JP4686887B2 - Deposition method - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a film forming method .
[0002]
[Prior art]
For example, a vertical heat treatment apparatus is known as an apparatus that collectively performs a film forming process on a large number of semiconductor wafers (hereinafter referred to as wafers). As shown in FIG. 6, this apparatus holds a large number of wafers W on a wafer boat 91, which is a wafer holder, and loads the wafer W into a vertical reaction vessel 92 from the lower side to open a lower end opening. The wafer W is closed and heated by a heater 93 provided around the reaction vessel 92 to supply a processing gas while heating the wafer W to a predetermined process temperature.
Recently, since a wide variety of semiconductor devices are required, a heat treatment may be required for a wide variety of wafers W in a small lot. For this reason, for example, if processing is performed for 150 wafers as a full product wafer, for example, when the wafer board 91 is in a full batch state in which the wafer boat 91 is fully loaded, a smaller number of wafers, for example, 100, 50, or 25 wafers. A recipe batch mode may be included in the recipe in which a product wafer is mounted on the wafer boat 91 and heat treatment is performed. The mounting state of the wafer W shown in FIG. 6 corresponds to the short batch mode, and the upper side is set as an empty area by lowering the wafer W.
[0003]
When such a short batch mode is performed, it is not advantageous from the viewpoint of cost to fill the wafer boat 91 with a sufficient number of dummy wafers. The reason is that the dummy wafer is expensive and is finally discarded after repeated use, so that the running cost increases. Therefore, by making various arrangements such as placing the product wafer, adjusting the pressure corresponding to the short batch, and using a few dummy wafers, the wafer boat 91 is not fully loaded while forming an empty area. We are considering heat treatment with high uniformity.
[0004]
[Problems to be solved by the invention]
By the way, if a thin film adheres to the inner walls of the wafer boat 91 and the reaction vessel 92 which are apparatus parts exposed to a heat treatment atmosphere and the film thickness increases, the film may be peeled off and a particle may be generated. Accumulated film thicknesses of the inner wall of the wafer boat 91 and the reaction vessel 92 are predicted based on the target film thickness of the wafer, and the timing for cleaning the wafer boat 91 and the reaction vessel 92 is determined based on the prediction result. . However, in the case where a wafer is formed in a short batch, since there is no wafer that consumes the film forming gas in the empty region, the film forming speed in the portion located in the empty region in the wafer boat 91 and the reaction vessel 92 is high. Becomes higher than the film forming speed of the portion located in the region where the film is placed. For this reason, as shown in an image of the reaction vessel 92 in FIG. 6, the accumulated film thickness of the former thin film 90 becomes larger than the accumulated film thickness of the latter thin film 90. As a result, it is necessary to clean the reaction vessel 92 before the predetermined cleaning timing, and there is a problem that the maintenance cycle is shortened. In addition, it is difficult to predict the maintenance cycle because the accumulated film thickness of the portion located in the empty area in the wafer boat 91 and the reaction vessel 92 cannot be grasped.
[0005]
The present invention has been made under such circumstances, and an object of the present invention is to perform a film forming process on a substrate in a short batch mode in which an empty region is present without full loading of the substrate in the holder. It is to provide a technique capable of performing maintenance at an appropriate timing .
[0006]
[Means for Solving the Problems]
In the present invention , the substrate is fully loaded into a holder for arranging and holding a large number of substrates in the length direction of the reaction vessel, the substrate is loaded into the reaction vessel, the inside of the reaction vessel is heated, and a processing gas is supplied into the reaction vessel. A full batch mode for forming a film on the substrate, and a short batch mode for holding the substrate in a part of the mounting area of the substrate in the holder and performing the film forming process with the remaining mounting area as an empty area. In a method for performing a film forming process using a film forming apparatus provided with
A step of placing a monitor substrate in the empty area and performing a shot batch mode; a step of measuring the film thickness of the monitor substrate after this step;
Based on the measurement result of the film thickness in this step, a step of predicting the cumulative film thickness of the device parts at the position corresponding to the empty area;
And a step of determining the timing for cleaning the device parts based on the predicted result of the accumulated film thickness .
[0007]
In the present invention, the “process of placing the monitor substrate in the vacant area and performing the shot batch mode” may be performed in an adjustment process before the film forming process is actually performed on the product wafer. You may perform in the process of performing the film-forming process with respect to a product wafer. According to the present invention, it is possible to predict the accumulated film thickness of the film adhering to the apparatus parts (in the embodiment, the reaction vessel and the wafer boat 4) located at the position corresponding to the empty area, and therefore, maintenance can be performed at an appropriate timing. Therefore, it is possible to prevent particle contamination due to film peeling from the device parts.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to an example in which the film forming method of the present invention is carried out by a vertical heat treatment apparatus. First, the configuration of the vertical heat treatment apparatus will be described with reference to FIGS. 1 and 2. This apparatus is composed of, for example, an inner tube 1a having both ends open and an outer tube 1b having both upper ends closed. A reaction tube 1 having a quartz double tube structure is provided. When viewed from the control system, the heat treatment atmosphere in the reaction tube 1 is divided into, for example, five zones. Around the reaction tube 1, for example, a heater 2 made of a resistance heating element is divided into, for example, a plurality of upper and lower parts, for example, five stages, and the heaters 2a, 2b, 2c, 2d at each stage are divided. , 2e are configured to take charge of heating control of the five zones.
[0013]
The inner pipe 1a and the outer pipe 1b are supported on a cylindrical manifold 3 on the lower side, and a plurality of supply ports are provided in the manifold 3 so that supply ports are opened in a lower region inside the inner pipe 1a. Gas supply pipe 31 (two gas supply pipes 31a and 31b are shown in the figure for the sake of convenience) and one end of a vacuum pump (not shown) is evacuated from between the inner pipe 1a and the outer pipe 1b. An exhaust pipe 32 to which the side is connected is connected. In this example, a reaction vessel is constituted by the inner tube 1a, the outer tube 1b and the manifold 3.
[0014]
Further, a lid 11 is provided so as to close the lower end opening of the manifold 3, and the lid 11 is provided on the boat elevator 12. A rotating table 14 is provided on the lid 11 via a rotating shaft 13 that is rotated by a drive unit (not shown). A substrate holder is provided on the rotating table 14 via a heat insulating unit 15 made of, for example, a heat insulating cylinder. A certain wafer boat 4 is mounted. As shown in FIG. 2, the wafer boat 4 is configured by providing a plurality of support columns 43 between the top plate 41 and the bottom plate 42, and a plurality of wafers W are formed on the support columns 43 at the periphery of each wafer W. By being held in the holding groove 44, it can be placed in a shelf shape. In order to place the product wafer W in a uniform heating atmosphere as much as possible, the wafer boat 4 is a monitor for monitoring a processing state while wafers called side wafers are placed on the upper end side and the lower end side during full batch. Since the wafers are also scattered and arranged, a number of grooves that allow for these wafers are provided in addition to the product wafers. For example, in the case of mounting 150 product wafers W, 170 holding grooves 44 are provided. Is formed. In FIG. 2, a portion indicated by 30 is a heating furnace including the heater 2.
[0015]
Further, the vertical heat treatment apparatus includes a control unit 5 as shown in FIG. Although this control unit 5 is simply shown as one block, in reality, an input operation unit such as a touch panel for setting recipes and parameters, etc., and a program according to a program designated by this input operation unit. Each controller for controlling the calorific value of the heater 2 (2a to 2e), the flow rate of the processing gas, the pressure in the reaction tube 1 and the like is included. As will be described later, a full batch mode and a short batch mode can be set as modes for mounting a wafer on the wafer boat 4, and the control unit 5 can select each zone according to these modes. The temperature setting value is read from the memory, and the heaters 2 (2a to 2a) of each stage are read by the PID control system, for example, based on the read value and the detection value of the temperature detection unit provided inside and outside the reaction tube 1, for example. 2e) is provided.
[0016]
Next, an adjustment process performed before the film forming process is performed on the product wafer will be described. In the above-described vertical heat treatment apparatus, the full batch mode and the short batch mode can be set as described above. In this example, the full batch mode is a product on the wafer board 4. In this state, the wafer W including 150 wafers is fully loaded. Specifically, six side wafers are placed on the upper side of the wafer board 4 and seven side wafers are placed on the lower side, respectively, and 150 product wafers are mounted between them. Seven monitor wafers are scattered in the group. On the other hand, in the short batch mode, as shown in FIG. 3, for example, seven side wafers SW are placed on the lower side, for example, 100 product wafers PW are placed thereon, and further, On this, five dummy wafers DW are mounted, and thus the wafers W (which will be denoted by the symbol “W” when describing the wafers as a whole) are mounted on the wafer boat 4 in a bottom-down manner. The upper stage side of the wafer W mounting area is an empty area (unmounted area) in which the wafer W is not mounted in the holding groove 44.
[0017]
In this example, in addition to the case where 100 product wafers PW are placed as types of the short batch mode, the case where 50 product wafers PW are placed, the case where 25 product wafers PW are placed, and Three types are available. FIG. 4 is a diagram schematically showing a mounting mode of the wafer W in the full batch mode and a mode of the wafer W in each shot batch. In either case, the product wafer PW is included in the product wafer PW group. A monitor-wafer MW is interposed to evaluate the processing state. Also in the short batch mode, the monitor wafer MW is interposed in the product wafer PW group according to the batch size. In this example, it corresponds to the downstream side of the flow of the processing gas in the product wafer PW group. For example, five dummy wafers DW are placed on the upper side to ensure the uniformity of the heat treatment. Note that the total number of stages (170 stages) and the ratio of the wafer placement area are not uniform in FIG.
[0018]
Then, the set temperature of each zone in the full batch mode and the short batch mode is adjusted. In FIG. 4, a product wafer PW is described as an embodiment in the case of obtaining an actual product, but in this temperature adjustment process, a dummy wafer DW is used instead of the product wafer PW. In this step, a wafer W is mounted on the wafer boat 4 corresponding to each mode, and a film formation process (process) is performed under the same processing conditions as those carried into the reaction container and actually performed on the product wafer. The thickness of the thin film formed on the monitor wafer MW is checked, and the set temperature of each zone, that is, the control system of the heaters 2 (2a to 2e) of each stage is input based on the result. Adjust parameters such as set temperature. An example of the film forming process will be described in the processing section of the product wafer.
[0019]
In the adjustment process in the short batch mode, the monitor wafer MW is also placed in the empty area as shown by the dotted line in FIG. 4, and the measurement result of the film thickness of the thin film formed on the monitor wafer MW Measurement of the film thickness of the thin film formed on the monitor wafer MW interposed in the bottom wafer W group, that is, the region where the product wafer PW is disposed (in this case, the dummy wafer DW is disposed). Based on the result, the setting of the zone corresponding to the empty area is set so that the film forming speed of the monitor wafer MW in the empty area is equal to or smaller than the film forming speed of the area in which the wafer W is bottomed. Adjust the temperature. That is, this set temperature is lower than the set temperature of the heater 2 in the full batch mode. In this case, it is necessary to adjust the temperature of the monitor wafer MW in the region where the product wafer PW is disposed so as not to impair the uniformity of the film thickness within the wafer surface and the uniformity of the film thickness between the wafers. is there. When the monitor wafers MW are placed in the empty area, if the number of the monitor wafers MW is too large, the amount of processing gas consumed by the monitor wafer MW increases, and the reaction container corresponding to the empty area in the actual process. Since it is difficult to evaluate the amount of the thin film adhering to the inner wall, for example, one monitor wafer MW is arranged in one zone.
[0020]
An example of the set temperature of the heater 2 at each stage determined in this manner is shown in FIG. Here, for convenience of explanation, when a short batch is performed by placing n product wafers PW, the empty area monitor wafer MW is placed in the seventh row from the top in L100. In L50 and L25, they are placed on the seventh and 46th stages from the top. In FIG. 4, TOP is the uppermost zone, CT is the second zone from the top, CB is the third zone, CB is the fourth zone, and BTM. Is the fifth zone. The set temperature of TOP is 780 ° C. in the full batch mode, but is as low as 775 ° C. in L100, L50, and L25. The set temperature of CT is 770 ° C. in the full batch mode, but is set to 768 ° C. and 766 ° C. in L50 and L25, respectively.
[0021]
As can be seen from the set temperature of the full batch mode, in this example, the temperature gradually increases around the process temperature of 770 ° C. as it goes from the upstream side to the downstream side in the process gas flow direction, that is, from the bottom to the top of the wafer boat 43. So-called tilt temperature control is performed so as to increase the inclination. By doing so, the uniformity of the film thickness between the wafers W increases.
[0022]
Next, a state in which a film forming process is performed on a product wafer using the above-described vertical heat treatment apparatus will be described. First, a batch size mode, for example, a full batch shown in FIG. 4, a mode selected from L100, L50, and L25 is input to the control unit 5 and shown in the wafer boat 4 in accordance with this mode. Wafers are transferred from the transfer arm that does not. The wafer arrangement state is as described in FIG. 4, but in the short batch mode (L100, L50, L25), the monitor wafer MW is not arranged in the empty area. Then, the boat elevator 12 is raised and the wafer boat 4 is carried into the reaction vessel, and the set temperature of each zone is increased to the value shown in FIG. 4 at a predetermined temperature increase rate. After the temperature of each zone in the reaction vessel is stabilized at the target temperature, a predetermined processing gas, such as dichlorosilane gas and ammonia gas, is supplied from the gas supply pipe 31 (31a, 31b) at a predetermined flow rate. Nitrogen gas is supplied as an active gas at a predetermined flow rate. These processing gases rise from under the wafer boat 4, are folded by the inner pipe 1 a, are exhausted from the exhaust pipe 32 through the gap between the inner pipe 1 a and the outer pipe 1 b, and the inside of the reaction vessel is evacuated by a vacuum pump (not shown). As a result, a predetermined degree of vacuum is maintained. At this time, the wafer boat 4 rotates around the vertical axis, the dichlorosilane gas and the ammonia gas react with each other, and a silicon nitride film as a reaction product is deposited on the wafer W to perform a film forming process.
[0023]
According to the above-described embodiment, when the short batch mode is performed, the monitor wafer MW is arranged in advance in the empty area, the film thickness of the monitor wafer MW is measured, and the film thickness (film formation speed) is the product. The set temperature of the vacant area is adjusted so as to be equal to the film thickness (film formation speed) of the wafer W placed in the mounting area of the wafer PW. In the empty area, as much as the wafer W does not exist compared to the case where the wafer W is fully loaded, more film is attached to the apparatus parts, in this example, the reaction vessel and the wafer boat 4. In this way, the set temperature is adjusted. As a result, the accumulated film thicknesses of the reaction vessel and the wafer boat 4 in the empty region and the wafer W mounting region are aligned, so that the maintenance cycle (cleaning cycle) can be prevented from being shortened.
[0024]
In the above, the shot batch mode is not limited to the case where the wafers W are placed under the wafer board 4 as described above, but the wafers W are placed over the wafer board 4 as shown in FIG. In this case, the lower side may be a free area, or the wafer W may be moved to the center of the wafer board 4 as shown in FIG. It may be the case.
[0025]
Further, the present invention is based on the measurement result of the film thickness of the monitor-wafer MW arranged in the empty area, and does not adjust the set temperature as in the above embodiment, and the reaction container at the position corresponding to the empty area, A method of simply predicting the accumulated film thickness of the wafer boat 4 is also included in the scope of rights. Furthermore, the adjustment of the set temperature of the empty area may be such that the film formation speed of the monitor-wafer MW in the empty area is lower than the film formation speed of the wafer W placed in the placement area of the product wafer PW. Furthermore, not only the temperature adjustment step, but also when the process is performed on the product wafer PW, the monitor wafer MW may be arranged in the empty area and the film thickness thereof may be monitored. The present invention can be applied not only to a vertical heat treatment apparatus but also to a horizontal heat treatment apparatus.
[0026]
【The invention's effect】
According to the present invention, when the film forming process is performed by the short batch in which the number of substrates smaller than the maximum number of substrates can be mounted on the substrate holder, the monitor wafer MW is arranged in the empty area and the film thickness is measured. Therefore, it is possible to predict the accumulated film thickness of the film adhering to the device parts (in the embodiment, the reaction vessel and the wafer boat 4) at the position corresponding to the empty area. Therefore, particle contamination due to film peeling from the device parts can be prevented. Further, based on the measurement result of the film thickness of the monitor-wafer MW, the film-forming speed of the monitor-wafer MW is equal to or less than the film-forming speed of the wafer W placed on the product wafer PW mounting area. Since the set temperature of the empty area is adjusted as described above, it is possible to suppress the maintenance cycle from being shortened.
[Brief description of the drawings]
FIG. 1 is a vertical side view showing a vertical heat treatment apparatus used in an embodiment of the present invention.
FIG. 2 is a schematic view showing the vertical heat treatment apparatus.
FIG. 3 is a side view showing an example of a mode of placing a wafer in the short batch mode.
FIG. 4 is an explanatory view showing a state in which a wafer is placed in a full batch mode and a short batch mode and a set temperature of a zone in a reaction vessel in association with each other.
FIG. 5 is an explanatory view showing another example of a wafer mounting mode in a short batch mode.
FIG. 6 is an explanatory view showing a state of adhesion of a thin film on the inner wall of a reaction vessel when a film is formed in a short batch mode by a conventional method.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Reaction tube 11 Lid 2 (2a-2e) Heater 3 Manifold 31 Gas supply tube 32 Exhaust tube 4 Wafer boat 44 Holding groove 5 Control part W Wafer PW Product wafer MW Monitor wafer DW Dummy wafer

Claims (1)

The substrate is packed in a holder that holds a large number of substrates in the length direction of the reaction vessel, loaded into the reaction vessel, heated inside the reaction vessel and supplied with processing gas into the reaction vessel to form a film on the substrate. A full batch mode for performing the processing, a short batch mode for performing the film forming process in a state where the substrate is held in a part of the mounting region of the substrate in the holder and the remaining mounting region is an empty region, In a method of performing a film forming process using a film forming apparatus comprising:
A process of placing a monitor substrate in the empty area and performing a shot batch mode;
After this step, measuring the film thickness of the monitor substrate,
Based on the measurement result of the film thickness in this step, a step of predicting the cumulative film thickness of the device parts at the position corresponding to the empty area;
And a step of determining a timing for cleaning the device parts based on a predicted result of the accumulated film thickness .

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