JP2000348997A - Fiducial mark, charged particle beam exposure system having the same and manufacture of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide fiducial marks which can prevent the charging up of a low thermal expansion substrate formed of a nonconduction material and can detect precise mark positions. SOLUTION: A fiducial mark 15 is formed of a substrate 35 formed of a nonconducting material with a low thermal expansion coefficient, mark bodies 31 formed on the surface and a conducting material layer 33, which is installed in the substrate and connected with a ground. Since electrons which are made incident on the fiducial mark substrate 35 escape to the ground from the conducting material layer 33, charge-up of the substrate can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fiducial mark irradiated with a charged particle beam such as an electron beam. Further, for example, in an electron beam exposure apparatus, an index mark formed on a first surface on which a mask, a reticle, and the like are disposed, and a fiducial mark on a second surface on which a sensitive substrate such as a wafer is disposed. The present invention relates to an apparatus for determining a relative position between the two and using them to perform a suitable alignment. In particular, the present invention relates to a fiducial mark capable of accurately detecting a mark position, and a charged particle beam exposure apparatus having such a fiducial mark and capable of forming a highly accurate pattern.
Further, the present invention relates to a method for manufacturing a highly accurate semiconductor device using such a charged particle beam exposure apparatus.

[0002]

2. Description of the Related Art A certain type of electron beam exposure apparatus illuminates a pattern on a mask with an electron beam and projects an electron beam passing through the mask onto a sensitive substrate (a wafer or the like) to form a pattern. Transcribe. In such an apparatus, a mask is mounted on a mask stage, and a wafer is mounted on a wafer stage.

One of the methods for finding the relative positional relationship between the mask stage and the wafer stage under certain conditions of the electron beam projection optical system is as follows. That is, an index mark through which an electron beam can pass is provided on the mask stage, a fiducial mark made of heavy metal or the like is provided on the wafer stage, and the electron beam passing through the mark on the mask stage is placed on the fiducial mark. By scanning and detecting reflected electrons from the fiducial mark, the relative positional relationship between the projected image of the index mark and the fiducial mark can be known. Based on the result, the alignment between the mask and the wafer can be obtained, and the distortion of the electron beam in the projection optical system can be known.

In this mark detection method, it is necessary to accurately grasp the position of the index mark on the mask stage with respect to the position coordinates of the mask stage. This is the same for the wafer stage. Therefore, the material of the fiducial mark is required to have as small a thermal deformation as possible due to electron beam irradiation.

[0005]

Therefore, the shot (SC
It is conceivable to manufacture a fiducial mark substrate by using a material having a low coefficient of thermal expansion such as Zerodur manufactured by HOTT (Germany). However, since this kind of low thermal expansion material is generally non-conductive, when it is irradiated with an electron beam, electric charges accumulate and become charged (charge up). When charge-up occurs, an electric field is generated around the fiducial mark, and the orbit of the electron beam is disturbed. Alternatively, when the charge-up is severe, discharge may occur and the fiducial mark may be destroyed.

As a countermeasure for preventing charge-up, a metal coating on the surface of Zerodur is conceivable, but this coating is highly likely to cause a decrease in the contrast of the reflected electron signal.
Therefore, there is a need for a method of preventing charge-up without causing a decrease in contrast and maintaining a low coefficient of thermal expansion of the substrate.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and a fiducial mark capable of preventing charge-up of a low thermal expansion substrate made of a non-conductive material and capable of accurately detecting a mark position, and An object of the present invention is to provide an electron beam exposure apparatus having such a fiducial mark and capable of forming a highly accurate pattern. Still another object is to provide a method for manufacturing a highly accurate semiconductor device using such a charged particle beam exposure apparatus.

[0008]

In order to solve the above-mentioned problems, a fiducial mark of the present invention comprises a substrate made of a non-conductive substance having a low coefficient of thermal expansion and a substrate formed on the surface of the substrate. A mark body that receives the charged particle beam irradiation, and a grounded conductive material layer provided in or on the substrate.

A charged particle beam exposure apparatus according to the present invention is an apparatus for irradiating a charged substrate with a charged particle beam to form a pattern; a charged particle beam irradiation position on a stage on which the sensitive substrate is placed; A fiducial mark for measuring a relative positional relationship with respect to the stage or a charged particle beam shape is provided. The fiducial mark includes a substrate made of a non-conductive material having a low coefficient of thermal expansion, and a surface of the substrate. And a mark body for receiving the charged particle beam irradiation formed thereon, and a conductive material layer provided in the substrate or on the back surface thereof and connected to ground.

The charge of electrons or ions incident on the fiducial mark substrate escapes from the conductive material layer to the ground, so that the charge up of the substrate can be prevented. Further, since the conductive material layer is not coated on the mark body, the contrast of the mark is hardly affected.

In the present invention, the conductive material layer is
It is preferable that the pattern shape has an effective shape for preventing charge-up without affecting the thermal expansion of the entire fiducial mark. Therefore, for example, the conductive material layer is formed in a mesh shape, or corresponding to the shape of the mark body,
The conductive material layer may be formed only at a portion that is directly irradiated with the charged particle beam.

A semiconductor device manufacturing method according to the present invention is characterized in that exposure in a lithography step is performed by using the above charged particle beam exposure apparatus.

Hereinafter, description will be made with reference to the drawings. FIG.
1 is a perspective view showing a configuration of an exposure apparatus (electron beam reduction transfer apparatus) according to one embodiment of the present invention. Mask stage 1
Receives an illumination beam B1 from above in the figure by an illumination optical system (not shown). On the mask stage 1, a beam forming pattern (index mark) 11, which is an aggregate of a plurality of band-shaped patterns, is formed. Normally, the beam forming pattern 11 has a hole in the mask stage 1 (or mask). The illumination beam B1 passes through the beam shaping pattern 11 and is shaped into a beam B2.

A projection optical system 3 is arranged below the mask stage 1. An electromagnetic lens, a dynamic focus coil, an astigmatism correction coil, a magnification / rotation adjustment coil, and the like (all not shown) are arranged in the projection optical system 3. The beam B2 incident on the projection optical system 3 is inverted and reduced by the operation of the projection optical system 3. The beam B3 reduced by the projection optical system 3 forms an image on the wafer stage 9.

A deflector 5 is arranged below the projection optical system 3. The deflector 5 deflects the beam B3 by electrostatic force or electromagnetic force, and irradiates the beam B3 to a desired position on the wafer stage 9. The beam B3 forms an image on the wafer stage 9 as described above. This focused beam is used as an index mark image 13. A fiducial mark 15 is formed on the wafer stage 9.

Above the wafer stage 9, a backscattered electron detector 7 is arranged. The reflected electron detector 7 detects electrons reflected by the beam B3 hitting the fiducial mark 15 on the wafer stage 9. By processing the signal of the backscattered electron detector 7, the relative positional relationship between the index mark image 13 and the fiducial mark 15 can be measured.

FIG. 1 is a diagram schematically showing details of a fiducial mark according to one embodiment of the present invention. (A) is a plan view and (B) is a side sectional view. The fiducial mark 15 includes a substrate 35 made of a substance having a low coefficient of thermal expansion (for example, Zerodur manufactured by Schott) and the substrate 35.
Mark body 3 of metal (W, Ta, etc.) formed on the surface of
One. In this example, the mark body 31 has a cross shape.

In the substrate 35, mesh-shaped conductive lines (conductive material layer) 33 are embedded. The mesh is formed in order to reduce the buried area as much as possible and not to impair the low thermal expansion characteristics of the substrate. A ground wire 37 is connected to the conductive wire 33, and electrons incident upon irradiation of the fiducial mark 15 with an electron beam are
It flows from the conductive line 33 through the ground line 37. Therefore, charge-up of the fiducial mark 15 can be avoided.

It is considered that the embedded depth of the conductive material layer (the thickness of the surface layer 35 of the substrate) is, for example, about several tens μm, which is effective. Specifically, it can be determined experimentally according to the acceleration voltage of the electron beam, taking into account the following items. (1) The reflected electron symbol of the fiducial mark is determined by the reflected electrons from the conductive material layer. Is made deep enough so that the decrease in contrast does not matter. (2) Electrons incident on the fiducial mark sufficiently flow to the ground, and shallow enough to avoid charging.

The method of manufacturing such a fiducial mark includes a method of embedding a conductive material layer at the time of molding a substrate, and a method of forming a conductive line 33 on a base layer 35b of a substrate 35, and then forming a conductive line 33 on the base material 35b. A method of forming the substrate surface layer (35a in FIG. 1) by film formation can be adopted.

FIG. 2 is a diagram schematically showing a configuration of a fiducial mark according to another embodiment of the present invention.
(A) is a plan view and (B) is a side sectional view. The fiducial mark 15 'in this example is such that Cr 45
A metal coating layer 41 is provided, and a part of the surface is a mark opening 42 where the substrate 45 is exposed. Then, a conductor layer pattern 43 having the same shape as or slightly larger than the mark opening is arranged below the mark opening 42. The mark opening 42 and the conductor layer pattern 43 on the left side of the drawing are
The mark opening 42 'and the conductor layer pattern 43' on the right side of the figure are square. Each conductor layer pattern 43, 43 'is connected to a ground wire 47, 47'. The surface coat layer 41 is also connected to the ground wire 47.

The pattern of the conductive layer can be designed and arranged in an optimum shape for the mark on the zero-dur surface, for example, by preventing the formation of a local earth loop or the like. In addition,
If there is an earth loop, when a potential difference occurs in the loop, a current may flow to generate a harmful magnetic field or noise may be put on the earth line.

Next, an example of the usage of the exposure apparatus of the present invention will be described. FIG. 4 is a flowchart showing an example of the semiconductor device manufacturing method of the present invention. The manufacturing process of this example includes the following main processes. Wafer manufacturing process for manufacturing a wafer (or wafer preparing process for preparing a wafer) Mask manufacturing process for manufacturing a mask to be used for exposure (or mask preparing process for preparing a mask) Wafer processing process for performing necessary processing on a wafer Wafer Chip assembling step of cutting out the chips formed on the chip one by one to make it operable Chip inspecting step of inspecting the resulting chips Each of the steps further includes several sub-steps.

Among these main steps, the main step that has a decisive effect on the performance of the semiconductor device is the wafer processing step. In this step, designed circuit patterns are sequentially stacked on a wafer, and a number of chips that operate as memories and MPUs are formed. This wafer processing step includes the following steps. A thin film forming step of forming a dielectric thin film to be an insulating layer, a wiring portion, or a metal thin film forming an electrode portion (using CVD or sputtering, etc.) An oxidation step of oxidizing the thin film layer or the wafer substrate Thin film layer or wafer substrate A lithography process of forming a resist pattern using a mask (reticle) in order to selectively process etc. An etching process of processing a thin film layer or a substrate according to a resist pattern (for example, using a dry etching technology) An ion / impurity implantation diffusion process Resist stripping step Inspection step for inspecting the processed wafer Further, the wafer processing step is repeated by a necessary number of layers to manufacture a semiconductor device that operates as designed.

FIG. 5 is a flowchart showing a lithography step which is the core of the wafer processing step shown in FIG. This lithography step includes the following steps. A resist coating step of coating a resist on a wafer on which a circuit pattern has been formed in the preceding step An exposing step of exposing the resist A developing step of developing the exposed resist to obtain a resist pattern Stabilizing the developed resist pattern Annealing Step for Using the exposure apparatus of the present invention in the above-mentioned exposure step, the accuracy of pattern formation in the lithography step is greatly improved.
In particular, the process related to realizing the required minimum line width and the overlay accuracy corresponding thereto is a lithography process, in particular, an exposure process including alignment control, and it has been difficult until now by applying the present invention. Semiconductor devices can be manufactured.

[0026]

As is apparent from the above description, according to the present invention, it is possible to prevent a charge-up of a low thermal expansion coefficient substrate made of a non-conductive substance and to provide a fiducial mark capable of accurately detecting a mark position. Can be provided. Further, a charged particle beam exposure apparatus having such a fiducial mark and capable of forming a pattern with high accuracy can be provided. Moreover,
A method for manufacturing a semiconductor device with high accuracy using such a charged particle beam exposure apparatus can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing details of a fiducial mark according to one embodiment of the present invention. (A) is a plan view and (B) is a side sectional view.

FIG. 2 is a diagram schematically showing a configuration of a fiducial mark according to another embodiment of the present invention. (A) is a plan view,
(B) is a side sectional view.

FIG. 3 is a perspective view showing a configuration of an exposure apparatus (electron beam reduction transfer apparatus) according to one embodiment of the present invention.

FIG. 4 is a flowchart illustrating an example of a semiconductor device manufacturing method according to the present invention.

FIG. 5 is a flowchart showing a lithography step which is the core of the wafer processing step shown in FIG. 4;

[Explanation of symbols]

REFERENCE SIGNS LIST 1 mask stage 3 projection optical system 5 deflector 7 backscattered electron detector 9 wafer stage 11 beam shaping pattern 13 shaping beam 15 fiducial mark 31 mark body 33 mesh conductive wire 35 substrate 35 a surface layer 35 b base layer 37 ground wire 41 metal Coat layer 42 Mark opening 43 Conductive material layer 45 Substrate 47 Ground wire

Claims (6)

[Claims] 1. A substrate made of a non-conductive substance having a low coefficient of thermal expansion, a mark body formed on a surface of the substrate for receiving a charged particle beam, and a conductive member provided in or on the back surface of the substrate and connected to ground. A fiducial mark comprising: a material layer. 2. A charged particle beam exposure apparatus for irradiating a charged substrate with a charged particle beam to form a pattern on a sensitive substrate, wherein a charged particle beam irradiation position and a stage are arranged on a stage on which the sensitive substrate is mounted. A fiducial mark for measuring a relative positional relationship or a charged particle beam bundle shape is provided, and the fiducial mark is formed on a substrate made of a non-conductive material with a low coefficient of thermal expansion, and formed on the surface of the substrate. A charged particle beam exposure apparatus comprising: a mark body receiving charged particle beam irradiation; and a conductive material layer provided in or on the substrate and connected to ground. 3. The charged particle beam exposure apparatus according to claim 1, wherein the conductive material layer is formed in a mesh shape. 4. The fiducial according to claim 1, wherein the conductive material layer is formed only in a portion to be directly irradiated with the charged particle beam according to a shape of the mark body. A mark or a charged particle beam exposure apparatus according to claim 2. 5. The fiducial according to claim 1, wherein the conductive material layer has a pattern shape effective for preventing charge-up without affecting the thermal expansion of the entire fiducial mark. A mark or a charged particle beam exposure apparatus according to claim 2. 6. A method for manufacturing a semiconductor device, comprising performing exposure in a lithography step using the charged particle beam exposure apparatus according to claim 2. Description: