JP2008218594A - Exposure method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a processing method for a semiconductor which requires no special apparatus when ID information for identifying a semiconductor wafer is recorded or read and the read processing of the ID information has no influence on the throughput. <P>SOLUTION: When the negative pattern is superposed on a plurality of shot positions on the wafer and exposure is carried out, mark positions at a plurality of specific shot positions among the plurality of shot positions are measured, and correction amounts are computed based on the statistical treatment of the measured values to carry out the alignment between the negative pattern and the wafer. When the reference layer used for alignment upon superposition exposure is subjected to exposure, the exposure is carried out by displacing the plurality of shot positions including the alignment marks by a minute amount as the amount corresponding to the information for identifying the wafer. The wafer identification information is acquired by detecting the displacement amount in the reference layer when the correction amount is determined through wafer alignment treatment in the exposure process for forming the patterns of the first hierarchy and the subsequent on the wafer, and by being based on the detected result. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an exposure method for exposing a plurality of shots on a substrate, and an identification method for identifying an exposed substrate.

Usually, in a series of manufacturing processes of a semiconductor device, there are hundreds of processes that require management of manufacturing conditions and the like. In each manufacturing process, it is necessary to set various and strict manufacturing conditions for each process. It is widely known that management of these manufacturing processes is performed using ID information consisting of alphanumeric character strings marked on the surface of a semiconductor wafer by a laser marking method. In addition, the marking of ID information may use the photolithographic method (patent document 1). In addition, there is a technique in which a barcode is arranged instead of a character string consisting of alphanumeric characters (Patent Document 2).
Japanese Patent Laid-Open No. 10-261559 JP-A-4-235893

  By the way, the ID information composed of alphanumeric character strings must have an area necessary on the surface of the semiconductor wafer to be configured in a place suitable for reading. In particular, when configuring ID information on the surface of a semiconductor wafer, it is necessary to prepare a margin for configuring ID information having a size that can be read at a position where the ID information can be easily read outside the chip generation region. Therefore, there is a problem that a very large restriction is imposed on the layout creation of shots arranged on a semiconductor wafer. Further, since the semiconductor wafer is exposed to high temperature heating and etching many times, there is a problem that the ID information on the surface of the semiconductor wafer is easily soiled and difficult to read.

Furthermore, an ID information reading device composed of alphanumeric character strings by a CCD camera or the like needs to read in a state where there is no shielding object between the character information to be read. For this reason, there exists a problem that the installation location of a reader is restricted. In addition, a semiconductor wafer to which ID information consisting of alphanumeric character strings is added must be fixed at a reading position for a specific time or passed at a specific reading speed, which affects the throughput of the semiconductor manufacturing apparatus. There is.
The above-described problem relating to ID information consisting of alphanumeric character strings also occurs in the case of ID information using a barcode and a barcode reader.
An object of the present invention is to provide a novel technique for performing at least one of providing identification information of a substrate to the substrate and obtaining identification information of the substrate from the substrate.

  In order to solve the above-described problems, an exposure method of the present invention is an exposure method for exposing a plurality of shots on a substrate, and includes a first generation step for generating a reference first shot layout, A second generation step of generating a second shot layout indicating the identification information by moving at least one specific shot included in the first shot layout by an amount of movement corresponding to the identification information; An exposure step for exposing the substrate in accordance with a second shot layout.

  ADVANTAGE OF THE INVENTION According to this invention, the novel technique which performs at least one of the provision of the identification information of this board | substrate to a board | substrate, and acquisition of the identification information of this board | substrate from a board | substrate can be provided.

  As a preferred embodiment of the present invention, an exposure method for exposing a plurality of shots on a semiconductor wafer (substrate) will be described. First, a reference first shot layout is generated (first generation step). Next, the second shot layout indicating the identification information is generated by moving at least one specific shot included in the first shot layout by a movement amount corresponding to the identification information of the wafer (second Generation step). Then, the wafer is exposed according to the second shot layout (exposure step).

  Here, the first shot layout is the same as in the conventional example, for example, a shot layout in which a plurality of shots are regularly arranged in the X and Y directions. For example, in FIG. 1, a shot indicated by hatching is a specific shot (hereinafter referred to as a marking shot). The arrangement of shots indicated by a solid line including this marking shot indicates the second shot layout. Further, the state where the marking shot is returned to the position of the dotted line before being moved by the movement amount according to the identification information shows the first shot layout.

  When the substrate is exposed again after the exposure step, the amount of misregistration of the marks arranged on each of a plurality of shots excluding the marking shot (hereinafter referred to as alignment shot) based on the first shot layout is used. Measure (measurement step). Then, a coordinate function in the first shot layout that approximates the measured positional deviation amount is calculated as the first function (calculation step). Here, the movement amount of the marking shot is set to be sufficiently larger than the error of the positional deviation amount calculated by the calculated first function. Thereby, the movement amount of the marking shot can be clearly distinguished from the positional deviation of each shot due to a process error.

For example, in the case of a linear function, the first function is represented by the following equation when the measured displacement amount is (Δx, Δy) and the coordinates in the first shot layout are (x, y). .
Δ _x = β _x x−θ _y y + s _x
Δy = θ _x x + β _y y + s _y
Here, β _x , β _y , θ _x , and θ _y are coefficients indicating x-direction wafer magnification, y-direction wafer magnification, wafer x-axis rotation, and wafer y-axis rotation, respectively, and s _x and s _y are x-direction wafers. It is a constant (zeroth order coefficient) indicating the shift and the wafer shift in the y direction.

Further, the first function can include a zero-order function of coordinates in the first shot layout. The zero-order function is a function such as the following expression, for example.
Δ _x = s _x
Δ _y = s _y

The substrate exposed according to the above exposure method can be identified as follows.
First, with reference to the first shot layout, the amount of misalignment of marks arranged in at least one marking shot and a plurality of alignment shots is measured (measuring step). The measurement is performed by calculating a coordinate function in the first shot layout as a first function, which approximates the amount of mark misalignment measured for a plurality of alignment shots (first calculation step). ). Next, the amount of positional deviation of the mark placed on the marking shot is calculated according to the calculated first function (calculation step). With respect to the mark placed on the marking shot, the movement amount is specified based on the difference between the measured positional deviation amount and the calculated positional deviation amount (identification step). The substrate is identified based on the specified movement amount (identification step).

The substrate identified according to the above identification method can be exposed as follows.
First, with respect to the mark placed on the marking shot, the measured displacement amount is corrected by the movement amount (correction step). A coordinate function in the first shot layout that approximates the corrected misalignment amount and the mark misalignment amount measured for the plurality of alignment shots is calculated as a second function (second calculation). Step). The alignment shot is exposed according to the amount of displacement calculated by the calculated second function, and marking is performed according to the amount of movement and the amount of displacement calculated by the calculated second function. The shot is exposed (exposure step).

  Each of the above-described methods can be created as a computer-executable program. For example, a CPU that controls the operation of an exposure apparatus that exposes a plurality of shots on the substrate can perform the above-described methods by operating according to the program.

An example of the operation of the exposure apparatus that operates according to the above program will be described.
When the reticle (original) pattern is overlaid and exposed at a plurality of shot positions on a semiconductor wafer (substrate to be exposed), positions of alignment marks at a plurality of specific shot positions among the plurality of shot positions are measured. Measurement is performed using an alignment sensor. Further, the correction amount is calculated from the statistical processing of the measured value, and the original plate and the semiconductor wafer are aligned. When exposing a reference layer used for alignment during overlay exposure, at least one shot position (partial shot position) including an alignment mark is used as an amount corresponding to information for identifying a semiconductor wafer. The exposure is shifted by a minute amount. In addition, the information for identifying the semiconductor wafer is used when the correction amount is obtained in the alignment process of the semiconductor wafer in the exposure process of the photolithography process for forming the pattern on the first layer or later formed on the semiconductor wafer. Detect and obtain the amount of shift in. That is, a shot position and a deviation amount thereof deviated from a specific shot layout serving as a reference are calculated from the position measurement value of the alignment mark, and information for identifying the semiconductor wafer is read from the calculated value.

Since the semiconductor wafer identification information added to the semiconductor wafer can be easily read by the alignment sensor of the semiconductor exposure apparatus, a dedicated reading apparatus such as an alphanumeric character string or bar code ID information is provided in the semiconductor exposure apparatus. No need to prepare for. In addition, since this semiconductor wafer identification information uses alignment marks for alignment processing at the time of overlay exposure, it may be difficult to read even when exposed to high temperature heat treatment or etching. No. Furthermore, since the reading process of the semiconductor wafer identification information is performed simultaneously with the alignment process at the time of overlay exposure, there is no problem of affecting the throughput of the semiconductor exposure apparatus.
Further, when the present invention is applied to a reference wafer for confirming the characteristics of a semiconductor exposure apparatus, the semiconductor exposure apparatus can automatically identify and perform processing only by setting the semiconductor wafer in the semiconductor exposure apparatus. .

Embodiments of the present invention will be described below with reference to the drawings.
[Example 1]
FIG. 4 shows the arrangement of an exposure apparatus according to an embodiment of the present invention. In FIG. 4, R is a reticle, W is a wafer, 1 is a projection lens (projection optical system), and S is an alignment optical system. Further, as components of the alignment optical system S, 2 is an illumination device for alignment, 3 is a beam splitter, 4 is an alignment scope, and 5 is an imaging device.

  Illumination light from the alignment illumination device 2 illuminates the mark on the wafer W via the beam splitter 3 and the projection lens 1, and an image of the mark is captured via the projection lens 1, the beam splitter 3, and the alignment scope 4. An image is formed on the device 5. The A / D conversion device 6 converts an imaging signal from the imaging device 5 into a digital signal. This digital signal is integrated by the integrating device 7 and then input to the position detecting device 8. The position detection device 8 detects mark position measurement information by a template matching method. The position detection device 8 has α, β, and γ templates, and can switch processing at high speed according to the type of mark. The position measurement information of each mark is statistically processed by the CPU 9 and converted into lattice information representing the position, magnification, and rotation of the entire wafer W, and the stage driving device 10 drives the XY stage 11 in accordance with the lattice information. Move the wafer. Reference numeral 12 denotes a storage device for storing information necessary for processing.

  In this embodiment, when exposing a reference layer used for alignment at the time of overlay exposure, a plurality of shot positions including alignment marks are minute amounts in the XY directions as an amount corresponding to information for identifying a semiconductor wafer. An example of a method of exposing by shifting is shown.

  FIG. 1 shows an example of measurement shot arrangement during alignment processing. The measurement shot group is divided into two groups. The first group is a shot group (pre-alignment shot) that is not used for semiconductor wafer identification, and the second group is a shot group (marking shot) that is used for semiconductor wafer identification. In FIG. 1, four pre-alignment shots (A1 to A4) and four marking shots (B1 to B4) are used. However, this number is not fixed, the number of pre-alignment shots should be two or more, and the number of marking shots only needs to be sufficient to represent the total number of IDs for identifying semiconductor wafers.

  When the alignment reference layer is formed on the semiconductor wafer, the pre-alignment shot is exposed at a position according to the shot layout. On the other hand, each marking shot is exposed to a position corresponding to information for identifying a semiconductor wafer among positions where shifts of 5 stages (−200 nm, −100 nm, 0 nm, 100 nm, 200 nm) are generated in the XY directions.

  FIG. 2 shows an example of the arrangement of marking shots. C is a marking shot position when the shot layout (first shot layout) is followed. D is the center point when shifted from the center of C by five steps in the XY direction (−200 nm, −100 nm, 0 nm, 100 nm, 200 nm). E is a marking shot position exposed at a position shifted by 200 nm in the X direction and 100 nm in the Y direction with respect to C.

  Here, the marking shot is exposed to a position shifted (moved) with 100 nm as a unit movement amount in each of the XY directions in accordance with information for identifying the semiconductor wafer. As this value, an amount that can be easily distinguished from the amount that is intentionally shifted to identify the semiconductor wafer and the amount that is detected as an overlay error due to the process by the alignment sensor is set.

  In such a marking shot position designation method, 25 combinations can be expressed by one marking shot. When the total number of marking shots is N, the number of combinations of marking shot positions is 5 × 5 to the Nth power. The number of marking shots may be a number that can sufficiently represent an ID for identifying a semiconductor wafer.

FIG. 3 is a flowchart showing a procedure for aligning the alignment reference layer in the exposure process of the photolithography process for processing the semiconductor wafer on which the pre-alignment shot and the marking shot are arranged.
First, the alignment marks of the pre-alignment shot and the marking shot are measured (Step 101, Step 102). Next, the primary linear correction amount (shift, magnification, rotation) of the temporary wafer is calculated based on the alignment mark measurement result of the pre-alignment shot (step 103). Using the temporary linear linear correction amount obtained here, the alignment mark measurement result of the marking shot is corrected and a correction residual (correction error) is calculated (step 104).

  The marking shot is exposed at a position where a shift in five stages in the XY direction (−200 nm, −100 nm, 0 nm, 100 nm, and 200 nm) is generated when the alignment reference layer is formed. Therefore, the amount deliberately shifted for the semiconductor wafer identification information, such as -200 nm when the correction residue is -250 nm to -150 nm, and -100 nm when the correction residue is -150 nm to -50 nm, is calculated for each marking shot. (Step 105).

  Thus, if it is known how the exposure position of each marking shot is shifted due to the wafer identification information, the wafer identification ID can be obtained from the combination of the shifted amounts of all the marking shots ( Step 106). In addition, the true linear linear correction amount (shift, magnification, rotation) is calculated from the value obtained by correcting the alignment mark measurement value of the marking shot with the shift amount for wafer identification and the alignment mark measurement value of the pre-alignment shot. (Step 107, Step 108). Thereafter, when the semiconductor wafer is exposed, the alignment process is performed using the primary linear correction amount of the true wafer and the amount deliberately shifted for the wafer identification information with respect to the marking shot.

  The measured values of the alignment marks of the actual pre-alignment shot and marking shot are applied to the procedure as shown in FIG. 3 for performing alignment with the alignment reference layer as shown in FIG. For easy understanding, the linear linear correction of the wafer is not performed for the magnification and rotation components, but only for the shift component. Table 1 shows the measured values of the alignment marks of the pre-alignment shot, and Table 2 shows the measured values of the alignment marks of the marking shot.

プリアライメントショットの位置合わせマークの計測値を使って、仮のウエハ一次線形補正量を計算すると表３の結果が得られる。

Using the measured value of the alignment mark of the pre-alignment shot, the temporary wafer primary linear correction amount is calculated, and the result shown in Table 3 is obtained.

仮のウエハ一次線形補正量を用いて、プリアライメントショット、及びマーキングショットの位置合わせマークの計測値を補正した残渣は、表４となる。

Table 4 shows the residues obtained by correcting the measurement values of the alignment marks of the pre-alignment shot and the marking shot using the temporary wafer linear correction amount.

表４のマーキングショットの位置合わせマークの計測値を補正残渣と、アライメント用基準層作成時にマーキングショットがそれぞれＸＹ方向５段階（−２００ｎｍ、−１００ｎｍ、０ｎｍ、１００ｎｍ、２００ｎｍ）のシフトを発生させた位置に露光されている。これを考慮すると、マーキングショットＢ１〜Ｂ４がウエハ識別のために故意にずらされた量が表５のようになる。

The measured values of the alignment marks of the marking shots in Table 4 were corrected residues, and the marking shots shifted in five stages in the XY directions (-200 nm, -100 nm, 0 nm, 100 nm, 200 nm) at the time of creating the alignment reference layer. The position is exposed. Considering this, the amount of the marking shots B1 to B4 intentionally shifted for wafer identification is as shown in Table 5.

マーキングショットはそれぞれＸＹ方向５段階にシフトが発生しているので、それぞれのマーキングショットの位置は、５×５のマトリックスと見なすことができ、ウエハ識別用ＩＤとして取り扱うことができる。表５で示すずらし量でマーキングショットの位置合わせマークの計測値を補正すると、表６で示す補正値を得ることができる。

Since the marking shots are shifted in five stages in the XY directions, the position of each marking shot can be regarded as a 5 × 5 matrix and can be handled as a wafer identification ID. When the measurement value of the alignment mark of the marking shot is corrected with the shift amount shown in Table 5, the correction value shown in Table 6 can be obtained.

表１で示すプリアライメントショットの位置合わせマーク計測値と、表６で示すずらし量を補正したマーキングショットの位置合わせマーク計測値から、表７に示す真のウエハ一次線形補正量を得ることができる。

From the alignment mark measurement value of the pre-alignment shot shown in Table 1 and the alignment mark measurement value of the marking shot obtained by correcting the shift amount shown in Table 6, the true wafer linear linear correction amount shown in Table 7 can be obtained. .

露光処理を行う場合は、マーキングショット以外は表７に示す補正量を用いて補正した位置に露光処理を行い、マーキングショットは、表５、及び表７に示す補正量を用いて補正した位置に露光処理を行う。

When performing the exposure process, the exposure process is performed at the position corrected using the correction amount shown in Table 7 except for the marking shot, and the marking shot is performed at the position corrected using the correction amount shown in Tables 5 and 7. Perform exposure processing.

By using the method as described above, it is not necessary to prepare a special apparatus for recording a wafer identification ID on a semiconductor wafer or reading it. Further, in this method, since the reading process of the semiconductor wafer identification information is performed simultaneously with the alignment process at the time of overlay exposure, there is no problem of affecting the throughput of the semiconductor exposure apparatus.
When this method is applied to a reference wafer for confirming the characteristics of a semiconductor exposure apparatus, the semiconductor exposure apparatus can automatically identify and process a wafer simply by setting the semiconductor wafer in the semiconductor exposure apparatus. .

[Example 2]
When the alignment reference layer is formed on the semiconductor wafer, in Example 1, a simple positional shift in the XY direction is used for the marking shot. However, the positional deviation necessary for identification of the semiconductor wafer is effective not only when the positional deviation in the XY direction is simple but also when the positional deviation depending on the wafer magnification or wafer rotation is generated. That is, as the positional deviation necessary for identifying the semiconductor wafer, one or a combination of X shift, Y shift, wafer magnification X, wafer magnification Y, shot magnification X, shot magnification Y, shot rotation, and shot skew is used. be able to.

  FIG. 5 shows the relationship between the alignment mark measurement value of the pre-alignment shot and the temporary wafer primary linear correction based on the alignment mark measurement value of the marking shot when the positional deviation based on the wafer magnification occurs. FIG. 5 shows a relationship diagram regarding the wafer magnification in the X direction. As shown in this figure, the pre-alignment shot and the marking shot have clearly different correction residues when provisional wafer primary linear correction is performed. Depending on the combination of correction residues of the respective marking shots, wafer identification information can be obtained from the measurement values of the alignment measurement marks on the marking wafer, as in the case of using a simple XY-direction misalignment.

  In the above, the provision or acquisition of wafer identification information has been described. However, the information to be given or acquired is not limited to the wafer identification information, but may be other information related to the wafer such as information on the exposure conditions for the wafer, and the other information may be added. Good.

[Example of device manufacturing]
Next, a manufacturing process of a micro device (a semiconductor chip such as an IC or LSI, a liquid crystal panel, a CCD, a thin film magnetic head, a micromachine, etc.) using the above exposure apparatus will be described.
FIG. 6 shows a flow of manufacturing a semiconductor device.
In step 1 (circuit design), a semiconductor device circuit is designed. In step 2 (mask production), a mask (also referred to as an original plate or a reticle) on which the designed pattern is formed is produced.
On the other hand, in step 3 (wafer manufacture), a wafer (also referred to as a substrate) 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 by lithography using the wafer and the exposure apparatus provided with the prepared mask.
The next step 5 (assembly) is called a post-process, and is a process for forming a semiconductor chip using the wafer manufactured in step 4. The post-process includes assembly processes such as an assembly process (dicing and bonding) and a packaging process (chip encapsulation). In step 6 (inspection), the semiconductor device manufactured in step 5 undergoes inspections such as an operation confirmation test and a durability test. A semiconductor device is completed through these processes, and is shipped in Step 7.

  The wafer process in step 4 includes an oxidation step for oxidizing the surface of the wafer, a CVD step for forming an insulating film on the wafer surface, and an electrode formation step for forming electrodes on the wafer by vapor deposition. Also, an ion implantation step for implanting ions into the wafer, a resist processing step for applying a photosensitive agent to the wafer, and an exposure step for exposing the wafer after the resist processing step through a mask having a circuit pattern using the exposure apparatus described above. Have. Further, there are a development step for developing the wafer exposed in the exposure step, an etching step for removing portions other than the resist image developed in the development step, and a resist stripping step for removing the resist that has become unnecessary after the etching. By repeating these steps, multiple circuit patterns are formed on the wafer.

It is a figure which shows the shot layout which concerns on one Example of this invention. It is a figure which shows the example of arrangement | positioning of the marking shot in FIG. It is a flowchart which shows the procedure which positions with respect to the reference layer for alignment. It is a figure which shows the structure of the alignment apparatus which concerns on one Example of this invention. It is a figure which shows the correlation of the alignment mark measured value of a pre-alignment shot, and the temporary wafer primary linear correction based on it, and the alignment mark measured value of a marking shot. It is a figure explaining the flow of the manufacturing process of a device.

Explanation of symbols

  1: projection lens, 2: illumination device, 3: beam splitter, 4: alignment scope, 5: imaging device, 6: A / D conversion device, 7: integrating device, 8: position detecting device, 9: CPU, 10: Stage drive device, 11: XY stage, 12: storage device, 13-16: alignment mark, R: reticle, W: wafer, S: optical system, α, β, γ: template.

Claims (8)

An exposure method for exposing a plurality of shots on a substrate,
A first generation step for generating a reference first shot layout;
A second generation step of generating a second shot layout indicating the identification information by moving at least one specific shot included in the first shot layout by an amount of movement corresponding to the identification information of the substrate; When,
An exposure step for causing the substrate to be exposed according to the second shot layout;
An exposure method comprising: After the exposure step, when the substrate is exposed again, the positional deviation amounts of the marks respectively arranged on the plurality of shots not including the at least one specific shot are based on the first shot layout. A measurement step to be measured,
A calculation step of calculating a function of coordinates in the first shot layout as a first function that approximates the measured displacement amount;
Have
2. The exposure method according to claim 1, wherein the movement amount is set to be sufficiently larger than an error of the positional deviation amount calculated by the calculated first function.   The exposure method according to claim 2, wherein the first function includes a zero-order function of coordinates in the first shot layout. An identification method for identifying a substrate exposed according to the exposure method according to claim 1,
Measurement for measuring the amount of misalignment of marks arranged on each of the at least one specific shot and a plurality of shots not including the at least one specific shot on the basis of the first shot layout. Steps,
A first calculation step of calculating, as a first function, a function of coordinates in the first shot layout that approximates the amount of mark displacement measured for the plurality of shots;
A calculation step of calculating a positional deviation amount of the mark arranged in the at least one specific shot according to the calculated first function;
A specifying step of specifying the movement amount based on a difference between the measured displacement amount and the calculated displacement amount with respect to a mark arranged in the at least one particular shot;
An identifying step for identifying the substrate based on the identified amount of movement;
The identification method characterized by having. A method for exposing a substrate identified according to the identification method of claim 4, comprising:
A correction step of correcting the measured positional deviation amount by the movement amount with respect to the mark placed on the at least one specific shot;
A second calculation step of calculating a function of coordinates in the first shot layout as a second function that approximates the corrected positional shift amount and the mark positional shift amount measured for the plurality of shots; ,
The plurality of shots are exposed according to the amount of displacement calculated by the calculated second function, and the amount of movement and the amount of displacement calculated by the calculated second function are Thus, an exposure step that causes the at least one specific shot to be exposed;
An exposure method comprising:   A program for causing a computer to execute the method according to any one of claims 1 to 5. An exposure apparatus that exposes a plurality of shots on a substrate,
An exposure apparatus that operates according to the program according to claim 6. Exposing the substrate using the exposure apparatus according to claim 7;
Developing the exposed substrate;
A device manufacturing method comprising:

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