Method of processing device wafer

A method of processing a device wafer includes the steps of applying a water-soluble protective film agent to a face side of the device wafer to form protective films thereon for protecting devices and leaving projected dicing lines exposed, dry-etching the device wafer through the protective films with a dry etching apparatus, recording a time when the water-soluble protective film agent is applied to the device wafer, confirming that the device wafer with the protective films formed thereon has been introduced into the dry etching apparatus, and issuing a warning if the introduction of the device wafer into the dry etching apparatus is not confirmed upon elapse of a predetermined time from the recorded time.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a method of processing a device wafer having a plurality of devices disposed on a face side thereof.

Description of the Related Art

For dry-etching a workpiece such as a device wafer, the devices disposed on a face side of the workpiece are coated with a resist film that is resistant to plasmas, and the resist film is used as a protective film in the dry etching process (see, for example, Japanese Patent Laid-open No. 2006-120834).

SUMMARY OF THE INVENTION

However, using a resist film as a protective film poses problems in that a resist film forming apparatus is required to form a protective film and an ashing apparatus is required to remove the protective film, tending to make the whole processing sequence complex and costly.

It is therefore an object of the present invention to provide a method of processing a device wafer to divide the device wafer into individual device chips more efficient than heretofore.

In accordance with an aspect of the present invention, there is provided a method of processing a device wafer having a plurality of devices disposed in respective areas demarcated on a face side thereof by a plurality of projected dicing lines, including the steps of applying, with a protective film forming apparatus, a water-soluble protective film agent to the face side of the device wafer to form protective films thereon for protecting the devices and leaving the projected dicing lines exposed, thereafter, dry-etching the device wafer through the protective films with a dry etching apparatus, recording a time when the water-soluble protective film agent is applied to the device wafer, confirming that the device wafer with the protective films formed thereon has been introduced into the dry etching apparatus, and issuing a warning if the introduction of the device wafer into the dry etching apparatus is not confirmed upon elapse of a predetermined time from the recorded time.

The protective film forming apparatus and the dry etching apparatus may be connected to a terminal apparatus through respective communication links, the method further including the step of calculating, with the terminal apparatus, the number of device wafers on which the protective films are to be formed based on an operation state of the dry etching apparatus.

The protective film forming apparatus and the dry etching apparatus may be connected to a terminal apparatus through respective communication links, the method further including the step of calculating, with the terminal apparatus, the number of device wafers on which the protective films are to be formed based on information input to the protective film forming apparatus and the dry etching apparatus.

The method of processing a device wafer according to the aspect of the present invention includes the protective film forming step for forming the protective films that protect the devices by applying the water-soluble protective film agent to the face side of the device wafer, while exposing the projected dicing lines, with the protective film forming apparatus, and the etching step for dry-etching the device wafer through the protective films with the dry etching apparatus. The protective films can easily be removed from the face side of the device wafer simply by supplying cleaning water thereto. Therefore, various pieces of equipment such as a resist film forming apparatus, an ashing apparatus, etc. are not required, resulting in a reduction in the cost, and the device wafer can efficiently be divided into individual chips.

The method of processing a device wafer according to the aspect of the present invention also includes the applying time recording step for recording the time when the water-soluble protective film agent is applied to the device wafer, the introduction confirming step for confirming that the device wafer on which the protective film forming step has been performed has been introduced into the dry etching apparatus, and the warning issuing step for issuing a warning if the introduction of the device wafer into the dry etching apparatus is not confirmed upon elapse of a predetermined time from the time recorded in the applying time recording step. Therefore, before the etching step, a warning is issued if the introduction of the device wafer into the dry etching apparatus is not confirmed in the introduction confirming step after elapse of a predetermined time from the time recorded in the applying time recording step. Consequently, it is possible to give a warning while the protective films can be removed from the device wafer, and the protective films may be removed and new protective films may be formed again on the face side of the device wafer. Therefore, it is unlikely to cause damage to the device wafer in its entirety.

In case the protective film forming apparatus and the dry etching apparatus are connected to the terminal apparatus through respective communication links, and the method further includes the calculating step for calculating, with the terminal apparatus, the number of device wafers on which the protective film forming step is to be performed based on an operation state of the dry etching apparatus, even if the processing time for the device wafer in the dry etching apparatus is longer than the processing time for the device wafer in the protective film forming apparatus, the protective film forming step and the etching step can be carried out after the appropriate number of device wafers on which to perform the protective film forming step has been calculated. In this manner, the dwelling time until the device wafer on which the protective films have been formed is introduced into the dry etching apparatus can be shortened. As a consequence, the device wafer can efficiently be divided into individual chips without deterioration of the protective films.

In case the protective film forming apparatus and the dry etching apparatus are connected to the terminal apparatus through respective communication links, and the method further includes the calculating step for calculating, with the terminal apparatus, the number of device wafers on which the protective film forming step is to be performed based on the information input to the protective film forming apparatus and the dry etching apparatus, since the protective film forming step can be carried out after the appropriate number of device wafers on which to perform the protective film forming step has been calculated, the device wafer can efficiently be divided into individual chips without deterioration of the protective films.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As depicted inFIG. 1, a device wafer W is a disk-shaped workpiece, for example, and has a face side Wa that is demarcated by a grid of projected dicing lines S into a plurality of areas with respective devices D disposed therein. The device wafer W also has a reverse side Wb, opposite the face side Wa, serving as a surface to be processed as described below. The face side Wa of the device wafer W bears an individual identification code ID such as a number, a bar code, or the like that identifies an individual device wafer. The individual identification code ID may be placed on the reverse side Wb or within the device wafer W, or applied to an object combined with the device wafer W such as a support plate or a protective tape that is stuck to the device wafer W or an annular frame that is integrally joined to the device wafer W by a tape.

2 Method of Processing a Device Wafer

Using a protective film forming apparatus1depicted inFIG. 2, a protective film for protecting the devices D on the device wafer W at the time the device wafer W is dry-etched is formed on the face side Wa of the device wafer W. The protective film forming apparatus1has an apparatus base100, a column101erected at a rear side of the apparatus base100along a Y-axis indicated by the arrow Y, and protective film forming means10disposed adjacent to the column101at a front side of the apparatus base100along an X-axis indicated by the arrow X.

The protective film forming means10includes a rotatable spinner table11for holding the device wafer W thereon, rotating means12for rotating the spinner table11, an ejection nozzle13for ejecting a predetermined amount of water-soluble protective film agent onto the device wafer W held on the spinner table11, and a tubular cover14surrounding the spinner table11. The spinner table11has an upper surface serving as a holding surface11afor holding the device wafer W under suction thereon. As depicted inFIG. 3, the rotating means12includes a rotatable shaft120having a vertical central axis and an upper end coupled to the spinner table11, and an electric motor121connected to the lower end of the rotatable shaft120. When the electric motor121is energized, it rotates the rotatable shaft120about its vertical central axis, rotating the spinner table11at a predetermined speed. The ejection nozzle13is connected to a water-soluble protective film agent source130.

As depicted inFIG. 2, the apparatus base100supports thereon a holding table16having a holding surface16afor holding the device wafer W under suction thereon, processing feed means17for processing-feeding the holding table16in a processing feed direction along the X-axis, and indexing feed means18for indexing-feeding the holding table16in an indexing feed direction along the Y-axis.

The processing feed means17includes a ball screw170extending along the X-axis, an electric motor171connected to an end of the ball screw170, a pair of guide rails172extending parallel to the ball screw170along the X-axis, and an X-axis base173movable along the guide rails172. The holding table16is supported on an upper surface of the X-axis base173, whose lower surface is held in sliding contact with the guide rails172. The ball screw170is threaded through a nut, not depicted, on a central portion of the lower surface of the X-axis base173. When the electric motor171is energized, it rotates the ball screw170about its central axis, moving the X-axis base173along the guide rails172thereby to processing-feed the holding table16along the X-axis.

The indexing feed means18includes a ball screw180extending along the Y-axis, an electric motor181connected to an end of the ball screw180, a pair of guide rails182extending parallel to the ball screw180along the Y-axis, and a Y-axis base183movable along the guide rails182. The holding table16is supported on an upper surface of the Y-axis base183through the processing feed means17. The Y-axis base183has a lower surface held in sliding contact with the guide rails182. The ball screw180is threaded through a nut, not depicted, on a central portion of the lower surface of the Y-axis table183. When the electric motor181is energized, it rotates the ball screw180about its central axis, moving the Y-axis base183along the guide rails182thereby to indexing-feed the holding table16along the Y-axis.

On a front surface of the column101, there are disposed delivery means15for delivering the device wafer W between the holding table16and the spinner table11, and laser beam applying means19for emitting a laser beam and processing the device wafer W with the laser beam. The laser beam applying means19includes an elongate casing190having a proximal end joined to the column101and extending along the Y-axis, and a processing head191disposed on a distal end of the elongate casing190. The elongate casing190houses therein a laser oscillator for laser oscillating and generating a laser beam having a wavelength that is absorbable by the water-soluble protective film agent. The processing head191houses therein a condensing lens, not depicted, for focusing the laser beam emitted from the laser oscillator.

The delivery means15includes a holder150for holding the device wafer W, a ball screw151extending along the X-axis, an electric motor152connected to an end of the ball screw151, a pair of guide rails153extending parallel to the ball screw151along the X-axis, and a movable unit154movable along the X-axis and supporting the holder150thereon. The movable unit154is held in sliding contact with the guide rails153and has a nut on a central portion thereof which is threaded over the ball screw151. With the device wafer W held by the holder150, when the electric motor152is energized, it rotates the ball screw151about its central axis, moving the movable unit154along the guide rails153thereby to deliver the device wafer W to either the spinner table11or the holding table16.

The protective film forming apparatus1includes control means20for controlling the various actuating mechanisms referred to above. The control means20has a storage device such as a memory and a central processing unit (CPU). The memory of the control means20stores processing conditions, information on the device wafer W to be processed, and so on. The processing conditions include, for example, a rotational speed of the spinner table11, an amount of water-soluble protective film agent to be supplied, a period of time over which the water-soluble protective film agent is to be ejected, a film thickness to which a water-soluble protective film is to be formed, a processing feed speed of the holding table16, an output power level of the laser beam, etc. The information on the device wafer W includes, for example, the individual identification code ID of the device wafer W, the number of projected dicing lines S, etc.

A protective film forming step is carried out using the protective film forming apparatus1thus constructed. The protective film forming step includes a protective film agent applying step for applying the water-soluble protective film agent and a projected dicing line exposing step for removing the water-soluble protective film agent to expose the projected dicing lines S to form a protective film.

As depicted inFIG. 3, the reverse side Wb of the device wafer W is placed on the holding surface11aof the spinner table11. A suction source, not depicted, connected to the holding surface11ais actuated to hold the device wafer W under suction on the holding surface11a. Then, the ejection nozzle13is turned to move the tip end thereof to a position above a central area of the device wafer W held on the spinner table11. The motor121is energized to rotate the rotatable shaft120about its central axis, thereby rotating the spinner table11at a rotational speed of 50 rpm, for example, in the direction indicated by the arrow A.

While the spinner table11is rotating, the injection nozzle13drops a water-soluble protective film agent2onto the face side Wa of the device wafer W. The water-soluble protective film agent2may include a water-soluble liquid resin such as polyvinyl pyrrolidone (PVP) or polyvinyl alcohol (PVA), for example. The water-soluble protective film agent2applied to the face side Wa is caused to flow radially outwardly from the central area of the face side Wa to cover the face side Wa in its entirety under centrifugal forces generated by the rotation of the spinner table11. Then, the spinner table11is rotated at 2000 rpm for 60 seconds, for example, drying the water-soluble protective film agent2on the face side Wa. In this manner, as depicted inFIG. 4, the entire face side Wa of the device wafer W is covered with a thin film2aformed from the water-soluble protective film agent2. If the thin film2ais not sufficiently dried by the rotation of the spinner table11, then it may additionally be dried by baking, for example.

Concurrent with the protective film forming step, a time at which the water-soluble protective film agent2is applied to the face side Wa of the device wafer W is recorded. The time at which the water-soluble protective film agent2is applied to the face side Wa may be a time when the water-soluble protective film agent2is applied and the thin film2ais formed to a predetermined thickness on the face side Wa, or a time when the drying of the water-soluble protective film agent2by the rotation of the spinner table11is completed, or a time when the injection nozzle13starts to drop the water-soluble protective film agent2onto the face side Wa of the device wafer W. The control means20depicted inFIG. 2stores the time at which the water-soluble protective film agent2is applied.

Then, the delivery means15removes the device wafer W from the spinner table11and delivers the device wafer W to the holding table16. When the device wafer W is placed on the holding surface16aof the holding table16, a suction source, not depicted, connected to the holding surface16ais actuated to hold the device wafer W under suction on the holding surface16a.

The processing feed means17moves the holding table16to a position below the laser beam applying means19, and positions the processing head191in alignment with one of the projected dicing lines S. Specifically, an alignment camera, not depicted, captures an image of the face side Wa of the device wafer W, and one of the projected dicing lines S which is to be processed is detected by processing the captured image according to pattern matching or the like, after which the holding table16is index-fed along the Y-axis by the indexing feed means18to position the projected dicing line S and the processing head191into alignment with each other.

Then, as depicted inFIG. 5, the holding table16is moved along the X-axis, for example, moving the processing head191and the device wafer W relatively to each other in a direction parallel to the device wafer W, while at the same time the processing head191applies a laser beam LB having a wavelength absorbable by the water-soluble protective film agent2to the thin film2aalong the projected dicing line S, thereby removing the thin film2afrom over the projected dicing line S. The laser beam LB may be applied a plurality of times to the thin film2aalong the projected dicing line S though the number of times that the laser beam LB is applied is not limited to any particular number.

After the laser beam LB has been applied along the projected dicing line S along the X-axis, removing the thin film2atherefrom, the holding table16depicted inFIG. 2is indexing-fed along the Y-axis to position the processing head191above an adjacent projected dicing line S. Then, the holding table16is moved along the X-axis and the processing head191applies the laser beam LB to the thin film2aalong the projected dicing line S, removing the thin film2afrom over the projected dicing line S, in the same manner as described above. The above process is repeated to remove the thin film2aalong all the projected dicing lines S, thereby exposing the projected dicing lines S as depicted inFIG. 6and forming protective films2bcovering the respective devices D for protecting the devices D in a dry etching process. The protective film forming step is now finished.

After the protective film forming step has been carried out, a dry etching process is performed on the device wafer W through the protective films2b, using a dry etching apparatus3depicted inFIG. 7. The dry etching apparatus3includes a chamber30having a processing space30adefined therein for performing a dry etching process (plasma etching process) on the device wafer W, the processing space30abeing surrounded by a bottom wall300, an upper wall301, and a side wall302of the chamber30. The side wall302has an opening303defined therein for taking the device wafer W therethrough into and out of the chamber30. A gate31for selectively opening and closing the opening303is mounted on the side wall302outside of the opening303. The gate31is vertically movable by opening and closing means32. The opening and closing means32includes an air cylinder320and a piston rod321movable by the air cylinder320and connected to the gate31. The air cylinder320is mounted on the bottom wall300of the chamber30by a bracket322.

The bottom wall300has a discharge port304defined therein that is held in fluid communication with a gas discharger33such as a vacuum pump or the like. When the gas discharger33is actuated, a used gas is discharged from the processing space30aout of the dry etching apparatus3through the discharge port304.

The chamber30houses therein a lower electrode unit34and an upper electrode unit35that are disposed in vertically facing relation to each other. The lower electrode unit34includes a chuck table340for holding the device wafer W thereon and a cylindrical support341supporting the chuck table340on its upper end. The support341extends vertically through a hole305defined in the bottom wall300and is sealed by an insulator36interposed between the support341and the bottom wall300.

The lower electrode unit34is electrically connected to a high-frequency power supply37. The upper electrode unit35is electrically connected to a high-frequency power supply, not depicted. When high-frequency voltages are applied to the lower electrode unit34and the upper electrode unit35, a reaction gas in the processing space30ais plasmatized. The high-frequency voltages may have frequencies and power levels adjusted for drawing etching species (ions) into the device wafer W.

A suction holder342made of a porous material is disposed on an upper portion of the chuck table340. The chuck table340has a suction groove343defined therein directly beneath the suction holder342and held in fluid communication with a suction source38through a suction channel344defined in the chuck table340and the support341. Suction forces from the suction source38are transmitted through the suction channel344and act in the suction groove343, causing the suction holder342on the chuck table340to hold the device wafer W under suction thereon. The chuck table340is not limited to the structure illustrated in the present embodiment, but may be an electrostatic chuck table with an electrode disposed therein. When a DC voltage is applied to the electrode in the electrostatic chuck table, the device wafer W is attracted to the electrostatic chuck table under electrostatic forces such as Coulomb forces.

The chuck table340and the support341also have cooling passageways345defined therein that are held in fluid communication with a coolant supply source39. When the coolant supply source39is actuated, a coolant from the coolant supply source39circulates through the cooling passageways345. Therefore, when a dry etching process is carried out, the lower electrode unit34can be cooled by the circulating coolant to remove heat therefrom.

The upper electrode unit35has a gas ejector350and a cylindrical support351that supports the gas ejector350. The gas ejector350has a plurality of ejection ports352defined therein for ejecting a reaction gas into the processing space30a. The ejection ports352are connected to reaction gas supply sources42and43through a flow passageway353defined in the support351and the gas ejector350. The reaction gas supply source42is filled with an etching gas such as SF6, for example. The reaction gas supply sources43is filled with a deposition gas such as C4F8, for example.

The support351extends through a hole306defined in the upper wall301of the chamber30, and is vertically movably supported by a seal44mounted in the hole306. A lifting and lowering mechanism40is connected to the upper electrode unit35. The lifting and lowering mechanism40includes an air cylinder400, a piston rod401movable by the air cylinder400, and a lifting and lowering member402connected to an upper end of the piston rod401and an upper part of the support351. When the lifting and lowering mechanism40is actuated, the support351and the gas ejector350are vertically moved.

The dry etching apparatus3further includes control means45for controlling the opening and closing means32, the gas discharger33, the high-frequency power supply37, the suction source38, the coolant supply source39, the lifting and lowering mechanism40, and the reaction gas supply sources42and43. The control means45has a storage device such as a memory and a CPU. The memory of the control means45stores etching conditions, information on the device wafer W, etc.

An identification code reading unit5for reading the individual identification code ID of the device wafer W is mounted on the side wall302above the gate31. The identification code reading unit5includes a bar code reader, for example. The identification code reading unit5can read the individual identification code ID on the device wafer W when the device wafer W moves through the opening303into the chamber30. The individual identification code ID that has been read by the identification code reading unit5is sent to the control means45. The position in which the identification code reading unit5is disposed is not limited to the position according to the present embodiment.

Before going to an etching step to be described below, the introduction of the device wafer W into the dry etching apparatus3is confirmed. Specifically, when the opening and closing means32lowers the gate31, opening the opening303, and the device wafer W is introduced through the opening303into the chamber30, the identification code reading unit5reads, from above, the individual identification code ID on the device wafer W on which the protective film forming step has been performed. The read individual identification code ID is sent from the identification code reading unit5to the control means45. The control means45refers to the information on the device wafer W stored in the memory, and if the read individual identification code ID and the individual identification code ID stored in the memory agree with each other, the control means45confirms that the device wafer W has been introduced into the chamber30of the dry etching apparatus3.

The device wafer W is placed on the suction holder342on the chuck table340, and the device wafer W with the face side Wa exposed upwardly is held under suction on the suction holder342by suction forces from the suction source38. Then, the upper electrode unit35is lowered toward the lower electrode unit34, and the reaction gas supply sources42and43supply an etching gas to the flow passageway353. The etching gas is then ejected from the ejection ports352in the gas ejector350, and a high-frequency voltage is applied between the gas ejector350and the chuck table340, plasmatizing the etching gas in the chamber30. A bias high-frequency voltage is applied to the device wafer W, drawing etching species (ions) into the device wafer W thereby to etch the device wafer W. The etching step according to the present embodiment is carried out according to a cycle etching process (Bosch process) in which etching and film deposition are repeatedly performed.

An example of conditions used in the etching step according to the present embodiment is as follows:

[Common Conditions for Eching and Film Deposition]

In the etching step, etching and film deposition are alternately repeated in several tens cycles. According to the present embodiment, one cycle of etching and film deposition is repeated 50 times, i.e., 50 cycles of etching and film deposition are carried out. The number of cycles of etching and film deposition is not limited to any particular number, but is established depending on the processed depth of grooves to be defined in the device wafer W.

In the etching step, according to the etching conditions, the reaction gas supply source42depicted inFIG. 7supplies an etching gas of SF6from the ejection ports352under a process pressure of 25 Pa for 5 seconds, and high-frequency electric power of 2500 W is applied to the upper electrode unit35, plasmatizing the etching gas. High-frequency electric power of 150 W is applied to the lower electrode unit34, drawing excited ions into the substrate of the device wafer W. Areas of the device wafer W that correspond to the projected dicing lines S are thus etched at a high rate. Since the devices D are covered with the protective films2bas masks, any damage to the devices D is minimized.

Then, according to the conditions for film deposition instead of the etching conditions, the reaction gas supply source43supplies a deposition gas of C4F8from the ejection ports352toward the exposed projected dicing lines S under a process pressure of 25 Pa for 3 seconds, and high-frequency electric power of 2500 W is applied to the upper electrode unit35, plasmatizing the etching gas. High-frequency electric power of 50 W is applied to the lower electrode unit34, drawing excited ions into the substrate of the device wafer W. A fluorocarbon (CxFy) film as a protective film is thus deposited on the inner side surfaces of the grooves that have been exposed by the etching process. In this manner, etching and film deposition (for side wall protection) are alternately repeated to perform anisotropic dry etching on the device wafer W along the projected dicing lines S, thereby forming etched grooves M to a predetermined processed depth in the device wafer W as depicted inFIG. 8. During the etching step, the inside of the processing space30adepicted inFIG. 7is kept under a predetermined pressure, and the gas discharger33discharges the used gas from the discharge port304.

According to the present embodiment, the predetermined processed depth of the etched grooves M in the device wafer W is set to such a depth that the device wafer W is not fully severed between the face side and the reverse side thereof. When the reverse side Wb of the device wafer W with the etched grooves M formed therein is subsequently ground by grinding stones or the like, the device wafer W is divided or separated into individual chips carrying the respective devices D thereon. Alternatively, the device wafer W may be divided into individual chips by being fully severed between the face side and the reverse side thereof in the etching step. In such an alternative case, since the device wafer W is divided into individual chips in the etching step, the total number of processing steps is reduced. After the etching step is finished, cleaning water may be supplied to the face side Wa of the device wafer W to remove the protective films2bwith ease.

As depicted inFIG. 9, the protective film forming apparatus1and the dry etching apparatus3are connected to a host computer6as a terminal apparatus through respective communication links. Specifically, the control means20of the protective film forming apparatus1is connected to the host computer6, and the control means45of the dry etching apparatus3is connected to the host computer6. The host computer6processes and manages data for the protective film forming apparatus1and the dry etching apparatus3. The host computer6includes, for example, a CPU for processing data according to control programs, a read only memory (ROM) for storing the control programs, etc., and a random access memory (RAM) for storing processed results and other items of information. The processing conditions set in the control means20of the protective film forming apparatus1and the control means45of the dry etching apparatus3, the information on the device wafer W, and the time at which the water-soluble protective film agent2is applied that is stored in the control means20in the applying time recording step are also stored in the RAM of the host computer6.

A warning is issued if the introduction of the device wafer W into the dry etching apparatus3is not confirmed in the introduction confirming step after elapse of a predetermined time from the time recorded in the applying time recording step. The predetermined time from the time recorded in the applying time recording step refers to a time zone in which at least the protective films2bcan be removed by cleaning from the face side Wa of the device wafer W without deterioration. For example, if the device wafer W is not introduced into the dry etching apparatus3even after 24 hours have elapsed from the applying time recorded in the RAM of the host computer6, then a predetermined warning is issued. The warning issuing step is carried out before the etching step is carried out after the protective film forming step has been carried out.

A warning may be issued from an administrator's terminal, not depicted, connected to the host computer6to the administrator, or from the protective film forming apparatus1or the dry etching apparatus3to the administrator. A warning may be displayed on a display screen of the protective film forming apparatus1, the dry etching apparatus3, or an administrator's terminal, or may be produced as a sound from a speaker, or may be given as turning-on of an indicator lamp. A device wafer W to which a warning is addressed is reprocessed by removing the protective films2bfrom the face side Wa of the device wafer W and forming a protective film again thereon prior to the etching step.

(First Example of Calculating Step)

The host computer6calculates the number of device wafers on which to perform the protective film forming step, based on the operation state of the dry etching apparatus3. The operation state of the dry etching apparatus3refers to a state of the dry etching apparatus3in which it has actually performed a dry etching process and obtained processed results. Specifically, the operation state of the dry etching apparatus3means an actual processing time that is consumed when the dry etching apparatus3has dry-etched a single device wafer W under the conditions (etching conditions and film deposition conditions) input to the control means45. If the processing time consumed by the dry etching apparatus3is longer than the processing time consumed by the protective film forming apparatus1, then the host computer6calculates the appropriate number of device wafers W on which the protective film forming apparatus1is to perform the protective film forming step, and then controls the protective film forming apparatus1to perform the protective film forming step. In this manner, the dwelling time until the device wafer W on which the protective films2bhave been formed in the protective film forming step is introduced into the dry etching apparatus3can be shortened. As a consequence, the device wafer W can efficiently be divided into individual chips without deterioration of the protective films2b.

(Second Example of Calculating Step)

The host computer6may calculate the number of device wafers on which to perform the protective film forming step, based on the information input to the protective film forming apparatus1and the dry etching apparatus3. Usually, the protective film forming apparatus1and the dry etching apparatus3can be supplied with device wafers W, using a cassette that houses a plurality of device wafers W horizontally therein. In other words, respective cassettes, each housing a plurality of device wafers W, are supplied to the protective film forming apparatus1and the dry etching apparatus3. The host computer6calculates a time required to process a device wafer W in the protective film forming apparatus1and the dry etching apparatus3each, based on the information of the device wafers W such as the number, type, size, individual identification codes ID, etc. of the device wafers W housed in the cassettes, and the processing conditions input to the protective film forming apparatus1and the dry etching apparatus3.

Then, the host computer6calculates processing timings and the appropriate number of device wafers W on which to perform the protective film forming step, in order to minimize the dwelling time after protective films2bhave been formed on the face side Wa of a device wafer W until the dry etching process. The host computer6then controls the protective film forming apparatus1to perform the protective film forming step based on the calculated data. Inasmuch as the protective film forming step is carried out after the appropriate number of device wafers W on which to perform the protective film forming step and the processing timings have been calculated, the device wafer W can efficiently be divided into individual chips without deterioration of the protective films2b, as is the case with the first example of calculating step.

The method of processing a device wafer according to the present invention includes the protective film forming step for forming the protective films2bthat protect the devices D by applying the water-soluble protective film agent2to the face side Wa of the device wafer W, while exposing the projected dicing lines S, with the protective film forming apparatus1, and the etching step for dry-etching the device wafer W through the protective films2bwith the dry etching apparatus3. The protective films2bcan easily be removed from the face side Wa of the device wafer W simply by supplying cleaning water thereto. Therefore, various pieces of equipment such as a resist film forming apparatus, an ashing apparatus, etc. are not required, resulting in a reduction in the cost, and the device wafer W can efficiently be divided into individual chips.

Upon elapse of a predetermined time after the protective films2bhave been formed by applying the water-soluble protective film agent2to the device wafer W, the protective films2btend to deteriorate in the dry etching process, and the protective films2bmay not be removed by cleaning water supplied after the device wafer W has been divided into individual chips. The protective films2bmay not be removed prior to the dry etching process. According to the present invention, the time when the water-soluble protective film agent2is applied to the device wafer W is recorded in the applying time recording step, and the warning issuing step for issuing a warning is carried out if the introduction of the device wafer W into the dry etching apparatus3is not confirmed in the introduction confirming step after elapse of a predetermined time from the time recorded in the applying time recording step, before the etching step is carried out after the protective films2bhave been formed by applying the water-soluble protective film agent2to the device wafer W. Consequently, it is possible to give a warning while the protective films2bcan be removed from the device wafer W, and the protective films2bmay be removed and new protective films2bmay be formed again on the face side Wa of the device wafer W. Therefore, it is unlikely to cause damage to the device wafer W in its entirety.