JP3359330B2 - Mask holding method and mask, and device manufacturing method using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art In recent years, the integration density of semiconductor integrated circuits has been increasing more and more, and the semiconductor manufacturing equipment for manufacturing them has also been reduced in printing line width as the integration density has increased. Exposure accuracy is required. In order to make the printing line width narrower, it is effective to shorten the wavelength of the light source used for exposure. Therefore, an X-ray exposure apparatus using X-rays having a shorter wavelength than ultraviolet light generally used at present is being developed.

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. 100 is a mask frame for reinforcement, 101 is a mask substrate made of silicon, 102
Denotes an inorganic film (mask membrane) formed by removing a part of the mask substrate by back etching, and 103 denotes a transfer pattern of a semiconductor circuit or the like drawn and formed on the mask membrane by an EB drawing apparatus 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 denotes a ring-shaped chuck base, in which a hole 111 through which exposure X-rays pass is provided. Reference numeral 112 denotes a magnetic unit.
And generate a magnetic force sufficient to attract and hold the X-ray mask. In this configuration, the mask frame 100 of the X-ray mask is a chuck base 110.
Is magnetically attracted to the holding surface by surface contact and held.
In addition to the magnetic attraction method, there is a vacuum attraction method. In this case, a vacuum port is provided 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 held by suction.

[0004] However, these suction holding methods are:
Since the mask frame 100 and the chuck base 110 are in surface contact, the contact surfaces of both need to be finished to a high flatness. If a transfer pattern is formed by an EB lithography apparatus at the time of manufacturing a mask, the mask frame 100
If there is any distortion such as warpage in the suction surface of the mask frame 100, the mask frame 100 is deformed by correcting the warp of the mask frame 100 when held on the chuck base 110 of the X-ray exposure apparatus. There is a possibility that the transfer pattern 103 is transmitted to the transfer pattern 103 via the mask membrane 102 and is distorted when writing. The thickness of the mask membrane 102 on which the transfer pattern 103 is formed is about 2 μm, and is several mm.
Its rigidity is very small as compared with the thick mask substrate 101 and mask frame 100. Therefore, the mask substrate 1
01 and the distortion of the mask frame 100 have a great influence on the mask membrane 102 and bring about a large distortion to the transfer pattern. This can be said to be a problem peculiar to a mask having a transfer pattern formed on an extremely thin mask membrane.

As a method for solving this problem, 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 in a distorted state at the time of pattern formation. (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 a kinematic mount. 117 is a conical (funnel-shaped) hole, 118 is a plane portion, and 119 is a V-groove having a cut groove formed linearly along the X direction in the figure. These are formed on the holding surface of the mask frame 100. Have been. FIG.
(B) shows a mask chuck for kinematic mounting. On the holding surface of the chuck base 110, there are provided three spherical projections 120 respectively engaging with the conical hole portion 117, the flat portion 118, and the V-groove portion 119 of the mask. Further, a clamp mechanism 115 for mechanically pressing and holding the mask at three points is provided.

In this configuration, 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, almost no external force for deforming the mask frame 100 is exerted when the mask is held during exposure, and the mask can be held (with no distortion) in the same state as when the mask pattern is formed by the EB lithography apparatus. The feature is that pattern distortion due to deformation of the mask support frame can be suppressed.

[0009]

However, when the mask is to be held vertically against the gravity by the kinematic mounting method described above, the mask must be clamped inevitably. Since the frictional force generated during the process and the weight of the mask are added, strictly speaking, it is excessively restrained, and it is difficult to accurately position the mask. In addition, as a result of the excessive constraint, a moment force is generated in the mask, which is a factor of causing pattern distortion.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and provides a kinematic mount system, a mask, and a device manufacturing method using the same, which can position and hold a mask with high accuracy even when inclined with respect to a horizontal direction. With the goal.

[0011]

According to an aspect of the present invention, there is provided an exposure mask, wherein a conical hole, a V-groove, and a plane portion are provided at three positions on a mask holding surface, and the mask is vertically set. The angle of the conical hole is made larger than the angle of the V-groove portion in a mask which is adapted to engage with projections provided at three places on the mask chuck holding surface when held on the mask chuck. This is a characteristic mask.

[0012]

<Embodiment 1> An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram of the mask chuck of the first embodiment, and FIG. 2 is a sectional view thereof. This shows a state where the mask is held vertically by the mask chuck 2 against the gravity. As the mask, a silicon mask substrate 7 is attached to a ring-shaped mask frame 1, and a membrane on which a transfer pattern 8 of gold or the like is formed is provided inside the mask substrate 7. On the back side of the mask frame 1, (1) a funnel-shaped conical hole 1a, (2) a straight V-shaped groove 1b whose ridge line is directed toward the conical hole 1a,
(3) The plane portions 1c are provided at three places. These are equally spaced on the same circumference centered on the mask center (12
(0 ° pitch). On the other hand, the mask chuck 2 is provided with protrusions 2a to 2c having hemispherical tips at three places, and the conical hole 1a, the V-groove 1b,
The flat portion 1c is opposed to and engaged with each other. Further, three clamp arms 3a to 3c are provided. Each clamp arm is capable of rotating and linearly moving, and the mask frame 1 is sandwiched between each clamp arm and the projection of the mask chuck. 3 may be modified as shown in FIG. 3. Instead of the linear motion of the clamp arm 3, the protrusions 2a to 2c independently protrude. Do.

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 that presses the mask, and then slightly move to the mask chuck side to move the mask frame 1 to the mask chuck 2. To capture. In this state, in the conical hole portion 1a and the V-groove portion 1b, the distance between the hemispherical projections 2a, 2b and the clamp arms 3a, 3b is smaller than the thickness T of the mask holding portion (see FIG. 4). At this point, the mask is suspended by being supported by the projections, thereby preventing the mask from falling. However, the mask is not strongly pressed and the mask can move slightly.

Here, first, only the clamp arm 3a is further moved to the mask chuck side, and the engaging conical hole 1a and the projection 2a are pressed as shown in FIG. Thereby, three degrees of freedom (XYZ) are positioned. Here, the tip of the projection 2a and the tip of the clamp arm 3a are exactly opposite. As shown in FIG. 4, the conical hole 1a
If is not accurately positioned, a moment force is generated in the mask frame by the amount of eccentricity ΔC, causing pattern distortion.

Next, the V-groove 1b and the protrusion 2b are pressed by further retracting the clamp arm 3b.
As a result, the two degrees of freedom (θX, θY) in the rotational direction of the mask are fixed. Finally, the remaining clamp arm 3c is pulled in to press the flat portion 1c and the protruding portion 2c to fix the remaining one degree of freedom (θZ). With this, the mask is positioned and fixed without excessive restraint in all six degrees of freedom. Will be.

FIG. 4 shows the relationship of the force acting on the conical hole 1a of the mask when the mask is supported by the conical hole. With the V-groove portion 1b and the flat portion 1c not fixed, conditions necessary for positioning and fixing the mask in the conical hole portion 1a with the pressing force fC of the conical hole portion 1a will be obtained. Here, let us consider a state as shown in FIG. 5, which is considered to be a severe condition, that is, a case where there is a conical hole 1a on the center line of the mask. Assuming that the groove angle θc of the conical hole portion 1a with respect to a plane parallel to the mask plane, the force F acting in the direction of gravity only needs to consider the weight W of the mask and the frictional force due to the clamp arm force fc, so that F = W + μ1 × fC (1) (μ1: friction coefficient between the clamp arm and the mask) From the balance of the forces, the normal force acting in the direction of the conical hole is as follows: Normal force NC = fC x cosθC + F x sinθC (2) Friction force acting on the conical hole Is the frictional force = μ2 × NC (3) (μ2: coefficient of friction between the protrusion and the mask) To overcome the frictional force and position and fix the mask, the lifting force = fC × sinθC−F × cosθC ≧ μ2 × (fC × cos θC + F × sin θC) (4)

First, three degrees of freedom (XYZ) are set in the conical hole 1a.
Next, it is better to position the V-groove part. This is because, when the flat part is positioned first, when the V-groove part 1b is finally positioned, an extra frictional force with the flat surface is applied. Is necessary.

The condition for positioning the V-groove portion 1b is as follows: W = 0 in equation (1), F = μ1 × fV (5) is substituted into equation (1) and calculation is performed to satisfy the relation of equation (4). I just need. However, the groove angle θv with respect to the plane parallel to the mask plane of the V-groove is used instead of θC, and fC is used instead of fC.
Use V.

In a modification shown in FIG. 6, that is, when the conical hole 1a and the V-groove 1b are arranged orthogonally to the direction of gravity, W 'in the equation (1) is used instead of W'. = ｛(W / 2) 2 + F'2｝ 1/2 where F '= μ2 × W / (2 sin θV) + μ1 × W cos θV / (2 sin θV) (1 ′) is substituted into equation (1). It can be obtained by performing calculations. The force acting on the V groove 1b is W '= W / 2,
Similarly, it is only necessary to substitute the expression (1) and satisfy the relationship of the expression (4).

As another modified example, when the V groove 1b is located on the center of gravity of the mask, instead of W in the equation (1),

[Outside 1]

Equation (1) may be substituted into equation (1) for calculation to satisfy equation (4).

FIG. 10 shows the mask's own weight W = 200 g, μ
The results when 1 = μ2 and θV = θC are shown. The horizontal axis indicates the angle (deg) of the conical hole 1a, and the vertical axis indicates the required pressing force in the conical hole 1a. As for the conical hole 1a, it can be seen that the conical hole 1a and the V-groove 1b can be positioned more easily if they are arranged horizontally with respect to the direction of gravity (that is, the configuration of FIG. 6).

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

When the positioning and fixing are first performed at the two positions of the V-groove 1b and the plane 1c, the V-groove 1b and the plane 1c are fixed.
A condition for overcoming the force generated in the step (1) and enabling positioning in the conical hole 1a is determined. FIG. 5 shows the force generated in the conical hole 1a and the mask. According to FIG.
For the groove 1b, the vector FV = μ1 × fV + μ2 × fV / cos θV (6) For the plane 1c, the vector FF = μ1 × fF + μ2 × fF (7) Therefore, the vector composition of the two forces is expressed by the vector F ′ = vector FV + Vector FF + vector W, here W = 0 for simplicity, so that the vector W is in any direction, in other words, the conical hole portion 1a and the V-groove 1b
Equation (2) can be applied to any position.

F ′ = FV cos α + FF cos (60 ° −α) (8) Here, the angle formed by the three points FCV = 60 °, tan α = 3/2
FF / (FV + 1 / 2FF).

F = F ′ + μ1 × fC (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).

Μ1 = μ2, θV = θC, fC = fV = f
FIG. 11 shows the calculation result when F is set. The horizontal axis indicates the coefficient of friction, and the vertical axis indicates the lifting force (dimensioned by fC) required to position the displaced mask by the conical hole. Positioning cannot be performed when the lifting force is in the negative range. In order to enable positioning, the angle θC of the conical hole 1a is 6
Even when the angle is set to 0 °, the coefficient of friction needs to be 0.12 or less. Furthermore, if the self-weight of the mask is taken into account, it can be seen that accurate positioning is difficult without any change.

Therefore, in order to enable positioning, the pressing force of the conical hole 1a is maximized, and the pressing forces at the other two locations are reduced. The force applied to the plane portion is the minimum force necessary to restrain the out-of-plane direction, and an extra frictional force will be generated even if more force is applied. Therefore, the relationship of the pressing force is expressed as FC (conical hole)> FV (V groove)> F
Most preferably, F (plane portion).

As another method, equation (9) is replaced with equation (2)
And the relationship between the angle θC of the conical hole and the angle θV of the V-groove may be set to satisfy θC> θV so as to satisfy the relationship of Expression (4).

<Embodiment 3> In addition to the above method, the friction coefficient μ
1 or the weight W of the mask can be reduced.
A specific example of a method for reducing μ1 will be described. Here, consideration is given to reducing the frictional resistance on the clamp arm side. With μ1 = 0 in the equations (1), (6) and (7), the values can also be obtained by substituting the equations into the equation (2) and performing calculations.

FIG. 12 shows the calculation results. The abscissa indicates the coefficient of friction, and the ordinate indicates the force for lifting the mask required for positioning (dimensioned by fC). Positioning cannot be performed in the negative range of the vertical axis. Although FIG. 12 does not consider the effect of the weight of the mask for simplicity, it can be seen that the effect of reducing friction is greater than that of FIG. The weight of the mask can be reduced to zero by using a weight compensation spring.

FIG. 7 shows a specific configuration for reducing the frictional resistance on the clamp arm side. Air is blown out 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 completed, the air blow is stopped and the solid contact is clamped.

<Embodiment 4> FIG. 8 shows an embodiment in which a spring having a high rigidity in a mask pressing direction of a mask and a low rigidity in a transverse direction perpendicular to the direction is used as a clamp arm. The clamp arm is composed of a plurality of parallel bar springs 1
Supported by 0. By bending the spring when pressing the mask frame, the same effect as reducing the friction coefficient μ1 can be obtained.

<Embodiment 5> Next, a specific example of reducing W will be described. FIG. 9 is a view showing a state in which the mask is transferred to the holding surface of the mask chuck 2 by the mask hand 11 and the mask is pressed by the mask hand 11. In order to facilitate the mounting of the mask, the clamp arm 3 which has been initially retracted is in a trapped state when the mask is pressed, thereby preventing the mask from falling. 12
Is a suction pad of the mask hand. Mask hand 11
After the positioning of the mask with respect to the mask chuck 2 is completed, the mask is fixed by the clamp arm 3. Since the weight W of the mask is supported by the mask hand 11, W = 0 substantially.

<Embodiment 6> Next, an embodiment of an exposure apparatus for manufacturing a micro device (semiconductor device, thin-film magnetic head, micromachine, etc.) using the above-described mask and mask chuck will be described. FIG. 13 is a diagram showing the configuration of the X-ray exposure apparatus of the present embodiment. In the figure, a synchrotron radiation 21 in a sheet beam shape emitted from an SR radiation source 20 is shown.
Is enlarged by the convex mirror 22 in a direction perpendicular to the radiation light orbit plane. The emitted 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.
It is guided to the line mask 24. The X-ray mask 24 is held on a mask chuck (not shown) by the mounting method 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, a scanning method, or the like.

Next, an embodiment of a device manufacturing method using the above-described exposure apparatus will be described. FIG. 14 shows a micro device (a semiconductor chip such as an IC or an LSI, a liquid crystal panel,
2 shows a flow of manufacturing a CD, a thin-film magnetic head, a micromachine, and the like. In step 1 (circuit design), the circuit of the semiconductor device is designed. Step 2 is a process for making a mask on the basis of the circuit pattern design. 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 lithography using the prepared mask and wafer. The next step 5 (assembly) is called a post-process, and is a process of forming a semiconductor chip using the wafer produced in step 4, and includes processes such as an assembly process (dicing and bonding) and a packaging process (chip encapsulation). including. In step 6 (inspection), an operation confirmation test of the semiconductor device manufactured in step 5 is performed.
An inspection such as a durability test is performed. Through these steps, a semiconductor device is completed and shipped (step 7).

FIG. 15 shows a detailed flow of the wafer process. Step 11 (oxidation) oxidizes the wafer's surface. Step 12 (CVD) forms an insulating film on the wafer surface. Step 13 (electrode formation) forms electrodes on the wafer by vapor deposition. In step 14 (ion implantation), ions are implanted into the wafer. Step 1
In 5 (resist processing), a photosensitive agent is applied to the wafer. Step 16 (exposure) uses the above-described exposure apparatus to print and expose the circuit pattern of the mask onto the wafer. Step 17 (development) develops the exposed wafer. In step 18 (etching), portions other than the developed resist image are removed. In step 19 (resist stripping), unnecessary resist 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 conventionally difficult to manufacture.

[0038]

According to the present invention, it is possible to avoid the influence of excessive restraint due to frictional force and the weight of the mask, thereby realizing accurate positioning and fixing of the mask and, at the same time, suppressing the occurrence of mask pattern distortion. .

[Brief description of the drawings]

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

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

FIG. 3 is a sectional view showing a modification of FIG. 2;

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

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

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

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

FIG. 8 is an explanatory view 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 embodiment in which pressing and positioning are performed by a mask hand.

FIG. 10 is a graph showing a necessary clamp arm force in a case where positioning and fixing are performed only by a conical hole.

FIG. 11 is a graph showing the required lifting force when three clamp arms are simultaneously held.

FIG. 12 is a graph showing a necessary lifting force when the frictional force between the clamp arm and the mask is set to 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 view for explaining a conventional magnetic chuck type mask chuck.

FIG. 17 is a view for explaining 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 Flat part 2 Mask chuck 2a-2c Projection part 3 Clamp arm 4 Mask hand 7 Mask substrate 8 Transfer pattern

Claims (3)

(57) [Claims] In an exposure mask, a conical hole, a V-groove, and a plane portion are provided at three locations on a mask holding surface, and when the mask is held vertically on a mask chuck, the mask chuck holding surface has three locations. Wherein the angle of the conical hole is greater than the angle of the V-groove. 2. The mask according to claim 1, wherein said mask is a mask for X-ray exposure. 3. A device manufacturing method comprising: holding a mask according to claim 1; and exposing and transferring a transfer pattern of the mask onto a wafer.