JPH0582966B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a wafer bonding device used for mirror-finishing silicon wafers.

[Prior Art] In the polishing step, which is the final processing step for silicon wafers, one side of the wafer is mirror-finished. During this processing, the wafer is bonded via wax onto an adhesive plate, which is a disk made of metal or ceramic, for example. Generally, this process involves (1) heating the adhesive plate to a temperature slightly higher than the softening point of the wax used, (2) melting and applying the wax to the heated adhesive plate at the location where the wafer is to be bonded; (3) Place the wafer on the applied wax, then press the wafer against the adhesive plate using a rod-shaped pressing jig whose tip has a contact surface that contacts the entire surface of the wafer uniformly, and press the wafer against the adhesive plate through the wax layer. (4) Finally, the wafer bonding plate is placed on a cooling plate to solidify the wax.

However, as electronic components have recently become more highly integrated, wafers have been required to have higher shape accuracy, and there has been a need to improve the uniformity of wax film thickness. In completely manual pasting work, the variation in film thickness depends on the skill level of the worker and is approximately 4.
~5 μm, and even in the case of semi-automatic pasting using a press, there is a variation of about 1 to 2 μm. If the wax film thickness becomes uneven, the parallelism of the wafer will decrease, and in order to make the wax film thickness uniform, the wafer will be strongly pressed against the adhesive plate using a pressing jig. occur and are undesirable.

[Problems to be Solved by the Invention] The present invention focuses on the above-mentioned problems.In the above-mentioned conventional technology, when pressurizing a wafer, the plate is heated only from the lower side, and when cooling the plate, the plate is heated only from the lower side. It was confirmed that because the wax was cooled by a water-cooled jacket, a temperature gradient was generated between the top and bottom surfaces of the wax film during solidification, making it difficult to control the wax film thickness. As a result, it is an object of the present invention to provide a wafer bonding device that facilitates bonding a wafer to a plate through a wax film of uniform thickness without being affected by such temperature gradients.

[Means for Solving the Problems] In order to achieve the above object, the present invention, as a result of numerous studies, provides heaters adjacent to each of the adhesive plate and the pressing body of the pressing mechanism, and The present invention was achieved by developing a wafer bonding apparatus that substantially eliminates the temperature gradient in the wax film by heating the wax film while controlling the temperature, thereby making it easier to control the wax film thickness.

The present invention provides a wafer bonding apparatus comprising an adhesive plate for melting and applying wax and a pressing member of a pressing mechanism for pressing the wafer onto the adhesive plate, in which a heater is provided adjacent to each of the adhesive plate and the pressing member, and the heater is It is characterized by being able to control the temperature in two stages: high temperature and low temperature.

In a preferred structure of the wafer pasting device of the present invention, the adhesive plate is provided on the cast aluminum heater,
Further, the same aluminum cast heater is provided on the end face of the lifting shaft of the pressing body, and the pressing body is configured to be fixed to the surface of this heater.

[Effect]

In the above means, there is no temperature gradient in the thickness direction in the wax film, and preliminary solidification of the wax is uniformly performed by the low temperature heating and pressing step.

[Example] The invention will now be described with reference to the accompanying drawings.

In FIG. 1, a disc-shaped cast aluminum heater 3 is provided on a base 1 via a heat insulating layer 2, and an adhesive plate 4 is placed on the heater 3 coaxially with the heater. A plurality of wafers 5 are placed on the main surface of the plate 4 at positions where they are to be bonded via wax. The wax can be applied directly to the intended bonding location on the plate, or it can be pre-applied to one side of the wafer to be bonded. On the other hand, an L-shaped support 6 is attached to the side surface of the base 1. An extending portion 7 of this support column 6 parallel to the main surface of the adhesive plate 4 is provided so as to be located directly above the adhesive plate 4, and a tip of this extending portion 7 is provided with an appropriate lifting mechanism so that it can be raised and lowered. A connected lifting shaft 8 is provided. Further, at the tip of the lifting shaft 8, a pressing body 9 made of a heat-resistant cushion material is provided coaxially with the lifting shaft 8 and operated by a suitable pressing mechanism. In this case, the pressing body 9 is laminated on the surface of the aluminum cast heater 3' formed coaxially with the axis thereof, and the other surface of the heater 3' is connected to the lifting shaft 8 through the heat insulating material layer 2'. Fix it to the tip of the

As mentioned above, the apparatus of the invention with both the upper and lower heaters 3 and 3' is operated in two stages: a hot pressurization step and a cold pressurization step. In the high-temperature pressing step, the entire wafer-wax-adhesive plate is heated to a temperature of approximately 190±2°C (in this case,
(plate surface temperature is approximately 180℃) and a pressure of approximately 600 to 1000g/ ^cm2 per wafer unit area.
Heat and pressurize for seconds.

After this high-temperature pressurization step is completed, in the subsequent low-temperature pressurization step, the temperature of both the upper and lower heaters is increased to 90±2℃ for approximately 90 seconds under the same pressure (in this case, the plate surface temperature is approximately 80℃). Become)
The wax is heated and pressurized, and held in this state until the wax is preliminarily solidified. In this low-temperature pressing step, the temperature is lowered to preliminarily uniformly solidify the wax while maintaining the state in which the wafers were accurately bonded in the previous high-temperature pressing step.

The plate holding the wafer with the wax preliminarily uniformly solidified in this manner in a highly precise state is cooled by conventional means to completely solidify the wax.

The temperature control of both heaters in the above operation can be performed by power control and on-off control using a heater temperature monitor (not shown). Further, the viscosity of the wax with respect to temperature changes during the above-mentioned high and low temperature pressurization is shown in FIG.

[Effects of the Invention] As explained above, according to the silicon wafer bonding apparatus of the present invention, there is no temperature gradient in the thickness direction in the wax film, and preliminary solidification of the wax is uniformly performed by the low-temperature heating and pressing step. Since this process is performed, it is possible to control the wax film thickness to be uniform across the entire wafer to approximately 0.5 to 1.0 μm, and to reduce the variation in wax film thickness to 0.5 μm or less for multiple wafers attached to the plate. I was able to do that.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the silicon wafer bonding apparatus of the present invention, and FIG. 2 is a curve diagram showing the viscosity of wax with respect to temperature changes during heating and pressurizing operations in the operation of the apparatus of the present invention shown in FIG. . 1... Base, 2, 2'... Heat insulation layer, 3, 3'...
...Aluminum cast heater, 4...Adhesive plate, 5...
... Wafer, 6 ... Support column, 7 ... Extension part, 8 ... Lifting shaft, 9 ... Pressing body.

Claims (1)

[Claims] 1. In a silicon wafer bonding apparatus comprising an adhesive plate for bonding wafers via wax and a pressing body of a pressing mechanism for pressing the wafer against such adhesive plate, a heater is provided adjacent to each of the adhesive plate and the pressing body, A silicon wafer bonding device characterized by having a heater that can control the temperature in two stages: high temperature and low temperature.