JP3191827B2 - Semiconductor substrate peeling device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a monolithic microwave integrated circuit (MMI) used in microwave and millimeter wave bands.
The present invention relates to an apparatus for peeling a wafer from a reinforcing substrate that has been bonded to reinforce the mechanical strength of the wafer after completion of the wafer process in the manufacture of a C (Microwave Monolithic Integrated Circuit).

[0002]

2. Description of the Related Art With the rapid development of information network systems in recent years, the demand for satellite communication / broadcasting systems has increased rapidly, and the frequency band has been increasingly higher. Under these circumstances, MMICs which have been researched and put into practical use mainly for military or special industrial applications have been actively researched for consumer applications. Although such MMICs include a uniplanar type which does not require a thin wafer, generally, a method of forming a wiring by a microstrip line is often used.

In this type of MMIC, the smaller the thickness of the wafer, the smaller the width of the microstrip line providing the same characteristic impedance, and thus the smaller the size of the microstrip line.
When etching a via (VIA) hole, there is an advantage that the etching time can be short and variation in the shape of the via hole is reduced, and usually 150 μm to 80 μm.
The thickness is reduced to about μm.

Therefore, after the wafer surface process such as the formation of semiconductor elements is completed, the wafer is thinned and
A backside process of etching the IA holes and depositing or plating metal on the backside is performed. In order to prevent a wafer weakened due to thinning from being cracked in the process, Then, a method is employed in which a back surface process is performed with the mechanical strength reinforced by adhering it to a reinforcing substrate made of quartz glass or silicon with an adhesive such as electron wax.

In this case, it is necessary to peel the wafer from the unnecessary reinforcing substrate after the back surface process is completed.
Conventionally, there is no suitable device for this, and it is performed manually.

[0006]

As described above, conventionally, after the wafer process of the MMIC is completed, the step of separating the wafer from the reinforcing substrate is performed manually.
As the diameter of the wafer increases from 3 inches to 4 inches, it is extremely difficult to remove the wafer from the reinforcing substrate without damaging the wafer. The yield in the stripping process was getting worse.

Accordingly, an object of the present invention is to provide an apparatus for separating a semiconductor substrate from a reinforcing substrate in order to solve the above problems.

[0008]

A fixing means for fixing a reinforcing substrate to which a semiconductor substrate is adhered by an adhesive, and an extruding means for extruding the semiconductor substrate in an extrusion direction substantially parallel to an adhesive surface and peeling the semiconductor substrate from the reinforcing substrate. Monitoring means for monitoring the stress generated in the semiconductor substrate; and control means for controlling the movement of the pushing means by a signal from the monitoring means.

The extruding means has an extruding member which abuts on the end surface of the semiconductor substrate and moves substantially parallel to the bonding surface, and a driving means for driving the movement of the extruding member. It may be characterized by controlling driving.

The monitoring means monitors the stress by a change in electrical characteristics of a monitor circuit on the semiconductor substrate, and the monitor circuit is a monitoring semiconductor circuit formed in advance on the semiconductor substrate. May be a feature. Alternatively, the monitoring means may monitor the stress by a load applied to the semiconductor substrate. Further, the apparatus may further include a sensor for detecting that the pushing member has come into contact with the semiconductor substrate, and the monitoring means starts monitoring when the contact is detected.

[0011]

The semiconductor substrate can be separated from the reinforcing substrate by extruding only the semiconductor substrate in parallel with the bonding surface while the reinforcing substrate is fixed. At this time, the stress generated in the semiconductor substrate is monitored by the monitoring means, and the pushing speed of the pushing means is controlled, so that the peeling operation can be performed within a range in which no excessive stress occurs in the semiconductor substrate.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 1 to 4 are views showing the configuration and operation of the peeling apparatus of the present embodiment, and FIG. 4 is a process sectional view showing the back surface process of the MMIC.

In FIG. 4, a resist 12 is applied to a GaAs substrate 11 on which a surface process such as formation of a semiconductor element has been completed (FIG. 4A), and this is reinforced with a reinforcing substrate made of quartz glass or silicon with an adhesive. 2 to reinforce (FIG. 4B).

The adhesive used here does not melt at about 80 ° C., but softens sufficiently at about 130 ° C. Further, it is an organic adhesive having an ultraviolet transmittance property, being insoluble in an etching solution for forming a via hole, and capable of stopping sputtering on the back surface. For example, a material generally called electron wax is used.

Next, after the back surface of the GaAs substrate 11 is polished to make it thinner (FIG. 4C), Si is formed by sputtering.
An O ₂ film 14 is formed (FIG. 4D), and a resist film 15 is applied and patterned (FIG. 4E). The SiO ₂ film 14 is etched using the resist pattern as a mask, and a via hole 16 is formed by etching using the SiO ₂ film 14 as a mask (FIG. 4F). Thereafter, the resist 15 and the SiO ₂ film 14 are removed (FIG. 4).
(G)), a back metal film 17 is formed by vapor deposition or plating (FIG. 4 (h)).

When the semiconductor element formed on the surface of the semiconductor substrate is used as a monitor circuit to be described later, a terminal required for monitoring is formed by a patterned back surface metal film 17 in a process of the back surface, This terminal and a semiconductor element used as a monitor circuit are connected to VI
It is necessary to connect via the A-hole 16.

After a series of back surface processes are completed, the wafer 1 is peeled from the reinforcing substrate 2 by using a peeling device.

FIG. 1 shows the configuration of the entire system of the peeling apparatus. In the drawing, the peeling apparatus of this embodiment includes a wafer fixing jig 3, a wafer pushing rod 41, an electric characteristic measuring probe 5, a computer 63, and the like. Note that a portion surrounded by a dotted line in FIG. 1 is a view of the wafer fixing jig 3 as viewed from above.

The wafer pushing rod 41 is fixed to a manipulator 43 driven by a motor 42, and is capable of changing the pushing speed of the wafer 1 under the control of the computer 63. The electric property measurement probe 5 is fixed to the wafer push rod 41 and moves in the same manner as the moving wafer 1. The probe 5 is, for example, probed on a monitor circuit formed on the wafer 1 in advance for this purpose. This monitor circuit may be of any type as long as its electrical characteristics change depending on the magnitude of the stress generated on the wafer 1. For example, in the case of an FET, its threshold voltage V depends on the magnitude of the stress applied to the wafer 1.
_{Since th} changes, it can be used.

Normally, on a wafer, a TEG (Test Element) is provided for each of a plurality of portions or chips of the wafer.
In this case, the circuit in the TEG is used as a monitor circuit.

Further, since the stress is generated almost uniformly on the entire surface of the wafer 1, the monitoring position is usually one of the central part of the wafer 1 or the part near the wafer push rod 41 which is adhered to the reinforcing substrate 2 to the end. Is set in place. Of course, monitoring may be performed at a plurality of locations. Then, the extracted signal is amplified by the amplifier 61, and A
The data is A / D converted by the / D converter 62 and sent to the computer 63.

This apparatus uses a hot plate 7 for melting electron wax and the like used for bonding.
Since the wafer fixing jig 3 is used while being heated to about 130 ° C., the wafer fixing jig 3 preferably has a low thermal conductivity and a certain weight, such as brass or the like, which is plated with nickel or the like. The jig 3 has a dent 31 shaped to match the reinforcing substrate 2 so that the reinforcing substrate 2 can be exactly fitted therein. The depth of the depression 31 is
Is 0.6 mm, which is 0.5 mm.

Since the portion for pushing out the wafer 1 is pushed against the orientation flat of the wafer 1, the shape may be a square pole, and the material may be any material which does not deform even when heated.

A portion on the front side of the wafer 1 on which the extruded wafer 1 rides is provided with a slit 3 in the jig 3 in order to prevent the peeled wafer 1 from sticking again.
2 is cut so that air can enter from under the wafer 1.

FIGS. 2 and 3 show a second embodiment.
This will be described below with reference to the drawings.

FIG. 2 is a perspective view of the second embodiment. FIG.
3 is a cross-sectional view taken along the center line in FIG. 3, and FIG. 3A is a view before the push rod comes into contact with the semiconductor substrate.
FIG. 3B is a diagram when the push rod is in contact with the semiconductor substrate and the probe is connected to the monitor circuit, and FIG. 3C is a diagram when the push rod is pushing the semiconductor substrate after coming into contact with the semiconductor substrate. FIG.

The reinforcing substrate 2 attached to the semiconductor substrate (wafer 1) described with reference to FIG. 4 is oriented in such a manner that the orientation flat 18 of the wafer 1 comes into contact with the pushing means in the recess 31 provided in the wafer fixing jig 3. Is fixed as shown in FIG. A recess 33 is further provided from the recess 31 to the outside in the pushing direction to facilitate placement and removal of the reinforcing substrate 2. A heating device (not shown) is provided below the depression 31 to heat the adhesive to about 130 ° C.

The wafer push rod 41 moves along a guide rail 44 provided on a table of the wafer fixing jig 3 by driving a manipulator (not shown) controlled by a computer (not shown). The wafer push rod 41 is provided with an OF pusher portion 45 that contacts the orientation flat (OF) 18 of the wafer 1 and a wafer pusher portion 46 that surrounds the OF pusher portion 45.
Further, the probe needle 51,
Probe 5 composed of arm 52 and vertical movement mechanism 53
Is attached.

An optical aperture 34 is provided in the depression 31 at a position substantially immediately below the orientation flat 18 of the wafer 1.
The LED 81 is installed upward so that light passes through the opening, and a photodiode 8 for detecting light from the LED 81 is provided.
2 is attached to the sensor support 84 so as to face downward with the reinforcing substrate therebetween. Usually, the reinforcing substrate 2 is a light transmissive substrate such as a quartz plate, and the wafer 1 does not transmit light.

Before the wafer push rod 41 comes into contact with the wafer 1, the photodiode 82 senses the light of the LED 81 leaking from these two gaps (FIG. 3A). When the wafer push rod 41 moving toward the wafer 1 comes into contact with the wafer 1, the light from this gap is shut off, and this is detected, and the vertical movement mechanism 53 detects the probe needle 5.
1 is lowered and connected to the monitor circuit on the wafer 1 (FIG. 3B). This connection operation is performed by the wafer pushing rod 4
1 may be performed during the movement, or may be performed after the movement is once stopped. Thereafter, until the wafer 1 is separated from the reinforcing substrate 2, the probe 5 measures the stress generated on the wafer 1 while the wafer pushing rod 41, that is, the wafer 1
(FIG. 3C).

The wafer 1 extruded and separated from the reinforcing substrate rides on a rod 35 fixed to a table of a wafer fixing jig 3. Here, the configuration of the monitor circuit and the configuration of the control system are the same as in the above-described embodiment.

Next, the actual peeling operation will be described. First, the wafer 1 is set on the wafer fixing jig 3. At this time, the reinforcing substrate 2 is correctly set in the recess 31 of the jig 3.

As described above, the operation of the present apparatus is controlled by the computer 63. The computer 63 receives the signal corresponding to the stress generated in the wafer 1 and processes the signal, and changes the rotation speed of the motor 42 for driving the manipulator 43 to change the rotation speed of the wafer pushing rod 4.
1 has a built-in control program having a portion for controlling the speed at which the wafer 1 is extruded, and by executing this, a peeling operation is performed.

First, the wafer 1 is extruded at an appropriate initial speed. The initial speed should be on the order of 10 microns / sec with great care. First, after extruding 10 μm, the electrical characteristics of the wafer 1 are examined to check whether a stress exceeding the breaking limit is applied to the wafer 1. The relationship between the electrical characteristics of the wafer 1 and the stress exceeding the breaking limit needs to be determined by preliminary experiments.

If a stress exceeding the breaking limit is not applied, the speed at which the wafer 1 is pushed out is doubled, for example, to 2 times.
Accelerate to 0 microns / sec. Further, after extruding 10 μm, the electrical characteristics of the wafer 1 are examined, and it is checked whether or not the stress exceeding the breaking limit is applied to the wafer 1. It accelerates twice to 40 microns / sec. Unless the stress exceeding the breaking limit is applied to the wafer 1, this may be repeated to accelerate the speed at which the wafer 1 is pushed out. If it is detected on the way that a stress exceeding the breaking limit is applied, the pushing speed is reduced to half.

In this manner, while the reinforcing substrate 2 is fixed to the jig 3, the wafer 1 is pushed out while checking the stress, and the wafer 1 is separated from the reinforcing substrate without damaging the wafer 1. be able to.

It should be noted that what is the initial speed of pushing the wafer 1 described above, how many μm is pushed out, the electrical characteristics of the wafer 1 are checked to check the stress, how much the acceleration / deceleration is, etc. This is merely an example, and the size of the wafer 1, the type of adhesive, and other conditions must be optimized.

Further, instead of monitoring the stress generated on the wafer 1 by the monitoring circuit formed on the wafer 1, the load applied to the wafer 1 may be monitored by a monitor circuit provided outside the wafer 1. . For example, the magnitude of the load applied to the wafer 1 may be detected by the load cell 54 attached to the contact portion of the OF pusher 18 with the wafer 1 (FIG. 2).

[0039]

As described above, according to the present invention, there are provided means for fixing a reinforcing substrate to which a semiconductor substrate is bonded, a mechanism for pushing the semiconductor substrate bonded to the reinforcing substrate parallel to the bonding surface, The apparatus provided with a means for monitoring the stress generated in the semiconductor substrate can automate the step of peeling the wafer from the reinforcing substrate after the completion of the MMIC wafer process, which has been conventionally performed manually by a skilled operator. Further, by using this apparatus, the yield in the same step can be improved.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram of a semiconductor substrate peeling apparatus and a plan view of a wafer fixing jig 3 showing a first embodiment of the present invention.

FIG. 2 is a schematic view of a semiconductor substrate peeling apparatus according to a second embodiment of the present invention.

FIG. 3 is a sectional view showing the operation of a semiconductor substrate peeling apparatus according to a second embodiment of the present invention.

FIG. 4 is a process cross-sectional view showing a back surface process of the MMIC.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Wafer (semiconductor substrate), 18 ... Orientation flat, 2 ... Reinforcement board, 3 ... Wafer fixing jig, 31 ...
Recesses for fixing the reinforcing substrate, 32 slits, 33 concave portions for taking out the reinforcing substrate, 34 light opening holes, 35 rods, 4
DESCRIPTION OF SYMBOLS 1 ... Wafer push rod, 42 ... Motor, 43 ... Manipulator, 44 ... Guide rail, 45 ... OF pusher, 46 ... Wafer pusher, 5 ... Probe for electric characteristic measurement, 51 ... Probe needle, 52 ... Arm, 53 ... Vertical movement Mechanism, 54: Load cell, 61: Amplifier, 62: A / D
Transducer, 63 ... Computer, 7 ... Hot plate, 8
1 ... LED, 82 ... Photodiode.

Claims (5)

(57) [Claims] 1. A fixing means for fixing a reinforcing substrate to which a semiconductor substrate is adhered by an adhesive; an extruding means for extruding the semiconductor substrate in an extrusion direction substantially parallel to an adhesive surface and peeling the semiconductor substrate from the reinforcing substrate; A peeling device for a semiconductor substrate, comprising: monitoring means for monitoring stress generated in a semiconductor substrate; and control means for controlling movement of the pushing means in accordance with a signal from the monitoring means. 2. The extruding means includes: an extruding member that abuts on an end surface of the semiconductor substrate and moves substantially parallel to an adhesive surface; and a driving unit that moves the extruding member. 2. The apparatus according to claim 1, wherein the driving of the driving means is controlled. 3. The monitoring means monitors the stress by a change in electrical characteristics of a monitor circuit on the semiconductor substrate, and the monitor circuit is a monitoring semiconductor circuit formed in advance on the semiconductor substrate. The apparatus for stripping a semiconductor substrate according to claim 1, wherein: 4. The apparatus according to claim 1, wherein the monitoring means monitors the stress by a load applied to the semiconductor substrate. 5. The apparatus according to claim 1, further comprising a sensor for detecting that the extruding member comes into contact with the semiconductor substrate, and wherein the monitor starts monitoring when the contact is detected. Semiconductor substrate peeling device.