1. Field of the Invention
The present invention relates to a method for manufacturing a semiconductor device, and particularly to a method for manufacturing a semiconductor device, which effects post-exposure development processing on a substrate such as a semiconductor wafer.
2. Description of the Related Art
In recent years, an exposure technique in which an excimer laser short in exposure wavelength and a high-sensitive chemical amplifying resist are utilized in combination, has widely been used in a lithography process for performing pattern formation of a semiconductor device, in order to adapt to high integration and micro-fabrication of the semiconductor device. The chemical amplifying resist is equivalent to one in which acid produced in the resist by exposure is diffused in the resist and a dissolution inhibiting agent contained in the same resist is decomposed to allow an exposure part to be soluble in a developing solution or developer. On the other hand, a scan system wherein in order to solve the difference in the amount of delivery of a developer between a central portion of a wafer and its peripheral portion, the developer is delivered while a developer supply nozzle is being scanned on the wafer, thereby to apply the developer onto the wafer, is being adopted for post-exposure development processing.
The inventions related to lithography of the semiconductor device have been described in, for example, the following patent documents.
The invention described in Japanese Patent Application No. Hei 9(1997)-237745 (see pp 3-5 and FIG. 1) relates to a method for performing pattern formation using a chemical amplifying resist, which upon exposure of a plurality of wafers, measures a change in sensitivity per unit time, of the resist under respective environments under which the wafers are left, i.e., under respective environments of (1) they are left in vacuum before exposure, (2) they are left in vacuum after exposure, (3) they are left in the atmosphere before exposure and (4) they are left in the atmosphere after exposure, calculates the optimum amount of exposure with the sensitivity change and time intervals taken for their leaving being defined as parameters and adjusts or controls the amount of exposure between the wafers or in the wafer. Thus, variations in dimension between the wafers or in the wafer are suppressed.
The invention described in Japanese Patent Application No. 2001-57334 (see pp 6-9 and FIG. 7) is one wherein a developer supply nozzle is scanned on a wafer twice or more to apply a developer and thereby a developer paddle formed on the wafer by the first scan is stirred by the delivery of a developer by a scan of the second time or later. Thus, development processing is evenly performed and hence the uniformity of pattern dimensions is improved.
The invention described in Japanese Patent Application No. 2003-272991 (see pp 4-6 and FIG. 1) relates to a method for performing pattern formation using a chemical amplifying resist, which calculates an exposure process tact time on the basis of information from an exposure device, i.e., wafer-surface illumination information, compares the exposure process tact time, an application process tact time and a development process tact time and adjusts a resist application process tact time according to the relationship of magnitude among the three. Thus, process processing times for respective wafers are held constant and variations in dimension between the wafers or in the wafer are suppressed.
Although the chemical amplifying resist is of a material very effective for miniaturization of the semiconductor wafer, it contains several dimension variable factors in terms of its property. The first variable factor is deactivation of acid due to a neutralization reaction with a basic substance in the atmosphere, e.g., ammonia (NH3) or the like. Since the chemical amplifying resist makes use of acid produced by photochemical reaction as already mentioned, the decomposition of a dissolution inhibiting agent becomes hard to occur in the surface of the resist when such acid makes a neutralization reaction with the basic substance in the atmosphere and is deactivated. Further, its surface becomes hard to dissolve so that a variation in pattern dimension becomes easy to take place. Therefore, a chemical filter is used within an area in a clean room which treats the chemical amplifying resist, in order to remove the basic substance in the atmosphere. Further, the formation of a protective film having acidic on the surface of the chemical amplifying resist, etc. have been performed. The second variable factor is diffusion of acid produced in the resist by exposure. The acid produced by exposure is gradually diffused into the resist in a draw-and-lay time from after exposure up to post bake, so-called PEB (Post Exposure Bake) and decomposes the dissolution inhibiting agent over a range wider than an exposure area. As a result, a line-width dimension of each pattern greatly decreases with respect to a desired value. A dimension varying phenomenon due to such two variable factors, i.e., the deactivation of acid and its diffusion is generally called “PED (Post Exposure bake Delay effect)”.
As to the dimension variation due to the deactivation of acid in PED, its influence can be kept to a minimum by use of the chemical filter, the protective film or the like. As to the dimension variation due to the diffusion of acid, however, it greatly depends on the draw-and-lay time from after exposure up to PEB. It was therefore difficult to suppress its influence. It was particularly difficult to solve a difference in draw-and-lay time in the same wafer, i.e., a difference in pattern dimension that occurs due to a difference in draw-and-lay time caused by an exposure order in the wafer.
On the other hand, it is known that development processing relates to the dependence of pattern dimensions of a resist on a developing time. Although generally slow as compared with a solution rate of an exposure area in the case of a resist, a non-exposure area is also gradually dissolved with a developing solution or developer. In particular, a boundary portion between the exposure area and the non-exposure area becomes more soluble. Therefore, there is a tendency that as the developing time, i.e., the time from the putting of the developer onto a wafer up to before a post-development rinse process becomes long, the pattern dimensions decrease. Thus, the development processing of the scan system causes a difference in pattern dimension in the same wafer depending on a scan direction and a scan speed.
The invention described in Japanese Patent Application No. Hei 9(1997)-237745 aims to solve variations in dimension due to PED by means of exposure processing and is not intended for execution of specially-set processing about development.
The invention described in Japanese Patent Application No. 2001-57334 aims to uniformly apply a developing solution or developer by scanning a developer supply nozzle plural times and is not intended for resolution of variations in dimension due to PED by development processing.
The invention described in Japanese Patent Application No. 2003-272991 aims to solve variations in dimension due to PED by adjusting a tact time for a resist application process and is not intended for execution of specially-set processing about development.
With the foregoing in view, it is an object of the present invention to provide a method for manufacturing a semiconductor device, which is capable of reducing a difference between pattern dimensions in a wafer surface due to PED (Post Exposure bake Delay effect).
According to one aspect of the present invention, for achieving the above object, there is provided a method for manufacturing a semiconductor device, comprising a resist deposition step for forming a resist film on the surface of a semiconductor substrate provided with a plurality of chips disposed in matrix form, an exposure step for sequentially exposing chip patterns with respect to the respective chips in a predetermined exposure order from the chip set as a starting point of the semiconductor substrate, and a development step for developing the respective chips in the order opposite to the exposure order from the chip set as an end point in the exposure order.
According to the method for manufacturing the semiconductor device, according to the present invention, development processing is carried out in the order opposite to an exposure order. Thus, for example, differences in dimension among resist patterns due to PED (diffusion) in a wafer can be canceled out by the development processing. Consequently, differences in pattern dimension in the same wafer can be reduced.
While the specification concludes with claims particularly pointing out and distinctly claiming the subject matter which is regarded as the invention, it is believed that the invention, the objects and features of the invention and further objects, features and advantages thereof will be better understood from the following description taken in connection with the accompanying drawings in which:
One embodiment of the present invention will be explained while taking, as an example, a case in which the present invention is applied to a process for forming the gate of a transistor.
[Development Processing Method]
Now consider where a semiconductor wafer 100 has such a 6×6 chip layout as shown in
A process up to PEB subsequent to execution from resist application to exposure in the present embodiment is similar to the normal photolithography. Described briefly, polysilicon corresponding to a gate electrode material is first formed over the whole area of the semiconductor wafer 100. Thereafter, a chemical amplifying resist for pattern formation is spin-coated on the polysilicon with BARC (Bottom Anti-Reflective Coating) corresponding to an antireflection film interposed therebetween. The thickness of the chemical amplifying resist is assumed to be 290 nm, for example. Then, pre-bake is carried out on a hot plate under the condition of 120° C./90 sec and thereafter exposure processing is effected. The exposure processing makes use of excimer laser as a light source and is stepped-and-repeated from a chip A to a chip B in the order indicated by a broken line as shown in
Meanwhile, as already mentioned, the chemical amplifying resist is accompanied by the problem that the line-width dimensions of the patterns decrease due to the acid diffusion produced during a draw-and-lay time thereof from after PED, especially, exposure up to PEB.
Next, development processing is effected on the semiconductor wafer 100 that has completed PEB. In general, as already mentioned, the development processing is accompanied by the problem that the pattern dimension decreases as the developing time becomes long.
Therefore, the present invention is characterized in that the development processing is performed from the chip side in which the draw-and-lay time from after exposure up to PEB is short, i.e., the chip side in which exposure processing is finally carried out. In particular, the development processing method of the scan system is characterized in that the scan direction of the developer supply nozzle is adjusted in such a manner that the development processing is carried out from the chip side in which exposure has finally been performed. Since the exposure processing is performed from a first line L1 to a sixth line L6 of the semiconductor wafer 100 as shown in
When the developer supply nozzle 5 is scanned from the direction arbitrary with respect to the semiconductor wafer 100 as in the conventional development processing method, the scan direction differ for each wafer. Therefore, when a development scan is started from the chip side long in draw-and-lay time from after exposure up to PEB, i.e., the chip side in which exposure has first been done, the difference in gate dimension between the chips due to PED (diffusion) further increases with development processing. When, for example, the developer supply nozzle 5 is scanned with respect to the semiconductor wafer 100 exposed in the order such as shown in
On the other hand, when the scan direction of the developer supply nozzle 5 is adjusted in such a manner that the development processing is started from the chip side short in draw-and-lay time with respect to the semiconductor wafer 100 as in the development processing method according to the present invention, each chip short in draw-and-lay time is set long in developing time, and each chip long in draw-ant-lay time is set short in developing time. Therefore, the differences in gate dimension among the chips due to PED (diffusion) are canceled out by the development processing. When, for example, the developer supply nozzle 5 is scanned with respect to the semiconductor wafer 100 exposed in the order such as shown in
[Development Processing Apparatus]
An annular cup 1 is disposed in the center of the development processing apparatus 1000. Waste liquid pipes la for discharging a developer and a cleaning or rinse solution are provided at the bottom of the cup 1. A spin chuck 2 for holding a semiconductor wafer 100 is disposed inside the cup 1. The spin chuck 2 is rotatably driven by a driving motor 3 in a state in which the semiconductor wafer 100 is fixed and held by vacuum suction. A detector 4 is a sensor for detecting an orientation flat (OF) or a notch indicative of a plane direction of the semiconductor wafer 100. The detector 4 is disposed in the neighborhood of the semiconductor wafer 100. A developer supply nozzle 5 is a nozzle for supplying a developing solution or developer to the surface of the semiconductor wafer 100. The developer supply nozzle 5 is shaped long and disposed with its longitudinal direction as the horizon, and is connected to a developer supply section 5b via a developer supply pipe 5a. Also the developer supply nozzle 5 is attached to its corresponding tip of a nozzle scan arm 5c. The nozzle scan arm 5c is horizontally movable on a guide rail 7 laid in one direction. A rinse nozzle 6 is a nozzle for supplying the cleaning or rinse solution to the surface of the semiconductor wafer 100 and is connected to a rinse solution supply section 6b via a rinse solution supply pipe 6a. Also the rinse nozzle 6 is attached to its corresponding tip of a nozzle scan arm 6c. The nozzle scan arm 6c is horizontally movable on the guide rail 7 laid in one direction. A controller 8 controls the driving motor 3 and the detector 4 and controls the operations of the developer supply nozzle 5 and the rinse nozzle 6 and the supply of the solutions from the developer supply section 5b and the rinse solution supply section 6b. Incidentally, a memory 8a, which stores a plurality of process recipes containing information about a scan direction and a scan speed of the developer supply nozzle 5 to be described later, and the direction of holding of the semiconductor wafer 100, etc., is provided inside the controller 8. A series of development processes are executed by a predetermined process recipe selected by a command issued from an operation unit 9.
The operation of the development processing apparatus 1000 according to the present invention will next be explained. The semiconductor wafer 100 in which predetermined patterns have been exposed and PEB has been executed, is first transferred to directly above the cup 1 by an unillustrated wafer transfer mechanism and adsorbed under vacuum by the spin chuck 2, followed by being held thereby.
Next, the driving motor 3 rotates and drives the spin chuck 2 in accordance with a command issued from the controller 8 to rotate the semiconductor wafer 100. When the detector 4 detects an orientation flat (OF) or a notch of the semiconductor wafer 100, the controller 8 controls the driving motor 3 to stop the spin chuck 2 at a predetermined position, e.g., a position where the orientation flat (OF) of the semiconductor wafer 100 is fixed and held so as to be parallel to the long-side part of the developer supply nozzle 5 as shown in
Next, the scan of the developer supply nozzle 5 is started from a predetermined direction in accordance with a command issued from the controller 8. Since the exposure processing is carried out from the side opposite to the orientation flat (OF) in the present embodiment, the direction of scanning of the developer supply nozzle 5 is set from the orientation flat (OF) side of the semiconductor wafer 100 to the side opposite to the orientation flat (OF), i.e., from P1 to P2 in
Subsequent processes are similar to the normal development processing method. They will be described in brief. A developer is applied by scan and thereafter still development is done for a predetermined time. When the still development is completed, the semiconductor wafer 100 is rotated by the spin chuck 2 so that the developer is chucked off. Subsequently, the rinse nozzle 6 is moved onto the semiconductor wafer 100 to deliver the rinse solution, whereby the developer that remains on the semiconductor wafer 100 is washed away by the rinse solution. Thereafter, the semiconductor wafer 100 is rotated at high speed by the spin chuck 2, so that the developer and rinse solution that remain on the semiconductor wafer 100 are blown off to dry the semiconductor wafer 100. A series of development processes are completed in this way.
According to the method for manufacturing the semiconductor device according to one embodiment of the present invention, the development processing is carried out from the chip side in which the draw-and-lay time from after exposure up to PEB, i.e., the chip side in which exposure has finally been done. Thus, since the developing time is set long to each chip short in draw-and-lay time and the developing time is set short to each chip long in draw-and-lay time, the differences among the pattern dimensions due to PED (diffusion) in the wafer can be canceled out. In the development processing method of the scan system in particular, the scan direction of the developer supply nozzle 5 is adjusted in such a manner that the development processing is done from the chip side in which exposure has finally been carried out. Consequently, the differences among the pattern dimensions due to PED (diffusion) can be canceled out by the development processing. Thus, it is possible to reduce the difference in pattern dimension in the same wafer and form the semiconductor device with satisfactory accuracy. It is also possible to improve manufacturing yields.
According to the apparatus for manufacturing the semiconductor device according to one embodiment of the present invention, it is equipped with the detector 4, which detects the orientation flat (OF) or notch of the semiconductor wafer 100. Therefore, the semiconductor wafer 100 can always be stopped on the spin chuck 2 as viewed in a predetermined direction. Thus, it is possible to realize the development processing method having taken into consideration the order of exposure of the semiconductor wafer 100, e.g., a development processing method of the present invention, which causes a developer supply nozzle 5 to be scanned in a predetermined direction from the orientation flat (OF) side to the side opposite to the orientation flat (OF) or the side opposite to the orientation flat (OF) to the orientation flat (OF) side with the orientation flat (OF) as the reference.
While the present invention has been described with reference to the illustrative embodiments, this description is not intended to be construed in a limiting sense. Various modifications of the illustrative embodiments, as well as other embodiments of the invention, will be apparent to those skilled in the art on reference to this description. It is therefore contemplated that the appended claims will cover any such modifications or embodiments as fall within the true scope of the invention.
Number | Date | Country | Kind |
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372037/2004 | Dec 2004 | JP | national |