JP2000251821A - Focus adjusting method of charged particle beam apparatus, and the charged particle beam apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate focus adjustment and to keep the magnification ratio or magnification of an image constant by varying a focus position in the X-axis direction and the Y-axis direction, according to the variation of an image surface position so as to set it to that of the new image surface. SOLUTION: An optical axis takes an X-Y-Z orthogonal coordinate system of the Z-axis. It is assumed that the magnetic permeability of vacuum is μ0, the absolute value of the charge of charged particles is (q), its sign is (s), the mass of the charged particles is (m), the axial potential is ϕ[Z], an object surface is Z0, an image surface is Z1, two paraxial trajectories in the X-direction are expressed by the expression I and the equation II on the object surface Z0, and two paraxial trajectories in the Y direction are expressed by the equation III and the equation IV on the object surface X0. The astigmatic field P2j [Z] of the j-th Q lens is expressed by the product of the axial astigmatic field distribution D2j [Z] per unit current multiplied by the expression V when the j-th Q lens is an electromagnetic Q lens, and by the quotient of the axial astigmatic field distribution D2j [Z] divided by ϕ Z, when the j-th Q lens is an electrostatic Q lens. A height deviation ΔZ of the image surface when the equation VI and the equation VII are satisfied is detected, and variations Ij, Ik of excitation currents or voltages of the j-th and k-th Q lenses are set in the equations VIII and IX, respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of irradiating a charged particle beam generated from a charged particle beam generator, such as a semiconductor exposure apparatus, onto an object surface to form an image of a pattern formed on the object surface on an image surface. More specifically, the present invention relates to a charged particle beam device using a Q lens,
The present invention relates to a method of adjusting the focus in accordance with a new image plane in both the X-axis direction and the Y-axis direction when the position of the image plane changes, and a charged particle beam apparatus capable of performing this method.

[0002]

2. Description of the Related Art As an example of a conventional charged particle beam apparatus, an outline of an electron beam exposure apparatus is shown in FIG. In FIG. 4, charged particles emitted from a charged particle source (not shown) illuminate the object surface 12 of the Q lens systems 14a and 14b via an illumination optical system (not shown). The charged particle beam that has exited the object surface 12 is imaged on the image plane 13 by the first Q lens 14a and the second Q lens 14b as shown by the electron beam trajectory 15X in the X-axis direction and the electron beam trajectory 15Y in the Y-axis direction. I do.

FIG. 5 shows an electrostatic Q lens viewed from the optical axis direction as an example of a Q lens. Q lens electrodes 21a and 2
The same voltage is applied to 1c, and the electrodes 21b and 21d are
A voltage opposite to that of the electrodes 21a and 21c is applied with reference to the voltage on the optical axis. FIG. 6 shows another example of the Q lens when the electromagnetic Q lens is viewed from the optical axis direction. A current is applied to the coils so that a magnetic field is generated in the same direction with respect to the optical axis on the Q lens magnetic poles 22a and 22c,
A current is applied to d so that a magnetic field is generated in a direction opposite to that of the magnetic poles 22a and 22c. By applying such an exciting current or voltage, the trajectory differs in each direction as shown in the trajectory 15X in the X direction and the trajectory 15Y in the Y direction in FIG.

[0004]

In the charged particle beam apparatus as described above, when the position of the image plane is shifted to the position indicated by 13 'as shown in FIG. 7, only one Q lens is adjusted. Even if the focus in one direction is focused, the focus in the other direction is further shifted. That is, as shown in FIG. 7, by adjusting the second Q lens 14b, the charged particle trajectory in the X-axis direction is set to 15x ′.
To the new image plane 13 ', the trajectory of the charged particle in the Y-axis direction becomes like 15y', and the new image plane 13 '
Will be further away from

[0005] Therefore, it is necessary to refocus by combining at least two Q lenses, which is very difficult to adjust. SUMMARY OF THE INVENTION The present invention has been made in view of the above-described conventional problems, and enables a focus adjustment to be easily performed, and further, a charged particle beam apparatus capable of maintaining a constant image magnification ratio or image magnification. It is an object to provide a focus adjustment method and a charged particle beam apparatus capable of performing the focus adjustment method.

[0006]

A first means for solving the above-mentioned problem is that a charged particle beam emitted from an object surface is imaged on an image plane by using two or more stages of Q lenses. In the apparatus, an XYZ orthogonal coordinate system with the optical axis as the Z axis is taken, the magnetic permeability of vacuum is μ ₀ , the absolute value of the charge of the charged particle is q, the sign is s, and the mass of the charged particle is m , The on-axis potential is φ
And [Z], the object plane is Z _o, the image plane and Z _i, the object plane two paraxial trajectory of X-direction Z _o at _{Xa [Z o] = 0,} Xa '[Z o] = 1 Xb [ _{Z o] = 1, Xb '} [Z o] = 0 object surface two paraxial trajectory in the Y-direction Z _o at _{Ya [Z o] = 0,} Ya' [Z o] = 1 Yb [Z o] = 1, Yb ′ [Z _o ] = 0, and the electromagnetic Q
In the case of a lens, on-axis astigmatic field distribution D2 _j per unit current
[Z] multiplied by s × μ ₀ × {2q / (φ [Z] m)} ^{1/2. In} the case of an electrostatic Q lens, axial astigmatic field distribution F2 _j [Z] per unit voltage Is divided by φ [Z] to obtain the astigmatism field P2 _j [Z] of the _j -th Q lens,

[0007]

(Equation 10)

Then, the height shift ΔZ of the image plane is detected, and the j-th and k-th excitation currents or voltage changes I _j and I _k of the Q lens are determined.

[0009]

[Equation 11]

A focus adjusting method for a charged particle beam apparatus, wherein Where '
The differential value of each variable by Z is shown.

In this specification, P2 _k [Z],
Although seemingly undefined quantities such as ΔZx _k are described, when P2 _j [Z], ΔZx _{j and the} like are defined, they are considered to be equivalent to those with different subscripts.

In an XYZ orthogonal coordinate system with the optical axis as the Z axis, the magnetic permeability of vacuum is μ ₀ , the absolute value of the charge of the charged particles is q, the sign is s, the mass of the charged particles is m, The on-axis potential is φ [Z], and in the case of an electromagnetic Q lens, the on-axis astigmatic field distribution D
2 [Z] multiplied by s × μ ₀ × {2q / (φ [Z] m)} ^{1/2. In} the case of an electrostatic Q lens, the axial astigmatic field distribution F2
The value obtained by dividing [Z] by φ [Z] is the astigmatism field P2 of the Q lens.
And [Z], the object plane Z _o, the image plane to city Z _i, the equation of paraxial trajectory, X "[Z] + φ '[Z] · X' [Z] / (2φ [Z]) + φ "[Z] ・ X [Z] / (4φ [Z])-P2 [Z] ・ X [Z] = 0… (15) Y" [Z] + φ '[Z] ・ Y' [Z ] / (2φ [Z]) + φ ″ [Z] · Y [Z] / (4φ [Z]) + P2 [Z] · Y [Z] = 0 (16)

[0013] The two paraxial trajectory of the X-direction in the object plane _{Z o Xa [Z o] =} 0, Xa '[Z o] = 1 (Wa _{trajectory) Xb [Z o] = 1} , Xb' [Z o ] = 0 (Wb trajectory) Two paraxial trajectories in the Y direction are represented by an object plane, Ya [ _Zo ] = 0, Ya '[ _Zo ] = 1 (Wa trajectory) Yb [ _Zo ] = 1, Yb' [ Z _o] = 0 (Wb trajectory) and a way to select, j-th quadrupole fields to calculate the change in the trajectory when the somewhat changed. That is, P2 [Z] → P2 [Z] +
When P2 _j [Z], the paraxial equation is defined as the trajectory changes as X [Z] → X [Z] + δX _j [Z] Y [Z] → Y [Z] + δY _j [Z]. To rewrite (in this case, use the paraxial equation to simplify the equation) δX _j "[Z] + φ '[Z] ・ δX _j ' [Z] / (2φ [Z]) + φ" [Z]・ ΔX _j [Z] / (4φ [Z])-P2 [Z] ・ δX _j [Z] = + P2 _j [Z] ・ X [Z]… (17) δY _j "[Z] + φ '[ Z] ・ δY _j '[Z] / (2φ [Z]) + φ "[Z] ・ δY _j [Z] / (4φ [Z]) + P2 [Z] ・ δY _j [Z] = -P2 _j [Z] · Y [Z] (18) is obtained.

Using the paraxial trajectory, the change of the trajectory due to the slightly changed quadrupole lens is calculated. δX _j [Z] = aX [Z] ・ Xa [Z] + bX [Z] ・ Xb [Z]… (19) δYj [Z] = aY [Z] ・ Ya [Z] + bY [Z] ・ Yb [Z]… (20) Find aX [Z], bX [Z], aY [Z], bY [Z], where aX '[Z] · Xa [Z] + bX' [Z] · Xb [Z] = 0 ... (21) Let aY '[Z] · Ya [Z] + bY' [Z] · Yb [Z] = 0 (22) be the solution condition.

When the paraxial equations (17) and (18) are rewritten, the X direction becomes aX '[Z] .Xa' [Z] + bX '[Z] .Xb' [Z] + aX [Z] {Xa "[Z] + φ '[Z] ・ Xa' [Z] / (2φ [Z]) + φ" [Z] ・ Xa [Z] / (4φ [Z])-P2 [Z] ・ Xa [ Z]} + bX [Z] {Xb "[Z] + φ '[Z] ・ Xb' [Z] / (2φ [Z]) + φ" [Z] ・ Xb [Z] / (4φ [Z] ) -P2 [Z] ・ Xb [Z]} = + P2 _j [Z] ・ X [Z]… (23) The Y direction is aY '[Z] ・ Ya' [Z] + bY '[Z] ・Yb '[Z] + aY [Z] {Ya "[Z] + φ' [Z] ・ Ya '[Z] / (2φ [Z]) + φ" [Z] ・ Ya [Z] / (4φ [Z]) + P2 [Z] ・ Ya [Z]} + bY [Z] {Yb "[Z] + φ '[Z] ・ Yb' [Z] / (2φ [Z]) + φ" [Z ] ・ Yb [Z] / (4φ [Z]) + P2 [Z] ・ Yb [Z]} = -P2 _j [Z] ・ Y [Z]… (24) After all, aX '[Z] · Xa' [Z] + bX '[Z] · Xb' [Z] = + P2 _j [Z] · X [Z]… (25) aY '[ Z] · Ya [Z] + bY ′ [Z] · Yb ′ [Z] = − P2 _j [Z] · Y [Z] (26) is obtained.

Equations (25) and (26) are calculated using the conditions of the previous solution aX '[Z] Xa [Z] + bX' [Z] Xb [Z] = 0 (21) aY '[Z] Ya [ Z] + bY '[Z] Yb [Z] = 0… (22) and solving for aX' [Z], bX '[Z], aY' [Z], bY '[Z], aX' [Z] = P2 _j [Z] · X [Z] · Xb [Z] / (Xa '[Z] · Xb [Z] -Xa [Z] · Xb' [Z])… (27) bX '[ Z] = -P2 _j [Z] ・ X [Z] ・ Xa [Z] / (Xa '[Z] ・ Xb [Z] -Xa [Z] ・ Xb' [Z])… (28) aY '[ Z] = -P2 _j [Z] / Y [Z] / Yb [Z] / (Ya '[Z] / Yb [Z] -Ya [Z] / Yb' [Z])… (29) bY '[ Z] = P2 _j [Z] ・ Y [Z] ・ Ya [Z] / (Ya '[Z] ・ Yb [Z] -Ya [Z] ・ Yb' [Z])… (30)

Here, the paraxial invariant is (Xb [Z] .Xa '[Z] -Xa [Z] .Xb' [Z]) φ [Z] ^1/2 = const = φ [Z ₀ ] ^{1 / 2} = Xb [Zi] ・ Xa '[Zi] ・ φ [Zi] ^1/2 … (31) (Yb [Z] ・ Ya' [Z] -Ya [Z] ・ Yb '[Z]) φ [ Z] ^1/2 = const = φ [Z ₀ ] ^1/2 = Yb [Zi] ・ Ya '[Zi] ・ φ [Zi] ^1/2 … (32) AX '[Z] = P2 _j [Z] ・ X [Z] ・ Xb [Z] ・ φ [Z] ^1/2 / φ [Z ₀ ] ¹ / ² … (33) bX' [Z] = -P2 _j [Z] / X [Z] / Xa [Z] / φ [Z] ^1/2 / φ [Z ₀ ] ¹ / ² … (34) aY '[Z] = -P2 _j [Z] ・Y [Z] ・ Yb [Z] ・ φ [Z] ^1/2 / φ [Z ₀ ] ¹ / ² … (35) bY '[Z] = P2 _j [Z] ・ Y [Z] ・ Ya [Z ] · Φ [Z] ^1/2 / φ [Z ₀ ] ^1/2 (36) Therefore, the deviation of the trajectory is obtained by integrating the expressions (33) to (36) with respect to Z from the object plane to the image plane (aX [z], bX [Z],
aY [Z], bY [Z]) and (19), (20),

[0018]

(Equation 12)

Xa [Z _i ] = Ya [Z _i ] = 0 at the image plane,

[0020]

(Equation 13)

## EQU1 ##

Xa [Z], Xb [Z] in equation [39] and Y in equation (40)
Substituting Ya [Z] and Yb [Z] for [Z],

[0023]

[Equation 14]

Is obtained.

Equations (41) and (43) show the amounts of displacement of the Wa trajectory from the optical axis on the image plane in the X-axis direction and the Y-axis direction, respectively, and equations (42) and (44) show the X-axis If the magnification in the direction (image size / object size) is Mx and the magnification in the Y-axis direction is My, points (Mx, 0), (0,
My) in the X-axis direction and the Y-axis direction. The defocus per unit current or unit voltage is represented by ΔZx _j , ΔZy _j
Then, δXaj [z _i ] = − Xa ′ [z _i ] ΔZx _j (45) δYaj [z _i ] = − Ya ′ [z _i ] ΔZy _j (46) From equation (43),

[0026]

(Equation 15)

## EQU1 ##

Consider a case in which there are two or more lenses and only the X and Y directions need to be focused. To realize this, when the image plane position changes by ΔZ, the j-th and k-th Q
Assuming that the excitation current or voltage of the lens is I _j , I _k , I _j · ΔZ x _j + I _k · ΔZ x _k = ΔZ (49) I _j · ΔZy _j + I _k · ΔZy _k = ΔZ ... (50) , Can be set. Where ΔZx _j , Δ
Zx _{k and the} like are defocuses per unit current and unit voltage, respectively, and are expressed by Expressions (47) and (48) (hereinafter, even if the suffixes are changed, the focus of each Q lens is changed). The amount of deviation is shown).

From these relational expressions, the expressions (3) and (4) are obtained, and the exciting current or applied voltage of any two Q lenses is calculated as follows.
If the adjustment is performed according to the equations (3) and (4), the X-direction focus and the Y-direction focus can be simultaneously adjusted to a new image plane.

[0030] A second means for solving the above-mentioned problem is as follows.
In a charged particle beam apparatus that forms an image of a charged particle beam emitted from an object surface on an image plane using two or more steps of a Q lens, an XYZ orthogonal coordinate system having an optical axis as a Z axis is taken, and a vacuum is taken. ₀ permeability mu, the absolute value of the charge of the charged particle q, its sign s, the mass of the charged particles m, the on-axis potential and φ [Z], the object plane Z _o, the image plane Z _i and then, Xa two paraxial trajectory of the X-direction in the object plane _{Z o [Z o] = 0} , Xa '[Z o] = 1 Xb [Z o] = 1, Xb' [Z o] = 0 Y -direction Are selected such that Ya [ _Zo ] = 0, Ya '[ _Zo ] = 1, Yb [ _Zo ] = 1, Yb' [ _Zo ] = 0 on the object plane, and the j-th About Q lens of
In the case of a lens, on-axis astigmatic field distribution D2 _j per unit current
[Z] multiplied by s × μ ₀ × {2q / (φ [Z] m)} ^{1/2. In} the case of an electrostatic Q lens, axial astigmatic field distribution F2 _j [Z] per unit voltage Is divided by φ [Z] to obtain the astigmatism field P2 _j [Z] of the _j -th Q lens,

[0031]

(Equation 16)

When the focus slightly changes from a certain in-focus state, the j-th and the k-th
The ratio of the two exciting current or voltage changes I _j and I _k

[0033]

[Equation 17]

A focus adjusting method for a charged particle beam apparatus, characterized in that the adjustment is performed while maintaining the above (claim 2). Here, 'indicates a differential value of each variable by Z.

This means copes with a change in the image plane position while keeping the focal positions in the X direction and the Y direction at the same position.

As can be seen from the above equations (49) and (50), in order to make the focal position shifts in the X-axis direction and the Y-axis direction coincide,
The exciting current or applied voltage between any two Q lenses may be changed according to _{I j · ΔZx j + I k} · ΔZx k = I j · ΔZy j + I k · ΔZy k ... (51). From this, the above equation (5) is obtained, and by adjusting any two Q lenses so as to satisfy the equation (5), the focal point in the X-axis direction and the focal point in the Y-axis direction are matched, The position can be changed.

A third means for solving the above-mentioned problem is:
In a charged particle beam apparatus that forms a charged particle beam emitted from an object surface on an image plane using n (n ≧ 3) stages of Q lenses, an XYZ orthogonal coordinate system having an optical axis as a Z axis taken, the magnetic permeability of vacuum mu _0, q the absolute value of the charge of the charged particles, and the code s, the mass of the charged particles m, and the on-axis potential phi [Z], the object plane Z _o, the image plane and Z _i, Xa two paraxial trajectory of the X-direction in the object plane _{Z o [Z o] = 0} , Xa '[Z o] = 1 Xb [Z o] = 1, Xb' [Z o] the _{Ya [Z o] = 0,} Ya '[Z o] = 1 Yb [Z o] = 1, Yb' [Z o] = 0 at = 0 Y directions of two paraxial trajectory object plane Z _o And the number of lenses used for focus adjustment is r
(N ≧ r ≧ 3), and in the case of the electromagnetic Q lens, the axial astigmatic field distribution D2 _r [Z] per unit current is represented by s × μ ₀ × ｛2q /
(Φ [Z] m)｝ ^{1/2. In} the case of an electrostatic Q lens, the axial astigmatic field distribution F2 _r [Z] per unit voltage is φ
The value obtained by dividing by [Z] is defined as the astigmatism field P2 _r [Z] of each lens, and the height deviation ΔZ of the image plane is detected and Q used for focus adjustment is obtained.
I ₁ the change in 1~r th r pieces of the excitation current or voltage of the lenses, I _2, ... when the I _r,

[0038]

(Equation 18)

[0039] I ₁ so as to satisfy, I _2, ..., a focus adjusting method of the charged particle beam apparatus characterized by setting the I _r (Claim 3). Here, 'indicates the differential value of each variable by Z, and F [Z] = I ₁ · P 2 ₁ [Z] + I ₂ · P _{2 2} [Z] +… + I _r · P 2 _r [Z]… ( 9).

When there are n or more adjustable Q lenses, by adjusting any r of them, both the X-axis and Y-axis directions can be focused on a new image plane. The focal position can be adjusted while keeping the magnification change of the image in the axial direction and the Y-axis direction at Mx / My. That is, when the focus changes by ΔZ, r
The excitation current or voltage Q lens to th, respectively I _1, I _2, ..., When _{I r I 1 · ΔZx 1 +} I 2 · ΔZx 2 + ... + I r · ΔZx r = ΔZ ... (52) _{I 1 · ΔZy 1 + I 2} · ΔZy 2 + ... + I r · ΔZy r = ΔZ ... (53) (δXb 1 [Z 1] · I 1 + δXb 2 [Z 2] · I 2 + ... + δXb r _{[Z r] · I r)} / Mx = (δYb 1 [Z 1] · I 1 + δYb 2 [Z 2] · I 2 + ... + δYb r [Z r] · I r) / My ... (54) so as to _{satisfy, I 1, I 2, ...} , may be set I _r.

Here, the formulas (52) and (53) are obtained by the above formulas (49) and (50).
It corresponds to an expression. The values in parentheses in equation (54) indicate the sum of changes in the image plane position of the Wb trajectory in the X-axis direction and the Y-axis direction in each Q lens, and these are represented by Mx and My, respectively. By making the divided values equal, the change in the magnification of the image position in the X-axis direction and the Y-axis direction can be expressed by Mx /
The focal position can be adjusted while maintaining My. From these equations, (47), (48), and (42), (44),
Equations (6) to (8) are obtained.

A fourth means for solving the above-mentioned problem is as follows.
In a charged particle beam apparatus that forms an image of a charged particle beam emitted from an object surface on an image plane using n (n ≧ 3) or more Q lenses, XYZ orthogonal coordinates with the optical axis as the Z axis Take the system,
The magnetic permeability of vacuum is μ ₀ , the absolute value of the charge of the charged particles is q, the sign is s, the mass of the charged particles is m, and the on-axis potential is φ [Z].
And then, the object plane Z _o, the image plane and Z _i, Xa two paraxial trajectory of the X-direction in the object plane _{Z o [Z o] = 0} , Xa '[Z o] = 1 Xb [Z o] _{= 1, Xb '[Z o} ] = 0 Y direction Ya two paraxial trajectories object plane _{Z o [Z o] = 0} , Ya' [Z o] = 1 Yb [Z o] = 1, Yb 'Select so that [Z _o ] = 0, and set the number of lenses used for focus adjustment to r
(N ≧ r ≧ 3), and in the case of the electromagnetic Q lens, the axial astigmatic field distribution D2 _r [Z] per unit current is represented by s × μ ₀ × ｛2q /
(Φ [Z] m)｝ ^{1/2. In} the case of an electrostatic Q lens, the axial astigmatic field distribution F2 _r [Z] per unit voltage is φ
The value obtained by dividing by [Z] is the astigmatism field P2 _r [Z] of each Q lens.
And then, I _1, I ₂ a variation of 1~r th excitation current or voltage of the Q lens used for focus adjustment, ..., and I _r,
When the focus is slightly out of focus

[0043]

[Equation 19]

[0044] I ₁ so as to satisfy, I _2, ..., a focus adjusting method of the charged particle beam apparatus characterized by adjusting keeping the ratio of I _r (Claim 4). Here, 'indicates the differential value of each variable by Z, and F [Z] = I ₁ · P 2 ₁ [Z] + I ₂ · P _{2 2} [Z] +… + I _r · P 2 _r [Z]… ( 9).

[0045] This means is used to determine the magnification Mx in the X-axis direction and the Y-axis direction.
/ My is kept at a predetermined value, and the focal positions in the X-axis direction and the Y-axis direction are made to coincide with each other to cope with a change in the image plane position.

As can be seen from the above equations (52) and (53), in order to make the focal position shifts in the X-axis direction and the Y-axis direction coincide,
The excitation currents or applied voltages of arbitrary r Q lenses are expressed as I ₁ · ΔZx ₁ + I ₂ · ΔZx ₂ + ... + I _r · ΔZx _r = I ₁ · ΔZy ₁ + I ₂ · ΔZy ₂ + ... + I _r · ΔZy _r ... (55) From this, the above equation (10) is obtained, and by adjusting any r number of Q lenses so as to satisfy the equation (10), while preventing the occurrence of astigmatism,
The focal position can be changed. At this time,
In order to adjust the focal position while maintaining the magnification ratio Mx / My in the X-axis direction and the Y-axis direction at a predetermined value, it is necessary to follow the above equation (58), and from this, equation (8) is obtained.

A fifth means for solving the above-mentioned problem is:
Instead of (8) in the third means or the fourth means, focusing of the charged particle beam apparatus characterized by adjusting keeping the ratio of I ₁ ~I _r so as to satisfy the following equation A method (claim 5).

[0048]

(Equation 20)

In the third means and the fourth means, the focal position is adjusted while maintaining the magnification ratio Mx / My in the X-axis direction and the Y-axis direction at a predetermined value. This means is the same as these means in that the focal point position is adjusted while making the focal points in the X-axis direction and the Y-axis direction coincide with each other.
The difference from these means is that focus adjustment is performed under conditions that eliminate the change in the magnification Mx in the axial direction. As can be seen from equation (54), in order for this condition to be satisfied, (δXb ₁ [Z ₁ ] · I ₁ + δXb ₂ [Z ₂ ] · I ₂ + ... + δXb _r [Z _r ] · I _r ) = 0 It is sufficient that the following holds. From this and equation (42), equation (11) is obtained.

A sixth means for solving the above-mentioned problem is:
Instead of (8) in the third means or the fourth means, focusing of the charged particle beam apparatus characterized by adjusting keeping the ratio of I ₁ ~I _r so as to satisfy the following equation A method (claim 6).

[0051]

(Equation 21)

In the third means and the fourth means, the focal position is adjusted while maintaining the magnification ratio Mx / My in the X-axis direction and the Y-axis direction at a predetermined value. This means is the same as these means in that the focal point position is adjusted while making the focal points in the X-axis direction and the Y-axis direction coincide with each other.
The difference from these means is that focus adjustment is performed under conditions that eliminate the change in the magnification ratio My in the axial direction. As can be seen from equation (54), for this condition to be satisfied, it is necessary to satisfy (δYb ₁ [Z ₁ ] · I ₁ + δYb ₂ [Z ₂ ] · I ₂ + ... + δYb _r [Z _r ] · I _r ) = 0 It is sufficient that the following holds. From this and equation (44), equation (12) is obtained.

A seventh means for solving the above-mentioned problem is:
In a charged particle beam apparatus that forms an image of a charged particle beam emitted from an object surface on an image surface using an n-stage Q lens, the optical axis is set to Z.
Taking an XYZ orthogonal coordinate system with the axis as the axis, the magnetic permeability of vacuum is μ ₀ , the absolute value of the charge of the charged particle is q, the sign is s, the mass of the charged particle is m, and the on-axis potential is φ [ Z], and the object surface is Z
_o , the image plane is Z _i, and the two paraxial orbits in the X direction are the object plane Z _o
In _{Xa [Z o] = 0,} Xa '[Z o] = 1 Xb [Z o] = 1, Xb' [Z o] = 0 the two paraxial trajectory in the Y-direction in the object plane Z _o Ya [Z _o ] = 0, Ya '[ _Zo ] = 1 Yb [ _Zo ] = 1, Yb' [ _Zo ] = 0, and the number of lenses used for focus adjustment is r
(N ≧ r), and in the case of the electromagnetic Q lens, the axial astigmatic field distribution D2 _r [Z] per unit current is s × μ ₀ × ｛2q / (φ
[Z] m)｝ ^{1/2. In} the case of an electrostatic Q lens, the axial astigmatic field distribution F2 _r [Z] per unit voltage is φ [Z].
Is divided into the astigmatic field P2 _r [Z] of each Q lens,
I _1, I ₂ a variation of 1~r th excitation current or voltage of the Q lens used for focus adjustment, ..., when the I _r

[0054]

(Equation 22)

[0055] I ₁ so as to satisfy, I _2, ..., a focus adjusting method of the charged particle beam apparatus characterized by adjusting keeping the ratio of I _r (Claim 7). Here, 'indicates the differential value of each variable by Z, and F [Z] = I ₁ · P 2 ₁ [Z] + I ₂ · P _{2 2} [Z] +… + I _r · P 2 _r [Z]… ( 9).

In this means, by adjusting an arbitrary r number of n-stage Q lenses, the focal points in the X-axis direction and the Y-axis direction can both be focused on the image plane, and the X-axis direction and the Y-axis can be adjusted. The change in the magnification in the axial direction can be adjusted arbitrarily. X
In order to match the focal position in the axial direction and the focal position in the Y-axis direction, the excitation current or the applied voltage of each of the r Q lenses used for the focus adjustment may be changed according to the above equations (6) and (7). .
The change in magnification in the X-axis direction and the Y-axis direction are expressed by equation (13) and (1
It can be changed according to equation 4). The expressions (13) and (14) are obtained from the expressions (42) and (44).

Eighth means for solving the above-mentioned problem is:
A charged particle beam apparatus (Claim 8) is provided with a power supply or a power supply control system enabling the first to seventh means.

By providing the power supply device or the power supply control system with such a function, any one of the first to seventh means can be achieved.

A ninth means for solving the above-mentioned problem is:
A charged particle beam device having an electromagnetic Q lens, wherein when a focus adjustment coil of a predetermined Q lens changes an amount of current flowing through the coil by the same amount, any one of the first to seventh means is used. The charged particle beam apparatus according to claim 9, wherein the number of turns is such that the focus adjustment method described above is realized.

According to this means, by changing the current flowing through the focus adjustment coil of each Q lens by the same amount, any one of the first to seventh means can be realized. Only one power supply device for focus adjustment is required, and the structure can be simple and inexpensive.

[0061]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a first embodiment of the present invention.
It is a schematic diagram of a charged particle beam device for explaining the example of.
In FIG. 1, 1 is an optical axis, 2 is an object plane, 3 is an image plane, 3 'is a new image plane, 4a is a first Q lens, 4b is a second Q lens, 5a is a power supply for the first Q lens, and 5b is a second Q lens. Lens power supply, 6 is a computer, 7X is the trajectory of the electron beam in the X-axis direction, 7
Y is the trajectory of the electron beam in the Y-axis direction, 7X 'is the new trajectory of the electron beam in the X-axis direction, and 7Y' is the new trajectory of the electron beam in the Y-axis direction.

In FIG. 1, similarly to the conventional charged particle beam apparatus, charged particles emitted from a charged particle source (not shown) are passed through an illumination optical system (not shown) to the object surfaces of the Q lens systems 4a and 4b. Illuminate 2. The charged particle beam that has exited the object surface 2 has a trajectory of 7X,
After passing through 7Y, an image is formed on the image plane 3 by the first Q lens 4a and the second Q lens 4b. Here, the position of the image plane changes,
Suppose it has changed to 3 '. The computer 6 receives data ΔZ (distance in the Z-axis direction between the image planes 3 and 3 ′) of defocus from an image plane height measuring device (not shown).

The computer 6 sets the Q lens 4a as the j-th Q lens and the Q lens 4b as the k-th Q lens (3),
The change amount of the excitation current or the applied voltage for the focus adjustment is calculated by the equation (4), and the calculated value is used as the Q lens power supply 5a, 5b.
Give to. The Q lens power supplies 5a and 5b
A change in the excitation current or the applied voltage of a and 4b is adjusted to a given value. As a result, the trajectories of the charged particle beam become like 7X ′ and 7Y ′, and both are imaged on the new image plane 3 ′, and no astigmatism occurs.

FIG. 2 is a schematic view of a charged particle beam apparatus for explaining a second embodiment of the present invention. In FIG. 2, reference numeral 5 denotes a power supply for a focus correction coil. In this embodiment, the Q lenses 4a and 4b
A lens is used. Each Q lens has a focus correction coil.
When the Q-th lens and the Q lens 4b are the k-th Q lens, the ratio is set to match the ratio given by the equation (5).

Under such conditions, the computer 6 receives data ΔZ (distance in the Z-axis direction between the image planes 3 and 3 ′) of defocus from an image plane height measuring device (not shown). You. Calculator 6 calculates the exciting current of Q lens 4a by equation (3),
The power is supplied to the power supply 5. The excitation current is supplied from the power supply device 5 to the Q lens 4a. Since the focus correction coils of the Q lens 4a and the Q lens 4b are connected in series, the current is supplied to the focus correction coil of the Q lens 4b. Also flows. The turn ratio of the focus correction coil is set to match the ratio given by the expression (5), so that the expression (4) is naturally satisfied in the Q lens 4b. As a result, the trajectories of the charged particle beam become like 7X ′ and 7Y ′, and both are imaged on the new image plane 3 ′, and no astigmatism occurs. Therefore, in this embodiment, only one power supply is required for the focus correction coil.

FIG. 3 is a schematic view of a charged particle beam apparatus for explaining a third embodiment of the present invention. In FIG. 3, reference numeral 8 denotes a shunt variable resistor. In this embodiment, electromagnetic Q lenses are used as the Q lenses 4a and 4b. Each Q lens has a focus correction coil, and the number of turns is the same. The value of the variable resistor 8 for shunting is such that the Q lens 4a is
When the lens 4b is a k-th Q lens, the power supply 5
Are adjusted to match the ratio given by equation (5).

Under these conditions, the computer 6 receives data ΔZ (distance in the Z-axis direction between the image planes 3 and 3 ′) of defocus from an image plane height measuring device (not shown). You. Calculator 6 calculates the exciting current of Q lens 4a by equation (3),
The power is supplied to the power supply 5. This exciting current is supplied from the power supply device 5 to the Q lens 4a.
The remaining current shunted flows through the focus correction coil of the Q lens 4b, and the equation (4) is naturally satisfied in the Q lens 4b. As a result, the orbit of the charged particle beam is
7X 'and 7Y', and both form an image on a new image plane 3 ', and no astigmatism occurs. Therefore, in this embodiment as well, only one power supply is required for the focus correction coil.

In the above embodiment, the number of Q lenses is two, but the number of Q lenses is n (n ≧ 3), and arbitrary r of them are first, second,
.., As the r-th Q lens, the excitation current or the applied voltage of each Q lens based on the defocus data ΔZ from the image plane height measuring device so as to satisfy the expressions (6) and (7). Can be adjusted to focus on a new image plane in both the X-axis direction and the Y-axis direction.

In addition, if the condition (8) is satisfied, the change in the magnification of the image in the X-axis direction and the Y-axis direction can be expressed by Mx / M.
The focus position can be adjusted while maintaining the value of y. By satisfying the expression (11) or the expression (12) instead of the expression (8), it is possible to perform the focus adjustment without changing the magnification of the image in the X-axis direction and the Y-axis direction, respectively. it can. Furthermore, if the expressions (13) and (14) are satisfied instead of the expression (8), the magnification change in the X-axis direction and the Y-axis direction can be kept at a predetermined value.

By adjusting the excitation current or applied voltage of the first, second,..., R-th Q lenses while satisfying the expression (10), the focal positions in the X-axis direction and the Y-axis direction can be adjusted. The focal position can be adjusted while keeping the movement amount the same.

In addition, if the condition (8) is satisfied, the change in magnification of the image in the X-axis direction and the Y-axis direction is represented by Mx / M.
The focus position can be adjusted while maintaining the value of y. By satisfying the expression (11) or the expression (12) instead of the expression (8), it is possible to perform the focus adjustment without changing the magnification of the image in the X-axis direction and the Y-axis direction, respectively. it can. Furthermore, if the expressions (13) and (14) are satisfied instead of the expression (8), the magnification change in the X-axis direction and the Y-axis direction can be kept at a predetermined value.

[0072]

As described above, according to the first aspect of the present invention, when the image plane position changes by ΔZ, the focal positions in the X-axis direction and the Y-axis direction are both changed by ΔZ.
And focus on the new image plane.

According to the second aspect of the present invention, it is possible to perform the focus adjustment while keeping the amount of movement of the focus in the X-axis direction and the Y-axis direction the same.

According to the third aspect of the present invention, when the image plane position changes by ΔZ, the focal positions in the X-axis direction and the Y-axis direction can both be changed by ΔZ, and the focus on the new image plane is changed. Can be matched. Also, the X-axis direction and Y
Focus adjustment can be performed while maintaining the ratio of the change in magnification of the image in the axial direction to the original magnification ratio.

In the invention according to the fourth aspect, the focus can be adjusted while keeping the same amount of movement of the focus in the X-axis direction and the Y-axis direction. Further, the focus can be adjusted while maintaining the ratio of the change in the magnification of the image in the X-axis direction to the magnification in the Y-axis direction at the original magnification ratio.

In the invention according to claim 5, the focus can be adjusted while preventing a change in magnification of the image in the X-axis direction.

In the invention according to claim 6, the focus can be adjusted while preventing a change in magnification of the image in the Y-axis direction.

According to the seventh aspect of the present invention, both the focal points in the X-axis direction and the Y-axis direction can be focused on the image plane, and the change in magnification in the X-axis direction and the Y-axis direction can be arbitrarily adjusted. Can be.

In the invention according to claim 8, claim 1 is
Accordingly, the focus adjustment method according to the seventh aspect can be realized.

According to the ninth aspect of the present invention, only one power supply device for focus adjustment is required, and the structure can be made simple and inexpensive.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a charged particle beam device for describing a first embodiment of the present invention.

FIG. 2 is a schematic diagram of a charged particle beam device for explaining a second embodiment of the present invention.

FIG. 3 is a schematic diagram of a charged particle beam device for describing a third embodiment of the present invention.

FIG. 4 is a schematic view showing an example of a conventional charged particle beam device.

FIG. 5 is a schematic diagram illustrating an example of a configuration of an electrostatic Q lens.

FIG. 6 is a schematic diagram illustrating an example of the configuration of an electromagnetic Q lens.

FIG. 7 is a diagram showing a state when an image plane changes in a conventional charged particle beam device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Optical axis 2 ... Object surface 3 ... Image surface 3 '... New image surface 4a ... 1st Q lens 4b ... 2Q lens 5 ... Power supply device of a focus correction coil 5a ... 1Q lens power supply 5b ... 2Q lens Power source 6 ... Computer 7X ... Orbit of electron beam in X-axis direction 7Y ... Orbit of electron beam in Y-axis direction 7X '... New orbit of electron beam in X-axis direction 7Y' ... New orbit of electron beam in Y-axis direction 8 ... Variable resistor for shunt

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) H01L 21/027 H01L 21/30 541F

Claims (9)

[Claims] 1. A charged particle beam apparatus for imaging a charged particle beam emitted from an object surface on an image plane by using two or more Q lenses, XYZ orthogonal coordinates having an optical axis as a Z axis. Take the system, the vacuum permeability is μ ₀ , the absolute value of the charge of the charged particles is q, the sign is s, the mass of the charged particles is m, and the on-axis potential is φ
And [Z], the object plane is Z _o, the image plane and Z _i, the object plane two paraxial trajectory of X-direction Z _o at _{Xa [Z o] = 0,} Xa '[Z o] = 1 Xb [ _{Z o] = 1, Xb '} [Z o] = 0 object surface two paraxial trajectory in the Y-direction Z _o at _{Ya [Z o] = 0,} Ya' [Z o] = 1 Yb [Z o] = 1, Yb ′ [Z _o ] = 0, and the electromagnetic Q
In the case of a lens, on-axis astigmatic field distribution D2 _j per unit current
[Z] multiplied by s × μ ₀ × {2q / (φ [Z] m)} ^{1/2. In} the case of an electrostatic Q lens, axial astigmatic field distribution F2 _j [Z] per unit voltage Is divided by φ [Z] to obtain the astigmatism field P2 _j [Z] of the j-th Q lens. Then, the height shift ΔZ of the image plane is detected, and the j-th and k-th two exciting currents or voltage changes I _j and I _k of the Q lens are calculated as follows: A focus adjustment method for a charged particle beam apparatus, characterized in that: Here, 'indicates a differential value of each variable by Z. 2. A charged particle beam apparatus for imaging a charged particle beam emitted from an object surface on an image plane using two or more Q lenses, wherein XYZ orthogonal coordinates having an optical axis as a Z axis. Take the system, the vacuum permeability is μ ₀ , the absolute value of the charge of the charged particles is q, the sign is s, the mass of the charged particles is m, and the on-axis potential is φ
And [Z], the object plane is Z _o, the image plane and Z _i, the object plane two paraxial trajectory of X-direction Z _o at _{Xa [Z o] = 0,} Xa '[Z o] = 1 Xb [ _Zo ] = 1, Xb '[ _Zo ] = 0 Two paraxial trajectories in the Y direction are represented by Ya [ _Zo ] = 0, Ya' [ _Zo ] = 1, Yb [ _Zo ] = 1 in the object plane. Yb ′ [Z _o ] = 0, and the electromagnetic Q
In the case of a lens, on-axis astigmatic field distribution D2 _j per unit current
[Z] multiplied by s × μ ₀ × {2q / (φ [Z] m)} ^{1/2. In} the case of an electrostatic Q lens, axial astigmatic field distribution F2 _j [Z] per unit voltage Is divided by φ [Z] to obtain an astigmatism field P2 _j [Z] of the j-th Q lens. When (s = a, b), when the focus slightly changes from a certain in-focus state, the change amounts I _j and I of the two excitation currents or voltages of the j-th and k-th of the Q lens are changed. The ratio of _k is given by And adjusting the focus of the charged particle beam apparatus. Here, 'indicates a differential value of each variable by Z. 3. A charged particle beam emitted from an object surface is represented by n (n
≧ 3) In a charged particle beam apparatus that forms an image on an image plane using a Q lens of a stage, an XYZ orthogonal coordinate system with the optical axis as the Z axis is used, the vacuum permeability is μ ₀ , the charged particles are The absolute value of the electric charge of q, the sign thereof is s, the mass of the charged particle is m, the on-axis potential is φ [Z], the object plane is Z _o , the image plane is Z _i, and two paraxial axes in the X direction Xa orbit in the object plane _{Z o [Z o] = 0} , Xa '[Z o] = 1 Xb [Z o] = 1, Xb' object plane to [Z _o] = 0 2 two paraxial trajectory in the Y-direction In _Zo , Ya [ _Zo ] = 0, Ya '[ _Zo ] = 1, Yb [ _Zo ] = 1, Yb' [ _Zo ] = 0, and the number of lenses used for focus adjustment is r.
(N ≧ r ≧ 3), and in the case of an electromagnetic Q lens, the axial astigmatic field distribution D2 _r [Z] per unit current is s × μ ₀ × ｛2q /
(Φ [Z] m)｝ ^{1/2. In} the case of an electrostatic Q lens, the axial astigmatic field distribution F2 _r [Z] per unit voltage is φ
The value obtained by dividing by [Z] is defined as the astigmatism field P2 _r [Z] of each lens.
I ₁ the change in 1~r th r pieces of the excitation current or voltage of the lenses, I _2, ... when the I _r, Equation 5] I _1, I ₂ so as to satisfy, ..., the focus adjusting method of the charged particle beam apparatus characterized by setting the I _r. Where '
Indicates the differential value of each variable by Z, and F [Z] = I ₁ · P 2 ₁ [Z] + I ₂ · P _{2 2} [Z] + ... + I _r · P 2 _r [Z] is there. 4. A charged particle beam emitted from an object surface is represented by n (n
≧ 3) In a charged particle beam apparatus that forms an image on an image plane using a Q lens of a stage, an XYZ orthogonal coordinate system with the optical axis as the Z axis is used, the vacuum permeability is μ ₀ , the charged particles are The absolute value of the electric charge of q, the sign thereof is s, the mass of the charged particle is m, the on-axis potential is φ [Z], the object plane is Z _o , the image plane is Z _i, and two paraxial axes in the X direction Xa orbit in the object plane _{Z o [Z o] = 0} , Xa '[Z o] = 1 Xb [Z o] = 1, Xb' object plane to [Z _o] = 0 2 two paraxial trajectory in the Y-direction In _Zo , Ya [ _Zo ] = 0, Ya '[ _Zo ] = 1, Yb [ _Zo ] = 1, Yb' [ _Zo ] = 0, and the number of lenses used for focus adjustment is r.
(N ≧ r ≧ 3), and in the case of the electromagnetic Q lens, the axial astigmatic field distribution D2 _r [Z] per unit current is represented by s × μ ₀ × ｛2q /
(Φ [Z] m)｝ ^{1/2. In} the case of an electrostatic Q lens, the axial astigmatic field distribution F2 _r [Z] per unit voltage is φ
The value obtained by dividing by [Z] is the astigmatism field P2 _r [Z] of each Q lens.
And then, I _1, I ₂ a variation of 1~r th excitation current or voltage of the Q lens used for focus adjustment, ..., and I _r,
When the focus is slightly deviated from a certain in-focus state I _1, I _2, ..., the focus adjusting method of the charged particle beam apparatus characterized by adjusting keeping the ratio of I _r to satisfy.
Here, 'indicates the differential value of each variable by Z, and F [Z] = I ₁ · P 2 ₁ [Z] + I ₂ · P _{2 2} [Z] +… + I _r · P 2 _r [Z]… ( 9). 5. Instead of (8) in claim 3 or claim 4, the following equation charged particle beam apparatus characterized by adjusting keeping the ratio of I ₁ ~I _r so as to satisfy Focus adjustment method. (Equation 7) 6. Instead of (8) in claim 3 or claim 4, the following equation charged particle beam apparatus characterized by adjusting keeping the ratio of I ₁ ~I _r so as to satisfy Focus adjustment method. (Equation 8) 7. An XYZ orthogonal coordinate system having an optical axis as a Z axis in a charged particle beam apparatus for imaging a charged particle beam emitted from an object surface on an image plane using an n-stage Q lens. Take
The magnetic permeability of vacuum is μ ₀ , the absolute value of the charge of the charged particles is q, the sign is s, the mass of the charged particles is m, and the on-axis potential is φ [Z].
And then, the object plane Z _o, the image plane and Z _i, Xa two paraxial trajectory of the X-direction in the object plane _{Z o [Z o] = 0} , Xa '[Z o] = 1 Xb [Z o] _{= 1, Xb '[Z o} ] = 0 Y direction Ya two paraxial trajectories object plane _{Z o [Z o] = 0} , Ya' [Z o] = 1 Yb [Z o] = 1, Yb 'Select so that [Z _o ] = 0, and set the number of lenses used for focus adjustment to r
(N ≧ r), and in the case of the electromagnetic Q lens, the axial astigmatic field distribution D2 _r [Z] per unit current is s × μ ₀ × ｛2q / (φ
[Z] m)｝ ^{1/2. In} the case of an electrostatic Q lens, the axial astigmatic field distribution F2 _r [Z] per unit voltage is φ [Z].
Is divided into the astigmatic field P2 _r [Z] of each Q lens,
I _1, I ₂ a variation of 1~r th excitation current or voltage of the Q lens used for focus adjustment, ..., [Expression 9] when the I _r I _1, I _2, ..., the focus adjusting method of the charged particle beam apparatus characterized by adjusting keeping the ratio of I _r to satisfy.
However, 'denotes a differential value by Z for each _{variable, F [Z] = I 1} · P2 1 [Z] + I 2 · P2 2 [Z] + ... + I r · P2 r [Z] ... ( 9). 8. One of claims 1 to 7
A charged particle beam device comprising a power supply or a power supply control system that enables the focus adjustment method described in the section. 9. A charged particle beam apparatus having an electromagnetic Q lens, wherein the focus adjustment coil of a predetermined Q lens changes the current flowing through the coil by the same amount. A charged particle beam device, wherein the number of turns is such that the focus adjustment method according to any one of the claims is realized.