JP2008140991A - Information processing apparatus and exposure apparatus - Google Patents

Abstract

A sample shot set that satisfies requirements for which measurement accuracy and measurement time are set is determined.
An information processing apparatus for determining a sample shot set to be measured in an apparatus that exposes each of a plurality of shots formed on a substrate, and includes an input / output unit and a processing unit. . The processing unit generates a plurality of sample shot sets from the plurality of shots based on the information regarding the arrangement of the plurality of shots input from the input / output unit. The processing unit also determines a sample shot set that satisfies a requirement in which measurement accuracy and measurement time are set from a plurality of sample shot sets.
[Selection] Figure 3

Description

  The present invention relates to an information processing apparatus that determines a sample shot set to be measured in an exposure apparatus, for example.

  Conventionally, the layout of each shot positioned on a substrate exposed by a semiconductor exposure apparatus can be created in consideration of process conditions such as the size of the substrate, the reticle pattern region, the shot size, and the chip size. All operations in the exposure apparatus such as alignment, focus leveling, and exposure are performed based on this layout.

  For example, when overlay exposure is performed on each shot area of the substrate, alignment between the reticle pattern and the chip pattern in each shot area is performed. Conventionally, global alignment has been used as an alignment method because of the balance between productivity and measurement accuracy. The global alignment is a method for obtaining an arrangement position of shots in the substrate from the measurement values of several shots (sample shots) in the substrate, and performing alignment of all shots in the substrate based on this. Here, a plurality of sample shot sets used for alignment are hereinafter referred to as “sample shot sets”. The exposure apparatus has one dedicated sample shot set automatic selection means for selecting a sample shot set that is recommended and optimal for alignment and focus leveling.

  An example of a conventional algorithm for selecting a sample shot set that has been optimized is that the sample shots are arranged so as to be distributed as far as possible except for the outer periphery of the substrate so that the circumference of the sample shots is substantially symmetrically distributed from the center of the substrate. It is to be selected. According to this selection algorithm, it is assumed that alignment is performed using a sample shot set automatic selection unit that has been conventionally used. As shown in FIG. 1a, consider a 26 × 33 mm exposure size layout for a substrate W1 of φ8 inches (200 mm). If a shot around the periphery of the substrate is a sample shot, an error is likely to occur in the measurement value used for alignment due to the influence of film thickness variation of the photosensitive material (resist) on the substrate W1, distortion of the substrate W1, and the like. Therefore, as described above, the condition of “excluding the periphery outside the substrate” is added to the selection of the sample shot set, and the sample shots S1 to S4 are arranged near the center of the substrate W1. When global alignment is performed using the sample shot set arranged in this way, the span between sample shots measured in the vicinity of the center of the substrate W1 is short. For this reason, the accuracy of measurement values such as the magnification and rotation of the shot arrangement in the substrate W1 is degraded.

  However, in recent years, in the case of a φ8-inch substrate, there are few variations in resist film thickness on the substrate, distortion of the substrate, and the like, and there are not many situations in which shots around the substrate can be used as sample shots. In such a situation, as shown in FIGS. 1b and 1c, the operator can manually select shots around the substrate as sample shots to increase the sample shot span and reduce the measurement error. .

Semiconductor manufacturing using a φ12 inch (300 mm) substrate has also shown an increasing trend in recent years. Considering an exposure size layout of 26 × 33 mm for a φ12 inch (300 mm) substrate, as shown in FIG. 1d, the sample shot span increases on the substrate W2. However, since the substrate W2 having a diameter of 12 inches (300 mm) is large, there are not a few situations where the influence of film thickness variation of the photosensitive material on the substrate W2, distortion of the substrate W2, and the like cannot be ignored. For this reason, when shots around the substrate W2 are used as sample shots for alignment and focus leveling, errors in measurement values tend to occur. If automatic selection means that uses shots around the outside of the substrate W2 of φ12 inch (300 mm) as a sample shot for alignment is used, the accuracy of measurement values such as magnification and rotation of the shot arrangement in the substrate W2 will be deteriorated as usual. Occurs. Therefore, it is desirable not to select shots around the outside of the substrate as sample shots for alignment and focus leveling as in the past for a substrate W2 of φ12 inches (300 mm).
JP 2001-118769 A

  In the prior art, the sample shot set selection algorithm basically focused on good measurement accuracy, and therefore, sample shots on the outer periphery of the substrate were selected as much as possible. However, if a sample shot on the outer periphery of the substrate is selected, the moving distance during alignment measurement increases. Therefore, there is a problem that a sample shot that gives an accuracy higher than that required by the process is selected, and the throughput decreases accordingly.

  An exemplary object of the present invention is to determine a sample shot set that satisfies requirements for which measurement accuracy and measurement time are set in view of the above-described problems.

  The present invention is an information processing apparatus that determines a sample shot set to be measured in an apparatus that exposes each of a plurality of shots formed on a substrate, and includes an input / output unit and a plurality of input from the input / output unit Based on information on the arrangement of shots, a plurality of sample shot sets are generated from a plurality of shots, and a sample shot set satisfying a requirement in which measurement accuracy and measurement time are set is determined from the plurality of sample shot sets. And a processing unit.

  According to the embodiment of the present invention, it is preferable that the processing unit uses a time for moving the substrate to perform measurement on the sample shot set as the measurement time.

  According to the embodiment of the present invention, it is preferable that the processing unit changes the plurality of generated sample shot sets using an optimization method. The optimization method preferably includes a genetic algorithm.

  According to the embodiment of the present invention, the processing unit selects a moving order that minimizes the moving time of the substrate for each sample shot set in at least one of generating the sample shot set and changing the sample shot set, In addition, it is preferable to use the movement time of the substrate calculated based on the movement order as the measurement time.

  According to the present invention, for example, it is possible to determine a sample shot set that satisfies a requirement in which measurement accuracy and measurement time are set.

In the present invention, an evaluation value S shown in Equation (1) is defined for a sample shot set. S = (k _a · S _a ) + (k _t · S _t ) (1)
Where S _a is an evaluation value indicating the measurement accuracy, the S _t is an evaluation value indicating a measurement time. S _t can be said that an evaluation value indicating a throughput. k _a, k _t is the weighting factor for S _a, S _t respectively.

  The larger the evaluation value S is, the more the sample shot set is optimized in accuracy and measurement time.

Sa is expressed as Equation (2).
S _a = E (0 ≦ E ≦ E _limit )
S _a = −E + k _E · E _limit (E> E _limit ) (2)
Here, E is a mathematical expression of the spread of the sample shot, and k _E is a weight constant for E _limit .

  E is expressed as Equation (3).

(3)
x, y, X, Y, and Z are expressed as Equation (4) where the position coordinate of the i-th sample shot is (sx _i , sy _i ), the number of sample shots is n, and the substrate radius is w. The

(4)
E _limit is expressed as Equation (5) using the required accuracy D required by the process.
E _limit = k _D・ D + C _D・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ （5）
Here, k _D and _CD are constants.

Evaluation value S _t indicating the measured time, each sample shot measured from the measurement start point, a movement time when reaching to the measurement end point is represented by the equation (6).

(6)
Here, V _max is the maximum speed of the device stage, and A is the acceleration of the device stage. stroke _S is the distance from the measurement start position to the first measurement sample shot. stroke _i is the distance to the (i-1) th sample shot and the (i) th sample shot. stroke _E is the distance from the measurement end position to the final measurement sample shot.

  Next, the sample shot set having the maximum S is searched using the evaluation value S of the sample shot set. However, the number of sample shot sets is very large considering the number of sample shots. Therefore, an optimal sample shot set is searched by using an algorithm generally called an optimization method (linear programming, dynamic programming, genetic algorithm, annealing method). The optimum sample shot set obtained by searching is determined as a sample shot set in measurement. In the process of searching for an optimal sample shot set, a movement order that minimizes the measurement time, that is, an optimal movement sequence is determined.

  In the present invention, an evaluation value in consideration of measurement measurement accuracy and an evaluation value in consideration of measurement time are used as the evaluation values of the sample shot set. Thereby, a sample shot set that satisfies the required accuracy and has the minimum measurement time, that is, the maximum throughput can be selected.

Hereinafter, embodiments of the present invention will be described.
[Embodiment for determining sample shot set]
1a to 1d are plan views showing layouts of shots exposed in a scanning semiconductor exposure apparatus.

  FIG. 1c shows a shot layout when a φ8 inch substrate is exposed. The screen size of one exposure is 22 × 22 mm in a semiconductor exposure apparatus (stepper) for performing static exposure, whereas it is as large as 26 × 33 mm in a scanning semiconductor exposure apparatus. In FIG. 1c, each of S1 to S4 (four shots) is a sample shot for alignment or global leveling in the exposure screen size layout of the scanning semiconductor exposure apparatus. The set of sample shots S1 to S4 constitutes one sample shot set.

  When selecting a sample shot set in this layout, conventionally, with the emphasis on measurement accuracy, as shown in FIG. 1b, the outermost shot in which the span between shots is large is selected as the sample shot. However, in the present invention, a sample shot set in which the measurement time is optimized is selected according to the required measurement accuracy.

  FIG. 3 is a flowchart showing an example of the sample shot set selection operation in the present embodiment. FIG. 2 is a block diagram showing a functional configuration of a system for performing this selection operation. In this embodiment, it is assumed that a sample shot set on the substrate W1 as shown in FIG. 1c is selected. In addition, Formula (1) is used as the sample shot set evaluation value, and a genetic algorithm is used as an optimization method used when changing at least a part of the sample shot set.

  When the sample shot set selection operation is started, first, in step 301, the processing apparatus (processing section) 2 stores the semiconductor process information 31 input by the operator by operating the input / output apparatus (input / output section) 1 in the storage section 3. Remember. The processing apparatus 2 and the input / output apparatus 1 constitute an information processing apparatus that determines a sample shot to be measured in the exposure apparatus. The semiconductor process information 31 includes information regarding the arrangement of a plurality of shots. The semiconductor process information 31 includes information on the substrate W1 diameter dW, the invalid exposure area iW, the X direction step size XS, the Y direction step size YS, the required measurement accuracy D, and the like as shown in FIG.

When the semiconductor process information 31 is input in step 301, the processing apparatus 2 starts an operation of automatically selecting an optimal sample shot set from step 302. The operation of automatically generating a sample shot set composed of at least two shots among a plurality of shots is executed by the generation unit 4 of the processing device 2. The generation unit 4 generates an optimal sample shot set from the semiconductor process information 31 and the exposure apparatus information 32 by using the mathematical algorithm (1) and a genetic algorithm used as an optimization method. The exposure apparatus information 32 is previously input to the processing apparatus 2 from an exposure apparatus information input unit (not shown) and stored in the storage unit 3. Exposure device information 32 is composed of information regarding constants such stage the maximum speed Vmax, the stage acceleration _{A, ka, k t, k} e, etc. k _d, C _d as shown in FIG.

  In step 302, the generation unit 4 of the processing device 2 generates a plurality of sample shot sets that are initial individuals in the genetic algorithm. The generation unit 4 generates the generated individuals so that the generated individuals are distributed in various ways. In step 303, the generation unit 4 improves the generated initial individual. The improvement of the initial individual is to optimize the movement sequence information portion in the individual representation of the sample shot set shown in FIG. 5, that is, to obtain the movement order that minimizes the measurement time. The improvement of the initial individual increases the convergence speed of the solution during the search.

  In step 304, the generation unit 4 calculates each evaluation value S of the improved initial solid. Steps 302 to 304 correspond to an initial individual generation part in a general genetic algorithm. From step 305, the changing unit 5 of the control device repeats the generation change in the general genetic algorithm, and changes at least some of the plurality of sample shot sets generated by the generating unit 4.

  In step 305, the changing unit 5 performs the selection of individuals, and selects and deletes individuals (sample shot sets) whose evaluation value S is less than a certain value.

  After step 306, the change unit 5 generates a new individual with the surviving individual as the parent in order to supplement the individual deleted by the kite. In step 306, the changing unit 5 selects a plurality of combinations of parent individuals for generating new individuals. Using roulette rules so that only some individuals are not biased, a combination of parent individuals is selected so that all living individuals can play a role as parent individuals as much as possible.

  In step 307, the changing unit 5 performs crossover with the combination of the parent individuals selected in step 306 to generate a new individual.

  In step 308, the changing unit 5 partially modifies the genetic information for some individuals among the new individuals generated in step 307 to cause mutation. This is in order not to fall into a local solution in the search for the final sample shot set.

  In step 309, the changing unit 5 improves the individual itself in the same manner as in step 303 for the new individual generated in step 307.

  In step 310, the changing unit 5 calculates an evaluation value S of each improved solid.

  In step 311, the changing unit 5 performs statistical processing of the evaluation values S of the individuals that are currently alive (individuals that have not been deceived in step 305 and individuals that are newly generated in step 307). If the variation in S is sufficiently small, it is assumed that the individual group is excellent, and the process proceeds to Step 312. If the variation in S is not sufficiently small, steps 305 to 310 are repeated again to improve the individual evaluation value S (optimization of movement sequence information).

  In step 312, the determination unit 6 determines the sample shot set to be used as the sample shot set to be used for the measurement of the most excellent individual, that is, the evaluation value S of the individual, which is the best among the sample shot set individuals.

  In step 313, the determined optimum sample shot set is reflected in the measurement of the exposure apparatus.

  FIG. 6 is a result example when a sample shot set is selected using the present embodiment. FIG. 6a shows the result of optimization with the required value D1 of measurement accuracy, and FIG. 6b shows the result of optimization with another required value D2 of measurement accuracy. D1 and D2 are more demanding values than D1.

  Compared to the sample shot set of FIG. 1c showing the prior art, the sample shot set of FIG. 6a has the sample shots arranged slightly from the inner periphery, and the throughput is slightly improved. In the sample shot set of FIG. 6b, since the required value of measurement accuracy is not so strict, the number of sample shots is reduced compared to the conventional example. Therefore, the sample shot set of FIG. 6b has a significant improvement in throughput as compared to the sample shot set of FIGS. 1c and 6a because the movement sequence is optimized.

  In this embodiment, a genetic algorithm is used as an optimization method for the sample shot set. However, the present invention can use other optimization methods other than the genetic algorithm, such as linear programming, dynamic programming, and annealing, as a sample shot set optimization method.

  In the present embodiment, the sample shot set is selected on the exposure apparatus when determining the process recipe before exposure. However, according to the present invention, a sample shot can be selected in advance in an external apparatus outside the exposure apparatus, and the determination result can be reflected on the exposure apparatus online.

In this embodiment, a sample shot set for measurement is selected. However, if there are other processes that require the selection of the sample shot set, the present invention can also be applied to the selection of the sample shot set in that case.
[Embodiment of exposure apparatus]
As shown in FIG. 8, the exposure apparatus includes an illumination device 101, a reticle stage 102 on which a reticle is mounted, a projection optical system 103, and a substrate stage 104 on which a substrate is mounted. The exposure apparatus projects and exposes the circuit pattern formed on the reticle onto the substrate, and is preferably a step-and-scan projection exposure system.

  The illumination device 101 illuminates a reticle on which a circuit pattern is formed, and includes a light source unit and an illumination optical system. The light source unit uses, for example, a laser as a light source. As the laser, an ArF excimer laser with a wavelength of about 193 nm, a KrF excimer laser with a wavelength of about 248 nm, an F2 excimer laser with a wavelength of about 153 nm, or the like can be used. The type of laser is not limited to an excimer laser, for example, a YAG laser may be used, and the number of lasers is not limited. When a laser is used as the light source, it is preferable to use a light beam shaping optical system that shapes the parallel light beam from the laser light source into a desired beam shape and an incoherent optical system that makes the coherent laser light beam incoherent. The light source that can be used for the light source unit is not limited to the laser, and one or a plurality of lamps such as a mercury lamp and a xenon lamp can be used.

  The illumination optical system is an optical system that illuminates the mask, and includes a lens, a mirror, a light integrator, a diaphragm, and the like.

  As the projection optical system 103, an optical system including only a plurality of lens elements, an optical system having a plurality of lens elements and at least one concave mirror or diffractive optical element, an all-mirror optical system, and the like can be used.

  The reticle stage 102 and the substrate stage 104 can be moved by, for example, a linear motor. In the case of the step-and-scan projection exposure method, each stage moves in synchronization. Further, in order to align the reticle pattern on the substrate, an actuator is separately provided on at least one of the substrate stage and the reticle stage.

Such an exposure apparatus can be used for manufacturing a semiconductor device such as a semiconductor integrated circuit or a device on which a fine pattern such as a micromachine or a thin film magnetic head is formed.
[Device Manufacturing Embodiment]
Next, an embodiment of a device manufacturing method using the above-described exposure apparatus will be described with reference to FIGS. FIG. 9 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.

  In step S1 (circuit design), a semiconductor device circuit is designed. In step S2 (mask production), a mask is produced based on the designed circuit pattern. In step S3 (substrate manufacture), a substrate is manufactured using a material such as silicon. Step S4 (substrate process) is called a pre-process, and an actual circuit is formed on the substrate using the mask and the substrate by the above exposure apparatus using the lithography technique. Step S5 (assembly) is called a post-process, and is a process for forming a semiconductor chip using the substrate manufactured in step S4. This process includes assembly processes such as an assembly process (dicing and bonding) and a packaging process (chip encapsulation). In step S6 (inspection), inspections such as an operation check test and a durability test of the semiconductor device manufactured in step S5 are performed. Through these steps, the semiconductor device is completed and shipped (step S7).

  FIG. 10 is a detailed flowchart of the substrate process in Step 4. In step S11 (oxidation), the surface of the substrate is oxidized. In step S12 (CVD), an insulating film is formed on the surface of the substrate. In step S13 (electrode formation), an electrode is formed on the substrate by vapor deposition. In step S14 (ion implantation), ions are implanted into the substrate. In step S15 (resist process), a photosensitive agent is applied to the substrate. In step S16 (exposure), the circuit pattern of the mask is exposed on the substrate by the exposure apparatus. The sample shot set used for measurement during the exposure process is determined by the method shown in [Embodiment of Sample Shot Set]. In step S17 (development), the exposed substrate is developed. In step S18 (etching), portions other than the developed resist image are removed. In step S19 (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 substrate.

It is a top view which illustrates the conventional sample shot set and the sample shot set in the embodiment of the present invention. It is a top view which illustrates the conventional sample shot set and the sample shot set in the embodiment of the present invention. It is a top view which illustrates the conventional sample shot set and the sample shot set in the embodiment of the present invention. It is a top view which illustrates the conventional sample shot set and the sample shot set in the embodiment of the present invention. It is a block diagram which shows the functional block diagram of the system which selects the sample shot set in embodiment of this invention. It is a flowchart which shows the operation | movement of selection of the sample shot set in this embodiment of this invention, and the optimization of the movement sequence. It is a figure which shows the specific example of semiconductor process information. The sample shot set in embodiment of this invention is shown with the individual expression of the genetic algorithm. It is a figure which shows the result of having selected the sample shot set in embodiment of this invention. It is a figure which shows the result of having selected the sample shot set in embodiment of this invention. It is a figure which shows the specific example of exposure apparatus information. It is a figure for demonstrating exposure apparatus. It is a flowchart for demonstrating manufacture of the device using an exposure apparatus. 10 is a detailed flowchart of the substrate process in Step 4 of FIG. 9.

Explanation of symbols

S1 to S4: Sample shot SHOT: Shot W1: φ8 inch substrate W2: φ12 inch substrate 1: Input / output device 2: Processing device 3: Storage unit 31: Semiconductor process information 32: Exposure device information 4: Generation unit 5: Selection unit 501: illumination system unit 502: reticle stage 503: projection optical system 504: substrate stage 505: exposure apparatus main body

Claims (7)

An information processing apparatus for determining a sample shot set to be measured in an apparatus that exposes each of a plurality of shots formed on a substrate,
An input / output unit;
Based on the information regarding the arrangement of the plurality of shots input from the input / output unit, a plurality of sample shot sets are generated from the plurality of shots, and measurement accuracy and measurement time are determined from the plurality of sample shot sets. An information processing apparatus comprising: a processing unit that determines a sample shot set that satisfies a set request.   The information processing apparatus according to claim 1, wherein the processing unit uses, as the measurement time, a time for moving the substrate in order to perform measurement on a sample shot set.   The information processing apparatus according to claim 1, wherein the processing unit changes the plurality of generated sample shot sets using an optimization method.   The information processing apparatus according to claim 3, wherein the optimization method includes a genetic algorithm.   The processing unit selects a movement order that minimizes the movement time of the substrate for each sample shot set in at least one of generating a sample shot set and changing the sample shot set, and based on the movement order 5. The information processing apparatus according to claim 3, wherein the movement time of the substrate calculated as described above is used as the measurement time.   An exposure apparatus that performs measurement on a sample shot set determined in the information processing apparatus according to claim 1. Exposing the substrate using the exposure apparatus according to claim 6;
And a step of developing the exposed substrate.

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