阅读说明：本技术 图形关键尺寸的量测方法 (Method for measuring critical dimension of graph ) 是由 栾会倩 吴长明 姚振海 金乐群 姜冒泉 于 2020-12-14 设计创作，主要内容包括：本申请公开了一种图形关键尺寸的量测方法,涉及半导体制造领域。该图形关键尺寸的量测方法包括利用曝光机对晶圆上的各个曝光单元进行曝光,所述晶圆被曝光后各个曝光单元上形成的特定图形不相同；利用套刻量测机台量测各个曝光单元上形成的特定图形的关键尺寸；在利用套刻量测机台量测各个曝光单元上形成的特定图形的关键尺寸时,针对各个曝光单元建立不同的参照图形；解决了目前曝光单元上特定图形差异较大时,套刻量测机台采用一个参照图形量测全部曝光单元容易出现报错的问题；达到了避免套刻量测机台量测失败,提高关键尺寸的量测稳定性的效果。(The application discloses a measuring method of a graph key dimension, and relates to the field of semiconductor manufacturing. The measuring method of the critical dimension of the graph comprises the following steps that an exposure machine is used for exposing each exposure unit on a wafer, and specific graphs formed on each exposure unit after the wafer is exposed are different; measuring the critical dimension of the specific pattern formed on each exposure unit by using an alignment measuring machine; when the critical dimension of a specific pattern formed on each exposure unit is measured by using an alignment measuring machine, different reference patterns are established for each exposure unit; the problem that when the difference of specific patterns on the exposure units is large at present, the alignment measuring machine adopts a reference pattern to measure all the exposure units and error reporting is easy to occur is solved; the effect of avoiding the measuring failure of the overlay measuring machine and improving the measuring stability of the key dimension is achieved.)

1. A method for measuring a critical dimension of a pattern, the method comprising:

exposing each exposure unit on the wafer by using an exposure machine, wherein specific patterns formed on each exposure unit are different after the wafer is exposed;

measuring the critical dimension of the specific pattern formed on each exposure unit by using an alignment measuring machine;

when the critical dimension of the specific pattern formed on each exposure unit is measured by using the overlay measuring machine, different reference patterns are established for each exposure unit.

2. The method of claim 1, wherein measuring the critical dimension of the specific pattern formed on each exposure unit using an overlay metrology tool comprises:

establishing different reference patterns for different exposure units, wherein the measurement parameters of the overlay measuring machine are set according to the corresponding focal length of each exposure unit;

and the overlay measuring machine station refers to the reference pattern corresponding to each exposure unit and respectively measures the key size of the specific pattern on each exposure unit.

3. The method of claim 2, wherein the metrology parameters of the overlay metrology tool include focus and contrast.

4. The method of any of claims 1 to 3, wherein the reference pattern for each shot corresponds one-to-one to a particular pattern on each exposure unit.

5. The method of claim 1, wherein when the focal lengths of the exposure units on the wafer are different, the method further comprises:

and monitoring the focal length change of the exposure machine according to the key size measured by the overlay measuring machine.

Technical Field

The application relates to the field of semiconductor manufacturing, in particular to a method for measuring a critical dimension of a graph.

Background

Integrated circuit fabrication mainly involves lithography, etching, deposition, thin film, CMP, etc. Among them, photolithography is a key process for pattern formation. In the photolithography process, the main steps of pattern formation are resist coating, exposure, and development, each of which is important. The machines used in the photolithography process are mainly a photoresist developer (i.e., Track) and an Exposure machine (i.e., Exposure Tool).

The stability of the focal length is an important parameter of the exposure machine and also a parameter that needs to be monitored daily. At present, one method for monitoring the focal length stability is to measure the critical dimensions of patterns close to the resolution limit of an exposure machine under different focal length conditions by using an overlay metrology tool (OVL) on the basis of the principle that the Critical Dimensions (CD) have significant differences under different focal length conditions, and perform data fitting, thereby achieving the purpose of monitoring the focal length change.

However, since the patterns have not only the difference of the critical dimension but also the contrast of the edge under different focal lengths, and the OVL tool cannot measure the patterns with a large difference between different exposure units (shots), which results in frequent error reporting.

Disclosure of Invention

In order to solve the problems in the related art, the present application provides a method for measuring a critical dimension of a pattern. The technical scheme is as follows:

in one aspect, an embodiment of the present application provides a method for measuring a critical dimension of a pattern, where the method includes:

exposing each exposure unit on the wafer by using an exposure machine, wherein specific patterns formed on each exposure unit are different after the wafer is exposed;

measuring the critical dimension of the specific pattern formed on each exposure unit by using an alignment measuring machine;

when the critical dimension of the specific pattern formed on each exposure unit is measured by using the overlay measuring machine, different reference patterns are established for each exposure unit.

Optionally, the measuring the critical dimension of the specific pattern formed on each exposure unit by using an overlay metrology tool includes:

establishing different reference patterns for different exposure units, wherein the measurement parameters of the overlay measuring machine are set according to the corresponding focal length of each exposure unit;

and the overlay measuring machine station refers to the reference pattern corresponding to each exposure unit and respectively measures the key size of the specific pattern on each exposure unit.

Optionally, the measurement parameters of the overlay measuring machine include a focal length and a contrast.

Optionally, the reference pattern corresponding to each shot corresponds to a specific pattern on each exposure unit one to one.

Optionally, when the focal lengths corresponding to the exposure units on the wafer are different, the method further includes:

and monitoring the focal length change of the exposure machine according to the key size measured by the overlay measuring machine.

The technical scheme at least comprises the following advantages:

exposing each shot on a wafer by using an exposure machine, wherein specific patterns formed on each shot after the wafer is exposed are different, establishing different reference patterns aiming at each shot, and measuring the key size of the specific pattern formed on each shot by using an overlay measuring machine; the problem that when the difference of specific patterns on the shots is large at present, all shots are measured by an OVL machine table by adopting one reference pattern, so that errors are easily reported is solved; the effect of avoiding the measurement failure of the OVL machine and improving the measurement stability of the key dimension is achieved.

Drawings

In order to more clearly illustrate the detailed description of the present application or the technical solutions in the prior art, the drawings needed to be used in the detailed description of the present application or the prior art description will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative efforts.

FIG. 1 is a flowchart illustrating a method for measuring a critical dimension of a pattern according to an embodiment of the present disclosure;

fig. 2 is a schematic diagram of an exposure unit shot on a wafer.

Detailed Description

The technical solutions in the present application will be described clearly and completely with reference to the accompanying drawings, and it is obvious that the described embodiments are some, but not all embodiments of the present application. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

In the description of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and simplicity of description, and do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present application. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

In the description of the present application, it is to be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; the connection can be mechanical connection or electrical connection; the two elements may be directly connected or indirectly connected through an intermediate medium, or may be communicated with each other inside the two elements, or may be wirelessly connected or wired connected. The specific meaning of the above terms in the present application can be understood in a specific case by those of ordinary skill in the art.

In addition, the technical features mentioned in the different embodiments of the present application described below may be combined with each other as long as they do not conflict with each other.

Referring to fig. 1, a flowchart of a method for measuring a critical dimension of a pattern according to an embodiment of the present application is shown, the method at least includes the following steps:

step 101, exposing each exposure unit on the wafer by using an exposure machine, wherein specific patterns formed on each exposure unit are different after the wafer is exposed.

The pattern to be measured, which is specially designed and can be recognized and measured by the measuring machine, formed on the exposure unit (shot) of the wafer is a specific pattern.

When the difference of the specific pattern on the shot of the wafer is large, if an overlay metrology (OVL) machine is used to measure a Critical Dimension (CD) of the specific pattern, a single reference pattern is still established, and the OVL machine considers that the specific pattern to be measured is not found, so that the measurement cannot be performed.

The reference pattern is used for enabling the OVL machine to confirm the shape and the characteristics of the specific pattern to be measured. Typically, the reference pattern is selected from a particular pattern on the shot.

Step 102, measuring the feature size of the specific pattern formed on each exposure unit by using an overlay measuring machine.

When the critical dimension of the specific pattern formed on each exposure unit is measured by using an overlay metrology tool, different reference patterns are established for each exposure unit.

Because the feature patterns on the shots on the wafer are different, the problem that the OVL machine cannot report errors can occur when the same reference pattern is adopted for CD measurement, therefore, different reference patterns are respectively established for the shots, and a specific pattern on each shot corresponds to one reference pattern.

After a reference graph is established for each shot needing to measure the CD of the specific graph, the OVL machine station measures the CD of the specific graph on the shot according to the reference graph corresponding to each shot.

In summary, according to the method for measuring the critical dimension of the graph provided by the embodiment of the present application, each shot on a wafer is exposed by using an exposure machine, specific graphs formed on each shot after the wafer is exposed are different, different reference graphs are established for each shot, and the critical dimension of the specific graph formed on each shot is measured by using an overlay measurement machine; the problem that when the difference of specific patterns on the shots is large at present, all shots are measured by an OVL machine table by adopting one reference pattern, so that errors are easily reported is solved; the effect of avoiding the measurement failure of the OVL machine and improving the measurement stability of the key dimension is achieved.

When it is necessary to monitor the focus stability of the exposure machine, as shown in fig. 2, different focal lengths are usually set for different shots on the wafer 21, such as: shot22 set the focal length to-0.8 and shot23 set the focal length to 0.3. The exposure machine exposes each shot according to the focal length set by each shot, a specific graph is formed on each shot, and then the OVL machine measures the key dimension of the specific graph on each shot. Another embodiment of the present application further provides a method for measuring a critical dimension of a pattern, which at least includes the following steps:

step 201, using an exposure machine to expose each exposure unit on the wafer, where the focal lengths corresponding to each exposure unit on the wafer are different, and the specific patterns formed on each exposure unit after the wafer is exposed are different.

When exposure is carried out, the specific graph patterns corresponding to the shots on the mask plate are the same, but the specific graphs formed on the shots on the wafer after exposure are different due to different focal lengths for exposure, namely the critical dimension CD is different, and the contrast is different.

Step 202, establishing different reference patterns for different exposure units, and setting measurement parameters of the overlay measurement machine according to the corresponding focal lengths of the exposure units.

Because the difference of specific patterns on each shot is large, in order to avoid measurement errors, measurement parameters of an alignment measurement machine are set according to different shot focal lengths, and the measurement parameters of the alignment measurement machine comprise focal lengths and contrast.

In order to avoid measurement errors, a respective reference graph needs to be established for each shot, and the reference graphs corresponding to the shots are different due to the fact that the specific graphs on the shots are different.

In step 203, the overlay metrology tool references the reference pattern corresponding to each exposure unit to measure the critical dimension of the specific pattern on each exposure unit.

And the reference patterns corresponding to the shots correspond to the specific patterns on the exposure units one by one.

Such as: 5 shots need to be measured: a. b, c, d and e, establishing a reference graph 1 for shot a, a reference graph 2 for shot b, a reference graph 3 for shot c, a reference graph 4 for shot d and a reference graph 5 for shot e, and measuring the shot a, the shot b, the shot c, the shot d and the shot e by referring to the reference graph 1, the reference graph 2, the reference graph 3 and the reference graph 4 by an OVL machine table when measuring the specific graph, and measuring the shot d, the shot by referring to the reference graph 5.

Step 204, monitoring the focus variation of the exposure machine according to the critical dimension measured by the overlay measuring machine.

The overlay measuring machine can measure the key size of the specific graph under different focal lengths, and perform data fitting, so that the effect of monitoring the focal length change of the exposure machine can be realized.

It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications of this invention are intended to be covered by the scope of the invention as expressed herein.