JPH01293539A - Forming method for bump of semiconductor device - Google Patents

Abstract

PURPOSE:To obtain a method for effectively forming a bump on a predetermined bonding pad with a less number of steps by filling a resin material mixed with heat resistant substance in the opening of a resist in which the pad is exposed, removing the resist, and then sintering the substance by baking. CONSTITUTION:When a bump 1 disposed on a bonding pad 3 provided on the surface of a semiconductor substrate 2 for attaching the other end of a wiring member connected at its one end to an extraction electrode is formed, only the arranging position of the pad 3 is exposed to form a resist 5, a resin material mixed with heat resistant conductive substance is filled in the opening of the resist 5 in which the pad 3 is exposed, and a resin material layer 10 is formed on the pad 3. Then, after the layer 10 is removed and the resist 5 is removed, the layer 10 is baked, the substance is sintered to form the bump 1. For example, as the resin material, epoxy resin paste containing silver is employed and then baked at 200-300 deg.C, and the silver is sintered.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a bonding technique for electrically connecting a semiconductor device main body and an external extraction electrode, and particularly relates to a bonding technique provided on the surface of a semiconductor substrate. The present invention relates to a method for forming a bump for attaching the other end of a wiring member which is placed on a pad and whose one end is connected to the external extraction electrode.

[Prior Art] As shown in FIG. 3, a semiconductor device is formed, for example, by using a p-type substrate (a) and implanting phosphorus (P), arsenic (As), etc. into the surface of this substrate (a). n+ region na)
(na) and an electrically insulating layer (is) on the surface of the substrate (a).
), a source electrode (St), a gate electrode (It), a drain electrode (dt), etc. are formed through an MO8 type semiconductor device, and a p-type substrate (a ) and the n+ region na formed on this substrate (a).
) to (na), p+ regions pa) to (pa), a base electrode (bt), an emitter electrode (eB), and a collector electrode formed on the surface of the substrate (a) via an electrical insulating layer (iS). Bipolar semiconductor devices configured with (at) and the like are generally known.

By the way, when mounting the above-mentioned semiconductor device, it is necessary to electrically connect the internal circuit of the semiconductor device and the external circuit provided outside the semiconductor device, and the following bonding method has conventionally been adopted. It is being

That is, this method is called a thermocompression bonding method, and as shown in FIG. Bonding pads (bp) to (bp) connected to various electrodes (1) to (1), etc. of group (b) are formed, and the bonding pads (bp) to (b
p) Bond one end of the metal wire (W) upward using a wire bonding machine (C) as shown in FIGS. 6(A) to (D), and connect the other end to an externally drawn voltage ff
1 (Ot) to electrically connect the internal circuit of the semiconductor device and the external circuit provided outside the semiconductor device, as shown in FIG. In addition, the bonding pad (b
Portions other than p) to (bp) are partitioned by an insulating oxide film (d).

However, since this thermocompression bonding method connects a wire (W) to each bonding pad (bp), it has the disadvantage that the bonding process takes a long time in semiconductor devices with a large number of electrodes. There is a drawback that the connection strength between the wire (W) and the wire (W) tends to vary, resulting in poor reliability.

Therefore, in order to eliminate the above-mentioned drawbacks, we have developed the
As shown in (B), bonding pads (bp) to (b
Bumps (e) to (e), which are protruding electrodes, are formed on the top of p), and metal foils such as copper (f), which are wiring members, are continuously connected to these bumps (e) to (e) as shown in Fig. 9. A method called the flip-chip method has been developed in which bonding is performed by fusion bonding. In this method, the metal oil (f) is melted onto the plurality of bumps (e) to (e) at the same time, compared to the thermocompression bonding method in which a wire (W) is connected to each bonding pad (bp). Since the bonding process can be bonded, the time required for the bonding process is shortened, and the bonding strength also has the advantage of being uniform.

[Problems to be Solved by the Invention] By the way, the conventional method for forming bumps in the above-mentioned flip-chip method was performed as follows.

That is, as shown in FIG. 10(A), a sputtering process is performed on the surface of the substrate (a) on which the bonding pad (bp) is exposed, and as shown in FIG. 10(B), Then, Ti--W alloy and ΔU are sequentially deposited.

Next, as shown in FIG. 10(C), a photoresist (h) is formed on the surface of the substrate (a) except for the area where the bonding pad (bp) is formed, and then Au plating is performed to form a photoresist (h) as shown in FIG. 10(C). Mushroom-shaped metal 11 as shown in D)! J
Form (i).

Then, as shown in FIG. 10(E), the photoresist 1-(h) is removed, and the Ti-W alloy and Au film outside the metal film (1) are removed by chemical etching. A heat treatment is performed to form bumps (e) as shown in FIG. 10(F).

However, when the bump (e) is formed by this plating method, the @ film metal grows in the width direction as well as in the thickness direction, so the bump (e) grows more than the bonding pad (bp).
), which has the disadvantage of increasing the size of the device, making it unsuitable for downsizing the device.In addition, there are problems in that there are many steps and complicated steps such as plating are required, which increases manufacturing costs. .

On the other hand, a transfer method is known as another method for forming bumps. That is, in this method, a metal piece for a bump is formed on a transfer seamill in advance, this transfer sheet is closely attached with one side of the metal facing toward the substrate, the metal piece is transferred onto a predetermined bonding pad, and This is a method of fusing.

However, even with this method, if the alignment between the metal piece and the bonding pad is poor, the metal piece will be placed protruding from the bonding pad, resulting in poor adhesive strength and poor yield. In addition, it is necessary to set the bonding pad larger than the metal piece in consideration of the positioning error of the transfer sheet, which has the same problem as the plating method described above that it is not suitable for miniaturizing the device. .

[Means for Solving the Problems 1] The present invention has been made in view of the above-mentioned problems, and its object is to reduce the number of steps and reliably form bumps on predetermined bonding pads. The goal is to provide a way to do so.

That is, the present invention is based on a method for forming a bump which is disposed on a bonding pad provided on the surface of a semiconductor substrate, and which attaches the other end of a wiring member whose one end is connected to an external extraction electrode. A resist forming process in which a resist is formed by exposing only the bonding pad, and a resin material mixed with a heat-resistant conductive substance is filled into the opening of the resist where the bonding pad is exposed, and the resin material is placed on the bonding pad. A resin material filling step to form a layer, a resist removal step to remove the resist except for the resin material layer, and a firing treatment to sinter the resin material layer and sinter a heat-resistant conductive substance to form bumps. The method is characterized by comprising the following steps.

In such a technical means, a photoresist material is preferable as the resist material in the resist forming step since it is necessary to open the portion of the resist where the bonding pad is provided. Note that it does not matter whether it is a positive type or a negative type. Further, since the height of the bump is determined depending on the thickness of the resist to be formed, it is desirable to form a resist with a certain thickness. As this forming method, for example, a method as described in F below can be adopted. That is, a thick first photoresist film is formed on the entire surface of the substrate, and a spin-on photoresist film is formed on this first seventh photoresist film.
After forming an oxygen-impermeable intermediate film made of Sio2 by the SOG method, a thin second photoresist film is formed on this intermediate film. Next, an exposure process is performed through a glass mask to selectively remove the second photoresist film and the intermediate film in the portions corresponding to the bonding pads, and then reactive ion etching (reactive ion etching) with less lateral etching is performed. A thick resist layer can be formed by removing the exposed first photoresist film by the RIE method. However, it goes without saying that there are other suitable methods than this method, and the present invention should not be construed as being limited to this method. Further, as for this resist, if there is a resist provided when forming a group of semiconductor elements on a substrate or forming various electrodes, it goes without saying that the resist may also be used. After that, a bonding pad is opened in a protective manner using this resist pattern as a mask.

Next, the resin material to be filled into the openings of the resist is a resin material mixed with a heat-resistant conductive substance, for example, a metal such as silver or palladium (Pd). There are basest etc. Further, as a method for filling the resin material into the opening, for example, the following method can be used. That is, a resin material mixed with a heat-resistant conductive material is made into a paste,
This is a method of injecting this into the opening by means such as a screen middle column method, and lapping to remove excess resin material and filling.

Next, the resin material is pre-baked at a low temperature and the resist film is removed. In this case, temporary firing can be omitted depending on the type of resin material used. This is a method in which the resin material is fired at a high temperature to form predetermined bumps.

Note that the conventional method can be applied as is to connect a wiring member such as a gold plate to this bump. Further, there is no particular restriction on the scope of application of this technical means, and it is naturally applicable to, for example, MO8 type semiconductor devices or bipolar type semiconductor devices.

[Operation] According to the technical means described above, by filling the openings of the resist with a resin material mixed with a heat-resistant conductive substance, the bump-forming resin material layer is reliably placed on the bonding pad. Therefore, bumps can be reliably formed on predetermined bonding pads without causing any positional shift during the next resist removal process and baking process.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a perspective view of a bump (1) formed according to this embodiment. First, as shown in FIG. ) on which an aluminum bonding pad (3) is placed.
Next, after oxidizing the substrate surface to form an insulating oxide film (4), a spinner device is used to apply No. 7 odd resist material (positive resist material manufactured by Tokyo Ohka Co., Ltd., trade name 0FPR).
-800) to a thickness of about 1 to 2 μm, and the first photoresist It! (5) is formed. Next, an oxygen-impermeable intermediate film (6) composed of 5 in 2 is formed on the surface of the first seventh odd resist film (5) by the SOG method, and a near odd resist material (Tokyo) is formed on the surface using a spinner device. Positive resist material manufactured by Ohkasha Product name TSHR-8700
) to a thickness of about 0.5 μm and apply the second photoresist! I
! (7) is formed.

Then, as shown in Figure 2(B), a glass mask (8
), pattern exposure of ultraviolet rays was applied to the surface of the substrate (2) for about 30 milliseconds using an aligner device, and the irradiated portions of the near photoresist film (7) were changed into a property that could be dissolved by a developing material. After that, as shown in FIG. 2(C), the altered portion of the second photoresist film (7) and the intermediate film (6) on the lower surface thereof are treated with a developing material (Nonmetal Developer trade name 8140-3 manufactured by Tokyo Ohka Co., Ltd.). Dissolve and remove.

Next, as shown in FIG. 2(D), R
After removing the exposed first photoresist film (5) by the IE method, the exposed insulating oxide 11 (4) is removed using a buffered hydrofluoric acid solution (buffered HF) as shown in FIG. 2(E). It is etched and removed to expose the bonding butt (3) as shown in FIG. 2(F).

Then, as shown in FIGS. 2(G) to (H), an epoxy resin paste (10) containing silver is placed on the surface of the substrate (2).
The paste (10) is injected into the opening (9) of the first photoresist film (5) using a screen middle column method, and the surface is lapped with an abrasive to form the first seventh photoresist film ( 5) Remove the paste (10) on the surface.

Next, after pre-baking the paste (10) at about 150°C, the substrate was immersed in an alkaline solution to peel off the first photoresist, IIW (5), and then heated at 200-300°C. Main firing was performed to form bumps (1) as shown in FIG. 2 (1).

As described above, the method of this embodiment has the advantage that the number of steps is smaller than the conventional method of forming bumps using the plating method, and bumps can be easily formed. This method has the advantage of being able to be miniaturized because it can be combined with the other bonding pads, and also has the advantage of being able to reliably form bumps on predetermined bonding pads, compared to conventional transfer methods.

[Effects of the Invention] As described above, the present invention reliably forms a bump-forming resin material layer on a bonding pad by filling the openings of a resist with a resin material mixed with a heat-resistant conductive substance. Therefore, it becomes possible to reliably form a bump on a predetermined bonding pad without causing positional shift in the next resist removal step and baking step.

Therefore, the present invention has the effect that a predetermined bump can be formed easily and with high precision, and also has the effect of further promoting miniaturization of semiconductor devices.

[Brief explanation of the drawing]

1 and 2 show an embodiment of the present invention, FIG. 1 is a perspective view of a bump formed by the method of the embodiment, and FIGS. 3 and 4 are schematic partial sectional views of a semiconductor device, FIG. 5 is a perspective view of a bonding pad, and FIG.
Figures (A) to (D) are process explanatory diagrams of the thermocompression bonding method, Figure 7 is a perspective view of the bonding pad after bonding, Figure 8 (A) is a perspective view of the bump formed by the conventional method, and Figure 8 (A) is a perspective view of the bump formed by the conventional method. 88(B) is a sectional view taken along line B-B in FIG. 8(A);
FIG. 9 is an explanatory diagram of a method of fusing metal oil to the bumps,
FIGS. 10(A) to 10(F) are explanatory views of the process of forming bumps by the plating method. [Description of symbols (1)... Bump (2) "... Substrate (3)... Bonding pad (5)... First photoresist film (10)... Paste patent applicant Fuji Xerox Co., Ltd. Representative Patent Attorney Tomohiro Nakamura (3 others) Figure 1 Figure 2 Figure 5: First photoresist film Figure 2 Figure 3 Figure 5 Figure 6 (A) CB ) (C) (D) Figure 7 Figure 8 (A) Figure 8 (8) Figure 9

Claims (1)

[Scope of Claims] A method for forming a bump which is disposed on a bonding pad provided on a surface of a semiconductor substrate and which attaches the other end of a wiring member whose one end is connected to an external extraction electrode, A resist forming process in which a resist is formed by exposing only the bonding pad, and a resin material mixed with a heat-resistant conductive substance is filled into the opening of the resist where the bonding pad is exposed, and a resin material layer is formed on the bonding pad. A resist removal step of removing the resist except for the resin material layer; A firing treatment step of firing the resin material layer and sintering a heat-resistant conductive substance to form bumps. A method for forming bumps in a semiconductor device, comprising the steps of: