CN108227390B

CN108227390B - Image quality detection method of photoetching machine

Info

Publication number: CN108227390B
Application number: CN201611199033.9A
Authority: CN
Inventors: 邢滨; 柏耸
Original assignee: Semiconductor Manufacturing International Shanghai Corp; Semiconductor Manufacturing International Beijing Corp
Current assignee: Semiconductor Manufacturing International Shanghai Corp; Semiconductor Manufacturing International Beijing Corp
Priority date: 2016-12-22
Filing date: 2016-12-22
Publication date: 2020-10-16
Anticipated expiration: 2036-12-22
Also published as: CN108227390A

Abstract

The invention provides an image quality detection method of a photoetching machine. The method comprises the following steps: providing a wafer, and forming a plurality of hole patterns which are spaced from each other on the surface of the wafer; carrying out defect scanning on the hole pattern to obtain a defect image; and analyzing the defect image to judge whether the defect image is abnormal or not so as to regularly monitor whether the imaging plane of the lens of the photoetching machine is abnormal or not. The method can improve the monitoring frequency, does not need to stop (down) a machine, reduces the time consumed by monitoring, has higher sensitivity, can timely find the problem at the initial stage of abnormity of an imaging plane of a photoetching machine, and avoids the loss of the product quantity rate.

Description

Image quality detection method of photoetching machine

Technical Field

The invention relates to the technical field of semiconductors, in particular to an image quality detection method of a photoetching machine.

Background

The imaging quality of the lithography machine directly affects key performance indexes of the lithography machine, such as CD uniformity, overlay accuracy, focal depth, exposure latitude and the like. Therefore, the field detection technology of the imaging quality of the photoetching machine is indispensable.

The Focus calibration (FOCAL) technology using alignment is an image quality detection technology for a high-resolution lithography machine, and can detect image quality parameters such as an optimal image plane, image plane inclination, field curvature, astigmatism and the like with high precision on site.

The FOCAL technology is to sequentially image a special mark pattern, namely FOCAL mark patterns, on silicon wafers at different FOCAL planes under the optimal exposure dose. Unlike the alignment mark of a common photoetching machine, the FOCAL mark contains a part of dense lines in one grating period, and the part of dense lines is called as a fine structure of the FOCAL mark. Due to the existence of the fine grating structure, the spatial distribution of the reflected light intensity of the FOCAL mark on the silicon wafer changes along with the change of the defocusing amount, so that the position of the mark corresponding to the extreme value of the reflected light intensity is shifted, and the shift is called alignment offset (alignment offset). The alignment offset is related to the line width of the FOCAL mark fine structure. After the silicon wafer is exposed under different defocusing amounts, FOCAL marking patterns with fine structures with different line widths are formed on the photoresist, so that different alignment offsets are generated. The alignment shift amount of the FOCAL mark exposed at the best image plane reaches a maximum value. Therefore, the alignment position deviation of the silicon chip mark is related to the defocusing amount, and the axial position deviation of the optimal image point corresponding to the mark is calculated according to the detected alignment position deviation of each FOCAL mark. And calculating parameters such as an optimal image surface, image surface inclination, field curvature, astigmatism and the like according to the axial position deviation of the optimal image points, thereby realizing the detection of the image quality parameters of the photoetching machine.

In wafer production, a defect image (defect map) passing through an exposure level (shot level) is found, and the defect is not caused by mask haze (mask haze) and level mapping anomaly (level mapping anomaly) due to the problem of scanning the angle of an imaging plane.

The traditional FOCAL method is: a specific FOCAL Mask is placed on a Mask (Mask) for exposure, then a signal of the Mask is collected by an Alignment (Alignment) system of a photoetching machine, and an imaging plan is obtained through simulation to monitor whether a lens and other related imaging devices are normal. This monitoring (monitor) action is typically performed when the tool is Periodically Maintained (PM) because it requires the tool to be stopped (down). If the monitoring frequency is to be enhanced, the production efficiency is affected.

Therefore, in order to save the testing time and reduce the testing cost, a new method for determining the FOCAL quickly and reliably needs to be found.

Disclosure of Invention

In this summary, concepts in a simplified form are introduced that are further described in the detailed description. This summary of the invention is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

In order to overcome the existing problems, the invention provides an image quality detection method of a photoetching machine, which comprises the following steps:

providing a wafer, and forming a plurality of hole patterns which are spaced from each other on the surface of the wafer;

carrying out defect scanning on the hole pattern to obtain a defect image;

and analyzing the defect image to judge whether the defect image is abnormal or not so as to regularly monitor whether the imaging plane of the lens of the photoetching machine is abnormal or not.

Optionally, the hole patterns are formed at intervals in the middle area and the two side areas of the wafer, and the hole patterns are more sensitive to the change of the focus.

Alternatively, when the number of defective dots appearing in one side region in the defective image abruptly increases, the imaging plane becomes abnormal.

Optionally, the method of forming the hole pattern includes:

providing a wafer, and forming a first material layer on the surface of the wafer;

forming a patterned mask layer on the first material layer, wherein an opening pattern is formed in the mask layer;

etching the first material layer by taking the mask layer as a mask so as to form a plurality of openings which are spaced from each other in the first material layer;

depositing a second material layer to cover the first material layer and fill the opening, wherein a hole pattern is formed in the second material layer in the opening;

and flattening the second material layer to the surface of the first material layer to expose the hole pattern.

Optionally, the first material layer comprises a dielectric layer;

the second material layer includes a metal layer.

Optionally, the mask layer includes a bottom anti-reflection coating and a photoresist layer stacked in sequence.

Optionally, the method for forming the opening pattern in the mask layer includes:

selecting a mask to expose and develop the photoresist layer so as to form the opening pattern in the photoresist layer;

and etching the bottom anti-reflection coating and the first material layer by taking the photoresist layer as a mask to form the opening.

Optionally, before the defect scanning, the hole pattern when the imaging plane is normal is scanned to determine whether there is a defect in the mask when the hole pattern is formed and to eliminate the influence of the mask.

Optionally, mask patterns are formed in the middle and two sides of the mask at intervals; the mask patterns are strip-shaped structures, and each strip-shaped structure is composed of a plurality of square patterns which are spaced from each other.

Optionally, the method further comprises:

performing FOCAL image quality detection on the wafer to determine the deviation angle of the imaging plane;

the imaging plane is adjusted.

In order to solve the problems in the prior art, the invention provides an image quality detection method of a lithography machine, wherein a special Mask (Mask) and a special monitoring graph arranged on the Mask are designed in the method, a short loop monitoring process is designed, and whether an imaging plane of a lens of the lithography machine is abnormal or not is regularly monitored by combining a method for finally observing whether Hole (Hole Void) defects (which have higher sensitivity to CD size) of defect scanning have specific distribution or not, so that the method is used as an auxiliary means of a traditional FOCAL method.

The conventional method is only carried out at the time of regular PM, and if the monitoring frequency is increased, the production yield is affected. The method can improve the monitoring frequency, does not need to stop (down) a machine, reduces the time consumed by monitoring, has higher sensitivity, can timely find the problem at the initial stage of the abnormity of the imaging plane of the photoetching machine, and avoids the loss of the product quantity rate.

Drawings

The following drawings of the invention are included to provide a further understanding of the invention. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

In the drawings:

FIG. 1 is a process flow diagram illustrating an image quality inspection method of a lithography machine according to the present invention;

FIGS. 2a-2e are schematic diagrams illustrating the process of the image quality detection method of the lithography machine according to the present invention;

FIG. 3 is a schematic structural diagram of a mask used in the image quality detection method of the lithography machine according to the present invention.

Detailed Description

In the following description, numerous specific details are set forth in order to provide a more thorough understanding of the present invention. It will be apparent, however, to one skilled in the art, that the present invention may be practiced without one or more of these specific details. In other instances, well-known features have not been described in order to avoid obscuring the invention.

It is to be understood that the present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, the size and relative sizes of layers and regions may be exaggerated for clarity. Like reference numerals refer to like elements throughout.

It will be understood that when an element or layer is referred to as being "on" …, "adjacent to …," "connected to" or "coupled to" other elements or layers, it can be directly on, adjacent to, connected to or coupled to the other elements or layers or intervening elements or layers may be present. In contrast, when an element is referred to as being "directly on …," "directly adjacent to …," "directly connected to" or "directly coupled to" other elements or layers, there are no intervening elements or layers present. It will be understood that, although the terms first, second, third, etc. may be used to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another element, component, region, layer or section. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the present invention.

Spatial relationship terms such as "under …", "under …", "below", "under …", "above …", "above", and the like, may be used herein for ease of description to describe the relationship of one element or feature to another element or feature as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, then elements or features described as "below" or "beneath" other elements or features would then be oriented "above" the other elements or features. Thus, the exemplary terms "below …" and "below …" can encompass both an orientation of up and down. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatial descriptors used herein interpreted accordingly.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. As used herein, the term "and/or" includes any and all combinations of the associated listed items.

In the following description, for purposes of explanation, specific details are set forth in order to provide a thorough understanding of the present invention. The following detailed description of the preferred embodiments of the invention, however, the invention is capable of other embodiments in addition to those detailed.

In wafer production, a defect image (defect map) passing through a horizontal shot (shot level) is found, and the defect is not caused by mask blurring (mask haze) or horizontal mapping abnormality (level mapping anomaly) and is caused by the problem of scanning the angle of an imaging plane.

In order to solve the above problem, the present application provides an image quality detection method for a lithography machine, the method including:

carrying out defect scanning on the hole pattern to obtain a defect image;

The method for forming the hole pattern comprises the following steps:

The method for forming the opening pattern in the mask layer includes:

In the invention, mask patterns are formed at intervals in the middle and on two sides of the mask plate; the mask pattern is a strip-shaped structure, and the strip-shaped structure is composed of a plurality of square patterns which are spaced from each other.

When the number of the defect points appearing in one side area in the defect image is suddenly increased, the imaging plane is abnormal.

For example, when the number of defect points appearing on the left side in the defect image suddenly increases, it indicates that the imaging plane is abnormal.

Example one

The image quality detection method of the lithography machine according to the present invention is described in detail below with reference to fig. 1 and fig. 2a-2e, and fig. 1 shows a process flow diagram of the image quality detection method of the lithography machine according to the present invention; FIGS. 2a-2e are schematic process diagrams illustrating the image quality detection method of the lithography machine according to the present invention.

The invention provides an image quality detection method of a photoetching machine, as shown in figure 1, the method mainly comprises the following steps:

step S1: providing a wafer, and forming a plurality of hole patterns which are spaced from each other on the surface of the wafer;

step S2: carrying out defect scanning on the hole pattern to obtain a defect image;

step S3: and analyzing the defect image to judge whether the defect image is abnormal or not so as to regularly monitor whether the imaging plane of the lens of the photoetching machine is abnormal or not.

The following describes in detail a specific embodiment of the image quality detection method of a lithography machine according to the present invention.

Firstly, a first step is executed, a wafer is provided, and a plurality of hole patterns which are mutually spaced are formed on the surface of the wafer.

In order to overcome the defects in the conventional FOCAL, the mask and the pattern formed on the surface of the wafer in the detection process are improved.

The inventors have found through experiments that the holes are more sensitive to the variation of the FOCAL length compared to the FOCAL marks of the dense lines in the conventional FOCAL, and the FOCAL length of the holes can be greatly changed when the imaging plane is changed, such as shifted, so that an image with abnormal defect distribution can be formed after the defect is scanned.

Therefore, a plurality of hole patterns which are mutually spaced can be formed on the surface of the wafer, so that the operation of the machine table is not stopped on line, the imaging plane is detected on line, the problem is timely found at the initial stage of the inclination of the imaging plane (image plane), and the loss of a large amount of product quantity rate is avoided after the problem is serious.

Specifically, the wafer may be at least one of the following materials: silicon, silicon-on-insulator (SOI), silicon-on-insulator (SSOI), silicon-on-insulator-silicon-germanium (S-SiGeOI), silicon-on-insulator-silicon-germanium (SiGeOI), and germanium-on-insulator (GeOI), among others.

In addition, an active region may be defined on the wafer. Other active devices may also be included on the active region and are not shown in the figures for convenience.

Various front-end devices may be formed on the wafer, and the front-end devices may include active devices, passive devices, MEMS devices, and the like.

For example, various transistors and rf devices may be formed on the wafer, the transistors being used to form various circuits, the rf devices being used to form rf components or modules, and interconnect structures being used to connect the transistors, the rf devices, and other components in the front end devices.

The method for forming the hole pattern comprises the following steps:

step 1: providing a wafer 201, and forming a first material layer 202 on the surface of the wafer;

step 2: forming a patterned mask layer on the first material layer, wherein an opening pattern is formed in the mask layer;

and step 3: etching the first material layer by taking the mask layer as a mask so as to form a plurality of openings which are spaced from each other in the first material layer;

and 4, step 4: depositing a second material layer to cover the first material layer and fill the opening, wherein a hole pattern is formed in the second material layer in the opening;

and 5: and flattening the second material layer to the surface of the first material layer to expose the hole pattern.

In step 1, for example, SiO may be used for the first material layer 202₂Fluorocarbon (CF), silicon oxide doped with carbon (SiOC), silicon carbonitride (SiCN), or the like. Alternatively, a film in which a SiCN thin film is formed on fluorocarbon (CF) or the like may be used. The fluorocarbon compound contains fluorine (F) and carbon (C) as main components. As the fluorocarbon, a fluorocarbon having an amorphous (non-crystalline) structure may be used. The first material layer 202 may also have a porous structure such as carbon-doped silicon oxide (SiOC).

The first material layer 202 may be deposited using conventional deposition methods, such as chemical vapor deposition, to cover the wafer.

And forming other material layers between the dielectric layer and the wafer, for example, forming an insulating layer or an interface layer.

In step 2, as shown in fig. 2a, a mask stack is formed on the first material layer, the mask stack comprising a bottom anti-reflective coating (BARC)203 and a photoresist layer 204.

Optionally, as an alternative embodiment, an Organic Distribution Layer (ODL) may be further formed between the bottom anti-reflective coating (BARC)203 and the first material layer 202.

And then, selecting a mask to expose and develop the photoresist layer so as to form the opening pattern in the photoresist layer.

In order to form a hole pattern sensitive to the imaging plane on a wafer, the mask is improved in the application, wherein the mask pattern is formed in the middle and two sides of the mask at intervals in the layout structure of the mask, as shown in fig. 3; the mask pattern is a strip-shaped structure, and the strip-shaped structure is composed of a plurality of square patterns which are spaced from each other.

The square pattern in the strip-shaped structure comprises a plurality of smaller square structures which are regularly arranged to form a direction structure array, so that the square pattern is formed.

In the application, a special monitoring pattern can be formed on the surface of the wafer only by improving the exposed mask plate, namely the Hole pattern, and whether the imaging plane of the lens of the photoetching machine is abnormal or not is regularly monitored by combining a method for finally observing whether the Hole (Hole Void) defects (higher sensitivity to the size of a CD) of defect scanning have specific distribution or not, and the method is used as an auxiliary means of the traditional FOCAL method.

Therefore, the method is simpler, and can be used for online detection at any time without being carried out when a machine is Periodically Maintained (PM). The improvements can increase the frequency of monitoring, further increase production efficiency, and find problems at the wafer production level to increase device yield.

After exposure, the opening pattern is formed in the photoresist layer, as shown in fig. 2 b.

In step 3, the bottom anti-reflective coating and the first material layer are etched using the photoresist layer as a mask to form the opening, as shown in fig. 2 c.

The dry etching is selected for the purpose in this step, and CF may be selected for the dry etching₄、CHF₃In addition, N is added₂、CO₂、O₂As an etching atmosphere, wherein the gas flow rate is CF₄10-200sccm，CHF₃10-200sccm，N₂Or CO₂Or O₂10-400sccm, the etching pressure is 30-150mTorr, and the etching time is 5-120s, preferably 5-60s, more preferably 5-30 s.

Optionally, after forming the opening, the method further includes a step of removing the mask layer.

Preferably, an oxidation method or an ashing method is selected to remove the photoresist layer and the bottom anti-reflection layer.

In step 4, a second material layer 205 is deposited, wherein the second material layer may be any material layer.

For better illustration in this embodiment, the second material layer is a metal material layer, such as metal W.

The second material layer 205 may be formed by Low Pressure Chemical Vapor Deposition (LPCVD), Plasma Enhanced Chemical Vapor Deposition (PECVD), electrochemical plating, Metal Organic Chemical Vapor Deposition (MOCVD), Atomic Layer Deposition (ALD), or other advanced deposition techniques.

At problematic locations in the imaging plane (image plane), the process window (window) is reduced due to the reduced critical dimension CD, resulting in a W hole defect (void defect), as shown in fig. 2 d.

In step 5, the second material layer is planarized to the surface of the first material layer to expose the hole pattern, i.e. to expose the top of the hole pattern, thereby forming a hole or an opening, as shown in fig. 2 e.

The holes obtained by the method are distributed in the middle, the left side and the right side of the surface of the wafer.

And executing a second step, and carrying out defect scanning on the hole pattern to obtain a defect image.

Specifically, before the defect scanning, the hole pattern when the imaging plane is normal is scanned to determine whether a defect exists in the mask when the hole pattern is formed and to eliminate the influence of the mask.

For example, it is first confirmed that, when an imaging plane (image plane) is normal, a pattern (map) obtained by a designed mask (mask) has no special phenomenon, so as to avoid the influence caused by the distribution of the mask critical dimension (mask CD).

And carrying out defect scanning on the hole pattern on the premise of determining that the mask has no influence on the scanning structure so as to obtain a defect image.

And step three, analyzing the defect image to judge whether the defect image is abnormal or not so as to regularly monitor whether the imaging plane of the lens of the photoetching machine is abnormal or not.

In this step, if the image plane (image plane) of the lithography machine is tilted in the following regular monitoring process, CD of the left and right holes (hole) will be reduced due to defocus (defocus), and after the metal W CMP, such reduction on CD will be amplified by the hole defect (void defect), so as to form a defect image (defect map) with a suddenly increased number of left side defects (defect) that will brighten (shot), and it is able to find problems in time at the initial stage of the tilt of the image plane (image plane), thereby avoiding the loss of a large amount of product yield after the problems are serious.

Whereas in case of problems of etching (Etch) and W deposition no special image appears, so that abnormality occurs in the image plane whenever the number of defect points appearing in one side region in the defect image is abruptly increased, for example, a bright defect point appears.

Performing step four, wherein the method further comprises: and carrying out FOCAL image quality detection on the wafer to determine the deviation angle of the imaging plane. The imaging plane is adjusted.

In particular, the detection method can realize online detection, which is an auxiliary method of FOCAL, and when the imaging plane has a problem, a conventional FOCAL imaging method needs to be executed to obtain more image quality details so as to determine the deviation angle of the imaging plane.

For example, a specific FOCAL Mask is placed on a Mask (Mask) for exposure, then a signal of the Mask is collected by an Alignment (Alignment) system of a lithography machine, and an imaging plan is obtained through simulation to monitor whether a lens and other related imaging devices are normal.

After determining the angle at which the imaging plane is tilted, further adjustments are made to the imaging plane.

The present invention has been illustrated by the above embodiments, but it should be understood that the above embodiments are for illustrative and descriptive purposes only and are not intended to limit the invention to the scope of the described embodiments. Furthermore, it will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, and that many variations and modifications may be made in accordance with the teachings of the present invention, which variations and modifications are within the scope of the present invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.

Claims

1. An image quality detection method of a lithography machine, the image quality detection method comprising:

planarizing the second material layer to the surface of the first material layer to expose the hole pattern;

carrying out defect scanning on the hole pattern to obtain a defect image;

2. The image quality detecting method according to claim 1, wherein the hole patterns are formed at intervals in the middle region and both side regions of the wafer, and the hole patterns are more sensitive to a change in focus.

3. The image quality detection method according to claim 1 or 2, wherein when the number of defect points appearing in one side region of the defect image increases suddenly, the imaging plane is abnormal.

4. The image quality detection method according to claim 1, wherein the first material layer includes a dielectric layer;

the second material layer includes a metal layer.

5. The image quality detection method according to claim 1, wherein the mask layer comprises a bottom anti-reflection coating and a photoresist layer which are sequentially stacked.

6. The image quality detecting method according to claim 5, wherein the method of forming the opening pattern in the mask layer comprises:

7. The image quality detection method according to claim 1 or 6, wherein before the defect scanning, the hole pattern when the imaging plane is normal is scanned to determine whether there is a defect in a mask when the hole pattern is formed and to exclude an influence of the mask.

8. The image quality detecting method according to claim 7, wherein a mask pattern is formed at intervals in the middle and both sides of the mask; the mask patterns are strip-shaped structures, and each strip-shaped structure is composed of a plurality of square patterns which are spaced from each other.

9. The image quality detection method according to claim 1, further comprising:

the imaging plane is adjusted.