JP2587292B2 - Projection exposure equipment - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection exposure apparatus used for manufacturing semiconductor circuit elements and the like, and more particularly, to a method in which an original and an object to be exposed are aligned after they are aligned. The present invention relates to a scanning projection exposure apparatus that transfers an image of an original onto an object to be exposed by scanning an exposure object integrally with a projection optical system.

[Prior Art] A mask, which is an original, and a wafer, which is an object to be exposed, are integrally moved with respect to a fixed projection optical system, and the mask is formed by irradiating and scanning slit light on the mask via the projection optical system. In an apparatus that exposes a pattern to a wafer, generally, a structure that carries a mask and a wafer and moves integrally (hereinafter, referred to as a structure)
If the coordinate system of the scanning y-axis and its orthogonal x-axis (referred to as a carriage) and the coordinate system of the axis y'-axis and its orthogonal x'-axis in the horizontal plane of the projection optical system are shifted in the rotation direction ( Angle θ), image plane distortion occurs, and the mask pattern
The image is transferred onto the wafer at an angle of 2θ with respect to the xy axis coordinate system.

As a method for solving such a defect, there has been a method of adjusting a transfer error using an actual mask and a wafer. In this method, the amount of displacement between the mask and the wafer is measured at a plurality of locations, but the position of the mask and the wafer is aligned at only one representative location, and at the other locations, only the amount of displacement is measured and calculated. Therefore, the shift amount, ie, the offset amount, after the position alignment of the mask wafer is corrected at only the one representative position, and the other shift amount measurement positions are measured ignoring any offset unique to the measurement position. And
The attitude adjustment is performed by calculating the attitude adjustment amount of the carriage mechanism.

[Problems to be Solved by the Invention] However, in the method of using a mask for transferring an actual semiconductor circuit element or the like and a wafer to be transferred for adjusting the attitude of the carriage mechanism, the following (1) and (2)
For this reason, in many cases, the offset value has a tendency to differ depending on the position of the displacement amount measurement within the wafer surface.

(1) A process such as heat treatment and film forming is repeated for a wafer with the formation of a semiconductor circuit element. However, due to anisotropy of the film forming, an offset value of a displacement amount measurement output between a central portion and a peripheral portion of the wafer. May be different.

(2) In the exposure step of forming a semiconductor circuit, it is necessary to apply a photoresist to a wafer. In general, the photoresist is dropped on a central portion of the wafer surface in a required amount and the wafer is rotated at a high speed to remove the photoresist. Spread radially and apply to a predetermined thickness. However, uneven coating of the photoresist is likely to occur on minute irregularities such as alignment marks on the wafer surface. In particular, the tendency of coating unevenness is often different between the central portion and the peripheral portion of the wafer.

Therefore, for these reasons, since the tendency of the offset amount at the alignment position between the mask and the wafer and the offset amount at the other misalignment measurement positions are different, the posture adjustment function using the carriage mechanism does not function sufficiently. However, there is a drawback that the image plane distortion cannot be corrected even when the image is transferred to the wafer.

[Means for Solving the Problems] To achieve the above object, a projection exposure apparatus according to the present invention comprises: an illuminating means for illuminating an original; and a projection optics for projecting a pattern of an original illuminated by the illuminating means onto an object to be exposed. System, a carriage mechanism for moving the master and the subject to be scanned integrally with the projection optical system by moving according to the guide mechanism for the master and the subject, and projecting the positional alignment between the master and the subject. Consider the output of the position detection means when the carriage mechanism is positioned at each of a plurality of positions on the movement path of the position detection means to detect through the optical system, and the unique offset amount at each position stored in advance. Drive control means for controlling the drive while adjusting the posture of the carriage mechanism according to each position.

[Operation] In this configuration, the positional relationship between the original and the object to be exposed, the projection magnification, the scanning direction due to the carriage mechanism, and the like change as the carriage mechanism moves. The amount of deviation, ie, the amount of offset from the alignment position between the original and the object to be exposed at each position on the movement path of the carriage mechanism also changes. Stored in the means. At the time of exposure, the posture of the carriage mechanism is adjusted in consideration of the offset amount unique to each position on the movement path of the carriage mechanism and the alignment at each position,
More accurate exposure is performed.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic configuration diagram of a reflection type projection exposure apparatus according to one embodiment of the present invention, in which a condenser lens 61 and a condenser lens 61 are sequentially arranged along the optical path of laser light 1 emitted from a laser light source 60.
A polygon mirror 62 is arranged.

Here, the laser light source 60, the condenser lens 61, and the polygon mirror 62, which are arranged in a direction orthogonal to the drawing (X direction), are shown rotated by 90 ° around the Z axis. The laser light l is scanned in the X direction by the rotation of the polygon mirror 62.

Along the optical path of the laser light l reflected by the polygon mirror 62, an f / θ characteristic lens 63, a splitting prism 76 for splitting the laser light l into two in the x direction, and two half mirrors 64 (one is It is located in the X direction perpendicular to the paper surface, and is not shown.
The same shall apply hereinafter), two objective lenses 65, a mask 66 having accurate alignment marks 101 (described later) at a plurality of locations, a reflective projection optical system 67, and a wafer 68 having accurate alignment marks 102 (described below) at a plurality of locations. Are located.

The mask 66 and the wafer 68 are integrally supported by a carriage 72, and the carriage 72 can be moved in the Y direction in the figure along a fluid bearing guide 78 by a carriage driving mechanism 77. When the circuit pattern of the mask 66 is exposed on the wafer 68, the carriage 72 is moved by being illuminated by a slit-like light source (not shown) extending in the X direction from above the mask 66.

The reflected light from the mask 66, the projection optical system 67, and the wafer 68 is 2
Reflected by the two half mirrors 64, and along the optical path of the reflected light, two condenser lenses 69 and two photoelectric conversion elements 70
Is arranged. The output of the photoelectric conversion element 70 is applied to an arithmetic processing circuit 71, which detects the relative positional relationship between the mask 66 and the wafer 68 based on the output of the photoelectric conversion element 70, and calculates the light of the magnification and the projection optical system 67 by an arithmetic expression described later. Calculates the amount of tilt of the carriage scanning axis, and sets the carriage drive mechanism 7
7. Control the control valves 79 and 80 to adjust the inclination and magnification of the optical axis of the projection optical system 67 and the carriage scanning axis.

The arithmetic processing circuit 71 includes a central processing unit (CPU) 81 that controls the operation of the arithmetic processing circuit 71, a ROM 82 that stores an operation sequence program of the CPU 81, a RAM 83 that stores arithmetic processing data, and a photoelectric conversion element 70. A mark measuring circuit 84 for measuring the interval between the marks on the mask 66 and the wafer 68 based on the output, a carriage driving circuit 85 for controlling the carriage driving mechanism 77, and driving data for converting the arithmetic processing data from a digital value to an analog value and setting it. Set valve 86, control valve drive circuit 8 that drives control valves 79 and 80
7 and an input / output interface 88.

FIG. 2A shows alignment marks used on the mask 66 and the wafer 68, and the marks 101a, 101b, 101c, and 101d.
The alignment mark 101 made of a mask 66 is formed on the mask 66, and the alignment mark 102 made of the marks 102a and 102b is formed on the wafer 68. Actually, as shown in FIG. 3, similar alignment marks are formed at twelve locations. In FIG. 3, 103 and 104 are alignment marks for visual observation. One of the alignment marks 103 and 104 is formed on the mask 66, and the other is formed on the wafer 68.

The measurement and adjustment operations in the above configuration will be described.
Referring to FIG. 1, a laser beam 1 emitted from a laser light source 60 is scanned by a polygon mirror 62 and divided by a split prism 76.
Is divided into two in the X direction. The two split lights pass through the half mirror 64 and go to the mask 66. The alignment mark 101 of the mask 66 and the alignment mark 102 of the wafer 68 are scanned by the laser light 1 via the optical system 67, and the scattered light from the marks 101 and 102 is reflected by the half mirror 64.
, Where some are reflected in the direction of the two photoelectric conversion elements 70. When the alignment mark 101 of the mask 66 and the alignment mark 102 of the wafer 68 are overlapped as shown in FIG. 2A, the alignment mark 102 of the wafer 6 is located between the alignment marks 101a and 101b of the mask 66.
a is present, the alignment mark 102b is located between the alignment marks 101c and 101d, and the laser light 1 is scanned in the scanning direction A (X direction) from left to right. And photoelectric conversion element
Reference numeral 70 denotes the laser beam shown in FIG.
At the intersection with 1,102, pulsed light is detected and
An output voltage having a waveform as shown in FIG. W ₁ , W
₂ ,..., W ₅ are pulse signal intervals.
By measuring the time intervals W ₁ , W ₂ ,..., W ₅ with the mark measuring circuit 84, the misalignment between the mask 66 and the wafer 68 is obtained.

That is, assuming that the shift in the X direction in FIG. 2A is Δx ₀ and the shift in the Y direction is Δy ₀ , Δx ₀ = (W ₁ −W ₂ + W ₄ −W ₅ ) / 4 (1) Δy ₀ = (− W ₁ + W ₂ + W ₄ −W ₅ ) / 4 (2) In the matched state, Δx ₀ and Δy ₀ are both zero because W ₁ = W ₂ = W ₄ = W ₅ .

However, is intended the distance W ₁ to _W-5 time measured based on the electric signal converted photoelectrically, [Delta] x _0, even if the [Delta] y ₀ are both become zero, actually the mask side alignment wafer-side alignment mark There is a case that it is not sorted to the mark. This shift amount (offset) remains as it is when the mask pattern is transferred onto the wafer. Therefore, if the alignment is performed by anticipating the shift amount from the beginning, when the mask pattern is transferred onto the wafer,
The relative displacement between the two can be made zero.

However, since the offset value when the position of the mask and the wafer are aligned is different between the central portion and the peripheral portion even within the same wafer, the offset amount is subtracted from the measurement result at each position where the deviation amount is measured. The actual shift amount of the mask wafer is calculated.

That is, the offset amount at a certain measurement point is (x ₀ , y ₀ )
Then, the actual shift amount between the mask and the wafer is as follows: Δx = Δx ₀ −x ₀ (1 ′) Δy = Δy ₀ −y ₀ (2 ′)

However, it is necessary to know this offset amount in advance.The mask and wafer are aligned, exposure is performed in that state, and from the exposure result, the actual deviation amount between the mask and wafer is measured using a vernier or the like. Register it in RAM83. Alternatively, the wafer is allocated to the mask using the manual alignment mark, and the deviation amount (x ₀ , Δy ₀ ) obtained by the position detection unit using photoelectric conversion at that time is registered in the RAM 83 as an offset amount.

In actual displacement amount measurement, as shown in FIG. 3, spaced in the X direction of the mask 66 and the wafer 68 by a distance C ₁ 2
Measure the alignment marks 101 and 102 at each location,
The actual misalignment amount between the mask and the wafer is obtained by the equations (1 ') and (2'). A shift amount R ₁ of the right mark ([Delta] x
_{R1, Δy R1),} the deviation amount of the left marks L ₁ a (Δx _L1, Δ
y _L1 ), the lateral (X-direction) magnification Mx is given by the following equation.

Also, measure the distance D ₁ only two positions of the alignment marks 101, 102 apart in the Y direction, alignment deviation of the right mark amount R ₂
The (Δx _R2, Δy _R2), the alignment deviation amount L ₂ of the left side mark ([Delta] x
_L2, when the [Delta] y _L2), the vertical (Y-direction) magnification My becomes the following equation.

Next, measurement of the angle θ between the scanning axes x and y will be described.

The two sets of alignment marks 101 in the x direction at the bottom of FIG.
When the laser beam l is scanned in the direction A in the drawing such that the two laser beams 102 are positioned on the optical axes of the two objective lenses 65, the two photoelectric conversion elements 70 and the arithmetic processing circuit 71 detect a matching state. The shift amounts Δx _L1 and Δy _L1 and the right shift amounts Δx _R1 and Δy _R1 are obtained. Subsequently, the arithmetic processing circuit 71
Command via the carriage drive mechanism 77
72 was moved in the Y direction by a distance D _1, by scanning the laser beam l in the drawing direction B, to measure the alignment of the different alignment marks 101 and 102, further displacement of the actual mask and the wafer by subtracting the offset amount Δx _L2 , Δy _L2 and Δx _R2 , Δy _R2 are obtained. Here, a shift angle θ between the left and right of the alignment marks 101 and 102 separated by a distance C _{1 in} the X direction between the mask 66 and the wafer 68.
x is approximately represented by the following equation.

θx = (1 / 2C) · (Δy _L1 −Δy _R1 + Δy _L2 −Δy _R2 ) ……
(5) In addition, the alignment marks spaced in the Y direction by a distance D ₁
The shift angle θy between the upper and lower sides of 101 and 102 is approximately expressed by the following equation.

θy = (1 / 2D) · (Δx _R1 −Δx _L1 −Δx _R2 −Δx _L2 ) ……
(6) These calculations are performed by the arithmetic processing circuit 71, and the control valve 79 is adjusted during the movement of the carriage so as to reduce the deviation angle, thereby eliminating the transfer distortion error. The amount to be adjusted is θ = (θy−θx) · 1/2 (7), where θx is a misalignment component and a component in which the optical axis and the scanning axis are not parallel in the horizontal plane.

In this manner, by determining and adjusting the angle θ to be adjusted at a plurality of positions, the transfer distortion error can be more accurately eliminated.

Next, the exposure procedure by the apparatus shown in FIG. 1 will be described with reference to FIG.

When exposure starts, first perform initial settings (step
401), after inputting the movement amount of the carriage 72 (step 402), input the offset amount (x ₀ , y ₀ ) for each displacement amount measurement point as described above (step 403).

Next, the first wafer is carried in (step 404), the position is aligned with the mask 66 at the center position of the carriage 72 (step 405), and the displacement amount is measured at each displacement measuring point (step 406). 408).

Then, when each deviation amount is measured, the posture adjustment amount of the carriage 72 is calculated in consideration of the offset amount input in step 403 (step 409), and based on this, the carriage 72 is moved while adjusting the posture and exposure is performed. Do (Step 41
0).

When the exposure of one wafer is completed in this way, the wafer is unloaded (step 411), and the next wafer is loaded (step 404).

When the exposure of all wafers of one lot is completed (step 412), the exposure operation is completed.

[Effects of the Invention] Conventionally, alignment was performed in consideration of an offset amount only at a position where position matching between an original and an object to be exposed was performed, and a shift amount was regarded as screen distortion at other measurement positions. According to this, it is possible to perform more appropriate image plane correction by taking the offset amount into consideration at other measurement points.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a reflection projection type exposure apparatus according to one embodiment of the present invention, and FIG. 2 is an explanatory diagram showing a relationship between alignment marks of a mask and a wafer and outputs of photoelectric conversion elements in FIG. FIG. 3 is a top view in which a mask and a wafer are superimposed,
FIG. 4 is a flowchart showing the operation of the apparatus using the present invention. 66: mask, 67: reflective projection optical system, 68: wafer, 70: photoelectric conversion element, 71: arithmetic processing circuit, 72: carriage mechanism, 77: carriage drive mechanism, 78: fluid bearing guide, 79, 80: control Valve: 81: Central processing unit (CPU), 83: RAM, 84: Mark measurement circuit, 85: Carriage drive circuit, 87 ... Control valve drive circuit, 101, 102: Alignment mark.

Claims (1)

(57) [Claims] An illumination means for illuminating an original; a projection optical system for projecting a pattern of the original illuminated by the illumination means onto an object to be exposed; and an original and an object by moving the original and the object to be exposed according to a guide mechanism. A carriage mechanism for integrally scanning the object to be exposed with respect to the projection optical system, position detecting means for detecting the positional alignment between the original plate and the object to be exposed via the projection optical system, and moving the carriage mechanism Drive control is performed while adjusting the attitude of the carriage mechanism in accordance with each position in consideration of the output of the position detecting means when each of the positions is located at each of a plurality of positions on the route and the unique offset amount at each position stored in advance. A projection exposure apparatus comprising: a driving control unit.