JPS614248A - Forming method of bump electrode - Google Patents

Abstract

PURPOSE:To make it possible to form a homogeneous bump electrode, by forming a shorting electrode, which shorts both semiconductor layers, on the first insulating film protecting the P-N junction between the P type and N type semiconductor layers, thereafter flowing a plating current to the shorting electrode, and forming the bump electrode. CONSTITUTION:Parts of a first insulating film 6 on a P<-> type semiconductor layer 2 and an N type semiconductor layer 3 are partially removed and window holes 20 and 21 are formed. Then, on the insulating film 6 between both window holes 20 and 21, a shorting electrode 22 comprising a Ti-Ag evaporated thin film and the like is deposited and formed. Thus the N type semiconducutor layer 3 and the P type semiconductor layer 2 are shorted. The specified part of the shorting electrode on the N type semiconductor layer 3 is made to remain, and a second insulating film 23 is deposited. A negative voltage is applied to the back surface of a P<+> type semiconductor substrate 1 in Ag plating liquid. A positive voltage is applied to an Ag plate 24 in the Ag plating liquid. Then, the plating current I does not flow in an N-P junction part but flows through the P<-> semiconductor layer 2 and the P<+> type semiconductor layer 1 from the shorting electrode 22. Positive Ag ions are attached to the exposed surface of the shorting electrode 22. A bump electrode 5' is grown and formed.

Description

[Detailed Description of the Invention] The present invention relates to a method of forming a bump electrode, and particularly to a method for forming a bump electrode, for example, N
The present invention relates to a method for forming a bump electrode on an N-type anode of a P-type anode and a P-type cathode type diode.

Most common diodes, such as constant voltage diodes, have a P-type anode and an N-type cathode, and the P-type anode is formed with an Ag bump electrode. The bump electrode in this N-type cathode type diode can be easily formed with a uniform size by applying a plating current in the forward direction of the PN junction, by depositing Ag positive ions on the anode side.

By the way, the above types of diodes are limited in their ability to improve temperature characteristics and reduce noise, so N-type anode and P-type cathode types have been developed as highly reliable diodes with improved temperature and noise characteristics. , some have been put into practical use as punch-through diodes. The basic structure of this P-type cathode type diode is shown in FIG. 4, and an example of the structure of the punch-through type diode is shown in FIG. 5, and will be explained in sequence below.

In Fig. 4, (1) is a P+ type semiconductor substrate with a high impurity concentration, (2) is a P'' type semiconductor layer with a low impurity concentration epitaxially grown on the P+ type semiconductor substrate (1), and (3) is a P+ type semiconductor layer with a low impurity concentration.
is an N-type semiconductor layer formed by selectively diffusing N-type impurities into the surface layer of a P-type semiconductor N(2), and (4) is a P-type semiconductor base layer.
@(1') is a back electrode formed in ohmic contact with the back surface, (5) is an Ag bump electrode formed in ohmic contact on the N-type semiconductor layer (3), and (6) is an NP junction. (7) This is an insulating film that insulates and protects the surface. The bump electrode (5) is made by applying a reverse voltage to the NP junction (7) to cause it to break down, and then passing a plating current in the opposite direction to deposit and grow 41 Ag positive ions on the N-type semiconductor layer (3). It is formed.

The bunch-through diode of the fifth vIl utilizes the C-B withstand voltage of an NPN transistor. type semiconductor layer, (10) is N
A P-type semiconductor layer partially formed on the surface layer of the −-type semiconductor layer (9), (11) an N-type semiconductor layer partially formed on the surface layer of the P-type semiconductor layer (10), and (12) The back electrode (13) is formed in ohmic contact with the back surface of the N-type semiconductor substrate (8), and the bump (13) is formed in ohmic contact on the N-type semiconductor layer (11). ′! pole, (14) is N-
type semiconductor 1if (9) and P type semiconductor layer (10) noP
N junction i (15) formed on the surface (9) −(
10) An electrode for short-circuiting between the electrodes, (16) is an insulating film. The bump electrode (13) is formed by applying a reverse voltage to the NP junction (17) between the P+ type semiconductor M (10) and the N type semiconductor layer (11) and passing a plating current in the opposite direction.

When a positive voltage is applied to the bump electrode (13) and a negative voltage is applied to the back electrode (12) of this bunch-through diode, the depletion Jit (1B ) extends, and this becomes the electrode (
14) When it reaches 14, it's bantisuru. - causes a breakdown. In this case, since the P type semiconductor layer (10) and the N- type semiconductor layer (9) have the same potential, the P type semiconductor Fi! (1
0), no minority carriers are injected into the N- type semiconductor layer (9), and as a result, a diode with good temperature characteristics and low noise can be obtained. The characteristics of such a bunch-through diode are disclosed in, for example, Japanese Patent Publication No. 30708 of 1982.

By the way, the formation of the anode bump electrode in the N-type anode and P-type cathode type diode described above is carried out by placing a large number of bump electrodes at once on a semiconductor wafer after impurity selection and dispersion has been completed. It will be done as follows. In this case, this is done by applying a voltage in the opposite direction to a large number of N-p junctions in the semiconductor wafer all at once to break down the NP junctions and causing current to flow in the opposite direction. There are variations in the breakdown voltage of the bump electrodes, and the height of the bump electrodes grown depending on the breakdown voltage may vary. In addition, there are many NP' junctions formed in the semiconductor wafer. l-l・
I. If there are any defects, defects may occur during bump electrode formation.
Since the current flows concentrated in the P junction, a bump electrode is formed only at the defective NP junction and does not swell anywhere else, but even if it swells, it shrinks and is too small to be of any practical use. There was such a problem.

The present invention has been made in view of the above-mentioned problems in forming bump electrodes of N-type anode and P-type cathode type diodes. In the method of forming a bump electrode on an N-type semiconductor layer, the P
A step of forming a shorting electrode for shorting the amphibic conductor layer on the first insulating film that protects the PN junction between the semiconductor layer and the N-type semiconductor layer; a step of applying a plating current to the exposed short electrode to form a bump electrode; and a step of selectively removing the short electrode to break the electrical connection between the bidirectional conductor layer. There is a patent 'which is characterized in that the bump 11w5 is formed by

Last month - The formation of bump electrodes using this technical means is performed at the stage of a semiconductor wafer in large numbers, and each bump electrode is grown by the current flowing through the short electrodes formed in large numbers on the semiconductor wafer, forming a diode. NPs forming
It is formed regardless of the magnitude of the breakdown voltage of the joint. Therefore, uniform /Nl pump electrode formation is possible.

Embodiments Specific embodiments of the method of the present invention will be described from section 7 onwards with reference to FIGS. 1 to 3.

FIGS. 1A to 1F show an example of the process of forming bump electrodes of the N-type anode and P-type cathode cube die of the basic structure shown in FIG. 4 according to the present invention. The same reference numerals are given to the same items as (a) to (a) in Figure 1.
)).

First, as shown in (a) in Figure 1, the first insulating film (
The portions above the N-type semiconductor layer (2) and the N-type semiconductor layer (3) in step 6) are partially removed to form window holes (20) and (21). Next, as shown in Figure 1 (b), both window holes (20
), (21) and a part or all of the insulating film (6) between the window holes (20), (21) by depositing a short electrode (22) made of a Ti-Ag vapor deposited thin film or the like. Then, the N-type semiconductor rfi (3) and the P-type semiconductor layer (2) are short-circuited. Next, as shown in Figure 1 (c), short 1! A short electrode ti (2
2) 5102.5I by CVD on the rejection membrane (6)
A second insulating film (23) such as 9N4 or polysilicon is deposited.

After that, as shown in (d) in Figure 1, a negative voltage is applied to the back surface of the P-type semiconductor substrate (1) in the Ag plating solution, and a positive voltage is applied to the Ag plate (24) in the Ag plating solution. Apply voltage. Then, since both semiconductor layers (3) and (2) are shorted by the short electrode (22), the plating current I becomes N.
It does not flow through the P junction but flows from the short electrode (22) to the P'' type semi-conductor layer (1) and through the P ten type semiconductor layer (1), thereby causing Ag plalow ions to form on the exposed surface of the short electrode (22). is deposited and a bump electrode (5°) grows. This bump electrode (5°) grows uniformly regardless of the variation in breakdown voltage of the NP junction. In addition, this bump electrode formation is performed all at once on many NP junctions provided on one semiconductor wafer, but even if one NP junction causes a short electrode, the plating current will not flow through the short electrode. Therefore, there is no fear of current concentration at this defective NP junction, and the process can be performed satisfactorily.

After forming the bump electrode (5°), next is the short electrode (22
) to selectively remove unnecessary parts. This removal can be done by using CVD with hydrochloric acid or the like without using a special resist, using the bump electrode (5') as a cover during etching.
The second insulating film (23) and the short electrode (22
) or remove the Ti in the short electrode (2) using nitric acid, etc.
2) Step of removing 8g in the middle, or (e) and (e) in Figure 1
As shown in (e) of Figure 1, this is done in the process of removing only the minimum amount necessary using a resist cover. In other words, first, as shown in (e) of Figure 1, the bump electrode (5') and the insulating film ( 2
3) After applying the resist cover (25) over the entire area, open a window in the vicinity of the bump electrode of the resist cover (25) to form a window hole (26). ), the insulating film (23) is partially removed by etching.

Next, the short electrode (22) is partially etched and removed as shown in FIG. At this stage, the N-type semiconductor layer (3) and the P-type semiconductor layer (
The short circuit 2) is removed and the desired diode is obtained.

Next, the method of the present invention applied to manufacturing the punch-through diode shown in FIG. 5 will be described below with reference to FIGS. 2A to 2E.

First, as shown in FIG. 2(A), the N of the insulating film (16) is
Window holes (28) and (29) are formed on the type semiconductor layer (11) and on the surface of the PN junction (15). In addition, the PN junction (
A medium-sized P impurity region (30) with a high impurity concentration is previously formed on the surface portion of the electrode 15) to improve the ohmic relationship with the subsequent short electrode, and to be used as a bypass region for the plating current. Next, as shown in Figure 2 (b), the window hole (28), (
29) and the first insulating film (1) between the window holes (28) and (29).
6) Form a short electrode (31) on top. Next, as shown in Figure 2 (c), short electrode (31) and insulation f! ii (16) 5i02 on the entire surface with CVD
After depositing the second insulating film (32) such as N-type semiconductor Jti? (11) A window hole (33) is formed by selectively removing the portion on which the bump electrode is to be formed.

After that, as shown in Figure 2 (d), N was added in the plating solution.
A negative voltage is applied to the green semiconductor substrate (8) and a positive voltage is applied to the Ag plate (34) in the plating solution. Then, from the short electrode (31), (30) - (9) - (8)
A plating current I flows through the path, and a bump electrode (13') grows inside the window hole (33). After that, short electrode (31
) are removed using the method described above. For example, as shown in FIG. 2 (e), the bump electrode (31) is used as a resist cover, and all of the insulation IJ (32) and the short electrode (31) except the one directly under the bump electrode (13') They can be removed by sequential etching. In this case, the bump electrode (13') is slightly etched by the etching solution (hydric acid, nitric acid, etc.) for the short electrode (31), but the thickness of the short electrode (31) is at most 100 m.
Bump electrode (13')
The height is about 50 μm or more, and there is a large difference between the two, so there is no problem.

The present invention is not limited to the above-mentioned embodiments, and in particular, the formation of short electrodes may be performed as follows. For example, in the short electrode forming step shown in (b) of FIG. 1, the central portion of the short electrode (22) on the N-type semiconductor layer (3) is selectively removed as shown in FIG. When the bump electrode is formed after the short electrode is formed in this way, the window hole of the short electrode (22) (
34) By concentrating the electric field at the edges, the bump electrode (5”°) that grows will swell higher in the center and have a good mountain-shaped shape.Also, although not shown, the short electrode for forming the bump electrode is not necessarily It is not necessary to form the ζ over 360 degrees; for example, the portion to be removed later may be formed in advance into a thin line so that later removal by etching or the like can be done easily and quickly.

According to the present invention, the bump electrode of the N-type anode in the N-type anode, P-type cathode type diode, etc. can be made to the same level as the bump electrode of the P-type anode-F, N-type Ka-r type diode. It can be uniformly formed in a desired shape, making it easy for N-type anode and P-type cathode type diodes to be used in many fields.

[Brief explanation of the drawing]

1 and 2 are manufacturing process cross-sectional views for explaining manufacturing methods of different embodiments of the present invention, and FIG.
Cross-sectional views showing examples of changes in some of the steps in the figure, Figures 4 and 5 +v! J is a basic cross-sectional view and a practical cross-sectional view of a diode to which the manufacturing method of the present invention is applied. (2) -P-type semiconductor layer, (3) -...N-type semiconductor layer, (5), (5'), (5'''>-bump electrode, (6
)--first insulating film, (10)--P-type semiconductor layer,
(11) - N-type semiconductor layer, (13), (13'') - bump electrode, (16) - first insulating film, (22) - short electrode, (23) - second insulating film, (31)-
・-Short electrode, (32) -Second insulating film, I-・
Plating current.

Claims (1)

[Claims] (1) In a method of forming a bump electrode on an N-type semiconductor layer partially formed on the surface layer of a P-type semiconductor layer, the P
forming a shorting electrode for shorting both semiconductor layers on a first insulating film that protects the PN junction between the semiconductor layer and the N-type semiconductor layer; a step of covering with a second insulating film;
A bump electrode comprising the steps of: forming a bump electrode by passing a plating current through the exposed short electrode; and selectively removing the short electrode to disconnect the electrical connection between the two semiconductor layers. Formation method.