JPS61131443A - Alignment device - Google Patents

Abstract

PURPOSE:To realize an extremely precise alignment by a method wherein reticle stages are caused to move along the directions X, Y and theta and a wafer stage is caused to be trimmed along the direction Z. CONSTITUTION:A laser interferometer LZ regulates the movement of a wafer stage WS with help of the mirror M6 of a reducing lens system PO and of the mirror M1 of the wafer stage WS. Reticle stages RX, RY and Rtheta are driven by the quantities required, respectively, along the directions X, Y and theta by pulse motors RX, RY and Rtheta. An eddy current type position sensor 15 if fixed to the base ZD of a piezoelectric element PZ and detects the upward movement (g) of a stage thetaZ. A Z-direction drive motor ZW causes gears G1 and G2 to rotate, and a screw rod G3 comes down rotating. The right-hand end of a lever ZL is pushed by a ball b1 and starts rotating clockwise. The left-hand end of the lever ZL, through the intermediary of a ball b2, is caused to move upward the base ZD together with the piezoelectric element PZ and a sensor IS installed thereon, which results in an upward movement or movement in the direction Z of a combination of the stage thetaZ and a wafer chuck WC, for the completion of the rough adjustment in preparation for a focusing process.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field] The present invention relates to an apparatus for printing or exposing a circuit pattern used in the manufacture of high-density integrated circuit chips such as semiconductor memories and arithmetic devices, particularly an alignment apparatus.

[Prior Art] Conventionally, this type of device has had drawbacks such as overlay accuracy, productivity, flexibility with other devices, large size and complexity, etc.

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

[Example] An example 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. IO is a light source system for exposure, and an elliptical mirror M1 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 cold mirror M2 for transmitting most of the infrared light and reflecting the ultraviolet light, an integrator lens system L1 for making the light distribution characteristics of the luminous flux uniform, a shutter ST, a lens system L2,
Reflection IM3, lens system L3, light shielding device BL, lens system L4, reflection 11tM4, lens system L5, reflection 11M5
, lens system L6, and reticle RT are sequentially arranged along the optical path, where reflections al1M3, M4, M
5 is for bending the optical axis at right angles to make the illumination system smaller, 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 the so-called TTL (Throuah
TheLenS) Optical system for alignment, R3
is the drive stage of the reticle RT in the X, Y, and θ directions, and the reduction lens system PO is the optical system for reduction exposure.
It has a reduction rate of 1/10. OA is an off-7 axis optical system for 7 alignments of wafer WF, WS is wafer WF
The drive stage Lz in the X, Y, Z, and θ directions is a laser interferometer, 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 BL. This light shielding device 8
L is the lens system L4. in FIG. L5. L6 is arranged so that its light-shielding surface is in a conjugate relationship with the circuit pattern surface CP of the reticle RT, and the reticle RT is
When the reticle is replaced with a reticle made of glass or the like having a different thickness and the refractive power changes, the reticle can be moved in the optical axis direction in order to maintain the above-mentioned conjugate relationship. In addition, a light shielding device rotating mechanism (not shown) rotates in the θ direction in conjunction with the rotation of the reticle RT, as shown in FIG. It is possible to move.

The light shielding device BL has four pulse motors and PM on the substrate ST.
1 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. NA1 to NA4, and four light shielding plates BL1 to BL4 fixed on the feed nut part NA and having sharp side edges d1 to d4 are arranged, and the four side edges d1 to d4 Configure a rectangular opening.

In the above configuration, the light beam emitted from the light source LP in FIG. 1 is transmitted to the optical element M1 when the shutter ST is opened. M
2. L 1. M3. L 2. Reflection and refraction are performed in the order of M4 to uniformly illuminate the light shielding device BL. The light beam irradiated to the outside of the opening of the light shielding device BL is transmitted through four light shielding plates 8.
The light flux that is blocked by L1 to 8L4 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 device BL and the pattern surface CP of the reticle RT are arranged in an optically conjugate relationship, so that the edge of the opening of the light shielding device BL is clearly placed on the circuit pattern surface CP. It is projected as a contour, and the area outside the circuit pattern surface CP of the reticle RT can be completely shielded from light.

Note that the light shielding device 1BL is provided in the θ direction (the second
(Fig. 1), and when the reticle RT is changed to a reticle with a different thickness, that is, a refractive power, the optical axis and direction (up and down arrows in Fig. 1) are used to maintain the conjugate relationship. It is possible to move to Further, the area and position of the opening of the light shielding device BL is determined by the pulse motors PM1 to MP4 being rotated in a predetermined manner by signals output from the electronic processing section of this device, and by the feed screws FG1 to FG1 connected to the shafts of the respective motors.
By moving the feed nuts NA1 to NA4 in one direction by FG4 and thereby moving the light blocking plates BL1 to BL4, the area of the opening in the direction perpendicular to the optical axis can be arbitrarily changed. The movement and adjustment of these four light shielding plates BLI to BL4 can be performed simultaneously, and therefore it is possible to perform exposure matching any area of the reticle RT.

FIG. 3 is a diagram showing cross section C of reticle stage R8 in FIG. 1, and FIG. 4 is a schematic top view thereof. In the figure, the substrate SL 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
When the set marks R5R and R8L of the retigel are aligned with L, so-called reticle alignment is performed.

'RY is the Y direction drive stage of reticle RT, RX,
Rθ is also the drive stage in the X direction and the θ direction, θB(
θ131. θ82. θ83) is a guide bearing for the rotation stage Rθ, and RC is a reticle chuck which has the function of attracting and fixing the reticle RT to the chuck RC using the suction force from the tube TLIR. RX,RY
, Rθ are pulse motors for driving each stage RX, RY, and Rθ, XL, YL, and θL are driving force transmission lever gears, BXl, RX2, BYI, BY2, respectively.
, Bθ are biasing springs that resist the force of the motor, respectively, and XB.

YB 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. For example, if the pulse motor PX is now rotated in the direction of the arrow, the lever XL will rotate in the direction of the arrow and its left end will push the X stage RX,
The stage RX moves to the left against the springs B X 1, 8 X 2. At this time, it is correctly moved only in the X direction by the guide block XS and guide bearing XG. Photo sensor PS and light shielding plate SM are detection systems for aligning the movement limit of reticle stage R8 and the center of reticle stage R8 with the optical axis of exposure lens system PO.

Further, when the pulse motor PO is driven and rotated, the substrate ST of the light shielding device BL, which is the second cause, is also rotated in the θ direction in conjunction with the rotational force transmission system DT shown by the dotted line in FIG.

FIG. 5 is a diagram schematically showing the TTL alignment optical system AS and off-axis optical system OA of FIG. 1. In the figure, 18 is a laser generation source, 2S is a condensing lens for focusing the laser system, 3S is a rotating polygon mirror, 4S is an f-theta lens, and 5S is a beam splitter. Laser source 1
The laser beam exiting from S is scanned according to the rotation of the rotating polygon R3S, and enters the optical system below the beam splitter 58. 6S is a field lens, IS is a field splitting prism, and the prism IS splits the scanning laser beam into two optical paths. In this respect, the prism IS can be referred to as a field and space dividing prism. 8R
, 8L are polarizing beam splitters, 9R, 9L are relay lenses, IOR, 10L are beam splitters, and the light reflected or passed through these elements is sent to objective lenses 11R, 11L.
The beam enters the beam, is reflected by objective mirrors 12R and 12L, and is imaged on reticle RT to perform scanning. Imaging lens 13R, 1
The system from 3L to photoelectric detectors 18R and 18L is a photoelectric detection system.

14R and 14L are color filters, and 15R and 15L are spatial frequency filters, which serve to block regularly reflected light and extract scattered light for photoelectric detection. 1'6R, 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, and the erector 22S1 prism 23S, television lens 24S, and image pickup tube CDO constitute an observation 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 parts by a field-segmenting prism IS placed on the conjugate plane of the reticle and wafer. The scanning line is perpendicular to the ridgeline of the field dividing prism 7S. In other words, the mirrors 10R, 1 are used to scan the laser in the vertical direction.
0L, 12R, and L2L are used.

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

CR and OL are high-magnification photoelectric high-resolution image pickup tubes, CDR.

The CDL is a low-magnification converter and consists of a CCO (charge coupled device) and the like.

FIG. 6 is a partial perspective view of the wafer stage WS shown in FIG. 1, in which a Y-direction moving stage WY is placed on a base WD, an X-direction moving stage Wx is mounted on it, and each X, Y stage WX, WY is X by servo motors XM and YM, respectively.
Guide GX in the Y direction.

Move along GY. 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 a wafer WF is suctioned and fixed thereon in the same manner as on the reticle side. The stage θ2 is fitted with a stage holder θH1,:1, and can be moved up and down in two directions and rotated in the θ direction by ball bearings BB and bl. Stage holder θH is fixed to X stage WX as shown. Pulse motors ZM and θM for driving in the Z and θ directions are fixed to a 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 E)W.

Is is an eddy current type position sensor and the base Z'D of the piezoelectric element PZ
, and detects the upward movement Ng of the stage θZ.

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 screw rod G
3 descends while rotating downward, the right end of lever ZL is pushed by ball b1 and rotates clockwise, and lever ZL
The left end of is connected to piezoelectric element PZ and sensor I via ball b2.
Since S is pushed upward via the base ZD, the integrated stage θZ and wafer chuck WC move upward, that is, in the Z direction. 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 amount of extension of the piezoelectric element. The amount of movement is detected by measuring the gap Q using the sensor TS. This provides fine adjustment.

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

CH and C8 are detection systems that determine a reference point in the rotational 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. If the distances from the end face of the reduction projection lens PO to the surface of the wafer WF measured by the nozzles AG1 to AG4 are respectively dl d2 , d3, and di, then the average distance is (di + d2 + d3 + d4)/4. Assuming that 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, in order to move the wafer WF to the imaging plane position, Δd - (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 402 performs various judgment processes,
Issue instructions according to each situation. Reference numeral 41Z is a register that stores command information such as the amount of rotation per rotation in the rotation direction and the rotation speed per rotation from the microprocessor 4oz to the pulse motor ZM. 42Z is a pulse motor control circuit, and register 4
In the initial state when the pulse motor ZM is subjected to open loop control based on the movement amount command information No. 12, the wafer W
The surface position of F is, for example, 2 m or more away 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. In addition,
The range that can be accurately measured with air sensor nozzles AG1 to AG4 is when the distance from the nozzle end face to the wafer surface is approximately 0.
．． This is when the distance is within 2m. Therefore, assuming that the predetermined imaging plane position is 0.1 am from the end face of the nozzle, accurate measurements can be made when the wafer surface moves upward and is within 0.1 as+ below the imaging plane position. After entering.

49Z is a circuit that converts changes in the fluid flow of air sensor nozzles AG1 to AG4 into voltage, and a reduction projection lens P
distances d1 and d2 from O to the wafer surface.

Voltage outputs Vl, V2, corresponding to d3, d4,
V3.

Generates V4. 50Z is an analog-to-digital converter (A
DC>, and the voltage V1 generated in the voltage conversion circuit 49Z
, V2, V3, and V4 are converted into digital signals and sent to the microprocessor 40Z. Here, since the initial position of the wafer WF is more than 2ffi away from the imaging plane position,
The microprocessor 4oz continues to give a movement command to the pulse motor ZM in the register 41Z until the wafer 2 axis rises and enters the measurement range of the air sensor nozzle. The wafer Z-axis rises due to the rotation of the pulse motor ZM, and when the wafer is within 0.1 vote of the imaging plane position, the air sensor nozzle AG
1 to AG4, the microprocessor 402 through the voltage conversion circuit 49Z and the analog-to-digital conversion circuit 5oz.
detects that it has entered the measurement range, and sends a stop command to the register 41Z Hebals motor ZM to stop the rise of the wafer WF. Next, the microprocessor 402 measures the surface position of the wafer WF via the air sensor nozzles AG1 to AG4, the voltage conversion circuit 49Z, and the analog-to-digital conversion circuit 5oz, and calculates the movement amount Δdl −do −(dl +d2 +d3 +d4
)/4. The movement resolution by the pulse motor ZM is 2 μm, and the microprocessor 402 gives a movement amount Δd1 in units of 2 μm to the register 41Z to raise the wafer 2 axes. 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. Air sensor nozzle A
If the measured distances by GI to AG4 are respectively d9 to d12, the microprocessor 402 will now read the register 4.
Δd2−do −(d9 +cNO+d11+d
12) Issue a command for the moving direction and amount of movement of the piezoelectric element Pz to be /4. The register 43Z stores this command, and also sends the command to the digital-to-analog converter 44Z.
and is output to the piezoelectric element drive voltage generation circuit 46Z.

The digital analog converter 44Z 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 eddy current type position sensor tS. 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 is output to a differential amplifier 45Z and an analog-to-digital converter 48Z.

The differential amplifier 45Z successively compares the amount of lateral movement of the wafer z11 by the piezoelectric element Pz detected by the eddy current type position sensor Is and the movement m instructed by the register 43Z, and drives the differential amplifier 45Z until the difference falls within the error range. do. 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 current type position sensor I
The amount of movement of the piezoelectric element PZ detected by s is converted into a digital form 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.

Measured value/pulse motor resolution - Quotient (pulse motor driven valve) Remainder (piezoelectric element driven valve) In other words, when the average value measured by air sensors AGI to AG4 is divided by the resolution of the pulse motor and ZM and the remainder is calculated, The remainder is driven by the piezoelectric element PZ. This allows coarse driving and fine driving to be performed suitably. Also, the quotient and the remainder are simultaneously stored in the registers 41Z and 432, and the pulse motor ZM and the piezoelectric element PZ are driven simultaneously. Since the lens is driven, the focus position can be reached at high speed.

The area indicated by A in the figure is the first shot area that is exposed first. In this way, the step-and-repeat type projection printer sequentially performs printing by moving the wafer WF mounted on the wafer chuck WC in the X and Y axis directions. By the way, when printing area A, the reduction projection lens PO and the air sensor nozzles AGI to AG4 are located as shown in the figure with respect to the wafer WF, so the air sensor nozzle AGI/Ac2
・Ac1 can detect and measure the surface position of wafer WF,
Air sensor nozzle AG4 cannot detect and measure the surface position of wafer WF. In other words, the wafer WF is reduced by the projection lens P.
As the microprocessor 40z approaches O, the microprocessor 40z can detect that the air sensor nozzles AGI, Ac2, and Ac1 have sufficiently entered the measurement range, but there is no response input from the air sensor nozzle AG4. Therefore, the microprocessor 402 determines that air sensor nozzle AG4 cannot be measured, and air sensor nozzle AGI・Ac2・A
Measured value of c1 d1 ・d2 ・d3 values are taken out and averaged to calculate the average distance to wafer WF (d1 + d2 + d3
)/3. Focus positioning of area A is performed based on this calculated value.

When exposure of area A is completed and area 8 is to be exposed next, the wafer surface position of exposure area B is detected in advance by air sensor nozzle AGI and the distance is measured before exposure of area B. The microprocessor 4oz gives the value to the register 43Z as a drive command amount. Next, the wafer WF is moved in the X direction so that the exposure area B is exposed to the reduction lens PO.
The piezoelectric element PZ continues to be driven based on the previously measured value until the piezoelectric element PZ is located under the , and the amount of movement is confirmed by the eddy current type position sensor Is, and when the movement of the predetermined fog is completed, the driving is terminated. In this way, while the wafer WF is moving from the exposure area A to the exposure area B, focusing in the next exposure area B can be completed. Therefore, it is possible to realize an exposure apparatus that utilizes the operation time of stage movement and has little wasted time.

FIG. 9 is a block diagram of the X, Y stage control circuit.

WX (WY) GtX, Y stage, D, D, C motor, and the X, Y stage and DC motor are coupled with a ball screw. The DC motor is driven by a motor driver MD. In addition, a tacho generator (speed signal generator) T is added to the DC motor, and the output of the tacho generator T is used as a driver M for speed control.
This is fed back to O. The positions of the X and Y stages are determined by the current position counter PC based on the output signal of the length measuring device LZ.
Measured at P. A laser interferometer is used as the sub-length device. The output of this length measuring device is a relative position output, and X,
Origin sensor X is used to detect the origin of the current position of the Y stage.
H, S (YH, S) and an origin detection circuit SO are provided, and the origin of the X and Y stages is detected by these outputs, the length measurement is started by the gate circuit AP, and the current position counter PCP detects the origin of the X and Y stages. The current positions of the X and Y stages are measured. The microprocessor CP, which controls the entire X and Y stages, uses a current position latch circuit PLP.
The current position of the X and Y stages can be known through this.

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, from the current position to the target position! It is used as a feedback signal for the position servo and as a means to detect the timing for setting the drive pattern of the X and Y stages. As a position servo feedback signal, the output of the difference device is input to the pit converter BG to match the number of pits of the D/A converter DAP, and the pit-converted output is input to the D-/A converter, which outputs its analog output. is input to the position servo amplifier GA as a position feedback signal. There is also a comparator COMP for generating a timing signal to set the drive pattern of the X and Y stages, and a pit converter BC.
The output of the movement amount setting latch RPL is compared, and when they match, a timing signal for setting the drive pattern is output from the comparator COMP. The timing signal is input to the address generator RAG of the random access memory RM in which drive pattern information is stored, a RAM address required at that timing is generated, and the drive pattern information is output from the random access memory RM. The timing signal is also input to the interrupt generator INT, which generates an interrupt signal, and the microprocessor CP receives the interrupt signal.
Can sense timing.

In addition to the movement amount data mentioned above, the drive pattern information includes DC
There is command value information to control the motor, and the command value information includes DC
There is current command value initial information that actually drives the motor, target command value information that becomes the target value, and various information that controls the process to reach the target command value. PCM is a current command value counter and generates a command value for driving the DC motor. C.L.V.
is a latch circuit for target command value information. FG is a III number generator that sets the division ratio of the divider DIV, and by dividing the pulse frequency of the oscillator DIV to a desired frequency, the value of the current command value counter PCV is set to the target command value latch. Controls the process to reach the CLV value. COMV is a comparator that compares the value of the current command value counter PC■ with the value of the target command value latch CLV and activates the gate AV until they match.At the same time, it sends an interrupt generator INT to the microprocessor at the same timing. This is notified by an interrupt signal. The value of the current command value counter PCv is input to the D/A converter DAV,
The analog output is inputted to the driver MD through the ON side of the changeover switch SW during speed servo control and becomes a 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 MO through the position servo amplifier GA and the OFF side of the changeover switch SW.

DMG is a drive mode generator, and this output signal turns the drive mode changeover switch SW 0N10FF. For example, 0NII becomes the speed servo control mode, the output of the D/A converter DAV is input to the driver MO, and the X and Y stages are driven by speed servo control 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 MO.
X.

The Y stage is driven by position servo control 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 section SS from time to to t4 in Fig. 10 is speed control, and from time t4 to t6.
The section PS up to is the position control section speed ttlJ.
The rabbit sub-section consists of an acceleration section AS that accelerates at a constant acceleration, a constant speed section BG that moves at a constant speed Vwax, a deceleration section CD that decelerates at a constant deceleration, and a constant speed section DE that moves at a constant speed ymtn. ing. Acceleration/deceleration straight line AB, Be
, 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 the 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.
It is divided into HASE1, PHASE2, and PHASE3, and the contents of each block are divided into four data '-
It is composed of data.

PHASEI data is from starting point A to o.

The data for PHASE2 is the data for controlling from the DOWN speed switching point C to the position servo switching point E, and the data for PHASE3 is the data for controlling from the DOWN speed switching point C to the position servo switching point E. This is data for controlling up to point P.

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

A method of controlling the Y stage will be explained. First, the microprocessor CP writes data necessary for driving into the random access memory RM. Next, set the target position to target position latch C.
LP and sends a start signal ST to the RAM address generator. This allows the RAM address generator RAG
The address P)-IAsEl is generated from the random access memory RM, and the φ speed data is stored in the current command value counter PC■, the MAX speed data is stored in the target command value latch CLV, the acceleration gradient data is stored in the function generator FG, and the travel amount is set. The amount of movement up to the DOWN speed switching point C is set in each latch RPL, and the drive mode generator [)
MG sets switch SW to ON fill. X
, 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 PC■ is the target command value C.
The acceleration operation AB shown in FIG. 10 is performed by the variable output of the counter PC■ which counts the output of the frequency divider DIV until it becomes equal to the value of LV. A constant speed operation BC is performed with a constant output.

Next, at the DOWN speed switching point C, a match signal is output from the comparator COMP and input to the RAM address generator RAG. As a result, the address of PHASE2 is generated from the RAM address generator RAG, and the current command value counter PC■ is generated from the random access memory RM.
MAX speed data to target command value latch CLV to M
The IN speed data, the deceleration gradient data in the function generator FG, and the movement amount until the date of position servo switching are set in the movement amount setting launch PRL, and the X and Y stages start deceleration operation. That is, the deceleration operation CD is performed in the same manner as described above until the value of the current command value counter PCV becomes equal to the value of the target command value CLV, and then the constant speed operation DE is performed.

Next, at the position servo switching point, the comparator COMP
A match signal is outputted from and inputted to the RAM address koji brewer RAG. This causes the RAM address generator to
The address of ASE3 is generated, and the random access memory RM stores the data corresponding to the movement m to the position servo switching point E, for example, 25μ before the target value, into the current command value counter PCv, and the target position data into the target command value latch CLV. , the position servo gradient data is set in the function generator FG, and the target stopping point P is set in the latch for setting the moving peak.At the same time, the position control mode is set in the drive mode generator DMG, and the switch SW is set to the OFF side. The X and Y stages are driven by position control. Next, the control end point F
At , match signals are output from the comparators COMV and GOMP, respectively, and input to the interrupt generator INT to generate an interrupt signal. When the microprocessor CP detects this, it considers that the basic X and Y stage control has been completed, and determines the permissible value (hereinafter referred to as tolerance) of the stage stop position accuracy. Microphone processor CP
transfers the data of the current position counter PCP to the current position latch P
The current position data is input via LP, and it is determined whether the difference from the target position is within the tolerance. When the stop position accuracy and fluctuation are within the tolerance, control is completed, and X,
The movement of the Y stage ends.

Figure 12 shows off-axis optical system O for TV alignment.
An embodiment of A is shown, and R11°1-1i in the figure is a light source for illumination, for example, a halogen lamp is used. R12
, L12 is a condenser lens, R13A.

R13B, L13A, and Li2S are the bright field diaphragm and dark field diaphragm that can be attached and removed interchangeably.In the figure, the bright field diaphragm R13A
, L13A is installed in the optical path, so the condenser lens R12, 112 connects the light source R11, Lll to the bright field aperture R.
(L) Image is formed on 13A. R14, L14 are relay lenses for illumination, R15a-b, L15a-t) are cemented prisms, and 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 Rj5a.
, 115a and semi-transparent reflective surface R15t), 115b
Equipped with Here, light source R, L11, condenser lens R
, L12, bright or dark field diaphragm R, L13A, B, relay lens R, L14, cemented prism R, 115a.

b. The objective lenses RL and LL constitute an illumination system, and the light beam emitted from the objective lenses RL, LL is directed to the wafer WF in FIG.
The alignment marks CRL (LR) 11, 12 or WPR (L) 1 are epi-illuminated.

R and Li2 are relay lenses, R and 117 are mirrors that switch the optical path from high magnification to low magnification, and R and Li2 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 alignment mark is the X coordinate value and the Y coordinate value.
It will be detected as a coordinate value. R, Li2 are imaging lenses, R2120 is an NA limiting aperture, the above-mentioned cemented lens R, l-158, b, relay lens R, L1
6, aR.

L17, index glass plates R, L17, imaging lenses R, L19, and high-magnification image pickup tubes OR, CL constitute a light receiving system, and the optical path passing through the objective lenses RL, LL is reflected by the inner reflective surface R, 1isa of the cemented prism. and semi-transparent surface R, 11sb
It is reflected again by the inner reflective surfaces R and L15a and goes to the relay lenses R and L16. Alignment mark *CRL (LR) on wafer WF in Figure 13 11.12
is the index glass plate R,1 having the reference mark TPR(L)
After being formed on 1g, the high magnification image pickup tube OR together with the reference mark image TPR(L).

The image is formed on the imaging surface 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 light sources R and Lll is converged by the condenser lenses R and L12 and illuminates the aperture of the bright field aperture R and L13A or the dark field aperture R21133. Then, it further passes through the illumination relay lens R1L14, passes through the semi-transparent surfaces R and L15b of the cemented prism, and passes through the reflective surfaces R and L15b.
The light is reflected by L15a and passes through objective lenses RL and LL to illuminate the wafer WF.

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 R1L15a, b, is reflected by the reflective surfaces R, L15a, is then reflected by the semi-transparent surfaces R, L15b, and the reflective surface R, 115a, and is emitted from the relay lens. After being relayed by R, 116 and forming an image on the index glass plate R, 118, the imaging lens R, L1
9, images are formed on the image pickup tubes CR and CL. Next, the state is switched to a dark field state so that the alignment mark image can be clearly detected, and this is used as an m-image to detect the position of the alignment mark. Depending on the position of an alignment mark detected by electrical processing to be described later, wafer stage WS moves so that the first shot (exposure) area of wafer WF occupies a prescribed position in the projection field of projection lens PO. R,L21
is a reflecting mirror, R and L22 are erectors, and R and L23 are R
, Same aperture as L20, CDR, CDL are COD for low magnification
The same effect as above is performed at a lower magnification. These optical systems are not necessarily a pair, but only one each is sufficient.

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 Coo, CDR
, CDL are connected to a first TV receiver Tv1 by a signal line L1, and the high magnification TV camera OR, CL is connected to a second TV receiver TV2 by a signal line L2.

The control box CB includes a main CPU, a control section MC including a high-speed calculation circuit, and a ROM.

Includes RAM. The ROM stores instructions as shown in the flowchart described later. The KO8 uses the console to set various parameters and perform various other controls, and the printer PRT prints out various statuses of the device. FIG. 15 shows an example of a display monitor when performing off-axis and TTL alignment. A in the diagram is a high-power TV
2 is used to perform off-axis alignment, and the high-magnification alignment of the reference mark TPR(L) of the reference glass plate R(L) 18 of the off-axis optical system OA in FIG. 12 and the wafer WF in FIG. 13 is shown. mark CRL
(LR)11.12 will be displayed, allowing you to check the alignment of both marks. B uses the low magnification TV1 to match the low magnification mark WPR(L)1 in Figure 13 and the electronically set standard (
cursor) line KSL to show how alignment is performed. C is the female mark WKR of the wafer WF on T■1 for low magnification using the TTL alignment optical system AS.

An example is shown in which the male marks WSR and WSL of WKL and reticle RT are displayed, and it can be seen that both marks are aligned 7 times at TTL. In addition, when using a wafer that cannot be automatically aligned, it is also possible to print a special manual alignment mark on the scribe area of the wafer WF and manually align it with the special manual alignment mark on the reticle. .

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.

FIG. 16A shows an example of the initial reticle configuration;
B also shows the second reticle, C shows how the first reticle RTI is sequentially exposed on the wafer WF surface, and D 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°RT
Circuit pattern (real element) provided on Z, 5CRI
, 5CL1.5CR2, 5CL2 are scribe areas provided on the left and right sides of the actual element, and the first reticle RT1 is provided with female marks WKR1, WKLl for use in 7-alignment with the second reticle RT2. Further, if necessary, the aforementioned special manual alignment marks MAR1 and MAL1 are arranged in place of the mark WKR(L)1 or in parallel as shown. Lower scribe area SC
Two high-magnification alignment marks CRR and CRL, which are smaller than the low-magnification alignment mark WPR(L), are prepared in U. If two pairs of these are provided on the left and right sides as shown in FIG. 13, the objective lenses RL of the off-axis optical system OA shown in FIG. 5 can be obtained.

This is preferable because the probability of falling within the field of view of LL increases. WPR,
WPL is the mark for low magnification alignment, R8R and R8L are the male marks for 7 alignments on the reticle, and the reference mark RKR on the lens PO in Figure 3.

The position of the reticle is set in accordance with RKL. R
KR and RKL have female mark shapes similar to WKRI and WKLI, and reticle auto-alignment is performed by the recommended mark alignment operation in the same way as in TTL auto-alignment.

On the second reticle RT2, female marks WKR2, WKL2 for next process alignment and male marks WSRI, WSLI for main process alignment are provided. RCNl
, RCN2 each indicate a reticle number and are provided in a coded manner, and these are sent to the 51st TTL alignment optical system A
The reticle number can be automatically identified by reading it with s.

This is produced simultaneously when the circuit pattern and each mark are produced. Similarly, WCN in FIG. 13 indicates a coded wafer number, which is written by TTL alignment optics As and read by TTL alignment optics AS or off-axis optics OA. Note that these are the first
Of course, it is also possible to determine the reticle and wafer numbers based on information specified in advance from the console KO8 in FIG. 4 or information sequentially specified in real time. In FIG. 16, when the first reticle R1 is inserted as shown in FIG. 5, the blade 8 in FIG.
First, as shown in FIG. 17A, an opening is set in L so that the area of the circuit pattern CP1 and the scribe areas 5CR1 and 5CLI on the left and right sides thereof are exposed. In this state, Figure 16C
1, 2, 3, etc. from right to left. ...is exposed.

That is, in the first shot (exposure) area 1, the special manual marks MARI and MALL of the reticle RT1 are MAR.
ll, MALLll, mamasu mark WKR1, W
KLl is exposed (printed) as WKRll and WKLll, and the circuit pattern CP1 is exposed (printed) as CPll. Note that in reality, the printed pattern on the reticle RT1 is projected through the projection lens PO, so a horizontally and vertically inverted image is printed on the wafer WF, but for ease of understanding, the diagram is shown assuming that the same image is printed. . The subsequent images are sequentially printed in the same manner. At that time, for example, circuit patterns CP11 and C
The scribe region SCR12111 between PI2 is shared by circuit patterns CP11 and CP12 to save wafer space. Therefore, a pair of left and right marks, for example WKR11
and WKLll are shifted vertically from each other. With this configuration, for example, marks WKR12 and WKL, 11 do not overlap, which is preferable. 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, the 20.26th area in FIG. Area S
The opening of the blade BL is set so that up to CU is exposed.

As a result, the high magnification alignment mark CRL of the reticle RT1.

CRRs are printed as CLR11, CRL11 and CLR12, CRL12 in the shot 2o and the 26th lower side scribe area, respectively, as shown in FIG.

Also, specific shot 41. and 45, Figure 17 C9
As shown in D, move the blade B so that the low magnification 7 alignment marks WPR and WPL of the reticle RTI are exposed respectively.
After setting the aperture of L, the shot area 41. in FIG. 13 is set.
Low magnification alignment marks W on the right and left sides of each of 45
Burned as PRI, WPLl. In this manner, the printing on the first wafer WF is completed. The shot order shown as 1 to 45 in FIG. 13 is preferable because the amount of movement of wafer stage WS is the shortest. The wafer that has been baked is replaced with the next wafer WF, and the same process is performed, and when 10 wafers are finished, the first reticle RT1
is ejected and the second reticle RT2 is inserted. The second reticle RT2 is configured as shown in FIG. 16B as described above, and in the first shot, the reticle RT2 is
2 male mark WSR1 and wafer WF female mark WK
After R11, WSLI and WKLll are precisely aligned by the TTL alignment optical system AS, they are exposed, and a reticle RT is placed on the circuit pattern Qp11.
The circuit pattern CP2 of No. 2 is printed as CR21. Furthermore, the male mark WSR1 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 RT2
There is a female mark WKR2 for the next process alignment.
, WKL2 are provided at positions shifted upward by one step as shown in FIG. 16B, and these marks are printed as new female marks WKRWKR21, WKL24, etc. in the 16th diagram.

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. Alternatively, the old mark may be used repeatedly. 'For special manual alignment, mark MAR2 on reticle RT2,
MAL2 and marks MAR11, M burned in the previous process
ALII 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 DJ is divided into M divisions in the Y direction.
i indicates the pixel in the first row and the i-th pixel in the row. The number of divisions M in the Y direction usually matches the number of horizontal scanning lines, and therefore, in order to divide into pixels, it is sufficient to perform sampling N times within the -horizontal synchronization signal section.

Therefore, addition in the X direction is Sx + -DATA (Pa) + DATA (P+
2) +...-+OA'TA (P+N),
Sx2 = DATA (R21) + DATA (R22
)+...+DATA (R2N), SxM
-DATA (PMI)+DATA (PM2)+
・・・・・・+DATA (PMN), Y direction addition is SY + -DATA (PtI)+DATA (R2
1) +...+DATA (PMI), Svz
=DATA (PLt)+DATA (R22)+・
...+DATA (PM2), SYM-DAT
A (P+N)+DATA (,R2N)+...
...+DATA (PMN), Hail.

When the addition is completed, the X and Y direction integration memories contain Sx +, Sx 21...SXM, SYI, respectively.
.

SY2. . . . SYM data is stored.

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

(B) 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 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 latch 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 adder 34■, 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 is an adder that adds data in the X direction, 39V is a latch that latches the output of the adder 38V, and 40V is an
This is a direction accumulation memory.

There is no particular limitation on the number of bits of digital data in these circuits, but for example, the analog-to-digital converter 32V is 8 bits, the adder 34V, 38V and the 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 40V in block X.

43V is the sequence and memory control circuit 41V
This is a control register for the microprocessor MPU to control, and the input of the register is connected to the 44V data bus of the microprocessor. Furthermore, the microprocessor MPU can access memories 36V and 40V via this data bus 44V.

45V, 46V, 47V, and 48V are buffers for this purpose, and the buffers 45V and 47V operate when the microprocessor MPU writes data to the memory 36.40, and the buffers 46V and 48V operate when reading data. 49V is the clock circuit, 50V, 51V
are a memory write address circuit and a memory read address circuit that generate a write address and a read address for the X-direction integration memory 36V. 52V is an address selector that switches between the read address and write address of the memory, and 53V is an address buffer when the microprocessor MPU accesses the 36V memory? The output of the address selector 52V is selected except when the microprocessor MPU accesses, and the output of the buffer 53V is prohibited. 54v is the X direction integration memory 40V
The memory address circuit 55V which generates the address of the memory address circuit 55V is an address selector which switches the address 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 synchronization signal, a blanking signal, etc. for the television based on the clock of the clock circuit 49V. 57V and 58V are the X position display register, Y position display register, and 59 connected to the data bus 44 of the microprocessor MPtJ, respectively.
V is a cross mark display circuit, and when the microprocessor outputs the position of the alignment mark detected during TV alignment to the X position display register 57V and Y position display register 58V, the mark display circuit 59V outputs the position of the alignment mark as a cross mark signal. , is sent to the video input terminal of the television camera control section. The information is also sent to the CPU shown in FIG. 9 via the microprocessor MPU, 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 data integration in the X direction and the data in the Y direction are performed by the adder 34.3 of the television alignment detection circuit.
8 performs addition and stores the added data in memory. The data addition is performed in units of one frame of the television signal, and if necessary, the addition may be completed with one frame, or the addition of a plurality of frames may be performed. In either case, during addition, the memory 36V,
The 40V data bus and address bus are electrically separated from the 44V data bus and address bus of the microprocessor MPU, the memory 36V address is connected to the address selector 52V, and the memory 40V address is connected to the address of the address circuit 54V. The addition is executed under the control of read/write signals and chip select signals generated from the sequence and memory control circuit 41V1 and the memory control circuit 42V.

When the addition of a predetermined number of frames is completed, an addition end signal is generated from the sequence and memory control circuit 41V on the interwoven signal line rNT.

After the addition end signal is generated, the microprocessor MPU
accesses memory 36V and memory 40V,
Detect the TV alignment mark position from the added data. When a microprocessor accesses a 36V or 40V memory, the memory address, read/write signal, chip select signal, etc. are naturally controlled by control signals from the microcomputer. Also, data in memory 36V is buffer 46v1 data in memory 40V is buffer? 48V to the data bus 44V and 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
At step V2, the process waits for the completion of addition, and when the addition of a predetermined number of frames is completed, the process advances to step SV3. Step SV
At step 3, the microprocessor searches for maximum and minimum values of the image density data stored in memory. When the maximum value and minimum value are found, the slice level X5L1 and WSRI are then set in step SV4.

The slice level WSLI is set to, for example, 70% of the difference between the maximum value and the minimum value of the image density data (referred to as the peak value).

Next, in step SV5, the slice level X5L1 is compared with the contents of the memory, and XLI and XR1 are determined from the coordinates (memory address) where the comparison result is inverted. Similarly, in step SV6, a slice level X5L2 of 20% of the peak value is set, and in step SV7, XL2 and XR2 are determined in the same manner as step SV5.

As described above, the binarization pattern shown in FIGS. 16(D) and (E), that is, the coordinates XL1. XR1゜XL2,X
R2 can be determined. At step S■8 (XR2-XL
2)/2 is calculated and compared to see if it is equal to
If the comparison values are significantly different, it is determined that it is not an alignment mark, and the process proceeds to step 5V10. When the process proceeds to step S10, for example, the slice level setting value is changed and the measurement is performed again, or it is assumed that there are no 7 alignment patterns on both sides, and the process proceeds to search for an alignment pattern. Similarly, Y coordinates YL1, 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. For example, the memory capacity for storing 0 image data becomes smaller.

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. 22, initial settings of all devices are performed. - To give an example, the memory RAM is zero cleared, the TTL alignment optical system is moved in the entire S direction, and the objective lens 11R (L) and the objective mirror 12R (L) are moved in the X direction, and the lens PO
The objective mirror 12R (
Various initial settings are performed, including setting the attitude of L) at 45° so that the laser beam can irradiate the mark position, setting the reticle stage, wafer stage, and blade to their initial states. In step SS2, the reticle RT is attracted to the reticle chuck RC by vacuum suction, and in step S83, the laser shutter BS is opened to remove the reticle R.
Prepare for T alignment. Next, in step 884, the entire optical system As is moved in the Y direction by a pulse motor (not shown), and the objective lens IIR (L) and the objective mirror 12R (L) are moved in the X direction by a pulse motor (not shown), so that they are placed on the reticle RT. Reticle set! -R8
The presence of R(L) is detected by detector 18R(L).

The distance between the mark R8R(L) detected in step SS5 and a predetermined reference point is measured by the detector 18R(L), and each pulse motor PX of the reticle stage R8 is moved by the distance measured in the next step 5S61. PY and Pθ are driven to move the set mark R3R(L) of the reticle RT to the vicinity of the reference mark RKR(L). At the same time, the objective lens 11R(L) and the objective mirror 12R(L) are returned to positions facing the reticle reference mark RKR(L) in preparation for fine alignment.

At step 887, the reticle reference map on the lens ρθ is
Reticle set mark R8 for KR(L) and reticle RT
The amount of deviation in the left and right X and Y directions from R (L) is the detector 18R.
(L). It is determined in step S88 whether the average value of each of the measured values is within the tolerance value, and if it is within the tolerance value, the process proceeds to the next step ssio, and if it has not yet reached the tolerance value, step SS9 Then, each pulse motor PX, PY, Pθ of reticle stage R3 is driven again, steps 337 and 8 are repeated, and reticle stage R8 is moved until it reaches within the tolerance. If the CPU determines that the permissible value has been reached, the process proceeds to step 5S10.

In step S S10, the exposure area of the reticle RT is set, and first, as shown in FIG. Ru.

Next, in step 811, the first wafer WF is attracted to the wafer chuck WC of the tongue stage WS. The wafer WF transported here is a wafer that has not been exposed to light even once, and therefore alignment marks have not yet been printed.

In the next step S312, the objective mirror 12R or 12L is moved to the detection position of the reticle number RCN on the reticle RT in order to identify the reticle number. Reticle RT
It usually takes several to 14 pieces to make one large-scale integrated circuit.
Since 65 sheets are prepared, if the reticle number RCN is encoded and provided at the time of creating each circuit pattern, the reticle number (type) can be automatically identified. Step S S 1
The reticle number RCN coded with 3 is the detector 18L.
Or read by 18R. 19R or 19L may be used as the illumination light source at this time. Since this is the first reticle, proceed to step S S14. In step 5314, the laser shutter BS is closed, and the lower side of the objective mirror 12R (L) is moved 45° so that it does not get in the way during exposure. Then, in step ssis, the wafer stage WSe?-bottoms XM and YMIC are moved by a predetermined amount in the ) area directly below the projection lens PO.This movement is carried out extremely accurately by the laser interferometer LZ.The lens P
The wafer WF with the first shot area set directly below O has air sensors AGI to AG attached to the lens PO.
The pulse motor ZM is driven to move the .theta.2 stage upward at high speed so as to reach within the focus detectable level of 4' (step SS16). After reaching the focus detectable level, each focus value is detected by F-sensors AG1 to AG4, and the customer shipment value is stored in the RAM and the average value is calculated (step S S17).
. This average value is taken as the focus value of the first shot area, and according to this value, the θ2 stage is moved upward or downward by the pulse motor ZM and/or the piezoelectric element PZ as described above until it reaches the target focus value (step S
S18). Next, the shutter ST of the exposure light source LP is opened and closed for a predetermined period of time to expose the first shot area of the wafer WF, and the TTL alignment female marks in the circuit pattern part CP of the reticle RT and the left and right scribe areas SCR (L) are opened and closed for a predetermined time. WKRn and WKLn are burned (step SS19). and/or manual alignment mark MARI as required.

MALL is also burned. Then step SS20
Determinations as shown in 22 and 24 are made, and if the second shot area is neither of the above, step 5825 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 is moved upward or downward by the motor ZM and/or the piezoelectric element PZ until the focus is reached. 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 5S2G
, 22, when the predetermined specific shot area is reached, the low magnification and high magnification alignment marks WPR(L)
, CRR(L) are exposed in step 5521.
．． At 23, the opening area of each blade BL is set. Further, when transitioning from the specific shot area to the normal shot area, the opening area of the blade 8L is returned to the normal shot area (step S S 10 in FIG. 17 A1).

When the final shot area has been exposed, the process advances from step 5S24 to step 8826. In step 5S26, the wafer stage WS is moved to a predetermined position in order to write the wafer number on the wafer WF, the laser shutter BS is opened for a sufficient time to write the wafer number, and the coded wafer number and/or lot number WCN is written on the wafer WF. Write on the end (see Figure 14).

In step 5S27, the wafer stage WS is ejected (
At the same time, the θ2 stage is moved to the initial lowest position by the pulse motor ZM. Next, it is determined in step 8828 whether the wafer WF that is being transported is the final wafer. This is done by comparing whether or not the number of wafers previously instructed by the operator from the console to the microprocessor has been reached. If it is not the final wafer, the process returns to step 5811 and the same process as described above continues.

As described above, the circuit pattern and the alignment mark of the first ticle are printed for the predetermined number of wafers and lots, and then the process is completed. The first group of wafers on which the circuit pattern and alignment mark of this reticle have been printed are then sequentially exposed from the second reticle to the n-th (final) reticle by precisely overlapping the same shot area on the same wafer. That is, when the second reticle is brought in, step S
The same operations as described above are performed from S1 to SS13,
In step 8813, it is detected that the reticle number is "2", so the process advances to step SS2'9. In step 5S29, the wafer WF is set directly below the air sensors AGI to AG4 attached to the lens PO2, and as described above, in step 5S30.31, the 62 stage is raised at high speed, and focus detection and average value calculation are performed. Proceed to 321-323. Step 5S3
21, the mirror R(L) 18 of the off-axis alignment optical system OA is set to a low magnification system, and the dark field aperture R(L)
) Select 13B.

At the same time, in step S3322, a low-magnification alignment mark WPR (
L)1 is set almost directly below the objective lens R(L)L.

At the same time, in step 58323, step 5
The θZ steady is moved upward or downward from the force average value detected in S31 until the target focus value is reached. The operation of moving one mark WPR(L)1 on the wafer WF under the objective lens R(L)L is performed using a predetermined constant. Step 58
33, the reference line KSL (cursor on the TV screen) and the pre-alignment set mark WPR (L) of the wafer WF
The amount of X and Y deviation from 1 is measured, and the amount of deviation is stored in the RAM. Next, in step 5834, one of a plurality of alignment modes A-C is selected, and accurate and fast alignment, stepping, and exposure are performed according to each alignment mode. Each alignment mode will be explained below.

In mode A, first, in step 5AII, the reference line KSL is
position and pre-alignment set mark W of wafer WF
The 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 X and Y deviation amount from PR (L) 1, and the high magnification alignment mark CR (L) of the wafer WF is set. .12 as objective lens R
(L) Set almost directly below L. At the same time, the θZ steady is rotated by the pulse motor θM according to the θ (rotation) direction deviation amount determined from the above-mentioned X and Y deviation amounts (step 5A12). Off-axis optical system OA in step SA2
The mirror R (Lo> 18 is set to a high magnification system, and the amount of X and Y deviation between the reference mark TPR (L) and the high magnification alignment mark CR (L) 11.12 is measured using this high magnification system (step SA3). ).In this step SA3, the amount of expansion and contraction of the wafer is also measured, and if it is within the allowable value, the value is distributed and added to each slip bond of X.Step SA4
It is determined whether the X and Y deviation amounts are within the allowable values, and if it is determined that they have not yet reached the allowable values, an alignment mark CR(L)1 is placed on the reference mark TPR(L).
The wafer stage WS is moved in the X, Y, and θ directions by the servo motors XM, YM and the pulse motor θM so that 1 and 12 are aligned (step 5A5), and step S
Return to A3 and repeat the same procedure, and when the value falls within the allowable value, proceed to step 5A61.62. Step SA
61, the wafer stage WS is moved in the X and Y directions by the servo motors XM and YM according to the value obtained by adding a constant to the current position of the wafer WF, and the wafer stage WS is moved in the X and Y directions to take the wafer WF's first shot (
The exposure area is set directly below the projection lens PO. At the same time, in step 5A62, the θZ steady of the wafer stage WS is moved upward by a fixed amount by the pulse motor ZM. This is because the focal length of the projection lens PO is shorter than the focal length of the objective lens R(1)L. Below, focus detection and average value calculation (step 5A7)
), θZ steady movement (SA81), mirror 12R (L
) posture change (SA82), exposure (SA9), sequential focus detection, step movement (SA 111.S
A 112) is repeated, and when it is determined that the exposure of the final shot has been completed (SAIO), step 5A is performed.
Proceed to step 12. In step S A 12, the wafer stage ws is moved by the servo motors XM and YM to a position where the wafer number WCN written in the first step can be detected. For example, when detecting with TT'L engineering AS, set the wafer number WCN directly below the lens PO, and use the encoded wafer number WC on the detector 18R or 18L.
Read N. In addition to the laser source IS, the light source 19R or 19L can also be used as the illumination light source at this time. Alternatively, it can also be read using an off-axis engineering system OA. In this case, wafer stage WS may be moved so that wafer number WCNIfi is set directly below either objective lens RL or LL. The read wafer number is stored in RAM. In step 5A14, 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 wafer is ejected, and the process ends.

If it is determined in step 5A15 that the final wafer is not yet completed, the process returns to step 5811 in FIG. 22, and the same procedure is followed thereafter.

In mode B in FIG. 24, first in step S81, for example, the shot area 13 in FIG.
Set by. At the same time, in step 3312.13, movement in the θ direction and two directions is performed. Next, the laser shutter BS is opened (step SB2), and the
, measure the amount of Y deviation. Here, Fig. 13 shot area 1
As shown in 3, the left and right deviations in the X direction IXLI,
R1, same Y direction YL1, YRI, each average value 31 X= (XLI +XR1)/2°81 Y=
(YLI +YR1)/2 is calculated and stored in the RAM (step 5B3). Next, a second designated shot (for example, FIG. 13, 19) is set directly below the projection lens PO, and similar average values 82X and 82Y are determined (step SB4.5). Then in step 3361 for each shot.

The calculated X and Y average deviation amounts for each shot S1X, S
2x, S1Y, and S2Y, the amount of X and Y deviations and the amount of deviation in the θ direction of the entire wafer (global) are determined by the following formula.

'GX=(81X+S2X)/2
゜GY=(SI Y+S2 Y)/2 tanGθshin((YL2 +YR2)/2− (YL
l +YR1)/2)/ where K is designated cylinder 1, 2nd
The distance between the marks on the shot is a constant.

At the same time, in step 5B62, the amount of expansion and contraction PE-81X-82X of the entire wafer due to thermal expansion etc. is determined.

Step SB determines whether each of the obtained values is within the allowable value.
Determine by 7. If it is determined that the value is outside the allowable value, the process advances to step 3881.82. In step 5881, a predetermined amount (ΦK) is added to the previously calculated X and Y deviation amount, and the wafer expansion/contraction is added to that value! Add the values obtained by equally distributing the iPE for each shot, and if the result calculated in step 5B82 includes the servo motor movement amount, add this value as well. According to the total value, the servo motor XM, The first designated shot area is again set directly below the projection lens PO by YM. In step 8882, the quotient obtained by dividing the deviation in the rotational direction by the resolution of the pulse motor θM is set as the amount of movement of the pulse motor θM, and if a remainder occurs, the remainder is set as the amount of movement 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 can be performed as a result. Normally, the X-axis and Y-axis of wafer stage WS are orthogonal in principle, and there is no θ component. However, in actual mechanical design, this complete orthogonality cannot be expected and a θ component always occurs. Therefore, by measuring the θ component when the device is assembled and controlling the amount of movement of the X and Y motors when operating the device, it is possible to move the wafer stage 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 slight angle that cannot be corrected by the pulse motor θM can be corrected by the movement 111fi adjustment of the servo motors XM and YM. Step SB9
Then, it is determined whether or not the pair of shot measurements described above have been repeated a predetermined number of times, and if not completed, the process returns to step SB3 and the above operations are repeated. By repeating this process, the wafer position gradually approaches the allowable value, and if it is determined in step S87 that it is within the allowable value, the process proceeds to the next step 5B12. When the specified number of times is completed, the laser shutter BS is closed (step S810) and the TTL measurement is ended. In step 5811, it is detected that the YES signal has not been sent within the specified number of times in step SB7, and preparations are made to advance the alignment mode to another mode, for example C. In step 3812, even if the global alignment of the entire wafer is completed in the previous step, if there is a rotational direction deviation for each shot, an exposure deviation will occur, so this mode is used to measure this.

Therefore, in step 5B12, first, YLI, YRl, YL2,
θ direction deviation amount tan SO2 for each shot from YR2
= (YLl-YRl)/Kl.

2 is calculated as tan SO2=(YL2-1YR2)/. It is determined whether the calculated SO2 and SO2 are within the allowable range (step S B 13), and if they are outside the allowable value, each value is an approximate value, that is, the inclination judgment is performed to determine whether the rotational deviation is in the same direction and the same inclination. 8814, 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, average Sθ=<Sθ1+3θ
2) Calculate /2 (step 8816) L/, drive the reticle stage R8 by the pulse motor Pθ until it reaches the average Sθ, and rotate the reticle RT (step S B 17). Next, the θ direction deviations Isθ1′ and Sθ2′ for each shot are measured again (step 881g) L,
, average SO2-(Sθ1'+Sθ2')/2 is determined whether or not it is within the allowable value (step 8819). If not, the process returns to step 5817 and the same operation is repeated. If the value falls within the tolerance in step 3319, step 5A81.62 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, alignment mode C will be explained.

First, in step 5cii, the first shot area of the wafer WF is moved directly under the reduction projection lens PO using the servo motor ,
Set by YM.

At the same time, the θ-2 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 Z.
It is moved upward by a predetermined amount by M (step 5C13).

Next, the air sensor AG detects the focus in the first shot area.
1 to AG4, the average value is calculated, and the θ2 stage is moved upward or downward by the pulse motor ZM and/or the piezoelectric element Pz until the target focus value is reached (step 5C2). Next, the objective lens 11R(L) and the objective mirror 12R(L) are moved to a position facing the reticle male mark WSR(L)n-1 of the reticle RTn (SC
3) Prepare for TTL alignment. Next, the laser shutter BS is opened (SSC4), and the mark WSR(L)n-1 on the reticle is irradiated with the laser light from the laser source 1S using the objective mirror 12R(L). Step SC
5 to start laser scanning and move the reticle RTn as is well known.
The first X between the male mark WSR(L)n-1 and the female mark WKR(L)n-1,m of the wafer WF.

Measure the amount of Y deviation. Step SC determines whether the first deviation amount is within a first tolerance value, for example, 0.1μ.
Judge with 6. Here, the deviation in the X and Y directions of each shot of the wafer with respect to the reticle is XL, YL, and XR on the left and right.
, YR, the average amount of deviation is given by SX-(XL+XR)/2°SY-(YL+YR)/2. Also, the amount of deviation tanSθ in θ (direction of rotation)
As in the previous example, is given by tanSθ-(YL-YR)/L. Here, the distance between the left and right marks WK(S)R-WK(S)L of each shot is a constant. If the average values SX and SY of each deviation are both within the allowable values in step SC6, alignment is completed and the laser shutter BS is closed (step 5C12), and the process proceeds to the next process.

If even one of the average deviations isX and SY is outside the allowable value, the process proceeds to step SC7 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 S01, Sθ is calculated from the above YL and YR. This calculated S
When the θ2 stage is rotated in the direction of eliminating the deviation according to θ, 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 m 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 G101, 102, otherwise step 5C
Proceed to 111-113. In steps 30101 and 102, since it is within the allowable value, the male mark W of the reticle RTn is determined according to the value obtained by adding the above-mentioned first and second X and Y deviation amounts, respectively.
SR(L)n-1 is the female mark WKR(L) of wafer WF.
) n-1.

The reticle stage R8 is moved in the X and Y directions by the pulse motors PX and PY so that it is in the middle of the reticle stage R8. At the same time, the pulse motor θM is driven by Δθ to rotate the θZ steady. In step 5C111, since it is outside the allowable value, the male mark WSR(L)n-1 of the reticle RTn is set according to the first X, Y deviation. Pulse motor PX is placed in the middle.

The reticle stage R3 is moved in the X and Y directions by PY. At the same time, the second X in step 5C112.

Mark WSR(L)n is placed in the same manner as described above according to the amount of Y deviation.
-1 is female mark WKR(L)n-1.

Wafer stage WS is moved in the X and Y directions by servo motors XM and YM so that it is in the middle of m. At the same time, in step 5C113, as in step 5C102, the θ2 stage is rotated by Δθ by the pulse motor θM. In this way, by selecting and aligning the reticle and wafer according to the tolerance values, 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, while driving by a servo motor has high speed but is insufficient in terms of accuracy, and the reticle side inherently has a longer travel distance than the wafer side. Considering that the reticle stage is short, if it is within the allowable value, the reticle stage is precisely driven by a pulse motor because the moving distance for correction is short, and if it is outside the allowable value, the moving distance for correction is short. Since the wafer stage 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 the result falls within the first allowable value in step SC6. In this way, high speed,
When the high-precision alignment is completed, the process proceeds to step 5C12 as described above, and then to step 5C13. In step 5C13, the objective lens 11R(L) and objective mirror 12R(L) are moved backward to predetermined positions so as not to interfere with exposure, and the objective mirror 12R(L) is vertically changed in attitude.

Next, the shutter ST is opened and closed for a predetermined period of time to perform exposure (step SC14). When the exposure is completed, the final shot area is determined in step 5C15, and if it is not the final shot area, the process proceeds to steps SC161 to SC164. S -
As described above, the wafer stage is moved to the next shot area in Terra 1161, and at the same time, the θ2 stage is moved up (down) until the focus detection value is reached (step 162
), the objective mirror 12R(L) is moved to a position opposite to the male mark WSR(L)n-1 of the reticle, and the attitude of the mirror 12R(L) is changed to 45" (step 5C163), and the reticle stage R8 is returned to the X and Y position memorized at the first shot. When these operations are completed, the process returns to step SC3, and precise overlay exposure is performed by so-called die-by-die alignment until the final shot is completed. When the final shot is completed, It is determined in step 5cis, and step S A 1
Returning to step 2, the same operation is repeated to complete the processing of 10 bits.

This device also has a manual alignment mode, and the above-mentioned special manual alignment mode and other manual alignment modes can be executed 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 19m are turned on or a diffuser plate DF is inserted into the optical path of the laser 1S.

In addition, when using the or-axis optical system OA, the light source R11
, Lll are turned on, and rough selection of dark field and bright field is made by selecting R13A, R13B, L13A, and L13B.

Further, each alignment mark is selected as shown in FIG. 15.

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

[Brief explanation of the drawing]

Figure 1 shows an example of a device according to the present invention! ! 2 is an overview of the blade, 3 and 4 are sectional views and a plan view of the reticle stage, 5 is an overview of the optical system, and 6.7 is an overview of the optical system. An overview diagram and a sectional view of the wafer stage, Figures 8 and 9 are block diagrams for driving the wafer stage in the Z direction and 12 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,
Figures 5A, B, and C are diagrams showing eight examples of television monitors, No. 16.
FIG. C1D is a diagram showing eight examples of reticles, FIG. 16 C1D is a diagram explaining how a wafer is exposed, and FIGS. 17A, B,
C and D are diagrams showing the aperture relationship between the reticle and the blade, the first
8 is a diagram showing an example of dividing a television screen, FIG. 19 is a diagram explaining addition and slice levels, FIG. 20 is a control block diagram thereof, FIG. 21 is a flowchart for explaining its operation, and FIG. 22 ~S5, Figure 22 81~S5, 2nd
4. FIGS. 81-B3 and FIG. 25-01-C3 are flowcharts illustrating the operation of each 7-line mode. 10... Exposure light source system, As... TTL alignment optical system, R, T... Reticle, R3... Reticle stage, PO... Reduction projection lens system, OA... Off-axis alignment Optical system, WF...
・Wafer, WS...Wafer stage, LZ...Laser interferometer.

Claims (1)

[Claims] 1. The first, second, and third pulse motors that move the reticle stage in the X, Y, and θ directions and the wafer stage are moved in the θ,
The wafer stage is connected to fourth and fifth pulse motors and a laser interferometer that move the wafer stage in the Z direction, and connected to first and second servo motors and an eddy current detector that move the wafer stage in the X and Y directions. An alignment device equipped with a piezoelectric element that moves the wafer stage minutely. 2. A first moving means for moving the wafer stage in the first direction, a second moving means for moving the wafer stage in the second direction, and a third moving means for moving the wafer stage in the second direction.
a third moving means for moving in the direction; a fourth moving means for moving in the fourth direction; and a third moving means for determining whether the first, second, third, and fourth movements are each within tolerance values. 1st, 2nd, 3rd
, a fourth discriminating means and a fifth moving means for moving the reticle stage in the first direction, and a sixth moving means for moving the reticle stage in the second direction.
a moving means for moving in a third direction; a seventh moving means for moving in a third direction; a fifth, sixth, and seventh determining means for determining whether the fifth, sixth, and seventh movements are each within an allowable value; and any of the above. and control means for converging within the tolerance by repeating the moving operation when the determining means determines that the value is outside the tolerance. 3. The position is measured by an off-axis mark detection means having multiple slice levels and an adder, a TTL mark detection means having a laser source, and a laser interferometer, and is moved in the X and Y directions by a servo motor, and is moved by a pulse motor and a piezoelectric An alignment device equipped with a wafer stage that moves in the Z direction using an element. 4. The alignment apparatus according to claim 3, wherein the wafer stage is moved in the θ direction by a pulse motor.