JP2007189176A - Exposure apparatus, exposure method, and manufacturing method of device having fine pattern - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aligner for reducing the growth of a carbon film and an oxide film on the surface of a mirror in an optical path space, restraining deterioration in optical characteristics, and extending the lifetime until overhauls by reducing the inflow of a contamination substance into the optical path space of the aligner from an external environment. <P>SOLUTION: The aligner is connected to the external environment 105 via a sealed space 103 for connection. The aligner has an apparatus 121 for supplying clean gas to the sealed space for connection or its periphery, so that the contamination substance entering the sealed space for connection from the external environment is reduced, when the external environment is connected to the sealed space for connection. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an exposure apparatus, an exposure method using ultraviolet rays as an exposure light source, and a method for manufacturing a device having a fine pattern such as a semiconductor device using these. In particular, extreme ultraviolet rays or soft X-rays (in this specification and claims, means light having a wavelength of 100 nm or less, sometimes referred to as “EUV (Extreme Ultraviolet) light”) is used as an exposure light source. The present invention relates to an exposure apparatus, an exposure method, and a method for manufacturing a device having a fine pattern using these.

  When a semiconductor element or a liquid crystal display element is manufactured by a photolithography process, a pattern image formed on a mask (including a reticle in the present specification and claims) is transferred to a photosensitive material through a projection optical system ( 2. Description of the Related Art A reduction projection exposure apparatus that reduces and projects each projection (shot) area on a wafer coated with a resist is used. Circuits such as semiconductor elements and liquid crystal display elements are transferred by exposing a circuit pattern onto a wafer or glass with the projection exposure apparatus, and are formed by post-processing.

In recent years, high density integration of integrated circuits, that is, miniaturization of circuit patterns has been promoted. In order to cope with this, the projection light in the projection exposure apparatus also tends to be shortened in wavelength. In other words, the KrF excimer laser (248 nm) has been used instead of the mainstream mercury lamp emission lines, and a projection exposure system using a short wavelength ArF excimer laser (193 nm) has been put to practical use. ing. Development of an exposure apparatus using an F ₂ laser (157 nm) and an optical exposure apparatus having a liquid immersion mechanism are also being promoted for further high density integration.

  Furthermore, in order to improve the resolving power of the optical system limited by the diffraction limit of light, projection lithography using EUV light having a shorter wavelength (11 to 14 nm) instead of conventional ultraviolet rays has been developed ( For example, Non-Patent Document 1). This technique is called EUV lithography, and is expected as a technique capable of obtaining a resolution of 45 nm or less that cannot be achieved by conventional optical lithography.

  FIG. 8 shows an outline of the projection optical system of such an exposure apparatus using EUV light. The EUV light emitted from the light source 31 becomes a substantially parallel light beam via a concave reflecting mirror 34 that acts as a collimator mirror, and enters an optical integrator 35 including a pair of fly-eye mirrors 35a and 35b.

  Thus, a substantial surface light source having a predetermined shape is formed in the vicinity of the reflective surface of the fly-eye mirror 35a, that is, in the vicinity of the exit surface of the optical integrator 35. The light from the substantial surface light source is reflected by the plane reflecting mirror 36 and then forms an elongated arc-shaped illumination area on the mask M. Here, an aperture plate for forming an arcuate illumination region is not shown. The light reflected on the surface of the mask M is then reflected in turn by the mirrors M1, M2, M3, M4, M5, and M6 of the projection optical system 37, and is formed as the exposure light 1 on the surface of the mask M. Is formed on the resist 3 coated on the wafer 2. The wafer 2 coated with the resist 3 is also called a sensitive substrate. Here, the mirror (reflecting mirror) is composed of a multilayer film in which two kinds of substances having different refractive indexes are laminated. Further, a capping layer may be formed on the multilayer film surface in order to improve the oxidation resistance of the multilayer film surface and reduce the formation of the carbon film.

  In general, EUV light is absorbed by any substance and does not pass through the air. For this reason, in an exposure apparatus using EUV light, in order to allow exposure light to reach the wafer surface with sufficient illuminance, it is necessary to reduce or eliminate light-absorbing substances on the exposure optical path and maintain the optical path space at a high vacuum. is there. For this purpose, it is necessary to construct the optical path space of the exposure apparatus using a substance that emits as little gas as possible. The exposure apparatus optical path space including the projection optical system 37 may be accommodated in a vacuum chamber (not shown in FIG. 8). As described above, the exposure apparatus using EUV light is capable of transferring a finer light-shielding pattern, but has a design in which it is necessary to exclude the light-absorbing substance (use of a member that emits the light-absorbing substance is limited). Not easy.

In general, organic substances and H ₂ O molecules are present in the vacuum chamber due to gas released from the organic substance constituting the vacuum chamber, backflow from the pump, and desorption of substances adhering to the surface of the non-organic substance. To do. Further, the resist is a substance including organic substances and H ₂ O molecules, and a large amount of these contaminant substances are released. In addition, a relatively large amount of organic substance having a relatively light weight and high vapor pressure, which is broken by light irradiation to the resist, is released in a larger amount. Contaminants in the exposure apparatus optical path space are adsorbed to the vacuum apparatus constituent member including the optical element. When the contaminant is adsorbed on the surface of the optical element, a carbon film or an oxide film is formed on the surface of the multilayer film by a photochemical reaction with the exposure light. Since both the carbon coating and the oxide film are composed of a light-absorbing material, this causes a reduction in mirror reflectivity. In general, when a 1 nm carbon film is laminated on the surface of the mirror, the reflectivity of the mirror decreases by about 1%. In addition, aberrations occur due to the carbon film or oxide film on the mirror surface, and the optical characteristics of the mirror deteriorate, for example, causing uneven illumination. As a result, the productivity of the exposure apparatus is reduced due to a decrease in the throughput of the exposure apparatus, and the apparatus life is shortened.

  On the other hand, as described above, in the exposure apparatus using extreme ultraviolet light, unlike the conventional light exposure apparatus, the optical path space is not filled with an inert gas. Is not easy. Further, it is not easy to reduce the reactivity of the photochemical reaction with the contaminants adsorbed on the surface of the multilayer film. Therefore, in order not to deteriorate the optical characteristics of the mirror, it is important to reduce the amount of contaminants entering the optical path space of the exposure apparatus.

  An apparatus such as a coater / developer may be added to the exposure apparatus. FIG. 7 is a view showing a configuration of a conventional exposure apparatus 101 provided with a coater / developer 105. A coater / developer 105 applies a resist to the wafer and transports it to the exposure apparatus 101. The coater / developer 105 is connected to the optical path space of the exposure apparatus 101 held in a high vacuum via a load lock (LL) chamber 103 having a pair of gate valves 111 and 113, which is a sealed space for connection. . First, the gate valve 113 is opened, the coater / developer 105 and the load lock chamber 103 communicate with each other, and the wafer is transferred to the load lock chamber 103. Thereafter, the gate valve 113 is closed, and the load lock chamber 103 is evacuated. Thereafter, the gate valve 111 is opened, the load lock chamber 103 and the exposure apparatus 101 communicate with each other, and the wafer is transferred to the exposure apparatus 101.

Since the coater / developer 105 performs a resist coating operation, a large amount of organic substances and H ₂ O molecules are released from the resist. Further, unlike the exposure apparatus 101, the coater / developer 105 is not sufficient for reducing substances that degrade optical characteristics, and therefore there are a large amount of organic substances and H ₂ O molecules that do not originate from the resist. When contaminants flow into the exposure apparatus via the connection closed space (load lock chamber) during resist conveyance, optical characteristics such as reflectivity deterioration of the multilayer mirror are deteriorated. For this reason, it is necessary to sufficiently reduce the amount of contaminants flowing into the exposure apparatus from an external environment such as a coater / developer.

D. Tichenor, et al. SPIE 2437 (1995) 292

  In this way, by reducing the inflow of contaminants from the external environment, such as a coater / developer, into the exposure device optical path space, the growth of carbon coatings and oxide films on the mirror surface in the optical path space is reduced, resulting in degradation of optical characteristics. There is a need for an EUV exposure apparatus that suppresses this and extends the life until overhaul. Furthermore, there is a need for an exposure method using the exposure apparatus and a method for manufacturing a device having a fine pattern using the exposure method.

  The exposure apparatus according to the present invention is connected to an external environment through a connection sealed space. In the exposure apparatus according to the present invention, when the external environment and the sealed space for connection are in contact with each other, a clean gas is placed in or around the sealed space for connection so as to reduce contaminants entering the sealed space for connection from the external environment. It has the apparatus which supplies this.

  In the exposure apparatus according to the present invention, the contamination substance adheres to the reflecting mirror of the projection optical system of the exposure apparatus by reducing the inflow of the contaminant substance from the external environment into the exposure apparatus optical path space using a clean gas. As much as possible, the deterioration of the optical characteristics of the reflecting mirror can be suppressed, and the life until overhaul can be extended.

  According to the present invention, by reducing the inflow of contaminant material from the external environment into the exposure apparatus optical path space, the contamination material adheres to the reflection mirror of the projection optical system of the exposure apparatus as much as possible. It is possible to provide an EUV light exposure apparatus, an exposure method, and a method for manufacturing a device having a fine pattern using this exposure method, in which deterioration of optical characteristics is suppressed and the life until overhaul is extended.

Hereinafter, embodiments of the present invention will be described. FIG. 1 is a schematic view showing the structure of an exposure apparatus according to the first embodiment of the present invention. The exposure apparatus according to the first embodiment is shown in FIG. 7 in that a clean gas (a gas containing less organic matter and H ₂ O) can be supplied from the supply source 121 to the load lock chamber 103. Different from the conventional extreme ultraviolet exposure apparatus. The load lock chamber 103 is filled with clean gas and maintained at a pressure higher than atmospheric pressure. Here, the clean gas includes a rare gas such as argon and an inert gas containing nitrogen. Air may also be used. These gases are preferably passed through a filter or the like to increase the cleanliness.

  Even when the gate valve 113 is opened and contacted with the coater / developer 105, if the pressure in the load lock chamber 103 is always kept higher than the pressure of the coater / developer 105, the inflow of contaminants from the coater / developer 105 is prevented. Can be prevented. However, the clean gas supply source 121 and the load lock chamber 103 are connected by piping. When the pipe diameter is not sufficient with respect to the pipe length, when the gate valve 113 is opened to communicate with the coater / developer 105, clean gas flows from the load lock chamber 103 to the coater / developer 105, while the supply source 121 Since the supply of clean gas from cannot catch up, the pressure in the load lock chamber 103 decreases. Even if the pressure in the load lock chamber 103 drops to the pressure of the coater / developer 105, clean gas continues to flow to the coater / developer 105 due to inertia. For this reason, when the flow of clean gas stops, the pressure of the coater / developer 105 is higher than the pressure of the load lock chamber 103. As a result, the contaminant material of the coater / developer 105 flows into the load lock chamber 103.

  In order to keep the pressure in the load lock chamber 103 higher than the pressure in the coater / developer 105 even when the gate valve 113 is opened to communicate with the coater / developer 105, the capacity of the clean gas supply source is increased. At the same time, the pressure may be set higher and the pipe diameter may be sufficiently larger than the pipe length. However, in some cases, the above design cannot be performed in terms of cost and equipment space.

  FIG. 2 is a schematic view showing the structure of an exposure apparatus according to the second embodiment of the present invention. The exposure apparatus of the present embodiment includes a clean gas buffer tank 123 near the load lock chamber 103. When clean gas flows from the load lock chamber 103 to the coater / developer 105 when the gate valve 113 is opened and contacted with the coater / developer 105, clean gas is supplied from the buffer tank 123 to the load lock chamber 103, and the load lock. The pressure in the chamber 103 is maintained. The capacity of the buffer tank 123 is sufficient to keep the pressure in the load lock chamber 103 always higher than the pressure in the coater / developer 105 while the load lock chamber 103 is in communication with the coater / developer 105. . By providing the buffer tank 123, the requirements for the pipe length and the pipe diameter upstream of the buffer tank 123 are alleviated.

  FIG. 3 is a schematic view showing the structure of an exposure apparatus according to the third embodiment of the present invention. The exposure apparatus of this embodiment includes a pressure control system that controls the pressure in the load lock chamber 103 to be constant. The pressure control system includes a pressure gauge 135 that detects the pressure in the load lock chamber 103, a controller 131 that determines a target value for the flow rate of clean gas supplied based on the detected pressure value, and a gas flow rate that is a target value. It consists of an actuator 133 for operating the valve opening of the control valve. The controller 131 may be a feedback controller having a proportional / integral control function, for example. The actuator 133 may be configured to receive the target value of the gas flow rate from the controller 131 and control the flow rate by a flow rate control system (not shown) based on the target value. A mass flow controller (MFC) may be used.

  In a state where the load lock chamber 103 is sealed, the pressure in the load lock chamber 103 is high, so that the operation amount such as the valve opening of the control valve is small, and the gas flow rate is reduced. When the load lock chamber 103 communicates with the coater / developer 105 and clean gas flows from the load lock chamber 103 to the coater / developer 105 and the pressure in the load lock chamber 103 decreases, the operation amount such as the valve opening of the control valve is reduced. It becomes larger and the gas flow rate is increased. Therefore, the gas pipe diameter may be sufficiently large, and a large amount of gas may be supplied only when necessary. Further, the pressure control system of this embodiment may be installed downstream of the buffer 123 in the second embodiment. By providing the pressure control system, the supply amount of clean gas is minimized, and the cost of clean gas can be reduced.

  FIG. 4 is a schematic view showing the structure of an exposure apparatus according to the fourth embodiment of the present invention. The exposure apparatus of this embodiment includes a differential pressure control system that controls the differential pressure between the pressure of the load lock chamber 103 and the pressure of the coater / developer 105 to be constant. The differential pressure control system includes a differential pressure gauge 137 that detects a differential pressure between the pressure of the load lock chamber 103 and the pressure of the coater / developer 105, and a target value of a flow rate of clean gas supplied based on the detected differential pressure value. And an actuator 133 for operating the valve opening of the control valve so that the gas flow rate becomes a target value. The controller 131 may be a feedback controller having a proportional / integral control function, for example. The actuator 133 may be configured to receive the target value of the gas flow rate from the controller 131 and control the flow rate by a flow rate control system (not shown) based on the target value.

  In the state where the load lock chamber 103 is sealed, the differential pressure between the pressure of the load lock chamber 103 and the pressure of the coater / developer 105 is large, so the operation amount such as the valve opening of the control valve is small, and the gas flow rate is reduced. Is squeezed. When the load lock chamber 103 communicates with the coater / developer 105 and clean gas flows from the load lock chamber 103 to the coater / developer 105, the pressure difference between the pressure of the load lock chamber 103 and the pressure of the coater / developer 105 decreases. The amount of operation such as the valve opening of the control valve is increased, and the gas flow rate is increased. Therefore, the gas pipe diameter may be sufficiently large, and a large amount of gas may be supplied only when necessary. Further, the pressure control system of this embodiment may be installed downstream of the buffer 123 in the second embodiment. By providing the pressure control system, the supply amount of clean gas is minimized, and the cost of clean gas can be reduced.

  As a fifth embodiment, instead of detecting the pressure by the pressure gauge 135 in the third embodiment or detecting the differential pressure by the differential pressure gauge 137 in the fourth embodiment, the gate valve 113 is in the open state from the closed state. It is also possible to generate a signal that detects that the transition has started, and to operate the actuator 133 by the controller 131 based on the signal. In this case, the controller 131 may be a feedforward controller that sets a predetermined valve opening target value or flow rate target value in the actuator 133.

  According to the control system of this embodiment, the valve opening target value and the flow rate target value can be increased by the controller 131 before the gate valve 113 is opened and the pressure in the load lock chamber 103 decreases. Therefore, even when there is a delay in the control system due to the piping, the pressure drop in the load lock chamber 103 can be prevented by increasing the gas supply amount before the pressure drop.

FIG. 5 is a schematic view showing the structure of an exposure apparatus according to the sixth embodiment of the present invention. The exposure apparatus of the present embodiment is configured such that clean gas (a gas containing less organic matter and H ₂ O) can be supplied from the supply source 121 to the boundary between the load lock chamber 103 and the coater / developer 105. In FIG. 5, the gas outlet is disposed outside the load lock chamber 103 and adjacent to the gate valve 113, but may be disposed inside the load lock chamber 103 and adjacent to the gate valve 113. . The gas jet outlet is flattened or the jet outlet is branched, for example, so that the gas is jetted out in a curtain shape to form a partition wall made of the gas. As a result, even when the gate valve 113 is opened and the load lock chamber 103 communicates with the coater / developer 105, the contamination substance can be prevented from flowing into the load lock chamber 103 from the coater / developer 105. If a plurality of jet outlets are provided at two positions facing each other, the inflow of contaminants can be prevented more efficiently. Based on a signal that detects that the gate valve 113 has started to move from the closed state to the open state, the gas is ejected in a curtain shape to form a partition wall by the gas only while the gate valve 113 is in the open state. Also good.

  FIG. 6 is a schematic view showing the structure of an exposure apparatus according to the seventh embodiment of the present invention. The exposure apparatus of this embodiment is different from the exposure apparatus according to the sixth embodiment of the present invention only in that the jet outlet is configured so that more gas flows in the direction of the coater / developer 105. The end of the pipe may be arranged in the direction of the coater / developer 105 so that more gas flows in the direction of the coater / developer 105. By allowing more gas to flow in the direction of the coater / developer 105, the inflow of contaminants from the coater / developer 105 to the load lock chamber 103 can be prevented more efficiently.

  When the partition wall made of gas functions sufficiently, the structure and function of the gate valve 113 may be simplified or omitted. By reducing the operation time of the gate valve 113, the throughput of the exposure apparatus is improved.

  Note that the gas outlet from the clean gas supply source 121 may be disposed in the exposure apparatus 101.

  Hereinafter, an example of an embodiment of a semiconductor device manufacturing method according to the present invention will be described. FIG. 9 is a flowchart showing an example of the embodiment of the semiconductor device manufacturing method of the present invention. The manufacturing process of this example includes the following processes.

(1) Wafer manufacturing process for manufacturing a wafer (or wafer preparation process for preparing a wafer)

(2) Mask manufacturing process for manufacturing a mask used for exposure (or mask preparation process for preparing a mask)

(3) Wafer processing process for performing necessary exposure processing on the wafer

(4) Chip assembly process for cutting out chips formed on the wafer one by one and making them operable

(5) Chip inspection process for inspecting completed chips

Each process further includes several sub-processes.

  Among these main processes, the main process that has a decisive influence on the performance of the semiconductor device is the wafer processing process. In this step, designed circuit patterns are sequentially stacked on a wafer to form a large number of chips that operate as CPUs or memories. This wafer processing step includes the following steps.

(1) A thin film forming process for forming a dielectric thin film to be an insulating layer, a wiring portion, or a metal thin film for forming an electrode portion (using CVD or sputtering)

(2) Oxidation process for oxidizing the thin film layer and wafer substrate

(3) Lithography process for forming a resist pattern using a mask (reticle) to selectively process a thin film layer, a wafer substrate, or the like

(4) An etching process (for example, using a dry etching technique) for processing a thin film layer or a substrate according to a resist pattern

(5) Ion / impurity implantation diffusion process

(6) Resist stripping process

(7) Inspection process for inspecting further processed wafers

The wafer processing process is repeated as many times as necessary to manufacture a semiconductor device that operates as designed.

  In the present embodiment, the above-described EUV light exposure apparatus is used in the lithography process. For this reason, by reducing the inflow of contaminants from the external environment into the optical path of the exposure apparatus, the optical characteristics of the reflecting mirror can be suppressed, and the exposure apparatus can be continued for a long time by extending the maintenance cycle. It becomes possible to drive. Therefore, a device having a fine pattern can be manufactured with high throughput.

1 is a schematic diagram showing the structure of an exposure apparatus according to a first embodiment of the present invention. It is a schematic diagram which shows the structure of the exposure apparatus by the 2nd Embodiment of this invention. It is a schematic diagram which shows the structure of the exposure apparatus by the 3rd Embodiment of this invention. It is a schematic diagram which shows the structure of the exposure apparatus by the 4th Embodiment of this invention. It is a schematic diagram which shows the structure of the exposure apparatus by the 6th Embodiment of this invention. It is a schematic diagram which shows the structure of the exposure apparatus by the 7th Embodiment of this invention. It is a figure which shows the structure of the conventional exposure apparatus which provided the coater / developer together. An outline of a projection optical system of an exposure apparatus using EUV light is shown. It is a flowchart which shows an example of embodiment of the semiconductor device manufacturing method of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Exposure light, 2 ... Wafer, 3 ... Resist, 37 ... Projection optical system, 101 ... Exposure apparatus, 103 ... Load lock chamber, 105 ... Coater / developer, 111, 113 ... Gate valve

Claims (10)

  An exposure apparatus connected to an external environment through a connection sealed space, so that when the external environment and the connection sealed space communicate with each other, the contaminants entering the connection sealed space from the external environment are reduced. An exposure apparatus comprising an apparatus for supplying a clean gas to or around the sealed space for connection.   It has a device for supplying clean gas to the connection sealed space so that the pressure in the connection sealed space is always kept higher than the pressure in the external environment when the external environment and the connection sealed space communicate with each other. The exposure apparatus according to claim 1, characterized in that:   The exposure apparatus according to claim 2, further comprising a buffer tank between the clean gas supply source and the connection closed space.   And a device for detecting a pressure of the connection sealed space and controlling a flow rate of the clean gas supplied from the clean gas supply source to the connection sealed space based on the pressure. Item 3. The exposure apparatus according to Item 2.   And a device for detecting a differential pressure between the external environment and the connection sealed space and controlling a flow rate of the clean gas supplied from the clean gas supply source to the connection sealed space based on the differential pressure. The exposure apparatus according to claim 2, wherein:   A device for detecting that the valve between the external environment and the sealed connection space is no longer closed, and controlling the flow rate of the clean gas supplied from the clean gas supply source to the sealed connection space The exposure apparatus according to claim 2, further comprising:   When the external environment and the connection sealed space communicate with each other, the apparatus has a device for ejecting clean gas to the boundary between the external environment and the connection sealed space to form the clean gas curtain. The exposure apparatus according to claim 1.   8. The exposure apparatus according to claim 7, wherein the apparatus for forming the clean gas curtain is configured to eject more of the clean gas in the direction of the external environment.   An exposure method comprising: exposing and transferring a light shielding pattern formed on a mask onto a sensitive substrate using the exposure apparatus according to claim 1.   A method for producing a device having a fine pattern, comprising: exposing and transferring a light-shielding pattern formed on a mask onto a sensitive substrate using the exposure method according to claim 9.

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