JPH104043A - Surface position detector and manufacture of device using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a surface position detector which is capable of very accurately detecting the position of a work surface by a method wherein a light volume control member capable of controlling a transmitted light in volume is provided, at least, to either a light source means or a photodetecting means when position data as to the surface of a work are detected through an oblique incidence method. SOLUTION: A slit image projected onto the surface of a wafer 4 by a light source means 5 is detected with a photodetecting means 6, data as to the incident position of the slit image on the photodetector 6a of photodetecting means 6 are detected. When the surface of the wafer 4 is moved in the AX direction of a light axis, the position of the slit image varies on the photodetector 6a. The positional variation Δof the slit image is measured, and the height variation δof the wafer 4 is detected. Furthermore, three or more points in a chip on the wafer 4 are measured to detect the inclination of the water 4, and the inclination of the wafer 4 is calculated from the measured value. The transmitted light of the light bulb 8 of the light source means 5 is regulated in volume so as to enable the peak value of the position data of the slit image detected by the photodetecctor 6b to be set at a proper value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface position detecting device and a method of manufacturing a device using the same, for example, a semiconductor device such as an IC or LSI, an imaging device such as a CCD, a display device such as a liquid crystal panel, a magnetic head, and the like. In a process of manufacturing a device, a pattern on a first object surface such as a reticle is projected onto a second object surface such as a wafer by a projection optical system in a projection exposure apparatus or a scanning exposure apparatus used in a lithography step. This is suitable for performing the alignment (focusing) of the wafer in the optical axis direction at that time.

[0002]

2. Description of the Related Art In recent years, as a fine processing technology for semiconductor devices such as ICs and LSIs, a circuit pattern image of a mask (reticle) is formed on a photosensitive substrate by a projection optical system (projection lens), and the photosensitive substrate is step-and-repeat. Various reduction projection exposure apparatuses (steppers) for performing exposure in a system have been proposed. In this stepper, a circuit pattern on a reticle is reduced and projected onto a predetermined position on a wafer surface via a projection optical system having a predetermined reduction magnification, and transferred.
After the end of the projection transfer, the stage on which the wafer is mounted is moved by a predetermined amount, and the step of performing the transfer again is repeated to expose the entire surface of the wafer.

In general, in order to transfer a fine circuit pattern using a stepper having a projection optical system, it is important to appropriately set a focus position on the wafer surface (a position in the optical axis direction of the projection optical system). It becomes. In particular, recently, as the degree of integration increases, it is required that the surface of the wafer be installed with a submicron accuracy with respect to the projection optical system.

FIG. 11 is a schematic view of a main part of a conventional projection exposure apparatus having a surface position detecting device for detecting positional information (optical axis direction information) of a wafer surface.

In FIG. 1, reference numeral 2 denotes a reticle which is a circuit original, 3 denotes a projection lens for reducing and projecting the original 2 to 1/5, 4 denotes a wafer coated with a resist, and 7 denotes a stage for moving the wafer. When the light source 1 is turned on and the reticle 2 is illuminated with the light beam from the light source 1, the circuit pattern on the reticle 2 forms an image on the wafer 4, and the circuit pattern is printed on the resist. When one shot is completed,
The stage 7 is step-driven and printed next to it. In this manner, circuit patterns are printed on the entire surface of one wafer in a matrix. In the IC mass production process, the exposure apparatus is constantly operated, and wafers are printed at a speed of about 60 wafers per hour.

The light source 101 and the light beam position detector 102 constitute a surface position detecting device that detects the height position (position in the optical axis direction) of the wafer 4. The surface position detecting device is a projection lens 3
The wafer 4 is positioned at the image forming position of the circuit pattern on the reticle 2 according to the above.

FIG. 12 is an explanatory diagram of a detection principle for detecting the height position of the wafer 4 in FIG.

In FIG. 1, a light beam 104 emitted from a light source 101 is reflected on a wafer surface 103 (wafer height 1), and a light beam position detector 102 detects a light beam position (for example, a peak position 102a).

Next, when the wafer 4 moves to the surface 103a (wafer height 2), the reflected light moves to the position 102b. There is a proportional relationship between the height variation δ of the wafer 4 and the variation Δ of the light beam position, and the height variation δ is detected by measuring the variation Δ.

[0010]

FIG. 13 is an enlarged schematic view showing the vicinity of the surface of the wafer 4 shown in FIG.

In FIG. 1, reference numeral 4a denotes a wafer substrate which has been subjected to a process in which a silicon substrate is subjected to a process such as sputtering or etching, and a photosensitive member (resist) indicated by 4b is further coated thereon. On the wafer surface with such a configuration,
When the light beam 104 from the light source 101 is irradiated, the reflected light from the wafer surface is reflected on both the surface of the wafer substrate 4a and the surface of the resist 4b, and the reflected lights interfere with each other.
Therefore, the position of the light beam on the light beam position detector 102 changes due to the thickness unevenness of the resist 4b and the process structure of the base,
Therefore, a height position detection error of the wafer 4 occurs. Therefore, a conventional exposure apparatus uses a halogen lamp as the light amount for the light source 101. Halogen lamps have an emission wavelength from 500 nm to 1100 nm and a wavelength width of about 60 nm.
Since the interference is as wide as 0 nm, the interference is averaged in a wavelength width of 600 nm. For this reason, the height detection system of the wafer 4 has a stable performance which is hardly affected by the unevenness of the thickness of the resist and the underlying process structure.

As described above, while the halogen lamp has excellent characteristics, it is necessary to change the light amount of the halogen lamp in accordance with the change in the reflectance of the wafer base. Conventionally, the voltage of the halogen lamp is changed by changing the voltage, but the speed of the change is on the order of several hundred mSec. However, in a step-and-scan method in which a large area can be exposed, for example, in a reduction projection exposure apparatus, it is particularly important to be able to adjust the amount of light at high speed on the order of mSec.

More specifically, this step-and-scan method scans a reticle and a wafer synchronously, thereby achieving a large LS having a chip size of about 25 × 32 mm.
This is a method suitable for manufacturing I and the like. In this step-and-scan method, a wafer is moved at a speed of 150 to 200 mm / sec.
Exposure is performed with a slit having a width of about 5 mm while scanning at a speed of. Therefore, it is necessary to measure and control the height of the wafer in real time in several tens of msec while scanning one chip of the wafer in the scanning direction. In one chip, high reflectivity and low reflectivity such as aluminum wiring are mixed. Therefore, when scanning is performed while detecting the wafer height in one chip, the light amount on the detector also changes in the order of mSec.

However, as described above, since the light quantity of the halogen lamp cannot be adjusted at high speed, the waveform after photoelectric conversion when the light flux position detector 102 receives light while scanning one chip is shown in FIG. As shown in FIG. 14A when the low-reflectance portion of the base on the IC chip is irradiated, and when the high-reflectance portion of the base on the IC chip in FIG. , There was a shortage. For this reason, the peak of the waveform cannot be determined accurately, and therefore, the height of the wafer cannot be detected with high accuracy. As a result, the resolution on the wafer when the circuit pattern is exposed is insufficient, and the defective chip And reduced yield.

According to the present invention, at least one of the light source means and the light receiving means is provided with a light amount adjusting member capable of controlling the amount of light passing therethrough when detecting positional information on the object surface by the oblique incidence method, or constitutes the light source means. By controlling the accumulation time of the charge accumulation type photoelectric conversion element, the level (intensity) of the output signal from the light receiving means is appropriately set, and the surface position of the object surface is detected with high accuracy, and the position is determined at the predetermined position. It is an object of the present invention to provide a surface position detecting apparatus capable of easily manufacturing a highly integrated device that can be set, and a method for manufacturing a device using the same.

[0016]

According to the present invention, there is provided a surface position detecting apparatus according to the present invention, wherein (1-1) an object plane provided in the vicinity of an image forming plane of a projection optical system is inclined from an optical axis of the projection optical system. When the pattern is projected by the light source means, the image of the pattern formed on the object surface is detected by the light receiving means, and when detecting the position information of the object surface in the optical axis direction using a signal from the light receiving means, The light source unit and / or the light receiving unit are provided with a light amount adjusting member capable of controlling the amount of light passing therethrough, and the output signal of the image of the pattern detected by the light receiving unit is adjusted.

(1-2) A pattern is projected from an oblique direction to the optical axis of the projection optical system by a light source means on an object surface provided in the vicinity of the image forming surface of the projection optical system, and formed on the object surface. When detecting the image of the pattern by the light receiving means, when detecting the position information in the optical axis direction of the object surface using a signal from the light receiving means,
The light receiving means has a charge storage type photoelectric conversion element, and adjusts an output signal of an image of the pattern by controlling a charge storage time of the photoelectric conversion element.

In particular, in the constitutional requirements (1-1) or (1-2), the object plane is made to coincide with the image plane of the projection optical system by a driving unit based on a signal from the light receiving unit. And

The scanning type exposure apparatus according to the present invention is characterized in that (2-1) a pattern on a first object plane is projected onto a second object plane placed on a movable stage by a projection optical system and the first object and the first object are scanned by a scanning means. In a scanning type exposure apparatus that performs projection exposure while scanning the movable stage in synchronization with a speed ratio corresponding to the projection magnification of the projection optical system, the projection exposure is performed on a second object plane provided near an imaging plane of the projection optical system. The pattern is projected by the light source means from an oblique direction to the optical axis of the optical system, the image of the pattern formed on the second object plane is detected by the light receiving means, and the second image is formed by using the signal from the light receiving means. When detecting the position information of the object surface in the optical axis direction, the light source means and / or the light receiving means are provided with a light amount adjusting member capable of controlling the amount of passing light, and an output signal of the image of the pattern detected by the light receiving means Is characterized by adjusting

In particular, the present invention is characterized in that the second object plane is made coincident with the image plane of the projection optical system by driving means based on a signal from the light receiving means.

The method for manufacturing a device according to the present invention has a structure (1)
After aligning the reticle with the wafer by using the position detecting device of (1) or (1-2) or by using the scanning type exposure apparatus of configuration (2-1), the pattern on the reticle surface is adjusted. Is projected onto a wafer surface, and thereafter, the wafer is subjected to a development process to manufacture devices.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic view of a main part of a first embodiment of the present invention, FIG. 2 is an enlarged explanatory view of a part of FIG. 1, and FIG. This embodiment shows a case where the present invention is applied to a scanning exposure apparatus using a step-and-scan method for manufacturing a device.

In FIG. 1, reference numeral 1 denotes an illumination system for irradiating exposure light, which emits exposure light from a DUV i-line or an excimer laser such as KrF or ArF. Reference numeral 2 denotes a reticle (first object) on which a circuit pattern is drawn, and is mounted on the reticle stage 10. 3 is a projection lens (projection optical system)
And the circuit pattern on the reticle 2 is reduced and projected on the wafer (second object) 4 coated with the resist. still,
In the present embodiment, the projection optical system 3
The projection exposure is performed while scanning (scanning) at a predetermined speed ratio while synchronizing according to the imaging magnification.

Reference numeral 5 denotes a light source means, which is a pattern for detecting the position of the wafer 4 in the optical axis direction of the projection lens 3, for example, a single or a plurality of slits 5b (one slit 5 in the figure).
b, only one light flux 5a1 is shown, but a plurality of light fluxes may be used), a light source unit 5a for illuminating the slit 5b, and an imaging optical system 5c for projecting and imaging the slit 5b on the surface of the wafer 4. And Reference numeral 8 denotes a light amount adjusting member (light valve) for adjusting the passing light amount, which is provided in the optical path of the light source means 5. 5a1 indicates a light beam that has passed through one slit.

Reference numeral 6 denotes a light receiving means, which has a detecting portion 6b and a re-imaging system 6c for re-forming a slit image formed on the surface of the wafer 4 on the detecting portion 6b. Reference numeral 6a1 denotes a reflected light beam based on the slit image formed on the surface of the wafer 4.
The detection unit 6b includes a photoelectric conversion element CCD (charge coupled device) capable of detecting the incident position information of the light beam,
It consists of SD (position sensing device) and the like.

Reference numeral 7 denotes x / for changing the position, inclination, etc. of the wafer 4.
The stage is capable of y / z and tilt. A driving unit (driver) 7a tilts the stage 7 in the x, y, and z directions and tilts. 9 is a control unit (controller)
The output signal from the light receiving means 6 is output to the drive unit 7a via the driver 6a in accordance with the output signal. Reference numeral 8a denotes a driver that adjusts the amount of light passing through the light valve 8 based on a signal from the control unit 9. That is, the amount of light incident on the surface of the wafer 4 is adjusted.

A driving unit (driver) 10a drives the reticle stage 10 in synchronization with the wafer stage 7 based on an instruction signal from the control unit 9. Control unit 9
Inputs a signal to the driver 8a and adjusts the amount of light passing from the light valve 8 so that the output value of the signal (peak value) obtained by the detection unit 6b becomes a constant value.

In the present embodiment, the slit image projected on the surface of the wafer 4 by the light source means 5 is detected by the light receiving means 6, and at this time information on the position of incidence of the slit image on the light receiving portion 6b (for example, peak position information). Has been detected.

The surface (wafer height) of the wafer 4 has an optical axis AX
When it moves in the direction, the position of the slit image on the light receiving unit 6b changes. The variation Δ at this time is proportional to the height variation δ of the wafer 4. Thus, the height variation δ is detected by measuring the variation Δ. Further, in order to detect the inclination of the wafer 4, at least three points are measured in the chips of the wafer 4, and the inclination of the wafer is calculated based on the measured values.

In this embodiment, the detecting section 6b of the light receiving means 6
The light passing amount from the light valve 8 serving as a light amount adjusting member provided on the light source means 5 side is adjusted so that the position information of the slit image detected by the above-mentioned method becomes an appropriate peak value.

Next, the configuration of the light valve 8 will be described. FIG. 2 is a schematic diagram in the case where the light valve 8 is composed of a liquid crystal.

As shown in the figure, a light valve 8 made of liquid crystal has a transmission portion 8a and a non-transmission portion 8b of appropriate size spatially distributed. This distribution is controlled by the controller 9 through the driver 8a. And the transmission section 8
By changing the ratio between the “a” and the opaque portion 8b, m
The amount of light incident on the wafer 4 is adjusted at a high speed equal to or lower than Sec.

FIG. 3 shows a slit image (light flux 5) from the light source 5 when the reticle 2 and the wafer are scanned and exposed in synchronization.
FIG. 9 is an explanatory diagram of signals obtained at the light receiving unit 6b when a1) is reflected by the high reflection unit and the low reflection unit on one chip on the surface of the wafer 4 and enters the light receiving unit 6b.

FIG. 3A shows a light valve 8 according to the present invention.
In the case where there is no signal, when the measurement point is applied to the high reflectance base, the peak of the slit image is saturated and the peak position cannot be obtained. Therefore, the height (surface) of the wafer 4 cannot be detected. FIG. 3B shows a case where the target is set in the controller 9 so that the output of the detection unit 6b is, for example, about 70% of the saturation level, and scanning is performed by controlling the amount of light transmitted through the light valve 8.

In order to make the output from the detection unit 6b close to the target value, the light amount is increased in the initial stage (A) in FIG. Next, at the position (b) in FIG. 3C, the amount of opaque pattern is increased because the light amount increases. Further, in FIG. 3C, the transmission pattern is increased so as to increase the light amount again.

In the present embodiment, the liquid crystal is used for the light valve 8 as described above, so that the light is quickly adjusted in accordance with the change in the reflectance of the base of the wafer 4 and the height of the wafer 4 is measured and controlled in real time. Therefore, a device with a high degree of integration can be easily formed by a scan exposure apparatus.

FIG. 4 is an explanatory diagram of another light amount adjusting member (light valve) applicable to the present embodiment. The light valve of this embodiment is also called a so-called variable aperture.
In this embodiment, the aperture blade 41 is opened and closed by the drive unit 42. In order to realize high-speed opening and closing of the aperture blade 41 at this time, an ultrasonic motor, an electromagnetic coil, or the like is used for the drive unit 42.

FIG. 5 is a schematic view of a main part of a second embodiment of the present invention. The present embodiment is different from the first embodiment in FIG. 1 in that the position of the light valve 8 is disposed in the light receiving means 6, and the other configuration is the same as the first embodiment. In the present embodiment, when the light valve 8 does not allow a physical space in the light source means 5 by design, it is arranged in the light receiving means 6 in this manner. In this embodiment, the light valve 8 may be provided on the light source means 5 side.

FIG. 6 is a schematic view showing a main part of a third embodiment of the present invention.
FIG. 7 is an enlarged sectional view of a part of the light valve 8 used in the third embodiment. The present embodiment is different from the first embodiment shown in FIG.
b, and the other configuration is the same.

The reflective element 8a constituting the light valve shown in FIG. 7 has a small rectangular mirror 71 of several tens of μm square.
Are arranged in a matrix in the order of several hundred thousand. The manufacturing method of this mirror is to create a cantilever structure by microfabricating a silicon crystal plate by lithography, etc., and to tilt each minute mirror as needed using electrostatic force, so that the angle of reflected light can be adjusted. The luminous flux is turned on or off by changing, and the light amount is adjusted using this.
In the present embodiment, since the reflection type is used, deterioration of the light valve due to heat can be prevented, so that the durability is high, and stable and high-speed light quantity control can be realized.

FIG. 8 is a schematic view of a main part of a fourth embodiment of the present invention. This embodiment is different from the first embodiment shown in FIG. 1 in that a CCD capable of controlling the charge accumulation time is used as the light flux position detection detector 6d, and the accumulation time can be controlled by the controller 9. The optical image on the CCD 6d is photoelectrically converted, the peak of the output waveform is detected, and the peak value is compared with the saturation level of the CCD 6d, calculated by the accumulation time controller 9 of the CCD 6d to be a predetermined level, and the result is used. Thus, the accumulation time of the CCD 6d is controlled. In this embodiment, an optical element is not used, and a purely electric light amount control system is used, so that an inexpensive device can be supplied.

Next, an embodiment of a device manufacturing method using the above-described exposure apparatus will be described.

FIG. 9 shows a flow of manufacturing a semiconductor device (a semiconductor chip such as an IC or an LSI, or a liquid crystal panel or a CCD).

In step 1 (circuit design), a circuit of a semiconductor device is designed. Step 2 is a process for making a mask on the basis of the circuit pattern design. On the other hand, in step 3 (wafer manufacturing), a wafer is manufactured using a material such as silicon. Step 4 (wafer process) is referred to as a preprocess, and an actual circuit is formed on the wafer by lithography using the prepared mask and wafer.

The next step 5 (assembly) is called a post-process, and is a process of forming a semiconductor chip using the wafer produced in step 4, and includes an assembly process (dicing and bonding) and a packaging process (chip encapsulation). And the like. In step 6 (inspection), inspections such as an operation confirmation test and a durability test of the semiconductor device manufactured in step 5 are performed. Through these steps, a semiconductor device is completed and shipped (step 7).

FIG. 10 shows a detailed flow of the wafer process. Step 11 (oxidation) oxidizes the wafer's surface. Step 12 (CVD) forms an insulating film on the wafer surface. Step 13 (electrode formation) forms electrodes on the wafer by vapor deposition. In step 14 (ion implantation), ions are implanted into the wafer. Step 1
In 5 (resist processing), a photosensitive agent is applied to the wafer. Step 16 (exposure) uses the above-described exposure apparatus to print and expose the circuit pattern of the mask onto the wafer.

In step 17 (development), the exposed wafer is developed. In step 18 (etching), portions other than the developed resist are removed. In step 19 (resist stripping), the resist that has become unnecessary after the etching is removed. By repeating these steps, multiple circuit patterns are formed on the wafer.

By using the manufacturing method of the present embodiment, it is possible to easily manufacture a highly integrated semiconductor device which has been conventionally difficult to manufacture.

[0049]

As described above, according to the present invention, at least one of the light source means and the light receiving means is capable of controlling the amount of light passing therethrough when detecting the position information of the object surface by the oblique incidence method. The level (intensity) of the output signal from the light receiving means is appropriately set by providing or controlling the accumulation time of the charge storage type photoelectric conversion element constituting the light source means, and thereby the surface position of the object surface is set. A surface position detection device capable of easily manufacturing a highly integrated device that can be detected at a high precision and set at a predetermined position, and a device manufacturing method using the same can be achieved.

[Brief description of the drawings]

FIG. 1 is a schematic view of a main part of a first embodiment of the present invention.

FIG. 2 is an enlarged explanatory view of a part of FIG. 1;

FIG. 3 is a diagram for explaining the operation of FIG. 1;

FIG. 4 is an explanatory view of another embodiment of a part of FIG. 1;

FIG. 5 is a schematic diagram of a main part of a second embodiment of the present invention.

FIG. 6 is a schematic diagram of a main part of a third embodiment of the present invention.

FIG. 7 is an enlarged explanatory view of a part of FIG. 6;

FIG. 8 is a schematic diagram of a main part of a fourth embodiment of the present invention.

FIG. 9 is a flowchart of a device manufacturing method of the present invention.

FIG. 10 is a flowchart of a device manufacturing method of the present invention.

FIG. 11 is a schematic diagram of a conventional surface position detecting device.

FIG. 12 is an enlarged explanatory view of a part of FIG. 11;

FIG. 13 is an enlarged explanatory view of a part of FIG. 11;

FIG. 14 is an explanatory diagram of a reflection characteristic on a wafer surface in a conventional surface position detection device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Illumination system 2 1st object (reticle) 3 Projection optical system 4 2nd object (wafer) 5 Light source means 6 Light receiving means 7 Stage 8 Light amount adjustment member (light valve) 9 Control part 10 Reticle stage

Claims (7)

[Claims] 1. An image of a pattern formed on an object plane provided in the vicinity of an image forming plane of a projection optical system by a light source means from an oblique direction with respect to an optical axis of the projection optical system. The light amount adjustment which can control the amount of light passing through the light source unit and / or the light receiving unit when detecting the position information of the object surface in the optical axis direction by using the signal from the light receiving unit. A surface position detecting device, wherein a member is provided to adjust an output signal of an image of the pattern detected by the light receiving means. 2. An image of a pattern formed on an object plane, which is projected from an oblique direction with respect to the optical axis of the projection optical system to an object plane provided in the vicinity of an image forming plane of the projection optical system by a light source means. Is detected by the light receiving means, and when the position information of the object surface in the optical axis direction is detected by using a signal from the light receiving means, the light receiving means has a charge storage type photoelectric conversion element, and the photoelectric conversion element Wherein the charge accumulation time is controlled to adjust the output signal of the image of the pattern. 3. The surface position detecting device according to claim 1, wherein the object surface is made to coincide with the image surface of the projection optical system by a driving unit based on a signal from the light receiving unit. 4. A pattern on a first object plane is placed on a movable stage by a projection optical system, and the first object and the movable stage are scanned by a scanning means to correspond to a projection magnification of the projection optical system. In a scanning type exposure apparatus that performs projection exposure while scanning in synchronization with a set speed ratio, a light source is provided on a second object plane provided in the vicinity of an imaging plane of the projection optical system from an oblique direction with respect to the optical axis of the projection optical system. Projecting the pattern by the means,
The image of the pattern formed on the object surface is detected by the light receiving means,
When detecting position information of the second object surface in the optical axis direction using a signal from the light receiving unit, the light source unit and / or the light receiving unit is provided with a light amount adjusting member capable of controlling a passing light amount. A scanning exposure apparatus wherein an output signal of an image of the pattern detected by a light receiving unit is adjusted. 5. The scanning type exposure apparatus according to claim 4, wherein said second object plane is made to coincide with an image plane of said projection optical system by a driving unit based on a signal from said light receiving unit. 6. A pattern on the reticle surface is projected and exposed on the wafer surface after the reticle is aligned with the wafer by using the surface position detecting device according to claim 1. And thereafter manufacturing the device through a developing process of the wafer. 7. After the reticle is aligned with the wafer using the scanning exposure apparatus according to claim 4, the pattern on the reticle surface is projected and exposed on the wafer surface, and then the wafer is developed. A device manufacturing method, wherein the device is manufactured through a processing step.