous light sources, the stability requirements for the structure will be higher, which seriously restricts the increase in productivity.

Based on the above background, how to improve and optimize detection efficiency while continuously improving detection accuracy has become a technical problem currently faced.

Summary of the invention

The object of the present invention is to provide an optical measurement device and method to improve detection accuracy and detection efficiency.

In a first aspect, the present invention provides an optical measurement device, including a stage for carrying an object to be measured, an illumination system for emitting a detection beam, and a focusing system for recording the passage of the detection beam through the optical component. The split light is respectively injected into the object to be measured and the reference focal plane, and is converged to the spectrum detector through the optical assembly. The spectrum detector is used to record the information of the interference beam formed after the detection beam is reflected by the object to be measured and the reference focal plane. The device also includes The imaging system is used to collect the imaging beam formed after the detection beam is reflected by the object to be measured. The imaging system includes the optical path of the microscope objective lens and the optical path of the camera; the focusing system and the imaging system share the optical path of the microscope objective lens. The device also includes a data processing system for obtaining the information of the interference beam from the spectrum detector, performing focal plane measurement of the object to be measured based on the information of the interference beam, and obtaining the image information formed by the imaging beam from the imaging system, and based on the image information Carry out overlay measurements on the object to be tested.

The beneficial effect of the optical measurement device provided by the present invention is that the sampling pulse light source of this embodiment replaces the traditional continuous light source, which can greatly reduce the sampling time, reduce the impact of platform vibration, and improve measurement accuracy and productivity.

Optionally, the lighting system also includes an infrared light source and an infrared illumination light path. In this embodiment, the measurement of infrared light is achieved by adding an infrared light source and an infrared illumination light path, which is suitable for the measurement of silicon wafers with poor visible light transmittance of some film layers, thereby improving process adaptability.

Optionally, the pulse light source is a xenon flash lamp or a pulse laser light source, and the pulse width of the pulse light source ranges from 1 us to 30 us.

Optionally, the reference surface optical path includes a photoelectric shutter device, an imaging objective lens and a reference surface, and the reference surface is the best focal plane of a known objective lens; the focal surface measurement optical path includes an analyzer and an imaging tube lens; The optical measurement device also includes a controller, the controller is connected to the focusing system, and the controller is used to control the photoelectric shutter device to be in an open state when performing focal plane measurement; when performing overlay measurement , the photoelectric shutter device is controlled to be closed. Because the traditional mechanical shutter opening and closing time is long and prone to vibration, this implementation uses a photoelectric shutter device to replace the traditional mechanical shutter switch, which can increase the shutter opening and closing time from milliseconds to microseconds.

Optionally, the controller is also used to adjust the switching voltage of the photoelectric shutter device according to the reflectivity of the object to be measured. In this way, the light transmittance of the reference optical path can be achieved, thereby ensuring that the measurement light intensity remains unchanged after the reflectivity of the measurement object changes.

Optionally, the illumination system includes a first dichroic prism; the first dichroic prism is located on the emission path of the detection light beam.

Optionally, the focusing system includes a second dichroic prism and a third dichroic prism, and the right-angled surfaces of the second dichroic prism and the third dichroic prism are at an angle of 45° to the receiving surface of the imaging system.

Optionally, the focusing light source is a continuous stable light source.

Optionally, the continuous stable light source is a white light source.

In a second aspect, the present invention also provides an optical measurement method. The method can apply the optical measurement device as described in any embodiment of the first aspect. The method includes:

Control the lighting system to emit detection beams;

The spectrum detector that controls the focusing system records the information of the interference beam formed after the detection beam is reflected by the object to be measured and the reference focal plane;

Control the imaging system to collect the imaging beam formed after the detection beam is reflected by the object to be measured;

Control the data processing system to obtain the information of the interference beam from the spectrum detector, perform focal plane measurement on the object to be measured based on the information of the interference beam, and obtain image information formed by the imaging beam from the imaging system, Overlay measurement is performed on the object to be measured based on the image information.

Compared with the existing technology, the optical measurement device and method proposed by the embodiments of the present invention can greatly reduce the sampling time, reduce the impact of platform vibration, and improve measurement accuracy and productivity by adjusting the traditional continuous light source to a pulse light source. In addition, Using a photoelectric shutter device to replace the traditional mechanical shutter switch can increase the shutter opening and closing time from milliseconds to microseconds, thus improving detection accuracy and efficiency.

Description of the drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings needed to describe the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. Those of ordinary skill in the art can also obtain other drawings based on these drawings without exerting creative efforts.

Figure 1 is a schematic structural diagram of an optical measurement device provided by an embodiment of the present invention;

Figure 2 is a schematic structural diagram of another optical measurement device provided by an embodiment of the present invention;

3A is a schematic diagram of the light transmission path of a photoelectric shutter device in an open state according to an embodiment of the present invention;

3B is a schematic diagram of the light transmission path of a photoelectric shutter device in a closed state according to an embodiment of the present invention;

Figure 4 is a schematic structural diagram of another optical measurement device provided by an embodiment of the present invention;

FIG. 5 is a schematic flowchart of an optical measurement method provided by an embodiment of the present invention.

Icon description:

Illumination system 01, focus system 02, imaging system 03, data processing system 04 and stage 05

Focusing light source 101, imaging light source 103, first transparent lens group 102, second transparent lens group 104

The first beam splitting prism 201 and the second beam splitting prism 202

Photoelectric shutter device 5, reference objective lens 6, reference surface 7, third beam splitting prism 8, imaging tube lens 9 and spectrum detector 10, imaging tube lens 11, camera 12, analyzer 13

Polarizer 501, electro-optical switch 502

Contents of the invention

In order to make the content of the present invention clearer and easier to understand, the content of the present invention will be further described below in conjunction with the accompanying drawings. Of course, the present invention is not limited to this specific embodiment, and general substitutions known to those skilled in the art are also covered by the protection scope of the present invention.

It should be noted that in the following specific embodiments, when describing the embodiments of the present invention in detail, in order to clearly show the structure of the present invention for ease of explanation, the structures in the drawings are not drawn according to general scales and are drawn. Partial enlargement, distortion and simplification are not included, and therefore, this should not be construed as a limitation of the present invention.

FIG. 1 is a schematic structural diagram of an optical measurement device according to an embodiment of the present invention. The optical measurement device includes: illumination system 01, focusing system 02, imaging system 03, data processing system 04 and stage 05. in:

Stage 05 is used to carry the object 4 to be tested. The object to be tested can be a wafer or other semiconductor device.

Illumination system 01, used to emit detection beams. As shown in FIG. 1 , the lighting system 01 includes an imaging light source 103 . In this embodiment, the imaging light source 103 is a pulse light source. Optionally, the pulse light source can be a xenon flash lamp or a pulse laser light source, and the pulse width of the light source can be 1 to 30 us.

The illumination system 01 also includes a first dichroic prism 201, and a first transparent lens group 102 and a second transparent lens group 104 disposed on both sides of the first dichroic prism 201. The focusing optical path includes the focusing light beam emitted by the focusing light source 101 passing through the first transparent lens group 102 and then entering the first dichroic prism 201 and being reflected by the first dichroic prism 201 . The imaging optical path includes that the imaging light beam emitted by the imaging light source 103 passes through the second transparent lens group 104 and then enters the first dichroic prism 201, and is transmitted through the first dichroic prism 201.

Focusing system 02 is used to separate the detection beam into the object to be measured and the reference focal plane through the optical component, and converge it to the spectrum detector through the optical component. The spectrum detector is used to record the detection beam passing through the to-be-measured object. Information about the interference beam formed after reflection between the measuring object and the reference focal plane.

Specifically, the focusing system 02 includes a microscope objective lens optical path, a reference surface optical path, and a focal plane measurement optical path. The optical path to be measured includes the second dichroic prism 202 and the microscope objective lens 3 on the side adjacent to the object to be measured. After the detection beam is reflected by the second dichroic prism 202, all the reflected light passes through the microscope objective lens 3 and irradiates the object to be measured. The optical path of the reference surface includes the reference surface 7 and the reference objective lens 6 . After the detection beam is transmitted through the second beam splitting prism 202 , all the transmitted light passes through the reference objective lens 6 and is irradiated to the reference surface 7 . The focal plane measurement optical path includes a third dichroic prism 8, an imaging tube lens 9 and a spectrum detector 10. The right-angled surfaces of the second dichroic prism 202 and the third dichroic prism 8 are both at an angle of 45° to the receiving surface of the imaging system. ° angle. After the light spot on the object to be measured 4 passes through the microscope objective lens 3 and the imaging tube lens 9, it is imaged on the focal plane of the imaging tube lens 9. In addition, after the light spot on the reference plane 7 passes through the reference objective lens 6 and the imaging tube lens 9, the light spot is also imaged on the focal plane of the imaging tube lens 9. The image is formed on the focal plane of the imaging tube lens 9. The data processing system 04 obtains the information of the interference beam from the spectrum detector 10 and performs focal plane measurement on the object to be measured 4 based on the information of the interference beam.

Specifically, when measuring the focal plane, if the interference principle is used for measurement, when the optical paths of the two are exactly the same, no interference will occur. When the measurement object changes vertically, the optical path difference between the two will occur, thus causing interference. Focal plane measurement is achieved by mathematically processing the interference signal. In addition, electro-optical detectors can be used to collect interference signals; at the same time, the principle of spectral modulation can also be used for measurement. At different vertical heights, the light intensity distribution of different wavelengths will change. By using a spectral detector to collect the spectral distribution, Thus achieving fixed focus plane measurement. It can be seen that focal plane measurement can be achieved based on the above lighting system and focusing system.

Imaging system 03 is used to collect the imaging beam formed after the detection beam is reflected by the object to be measured 4. The imaging system 03 includes a microscope objective light path and a camera light path. The microscopic objective light path includes a microscope objective lens and a camera light path. Imaging tube lens 11; the focusing system 02 and the imaging system 03 share the optical path of the microscope objective lens. The camera optical path includes camera 12.

Specifically, during the overlay measurement, after the detection beam passes through the second dichroic prism 202, the reflected light passes through the microscope objective lens 3 and is irradiated onto the mark on the object to be measured 4, and the image is formed after reflection by the microscope objective lens 3 and the imaging tube lens 11. The light beam is incident on the camera 12, and the data processing system 04 calculates the mark through an algorithm to obtain the overlay error. It can be seen that during the overlay measurement process, the data processing system 04 can obtain the image information formed by the imaging beam from the imaging system, and perform overlay measurement on the object to be measured based on the image information.

In a possible embodiment, as shown in FIG. 2 , the reference surface optical path includes a photoelectric shutter device 5 , a reference objective lens 6 and a reference surface 7 . The focal plane measurement optical path includes a focusing light source 101, an analyzer 13, and an imaging tube lens 9. The focus light source 101 may be a continuous stable light source, and the continuous stable light source may be a white light source. In this embodiment, the optical measurement device further includes a controller (not shown in the figure), the controller is connected to the focusing system, and the controller is used to control the photoelectric The photoelectric shutter device 5 is in an open state; when overlay measurement is performed, the photoelectric shutter device 5 is controlled to be in a closed state. The analyzer 13 can ensure that the two light path branches incident on the spectrum detector 10 are consistent.

As shown in FIG. 3A , the photoelectric shutter device 5 includes a polarizer 501 and an electro-optical switch 502 . The polarizer 501 is used to form polarized light, and the electro-optical switch 502 can be rotated to control the emission of polarized light. When the electro-optical switch 502 is in the open state, P-polarized light and S-polarized light pass through the polarizer 501 and the electro-optical switch 502, and the reference objective lens 6 emits S-polarized light. The S-polarized light is incident on the reference surface, and then the S-polarized light is reflected It can be reflected through the reference objective lens 6, polarizer 501 and electro-optical switch 502.

As shown in Figure 3B, when the electro-optical switch 502 is in a closed state, P-polarized light and S-polarized light pass through the polarizer 501 and the electro-optical switch 502, and the reference objective lens 6 emits S-polarized light, and the S-polarized light is incident on the reference surface, Then, the reflected S-polarized light passes through the reference objective lens 6 and the polarizer 501 and cannot be emitted from the electro-optical switch 502, thereby blocking the light beam.

In the above embodiment, the photoelectric shutter device 5 is used, so the transmitted light intensity can be quickly adjusted. When the reflectivity of the object to be measured 4 changes, the voltage of the photoelectric shutter device can be adjusted year-on-year, thereby adjusting the light transmittance ratio, thereby Ensure the consistency of the light intensity with the reference light path.

In another embodiment of the present invention, as shown in Figure 4, an infrared light source 105 and an infrared illumination light path can be added to the device shown in Figure 1. The infrared illumination light path includes an illumination lens group 106 and a spectroscopic lens 203. The infrared light source The infrared light emitted from 105 is injected into the object to be measured 4 through the illumination lens group 106, the dichroic lens 203 and the dichroic lens 201, thereby achieving the measurement of infrared light, thereby increasing the accuracy of silicon wafers with poor visible light transmittance of some film layers. measurement to improve process adaptability.

FIG. 5 is a flow chart of an optical measurement method according to an embodiment of the present invention. As shown in Figure 5, the optical measurement method can be executed by the controller. The optical measurement method includes the following steps:

S501, control the lighting system to emit detection beams.

S502, control the spectrum detector of the focusing system to record the information of the interference beam formed after the detection beam is reflected by the object to be measured and the reference focal plane.

S503. Control the imaging system to collect the imaging beam formed after the detection beam is reflected by the object to be measured.

S504, control the data processing system to obtain the information of the interference beam from the spectrum detector, perform focal plane measurement on the object to be measured based on the information of the interference beam, and obtain the image formed by the imaging beam from the imaging system information, and perform overlay measurement on the object to be measured based on the image information.

In addition, the controller can also control the switching state of the photoelectric shutter device 5 according to measurement needs. Because the traditional mechanical shutter opening and closing time is long and prone to vibration, this implementation uses a photoelectric shutter device to replace the traditional mechanical shutter switch, which can increase the shutter opening and closing time from milliseconds to microseconds.

In summary, compared with the existing technology, the optical measurement device and method proposed in the embodiments of the present invention can greatly reduce the sampling time, reduce the impact of platform vibration, and improve measurement accuracy and productivity by adjusting the traditional continuous light source to a pulse light source. In addition, the photoelectric shutter device is used to replace the traditional mechanical shutter switch, which can increase the shutter opening and closing time from milliseconds to microseconds, thereby improving detection accuracy and detection efficiency.

The above are only preferred embodiments of the present invention. The embodiments are not intended to limit the scope of patent protection of the present invention. Therefore, any equivalent structural changes made using the contents of the description and drawings of the present invention should be included in the same way. within the protection scope of the present invention. The above description of the disclosed embodiments enables those skilled in the art to make or use the present invention.

Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be practiced in other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

An optical measurement device, characterized by including:

The stage is used to carry the object to be tested;

An illumination system, used to emit a detection beam, the illumination system includes an illumination light source and an illumination light path, wherein the imaging light source is a pulse light source;

The focusing system is used to separate the detection beam into the object to be measured and the reference focal plane through the optical component, and converge it to the spectrum detector through the optical component. The spectrum detector is used to record the detection beam passing through the detection beam. Information about the interference beam formed after reflection between the object and the reference focal plane; the focusing system includes a microscope objective optical path, a reference surface optical path and a focal plane measurement optical path, and the focal plane measurement optical path includes the spectrum detector;

Imaging system, used to collect the imaging beam formed after the detection beam is reflected by the object to be measured. The imaging system includes a microscope objective light path and a camera light path. The microscope objective light path includes a microscope objective lens and an imaging tube lens. ;The focusing system and imaging system share the optical path of the microscope objective lens;

A data processing system for obtaining information about the interference beam from the spectrum detector, performing focal plane measurement on the object to be measured based on the information about the interference beam, and obtaining an image formed by the imaging beam from an imaging system information, and perform overlay measurement on the object to be measured based on the image information.
The optical measurement device according to claim 1, wherein the lighting system further includes an infrared light source and an infrared illumination light path.
The optical measurement device according to claim 1 or 2, wherein the pulse light source is a xenon flash lamp or a pulse laser light source, and the pulse width of the pulse light source ranges from 1 us to 30 us.
The optical measurement device according to claim 1, wherein the reference surface optical path includes a photoelectric shutter device, an imaging objective lens and a reference surface, and the reference surface is the best focal plane of a known objective lens;

The focal plane measurement optical path includes a focusing light source, an analyzer and an imaging tube lens;

The optical measurement device also includes a controller, the controller is connected to the focusing system, and the controller is used to control the photoelectric shutter device to be in an open state when performing focal plane measurement; when performing overlay measurement , the photoelectric shutter device is controlled to be closed.
The optical measurement device according to claim 4, wherein the controller is further used to adjust the switching voltage of the photoelectric shutter device according to the reflectivity of the object to be measured.
The optical measurement device according to claim 1, wherein the illumination system includes a first dichroic prism; and the first dichroic prism is located on the emission path of the detection light beam.
The optical measurement device according to claim 6, wherein the focusing system includes a second beam splitting prism and a third beam splitting prism, and the right-angled surfaces of the second beam splitting prism and the third beam splitting prism are aligned with the The receiving surface of the imaging system is at a 45° angle.
The optical measurement device according to claim 4, wherein the focusing light source is a continuous stable light source.
The optical measurement device according to claim 8, wherein the continuous stable light source is a white light source.
An optical measurement method using the optical measurement device according to any one of claims 1 to 8, characterized in that it includes:

Control the lighting system to emit detection beams;

The spectrum detector that controls the focusing system records the information of the interference beam formed after the detection beam is reflected by the object to be measured and the reference focal plane;

Control the imaging system to collect the imaging beam formed after the detection beam is reflected by the object to be measured;

Control the data processing system to obtain the information of the interference beam from the spectrum detector, perform focal plane measurement on the object to be measured based on the information of the interference beam, and obtain image information formed by the imaging beam from the imaging system, Overlay measurement is performed on the object to be measured based on the image information.