JP3123956B2 - Electrostatic suction device and electron beam lithography device using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic chucking apparatus and an electron beam lithography apparatus using the same, and more particularly, to an electrostatic chucking apparatus suitable for electrostatically holding a sample in a vacuum atmosphere and an electron device using the same. The present invention relates to a line drawing apparatus.

[0002]

2. Description of the Related Art In an apparatus using an electron beam, for example, an electron beam lithography apparatus, a sample is moved with acceleration / deceleration when writing the sample. For this reason, a function of holding the sample is required so that the sample does not shift from a predetermined position. Furthermore, a wafer that has undergone a process such as film formation has a shape that is warped to a convex or concave shape by several tens of μm. Therefore,
It is necessary to correct this warp to a flat surface in terms of drawing accuracy.

[0003] In response to this requirement, a reduction projection exposure apparatus (stepper) for performing the same pattern exposure holds a sample under atmospheric pressure, so that the sample can be corrected by vacuum suction. However, this method cannot be used in an electron beam lithography apparatus that performs lithography in a vacuum atmosphere or a scanning electron microscope (SEM) for length measurement and appearance inspection. Therefore, an electrostatic attraction device utilizing electrostatic force is used. In this electrostatic suction device, a voltage is applied between a wafer as a sample and a dielectric material forming a sample holder to generate an electric charge, thereby securing an attraction force.

However, an extremely hard insulator such as an oxide film is deposited on a silicon wafer to be adsorbed. For this reason, it is necessary to remove or destroy this insulating film to establish conduction with the wafer. Conventionally, the surface of the wafer has been damaged by using a conductive diamond needle or the like to establish conduction. Further, as described in JP-A-7-302746, there is provided a mechanism for bringing a sharp edge of a cemented carbide material into contact with a side surface of a wafer to establish conduction.

[0005]

However, simply pressing a sharp object against the side surface of the wafer causes contact resistance between the wafer and the wafer, and the leak current of the dielectric flowing through the wafer causes the wafer to be reliably removed. Cannot be at ground potential. There is a serious problem that the trajectory of an electron beam which is deflected and irradiated from an oblique direction of the wafer by an unnecessary electric field near the wafer caused by the potential of the wafer is bent.

An object of the present invention is to provide a contact resistance between a sample and a conductive jig.
It is an object of the present invention to provide an electrostatic adsorption device suitable for minimizing the potential of a sample generated by resistance and leakage current and reducing the influence of the potential on an electron beam trajectory, and an electron beam lithography apparatus using the same. is there.

[0007]

According to the present invention, according to one aspect, the dielectric material is held between a dielectric for holding the sample and the sample so as to adsorb and hold the sample on the dielectric.
And adsorbing power source for applying a voltage via a contact with the sample
And a conduction jig for connecting the sample to a ground potential.
In the electrostatic chuck, the contact resistance between the sample and the conductive jig
Power offset are provided to be applied to the voltage the conduction jig to offset the potential generated on Therefore the sample leakage current and.

[0008] In the present invention, according to another aspect, electrostatic
A means for generating a sagittal beam and a sample using the generated electron beam
To form a predetermined pattern on the sample.
Means for electrostatically adsorbing the sample.
In the electron beam lithography apparatus, the electrostatic chuck is
Is provided.

[0009]

FIG. 1 shows an embodiment of an electrostatic chuck according to the present invention. In FIG. 1, an electrode 3 is embedded in a dielectric 2 that holds a wafer 1 as a sample by suction, and the electrode 3 is connected to a DC power supply 4 for suction. The dielectric 2 is placed on a base pallet 5 having conductivity, and the base pallet 5 is grounded so that the potential becomes zero. The sharp edge of the conduction jig 7 is pressed against the side surface of the wafer 1 by using the elastic force of the adjustment spring 6.
The conduction jig 7 is connected to an offset DC power supply 8 having a polarity opposite to that of the suction DC power supply 4, so that the potential of the conduction jig 7 can be adjusted. This potential is controlled by the controller 10 based on a measurement value measured in a non-contact manner by the surface voltmeter 9 installed on the wafer 1. Here, the conduction jig 7 must be electrically insulated from the base pallet 5 by the insulating sheet 11. Also,
Since the conduction jig 7 has a potential, the cover 12 having the ground potential
Need to be covered by

The operation of the embodiment shown in FIG. 1 will be described below. The conductive jig 7 is pressed against the wafer 1 placed on the suction surface of the dielectric 2 from the side surface. At this time, the wafer 1 is fixed at the regular position by the stopper 13 around the wafer 1. Here, the switch 14 is closed and a voltage is applied to the dielectric 2 to cause the wafer 1 to be attracted to the attracting surface of the dielectric 2.

Since a leak current flows through the wafer 1, a potential is generated on the wafer 1 due to the contact resistance between the conductive jig 7 and the wafer 1. For example, if the leak current is 200 μA and the contact resistance is 5 kΩ, a potential of 1 V is generated on the wafer 1. Here, the deflection amount of the electron beam is 5 μm.
It has been experimentally confirmed that, when m is used, the generated 1 V potential causes the electron beam to be attracted to the wafer 1 and causes a shift of about 10 nm. Since this shift amount and the potential of the wafer 1 are in a proportional relationship, the potential is 50
There is no problem at 0 mV or less, but a value exceeding 0 mV affects the drawing accuracy. Therefore, the potential is measured by the surface voltmeter 9 and a reverse voltage is applied to the conduction jig 7 so that the potential decreases. That is, when a potential of 1 V is generated in the wafer 1, if the offset DC power supply 8 is adjusted to -1 V, the wafer 1 is set to 0 V (ground potential).
Can be

FIG. 2 shows another embodiment of the electrostatic suction device according to the present invention. In the figure, a conductive jig 7 having a sharp needle shape is pressed against the back surface of the wafer 1 by using the elastic force of an adjustment spring 6. Also, wafer 1
The wafer 1 is pressed from above by the holding jig 15 so that the wafer 1 does not float up. The holding jig 15 has a curved shape so that the wafer 1 is not damaged. An offset DC power supply 8 having a polarity opposite to that of the suction DC power supply 4 is connected to the conduction jig 7 so that the potential of the conduction jig 7 can be adjusted. This potential is controlled by the controller 10 based on the measured value of the ammeter 16 incorporated in the electrostatic chuck circuit, that is, the value of the leak current. Here, the potential generated on the wafer 1 is considered to be proportional to the leak current from Ohm's law, and the leak current differs depending on the state of the back surface of the wafer. Therefore, if the relationship between the leak current and the potential of the wafer 1 is determined in advance, and this potential is applied to the conduction jig as an offset, it is possible to deal with wafers having different back surfaces. The structure of the dielectric 2 and the basic operation of the present embodiment are the same as those of the embodiment of FIG.

FIG. 3 shows still another embodiment of the electrostatic suction device according to the present invention. In the figure, two plate-like electrodes 23a and 23b are embedded in a dielectric 2 that sucks and holds a wafer 1, and a positive voltage is applied to one electrode 23a and a negative voltage is applied to the other electrode 23b. Are connected to DC power supplies 24a and 24b, respectively. In one of the DC power supplies 24b, the controller 10 controls the applied voltage based on the measurement value of the surface voltmeter 9 installed on the wafer 1 in a non-contact state. This allows
The wafer 1 can be set to the ground potential without bringing the conductive jig into contact with the wafer.

FIG. 4 shows still another embodiment of the electrostatic chuck according to the present invention. In the drawing, a conductive jig 7 having a sharp needle shape is pressed against the back surface of the wafer 1 and a holding jig 15 is pressed against the front surface. An offset DC power supply 8 is connected to the conduction jig 7 so that the potential of the conduction jig 7 can be adjusted. Here, the potential of the wafer 1 is measured by the contact 25 pressed against the back surface of the wafer 1 and the voltmeter 26 connected thereto, and the potential of the conduction jig 7 is controlled. By increasing the input impedance of the voltmeter 26, a highly accurate potential measurement can be performed. In addition, since measurement during writing can be performed as compared with a surface voltmeter, generation of a wafer potential in real time can be suppressed.

FIG. 5 shows an embodiment of an electron beam lithography apparatus equipped with the electrostatic suction device of the present invention. In the figure, an electron beam 18 emitted from an electron gun 17 is formed by an aperture 19 and a lens 20 and irradiates the wafer 1, and the trajectory of the electron beam is controlled by a plate-like deflector 21. A base pallet 5 and a dielectric 2 are provided on the stage 22, and the drawing position of the wafer 1 held electrostatically on the base pallet 5 is controlled by the movement of the stage 22. Thus, a desired pattern can be formed on the wafer 1.

The conduction jig 7 attached to the base pallet 5 is connected to the offset DC power supply shown in FIG. 1 so that the potential of the wafer 1 can be reduced. As a result, the influence of the potential of the wafer 1 on the electron beam trajectory is smaller than in the conventional apparatus, and the drawing accuracy can be improved.

In the embodiment shown in FIG. 5, as the electrostatic chucking device for the wafer 1, not only the electrostatic chucking device shown in FIG. 1 but also any of the above-mentioned FIGS. May be used.

[0018]

According to the present invention, the contact between the sample and the conductive jig is achieved.
Provided are an electrostatic chucking device suitable for minimizing the potential of a sample generated by resistance and leak current and reducing the influence of the potential on an electron beam trajectory, and an electron beam writing apparatus using the same.

[Brief description of the drawings]

FIG. 1 is a schematic view of an embodiment of an electrostatic suction device according to the present invention.

FIG. 2 is a schematic view of another embodiment of the electrostatic chuck according to the present invention.

FIG. 3 is a schematic view of still another embodiment of the electrostatic chuck according to the present invention.

FIG. 4 is a schematic view of still another embodiment of the electrostatic chuck according to the present invention.

FIG. 5 is a schematic view of an embodiment of an electron beam lithography apparatus according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Wafer, 2 ... Dielectric, 3 ... Electrode, 4 ... DC power supply for adsorption, 5 ... Base pallet, 6 ... Adjusting spring, 7 ... Conducting jig, 8 ... DC power supply for offset, 9 ... Surface potential meter, 10
... Controller, 11 ... Insulation sheet, 12 ... Earth potential cover, 13 ... Stopper, 14 ... Switch, 15 ... Pressing jig, 16 ... Ammeter, 17 ... Electron gun, 18 ... Electron beam, 19 ... Aperture, 20 ... Lens , 21 ... deflection plate,
22 ... stage, 23a, 23b ... electrode, 24a, 24
b: DC power supply, 25: contact, 26: voltmeter.

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masaru Matsushima 1-280 Higashi Koigakubo, Kokubunji-shi, Tokyo Central Research Laboratory, Hitachi, Ltd. (56) References JP-A-7-211770 (JP, A) JP-A-7 -302746 (JP, A) JP-A-4-250615 (JP, A) JP-A-9-246366 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/027 B23Q 3/15 H01J 37/20 H01J 37/305

Claims (6)

(57) [Claims] And 1. A dielectric for holding a sample, an adsorption power source for applying a voltage through said dielectric between said sample to adsorb hold the sample in the dielectric tangent on the sample
A conductive jig for touching and connecting the sample to ground potential
The electrostatic chuck, the contact resistance between the sample and the conductive jig
Anti a power offset for the voltage to offset the potential generated in the leakage current depending on the sample applied to the conductive jig
An electrostatic attraction device characterized by being provided . 2. An offset power supply according to claim 1,
An electrostatic suction device , wherein a voltage having a polarity opposite to that of the power supply for suction is applied to the conduction jig . 3. The apparatus according to claim 2, further comprising means for measuring a potential of said sample, and a controller for controlling a voltage of said offset power supply based on the measured potential.
An electrostatic attraction device characterized in that the device is radiated. 4. The controller according to claim 3, wherein:
Wherein as the potential of the sample is equal to or less than ± 500 mV O
Electrostatic chuck and controlling the power supply offset. 5. The controller according to claim 2, further comprising: a means for measuring a current flowing through the sample, and a controller for controlling a voltage of the offset power supply based on the measured current.
An electrostatic attraction device characterized by having a rag. 6. A means for generating an electron beam, and means for generating the electron beam.
The sample is irradiated with an electron beam
Means for forming a turn; and electrostatic means for electrostatically adsorbing the sample.
An electron beam lithography apparatus including a suction device;
The mounting device is an electrostatic device according to any one of claims 1 to 5.
An electron beam lithography apparatus comprising an adsorption device.