JPH07142356A - Resist pattern forming method and resist pattern forming system used therefor - Google Patents

Abstract

PURPOSE:To improve a line width stability by accurately controlling a time from exposure of a photoresist layer to PEB (postexposure heat treating) and a time from the PEB to cooling. CONSTITUTION:A system in which an exposure unit 9 is connected to a heating unit 5 for conducting PEB or a cooling unit 13 by a special purposed conveying system 6 independent from a main conveying system 2 is built. This is a structure in which a heating unit and a cooling unit contained in a conventional resist coating/developing unit are connected to a conventional exposure unit, and a heating unit and a cooling unit may be contained in the conventional exposure unit. Thus, since a predetermined time between the steps for affecting largest influence to a resist reaction can be accurately and rapidly managed by the special purposed conveying system, a preferable pattern can be formed even when the chemically amplifying resist material is used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resist pattern forming method applied to microfabrication such as semiconductor device manufacturing and a system used therefor, and particularly to time management from the end of exposure to heat treatment and / or cooling. TECHNICAL FIELD The present invention relates to a method and apparatus for improving the line width stability of a resist pattern through performing accurately.

[0002]

2. Description of the Related Art In the field of semiconductor device manufacturing,
The reduction of rules is progressing at an accelerating rate, and next-generation 64
In MDRAM, around 0.35 μm, the next generation 256M
In the DRAM, a fine processing technique capable of achieving a minimum processing size of about 0.25 μm is required. The key technology for realizing this fine processing is photolithography, and one of the options is KrF excimer laser light (λ = 24).
Research on far-ultraviolet lithography using a deep-ultraviolet light source such as 8 nm) and a chemically amplified resist is actively conducted.

In the chemically amplified resist, the acid decomposed and produced from the photo-acid generator by exposure acts as a catalyst for the resist reaction such as crosslinking, polymerization and functional group conversion of the base resin in the subsequent PEB (post-exposure heat treatment) step. Is a type of photoresist material that causes a local change in solubility with respect to the developing solution. However, since the acid serving as the catalyst is extremely small, it is known that the line width stability when using the chemically amplified resist material is greatly affected by a slight variation in processing conditions.

These fluctuation factors are hidden in all areas of photolithography, such as exposure, resist coating, baking, and development, and various measures for eliminating them are exposed by an exposure apparatus or a resist coating / developing apparatus (coater / developer). )
Is proposed. One of the countermeasures related to the resist coating / developing apparatus is process management called so-called tact management. This is a method in which the process time (tact time) in each unit that performs resist coating, baking, development, etc. is set to a certain value so that all wafers are processed with the same process flow. is there. By this method, the stagnation of the wafer in the rate-determining part of the apparatus and the variation in the baking time due to the stagnation were eliminated, and the line width stability was improved to a certain extent.

[0005]

However, in pattern formation using a chemically amplified resist, the parameter that has the greatest effect on pattern accuracy is the time from the end of exposure to the start of PEB. For example, in the case of using a positive resist, if the acid generated by exposure diffuses into the unexposed area within this time and decomposes the dissolution inhibitor excessively, the line width of the pattern becomes narrow and the contrast decreases. To do. Conversely, if HMDS (hexamethyldisilazane) used for hydrophobizing treatment, resist developer, clean room wall paint, HEPA filter, or other alkali vapor is present in the atmosphere at this time, the acid is lost by this. Live and thick line width.

However, the above-mentioned tact management manages the time between the steps performed inside the resist coating / developing apparatus, and the timing between one of these steps and the step performed by the exposure apparatus. No adjustment can be made. As a result, the following problems occur. In the tact management, the process time fluctuates with the tact time as one unit. For example, when the tact time is set to 100 seconds, a wafer whose exposure is completed in 100 seconds is immediately transferred to the PEB process, but a wafer whose exposure took 101 seconds is further 99 times until the next transfer timing comes. You have to wait for a second. That is, 1 in the previous step
The process time difference of seconds is expanded to the time difference of 100 seconds before the start of the next process.

According to the experiments of the present inventor, when a line pattern having a width of 0.35 μm is formed using a chemically amplified resist material (manufactured by Shipley Co .; trade name XP8843),
When the time from exposure to PEB was changed for 100 seconds, the line width was changed by 0.05 μm. Further, the line pattern is 0.1 ppm in an amine atmosphere of 1 ppm.
It also fluctuated by 0 μm. According to a trial calculation by the present inventor, 0.35 μm
The allowable range of line width uniformity in the design rule is ±
0.023 μm, and the above-mentioned variation is clearly beyond this range.

In order to eliminate such a contradiction in tact management, it is conceivable to reset the tact time for each layer of the device or set the longest possible tact time. However, these measures require complicated operations, significantly reduce the throughput, PEB
Since the subsequent wafer is held in a high temperature state for a long time (overbaking) without being sent to the cooling / temperature control unit, the line width uniformity is significantly deteriorated, which is a practical countermeasure. Absent.

Therefore, the present invention provides a method for improving the line width uniformity of a resist pattern without inducing such an adverse effect.
And it aims at providing the system which can implement | achieve this.

[0010]

The problems relating to the conventional time management as described above are caused by the fact that the control of the resist coating / developing apparatus and the control of the exposure apparatus are performed separately. The present inventor considers these two devices as an integrated system and controls the time required between processes sensitive to time fluctuations to be constant and the shortest, and to make this control independent from the control between other processes. He came up with the idea and proposed the present invention.

That is, in the resist pattern forming method of the present invention, the time from the end of exposure to the resist material layer on the substrate to the start of heat treatment is controlled to be constant and independent of the time between other steps. is there. This control may be further combined with a control in which the time from the end of the heat treatment to the start of cooling is constant.

The above-mentioned exposure is not limited to exposure by excimer laser light, but may be energy beam irradiation by, for example, an electron beam or an ion beam.
The method of the present invention exerts a particularly excellent value in pattern formation using a chemically amplified resist material that is most sensitively affected by the time required between (exposure) → (PEB) → (cooling).

On the other hand, the resist pattern forming system of the present invention is for realizing the above-mentioned method,
An exposure unit for exposing the resist material layer on the substrate, a heating unit for heating the substrate, a main transport system for loading and unloading the substrate into and out of the system, and these two units are connected to each other, and the main transport system is connected to the main transport system. It is equipped with an independent dedicated transport system.

Further, a cooling / temperature control unit may be added, and these three units may be connected to an independent dedicated transport system. In any case, this system includes, in addition to the units described above, a hydrophobic treatment unit, a resist coating unit, a developing unit, a carrier station accommodating a wafer cassette, etc., which are provided in a normal resist coating / developing apparatus. You may have it.

Further, as another configuration, the exposure unit itself may have a built-in heating unit for heating the exposed substrate, and may further have a built-in cooling unit for cooling the heated substrate. . In these cases, the transfer of the substrate from the exposure unit for exposing the resist material layer on the substrate to the heating unit and the cooling unit is performed by a dedicated transfer system built in the exposure unit.

In the resist pattern forming system having each of the above-mentioned constitutions, the process time in each unit or each part connected by the dedicated transfer system is kept constant based on the operation of the dedicated transfer system. It is possible to provide operation control means for doing so.

[0017]

According to the resist pattern forming method and the resist pattern forming system of the present invention, when a chemically amplified resist is used, the transfer between steps or units that most greatly affects the pattern forming accuracy is accurate. It will be done in no time. That is, it is possible to accurately control the time from the exposure having the greatest influence to the PEB start, and the time from the PEB having the next greatest influence to the cooling start. Moreover, since a dedicated transfer system is used for this transfer, the processes connected by this are not affected by other rate-determining processes. Therefore, for example, exposed wafers may be exposed to the outside air for a long time without being carried into the heating unit, or wafers that have undergone PEB in the heating unit may be left without being carried out to the cooling / temperature control unit. Disappears. As a result, it is possible to prevent the thinning of the line width due to the diffusion of the acid after exposure or the thickening of the line width due to the deactivation of the acid.

In particular, when the exposure unit and the heating unit and / or the cooling / temperature adjusting unit are integrated in the exposure unit, the PEB can be exposed without exposing the exposed wafer to the outside air.
Since it can be sent to the process and the subsequent cooling / temperature control process, extremely high line width management becomes possible.

[0019]

EXAMPLES Specific examples of the present invention will be described below. However, the present invention is not limited to these embodiments, and the details of the system configuration and operation can be changed as appropriate.

Embodiment 1 In this embodiment, an exposure unit (Exp) and a heating unit (H) integrated via an interface (I / F) are used.
FIG. 1 shows the configuration of a resist pattern forming system provided with a dedicated transfer system between P) and the method of using the same.
Will be described with reference to.

In this system, a conventional resist coating / developing apparatus and an exposure apparatus are connected by an interface 8 in terms of configuration, and it is possible to control the transportation within each apparatus and the transportation between both apparatuses.

That is, the part corresponding to the conventional resist coating / developing device is a carrier station (C / S) containing a wafer cassette containing a plurality of wafers.
1. A wafer stage (W / S) for temporarily placing a wafer placed on a main transfer system 2 for picking up one wafer at a time from here and transferring it to various processing units 12, and a transfer arm 3 of the main transfer system 2. ) 4, a transfer arm 7 for loading / unloading a wafer to / from the exposure unit 9 via the interface 8.
The main constituent elements are a dedicated transport system 6 provided with, a heating unit (HP) 5 having a built-in hot plate for performing PEB, and the like.

The processing unit 12 generally includes a hydrophobic treatment unit, a resist coating unit, a heating unit for performing pre-baking and post-baking, a developing unit, a cooling / temperature adjusting unit and the like. However, these types and numbers can be appropriately selected according to the desired process, and therefore, the details are not particularly specified in this figure, and are shown in a halftone color as a whole.

The exposure unit (Exp) 9 has the same structure as that of a normal exposure apparatus, and is provided with an exposure stage 10, a transfer arm 11 for mounting a wafer on the exposure stage 10, and the like. The point of the above configuration is the heating unit (H) that performs PEB.
5 is independent of the heating unit for heating for other purposes,
This is arranged at a position closest to the exposure unit (Exp) 9 and the transfer system (exclusive transfer system 6) for transferring the wafer from the exposure unit 9 to the heating unit (H) 5 is separated from the main transfer system 2. That is.

The operation when the above system is used is roughly as follows. First, the wafer, which has undergone resist coating, pre-baking, and cooling in any of the processing units 12, is transferred to the wafer stage 4 by the transfer arm 3 of the main transfer system 2.
Placed on. This wafer is carried into the exposure unit (Exp) 9 through the interface (I / F) 8 by the carrier arm 7 of the dedicated carrier system 6, and is placed on the exposure stage 10 by the carrier arm 11 to undergo predetermined exposure. .

The exposed wafer is an interface (I /
F) 8 is carried out, and it is immediately carried into the heating unit (H) 5 by the dedicated carrier system 6 to receive PEB. PE
The wafer for which B has been completed is placed on the wafer stage (W / S) 4 by the dedicated transfer system 6 and then transferred to any of the processing units 12 by the main transfer system 2 for cooling, development, post-baking, etc. Receive processing.

According to the system configuration and the method of use as described above, the time from the end of exposure to the start of PEB is limited to the exclusive carrier system 6.
Depends only on the behavior of. Therefore, whether or not tact management is performed between the processing units 12 in which the main transport system 2 is involved, where the rate control occurs, and the like do not affect the above time at all. If the wafer is processing unit 1
2 or even on the transfer arm 3, the wafer after exposure is temporarily stopped on the transfer arm 7 or on the wafer stage (W / S) 4 while the PEB is quickly completed within a fixed time. Can be kept waiting.

In this system, a chemically amplified resist material (manufactured by Shipley Co .; trade name XP8843) was actually used.
When pattern formation was performed by KrF excimer laser lithography, it was possible to achieve a line width uniformity of ± 0.020 μm in a line pattern having a width of 0.35 μm.

Embodiment 2 In this embodiment, an exposure unit (Exp) and a heating unit (H) integrated via an interface (I / F) are used.
The configuration of a resist / pattern forming system provided with a dedicated transfer system between P) and the cooling / temperature control unit (C) and the method of using the same will be described with reference to FIG.
Note that the reference numerals in FIG. 2 are partially common to those in FIG.

This system is different from the system described in the first embodiment in that the heating unit (HP) 5 and the cooling unit (C) 13 are also in the range in which the dedicated transfer system 6 is in charge.

When the above system is used, the wafer which has been exposed in the exposure unit (Exp) 9 is first transferred to the heating unit (H) 5 by the transfer arm 7 of the exclusive transfer system 6 through the interface (I / F) 8. And receive PEB here. The wafer that has completed PEB is immediately carried into the cooling / temperature control unit (C) 13 by the transfer arm 7. The wafer is now cooled to a temperature approximately equal to the room temperature of the clean room, and then the wafer stage (W /
S) 4 is conveyed to another processing unit 12 and undergoes processing such as development and post-baking.

According to the system configuration and the method of use, the PE from the end of exposure to the start of PEB is
The time from the end of B to the start of cooling can be controlled independently of the main transport system 2. With this system, a chemically amplified resist material (manufactured by Shipley Co .; trade name XP8843) is actually used.
Pattern formation by KrF excimer laser lithography was performed, and a line pattern with a width of 0.35 μm, ± 0.
A line width uniformity of 015 μm could be achieved.

Embodiment 3 In this embodiment, a resist pattern forming system in which a heating unit (HP) and a cooling unit (C) are incorporated in an exposure unit (Exp) 25 will be described with reference to FIG. This system has a structure in which a heating unit and a cooling / temperature adjusting unit included in a conventional resist coating / developing apparatus are integrated into the exposure apparatus by integrating them.

That is, the part corresponding to the conventional resist coating / developing device is the carrier station (C / S).
21, a main transport system 22 having a transport arm 23, a processing unit 30 for performing various processes, and the like, which are connected to an exposure unit 25 via an interface (I / F) 24. The processing unit 30 generally includes a hydrophobic treatment unit, a resist coating unit, a heating unit for performing pre-baking and post-baking, a developing unit, a cooling / temperature adjusting unit, and the like.

On the other hand, the exposure unit (Exp) 25 is a heating unit (HP) for performing PEB in addition to the structure of a normal exposure apparatus such as the exposure stage 26 and the transfer arm 27.
28, and cooling / cooling for cooling the wafer after PEB
It incorporates a temperature control unit (C) 29. The exposure stage 26 and the heating unit (HP) 28 are sufficiently insulated from each other.

Although only one transfer arm 27 is shown in the figure, if one transfer arm covers all the transfer in the exposure unit (Exp) 25, the heating unit (HP) is actually used. The heat of the wafer carried out from 28 is accumulated in the transfer arm 27, which may raise the temperature of the wafer placed on the exposure stage 26. Therefore, in practice, it is desirable to separately install the transfer arm for the exposure stage 26 and the transfer arm for the heating unit (HP).

The point of the above configuration is that the heating unit (H) 28 for PEB and the cooling / temperature control unit (C) 29 for cooling / temperature control immediately after the PEB are connected to the exposure unit (Exp) 2.
5 is that the process of exposure->PEB-> cooling can be performed quickly without exposing the wafer to the outside air by installing it inside No. 5. The operation when using the above system is roughly as follows.

The wafer after the resist coating and pre-baking is carried into the exposure unit (Exp) 25 through the interface (I / F) 24, and placed on the exposure stage 26 by the transfer arm 27. The exposed wafer is immediately carried into the heating unit (HP) 28 to receive the PEB, and immediately after the PEB is finished, the wafer is cooled in the cooling / temperature adjusting unit (C) 29. The cooled wafer is unloaded via the interface (I / F) 24, and is transferred by the transfer arm 23 of the main transfer system 22 to the processing unit 30 that performs a predetermined process.

According to such a system configuration and a method of use, the transfer of exposure → PEB → cooling can be performed in a minimum time, and during this period, the wafer does not come into contact with the outside air. With this system, a chemically amplified resist material (manufactured by Shipley Co., Ltd .; trade name XP8843) was used to actually produce KrF.
When pattern formation was performed by excimer laser lithography, it was possible to achieve a line width uniformity of ± 0.015 μm in a line pattern having a width of 0.35 μm.

[0040]

As is apparent from the above description, when the present invention is applied, the time from the end of exposure to the start of PEB, which has the greatest influence on the resist reaction, and the P
Since the time from the end of EB to the start of cooling is controlled accurately and shortly, the line width uniformity of the resist pattern can be remarkably improved. In particular, when using a chemically amplified resist material that is sensitive to the above time variations,
It is extremely effective. The present invention greatly contributes to high integration and high performance of semiconductor devices through such high reliability of resist pattern formation.

[Brief description of drawings]

FIG. 1 is a schematic plan view of a resist pattern forming system including a dedicated transfer system between an exposure unit (Exp) and a heating unit (HP) integrated via an interface (I / F). .

FIG. 2 is a resist pattern having a dedicated transfer system between an exposure unit (Exp), a heating unit (HP), and a cooling / temperature control unit (C) integrated via an interface (I / F). It is a schematic plan view of a forming system.

FIG. 3 is a schematic plan view of a resist pattern forming system including an exposure unit (Exp) that incorporates a heating unit (HP) and a cooling / temperature control unit (C).

[Explanation of symbols]

 1, 21 ・ ・ ・ Carrier station (C / S) 2, 22 ・ ・ ・ Main transfer system 3, 23 ・ ・ ・ (Main transfer system) transfer arm 5, 29 ・ ・ ・ Heating unit (HP) 6 ・..Dedicated transport system 7 ... (Dedicated transport system) transport arm 9,25 ... Exposure unit (Exp) 10,26 ... Exposure stage 11, 27 ... Transport arm (in the exposure unit) 13, 28 ... Cooling unit (C) 8, 24 ... Interface (I / F)

Claims (8)

[Claims] 1. A method for forming a resist pattern, wherein the time from the end of the exposure of the resist material layer on the substrate to the start of the heat treatment is controlled to be constant and independent of the time required for other steps. 2. The resist pattern forming method according to claim 1, wherein the time from the end of the heat treatment to the start of cooling is controlled to be constant. 3. The resist pattern forming method according to claim 1, wherein the resist material layer is formed using a chemically amplified resist material. 4. An exposure unit for exposing a resist material layer on a substrate, a heating unit for heating the substrate, a main transport system for loading and unloading the substrate into and out of the system, the exposure unit and the heating unit. A resist pattern forming system comprising: a main transfer system and a dedicated transfer system independent of the main transfer system. 5. An exposure unit for exposing a resist material layer on a substrate, a heating unit for heating the substrate, a cooling / temperature control unit for cooling / controlling the temperature of the heated substrate, and at least for the inside and outside of the system. A resist pattern forming system comprising: a main transfer system for loading and unloading a substrate; and a dedicated transfer system that connects the exposure unit, the heating unit, and the cooling unit and is independent of the main transfer system. 6. A resist pattern comprising an exposure unit for exposing a resist material layer on a substrate, a heating unit for heating the substrate after exposure, and an exposure unit containing a dedicated transport system for connecting both of these units. Forming system. 7. An exposure unit for exposing a resist material layer on a substrate, a heating unit for heating the exposed substrate, a cooling / temperature adjusting unit for cooling / controlling the heated substrate, and connecting these units. A resist pattern formation system that includes an exposure unit that incorporates a dedicated transport system that 8. An operation control means for maintaining a constant process time in each unit or each section connected by the exclusive transfer system based on the operation of the exclusive transfer system. The resist pattern forming system according to claim 7.