JP2765422B2 - Exposure apparatus and method for manufacturing semiconductor device using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure apparatus and a method for manufacturing a semiconductor device using the same, and more particularly to a projection optical system for projecting an electronic circuit pattern on a reticle surface when manufacturing a semiconductor device such as an IC or LSI. When the light is projected onto the wafer surface by the lens (lens), an appropriate exposure amount is always provided on the wafer surface so that a highly accurate projection pattern image can be obtained.

[0002]

2. Description of the Related Art Conventionally, a projection exposure apparatus (aligner) which is relatively easy to achieve high resolution and high throughput has been used for manufacturing semiconductor devices such as ICs and LSIs. This projection exposure apparatus exposes another area while moving the wafer each time one exposure is completed, as compared with a batch exposure method in which a pattern image is formed on the entire wafer surface by one exposure. Is repeatedly performed a plurality of times to form a pattern image on the entire wafer surface, and a step-and-repeat exposure method is often used.

At this time, the projection optical system converts the electronic circuit pattern on the reticle surface to a predetermined projection magnification, for example, 1 on the wafer surface.
Reduction projection is performed at / 5 or 1/10. In this case, the image quality of the pattern transferred onto the wafer surface depends on the performance of the illumination device,
For example, it is greatly affected by the amount of light (exposure amount) on the surface to be irradiated and its fluctuation.

The applicant of the present invention has disclosed a light amount control device which is controlled so that the irradiation light amount on a surface to be irradiated becomes a predetermined value, and which is particularly suitable for an exposure apparatus for manufacturing semiconductors, for example, as disclosed in Japanese Patent Application Laid-Open No. 62-187815.
And JP-A-63-193130 and JP-A-4-48714.

[0005] In particular, in Japanese Patent Application Laid-Open No. 4-48714, an incident light beam is amplitude-divided into two light beams in an optical path between a light source and an irradiation surface, and one of the light beams is irradiated onto a surface to be irradiated (reticle).
On the side, a half mirror (light splitting member) for guiding the other light beam to the photodetector is arranged, and the light beam passing through the half mirror is detected by the photodetector, thereby irradiating the light amount on the irradiated surface, That is, an exposure apparatus that controls an exposure amount on a wafer surface has been proposed.

[0006]

A light splitting member is arranged in an optical path between a light source and an irradiation surface, and one of the two light beams split by the light splitting member is directed to the irradiation surface side. The other method is to guide the other light beam to a photodetector, and to control the amount of exposure to the irradiated surface, that is, the wafer surface, using a signal obtained by the photodetector. It is assumed that the ratio to the upward exposure is always constant.

However, each optical element in the optical path from the light splitting member to the wafer absorbs the exposure light, and the transmittance changes over time or the transmittance changes due to changes in the environment (humidity, temperature, etc.). Then, it becomes difficult to provide an optimum exposure amount on the wafer surface even using a signal obtained by the photodetector.

According to the present invention, the exposure amount on the wafer surface can be reduced even if the transmittance of each optical element in the optical path from the light splitting member to the wafer changes over time or changes due to environmental changes. An object of the present invention is to provide an exposure apparatus that can be appropriately controlled and a method for manufacturing a semiconductor device using the same.

[0009]

According to the present invention, there is provided an exposure apparatus, comprising: (1-1) an exposure apparatus for exposing and transferring a pattern onto a substrate surface; Detecting means for detecting the position of a part of the exposure light from the position where the part of the exposure light is extracted to the substrate surface; A correction value for correcting the detection result of the detection means is derived from a history and information stored in the storage means, the detection result of the detection means is corrected using the correction value, and the exposure amount on the substrate surface is corrected. And control means for controlling the In particular, (1-1-1) the exposure history is a supply time of the exposure light. (1-1-2) The exposure history is a time that has elapsed since the supply of the exposure light was stopped. (1-1-3) The exposure light is an excimer laser light or the like.

(2-1) In an exposure apparatus for exposing and transferring a pattern onto a substrate surface, detecting means for extracting a part of the exposure light and indirectly detecting the amount of light on the substrate surface; Storage means for storing variation information on changes in the environment of the transmittance of the optical member existing between the position where a part of the optical member is taken out and the substrate surface, and the current environment and the information stored in the storage means. Control means for deriving a correction value for correcting the detection result of the detection means, correcting the detection result of the detection means using the correction value, and controlling the exposure amount on the substrate surface. I have. In particular, (2-1-1) the change in the environment is a change in humidity. (2-1-2) The change in the environment is a change in temperature. (2-1-3) The exposure light is an excimer laser light or the like.

The method of manufacturing a semiconductor device according to the present invention includes the steps of: (3-1) exposing and transferring a pattern onto a substrate surface using the exposure apparatus of the present invention, and developing the substrate to manufacture the semiconductor device. It is characterized by:

[0012]

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

In the figure, reference numeral 2 denotes an elliptical mirror. Reference numeral 1 denotes an arc tube as a light source, which has a high-luminance light emitting section 1a that emits ultraviolet rays, far ultraviolet rays, and the like. The light emitting unit 1a is arranged near the first focal point of the elliptical mirror 2. Reference numeral 3 denotes a cold mirror, which is formed of a multilayer film and transmits most infrared light and reflects most ultraviolet light. The elliptical mirror 2 forms a light emitting unit image (light source image) 1b of the light emitting unit 1a near the second focal point via the cold mirror 3. Reference numeral 4 denotes a shutter, which is arranged near the second focal point of the elliptical mirror 2.

Reference numeral 5 denotes an optical system which forms a light-emitting portion image 1b formed near the second focal point on an incident surface 6a of an optical integrator 6. The optical integrator 6 is configured by arranging a plurality of microlenses 6-i (i = 1 to N) two-dimensionally at a predetermined pitch.
A secondary light source is formed near b.

Reference numeral 7 denotes a condenser lens. A plurality of light beams emitted from the secondary light source near the emission surface 6b of the optical integrator 6 are condensed by the condenser lens 7, and partially reflected by the half mirror 8 as a light dividing member to be directed to the masking blade 10. The masking blade 10 is uniformly illuminated. The masking blade 10 is made up of a plurality of movable light shielding plates so that an arbitrary opening shape is formed.

Reference numeral 9 denotes an integrated light amount detector which detects a light beam passing through the half mirror 8 and indirectly detects an exposure amount on a surface of a wafer 14 described later. Reference numeral 11 denotes an imaging lens, which transfers the opening shape of the masking blade 10 to the surface of the reticle 12 as a surface to be irradiated, and uniformly illuminates a required area on the surface of the reticle 12.

A projection optical system 13 projects a circuit pattern on the reticle 12 on a wafer (substrate) 14 mounted on a wafer chuck 15 in a reduced size. Reference numeral 16 denotes a wafer stage.

An exposure detector 17 is provided so that its light receiving surface is substantially flush with the wafer 14. The exposure detector 17 sets the masking blade 10 to, for example, a 10 mm square in terms of the surface of the wafer 14, detects the total luminous flux, and detects the actual illuminance on the surface of the wafer 14, that is, the exposure.

Numeral 19 denotes an arithmetic means. In its storage unit, information on the variation of the transmittance of the optical elements arranged in the optical path from the light dividing member 8 to the wafer 14 based on the exposure history and the transmittance of the transmittance due to the environmental change are obtained. Fluctuation information is stored. The calculating means 19 determines the exposure amount on the surface of the wafer 14 using the signal from the integrated light amount detector 9 and the transmittance fluctuation information stored in the storage unit. The arithmetic means 19 controls the opening and closing of the shutter 4 to control the exposure amount on the surface of the wafer 14.

In addition, the calculating means 19 determines the exposure amount on the surface of the wafer 14 using the measurement result of the irradiation light amount obtained by the integrated light amount detector and the measurement result obtained by the exposure amount detector 17 before the pattern transfer. doing.

In this embodiment, as described above, the wafer 1
By appropriately setting the exposure amounts on the four surfaces, the pattern on the reticle 12 surface is transferred to the wafer surface. The semiconductor device is manufactured through a predetermined development process.

Next, a method of controlling the amount of exposure on the surface of the wafer 14 by the calculating means 19 of this embodiment will be described.

The parameter by which the transmittance of each optical element from the light splitting member 8 to the surface of the wafer 14 varies depending on the exposure history is obtained in advance by experiments.

FIGS. 2 to 4 show the illuminance (measured value) I ₁ on the integrated light amount detector 9 and the wafer 1 during exposure and non-exposure.
Ratio to illuminance (actual illuminance) I ₂ on four surfaces (exposure correction value)
FIG. 5 is an explanatory diagram showing a change in φ (= I ₁ / I ₂ ) with time t on the horizontal axis.

In FIG. 2, when exposure is performed for the first time (t = t ₀ ), the ratio (hereinafter referred to as “exposure correction value”) φ at that time is set to φ = 1.

In the figure, sections A, C, and E indicate changes in the exposure correction value φ during exposure, and sections B and D indicate changes in the exposure correction value φ during non-exposure.

Now, exposure starts at t = t ₀ (section A). The value of the exposure correction value φ _K at a certain time (t = t _K ) in the section A is as follows: φ _K = f ₁ (t _K −t ₀ , e _A , e _B , φ ₀ )
・ ・ (1)

Here, e _A is the amount of light incident on the imaging lens 11 per unit time, e _B is the amount of light incident on the projection optical system B per unit time, and φ ₀ is the exposure correction immediately before the start of exposure. Value, in this case φ ₀ = 1. Light amount e _A ,
Since e _B depends reflected light from the light dividing member 8, the opening area S _m of the masking blade 10, the average transmittance R _r of the reticle 12, equation _{(1), φ K = f 2 (t} K -t ₀ , I ₁ , S _m , R _r , φ ₀ ) (2)

Then, by inputting (or automatically reading) the opening area S _m of the masking blade 10 and the average transmittance R _r of the reticle 12 at the time of exposure to the arithmetic means 19, the exposure correction value φ that changes every moment is obtained. The calculated exposure amount is accurately controlled based on the calculated exposure correction value φ.

Next, it is assumed that the exposure is stopped at t = t ₁ and the exposure is started again at t = t ₂ . The exposure correction value φ _{1 at} t = t ₁ is φ ₁ = f ₂ (t ₁ −t ₀ , I ₁ , S _m , R _r , φ
₀₎ is calculated by, t = exposure in t ₂ correction value phi ₂
Is calculated by φ ₂ = f ₃ (t ₂ −t ₁ , φ ₁ ).
After starting exposure, the exposure correction value at t = t _J φ _J is phi _J =
It is calculated by f ₂ (t _J −t ₂ , I ₁ , S _m , R _r , φ ₂ ). By storing the immediately preceding exposure correction value and the elapsed time in this way, the exposure history (exposure time,
From the non-exposure time), the current exposure correction value can always be calculated. The functions f ₂ and f ₃ are obtained in advance by experiments.

In this embodiment, the exposure correction value φ during the exposure is
Is calculated every moment, and exposure control is performed for each shot. However, the exposure time for one shot is very short, and there is almost no change in the exposure correction value. 1 for each wafer
The exposure may be performed by calculating two exposure correction values φ.

FIG. 3 shows one exposure correction value φ for each shot.
FIG. 5 is an explanatory diagram when the exposure is performed by calculating the following equation. Time t ₀
The first shot during ~t _1, t ₂ second shot during ~t _3, the change in the exposure correction value of each time doing the exposure of the third shot between t ₄ ~t ₅ is a dotted line It is shown.

In this embodiment, the first shot uses the exposure correction value φ ₀ , the second shot uses the exposure correction value φ ₂ , and the third shot uses the exposure correction value φ ₄ as a fixed exposure correction value for each shot. ing. Each exposure correction value (φ ₁ , φ
₂ , φ ₃ ...) Are the same as in the first embodiment.

FIG. 4 is an explanatory view in which one exposure correction value is calculated for each wafer and exposure is performed. The first wafer during the time t ₀ ~t _1, from time t ₂ is subjected to exposure of the second wafer, the exposure of each wafer contains an exposure of a large number of shots.

In this embodiment, a fixed exposure correction value is used at each wafer exposure. In this case, the exposure times during the exposure of one wafer, but non-exposure is repeated so on are calculated every second exposure correction value may be calculated exposure correction value phi _1, between each shot non-exposure time is the overall exposure of the first wafer may be calculated exposure correction value phi ₁ from one exposure and considered average amount of incident light is shorter.

If the transmittance changes due to an environmental change, it is better to monitor the environmental change with a sensor (not shown) and correct the result and calculation.

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

This embodiment is different from the first embodiment shown in FIG. 1 in that a light source 20 such as a KrF excimer laser which emits pulses is used as a light source.
And the other configuration is the same.

In this embodiment, since the exposure and non-exposure are repeated during one-shot exposure, the concept of the average incident light amount described above is applied.

In each of the above embodiments, an example in which the exposure correction value is calculated based on the exposure history has been described. An exposure correction value may be calculated.

Further, the calibration may be performed every certain period in order to correct the deviation between the calculated value of the exposure correction value and the actual value at the time of execution.

[0042]

As described above, according to the present invention, even if the transmittance of each optical element in the optical path from the light splitting member to the wafer changes over time or changes due to environmental changes,
The exposure amount on the wafer surface can be appropriately controlled.

[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 explanatory diagram of an exposure correction value according to the first embodiment of the present invention.

FIG. 3 is an explanatory diagram of an exposure correction value according to the first embodiment of the present invention.

FIG. 4 is an explanatory diagram of an exposure correction value according to the first embodiment of the present invention.

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 20 Light source 2 Elliptic mirror 3 Cold mirror 4 Shutter 5 Optical system 6 Optical integrator 7 Condensing lens 8 Light splitting member 9 Integrated light amount detector 10 Masking blade 11 Imaging lens 12 Reticle 13 Projection optical system 14 Wafer 17 Exposure amount detection Unit 19 arithmetic means

Claims (9)

(57) [Claims] 1. An exposure apparatus for exposing and transferring a pattern onto a substrate surface, a detecting means for extracting a part of the exposure light and indirectly detecting a light amount on the substrate surface, and extracting a part of the exposure light. Storage means for storing variation information with respect to the exposure history of the transmittance of the optical member existing from the position to the substrate surface, and the detecting means based on the exposure history up to now and the information stored in the storage means. Control means for deriving a correction value for correcting the detection result, correcting the detection result of the detection means using the correction value, and controlling an exposure amount on the substrate surface. 2. The exposure apparatus according to claim 1, wherein the exposure history is a supply time of the exposure light. 3. The exposure apparatus according to claim 1, wherein the exposure history is a time elapsed since supply of the exposure light was stopped. 4. An exposure apparatus according to claim 1, wherein said exposure light is an excimer laser light. 5. An exposure apparatus for exposing and transferring a pattern onto a substrate surface, a detecting means for extracting a part of the exposure light and indirectly detecting a light amount on the substrate surface, and extracting a part of the exposure light. Storage means for storing variation information on changes in the environment of the transmittance of the optical member existing between the position and the substrate surface, and detection of the detection means from a current environment and information stored in the storage means. An exposure apparatus comprising: a control unit that derives a correction value for correcting a result, corrects a detection result of the detection unit using the correction value, and controls an exposure amount on the substrate surface. 6. The exposure apparatus according to claim 5, wherein the change in the environment is a change in humidity. 7. The exposure apparatus according to claim 5, wherein the change in the environment is a change in temperature. 8. An exposure apparatus according to claim 5, wherein said exposure light is excimer laser light. 9. A method for manufacturing a semiconductor device, comprising: exposing and transferring a pattern onto a substrate surface using the exposure apparatus according to claim 1; and developing the substrate to manufacture a semiconductor device.