Sintering press

Abstract

A press for pre-sintering or sintering silicon wafers includes a lower block and an upper block, the lower block including a lower base and a lower plate, the lower plate resting only on the upper surfaces of at least three compression load cell bodies, the load cell bodies being supported by the lower base such that the upper surfaces are substantially coplanar with one another.

Description

Technical Field

[0001] The present invention relates to the field of the manufacturing process of silicon wafers, and more particularly to a press machine suitable for performing pre-sintering or sintering of silicon wafers.

Background Art

[0002] Pre-sintering (also known by the term "wafer stacking") and sintering ("wafer sintering") are two stages of the manufacturing process of silicon wafers that can be achieved with the same dedicated press machine, and the working parameters of the press machine operation, particularly the temperature, are quite different from each other.

[0003] According to the preamble of claim 1, a press machine for pre-sintering or sintering a silicon wafer includes a lower block and an upper block. The lower block includes a lower base and a lower plate supported by the lower base and forming a lower surface for supporting the silicon wafer to be sintered. The upper block includes under an upper plate forming an upper surface facing the lower surface.

[0004] The press machine is provided with actuator means suitable for translating the lower plate and / or the upper plate between a mutually separated inactive position and an active position where the upper surface applies a predetermined pressure to the silicon wafer present on the lower surface.

[0005] The pre-sintering and sintering of silicon wafers should meet the following prerequisites in order to be considered reliable: - A freely programmable process temperature from about 100°C to about 350°C; - A process temperature that is uniformly distributed on the processed wafer with an allowable deviation of about ±3°C; - A freely programmable process pressure from about 1 MPa to about 40 MPa; - A process pressure that is uniformly distributed on the processed wafer with an allowable deviation of about ±0.5 MPa.

[0006] To meet these requirements, the press machine must guarantee the following: - Strength and absolute rigidity of the lower and upper surfaces; - The absolute degree of parallelism between the lower surface and the upper surface. [Overview of the project]

[0007] The object of this invention is to propose the above-described type of press machine that can satisfy the requirements cited above.

[0008] The above-mentioned objective is achieved by the pre-sintering or sintering press machine described in claim 1. [Brief explanation of the drawing]

[0009] The features and advantages of the press machine according to the present invention will become apparent from the following description of preferred exemplary embodiments thereof, given as non-limiting examples with reference to the attached figures.

[0010] [Figure 1] Figure 1 is a perspective view of a press machine according to one embodiment of the present invention. [Figure 2] Figure 2 is a perspective view of a press machine according to another embodiment of the present invention. [Figure 3] Figure 3 is a schematic side view of the press machine shown in Figure 2. [Modes for carrying out the invention]

[0011] In the following description, elements common to various embodiments will be indicated by the same reference numeral.

[0012] In the attached drawings, reference numeral 1;100 denotes a press machine for pre-sintering or sintering silicon wafers as a whole.

[0013] According to a general embodiment, the press machine 1;100 includes a lower block 10;110 and an upper block 12;112.

[0014] The lower block 10;110 includes a lower base 14;114 and a lower plate 16;116 supported by the lower base and forming a lower surface 16';116' for supporting a silicon wafer to be pre-sintered or sintered.

[0015] In some embodiments, as shown in the drawings, the lower plates 16;116 may include two overlapping, rigidly connected plate portions (for example, shown as 116a and 116b in Figures 2 and 3), where the upper portion 116a on which the silicon wafer rests is a heating plate, and the upper portion 116b in contact with the load cell is kept at a low temperature.

[0016] The upper blocks 12;112 include upper plates 18;118 that form upper surfaces 18';118' facing the lower surfaces 16';116'.

[0017] The press machine includes, for example, hydraulic or electric actuator means suitable for moving the lower plates 16;116 and / or upper plates 18;118 between a non-active position of mutual separation and an active position in which the upper surface exerts a predetermined pressure on the silicon wafer of the lower surface.

[0018] According to one aspect of the present invention, the lower plates 16;116 rest only on the top surfaces of at least three compression load cell bodies 20, which are supported by lower bases 14;114 such that their top surfaces are substantially coplanar with each other.

[0019] In the embodiment shown in Figure 1, the lower plate 16 rests on the bodies 20 of three load cells arranged, for example, at the vertices of an equilateral triangle.

[0020] In the embodiments shown in Figures 2 and 3, the lower plate 116 rests on the bodies 20 of four load cells arranged, for example, at the vertices of a square.

[0021] The number of load cell bodies may depend on the pressure applied to the sintered surface and / or the silicon wafer.

[0022] The load cell body 20 is suitable for flexing in such a way that the lower plate can pivot to compensate for any non-parallelism between the lower surface and the upper surface, and / or any non-parallelism between the upper surface of the silicon wafer and the lower and / or upper surfaces.

[0023] Thus, by using the load cell body 20, or the casing, as the sole support element of the lower plate, complete adhesion between the lower surface 16’;116’ and the upper surface 18’;118’ becomes possible.

[0024] In one embodiment, the load cell body 20 does not have a pressure sensor. Thus, in that case, the load cell is used solely as a pivoting support means.

[0025] In other embodiments, the load cell body 20 comprises a pressure sensor, such as a strain gauge, suitable for detecting the pressure exerted on the silicon wafer by the upper surface.

[0026] Thus, in this case, the load cell performs both the function of pivoting support of the lower plate and the function of a pressure sensor.

[0027] In one embodiment, the load cell bodies 20 have substantially the same height. For example, the upper surfaces of the load cell bodies are simultaneously subjected to a grinding process so that the bodies have the same height.

[0028] In one embodiment, the load cell bodies are identical to each other.

[0029] In some embodiments, the lower plates 16;116 are held in place by connecting bars 22;122, such as adjustable deflection bars. In other words, the connecting bars 22;122 prevent the lower plates 16;116, which are exclusively stationary on the load cell body 20 and not subject to other constraints, from moving in an undesirable manner relative to the load cell body 20.

[0030] For example, in the case of a rectangular lower block 10;110, at least two opposing sides of the lower plate 16;116 are connected to the respective opposing sides of the lower base 14;114 by their respective connecting bars 22;122. Specifically, each connecting bar 22;122 is, under The vertices of the lower plates 16;116 are connected to the opposite vertices of each side of the lower base 14;114. Preferably, the bars 22;122 on the opposing sides of the lower block are further connected to each vertex in opposite ways. In other words, the two opposing bars connect the opposing vertices of the lower plate (i.e., the ends of the diagonals of the rectangle defining the outer perimeter of the lower plate as seen in the plan view) to the opposing vertices of the lower base.

[0031] In one embodiment, the connecting bars 22;122 are connected to the lower plates 16;116 and lower bases 14;114 by ball joints 24, allowing any inclination of the lower plates relative to the lower bases without affecting the interaction between the lower plates and the load cell body.

[0032] In one embodiment, the load cell body has a maximum deflection of approximately 0.5 millimeters at the nominal load.

[0033] For example, a press machine can compensate for non-parallelism of up to approximately 0.3 millimeters from edge to edge of a surface defined by the centerline of a load cell.

[0034] For embodiments of the press machine according to the present invention, a number of modifications, adaptations, and substitutions of elements with other functionally equivalents can be made without departing from the scope of the following claims to meet incidental needs. Each feature described as belonging to a possible embodiment can be obtained independently of other described embodiments.

Claims

1. A press (1;100) for pre-sintering or sintering a silicon wafer, comprising a lower block (10;110) and an upper block (12;112), The lower block (10;110) includes a lower base (14;114) and a lower plate (16;116) supported by the lower base (14;114) and forming a lower surface (16';116') for supporting a silicon wafer to be sintered, The upper block (12; 112) includes an upper plate (18; 118) that forms an upper surface (18; 118') opposite the lower surface (16'; 116'), The press machine (1;100) includes actuator means suitable for moving the lower plate (16;116) and / or the upper plate (18;118) in parallel between a mutually separated inactive position and an active position in which the upper surface (18';118') exerts a predetermined pressure on the silicon wafer present on the lower surface (16';116'), The lower plates (16; 116) rest only on the upper surfaces of at least three compression load cell bodies (20). At least three compression load cell bodies (20) are the elements that support the lower plate. The load cell body is supported by the lower base (14; 114) such that its upper surfaces are substantially coplanar with each other. The load cell body (20) is flexible in such a manner that the lower plate (16; 116) can pivot in order to compensate for any nonparallax between the lower surface (16'; 116') and the upper surface (18'; 118'), and / or any nonparallax between the upper surface (18'; 118') of the silicon wafer and the lower surface and / or upper surface. Press machine (1:100).

2. The load cell body (20) does not have a pressure sensor. The press machine (1;100) according to claim 1.

3. The load cell body (20) is equipped with a pressure sensor suitable for detecting the pressure exerted on the silicon wafer by the upper surface (18'; 118'). The press machine (1;100) according to claim 1.

4. The load cell body has substantially the same height, A press machine according to any one of claims 1 to 3 (1; 100).

5. The lower plate (16; 116) is held in a predetermined position by connecting bars (22; 122) that connect the lower plate (16; 116) to the lower base (10; 110), A press machine (1;100) according to any one of claims 1 to 4.

6. At least two opposing sides of the lower plate (16; 116) are connected to the respective opposing sides of the lower base (14; 114) by their respective connecting bars (22; 122). The press machine (1;100) according to claim 5.

7. Each connecting bar (22; 122) connects the vertices of the lower plate (16; 116) to the opposite vertices of the respective sides of the lower base (14; 114), The press machine (1;100) according to claim 6.

8. The connecting bars (22; 122) are connected to the lower plates (16; 116) and the lower base (14; 114) by ball joints (24). A press machine (1;100) according to any one of claims 5 to 7.

9. The load cell body has a maximum deflection of 0.5 mm at a nominal load. A press machine (1;100) according to any one of claims 1 to 8.

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