Patent Application
20140091229
This application claims the benefit of Japanese Patent Application No. 2011-139965, filed Jun. 23, 2011, which is hereby incorporated by reference herein in its entirety.
The present invention relates to a charged particle beam optical system used for charged particle beam exposure equipment, such as electron beam exposure equipment or ion beam exposure equipment, which are used for exposure of a semiconductor integrated circuit, or the like. In particular, the present invention relates to an electrode for an electrostatic lens (typically, an electrode for an electrostatic objective lens).
As exposure equipment for exposing patterns in which fine patterns having a width of 0.1 micrometers or less are packed at high density, the electron beam exposure equipment is quite prospective. In particular, an electron beam exposure equipment that is capable of patterning with multiple electron beams, simultaneously, without using a photomask is quite prospective because it can support flexible production with high throughput. When the electron beam is used for patterning, however, chemical substances of a resist, or the like, at the spot irradiated by the electron beam may be scattered, and hence, it is inevitable that the resist, or the like, adheres to lenses, particularly, to an objective lens closest to a sample (object). This adhesion of the resist, or the like, causes deterioration of optical characteristics of the lens, and is apt to be an obstacle for long-term use.
In order to solve this problem, Japanese Patent No. 3166946 discloses the following electron beam exposure equipment. Specifically, this apparatus includes a conductive pi ate having an electron beam passage between the sample and an electron beam focusing objective lens or a beam deflector. With this structure, it is possible to prevent an evaporated substance of the sample, reflected electrons, and secondary electrons from entering the electron beam passage formed by the electron beam focusing objective lens and the beam deflector.
In the field of semiconductor devices, finer patterning is required, and at the same time, high resolution exposure equipment is demanded so as to realize the finer patterning. In order to respond to this demand, if the resolution of the exposure equipment is increased, the distance between the objective lens and the sample becomes smaller. In the conventional example disclosed in Japanese Patent No. 3166946, the conductive plate is disposed for preventing the evaporated substance of the sample, or the like, from entering the objective lens, as described above. When the distance between the objective lens and the sample becomes smaller, however, it may be physically difficult to dispose the conductive plate properly.
In view of the above-mentioned problem, an electrode of the present invention to be used for an electrostatic charged particle beam lens includes at least one through hole. The at least one through hole includes a first region having a first opening contour and a second region having a second opening contour to be positioned on an upstream side of a charged particle beam with respect to the first region. The first opening contour is included in the second opening contour when viewed in an optical axis direction.
According to the electrode of the present invention, the opening contour of the first region is included in the opening contour of the second region when viewed in the optical axis direction, and hence, a scattered substance, or the like, of an object is blocked by the first region so as to hardly reach the second region and a region closer to a charged particle source with respect to the second region. Therefore, it is possible to realize the electrode in which the scattered substance or the evaporated substance of the object can hardly reach the second region and a region closer to the charged particle source with respect to the second region. In addition, it is not necessary to dispose an additional shield plate, or the like, and hence, the space between the lens including the electrode and the object can be decreased.
Further features of die present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings,
An electrode of the present invention has a teal are that a through hole tor transmitting a charged particle beam is formed so that a first opening contour of the through hole on the downstream side is included in a second opening contour of the through hole on the upstream side, when viewed in the optical axis direction. The charged particle beam propagates along the optical axis at substantially the center of the through hole from the upstream side to the downstream side, and irradiates the object. In this action, a scattered substance, or the like, is likely to enter the electrode. By setting the first opening contour on the downstream side to be smaller than the second opening contour on the upstream side, it is possible to prevent scattered substances, or the like, from entering. What degree to set the first opening contour on the downstream side smaller is appropriately designed, in accordance with how to use the electrode or a specification of the electrode. In the present invention, the phrase “along the optical axis” includes the phrase “substantially along the optical axis”. In other words, this includes not only the case of being strictly aligned with the optical axis, but also, the case of being regarded as being substantially along the optical axis, even if deviated within an error range.
Hereafter, embodiments of the present invention are described. However, dimensions, materials, shapes, relative positions, and the like, of components described in the following embodiments should not be interpreted as limiting the present invention, unless otherwise noted.
With reference to
As illustrated in
In other words, the first region having the relatively smaller internal diameter has a shield plate structure, which has a function of preventing scattered substances, evaporated substances, or the like, of a sample as the object to be irradiated by the charged particle beam from entering the second region β, or the charged particle source side with respect to the electrode 1. In other words, the region corresponding to a difference between the internal diameter φ1 and the internal diameter φ2 of the first region (doughnut-shaped region in
Here, the through hole 4 is illustrated as a through hole having two internal diameters, in which the shield plate structure region for blocking the scattered substances, the evaporated substances, or the like, of the sample is the first region α, and the region to which the scattered substances, the evaporated substances, or the like, of the sample should not adhere, is the second region β. Here, the through hole 4 may have other regions having an internal diameter or an opening contour different from the first region α or the second region β.
The reason why the above-mentioned shield plate structure region as the first region α has an effect of blocking the scattered substances, the evaporated substances, or the like, of the sample as the object to be irradiated by the charged particle beam, is that the scattered substances, the evaporated substances, or the like, are scattered linearly when the charged particle beam irradiates the object. The step of irradiating the object with the charged particle beam is performed in a vacuum or a low pressure atmosphere. Therefore, the scattered substances, the evaporated substances, or the like, are scattered radially and linearly from the position irradiated with the charged particle beam. Therefore, the shielding effect can be obtained by disposing the first region α on the straight line connecting the position irradiated with the charged particle beam and the second region β as the region to which the scattered substances, the evaporated substances, or the like, of the sample should not adhere (on the propagation path of the scattered substances, the evaporated substances, or the like).
Exemplary specific material and dimensions in this embodiment are described. The electrode 1 is made of single crystal silicon, or the like. A surface of the electrode 1 and a side wall of the through hole 4 may be covered with a conductive material film as necessary. As the conductive material, a material having good adhesiveness to silicon, high conductivity, and resistance to oxidization is selected. For instance, the conductive material is selected from titanium, platinum, gold, molybdenum, and the like. The electrode 1 has a total thickness of one hundred micrometers and is formed of a first region α having a thickness often micrometers and a second region β having a thickness of ninety micrometers. The internal diameter φ1 of the first region α is twenty micrometers, and the internal diameter φ2 of the second region β is thirty micrometers.
Next, a manufacturing method of this embodiment is described. First, a groove having an internal diameter of thirty micrometers and a depth of ninety micrometers is formed in a silicon substrate having a thickness of one hundred micrometers by photolithography technology and deep dry etching technology, to thereby form a region corresponding to the second region β. Next, using photolithography technology and dry etching technology, a through hole having an internal diameter of twenty micrometers is formed, to thereby form a region corresponding to the first region α. In this way, the electrode 1 can be formed. Here, it is also possible to manufacture at least one of the first region α and the second region β with a silicon on insulator (SOI) substrate by photolithography technology and deep dry etching technology, so as to form the electrode 1 by joining the regions by the use of a wafer bonding technique. In addition, it is also possible to form the through hole by patterning both sides of the silicon substrate using photolithography technology, and by etching both sides using dry or wet etching technology,
If the electrode 1 is manufactured by the steps of forming the first region α using an SOI substrate including a device layer having a thickness of ten micrometers, forming the second region β using a silicon substrate having a thickness of ninety micrometers, and joining the regions by the use of wafer bonding technique, an actual shape of the electrode 1 may be as illustrated in
A description is given of a case wherein the through hole is formed, by patterning both sides of a silicon substrate having a thickness of one hundred micrometers using photolithography technology, and by etching both sides using dry or wet etching technology. In this case, the opening contour of the through hole may have a tapered shape as illustrated in
In addition, there is another case as illustrated in
According to the embodiment described above, as the electrode for the objective lens to be used closest to the object to be irradiated by the charged particle beam, it is possible to realize an electrode including the first region having the shield plate function of preventing the scattered substances, the evaporated substances, or the like, of the sample from entering the second region or the charged particle source side with respect to the electrode.
With reference to
As illustrated in
In general, the performance of the electrostatic charged particle beam lens is determined by a shape of an electrostatic field formed in a region through which the charged particle beam passes. This corresponds to the electrostatic field formed in the regions of the through holes 4A to AC through which the charged particle beam passes, as illustrated in
When the sample is irradiated by the charged particle beam, a material forming the sample surface, for example, an organic substance forming the resist is scattered and evaporated from the sample surface. The scattered substance and the evaporated substance from the sample surface adhere to a part of the objective lens close to the sample. When the scattered substance and the evaporated substance and the sample surface adhere to the objective lens, the electrostatic field formed in the objective lens is changed from an Initial state due to electrification, or the like. Then, aberration characteristics of the objective lens get worse.
In this embodiment the electrode having the shield plate structure on the sample side is used as the electrode 1C closest to the sample in tire objective lens. Thus, it is possible to suppress adhesion of Ore scattered substance and the evaporated substance from the sample surface to a portion of the lens particularly affecting aberration characteristics of the lens. The first region α having a function of blocking the scattered substance and the evaporated substance from the sample surface has very little influence to aberration characteristics of the lens. Therefore, in many cases, there is not a problem, even if the scattered, substance and the evaporated substance from the sample surface adhere to this portion. In addition, there is not a problem, even if the opening contour is made smaller than other parts.
Exemplary specific materials and dimensions in this embodiment are described. The first embodiment is applied to the electrode 1C. The electrodes 1A and 1B are made of single crystal silicon. A surface of each electrode and side walls of the through holes 4A and 4B may be covered with a conductive material film. As the conductive material, a material having good adhesiveness to silicon, high conductivity, and resistance to oxidization is selected. For instance, the conductive material is selected from titanium, platinum, gold, molybdenum, and the like. Each of the electrodes 1A and 1B has a thickness of one hundred micrometers. Each of the through holes 4A and 4B has an internal diameter of thirty micrometers. The electrodes 1A, 1B, and 1C are electrically insulated in the direction of the optical axis 3 and are disposed with spaces of four hundred micrometers each. The electrodes 1A, 1B, and 1C may be disposed via insulating glass or an insulating material. Electrical potentials can be applied to the electrodes 1A, 1B, and 1C, individually. For instance, −3.7 kV is applied to the electrode 1B, and the electrodes 1A and 1C are set to the ground potential. Thus, an Einzel-type electrostatic lens van be constituted,
Next, a manufacturing method of this embodiment is described. The first embodiment is applied to the electrode 1C. As to the electrodes 1A and 1B, the through holes 4A and 4B are formed in a silicon substrate having a thickness of one hundred micrometers by photolithography technology and silicon deep dry etching.
As described above, in the charged particle beam objective lens of this embodiment, the electrode having the shield structure is used as the electrode closest to the sample. Thus, it is possible to suppress adhesion of the scattered substances and the evaporated substances from the sample to the second region or the inside of the lens, which affect aberration characteristics, and to provide an electrostatic charged particle beam objective lens that hardly changes aberration characteristics even if the sample is irradiated with the charged particle beam for a long time.
With reference to
The electrode 1C has a structure including the first region α and the second region β. There is a case wherein the center position of the through hole is shifted between the first region α and the second region β due to a manufacturing problem, such as misalignment in the photolithography step and the bonding step. Therefore, it is desired to design the shape of the electrode 1C and a relative positional relationship between the electrode IC and the sample 2 considering a positional shift in the manufacturing process. In particular, as the resolution of the patterning apparatus as the exposure equipment is increased more, the distance between the objective lens and the sample 2 becomes smaller. Therefore, the scattered substance from the sample surface, which is scattered when the sample is irradiated with the charged particle beam, is more likely to adhere to the objective lens. Therefore, it is very important to design the shape of the electrode IC and the relative positional relationship between the electrode IC and the sample 2 to meet a preferred condition,
The shape of the electrode 1C and the relative positional relationship between the electrode 1C and the sample 2 is set to the relationship expressed by the following inequality:
x/yφ1/(WD+h−y),
Thus, it is possible to provide a charged particle beam exposure equipment in which aberration characteristics of the objective lens are hardly changed even if the patterning is performed for a long time.
With the structure satisfying the relationship expression above, the second region β is not directly viewed from the sample 2 at all. Therefore, the scattered substances, the evaporated substances, or the like, of the sample, which may adhere to the second region β, can be blocked more appropriately by the first region α.
With reference to
Electron beams 113 and 114 radiated in a wide range from the irradiation optical system crossover 112 are collimated by a collimator lens 115 to be parallel beams 116 to irradiate an aperture array 117. Multiple electron beams 118 split by the aperture array 117 are focused individually by a focus lens array 119 and form images on a blanker array 122. Here, the focus lens array 119 is an electrostatic lens including three multitude electrodes and is an Einzel-type electrostatic lens array controlled by a lens control circuit 105, in which a negative voltage is applied only to the intermediate electrode out of the three electrodes, and the upper and lower electrodes are connected to the ground. In addition, the aperture array 117 is disposed at a pupil plane position of the focus lens array 119 (front focal plane position of the focus lens array) so as to have a role to define a numerical aperture (NA) (convergence half angle). The blanker array 122 is a device having individual deflection electrodes and turns on and off the beams individually according to a lithography pattern based on a blanking signal generated by a lithography pattern generation circuit 102, a- bitmap conversion circuit 103, and a blanking command circuit 106. A voltage is not applied to the deflection electrode of the blanker array 122 when the beam is in an on state, while the voltage is applied to the deflection electrode of the blanker array 122 when the beam is in an off state, so as to deflect the multiple electron beams. Multiple electron beams 125 deflected by the blanker array 122 are blocked by a stop aperture array 123 disposed in a post stage (on the downstream side) so that the beams become the off state. Multiple aligners 120 are controlled by an aligner control circuit 107 so as to adjust an incident angle and an incident position of the electron beam. In addition, a controller 101 controls the entire circuit.
In this embodiment, the blanker array has two stages, in which a second blanker array 127 and a second stop aperture array 128 having the same structures as that of the blanker array 122 and the stop aperture array 123 are disposed in the post stage. The multiple electron beams after passing through the blanker array 122 form images on the second blanker array 127 by a second focus lens array 126. Further, the multiple electron beams are focused by third and fourth focus lenses so as to form images on a wafer 133. Here, the second focus lens array 126, a third focus lens array 130, and a fourth focus lens array 132 are Einzel-type electrostatic lens arrays, similar to the focus lens array 119.
In particular, the fourth focus lens array 132 is the objective lens, and a reduction ratio thereof is set to approximately one hundred. Thus, an electron beam 121 (having a spot diameter of two micrometers in FWHM) on an intermediate image formation plane of the blanker array 122 is reduced to 1/100 on the surface of the wafer 133 so that images of the multiple electron beams having a spot diameter of approximately twenty nm in FWHM are formed on the wafer. Each through hole of the fourth focus lens array 132 has the above-mentioned shield plate structure (not shown) according to the present invention. Therefore, the scattered substance and tire evaporated substance from the surface of the wafer 133 are prevented from adhering to a portion of the fourth focus lens array 132 that strongly affects the objective lens characteristics. Scanning of the wafer 133 by the multiple electron beams can be performed by a deflector 131. The deflector 131 is formed of opposing electrodes. In order to perform two-stage deflection in the X and Y directions, four-stage opposing electrodes are disposed- (
The wafer 133 is moved continuously in the X direction by a stage 134 during the patterning. Then, based on a result of measurement in actual tune by a laser rangefinder, an electron beam 135 on the wafer surface is deflected in the Y direction by the deflector 131, and the beams are turned, on and off individually according to the lithography pattern by the blanker array 122 and the second blanker array 127. A beam 124 indicates the on beam, and beams 125 and 129 indicate off beams. Thus, a desired pattern can be patterned on the surface of the wafer 133 at high speed in a short patterning time. As described above, the multi-charged particle beam exposure equipment according to this embodiment includes the electrostatic charged particle beam objective lens of the present invention, and multiple charged particle beams from the charged particle source pass through multiple through holes of the electrode of the objective lens and irradiate the object. In this way, by using multiple charged particle beams for patterning, it is possible to provide a charged particle beam exposure equipment that can be used with high throughput for a long time.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications, and equivalent structures and functions.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2011-139965 | Jun 2011 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2012/063235 | 5/17/2012 | WO | 00 | 11/21/2013 |
