JPH03181117A - Electron beam exposure system and electron beam exposing method - Google Patents

Abstract

PURPOSE:To easily detect the operation of electrostatic force by providing a means, which measures the current flowing in the high resistance layer of an electrostatic chuck part for suckling a wafer with the voltage applied between the wafer and the electrode of a substrate. CONSTITUTION:An ammeter A2 is provided between an electrode 4 and a power source V as the means for measuring the current which flows in the high resistance layer 6 being the voltage application layer 6 of a chuck part 7 in the case where voltage V is applied to the electrostatic chuck part 7. The current flowing in the ammeter A2 is normally a little since the layer 6 is high resistance, so the discrimination from the case where the wire is down is difficult. But the displacement current, which is the current immediately after voltage application and flows to the part forming the capacitor of the chuck part 7, ksi flows to some degree, however in case that the wire is down there is no displacement current, nor flows a stationary current. Accordingly, by measuring the displacement current immediately after voltage application or the stationary current, it can be detected whether stationary current works or not from the magnitude.

Description

[Detailed Description of the Invention] [Summary] The present invention relates to an electron beam exposure apparatus and an electron beam exposure method, and the present invention relates to an electron beam exposure apparatus and an electron beam exposure method that accurately detect the degree of adhesion between a wafer and an electrostatic chuck in an electron beam exposure apparatus using an electrostatic chuck. In order to expose a wafer with a large and clear image, a base part consisting of an electrode and a high-resistance layer covering the electrode is used in the sample mounting part of an electron beam exposure system. An electrostatic chuck part that attracts the wafer by applying a voltage between the wafer placed on the upper surface and the electrode of the base part; The device is configured to include means for measuring the current flowing through the high resistance layer of the chuck portion.

[Industrial application field]

The present invention relates to an electron beam exposure apparatus and an exposure method for substrates such as wafers using an electrostatic chuck.

[Conventional technology]

In recent years, various exposure apparatuses are required to draw fine patterns on substrates such as wafers.

Therefore, it is necessary to use an electrostatic chuck method to hold a substrate such as a wafer at the highest possible level of flatness.

Electron beam exposure apparatus 1 using conventional electrostatic chuck 1
A specific example is shown in FIG. In FIG. 5, a sample mounting part 3 of an electron beam exposure apparatus l having an exposure beam irradiation means 2 is composed of a holder 8, an electrode 4 provided on the holder, and a high resistance layer 6 covering and surrounding the holder 8. After placing a wafer 5 as a substrate on the upper surface of the electrostatic chuck section 7, an appropriate voltage V is applied between the wafer 5 and the electrode 4. By doing so, positive and negative charges are generated in a high resistance layer that acts as a voltage application layer, and the wafer 5 is attracted to the upper surface of the electrostatic chuck section 7 by the attraction force, thereby holding the wafer in a flat state. It is.

Note that the voltage is applied to the wafer 5 through a suitable conductive pin 9, and the conventional electron beam exposure apparatus is provided with a Faraday cube 10 for measuring the intensity of the exposure beam. The intensity of the exposure beam was measured by making the irradiated beam strike the Faraday tube 10 and measuring the current generated at that time using an ammeter A1.

However, in such a conventional electron beam exposure apparatus, even if a voltage is applied to the electrostatic chuck, it cannot be confirmed whether the electrostatic chuck is accurately performing its adsorption function. In other words, since the electrostatic chuck part is originally an oven due to the high resistance layer interposed therebetween, even if a part of the wiring leading to the electrostatic chuck part is broken, this breakage cannot be detected from the outside. There wasn't.

In addition, in such electron beam exposure, it is necessary to accurately and clearly image an extremely fine pattern on the wafer, and therefore the focal length must be maintained accurately over the entire wafer, otherwise the resolution will deteriorate. This causes a problem that the image becomes blurred. Therefore, when a wafer is held in contact with an electrostatic chuck, its flatness, that is, its adhesion, must be as high as possible.

In other words, it is desirable that there be as little space as possible between the wafer and the upper surface of the electrostatic chuck section.

However, in conventional devices, it has not been possible to determine whether flatness or adhesion is maintained at a high level simply by applying a voltage to the electrostatic chuck section.

In reality, it is only when the flatness of the wafer is measured and the flatness of the wafer is not corrected that one can know that the wafer is not being attracted.Alternatively, even if the voltage is applied correctly, the flatness of the wafer is due to dust. There is also the problem that it takes time to judge when the degree correction cannot be done correctly.

That is, in the conventional electron beam exposure apparatus, there has been a problem in that it is not possible to quickly determine whether voltage is being applied correctly to the electrostatic chuck or whether the attraction force is working.

[Problem to be solved by the invention]

The purpose of the present invention is to improve the above-mentioned drawbacks of the prior art, and to easily check whether the correct voltage is applied to the electrostatic chuck, the suction force is working properly, and the flatness, that is, the adhesion is corrected. An electron beam exposure apparatus and an exposure method capable of detecting the degree of adhesion between the wafer and the electrostatic chuck and adjusting the degree of adhesion between the wafer and the electrostatic chuck; The present invention aims to provide an exposure apparatus that can measure the beam intensity even during exposure and adjust the beam intensity to an appropriate value.

[Means to solve the problem]

The electron beam exposure apparatus according to the present invention employs the following technical configuration in order to achieve the above-mentioned object. That is, in the sample mounting part of an electron beam exposure apparatus, a base part consisting of an electrode and a high-resistance layer covering the electrode, a wafer placed on the upper surface of the base part, and an electrode of the base part are connected. An electrostatic chuck section configured to attract the wafer by applying a voltage therebetween, and means for measuring a current flowing through the high resistance layer of the electrostatic chuck section when voltage is applied to the electrostatic chuck section. The electron beam exposure apparatus is equipped with an electron beam exposure device, and the sample mounting section has a base section composed of an electrode and a high resistance layer covering the electrode, and the sample mounting section is placed on the upper surface of the base section. In an electron beam exposure apparatus including an electrostatic chuck part that applies a voltage between a wafer and an electrode of the base part to attract the wafer, the voltage value applied to the high resistance layer This is an electron beam exposure method in which an exposure operation is performed after measuring the degree of adhesion between the electrostatic chuck part and the wafer from the current value flowing therein.

Furthermore, in the electron beam exposure apparatus of the present invention, the electrostatic chuck section of the wafer is determined based on the voltage value applied to the high resistance layer and the current value flowing through the high resistance layer when voltage is applied to the electrostatic chuck section. The method may include means for determining the degree of adhesion and adjusting the degree of adhesion based on the degree of adhesion to obtain appropriate adhesion, and further includes means for measuring the current flowing on the wafer when the beam is irradiated onto the wafer. It may be provided.

[For production]

In the present invention, by measuring the current flowing through the electrostatic chuck and, in some cases, the displacement current, it is possible to measure whether a predetermined voltage is properly applied to the electrostatic chuck and attracting the wafer, and also to determine whether the applied voltage value and the displacement current are measured. The flatness, that is, the degree of adhesion between the Ueno and the electrostatic chuck is determined from the current value or the displacement current value, and if necessary, the applied voltage can be adjusted to ensure the desired adhesion. In addition, the intensity of the electron beam can be measured by measuring the current flowing through the wafer while the beam is being exposed. It is possible to immediately measure the intensity of the beam, that is, to adjust the beam intensity.

〔Example〕

A first specific example of the electron beam exposure apparatus according to the present invention will be described below.
This will be explained based on FIGS. 4 to 4.

FIG. 1 is a diagram explaining the principle of an electron beam exposure apparatus according to the present invention, and the basic configuration is the same as that of the conventional exposure apparatus shown in FIG. Therefore, the same members as in FIG. 5 are given the same reference numerals as in FIG. 5, and their individual explanations will be omitted. Therefore, one of the features of the present invention is that the electrostatic chuck not only provides information on whether the wafer is properly held on the electrostatic chuck, but also
The purpose of this is to obtain information on the state in which the electrostatic chuck part 7 is being attracted and to make appropriate adjustments based on that information.
A means for measuring the current (1) flowing through the high resistance layer 6, which is the voltage application layer, is provided, and specifically, an ammeter A2 is provided between the electrode 4 of the electrostatic chuck section and the power source V. It is. When a voltage is applied between the wafer 5 and the electrode 4 in the electrostatic chuck section, a current I flows in the direction of the arrow shown in FIG. 1, and this is measured. Such current may be a displacement current.

The current 11 flowing through the electrostatic chuck section varies depending on the material of the high resistance layer of the electrostatic chuck section.

That is, when using a material with relatively low resistivity, such as SnO□, when a voltage is applied to the electrostatic chuck, a current as shown in graph A in FIG. 2 flows, making it easy to measure.
Even if the circuit is disconnected, it can be easily determined. On the other hand, when a material with relatively high resistivity, such as AI2203, is used, even if a voltage is applied, the current flowing through the electrostatic chuck section is small as shown in graph B of FIG. When the displacement current is measured when the wire is disconnected, the result is as shown in graph C in FIG.

A method for detecting whether a voltage is correctly applied to the electrostatic chuck section due to the difference in materials and whether or not electrostatic force is acting on the wafer will be described in detail.

First, consider the case where 5n02 is used as the material of the high resistance layer 6. The resistivity of the SnO2 is about 10''ΩCm, the thickness of the high resistance layer is 300μm, and when a voltage of IKV is applied to the electrostatic chuck when trying to pick up a 4 inch φ wafer, the current meter As mentioned above, the current flowing through A2 is as shown in graph A in Figure 2, and a steady current of about 10-7 to IP9A (about 100 nA) flows except immediately after voltage application.Therefore, this level of current can be easily measured. If wire breakage occurs (graph C in Figure 2)
) can be easily identified.

On the other hand, when A1□03 is used as the material of the high resistance layer 6,
The resistivity of A A' 203 is as high as 1015 Ωam or more, and the current flowing through ammeter A2 under the same conditions as above is the second
Graph B in the figure shows that the current at steady state is approximately 10-”A.
(approximately 1 nA or less). Therefore, in this state, it is difficult to distinguish the difference from the case where the wire is disconnected. However, the current immediately after voltage application is a displacement current that flows through the portion of the electrostatic chuck that forms the capacitor, and a certain amount of current flows.

On the other hand, if the wire is broken in the middle, the displacement current flowing through the part forming the capacitor of the electrostatic chuck part does not work, so there is almost no displacement current and the steady current is almost zero even immediately after voltage application.

Therefore, it is possible to measure the displacement current or steady current after applying a voltage, and to detect whether an electrostatic force is acting on the wafer based on the magnitude of the displacement current or steady current.

Next, in the present invention, the adhesion between the wafer and the electrostatic chuck part is measured and adjusted so that appropriate adhesion is obtained. An example of a specific means for achieving this is shown below. Explain.

FIG. 3(a) shows a case where the adhesion between the wafer 5 and the electrostatic chuck section 7 is poor, and FIG. 3(b) shows a case where the adhesion is good. In other words, in the figure above, when a suitable voltage V is applied, the flatness is poor and there are many gaps and spaces P between the two, and when the adhesion is low, the contact area between the two is small, so the current flowing to the ammeter A2 is small. When the adhesion is high as shown in FIG. 3(b), the contact area between the two becomes large, so the current flow becomes large. This relationship is shown in the graph in Figure 3C, where the vertical axis represents the current flowing through the ammeter A2 and the horizontal axis represents the applied voltage V when the material of the high resistance layer is SnO□. It shows. In the figure, graph D shows the case where the adhesion is good, and graph E shows the case where the adhesion is poor.

Therefore, we have collected a large amount of data showing this relationship in advance, and when a certain material is used, the current is I when the applied voltage Va is
If it is determined that the adhesion is good if the current is a (nA) or more, then it is possible to estimate and judge whether the adhesion is good or bad by measuring the current value with respect to the applied voltage.

At the same time, it is also possible to determine the current level of adhesion and how much voltage must be applied to adjust it.

Specifically, for example, if it is determined that the adhesion of the wafer will be less than a predetermined value when the applied voltage and the flowing current are lowered, then in the case of Figure 3, the applied voltage V can be changed to a change value (Graph F in Figure 3).
You can compare it with At this time, if the wafer has good adhesion, the applied voltage vb may be sufficient, and if the wafer has poor adhesion, the applied voltage Vc may be applied.
It turns out that it is best to adjust it accordingly. If the relationship between applied voltage and current to achieve a constant adhesion is nonlinear, data may be acquired in advance.

When A n 03 is used as the material, since almost no current flows, the same determination can be made by using the value of the displacement current or the peak value of the displacement current.

Next, other specific examples of the present invention will be explained.

FIG. 4 shows another specific example of the electron beam exposure device according to the present invention, and the difference from the specific example in FIG. An ammeter A3 is provided between the voltage V and the voltage V. The ammeter A3 is provided to measure the strength of the electron beam current from the difference between the current flowing through the electrostatic chuck section when a voltage is applied to the electrostatic chuck section and when the wafer is irradiated with the electron beam. It is something that can be done. Conventionally, as mentioned above, the intensity of the electron beam irradiated onto the wafer can be determined by installing a Faraday tube 10 or the like, in which the beam is intentionally deflected and irradiated, and the current at that time is measured by an ammeter A.

However, it was not economical because the installation of the Faraday tube 10 and the ammeter A1 increased the area of the device and required an additional device and program to deflect the beam. Ta.

In this embodiment of the present invention, a Faraday tube is not provided, and the ammeter A3 is simply placed between the conduction pin 9 and the power supply voltage V, so that the electron beam current increases while the wafer is being irradiated. It is possible to measure the

In other words, in this embodiment of the present invention, during the actual irradiation of a regular image onto the wafer or during the irradiation of a test beam onto the wafer before irradiation (at this time, the electrostatic chuck is already at an appropriate voltage). (assuming that the adhesion between the wafer and the electrostatic chuck is appropriate) Measure the current values of ammeters A2 and A3, and calculate the difference between the current values (
A3-A2) determines the current value caused by the electron beam.

The beam intensity can be adjusted by comparing the current value with a separately prepared data table or table showing the relationship between the type of wafer and the beam intensity and feeding it back to the irradiation beam generation control means (not shown). Another specific example of the present invention is shown in FIG.

In this specific example, the electrode 4 is divided into two, the first electrode 4
A and the second electrode 4B, and a voltage is applied as shown between the picture electrodes 4A and 4B, and at this time, the current flowing through the high resistance layer of the electrostatic chuck part is measured. It is. In the present invention, as explained above, using the above-mentioned electron beam exposure apparatus, it is confirmed that the wafer is properly electrostatically attracted by the electrostatic chuck, and that the adhesion between the two is sufficiently appropriate. If necessary, it is possible to form a highly accurate pattern by making adjustments and then writing formal pattern data on the wafer using an electron beam. Further, depending on the case, the above exposure method can be executed after adjusting the beam intensity. For example, if the adhesion of the wafer varies by 50 μm, a pattern width of 0.5 μm or less cannot be formed over the entire surface of the wafer. However, if the adhesion of the wafer is 5 μm or less, a pattern of about 0.1 to 0.3 μm can be formed on the entire surface of the wafer.

〔effect〕

As explained above, according to the present invention, it is possible to easily determine whether the electrostatic chuck is attracting a wafer or whether the wafer adhesion has been corrected. It is possible to manufacture precision ICs.

[Brief explanation of drawings]

FIG. 1 is a diagram explaining the principle of the present invention. FIG. 2 is a diagram showing current characteristics in the present invention. FIG. 3(a) is a diagram showing an example where the adhesion between the electrostatic chuck and the wafer is poor. FIG. 3(b) is a diagram showing an example in which the adhesion is similarly good. FIG. 3(C) is a diagram showing the relationship between the current flowing through the electrostatic chuck and the adhesion. FIG. 4 is a diagram showing another specific example of the present invention. FIG. 5 is a diagram showing an example of a conventional electron beam exposure apparatus. FIG. 6 is a diagram showing another specific example of the present invention. 1... Electron beam exposure device, 2... Electron beam radiator, 3... Sample mounting table, 4
...electrode, 5.wafer substrate, 6.
...High resistance layer, 7...Electrostatic chuck, 8
...Holder, 9...Conductivity bottle, 10
...Faraday Katsubu.

Claims (1)

[Scope of Claims] 1. A base part consisting of an electrode and a high-resistance layer covering the electrode, and a wafer placed on the upper surface of the base part in a sample mounting part of an electron beam exposure apparatus. An electrostatic chuck part that attracts the wafer by applying a voltage between it and an electrode of the base part, and a high resistance layer of the electrostatic chuck part when voltage is applied to the electrostatic chuck part. An electron beam exposure apparatus characterized by comprising: means for measuring current. 2. Means is provided for determining the degree of adhesion of the wafer to the electrostatic chuck section from the voltage value applied to the high resistance layer and the current value flowing through the high resistance layer when voltage is applied to the electrostatic chuck section. 2. The electron beam exposure apparatus according to claim 1, wherein: 3. The electron beam exposure apparatus according to claim 1 or 2, further comprising means for measuring the current flowing on the wafer when the beam is irradiated onto the wafer. 4. The sample mounting part has a base part composed of an electrode and a high resistance layer covering the electrode, and a space between the wafer placed on the upper surface of the base part and the electrode of the base part. In an electron beam exposure apparatus that includes an electrostatic chuck section that attracts the wafer by applying a voltage to the high-resistance layer, the electrostatic An electron beam exposure method characterized by performing an exposure operation after measuring the degree of adhesion between a chuck part and a wafer. 5. The electron beam exposure method according to claim 4, wherein the intensity of the electron beam is adjusted by measuring the current value flowing on the wafer during electron beam exposure and calculating the intensity of the electron beam. 6. In the sample mounting part of the electron beam exposure apparatus, a base part consisting of first and second electrodes and a high resistance layer covering the first and second electrodes, and a top surface of the base part. an electrostatic chuck section having a wafer to be placed thereon and attracting the wafer by applying a voltage between the first electrode and the second electrode; Means for measuring the current flowing through the high resistance layer of the electrostatic chuck section when a voltage is applied between the electrodes is provided, and the voltage value and the first electrode and the second electrode are measured.
An electron beam exposure method characterized in that an exposure operation is performed after measuring the degree of adhesion between the electrostatic chuck part and the wafer based on the value of the current flowing between the electrodes. 7. In the sample mounting part of an electron beam exposure apparatus, a base part consisting of first and second electrodes and a high resistance layer covering the first and second electrodes, and a top surface of the base part an electrostatic chuck section having a wafer to be placed thereon and attracting the wafer by applying a voltage between the first electrode and the second electrode; An electron beam exposure apparatus comprising means for measuring a current flowing through the high resistance layer of the electrostatic chuck section when a voltage is applied between the electrodes.