JPS62219086A - Mask mismatching inspection device - Google Patents

Abstract

PURPOSE:To measure mask mismatching in a semiconductor device manufacturing process at high accuracy and high efficiency by providing an object holding part, an optical system, a photoelectric conversion part, a positioning control part and a decision part deciding mask mismatching based on a picture signal. CONSTITUTION:A wafer 10 is held at the prescribed position in a vacuum chuck 14, and a magnification switching part 12 sets the optical system 17 to a low magnification based on a control signal SC3. Then an ITV camera 20 forms the magnified optical image of the wafer 10. Next the dislocation of the rotation of the wafer 10 is detected and corrected from the position relation between marks in wafers. Continuously dislocation from the inspection positions of patterns to be inspected K1 and K2 is detected, and an X-Y table 16 is driven in the directions of arrows X and Y. Said patterns K1 and K2 are shifted to the center of a visual field to set the optical system 17 to a high magnification. The processing is repeated until the patterns K1 and K2 attain desired sizes.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a mask misalignment inspection device used for detecting mask misalignment in, for example, a semiconductor manufacturing process.

(Prior Art) A semiconductor manufacturing process includes a process of forming a circuit pattern on a wafer, and an inspection is performed to see if this circuit pattern has been formed with high precision. FIG. 8 shows a part of the semiconductor manufacturing process, in which a wafer (1) is attached to a silicon substrate (St) (2) with an 8i0. An insulating film (3) consisting of the following is formed.

First, as shown in FIG. 8(b), a resist (4) is applied to the Ueno film (1). Thereafter, a mask (5) is applied, exposure is performed, and development is then performed. When this development is completed, the portion (6) of the resist (4) irradiated with light melts, and the masked portion remains as is, as shown in FIG. 8(d). Thereafter, machining and cutting are performed as shown in FIG. 8(e). Here, mask (5)
If it is not precisely aligned with the predetermined position, the portion to be etched will be so small that, for example, the position and amount of the impurity to be bonded will be different, and the predetermined properties will not be exhibited. For this reason, after the development process, an inspection is performed to see if the masked position is accurate. Incidentally, this inspection is performed by measuring the positions of the edge portions (7a) and (7b) of the resist (4). In addition, each line (
7a) and (7b) are formed in a linear shape when viewed from the top of the wafer (1).

The distance between these lines, that is, the position and distance of the edge portions (7a) and (7b) will be measured. Therefore, conventionally.

This measurement was performed by an operator using an optical microscope, but recently a method has been developed that uses laser light to measure the position of the edge portions (7a) and (7b) of the resist (4) because the reflected light level is far away. Further, the position of the edge portions (7a) and (7b) of the resist (4) is measured from interference light using an optical slit.

(Problems to be Solved by the Invention) However, in each of the above methods, the entire apparatus used is complicated and expensive. moreover.

The above method takes time to measure one edge part (7a), (7b), and online IIJ
This cannot be applied to certain situations. It should be noted that one worker requires skill to perform measurements through an optical microscope.

Therefore, 1. the present invention was made in consideration of the above circumstances, and an object thereof is to provide a mask misalignment inspection device that can inspect mask misalignment in a semiconductor manufacturing process with high precision and high efficiency. .

[Structure of the invention]

(Means and effects for solving the problem) An inspection object holder that holds an inspection object on which an inspection pattern on which mask misalignment is detected can be freely positioned, and an optical image of the inspection pattern. an optical system configured to freely change the magnification; a photoelectric conversion section for capturing the optical image; a positioning control section for positioning the pattern to be inspected; The mask misalignment is determined with high accuracy and efficiency.

(Example) Hereinafter, two embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a mask misalignment inspection device of this embodiment. This misalignment measuring device.

Holding mechanism (11) that holds and positions the wafer (11)
and.

An imaging mechanism (L) that images the wafer α held by this holding mechanism a1) and outputs an image signal SA, and measures mask alignment misalignment based on the image signal SA output from this imaging mechanism α2. The holding mechanism (11) is composed of a calculation control mechanism (11).
Vacuum chuck I, which can be attached and detached by vacuum.

A θ table α9 on which the vacuum chuck (14 is mounted and driven to rotate in the direction of the arrow θ) and a θ table α9 on which the θ table α9 is mounted and driven forward and backward in both directions of the arrows X and Y in a plane orthogonal to the rotational axis of the θ table α9 The holding mechanism aυ is driven based on a control signal SC1 from an arithmetic control mechanism (13).On the other hand, the imaging mechanism a is It is mainly an optical microscope, and consists of an optical system (l?) consisting of a combination of multiple optical lenses that magnify the optical image of the wafer Q held in the vacuum chuck I, and one optical system (l?) that magnifies the optical image of the wafer αe held in the vacuum chuck I. Illumination light is projected onto the wafer held by the vacuum chuck (14) through a support part (18) which is moved up and down in the direction of arrow Z at an upper position, and an optical system (17) attached to this support part. ITV (Ind.
ustrial Te1evision) camera (to) and the image signal 8A output from this ITV camera.
When the optical image of the wafer Ql shown by is blurred, the focus of the optical system is held on the vacuum chuck α by the control signal SC output from the arithmetic and control mechanism α3 in order to correct this blur. Support part α so that it is above 101
The magnification of the optical system αη is switched based on the automatic focusing unit 01) that drives the sand to raise and lower the optical system (L'7), and the control signal SC3 for switching the magnification output from the arithmetic control mechanism (19). It consists of a magnification switching unit (2) whose main body is a heart-moving revolver that performs driving.

The arithmetic control mechanism 0 includes an automatic position recognition section (c) that automatically detects the position of the pattern to be inspected, which will be described later, based on the image signal 8A output from the ITV camera (to), and an automatic position recognition section (c) that automatically detects the position of the pattern to be inspected, which will be described later. The mask misalignment inspection section automatically performs mask misalignment inspection based on detected and positioned detection patterns.

Therefore, the automatic position recognition unit (c) has a converter (c) which converts the analog image signal 8A into an analog-to-digital (A/D) and outputs a digital image signal 8D, and a converter (c) which converts the analog image signal 8A into a digital image signal 8D. An image memory 2 stores the wafer image data indicated by the image signal 8D output from the image memory 8D at a predetermined address, and the control signal sc1. sc
,,sc, and performs positioning of the inspection pattern according to a program described later.
). In addition, the input side of the 1-alignment deviation inspection unit C241 is connected to the image memory (to), and the 1-alignment deviation inspection unit C241 inputs image data into 1
An example of a spatial filter section that reads out each pixel, sequentially differentiates it, and outputs differential data having a peak value corresponding to the position of the edge of the pattern to be inspected, and the differential data output from this spatial filter section (to) is temporarily stored. memory section (
), this memory section - which judges the mask alignment misalignment based on the differential data stored in it, and the judgment section which is mainly made up of a microcomputer, etc., and the printer and cathode ray tube which display the judgment results of this judgment section (2). It consists of a display section Gυ, etc. The spatial filter section is connected to the output side of the 1-image memory (c), and the first spatial filter circuit (c) performs first-order differentiation of the image signal SD.
(to) and a second spatial filter circuit (to) that differentiates the first-order differential signal SR output from the first spatial filter circuit 03 and outputs a second-order differential signal 8F. Then, these first and second spatial filter circuits Oa,
(33 is an 8-pixel inputting one image signal 8D pixel by pixel as shown in FIG. 2) (for one scan of an ITV camera) three shift registers connected in series,
(to), (7) and shift register (goods), (to), (
A differentiation area 07) for extracting the first 3 bits of (to) and storing them in the corresponding address, and a weighting coefficient area (to) for storing a weighting coefficient for each address.
These differentiator area 07) and weighting coefficient area (
A product-sum calculation circuit connected to the output side of It consists of 1 and 1. Also 1
The determination unit (to) detects each peak position corresponding to each edge position of the pattern to be inspected using the second-order differential signal 8F output from the spatial filter unit (c), and performs a predetermined calculation described later. It has become.

Next, the operation of the misalignment inspection apparatus having the above configuration will be explained according to the flowchart shown in FIG.

First, the wafer CIG is held in a predetermined position on the vacuum chuck I. Next, based on the control signal SC3, the optical system (LD) is set to a low magnification by the 1 magnification switching section (2) (step (
40). Next, the optical system was installed using the ITV camera (towards).
An enlarged optical image of the wafer a0 that has passed through is captured (step (41)). Next, the automatic focusing unit Qυ is activated by the control signal SC1 output from the arithmetic control mechanism α3, and automatic focusing of the optical system αη is performed (step (6)
)). , next, based on the positional relationship between a pair of wafer marks (not shown) formed on the wafer αQ.

A rotational deviation of wafer a is detected (step (43)).

Next, a control signal SC□ for correcting the rotational deviation is output from the arithmetic control mechanism 0 to the holding mechanism (11).

0 table (151) is rotated by a predetermined amount, and the rotational deviation of the wafer α is corrected (step (44). Next, the rotational deviation of the wafer α is corrected (step (44). A positional deviation of 1.Kt from the inspection position is detected in the pattern to be inspected (step (c)).Next.

In order to correct this positional deviation, the X-Y table αe is driven in the directions of arrows X and Y to bring the pattern to be inspected Kh dog to the center of the visual field (step (46)). Then, the optical system αη is made to have a high magnification by the control signal SCs (step (4?)). Then, apply 1. to the pattern to be inspected in the same manner as before. Position the camera so that line A-B of K is at the center of the field of view. This process is repeated until the pattern to be inspected has a desired size. Next, I
The finally positioned inspection pattern is imaged by a TV camera, and the image data indicating the inspection pattern Kl near the A-B line obtained at this time is stored in the image memory (c).
At this time, this image memo IJ I:? [Mask misalignment inspection is performed based on the image data stored in i (step combination). by the way.

As for the brightness level of the image data on the AB line, as shown in FIG. 5, the brightness level of the edge portion of the resist is lower than that of the other portion. Thus.

The image data stored in the image memory is sequentially read out pixel by pixel and output to the first spatial filter circuit 0. Then, in this first spatial filter circuit G, one image data is transferred one pixel at a time to the shift register C34)
, C3!19. @ J is captured, and every time this one pixel is captured, the area for differentiation C3? ) and the corresponding weighting coefficient in the weighting coefficient area are integrated in the product-sum operation circuit OI, and then these integrated values are converted into a first-order differential signal 8E (see Figure 6). Output to the second spatial filter circuit (to). Next, from the second spatial filter circuit Q into which the first-order differential signal SE has been input, a second-order differential signal SF (see FIG. 7) is outputted to the memory section in the same manner.
Stored as second-order differential data. Furthermore, the signals shown in Figs. 5 to 7 are as follows.

It shows digital data in analog form. Thus,
The second-order differential data shown in FIG. 7 has peak values Pi, P corresponding to the edges of , K, on the inspection pattern on line A-B.
2. P3. P4 appears. Next, 1 judgment part (to)
Then, the intervals J, L' between the peak values P1 and P2 and between P3 and P4 are calculated. Then, these intervals 1. L'
Calculate the difference ΔL, and if this difference ΔJ is larger than the set value.

It is determined that "the mask alignment is slightly misaligned", and if the difference ΔJ is within the set value, it is determined that "the mask alignment is even misaligned". Next, the determination result in this determination section (to) is displayed on the 1 display section 01) (step (4)).

As described above, the mask misalignment inspection device of this embodiment is a relatively simple device that can measure mask misalignment in the semiconductor device manufacturing process with high precision and high efficiency. As a result, the reliability of mask misalignment inspection is improved, which can contribute to improved yield and productivity of semiconductor devices.

Note that other image sensors may be used instead of the ITV camera. Furthermore, a smoothing circuit may be provided before the spatial filter section (c) for the purpose of noise removal. Furthermore, the calculation of one interval , may be performed by a binarization method without being based on the second-order differential data.

Furthermore, the X-Y table (161) may be provided with a function of moving up and down in the direction of arrow Z.

〔Effect of the invention〕

The mask misalignment inspection device of the present invention can measure mask misalignment in a semiconductor device manufacturing process with high precision and high efficiency. As a result, the reliability of mask misalignment inspection is improved, which can contribute to improved yield and productivity of semiconductor devices.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a mask misalignment inspection device according to an embodiment of the present invention, FIG. 2 is a block diagram of the spatial filter section in FIG. 1, and FIG. 3 is an operation of the mask misalignment inspection device of FIG. 1. 70-chart for explaining, FIG. 4 is a diagram showing an inspection pattern, and FIGS. 5 to 7 are diagrams showing signal processing of image data. FIG. 8 is an explanatory diagram of the semiconductor manufacturing process. α groan: Kueha (tested object). ←η: Holding mechanism (test object holding part). αη: Optical system. (b): ITV camera (photoelectric conversion section). (c): Automatic position recognition unit (positioning control unit). c24): Misalignment determination unit (determination unit). Agent Patent Attorney Noriyuki Ken Yudo Takehana KikuoFigure 1Figure 8Figure 5Figure 6Figure 7

Claims (1)

[Scope of Claims] A mask misalignment inspection device characterized by having the following configuration. (a) A test object holder that removably holds a test object on which a test pattern in which mask misalignment is detected is formed, and also positions and drives the test pattern to an inspection position. (b) An optical system that forms an optical image of the object to be inspected held in the object-to-be-inspected holding section, with the magnification being freely switchable. (c) A photoelectric conversion unit that captures an optical image formed by the optical system and outputs an image signal. (d) A positioning control section that outputs a control signal to the object holding section based on the image signal output from the photoelectric conversion section and corrects the position of the pattern to be inspected. (E) A determination unit that inputs an image signal indicating the pattern to be inspected outputted from the photoelectric conversion unit and determines the mask misalignment.