Patent Application
20070251613
In the following, a heat treatment apparatus 2 for subjecting a semiconductor wafer (hereinafter, abbreviated as a wafer) W representing, for example, a substrate, to which surface a resist liquid as a coating liquid is applied, to heat treatment and forming a resist film on a surface of wafer W will be described as an exemplary heat treatment apparatus 2 for carrying out a heating method according to the present invention, with reference to
Heat treatment apparatus 2 includes a housing 20 representing a treatment chamber, and housing 20 is partitioned into an upper region 20A and a lower region 20B by a floor plate 22. A wafer W transfer port 21 is formed in a sidewall of upper region 20A. Assuming the side of transfer port 21 as the front, a cooling plate 33 is provided on the front side, and a hot plate portion 4 is provided on the rear side. Upper region 20A is a region where transfer, heat treatment, and cooling of wafer W is performed by cooling plate 33 and hot plate portion 4, and lower region 20B is a region where movable portions of cooling plate 33 and hot plate portion 4 as well as an exhaust fan 87 are accommodated. In floor plate 22, an opening portion 31a for movement of cooling plate 33 between the front side (a home position) and the rear side (a position above hot plate 53) in a direction of X in the drawing is provided.
A cooling gas discharge port 60 is provided above cooling plate 33 at the home position, and cooling gas discharge port 60 is connected to a cooling gas source 63 where N2 gas or the like is stored, through a top wall of housing 20 via a cooling gas supply path 61 and a valve 62. Cooling gas discharge port 60 is provided at a plurality of locations, for example at five locations, so that entire cooling plate 33 at the home position is uniformly cooled. Cooling gas discharge port 60, cooling gas supply path 61, valve 62, and cooling gas source 63 constitute the cooling mechanism.
Cooling plate 33 will now be described with reference to
Cooling plate 33 is formed as a plate in a substantially annular shape, composed, for example, of aluminum, having a thickness of approximately 4 mm, and having a diameter substantially the same as wafer W. In cooling plate 33, in order to pass/receive wafer W to/from hot plate 53 and the not-shown transfer mechanism, a notch 34 and slits 36a, 36b are formed. In addition, in cooling plate 33, a temperature detection portion 32a is embedded, for example in three locations, at regular intervals along the circumferential direction of wafer W, so that the temperature of wafer W is detected by a temperature detector 32b and the detected temperature is transmitted to a control unit 10 which will be described later. Temperature detection portion 32a and temperature detector 32b constitute the temperature detection portion.
A transfer mechanism 40 passing/receiving wafer W to/from cooling plate 33 has a transfer arm 41 in a horseshoe shape extending horizontally and a transfer base 42 supporting transfer arm 41, for example as shown in
Hot plate portion 4 will now be described. As shown in
A plurality of holes 54 are provided in the central portion of hot plate support member 5 and hot plate 53, so that wafer W can be passed between hot plate 53 and cooling plate 33 by means of a support pin 26a connected to a drive mechanism 26.
A top plate 83 is provided above hot plate support member 5 and top plate 83 is fixed to the upper surface of exhaust chamber 86 by a support portion 84, so that a flow of gas from the front to the rear between hot plate 53 and top plate 83 is straightened.
Exhaust chamber 86 including a plurality of exhaust holes 86a is provided in the rear of hot plate portion 4, and atmosphere in upper region 20A is exhausted outside housing 20 through exhaust chamber 86.
Opening portions 86b and 86c are formed on the front and rear sides in the central portion in a direction of width of exhaust chamber 86, and opening portion 86c is connected to a housing 88 that accommodates exhaust fan 87. One end side of an exhaust pipe 89 is connected to housing 88, and the other end of exhaust pipe 89 is connected, for example, to a not-shown factory exhaust path provided outside housing 20, through a wall surface of housing 20. Atmosphere in lower region 20B is exhausted outside housing 20 by exhaust fan 87 through exhaust chamber 86.
By forming such an airflow, vapor or the like of the solvent in the resist liquid applied to wafer W in upper region 20A and particles or the like generated from a movable portion of cooling plate 33 or hot plate portion 4 in lower region 20B are suctioned by exhaust fan 87 and exhausted outside housing 20.
A gas supply path 24 is connected in the central portion in the direction of Y of gas discharge portion 85 described previously, and gas supply path 24 is connected to a gas supply source 57a provided outside housing 20, through a wall surface of housing 20. Gas supply source 57a stores a clean purging gas, for example, an inert gas such as N2 gas, so that heated hot plate 53 or wafer W can be cooled through gas discharge port 85a implemented by a plurality of small holes arranged along a direction of width of gas supply path 24 and gas discharge portion 85. The purging gas is exhausted outside housing 20 by means of exhaust fan 87 through exhaust chamber 86.
As shown in
A heat treatment method in an embodiment of the present invention using heat treatment apparatus 2 will now be described with reference to
Initially, cooling plate 33 moves from the home position shown in
Meanwhile, first wafer W to which surface a resist liquid is applied and of which initial temperature t1 is set, for example, to room temperature of 23° C. is loaded into housing 20 through transfer port 21 by transfer mechanism 40 described already, and placed on cooling plate 33 as described already (step S3). Then, transfer mechanism 40 exits from housing 20.
The timing at which cooling plate 33 returns to the home position in step S2 is set to timing immediately before first wafer W in the successive treatment is placed on cooling plate 33. Therefore, actually, for example, cooling plate 33 may be controlled such that cooling plate 33 moves to a position above hot plate 53 at the time of turn-on of the coating and development apparatus, returns to the home position as soon as temperature is raised to set temperature T2, again moves to the position above hot plate 53 for compensating for slight heat loss slightly before loading of first wafer W, returns to the home position after set temperature T2 is attained, and receives first wafer W.
Then, when cooling plate 33 moves to the position above hot plate 53, support pin 26a is elevated and supports the rear surface of wafer W placed on cooling plate 33. When cooling plate 33 returns to the home position, support pin 26a lowers, and wafer W is placed on projection 55 of hot plate 53. Thereafter, wafer W is heated to heat treatment temperature t2 such as 110° C. and held for a period set in advance, such as 60 seconds, for heat treatment (step S4).
Thereafter, support pin 26a is elevated and supports wafer W. In succession, cooling plate 33 again moves from the home position to the position above hot plate 53, wafer W is placed on cooling plate 33 of which temperature has attained, for example to 50° C., and the heat is transmitted to cooling plate 33 (step S5).
Thereafter, cooling plate 33 returns to the home position. Then, transfer mechanism 40 described already comes to receive wafer W at regular time intervals. Here, wafer W is cooled by cooling plate 33 until reception, for example for 30 seconds, and the temperature of cooling plate 33 and the temperature of wafer W both attain, for example, to 60° C.
Thereafter, transfer mechanism 40 enters housing 20 through transfer port 21, receives wafer W on cooling plate 33, and transfers wafer W out of housing 20 (step S6). Thereafter, transfer mechanism 40 transfers subsequent wafer W (second wafer in this example) into housing 20, and step S3 to step S6 are repeated.
As will be described later, transfer mechanism 40 includes two arms. Transfer mechanism 40 receives wafer W that has been subjected to heat treatment from cooling plate 33 and immediately thereafter passes wafer W to be treated to cooling plate 33. Here, time interval for transferring wafer W is constant, because it is scheduled transfer. In the subsequent successive treatment, as shown in
As described above, after a prescribed number of wafers W in one lot (one unit) are subjected to successive treatment, successive treatment of wafers W in next lot is performed.
An example in which wafers W are successively subjected to heat treatment and thereafter heat treatment is continued with varied heat treatment temperature t2 of wafer W will now be described.
Initially, in varying heat treatment temperature t2 of wafer W, set temperature T2 of cooling plate 33 in accordance with the recipe to be applied to the next lot is read from a memory unit in control unit 10, and cooling plate 33 is heated or cooled until the temperature value detected by the temperature detection portion of cooling plate 33 attains to set temperature T2. If heat treatment temperature t2 of wafer W is set to a temperature higher than before, the stabilization temperature of cooling plate 33 is raised as shown in the experiment example which will be described later. Accordingly, cooling plate 33 is positioned above hot plate 53 and heated until the detected temperature value attains to set temperature T2. Meanwhile, if heat treatment temperature t2 is set to a temperature lower than before, the stabilization temperature of cooling plate 33 is lowered. Here, cooling plate 33 should be cooled in order to avoid lowering in throughput. Such an example will be described with reference to
Cooling plate 33 is at high initial temperature T3 such as 80° C. at the home position shown at the left end in
Then, as described previously, heat treatment and cooling of wafer W is performed, and thereafter successive heat treatment of second and subsequent wafers W is performed.
By the method above, as temperature of cooling plate 33 can quickly be lowered from high initial temperature T3 to set temperature T2 in step S91, heat treatment can be performed without reducing an operating time of heat treatment apparatus 2.
After successive treatment of one lot ends and heat treatment temperature t2 of wafer W is changed by using the method described above, if time interval until loading into housing 20 of wafer W in the next lot is long enough for the temperature of cooling plate 33 to lower, cooling plate 33 may move to the position above hot plate 53 for compensation of heat loss, as in the case of turn-on of power of the coating and development apparatus described already.
According to heat treatment apparatus 2 of the present invention, in successively subjecting wafers W to heat treatment, before the successive treatment, cooling plate 33 is heated in advance by hot plate 53 so that the temperature of cooling plate 33 is adjusted to set temperature T2 at which the temperature of cooling plate 33 is stabilized based on balance between heat absorption and heat dissipation therein during the successive treatment. Thus, the temperature of wafer W when it is unloaded from housing 20 (step S6) is uniform among wafers W. Therefore, variation in heat treatment among wafers W can be suppressed, and for example, variation in the thickness of the resist film or in the line width of the pattern can be lowered.
In the present embodiment, it is not necessary to provide a cooling mechanism such as a cooling pipe or a Peltier element in cooling plate 33, for the following reasons. Specifically, if heated wafer W is cooled by using cooling plate 33 so as to reduce the time for cooling, heat dissipation does not proceed fast enough relative to heat absorption from wafer W unless high cooling capability is ensured. Consequently, the cooling temperature (the temperature to which wafer W is cooled by cooling plate 33) is successively increased until several wafers W are treated after the start of successive treatment. Meanwhile, the present inventors have found that, if cooling to a temperature half the heated temperature can be attained in spite of the cooling temperature being higher than in the conventional example, finishing of the treatment of wafer W, such as the line width of the pattern, is not affected. In contrast, if there is variation in the cooling temperature among wafers W in the lot, variation in finishing of wafer W is caused, which results in lower yield. Therefore, turning to the concept to attain the cooling temperature at substantially the same level among wafers W rather than to the cooling temperature itself, such a method as finding in advance a temperature of the cooling plate, at which cooling temperatures are substantially the same among all wafers W to be subjected to successive treatment, and raising in advance the temperature of cooling plate 33 to that temperature has been adopted. Accordingly, a design without requiring great cooling capability and without a cooling mechanism in cooling plate 33 as in the present embodiment can be adopted. Thus, smaller size and lighter weight of the apparatus can be achieved, and in addition, accidents in electric system, e.g., due to leakage of a coolant, or lower quality such as generation of particles in wafer W can be suppressed.
In the embodiment described above, the temperature of cooling plate 33 is adjusted in advance such that first wafer W and second wafer W in the lot are cooled to the same temperature, however, the present invention is not limited to an example where “the same temperature is attained.” Namely, the present invention aims to suppress non-uniformess in heat treatment among wafers to thereby improve yield, by heating cooling plate 33 so that difference in the cooling temperature of wafer W between first wafer W and next wafer W in the lot is made smaller even though cooling plate 33 has low cooling capability. In other words, attention being paid to “the same temperature,” the present invention aims to decrease the number of wafers W to be treated until “the same temperature” is attained in successive treatment of wafers W under the same condition. Thus, even though the cooling temperature is not the same, first wafer W and second wafer W attain to temperatures close to each other, and the heat treatment finishing state can be uniform from the first wafer in the lot, without high cooling capability, for example without a cooling mechanism. Therefore, the effect above can be obtained even if the cooling temperature of second wafer W is higher than that of first wafer W, for example, by 10° C.
As a method of heating cooling plate 33, in the present embodiment, before cooling of wafer W, hot plate 53 is used as the heating mechanism, and cooling plate 33 is then moved to the position above hot plate 53 so as to receive heat from hot plate 53. The present embodiment, however, is not limited to such a method, and for example, a heater or the like serving as the heating mechanism may be embedded in cooling plate 33. Such an example will now be described with reference to
In cooling plate 33 in
At the time of turn-on of power of heat treatment apparatus 2 described already, the surface of hot plate 53 is heated by heater 53a to heat treatment temperature t2 set in advance, such as 110° C. In addition, as shown in
In the present example, wafer W is received from transfer mechanism 40 (step S3) without performing step S1 and step S2 described already. Thereafter, as in the example described above, heat treatment and cooling in the successive treatment of wafer W is performed.
As described above, by embedding heater 35 in cooling plate 33, the time for adjusting the temperature of cooling plate 33 to set temperature T2 (the time from step S1 to step S2 described already) can be shortened. In addition, as the temperature of cooling plate 33 can be adjusted with high accuracy in order to make the temperature of wafers W more uniform at the time of unloading of wafer W, temperature difference between wafers W is less likely. It is noted that temperature adjustment by heating of cooling plate 33 by heater 35 may performed, for example, on the first to fourth wafers W in the lot, and thereafter heating control output to heater 35 may be turned off.
In addition, in the example described above, as the method of cooling cooling plate 33 at the time of switching of the lots, cooling is carried out in such a manner that cooling gas discharge port 60, cooling gas supply path 61, valve 62, and cooling gas source 63 are used as the cooling mechanism and cooling plate 33 is blown with a cooling gas, however, the following structure may be adopted.
Upper chamber 39a is structured such that a fan 28 serving as the cooling mechanism is connected to one opening and fan 28 is driven with electric power from a not-shown power supply, thereby sending air into upper chamber 39a. As fin 38 is cooled by the air sent into upper chamber 39a, cooling plate 33 can quickly be cooled through the top wall of upper chamber 39a and coupling bracket 31.
An experiment conducted in order to confirm how the stabilization temperature of cooling plate 33 varies depending on heat treatment temperature t2 of wafer W will now be described.
In the experiment, heat treatment apparatus 2 described already was used and the experiment was conducted under the following process conditions. Under each condition, 25 wafers W were subjected to successive heat treatment. Meanwhile, heating of cooling plate 33 at the time of turn-on of power of heat treatment apparatus 2 described already (step S1 to step S2) was not conducted.
Process Conditions
Heat treatment temperature t2 of wafer W was set to 90° C.
Heat treatment temperature t2 of wafer W was set to 110° C.
Heat treatment temperature t2 of wafer W was set to 130° C.
Heat treatment temperature t2 of wafer W was set to 150° C.
Heat treatment temperature t2 of wafer W was set to 170° C.
Result of Experiment
In Experiment Example 2, a terminal for measuring a temperature was connected to wafer W. The temperature of cooling plate 33 and wafer W was measured when the temperature of wafer W attained to 110° C. (step S4), when cooling of wafer W was started (step S5), and when wafer W was unloaded from housing 20 (step S6), and
In addition, Table 1 shows heat treatment temperature t2 of wafer W and the stabilization temperature of cooling plate 33 in each experiment example.
It can be seen from
In addition, as to the stabilization temperature of cooling plate 33, it can be seen as shown in Table 1 that as heat treatment temperature t2 of wafer W was higher, the stabilization temperature of cooling plate 33 (cooling temperature of wafer W) was higher.
It is noted that, for example, heat treatment temperature t2 of wafer W in a range from 90° C. to 130° C. refers to a temperature range used for a process for drying the solvent in the resist liquid, and for example, heat treatment temperature t2 of wafer W in a range from 130° C. to 170° C. refers to a temperature range used for a process for heat treatment of exposed wafer W. Accordingly, it was found that the temperature difference between set temperature T2 and temperature T3 of cooling plate 33 that should be changed at the time of change in heat treatment temperature t2 of wafer W in each process is within a range of 20° C. at the maximum.
In succession, one embodiment where heat treatment apparatus 2 described already is applied to the coating and development apparatus will be described.
In carrier block S1, a carrier base 91 for carrier 90, an opening/closing portion 92 provided in a wall surface, a transfer arm C for taking wafer W out of carrier 90 through opening/closing portion 92 are provided.
Treatment block S2 surrounded by a housing 93 is connected to the rear side of carrier block S1. In treatment block S2, in this example, first and second unit blocks (DEV layer) B1, B2 for development treatment arranged in two lowest layers, a third unit block (TCT layer) B3 for performing treatment for forming an antireflection coating on the upper layer side of the resist film, a fourth unit block (COT layer) B4 for performing treatment for applying the resist liquid, and a fifth unit block (BCT layer) B5 for performing treatment for forming an antireflection coating on the lower layer side of the resist film are allocated.
Each of these unit blocks B1 to B5 includes a liquid treatment unit for applying a chemical to wafer W, various heating/cooling treatment units for pre-treatment and post-treatment for the treatment performed in the liquid treatment unit, and main arms A1 to A5 serving as the transfer mechanism dedicated for passing/receiving wafer W to/from the heating/cooling treatment units in the apparatus. Transfer mechanism 40 described already represents main arms A1 to A5.
As each layer B1 to B5 is structured substantially similarly, COT layer B4 shown in
Various units for pre-treatment and post-treatment described above include, for example, a cooling unit (COL) for adjusting a temperature of wafer W to a prescribed temperature before application of the resist liquid, a heating unit (CHP) 95 called, for example, a pre-baking unit, for heat treatment of wafer W after application of the resist liquid, an edge exposure apparatus (WEE) for selectively exposing only an edge portion of wafer W, and the like. In this embodiment, heat treatment apparatus 2 described in connection with
Main arm A4 includes two arms that can be driven independently, and it is structured so as to be capable of movement forward/backward, movement upward/downward, pivot around a vertical axis, and movement in the direction of Y.
The region adjacent to carrier block S1 of transfer region R1 serves as a first wafer W delivery region R2. In region R2, as shown in
As shown in
The region adjacent to interface block S3 of transfer region R1 serves as a second wafer W delivery region R3. In region R3, as shown in
As shown in
As to other unit blocks, DEV layers B1 and B2 are structured similarly. A development unit including a plurality of development portions for development treatment of wafer W is provided. Shelf units U1 to U4 are structured similarly to COT layer B4 except for including a heating unit (PEB) called, for example, a post-exposure baking unit for heat treatment of exposed wafer W, a cooling unit (COL) for adjusting a temperature of wafer W to a prescribed temperature after treatment in the heating unit (PEB), and a heating unit (POST) called, for example, a post-baking unit for heat treatment of wafer W after development treatment for removal of moisture. These heating units provided in DEV layers B1 and B2 are structured, for example, in a manner the same as heating unit 95 provided in COT layer B4, and they are different from heating unit 95 only in the temperature and time for treatment.
In addition, in TCT layer B3, an antireflection coating forming unit for applying a chemical for forming antireflection coating to wafer W before application of the resist liquid is provided.
Meanwhile, exposure apparatus S4 is connected to the rear side of shelf unit U6 in treatment block S2, with interface block S3 being interposed. Interface block S3 includes an interface arm B for passing/receiving wafer W to/from shelf unit U6 in treatment block S2 and exposure apparatus S4, and interface block S3 is structured to pass/receive wafer W to/from second delivery stages TRS6 to TRS9 in respective first to fourth unit blocks B1 to B4.
Here, the flow of wafer W in the resist pattern forming apparatus will be described with reference to an example where antireflection coatings are formed on and under the resist film. Initially, carrier 90 is loaded from the outside into carrier block S1, and wafer W is taken out of carrier 90 by transfer arm C through opening/closing portion 92. Wafer W is initially passed from transfer arm C to first delivery stage TRS2 of shelf unit U5 in second unit block B2, and thereafter, for delivery of wafer W to BCT layer B5, wafer W is passed to main arm A5 of BCT layer B5 by first delivery arm D1 through first delivery portion TRS5. Then, in BCT layer B5, main arm A5 transfers wafer W in the order of the cooling unit (COL), the first antireflection coating forming unit, the heating unit (CHP), and second delivery stage TRS10 of shelf unit U6, thereby forming the first antireflection coating.
In succession, wafer W in second delivery stage TRS10 is transferred to second delivery stage TRS9 by second delivery arm D2, for delivery of wafer W to COT layer B4, and thereafter passed to main arm A4 of COT layer B4. Then, in COT layer B4, main arm A4 transfers wafer W in the order of the cooling unit (COL), coating unit 94, heating unit (CHP) 95, and first delivery stage TRS4, thereby forming the resist film on the first antireflection coating.
Thereafter, wafer W in delivery stage TRS4 is transferred to first delivery stage TRS3 by first delivery arm D1, for delivery of wafer W to TCT layer B3, and passed to main arm A3 of TCT layer B3. Then, in TCT layer B3, main arm A3 transfers wafer W in the order of the cooling unit (COL), the second antireflection coating forming unit, the heating unit (CHP), the edge exposure apparatus (WEE), and second delivery stage TRS8 of shelf unit U6, thereby forming the second antireflection coating on the resist film.
In succession, wafer W in second delivery stage TRS8 is transferred to exposure apparatus S4 by interface arm B, where prescribed exposure treatment is performed. Wafer W that has been subjected to exposure treatment is transferred to second delivery stage TRS6 (TRS7) of shelf unit U6 by interface arm B, for delivery to DEV layer B1 (DEV layer B2), wafer W on stage TRS6 (TRS7) is received by main arm A1 (main arm A2) of DEV layer B1 (DEV layer B2), and initially transferred in the order of the heating unit (PEB), the cooling unit (COL), the development unit, and the heating unit (POST) in DEV layer B1 (B2), whereby the prescribed development treatment is performed. Wafer W thus subjected to development treatment is transferred to first delivery stage TRS1 (TRS2) for delivery of wafer W to transfer arm C, and returned by transfer arm C to original carrier 90 placed on carrier block S1.
Although the present invention has been described and illustrated in detail, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, the spirit and scope of the present invention being limited only by the terms of the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-122455 | Apr 2006 | JP | national |
