JPH0519814B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for manufacturing a multilayer integrated circuit in which two types of integrated circuit layers (hereinafter referred to as active layers) are adhered to each other. More specifically, the present invention relates to a method of manufacturing a semiconductor device in which metal bumps provided on different active layers are connected using a diffusion welding method in order to exchange signals and power between the active layers.

[Conventional technology]

A multilayer integrated circuit is an integrated circuit in which functional elements such as transistors, resistors, and capacitors are arranged three-dimensionally. According to the multilayer structure, there are two functional elements.
Compared to conventional integrated circuits that are arranged dimensionally, it is expected that the degree of integration and circuit design will be improved, and the operating speed will be faster due to shorter wiring lengths. One possible method for realizing a multilayer integrated circuit is to separately manufacture conventional functional layers in which functional elements are arranged two-dimensionally, and then stack these active layers in sequence. In order to realize a multilayer structure circuit by this method, it is necessary to provide metal bumps on the surface of the active layer for wiring between the active layers. Further, there is a diffusion welding method as a method for connecting metal bumps provided on each active layer.

An example of a method for manufacturing a multilayer integrated circuit is shown in FIGS. 2a to 2c. In FIG. 2a, the first active layer 1
01 and the second active layer 201 are manufactured separately. In addition, 102 and 103 in the figure are the first active layer 1.
01 consists of silicon, gallium arsenide, quartz,
Substrate such as sapphire, and functional element layer, 104
are first metal bumps made of gold or the like formed on the surface of the first active layer 101. Reference numerals 202 and 203 denote substrates such as silicon, gallium arsenide, quartz, and sapphire constituting the second active layer 201, and functional element layers; 204 denotes a second substrate made of gold or the like formed on the surface of the second active layer 201; It is a metal bump. The functional element layer of each active layer is usually formed using a well-known semiconductor integrated circuit manufacturing process, such as NMOS,
Manufactured using PMOS, CMOS, bipolar, or gallium arsenide processes. Further, the metal bumps can be obtained by forming a metal film pattern using a selective plating method, a photolithography method, or the like.
Next, as shown in FIG. 2b, the first active layer 10
The first and second active layers 201 are aligned so that their surfaces face each other until the metal bumps 104 and 204 provided on the surfaces of the respective active layers are at the same position. As an example of alignment method,
There is an off-axis method used in reduction projection exposure devices. In this method, two alignment locations are first provided in the alignment device. Each alignment location is provided with a stage for fixing a chip or wafer and alignment reference marks, and the distance between the alignment reference marks is predetermined. First, after fixing the first active layer 101 and the second active layer 201 to their respective stages, the stages are moved slightly to align each alignment reference mark with the alignment mark provided on the chip or wafer. let

Next, for example, the stage on which the first active layer 101 is fixed is moved by the distance between the alignment reference marks, so that the first active layer 101 is fixed to the second active layer 20.
Set the relative position so that it is directly below 1. As a result, both active layers 101 and 201 are aligned with mechanical precision (1 μm or less) by moving the stage. Subsequently, as shown in FIG. 2c, the surfaces of the metal bumps 104 and 204 provided on the first active layer 101 and the second active layer 201, respectively, are brought into contact with each other and heated at a predetermined pressure. , diffusion welding is caused between both metal bumps 104 and 204 to bond the first active layer 101 and the second active layer 201 together. When the above steps are completed, a two-layer integrated circuit is realized. An important process in the manufacturing method shown above is the diffusion welding method.

In the diffusion welding method, a pressure of several kilograms/ ^mm2 is applied to the contact surfaces of two types of metals or of the same type heated to around 300℃, and the two metals are bonded by solid phase diffusion of the molecules of both metals at the contact surfaces. Compared to other bonding methods, such as methods using conductive adhesives or methods that bond by melting low-melting point metals such as solder, this method has a lower electrical resistance at the bonded part and is also capable of bonding fine patterns. It has characteristics such as strong adhesive strength. For this reason, the diffusion welding method is widely used in integrated circuit mounting processes, such as bonding between pads within an integrated circuit chip and lead wires of a package. By the way, since conventional bonding is for one pad (area approximately 0.01 mm ² ), it is easy to apply pressure [Electronic Materials, December 1972 issue,
Pages 152-161]. A beam lead method is also known as a method for simultaneously bonding multiple pads [Electronic Materials, February 1973 issue, pages 159-162]. In order to bond multiple pads simultaneously, the pressure applied to each pad must be uniform. For this reason, in this system, the beam leads are given elasticity so that the pressure between each beam lead and the pad is made uniform.

The diffusion welding shown in FIG. 2c also involves bonding a plurality of first and second metal bumps at the same time, so a uniform pressure is applied perpendicularly to the contact surface between the first active layer 101 and the second active layer 201. I need to put it on.

[Problem that the invention seeks to solve]

However, since the active layers 101 and 201 are both formed on hard substrates such as silicon single crystal, gallium arsenide single crystal, quartz, sapphire, etc., the bonding and beam lead methods described above can hardly uniformly coat the active layers 101 and 201. can't put pressure on it. As a result, the metal bumps provided on the surface of each functional layer are not sufficiently spread welded over the entire surface, and if there is a partial electrical connection between each functional layer or the resistance of the bonding surface becomes uneven, problems are likely to occur.

The present invention solves the above drawbacks and provides a method for uniformly applying pressure to completely diffusion weld a plurality of metal bumps provided on the surface of each active layer.

[Means for solving problems]

The present invention provides a plurality of first and second metal bumps on the surfaces of the first and second active layers, respectively, on which functional elements such as transistors, resistors, and capacitors are formed, and then The surfaces of the layer and the second active layer are opposed to each other to form a corresponding first active layer.
and on a flat surface provided on a fixing support in the process of manufacturing a multilayer integrated circuit by aligning the positions of the second metal bumps and bonding the first and second metal bumps by diffusion welding. , the first and second active layers, which have already been aligned in the above step, are installed one above the other so that the first active layer is on the bottom, and then the first and second active layers are placed on top of the first active layer. A buffer block having a flat surface with parallel upper and lower surfaces is placed on the surface of the second active layer, and a movable support is placed on the top surface of the buffer block via a hard ball, and then a fixed support is placed on the top surface of the second active layer. This method of manufacturing a semiconductor device is characterized in that heating is performed while applying pressure between a tool and a supporting tool.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 shows the diffusion welding method according to the present invention using a cross-sectional view.
In the step of FIG. 2b, the first active layer 101 and the second active layer 20 are brought into contact with each other after alignment.
1 installed on a fixed support 301. The surface of the fixing support 301 made of iron or the like is finished flat by polishing or the like, so that the back surface of the first functional layer 101 and the surface of the first functional layer 301 can be brought into close contact with each other. Further, a vacuum chuck hole, a guide jig, etc., for fixing the first active layer 101 and the like may be provided on the surface of the layer 301. Next, Figure 1b
As shown in FIG. 2, a buffer metal block 302 made of iron or stainless steel is installed on the back surface of the second active layer 201 to cover at least the entire back surface of the second active layer, and a hard ball 303 made of iron or the like is placed on the buffer metal block 302. Set up. Buffer metal block 302
The surface that contacts the back surface of the second active layer 201 and the surface that contacts the hard ball 303 need to be parallel to each other and finished flat. Further, the relative position is set so that the contact point between the buffer metal block 302 and the hard ball 303 is near the center of the back surface of the second active layer 201. Finally, as shown in FIG. 1c, the pressure device 305 is pressed down from above the hard ball 303 via the movable support 304 to press the hard ball 303 and heat it for a predetermined period of time. Pressure device 305
In addition, if a screw tightening torque is used, or a pneumatic or hydraulic compressor is used, the pressure can be freely controlled. Metal bumps 104, 204
Examples of pressure, temperature, and time when the material is made of gold are 3 Kg/mm ² , 300° C., and 30 minutes, respectively.

The feature of the method described above is that the hard ball 303 and the buffer metal block 302 always contact at one point, so even if the pressure direction of the pressure device 305 is not perpendicular to the back surface of the second active layer 201, In the metal block 302, the direction of the pressure is corrected to a direction perpendicular to the back surface of the metal block 201, and furthermore, the pressure concentrated at the contact point between the buffer metal block 302 and the hard ball 303 is transferred to the second active layer 201. It is to be uniformly distributed on the contact surface between the back surface and the buffer metal block 302. As a result, since a vertical and uniform pressure is always applied to the contact surface between the first and second active layers, the plurality of metal bumps provided on the surfaces of the first and second active layers are Diffusion welding is done in the same way.

In the above description, a specific material was described as an example, but the material is not limited to this. For example, as the metal bump, in addition to gold, aluminum, copper, etc. can be considered. In addition to iron and stainless steel, brass, titanium alloy, fine ceramics, and the like are also suitable as materials for the fixed support base, buffer block, hard ball, etc. Furthermore, although the first and second active layers have been described as one functional element layer, two or more functional element layers using silicon on insulator (SOI) or the like may be provided.

〔Effect of the invention〕

As described above, according to the method of the present invention, heating is performed while applying pressure uniformly over a wide area, and
A multilayer integrated circuit in which metal bumps on the surfaces of two active layers are evenly bonded to each other can be realized. Further, according to the present invention, in order to enable connection between metal bumps formed on two types of hard substrates, for example,
This has an effect that can be widely applied to high-density mounting technology in which a plurality of integrated circuit chips are mounted on a ceramic substrate on which only a wiring pattern is formed.

[Brief explanation of drawings]

1A to 1C are cross-sectional views showing the manufacturing method of the present invention in order of process, and FIGS. 2A to 2C are cross-sectional views showing the manufacturing process of a conventional multilayer integrated circuit. 101 is the first active layer, 102, 103, 10
4 are a substrate, a functional element layer, and a first metal bump, respectively constituting the first active layer 101;
1 is a second active layer; 202, 203, and 204 are a substrate, a functional element layer, and a second metal bump constituting the second active layer 201, respectively; 301 is a fixing support; 302 is a buffer metal block; 303 304 is a hard ball, 304 is a movable support, and 305 is a pressure device.

Claims (1)

[Claims] 1. A plurality of first and second metal bumps are respectively provided on the surfaces of the first and second active layers on which functional elements such as transistors, resistors, capacitors, etc. are formed, and then The surfaces of the second active layer are made to face each other, the positions of the corresponding first and second metal bumps are matched by alignment, and the first and second metal bumps are bonded by diffusion welding to form a multilayer. In the process of manufacturing a structural integrated circuit, the first and second active layers, which have already been aligned in the process, are placed on a flat surface provided on a fixing support so that the first active layer is on the bottom. A buffer metal block having a flat surface with parallel upper and lower surfaces is installed on the back surface of the second active layer provided on the first active layer, and 1. A method for manufacturing a semiconductor device, which comprises: installing a movable support on the top surface of a metal block via a hard ball; and then heating while applying pressure between the fixed support and the movable support.