Method of controlling a potential difference between a stencil mask and a substrate of semiconductor device

A method of manufacturing a semiconductor device is disclosed, which comprises setting a stencil mask above a substrate to be processed in confronting to the substrate, the stencil mask having an opening, and irradiating the substrate with charged particles through the opening of the stencil mask, while adjusting a potential difference between the stencil mask and the substrate depending on a value of a current flowing between the substrate and the stencil mask.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of the priority from the prior Japanese Patent Application No. 2002-375979, filed Dec. 26, 2002, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of manufacturing a semiconductor device using, for example, a stencil mask as a transfer mask and an apparatus for manufacturing the semiconductor device.

2. Description of the Related Art

There has been known a method in which in semiconductor device manufacturing process, a stencil mask having a predetermined pattern is set above a substrate to be processed at a predetermined distance and charged particles such as electrons or ions are projected onto the substrate through openings defining the pattern of the stencil mask. In the method, charged particles (ion beam) such as ions accelerated from a particle source by a predetermined energy pass through a scanner and a magnet to be formulated into a patterned ion beam. The patterned ion beam is projected onto the substrate through the openings formed in the stencil mask. The substrate to be processed mentioned here is a semiconductor substrate, on the surface of which a semiconductor device is to be formed or has been formed, not shown.

There is a disadvantage that, when a substrate is processed using the charged particles, residue charges are accumulated on the substrate so that the semi-conductor device formed on the substrate may be destroyed by being charged due to the accumulated charges. A conventional method is known to overcome this disadvantage (Jpn. Pat. Appln. KOKAI Publication No. 9-283411, see page 4). In this method, secondary electrons or plasma electrons are generated to neutralize the accumulated charges, thus preventing the destruction of a substrate due to the accumulated charges.

Jpn. Pat. Appln. KOKAI Publication No. 2002-203806 FIGS. 29 and 35) discloses a method of controlling the amount of charges accumulated on a substrate to be processed. In the method, a distance and a potential difference between a stencil mask and the substrate to control the amount of charges accumulated on the substrate. The controlling of the amount of charges is carried out by providing a power supply between the stencil mask and the substrate, or by providing a power supply between the stencil mask and the ground and also another power supply between the substrate and ground.

However, neutralizing the accumulated charges by generating secondary electrons or plasma electrons is sensitive to the amount of charges on the substrate and the stencil mask, the amount of energy on charged particles, degree of vacuum in the apparatus, etc., and the amount of neutralized charges greatly changes depending on these factors. As a result, with the method of neutralizing the accumulated charges by generating secondary electrons or plasma electrons, the neutralized charge amount may be insufficient or an excessive amount of electrons may be supplied to cause negative charging, which possibly destroy the semiconductor devices. Further, the charge neutralizing mechanism, which generates the secondary electrons or plasma electrons, is complicated in structure.

On the other hand, according to the method of controlling the amount of the charges accumulated on the substrate by changing a distance and a potential difference between the stencil mask and the substrate, yield is improved. However, it is necessary to set up the distance and the potential difference between the stencil and the substrate before an ion implantation process is carried out. There is no problem if the irradiation condition of the charged particles is stable and the state of the apparatus is stable during the processing. However, if the apparatus is unstable, and the irradiation amount (current amount) of the charged particles per unit time changes during the processing, the neutralized charge amount may be insufficient, or an excessive amount of electrons may be supplied to cause negative charging, which leas to a possible destruction of the semiconductor devices.

BRIEF SUMMARY OF THE INVENTION

According to an aspect of the present invention, there is provided a method of manufacturing a semiconductor device comprising:

setting a stencil mask above a substrate to be processed in confronting to the substrate, the stencil mask having an opening; and

irradiating the substrate with charged particles through the opening of the stencil mask, while adjusting a potential difference between the stencil mask and the substrate depending on a value of a current flowing between the substrate and the stencil mask.

According to another aspect of the present invention, there is provided a method of manufacturing a semiconductor device comprising:

setting a stencil mask above a substrate to be processed in confronting with the substrate, the stencil mask having an opening; and

irradiating the substrate with charged particles through the opening of the stencil mask, while adjusting a potential difference between the stencil mask and the substrate depending on a ratio between a value of a current flowing in the substrate and a value of a current flowing in the stencil mask.

According to a further aspect of the present invention, there is provided a manufacturing apparatus of a semiconductor device, comprising:

a stencil mask set above a substrate to be processed in confronting to the substrate, the stencil mask having an opening;

a particle source which irradiates the substrate to be processed with charged particles through the opening of the stencil mask;

a first power supply which is connected to the stencil mask and changes a potential of the stencil mask; and

a first ammeter connected to the substrate to be processed.

DETAILED DESCRIPTION OF THE INVENTION

FIRST EMBODIMENT

FIG. 1shows a semiconductor manufacturing apparatus according to a first embodiment of the present invention.

In a semiconductor manufacturing process, a stencil mask11having a predetermined pattern formed by openings formed in the stencil mask is set above a substrate12to be processed at a distance. Charged particles13(ion beam) such as ion accelerated by an energy pass through a scanner and a magnet are formulated into a pattern of charged particles. The patterned ion beam13is irradiated onto the substrate12through the openings formed in the stencil mask. The substrate12to be processed mentioned here is a semiconductor substrate, in which a semiconductor device is to be formed or has been formed, not shown.

The stencil mask11is connected to a power supply14which is also connected to ground. Thus, a potential of the stencil mask11can be controlled, with an outer wall of the apparatus or ground as a reference potential. The substrate12is connected to the outer wall of the apparatus or ground through an ammeter15. Thus, current flowing from the substrate can be measured by the ammeter15.

When the irradiation amount of the ion beam13is not changed in a semiconductor manufacturing process such as an ion implantation process, that is, when the quantity of the charged particles applied to the substrate12is constant, a current I1measured by the ammeter15is also constant. That is, an appropriate current value for processing condition of processing the substrate12exists and the appropriate current value is usually constant. Although most preferably, the constant value of the current I1is 0(A), it is not restricted to this value but may be other constant value than 0(A).

If electrical balance between the stencil mask11and the substrate12is get out due to factor variations of the apparatus so that the neutralizing effect is lowered, excessive positive charges may begin to be accumulated on the surface of the substrate12. The excessive positive charges accumulated on the surface of the substrate12flow to the outer wall of the apparatus so that the current I1increases. Thus, according to this embodiment, the current I1flowing to the substrate12is measured and if the current I1becomes larger than the appropriate current value for some reason during ion implantation, the positive charges which begin to be accumulated on the substrate12can be neutralized by lowering a potential of the stencil mask11by the power supply14. If the potential of the stencil mask11is lowered too much when the potential of the stencil mask11is adjusted, negative charges are then accumulated on the surface of the substrate12, and a current I2becomes smaller than an appropriate current value. The current I2is a current flowing through the power supply14. In this case, the negative charges which begin to be accumulated on the substrate12can be neutralized by increasing the potential of the stencil mask11by the power supply14.

Thus, according to this embodiment, even if the neutralizing condition changes due to an instable state of the apparatus, in the semiconductor manufacturing process using the charged particles such as ion implantation process, the potential of the stencil mask can be changed following the state of the apparatus. Consequently, the possibility that the semiconductor device may be destroyed due to the charges accumulated on the substrate is reduced, thus yield is improved.

SECOND EMBODIMENT

FIG. 2shows a semiconductor manufacturing apparatus according to a second embodiment of the present invention. Reference numerals corresponding to those used inFIG. 1are attached to the corresponding components, and description thereof is omitted.

In a semiconductor manufacturing process, a stencil mask21having a predetermined pattern formed by openings formed in the stencil mask is set above a substrate22to be processed at a distance. Charged particles23(ion beam) such as ion accelerated by an energy pass through a scanner and a magnet are formulated into a pattern of charged particles. The patterned ion beam23is irradiated onto the substrate22through the openings formed in the stencil mask. The substrate22to be processed mentioned here is a semiconductor substrate, in which a semiconductor device has been formed, not shown.

The stencil mask21is connected to a power supply24which is also is connected to ground (i.e. an outer wall of the apparatus) through an ammeter25. Thus, a potential of the stencil mask21can be controlled, with the outer wall of the apparatus or ground as a reference potential. Further, a current flowing from the stencil mask21can be measured by the ammeter25. The substrate22is connected to ground (i.e. an outer wall of the apparatus) through an ammeter26. Thus, a current flowing from the substrate can be measured by the ammeter26.

When the irradiation amount of the ion beam23is not changed in a semiconductor manufacturing process such as an ion implantation process, that is, when the quantity of the charged particles applied to the substrate22is constant, a current I1measured by the ammeter25is also constant. That is, an appropriate current value for processing condition of processing the substrate22exists and that the appropriate current value is usually constant. Although most preferably, the constant value of the current I1is 0(A), it is not restricted to this value but may be other constant value than 0(A).

However, if the irradiation amount of the ion beam23per unit time changes with time in the semiconductor manufacturing process such as an ion implantation process, the quantity of the charged particles applied to the substrate22per unit time also changes, so that the current I1measured with the ammeter26also changes. On the other hand, the ratio of the current I1flowing from the substrate22with respect to the current I2flowing from the stencil mask21, that is, a current ratio I1/I2, is constant, since the neutralizing effect is maintained if the electrical balance between a stencil mask21and the substrate22is stabilized. That is, an appropriate current ratio depending on the processing condition of processing the substrate22exists, and usually that value is constant.

If electrical balance between the stencil mask21and the substrate22is get out due to factor variations of the apparatus so that the neutralizing effect is lowered, excessive positive charges may begin to be accumulated on the surface of the substrate22. If excessive positive charges begin to be accumulated on the surface of the substrate22, the ratio of the current I1flowing from the substrate22with respect to the current I2flowing from the stencil mask21, that is, the current ratio I1/I2is increased. Then, according to this embodiment, the current ratio I1/I2is measured and if the current ratio I1/I2becomes larger than its appropriate current ratio for some reason in the ion implantation process, the positive charges which begin to be accumulated on the substrate22can be neutralized by lowering the potential of the stencil mask21through a power supply24. If the potential is lowered too much when the potential of the stencil mask21is adjusted, negative charges are accumulated on the surface of the substrate22, and the current ratio I1/I2becomes smaller than the appropriate current ratio. In this case, the negative charges which begin to be accumulated on the substrate22can be neutralized by lowering the potential of the stencil mask21by the power supply24.

Thus, according to this embodiment, even if the irradiation amount of the ion beam changes with time in the semiconductor manufacturing process using the charged particles such as an ion implantation process, yield can be improved by reducing the possibility that the semiconductor device may be destroyed due to the charges accumulated on the substrate.

THIRD EMBODIMENT

FIG. 3shows a semiconductor manufacturing apparatus according to a third embodiment of the present invention. Reference numerals corresponding to those used inFIG. 1are attached to the corresponding components, and description thereof is omitted.

In a semiconductor manufacturing process, a stencil mask31having a predetermined pattern formed by openings formed in the stencil mask is set above a substrate32to be processed at a distance. Charged particles33(ion beam) such as ion accelerated by an energy pass through a scanner and a magnet are formulated into a pattern of charged particles. The patterned ion beam33is irradiated onto the substrate32through the openings formed in the stencil mask. The substrate32to be processed mentioned here is a semiconductor substrate, in which a semiconductor device has been formed, not shown.

The stencil mask31is connected to a power supply34which is also is connected to ground (i.e. an outer wall of the apparatus) through an ammeter35. Thus, a potential of the stencil mask31can be controlled, with the outer wall of the apparatus or ground as a reference potential. Further, a current flowing from the stencil mask31can be measured by the ammeter35. The substrate32is connected to a power supply36which is also is connected to ground (i.e. an outer wall of the apparatus) through an ammeter37. Thus, a potential of the substrate32can be controlled, with the outer wall of the apparatus or ground as a reference potential. Further, a current flowing from the substrate32can be measured by the ammeter37.

When the irradiation amount of the ion beam33is not changed in a semiconductor manufacturing process such as an ion implantation process, that is, when the quantity of the charged particles applied to the substrate32is constant, a current I1measured by the ammeter35is also constant. That is, an appropriate current value for processing condition of processing the substrate32exists and the appropriate current value is usually constant. Although most preferably, the constant value of the current I1is 0(A), it is not restricted to this value but may be other constant value than 0(A).

However, if the irradiation amount of the ion beam33per unit time changes with time in the semiconductor manufacturing process such as an ion implantation process, the quantity of the charged particles applied to the substrate32per unit time also changes, so that the current I1measured with the ammeter36also changes. On the other hand, the ratio of the current I1flowing from the substrate32with respect to the current I2flowing from the stencil mask31, that is, a current ratio I1/I2is constant, since the neutralizing effect is maintained if the electrical balance between a stencil mask31and the substrate32is stabilized. That is, an appropriate current ratio depending on the processing condition of processing the substrate32exists, and usually that value is constant.

If electrical balance between the stencil mask31and the substrate32is get out due to factor variations of the apparatus so that the neutralizing effect is lowered, excessive positive charges may begin to be accumulated on the surface of the substrate32. If excessive positive charges begin to be accumulated on the surface of the substrate32, the ratio of the current I1flowing from the substrate32with respect to the current I2flowing from the stencil mask31, that is, the current ratio I1/I2is increased. Then, according to this embodiment, the current ratio I1/I2is measured and if the current ratio I1/I2becomes larger than its appropriate current ratio for some reason in the ion implantation process, the positive charges which begin to be accumulated on the substrate32can be neutralized by decreasing the potential difference between the stencil mask31and the substrate32through power supplies34,36. If the potential difference is lowered too much when the potential difference between the stencil mask31and the substrate32is adjusted, negative charges are then accumulated on the surface of the substrate32, and the current ratio I1/I2becomes smaller than the appropriate current ratio.

According to the present embodiment, the negative charges which begin to be accumulated on the substrate32can be neutralized by adjusting the power supplies34,36to thereby increase the potential difference between the stencil mask31and the substrate32. At this time, considering an influence upon the semi-conductor device, it is preferable that the power supply36connected to the substrate32is used as a supplement of the power supply34. An optimum neutralization can be attained since the potentials of the stencil mask31and the substrate32can be independently adjusted by using the power supplies34,36connected to the stencil mask31and the substrate32. Thus, according to the present embodiment also, the possibility that the semiconductor device may be destroyed due to the charges accumulated on the substrate is lowered and thus yield can be improved, even if the irradiation amount of the ion beam changes with time in the semiconductor manufacturing process using the charged particles such as ion implantation process.

As described in detail above, according to the embodiments of the present invention, the possibility that the semiconductor device may be destroyed by the charges accumulated on the substrate in the semi-conductor manufacturing process using the charged particles such as the ion implantation process can be decreased, thereby improving the yield.