KR101503027B1 - Method of wafer bonding - Google Patents

Abstract

In semiconductor device fabrication, a direct bonding method for a semiconductor substrate is used. Conventional semiconductor substrate joining methods have problems of mass production of defective products due to void generation and distortion. The method for directly bonding a semiconductor substrate according to the present invention activates a bonding surface between two semiconductor substrates, presses them together to form an initial bonding, transfers heat from a central portion to an edge of the bonded substrate in a heat treatment process, The quality of the product and the yield can be improved.

Description

[0001] METHOD OF WAFER BONDING [0002]

The present invention relates to a method of manufacturing a semiconductor device. More particularly, the present invention relates to a method of joining semiconductor substrates

BACKGROUND ART [0002] As the types of semiconductor devices have been diversified, techniques for joining semiconductor substrates have been developed. [0003] Direct bonding techniques for semiconductor devices have problems in mass production of defective products. For example, problems such as void generation, distortion, and the like reduce the quality and yield of products.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a direct bonding method of a semiconductor substrate with improved yield.

As a means for achieving the above object, the semiconductor substrate bonding method of the present invention activates bonding surfaces of two substrates using plasma. The bonding surfaces are brought into contact with each other, and the bonding is performed vertically to perform the initial bonding. The center portion of the initially bonded semiconductor substrate is selectively heated to transfer heat to the edge of the substrate to form a junction.

It is possible to reduce the frequency of occurrence of defective bonded substrate in manufacturing a semiconductor substrate and increase the product yield.

FIGS. 1A and 1G are process cross-sectional views illustrating a process of manufacturing a semiconductor substrate direct junction according to an embodiment of the present invention.
2A and 2B are a cross-sectional view and a plan view illustrating a semiconductor substrate direct bonding apparatus according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. However, the present invention is not limited to the embodiment described here, but can be applied to other materials. Rather, the embodiments disclosed herein are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

FIGS. 1A and 1G are cross-sectional views illustrating a semiconductor substrate manufacturing process according to an embodiment of the present invention.

Referring to FIG. 1A, a first substrate 10 is provided that includes a first surface 10a and a second surface 10b opposite the first surface 10a. The first substrate 10 may be a silicon substrate. The first substrate 10 is polished, and the thickness thereof can be reduced. For example, the first substrate 10 may be polished such that the thickness of the first substrate is 275 m.

Referring to FIG. 1B, an insulating film 13 may be formed on the first surface 10a and the second surface 10b of the first substrate 10. For example, the insulating film 13 may be an oxide film or a nitride film. The insulating layer 13 may be formed by chemical vapor deposition (CVD) or thermal oxidation. For example, the thickness of the insulating film 13 may be about 1000 angstroms. Impurities on the surface of the insulating film 13 can be removed. For example, impurities on the surface can be removed using a cleaning solution. The cleaning solution may be a mixed solution of ammonia, hydrogen peroxide and water. For example, the composition ratio of ammonia, hydrogen peroxide, and water constituting the cleaning solution may be about 1: 1: 5. For example, the temperature of the cleaning solution may be about 75 ° C. For example, the cleaning time can be about 10 minutes.

Referring to FIG. 1C, the insulating film 13 on the first surface 10a of the first substrate 10 may be activated. For example, the insulating film 13 of the first substrate 10 can be activated by using plasma. For example, the plasma may be an oxygen plasma. The plasma may be generated by using a high frequency as an energy source. For example, the range of the high frequency power may be 150 to 250 W. The plasma may be generated at a pressure lower than atmospheric pressure. For example, the pressure may be 0.05 torr. The insulating layer 13 on the first surface 10a of the first substrate 10 may be activated to form the first activation layer 15. [

Referring to FIG. 1d, a second substrate 20 is provided that includes a third surface 20a and a fourth surface 20b opposite the third surface 20a. The second substrate 20 may be a quartz substrate. Impurities on the surface of the second substrate 20 can be removed. For example, impurities on the surface can be removed using a cleaning solution. The cleaning solution may be a mixed solution of ammonia, hydrogen peroxide and water. For example, the composition ratio of ammonia, hydrogen peroxide, and water constituting the cleaning solution may be about 1: 1: 5. For example, the temperature of the cleaning solution may be about 75 ° C. For example, the cleaning time may be about 10 minutes. The third surface 20a of the second substrate 20 may be activated using plasma. For example, the plasma may be an oxygen plasma. The plasma may be generated by using a high frequency as an energy source. For example, the range of the high frequency power may be 150 to 250 W. The plasma may be generated at a pressure lower than atmospheric pressure. For example, the pressure may be 0.05 torr. The third surface 20a of the second substrate 20 may be activated to form the second activation layer 23.

Referring to FIG. 1E, the first activation layer 15 and the second activation layer 23 may be in contact with each other to be initially bonded. The first and second activation layers 15 and 23 may be initially bonded so that the first bonding layer 14 may be formed. The first bonding layer 14 may be formed by vertically pressing the first and second activation layers 15 and 23. A void 12 may be present in the first bonding layer 14.

Referring to FIG. 1F, the first bonding layer 14 may be heat-treated. As a result, a bonded substrate having the second bonding layer 18 from which the void 12 is removed can be formed. A bonded substrate having the second bonding layer 18 formed between the first surface 10a of the first substrate 10 and the third surface 20a of the second substrate 20 is formed.

Referring to FIG. 1G, the bonded substrate can be processed to suit its purpose. For example, the upper insulating film 13 formed on the second surface 10b of the first substrate 10 may be removed. The bonded substrate can be used in a semiconductor device manufacturing process. For example, trenches of various shapes can be formed by a lithography process. The shape of the trench may be V-shaped, U-shaped, or rectangular.

2A and 2B are views for explaining a semiconductor substrate direct bonding apparatus according to an embodiment of the present invention.

Referring to FIGS. 2A and 2B, the heat treatment process of FIG. 1F may be performed inside the heating furnace 100. The heating furnace 100 may include a first heater 110 that heats the bonded substrate stack and a second heater 130 that surrounds the first heater 110. The inside of the heating furnace 100 may have an atmospheric pressure atmosphere.

Referring to FIG. 2A, a central portion of the fourth surface 20b of the second substrate 20 may be positioned on the first heater. The second substrate 20 may have a smaller thermal expansion coefficient than the first substrate 10. The direction of heat transfer from the first heater 110 may be radial. For example, the heat may be transmitted from the central portion of the bonded substrate to the edge. Due to the radially transmitted heat, voids 12, which were generated during the initial bonding, may escape to the outside of the initially bonded substrate between the first substrate 10 and the second substrate 20. The directly bonded substrate from which the voids 12 have been removed can be formed by the heat treatment process.

10: first substrate
10a: first side
10b: second side
12: void
13: Insulating film
14: first bonding layer
15: first activation layer
18: second bonding layer
20: second substrate
20a: Third side
20b: fourth surface
23: Second activation layer
100: heating furnace
110: first heater
130: second heater

Claims (4)

Activating the junction surfaces of the two wafers using plasma;
Performing an initial bonding by causing the bonding surfaces of the wafers to abut against each other and applying pressure vertically;
Selectively heating a center portion of the wafer having a smaller coefficient of thermal expansion among the initially bonded wafers to transfer heat from the central portion of the wafers to the edge to thereby bond the wafers to each other, wherein the heating is started after the initial bonding is performed Wafer bonding method. The method according to claim 1,
Wherein after activating the two wafer bonding surfaces, the bonding surfaces of each of the wafers further comprise forming a first activation layer and a second activation layer. 3. The method of claim 2,
And performing the initial bonding to form a first bonding layer. The method of claim 3,
Further comprising selectively heating a central portion of the wafers including the first bonding layer to form a void-removed second bonding layer.

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