JPS61131440A - Reticle and wafer alignment device - Google Patents

Abstract

PURPOSE:To enable to obtain an extremely high matching precision by a method wherein the title device is provided with the circuit pattern of a reticle and a code mark for reticle discrimination. CONSTITUTION:The alignment device is a reticle and wafer aligment device provided with the circuit pattern of a reticle and a code mark for reticle discrimination. That is, the light-shielding unit BL is disposed in such a way that its surface to light-shield has a conjugate relation with the circuit pattern surface CP of the reticle RT by lens systems L4, L5 and L6, the reticle RT is replaced to a reticle, which is different in the thickness of its transparent part such as glass, and when the refracting power is made to vary, the light-shielding unit BL can be made to shift to the optical axis direction for maintaining the conjugate relation. Moreover, the light-shielding unit can be made to rotate by its rotational mechanism in the (theta) direction interlocking to the rotation of the reticle RT for positioning the rotational direction thereof with that of a wafer WF, which is disposed in the lower direction of the reticle RT and is subjected to exposure.

Description

DETAILED DESCRIPTION OF THE INVENTION Field C: The present invention relates to an apparatus for printing or exposing circuit patterns used in the manufacture of high-density integrated circuit chips for semiconductor memories, arithmetic devices, etc., and particularly to a reticle and wafer alignment apparatus.

[Prior art] Conventionally, this type of equipment has problems with its overlay accuracy, productivity, flexibility with other equipment, and large size. ! There was a problem with masculinization, etc.

[Objective] The present invention solves the above-mentioned difficulties and achieves extremely high overlay accuracy,
It is an object of the present invention to provide an apparatus and method with high productivity (high speed), high flexibility, and simple configuration.

[Embodiment J] An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram of an exposure apparatus for exposing a circuit pattern surface CP formed within the plane of a circuit pattern mask, so-called reticle RT, onto a wafer WF. Reference numeral 10 denotes a light source system for exposure, in which an ellipse lIM1 is placed near a light source LP such as an ultra-high pressure mercury lamp to effectively condense the luminous flux emitted from the light source LP, and then sequentially along the optical path, a red Cold mirror M2 to transmit most of the external light and reflect ultraviolet light, integrator lens system L1 to make the light distribution characteristics of the luminous flux uniform, 8 shutters, lens system L2
, reflection tltM3, lens system L3, light shielding device BL, lens system L4, reflection! UM4, lens system L5, reflection 11
M5, lens system L6, and reticle RT are sequentially arranged along the optical path, where reflections 11M3, M4,
M5 is for bending the optical axis at right angles to downsize the illumination system, and lens system L3 is for condensing the light from the light source LP to uniformly illuminate the light shielding device BL. It is something. AS is so-called TTL (Throughoh
Thelens) optical system for alignment, R
5 is a stage for driving the reticle RT in the X, Y, and θ directions;
The reduction lens system PO is an optical system for reduction exposure from 1/S.
It has a reduction rate of 1/10. OA is an off-axis optical system for 7 alignments of wafer WF, WS is wafer WF
The drive stage LZ is a laser interferometer in the X, Y, Z, and θ directions, and the movement of the wafer stage WS is controlled by the mirror M6 of the reduction lens system PO and the mirror M1 of the wafer stage WS. Fig. 2 is a perspective view of the light shielding device!fBL.
If the light-shielding surface is placed in a conjugate relationship with the circuit pattern surface CP of the reticle RT, and the reticle RT is replaced with a reticle whose transparent part is thicker, such as glass, and the refractive power changes. In addition, it is movable in the optical axis direction in order to maintain the above conjugate relationship. In addition, a light shielding device rotation mechanism (not shown) rotates θ as shown in FIG.
It is possible to rotate in the direction.

The light shielding 11fBL has four pulse motors and P on the board ST.
MI to PM4, four feed screw parts FG1 to FG4 that are each fixed to the rotating shaft of each motor PM and rotatable, and four feed nut parts that are movable in one direction by the rotation of each motor PM and feed screw part FG. N'A1 to NA4, and the sharp side edges (
edge) 4 light shielding plates BLI~B with dl~d4-
L4 are respectively arranged, and the four side edges d1 to d4 constitute a rectangular opening.

Upper P! 1I4IR&:, the luminous flux emitted from the light source LP in FIG. 1 passes through the optical element M1. when the shutter ST' is opened. M2. L 1. M3. L 2. M
Reflection and refraction are performed in the order of 4 to uniformly illuminate the light shielding device 1BL. The light flux irradiated to the outside of the opening of the light shielding device BL is
The light beam that is shielded by the four light shielding plates 8L1 to BL4 and passes through the opening illuminates the circuit pattern surface CP of the reticle RT, as shown by the solid line in the figure. Here, the light shielding surface of the light shielding 11tBL and the pattern surface CP of the reticle RT
are arranged in an optically conjugate relationship, so the edge of the opening of the light shielding device f8L is projected with a clear outline onto the circuit pattern surface CP of the reticle RT, and the edge of the opening of the light shielding device f8L is projected onto the circuit pattern surface CP of the reticle RT. area can be completely shielded from light.

In addition, the light-shielding bag MBL is attached to the circuit pattern surface C of the reticle RT.
It is rotatable in the θ direction (Fig. 2) for rotational alignment with P, and when the reticle RT is changed to a reticle with a different thickness, that is, with a different bending strength, the above conjugate relationship It is movable in the optical axis direction (up and down arrows in FIG. 1) to maintain the Further, the area and position of the opening of the light shielding device BL are determined by the pulse motors PM1 to MP4 being rotated in a predetermined manner according to a signal output from the electronic processing section of this device.
Feed screws FG1 to FG4 connected to the shaft of each motor
The feed nuts NAi to NA4 move in one direction, and the light shielding plates BLI to BL4 accordingly move, thereby opening the opening surface in the direction perpendicular to the optical axis.

The product can be changed arbitrarily. The movement and adjustment of these four light shielding plates BL1 to BL4 can be performed simultaneously, thus making it possible to expose an arbitrary area of the reticle RT.

FIG. 3 is a cross-sectional view of the reticle stage R3, which is the first cause, and FIG. 4 is a schematic top view of the substrate S in FIG.
L is fixed to the reduction lens PO, a part of which protrudes upward, and reticle reference marks RKR, RKL are provided on its upper surface. This reticle reference mark RKR, RK
The set marks R5R and R8L of the reticle are aligned with L, and so-called reticle alignment is performed.

RY is the Y-direction drive stage of reticle RT, RX, Rθ
is also a drive stage in the x direction and θ direction, θB (θB
t, θB2. θ83) is the guide bearing for the rotation stage Rθ, RC is the reticle chuck and the tube TU
It has a function of attracting and fixing the reticle RT to the chuck RC using the suction force from R. RX, RY, and Rθ are pulse motors for driving each steady gear RX, RY, and Rθ, respectively. XL, YL, and θL are drive force transmission lever gears, and BXI, RX2, BYI, aY2, and Bθ are each for resisting the force of the motor. The biasing spring, XB.

VB is a guide block that cooperates with guide bearings XG and YG, respectively. Desired amount X depending on the rotation of each motor
, Y, and θ directions.1 For example, when the pulse motor PX is now rotated in the direction of the arrow, the lever XL rotates in the direction of the arrow, and its left end pushes the X stage RX,
Stage RX has spring BX1. Move to the left against BX2. At this time, it is correctly moved only in the X direction by the guide block X8 and guide bearing XG. Photo sensor PS and light shielding plate SM are detection systems for aligning the movement limit of reticle stage R3 and the center of reticle stage R8 with the optical axis of exposure lens system PO.

Furthermore, when the pulse motor PO is driven and rotated, the light shielding HI shown in FIG.
The eight BL boards also move slowly and rotate in the θ direction.

Fig. 5 is a diagram schematically showing the TTL alignment optical system AS and off-axis optical system OA in Fig. 1. In Fig. 1, 18 is a laser source, 2S is a condenser lens that focuses the laser system, and 3S is a rotating A polygon mirror, 4S is an r-θ lens, and 5S is a beam splitter. Laser source 1
The laser beam exiting S is scanned according to the rotation of the rotating polygon II 38, and enters the optical system under the beam splitter 5scc, where 6S is a field lens, IS is a field dividing prism, and the prism IS is a scanning laser beam. 2°
split into two optical paths. In this respect, the prism 7S can be referred to as a field and space dividing prism. 8R,
8L is a polarizing beam splitter, 9R and 9L are relay lenses, 10R and IOL are beam splitters, and the light that passes through these elements is sent to objective lenses 11R and 1
1L, is reflected by objective mirrors 12R and 12L, and is imaged on reticle RT for scanning.
, 13L to the photoelectric detectors 18R, 18L is a photoelectric detection system.

14R and 14L are color filters, and 15R and ISL are spatial frequency filters, which serve to block specularly reflected light and extract scattered light for photoelectric detection. 16R and 16L are reflective mirrors,
17R and 17L are condenser lenses. light source 19
R, 19L, condenser lens 20R, 20L.

The color filters 21R and 21L constitute an illumination optical system for observation, including an erector 22S1, a prism 23S, a television lens 24S, and a picture tube CDo. Configure the investigation system.

In this example, in order to use the amount of light effectively, the optical path of the scanning laser beam is divided into left and right sides by a field dividing prism IS placed on a plane conjugate to the reticle and the sea urchin. The scanning line is perpendicular to the ridgeline of the field dividing prism 7S. In other words, mirrors 10R and 10 are used to scan the laser in the vertical direction.
L, 12R, and 12L are used.

Furthermore, as shown in the figure, since the left and right scanning optical systems are configured asymmetrically, the left and right objective lenses 11R and 11L are arranged alternately corresponding to the positions of the 7 alignment marks WR and W on the reticle RT. . OAR and OAL are a pair of off-axis optical systems for alignment, and are used for the 7-alignment operation described later.

CR and CL are high-magnification charging high-resolution imaging tubes, CDR.

COL is a converter for low magnification and consists of COD (charge coupled device) and the like.゛Figure 6 is a partial perspective view of the wafer stage WS in Figure 1, with a Y-direction moving stage WY on the base WD and an
A direction moving stage WX is mounted, and each X and Y stage W
X, WY are servo motors XM, YMIC, J, *r respectively
X, Y directions t, fn: Move along the edge in ax, aY. XH-XS and YH-YS are detection systems for initial reset of the X and Y stages, respectively. Xo is a hole for a stage θ2 that rotates in the θ direction and moves up and down in two directions. A wafer chuck WC is mounted on the stage θ2 as shown in FIG. 7, and the wafer WF is fixed thereon by suction in the same manner as the copper reticle. The stage θ2 is fitted into the stage holder θH, and can be moved up and down in two directions and rotated in the θ direction by ball bearings 8B and bl. Stage holder θH is fixed to X stage Wx as shown.

Pulse motors ZM and θM for driving in the 2 and θ directions are fixed to the stage holder θH.

A piezoelectric element PZ in which a large number of donut shapes are stacked is arranged at the center of the stage θ2. The piezoelectric element PZ, stage θ2, and wafer chuck WC are integrated with screws 8W.

(2) S is an eddy current type position sensor fixed to the base zD of the piezoelectric element PZ, and detects the amount of upward movement of the stage θ2. A lever ZL is further rotatably supported on the stage holder θH, and a nut N is fixed to the stage holder θH. When the two-way drive motor ZM is driven, the gears Gl and G2 rotate and the threaded rod G3 rotates downward and descends, and the right end of the lever ZL is pushed by the ball b1 and rotates clockwise. Lever Z
The left end of L pushes up the piezoelectric element PZ and sensor Is upward via the base ZD via the pole b2, so that the integrated stage θ2 and wafer chuck WC move upward, that is, in two directions. In this way, coarse movement for focusing is performed. Thereafter, the piezoelectric element PZ is driven from that position and extends in the z-axis direction using the lever ZL as a fulcrum. Therefore, the wafer chuck WC and the θ2 stage move upward by the extension valve of the piezoelectric element. The amount of movement is detected by measuring the gap Q using the sensor Is.

This provides fine adjustment.

When the θ direction drive motor θM is driven, the gear trains G4, G
Stage θ2 and wafer chuck W via S and G6
C rotates smoothly by pole bearings BB and b2.

CH, O8 is a detection system that determines a reference point in the rotation direction.

A G attached to the reduction projection lens PO 1. A.G.
3 is an air micro sensor nozzle, and AG2 (not shown)
．． The distance to the surface of the wafer WF is measured using, for example, four devices including AG4. The distances from the end face of the reduction projection lens PO to the surface of the wafer WF measured by nozzles AG1 to AG4 are respectively d1d2. Assuming that d3 and d4, the average distance is (dl + d2 + d3 + d4)/4. If the distance between the imaging plane position of a predetermined reduction projection lens PO and the end face of the reduction projection lens PO is do, then in order to move the wafer WF to the imaging plane position, Δd−do −(dl +d2 +d3 +d4)/
It is sufficient to move the wafer 2 mechanism by an amount Δd equal to 4.

As a result, the average plane of the wafer WF becomes the imaging plane position.

FIG. 8 is a block diagram for controlling the automatic focusing mechanism.
The microprocessor 40Z performs various judgment processes,
A register 412 issues commands in accordance with each case, and stores command information such as rotation direction 0 rotation amount 1 rotation speed from the microprocessor 402 to the pulse motor ZM. 42z is a pulse motor vIm circuit, which controls the pulse motor Z based on the transfer IPII command information of the register 412.
Perform oven loop control for M. In the initial state, the surface position of the wafer WF is, for example, two or more heads apart from the imaging plane position. This is to prevent the wafer WF from colliding with the reduction projection lens PO even if the thickness of the wafer WF is greater than the specified thickness.

Note that the range in which air sensor nozzles AGI to AG4 can be accurately measured is when the distance from the end face of the nozzle to the wafer surface is within about 0.2 Jw. Therefore, assuming that the predetermined image forming plane position is at 0, IJllI from the nozzle end face, accurate measurement can only be performed when the wafer surface moves upward and within 0.1 inch below the image forming plane position. After entering.

49Z is a circuit that converts changes in the fluid flow rate of air sensor nozzles AGI to AG4 into voltage, and is connected to the reduction projection lens PO.
and the distance to the surface of the sea urchin di, d2.

d3, d41. : Corresponding voltage output Vl, V2
, V3.

Generate v4. 50Z is an analog-to-digital converter (A
DC>, and the voltage Vl generated in the voltage conversion circuit 49Z
, V2, V3, and V4 are converted into digital signals and sent to the microprocessor 402. Here, since the initial position of the wafer WF is more than two feet away from the imaging plane position, the microprocessor 402 sends a movement command to the pulse motor ZM to the register 41Z until the two wafer axes rise and enter the measurement range of the air sensor nozzle. Continue to give. Pulse motor ZM
When the wafer two axes rise due to the rotation of
AG41! The microprocessor 402 detects that it has entered the measurement range through the pressure conversion circuit 49Z and the analog-to-digital conversion circuit 5oz, and sends a stop command to the register 412 Hebals motor ZM to stop the rise of the wafer WF1.
Next, the microprocessor 40Z controls the air sensor nozzle A.
G1~AG4. The surface position of the wafer WF is measured via the voltage conversion circuit 49Z and the analog-to-digital conversion circuit 502, and the movement of the wafer 2 mechanism] Δdl −do −(dl +d2 +d3 +d4
) /4 is calculated. The movement resolution by the pulse motor ZM is 2 μm, and the microprocessor 40z has a resolution of 2 μm.
A unit movement amount Δd1 is given to the register 41Z to raise the wafer 2 axis. As a result, the surface position of the wafer is located within an accuracy of about 2 μm with respect to the focal plane position. Here, the distance to the wafer surface is also measured. Measurement distances by air sensor nozzles AGI to AG4 are d9 to d12, respectively.
Then, the microprocessor 402 writes Δd2−do −(d9 +d1G+dll+
612) The register 43Z issues a command for the direction of movement and the amount of movement of the piezoelectric element PZ, which is 43.
zLt5 and the piezoelectric element drive voltage generation circuit 46Z.

The digital-to-analog converter 1544z outputs the digital value of the register 43Z as an analog voltage to the differential amplifier 45Z as a command voltage. 46z is a piezoelectric element drive voltage generation circuit, which generates approximately 2 of the maximum voltage VH applied to the piezoelectric element Pz.
The differential amplifier 4
Occurs according to the output of 5Z. When the wafer WF moves up and down by driving the piezoelectric element Pz, the amount of movement can be detected and measured by the iu flow type position sensor [S]. The output of the eddy current type position sensor Is is converted into a voltage proportional to the amount of displacement by a displacement voltage conversion circuit 47Z, and outputted to a differential amplifier 45Z and an analog-to-digital converter 1tlaaZ.

The differential amplifier 45Z successively compares the amount of movement of the wafer zII structure by the piezoelectric element PZ detected by the eddy II type position sensor IS with the amount of movement instructed by the register 43Z until the difference falls within the error range. drive As a result, the surface of the wafer WF can be accurately positioned with respect to the predetermined imaging plane position.

The analog-to-digital converter 48Z is an eddy electric I-type position sensor I
The amount of movement of the piezoelectric element Pz detected by S is converted into a digital amount and transmitted to the microprocessor 402. The processor 402 detects this and knows that the imaging plane position has been reached, and moves on to the next control.

Alternatively, simultaneous control as shown below is also possible.

That is, the operation classification of the pulse motor ZM and the piezoelectric element PZ is based on the following equation.

Measurement [/Pulse motor resolution - Quotient (Pulse motor driven valve) Remainder (Piezoelectric element driven valve) In other words, when the average value measured by the air sensors AGI to AG4 is divided by the resolution of the pulse motor ZM and the remainder is calculated - 1 the remainder is driven by a piezoelectric element PZ. This allows coarse drive and fine I! 1 movement is preferably performed. Also, store the quotient and remainder in registers 41z and 432 at the same time,
Since the pulse motor ZM and the piezoelectric element PZ are driven simultaneously, the focus position can be reached at high speed.

This is the first shot area of flibXLtR indicated by A in the figure, which is exposed first. In this way, the step-and-repeat type projection printing machine sequentially prints the wafer placed on the wafer chuck WC by moving it in the WFt-X and Y-axis directions.
By the way, when printing Ii[A, the reduction projection lens PO and the air sensor nozzles AG1 to AG4 are attached to the wafer WF.
is located as shown in the figure, so air sensor nozzle AGI
- AC2 and AC3 can determine the surface position of the wafer WF on the detection side, but the air sensor nozzle AG4 cannot detect and measure the surface position of the wafer WF. That is, as the wafer WF approaches the reduction projection lens PO, microprocessor 4
02 can detect that air sensor nozzle AG1, AC2, and AC3 are sufficiently within the measurement range,
There is no response input from the F-sensor nozzle AG4, so the microprocessor 402 determines that the air sensor nozzle AG4 is unable to measure, and the air sensor nozzle AG1/A
Measured values d1, d2, and d3 of G2 and AG3 are taken out and averaged to determine the average distance to the wafer WF (dl + d
2 +d3. )/3. Focus positioning of area A is performed based on this calculated value.

When the exposure of g1 area A is completed and the exposure of am of B is performed next, the wafer surface position of the exposure area Ij area B is detected in advance by the air sensor nozzle AGI and the distance is measured before the exposure of B. This measured value is sent to the microprocessor 401.
is given as the drive command amount to the register 43Z.Then, the wafer is moved in the WFfX direction until the exposure area B is located under the reduction lens PO, and the piezoelectric element PZ continues to drive in accordance with the previous measurement value. Whirlpool N5! The amount of movement is measured using the shaped position sensor Is! i! When the predetermined amount of movement is completed, the drive is terminated. In this way, the wafer WF is placed in the exposure area A.
Focusing in the next exposure area B can be completed while moving from the exposure area B to the exposure area B. Therefore, exposure VOW with less wasted time can be realized by utilizing the operation time of stage movement.

Figure 9 is a block diagram of the four circuits of the X and Y stages t'i
6. WX (WY) is an X, Y stage, and D is a DC motor, and the X, Y stage and DC motor are coupled with a pole screw. DC motor is motor driver M
Driven by D. Further, a tough generator (speed signal generator) is added to the DC motor, and the output of the tacho generator T is fed back to the driver MD for speed IIItl. The positions of the X and Y stages are measured by a current position counter PCP based on the output signal of the length measuring device LZ. A laser interferometer is used as the length measuring device. The output of this length measuring device is a relative position output,
Origin sensors XH, S (YH, S) and an origin detection circuit SO are provided to detect the origin of the current position of the X and Y stages, and the outputs of these detect the origin of the X and Y stages, and the gate circuit AP detects the origins of the X and Y stages. , length measurement is started,
The current positions of the X and Y stages are measured by a current position counter PCP. The microprocessor CP that controls the entire X and Y stage has a current position latch circuit P.
The current position of the X and Y stages can be known through the LP.

CLP is a target position latch for the X and Y stages, and the target position of the stage is set by the microprocessor CP. DIF is a difference device, and current position counter PC
It outputs the difference between P and the target position latch CLP. In other words, it indicates the amount of movement from the current position to the target position, and at the same time serves as a feedback signal for the position servo, it is also a feedback signal for the 0 position servo, which is used as a means to detect the timing for setting the drive pattern of the X and Y stages. As for the output of the differentiator, D/A converter D
The signal is input to a pit converter BG for matching the bit number of AP, the bit-converted output is input to a D/A converter, and its analog output is input to a position servo amplifier GA as a position feedback signal. There is also a comparator COMP to generate a timing signal for setting the drive pattern of the X and Y stages.The output of the pit converter BG and the latch RPL for setting the movement amount are compared, and when they match, the output from the comparator COMP is sent for setting the drive pattern. A timing signal is output. The timing signal is applied to a random access memory R in which drive pattern information is stored.
The information is input to the address generator RAG of M, a RAM address required at that timing is generated, and drive pattern information is output from the random access memory RM. Also, the timing signal is interrupt occurrence 1! [Input into NT, an interrupt signal is generated, and the microprocessor CP can sense its timing.

In addition to the movement amount data mentioned above, the drive pattern information includes DC
There is command value information for controlling the motor with D.
The current command value initial information that actually drives the C motor, the target command value information that becomes the target value, and the process to the target command value are
There are various types of information. pcv is a current command value counter, which generates a command value for driving the DC motor. CLV is a latch circuit for target command value information. F
G is a function generator that sets the frequency division ratio of the frequency divider DIV, and by dividing the pulse frequency of oscillation 5otv to a desired frequency, the value of the current command value counter PCv is set as the target command value latch. The process to reach the CLV value will be explained. COMV is a comparator that compares the value of the current command value counter PCv with the value of the target command value latch CLV and enables the gate AV until they match, and at the same time informs the microprocessor of the matched timing of the interrupt generator INT. It is notified by an interrupt signal. The value of the current command value counter PCv is input to the D/A converter DAV, and its analog output is sent to the speed servo ill 1.
At the time, the changeover switch SW is set to 0NII to the driver MO.
It is input through and becomes the speed command value.

Further, during position servo control, the position command value is input to the adder circuit AD, and the output of the converter DAP, that is, the addition signal with the position feedback signal is input to the driver MD through the position servo amplifier GA and the changeover switch SW 0FFII.

DMG is a drive mode generator, and this output signal turns the drive mode changeover switch 5WJFrON10FF 0. For example, the ON side becomes the speed servo control mode, and the D/A
The output of the converter DAV is input to the driver MD, and the X and Y stages are driven by the speed servo v1w during the operation start section. On the OFF side, the position servo control mode is entered, and the output of the position servo amplifier GA is input to the driver MD.

The Y stage is driven by the position servo lll1 during the operation end section.

FIG. 10 is a diagram showing changes in the speed of the stage when time is plotted on the horizontal axis and speed is plotted on the vertical axis. The zone WSS from time to to t4 in FIG. 10 is speed control, and from time t4 to t6.
Ward up to! lPS is the speed ll which is the position control section
lll1 section is an acceleration section 11AB that accelerates at a constant acceleration.
, constant speed section r:asc in which movement is performed at a constant speed V wax, deceleration section CD ~ in which deceleration is performed at a constant deceleration rate, constant speed V s
It consists of a constant speed section DE that moves at in. The acceleration/deceleration straight lines AB, BC, CD and DOWN speed switching points are determined by the difference between the current position point A and the target position point P, that is, the moving distance.

This is determined, for example, by the microprocessor CP referring to a data table for acceleration/deceleration, maximum speed, and DOWN speed switching point corresponding to the moving distance. The obtained data are stored in the random access memory RM shown in FIG. 9 by the microprocessor CP. FIG. 11 is a diagram showing the contents of the random access memory.

The contents of the random access memory RM are three blocks P.
HASE1. It is divided into PHASE2 and PHASE3, and the contents of each block are composed of four data.

PHASEI's y'-9 is start aA or '300W
Data archive that controls up to N speed switching point C,
The data of PHASE2 is DOWN switch point C.
The data for PHASE3 is the data for controlling from the position servo switching point E to the stop point P.

Next, use FIG. 9, FIG. 10, and FIG. 11 to make X.

The all 111 method of Y stage will be explained. First, the microprocessor CP sets the zero-order target position for writing data necessary for driving into the random access memory RM in the target position latch CLP, and also sends a start signal ST to the RAM address generator. As a result, the address of PHASEI is generated from the RAM address generator RAG, and the address of PHASEI is generated from the random access memory RM to the current command value counter PCv.
The speed data, the MAX speed data in the target command value latch CLV, the acceleration gradient data in the function generator FG, and the travel amount to the travel amount setting latch RPL&:DOWN speed switching point C are set, and the drive mode is generated! SDMG is set to switch 5WeON side. X,
The Y stage starts an acceleration operation as shown in FIG. 10A-8 toward the target position by the output of the converter DAV. That is, the value of the current command value counter PCv is the target command value CL.
Divide until it equals the value of V! The acceleration operation AB shown in FIG. 10 is performed using the variable output of the counter PCv that counts the output of 1 DIV, and after a match is reached, the constant speed operation BC is performed using the constant output of the counter PCV whose input to the divider DIV is cut off.

Next, at the DOWN speed switching point C, a match signal is output from the comparator COMP, and a RAM address is generated! ! Input to IRAG. As a result, the address of PHASE2 is generated from the RAM address generator RAG,
Current command value counter P from random access memory RM
MAX speed data in C■, target command value latch CLV
The MIN speed data is set in the function generator FG, the deceleration gradient data is set in the function generator FG, and the movement amount up to the position servo switching point ε is set in the movement amount setting latch PRL, and the X and Y stages start deceleration operation. That is, the current command value counter PCv
The deceleration operation CD is performed in the same manner as described above until the value of CLV becomes equal to the value of the target command value CLV, and after that, the constant speed operation Dε is performed.

Next, at the position servo switching point, the comparator GOMP
A match signal is output from the RAM address generator RAG. This causes the PH from the RAM7 address generator to
The address of ASE3 is generated, and the random access memory RM stores the data corresponding to the amount of movement to the position servo switching point E, for example, 25μ before the target value, in the current command value counter PC■, and the target position data in the target command value latch CLV. , the function occurs! The position servo gradient data is set in SFG and the target stopping point P is set in the movement amount setting latch, and at the same time, the position servo gradient data is set in the drive mode generator DMG.
The I mode is set, the switch SW is set to 0FFfull, and the X and Y stages are position controlled wf! Ill m n end point F! At p-, match signals are outputted from the comparators COMV and GOMP, respectively, and inputted to the interrupt generator INT to generate an interrupt signal. The microprocessor CP that detects this assumes that the basic X, Y stage control has been completed, and determines the permissible value (CJX lower tolerance) of the stage stop position accuracy.The microprocessor CP uses the current position counter P
The current position data is inputted to the CP via the current position latch PLP, and it is determined whether the difference from the target position is within the tolerance, and the stop position fi! The control is completed when the accuracy and variation are within the tolerance, and the movement of the X and Y stages ends.

Figure 12 shows off-axis optical system O for TV alignment.
An embodiment of A is shown, and R11°Lll in the figure is a light source for illumination, for example, a halogen lamp is used. R12
, L12 is a condenser lens, R13A.

R13B, Li2Q, and 113B are the bright field diaphragm and dark field diaphragm that can be attached and detached interchangeably. In the figure, the dark field diaphragm R13A
, Li2Q is installed in the optical path, so the condenser lenses R12 and L12 connect the light sources R11 and Lll to the bright field aperture R.
(L) Image is formed on 13A. R14 and L14 are relay lenses for illumination, and R15a-b and l-15a-b are cemented prisms. This cemented prism has the function of making the optical axis of the illumination system and the optical axis of the light receiving system coaxial, and has an inner reflective surface. R15a
, L15a and transflective surfaces R15b and L15t). Here, light sources R, L11, condenser lenses R, L
12. Bright or dark field diaphragm R, Li2Q, B1 relay lens R, L14, cemented prism R, L15a.

b. The objective lenses RL and LL constitute an illumination system, and the light flux emitted from the objective lenses RL and LL is reflected onto the alignment marks CRL (LR) 11, 12 or WPR (L) 1 of the wafer WF shown in FIG. illuminate.

R and L16 are relay lenses, R and L17 are mirrors that switch the optical path from high magnification to low magnification, and R and L18 are index glass plates having reference marks TPR and TPL for TV alignment.
The reference mark TPR(L) has a function of providing the origin of coordinates, so to speak. Therefore, the 7 alignment mark is the value of the X coordinate and the Y
It will be detected as a coordinate value. R, L19 is W
i-shade lens, R1L20 is NA limited aperture, cemented lens R, l-15a, b mentioned above, relay lens R, L
16, mirror R1L17, m [gas plate R, L17, l1r
Ii Lenses R, L19 and high magnification m images 1ICR, CL constitute a light receiving system, and the optical path passing through the objective lenses RL, LL is reflected by the inner reflecting surfaces R, L15a of the cemented prism, and then reflected by the rod transmitting surfaces R, L15b. , again the inner reflective surfaces R, L1
It is reflected by 5a and goes to relay lenses R and L16. 13th
7 alignment marks on wafer WF in the figure @CRL (L
R) 11.12 is cm@let@'IICR along with the reference mark image TPR(L), which is formed on the index glass plate R and L18 that are adjacent to the reference mark TPR(L).

The image is formed on the m image plane of CL. To explain in detail the operation of the high magnification system of the optical system with the above configuration, the luminous flux from the illumination lights IR and L11 is converged by the condenser lenses R and L12, and the bright field diaphragm R and L13A or the aperture of the bright field diaphragm R1113[3] further passes through the illumination relay lens R1L14, passes through the semi-transparent surfaces R and L15b of the cemented prism, and illuminates the reflective surface R.
, L15a, and illuminates the wafer WF through the objective lenses RL and LL.

The light beam reflected on the surface of the wafer WF is passed through the objective lens R(L)
The image is formed by the lens L, enters the cemented prism R1115a, b, is reflected by the reflective surfaces R, L1sa, is then reflected by the semi-transparent surfaces R, L15b, and the reflective surfaces R, L15a, and is emitted from the relay lens. After being relayed by R, L16 and forming an image on the index glass plate R, L1a, the imaging lens R, L
19, the image is formed on the image pickup tubes OR, CL to a zero-order dark field state so that the alignment mark image can be clearly detected, and the position of the alignment mark image is detected by capturing the image. Depending on the position of the alignment mark detected by electrical processing to be described later, the wafer stage WS aligns the first shot (exposure) area of the wafer WF with the projection lens PO.
Move to occupy the prescribed position of the projected buffalo. R, L2
1 is a reflection mirror, R and L22 are erectors, R2L23 is an aperture similar to R and L20, and CDR and CDL are CO for low magnification.
These optical systems that perform the same effect as described above at low magnification in D are not necessarily a pair, but only one each.

However, if they are paired, they can be detected simultaneously, so high speed and high accuracy can be expected.

Figure 14 is a block diagram of the entire device.
In addition to the HT shown in the figure, it includes a sub CPU and a drive circuit, ie, each unit control circuit as shown in FIG. 8.9, for example. Also low magnification television (Tv) camera CDO, CDR
, CDL is 11 TV, signal line L to receiver TVI
1, and the high magnification TV camera OR, OL is connected to the second T.
It is connected to the V receiver TV 2 by the signal line L2.

The control box CB includes a main CPU, a ms part MC containing a high-speed arithmetic circuit, and a ROM.

Includes RAM. The ROM stores instructions as shown in the flowchart below. The KO5 uses the console to set various parameters and perform various other controls, and the printer PRT prints out various states of the device. Figure 15 shows an example of a display monitor when performing off-axis and clove L alignments.
2 is used to perform off-axis alignment, and the reference mark TPR(L) of the index glass plate R(L) 18 of the off-axis optical system OA in FIG. 12 and the reference mark TPR(L) of the wafer WF in FIG. 13 are shown. High magnification alignment mark CRL
(LR) 11.12 will be displayed, allowing you to check the alignment of both marks. B shows how alignment is performed by comparing the low magnification mark WPR(L)1 in FIG. 13 with the electronically set reference (cursor) IiKSL using the low magnification TV1, and C shows TTL. Alignment optical system A
Put the female mark WK of wafer WF on TV1 for low magnification using s.
R.

An example is shown in which the male marks WSR and WSL of WKL and reticles R and T are displayed, and it can be seen that both marks are aligned 7 times at TTL. In addition, when using a wafer for which automatic 7-alignment is not possible, a special manual alignment mark can be printed on the scribe area of the wafer WF and alignment with the special manual alignment mark on the reticle can be performed manually. can. In this case, cross marks such as those shown in A and B are preferable to recommended marks because they are easier to visually align.

I! Figure 18A shows an example of the initial reticle configuration.

B also shows the second reticle, C shows how the first reticle RT1 is sequentially exposed on the wafer WF surface, and O shows the contents of the second reticle RT2 being overlapped and sequentially exposed. Show how it goes.

In the figure, CPI and CF2 are reticle RT1. RTz
Circuit pattern provided above (actual element), 5CRI
, 5CL1.5CR2, 5CL2 are scribe areas provided on the left and right sides of the actual element, and the first reticle RTI has a female mark WKR1 for use in 7 alignment with the second reticle RT2.

WKLl is provided. Also, if necessary, use the above-mentioned special manual alignment mark MARI.

MALI is placed in place of mark WKR(L)1 or in parallel as shown. The lower scribe area m5CU includes a high-magnification alignment mark CRR that is smaller than the low-magnification alignment mark WPR(L).

Two CRLs are prepared. It is preferable to provide a pair of WPRs, two on each side, as shown in FIG. 13, since this increases the probability that the WPR will fall within the field of view of the objective lenses RL and LL of the off-axis optical system OA shown in FIG.

WPL is a mark for low magnification alignment, R2H and R3L are male marks for 7 alignments of the reticle, and the position of the reticle is set in alignment with the reference marks RKR and RKL on the lens PO in FIG. RKR, RKL are WKRI
, has a female mark shape similar to WKLI, and TT
Similar to the L auto 7 alignment, reticle auto alignment is performed by aligning the recommendation marks.

On the second reticle RTZ, female marks WKR2, WKL2 for next process alignment and male marks WSRI, WSL1 for main process 7 alignment are provided. RCNl
, RCN2 each indicate a reticle number and are provided in a coded manner.
By reading St', the reticle number can be automatically identified.

This information is created simultaneously when the circuit pattern and each mark are created. Similarly, WCN in FIG. 13 indicates the hooded wafer number, which is written by the TTL alignment optics AS and read by the TTL alignment optics As or the off-axis optics OA. Note that these are the first
Of course, it is also possible to discriminate the reticle and wafer numbers based on information instructed in advance from the console KOS shown in FIG. 4 or information sequentially instructed in real time. In FIG. 16, first, the first reticle R
When the TI is inserted as shown in Fig. 5, the blade B in Fig. 2
First, as shown in FIG. 17A, an opening is set in L so that the area of the circuit pattern CPI and the scribe areas 5CR1 and 5CLI on the left and right sides thereof are exposed. In this state M16Fj
! 1.2.3 in order from right to left like JC. ...is exposed.

That is, in the first shot (exposure) area 1, the special manual marks MARI and MALL of the reticle RTI are MA
As RIl, MALLll, the mark WKRI
, WKLI is exposed (printed) as WKRll, WKLll, and circuit pattern CP1 is exposed (printed) as CPll. In actuality, the printed pattern on the reticle RTI is projected through the projection lens PO, so the horizontally and vertically inverted image is displayed on the wafer. Although the image is printed on the WF, for ease of understanding, the illustration assumes that the same image is printed. Thereafter, the circuit pattern CP11 is sequentially printed in the same manner.
and CP 12 scribe area S CR12L 1
1 is shared by circuit patterns CPII and 12 in order to save on wafers. Therefore, a pair of left and right marks such as W
KRll and WKLll are shifted vertically from each other.

With this configuration, for example, marks WKR12 and WKL
In this way, exposure and steps are repeated sequentially in the order of shot numbers 1 to 45 shown in FIG. 13, and when a specific shot, for example, area 20. As shown in FIG. B, the opening of the blade BL is set so that the lower side scribe area SCU is exposed. As a result, the high magnification alignment marks CRL and CRR of reticle RT1 are set to shot 2 as shown in the 13th cause.
CLR11 in the 0 and 26th lower side scribe areas respectively
, CRL11 and CLR12, CRL12.

Also, specific shot 41. and 45, Figure 17 C1
As shown in D, move the blade B so that the low magnification alignment marks WPR and WPL of the reticle RT1 are exposed.
After setting the aperture of L, the shot area 41. in FIG. 13 is set.
, 45 are printed as low-magnification alignment marks WPRI and WPLI on the right and left sides, respectively, of 0 or more, thereby completing the printing on the first wafer WF. The shot order shown as 1 to 45 in FIG. 13 is preferable because the movement of the wafer stage WS is 1hjl as it is the shortest.The wafer that has been baked is replaced with the next wafer WF, and the same process is performed to complete 10 wafers. Then, the first reticle RT1 is ejected and the second reticle RT2 is inserted. As described above, the second reticle RT2 is configured as shown in FIG. 16B, and during the first shot, the male mark WSR1 of the reticle RT2 and the female mark WKR11 of the wafer WF are connected, and also the male mark WSR1 of the reticle RT2 and the female mark WKLll of the wafer WF are connected to each other before exposure. TTL
After seven precise alignments are performed by the alignment optical system AS, exposure is performed, and the circuit pattern CP2 of the reticle RT2 is printed as CF3I on the circuit pattern CP11. Further, the male mark WSRI of the reticle RT2 is burned into the middle of the female marks WKR11 and WKL11 of the wafer WF, and is no longer usable. Therefore, reticle R
T2 has female mark WKR for next process alignment.
2. WKL2 is provided at a position shifted one step upward as shown in FIG. 16B, and this mark is printed as new female marks WKR21, WKL21, etc. in FIG. 16. In this way, new marks are sequentially provided and old marks are not used, which is preferable because it allows error-free reading without reducing reading sensitivity.

Also, in the illustrated example, the scribe area is saturated with two reticles for ease of understanding, but the number of reticles is usually 10.
A few sheets are sufficient, and a normal scribe area has a sufficient size considering the size of the chip area, the size of the mark, the sensitivity of the reading means, etc. Also, old marks may be used repeatedly, and marks MAR2 and M on reticle RT2 may be used during special manual alignment.
AL2 and marks MAR11 and MA smoked in the previous process
LII, etc. are performed by the low magnification TV monitor TV2.

Figure 18 shows the TV screen in Figures 14 and 15 in the X direction.
This shows how the pixel pJ is divided into M parts in the Y direction.
1 indicates the pixel in the J-th row and the i-th row. The number of divisions M in the Y direction usually matches the number of horizontal scanning lines, so in order to divide into pixels, it is necessary to All you have to do is perform sampling N times.

Therefore, the addition in the X direction is 5x1-DATA (Pa) + DATA (Pv)
+...+DATA (P+N), 'Sx
2-DATA (Pz+)+DATA (P22
)+...+DATA (Pg N), SX
M = DATA (PM + ) + DATA (PM
z )+...+DATA (PMN), addition in the Y direction is SY I =DATA (Pa)+DATA (P2
1)+......+DATA(PM
Electric), Sv z = DATA (P) + DAT
A (P22)+...+DATA (PMz
), SYM-DATA (P+N)+DATA
(PzN)+・・・・・・+DATA (PMN
), Hail to you.

When the addition is completed, the X and Y direction integration memories contain Sx+ #Sxz, ""SxM, and SYI, respectively.

Data of Svz, . . . , Sl/M is stored.

An example of the alignment mark is the cross-pattern mark shown in FIG.
The concentration distribution becomes as shown in C).

(8) shows the addition result in the X direction, and (C) shows the addition result in the Y direction. The characteristics of the concentration distribution in FIGS. 19(B) and (C) are as follows:
As can be seen from the figure, the added density of the mark is in two stages. For these two-stage concentration distribution, the first
As shown in Figure 9 (C), two slice levels, e.g.
When 5L1 and X5L2 are provided, the binarization patterns become the patterns shown in FIGS. 19(D) and (E), respectively.

Therefore, when the centers of these binarized patterns coincide, these become the center coordinates of the 7-alignment mark.

The block diagram in Fig. 20 shows an example of an alignment mark detection circuit, where the block X surrounded by a broken line is a block that adds the density of pixels in the X direction, and the block Y is a block that adds the density of pixels in the Y direction. be.

In Fig. 20, 31V is a video amplifier, 32V is an analog-to-digital converter, and 33V is a latch circuit.The video signal sent from the TV camera control section is amplified by the video amplifier 31V, and digitized by the analog-to-digital converter 32V. After that, it is stored in the watch 33V. The output data of the latch 33V is the addition block X in the X direction.
and is output to addition block Y in the Y direction. In block Y, 34V is an adder that adds data in the Y direction, and 35
V is an addition output latch that latches the output data of the W adder 34V, 36■ is a Y-direction integration memory that stores the data of the addition output latch 35V, and 37V is an addition input latch that latches the output data of the memory 36V.

In block X, 38V &; an adder that adds data in the tX direction; A latch that latches the output of 138V, and 40V is an X-direction integration memory that stores the output data of the latch 39V.

There is no particular limitation on the number of digital data pits in these circuits, but for example, an analog-digital converter 32V has 8 pits, an adder 34V, 38V, and a memory 36V,
40V has a 16 pit configuration.

41V is a sequence and memory control circuit that controls read/write and chip selection of the memory 36V, and 42V is a memory control circuit that controls the memory 40 in block X.

43V is the sequence and memory control circuit 41■
This is a control register for the microprocessor MPU to control I'l Ill, and the input of the register is connected to the data bus 44V of the microprocessor. Also, the microprocessor MPU can access the memory 36V and 40V via this data bus 44V, and the 6, 45V, 46V, 47V, and 48V are buffers for this purpose, and the buffers 45V and 47V are for the microprocessor MPU. The buffers 46V and 48V operate when writing data to the memories 36 and 40, and when reading data. 49V is the clock circuit, 50V,
51V is a memory write address circuit and a memory read address circuit that generate write addresses and read addresses for the X-direction integration memory 36V. 52■ is an address selector that switches between the read address and the write address of the memory, and 53V is an address buffer when the microprocessor MPtJ accesses the memory 36V? and
The output of the address selector 52V is selected except for rf accessed by the microprocessor MPLJ, and the buffer? Output of 53V is prohibited. '54v is a memory address circuit that generates an address for the 40V X-direction integration memory, and 55V is an address selector that switches between the 7 addresses of the memory address circuit 54V and the address generated when the microprocessor MPU accesses the memory 40V. 56V is a television synchronization signal generation circuit that generates a horizontal synchronization signal, a vertical periodic signal, a blanking signal, etc. for the television based on the clock of the clock circuit 49V. 57
V, 58V are an X position i1 display register and a Y position display register, which are connected to the data bus 44 of the microprocessor MPU, and 59V is a cross mark display circuit. is the X position display register 57
By outputting it to the V and Y position display register 58V, the mark display circuit 59V outputs it as a cross mark signal.
Sent to the video input terminal of the TV camera control section. It is also sent to the CPLJ in FIG. 9 via the microprocessor MPLJ, and the wafer stage is moved to the mark identification position by the servo motor.

The functions of the above-mentioned television alignment detection circuit are: (1) integration of data in the X direction, (2) integration of data in the Y direction, and (2) display of an alignment mark on the television screen.

Of these, the integration of the data in the X direction and the data in the Y direction are performed by the adder IIi of the television alignment detection circuit.
．． 38 performs the addition and stores the added data in memory. Addition of data is performed in units of one frame of the television signal, and if necessary, the addition of one frame may be sufficient to complete the addition, or? ! ! Addition of several frames may also be performed. In either case, during addition, the memory 36V, 4
The 0V data bus and address bus are electrically separated from the 44V data bus and address bus of the microprocessor MPU, and the address of the memory 36V is connected to the address selector 52V, and the 7 address of the memory 40V is connected to the address of the address circuit 54V. The addition is performed after ill--tll of the read/write signal and chip select signal generated from the sequence and memory control circuit 41V and the memory control circuit 42V.

When the addition of the predetermined number of frames is completed, the interlaced signal 1 is output from the sequence and memory control circuit 41V.
An addition end signal is generated on 1m1NT.

After generation of this addition end signal, the microprocessor MPt
J accesses the memory 36V and the memory 40V and detects the position of the television alignment mark from the added data. When the microprocessor accesses the 36V or 40V memory, the memory address, read/write signal, chip select signal, etc. are naturally controlled by the microcomputer's control signals. Also, the data in the memory 36V is buffered at 46V. J40V (7) data is transferred to data bus 44 via yVy48V4i:lil
V and is read by the microprocessor.

This will be explained in more detail using the flowchart shown in FIG. When an addition start command is issued by the microprocessor in step Sv1, addition in the X and Y directions is started as described above. Microprocessor is step S
Step SV waits in a state where addition is completed at V2, and proceeds to step SV3 when addition of a predetermined number of frames is completed.
At step 3, the microprocessor searches for maximum and minimum values of the image m1 degree data stored in memory. When the 71 maximum value and minimum value are found, the slice level X5LI and WSRI are set in step SV4.

The slice level WSL1 is, for example, a value of 10% of the difference between the maximum value and the minimum value (referred to as the peak value) of the image density data.

Next, in step S5, the slice level "X5LI" is compared with the contents of the memory, and XLI and XR1 are obtained from the coordinates (memory address) where the comparison result is inverted.Similarly, in step SV6, the peak value is A slice level X5L2 having a value of 20% is set, and XL2 and XR2 are determined in step SV7 in the same manner as step Sv5.

As described above, the binarization pattern shown in FIGS. 16(D) and (E), that is, the coordinates XLI and XR1.

XL2 and XR2 can be determined. r to step SV8
(XR2-XL2)/2 is ill XR1-XLl)
/2, and if they are almost equal, it is determined that the detected coordinates are alignment marks and the process proceeds to step SV9, and if the comparison values are significantly different, it is determined that they are not alignment marks. Step 5 VIO
If you proceed to Step 5vio, for example, change the slice level setting value and measure again, or assume that there is no 7-line pattern on the screen and proceed to the process of searching for a 7-line pattern.Similarly, change the Y coordinate. Y
LI, YRI, YL2, and YR2 can also be determined.

The advantage of the embodiment shown in FIG. 16 is (2) Random noise is averaged by the addition, and the S/N ratio is improved. ■Position detection in the X direction and Y direction can be performed independently, making detection easier. (ii) The capacity of the memory for storing image data is reduced.

Hereinafter, the operation of the present invention will be explained according to the flowcharts shown in FIGS. 22-25.

First, in step SS1 of FIG.
! Perform the initial WA settings for the device - for example, memory RA
Zero clear M, TTL alignment optical system Move the optical system in the entire S direction, move the objective lens 11R (L) and the objective mirror 12R (L) in the X direction, and mark the reticle reference mark RKR (mW) on the lens PO. L
) and the objective mirror 12
Step SS2: Setting the attitude of R (L) at 45° so that the laser beam can irradiate the mark position, setting the reticle stage, wafer stage, blade to the initial state, and performing various other initial settings. Now reticle R
The reticle chuck RC1: adsorbs T by vacuum suction, and in step SS3, the laser shutter BSe is opened to prepare for alignment of the reticle RT6.Then, in step S
In S4, the entire optical system As is moved in the Y direction by a pulse motor (not shown), and the objective lens t1R(L) and the objective mirror 12R(L) are moved in the The presence of reticle set mark R5R(L) is detected by detector 18R(L). The mark R8R (
L) and the distance from the predetermined reference point are measured by the detector 18R(L), and in the next step 5861, each pulse motor PX of the reticle stage R3 is
, PY, and Pθ to set the set mark R on the reticle RT.
3R(L) is moved near the reference mark RKR(L). At the same time, the objective lens 11R (L) and the objective mirror 12
R(L) is returned to a position facing the reticle reference mark RKR(L) in preparation for fine alignment.

In step SS7, the reticle reference mark R on the lens ρθ is
Reticle set mark R3 of KR(L) and reticle RT
Detects the amount of deviation from R (L) in the left and right X and Y directions! ! 11
Detected by 8R(L). It is determined in step SS8 whether the average value of each of the measured values is within the allowable value, and if it is within the allowable value, the process proceeds to the next step ssio, and if it has not yet reached the allowable value, step SS9 - again, each pulse motor PX, PY, P of reticle stage R8
θ is driven, step 5S1.8 is repeated, and the reticle stage R3 is moved until the value is within the tolerance. If the CPU determines that the allowable value has been reached, step S S10
In step s io, the exposure area of the reticle RT is set, and first, as shown in FIG.
The opening lj area of the blade BL is set so that the area lj is exposed. .

Next, in step 311, the first wafer WF is attracted to the wafer chuck WC of the wafer stage ws. The wafer WF transported here is a wafer that has never been exposed to light, and therefore alignment marks have not yet been printed.

In the next step S S 12, in order to identify the reticle number, the objective mirror 12R or 12L is moved to the detection position of the reticle number RCN on the reticle steering wheel. Reticle R
T usually takes several to 1 to produce one large-scale integrated circuit.
4.5 sheets are prepared, so when creating each circuit pattern, reticle number J! If the RCN is encoded and provided, the reticle number (class 81) can be automatically identified. Step S
The reticle number RCN encoded in S13 is read by the detector 18L or 18R. As a lighting source at this time? You may use 9R or 19L, but for now it is the first reticle, so step 8814
In Step 5514, the laser shutter BS is closed, and the attitude is changed from the 45° attitude to vertical (two directions) so that the lower side of the objective mirror 12R (L) does not interfere during exposure.6 Next, Step S15 The wafer stage WS is moved by a predetermined amount in the X and Y directions by the servo motors XM and YM, and the first shot (exposure) of the wafer WF is performed.
The area is set directly below the projection lens PO. This movement is carried out extremely accurately by a laser interferometer LZ. Wafer WF with the first shot area set directly below the lens PO
are air sensors AG1 to A attached to lens PO.
The pulse motor ZM is driven to move the θ2 stage upward at high speed so as to reach the focus detectable level of G4 (step 5S16). After reaching the focus detectable level, each focus value is set by the air sensors AGI to AG4. Each detected value is stored in the RAM and an average value is calculated (step 3317). This average value is used as the focus value of the first shot area, and the pulse motor ZM and/or the piezoelectric element is controlled according to this value as described above. The θ2 stage is moved upward or downward by PZ until it reaches the target focus value (step 5S18), and then the shutter ST of the exposure light ILP is opened and closed at a predetermined 8[degrees] to expose the first shot area of the wafer WF. , female marks W for TTL alignment in the circuit pattern part CP of the reticle RT and the left and right scribe areas SCR (L)
KRn and WKLn are burned (step 5S19)
, and/or manual alignment mark MAR1 as required.

MALI is also burned in the first step S S 20
Determinations as shown in 22 and 24 are made, and if the second shot area is neither of the above, step 5325 is performed.
1, proceed to 252. In steps 251 and 252, as described above, the focus is detected by the air sensor corresponding to the next shot area, and the θ2 stage controls the motor ZM and/or the pressure 1! until that value is reached. It moves upward or downward depending on the element PZ. At the same time, wafer stage WS is moved to X by servo motors XM and YM.

The camera moves in the Y direction, and the next shot area moves directly below the lens PO. This movement is also performed extremely accurately by the laser interferometer LZ, and similarly precise step feeding, focus detection, and exposure are sequentially performed. Step 3320
．． 22, when the predetermined specific shot area is reached, the low magnification and high magnification alignment mark WPR (L)
, CRR(L) are exposed in step 5521.
．． At 23, the opening w4wt of each blade BL is set. Furthermore, when transitioning from a specific spot area to a normal shot area, the Sekiguchi area of the blade BL is returned to the normal shot area [(Step S S10 in FIG. 17 A1). When the final shot area is exposed, step 5324 Then, the process proceeds to step 5S2G. In step 8826, the wafer stage WS is moved to write the wafer number on the wafer WF.
is moved to a predetermined position, the laser shutter BS is opened when sufficient for writing, and the coded wafer number and/or loft number WCN is transferred to the edge of the wafer WF (see FIG. 14).
In step 5S27, the wafer stage WS is moved to the wafer ejection (receiving) position and the wafer is ejected. At the same time, the θ2 stage is moved to the initial lowest position by the pulse motor ZM. It is determined in step 5S28 whether or not it is a wafer. This is done by comparing whether the number of wafers has reached the number instructed by the operator to the microprocessor from the console in advance, and if it is not the final wafer, step S
Return to S11 and continue the same steps as described above.

As described above, the printing of the circuit pattern and the mark for the 7th alignment of the ticle is completed after performing the printing for the predetermined number of wafers and otters. The details of the first wafer on which the circuit pattern and alignment mark of this reticle have been printed are then precisely overlaid and exposed in the same shot area on the same wafer from the second reticle to the nth (l final) reticle. That is, when the second reticle is brought in, step S
The same operations as described above are performed from SI to 5S13, and in step S13, it is detected that the reticle number is "2", so the process proceeds to step 5529. In step 5S29, the wafer WF is attached to the lens PO. In step 3830.31, the 02 stage is raised at high speed, focus detection and average value calculation are performed, and the process proceeds to steps 5S321 to 323. In step 5S321, the mirror R(L) of the off-axis alignment optical system OA is
1g set to low magnification system, and dark field comparison R (L) 13B
Select.

At the same time, in step 58322, the mechanically prealigned wafer WF is marked with a low magnification 7 alignment mark WPR (
L) 1 is set almost directly below the objective lens R(L)L.

At the same time, in step 5S323, step 5
The θ2 stage is moved upward or downward from the focus average value detected in step 831 until it reaches the target focus value. Mark WPR(L)1 on wafer WF with objective lens R
(L) The movement below L is performed using a predetermined constant. Step 583
3, the reference 11KsL (cursor on the TV screen) and the wafer WF pre-alignment set mark WPR (L)
The amount of X and Y deviation from 1 is measured, and the amount of deviation is stored in the RAM.Next, in step 5S34, one of the plurality of 7 alignment modes A-C is selected, and accurate and high-speed positioning is performed according to each 7 alignment mode. Alignment, stepping, and exposure are performed. Each of the 7-line modes will be explained below.

In mode A, first, in step 5A11, the reference line KSL is
position and wafer WF alignment set mark W
Wafer stage WS is moved in the X and Y directions by servo motors XM and YM according to the value obtained by adding a constant to the amount of X and Y deviation from PR(L)1, and high-magnification alignment mark CR(L)11. of wafer WF is moved. 12 is the objective lens R (1)
Set it almost directly below L. At the same time, the 02 stage is rotated by the pulse motor θM according to the amount of deviation in the θ (rotation) direction calculated from the above X and Y deviation stars (Step 5A1
2). In step SA2, the mirror R (L) 18 of the off-axis optical system OA is set to a high magnification system, and the reference mark TPR (L) and the high alignment mark OR are set by this high magnification system.
(L) 11. The X and Y deviations from 12 are measured (step 5A3), and the amount of expansion and contraction of the wafer is also measured in this step SA3, and if it is within the allowable value, the value is used as the deviation of each of the Add the distribution to the amount. In step SA4, it is determined whether the X and Y deviation amounts are within the allowable value, and if it is determined that they have not yet reached the allowable value, the reference mark TPR is
Move the wafer stage WS using the servo motor
The wafer W is moved in the X, Y, and θ directions by YM and pulse motor θM (step 5A5), and the process returns to step SA3 and repeats the same procedure. When the value is within the tolerance, the process proceeds to step 5A61.62. In step 5A61, the wafer W
Wafer stage WS is moved in the X and Y directions by servo motors XM and YM in accordance with the value obtained by adding a constant to the current position of wafer WF to set the first shot (exposure) area of wafer WF directly below projection lens PQ. At the same time step 5A62
Now, the θ2 stage of wafer stage WS is moved upward by a predetermined distance by pulse motor ZM. This is objective lens R
(L) This is because the focal length of the projection lens PQ is shorter than the focal length of L. Hereafter, as in the previous example, focus detection, average value calculation (step 5A7), θZ steady movement (SA81), and attitude change of mirror 12R (L) (
SA82), exposure (SA9), sequential focus detection, step movement (SA111.SA112)
) is repeated, and if it is determined (SAIO)L that the exposure of the final shot has been completed, the process proceeds to step SA12. In step 5A12, the wafer stage WS is moved by the servo motors XM and YM to a position where the wafer number WCN entered in the first step can be detected.
N is set directly below the lens PO, and the encoded wafer number WCN is read at the detection g$ 18R or 18L. In addition to the laser source Is, the illumination light source at this time is the light [1
9R or 19L can also be used. Alternatively, it can also be read using an off-axis engineering system OA. At this time, wafer stage WS may be moved so that wafer number WCN is set directly below either objective lens RL or LL. The read wafer number is stored in RAM. In Step 3 A14, the θ2 stage is moved to the lowest position by the pulse motor ZM, and at the same time the wafer stage WS is moved to the wafer ejection (receiving) position.
The process ends after the wafer is discharged. Step S A 15
If the finished wafer has not yet been completed, please refer to Fig. 22-8.
The process returns to step 5S11 of step 2, and the same procedure is followed thereafter.

Mode B1 in FIG. : First step SB1
For example, specify the shot area 13 in FIG.
That fits! is set directly below the projection lens PO by servo motors XM and YM. At the same time, step 5B1
2 and 13, movement in the θ direction and two directions is performed. Next, the laser shutter BS is opened (step 382), and the TTL
Measure the amount of X and Y deviation. Here, as shown in shot area 1i113 in FIG. 13, the left and right deviations I in the X direction
XLI, XRI, same Y direction YL1. Assuming YR1, each average value is 31 X-(XLI +XR1)/2°S
Calculate I Y-(YLI +YR1)/2, RAM
Then, the second specified shot (for example, FIG. 13, 19) is stored and stored in the projection lens PO (step 5B3).
to find the similar average value S2X, 32Y (step SB4.5), then step 5B61
From X, Y average deviation ff1sIX, S2 X, 81 Y, S2 Y for each shot calculated separately for each shot.
) The amount of deviation in X and Y and the amount of deviation in the θ direction of Z (all cloval) are determined by the following formula.

GX-(SI X+S2
+YR1)'/2)/ where K is the distance between the designated first and second shot marks and is a constant.

At the same time, in step 5B62, the expansion and contraction of the entire wafer due to thermal expansion and the like is determined.

Step SS determines whether each of the obtained values is within the allowable value.
Determine by 7. If it is determined that it is outside the r'+ capacity value, proceed to step 3381.82. In step 5881, a predetermined amount (K) is added to the previously calculated X and Y deviation amounts,
Add to that value the value obtained by equally distributing the wafer's expansion/contraction APE for each shot, and if there is a servo movable amount in the result roughly calculated in step 3882, add this value as well, and the total value Accordingly, the first designated shot area is again set directly below the projection lens PO by the servo motors XM and YM. In step 8882, the quotient obtained by dividing the amount of deviation in the rotational direction by the resolution of the pulse motor θM is set as the moving amount of the pulse motor θM, and if a remainder occurs, the remainder is set as the moving amount of the servo motors XM and YM. By controlling the movement of the servo motors XM and YM in the X and Y directions, θ correction is performed as a result.1 Normally, the X and Y axes of the wafer stage WS are orthogonal in principle. θ
There are no ingredients. However, in actual mechanical design, this complete orthogonality cannot be achieved and a θ component is always generated. Therefore, the θ component is measured when the vtW1 assembly is completed, and the amount of movement of the X and Y motors is controlled when operating the device. As a result, the wafer stage can be moved in a direction that eliminates the θ component. This principle is called orthogonality correction. In step 5B81.82, this principle is utilized, and it is extremely preferable that the minute angle that cannot be corrected by the pulse motor θM can be corrected as a result by the movement adjustment of the servo motors XM and YM.In step SB9, the above-mentioned pair of It is determined whether the shot measurement has been repeated a predetermined number of times, and if it has not been completed, the process returns to step SB3 and the above operation is repeated. Through this repetition, the wafer position gradually approaches the allowable value, and in step 387, the wafer position falls within the allowable value. If it is determined that this is the case, the process advances to the next step 5B12. When the specified number of times is completed, the laser shutter BS is closed (step SB10) and the TTL measurement is completed. In step 5B11, it is detected that the YES signal has not been sent within the specified number of times in step SB1, and preparations are made to advance the alignment mode to another mode, for example C. In step 5812, the global alignment of the entire wafer is performed in the previous step. Even if the process is completed, if there is a deviation in the rotational direction for each shot, an exposure deviation will occur, so this mode is used to measure this.

Therefore, in step S B12, first, YLI, YRl, YL2 measured at the end of each of the first and second designated shots are measured.
, θ direction deviation mtan SO for each shot from YB2
2-(YLI-YRI)/Kl.

2 is calculated as tan SO2-(YL2-YB2)/. It is determined whether or not the output SO2, S02 is within the allowable range (step 8813), and if it is outside the allowable value, each value is an approximate value, that is, the inclination judgment to determine whether the rotational deviation is in the same direction and the same inclination is performed in step 8813. 5B14, and if the inclination of each shot is inconsistent, it is determined that precise overlay exposure is difficult in this mode, and the mode is switched to mode C (step S B 19). Since exposure is possible when they have similar slopes, the average Sθ-(Sθ1+Sθ2)
/2 is calculated (step 5816) L/, the reticle stage R8 is driven by the pulse motor Pθ until it reaches the average Sθ, and the reticle RT is rotated (step S
B17). Next, the amount of deviation S in the θ direction for each shot is calculated again.
Measure θ1' and Sθ2' (step 5B18) L/, and determine whether the average SO2-(Sθ1'+Sθ2')/2 is within the allowable value (step 3819) L/; if not, return to step 5817 and do the same. If the value falls within the tolerance in step 5B19, step 5A61.62 of FIG. 23A2 is accessed, exposure and steps are executed in the same manner as in mode A, and wafer processing in mode B is achieved.

Next, 7 alignment mode C will be explained.

First, in step 5C11, the first shot area of the wafer WF is reduced according to the value obtained by adding a constant to the X and Y deviation amount between the position of the reference IKSL and the alignment set mark WPR(L)1. XM,
Set by YM.

At the same time, the θ2 stage is rotated by the pulse motor θM according to the value calculated from the above X and Y deviation amounts (step 5C12), and the θ2 stage is moved by the pulse motor ZM.
(step SC13).

Next, focus in the first shot area using the air sensor AG.
I to AG4 detect the average value, and move the θ2 stage upward or downward by the pulse motor ZM and/or piezoelectric element Pz until the target focus value is reached (step 5C2G, then the objective lens 11R' (L) and the objective mirror 12R(L) to the position opposite to the reticle male mark WSR(L)n-1 of the reticle RTn (S
C, 3) Prepare for TTL alignment. Next, open the laser shutter BS (SSC4) and turn on the laser source 1S.
The objective mirror 12R(L) irradiates the mark WSR(L)n-1 on the reticle with laser light from the laser beam. In step SC5, laser scanning is started and the reticle R is
The first X between the male mark WSR(L)n-1 of Tn and the female v-mark WKR(L)n-1, m of wafer WF.

Measure the amount of Y deviation. Step S0 determines whether the first deviation amount is within a first tolerance value, for example, 0.1μ.
Judge with 8. Here, the amount of deviation in the X and Y directions of each shot of the wafer with respect to the reticle is XL・, YL, and
Assuming R and YR, the average amount of deviation is given by SX-(XL+XR)/2°SY-(YL+YR)/2. Also, the amount of deviation in θ (direction of rotation) 'tan5
As in the previous example, θ is given by tan3θ−(YL−YR)/L. Here, the distance between the left and right marks WK (S)R-WK (S)1 of each shot is a constant. If the average values SX and SY of each deviation amount are both within the allowable value in step SC6, the alignment is completed and the laser shutter 88 is opened (step 5C12), and the process proceeds to the next process.
If even one of the average deviation amounts SX and SY is outside the allowable value, the process proceeds to step S01 to perform alignment.

Note that various values such as 0.3μ, 0.5μ, etc. can be specified as this tolerance value from the console. In step SC7, Sθ is calculated from the above YL and YR. When the 02 stage is rotated in the direction of eliminating the deviation according to this calculated Sθ, the amount of deviation occurs again in the X and Y directions. This is because the center of the wafer and the center of each shot overlap. This second X.

Since the Y deviation amount can be calculated in advance, it is calculated in step SC8. In step SC9, the calculated X and Y deviation amount is set to a second tolerance value, for example, 3μ.
It is determined whether or not it is within the range, and if it is within the range, step 5
Proceed to C101, 102, otherwise step S C
Proceed to steps 111 to 113, and in step 5C101 and 102, the male mark WS of the reticle RTn is set according to the value obtained by adding the first and second X and Y deviation amounts, respectively.
R(L)n-1 is female mark WKR(L) of wafer WF
n-1.

The reticle stage R3e is moved in the X and Y direction by the pulse motors PX and PY so that it is located in the middle of the reticle stage R3e. At the same time, the pulse motor θM is driven for 40 minutes to rotate the θ2 stage. In step 50111, since it is outside the allowable value, the male mark WSR(L)n-1 of the reticle RTn is placed between the female mark WKR(L)n-1,m of the reticle RTn according to the first X, Y deviation amount. Pulse motor PX to enter.

, PY moves the reticle stage R8 in the X and Y directions. At the same time, a second X is generated in step 5C112.

Mark WSR(L)n is placed in the same manner as described above according to the amount of Y deviation.
Wafer stage W is moved by servo motors
Move in the SeX and Y directions. At the same time step S C1
13, as in step 5C102, the pulse motor θM
The θ2 stage is rotated by Δθ. In this way, by selecting reticles and wafers according to tolerance values and performing seven alignments, high-speed alignment and high overlay accuracy can be achieved at the same time. In other words, driving by a pulse motor has high precision but requires a long driving time, whereas driving by a servo motor has high speed but is insufficient in terms of fI4a, and the reticle side inherently has a longer moving distance than the wafer side. When the distance is within the allowable value, the reticle stage is driven finely by a pulse motor because the moving distance for correction is short, and when it is outside the allowable value, the reticle stage is driven finely for correction. Since the moving distance is long, it is preferable to drive the wafer stage at high speed with a servo motor. Furthermore, since the reticle stage side is also driven for correction at this time, sufficient accuracy can be maintained. The above operations are repeated until it falls within the first tolerance value in step SC6. When the high-speed, high-precision 7 alignment is completed in this way, proceed to step 5C as described above.
12, and then to step 5013. In step 5C13, the objective lens 11R is adjusted so as not to interfere with the exposure.
(L) and the objective mirror 12R(L) are moved backward to a predetermined position, and the attitude of the objective mirror 12R(L) is changed vertically.

Next, the shutter ST is opened and closed at a predetermined time ra+ to execute exposure (step 5C14). When the exposure is completed, the final shot area is determined in step 5C15, and if it is not the final shot area, proceed to steps SC161 to 164, step 16
1, the wafer stage is moved to the next shot area as described above, and at the same time, the 02 stage is moved up (down) until the focus detection value is reached (step 162), and the objective mirror 12R (L) is moved to the mark WSR on the reticle. (L
) n-1 to a position opposite to mirror 12.
Change the attitude of R(L) to 45° (Step 5G1B3
), and returns the reticle stage R8 to the X and Y positions memorized at the time of the first shot. When these operations are completed, the process returns to step SC3, where precise overlay and exposure are performed using so-called die-by-die alignment until the final shot is completed. will be carried out. When the final shot is completed, it is determined in step 5C15, and the process returns to step S A 12 to repeat the same operation to complete the processing for 10 shots.

This device also has a manual alignment mode, which allows the above-mentioned special manual alignment mode and other manual alignment modes to be performed from any step by interrupt processing. May be used where possible. When performing alignment using the TTL optical system As shown in FIG. 5, the light sources 19R and 19L are turned on or the diffuser plate DF4irn is inserted into the optical path of the laser IS.

In addition, when using the or-axis optical system OA, the light source R11
, 1-11 are turned on, and dark field and bright field are selected by aperture R13A, R13B, L13A, and Li2S.

Further, the selection of each of the seven alignment marks is performed as shown in FIG.

[Effects] As described above, the present invention can greatly contribute to extremely high I-fitting accuracy, high productivity (high speed), high flexibility, miniaturization, etc.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an outline of an apparatus according to an example of the present invention, FIG. 2 is an overview of a blade, FIG. 3.4 is a sectional view and plan view of a reticle stage, and FIG. 5 is an optical system. Fig. 6.7 is an overview and cross-sectional view of the wafer stage, Fig. 8.9 is a two-direction drive block diagram and an X (Y) direction drive block diagram of the wafer stage, and Fig. 1o, ii The figure is a diagram for explaining the operation of Figure 9.
Fig. 2 is an overview diagram showing an example of the off-axis optical system in Fig. 5, Fig. 13 is a top view of the wafer, Fig. 14 is a block diagram of the entire device, and Fig. 15 A, B, and C show each side of the television monitor. 16A and B are views showing each side of the reticle.
6C and D are diagrams explaining the state of exposure of the wafer, the first
Figures 7A, B, C, and D are diagrams showing the aperture relationship between the reticle and the blade, Figure 18 is a diagram showing an example of dividing a television screen, and Figure 1
Figure 9 is a diagram explaining the addition and slice levels, and Figure 20 is the l! If llll1 block diagram, FIG. 21 is a flowchart for explaining its operation, and FIG. 22 is a flowchart for explaining its operation.
, FIG. 23 A1-A3. FIGS. 24B1 to 83.125C1 to C3 are flowcharts for explaining the operation of each of the 7 alignment modes. 10-...Light source system for exposure, AS...TTL alignment optical system, RT...Reticle, R8...Reticle stage, PO...Reduction projection lens system, OA...Off-axis alignment optical system , WF...
・Wafer, WS...Wafer stage, LZ...Laser interferometer. Figure 1 Figure 2 Figure 3rIIJ Figure 18N Figure 19

Claims (1)

[Claims] 1. A reticle including a circuit pattern and a code mark for identifying the reticle. 2. A wafer with a circuit pattern and a code mark for identifying the wafer. 3. An alignment device comprising a reticle code mark reading means, a wafer code mark writing means, and a wafer code mark reading means.