JPH04111730U - Molecular beam epitaxy equipment - Google Patents

Abstract

(57) [Summary] [Purpose] Preventing the scattering of excess material molecular beams into the ultra-high vacuum chamber and scattering the material molecular beams toward the semiconductor wafer while the temperature inside the cell remains stable. The purpose is to [Structure] Double shutters 2 and 3 are arranged on the opening surface of a cell 1, and when the substance supplied into the cell is heated to a predetermined temperature,
Once the shutter 2 close to the cell opening surface is opened to stabilize the temperature change inside the cell, the shutter 3 is opened, and the molecular beam of the substance evaporated at the desired temperature is scattered toward the semiconductor wafer W to achieve the desired concentration. A crystal film of is grown on a semiconductor wafer W.

Description

[Detailed explanation of the idea]

0001

[Industrial application field]

This invention uses a molecular beam epitaxy device (hereinafter referred to as MBE). ), and particularly relates to improvements in cells that serve as sources of molecular beams.

0002

[Conventional technology]

When forming an epitaxial growth layer on a semiconductor wafer, an MBE device is used. There may be cases where For example, as shown in FIG. 3, this MBE device has an inverted bowl shape. A semiconductor wafer W is placed on a plane that includes the center point of the concave curved surface of the ultra-high vacuum chamber 100. There is a cell near the bottom that is the source of molecular beams for epitaxial growth. Some devices have multiple holes 101 for each substance.

0003 For example, as shown in FIG. 4, the cell 101 is made of a ceramic crucible 102. A tungsten heater 103 for heating is wound around the tungsten heater 103 for heating. The area around the heater 103 is covered with thin tantalum plates 104 in multiple layers to increase the heat retention effect, A donut-shaped cap 105 is attached to the mouth side of the crucible 102. Highly purified materials such as gallium and arsenic are supplied to grow semiconductor wafers W. has been done. Then, returning to FIG. 3 again, the substrate 106 to which the cell 101 is attached A disc-shaped shutter 107 that opens and closes the opening of the cell 101 is connected to an external step. It is rotatably attached to a shaft 109 connected to a ping motor 108 or the like.

0004 In the MBE apparatus with the above configuration, a semiconductor wafer is placed above the ultra-high vacuum chamber 100. the opening surface of the cell 101 is covered with the shutter 107, and the button of the cell 101 is placed. The gsten heater 103 is energized and the crucible 102 is heated by the heat generated. , is supplied into the crucible 102 by bringing the crucible 102 to a predetermined high temperature state. The molecular beam is scattered toward the semiconductor wafer W by evaporating the substance, and the collision An epitaxial growth layer is formed on the surface of the semiconductor wafer W. like this In a typical MBE device, the amount of material evaporated is controlled by subtle changes in the heating temperature of the crucible 102. Because the molecular weights are different, the concentration of the epitaxial growth layer formed on the semiconductor wafer W is This has the advantage that the degree change can be easily adjusted.

[0005]

[Problem that the idea aims to solve]

However, in the above MBE device, the opening surface of the cell 101 and the shutter 107 are The distance h from the mounting position is about 30 to 50 mm, which is relatively far away. Therefore, the steam released before heating the crucible 102 and reaching the predetermined temperature is It leaks from the gap between the crucible 107 and the opening surface of the crucible 102, and the ultra-high vacuum chamber There are problems such as excess substances adhering to the inside of the 100 and requiring frequent maintenance. Ta.

[0006] In order to prevent this, move the shutter 107 close to the opening surface of the cell 101 so that there is no gap. When the shutter 107 is narrowed, the crucible 102 and the ultra-high vacuum chamber are separated at the moment the shutter 107 is opened. - 100, the temperature of the crucible 102 instantly drops below a predetermined temperature, Therefore, substances evaporated at a temperature lower than the desired temperature become scattered, and the semiconductor There was a problem in adjusting the concentration of the epitaxial growth layer formed on the wafer W.

[0007]

[Means to solve the problem]

In order to solve the above problems, the molecular beam epitaxy device of the present invention obtains molecular beams. A molecular beam that consists of multiple cells holding substances to be used in an ultra-high vacuum chamber. This is an epitaxy device in which multiple shutters are placed on the opening surface of the cell. Features.

[0008]

[Effect]

In the molecular beam epitaxy device with the above configuration, the When multiple cells are heated and the temperature approaches a predetermined temperature, the opening side of the cells is activated by multiple shutters. Open the shutter closest to . This reduces the temperature between the ultra-high vacuum chamber and the inside of the cell. However, maintain this state to stabilize the temperature inside the cell before closing the outer shutter. When opened, a molecular beam of a substance is placed in an ultra-high vacuum chamber that evaporates at a desired temperature. It can be scattered towards the semiconductor wafer.

[0009]

【Example】

An embodiment of the present invention will be described below with reference to the drawings.

0010 Figure 1 shows a cell diagonal that is a feature of a molecular beam epitaxy device according to an embodiment of the present invention. This is a perspective view, and FIG. 2 is an enlarged longitudinal sectional view thereof. In the figure, cell 1 is the cell mentioned above. 101 is substantially the same except that double shutters 2 and 3 are provided, so the same part The same reference numerals are given to the members, and the explanation thereof will be omitted here. That is, this cell 1 is an ultra-high vacuum chamber. The shutters 2 and 3 provided in the cell 1 are similarly provided in the chamber 100. Both cover the opening surface and are inserted into the substrate 106 on which the cell 1 is attached. It is rotatably attached to the stepping motors 4 and 5 via shafts 21 and 31, respectively. There is. Shutter 2 is placed near the opening surface of cell 1, and shutter 3 is placed outside it. placed on the side. Specifically, the distance H1 between the opening surface of cell 1 and shutter 2 is Approximately 5 mm, and the distance H2 between shutter 2 and shutter 3 is approximately 3 mm, which is the same as the conventional shutter. It is 0 to 50 mm. In addition, the shutter 2 may only cover the opening surface of the cell 1. Therefore, it is sufficient that the area is approximately the same, and the shutter 3 should have a wider area than that. ing.

[0011] In the molecular beam epitaxy apparatus using the cell 1 having the above configuration, the crucible 10 of the cell 1 is A high-purity substance to be grown on the semiconductor wafer W is supplied into each of the two chambers, and the shutter is 2 and 3, respectively, with the opening surface of cell 1 closed, the tungsten heater 103 is passed through. The temperature of the pot 102, which is heated by electricity, is raised. This heats the substance and creates steam will occur. However, shutter 2 covers the area near the opening surface of cell 1. As a result, the molecular beam that has become vapor flows from around the shutter 2 to the ultra-high vacuum chamber 100. It becomes difficult to scatter inside. Therefore, in a state that does not contribute to growth on the semiconductor wafer W, Because excess molecular beams are difficult to scatter into the ultra-high vacuum chamber 100, Dirt is drastically reduced and maintenance frequency is improved.

0012 Then, the substance is heated to a desired temperature and evaporated, and the molecular beam is directed onto the semiconductor wafer W. When growing a crystal film by scattering, for example, growth starts when the temperature reaches a predetermined temperature. Approximately 5 minutes before the shutter 2 shaft 21 is connected to the The shutter 2 is rotated to open the opening surface of the cell 1. When shutter 2 is opened The temperature inside cell 1 will drop momentarily, but if you keep heating it in this state for about 5 minutes, the desired temperature will be reached. Return to temperature. During this time, the shutter 3 prevents the vapor of low temperature substances from scattering. can. Since the substance in the crucible 102 reaches the desired temperature within a short time, at this time The shutter 3 is activated by operating the stepping motor 5 to which the shaft 31 of the shutter 3 is connected. Open. As a result, the molecular beam that has turned into vapor beams toward the semiconductor wafer W. The crystals scatter in a cloud shape and grow a crystal film having a predetermined concentration.

[0013] By providing double shutters 2 and 3 in cell 1 in this way, until the predetermined temperature is reached, The scattering of the molecular beam that evaporates into the ultra-high vacuum chamber 100 is directed to the opening side of the cell 1. The installed shutter 2 can prevent dirt inside the ultra-high vacuum chamber 100. It is kept to the minimum necessary, and only shutter 2 is opened a little before actually growing the crystal film. In anticipation of temperature fluctuations within the ultra-high vacuum chamber 100 and cell 1, the temperature is heated to a predetermined temperature. Since the shutter 3 is opened after heating is maintained until The sub-beams can be accurately scattered toward the semiconductor wafer W. At this time, Since the shutter 3 is located away from the opening surface of the cell 1, the temperature inside the cell 1 decreases when it is opened. The molecular beam is transferred to semiconductor wafers by evaporating the substance at a precise temperature without any drop in temperature. It can be scattered by W. Therefore, in the crystal film grown on the semiconductor wafer W, With this method, a crystal film with a desired concentration can be grown accurately without causing subtle concentration changes.

[0014] In the example, a double shutter was attached to the opening surface of cell 1. , by arranging three or more multiple shutters and controlling the opening and closing of each shutter. There is no problem in adjusting the scattering of the wire, but it is not practical when considering control and maintenance. A double shutter as shown in the example is suitable.

[0015]

[Effect of the idea] As is clear from the above explanation, the molecular beam epitaxy device of the present invention can Molecules of substances generated by heating and evaporation by a shutter placed near the opening surface It can prevent the wire from leaking into the ultra-high vacuum chamber, and the ultra-high vacuum due to excess molecular beam can be prevented. Contamination inside the empty chamber can be prevented. Also, open the shutter far from the cell opening surface. Before opening the cell, open the shutter closest to the opening surface to stabilize the temperature inside the cell, and then move it away from the cell. The shutter can be opened to directly deposit a crystal film with a predetermined concentration on a semiconductor wafer. It has the effect of being able to grow reliably.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a characteristic cell used in a molecular beam epitaxy apparatus according to an embodiment of the present invention.

FIG. 2 is an enlarged sectional view of a main part of the cell in FIG. 1.

FIG. 3 is a schematic cross-sectional view of a conventional molecular beam epitaxy apparatus.

FIG. 4 is an enlarged sectional view of a main part of a cell used in a conventional molecular beam epitaxy apparatus.

[Explanation of symbols]

1 cell 2,3 Shutter 100 Ultra-high vacuum chamber

Claims (1)

[Scope of utility model registration request] 1. A molecular beam epitaxy apparatus comprising a plurality of cells holding substances for obtaining a molecular beam in an ultra-high vacuum chamber, characterized in that multiple shutters are arranged on the opening surfaces of the cells. Molecular beam epitaxy equipment.