Apparatus and method for processing sample, and charged particle radiation apparatus

In order to prevent a sample from thermally expanding and contracting when the sample is placed on a sample stage inside a vacuum chamber, the related art has proposed a coping method of awaiting observation by setting a standby time from when the wafer is conveyed into the vacuum chamber until the wafer and the sample table are brought into thermal equilibrium. In addition, the coping method is configured so as to await the observation until the wafer is cooled down to room temperature when the wafer is heated in the previous step. Consequently, throughput of an apparatus decreases. A temperature control mechanism which can control temperature of the sample is installed inside a mini-environment device. The sample temperature control mechanism controls the temperature of the sample inside the mini-environment device so as to become a setting temperature which is set in view of a lowered temperature of the sample inside a load lock chamber.

TECHNICAL FIELD

The present invention relates to an apparatus for processing a sample, and for example, the present invention is applicable to an apparatus and a charged particle radiation apparatus which have a sample temperature control mechanism.

BACKGROUND ART

As semiconductor devices have recently been miniaturized, not only manufacturing apparatuses but also inspection or evaluation apparatuses need to be more precise corresponding to the miniaturization. A measurement apparatus for evaluating whether or not shapes and dimensions of a pattern formed on a semiconductor wafer are correct includes a scanning electron microscope provided with a length measurement function (hereinafter, referred to as a critical dimension-scanning electron microscope (CD-SEM) or a length measurement scanning electron microscope (SEM) in some cases).

As disclosed in PTL 1, the length measurement SEM is an apparatus which radiates an electron beam onto a wafer, performs image processing on a secondary electron signal obtained therefrom, and determines an edge of a pattern from a change in light density therein so as to derive dimensions.

In order to correspond to the miniaturization of the semiconductor devices, it is important to obtain a secondary electron image having much less noise by employing high observation magnification. Therefore, it is necessary to improve contrast by superimposing many secondary electron images on one another. A precise sub-nanometer order is required for a relative position change between an electron beam radiation position and a measurement target pattern on the wafer when an SEM image is acquired.

Here, if there is a temperature difference between the wafer serving as an observation target and a sample table of a sample stage on which the wafer is mounted in a vacuum chamber, the wafer is subjected to thermal expansion and contraction until the wafer is brought into a thermal equilibrium state. This thermal expansion and contraction causes the above-described relative position change, thereby degrading the SEM image.

In order to convey the wafer present in the atmospheric environment into the vacuum chamber, it is necessary to use a load lock chamber or the like. That is, after the wafer is conveyed to the load lock chamber at the atmospheric pressure, the inside of the load lock chamber is subjected to vacuum evacuation, and the wafer is conveyed onto the sample table inside the vacuum chamber. The vacuum evacuation of the load lock chamber is rapidly carried out. Accordingly, air temperature inside the load lock chamber is lowered due to adiabatic expansion. As a result, the wafer is cooled. If the wafer is conveyed to the sample table in this state, a temperature difference occurs between the wafer and the sample table.

In addition, even in a case where the wafer is observed immediately after the wafer is heated through a baking process in the previous step (wafer processing step), the temperature difference is likely to similarly occur between the wafer and the sample table.

In order to solve these problems, the related art has proposed a coping method of awaiting observation by setting a standby time from when the wafer is conveyed into the vacuum chamber until the wafer and the sample table are brought into thermal equilibrium. In addition, the coping method is configured so as to await the observation until the wafer is cooled down to room temperature when the wafer is heated in the previous step.

In addition, PTL 2 discloses a technique of providing a temperature control mechanism inside the load lock chamber.

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

Technical Problem

The coping method of setting a standby time before observation as described above decreases the throughput of an apparatus. In addition, according to the technique of controlling the temperature inside the load lock chamber as disclosed in PTL 2, heat transfer performance is poor. Consequently, a long time is required until the temperature of a sample (wafer) becomes a desired temperature, thereby decreasing the throughput of the apparatus.

Other aspects and novel features will become apparent from the following description and the accompanying drawings.

Solution to Problem

As means for achieving aspects disclosed in the present application, a schematic configuration of representative means will be briefly described as follows.

That is, an apparatus for processing a sample includes a temperature control mechanism installed therein which can control the temperature of a sample inside a mini-environment device.

Advantageous Effects of Invention

According to the above-described apparatus for processing a sample, throughput of an apparatus can be considerably improved.

DESCRIPTION OF EMBODIMENTS

Hereinafter, an apparatus according to an embodiment will be described in detail with reference to the drawings.

FIG. 5is a configuration diagram of the apparatus according to the embodiment. An apparatus10has a vacuum chamber9, a load lock chamber12, and a mini-environment device13. The apparatus10processes a sample on a sample table6inside the vacuum chamber9. The load lock chamber12conveys the sample into the vacuum chamber9from the atmospheric environment. The mini-environment device13forms a small clean environment inside a clean room, and conveys the sample into the load lock chamber12from a conveyance-purpose sealed container. In addition, the mini-environment device13has a temperature control mechanism TCS for the sample inside the mini-environment device13. In this manner, before the sample is observed, the sample is quickly controlled so as to have a desired temperature in the atmospheric environment which shows good heat transfer performance. Accordingly, throughput of the apparatus can be considerably improved by omitting a standby time inside the vacuum chamber9.

Preferably, a first temperature sensor8for measuring the temperature of the sample table6is accommodated in the vacuum chamber9. A second temperature sensor7for measuring the temperature of the sample inside the mini-environment device13is preferably accommodated in the mini-environment device13. In addition, it is preferable to cause the sample temperature control mechanism TCS to measure the temperature of the sample table6so as to control the temperature of the sample inside the mini-environment device13to become a setting temperature which is set in view of a lowered temperature of the sample inside the load lock chamber12. In this manner, prior to observation, various samples having different temperature are quickly controlled so as to have a desired temperature in the atmospheric environment which shows good heat transfer performance. Accordingly, throughput of the apparatus can be considerably improved by omitting a standby time inside the vacuum chamber9.

EMBODIMENT

Hereinafter, according to an embodiment, a length measurement SEM which is a charged particle radiation apparatus will be described as an example. However, without being limited thereto, the embodiment is also applicable to electron microscopes, ion microscopes, defect inspection apparatuses, or the like. In addition, the apparatus according to the embodiment is also applicable to not only the charged particle radiation apparatuses but also manufacturing apparatuses, inspection apparatuses, and evaluation apparatuses for processing a sample in vacuum. Additionally, in addition to a wafer, the sample includes those which have a pattern formed on a substrate, such as photomasks, reticles, liquid crystal display devices, and the like.

FIG. 1is an overall configuration diagram of the length measurement SEM according to the embodiment. A length measurement SEM100has a column104, a vacuum chamber109, a load lock chamber112, and a mini-environment device113. The vacuum chamber109accommodates a sample stage106for mounting a wafer (sample)105thereon. The load lock chamber112is configured to convey the wafer105into the vacuum chamber from the atmospheric environment. The mini-environment device113is configured to form a small clean environment inside a clean room.

Next, a conveyance route before the wafer105is observed will be described. The wafer105inside a front opening unified pod (FOUP)118is conveyed to a sample table121inside the load lock chamber112by an air conveyance robot114disposed inside the mini-environment device113after a gate valve120is opened. Thereafter, the gate valve120is closed so that the inside of the load lock chamber112is subjected to vacuum evacuation. Thereafter, a gate valve110installed between the vacuum chambers109is opened, and the wafer105is placed on the sample table106on a sample stage107by a vacuum conveyance robot111.

During observation, the sample stage107is driven so as to move the wafer105to any desired position. Two-dimensional scanning is performed on the wafer105by using an electron beam102radiated from an electron gun101disposed inside the column104. A signal (secondary electron signal, reflected electron signal, or the like) generated by the incident electron beam102is captured by a detector103. Although not illustrated, an observation image is displayed on an image display device, based on the detected signal.

According to the above-described embodiment, in the present embodiment, the temperature of the sample table106can always be measured by installing a temperature sensor A (first temperature sensor)108in the sample table106. In addition, the temperature of the wafer105which is an observation target can be measured by installing a temperature sensor B (second temperature sensor)117so as to come into contact with the wafer105, in a conveyance arm116of the air conveyance robot114present inside the mini-environment device113. Furthermore, a heat exchanger119is disposed in a fan filter unit (FFU)115installed so as to maintain a clean environment inside the mini-environment device113. Accordingly, wind which is set to have any desired temperature can be blown therefrom (this is also referred to as sample temperature control mechanism).

FIG. 6is a flowchart illustrating an operation of the length measurement SEM according to the embodiment. A temperature control method in the conveyance route until the wafer (sample)105is observed will be described with reference toFIG. 6. When the wafer105inside the FOUP118is held by the conveyance arm116, a temperature (T1) of the wafer105is measured (Step S1A). Concurrently with this process, a temperature (T2) of the sample table106is also measured (Step S1B), and a temperature difference (T1-T2) between the wafer105and the sample table106is acquired (Step S2). A wind volume and a wind temperature of the FFU115are adjusted to control the temperature so that the temperature difference obtained here becomes a predetermined temperature difference (Step S3). The wafer105is conveyed into the load lock chamber112(Step S4). The subsequent processes until the observation are the same as those described above. That is, the load lock chamber112is subjected to the vacuum evacuation (Step S5), and the wafer105is conveyed to the sample table106(Step S6).

Although described above, the reason of controlling the temperature difference so as to become the predetermined temperature difference is that the wafer105is cooled due to adiabatic expansion when the inside of the load lock chamber112is subjected to the vacuum evacuation. For example, a method for obtaining the predetermined temperature difference includes the following three methods.

(1) Wafer Temperature Profile

The temperature of the wafer105to be cooled inside the load lock chamber112is measured in advance using a thermometer-incorporated wafer. The wafer has a function incorporated therein for storing the temperature in a time-series manner. The temperature can be measured by examining stored content after the wafer is unloaded from the apparatus.

(2) Sample Table Temperature Change

The wafer105whose temperature is controlled to several patterns by the FFU115is placed on the sample table106. Thereafter, the temperature sensor A108observes a temperature change in the respective patterns, and the predetermined temperature difference is obtained from the pattern whose temperature change is minimized.

(3) Relative Position Change

After the wafer105whose temperature is controlled to several patterns by the FFU115is placed on the sample table106, observation is performed by skipping the standby time until the wafer105and the sample table106are brought into thermal equilibrium so as to obtain a predetermined temperature difference from a pattern in which an amount of thermal expansion and contraction of the wafer105minimizes a relative position change.

According to any one of the above-described methods, an apparatus manufacturer can obtain a predetermined temperature difference, and then can register the predetermined temperature difference in an apparatus in advance before or when the apparatus is delivered to a user.

The above-described operation of the length measurement SEM according to the present embodiment is controlled by a control unit (not illustrated).

According to the above-described configurations and processes, prior to observation, various wafers105having different temperatures are quickly controlled so as to have desired temperatures in the atmospheric environment which shows good heat transfer performance. Accordingly, the throughput of the apparatus can be considerably improved by omitting the standby time inside the vacuum chamber109. In addition, since there is no temperature difference between the wafer and the sample table, the relative position change is not caused by thermal expansion and contraction. Accordingly, it is possible to very precisely measure and inspect the pattern. Furthermore, unlike PTL 2, the temperature of the load lock chamber is not changed. Therefore, there is no problem that the temperature of the adjacent vacuum chamber may also be unintentionally changed.

Modification Example 1

FIG. 2is an overall configuration diagram of a length measurement SEM according to Modification Example 1. A configuration is adopted in which the temperature of the wafer105inside the mini-environment device113is predicted by causing a temperature sensor C (second temperature sensor)201to measure the temperature of the conveyance arm116. This configuration is advantageously adopted in terms of the contamination of the wafer105, since the temperature sensor C201does not come into contact with the wafer105. Other configurations, processes, and advantageous effects of a length measurement SEM100A are the same as those of the length measurement SEM100according to the embodiment inFIG. 1.

Modification Example 2

FIG. 3is an overall configuration diagram of a length measurement SEM according to Modification Example 2. A configuration is adopted in which the temperature of the wafer105inside the mini-environment device113is measured by a temperature sensor D (third temperature sensor)301of a non-contact type. Other configurations, processes, and advantageous effects of a length measurement SEM100B are the same as those of the length measurement SEM100according to the embodiment inFIG. 1.

Modification Example 3

FIG. 4is an overall configuration diagram of a length measurement SEM according to Modification Example 3. A configuration is adopted in which the temperature of the wafer105is controlled inside a separate temperature control chamber401which is installed inside the mini-environment device113. The heat exchanger119is not disposed inside the FFU115, and the heat exchanger119is disposed inside the temperature control chamber (sample temperature control mechanism)401which has an FFU function. According to this configuration, the temperature can be controlled in a chamber which is smaller than the mini-environment device113. Accordingly, the time required for controlling the wafer105so as to have a desired temperature is shortened. Other configurations, processes, and advantageous effects of a length measurement SEM100C are the same as those of the length measurement SEM100according to the embodiment inFIG. 1. In addition, although not illustrated, the same advantageous effect may also be obtained if the respective configurations described in Modification Example 1 inFIG. 2and Modification Example 2 inFIG. 3are applied to the configuration inFIG. 4.

Hitherto, the present invention has been described in detail with reference to the embodiment and the modification examples. However, without being limited to the above-described embodiment and modification examples, the present invention can be modified in various ways, as a matter of course.

REFERENCE SIGNS LIST