JP2000021820A - Division work method for semiconductor wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To dissolve the trouble that a mark showing crystal orientation cannot be found by grinding the back of a wafer by dividing the wafer until a cut groove which has cut the semiconductor wafer incompletely is exposed. SOLUTION: A back grinding process where a semiconductor wafer 1 is installed and a back B of the semiconductor wafer is ground until a cut groove 20 formed in an incomplete cut process is exposed, while a chuck table is made to rotate, a positioning process which is a division work method and which turns a mark that is formed on the semiconductor wafer and shows a crystal orientation to a required direction at the loading of the semiconductor wafer on the chuck table in the back grinding process, a positioning stop process where the chuck table stops by turning the mark, that is formed on the semiconductor wafer and shows the crystal orientation to the required direction and a semiconductor wafer carry-out process for carrying out the semiconductor wafer from the chuck table, in a state where the mark that is formed in the semiconductor wafer and shows the crystal orientation turns in the required direction are contained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dividing method for cutting a semiconductor wafer on which a plurality of semiconductor pellets such as ICs partitioned by streets are formed by cutting each semiconductor pellet.

[0002]

2. Description of the Related Art This kind of division processing is performed by a dicing process. In many cases, a back surface grinding process is performed before a semiconductor wafer is transferred to a dicing process. In this backside grinding step, the backside of the semiconductor wafer is ground to a desired amount and thinly processed in order to enhance the heat dissipation of the semiconductor pellets. Then, after grinding the back surface, the semiconductor wafer is transported to a dicing process, and is divided into individual semiconductor pellets by cutting along the street.

However, the cutting in the dicing process has the following problems. (1) A semiconductor wafer is supported on a frame via a tape and is completely cut by a dicing blade. However, since the blade reaches the adhesive layer of the tape, an adhesive adheres to the blade and the life of the blade is shortened. (2) The blade winds up the adhesive material of the tape, and the dusty adhesive material adheres to the surface of the wafer and adversely affects the pellet. (3) Chipping occurs on the back surface of the cut pellet,
This leads to a reduction in the quality of the pellet. (4) The cutting of the semiconductor wafer causes a slight change in the tension of the tape, resulting in a misalignment between the street to be cut and the blade, thereby reducing cutting accuracy.

In order to solve such a problem, Japanese Patent Application Laid-Open Nos. 62-4341 and 64-38209 have been proposed.
Has been proposed. These inventions use a dicing process prior to backside grinding to incompletely cut the semiconductor wafer, and then divide the wafer into individual pellets by grinding the backside of the wafer until the incompletely cut grooves appear. I do. "

[0005]

However, in particular, when the mark indicating the crystal orientation of the semiconductor wafer is an "orientation notch", if the outer periphery is chipped in the grinding process of the semiconductor wafer, the chip is lost after the grinding. And the orientation notch cannot be distinguished from each other, and the crystal orientation cannot be known in the subsequent processing steps, which has been pointed out as a new problem that hinders proper processing.

[0006] Therefore, in order to realize the proposed technique, there is a problem that the crystal orientation of the semiconductor wafer must be identified so that proper processing can be performed without any problem.

[0007]

SUMMARY OF THE INVENTION As a specific means for solving the problems of the prior art, the present invention provides a method for cutting a street of a semiconductor wafer on which a plurality of semiconductor pellets are formed by dividing the street into a required depth. Imperfect cutting step to form, the taped step of sticking the protective tape with the cut groove formed surface and the adhesive surface of the protective tape facing each other, so that the back surface of the semiconductor wafer is turned upside down The semiconductor wafer is placed by bringing the surface on which the protective tape is stuck into contact with the chuck table surface, and rotating the chuck table until at least the cut groove formed in the incomplete cutting step is exposed. A back grinding step of grinding the back surface of the semiconductor wafer, wherein the semiconductor wafer is placed on the chuck table in the back grinding step. An alignment step mark indicating the crystal orientation formed Eha is to face the required direction,
After the back grinding step is completed, a positioning stop step in which the chuck table stops the mark indicating the crystal orientation formed on the semiconductor wafer in a required direction, and the mark indicating the crystal orientation formed on the semiconductor wafer is in the required direction And a semiconductor wafer unloading step of unloading the semiconductor wafer from the chuck table in a state facing the semiconductor wafer.

Further, after the unloading step of the semiconductor wafer,
The mark indicating the crystal orientation formed on the semiconductor wafer is conveyed to the cleaning step so as to face a required direction, and after the cleaning step is completed, the mark indicating the crystal orientation is carried out in a state where the mark indicates the required direction. Is included as an additional requirement.

In the method for dividing a semiconductor wafer according to the present invention, incomplete cutting is performed along the streets on the front side of the semiconductor wafer, a protective tape is adhered to the front side, and the rear side has a predetermined thickness. By grinding over the entire length, the adhesive can be attached to the blade, chipping does not occur on the back surface of the pellet, or the cutting accuracy is not adversely affected, and the division can be performed efficiently, and the crystal orientation in the semiconductor wafer can be changed. The mark that indicates
In the grinding process, when an unexpected chip occurs on the peripheral surface, even if a situation where the mark cannot be identified by mechanical search or visual observation occurs, from the grinding process to the cleaning process,
In the transfer step and the pellet pick-up step, each step is performed in a state where the position and orientation of the semiconductor wafer 1 can be accurately recognized.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A dividing method according to the present invention will be described in more detail with reference to the illustrated embodiments. First, FIG.
In the above, a plurality of semiconductor pellets such as ICs partitioned by streets are formed on the front side of the semiconductor wafer 1 to be cut. The dicing apparatus 2 for cutting the semiconductor wafer 1 is provided with a spindle unit 3 capable of precisely and arbitrarily moving forward and backward and moving up and down similarly to a commonly used one. A circular blade 4 is attached to the portion, and the circular blade 4
This is for cutting the semiconductor wafer 1 placed thereon.

Further, the dicing apparatus 2 is provided with an alignment means 6 for performing precise alignment between the street and the blade and displaying the status on the display unit 8. Further, the mounting portion 10 of the cassette 9 containing a plurality of semiconductor wafers 1 and the semiconductor wafer 1
Means 11 for taking out or storing a semiconductor wafer 1
Arm 12 for mounting the semiconductor wafer 1 on the chuck table 5, an arm 14 for transporting the cut semiconductor wafer 1 to the cleaning area 13, and the like. Then, the dicing apparatus 2 performs an incomplete cutting step of cutting a street of the semiconductor wafer to a required depth to form a cutting groove.

A large number of semiconductor wafers 1 to be supplied to the dicing apparatus 2 are contained in a cassette 9, and the semiconductor wafers are sequentially taken out, placed on a chuck table 5, and formed on the surface of the semiconductor wafer. In order to align the street with the blade, incomplete cutting is performed along the street after alignment by the alignment means. The depth of the cut groove is a depth slightly exceeding the finished thickness of the semiconductor pellet. For example, when the finished thickness is 300 μm and the thickness of the semiconductor wafer is 700 μm, it is slightly more than 300 μm.
Since the semiconductor pellets do not fall apart due to incomplete cutting, it is not necessary to attach a tape to the back surface of the semiconductor wafer and integrate it with the frame.

The semiconductor wafer 1 incompletely cut in this way is returned to a predetermined position of the cassette 9 through the cleaning area 13 and is transported to the next backside grinding step through a tape attaching step.

That is, as shown in FIGS. 2 and 3, the incompletely cut semiconductor wafer 1 is cut into the cut groove 20 on the surface A side.
Is adhered with the adhesive surface of the protective tape 21 facing the surface where is formed. In this case, the protective tape 2 used
As 1, a UV tape that is convenient for peeling the protective tape 21 described below is preferable.

FIGS. 4 and 5 show a semiconductor wafer 1 of this kind.
As shown in FIG. 5, various marks 22 indicating the crystal orientation are formed. For example, the mark 22 is an orientation flat (FIG. 4) or an orientation notch (FIG. 5).

The semiconductor wafer 1 to which the protective tape 21 has been adhered is transported to the next back side grinding step in a state where a large number of semiconductor wafers 1 are stored in the cassette 9. 21 are stored such that the attachment surface is located on the lower surface side and the back surface B is located on the upper surface side.

With the cassette 9 thus housed in the cassette 9 as shown in FIG.
It is set to a predetermined position of 0. If necessary, an empty cassette 9a for accommodating the semiconductor wafer after the grinding process may be set at a position facing the cassette 9 set.

The grinding device 30 is provided with, for example, a grinding means 31 for rough cutting and a grinding means 32 for finishing. Then, the semiconductor wafer 1 is loaded from the cassette 9.
A take-out and storage means 33 for taking out and storing the cassette in the cassette 9a after the grinding process is provided, and a pair of positioning tables 34 and 35 are arranged in a range where the take-out and storage means 33 can reach.

A temporary receiving table 36 is provided at a position close to one of the positioning tables 34 and the other positioning table 35 is provided.
A cleaning means 37 is disposed at a position close to the cleaning means 37. The cleaning means 37 comprises a spinner table 38 located inside a transparent resin case which automatically opens and closes, and a cleaning water discharge nozzle 39. Have been.

A turntable 40 rotating clockwise is disposed adjacent to the temporary receiving table 36 and the cleaning means 37, and the turntable has four chuck tables 4
1, 42, 43 and 44 are provided. Then, from the positioning table 34 to the temporary receiving table 36 and the temporary receiving table 36
Semiconductor wafer 1 from wafer to chuck table 41
And a transfer unit 46 for transferring the ground semiconductor wafer 1 from the chuck table 44 to the cleaning unit 37 and from the cleaning unit 37 to the positioning table 35.

Therefore, the semiconductor wafers 1 sequentially supplied for backside grinding are first taken out from the cassette 9 side by the take-out and storage means 33, placed on the positioning table 34, and mechanically centered on the semiconductor wafer 1. Is performed.

Then, the semiconductor wafer 1 is placed on the chuck table 41 by the transfer means 45 with or without the temporary receiving table 36. At this time, the mark 22 indicating the crystal orientation formed on the semiconductor wafer 1 is placed on the chuck table 41 in a state of facing in a required direction.
The state of facing in the required direction means that the mark 22 indicating the crystal orientation detected by, for example, a light detection sensor or the like is positioned in a fixed direction on the positioning table 34 or the temporary receiving table 36. While being placed on the table 41, the chuck table 4
The mark 22 is placed such that the direction of the mark 22 is constant.

The semiconductor wafer 1 thus mounted
Is positioned at the position of the grinding means 31 for rough cutting by the indexing rotation of the turntable 40, and under the rotation of the chuck table, predetermined grinding is performed by the grinding wheel 47, and if necessary, the grinding means for finishing is provided. Under the rotation of the chuck table positioned at 32, predetermined finishing grinding is performed by the grinding wheel 48.

By these roughing and finish grinding,
Since the back surface B side of the semiconductor wafer 1 is cut by a predetermined amount, the cut groove 20 from the incompletely cut surface A side is exposed on the back surface B side, and each pellet becomes an independent state.

Then, by the indexing rotation of the turntable 40, the chuck table 41 is positioned at the position of the chuck table 44 shown in FIG. 6, and a mark indicating the crystal orientation formed on the semiconductor wafer held by the chuck table 41 is displayed. Pointed in the required direction. That is, when the semiconductor wafer is placed on the chuck table 41, the semiconductor wafer is oriented in the same direction as the direction in which the mark indicating the crystal orientation is oriented, or in a direction having a relative positional relationship with the direction.

In order to make this possible, the chuck tables 41, 42, 43, 44 are preferably constructed as follows. That is, as shown in FIGS. 7 and 8, a drive motor 51 such as a DC motor for rotating the chuck table during grinding is disposed below the table 60 (corresponding to the chuck tables 41 to 44). A detection plate 52 is provided at an upper portion, and a light shielding portion 52a provided on an outer periphery of the detection plate enters an optical sensor 53 including a light emitting element and a light receiving element to block light. .

As shown in FIG. 6, when each of the chuck tables of the turntable 40 is at the position of the chuck table 41 and at the position of the chuck table 44, the driving of the drive motor 51 is stopped, and the pulse motor 55 is turned off. It is connected via the clutch 54. And table 6
Rotate the detection plate 52 to 0 and rotate the light sensor 53 until the light sensor 53 shields the optical sensor 53, and stop the rotation when the light is shielded. Accordingly, each chuck table is oriented in a required direction when it is at the position of the chuck table 41 and the position of the chuck table 44.

In this case, since the position of the chuck table 41 and the position of the chuck table 44 are misaligned by 270 °, the direction of the mark indicating the crystal orientation formed on the semiconductor wafer is also 270 ° (90 °). Will occur. In order to avoid this, the optical sensors are provided at two positions shifted by 270 ° (90 °), and the optical sensors are appropriately switched between positioning at the position of the chuck table 41 and positioning at the position of the chuck table 44. With such a configuration, the mark indicating the crystal orientation can be oriented in the same direction. In the grinding step, the connection of the pulse motor 55 is cut off by the action of the clutch 54, and the driving of the drive motor 51 rotates each chuck table to perform the grinding of the semiconductor wafer.

Then, the semiconductor wafer 1 on which the grinding process for the back surface B has been completed is placed on the spinner table 38 in the cleaning means 37 from the position of the chuck table 44 by the transport means 46. Also at this time, the position of the mark 22 indicating the crystal orientation in the initial state of mounting on the spinner table 38 has been accurately recognized.

However, in the cleaning means 37,
The spinner table 38 rotates at a high speed while supplying the cleaning water from the cleaning water discharge nozzle 39 to remove contaminants such as cutting chips adhered in the cutting process. At the high speed rotation, the stop position is uncertain. In addition, the position of the mark 22 indicating the crystal orientation cannot be determined.

Therefore, the drive section of the spinner table 38 is improved in the same manner as the chuck tables 41 to 44, and a stop position establishing means is provided. That is, as shown in FIGS. 7 and 8, a drive motor 51 such as a DC motor is attached to a drive shaft 50 of a table 60 (corresponding to the spinner table 38), and a detection plate 52 is attached to the drive shaft 50. The light-shielding portion 52a is formed on the outer peripheral surface of the detection plate 52, and an optical sensor 53 is disposed at a position where the light-shielding portion passes. Then, the light shielding unit 52a is configured to stop at a position where the light of the optical sensor 53 is shielded.

In order to establish the stop position, a pulse motor 55 is provided via a clutch 54. When the pulse motor 55 is driven, the light shielding portion 52a of the detection plate 52 blocks the light from the optical sensor. Rotate accurately until it stops.

That is, at the time of cleaning, the clutch 54
The spinner table 38 is rotated at a high speed by the drive motor 51 and the clutch 54 is operated after the rotation for cleaning is stopped.
5, the detection plate 52 is rotated together with the spinner table 38, and the light shielding unit 52a is rotated to a position where the light of the optical sensor is shielded, and stopped at the position where the light is shielded.

Accordingly, the stop position is a position where the semiconductor wafer 1 which has been subjected to the grinding step first is placed on the spinner table 38 by the transfer means 46, and the position of the mark 22 indicating the crystal orientation is the initial position. , The relative positional relationship is maintained. The spinner table 38, like the chuck table,
The semiconductor wafer 1 is suction-supported by the suction means, and no deviation occurs. Further, two or more optical sensors may be provided at a predetermined angle so that the stop position can be changed or selected arbitrarily.

In the grinding device 30, since the turntable 40 sequentially rotates clockwise, the chuck tables 41 to 44 sequentially move to the mounting position, the rough cutting position, the finishing position, and the transfer position of the semiconductor wafer 1. That is, the chuck table 44 after the transfer is moved again to the mounting position, that is, the position of the illustrated chuck table 41, and the new unground semiconductor wafer 1 is mounted.

Although the crystal orientation is recognized from the spinner table 38, the ground semiconductor wafer 1 is unloaded by an appropriate unloading means, not shown.

When the protective tape 21 adhered to the front surface A of the semiconductor wafer 1 is a UV tape, the protective tape 21 can be easily peeled off by irradiating ultraviolet rays to deteriorate the adhesiveness. The semiconductor device is supported by the frame in a state where the surface A on which a circuit such as an IC is formed is exposed, and is conveyed to the next step of picking up each semiconductor pellet.

In any case, according to the present invention, after the surface A of the semiconductor wafer 1 is incompletely cut along the street, the protective tape 2 is formed on the surface A.
1 is attached, and the back surface B side is ground over a predetermined thickness, so that the cut groove formed on the front surface A side is exposed. Unlike, adhesive material adheres to the blade or pellet, chipping occurs on the back of the pellet,
Alternatively, the division can be performed cleanly and efficiently without affecting the cutting accuracy.

In particular, when the mark 22 indicating the crystal orientation on the semiconductor wafer 1 has an unexpected chip on the peripheral surface in the grinding step, the mark 22 cannot be identified by mechanical search or visual observation. In each of the steps from the grinding step to the cleaning step and the transfer step, each step is performed in a state where the position and orientation of the semiconductor wafer 1, that is, the position of the mark indicating the crystal orientation can be accurately recognized. The inconvenience caused by the fact that the user does not understand is solved. In addition, since the protection tape 21 is relatively flexible, the cutting groove formed from the front side by grinding the back surface of the semiconductor wafer is exposed on the back surface and divided into pellets.
It cannot be stored in the cassette, and is directly carried out of the spinner table. However, the protective tape 2
If a hard tape is used for the cassette 1, it can be accommodated in the cassette 9 a.

[0040]

As described above, according to the method for dividing a semiconductor wafer according to the present invention, a groove is formed by cutting a street of a semiconductor wafer having a plurality of semiconductor pellets formed by dividing the street into a required depth. Imperfect cutting step, and the tape-attaching step of adhering the protective tape such that the surface on which the cut grooves are formed and the adhesive surface of the protective tape face each other, so that the back surface of the semiconductor wafer is facing up, The surface where the protective tape is stuck is placed in contact with the chuck table surface, and the semiconductor wafer is placed. While rotating the chuck table, the back surface of the semiconductor wafer is exposed at least until the cut groove formed in the incomplete cutting step is exposed. And a back grinding step of grinding the semiconductor wafer, wherein the semiconductor wafer is placed on a chuck table in the back grinding step. After the alignment step in which the mark indicating the crystal orientation formed on the wafer is oriented in the required direction and the back surface grinding step is completed, the chuck table moves the mark indicating the crystal orientation formed on the semiconductor wafer in the required direction. And a semiconductor wafer unloading step of unloading the semiconductor wafer from the chuck table with the mark indicating the crystal orientation formed on the semiconductor wafer facing a required direction. (1) Since the division of the semiconductor wafer is performed in a state where the crystal orientation of the semiconductor wafer can always be recognized, it is possible to extremely efficiently separate the individual semiconductor pellets. When notched chipping occurs, the orientation notation indicating the crystal orientation by mechanical search or visual inspection Even if there is a situation where the mark cannot be identified as a chip, each step is performed in a state where the position of the mark indicating the crystal orientation is accurately recognized from the grinding step to the cleaning step and the transporting step, so that the final The semiconductor pellet pick-up operation can be performed without any trouble. (3) In addition, adhesive material adheres to the blade or the pellet in the cutting process, chipping occurs on the back surface of the pellet, or the cutting accuracy is reduced. Various excellent effects such as eliminating adverse effects are exhibited.

[Brief description of the drawings]

FIG. 1 is a perspective view schematically showing a cutting apparatus for performing a method of the present invention.

FIG. 2 is a schematic side view showing a situation in which a protective tape is adhered to a front surface side of a semiconductor wafer incompletely cut by the cutting device.

FIG. 3 is a schematic side view showing a state in which a protective tape is attached to a front surface side of the semiconductor wafer.

FIG. 4 is a schematic rear view of the semiconductor wafer to which the protective tape is attached and which has a mark of an example of a crystal orientation.

FIG. 5 is a schematic back view of a semiconductor wafer to which the protective tape is attached and which has a mark of a crystal orientation in another example.

FIG. 6 is a perspective view schematically showing an example of a grinding apparatus used in a step of grinding the back surface side of the semiconductor wafer to which the protective tape is attached.

FIG. 7 is a schematic side view showing a stop position establishing means of a spinner table of a cleaning means in the grinding device.

FIG. 8 is a plan view taken along line CC of FIG. 7;

[Explanation of symbols]

1 ... semiconductor wafer, 2 ... dicing equipment, 3 ...
... Spindle unit, 4 ... Blade, 5 ... Chuck table, 6 ... Imaging unit, 8 ... Video display unit,
9, 9a ... cassette, 10 ... mounting part, 11 ...
Means for taking out or storing, 12, 14, ..., arm,
13: cleaning area, 20: cutting groove, 21: protective tape, 22: mark, 30: cutting device, 31
…… Cutting means for rough cutting 32 …… Cutting means for finishing
33 ... means for taking out or storing, 34, 35 ...
... Positioning stand, 36 ... Temporary holder, 37 ... Cleaning means, 38 ... Spinner table, 39 ... Washing water discharge nozzle, 40 ... Turn table, 41-44 ...
Chuck table, 45, 46, transport means, 47,
48 cutting wheel, 50 drive shaft, 51 drive motor, 52 detection plate, 52a light shielding section, 53 sensor, 54 clutch, 55
... Pulse motor, A ... Top surface, B ... Back surface.

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Toshiaki Takahashi 2-14-3 Higashi-Kojiya, Ota-ku, Tokyo Inside Disco Corporation (72) Inventor Yutaka Koma 2-14-3 Higashi-Kojiya, Ota-ku Tokyo Prefecture Disco Corporation F Terms (reference) 3C069 AA01 BA04 BB04 CA05 CB02 CB04 DA07 EA01 EA02 EA03 EA05

Claims (2)

[Claims] 1. An incomplete cutting step of cutting a street of a semiconductor wafer, on which a plurality of semiconductor pellets are formed by being partitioned by streets, to a predetermined depth to form a cutting groove, and a surface on which the cutting groove is formed and a protective tape. A tape attaching step of attaching a protective tape such that the back surface of the semiconductor wafer is turned upside down, and a surface on which the protective tape is attached is brought into contact with a chuck table surface to face the semiconductor wafer. A back surface grinding step of grinding the back surface of the semiconductor wafer until at least a cut groove formed in the incomplete cutting step is exposed while rotating the chuck table, When placing the semiconductor wafer on the chuck table in the backside grinding process, make the mark indicating the crystal orientation formed on the semiconductor wafer face the required direction An alignment step, after the back grinding step is completed, a positioning stop step in which the chuck table stops the mark indicating the crystal orientation formed on the semiconductor wafer in a required direction, and a crystal orientation formed on the semiconductor wafer. A semiconductor wafer unloading step of unloading the semiconductor wafer from the chuck table in a state where the indicated mark is oriented in a required direction. 2. After the semiconductor wafer unloading step, the mark indicating the crystal orientation formed on the semiconductor wafer is conveyed to the cleaning step so as to face a required direction. Even after the cleaning step is completed, the crystal orientation is changed. 2. The method according to claim 1, wherein the mark is carried out in a state where the mark is directed in a required direction.