JPH04137615A - Method of confirmation of continuity - Google Patents

Abstract

PURPOSE:To securely confirm wafer grounding during waiting and image drawing by insulating grounding conductive needles except selected one, applying voltage to the selected grounding conductive needle, and reading the potential of the wafer at that time with a non-contact electrometer. CONSTITUTION:Contact switches 7 of conductive needles except for that of one conductive needle to confirm continuity is switched over to terminal (a). The contact switch 7 of the selected conductive needle 1 is switched over to terminal (b) and appropriate voltage is applied from a DC voltage source 6 to the conductive needle 1. When the indication of a non-contact electrometer 4 at that time approximates to the voltage value applied from the power source 6, it is judged that the conductive needle 1 is connected to a wafer 2. After all the conductive needles 1 are examined, the contact switches 7 of the conductive needles 1 are switched over to terminal (c) and the wafer 2 is grounded. When the potential of the wafer 2 is continuously measured with the non-contact electrometer 4 during image drawing after then, changes of the potential of the wafer caused by electrification occurring when the wafer 2 lifts from the ground are detected.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention measures the potential of a wafer in a charged beam lithography system without contact, and determines whether or not the wafer and a ground conductive needle are electrically connected based on the measurement results. The present invention relates to a continuity confirmation method for determining whether

[Prior Art] In a charged beam lithography system, if a wafer is not grounded during lithography, charged particles will accumulate on the wafer. Therefore, the wafer becomes charged with the same sign as the charged particles over time.

FIG. 4 is an explanatory diagram illustrating the influence that wafer charging has on a charged beam. In the figure, 2 is a wafer, 9 is a charged beam, 13 is a switch, and 14 is a charge. In addition,
The solid line portion of the charged beam 9 indicates the actual trajectory of the charged beam when the wafer is charged, and the dotted portion indicates the ideal trajectory of the charged beam when the wafer is not charged. When the wafer is charged, as shown in FIG. 4, the trajectory of the charged beam 9 is affected by electrostatic force, causing an error in the writing position. Therefore, the wafer 2 needs to be reliably grounded by closing the switch 13.

If the wafer 2 to be imaged in a charged beam lithography apparatus is mounted on a lithography stage as it is, an insulator such as an oxide film will be provided on the surface of the wafer 2, so that wafer 2 will be lithographically drawn without being electrically grounded. For this reason, conventionally, as shown in FIG. 5, a conductive needle 1 is placed directly on the wafer 2 placed on a stage (insulator) 3 for grounding. In reality, the surface of the wafer 2 is coated with a resist, which is an insulator, so the conduction needle 1 needs to penetrate through this film and come into contact with the wafer 2. Poor contact often occurs due to resist sticking. For this reason, conventionally, as shown in FIG.
Apply a DC voltage power source for continuity checking between the continuity needles 1 by placing them upright, check the continuity between the continuity needles 1 using the continuity confirmation ammeter 10, and then connect the continuity needles 1 that are sure to have continuity to the contact switch. 8
It is switched and grounded.

[Problems to be Solved by the Invention] In the conventional technology, there are two cases: when only one of the plurality of conductive needles 1 is electrically connected to the wafer 2, and when all the conductive needles 1 are not electrically conductive. There was a problem that discrimination could not be performed. Another problem is that it is difficult to check whether or not the wafer 2 is grounded during drawing because current must be passed directly through the wafer 2.

[Means for Solving the Problems] In order to solve such problems, the continuity confirmation method according to the present invention measures the potential of the wafer without contact, and based on the measurement result, it is determined that the wafer and the grounding conductive needle are connected to each other. This method determines whether or not the That is, it is equipped with a plurality of ground conductive needles for grounding the wafer to be drawn with the R electric beam lithography system, and the ground conductive needles other than the one ground conductive needle selected to confirm the state of conduction with the wafer are provided. While setting the needles in an insulating state, voltage is applied to one selected grounding conduction needle, and the potential of the wafer at this time is read with a non-contact electrometer via a non-contact probe, thereby establishing continuity between the wafer and the grounding needle. This is a continuity confirmation method that checks continuity with the needle.

[Operation] Apply a voltage to the grounding conductive needle whose continuity you want to check, and measure the wafer potential at that time with a non-contact electrometer. The current voltage will be displayed. This makes it possible to check the conduction state with the wafer for each ground conduction needle. As a result, when the wafer potential was subsequently measured with a non-contact electrometer even after the grounding needle, which had been confirmed to have continuity with the wafer, was dropped to the ground, it was found that the wafer was floating from the ground. It is also possible to detect changes in the wafer potential due to charging, and therefore it is possible to determine whether the wafer is grounded even during writing.

[Example code] Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a configuration diagram showing an embodiment of a device to which a continuity checking method according to the present invention is applied. In the same figure, Figure 4~
Portions equivalent to those in the conventional explanatory diagram of FIG. 6 are given the same reference numerals, and their explanation will be omitted. In FIG. 1, 4 is a non-contact potentiometer (electrostatic potentiometer), 5 is a probe for a non-contact potentiometer,
6 is a DC voltage source for continuity testing, and 7 is a contact switch.

Next, the operation of the apparatus configured as above will be explained.

First, if there are a plurality of conductive needles 1, the contact switch 7 of the conductive needles other than the one conductive needle whose conductive state is to be checked is switched to the terminal a side. This means that when there are multiple conduction needles l,
This is done to insulate everything other than the continuity needle that is being tested for continuity.

Then, the contact switch 7 of the current continuity needle 1 of interest is switched to the terminal side, and an appropriate voltage (2) is applied from the continuity testing DC voltage source 6 to this continuity needle 1. When the reading VR of the non-contact electrometer 4 at this time is approximately equal to the voltage value V applied from the above-mentioned DC voltage power supply 6 for continuity, it is assumed that the continuity needle 1 of interest is electrically connected to the wafer 2. to decide. The voltage value at this time is actually slightly lower than the applied voltage value (2) due to the line resistance of the conductive needle 1. For example, when 30V is applied, the voltage drop is within 1 (2). However, in this case, it is assumed that the non-contact electrometer probe 5 is placed close to the surface of the wafer 2.

That is, as shown in FIG. 2, when a voltage is applied to the conductive needle 1 whose conductivity is to be checked and the potential of the wafer 2 at that time is measured with a non-contact electrometer 4, it is determined that the conductivity between the wafer 2 and the conductive needle 1 is confirmed. When the voltage is off, the applied voltage is displayed on the non-contact electrometer 4. This makes it possible to check the conduction state one by one. When all the conduction needles 1 have been checked in this way, the contact switch 7 of each conduction needle 1 is switched to the terminal C side and the wafer 2 is grounded.

Even during drawing after the conductive needle 1, which has been confirmed to be electrically conductive with the wafer, is dropped to the ground, the wafer 2 remains as shown in FIG.
By continuing to measure the potential of the wafer with the non-contact electrometer 4, it is possible to detect a change in the wafer potential due to charging that occurs when the wafer 2 is lifted from the ground. In this way, the grounding state of the wafer 2 can be determined even during writing.

In this way, it is possible to check the conductivity of all the conduction needles 1 during standby, and also to check the grounding state of the wafer 2 during writing.

Note that in this embodiment, a DC voltage source is used to confirm continuity, but the same effect can be obtained by using an AC voltage source.

[Effects of the Invention] As described above, according to the continuity checking method according to the present invention, the grounding of the wafer 2 can be reliably checked regardless of whether it is on standby or during writing. Therefore, this continuity checking method can be applied to a charged beam lithography apparatus such as an electron beam lithography apparatus, and there is an effect that a significant improvement in the operating rate of the apparatus and the yield of lithography can be expected.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing an embodiment of a device to which the continuity checking method according to the present invention is applied, FIGS. 2 and 3 are explanatory diagrams illustrating the operation of this continuity checking, and FIGS. 4 to 6 FIG. 2 is an explanatory diagram illustrating a conventional continuity confirmation method. 1... Conductive needle, 2... Wafer, 3... Stage (insulator), 4... Non-contact type electrometer (electrostatic potentiometer), 5... Non-contact type potential difference Measuring probe, 6...
・DC voltage source for continuity testing, 7...Contact switch, 9.
...Charged beam. Patent Applicant: Nippon Telegraph and Telephone Corporation Agent Masaki Inuyamakawa

Claims (1)

[Claims] A plurality of ground conductive needles are provided for grounding a wafer to be drawn by a charged beam lithography device, and the ground conductive needles other than one ground conductive needle selected to confirm the conductive state with the wafer are provided. While setting the wafer to an insulated state, a voltage is applied to one selected grounding conductive needle, and the potential of the wafer at this time is read with a contact electrometer via a non-contact probe, thereby connecting the wafer and the grounding conductive needle. A continuity confirmation method characterized by confirming continuity with.