JPH08321447A - Wafer processing method with foreign matter eliminating function - Google Patents

Abstract

PURPOSE: To transfer foreign matters existing on a contact face on a rear face of a wafer to a plate-like member and thereby eliminate the foregin matters and then prevent a disconnection and the deterioration in performance of an element due to the foregin matters by conducting the same operations as in a usual wafer processing using the plate-like member of such an area as to cover a member which is brought into contact with the rear face of the wafer in the usual operations. CONSTITUTION: After processing one rot or 25 pieces of processed wafers or processing a plurality of rots, the same operations as in a usual wafer processing are done with an unprocessed dummy wafer 9. In the operations, however, etching is not conducted and noble gas is introduced and bias voltage is not applied lest the dummy wafer 9 should be sputtered. However, when the processed wafer is carried into an etching equipment and is attracted by static electricity suction, foreign matters attaching to the processed wafer now attach to a rear face of the dummy wafer 9 and then they are carried away from an unload chamber 20 together with the dummy wafer 9. By this method, a system becomes a clean one with the reduced number of foreign matters on a rear face of a processed wafer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for removing foreign matter adhering to a member which contacts the back surface of a wafer.

[0002]

2. Description of the Related Art With the high integration of semiconductor devices, the line width of circuit patterns has become extremely small. In the current semiconductor devices, the minimum line width has been reduced to the submicron order. Usually, the size of foreign matter that affects the element is one-tenth or more of the minimum line width, and even a very fine foreign matter poses a problem.

Therefore, the foreign matter generated between the holding device for fixing the wafer during wafer transfer and processing and the back surface of the wafer is reduced,
In addition, a structure is considered in which foreign matter generated is unlikely to adhere to the back surface of the wafer. For example, there is a method in which a large number of quadrangular pyramid-shaped supporting portions having the same height are formed on the surface supporting the wafer, and a low dust-generating material such as polycrystalline diamond is arranged at the vertices of the quadrangular pyramids. An example thereof is disclosed in JP-A-6-204324.

However, even if such a holding method is used, a contact portion naturally exists and foreign matter adheres to the back surface. In addition, since the wafer also contacts the susceptor such as a robot that transfers the wafer to the processing chamber on the back surface, foreign matter on the back surface also occurs at this part, which moves to another processing chamber or support and spreads over the entire equipment. It will be going. The foreign matter generated on the contact portion on the back surface of the wafer increases as the number of processed wafers increases unless measures such as stopping and cleaning the entire apparatus are taken.

The foreign matters on the back surface of the wafer also cause problems in processing the wafer. For example, a wafer process requires a cleaning step, but there is a problem that foreign matter adhering to the back surface is detached by cleaning and then reattaches to the processing surface. Further, in the processing of a very fine line width as in the current case, back surface foreign matter becomes a cause of defocus in the drawing apparatus. Therefore, reduction of foreign matter adhering to the back surface of the wafer during transportation and processing has become a very important technical issue.

[0006]

In a wafer processing apparatus, an electrostatic chucking device is often used for transporting a wafer in a vacuum and for fixing the wafer during processing. The electrostatic adsorption device has advantages such as correction of warpage of the wafer during processing, improvement of thermal conductivity for temperature control of the wafer during processing, and reduction of foreign matter generated from a mechanical contact portion.

However, even in the processing apparatus using the electrostatic attraction device, the wafer comes into contact with the transfer system and the back surface of the electrostatic attraction device, so that foreign matters are generated in these portions. In a highly integrated semiconductor device, foreign matter generated on the back surface of the wafer poses a problem. For example, if foreign matter is transferred to the wafer processing surface during the cleaning process, the portion on which the foreign matter is placed may not be etched, or if a film is formed with the foreign matter placed, it may cause disconnection. Further, in the processing of a fine line width, even a minute back surface foreign matter in the drawing device causes defocus.

However, even if the surface treatment as disclosed in Japanese Unexamined Patent Publication No. 6-204324 is used in the electrostatic adsorption device, the generation of foreign matter is inevitable, and as the number of processed sheets increases, it gradually increases and finally It is expected that the equipment will be contaminated. Further, Japanese Patent Laid-Open No. 6-204324 does not disclose cleaning of foreign matters in the processing apparatus.

A first object of the present invention is to provide a wafer processing method having a function of removing foreign matter generated in a contact portion with a back surface of a wafer in a processing apparatus.

A second object of the present invention is to provide a wafer processing method capable of efficiently removing foreign matters using a plate member.

[0011]

A first object of the present invention is, in a wafer processing apparatus having a wafer transfer, fixing, and processing function, a plate-like member having an area covering a portion which comes into contact with the back surface of the wafer during normal operation. Is achieved by performing the same operation as in normal processing.

Alternatively, it can be achieved by using the above-mentioned plate-like member in the processing apparatus to perform only the operations of conveying and fixing. Further, it is achieved by bringing the plate-like adsorbent into contact with the contact surface with the wafer in the processing apparatus.

The second object can be efficiently achieved by preparing a load chamber and an unload chamber of a plate-shaped member separately from a load chamber and an unload chamber of a normal processing wafer. .

[0014]

In the method for processing a wafer with a foreign matter removing function of the present invention, a normal operation is performed by using a plate-like member having an area covering a portion which comes into contact with the back surface of the wafer during a normal operation such as an operation such as transfer, fixing and processing. To perform. Therefore, at this time, the foreign matter existing on the contact surface on the back surface of the wafer can be removed by transferring it to the plate member. As a result, foreign matter on the back surface of the processing wafer can be reduced, so that it is possible to prevent disconnection of elements and deterioration of performance due to foreign matter, and it is possible to provide a processing method with high yield.

Further, in the wafer processing apparatus which embodies the wafer processing method with the foreign matter removing function of the present invention, in addition to the loading chamber and the unloading chamber for the processing wafer during the normal processing, the loading chamber for the plate-shaped member is provided. And unload room.
Therefore, it is possible to continuously remove foreign matter on the contact surface with the back surface of the wafer in the processing apparatus without disturbing the normal processing of the wafer processing apparatus. As a result, the apparatus can minimize the reduction in throughput of the processing apparatus due to the removal of foreign matter.

[0016]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a first embodiment of the present invention, which is applied to a magnetic field microwave plasma processing apparatus. The operation of the apparatus shown in FIG. 1 will be described. A discharge tube 2 is provided above a vacuum processing chamber 1 constituted by a quartz tube 29, and an atmospheric space 3 is prepared. Reference numeral 4 is a waveguide for introducing the microwave 5. A coil 6 for generating a magnetic field is provided around the discharge tube 2. An electrostatic adsorption device for mounting a wafer is provided in the vacuum processing chamber 1, and the wafer being processed is electrostatically fixed here. Here, a plate member 9 for removing foreign matter is placed. A high frequency power supply 10 for controlling the incidence of ions in the plasma 7 on the wafer and a DC power supply 11 for controlling the DC voltage applied to the electrostatic adsorption device are connected to the electrostatic adsorption device 8. . Reference numeral 12 is a switch 12 for turning on and off the operation of the electrostatic adsorption device. When the wafer is subjected to plasma treatment, for example, etching treatment, with this apparatus, the treatment introduced into the discharge tube by the interaction of the electric field of the microwave 5 introduced into the discharge tube 2 through the waveguide 4 and the magnetic field of the coil 6 By processing the gas 13 into plasma and controlling the high-frequency bias by the high-frequency power source 10, it is possible to control the incidence of ions in the plasma on the wafer and perform processing. Note that 30
Is an exhaustion of unnecessary gas and a reaction product generated by etching, and is connected to a vacuum pump (not shown).

Next, an explanation will be given of a procedure for performing a normal process on a processing wafer by using this apparatus and a procedure for removing a foreign substance by using a plate-like member with reference to FIG. First, the wafer cassette is transferred to the load chamber 15 with the wafer for processing placed in the wafer cassette 14. The wafer cassette may be transferred manually or by a transfer robot (not shown). Next, the wafer is taken out from the wafer cassette 14 by the susceptor 18 attached to the end of the arm by a combination of the expansion / contraction operation, rotation operation, and elevating operation of the arm 17 of the transfer robot 16, and electrostatic charges in the vacuum processing chamber 1 are taken. It is moved onto the adsorption device 8 (at the bottom of the plate member). After that, as described above, the processing gas is introduced and the microwave is introduced to generate the plasma 7 in the vacuum processing chamber 1 by the interaction with the magnetic field of the coil. At this time, a DC voltage is also applied to the electrostatic adsorption device 8 to form a circuit via plasma to electrostatically fix the wafer to the electrostatic adsorption device 8. Further, the temperature of the wafer being processed can be controlled (not shown) by using the electrostatic adsorption device 8. When the etching process is completed, the electrostatic adsorption device and plasma discharge are stopped. After that, the wafer is taken out of the vacuum processing chamber 1 by the transfer robot 19 and transferred into the ashing device 31. The ashing device 31 performs a process of removing the resist and unnecessary adsorbed substances on the surface during the process, but the detailed description thereof is omitted here. After the ashing is completed, the wafer is put into the wafer cassette 20 provided in the unload chamber 24 by the operation of the transfer robot 19 again. The above is the procedure for performing normal processing on a processing wafer. In the first embodiment of the present invention, an unprocessed dummy wafer is processed after processing 25 processing wafers in one lot or after processing a plurality of lots. 9 is used to perform the same operation as in the normal wafer processing. However, in this embodiment, etching is not carried out, and a bias gas is not applied by introducing a rare gas such as argon instead of the etching gas so that the dummy wafer 9 which is a plate-shaped member is not sputtered. However, when they are transported in the etching apparatus and electrostatically adsorbed, the foreign substances attached to them adhere to the back surface of the dummy wafer 9. Then, the adhered foreign matter is removed from the unload chamber 20 to the outside together with the dummy wafer. The foreign matter in the apparatus is removed by these series of operations. The back surface of the dummy wafer 9 is clean and no foreign matter is attached. This dummy wafer may be used by turning over a normal processing surface (mirror surface processing) so as to come into contact with a transfer device or a fixing device.

FIG. 3 is a schematic view showing how foreign matter adheres to the dummy wafer. As shown in FIG. 3, a normal surface has roughness 21 and undulations 22 that occur during machining. On the surface, there is a foreign substance 23 generated due to contact with the processing wafer or the like. The size of the foreign matter that becomes a problem in the apparatus as shown in this embodiment is on the order of several microns to submicrons, but these particles are charged for some reason. For example, it is conceivable that foreign matter generated by destruction due to mechanical contact is charged by friction on the fracture surface. In addition, if contact occurs between different materials, electrification occurs due to a difference in electron energy level between the materials.
Furthermore, when a holding method such as an electrostatic adsorption device is adopted, charging is generated due to exposure to an electric field, and in a device using plasma, charging is performed by the incidence of electrons or ions. In addition, if a plate-shaped member (a dummy wafer in this embodiment) is introduced, the foreign substance is electrostatically attached to the wafer due to the physical contact between the foreign substance and the plate-shaped member and the potential difference between the foreign substance and the dummy wafer. As a result, the foreign matter on the contact surface is removed. That is, in the wafer processing apparatus configured as described above, it is possible to reduce the foreign matter existing at the portion where the back surface of the wafer comes into contact by a normal processing by adhering the foreign matter to the dummy wafer which is not related to the product. Therefore, foreign matter on one surface of the processing wafer can be reduced with a very simple structure, and the yield of the apparatus can be improved.

FIG. 4 is an explanatory view showing the second embodiment of the present invention. In this embodiment, a terminal 33 for electrically connecting the electrostatic chucking device in the wafer processing chamber from the back surface of the object to be chucked.
Is attached, it is possible to directly conduct electricity from the wafer. Therefore, it is not necessary to generate plasma for attracting the wafer. In the figure, 34 is an electrode, 35 is a dielectric, 36 is an electric circuit, and 37 is a support. Therefore, in the foreign matter removing method of the present invention, when performing the foreign matter removal using the plate-shaped member,
The step of generating plasma, which is essential for the actual etching process, is omitted.

In such a foreign matter removing method, since the step of generating plasma is omitted, the time required for generating plasma can be eliminated, so that the time required for removing foreign matter can be shortened and the operating rate of the apparatus can be further improved. Can be raised. Further, since the plasma does not enter the plate-shaped member, it is possible to eliminate contamination in the device due to the sputtering action of the plate-shaped member, and it is possible to provide a cleaner device.

FIG. 5 shows a third embodiment of the present invention, in which the foreign matter removing method of the present invention is applied to a thermal CVD apparatus.
The operation of normal processing of this apparatus will be described. A wafer is placed on the susceptor 42 heated by the heater 40. The inside of the processing chamber 41 is depressurized to several Torr, and when the processing gas is introduced into the processing chamber 41 through the gas inlet 38, the processing gas is thermally decomposed and desired film formation can be performed. Reference numeral 39 is an exhaust port for exhausting unnecessary processing gas and reaction products. The difference from the first and second embodiments is that when applied to a magnetic field microwave plasma etcher, the wafer was fixed by an electrostatic adsorption device, but in this embodiment, the wafer is fixed. Is simply placed on the susceptor. When the present invention is applied to the wafer holding method in which the wafer is simply placed in this manner, the plate-shaped members may be brought into contact with each other. Even in such a case, the foreign matter is physically contacted with the foreign matter when the plate-like member is placed on the susceptor, and the foreign matter is removed by the electrostatic force due to the potential difference between the plate-like member and the foreign matter. Adhere to the strip-shaped member. Therefore, foreign matter in the apparatus can be removed and a clean process can be performed.

In the first to third embodiments of the present invention, the dummy wafer is used as the plate-shaped member, but any other material can be used as long as it has an area larger than the area of the portion in contact with the wafer in the processing apparatus. But it's okay. At this time, it is clear that materials that cause heavy metal contamination should be avoided as much as possible. For example, polymer materials and ceramic materials are considered as candidates. Furthermore, in the first to third embodiments of the present invention, the frequency with which the plate-shaped member is used and the number of times the plate-shaped member is used at one time are not referred to. It may be carried out when it becomes clear, but if it is decided in advance how many sheets will be used, the operation will become easier. Further, it is more effective to repeat not only one sheet but a plurality of sheets when using the plate member.

FIG. 6 is an explanatory view showing the fourth embodiment of the present invention. In this embodiment, in addition to the normal processing wafer loading chamber 15 and unloading chamber 24, the loading chamber 2 for the plate-shaped member is provided.
5 and the unload chamber 26. Wafer cassettes 27 and 28 are prepared in the load chamber and the unload chamber, respectively. Normally, as shown in the first embodiment, not only the transfer robot can transfer the processed wafer and the process in each processing chamber, but also the transfer robot 16 moves the plate-shaped member to the wafer during the foreign matter removing operation. After the cassette 27 is removed and the foreign matter removing operation is performed, finally, the wafer cassette 28 dedicated to the plate-shaped member is used.
Can be paid to.

In the wafer processing method having the foreign matter removing function configured as described above, the plate-like member with the foreign matter can be processed without using the wafer cassette of the processing wafer. Since it is possible to avoid the problem that the number of wafers does not match, workability is improved and foreign matter can be isolated, so that it is not detached and contaminated in the apparatus.

FIG. 7 shows a fifth embodiment of the present invention. The control system shown in the figure has the role of controlling the operation of the transfer robot and the sequence of processing in each processing chamber.
Then, in a normal process, the control system is set to a sequence for performing a foreign matter removing operation for each preset number of sheets. Further, in the present invention, the sequence for using the plate-shaped member can be independently used. Therefore, even if the contact surface with the wafer is contaminated by the foreign matter due to damage or dropping of the wafer due to some accident or the like, the foreign matter can be easily removed.

Further, the number of wafers to be processed and the number of foreign matter removals until the foreign matter removal by the plate-shaped member can be freely set. Therefore, the foreign matter can be removed without disturbing the normal processing of the wafer processing apparatus, so that the decrease in the throughput of the apparatus can be suppressed to the minimum.

In the embodiment of the present invention, the example in which the foreign matter removing method is applied to the magnetic field microwave plasma etcher and the CVD apparatus has been described, but the present invention is not limited to this, and other processes of semiconductor processing, for example, ion implantation. It can be effectively applied to a device such as a device and a drawing device.

[0029]

According to the present invention, it is possible to operate a wafer processing apparatus using a plate-shaped member having an area which covers a portion which comes into contact with the back surface of the wafer during normal operations such as transfer, fixing and processing. I can. At this time, foreign matter existing on the contact surface on the back surface of the wafer can be removed by transferring it to the plate-shaped member. As a result, a clean device in which foreign matter on the back surface of the processing wafer is reduced can be provided, and a device having a high operating rate and a high yield can be provided.

Further, in addition to the loading chamber and the unloading chamber for the processing wafer at the time of the normal processing, the loading chamber and the unloading chamber for the plate-shaped member are provided. Therefore, the foreign matter on the contact surface with the back surface of the wafer in the processing apparatus can be continuously removed from the normal processing, and the foreign matter can be removed while minimizing the decrease in throughput.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a first embodiment of the present invention.

FIG. 3 is an explanatory view of the principle of foreign matter removal using a plate member.

FIG. 4 is an explanatory diagram showing a second embodiment of the present invention.

FIG. 5 is an explanatory diagram showing a third embodiment of the present invention.

FIG. 6 is an explanatory diagram showing a fourth embodiment of the present invention.

FIG. 7 is a flowchart showing a fifth embodiment of the present invention.

[Explanation of symbols]

1 ... Vacuum processing chamber, 2 ... Discharge tube, 3 ... Atmosphere space, 4 ... Waveguide, 5 ... Microwave, 6 ... Coil, 7 ... Plasma, 8 ...
Electrostatic adsorption device, 9 ... Plate-shaped member, 11 ... DC power supply, 12 ...
Switch, 13 ... Process gas, 29 ... Quartz tube, 30 ... Exhaust.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tetsunori Kaji 794 Azuma Higashitoyo, Shimomatsu City, Yamaguchi Prefecture Stock company Hitachi Kasado Factory (72) Inventor Takahashi 794 Azuma Higashitoyo, Shimomatsu City, Yamaguchi Prefecture Company Hitachi Kasado Plant (72) Inventor Nobuo Tsumaki 502 Kintatemachi, Tsuchiura City, Ibaraki Prefecture

Claims (10)

[Claims] 1. A wafer processing apparatus having at least one of a function of carrying a wafer, a function of fixing the wafer, and a function of processing the wafer in a fixed state while holding the wafer, Before or after, using a plate-shaped member having an area that covers the portion that contacts the back surface of the wafer during normal operation, the same operation as during normal wafer processing is performed to remove foreign matter adhering to the back surface of the wafer. A method of processing a wafer with a foreign matter removing function. 2. A wafer processing method with a foreign matter removing function according to claim 1, wherein foreign matter adhering to the back surface of the wafer is removed without carrying out actual processing while carrying or fixing the plate-shaped member while holding it. 3. The wafer processing method with a foreign matter removing function according to claim 1, wherein foreign matter adhering to the back surface of the wafer is removed by bringing the plate-shaped member into contact with the surface of the wafer in contact with the wafer. 4. A wafer processing method with a foreign matter removing function according to claim 1, wherein the foreign matter adhering to the back surface of the wafer is removed by repeating the operation of holding or fixing the plate-shaped member. 5. The wafer processing method with a foreign matter removing function according to claim 1, wherein the plate-shaped member is a silicon wafer. 6. The wafer processing method with a foreign matter removing function according to claim 1, wherein the plate-shaped member is made of a polymer material or a ceramic material. 7. The wafer processing method according to claim 1, 2, 3 or 4, wherein a plurality of the plate-like members are continuously used and a foreign matter removing function is used. 8. A wafer processing method with a foreign matter removing function according to claim 1, 2, 3 or 4, wherein the plate-shaped member is used for each preset number of wafers. 9. The wafer processing method with a foreign matter removing function according to claim 8, wherein the loader chamber for the plate-shaped member and the unloader chamber are provided separately from the actual processing wafer loader chamber and the unloader chamber. 10. The sequence according to claim 9, wherein the sequence for using the plate-shaped member is incorporated in a sequence for normal wafer processing, and the sequence for using the plate-shaped member can be used independently. Wafer processing method with various foreign matter removal functions.