JP3394158B2 - Magnification correction device and magnification correction method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnification correction apparatus and a magnification correction method used in an exposure apparatus for transferring and forming an original pattern on a wafer when forming a semiconductor element.

[0002]

2. Description of the Related Art A semiconductor device is formed by reducing and transferring a mask pattern as an original image by using an excimer laser having an ultraviolet ray or a short wavelength. In addition, recently, one-to-one proximity exposure using X-rays with a shorter wavelength has been performed, and 0.2 μm
The following fine patterns are formed. With the miniaturization of the pattern, it is necessary to accurately align the positions of the base pattern and the mask pattern, which are previously formed on the wafer to be exposed, with each other. The alignment between the base pattern and the mask pattern is
This is done by detecting marks written for position detection on both, and aligning the positions of the wafer and the mask. Even if the alignment is accurate in the actual exposure, an overlay error will occur between the base pattern and the mask pattern due to some factor. The following two points are listed as the main causes of such an overlay error. (1) The wafer that has undergone the semiconductor processing process expands and contracts, and the chip size on the wafer differs. (2) The magnification varies depending on the distortion of the optical system during transfer.

The present invention is intended to minimize the pattern position deviation at the time of pattern transfer, and relates to a technique for improving overlay of a semiconductor exposure apparatus.

In general, as a method of correcting the magnification in the exposure apparatus, in the reduction projection exposure, a method of changing the magnification of the projection lens to control the size of the projected pattern is adopted. This is achieved by changing the lens distance of the projection lens and changing the internal pressure of the projection lens mechanism.

Further, the following four types of methods have been proposed for an X-ray exposure apparatus that performs one-to-one transfer. (A) Method of correcting in the manufacturing process of X-ray mask pattern (b) Method of utilizing position shift of transfer pattern caused by change in gap between mask and wafer due to spread of irradiated X-rays (c) X at exposure A method for correcting the dimension by applying a tensile force or a compressive force to the linear mask to cause the deflection (d) A method for controlling the temperature of the mask and the wafer to perform the dimension correction (Japanese Patent Application No. 7-217272).

[0006]

[Problems to be Solved by the Invention] In reduction projection exposure, changing the magnification of the lens system also changes the focal length, which is becoming more and more severe in forming fine patterns. Exposure trends are becoming increasingly difficult.

On the other hand, in the equal-magnification exposure method, the above method (a)
Each of (d) to (d) has the following problems. The method according to (a) is economically disadvantageous because the mask is remade every time the magnification is different. In the method according to (b), it is necessary to accurately match the proximity gap between the mask and the wafer, and a complicated mechanism is required for forming the gap. Further, recently, X-ray exposure using synchrotron radiation light as a light source has been performed, the spread of irradiated X-rays is small, and it is difficult to control the pattern position by gap control. The method according to (c) has been proposed in which an external force is applied to the mask, which is the original pattern, to cause in-plane distortion in the mask and the pattern position is corrected (SPlE Vo1.2.
437 / p140-p150).

This will be described with reference to FIG. 4. 11 is a mask, 12 is a mask frame, 13, 14, 15, 16
Is a forcing force applied to the mask frame 12 to distort the mask 11. This force is experimentally given by four screws. By such a method, the mask 11
Is forcibly bent to distort the mask pattern, which is the original image of the pattern, to control the dimensions. According to the calculation, magnification correction of about 10 ppm is possible.

However, in order to mount such a magnification correction mechanism on the mask holding mechanism, the strength of the holding mechanism is required and a complicated mechanism for applying a force is required.
Furthermore, since the internal stress of the mask differs from mask to mask, in order to perform accurate magnification correction between different masks, the force applied to each mask must be changed, and accurate magnification correction is extremely difficult. is there.

The method (d) is a method of measuring the relative magnification between the mask and the wafer during exposure, controlling the temperatures of the mask and the wafer, and correcting the relative dimensional error. As a premise of this, there are cases in which the temperatures of the mask and the wafer can be set separately. However, the mask and the wafer are in contact with each other with a proximity gap of 30 μm or less, and when the mask and the wafer face each other, the temperatures of the two tend to be the same temperature, and it is actually difficult to give a temperature difference between the mask and the wafer. . Therefore, there is a demand for a mechanism and method that can control the dimensions even when the temperature of the mask and that of the wafer are the same. Further, the difference in temperature during exposure also affects the alignment detection accuracy for detecting the relative position between the mask and the wafer, which causes an alignment error.

As described above, according to the conventional method, in the reduction projection exposure, the focal length of the lens is different for the purpose of magnification correction, and the structure of the projection optical system has a very large structure such as a lens mechanism for correcting this. There was a problem that it became complicated. Further, in the one-to-one transfer, since the force is applied to the mask, the original positional accuracy of the original pattern is deteriorated. In addition, there is a problem that the structure of the mask holding mechanism becomes complicated,

The present invention has been made in order to solve the above-mentioned conventional problems, and its purpose is to:
An object of the present invention is to provide a magnification correction device and a magnification correction method that improve overlay accuracy by performing magnification correction with high precision economically and accurately with a mask pattern that is an original image and a pattern on a wafer. .

[0013]

In order to achieve the above-mentioned object, a magnification correction apparatus according to the present invention comprises a chuck mechanism for holding and fixing a substrate, and a chuck mechanism for controlling the temperature of the chuck mechanism and the substrate. Alternatively, a temperature control mechanism for expanding and contracting one of the two is provided, and the chuck mechanism is formed of a material having a linear expansion coefficient different from that of the substrate.
However, it is a temperature control mechanism with embedded heating and cooling elements,
The heating element and the cooling element are formed as a pair of square exposure chips.
Place in the diagonal direction and in the direction perpendicular to each side, and
It is characterized by having a temperature gradient in the perpendicular direction .

Further, the magnification correction method according to the present invention is a substrate
Chuck mechanism for holding and fixing
Either or both by controlling the temperature of the mechanism and the substrate
And a temperature control mechanism for expanding and contracting the chuck,
The mechanism must be made of a material whose coefficient of linear expansion is different from that of the substrate.
In the magnification correction method using the magnification correction device, the substrate and the chuck mechanism are heated or cooled to control the temperature, and then the substrate is held by the chuck mechanism. Is generated to control the size of the substrate. Further, the magnification correction method according to the present invention is for holding and fixing a substrate.
The chuck mechanism and the temperature of the chuck mechanism and the substrate.
Temperature control that expands and contracts both or one by controlling the temperature
And a linear expansion of the chuck mechanism with the substrate.
In a magnification correction method using a magnification correction device formed of materials having different coefficients , a substrate is heated or cooled to be temperature-controlled and then mounted on a chuck mechanism, and the size of the chuck mechanism is expanded by heat transferred from the substrate. It is characterized in that the substrate is held by the chuck mechanism at the time of contraction, and then the temperature of the substrate and the chuck mechanism is set to a predetermined temperature to generate thermal stress, thereby controlling the size of the substrate. Furthermore, the magnification correction method according to the present invention is characterized in that after the magnification correction is performed outside the transfer device in advance, the substrate is loaded into the transfer device together with the chuck mechanism.

As the substrate, a wafer, a semiconductor substrate, a glass substrate or the like is used. The magnification correction device and the magnification correction method according to the present invention can correct the magnification based on the following principle. For ease of understanding, we make the following assumptions: Before the chuck, the wafer and the chuck mechanism freely expand and contract in the surface direction along with the temperature change. However, after holding (chucking), it is assumed that the chuck mechanism and the wafer are fixed with a sufficient force so that there is no slip between them. That is, after chucking, the dimensions of the wafer and the chucking mechanism also change with temperature. Under this assumption, expansion and contraction of the wafer and the chuck mechanism will be considered.

First, the case of expanding the pattern will be described.
As an example, a chuck mechanism whose coefficient of linear expansion of the chuck mechanism is larger than that of the wafer is used. The temperature of the wafer and the chuck mechanism is set higher than the exposure temperature, and the wafer is chucked when it reaches a predetermined temperature. After chucking the wafer, the temperature of the wafer and the chuck mechanism is returned to the exposure temperature. Then, thermal stress is generated in the wafer and the chuck mechanism, the wafer is compressed, and the chuck mechanism is pulled. With this wafer compressed, the original pattern is exposed and transferred. After that, when the chucking force is removed and the state in which the thermal stress is not applied is restored, the compressed wafer returns to its original state, and the transferred pattern has a larger size than the original pattern.

This will be described more clearly with reference to FIG. In the figure, 1 is a wafer and 2 is a chuck mechanism. When the temperature is raised by t, the wafer 1 and the chuck mechanism 2 freely expand as shown by the broken line ((a) in the figure). The wafer 1 is chucked at this temperature ((b) in the figure) and returned to the original temperature ((c) in the figure). Since the coefficient of linear expansion of the chuck mechanism 2 is larger than that of the wafer 1, the chuck mechanism 2 is
The wafer 1 shrinks more than that. When the temperature returns to the original temperature, the wafer 1 contracts beyond the original free state, and thermal stress is generated in the wafer 1. In this state, the original pattern on the mask is transferred to the wafer 1. After transfer, when the chuck mechanism 2 is removed and the stress is released, the contracted wafer 1 returns to its original size, and the transferred pattern expands. This dimensional change occurs isotropically if the material of the chuck mechanism 2 is uniform, so that it can be similarly enlarged / reduced regardless of the position of the chip.

This will be described using mathematical expressions. The linear expansion coefficients of the wafer 1 and the chuck mechanism 2 are αw and αc, respectively, and the elastic coefficients thereof are Ew and Ec, respectively. Further, the thermal stresses are σw and σc. If the temperature is increased by t before chucking, the dimensions of the wafer 1 and the chuck mechanism 2 at the point R from the center are αw · Rt and αc · Rt. When the free displacement is returned to the original temperature while being restrained by the chuck mechanism 2, thermal stress is generated in the wafer 1 and the chuck mechanism 2. This thermal stress can be represented by σw · R / Ew and σc · R / Ec. The displacement of the wafer 1 is represented by the total of both displacement due to thermal expansion and displacement due to thermal stress. The displacement of the chuck mechanism 2 is also the same, and the displacement of the wafer 1 and the displacement of the chuck mechanism 2 are equal. If this displacement is λ, then λ = αw · R · t + σw · R / Ew = αc · R + σc ·
R / Ec Further, since the forces acting on both are equal, σw · Sw + σc · Sc = 0, where Sw and Sc are equivalent cross-sectional areas of the wafer and the chuck mechanism. When Sw · Ew / Sc · Ec = k is set and solved, λ = αw− (αw−αc) / (1 + k) = αc + (αw
It can be expressed by −αc) k / (1 + k). k << 1, that is, if the elastic deformation of the chuck mechanism 2 is sufficiently smaller than the elastic deformation of the wafer 1, then λ = αw + (αw−αc) (1-k) = αc− (αw−
αc) k (1-k). That is, it can be understood that the larger the difference in the coefficient of linear expansion and the larger the difference in the elastic deformation, the larger the displacement due to the temperature change and the easier the magnification correction becomes.

In the case of shrinking, the temperature is lowered below the exposure temperature and chucking is performed, and the original pattern is transferred, and the transferred pattern is shrunk according to the same principle.

Here, it is assumed that the wafer 1 and the chuck mechanism 2 do not slip at all after chucking. However, even if the wafer 1 slightly slips, thermal stress is generated as long as there is a frictional force, which causes the wafer 1 to expand and contract. To do.

The case where the linear expansion coefficient of the chuck mechanism 2 is larger than that of the wafer 1 has been described as an example.
On the contrary, when the coefficient of linear expansion of the chuck mechanism 2 is smaller than that of the wafer 1, temperature change is similarly applied to generate thermal stress, and expansion / contraction can be realized.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below in detail based on the embodiments shown in the drawings. FIG. 2 is a sectional view of a magnification correction device according to the present invention. In the figure, 1 is a wafer, 2 is a chuck mechanism, 3 is a vacuum suction mechanism for holding and fixing the wafer 1, 4 is a temperature control unit (temperature control mechanism) for raising and lowering the wafer temperature and controlling the temperature, 5 Is a heating element, 6 is a cooling element, 7 is a transfer device for transferring the wafer 1 from the temperature control unit 4 to the chuck mechanism 2, 8 is a mask on which an original pattern is written, 9 is an illumination optical system for transferring the pattern, Reference numeral 10 is a stage for moving the wafer 1 to the exposure position. In this example, the chuck mechanism 2 is made of a material such as aluminum having a larger linear expansion coefficient than the wafer 1.

In order to enlarge the pattern with such a magnification correction device, the temperature of the wafer 1 is raised by the temperature controller 4.
The wafer 1 is taken out by the transfer device 7 and the chuck mechanism 2
Put it on top. When the wafer 1 is placed on the chuck mechanism 2,
The chuck mechanism 2 receives heat from the wafer 1 and its temperature rises and expands. After the chuck mechanism 2 expands, the vacuum suction mechanism 3 is operated to hold and fix the wafer 1 by the chuck mechanism 2. After that, the temperatures of the wafer 1 and the chuck mechanism 2 decrease. As the temperature decreases, a compressive thermal stress is generated in the wafer 1 and a tensile thermal stress is generated in the chuck mechanism 2, so that the wafer 1 contracts and the chuck mechanism 2 expands. When the temperature drops to the exposure temperature, the original pattern is transferred. After the transfer, when the vacuum suction is cut off and the holding and fixing of the wafer 1 by the chuck mechanism 2 is released, the contracted wafer 1 returns to the original size, and the transferred pattern is expanded more than the original pattern.

Although a crystal of silicon is often used for the wafer 1, a semiconductor substrate of Group 3 or 5 of the periodic table or a glass substrate for liquid crystal can be similarly considered.

For the chuck mechanism 2, it is preferable to use a material such as aluminum having a coefficient of linear expansion larger than that of the wafer 1. In recent years, ceramic materials having a large linear expansion coefficient have become available, and such composite materials can also be used. Further, although a vacuum chuck is used for holding and fixing the wafer 1 by the chuck mechanism 2, an electrostatic chuck using an electrostatic force can also be used.

The temperature control unit 4 may be a contact type such as a plate or an atmosphere temperature control type such as a furnace in order to raise or lower the temperature of the entire wafer 1. In this example, the size control is performed without mounting the temperature control unit 4 on the chuck mechanism 2, but the chuck mechanism 2
It is also possible to change the size by providing a temperature control section 4 on the wafer, mounting the wafer 1 after controlling the temperature of the chuck mechanism 2 itself, fixing the wafer 1 by chucking, and changing the temperature to the exposure temperature. Is.

Further, looking at the dimensions of the wafer 1 deformed by this method in detail, when the temperature of the entire surface of the wafer 1 or the chuck mechanism 2 is uniformly changed to perform chucking and thermal stress is generated to deform the wafer 1. In the chip shape, the displacement is small in the diagonal direction, and the displacement is large near the midpoint of each side. As a method for solving this problem, it is preferable to provide a temperature gradient between the diagonal direction of the chip and the midpoint direction of each side so that the temperature control unit 4 has a large displacement in the diagonal direction. Specifically, as shown in FIG. 3, if a heating element 5 is diagonally arranged and a cooling element 6 is arranged in a direction perpendicular to the side with respect to the chip and the temperature is controlled, accurate scaling can be performed. is there.

[0028]

As described above, according to the magnification correcting apparatus and the magnification correcting method of the present invention, the magnification error can be easily corrected depending on the size of the area of the base pattern formed on the exposure wafer, and the overlay accuracy can be improved. Can be improved. Further, the temperature at the time of exposure is not disturbed by the dimension correction and can be kept constant at all times, so that an alignment error does not occur due to different temperatures. Further, it is not necessary to greatly increase the temperatures of the wafer and the chuck mechanism, and the time required to reach the exposure temperature is shortened, which is very advantageous in increasing the processing speed. Further, the chuck mechanism and the temperature control of the wafer can be controlled in advance in a place other than the exposure apparatus, and the dimensions can be controlled offline by checking.

[Brief description of drawings]

FIG. 1 is a diagram for explaining the principle of the present invention.

FIG. 2 is a cross-sectional view showing an embodiment of a magnification correction device according to the present invention.

FIG. 3 is a plan view showing a temperature control mechanism for providing a temperature gradient.

FIG. 4 is a diagram for explaining a conventional scaling method,
(A) is a front view of a wafer and a chuck mechanism, (b) is a sectional view.

[Explanation of symbols]

1 ... Wafer, 2 ... Chuck mechanism, 3 ... Vacuum suction mechanism, 4
... Temperature control part, 5 ... Heating element, 6 ... Cooling element, 7 ... Transfer device, 8 ... Mask, 9 ... Illumination optical system, 10 ... Stage,
11 ... Mask, 12 ... Mask frame, 13, 14, 1
5, 16 ... Force to push the mask from outside the mask surface.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-6-208942 (JP, A) JP-A-59-46030 (JP, A) JP-A-7-115055 (JP, A) JP-A-4- 293225 (JP, A) JP-A-55-32022 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01L 21/027 G03F 7/207

Claims (4)

(57) [Claims] 1. A chuck mechanism for holding and fixing a substrate, and a temperature control mechanism for controlling the temperature of the chuck mechanism and the substrate to expand or contract one or both of the chuck mechanism and the substrate. Made of materials with different linear expansion coefficients , the temperature control mechanism cools the heating element and
A temperature control mechanism having an embedded element, wherein the heating element and
Place the cooling element on the diagonal of the square exposure chip and at right angles to each side.
Temperature gradients in diagonal and perpendicular directions
Magnification correction apparatus characterized by remembering. 2. A chuck machine for holding and fixing a substrate.
Control the temperature of the chuck mechanism and the substrate.
And a temperature control mechanism that expands and contracts both or one
And the chuck mechanism has a coefficient of linear expansion different from that of the substrate.
In a magnification correction method using a magnification correction device formed of a material , the substrate and the chuck mechanism are heated or cooled to control the temperature, the substrate is held by the chuck mechanism, and then the temperature of the substrate and the chuck mechanism is set to a predetermined value. A method for correcting magnification, which comprises controlling the size of the substrate by controlling the temperature to generate thermal stress. 3. A chuck machine for holding and fixing a substrate.
Control the temperature of the chuck mechanism and the substrate.
And a temperature control mechanism that expands and contracts both or one
And the chuck mechanism has a coefficient of linear expansion different from that of the substrate.
In a magnification correction method using a magnification correction device formed of a material , the substrate is heated or cooled to control the temperature and then mounted on the chuck mechanism, and the size of the chuck mechanism is expanded or reduced by the heat transferred from the substrate. A magnification correction method characterized in that the substrate is held by the chuck mechanism at a point of time, and then the temperature of the substrate and the chuck mechanism is set to a predetermined temperature to generate thermal stress to control the size of the substrate. 4. The magnification correction method according to claim 2, wherein after the magnification correction is performed outside the transfer device in advance, the substrate is loaded into the transfer device together with the chuck mechanism.