JPS60136746A - Projection optical device - Google Patents

Abstract

PURPOSE:To correct variations in magnification and image formation surface with high precision by providing an air chamber which is shielded from the outside air at at least one position between lens element of a projection objective lens, and further providing a pressure controller which controls the pressure of the air chamber. CONSTITUTION:Four air rooms (J, K, L, and M) corresponding to the 11th space (k), the 12th space (l), and the 13th space (m) are coupled by a communication part 11a in the projection objective lens 1, and shield from the atmosphere, an its pressure is controlled through a pipe 11 as a pressure control space. Then, a pressure controller 12 is supplied to air having constant sationary pressure from a pressurized air supplying device 4 through a filter 13 and the air is discharged by an exhaust system 8 when necessary. Consequently, variations in magnification and image forming surface are corrected with high precision.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to a projection optical device that can correct the imaging performance of a projection optical system with high precision.

(Background of the invention) In recent years, reduction projection exposure devices (hereinafter referred to as steppers) have
It has been introduced into many SI production sites and has brought great results, but one of its important features is overlay matching/alignment accuracy. An important factor among the factors that affect the matching accuracy is the magnification error of the projection optical system. The size of patterns used in VLSIs is becoming increasingly smaller year by year, and the need for improved matching accuracy is also becoming stronger. Therefore, it is becoming increasingly necessary to adjust the projection magnification to a predetermined value σ).

Currently, the magnification of the projection optical system is adjusted at the time of installation of the apparatus, so that the magnification error can be ignored. However, in order to fully cope with the increasing density of VLSI, it is necessary to correct magnification errors caused by changes in environmental conditions, such as slight pressure fluctuations in the clean room during equipment operation. It is also necessary to correct magnification fluctuations that occur when the lens/lens system itself changes in temperature due to absorption of exposure energy. Moreover, changes in magnification due to changes in environmental conditions such as changes in atmospheric pressure or increases in temperature of the projection lens system itself are generally accompanied by changes in the imaging plane. In a projection objective lens that requires high resolution, N and A are large and the depth of focus is small, so even slight fluctuations in the imaging plane must be sufficiently corrected.

Conventionally, in projection optical systems other than steppers, in order to correct the projection magnification, the distance between the object area and the projection lens relative to the image plane is mechanically changed, or the lens element in the projection lens is moved in the optical axis direction. A method was taken. However, if the above method of changing the optical aperture in the optical axis direction is applied to a device such as a stepper, which has extremely high-precision magnification and imaging plane settings, the eccentricity of the mechanical movable part (
(shift, tilt), it is difficult to apply displacement while keeping the optical axis correct. As a result, the optical system including the object is no longer coaxial, resulting in a disadvantage that a magnification distribution asymmetrical with respect to the optical axis occurs on the image plane. In addition, in order to accurately set the magnification so that an error of 0.05 μm or less occurs on the wafer, the amount of change in the optical member must be decentered (shifted,
It is necessary to control the thickness to within several μm to 1 μm, including the tilt (tilt), and it is very difficult to achieve this.

(Object of the Invention) An object of the present invention is to eliminate these drawbacks and provide a projection optical device that can correct variations in magnification and imaging plane with high precision without causing asymmetry in optical performance. .

(Summary of the Invention) Prior to the present invention, the present inventor first developed a projection optical apparatus having a projection objective lens for projecting and exposing a pattern on a reticle onto a wafer. death/
An air chamber isolated from outside air is provided at at least one location between the projection objective lenses, and a pressure controller is provided for controlling the pressure of the air chamber, and the pressure controller controls the pressure of the air chamber in the projection objective lens. A patent application filed in 1983 describes a device in which the optical performance of the projection objective lens can be adjusted by changing the projection objective lens.
It was proposed as No.-137377. The present invention is based on the above-mentioned projection optical device proposed earlier.
The value of the ratio between the amount of change in magnification of the projection objective lens and the amount of change in the imaging plane due to the air chamber whose pressure is controlled by 7, thereby simultaneously correcting variations in both magnification and imaging plane due to predetermined factors with high precision by controlling the pressure of one air chamber consisting of at least one lens interval. It is.

Now, in the pressure control air chamber formed by shielding at least one lens interval from the atmosphere in the projection objective lens, the amount of change in magnification caused by a unit pressure change is the magnification at each lens interval whose pressure is integrally controlled. It is the sum of the amount of change, and is not expressed as ΣΔXc. Further, the amount of change in the image plane caused by a unit pressure change in this air chamber is the sum of the amount of change in the image plane at each lens interval that is similarly pressure controlled, and is expressed as ΣΔZc. Now, when looking at the case of correcting variations in the magnification of the projection objective lens and the imaging plane caused by variations in atmospheric pressure, the variations occurring in the entire system are caused by the variations between the reticle as the projection original plate and the wafer site as the photosensitive object surface. It is equal to the variation that occurs in all the air spaces remaining except for the air spaces that form the air chambers described above, which are isolated from the outside air and are integrally pressure controlled. The amount of magnification change Δx(p) that occurs in all remaining air intervals due to a unit pressure change in atmospheric pressure is the sum of the amount of magnification change in each of these remaining all air intervals, and Δx(p) = ΣΔX 几. expressed. Further, the amount of change in the imaging plane Δz(p) is also the sum of the amount of change in the imaging plane for each of these total air intervals, and is expressed as ΔZ(P)=ΣΔZR. Therefore, the ratio of the magnification variation due to atmospheric pressure fluctuation to the imaging plane variation is defined as the variation ratio v (p), and V (P ) - ΔZ (P) / ΔX (P) (1)
It is defined as On the other hand, the correction ratio C is defined as C-ΣΔZ C/ΣΔX c f21 , which is the ratio of the magnification change amount that can be changed by -C in the air chamber that performs the above-mentioned integrated pressure control and the imaging plane change amount. Then, the fluctuation ratio v(p) due to atmospheric pressure fluctuation
By providing an air chamber having a correction ratio C equal to , it becomes possible to simultaneously correct both magnification changes and imaging plane changes due to atmospheric pressure fluctuations. That is, (11
(From Equation 21, an integral pressure-controlled air chamber may be formed by combining the lens intervals in the projection objective lens as follows.

Here, if we rewrite the above equation (3), we get: This value α represents the ratio of the amount of variation to the amount of correction for pressure changes,
This means that it is sufficient to apply a pressure change that is the opposite of the pressure in the integral pressure control air chamber multiplied by α in response to the atmospheric pressure fluctuation amount, and can also be called a control rate. In other words, if the pressure in the control air chamber is reversely reduced or increased by α·ΔP with respect to the atmospheric pressure fluctuation ΔP, the resulting magnification change ΔX is: ΔX=ΔP·Δx(p)− α・ΔP, ΣΔXc (5)
=ΔP·(ΔX(i))−α·ΣΔXcl. (4
) From the formula, α, ΣΔXC−ΔX ('P), so ΔX=ΔP・(ΔX(P)−ΔX(P)1, so ΔX
= o (g), and the magnification variation is completely corrected.

Similarly, the amount of change in the imaging plane after correction ΔZ, Δ2=ΔP, Δ
z(p)−α・ΔP, ΣΔZc (given as 61, (
From equation 4), α, ΣΔZC-Δz(p), so ΔZ-0(d) is obtained, and the fluctuation of the imaging plane is also corrected at the same time.

In the above explanation, it was assumed that the magnification and imaging plane are corrected due to atmospheric pressure fluctuations, but as mentioned above, as with Lfc, there are also factors that cause fluctuations in the magnification and imaging plane of the projection objective lens. First, there are temperature changes in the lens itself due to environmental temperature changes and absorption of exposure energy. Although it is possible to maintain a steady state of the environmental temperature as a projection optical device with considerable accuracy, it has been difficult to compensate for temperature changes in the lens itself due to absorption of exposure energy. For example, variations in magnification and image plane caused by temperature changes in the lens itself caused by exposure energy irradiation can be simultaneously corrected to a high degree.

In other words, the amount of change in magnification per unit incident energy of the entire projection objective/zoom system is ΔX(E), and the amount of change in the imaging plane is ΔZ(E
), then the ratio of the magnification variation due to temperature change based on exposure energy absorption of the lens to the imaging plane variation is:
The fluctuation ratio V(E) is V(E)=ΔZ(E)/ΔX
(E) (71) Therefore, the correction ratio C by the integrated pressure control fi11 air chamber shown in the above equation (2) is
The lens spacing may be combined so that the variation ratio V(E) due to absorption of exposure energy by the lens is equal to the variation ratio V(E) shown in equation (7).

That is, What is necessary is to form a pressure-controlled air chamber such that

Now, by multiplying the denominator on the left side of equation (8) by ΔE and the denominator and numerator on the right side by ΔP, we get -1, (9), and this value α′ is also the same as α in equation (4). This can be called the control rate.

Therefore, in this case, when the exposure energy to σ/z changes by ΔE, the pressure in the pressure control air chamber σ) is changed to −α′
・By changing by ΔP, the magnification change amount after correction ΔxVi ΔX=ΔE, ΔX(E)−α′, ΔP, ΣΔXc, and from equation (9), α′・ΔP, ΣΔXc−ΔE, Since it is ΔX(E), it becomes Δ¥−〇, and the change in magnification is completely corrected.

Similarly, the amount of change in the imaging plane after correction ΔZ, J7
==ΔE, ΔZ (E)-a'-ΔP, ΣΔZc, and using equation (9), it becomes ΔZ-0, and it is clear that the imaging plane can also be corrected at the same time.

(Examples) Hereinafter, the present invention will be described based on Examples of the present invention. FIG. 1 is a lens arrangement diagram showing an example of a projection objective lens used in a SDPAR, and a predetermined pattern on a reticle (fL) is reduced and projected onto a wafer (W) by this objective lens. In the figure, light rays representing the conjugate relationship between on-axis object points between the wafer and the reticle are shown. This objective lens is ``1 + ''2 +...L□4 in order from the reticle (R) side.
There are a total of 15 lenses (a+1)+e+...0 between each lens and the reticle (R) and wafer (W) in order from the reticle side. An air gap is formed. Table 1 shows the specifications of this objective lens.
Shown below. However, r is the radius of curvature of each lens/z plane, D is the center thickness and air gap of each lens, and N is the i-line (λ-3
65.0 nm), and the leftmost number in the table represents the order from the reticle side. Also, Do is the distance between the reticle and the front lens, D3
1 represents the distance between the final lens and the wafer (W).

In this objective lens, the air distance a.

If bl...00 atm is changed by +167.5 mm) Ig, the relative refractive index of each air interval is 1.
00005, and the magnification change at this time and the change in the imaging plane, that is, the conjugate plane with the reticle (R.) are shown in Table 2VC. However, the magnification change ΔX is the amount of movement μm of the image point formed at a position 5.66 mm away from the optical axis when there is no change in air pressure on the imaging plane after the change in air pressure for each air interval.
It is expressed in units, and the image forming plane when there is no atmospheric pressure fluctuation, that is, the case where it is projected more sharply onto a predetermined wafer surface (enlargement), is shown as a stop sign (7).Also, the change in the image forming plane ΔZ is the change on the axis. It is shown as a change in the imaging point, and a stop sign is shown when it moves away from the objective lens. Both positions are in μm units.

Table 1 Table 2 The projection optical device according to the first embodiment of the present invention using the projection objective lens having the above-mentioned characteristics has four continuous lens intervals from the 10th space j to the 13th space mt. The structure is such that it is isolated from the atmosphere and communicated with it for integral pressure control, thereby simultaneously correcting fluctuations in both magnification and imaging plane due to fluctuations in atmospheric pressure.

Here, the amount of change in magnification ΣΔXc and the amount of change in imaging plane Σ that occur with respect to a unit pressure change at four zoom intervals J + k + l + m as air chambers that perform pressure control
For unit pressure change of ΔZc and atmospheric pressure.

The double height change Δx ('p) and the imaging plane change amount ΔΣ(P) which occur in the air spacing of the entire system excluding the pressure control air chamber are calculated from Table 2, and are as shown in Table 3 below. In the table, the correction ratio C due to the pressure-controlled air chamber and the fluctuation ratio v(p) due to fluctuations in dog air fluid are also listed.

Table 3 (First Example) In such a configuration, the correction ratio C is 0.929 (=C/V(P)) with respect to the fluctuation ratio V(P), which is almost the same relationship, and ( 5) As shown in the LgJ equation and (+3)(g+ equation, both the magnification variation and the imaging plane variation should be corrected at the same time. Here, the control rate α shown in equation (4) is ) is the average value of the control rate for image plane variation given by the left side of equation (4) and the control rate for magnification variation given by the middle side of equation (4), then α = 0.62. When the atmospheric pressure fluctuation is the same as shown in Table 2 (+157.5 mm, 14 g), by substituting each value into equation (5), ΔX = 0.374
-0.62XO,63=-0,017. This value is the amount of magnification change when no correction is made in the entire system +
It can be seen that it is less than 2% of 1.004 and can be sufficiently corrected. On the other hand, by substituting each value into equation (6), ΔZ=5.78-0.62x9.05=0.169. This value is about 1% smaller than the imaging plane change if + 14-83 when no correction is made in the entire system, and it is clear that the correction can be made extremely well.

Figure 2 shows how magnification correction and imaging plane correction can be achieved simultaneously by shielding the space between the four lenses in the projection objective lens from the atmosphere and controlling the pressure of the integrally formed air chamber. 1 is a schematic configuration diagram of a projection optical device according to a first embodiment that is capable of The projection objective Lens/Z (1) transfers the pattern on the Revucle (R) uniformly illuminated by the illumination device (2) to the Ueno lens (V) placed on the stage (3).
Reduce and project to v>b. In the projection objective (1),
between the 10th wall j,, the 11th space, the 12th space 1 and the 1st space
4 air chambers (J, ni, L.) corresponding to 6 spaces m.

M) is connected by a communication part (11a) and isolated from the atmosphere, and its pressure is controlled through a pipe (11) as a pressure control space. Spaces whose pressure changes with atmospheric pressure are omitted from FIG. 2 to avoid complicating the drawing. The pressure control space is connected by a pipe (11) to a pressure controller (12) provided outside the objective/space. The pressure controller (12) is constantly supplied with air at a constant pressure from the pressurized air supply device (4) through the filter (16).
Further, the air is exhausted by an exhaust device (8) as required. On the other hand, a pressure sensor (14) for detecting the internal pressure is provided on the side of the air chamber, and this output 4g is sent to the computing unit (5).

The measured value of atmospheric pressure is inputted to the measuring device (5) from the measuring device (6). The performance device (5) contains the amount of change in magnification ΣΔXc per unit pressure in the air chamber in the pressure control space, the amount of change in imaging plane ΣΔZC, and the amount of change in magnification per unit pressure Δx(p) in the entire system excluding the pressure control space. ) and the amount of change in the imaging plane ゛Δz(p) are stored, and the control rate α shown in equation (4) is determined based on these values. and,
The calculator (5) calculates the amount of variation ΔP of atmospheric pressure with respect to the reference state based on the input signal from the measuring device (6), and multiplies the required pressure control amount, that is, the amount of atmospheric pressure variation, by a control rate of the opposite sign. A pressure control signal corresponding to the value -k·ΔP is sent to the pressure controller (12). The pressure controller (12) then controls the pressurized air supply (4) according to the signal from the computing unit (5).
The amount of air flowing into the exhaust device (8) and the amount of air flowing out to the exhaust device (8) are changed as appropriate, and the pressure in the pressure control air chamber is changed by -k·ΔP.

Through this series of operations, the pressure in the pressure control air chamber is controlled in response to changes in atmospheric pressure, and the magnification and imaging plane of the projection objective are always kept constant.

In the first embodiment described in ``-'', four consecutive lenses/lens intervals with dimensions of the 10th space to the 13th space are integrated into pressure-controlled air chambers, and the pressure at all other lens intervals can change with the atmospheric pressure. However, it is also possible to not control the pressure or to seal off part or all of the space from the atmosphere. For example, in the configuration of the first embodiment, the lens interval corresponding to the fourteenth space n may be sealed and sealed from the atmosphere. Regarding the case of the second embodiment, the amounts of change, correction ratios, and fluctuation ratios are shown in Table 4, similar to Table 6.
Table 4 (Second Embodiment) As shown in Table 4, the pressure control air chamber is the same as in the first embodiment, so ΣΔXc, ΣΔZc and correction ratio C are the same as in Table 6. Magnification variation ΔX, (P) and imaging plane variation ΔZ (P) caused by changes in atmospheric pressure in the entire system
Each position of is different from each position of each change phase division table 3 in the 14th space n. Therefore, the variation ratio V'(P) is also as shown in Table 3.
This is different from the case of . In this case, the correction ratio C is 1. o63C-C/V(P)),
The variation ratio, correction ratio, and σ-) ratio are closer to 1 than in the first embodiment. Here again, the control rate α shown in equation (4)
If α is the average value of the control rate of 'T4 for each fluctuation, then α=0
．． It is 59. Therefore, as in the case of the first embodiment, (
Substituting each value into equations 5) and (6) and calculating the resulting amount of variation, ΔX = 0.382-0.59 x 0.6 = 0.
010ΔZ=5.16-0.59 x 9.05=-
o, 18. This magnification variation amount ΔX is 1% of the case without correction, and the image formation plane variation amount ΔZ is also 1% of the case without correction.
It is clear that both of them can be corrected extremely well.

The projection optical device according to the second embodiment is not particularly illustrated because it merely adds a configuration for sealing the 14th space from the atmosphere to the device according to the first embodiment shown in FIG. . In addition, in the case of the second embodiment, since the amounts of fluctuation and control rate σ) values occurring in the entire system are different, the memorized values and i1 calculated values in the computing unit (5) are naturally different, but the operation of each member is substantially different. Same 0 In the first and second embodiments described above, variations in magnification and imaging plane were corrected based only on atmospheric pressure variations, but in reality, as mentioned above, the projection objective lens itself absorbs exposure energy. As the temperature changes due to absorption, the magnification and imaging plane may change accordingly. For this, sea urchin/%
In addition to the exposure energy required for the - exposure, it is desirable to provide the projection objective itself with constant exposure energy. In other words, by keeping the energy incident on the projection objective constant per unit time, it is possible to eliminate variations in magnification and image plane caused by exposure energy.

Here, a method for keeping constant the exposure energy applied to the projection objective lens per unit time will be described in detail. In practice, it is good to set the unit time to a time that is sufficiently short compared to the saturation time of magnification change and imaging plane change. If the unit time is shortened, there is a tendency for the depth magnification and the precision of the imaging surface σ) to increase. Since the saturation time varies depending on the device, it is approximately several minutes to several tens of minutes, so it is sufficient to select a value between several tens of seconds and several minutes as the unit time. In the above method, the magnification and imaging plane change depending on the incident energy, and are used after reaching a saturated state. Therefore, when restarting a stepper that is not in use, the waiting time is reduced by saturating the magnification.・It becomes important.

In order to reduce this waiting time, it is convenient to initially store more incident energy per unit time as the warm/warm time than during use, and to cause changes in magnification and imaging plane to occur in a short time.

The energy that enters the projection optical system per unit time is affected by the brightness of the YC source, the transmittance of the reticle, the reflectance of the wafer, etc., but the most temporal variation is when the projection optical system opens within a unit time. This is the percentage of time that the illumination light is incident on the projection optical system (hereinafter expressed as τ). Therefore, it is most important to keep this τ value constant in order to compensate for the magnification error. For example, one unit of time is one sea urchin during standard operation of the stepper.
・Use the processing time τ. It is given by the following equation rij during steady exposure operation.

Here, t11d is the time required for exchanging the wafer, t2 is the wafer N setting time, to is the exposure time per shot, and tc is the stepping time NU, which is the number of shots per 1 wafer. Since the shutter is opened and the exposure energy is incident on the projection objective lens for only the exposure time, one sheet of Ueno/A/D NtO is produced. When Ueno is being processed one after another, the same repetition is always performed).
τld does not change. However, if for some reason the urethane is not supplied continuously for one time, or the equipment breaks down, the time will normally pass while the holder is closed, so it will be too late to start the next ueno exposure. When the town is opened, a change in the ratio and 0/imaging surface occurs. Therefore, in order to prevent the reduction in energy when the normal exposure operation is stopped, the shutter is opened at a certain ratio so that the exposure energy is incident on the projection objective lens. Here, the opening/closing operation of the shutter may be determined as follows in order to maintain τ in equation (10). That is, the time required for determining that the apparatus has stopped the regular exposure operation is defined as t3. During this time, the shutter remains closed. In order to prevent the next decrease, it is necessary to keep the shutter open for a period of time t4. Then, the shutter is operated so that τ=t4/(t3+t4) is satisfied. Therefore, t4 is given by t3/'(1-τ) at t4-. At this time, if τ in equation (10) is used, a decrease in τ can be avoided.

FIG. 6 is a diagram illustrating an example of changes over time in the opening and closing of the shutter. The shutter is open at a high level, and the shutter is closed at a low level.

I'm here. Wafer exchange time t1. Ueno alignment time t2. This is an example in which the exposure time 10 and the stepping time tc, which are repeated 0.N times, take η5i☆time T. (t3+t4) is the unit time T for calculating τ, so as mentioned above, the shorter it is, the better the 87 degree is, but the processing time for one Ueno sheet, that is, the value of the denominator of the formula (00) or less, is [2 There is no problem. (t3+t4) If the exposure operation does not return to normal even after the elapse of time, (t3+t4)
If t4) can be repeated n times, a decrease in τ can be prevented. In this example, the measurement of t5, t4, and τ and the determination that the steady operation has stopped may be made by an electronic circuit, or may be made by an operator and the respective numerical values may be input manually. Also, since τ=t4/(t+t4) is the term to be controlled, t3. Needless to say, the same effect can be obtained even if t4 is divided into i pieces. The example shown in the lower part of FIG. 3 is a case where it is divided into two parts.

That is, the shirt shutter opening time tl for each divided portion.

When the shutter open time is t4i, it is sufficient to satisfy Σt4i Σt3i+Σt4i. The value of this denominator is equal to coronation time 1.

Now, FIG. 4 is a schematic configuration diagram of a sixth embodiment according to the present invention, and the inside of the projection objective lens is shown as a cross-sectional view 7. In the figure, members having the same functions as those in the first embodiment are given the same reference numbers.In the third embodiment, by controlling the pressure at a part of the lens interval in the projection objective lens, This system simultaneously corrects the magnification and imaging plane due to changes in the temperature of the projection objective lens caused by absorption of exposure energy and changes in environmental temperature.The 14 lenses that make up the objective lens base □＋L2 ＋・・・・・・、L□
4 are the first support barrel (101) and the second support barrel (101).
1 (12), 14th support barrel (114)
Supported by By stacking these 14 support barrels 1+, an internal barrel is substantially formed, which is integrally housed and supported by the outer barrel (20)K and fixed by a presser ring (21). ing.

The first support barrel (101) to the fourteenth support barrel (114) respectively support the seventh lens L7 to the fourteenth lens L14.
), 16 spaces B-N are formed in the lens barrel, and these spaces 13 to N are respectively connected to the first
This corresponds to the air spacing b−n shown in the figure. Here, the seventh support barrel (107) that supports the seventh lens L7 and the eighth support barrel 1 [1B] that supports the eighth lens each have a through hole (107a) for communicating the adjacent air chambers.
and (1osa) are formed. So (6, te, 6th
The six lens spaces G, H, and I are integrally formed by the sixth support barrel (106) that supports the lens L6 and the ninth support barrel (1o9) that supports the ninth lens L6. It is isolated from the atmosphere to form a single air chamber, and a pressure controller (
12) is connected to the vibrator (11) (7 lever) to control the pressure in the sealed air chamber. The objective lens is kept at a constant pressure and sealed from the atmosphere by the first support barrel (101) to the seventh support barrel (107) and the ninth support barrel (109) to the fourteenth support barrel (114). The pressure is controlled integrally among the lens spaces in the lens space.51 The remaining lens spaces except for one lens space G, H, and I are not sealed from the atmosphere, so this is due to atmospheric R fluctuations. Changes in the magnification and image plane caused by the lens can be almost ignored.For this reason, it is necessary to correct changes in the magnification and image plane caused by other factors, such as changes in the temperature of the lens itself due to absorption of exposure energy. Therefore, as shown in Table 2 above,
Based on the value, the pressure ft+li is determined by the total air chambers in the six lens spaces 0. When multiplying the magnification change ΣΔXC and the imaging plane change ΔΣZ at H and I by C and the correction ratio C, the table 5 above is obtained.
It is as follows.

Table 5 (Third Embodiment) Therefore, according to the sixth embodiment, it is possible to correct the factors that cause the variation ratio of magnification and imaging dlr variation of about 113. For example, if a projection objective lens absorbs exposure energy and its temperature rises,
The magnification tends to fluctuate with a small positive or negative value in the direction in which the image forming surface approaches the objective lens, that is, in the negative direction. , by reducing the pressure in the pressure-controlled air chamber, positive magnification change and negative image plane change can be produced in the ratio of -1:16, so that the objective lens due to the absorption of light energy It is possible to simultaneously correct six negative imaging plane changes and positive magnification changes due to temperature rise.

Note that the projection objective lens itself absorbs the exposure energy,
Changes in magnification and the imaging plane when the temperature rises vary greatly depending on the material of the objective lens, so it is necessary to accurately measure each variation using real numbers for each projection objective lens. VIE)
It is desirable to configure a pressure-controlled air chamber by combining lens spaces so that the correction ratio C has a value closest to . Shrewd,
Regarding the control ratios α and α', please refer to the above-mentioned 1. Regarding the second embodiment, it is considered effective not to necessarily use the average value of each control rate for the magnification and the imaging plane, but to adopt the control rate that requires stricter correction changes. Ru. Furthermore, although the structure L-1 of the sixth embodiment is such that the entire mass space is sealed except for the steam space where the discharge pressure is controlled, only a part of it is sealed 5, and the rest is kept at atmospheric pressure and at constant pressure. Even if the optical system is a 1,140-dimensional image, there may be cases in which variations in magnification and imaging plane due to atmospheric pressure fluctuations occur in the entire optical system, and within the scope of the present invention, Those skilled in the art will be able to easily find the optimum combination of pressure control space and sealed space depending on the type of pressure control space.

By the way, at this size, the air contains N2.0 as atmospheric pressure.
2, CO2, H2O, etc. We have only considered the total pressure without considering the partial pressure of each gas. (1) Since controlling the refractive index of the excluded air is not important in the present invention, it is possible to use only N2 instead of air during hunting, or to control the partial pressure of each gas while keeping the total pressure constant. Changing the refractive index is also naturally included in the present invention.

(Effects of the Invention) As described above, according to the present invention, fluctuations in the projection magnification and imaging plane of the stepper due to changes in atmospheric pressure and temperature changes in the lens itself due to absorption of exposure process noise can be avoided by using the projection objective. It is possible to perform correction with high precision without applying mechanical movement to the members in the / lens system, and therefore without producing asymmetric optical performance. Since the printing exposure is always performed stably on the wafer surface and the overlaying is performed with high precision, it contributes greatly to the manufacture of semi-solid elements such as ultra-LSIs that are even higher density and more compact. It is a thing〇

[Brief explanation of the drawing]

FIG. 1 is a lens configuration diagram of a projection objective for a stepper according to an embodiment of the present invention, FIG. 2 is a schematic configuration diagram of a first embodiment of a projection optical device according to the present invention, and FIG. 1,
FIG. 4 is a diagram illustrating the opening and closing of the switch for lightless control that can be applied to the second embodiment, and FIG. 4 is a schematic configuration diagram of the sixth embodiment. (Explanation of key numbers of main parts) R5...Projection original plate (Regcle) W...
・Photosensitive object (Ueno) Lyo+ L2~L14...Lens a, b'=o
- Air spacing B, C-N...S/Z Space 1...Projection objective S/Z 12...Pressure controller Applicant Nippon Kogaku Kogyo Co., Ltd. Agent Watanabe Takao Figure 1 Figure 2 E Figure 40

Claims (1)

[Claims] A projection objective lens for projecting and exposing butter on a projection original plate onto a photosensitive object surface, and a lens element forming the projection objective lens in the projection objective lens. An air chamber configured by shielding at least one part of the image space from the atmosphere is provided, and the ratio between the amount of change in magnification of the projection objective lens and the amount of change in the imaging plane that occurs when the pressure inside the air chamber changes is provided. The value is configured to be approximately equal to the ratio of the amount of change in magnification of the projection objective lens and the amount of change in the imaging plane due to a predetermined factor, and a pressure controller is provided to control the pressure in the air chamber, and the pressure A projection optical device characterized in that by controlling the pressure in the air chamber by a controller, it is possible to simultaneously correct changes in both the magnification of the projection objective lens and the imaging plane caused by the predetermined factors.