JPH07153665A - Mask holding method and mask as well as manufacture of device using it - Google Patents

Abstract

PURPOSE:To position and hold a mask with high accuracy even when the mask is tilted to the horizontal direction by a method wherein a conical-hole part is pressed first. CONSTITUTION:Individual clamp arms 3a to 3c are turned to the side on which a mask is pressed, they are then moved slightly to the side of a mask chuck, and a mask frame 1 is captured by the mask chuck 2. In this state, the distance between hemispherical protrusions 2a, 2b and the clamp arms 3a, 3b is smaller than the thickness of a mask-holding part at a conical-hole part 1a and a V- groove 1b. As a result, a mask is supported by the protrusions at two parts and it is set to a suspended state. At this time, only thr clamp arm 3a is moved further to the side of the mask chuck, and it presses the conical-hole part 1a and the protrusion part 2a which are coupled. Thereby, the influence of an excessive restraint due to a frictional force and due to the own weight of the mask is avoided, the mask can be positioned and fixed precisely, and, at the same time, it is possible to restrain the deformation of a pattern on the mask from being caused.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of holding a mask used in an exposure apparatus.

[0002]

2. Description of the Related Art In recent years, the degree of integration of semiconductor integrated circuits has become higher and higher, and the semiconductor manufacturing equipment for manufacturing them has a higher printing line width due to the higher integration density. Exposure accuracy is required. To make the printing line width narrower, it is effective to shorten the wavelength of the light source used for exposure. Therefore, development of an X-ray exposure apparatus using X-rays having a wavelength shorter than that of ultraviolet light, which is generally used at present, is underway.

FIG. 16 schematically shows an X-ray mask and a mask chuck mounted on a conventional X-ray exposure apparatus. FIG.
(A) is an X-ray mask. Reference numeral 100 denotes a reinforcing mask frame, 101 denotes a mask substrate made of silicon, and 102.
Is an inorganic film (mask membrane) formed by removing a part of the mask substrate by back etching, and 103 is a transfer pattern of a semiconductor circuit or the like drawn and formed on the mask membrane by an EB drawing device or the like. Reference numeral 105 denotes a magnetic ring made of a magnetic material, which is embedded in the mask support frame 1. FIG. 16B shows a magnetic chuck type mask chuck. Reference numeral 110 is a ring-shaped chuck base, and a hole 111 through which an X-ray for exposure passes is provided inside. Reference numeral 112 denotes a magnetic unit, which is the magnetic ring 105.
Corresponding to the above, the magnetic force is sufficient to attract and hold the X-ray mask. In this structure, the mask frame 100 of the X-ray mask is the chuck base 110.
It is magnetically attracted and held by the holding surface of the.
In addition to this magnetic attraction method, there is also a vacuum attraction method. In that case, a vacuum port is used instead of the magnetic unit, and the mask frame and the chuck base are brought into surface contact with each other by a vacuum force to be attracted and held.

However, these adsorption holding methods are
Since the mask frame 100 and the chuck base 110 are in surface contact with each other, it is necessary to finish the contact surfaces between them with high flatness. If the transfer pattern is formed by the EB drawing device during mask fabrication, the mask frame 100
If there is a slight distortion such as a warp on the suction surface of the mask frame 100, the warp of the mask frame 100 is corrected and the mask frame 100 is deformed when the mask frame 100 is held by the chuck base 110 of the X-ray exposure apparatus. 101 is transmitted to the transfer pattern 103 through the mask membrane 102, and the transfer pattern 103 may be distorted with respect to the time of drawing. The thickness of the mask membrane 102 on which the transfer pattern 103 is formed is about 2 μm and is several mm.
Compared with the thick mask substrate 101 and the mask frame 100, the rigidity thereof is very small. Therefore, the mask substrate 1
01 and the distortion of the mask frame 100 have a great influence on the mask membrane 102 and also cause a large distortion on the transfer pattern. This can be said to be a problem peculiar to a mask in which a transfer pattern is formed on an ultrathin mask membrane.

As a method of solving this, when the mask is chucked by the mask chuck, the X-ray mask is not deformed by the holding force, in other words, the mask frame is held while maintaining the distorted state at the time of pattern formation. A method of doing so (hereinafter referred to as a kinematic mount) has been proposed.

FIG. 17 shows an example of a kinematic mount. FIG. 17A shows an X-ray mask for kinematic mount. Reference numeral 117 is a conical (funnel-shaped) hole portion, 118 is a flat surface portion, and 119 is a V groove portion in which a linear cut groove is formed along the X direction in the drawing, and these are formed on the holding surface of the mask frame 100. Has been done. FIG. 17
(B) shows a mask chuck for a kinematic mount. On the holding surface of the chuck base 110, spherical protrusions 120 that engage with the conical hole portion 117, the flat surface portion 118, and the V groove portion 119 of the mask are provided at three locations. Further, a clamp mechanism 115 for mechanically pressing and holding the mask at three points is provided.

In this structure, the holding state shown below is established at each point, and the six degrees of freedom of the mask are positioned without excessive constraint.

[0008] According to this kinematic mount, an external force that deforms the mask frame 100 hardly acts when holding the mask during exposure, and the mask can be held (strain-free) in the same state as when the mask pattern is formed by the EB drawing device. The feature is that pattern distortion due to deformation of the mask support frame can be suppressed.

[0009]

However, when the mask is held vertically against the gravity by the above-mentioned kinematic mount method, the mask must be clamped, and the clamp mechanism and the mask must be clamped. Since the frictional force and the self-weight of the mask are added between them, if strictly viewed, they are over-constrained, and accurate positioning of the mask is difficult. Further, as a result of excessive restraint, moment force is generated in the mask, which also causes pattern distortion.

The present invention has been made to solve the above-mentioned problems, and provides a kinematic mount system and a mask capable of highly accurately positioning and holding the mask even when tilted with respect to the horizontal direction, and a device manufacturing method using the same. With the goal.

[0011]

According to one mode of the present invention for solving the above-mentioned problems, a conical hole portion, a V groove portion, and a flat surface portion provided on a mask are engaged with three protrusions provided on a mask chuck, respectively. In the method of pressing and holding the mask at three positions, the conical hole portion is first pressed, which is a mask holding method.

Further, according to another aspect of the present invention, the conical hole portion, the V groove portion, and the flat surface portion provided on the mask and the three projection portions provided on the mask chuck are engaged with each other and pressed, and at three positions. In the method of holding a mask, the pressing force of the conical hole portion is maximum, which is a mask holding method.

[0013]

【Example】

<Embodiment 1> An embodiment of the present invention will be described with reference to the drawings. 1 is a block diagram of the mask chuck of the first embodiment, FIG.
Is a sectional view thereof. The mask is held vertically on the mask chuck 2 against gravity. As for the mask, a silicon mask substrate 7 is attached to a ring-shaped mask frame 1, and a membrane having a transfer pattern 8 made of gold or the like is provided inside the mask substrate 7. Further, on the back surface side of the mask frame 1, (1) a funnel-shaped conical hole portion 1a, (2) a straight V-shaped groove portion 1b whose ridge line faces the conical hole portion 1a, (3) a flat surface portion 1c,
Are provided at three locations. These are provided at three equal intervals (120 ° pitch) on the same circumference with the mask center as the circle center. On the other hand, the mask chuck 2 is provided with protrusions 2a to 2c having hemispherical tips at three positions so as to face and engage with the conical hole portion 1a, the V groove portion 1b and the flat surface portion 1c, respectively. There is. Further, three clamp arms 3a to 3c are provided. Each clamp arm can rotate and move linearly, and the mask frame 1 is sandwiched by each clamp arm and the protrusion of the mask chuck. As a modified example, the configuration shown in FIG. 3 may be used.
2 to 2c are independently projected, and the clamp arm 3 performs only a rotating operation.

The operation procedure of this embodiment will be described below. When the mask is conveyed to the mask chuck surface by a mask hand (not shown), the clamp arms 3a to 3c rotate to the side for pressing the mask, and then move slightly to the mask chuck side to move the mask frame 1 to the mask chuck 2 To capture. In this state, the distance between the hemispherical protrusions 2a, 2b and the clamp arms 3a, 3b in the conical hole 1a and the V-shaped groove 1b is smaller than the thickness T (see FIG. 4) of the holding portion of the mask. At this point, the mask is supported by the protrusions and hangs down to prevent the mask from falling. However, the mask can move slightly rather than being strongly pressed.

Here, first, only the clamp arm 3a is further moved to the mask chuck side, and the conical hole portion 1a and the projection portion 2a which are engaged with each other are pressed as shown in FIG. As a result, three degrees of freedom (XYZ) are positioned. Here, the tip of the protrusion 2a and the tip of the clamp arm 3a exactly face each other. For example, as shown in FIG. 4, the conical hole portion 1a
Is not accurately positioned, a moment force is generated in the mask frame due to the amount of eccentricity δ _C , which causes pattern distortion.

Next, the V-groove 1b and the projection 2b are pressed against each other by further retracting the clamp arm 3b.
With this, the two degrees of freedom (θ _X, θ _Y ) in the rotation direction of the mask are fixed. Finally, the remaining clamp arm 3c is pulled in and the flat surface 1c and the projection 2c are pressed to fix the remaining 1 degree of freedom (θ _Z ), which allows the mask to be positioned and fixed without excessive constraint in 6 degrees of freedom. Will be.

FIG. 4 shows the relationship of the forces acting on the conical hole portion 1a of the mask when the mask is supported by the conical hole portion. With the V-groove portion 1b and the flat surface portion 1c not fixed, the condition necessary for positioning and fixing the mask in the conical hole portion 1a by the pressing force f _C of the conical hole portion 1a will be obtained. Here, let us consider the condition shown in FIG. 5, which is considered to be under severe conditions, that is, the case where the conical hole portion 1a exists on the center of gravity of the mask. Assuming that the groove angle θc of the conical hole 1a with respect to the plane parallel to the mask plane is the force F acting in the direction of gravity, it is sufficient to consider only the weight W of the mask and the frictional force due to the clamp arm force fc, so F = W + μ ₁ × f _C (1) (μ ₁ : coefficient of friction between clamp arm and mask) From the balance of forces, the normal force acting in the direction of the conical hole is the normal force N _C = f _C × cos θ _C + F × sin θ _C (2) The frictional force acting on the conical hole is frictional force = μ ₂ × N _C (3) (μ ₂ : Friction coefficient between the protrusion and the mask) To overcome the frictional force and position and fix the mask, pull up force _{= f C × sinθ C -F ×} cosθ C ≧ μ 2 × (f C × cosθ C + F × sinθ C) (4) should satisfy.

First, the conical hole portion 1a has three degrees of freedom (XYZ).
After positioning the V groove, it is better to position the V groove. This is because if the flat surface is positioned first, when the V groove 1b is finally positioned, an excessive frictional force with the flat surface is applied, and a larger force is applied to the positioning. Is necessary.

The condition for positioning the V groove portion 1b is that W = 0 in the equation (1) and F = μ ₁ × f _V (5) is substituted into the equation (1) to perform the calculation, and the relation of the equation (4) is obtained. Should be satisfied. However, using a groove angle theta _v against a plane parallel to the mask plane of the V-groove instead of theta _C, f instead of f _{C
Use V.}

As a modified example, in the state shown in FIG. 6, that is, when the conical hole portion 1a and the V groove portion 1b are arranged orthogonal to the direction of gravity, W'instead of W in the equation (1) is used. = {(W / 2) ² + F ′ ² } ^1/2 where F ′ = μ ₂ × W / (2 sin θ _V ) + μ ₁ × W cos θ _V / (2 sin θ _V ) (1 ′) ) And calculate it. The force applied to the V groove portion 1b is W '= W / 2,
Similarly, the relationship of Expression (4) may be satisfied by substituting it into Expression (1).

As another modification, when the V groove 1b is on the center of gravity of the mask, instead of W in the formula (1),

[0022]

[Outer 1] Should be substituted into the equation (1) for calculation to satisfy the relation of the equation (4).

In FIG. 10, the weight of the mask W = 200 g, μ
The results when ₁ = μ ₂ and θ _V = θ _C are shown. The horizontal axis shows the angle (deg) of the conical hole portion 1a, and the vertical axis shows the necessary pressing force at the conical hole portion 1a. Regarding the conical hole portion 1a, it can be seen that the conical hole portion 1a and the V groove portion 1b can be positioned more easily if they are arranged horizontally with respect to the direction of gravity (that is, the form of FIG. 6).

<Embodiment 2> In the above embodiment, the conical hole portion, V
A method of fixing the mask by pressing the groove portion and the flat portion in this order was used, but another method will be described below.

When the two parts of the V-groove portion 1b and the flat surface portion 1c are initially positioned and fixed, the V-groove portion 1b and the flat surface 1c are fixed.
The condition for overcoming the force generated in step 1 and enabling positioning in the conical hole 1a is obtained. FIG. 5 shows the force generated in the conical hole portion 1a and the mask. From the figure, V
For groove 1b, vector F _V = μ ₁ × f _V + μ ₂ × f _V / cos θ _V (6) For plane 1c, vector F _F = μ ₁ × f _F + μ ₂ × f _F (7) In the vector synthesis of, vector F ′ = vector F _V + vector F _F + vector W, and here, for simplification, W = 0 is set. Part 1a and V groove 1b
Equation (2) can be applied wherever is.

F ′ = F _V cos α + F _F cos (60 ° −α) (8) Here, the angle formed by the three FCVs = 60 °, tan α = 3/2
F _F / (F _V +1/2 F _F )

F = F ′ + μ ₁ × f _C (9) The equation (9) may be substituted into the equation (1) and the same calculation may be performed to satisfy the relation of the equation (4).

Μ ₁ = μ ₂ , θ _V = θ _C , f _C = f _V = f
The calculation result when _F is shown in FIG. The horizontal axis represents the coefficient of friction, and the vertical axis represents the pulling force (dimensioned at f _C ) required to position the misaligned mask by the conical hole portion. Positioning cannot be performed if the pulling force is in the negative range. In order to enable positioning, the angle θ _C of the conical hole 1a = 6
Even when the angle is 0 °, it is necessary that the coefficient of friction is 0.12 or less. Furthermore, if the weight of the mask is taken into consideration, it is difficult to perform accurate positioning as it is.

Therefore, in order to enable the positioning, the pressing force of the conical hole portion 1a is maximized and the pressing forces of the other two places are weakened. The force applied to the plane portion may be the minimum force required to restrain the out-of-plane direction, and even if a force greater than this is applied, an excessive frictional force is generated. Therefore, the relationship of the pressing force is F _C (conical hole portion)> F _V (V groove portion)> F
Most preferably, it is _F (flat part).

As another method, the equation (9) is replaced by the equation (2).
And the relationship between the angle θ _C of the conical hole portion and the angle θ _V of the V groove portion may be set to θ _C > θ _{V so} as to satisfy the relationship of Expression (4).

<Example 3> In addition to the above method, the friction coefficient μ
_{It is possible} to reduce the self-weight W of ₁ or the mask.
A specific example of a method of reducing μ ₁ will be described. Here, consider reducing the frictional resistance on the clamp arm side. It can be obtained by setting μ ₁ = 0 in the equations (1), (6) and (7) and substituting each equation into the equation (2) to perform the calculation.

FIG. 12 shows the calculation result. The horizontal axis represents the coefficient of friction, and the vertical axis represents the force for pulling up the mask necessary for positioning (dimensioning at f _C ). Positioning cannot be performed if the vertical axis is in the negative range. Although FIG. 12 does not consider the influence of the weight of the mask for simplification, it can be seen that the effect of reducing friction is greater than that in FIG. The weight of the mask can be reduced to 0 by using a weight compensation spring.

FIG. 7 shows a specific structure for reducing the frictional resistance on the clamp arm side. Air is ejected from the tip of the clamp arm to reduce the friction coefficient at the contact point between the mask frame 1 and the tip of the clamp arm. . When the positioning is complete, the air blow is stopped and the solid contact clamps.

<Embodiment 4> FIG. 8 shows an embodiment in which a spring material having a high rigidity in the mask chuck pressing direction of the mask and a low rigidity in the lateral direction orthogonal thereto is used as the clamp arm. Clamp arm has multiple parallel bar springs 1
Supported by 0. By bending the spring when the mask frame is pressed, the same effect as that of reducing the friction coefficient μ ₁ can be obtained.

<Embodiment 5> Next, a specific example of reducing W will be described. FIG. 9 is a diagram showing a state where the mask hand 11 conveys the mask to the holding surface of the mask chuck 2 and the mask hand 11 presses the mask. In order to make it easier to attach the mask, the clamp arm 3 that was initially retracted is in a trapped state when the mask pressing operation is performed to prevent the mask from falling. 12
Is a suction pad of the mask hand. Mask hand 11
After the mask is completely positioned with respect to the mask chuck 2, the clamp arm 3 fixes the mask. The weight W of the mask is substantially W = 0 because the mask hand 11 supports it.

<Embodiment 6> An embodiment of an exposure apparatus for manufacturing a microdevice (semiconductor device, thin film magnetic head, micromachine, etc.) using the mask and mask chuck described above will be described. FIG. 13 is a view showing the arrangement of the X-ray exposure apparatus according to this embodiment. In the figure, a sheet beam-shaped synchrotron radiation 21 emitted from an SR radiation source 20.
Are enlarged by the convex mirror 22 in a direction perpendicular to the orbital plane of the emitted light. The radiated light reflected and expanded by the convex mirror 22 is adjusted by the shutter 23 so that the exposure amount in the irradiation area becomes uniform, and the radiated light passed through the shutter 23 is X.
It is guided to the line mask 24. The X-ray mask 24 is held by a mask chuck (not shown) by the mounting method as described above. The exposure pattern formed on the X-ray mask 24 is exposed and transferred onto the wafer 25 by a step & repeat method or a scanning method.

Next, an embodiment of a device manufacturing method using the above-described exposure apparatus will be described. FIG. 14 shows microdevices (semiconductor chips such as IC and LSI, liquid crystal panels, C
A flow of manufacturing a CD, a thin film magnetic head, a micromachine, etc. is shown. In step 1 (circuit design), a semiconductor device circuit is designed. In step 2 (mask manufacturing), a mask having the designed circuit pattern is manufactured. On the other hand, in step 3 (wafer manufacturing), a wafer is manufactured using a material such as silicon. Step 4 (wafer process) is called a pre-process, and an actual circuit is formed on the wafer by the lithography technique using the mask and the wafer prepared above. The next step 5 (assembly) is called a post-process, and is a process of forming a semiconductor chip by using the wafer manufactured in step 4, such as an assembly process (dicing, bonding), a packaging process (chip encapsulation), and the like. including. In step 6 (inspection), an operation confirmation test of the semiconductor device manufactured in step 5,
Conduct inspections such as durability tests. Through these steps, the semiconductor device is completed and shipped (step 7).

FIG. 15 shows the detailed flow of the wafer process. In step 11 (oxidation), the surface of the wafer is oxidized. In step 12 (CVD), an insulating film is formed on the wafer surface. In step 13 (electrode formation), electrodes are formed on the wafer by vapor deposition. In step 14 (ion implantation), ions are implanted in the wafer. Step 1
In 5 (resist processing), a photosensitive agent is applied to the wafer. In step 16 (exposure), the circuit pattern of the mask is printed and exposed on the wafer by the exposure apparatus described above. In step 17 (development), the exposed wafer is developed. In step 18 (etching), parts other than the developed resist image are removed. In step 19 (resist stripping), the resist that is no longer needed after etching is removed. By repeating these steps, multiple circuit patterns are formed on the wafer. By using the manufacturing method of this embodiment, it is possible to manufacture a highly integrated semiconductor device, which has been difficult to manufacture in the past.

[0039]

According to the present invention, the influence of excessive restraint due to the frictional force and the weight of the mask can be avoided, whereby accurate positioning and fixing of the mask can be realized, and at the same time generation of pattern distortion of the mask can be suppressed. .

[Brief description of drawings]

FIG. 1 is a configuration diagram of a first embodiment of the present invention.

FIG. 2 is a sectional view of the configuration of the first embodiment.

FIG. 3 is a cross-sectional view showing a modified example of FIG.

FIG. 4 is an explanatory diagram showing a condition of a force applied to a conical hole portion.

FIG. 5 is a diagram showing a force applied to a mask when a conical hole portion is located on the mask center of gravity line.

FIG. 6 is a diagram showing a force applied to a mask in which a conical hole and a V groove are horizontally arranged with respect to gravity.

FIG. 7 is an explanatory diagram of an embodiment in which air is ejected from the tip of a clamp arm.

FIG. 8 is an explanatory diagram of a clamp arm using a spring material having high rigidity in a pressing direction and low rigidity in a lateral direction.

FIG. 9 is an explanatory diagram of an example of pressing and positioning with a mask hand.

FIG. 10 is a graph showing a necessary clamp arm force when positioning and fixing is performed only with a conical hole portion.

FIG. 11 is a graph showing a necessary pulling force when a clamp arm is used at three locations simultaneously.

FIG. 12 is a graph showing a necessary pulling force when the frictional force between the clamp arm and the mask is zero.

FIG. 13 is an overall view showing an embodiment of an X-ray exposure apparatus.

FIG. 14 is a diagram showing a flow of a device manufacturing method.

FIG. 15 is a diagram showing a detailed flow of a wafer process.

FIG. 16 is a diagram illustrating a conventional magnetic chuck type mask chuck.

FIG. 17 is a diagram illustrating a conventional kinematic mount type mask chuck.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Mask frame 1a Conical hole part 1b V groove part 1c Plane part 2 Mask chucks 2a to 2c Projection part 3 Clamp arm 4 Mask hand 7 Mask substrate 8 Transfer pattern

Claims (11)

[Claims] 1. A method of holding a mask at three locations by engaging a conical hole portion, a V-shaped groove portion, and a flat surface portion provided on a mask with three protrusions provided on a mask chuck, respectively, and pressing them against each other. A mask holding method characterized in that a conical hole portion is first pressed. 2. The mask holding method according to claim 1, wherein the V groove portion is pressed next to the conical hole portion. 3. A method of holding a mask at three locations by engaging a conical hole portion, a V groove portion, and a flat surface portion provided on a mask with three protrusions provided on a mask chuck, respectively, and pressing the projections. A method for holding a mask, wherein the pressing force of the conical hole portion is maximum. 4. The mask holding method according to claim 1, wherein the pressing force of the V-shaped groove portion is large next to the conical hole portion. 5. The mask holding method according to claim 1, wherein the mask is held vertically against gravity. 6. The mask holding method according to claim 1, wherein the pressing is performed by a clamp mechanism. 7. The mask holding method according to claim 1, wherein the pressing is performed by a mask hand that supplies the mask to a mask chuck. 8. A device manufacturing method, comprising: holding a mask by the mask holding method according to claim 1; and exposing and transferring a transfer pattern of the held mask onto a wafer. Method. 9. The device manufacturing method according to claim 8, wherein the exposure transfer is performed by X-ray. 10. An exposure mask is provided with a conical hole portion, a V groove portion, and a flat surface portion at three positions on a mask holding surface, and when the mask is held by a mask chuck, it is provided at three positions on the mask chuck holding surface. A mask adapted to be engaged with each of the protrusions, wherein the angle of the conical hole is larger than the angle of the V groove. 11. The mask according to claim 10, wherein the mask is a mask for X-ray exposure.