JPS5814543A - Substrate for semiconductor element - Google Patents

Abstract

PURPOSE:To remove flashes without damaging the flatness of a W or Mo semiconductor substrate, by rounding off the angles of the substrate by barrel polishing. CONSTITUTION:Rough discs having a diameter of 12mm. and a thickness of 2mm. are put in a hexagonal stainless barrel vessel to about 1/3 of the capacity thereof, green carborundum (80 meshes) and a small quantity of barrel grindstones (having diameters of 5-10mm.) are put therein in an amount nearly equal to that of the Mo discs, water is added so that the content is about 3/4 of the capacity, and then processing is made for one hour at 70rpm. As the result, the angles of substrates are given smooth roundness (0.5-1R) throughout the entire peripheries of both front and back surfaces thereof, and thereby excellent substrates having the surface roughness of about 10mu at maximum and the parallelism of 10-20mum are prepared. Thus, the semiconductor substrates which are highly excellent in intimate adhesion can be obtained.

Description

[Detailed description of the invention] The present invention relates to a semiconductor element substrate.

Conventionally, tungsten substrates or molybdenum substrates have been widely used as semiconductor element substrates, also called heat-retaining trowel substrates, because their coefficient of thermal expansion is similar to that of silicon. These substrates are used by being bonded together with a rectifying element made of silicon, which is a semiconductor, by a method such as an alloying method, but the bonded surface is required to have a high degree of smoothness.

Conventionally, this substrate is obtained by press punching a plate material obtained by rolling. Thereafter, in order to obtain flatness of the substrate, the edges of the press punch are removed by chamfering with a lathe or a grindstone. However, the substrate obtained by these processes may be slightly bent due to the pressing of the tool on the edge part, which may impair the adhesion with the semiconductor element.The present invention is based on these circumstances. The object of the present invention is to provide a substrate for a semiconductor device from which pars are removed without impairing the flatness of the substrate.

The tungsten or molybdenum substrate according to the present invention is usually a disk and is made by molding and sintering tungsten or molybdenum powder, or by forging after molding and sintering tungsten or molybdenum powder. Alternatively, it is manufactured by roll processing into a sheet (plate), which is then further manufactured by press punching. The thickness of the rough plate is usually 1 to 2 vans, and the size of a circular plate is usually 7 to 40 m5p, but there are also plates of 60 va1 or more for use in large rectifying elements.

The barrel for obtaining the substrate of the present invention refers to a cylindrical container with both ends closed, and its material is stainless steel or a barrel. As the polishing abrasive grains, for example, carborundum (8
10), alumina (kl, O,), etc. are preferable, and green carborundum is particularly preferable. The particle size used is 60 mesh, 80 mesh, 180 mesh, 240 mesh, etc. depending on the required surface smoothness. More preferably, a grindstone having a diameter of 3 to 10 iua is mixed. The liquid put into the barrel together with the abrasive grains is usually water, and an oil-extracting liquid thereof can also be used.

It is preferable to use water for ease of cleaning after polishing. The polishing operation is usually carried out at room temperature, but there is no problem even if there is a slight temperature rise due to frictional heat during polishing.

During polishing, a barrel containing a tungsten or molybdenum rough plate, the abrasive grains, and the polishing liquid is rotated about the axis of the barrel, thereby bringing the abrasive grains into contact with the surface of the rough plate. The polishing is performed at a speed of 30 to 300 revolutions per minute. The time required for one polishing process varies depending on the properties of the abrasive grains, the surface roughness of the rough plate, and the number of rotations of the barrel, but is usually 0.5 to 2 hours.

The substrate of the present invention obtained as described above can have substantially even rounded corners at the end portions of the surface without being subjected to stress that would cause the substrate to bend, and has extremely high surface smoothness.

An example will be described.

Approximately 173 rough molybdenum plates (discs) with a diameter of 12 mm and a thickness of 2 fl are placed in a stainless steel barrel container made of a hexagonal prism with a diagonal length of approximately 251 mm and a length of 30 α. and a small amount of barrel whetstone (diameter 5 to 101 Jl), about the same amount as the rough molybdenum plate, and water, the total amount is about 3 times the size of the container.
/4 and rotate this barrel container at 70 rpm.
Rotated time.

The corners of the obtained substrate have a smooth roundness (0,5 to 1) L) over the entire circumference on both the front and back sides, and the surface roughness is approximately 10 μm at maximum, and the parallelism is 10 to 20 μm, which is an extremely high flat surface. It was a state.

The degree of adhesion of this substrate and a comparative substrate (which was deburred with a grinding wheel) to the semiconductor element was examined.

A copper disk with the same diameter and thickness of 3 cm was hot-pressed to a semiconductor element made of molybdenum with a diameter of 40 m and a thickness of 1 m.

This copper disk portion was gripped from the side and peeled off, and the peeled surface of molybdenum was observed. If copper remains on the peeled surface and remains, the adhesion is good; if the outer edge of the peeled surface is coated with molybdenum, the adhesion is poor. The results were as shown in the table.

If the adhesion is poor, the width should be 1 mm around the entire outer edge.
A molybdenum base of about +W was found.

As is clear from the above, the substrate of the present invention has extremely excellent adhesion.

Claims (1)

[Claims] T1) A substrate for a semiconductor device, characterized in that corners of the substrate are rounded by barrel polishing. (2) The substrate for a semiconductor device according to claim 1, wherein the substrate is made of tungsten or molybdenum.