JPH01319948A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To make the quantity and the thickness of bond uniform and maintain the constant bonding strength by forming a semi-hardened thermosetting resin layer as bond on a silicon wafer before cutting off and then cutting off and fixing the silicon wafer. CONSTITUTION:A semi-hardened (stage B) thermosetting resin layer 2 is formed on the whole rear of a silicon wafer 1 having a circuit patterned thereon by printing or other methods, the wafer is cut off into pieces of specific sizes, and a cut piece is mounted and bonded by thermocompression on the tab of a lead frame 4. This prevents void from being produced in bonding the cut piece to the lead frame. Since thermosetting resin as bond is formed on the rear of the silicon wafer before cutting off, a bond layer of uniform quantity and thickness in comparison with the conventional methods is formed to prevent insufficient bonding strength and characteristic which reduce the reliability.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for manufacturing a semiconductor device and a silicon wafer for manufacturing a semiconductor device.

<Prior Art> In the manufacture of semiconductor devices such as ICs and LSIs, there is a step of fixing an element made of a semiconductor chip (a silicon wafer patterned with a circuit cut into a predetermined size) to a lead frame. Traditionally, this process uses a paste bonding agent to secure the chip, and the paste bonding agent is usually formed on the tab of the lead frame by a dispensing method or screen printing method, and then the formed bond is The method used is to place the chip on top of the agent and heat it to harden it. After wire bonding is performed on the parts joined in this way, it is common to perform sealing using a resin molding method or the like.

<Problems to be Solved by the Invention> However, in the above-mentioned conventional methods, if the paste-like bonding agent has variations in viscosity or deterioration, the amount and thickness of the bonding agent formed will vary, and as a result, The strength of the resulting joined product also varies, resulting in poor reliability. In addition, sometimes due to insufficient strength, chips bonded in later processes (such as wire bonding process) may peel or fall off, or if the amount of paste is large, the paste may ooze out, resulting in poor characteristics as a semiconductor element. This may reduce reliability.

Therefore, an object of the present invention is to provide a method for manufacturing a semiconductor device in which the amount and thickness of the bonding agent can be made uniform without variation, and the bonding strength of the chips can be maintained constant.

<Means for Solving the Problems> As a result of repeated studies by the present inventors to achieve the above object,
By forming a semi-hardened thermosetting resin layer as a bonding agent on a silicon wafer before cutting, and then cutting and fixing it, it is possible to manufacture semiconductor devices with improved reliability and no variation in the amount of bonding agent formed. This discovery led to the completion of the present invention.

That is, the present invention forms a semi-cured thermosetting resin layer on the entire back surface of a silicon wafer patterned with a circuit,
The present invention relates to a method for manufacturing a semiconductor device, characterized in that after cutting to a predetermined size, the cut piece is placed on a tab of a lead frame and thermally compressed, and a silicon wafer for manufacturing the semiconductor device. .

As shown in FIG. 1(a), in the present invention, a thermosetting resin layer 2 in a semi-cured state (B stage) is formed on the entire back surface of a silicon wafer 1 on which a circuit has been patterned by printing or the like.

Although any method can be adopted as the forming method, the following method is typically used.

■A method in which B-stage thermosetting resin is melted at a temperature above the melting point and below the curing temperature and coated with a hot melt coater.

■ B-stage thermosetting resin is N-methyl-2-pyrrolidone, dimethylformamide, dimethylacetamide,
A method of dissolving it in an organic solvent such as ketones, casting it onto the back side of a silicon wafer using a dispenser nozzle, and then drying it at a temperature below the curing temperature.

By using a B-stage thermosetting resin, the viscosity and thickness can be easily adjusted, and curing and fixing in the subsequent thermocompression bonding process are improved. As such a thermosetting resin, those conventionally used as a bonding agent can be used, but preferably resins containing bismaleimide and triazine resin monomers as main components are used. Such a resin has a bismaleimide represented by the general formula (where Ar represents a divalent aromatic group) and a bismaleimide represented by the general formula, N=c OArt Oc
=N (However, Ar2 represents a divalent aromatic group, and the above-mentioned Ar.

(which may be the same as or different from) and a triazine resin having a triazine ring obtained by cyclopolymerizing three or more molecules of the dicyanate and having a cyanate group at the end of the molecule, A typical example is BT resin (manufactured by Mitsubishi Gas Chemical Co., Ltd.).

The thickness of the thermosetting resin is in the range of 5 to 100 μm, preferably 10 to 50 μm.

, if it is less than 5 μm, the bonding strength will be insufficient, and 1
If the thickness exceeds 0.00 μm, the thermal conductivity will be poor, which is not preferable.

In the present invention, after forming a B-stage thermosetting resin layer on the entire back surface of the silicon wafer as described above,
Cut it into a predetermined size as shown in Figure 1(b), and
As shown in FIG. 1C, the cut piece (semiconductor chip 3) is placed on the tab of the lead frame 4 using a glue bonder or the like and bonded by thermocompression to form a semiconductor device (see FIG. 1D). The heating conditions during thermocompression bonding should be at least the curing temperature of the thermosetting resin (170'C in the case of BT resin), preferably 200-35°C.
The temperature should be around 0°C.

In the present invention, a B-stage thermosetting resin is used as the bonding agent and is formed on the back side of the silicon wafer in advance, thereby preventing the generation of voids when the cut pieces are bonded (temporarily bonded) to the lead frame. be able to. In addition, since the thermosetting resin as a bonding agent is previously provided on the back side of the silicon wafer before cutting, the bonding agent layer is formed in a uniform amount and thickness compared to conventional methods, resulting in insufficient bonding strength and poor characteristics. It is possible to prevent a decrease in reliability such as the following.

Further, in the present invention, the thermosetting resin may include gold, silver,
Metal powder such as copper, nickel, aluminum, etc. can be blended as a conductive filler and used when conductivity is required. As a compounding method, for example, 100 to 900 parts by weight of a conductive filler is mixed with 100 parts by weight of a thermosetting resin, and a mixing roll, a kneader, etc. are used in a molten state above the melting point of the resin and below the curing temperature. to mix it evenly,
Examples include a method in which the resin is dissolved in a suitable solvent and then uniformly mixed with the conductive filler at the above ratio.

<Example> EXAMPLES The present invention will be specifically explained below with reference to Examples.

Example 1 Silicon wafer (diameter 12.5 cm, JIEcC35
BT resin (manufactured by Mitsubishi Gas Chemical Co., Ltd., BT2070) heated to 100°C and melted is uniformly coated on the entire back surface of the 0 μm) using a hot melt coater to a thickness of 25 μm, and cooled. A silicon wafer on which a thermosetting resin layer for a stage was formed was fabricated.

Next, the obtained silicon wafer was diced into a size of 3 x 3.3 mm square, and the obtained cut pieces (chips) were cut into 4 pieces.
i! with Gui bonder on 6 tabs of lead frame made of 2-alloy! Then, thermocompression bonding was performed at 300° C. for 10 seconds to obtain a semiconductor device.

When the bonding strength between the chip and the lead frame in the obtained semiconductor device was measured using a push-pull gauge, the shear stress showed a value of 5 kg/cffl at room temperature, which was found to be sufficient strength for practical use. . Also,
No voids were observed at the adhesive interface between the adhesive and the lead frame, and the adhesive was bonded with a uniform thickness.

Example 2 BT resin (manufactured by Mitsubishi Gas Chemical Co., Ltd., BT-2470) 10
0 g is uniformly dissolved in a mixed solvent of 50 g of methyl ethyl ketone and 50 g of N-methyl-2-pyrrolidone. Next, silver powder (manufactured by Kashitsu Kinzoku Co., Ltd., A
gc-L) 400 g to prepare a conductive paste.

The obtained paste was applied uniformly to the entire back surface of a silicon wafer (diameter 12.5 cm, thickness 350 μm) through the nozzle of a dispenser so that the thickness after drying was 10 μm, and dried at 150°C for 30 minutes. A silicon wafer on which a B-stage thermosetting resin layer was formed was fabricated.

Next, the obtained silicon wafer was placed on the tab of a lead frame in the same manner as in Example 1, and thermocompression bonded at 250° C. for 10 seconds to obtain a semiconductor device.

When the bonding strength between the chip and the lead frame in the obtained semiconductor device was measured in the same manner as in Example 1, it showed a shear stress of 13 kg/aft at room temperature and 2 kg/c+fl at a temperature of 250°C. , which showed sufficient strength for practical use.

In addition, no voids were observed, and the volume resistivity of the bonding layer was determined by the four-probe method to be 1.0X10-'3Ω・c.
m value, and showed sufficient conductivity for practical use.

<Effects of the Invention> As described above, according to the manufacturing method of the present invention, a B-stage thermosetting resin layer is formed in advance on the entire back surface of a silicon wafer on which a circuit has been patterned. When the resin layer is cut into chips, there is little variation in the thickness of the resin layer among the chips, and variations in bonding strength with the lead frame can also be prevented, thereby improving reliability.

Furthermore, since the conventional curing time in the bonding process can be reduced, work efficiency is improved and automation is facilitated.

[Brief explanation of the drawing]

FIGS. 1(a) to 1(d) are process diagrams showing the method for manufacturing a semiconductor device of the present invention.

Claims (4)

[Claims] (1) Form a semi-cured thermosetting resin layer on the entire back surface of a silicon wafer patterned with a circuit, cut it to a predetermined size, and place the cut piece on the tab of a lead frame. A method for manufacturing a semiconductor device characterized by thermocompression bonding. (2) Claim in which the thermosetting resin contains a conductive filler (
1) The method for manufacturing the semiconductor device described above. (3) A silicon wafer for manufacturing semiconductor devices, in which a semi-hardened thermosetting resin layer is formed on the entire back surface of a silicon wafer patterned with circuits. (4) Claim in which the thermosetting resin contains a conductive filler (
3) The silicon wafer for manufacturing a semiconductor device as described above.