JP2001274069A - Resist pattern forming method and semiconductor manufacturing system - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To perform a heat treatment with excellent uniformity on a wafer surface even for a warped wafer, thereby improving the processing accuracy of a resist pattern. SOLUTION: After exposing an LSI pattern to a resist film on a wafer in an exposure apparatus 10, the wafer is placed on a hot plate in a PEB unit 26 and subjected to a heat treatment. In the method of forming a resist pattern for developing the wafer, the amount of warpage of the wafer is measured in the exposure apparatus 10 before the step of heating, and the hot plate is heated based on the measured amount of warpage in the step of heating the wafer. The temperature of the hot plate is changed in the in-plane direction such that the longer the distance between the substrate and the hot plate on the substrate mounting surface becomes, the larger the amount of supplied heat becomes.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lithography technique for forming a desired pattern on a resist formed on a substrate to be processed, and more particularly to a method of forming a resist pattern and a semiconductor in which the influence of warpage of the substrate to be processed is taken into consideration. Related to manufacturing system.

[0002]

2. Description of the Related Art In a lithography process of a semiconductor device, application of a chemically amplified resist has become indispensable with miniaturization of a semiconductor element. In a process using this type of resist, P is applied after exposure to diffuse the acid generated by exposure.
A heat treatment step called EB (Post Exposure Bake) is required. And the resist pattern size is PE
Since the temperature greatly depends on the processing temperature of B, temperature uniformity within the substrate surface and between the substrates is required.

In the PEB process, a method is generally used in which a semiconductor substrate is placed in a state where a small gap (proximity gap) is provided between a temperature-controlled hot plate and a substrate and a hot plate are in close contact with each other. ing. A heating device for performing the PEB process usually uses a flat hot plate.

Incidentally, since a dielectric film as a capacitor material of a transistor, a metal film used for wiring, an interlayer insulating film, and the like are already formed on a semiconductor substrate on which a lithography process is performed, the semiconductor substrate is warped. It often occurs. When such a semiconductor substrate is subjected to heat treatment using a hot plate in a heating device, a difference occurs in the distance between the hot plate and the substrate in the substrate surface, so that the temperature variation on the substrate surface increases. Had occurred.

In order to solve these problems, a plurality of temperature sensors are provided on the upper surface of the hot plate, and the amount of warpage of the substrate is indirectly detected by detecting a temperature change before and after placing the semiconductor substrate on the hot plate. A heat treatment apparatus that changes the set temperature of the hot plate when the amount of warpage is equal to or larger than the allowable range has already been proposed (Japanese Patent Laid-Open No. Hei 1 (1994)).
No. 1-329941). However, in this type of apparatus, it is difficult to perform heat treatment with excellent temperature accuracy because the heat treatment proceeds before the amount of substrate warpage is fed back to the heat treatment temperature. Further, since a plurality of temperature sensors are separately required, a new problem that the cost is increased has occurred.

[0006]

As described above, conventionally, when a semiconductor substrate subjected to pattern exposure has a warped shape, heat treatment with a hot plate in a PEB process or the like after exposure may cause a problem in the substrate surface. In this case, there is a problem that temperature variations occur and the processing accuracy of a finally obtained resist pattern is reduced.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a substrate to be processed having a warped shape, and even if the amount of warpage differs for each substrate, the in-plane surface of the substrate can be obtained. Heat treatment with excellent uniformity
An object of the present invention is to provide a method of forming a resist pattern and a semiconductor manufacturing system that can contribute to improvement in processing accuracy of a resist pattern.

[0008]

(Structure) In order to solve the above-mentioned problem, the present invention employs the following structure.

That is, the present invention provides a step of forming a resist film on a substrate to be processed, a step of exposing a desired pattern to the resist film, and a step of placing the substrate having the pattern exposed on the resist film on a hot plate. In the resist pattern forming method including a step of performing a heat treatment and a step of performing a development treatment on the heat-treated resist film, measuring the amount of warpage of the substrate to be processed before the step of performing the heat treatment, In the step of heating the substrate to be processed, the amount of heat supplied by the hot plate is controlled according to the measured amount of warpage.

Here, preferred embodiments of the present invention include the following. (1) As means for controlling the amount of heat supplied by the hot plate, the temperature of the hot plate is adjusted in the in-plane direction so that the longer the distance between the substrate to be processed and the hot plate on the substrate mounting surface of the hot plate, the larger the amount of heat supplied. Change with.

(2) As means for controlling the amount of heat supplied by the hot plate, the temperature of the hot plate is controlled so that the larger the amount of warpage of the substrate to be processed, the greater the total amount of heat supplied by the hot plate.

(3) As means for measuring the amount of warpage of the substrate to be processed, an in-plane of vacuum chuck pressure for fixing the substrate to be processed on a stage in an exposure apparatus for exposing a desired pattern on a resist film. Obtaining a distribution and calculating the amount of warpage based on this distribution.

Further, the present invention provides a resist coating apparatus for forming a resist film on a substrate to be processed, an exposure apparatus for exposing a desired pattern to the substrate on which the resist film is formed, and an exposure apparatus for exposing the pattern. A heating device for placing the processed substrate on a hot plate and performing a heating process, a developing device for performing a developing process on the heated processed substrate, and transporting the processed substrate between the respective devices. And a heating mechanism for measuring the amount of warpage of the substrate to be processed, wherein the heating device is configured to control the heating plate based on the amount of warpage of the substrate measured by the measuring unit. The temperature distribution in the in-plane direction of the hot plate is controlled such that the longer the distance between the substrate to be processed and the hot plate on the substrate mounting surface, the larger the amount of heat supplied.

The present invention also provides a resist coating apparatus for forming a resist film on a substrate to be processed, an exposure apparatus for exposing a desired pattern on the substrate on which the resist film has been formed, and an exposure apparatus for exposing the pattern. A heating device for placing the processed substrate on a hot plate and performing a heating process, a developing device for performing a developing process on the heated processed substrate, and transporting the processed substrate between the respective devices. A transfer mechanism, and a means for measuring the amount of warpage of the substrate to be processed, wherein the heating device has an amount of warpage based on the amount of warpage of the substrate measured by the measuring means. It is characterized in that the temperature of the hot plate is controlled so that the total amount of supplied heat increases as the temperature increases.

Here, preferred embodiments of the present invention include the following. (1) The means for measuring the amount of warpage of the substrate to be processed is provided in a vacuum chuck mechanism for fixing the substrate to be processed on a stage in an exposure apparatus, and a function of detecting an in-plane distribution of vacuum chuck pressure is provided. Calculate the amount of warpage according to the detected in-plane distribution.

(2) The heating plate of the heating device has a plurality of concentric annular heaters having different diameters, and each heater can independently control the temperature.

(Function) As described above, the substrate to be subjected to the pattern transfer in the lithography step generally has a warped shape because various films are formed on the base. When such a substrate is subjected to heat treatment with a hot plate, the distance between the hot plate and the substrate is different in the substrate surface, so that the amount of heat supplied varies in the substrate surface. There is a close relationship between the amount of heat supplied in a heat treatment step called PEB performed after exposure and the size of a resist pattern formed after development. Therefore, if there is a large variation in the amount of heat supplied in the PEB process, dimensional uniformity will be deteriorated.

In the present invention, prior to the PEB process (for example, in an exposure apparatus), data on the amount of warpage of the substrate is obtained,
The amount of heat supplied from the hot plate at the time of PEB is controlled based on the amount of warpage. As a first method of controlling the amount of heat, the temperature of the hot plate is changed in the in-plane direction such that the longer the distance between the substrate and the hot plate on the substrate mounting surface of the hot plate, the greater the amount of heat supplied, so that the substrate is It can be heated uniformly within. As a second method of controlling the amount of heat, the temperature of the hot plate is controlled so that the total amount of heat supplied by the hot plate increases as the amount of warpage of the substrate to be processed increases, so that the substrates having different amounts of warp can be uniformly controlled. Heat treatment can be performed.

Further, since feed-forward control is used instead of feedback control, there is no delay in temperature control, and more accurate temperature control can be performed. Furthermore, there is no need to provide a plurality of temperature sensors in the heating device, and there is no disadvantage such as an increase in cost. Therefore, according to the present invention, the substrate to be processed has a warped shape, and even if the amount of warpage differs for each substrate, it is possible to perform heat treatment with excellent uniformity within the substrate surface and between the substrates, It is possible to contribute to improvement in processing accuracy of the resist pattern.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to the illustrated embodiments.

(First Embodiment) FIG. 1 shows a first embodiment of the present invention.
1 is a configuration diagram schematically showing a semiconductor manufacturing system according to an embodiment.

The exposure apparatus 10 and the resist processing apparatus 20 are connected via an interface unit 30.
The exposure apparatus 10 exposes a wafer mounted on a stage to a pattern formed on a projection exposure substrate (mask), and apart from this basic function, as will be described later, Of the wafer can be measured.

The resist processing apparatus 20 includes a wafer station 21 on which a plurality of wafers are set, and a first coating unit 22 (C) for coating an antireflection film on the wafer.
OT1), a second coating unit 23 (COT2) for coating a resist on the wafer, a first baking unit 24 (HP1) for baking the antireflection film, and a second baking for pre-baking the resist Unit 25
(HP2), a third bake unit 26 (HP3) for post-baking the resist, a developing unit 27 for developing the resist, a cooling unit and a transport unit (not shown), and the like. Here, the baking unit 26 heats the wafer placed on the hot plate, and is capable of variably controlling the temperature of the hot plate surface in a plane as described later.

Next, the process of forming a resist pattern according to this embodiment will be described with reference to the flowchart of FIG.

First, a wafer (not shown) mounted on the wafer station 21 was transferred to the first coating unit 22 by a transfer unit, and an antireflection film was coated on the wafer (step 1). Subsequently, the wafer is first transferred by the transfer unit.
Was transferred to the baking unit 24 and baked at 190 ° C. for 60 seconds to form an antireflection film having a thickness of 60 nm (step 2).

Next, the wafer was once transported to a cooling unit to perform a cooling process, and then the wafer was transported to a second coating unit 23, where a positive chemically amplified resist was applied (step 3). Subsequently, the wafer was transported to the second bake unit 25, and a heat treatment for volatilizing a solvent in the resist called prebake was performed at 140 ° C. for 90 seconds (step 4). As a result, a 400 nm resist film was formed on the antireflection film.

Next, after transferring the wafer to the cooling unit and cooling it to around room temperature, the interface unit 3
After that, the wafer was conveyed to the exposure apparatus 10 and a desired latent image was transferred to a resist film using a projection exposure mask (Step 5).

In the exposure step, if the focus shifts when the mask pattern is reduced and projected, the optical image is greatly deteriorated, and a desired pattern cannot be obtained. For this reason, in the exposure apparatus, a vacuum chuck function is provided on a stage for supporting the wafer in order to reduce a focus shift due to the warpage of the wafer, so that the wafer becomes flat on the stage.

In the present embodiment, the amount of warpage of the wafer is calculated based on the pressure distribution of the vacuum chuck. With reference to FIG. 3, a method for obtaining the pressure distribution of the vacuum chuck will be described. FIGS. 3A and 3B schematically show a plan view and a cross-sectional view of the wafer stage, and FIG. 3C shows a pressure change at the time of the vacuum chuck.

As shown in FIGS. 3A and 3B, four concentric grooves 41 having different diameters are provided on the front side of the wafer stage 40, and these grooves 41 are connected to a common vacuum system. Have been. Each groove 41 is provided with a pressure sensor 42, and as shown in FIG. 3 (c), a pressure change with respect to the time from the start of chucking can be monitored.

Here, the chucking is completed at time t1. The distance between the stage and the substrate, that is, the amount of substrate warpage at the chucking position is closely related to the chucking completion time t1, and the larger the amount of substrate warpage, the longer the chucking completion time t1. . Accordingly, the relationship between the time t1 at each chucking position and the amount of warpage of the substrate is obtained in advance, so that the amount of warpage of the substrate can be calculated from the time t1.

The grooves 41 need not necessarily be continuous in the radial direction, but may be separated by providing partitions at regular intervals. In this case, by providing a pressure sensor for each groove separated in the radial direction, pressure can be detected at a plurality of positions also in the radial direction, and detection with higher resolution can be performed.

FIG. 4 is a contour diagram of the amount of wafer warpage obtained based on the detection signal of the pressure sensor. In this figure, the center is concave. Note that this data corresponds to an example in which the groove 41 is separated in the radial direction, and a pressure sensor is provided in each of the separated grooves.

The wafer warpage amount data thus obtained is temporarily stored inside the exposure apparatus 10 as shown in FIG. 5, and is baked after exposure (PEB unit).
It is sent to the heater control unit 65 of FIG. Then, the data control unit 65 sets the temperature of the heat treatment by the hot plate 60 based on the wafer warpage amount data.

Here, the structure of the hot plate 60 installed in the bake processing unit 26 and a method of setting the heat processing temperature will be described. The heat treatment temperature was 140 ° C. FIG.
(A) is a sectional view of the configuration of the hot plate 60 of the PEB unit 26, and (b) is a plan view of a heater pattern of the hot plate 60.

A plurality of (for example, three) concentric heaters 61, 62, 63 having different diameters are provided on the back side of the circular hot plate 60, and each heater is a thermocouple embedded in the hot plate 60 (see FIG. (Not shown), each of which is independently temperature-controlled. The wafer 50 is set on the front side of the hot plate 60. To prevent contamination of the back surface of the wafer due to contact with the hot plate 60, a proximity gap 55 is provided at the outer peripheral portion.
(0.1 mm). 140 in wafer plane
In order to perform a uniform heat treatment at a temperature of ° C., a correlation as shown in FIG. 7 was used.

FIG. 7 shows the relationship between the hot plate set temperature required for the wafer processing temperature to reach 140 ° C. when the distance between the wafer 50 and the hot plate 60 changes. When the wafer warpage d is 0, the distance between the wafer 50 and the hot plate 60 is 0.1 mm of the proximity gap 55, and the hot plate set temperature is 140 ° C. When the warpage of the wafer 50 is concave, the distance between the wafer 50 and the hot plate 60 decreases as the wafer warpage d increases, so that, for example, the region where the wafer warpage d = 20 μm shown in FIG. 62 corresponds to 139.75 ° C., which is the conventional set temperature of 1
The temperature was set lower than 40 ° C., and in the region of d = 40 μm (corresponding to the heater 63), the temperature was further set to 139.55 ° C. (step 6).

After the exposure, the wafer 50 is returned to the resist processing apparatus 20 via the interface unit 30 and is further transported to the PEB unit 26 by the transport unit. Baking treatment was performed at 140 ° C. for 90 seconds (step 7). As described above, by determining the set temperature of each heater of the hot plate 60 according to the distance between the wafer 50 and the hot plate 60 from the previously measured wafer warpage amount, the temperature uniformity (3σ) within the wafer surface is determined. Improved from 0.72 ° C. to 0.23 ° C.

Next, the wafer 50 was cooled to near room temperature by a cooling unit (not shown), and an alkali developing process was performed for 90 seconds in the developing unit 27 (step 8).
After the development process, perform rinsing process and spin drying process,
The wafer 50 was transferred to the wafer station 21.

As a result of measuring the dimension of the resist after development in the wafer surface, the in-plane uniformity of the 180 nm line & space pattern, which is one of the circuit patterns, was determined under the PEB processing conditions where the set temperature was not optimized. Was greatly improved to 6.4 nm as compared with 14.1 nm (3σ) when the above was performed. Further, even if the distribution and the amount of the warp are different for each wafer to be processed, the dimensional uniformity between the wafers can be improved because the PEB processing is performed under the heating condition according to each wafer.

(Second Embodiment) In the first embodiment, in-plane variations in wafer heating are eliminated.
The present embodiment is designed to eliminate variations between wafers.

FIGS. 8A and 8B are diagrams showing the configuration of the hot plate used in the present embodiment, wherein FIG. 8A is a sectional view and FIG. 8B is a plan view. In the first embodiment, three concentric heaters 61, 6
Although a bake unit composed of 2 and 63 was used, only a single heater 61 was used in this embodiment.

In the heating apparatus having a single heater 61 as a heat source as in the present embodiment, the heater temperature cannot be corrected within the wafer surface due to its structure, but the distance between the wafer 50 and the hot plate 60 must be increased. It is possible to average over the wafer surface and change the set temperature for each wafer based on the distance. This makes it possible to reduce the variation in the amount of supplied heat between wafers.

The present invention is not limited to the above embodiments. In the embodiment, a bake unit including three concentric heaters or a single heater is used. However, the number of heaters and the heater shape are not limited thereto, and can be appropriately changed according to specifications. Further, the heater is not necessarily limited to a concentric shape, but may be any heater that is separated into a plurality of pieces so that a temperature difference can be formed in the in-plane direction on the hot plate surface side.

In the present embodiment, the amount of warpage of the wafer is calculated based on the pressure distribution of the vacuum chuck, but the present invention is not limited to this. For example, as shown in FIG. 9, even if a Z sensor 80 for detecting the height position of a wafer is used in the exposure apparatus 10 and the amount of warpage of the wafer is calculated based on data obtained by the sensor 80, Good. Alternatively, the back surface of the wafer may be irradiated with monochromatic light, and the amount of warpage of the wafer may be calculated based on the interference fringes.

Further, in the embodiment, the case where the wafer is warped in a concave shape is shown. However, the same effect can be obtained by using the above-described heating condition setting method even in a wafer having a convex shape. Further, in the embodiment, the amount of warpage of the wafer is fed forward under the PEB heating condition, but the present invention is not limited to this. The amount of warpage of the wafer may be measured before the heat treatment other than PEB, and the wafer may be fed forward to the heat treatment performed after application of the antireflection film or the resist.

In addition, various modifications can be made without departing from the spirit of the present invention.

[0048]

As described above in detail, according to the present invention, the amount of warpage of a substrate is measured before the step of subjecting the substrate to be subjected to the PEB heat treatment. By controlling the amount of heat supplied by the hot plate,
Even when the substrate to be processed is warped, heat treatment with excellent uniformity can be performed. For this reason, it is possible to reduce the dimensional variation in the dimension of the resist pattern formed on the substrate to be processed in the substrate surface. As a result, it is possible to improve the reliability and the manufacturing yield of devices manufactured through the subsequent steps.

[Brief description of the drawings]

FIG. 1 is a configuration diagram schematically showing a semiconductor manufacturing system according to a first embodiment.

FIG. 2 is a flowchart for explaining a resist pattern forming process in the first embodiment.

FIGS. 3A and 3B are a plan view and a cross-sectional view illustrating a stage configuration, illustrating a method for obtaining a pressure distribution of a vacuum chuck, and a diagram illustrating a pressure change during the vacuum chuck.

FIG. 4 is a contour diagram of the amount of warpage of the wafer and a cross-sectional view schematically showing a state in which the wafer is warped.

FIG. 5 is a diagram schematically illustrating a state in which a wafer warpage amount is calculated from a vacuum chuck pressure obtained in an exposure apparatus, and the calculated amount is fed forward to a PEB unit.

FIG. 6 is a cross-sectional view and a plan view illustrating a configuration of a bake unit.

FIG. 7 is a view showing a hot plate temperature condition required when a wafer is heated to 140 ° C.

FIGS. 8A and 8B are a cross-sectional view and a plan view illustrating a configuration of a bake unit having a single heater, for explaining the second embodiment.

FIG. 9 is a diagram illustrating a modification of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Exposure apparatus 20 ... Resist processing apparatus 21 ... Wafer station 22, 23 ... Coating unit (COT1, 2) 24, 25 ... Bake unit (HP1, 2) 26 ... Bake unit (HP3: PEB unit) 27 ... Development unit ( EDV) 30 interface unit 40 wafer stage 41 groove 42 pressure sensor 50 wafer (substrate to be processed) 60 hot plate 61, 62, 63 heater 65 heater control unit

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H096 AA25 BA20 CA14 FA01 FA10 GA29 GB03 JA03 LA16 LA30 5F046 AA17 CC08 CC10 CC11 CD01 CD05 DA05 DA29 DB06 DC11 KA04 LA18

Claims (8)

[Claims] A step of forming a resist film on a substrate to be processed; a step of exposing a desired pattern to the resist film;
A method of forming a resist pattern, comprising: placing a substrate having a pattern exposed on the resist film on a hot plate and performing a heat treatment; and performing a development process on the heat-treated resist film. Measuring the amount of warpage of the substrate to be processed before performing the step of heating, and controlling the amount of heat supplied by the hot plate in accordance with the measured amount of warpage in the step of heating the substrate to be processed. A method for forming a resist pattern. 2. A means for controlling the amount of heat supplied by the hot plate, such that the longer the distance between the substrate to be processed and the hot plate on the substrate mounting surface of the hot plate, the larger the amount of heat supplied. 2. The method according to claim 1, wherein the temperature of the plate is changed in an in-plane direction. 3. A means for controlling the amount of heat supplied by the hot plate, wherein the temperature of the hot plate is controlled such that the larger the amount of warpage of the substrate to be processed, the greater the total amount of heat supplied by the hot plate. 2. The method for forming a resist pattern according to claim 1, wherein: 4. A vacuum chuck pressure for fixing the substrate to be processed on a stage in an exposure apparatus for exposing a desired pattern on the resist film as means for measuring the amount of warpage of the substrate to be processed. The in-plane distribution is obtained, and the amount of warpage is calculated based on the distribution.
The pattern forming method according to any one of the above. 5. A resist coating apparatus for forming a resist film on a substrate to be processed, an exposure apparatus for exposing a desired pattern on the substrate on which the resist film is formed, and a processing apparatus on which the pattern is exposed. A heating device that places a substrate on a hot plate and performs a heating process; a developing device that performs a developing process on the heated processed substrate; and a transport mechanism that transports the processed substrate between the devices. And a means for measuring the amount of warpage of the substrate to be processed, wherein the heating device is configured to mount the hot plate on the substrate based on the amount of warpage of the substrate measured by the measuring means. A semiconductor manufacturing system, wherein the temperature distribution in the in-plane direction of the hot plate is controlled such that the longer the distance between the substrate to be processed and the hot plate on the mounting surface, the larger the amount of heat supplied. 6. A resist coating apparatus for forming a resist film on a substrate to be processed, an exposure apparatus for exposing a desired pattern on the substrate on which the resist film is formed, and a processing apparatus for exposing the pattern. A heating device that places a substrate on a hot plate and performs a heating process; a developing device that performs a developing process on the heated processed substrate; and a transport mechanism that transports the processed substrate between the devices. And a means for measuring the amount of warpage of the substrate to be processed, wherein the heating device, based on the amount of warpage of the substrate measured by the measuring means, the larger the amount of warpage, the greater the total Wherein the temperature of the hot plate is controlled so that the amount of supplied heat increases. 7. A means for measuring an amount of warpage of a substrate to be processed detects an in-plane distribution of a vacuum chuck pressure in a vacuum chuck mechanism for fixing the substrate to be processed on a stage in the exposure apparatus. 7. The semiconductor manufacturing system according to claim 5, wherein a function is provided to calculate a warpage amount according to the detected in-plane distribution. 8. The semiconductor manufacturing system according to claim 5, wherein the heating plate of the heating device has a plurality of concentric annular heaters having different diameters, and each heater can independently control the temperature.