JPH023930A - Manufacture of multilayer electrode in semiconductor device - Google Patents

Abstract

PURPOSE:To prevent the permeation of metal constituting a second metal electrode into the lower part material by forming a first layer at a deposition rate smaller than a second layer, forming the first layer thicker than the second layer, and blocking the pass of the metal constituting the second metal electrode layer. CONSTITUTION:Cr layers 5a, 5b on an Al layer 4 side are subjected to vapor deposition at a comparatively small deposition rate, and a Cr layer 5c adjacent to a Cu layer 6 is subjected to vapor deposition at a comparatively large deposition rate. That is, the vacuum deposition is performed as follows: when the Cr layers 5a, 5b are formed, a beam current value is made small, and when the Cr layer 5c is formed, the beam current value is made large. Since the Cr layer 5b with a thickness formed at a reduced deposition rate is arranged in this manner, Cu diffusion from the Cu layer 6 to the Al layer 4 can be decreased, thereby increasing the adhesion between the Al layer 4 and an SiO2 layer 2, and preventing the exfoliation of this part.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a multilayer electrode in a semiconductor device, and more particularly, to a method for manufacturing a multilayer electrode in a semiconductor device in which at least two metal electrode layers made of different materials are laminated. The present invention relates to a method for manufacturing an electrode.

[Prior Art and Problems to be Solved by the Invention] The bump electrode (C protrusion (I electrode)) of a flip chip has a multilayer polar structure in which metal electrode layers made of different materials are stacked one on top of the other. The poles of the conventional bang are sequentially vacuum-deposited on the soil of the 5iQ2 film (silicon oxide layer) compounded on the ± of the silicon conductor area. (Rem)N1.Consists of a Cu (copper) layer, a thick Cu layer formed on the Cu layer by Km plating, and a Ushida layer further formed on it.The A1 layer is a bump electrode. There is a wiring pole layer 1 which is in orbital contact with the semiconductor region at a distance from the bump. There is also a case where the AI field is in orbital contact with the conductor area directly under the bump ik pole.C.
The U layer is a gold elliptical layer to ensure good soldering.

Further, the Cr layer is a buffer gold layer that improves the connection between the A1 layer and the Cu layer.

Bumps [f& are required to have particularly high tensile strength, but conventionally this type of multilayer 1! In the case of poles, there was a relatively high frequency of cases in which the specified tensile strength could not be obtained. In particular, many peelings were observed at the interface between the wiring electrode layer (AI layer) and the 5iU2 film. The cause of this is that the metal (Cu) that makes up the gold elliptical layer (Cu7m) is so strong that the sofa gold! The wiring electrode re (A, 1
layer) in a fairly large amount, and the wiring'! ! This is because the adhesive strength between the i-polar island (A1 layer) and the S lo2 film decreases. If heavy metals such as Cu'PAu (gold) are used as the metal for Ushida Tsuke, if those metals diffuse into the Ushida conductor area, it may cause property deterioration.

By the way, in Japanese Patent Application Laid-Open No. 54-92176.

In a multilayer electrode structure in which a KAI layer is formed on top of tantalum (tantalum) 1-, AI of AIJ- is 'I'a ff
It has been disclosed that an A1 layer containing a large amount of aluminum oxide is formed on the Ta layer side of the Al/- in order to suppress the diffusion of the aluminum oxide into the F layer.
It may be combined with a structure formed in a Ta layer containing a large amount of total tantalum oxide on the A1 layer side of the layer. The formation of a metal layer containing a large amount of these oxides is caused by moisture and oxygen quickly entering the vacuum chamber during vacuum deposition (as a result, the pressure in the vacuum chamber increases), and deposition in a relatively highly oxidizing atmosphere. I do. Before and after this evaporation, all the evaporation steps contain almost no oxide, so after all the evaporation steps are carried out while keeping the pressure in the vacuum chamber at a predetermined non-vacuum state, the pressure in the vacuum chamber is The pressure is increased, and then the pressure in the vacuum chamber is brought back to a predetermined high vacuum state to complete the process.

When the invention disclosed in the above-mentioned publication is applied to the formation of bump electrodes of 7 lithographic chips, the layer adjacent to the Cr layer of the Cu layer formed by vacuum evaporation is made of Cu containing a large amount of copper oxide.
If necessary, a layer of the Cr layer in contact with the Cu layer and Va may also be formed as a Cr layer containing a large amount of chromium oxide. However, when the Cu layer and Cr layer made of different metals are formed in this way, the adhesive strength between the Cu layer and the Cr layer decreases, and as a result, the tensile strength required for the bump 111 pole cannot be achieved. . Moreover, changing the pressure inside the vacuum chamber during vacuum deposition is difficult to control and takes more time, which is not ideal for "vacuum deposition."

Therefore, the object of the present invention is to provide multilayer II with high sea-opening adhesive strength.
The object of the present invention is to provide a method for manufacturing poles with good mass productivity.

[Means to solve the problem]

To achieve the above object, the present invention provides a semiconductor device in which at least a first metal electrode layer and a second metal electrode layer made of a material different from the first metal electrode layer are successively formed adjacent to each other.
In the method for manufacturing a 1 m pole, a first layer that is a part of the first metal electrode layer is formed by a vacuum evaporation method to a first thickness at a first evaporation rate, and the first layer is a part of the first metal electrode layer. A second layer, which is another part of the layer, is deposited on the first layer to a second thickness thinner than the first thickness at a second deposition rate that is greater than the first deposition rate. formed by and then,
The present invention relates to a method for manufacturing a multilayer electrode in a semiconductor device, characterized in that the second metal electrode layer is formed on the second layer.

In addition, to explain the correspondence relationship between the above invention and the embodiments, the first metal electrode layer is the Cr layer 5, and the first layer is the first and second Cr layers 5a and 5b. The layer is the third Cr
This is layer 5c. Second gold IWiI! The pole layer is the Cu layer 6.

[For production]

The second layer in the above invention is formed at a higher deposition rate than the first layer, so it is laminated with the second gold 1iJ electrode layer with greater adhesive strength than the first layer. .

The first J- layer is formed at a lower deposition rate than the second layer and is thicker than the second layer, so the second layer is less dense than the second layer. It has a great effect on preventing the metals that make up the structure from passing through. For this reason, the first
The second metal 1 in the lower evil material of the metal electrode layer! The occurrence of defects caused by penetration of the metal constituting the pole layer is suppressed.

〔Example〕

The bump electrode according to the 15iIIIc embodiment of the present invention and its manufacturing method will be described below.

The bump electrode 1 in FIG. 2 is formed on a thermally oxidized Si02 film 3 which is coated on a semiconductor region 2 made of silicon, an AlNd, and a Cr layer 5. Cu layer 6, 7
, and has a multilayer structure consisting of solder layers 8.

In fabricating the bump electrode 1, first, the A1 layer 4 is formed on the SiO2 film 6 as a t-pole layer. 41 Layer 4 connects the bump to the bottom layer of pole 1 and semiconductor tilted wall 2.
It is emitted from the part that is in ohmic contact with the (not shown) and the part that connects them.

The A1 layer 4 is vacuum-deposited over the entire surface and then formed into a desired pattern by photo-etching. AI/? #4
The thickness is approximately 1 μm. 41 Layer 4 was vacuum deposited using the well-known electron impact method (electron beam evaporation method).
First, a semiconductor substrate as a deposition target and an Aj plate as a thin film material are placed facing each other in a vacuum chamber (Pelger) maintained at a predetermined pressure (approximately 1 Q Torr). Next, A
The I plate is irradiated with an electron beam and heated to evaporate the AI material. The evaporated A1 molecules or AI atoms scatter to the semiconductor substrate and condense on its surface to form an A1 layer.

Next, a protective film 9 made of quartz glass is formed on the upper surface of the A1 layer 4 by sputtering. Note that the protective film 9 is formed on the entire surface, and then the openings 10 are formed by photo-etching with the bumps corresponding to the locations where the poles 1 are to be formed.

Next, a Cr layer and a Uu layer are formed on the entire surface by next nitride deposition, and the opening 10 portion is left by etching 7, and the 01 layer and 5.0 layer are etched. A Cu layer 6 is formed. Cr) *5. The vacuum M of the Cu layer B was also measured by the piezoelectric impact method as with the A1 layer 4.
The Cr layer 5 and the Cu layer 6 are electrically connected to the 41 layer 4 through the opening 10. The thickness of the Cu layer 5 is approximately 3 μm. The thickness of Cr/ii5 will be described later.

Next, to ensure the height of the bump electrode 1.

On the top of Uu 1m 6! A CuHz7 layer with a thickness of about 30 μm is selectively formed by plating. Subsequently, a hemispherical solder layer 8 is provided on the upper surface of the CuI plate 7 by placing and melting a solder dip or a solder ball.

The above explanation is the same as the conventional manufacturing method for 11 bump poles. The difference between this embodiment and the conventional example is that the 01 layer 5, which is a buffer metal layer, is changed in deposition rate and thickness to the first, second and third 01 layers 5a as shown in FIG.

The reason is that 5b and 5cK were formed separately. R mouth.

The first and second 01 layers 5a and 5b on the side of the AI layer 4 are completely deposited at a relatively low deposition rate, and the third Cr layer 5c adjacent to the Cu layer 6 is deposited at a relatively high deposition rate. vacuum evaporate. In this example, the first. second and third Cr/1I
5a, 5b, and 5c were deposited every minute. The vapor deposition rate is controlled by changing the beam current value of the electron beam that is made to collide with the Cr material as the thin film material. That is, the first and second 01 layers 5a.

When forming 5b, reduce the beam current value.

When forming the third Cr layer 5C, the beam current value is increased and vacuum evaporation is performed. The thickness of the second Cr layer 5b is the same as that of the first Cr layer 5b.
and the thickness of the third 01 layers 5a, 5c (in this example, the first, second and third 01 layers 5a, 5b, 5c
The cleanliness of each is tz500A.

They are 3500A and 500A.

The bump electrode of this example has the following effects.

fi+ Thick second O formed by reducing the deposition rate
By throwing the Cr layer 5b, A1 from the Cu layer 6
The total diffusion of Cu into layer 4 can be reduced.

The degree of adhesion between the 41 layer 4 and the 5102 film 2 is controlled, and peeling at this point can be prevented. This mechanism is as follows. When the pressure inside the vacuum chamber is lowered to about 110 Torr during vacuum deposition.

The residual gas contains a relatively large amount of Hz0 (moisture). Since Cr is a highly active metal, a portion of Cr reacts with this Hz O to generate chromium oxide and Hz (hydrogen) gas. In fact, analysis of the residual gas in the vacuum chamber shows that as Cr deposition progresses, Hz0 decreases and H
It is recognized that z increases.

In this way, the first step was performed using vacuum evaporation at a lower evaporation speed.
The second 01 layers 5a and 5b have a high degree of oxidation, and the sixth Cr layer 5c, which is vacuum-deposited at a high deposition rate, has a low degree of oxidation.

Although the relationship between the degree of oxidation and the inhibition of CU diffusion is not clear, 1
Let's think about it as follows. Chromium oxide, which is produced by oxidation, is present at the grain boundaries of the minute Cr particles that make up the Cr layer, and the presence of this chromium oxide prevents the diffusion of CU, which would otherwise proceed through the grain boundaries. It works even better. Therefore, the second Cr layer 5b, which is highly oxidized, has a greater ability to completely inhibit Cu diffusion than the sixth Cr layer 5C, which is less oxidized.

Of course, the first Or layer 5a is also the third Cr layer 5c!
It is mainly the second C layer 5b that has a large ability to inhibit the diffusion of 1 lcu, but reduces the diffusion of Cu in terms of the degree of oxidation and thickness. In this example, it was confirmed by Auger analysis that the Cu content of the A1A1 layer was significantly reduced compared to the conventional one.

(2(3rd Cr J so 5 including @ contact part with Cυ layer
C is vacuum deposited to increase the deposition rate and reduce the degree of oxidation. Therefore, the adhesive strength with the CU layer 6 is high. Note that when the Cr layer 5 is formed at a lower deposition rate over the entire thickness, the effect of inhibiting Cu diffusion can be increased, but the adhesive strength between the 01 layer 5 and the CuJ layer 6 is reduced.

(31 The rate of vacuum deposition of the first 01 layer 5a is
It is larger than /15b. Therefore, the first 0
The difference Ng1 degree between the 1st layer 5a and the 41st layer 4 is large.

However, since the adhesion between the Cr layer and the A1 layer is relatively good, the deposition rate of the first 01 layer 5a is set lower than that of the third Cr layer 5c.

(41 By keeping the deposition rate approximately constant and controlling the H20 content by changing the pressure in the vacuum chamber, it is possible to obtain the CR layers 5a, 5b, and 5c having the same effects as above. When forming the second 01 layers 5a and 5b, the pressure in the vacuum chamber is increased, and when forming the third Cr layer 5c, the pressure inside the vacuum chamber is decreased and vacuum evaporation is performed. In mass production, it is difficult to change the internal pressure rapidly and greatly.In this respect, the method of the embodiment in which the film quality of the CR layer 5 is controlled by the vapor deposition rate is highly practical. Even if the pressure is not changed to the extreme layer, the pressure in the Makabe tank increases gradually from the deposition of the first layer to the deposition of the second and sixth layers. However, this is negligible. .

[Modified example]

The present invention is not limited to the above-mentioned actual example, but can be modified as follows.

ill The adhesion between the A1 layer and the Cr layer is relatively good, so the first C layer acts as an adhesive layer with the 41 layer 4.
The r layer 5aOM may be formed at the same deposition rate as the second Or layer 5b. In other words, the 01 layer 5 may be vacuum-deposited at different deposition rates to form a two-dimensional structure. Moreover, it is good also as four or more layers. In this case, the region including the adhesive portion with the 01 layer 6 is vacuum-deposited at a high deposition rate, and the region of two or more layers located below this axis is vacuum-deposited at a low deposition rate.

(2) 01 layer 5 by continuously changing the steaming speed 7#I
may be formed. For example, start with a medium evaporation rate, gradually reduce the evaporation rate to 1, then keep it constant at a low evaporation rate, then gradually reduce the evaporation rate to a high evaporation rate to form the 01 layer 5. finish.

13. What is the pressure in the vacuum chamber? ! ! 01 as constant
It is convenient to carry out a true wall deposition of layer 5. However, the method of controlling the degree of oxidation of the 01 layer 5 by changing the deposition rate is the main method, and the method of controlling the content of HtO in the vacuum chamber by slightly changing the pressure in the vacuum chamber may be combined as an auxiliary method. .

+41 For production, use Aυ (gold), Ag (silver), I'yi (nickel), etc. as the metal layer, and use the buffer electrode or buffer as the pole! Even when Ti (titanium) or the like is used as the electrode, the present invention is effective if the 71 layer is formed like the 01 layer 5.

(51 Even if the first metal electrode field is adjacent to the semiconductor thin wire, when peeling between the first metal! pole layer and the semiconductor @ castle is a problem, or the second metal '11! @ IN 1. The present invention is effective when deterioration of characteristics due to metal penetration into semiconductor thin wires becomes a problem.

Further, even in a structure where the first gold F4 electrode layer is adjacent to an insulator, the present invention is effective when PJ-like peeling and deterioration of IP quality are a problem.

(The present invention is particularly effective when used as poles for bumps that require a high mechanical strength of 61%, but it can also be applied to poles for multi-layered pads constituting wire honting pads, for example.

〔Effect of the invention〕

As described above, the present invention provides a highly practical multi-layer conductor device that has high tensile strength, is highly reliable, and does not cause deterioration of electrical characteristics.
') It can be provided by 5 methods.

[Brief explanation of the drawing]

FIG. 1 is a partially enlarged sectional view of a bump electrode according to an embodiment of the present invention. FIG. 2 is a sectional view showing a bump electrode of one embodiment. ,! 1=AI layer, 5-Cr h, 5 a=-1st
Cr1iii, 5b... second Cr layer, 5c...
Third Cr layer, 6...Cu layer. Agent Nori Takano Figure 1 Figure 2

Claims (1)

[Scope of Claims] [1] A method for manufacturing a multilayer electrode in a semiconductor device in which at least a first metal electrode layer and a second metal electrode layer made of a material different from the first metal electrode layer are successively formed adjacent to each other, comprising: a first layer that is a part of the first metal electrode layer is formed by a vacuum evaporation method to a first thickness at a first evaporation rate; forming a second layer on the first layer to a second thickness thinner than the first thickness at a second deposition rate higher than the first deposition rate; . A method for manufacturing a multilayer electrode in a semiconductor device, comprising forming the second metal electrode layer on the second layer.