JPH08203895A - Method for filling hole by high pressure reflow - Google Patents

Abstract

PURPOSE: To fill a contact hole with a part of metal film by high pressure reflow by making the contact hole such that the contact resistance is not increased. CONSTITUTION: A plurality of contact holes 14 are made through an insulation film 13 for one electrical connection. Minimum diameter of each contact hole 14 (14a-14d) is set smaller than the thickness of a metal film 16 deposited on the insulation film 13. The metal film 16 is then deposited on the insulation film 13 while leaving a space in each contact hole 14a-14d and then pressure is applied to the surface of the metal film 16 so that a part of the metal film 16 is pushed into each contact hole 14a-14d thus filling each contact hole 14a-14d with a part of the metal film 16. Minimum diameter of the plurality of contact holes 14a-14d is preferably set at 0.6μm or less.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for filling holes in semiconductor device manufacturing, and more particularly to a method for filling holes by high pressure reflow.

[0002]

2. Description of the Related Art Design rules are becoming finer with the increase in the degree of integration of LSIs. As a result, the aspect ratio of the hole (for example, connection hole) (connection hole depth / connection hole diameter)
As a result, it has become difficult to embed a metal wiring material in the connection hole by the conventional sputtering or CVD method.

If there is a void (a space which is not filled with a metal wiring material and is a space) in the connection hole, the resistance is increased in the via hole and the contact hole, and the electromigration resistance is caused by current concentration in the void portion. Is a concern. Therefore, it is desired to embed the metal wiring material inside the connection hole without generating a void.

A high pressure reflow method has been proposed as a technique for achieving this. In this method, a metal film to be a wiring material is formed on the insulating film by sputtering while leaving a space inside the connection hole. After that, while heating the substrate without exposing it to the atmosphere, the surface of the metal film is pressed in a high-pressure inert gas atmosphere to push a part of the metal film into the inside of the connection hole.

[0005]

However, the above-mentioned high-pressure reflow method has a limitation in forming a metal film on the insulating film while leaving a space inside the connection hole. When the diameter of the connection hole is large, for example, when it exceeds 0.6 μm, as shown in FIG. 2, the opening 114 is formed in the metal film 113 on the connection hole 112 formed in the insulating layer 111. It That is, the internal space of the connection hole 112 and the metal film 1
The space above 13 is in communication. Therefore, even if the high pressure reflow method is performed, a part of the metal film 113 cannot be pushed into the inside of the connection hole 112 by the pressure.

Therefore, if the diameter of the connection hole is reduced, the metal film can be formed in a state where a space is left inside the connection hole and the connection hole is covered, and the high pressure reflow method can be applied. When the connection hole is used as a connection hole for wiring such as a contact hole or a via hole, there arises a problem that the contact resistance is significantly increased.

It is an object of the present invention to provide a method of filling holes by high pressure reflow, which enables formation of holes (for example, connection holes) without increasing contact resistance and enables application of the high pressure reflow method. .

[0008]

SUMMARY OF THE INVENTION The present invention is a method for filling holes by high pressure reflow, which has been made to achieve the above object. That is, a plurality of holes are formed in the insulating film for one electrical connection. At that time, each minimum diameter of each hole is formed smaller than the value of the film thickness of the metal film formed on the insulating film. After that, a space is left in each hole to form a metal film on the insulating film, and then a pressure is applied to the surface of the metal film to push a part of the metal film into each hole, so that each hole is metalized. Embed in part of the membrane. The minimum diameter of each of the plurality of holes is desirably set to a maximum of 0.6 μm or less.

[0009]

In the method of filling holes by high pressure reflow as described above, a plurality of holes are formed in the insulating film for one electrical connection, so that the diameter of each hole can be small. Therefore, the metal film is formed with a space left inside each hole due to the film forming characteristics of the metal film. Then, by performing the high pressure reflow method, a part of the metal film is embedded inside each hole.

Since the minimum diameter of each hole is smaller than the value of the film thickness of the metal film formed on the insulating film, when the metal film is formed, the metal film is surely formed on each hole. To be covered. That is, no opening is formed in the metal film on each hole when the metal film is formed. Therefore, a space is formed inside each hole. If the minimum diameter of each hole is made larger than the value of the film thickness of the metal film, the metal film cannot cover each hole. That is, an opening communicating with the hole is formed in the metal film on each hole. Therefore, the minimum diameter of each hole must be smaller than the thickness of the metal film. Moreover, by setting each minimum diameter of the plurality of holes to 0.6 μm or less,
When the metal film is formed, the holes are surely covered with the metal film.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the manufacturing process chart of FIG.

As shown in FIG. 1A, lower wiring 12 is formed on the substrate 11. The lower layer wiring 12 is
For example, titanium nitride (TiN) layer / aluminum-copper (A
It has a four-layer structure such as 1-Cu alloy layer / titanium nitride (TiN) layer / titanium (Ti) layer. An interlayer insulating film 13 is formed as an insulating film on the substrate 11 so as to cover the lower wiring 11. A plurality of holes, for example, connection holes 14, are formed in the interlayer insulating film 13 for one electrical connection. The diameter of each of the plurality of connection holes 14 is smaller than the thickness of the metal film to be formed on the interlayer insulating film 13. Further, the diameter of the plurality of connection holes 14 needs to be formed to be 0.6 μm or less. Therefore, for example, a metal film of 0.50μ
When forming to a film thickness of m, the diameter is smaller than 0.50 μm. Moreover, the plurality of connection holes 14 must secure the area of the connection portion which is equal to or wider than that in the case where one electrical connection is formed by one connection hole.

Here, each diameter of the plurality of connection holes 14 is set to 0.4.
The number of the plurality of connection holes 14 in the case of 0 μm will be calculated. Now, assuming that one electrical connection is formed by one connection hole having a diameter of 0.80 μm, if this one electrical connection is formed by a plurality of connection holes 14 having a diameter of 0.40 μm, The number of the plurality of connection holes is obtained as follows. First, the area S1 of the connection portion of one connection hole is S1
= Π × (0.8) ² /4=0.16π (μm ² ). On the other hand, the area S2 of each connection portion in the plurality of connection holes 14 having a hole diameter of 0.40 μm is S2 = π × (0.40) ²
/4=0.04π (μm ² ) The area S1 of the connecting portion when one connecting hole is formed and the total area n · S2 of the connecting portion when a plurality of (for example, n) connecting holes are formed are
The relationship of S1 ≦ n · S2 is required. Therefore, the number n of the plurality of connection holes 14 is n ≧ S1 / S2 = 4 (pieces). Therefore, in the above case, as shown in the layout diagram of (2) of FIG. 1, at least four connection holes 14 (14a, 14b,
14c, 14d) may be formed.

Thereafter, as shown in FIG. 1C, a barrier metal layer 15 is formed on the inner walls of the connection holes 14a to 14d by, for example, sputtering. The film forming conditions at this time are, for example, a sputtering gas flow rate of 100 s.
ccm argon (Ar) is used, the pressure of the film forming atmosphere is 0.4 Pa, the substrate temperature is 150 ° C., and the DC power is 4 kW.
Set to. The barrier metal layer 15 may not be necessary depending on the material of the metal film formed later.

Subsequently, a metal film 16 is formed on the surface of the barrier metal layer 15 by sputtering. The metal film 16 is made of, for example, aluminum-copper (Al-Cu),
It is formed of a material used for manufacturing a semiconductor device such as aluminum-silicon-copper (Al-Si-Cu), copper (Cu), and silver (Ag). Here, as an example, Al-Cu
The metal film 16 made of an alloy will be described. The film forming conditions at this time are, for example, a sputtering gas flow rate of 100 sc.
cm of argon (Ar) was used, the pressure of the film forming atmosphere was set to 0.4 Pa, the temperature of the substrate 11 was set to a predetermined temperature within the range of no heating to 500 ° C., and the DC power was set to 20 kW. When the metal film 16 is formed, the connection holes 14a ...
Since 14d has a diameter of 0.40 μm, a space is formed inside each of the connection holes 14a to 14d due to the characteristics of sputtering. That is, each connection hole 14a-14d
The metal film 16 is formed on the insulating film 13 with a space left inside. Moreover, since the pressure of the atmosphere at the time of sputtering is about 0.4 Pa, the space formed in each of the connection holes 14a to 14d is in a state close to vacuum. In addition, in the drawings after (3) above, the connection holes 14c and 14d are not shown because they are hidden behind the connection holes 14a and 14b.

Subsequently, as shown in (4) of FIG.
While heating 1, the pressure is applied to the surface of the metal film 16. The heating temperature at this time is, for example, 150 ° C to 500 ° C.
Is set to a predetermined temperature within the range of, and the pressure to be applied is set to, for example, 1 MPa or more. When the pressure is applied, the inside of each of the connection holes 14a to 14d is in a state close to a vacuum as described above, and since the substrate 11 is heated, a part of the metal film 16 is partially connected to the connection holes 14a to 14d.
Is pushed inside each. As a result, as shown in (5) of FIG.
Embedded by a part of.

In the above embodiment, since a plurality of connection holes 14a-14d are formed in the insulating film 13 for one electrical connection, the connection holes 14a, 14b, 14c,
The diameter of 14d becomes smaller. Moreover, each connection hole 14a-14d
Is formed with a diameter smaller than the thickness value of the metal film 16 formed on the insulating film 13, and each diameter is set to 0.6 μm or less. Therefore, the metal film 16 is formed on the insulating film 13 by sputtering. When formed, each connection hole 14a-14d
The top is surely covered with the metal film 16. Therefore, the high pressure reflow method can be performed.

In the above embodiments, the connection hole has a circular cross section, but the present invention can be applied to an oval cross section, an elliptical cross section or a rectangular cross section. In that case, it is necessary to satisfy the condition that the minimum diameter of each cross-sectional shape of the plurality of connection holes 14 is equal to or less than the thickness of the metal film 16 and equal to or less than 0.6 μm.

[0019]

As described above, according to the present invention,
Since multiple holes are formed for one electrical connection, the same connection resistance as when one hole with a large diameter is provided for one electrical connection is ensured, and the maximum number of holes The small diameter can be reduced. Therefore, each hole can be covered with a metal film. The minimum diameter of each hole is smaller than the value of the film thickness of the metal film formed on the insulating film, and is 0.6 μm or less. Therefore, a metal is left on each hole with a space left. It can be covered with a membrane. Therefore, it is possible to embed a part of the metal film inside the plurality of holes by the high pressure reflow method without increasing the connection resistance for electrical connection.

[Brief description of drawings]

FIG. 1 is a manufacturing process diagram of an example of the present invention.

FIG. 2 is an explanatory diagram of a problem.

[Explanation of symbols]

 13 insulating film 14, 14a to 14d hole 16 metal film

Claims (2)

[Claims] 1. After forming a hole in an insulating film, a metal film is formed on the insulating film while leaving a space in the hole, and then pressure is applied to the surface of the metal film while heating. A method of embedding a hole by high pressure reflow in which a part of the metal film is pushed into the hole to embed the hole in the part of the metal film, wherein the hole is formed of a plurality of holes for one electrical connection. ,
Further, at least the minimum diameter of each of the plurality of holes is set to a value equal to or less than the film thickness of the metal film, which is a method of filling holes by high pressure reflow. 2. The method of embedding holes by high pressure reflow according to claim 1, wherein the plurality of holes have at least the minimum diameter of each hole set to 0.6 μm or less. .