JP2009088142A - Exposure apparatus, exposure method, and manufacturing method for device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exposure apparatus capable of more proper distortion adjustment that is carried out by considering response or slit width in stage control. <P>SOLUTION: The exposure apparatus scans a circuit pattern drawn on a form placed on a form stage through a projection optical system to form a light-exposed circuit pattern on a board placed on a board stage. The exposure apparatus has a calculating means that calculates an adjustment rate by linear programming using a dummy variable, based on distortion data and a slit width measured in advance. In an exposure method for scanning the circuit pattern drawn on the form placed on the form stage through the projection optical system to form the light-exposed circuit pattern on the board placed on the board stage, the adjustment rate is calculated by linear programming using the dummy variable, based on the distortion data and the slit width measured in advance. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an exposure apparatus and an exposure method for projecting and exposing an original electronic circuit pattern onto a substrate.

In general, an exposure apparatus 101 (so-called scanner) that performs projection exposure by step-and-scan has a reticle stage 2 (original stage) as shown in FIG.
The reticle stage 2 mounts and holds the reticle 1 on which a circuit pattern is drawn, and scans and moves in a substantially constant direction.
Further, the projection optical system 4 having a plurality of adjustment lenses 3 that can be moved minutely and a wafer 5 that is a substrate onto which the circuit pattern of the reticle 1 is projected and transferred, on a wafer stage 6 (substrate stage), that is, The wafer 5 is held and moved on the substrate stage.
The scanning direction is defined as the Y direction, the optical axis direction is defined as the Z direction, and the direction orthogonal to the scanning direction and the optical axis direction is defined as the X direction.

Here, a means for distortion correction will be described.
In the case of a scanning semiconductor exposure apparatus, the reticle stage 2 and the XY stage 5 usually move synchronously in the Y direction at a movement distance ratio equal to the reduction magnification.
At this time, if the synchronization position in the Y direction is finely adjusted, the distortion magnification in the Y direction can be adjusted as shown in FIG.
If the fine adjustment is made in the X direction, the distortion as shown in FIG. 2B can be adjusted.
Further, if the fine adjustment is made in the θ direction (around the Z axis), the distortion as shown in FIG. 2C can be adjusted.
Furthermore, if a part of the lens of the projection optical system is finely adjusted, the magnification in the X direction as shown in FIG. 2D can be corrected.
Furthermore, if a plurality of lenses are combined and adjusted, distortion proportional to the cubic function or quintic function in the X direction can be adjusted.
2A to 2D show a case where the amount of adjustment during scanning is simple, more complicated distortion can be corrected by changing the amount of adjustment in various ways.

Next, a conventional distortion correction method will be described.
In a collective exposure type semiconductor exposure apparatus, Japanese Patent Laying-Open No. 2003-367886 (Patent Document 1) proposes a correction method for minimizing the maximum absolute value of distortion in a shot.
This conventional example proposes a correction solution that minimizes the maximum absolute value of distortion in a shot by linear programming using a dummy variable.
However, this conventional example does not take into consideration the influence of the response at the time of synchronous scanning and the moving average exposure of the slit width on the distortion.
On the other hand, in the case of a scanning semiconductor exposure apparatus, Japanese Patent Laying-Open No. 2003-273007 (Patent Document 2) proposes a method of inspecting and correcting distortion at each scanning speed.
This conventional example proposes a distortion correction method that takes into account the effects of responsiveness during synchronous scanning and moving average exposure of the slit width.
However, this conventional method needs to inspect the distortion in the shot in advance for each scanning speed, and does not show a solution for minimizing the maximum absolute value of the distortion in the shot.
JP 2003-367886 A JP 2003-273007 A

The distortion correction method of Patent Document 1 does not take into account the influence of the responsiveness at the time of synchronous scanning and the moving average exposure of the slit width on the distortion. Therefore, the correction is not necessarily performed when the scanning speed is high or the slit width is wide. Couldn't do enough.
In addition, since the distortion correction method of Patent Document 2 needs to perform a distortion inspection for each scanning speed, the time required for the inspection process increases, and the obtained correction solution does not minimize the maximum absolute value of the distortion. .
SUMMARY OF THE INVENTION An object of the present invention is to provide an exposure apparatus capable of more appropriate distortion adjustment in consideration of stage control responsiveness or slit width.

  An exposure apparatus of the present invention for solving the above-described problems is an exposure apparatus that scans and exposes a circuit pattern drawn on an original mounted on an original stage onto a substrate mounted on the substrate stage via a projection optical system. In the present invention, an arithmetic means for calculating an adjustment amount by linear programming using a dummy variable is provided based on distortion data and slit width measured in advance.

  Furthermore, the exposure method of the present invention is pre-measured in an exposure method in which a circuit pattern drawn on an original mounted on the original stage is scanned and exposed to a substrate mounted on the substrate stage via a projection optical system. Based on the distortion data and the slit width, the adjustment amount is calculated by linear programming using a dummy variable.

  According to the present invention, it is possible to provide an exposure apparatus capable of more appropriate distortion adjustment in consideration of stage control responsiveness or slit width.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
The exposure apparatus of this embodiment will be described with reference to FIGS.
An exposure apparatus 101 (so-called scanner) that performs projection exposure by step-and-scan has a reticle stage 2 (original stage) as shown in FIG.
The reticle stage 2 scans and moves while mounting and holding the reticle 1 on which a circuit pattern is drawn.
Further, the apparatus includes a projection optical system 4 having a plurality of minutely movable lenses 3, a wafer 5 that is a substrate onto which the circuit pattern of the reticle 1 is projected and transferred, and a wafer stage that is a substrate stage that holds and moves the wafer 5. 6.
The scanning direction is defined as the Y direction, the optical axis direction is defined as the Z direction, and the direction orthogonal to the scanning direction and the optical axis direction is defined as the X direction.
Further, the exposure apparatus 101 includes an illumination device 13 and a control device 111.
The control device 111 has a CPU 106 and a storage device (not shown).
Furthermore, the control device 111 has a calculation unit 104.
The calculation unit 104 acquires distortion data and slit width information measured in advance from the input device 103 or the data reading device 102, and based on this information, at least one of the lens 3, the reticle stage 2, and the wafer stage 6 is acquired. The adjustment amount is calculated.
The calculation unit 104 is a calculation unit that calculates an adjustment amount by linear programming using a dummy variable based on distortion data and a slit width.
The calculation unit 104 calculates the adjustment amount so as to minimize the distortion having the slit width and the adjustment amount as parameters.
Further, this adjustment amount is the driving amount of the reticle stage 2 and the wafer stage 6 or the driving amount of the lens 3 of the projection optical system 4.
For example, a keyboard is used as the input device 103, and the exposure device 101 may be included in the input device 103 and the data reading device 102.

With reference to FIG. 4, the exposure method of the Example of this invention is demonstrated.
First, the slit width in the scanning direction and distortion data measured in advance are input. (Step 201) Of course, the data may be read by a data reading device.
Here, the instructed scanning speed may be further input as the data.
Next, when there is no allowable range (step 202), a solution that minimizes the maximum absolute value of distortion in the scanning exposure apparatus by linear programming using dummy variables is used. (Step 204)
Next, based on the input data, the stage movement profile during scanning, which is the adjustment amount in the translation direction of each of XYZ and the adjustment amount in the rotation direction of each axis of XYZ at the instructed positions of the reticle stage 2 and the wafer stage 6 To decide. (Step 205)
If there is an allowable range (step 202), at least one allowable range of the position, velocity, acceleration and jerk of the reticle stage 2 and wafer stage 6 is input as the data. (Step 203)
Further, the stage is driven according to the stage movement profile to adjust the distortion.

Next, an example in which a lens is driven will be described with reference to FIG.
First, the slit width in the scanning direction and distortion data measured in advance are input. (Step 201) Of course, the data may be read by a data reading device.
Here, the instructed scanning speed may be further input as the data.
Next, when there is no allowable range (step 202), a solution that minimizes the maximum absolute value of distortion in the scanning exposure apparatus by linear programming using dummy variables is used. (Step 204)
Next, a lens adjustment profile during scanning is determined based on the input data.
That is, a lens adjustment profile during scanning, which is an adjustment amount in the translation direction of each of XYZ of the lens 3 of the projection optical system 4 and an adjustment amount in the rotation direction of each axis of the XYZ at the instructed positions of the reticle stage 2 and the wafer stage 6. To decide. (Step 205a)
When there is an allowable range (step 202), at least one allowable range of the adjustment amount of the lens 3 of the projection optical system 4, the speed of the adjustment amount, the acceleration of the adjustment amount, and the jerk of the adjustment amount is input as the data. To do. (Step 203a)
Further, the distortion is adjusted by driving the lens according to the lens adjustment profile.
Further, the stage movement profile and the lens adjustment profile may be recorded and used as a function or table of designated positions of the reticle stage 2 and the wafer stage 6 in some cases.
Further, the stage movement profile and the lens adjustment profile may be recorded and used as a function or table of time based on at least the scanning start time.

In the exposure method of this embodiment, a specific procedure will be described by applying the method for minimizing the maximum absolute value disclosed in Patent Document 1 in the semiconductor exposure apparatus of this embodiment.
First, the scanning direction distance after the start of scanning exposure for one shot on the surface of the wafer 5 is defined as Y _i .
Next, distortion data d ₀ (Y _i ) before correction is obtained from distortion inspection at an arbitrary scanning speed.
Then, the slit width h, the maximum absolute value d _maX of the distortion correction amount allowed during scanning, the allowable stage acceleration value a _maX caused by the distortion correction, and the allowable value s _maX of the jerk absolute value are given.
At this time, the distortion d ₁ (Y _i ) when the stage position correction amount e (Y _i ) at the scanning direction distance Y _i is given is expressed by the equation (1).

ここでq_jは走査方向距離Ｙ_iのパターンが転写可能な位置を通過してからパルス発光されるまでの距離であり、ｎは１つのパターンが転写される時に受けるパルス数である。なお連続露光の場合はｎを大きくして近似すればよい。
なお、走査方向距離がＹ_i+q_jのときの時刻をt（i，j）とする。このとき、走査中のステージ速度v（i，j）、走査中のステージ加速度ａ（i，j）は式（２）〜（３）で表わされる。
なお、式（２）のv０は速度の平均値であり、ディストーションがＹ方向であれば公称の走査速度となり、ディストーションがＸ方向であれば零となる。

Here, q _j is the distance from when the pattern having the scanning direction distance Y _i passes through the transferable position to when the pulse is emitted, and n is the number of pulses received when one pattern is transferred. In the case of continuous exposure, n may be increased and approximated.
It is assumed that the time when the scanning direction distance is Y _i + q _j is t (i, j). At this time, the stage speed v (i, j) during scanning and the stage acceleration a (i, j) during scanning are expressed by equations (2) to (3).
Note that v0 in the equation (2) is an average value of the speed, and is a nominal scanning speed if the distortion is in the Y direction, and is zero if the distortion is in the X direction.

ここで、パルス発光の時間間隔が一定時間τであるとすれば、式（２）〜（３）は式（４）〜（５）に書き直される。

Here, if the time interval of the pulse emission is a fixed time τ, the equations (2) to (3) are rewritten to the equations (4) to (5).

さらに、走査中のステージジャークs（i，j）は式（６）で表わされる。

Further, the stage jerk s (i, j) during the scanning is expressed by the equation (6).

補正によって、ディストーションの最大絶対値を最小化する場合は、線形計画問題において式（７）の目的関数をダミー変数tとし、式（８）〜（９）で補正後のディストーションｄ_１（i，j）の絶対値をt以下にすると、その最大絶対値を最小化する。
また、ステージ制御の応答性を考慮して、無理なステージ位置補正量ｅ（Ｙ_i）とならないようにするには、式（１０）〜（１５）で示すように、加速度ａ（i，j）やジャークs（i，j）、場合によっては速度v（i，j）の上限値を規定する。

When the maximum absolute value of the distortion is minimized by the correction, the objective function of the equation (7) is set as a dummy variable t in the linear programming problem, and the distortion d ₁ (i, i, i) corrected by the equations (8) to (9) is used. If the absolute value of j) is less than or equal to t, the maximum absolute value is minimized.
In order to prevent an unreasonable stage position correction amount e (Y _i ) in consideration of the stage control responsiveness, as shown in equations (10) to (15), acceleration a (i, j ), Jerk s (i, j), and in some cases, an upper limit value for speed v (i, j).

こうして、線形計画問題を解くと、ステージ制御の応答性を考慮した上で、補正後ディストーションの最大絶対値を最小化する、最適なステージ位置補正値ｅ（Ｙ_i）が得られる。
あるいは、補正によって、ディストーションの２乗和を最小化したい場合は、２次計画問題において式（１６）の目的関数を補正後ディストーションｄ_１（Ｙ_i）の２乗和とすればよい。
ステージ制御の応答性を考慮して、無理なステージ位置補正量ｅ（Ｙ_i）とならないようにするには、式（１７）〜（２２） と同様に加速度ａ（i，j）やジャークs（i，j）、場合によっては速度v（i，j）の上限値を式（１７）〜（２２）で規定する。

In this way, when the linear programming problem is solved, the optimum stage position correction value e (Y _i ) that minimizes the maximum absolute value of the corrected distortion in consideration of the response of the stage control can be obtained.
Alternatively, when it is desired to minimize the square sum of distortion by correction, the objective function of Expression (16) in the quadratic programming problem may be the square sum of the corrected distortion d ₁ (Y _i ).
In order to prevent an unreasonable stage position correction amount e (Y _i ) in consideration of the responsiveness of stage control, the acceleration a (i, j) and jerk s (I, j), and in some cases, the upper limit value of the speed v (i, j) is defined by equations (17) to (22).

こうして、２次計画問題を解くと、ステージ制御の応答性を考慮した上で、補正後ディストーションの２乗平均値を最小化する、最適なステージ位置補正値ｅ（Ｙ_i）が得られる。

Thus, when the quadratic programming problem is solved, the optimum stage position correction value e (Y _i ) that minimizes the mean square value of the corrected distortion in consideration of the response of the stage control can be obtained.

The size of shots and slits common to the embodiments of the present invention will be described.
In FIG. 6, a region 7 having a length in the Y direction of 31.2 mm is a shot. When a shot is transferred by scanning exposure, a slit region 8 having a width of 7.7 mm exposed at the same time is transferred while moving in the Y direction on the shot and reaches the region 9. The moving distance between them is 40.7 mm between the slit regions.
Distortions in the shot are set at equal intervals in the Y direction and include 13 evaluation lines 10 with line numbers from −6 to 6 and 9 evaluation lines 11 set at equal intervals in the X direction. Measure with the overlay mark formed at the intersection.
On the other hand, distortion correction is performed by changing the scanning profile of the stage 2 and the adjustment lens 3.
Specifically, the stage 2 and the adjustment lens 3 are adjusted according to the adjustment instruction values of X, Y, and θ recorded at 17 adjustment points obtained by adding four 13 evaluation lines 10 extending in the X direction and four in the Y direction. Scan while.

In the first embodiment, a case where there is a distortion as shown in the map of FIG. 7 is targeted.
The distortion is shifted by 10 nm in the X direction on the evaluation line in the center in the Y direction.
In the conventional example, the stage is scanned with the profile of FIG. 8A so that the center of the slit is shifted by 10 nm at the center of the shot as in the case of distortion.
However, the shift amount of the transfer pattern is as shown in FIG. 8B where the moving profile is moving averaged within the slit width range.
For this reason, the corrected distortion shown in FIG. 9 is not satisfactorily corrected.
On the other hand, in the first embodiment, the linear programming shown in the formulas (1) to (15) is used.
Thereby, it is possible to optimize the corrected distortion in consideration of the moving average corresponding to the slit width.

FIG. 10A shows the stage movement profile of the first embodiment, and FIG. 10B shows the distortion correction amount.
Note that the speed, acceleration, and jerk constraints in Equations (10) to (15) are relaxed, so that the profile in FIG.
However, the distortion before correction shown in FIG. 7 and the distortion correction amount shown in FIG. 10B are in good agreement, and it can be seen that the corrected distortion shown in FIG. 11 is small.
According to the first embodiment, in the exposure apparatus, in-device deviation is often dominant with respect to product performance. However, if linear programming is used, the responsiveness of stage control is improved by using the constraint condition. An optimum stage position correction amount can be set in consideration.
For this reason, it can adjust more accurately compared with the method of the prior art, improving the performance of the exposure apparatus and improving the yield.
In the case of scanning exposure, when the movement path and movement speed of the reticle and wafer being scanned are changed, the distortion in the shot also changes.
In the conventional example, distortion has been corrected using this, but since the averaging is performed by the slit width in the scanning direction and the response of stage movement is limited, fine distortion correction is difficult.
In the first embodiment, in consideration of these influences, a profile that changes the movement path and movement speed of the reticle and the wafer is optimized so that the maximum absolute value of distortion is minimized.

The second embodiment is a case where constraints are given by Equations (12) to (13) such that the acceleration during scanning exposure is 0.02 m / sec ² or less.
FIG. 12 shows a stage movement profile of the second embodiment.
The profile shown in FIG. 12 is moderately changed due to the acceleration constraint using the equations (12) to (13), but the corrected distortion shown in FIG. 13 is shown in FIG. It is larger than the result of Example 1.

In Example 3, the case where there is distortion as shown in the map of FIG. 14 is targeted.
In the distortion, the magnification in the X direction is large on the evaluation line at the center in the Y direction.
In the conventional example, similarly to the distortion, the projection magnification is manipulated with the profile of FIG. 15 so that the both ends of the X direction are enlarged by 10 nm at the center of the shot.
However, since the shift amount of the transfer pattern is a moving average of the movement profile in the range of the slit width, the corrected distortion shown in FIG. 16 cannot be satisfactorily corrected.
Therefore, in the third embodiment, it is possible to minimize the distortion after correction in consideration of the moving average corresponding to the slit width by the linear programming shown in the equations (1) to (15).

FIG. 17 shows a stage movement profile of the first embodiment.
Note that the speed, acceleration, and jerk constraints in Equations (10) to (15) are relaxed, so that the profile in FIG. 17 changes rapidly.
However, the corrected distortion shown in FIG. 18 is much smaller than the uncorrected distortion shown in FIG.

Next, an embodiment of a device manufacturing method using the above-described exposure apparatus will be described with reference to FIGS.
FIG. 19 is a flowchart for explaining how to fabricate devices (ie, semiconductor chips such as IC and LSI, LCDs, CCDs, and the like). Here, a semiconductor chip manufacturing method will be described as an example.
The method comprises the steps of exposing a wafer using an exposure apparatus and developing the wafer, and specifically comprises the following steps.
In step 1 (circuit design), a semiconductor device circuit is designed.
In step 2 (mask production), a mask is produced based on the designed circuit pattern.
In step 3 (wafer manufacture), a wafer is manufactured using a material such as silicon.
Step 4 (wafer process) is called a pre-process, and an actual circuit is formed on the wafer using the mask and the wafer by the above exposure apparatus using the lithography technique.
Step 5 (assembly) is referred to as a post-process, and is a process for forming a semiconductor chip using the wafer produced in step 4, and an assembly process such as an assembly process (dicing, bonding), a packaging process (chip encapsulation), or the like. including.
In step 6 (inspection), the semiconductor device manufactured in step 5 undergoes inspections such as an operation confirmation test and a durability test.
Through these steps, a semiconductor device is completed and shipped (step 7).

FIG. 20 is a detailed flowchart of the wafer process in Step 4.
In step 11 (oxidation), the surface of the wafer is oxidized.
In step 12 (CVD), an insulating film is formed on the surface of the wafer.
In step 13 (electrode formation), an electrode is formed on the wafer.
In step 14 (ion implantation), ions are implanted into the wafer.
In step 15 (resist process), a photosensitive agent is applied to the wafer.
Step 16 (exposure) uses the exposure apparatus to expose a circuit pattern on the mask onto the wafer.
In step 17 (development), the exposed wafer is developed.
In step 18 (etching), portions other than the developed resist image are removed.
In step 19 (resist stripping), the resist that has become unnecessary after the etching is removed.
By repeatedly performing these steps, multiple circuit patterns are formed on the wafer.

It is a schematic block diagram of the scanning semiconductor exposure apparatus with which the exposure method of this invention is applied. It is explanatory drawing of the typical example of distortion correction. It is a block block diagram of the exposure apparatus of FIG. It is explanatory drawing of the exposure method of the Example of this invention. It is explanatory drawing of the exposure method of the Example of this invention. It is explanatory drawing of the measurement and correction | amendment of distortion. It is explanatory drawing of the example (X shift) of the distortion before correction | amendment. It is explanatory drawing of the correction | amendment profile and distortion correction part (X shift) of the exposure method of a prior art example. It is explanatory drawing of the distortion (X shift) after correction | amendment of the exposure method of a prior art example. It is explanatory drawing of the correction | amendment profile (X shift and no restrictions) of the exposure method of the Example of this invention. It is explanatory drawing after distortion (X shift and no restrictions) of the exposure method of the Example of this invention. It is explanatory drawing of the correction profile (with X shift and acceleration restrictions) of the exposure method of the Example of this invention. It is explanatory drawing of the distortion after correction | amendment (with X shift and acceleration restrictions) of the exposure method of the Example of this invention. It is explanatory drawing of the example (X magnification) of the distortion before correction | amendment. It is explanatory drawing of the correction profile (X magnification) of the exposure method of a prior art example. It is explanatory drawing of the distortion (X magnification) after correction | amendment of the exposure method of a prior art example. It is explanatory drawing of the correction profile (X magnification and no restrictions) of the exposure method of this invention. It is explanatory drawing after correction | amendment (X magnification and no restrictions) of the exposure method of this invention. It is a flowchart for demonstrating manufacture of the device using an exposure apparatus. FIG. 20 is a detailed flowchart of the wafer process in Step 4 of the flowchart shown in FIG. 19. FIG.

Explanation of symbols

1: Reticle 2: Reticle stage 3: Adjustment lens 4: Projection optical system 5: Wafer 6: Wafer stage 7: Shot 8: Slit area (before scanning)
9: Slit area (after scanning)
10: Measurement row 11: Measurement column 12: Correction profile during scanning 101: Exposure apparatus

Claims (7)

In an exposure apparatus that scans and exposes a circuit pattern drawn on an original mounted on an original stage onto a substrate mounted on the substrate stage via a projection optical system,
An exposure apparatus comprising: an arithmetic unit that calculates an adjustment amount by linear programming using a dummy variable based on distortion data and slit width measured in advance.   2. The exposure apparatus according to claim 1, wherein the calculation means calculates the adjustment amount so as to minimize the distortion having the slit width and the adjustment amount as parameters.   The exposure apparatus according to claim 1, wherein the adjustment amount is a driving amount of the original stage and the substrate stage or a driving amount of a lens of the projection optical system. In an exposure method in which a circuit pattern drawn on an original plate mounted on the original plate stage is scanned and exposed to a substrate mounted on the substrate stage via a projection optical system,
An exposure method, wherein an adjustment amount is calculated by linear programming using a dummy variable based on distortion data and slit width measured in advance.   5. The exposure method according to claim 4, wherein the calculation means calculates the adjustment amount so as to minimize the distortion having the slit width and the adjustment amount as parameters.   6. The exposure method according to claim 4, wherein the adjustment amount is a driving amount of the original stage and the substrate stage or a driving amount of a lens of the projection optical system. A step of exposing the wafer using the exposure apparatus according to claim 1;
And a step of developing the wafer.

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