阅读说明：本技术 用于通过非相干照明混合的对准的图像改善 (Image improvement for alignment by incoherent illumination mixing ) 是由 塔纳·科斯坤 黄·J·郑 于 2018-06-19 设计创作，主要内容包括：提供确定在无掩模式光刻系统中实际特征/标记位置与设计特征/标记位置之间的偏移的方法和设备。例如,在一个实施方式中,提供一种包括打开在无掩模式光刻系统中的相机快门的方法。将光从镜阵列中的非相邻镜配置朝向第一基板层引导。在相机上捕获和累积所述第一基板层的图像。使用不同非相邻镜配置重复地引导光和捕获图像,以覆盖所述相机在所述第一基板层上的整个视场(FOV)。之后,关闭所述相机快门并将累积的图像存储在存储器中。(Methods and apparatus are provided for determining an offset between actual and design feature/mark positions in a maskless lithography system. For example, in one embodiment, a method is provided that includes opening a camera shutter in a maskless lithography system. Light is directed from non-adjacent mirror arrangements in the mirror array towards the first substrate layer. Capturing and accumulating an image of the first substrate layer on a camera. Repeatedly directing light and capturing images using different non-adjacent mirror configurations to cover an entire field of view (FOV) of the camera on the first substrate layer. Thereafter, the camera shutter is closed and the accumulated image is stored in memory.)

1. A method, comprising:

opening a camera shutter in a maskless lithography system;

directing light from a non-adjacent mirror arrangement in the mirror array towards the first substrate layer;

capturing and accumulating images of the first substrate layer on a camera;

repeatedly performing the directing and the capturing using different non-adjacent mirror configurations to cover an entire field of view (FOV) of the camera on the first substrate layer;

closing the camera shutter; and

the accumulated image is stored in a memory.

2. The method of claim 1, wherein the non-adjacent mirrors are configured in an alternating pattern of open to receive light mirrors adjacent to closed to not receive light mirrors.

3. The method of claim 1, wherein the non-adjacent mirrors are configured as a repeating sequence of a mirror that is open to receive light followed by two closed mirrors that do not receive light.

4. The method of claim 1, the method further comprising:

measuring actual marker positions on the first substrate layer from the accumulated image of the first substrate layer using image processing; and

comparing the design mark location of the first substrate layer to the actual mark location; and

determining an offset of the actual marker positions on the first substrate layer from the comparison of the design marker positions of the first substrate layer.

5. The method of claim 1, further comprising:

opening the camera shutter;

directing light from the non-adjacent mirror arrangement towards a second substrate layer located on top of the first substrate layer;

continuously capturing and accumulating images of the second substrate layer;

repeatedly performing the directing and the capturing using different non-adjacent mirror configurations to cover an entire FOV of the camera on the second substrate layer; and

closing the camera shutter

6. The method of claim 5, the method further comprising:

measuring actual marker positions on the second substrate layer from accumulated images of the second substrate layer using image processing to determine actual marker positions within the FOV of the camera;

comparing the design marking locations of the second substrate layer to the actual marking locations on the second substrate layer; and

determining an offset of the actual marking position on the second substrate layer from the comparison of the design marking positions of the second substrate layer.

7. The method of claim 5, the method further comprising:

measuring actual marker positions on the second substrate layer from the accumulated images of the second substrate layer;

comparing the design marking locations of the first substrate layer to the actual marking locations on the second substrate layer; and

determining an offset from the comparison of the design mark positions of the second substrate layer to align the actual mark positions on the second substrate layer with the design mark positions on the first substrate layer.

8. A method, comprising:

opening a camera shutter in a maskless lithography system;

moving the substrate;

directing light from at least one non-adjacent mirror arrangement to the moving substrate;

continuously capturing and accumulating images in the camera to cover an entire camera field of view (FOV) on a first substrate layer on the moving substrate;

closing the camera shutter; and

the accumulated image is stored in a memory.

9. The method of claim 8, the method further comprising:

measuring actual marker positions on the first substrate layer from the accumulated image of the first substrate layer using image processing;

comparing the design mark location of the first substrate layer to the actual mark location; and

determining an offset of the actual marking location on the first substrate layer from the comparison of the design marking location of the first substrate layer.

10. The method of claim 8, the method further comprising:

moving the substrate;

opening the camera shutter;

directing light from the at least one non-adjacent mirror arrangement to the moving substrate;

continuously capturing and accumulating images to cover an entire FOV on a second substrate layer on the moving substrate;

closing the camera shutter; and

the accumulated image is stored in a memory.

11. The method of claim 11, the method further comprising:

measuring actual marker positions on the second substrate layer from the accumulated images of the second substrate layer using image processing;

comparing the design marking locations of the second substrate layer to the actual marking locations on the second substrate layer; and

determining an offset of the actual marking position on the second substrate layer from the comparison of the design marking positions of the second substrate layer.

12. The method of claim 11, the method further comprising:

measuring actual marker positions on the second substrate layer from the accumulated images of the second substrate layer using image processing;

comparing the design marking locations of the first substrate layer to the actual marking locations on the second substrate layer; and

determining an offset from the comparison of the design mark positions of the second substrate layer to align the actual mark positions on the second substrate layer with the design mark positions on the first substrate layer.

13. A lithography system, comprising:

a light source;

a mirror array adapted to have a non-adjacent mirror configuration to receive light from the light source and to reflect light towards a substrate layer;

a beam splitter adapted to receive light reflected from the mirror array and light reflected from the substrate layer;

a camera coupled to the beam splitter and adapted to capture and accumulate images on the substrate layer that are visible by reflecting light from the substrate layer; and

a processor coupled to the light source and the mirror array to select the non-adjacent mirror configuration, the beam splitter, and the camera.

14. The system of claim 14, further comprising:

a platform adapted to support the substrate layer, wherein a position of the platform is fixed relative to the substrate layer, the platform adapted to receive instructions from the process to move in at least one of a direction parallel to an X-axis and a direction parallel to a Y-axis while the camera captures an image; and wherein the processor is adapted to change the non-adjacent mirror configuration to at least one other non-adjacent mirror configuration when the camera captures an image.

Technical Field

Embodiments of the present disclosure relate generally to the field of maskless lithography, and more particularly to reducing measurement errors in the actual position of alignment marks and/or features on a substrate.

Background

Microlithography techniques are commonly used to produce electrical features on substrates. A photosensitive photoresist is typically applied to at least one surface of the substrate. Next, a photolithographic mask or pattern generator, such as a micromirror array, exposes selected areas of the photosensitive photoresist as part of the pattern. The light causes chemical changes in the photoresist in selected areas to prepare these selected areas for subsequent material removal and/or material addition processes to produce electrical features. The precise positioning of the electrical features on the substrate determines the quality of the electrical interconnections.

Alignment techniques are used to ensure proper alignment of the layers with respect to each other during the manufacturing process. Generally, alignment marks are used in these layers to assist in alignment of features in the different layers. Increasing the accuracy of the identification of the position of the alignment mark may provide a more accurate alignment of the layers and thus reduce overlay errors.

Therefore, there is a need in the art to increase the accuracy of the alignment layer.

Disclosure of Invention

Embodiments of the present disclosure generally relate to determining more accurate locations of alignment marks and/or features on a substrate. For example, in one embodiment, a method is presented that includes opening a camera shutter in a maskless lithography system. Light is directed from non-adjacent mirror arrangements in the mirror array towards the first substrate layer. An image of the first substrate layer is captured and accumulated on the camera. The light is repeatedly directed and the image is captured using different non-adjacent mirror configurations to cover the entire field-of-view (FOV) of the camera on the first substrate layer. Thereafter, the camera shutter is closed and the accumulated image is stored in the memory.

In another embodiment, a method of opening a camera shutter in a maskless lithography system is presented. As the substrate moves, light is directed from at least one non-adjacent mirror arrangement to the moving substrate. Images are captured and accumulated in the camera continuously to cover the entire camera field-of-view (FOV) on the first substrate layer on the moving substrate. Then, closing the camera shutter; and storing the accumulated image in a memory.

In yet another embodiment, a lithography system is provided that includes a light source. Also included is a mirror array adapted to have a non-adjacent mirror configuration to receive light from the light source and to reflect light toward the substrate layer. The beam splitter is adapted to receive light reflected from the mirror array and light reflected from the substrate layer. A camera is coupled to the beam splitter and adapted to capture and accumulate images on the substrate layer that are visible by reflecting light from the substrate layer. A processor is coupled to the light source, the mirror array to select a non-adjacent mirror configuration, the beam splitter, and the camera.

Other embodiments of the present disclosure provide for other methods, devices, and systems having features similar to the devices and methods described herein.

Drawings

So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this disclosure and are therefore not to be considered limiting of its scope, for the disclosure may admit to other equally effective embodiments.

Fig. 1 depicts a perspective view of an apparatus according to embodiments disclosed herein.

Fig. 2 depicts an example of illumination light directed toward a substrate according to embodiments disclosed herein.

Fig. 3 depicts an example of alignment mark position shift on a substrate layer due to light that is not orthogonal to the substrate.

Fig. 4A, 4B, 4C, and 4D depict simulated images illuminated at different focus levels (focus levels) by orthogonal light reflected by an isolated mirror.

Fig. 5 depicts an embodiment of a high level block diagram of a semi-isolated pattern generation system to reduce measurement error of actual positions of alignment marks and/or features on a substrate in accordance with embodiments disclosed herein.

Fig. 6 depicts an embodiment of a method of detecting layer shifting according to embodiments disclosed herein.

Fig. 7 depicts an embodiment of a method of detecting layer shifting according to embodiments disclosed herein.

To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures.

Detailed Description

In the following description, numerous specific details are set forth in order to provide a more thorough understanding of the present disclosure. However, as will be apparent to one of ordinary skill in the art, numerous changes using different configurations can be made without departing from the scope of the present materials. In other instances, well-known features have not been described in detail to avoid obscuring the present material. Accordingly, the present disclosure is not limited to the specific illustrative embodiments shown in the specification, and all such alternative embodiments are intended to be included within the scope of the appended claims.

The wavelength used to illuminate the alignment marks and/or features is different than the wavelength sensed by the photoresist. For example, a typical wavelength used to expose a photoresist to create a pattern is 403 nm. Therefore, the wavelength of 403nm is not used for illumination in alignment. Examples of wavelengths that may be used for illumination are about 400nm to about 700nm (excluding about 403 nm). Some typical colors that may be used for illumination are red (about 650nm), amber (about 570nm to about 620nm), and blue (about 475 nm).

Fig. 1 depicts a perspective view of a system 100 according to the disclosure herein. System 100 includes micro-mirror array 102, light source 104, projection optics 108, camera 114, beam splitter 109, and processor 116. The system 100 also includes a platform 112.

Processor 116 controls light source 104, camera 114, and micro-mirror array 102. The several mirrors in the micro mirror array 102 are individually controlled by signals from the processor 116. In one embodiment, the micro mirror array 102 may be a digital mirror device (digital mirror device) of model DLP9500, manufactured by Texas instruments Incorporated of Dallas (Dallas) Tex. The plurality of mirrors may have a number of mirrors configured in a number of different ways. For example, in one embodiment, the plurality of mirrors are configured in 1920 columns and 1080 rows.

The "turned ON" mirror is defined herein as a mirror that has been positioned by the processor 116 to receive and redirect light toward the substrate 110. A mirror that is "turned OFF" is defined herein as a mirror that has been positioned by the processor 116 such that the mirror does not pass light toward the substrate 110. Each mirror in the mirror array can be assembled to be individually actuatable (or digitally controlled) from a passive position (i.e., "off") to an active position (i.e., "on").

In one embodiment, the processor 116 sends instructions to the micro mirror array 102 for at least one semi-insulating mirror arrangement to reflect light toward the substrate 110. "configuration" and "pattern" are used interchangeably herein. As used herein, a "semi-isolated mirror configuration" is defined as a mirror configuration in which any mirror that is open and has an adjacent mirror is adjacent only to the closed mirror. When the mirror is open, the mirror is immediately adjacent to the closed mirror. For example, a semi-isolated configuration may include a sequence such as open, closed, open, etc., or a sequence such as open, closed, open, etc.

The camera 114 may include a photosensor (not depicted), such as a charge coupled device (charged coupled device), to read at least one alignment mark 120 on the substrate 110 to register (register) the substrate 110 to the stage 112 and the micromirror array 102. The camera 114 may be coupled to the processor 116 to facilitate determining the relative position of alignment marks and/or features on the substrate 110.

The stage 112 can support the substrate 110 and move the substrate 110 relative to the micromirror array 102. The stage 112 uses at least one motor 118 to move the substrate 110 relative to the micro mirror array 102 in the X-direction and/or the Y-direction. The stage 112 may also include at least one linear encoder (not depicted) to provide position information to the processor 116 regarding changes in position of the stage 112 in the X-direction and/or the Y-direction.

Light 105 is transmitted from the bottom surface 107 of the micro mirror array 102 in the light path 106 through the projection optics 108 toward the substrate 110. Light 103 reflects from substrate 110, travels through beam splitter 109 and toward camera 114. The projection optics 108 may include a reduction ratio (reduction ratio) to reduce the size of the light 105 on the substrate 110. The reduction ratio may range from 2:1 to 10: 1. In this regard, the projection optics 108 can include at least one lens, including at least one convex and/or concave surface between the substrate 110 and the micromirror array 102. The projection lens 108 may comprise a highly transmissive material (e.g., quartz) for several wavelengths of the light 105 to focus the light 105 on the substrate 110.

Fig. 2 depicts an example of illumination rays directed toward a substrate 110, according to embodiments disclosed herein. Fig. 2 depicts a substrate 110 having alignment marks 202 and alignment marks 203. Light 204 that is non-orthogonal (i.e., non-perpendicular) to alignment mark 202 illuminates alignment mark 202. Image 206 shows the simulated effect of illumination by non-perpendicular light rays 204. In particular, a pupil (pupil)207 in the image 206 represents the illuminated portion of the alignment mark 202. Pupil 207 is offset from the center of image 206. The pupil shifted from the center of the image simulation indicates that the recognized position of the alignment mark is shifted from the actual position of the alignment mark.

Light ray 210 represents light normal to alignment mark 203. Image 208 shows the simulated effect of illumination by vertical ray 118. In particular, image 208 includes pupil 209, with pupil 209 being located at the center of image 208. Pupil 209, which is centrally located in image 208, represents little or no offset of the identified pupil 209 position from the actual position of pupil 209.

Fig. 3 depicts another view of alignment marks 202 on substrate 110 and positional offset due to non-orthogonal light 204. For simplicity, FIG. 3 shows only a positional shift in one dimension (i.e., along the X-axis (i.e., "Δ X"). 3 shows that non-orthogonal light can produce a shift that can also be affected by image focus changes (denoted by "Δ f").

Fig. 4A, 4B, 4C, and 4D depict simulated images 400, 404, 402, and 406 illuminated by orthogonal light reflected by an isolated mirror at different focus levels (focus levels), respectively. Because the respective images 400, 404, 402, and 406 are captured using orthogonal light, the pupil in each of these images is centered.

Pupil 401, depicted in FIG. 4A, is larger than pupils 405, 403, and 407. As the size of the pupil increases, the total amount of light of the image that is not orthogonal to the illumination also increases. The radius of light from the center of pupil 401 is greater than the radius of light in pupils 405, 403 and 407. The light on the periphery of the pupil is not orthogonal to the surface of the alignment mark 120. The larger the radius of the pupil, the larger the total amount of non-orthogonal light in the periphery and pupil.

The pupil 403 in fig. 4C is a simulated image at a different focus than the pupil 401. Pupil 403 also has a smaller radius and less non-orthogonal light than pupil 401. In FIG. 4D, pupil 407 has a positive defocus (defocus) above the focus of pupil 403; and in fig. 4B, pupil 405 has negative defocus below the focus of pupil 403. Although the pupils 401, 405, 403 and 407 have different focal points, fig. 4A, 4B, 4C and 4D show that the image systems produced by orthogonal light are relatively insensitive to focal point changes.

Fig. 5 depicts an embodiment of a high-level block diagram of a semi-isolated pattern generation system 500, the semi-isolated pattern generation system 500 to reduce position offset errors due to focus variation and sample thickness, in accordance with an embodiment disclosed herein. For example, the semi-isolated pattern generation system 500 is suitable for use in performing the methods of fig. 6 and 7. The semi-isolated pattern generation system 500 includes a processor 510 and a memory 504, the memory 504 being used to store control programs and the like.

In several embodiments, the memory 504 also includes programs that select and change the semi-isolated pattern configuration (e.g., "semi-isolated pattern module 512"). In other embodiments, memory 504 includes a program (not shown) for controlling the movement of platform 112.

The processor 510 interacts with conventional support circuitry 508, such as power supplies, clock circuits, cache memory, and the like, and circuitry that assists in executing the software routines 506 stored in the memory 504. As such, it is contemplated that some of the process steps discussed herein as software programs (software processes) may be loaded from storage (e.g., optical drives, floppy drives, disk drives, etc.) and applied to memory 504 and operated on by processor 510. Thus, several steps and methods of the present disclosure may be stored on a computer readable medium. The semi-isolated pattern generation system 500 also includes input-output circuitry 502. Input-output circuitry 502 forms an interface between several functional elements that communicate with matching system 500 and the micromirror control system to load and display semi-isolated patterns on the micromirror array.

Although fig. 5 depicts semi-isolated pattern generation system 500, and semi-isolated pattern generation system 500 is programmed to perform several control functions in accordance with the present disclosure, the term computer is not limited to just those integrated circuits referred to in the art as computers, but broadly refers to computers, processors, microcontrollers, microcomputers, programmable logic controllers, application specific integrated circuits (application specific integrated circuits), and other programmable circuits, and these names are used interchangeably herein. Furthermore, although a semi-isolated pattern generation system 500 is depicted, this figure is for purposes of brevity only. It will be appreciated that the methods described herein may be used in separate systems or in the same system through software changes.

In one embodiment, camera 114 captures images in camera 114. When the camera shutter is open, the first mirror that is open configures the illumination substrate and captures an image. The image captured by camera 114 is pixelated because each pixel in the camera acts as a sensor and some of the camera pixels will not receive light reflected from the substrate (i.e., because some of the mirrors are off). When the shutter is open, the other mirror configuration is open to illuminate the substrate; and the camera 114 captures the pixelated image. Each image accumulated may also be referred to as a "frame". The shutter is closed and the captured image is accumulated by combining the frames. In one embodiment, the camera shutter remains open, and after the camera shutter closes, images are accumulated and processed in the camera 114. In another embodiment, the camera shutter is closed and opened for each frame; and the accumulated images are sent to the processor 116 for processing.

After image acquisition, image processing is performed. The shape of the alignment mark is also known and the image on the camera is correlated (correct) with the known alignment design. The correlation provides an approximate position relative to the center of the field of view (FOV) of camera 114. Based on the position of the image relative to the center of the FOV of camera 114, the position of the alignment mark may be determined. Because the design of the alignment marks is known, the edges of the alignment marks may be detected to determine the shape of the alignment marks in the image. The processed image of the alignment mark may be compared to the design mark.

Fig. 6 depicts an embodiment of a method 600 of reducing positional offset of alignment marks and/or features according to embodiments disclosed herein. At block 602, a camera shutter on the camera 114 is opened to capture an image from a light emitting portion of the substrate 110.

At block 604, light 105 from light source 104 is directed toward the mirror array on bottom surface 107 of micro mirror array 102. The processor 116 has turned some mirrors in the mirror array on and some off to produce a semi-isolated pattern configuration. For example, a first mirror may be open and those mirrors immediately adjacent to that mirror closed (such that the sequence is open, closed, etc.). The opened mirror directs light toward the substrate 110, and light reflected from the substrate 110 is exposed, which may illuminate the alignment mark. The closed mirror does not direct light toward the substrate 110. Those portions of the substrate 110 that are illuminated by the alignment marks 120 or features are accomplished by light that is substantially orthogonal to the illuminated portions of the substrate.

At block 606, camera 114 begins capturing and accumulating images of the illuminated portion of alignment mark 120. At block 608, the processor 116 changes the current semi-isolated pattern configuration to a different semi-isolated pattern configuration during image capture and accumulation. For example, different semi-isolated patterns may be first mirror off and second mirror on (such that the sequence is off, on, etc.). Because the semi-isolated patterns are different, different portions of the alignment mark 120 on the substrate 110 are illuminated. Camera 114 captures and accumulates images of the illuminated portion of alignment mark 120. The processor 116 repeatedly changes the semi-isolated pattern configuration to illuminate different portions of the alignment mark 120 in the camera FOV and captures and accumulates images of the illuminated portions until the entire FOV of the camera 114 is covered.

After the full semi-isolation pattern is loaded and displayed on the micro-mirrors, the camera shutter on the camera 114 is closed at block 610. The images captured and accumulated on the camera form a complete picture of the alignment marks 120 in the FOV of the camera 114. The images are then stored in memory 504 and processed in processor 510 to find the position of the alignment marks in the camera FOV. Image processing algorithms, such as correlation or edge detection, may be used to find the position of the alignment marks.

Fig. 7 depicts an embodiment of a method 700 of detecting positional shifts of alignment marks and/or features according to embodiments disclosed herein. In block 702, in preparation for capturing and accumulating images in the camera 114 from the light emitting portion of the substrate 110, the camera shutter on the camera 114 is opened. At block 704, the processor 116 moves the platform 112 relative to the micro-mirror array 102 as described above while the camera shutter is open. The processor 116 directs the stage 112 to move slowly (i.e., at a speed that allows all images to be captured) in a direction that is parallel to the X-direction and/or parallel to the Y-direction.

At block 706, light 105 from light source 104 is directed toward the mirror array on bottom surface 107 of micro mirror array 102. The processor 116 has turned some mirrors in the mirror array on and some off to produce a semi-isolated pattern configuration. For example, a first mirror may be open and the mirrors immediately adjacent to that mirror are closed (such that the sequence is open, closed, etc.). The opened mirrors direct light toward alignment marks 120 on the substrate 110. Those portions of the substrate 110 that are illuminated by the alignment marks 120 or features are accomplished by light that is substantially orthogonal to the illuminated portions of the substrate. At least one non-adjacent mirror configuration illuminates when the platform 112 is moving. In one embodiment, multiple non-adjacent mirror configurations (i.e., the processor 116 changing the current semi-isolated pattern to at least one other semi-isolated pattern) are turned on while the platform 112 is moving.

At block 708, the camera 114 continuously captures and accumulates images of the illuminated portion of the alignment mark 120 in the camera 104. The captured images are those portions of the illumination of the alignment mark 120. During this process, all captured images are accumulated in the camera to produce images that are sampled in the camera FOV. At block 710, the camera shutter is closed to stop image accumulation on the camera 104. The images are then stored in memory 504 and processed in processor 510 to find the position of the alignment marks in the camera FOV. Image processing algorithms, such as correlation or edge detection, may be used to find the position of the alignment marks.

While various aspects have been described herein as using methods and systems to increase the accuracy of layer alignment by reducing measurement errors in the actual location of alignment marks, these illustrations are not intended to limit the scope of the present materials described herein in any way.

In conclusion, while the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof. The scope of the invention is therefore defined by the appended claims.