JP2005072140A - Method of manufacturing semiconductor device and method of processing semiconductor wafer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a defective pickup caused by insufficient formation of an oxide film on a rear face of a wafer, in a semiconductor device manufacturing method which includes an in-line process wherein immediately after finishing grinding the rear face, a dicing tape is pasted to the ground face. <P>SOLUTION: The method of manufacturing the semiconductor device comprises processes of grinding the rear face of the silicon wafer having a circuit formed on the surface, oxidizing the rear face of the silicon wafer to form the oxide film, pasting the dicing tape to the rear face of the silicon wafer, and then dicing the wafer into chips, and picking up the silicon chips. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a semiconductor device manufacturing method comprising a silicon wafer back grinding step, a wafer dicing step, and a chip pick-up step, and a semiconductor wafer processing apparatus used in this manufacturing method, particularly when a so-called in-line process is employed. The present invention relates to a method for manufacturing a semiconductor device and a semiconductor wafer processing apparatus that can reduce pickup defects in a chip pickup process as a final process.

  In recent years, IC cards have been widely used, and further reduction in thickness has been desired. For this reason, it is necessary to reduce the thickness of a semiconductor chip, which has conventionally been about 350 μm, to a thickness of 50 to 100 μm or less. In addition, increasing the diameter of the wafer has been studied in order to improve productivity.

  Grinding the back surface of a wafer after forming a circuit pattern has been conventionally performed. At that time, a surface protection sheet is attached to the circuit surface to protect the circuit surface and fix the wafer, and then perform back surface grinding. Thereafter, the semiconductor device is manufactured through various processes such as dicing, die bonding, and resin sealing.

  When dicing a semiconductor wafer into chips, a dicing tape is attached to the back surface (ground surface) of the semiconductor wafer, and the wafer is diced while holding the wafer on the dicing tape. Various dicing tapes are on the market, and in particular, an ultraviolet curable adhesive tape called a UV tape is preferably used. The UV tape has a property that the pressure-sensitive adhesive layer is cured by irradiation with ultraviolet rays, and the adhesive force is lost or drastically reduced. Therefore, at the time of dicing the wafer, the wafer can be fixed with sufficient adhesive force, and the chip can be easily picked up by curing the pressure-sensitive adhesive layer after completion of dicing.

  In order to attach the dicing tape, the wafer after the back surface grinding is transferred to a dicing tape attaching device (mounter). At this time, the wafer is stored in a storage device called a wafer cassette and transferred to the mounter.

  However, if the wafer is ground to an extremely thin thickness, the wafer itself loses its self-supporting property and may be damaged even by its own weight. For this reason, it is difficult to house a wafer ground to an extremely thin thickness in a wafer cassette.

  In order to give a supporting function to a semiconductor wafer having a reduced strength, it has been proposed that a dicing tape is immediately attached to the grinding surface after the in-line process, that is, the back surface grinding, and then transferred to the dicing process. For example, Patent Document 1 describes an example of such an inlining process. According to such a process, even if the wafer is ground to a very thin thickness and has a reduced strength, the back surface is reinforced with dicing tape, so that the support function is improved and the wafer cassette can be transferred. Become.

  However, as a result of such in-line implementation, an unexpected problem of increased chip pickup defects occurred. This is a problem that the adhesive force between the back surface of the chip and the pressure-sensitive adhesive layer increases, and it becomes difficult to pick up the chip. Even when a UV tape is used as the dicing tape, the pick-up failure increases.

When the present inventors diligently investigated the cause, the following facts were found.
(1) In the in-line process, since the dicing tape is adhered to the ground surface immediately after the back surface grinding is completed, there is almost no oxide film formation on the back surface.
(2) On the other hand, in the conventional process, after the backside grinding is completed, the wafer is stored in a wafer cassette, transferred with the backside exposed, and then the dicing tape is attached to the grinding surface, so the backside is exposed to air. The formation time of the oxide film on the back surface is longer than that in (1).
(3) When the formation of the oxide film is large, the affinity between the back surface and the pressure-sensitive adhesive layer is weak. On the other hand, when the formation of the oxide film is small, the affinity between the back surface and the pressure-sensitive adhesive layer is strong. It may cause pickup failure.
JP 2002-343756 A

  The present invention has been made in view of the prior art as described above, and in a semiconductor device manufacturing method including an in-line process in which a dicing tape is attached to a grinding surface immediately after completion of back surface grinding, An object of the present invention is to eliminate a pickup failure caused by insufficient formation of an oxide film.

The present invention has been completed based on the above findings (1) to (3), and an oxide film is intentionally formed on the back surface of the wafer after the back surface grinding and before the dicing tape is attached. It is characterized by. That is, a method for manufacturing a semiconductor device according to the present invention includes:
Grinding the back surface of the silicon wafer having a circuit formed on the surface;
A step of oxidizing the back surface of the silicon wafer to form an oxide film;
It includes a step of attaching a dicing tape to the back surface of the silicon wafer, dicing the wafer into chips, and a step of picking up silicon chips.

  In the above manufacturing method, it is preferable to perform the oxidation treatment on the back surface of the silicon wafer by short-wavelength ultraviolet irradiation in an oxygen-containing atmosphere.

  One aspect of a semiconductor wafer processing apparatus according to the present invention includes a wafer back grinding apparatus and a short wavelength ultraviolet irradiation apparatus for the wafer back surface.

  In another aspect of the semiconductor wafer processing apparatus according to the present invention, the semiconductor wafer processing apparatus includes a short-wavelength ultraviolet irradiation device for the wafer back surface and a dicing tape attaching device.

  According to such a method of manufacturing a semiconductor device according to the present invention, in the method of manufacturing a semiconductor device including an in-line process in which a dicing tape is attached to the ground surface immediately after the back surface grinding is finished, the formation of the oxide film on the back surface of the wafer is performed. It is possible to reduce pickup defects due to the shortage.

  Hereinafter, the present invention will be described more specifically with reference to the drawings.

  In the method of manufacturing a semiconductor device according to the present invention, as shown in FIG. 1, first, the back surface of the silicon wafer 1 on which a circuit is formed is ground.

Formation of a circuit on the wafer surface can be performed by various methods including conventionally used methods such as an etching method and a lift-off method. In the semiconductor wafer circuit forming step, a predetermined circuit is formed. The thickness of the wafer 1 before grinding is not particularly limited, but is usually about 650 to 750 μm.

  Moreover, it is preferable to affix on the surface protection sheet 2 to a circuit surface in order to protect a surface circuit at the time of back surface grinding. As the surface protective sheet 2, various releasable pressure-sensitive adhesive sheets used for this type of application are used without particular limitation.

  The back surface is ground by a known method using a grinder 3 and a suction table 4 for fixing the wafer. After the back surface grinding step, before the step of forming the oxide film, a process of removing the crushed layer generated by grinding may be performed. Immediately after performing the process of removing the crushed layer on the ground surface, the oxide film is often removed from the treated surface. Examples of such treatment include chemical etching, plasma etching, and CMP (Chemical Mechanical Etching).

  According to the object of the present invention, in order to adapt to in-line processing suitable for ultra-thin processing, the finished thickness by back grinding is preferably about 20 to 100 μm. However, since it can be applied to a normal process, a normal finish thickness of about 100 to 400 μm is also applicable.

  By such back surface grinding, the wafer has a predetermined thickness, and at the same time, the oxide film formed on the back surface of the wafer during circuit formation is removed.

  The present invention is characterized in that the back surface of the wafer 1 after such back surface grinding is subjected to an oxidation treatment to form an oxide film. If a dicing tape is attached to the back surface of the wafer on which no oxide film is formed, the affinity between the back surface and the pressure-sensitive adhesive layer of the dicing tape is too high, which causes a pickup failure in the pickup process described later. On the other hand, when an oxide film is formed on the back surface, the interaction between the back surface and the pressure-sensitive adhesive layer is small, and pickup defects can be reduced.

  The back surface oxidation treatment is performed by various methods. For example, various oxidation treatment methods are known for forming circuits on the wafer surface. In the present invention, oxidation treatment is performed on the back surface of the wafer using such a known surface oxidation method to form an oxide film. can do.

More specifically, the following methods (1) to (8) can be employed.
(1) Performed by short-wavelength ultraviolet irradiation in an oxygen-containing atmosphere using the sealable short-wavelength ultraviolet irradiation apparatus 10.

  The short wavelength ultraviolet ray means an ultraviolet ray having a wavelength of about 150 to 300 nm, and a short wavelength light source 5 such as a low pressure mercury lamp (185 nm) or an excimer lamp (172 nm) is particularly preferably used. When such short-wavelength ultraviolet irradiation is performed in an oxygen-containing atmosphere, ozone and oxygen radicals are generated, and an oxide film can be efficiently formed on the back surface of the wafer.

The amount of ultraviolet irradiation is preferably 100 to 6000 mJ / cm ² , more preferably 300 to ²
000 mJ / cm ² . The oxygen concentration in the irradiation atmosphere can be used at a normal air concentration (about 20%), and irradiation under reduced pressure may be used as long as the oxygen partial pressure is the same. Alternatively, high concentration oxygen may be positively supplied to the ultraviolet irradiation region.
(2) Performed by plasma treatment in an oxygen-containing atmosphere.
(3) Performed by anodization.
(4) Performed by implantation of oxygen ions.
(5) Performed by sputtering.
(6) Performed by CVD (Chemical Vapor Deposition).
(7) It is carried out by rubbing and sliding the back surface of the wafer with a polisher having a sliding surface made of soft resin containing water or water containing abrasive grains (see JP-A-6-192810).
(8) An oxidant solution such as an ozone solution, an ammonia aqueous solution, a hydrochloric acid aqueous solution, or a sulfuric acid aqueous solution is supplied to the back surface of the wafer.

  Among these, the method (1) is preferably employed because the apparatus is simple and is a dry process.

  The oxidation treatment of the back surface of the wafer 1 is performed immediately after the back surface of the wafer 1 is ground. Specifically, by using the semiconductor wafer processing apparatus of the present invention, which will be described later, the process can be continuously performed. Therefore, after the backside grinding of the wafer 1, about 0.5 to 5 minutes, An oxidation treatment can be performed.

Such oxide film formed on the wafer back surface by oxidation treatment is a SiOx (x is an arbitrary value of 0 to 2), oxide film SiO ₂ becomes long is sufficient oxidizing treatment, the wafer grinding surface not It becomes the active surface. When the oxidation is insufficient or not performed, x becomes a value close to 0, and the wafer grinding surface immediately after grinding causes a chemical reaction or some kind of interaction with the adhesive of the dicing tape in an active state.

  The oxygen concentration in silicon in the oxide film is detected as (O / Si value) by XPS (X-ray Photoelectron Spectroscopy). Since it is difficult to directly measure the thickness of the oxide film, it is estimated by measuring (O / Si value) while changing the detection angle in the XPS measurement. When the detection angle is large (close to 90 °), the oxygen concentration in a relatively deep portion can be measured, and when the detection angle is small, the oxygen concentration in a relatively shallow portion can be measured.

  Next, a dicing tape 6 is attached to the back surface of the wafer. As shown in FIG. 3, the dicing tape 6 is generally attached by a device called a mounter provided with a roller 7, but is not particularly limited.

  As the dicing tape 6, various adhesive tapes used for this type of application are used without particular limitation, and in particular, an ultraviolet curable adhesive tape called a UV tape requires a small pickup force. Therefore, the effect is remarkable and it is preferably used.

  If the oxidation treatment on the back surface of the wafer 1 is completed, the interaction between the wafer grinding surface and the adhesive has already been reduced and the pick-up force has been reduced, so how much is left until the dicing tape is applied to the wafer grinding surface. There is no problem even if there is a period to do. Moreover, no matter what time the oxidation treatment is performed after wafer grinding, there is no problem because the wafer grinding surface becomes a stable oxide film if the oxidation treatment after wafer grinding is performed.

  However, in the in-line processing apparatus in which the grinder and the dicing tape attaching apparatus are integrated, the problem of the present invention appears remarkably. Therefore, between the wafer grinding process and the oxidation process on the back surface of the wafer, and between the oxidation process on the wafer back surface and the application process of the dicing tape, it takes about 0.5 to 3 minutes, for example, without taking time. preferable.

  When dicing the wafer 1, the peripheral portion of the dicing tape 6 is fixed by the ring frame 8 (see FIG. 4), and then the wafer is chipped by a known method such as using a rotating round blade such as a dicer (see FIG. 4). 5). The surface protective sheet 2 is peeled off at any stage after the dicing tape 6 is attached.

  Next, the obtained chip 9 is picked up from the dicing tape 6. The pickup of the chip is generally performed using a suction collet from the circuit surface side, and at the same time as the suction by the collet, the chip may be pushed up from the dicing tape 6 side by a push-up pin. Further, when a UV tape is used as the dicing tape 6, it is preferable to reduce the adhesive force by irradiating the pressure-sensitive adhesive layer with ultraviolet rays prior to chip pickup.

  According to the present invention, by forming the oxide film on the back surface of the silicon wafer, the interaction between the back surface and the pressure-sensitive adhesive layer of the dicing tape is reduced, so that pickup defects can be reduced.

  The first semiconductor wafer processing apparatus according to the present invention is an apparatus provided with a short-wavelength ultraviolet irradiation apparatus in a conventionally known wafer back surface grinding apparatus (grinder). The short-wavelength ultraviolet irradiation device is located downstream from the position for wafer grinding so that the grinding surface of the wafer can be irradiated, and a wafer stocker is located further downstream. The short-wavelength ultraviolet irradiation device includes a short-wavelength light source, preferably a low-pressure mercury lamp (185 nm), an excimer lamp (172 nm), and a sealable container having an oxygen supply port as necessary. In addition, an apparatus for removing a crushed layer such as a chemical etching apparatus, a plasma etching apparatus, or a CMP apparatus may be disposed between the position for wafer grinding and the short wavelength ultraviolet irradiation apparatus.

  If the semiconductor wafer processing apparatus having such a configuration is used, the grinding surface can be oxidized immediately after the backside grinding of the wafer, and the dicing tape is affixed after an arbitrary standing time after the grinding process. Will be able to do.

  The second semiconductor wafer processing apparatus according to the present invention is an apparatus including a conventionally known dicing tape attaching apparatus and a short wavelength ultraviolet irradiation apparatus. The short wavelength ultraviolet irradiation device is located upstream of the tape application position so that the wafer grinding surface can be irradiated before the dicing tape is applied. Further, a wafer stocker may be arranged on the upstream side. Moreover, the apparatus for removing the above-mentioned crushing layer may be arrange | positioned between a short wavelength ultraviolet irradiation device and a tape sticking position. When the semiconductor wafer processing apparatus having such a configuration is used, the wafer grinding surface is always sufficiently oxidized and chemically stabilized when a dicing tape is applied. For this reason, the pick-up force does not increase even if the dicing tape is applied to the wafer that has been left for an arbitrary period after the grinding step.

  Further, the wafer back grinding device, the short wavelength ultraviolet irradiation device, and the dicing tape attaching device may be an inline-compatible processing device arranged in this order. With such an apparatus, an increase in chip pick-up force can be prevented by performing an oxidation treatment even if the dicing tape is applied immediately after the back surface grinding of the wafer.

  According to such a semiconductor wafer processing apparatus according to the present invention, it is possible to in-line the process of adhering the dicing tape to the ground surface immediately after completion of the back surface grinding, and further, an oxidation treatment process on the back surface of the wafer is interposed between the processes. By doing so, the problem of poor pickup due to inlining is solved.

According to the method for manufacturing a semiconductor device according to the present invention, according to the present invention, by forming an oxide film on the back surface of the silicon wafer, the interaction between the back surface and the adhesive layer of the dicing tape is achieved. Therefore, pickup defects can be reduced, and improvement in production efficiency is achieved.
(Example)
EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to these Examples.
(Example 1)
An untreated silicon wafer (200 mm diameter) was ground using a wafer grinding apparatus (DFG-840, DFG-840) until the finished thickness was 350 μm. The ground wafer was set in a short-wavelength ultraviolet irradiation device (manufactured by Oak Manufacturing Co., Ltd., VUM-3037-F, using a low-pressure mercury lamp, ultraviolet wavelengths 185 nm and 254 nm) and irradiated within 30 seconds after grinding. The ultraviolet irradiation conditions were an illuminance of about 10 mW / cm ² , a light amount of 1800 mJ / cm ² , an irradiation time of 3 minutes, and an irradiation distance of 15 mm.

As the dicing tape, an ultraviolet curable adhesive tape (Adwill D675 manufactured by Lintec Corporation) was used.

Within 30 seconds after irradiation, a dicing tape was affixed to the ground surface of the wafer, and immediately after that, the wafer was diced to a size of 10 mm × 10 mm with a dicing apparatus (A-WD-4000B, manufactured by Tokyo Seimitsu Co., Ltd.). Next, immediately UV irradiation equipment (Rintec, RAD2000m / 8, UV wavelength region 365nm
) Was irradiated with ultraviolet rays to cure the adhesive layer of the dicing tape. The tip was pushed up using a load measuring device provided with a needle at the tip, and the pick-up force was measured.

In addition, a sample that was not diced in the same process was prepared, and the adhesive force of the dicing tape to the ground surface of the wafer was measured according to JIS Z0237. The results are shown in Table 1.
(Example 2)
In Example 1, the same process as in Example 1 was performed except that the time from dicing tape application to dicing was set to 24 hours. The results of pick-up force and adhesive strength are shown in Table 1. (Examples 3 and 4)
In Examples 1 and 2, a non-ultraviolet curable adhesive tape (Adwill G-12, manufactured by Lintec Co., Ltd.) was used as the dicing tape, and ultraviolet irradiation after dicing was not performed. The process was performed. The results of pick-up force and adhesive strength are shown in Table 1.
(Comparative Examples 1-4)
In Examples 1 to 4, the same steps as in Examples 1 to 4 were performed except that short-wavelength ultraviolet irradiation immediately after wafer grinding was not performed and the time until the dicing tape was applied was adjusted accordingly. went. The results of pick-up force and adhesive strength are shown in Table 1.

1 shows one step of a method of manufacturing a semiconductor device according to the present invention. 1 shows one step of a method of manufacturing a semiconductor device according to the present invention. 1 shows one step of a method of manufacturing a semiconductor device according to the present invention. 1 shows one step of a method of manufacturing a semiconductor device according to the present invention. 1 shows one step of a method of manufacturing a semiconductor device according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Silicon wafer 2 ... Surface protection sheet 3 ... Grinder 4 ... Suction table 5 ... Short wavelength light source 6 ... Dicing tape 7 ... Roller 8 ... Ring frame 9 ... Chip 10 ... Short wavelength ultraviolet irradiation device

Claims (4)

Grinding the back surface of the silicon wafer having a circuit formed on the surface;
A step of oxidizing the back surface of the silicon wafer to form an oxide film;
A method for manufacturing a semiconductor device, comprising: attaching a dicing tape to a back surface of a silicon wafer; dicing the wafer into chips; and picking up silicon chips. The method for manufacturing a semiconductor device according to claim 1, wherein the oxidation treatment of the back surface of the silicon wafer is performed by short-wave ultraviolet irradiation in an oxygen-containing atmosphere. A semiconductor wafer processing apparatus comprising a wafer back surface grinding device and a short wavelength ultraviolet irradiation device for the wafer back surface. A semiconductor wafer processing apparatus comprising a short-wavelength ultraviolet irradiation device on a wafer back surface and a dicing tape sticking device.

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