JP4281447B2 - Manufacturing method of semiconductor device - Google Patents

Description

  The present invention relates to a method for manufacturing a semiconductor device in which a metal formed on a semiconductor substrate is alloyed with a semiconductor material.

In Si-based devices, a maximum impurity concentration of 1 × 10 ²⁰ is realized regardless of n-type or p-type, so that non-alloy ohmic contacts can be easily obtained. On the other hand, in compound semiconductor devices (especially electronic devices), the maximum impurity concentration is a low value of about 1 to 2 × 10 ¹⁹ , and it is difficult to realize non-alloy ohmic contact at this level of impurity concentration. Accordingly, an operation (alloy) for diffusing metal into the semiconductor substrate to form an alloy is required.

The alloying conditions for the ohmic metal are generally about 400 to 500 ° C. for about 1 to 2 minutes. In this case, it is rapidly heated from room temperature to the alloy temperature, and rapidly cooled to room temperature after completion of the alloy. This is because alloying is performed without disturbing the profile of the doped impurity. The doping is usually performed by ion implantation of an n-type impurity (Si in the case of GaAs). Depending on the implantation conditions, it is possible to realize an n ⁺ layer thinned to a thickness of about 100 nm, and it is required to alloy without disturbing the thin layer profile.

  In such a rapid heating / cooling process of a semiconductor substrate, distortion is induced in the substrate due to a thermal history, and in an extreme case, the substrate may be self-destructed. That is, the substrate may be broken simply by taking out the substrate from the alloy furnace or mounting the substrate from the room temperature to the high temperature part of the alloy furnace.

In order to prevent the substrate from being broken in such a rapid heating / cooling process, various methods have been proposed. For example, in each of Patent Documents 1 and 2, a process of raising the temperature to the processing temperature after holding the temporary substrate at an intermediate temperature, or lowering the temperature to room temperature after holding the substrate at the intermediate temperature is performed.
Japanese Patent Laid-Open No. 11-176902 Japanese Patent Application Laid-Open No. 7-147311

  However, the above-described conventional technique requires an intermediate temperature chamber that raises or lowers the temperature to an intermediate temperature, which complicates the apparatus configuration and process.

  Patent Document 1 also discloses a method of pre-heating or pre-cooling a substrate with a transfer arm, but in order to heat and cool the substrate with the transfer arm, if there is not enough area to cover the entire surface of the substrate, the substrate The whole cannot be heated or cooled. At this time, if the area of the transfer arm is enlarged to cover the entire surface of the substrate, the substrate cannot be received by lift pins.

  The present invention has been made in view of the above circumstances, and a metal and a semiconductor formed on a semiconductor substrate without incurring the complexity of the apparatus configuration and process to reduce the risk of thermal cracking of the semiconductor substrate. It is an object of the present invention to provide a method for manufacturing a semiconductor device that can be favorably alloyed with a material.

  The method for manufacturing a semiconductor device according to the present invention is a method in which a substrate made of a semiconductor material is carried into a heating furnace including a heating section, and alloying of the metal formed on the substrate and the semiconductor material is performed. In this method, the temperature of the heating unit is maintained at a temperature that enables alloying of the metal and the semiconductor material, the substrate is loaded into the heating furnace and held on the heating unit for a predetermined time, and then the substrate is placed on the heating unit. Is contacted to alloy the metal and the semiconductor material, the substrate is separated from the heating unit, the substrate is held on the heating unit for a predetermined time, and then the substrate is unloaded from the heating furnace and cooled.

  According to this method, since intermediate heating and intermediate cooling are performed on the heating unit, it is not necessary to provide a separate intermediate temperature chamber, and the process of taking in and out the intermediate temperature chamber can be omitted. Therefore, it is possible to satisfactorily alloy the metal formed on the substrate and the semiconductor material without complicating the apparatus configuration and the process in order to reduce the risk of thermal cracking of the substrate.

  The inside of the heating furnace is preferably maintained at a temperature higher than room temperature at which the alloying of the metal and the semiconductor material does not proceed. By distinguishing between the intermediate heating and cooling processes and the alloying process, good alloying can be achieved.

  It is preferable that the substrate is carried into and out of the heating furnace by a transfer arm, and the substrate is brought into contact with and separated from the heating unit by lift pins provided in the heating unit so as to be movable up and down.

  The tip of the lift pin that contacts the substrate is preferably flat. In this way, the contact area between the substrate and the lift pins is increased, so that thermal stress is dispersed and the risk of thermal cracking is reduced.

  The tip of the lift pin is preferably opened in the radial direction of the lift pin when supporting the substrate. In this way, the contact area between the substrate and the lift pins is further increased.

  The tip of the lift pin preferably has a plurality of support pieces extending along the axial direction of the lift pin, and the plurality of support pieces are preferably deployed in the radial direction of the lift pin when supporting the substrate.

  It is preferable that at least a portion of the transfer arm that contacts the substrate is made of quartz. By deteriorating the heat conduction, the temperature change of the substrate is reduced and the thermal stress is relieved.

  Before bringing the transfer arm into contact with the substrate for unloading the substrate from the heating furnace, it is preferable to introduce the transfer arm into the heating furnace and hold it for a predetermined time to heat it. By reducing the temperature difference between the substrate and the transfer arm, the thermal stress is alleviated.

  According to the present invention, it is possible to satisfactorily alloy the metal formed on the semiconductor substrate with the semiconductor material without reducing the complexity of the apparatus configuration and process in order to reduce the risk of thermal cracking of the semiconductor substrate. A method for manufacturing a semiconductor device is provided.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted.

  FIG. 1 is an exploded perspective view showing an alloy heat treatment apparatus (hereinafter also referred to as “heat treatment apparatus”) 10 suitable for carrying out the semiconductor device manufacturing method according to the present embodiment. FIG. 2 is a side view schematically showing the configuration of the heat treatment apparatus 10. In FIG. 2, for convenience of explanation, a furnace main body 14 and an upper cover 16 of the heat treatment furnace 12 to be described later are omitted.

  As shown in FIG. 1, the heat treatment apparatus 10 includes a heat treatment furnace 12 whose outer shape is a rectangular parallelepiped shape. The heat treatment furnace 12 includes a furnace main body part 14 whose upper end is opened and an upper lid part 16 that closes the upper end of the furnace main body part 14. The furnace body 14 is partitioned into a heating chamber (heating furnace) 20 and a cooling chamber 22 by a partition wall 18.

  The heating chamber 20 is provided with a hot plate 24 for heating the semiconductor substrate W, and the cooling chamber 22 is provided with a cooling plate 26 for cooling the semiconductor substrate W. The upper surfaces of the hot plate 24 and the cooling plate 26 have substantially the same area as the semiconductor substrate W. The hot plate 24 is provided with three holes 28 penetrating the upper and lower surfaces, and the three holes 28 are respectively provided with lift pins 30 that advance and retreat in the vertical direction. The cooling plate 26 is provided with three holes 32 penetrating the upper and lower surfaces, and the three holes 32 are respectively provided with lift pins 34 that advance and retreat in the vertical direction. By supporting the semiconductor substrate W by the lift pins 30 and 34 and moving the semiconductor substrate W in the vertical direction, the semiconductor substrate W is brought into contact with or separated from the hot plate 24 or the cooling plate 26. These lift pins 30 and 34 can be made of metal (SUS), but are preferably made of ceramics having poor thermal conductivity, quartz, or heat-resistant Teflon (registered trademark).

  The tip portions of the lift pins 30 and 34 that come into contact with the semiconductor substrate W are provided flat as shown in FIG. The lift pins 30 and 34 support the semiconductor substrate W at the push-up position P shown in FIG. 3 and do not interfere with the transfer arm 36.

  In the direction in which the heating chamber 20 and the cooling chamber 22 are arranged (hereinafter referred to as “substrate transport direction”) and on the side of the cooling chamber 22, as shown in FIGS. A transfer arm 36 for loading and unloading W is provided. The arm portion 38 of the transfer arm 36 is made of metal. The transfer arm 36 can advance and retreat in the substrate transfer direction, and a support portion 40 that supports the semiconductor substrate W is provided at the tip. As shown in FIG. 3, the support portion 40 is provided with a vacuum suction hole 42, and the semiconductor substrate W is supported by vacuum suction at the central portion. Here, at least a portion of the support portion 40 that contacts the semiconductor substrate W is preferably formed of ceramics, and more preferably formed of quartz.

  An opening 44 for carrying the carrier arm 36 supporting the semiconductor substrate W into and out of the cooling chamber 22 on the side wall of the furnace main body 14 defining the cooling chamber 22 and facing the carrier arm 36. Is provided. Further, the partition wall 18 is provided with an opening 46 through which the transport arm 36 supporting the semiconductor substrate W introduced into the cooling chamber 22 is further carried into and out of the heating chamber 20.

  Next, a method for manufacturing a semiconductor device using the heat treatment apparatus 10 having the above configuration will be described. 4 to 9 referred to in the following description, only the positional relationship between the hot plate 24, the cooling plate 26, and the transfer arm 36 is illustrated for convenience of description.

  First, as shown in FIGS. 1 and 2, the semiconductor substrate W is vacuum-sucked and supported by the transfer arm 36. The semiconductor substrate W is made of a compound semiconductor such as GaAs, for example, and a metal such as Al or W is formed on the upper surface thereof.

  Then, the temperature of the hot plate 24 is heated to a temperature T1 at which the alloying of the semiconductor substrate W and the metal proceeds, for example, 350 ° C. <T1 <500 ° C. In the following series of steps, the temperature of the hot plate 24 is always maintained at a constant temperature T1.

  Next, the transfer arm 36 supporting the semiconductor substrate W is introduced into the heat treatment furnace 12 through the opening 44, passed through the cooling chamber 22 as it is, and further introduced into the heating chamber 20 through the opening 46, thereby heating. The semiconductor substrate W is carried into the chamber 20. At this time, both the lift pin 34 provided on the cooling plate 26 and the lift pin 30 provided on the hot plate 24 are in a state of being accommodated in the plate, and do not hinder the transport of the semiconductor substrate W.

  The semiconductor substrate W carried into the heating chamber 20 is stopped above the hot plate 24. After stopping the semiconductor substrate W, the vacuum suction is released and the lift pins 30 and 34 are raised simultaneously, and the semiconductor substrate W is lifted from the transfer arm 36 as shown in FIG. Then, with the semiconductor substrate W lifted, the transfer arm 36 is moved to a position beyond the right cooling plate 26 as shown in FIG.

  Next, in a state where the semiconductor substrate W is lifted by the lift pins 30, for example, the semiconductor substrate W is intermediately heated while being held for a predetermined time of about 20 seconds to 30 seconds. At this time, the temperature in the heating chamber 20 is higher than the room temperature (27 ° C.) and the alloying of the semiconductor substrate W and the metal does not proceed, for example, 27 ° C. <T 2 <300 ° C., preferably 250 ° C. <T 2 <300. It is preferable that the temperature is maintained at ° C. In this way, the intermediate heating process and the alloying process are distinguished, and good alloying is achieved.

  Here, the holding of the semiconductor substrate W over the hot plate 24 by the lift pins 30 for a predetermined time is an intentional holding for intermediate heating of the semiconductor substrate W and is mounted on the hot plate 24. In order to connect to the next process, it is distinguished from simple holding that stops the semiconductor substrate W above the hot plate 24. By such intermediate heating of the semiconductor substrate W, the temperature of the semiconductor substrate W is raised to 40% to 80% of the temperature T1 of the hot plate 24.

  Then, as shown in FIG. 6, the lift pins 30 are lowered and the semiconductor substrate W is mounted on the hot plate 24. In this state, the semiconductor substrate W is heated for a predetermined time of, for example, about 1 minute to 2 minutes, and alloying of the semiconductor substrate W and the metal is attempted. The alloy condition is normally defined as the temperature of the hot plate 24 and the time for placing the semiconductor substrate W on the hot plate 24. The temperature of the semiconductor substrate W itself does not increase to the alloy temperature (hot plate temperature) at the moment when it is placed on the hot plate 24, but the thermal conductivity between the hot plate 24 and the semiconductor substrate W, and the semiconductor Depending on the heat capacity of the substrate W, it rises gradually.

  Next, the semiconductor substrate W is lifted by raising the lift pins 30 and held for a predetermined time of, for example, about 20 seconds to 30 seconds in a state of being separated from the hot plate 24, and the semiconductor substrate W is subjected to primary intermediate cooling. Also at this time, it is preferable that the inside of the heating chamber 20 is maintained at the above-described temperature T2.

  Here, the holding of the semiconductor substrate W above the hot plate 24 by the lift pins 30 for a predetermined time is intentional holding for primary intermediate cooling of the semiconductor substrate W, and the semiconductor substrate W is held by the transfer arm 36. Is connected to the next step of unloading from the heating chamber 20, so that it is distinguished from mere holding for stopping the semiconductor substrate W above the hot plate 24. By such primary intermediate cooling of the semiconductor substrate W, the temperature of the semiconductor substrate W is lowered to 40% to 80% of the temperature T1 of the hot plate 24.

  Next, the transfer arm 36 that has been waiting to the right enters the heating chamber 20 and is moved below the semiconductor substrate W, and then the lift pins 30 are lowered to place the semiconductor substrate W on the transfer arm 36. Let Here, before bringing the transfer arm 36 into contact with the semiconductor substrate W, it is preferable to introduce the transfer arm 36 into the heating chamber 20 and hold and heat it for a predetermined time of about 10 seconds to 60 seconds. In this way, the temperature difference between the semiconductor substrate W and the transfer arm 36 is reduced, and the thermal stress is alleviated. Then, the semiconductor substrate W is vacuum-sucked by the support unit 40, the transport arm 36 is moved backward, and the semiconductor substrate W is carried into the cooling chamber 22.

  The semiconductor substrate W carried into the cooling chamber 22 is stopped above the cooling plate 26. After the semiconductor substrate W is stopped, the lift pin 34 is raised simultaneously with releasing the vacuum suction, and the semiconductor substrate W is lifted from the transfer arm 36 as shown in FIG. Then, with the semiconductor substrate W lifted, the transfer arm 36 is moved to the right standby position as shown in FIG.

  Next, in a state where the semiconductor substrate W is lifted by the lift pins 34, the semiconductor substrate W is held for a predetermined time, for example, about 10 seconds to 30 seconds, and the semiconductor substrate W is subjected to secondary intermediate cooling. At this time, the temperature T3 in the cooling chamber 22 is preferably maintained at 27 ° C. <T3 <200 ° C., preferably 50 ° C. <T3 <150 ° C., for example. In this way, the temperature difference between the semiconductor substrate W and the lift pins 34 is alleviated.

  Here, the holding of the semiconductor substrate W above the cooling plate 26 by the lift pins 34 for a predetermined time is intentional holding for secondary intermediate cooling of the semiconductor substrate W, and is mounted on the cooling plate 26. In order to connect to the next process of performing, the semiconductor substrate W is distinguished from mere holding for stopping the semiconductor substrate W above the cooling plate 26.

  Then, as shown in FIG. 9, the lift pins 34 are lowered and the semiconductor substrate W is mounted on the cooling plate 26. In this state, the semiconductor substrate W is cooled for a sufficient time, for example, about 1 minute to 2 minutes. At this time, a large amount of nitrogen gas may be blown from above the semiconductor substrate W to cool it in a reinforcing manner.

  Next, the semiconductor substrate W is lifted by lifting the lift pins 34, separated from the cooling plate 26, and the semiconductor substrate W is held above the cooling plate 26. At the same time, the transfer arm 36 that has been waiting to the right enters the cooling chamber 22 and is moved below the semiconductor substrate W, and then the lift pins 34 are lowered to place the semiconductor substrate W on the transfer arm 36. Let Then, the semiconductor substrate W is vacuum-sucked by the support unit 40, and as shown in FIG. 2, the transfer arm 36 is moved backward to carry the semiconductor substrate W out of the heat treatment furnace 12, and the semiconductor substrate W is recovered.

  Next, operations and effects of the semiconductor device manufacturing method according to the present embodiment will be described.

  Since intermediate heating and primary intermediate cooling are performed above the hot plate 24, it is not necessary to provide a separate intermediate temperature chamber, and the process of taking in and out the intermediate temperature chamber can be omitted. Therefore, it is possible to satisfactorily alloy the metal formed on the semiconductor substrate W with the semiconductor material without incurring the complexity of the apparatus configuration and process in order to reduce the risk of thermal cracking of the semiconductor substrate W. is there. Thereby, even when the impurity concentration is low like a compound semiconductor, it is possible to obtain a semiconductor device having a good ohmic contact.

  Since the inside of the heating chamber 20 is maintained at a temperature higher than room temperature and does not allow alloying between the metal and the semiconductor material, the process of intermediate heating and primary intermediate cooling is distinguished from the alloying process, and good alloying is achieved. Figured.

  Since the tip portions of the lift pins 30 and 34 that are in contact with the semiconductor substrate W are flat, the contact area between the semiconductor substrate W and the lift pins is increased, the thermal stress is dispersed, and the risk of thermal cracking is reduced.

  If at least a portion of the support portion 40 of the transfer arm 36 that is in contact with the semiconductor substrate W is made of quartz, the heat conduction is deteriorated, the temperature change of the semiconductor substrate W is reduced, and the thermal stress is alleviated.

  Before bringing the transfer arm 36 into contact with the semiconductor substrate W to carry the semiconductor substrate W out of the heating chamber 20, the transfer arm 36 is introduced into the heating chamber 20 and held and heated for a predetermined time. The temperature difference with the arm 36 is reduced, and the thermal stress is relaxed.

  The present invention is not limited to the above-described embodiment, and various modifications can be made. For example, as shown in FIG. 10, the diameters of the tip portions of the lift pins 30 and 34 may be expanded into a flat plate shape with a flat upper surface. Alternatively, as shown in FIG. 11, the tip portions of the lift pins 30 and 34 have a plurality of support pieces 80 extending along the axial direction of the lift pins 30 and 34, and the plurality of support pieces 80 support the semiconductor substrate W. When it does, it is preferable to comprise so that it may expand | deploy to the radial direction of the lift pins 30,34. In this way, the contact area between the semiconductor substrate W and the lift pins 30 and 34 is further increased, the thermal stress is dispersed, and the risk of thermal cracking is further reduced.

It is a disassembled perspective view which shows the alloy heat processing apparatus suitable for enforcing the manufacturing method of the semiconductor device which concerns on this embodiment. It is a side view which shows typically the structure of an alloy heat processing apparatus. It is a figure for demonstrating support of the semiconductor substrate by a conveyance arm and a lift pin. It is a figure for demonstrating a mode that the semiconductor substrate carried in the upper part of a hotplate with the conveyance arm is supported with a lift pin. It is a figure for demonstrating a mode that a semiconductor substrate is intermediately heated above a hotplate. It is a figure for demonstrating a mode that a semiconductor substrate is heated and alloying is performed on a hotplate. It is a figure for demonstrating a mode that the semiconductor substrate carried in the upper part of the cooling plate with the conveyance arm is supported with a lift pin. It is a figure for demonstrating a mode that the semiconductor substrate is subjected to secondary intermediate cooling above the cooling plate. It is a figure for demonstrating a mode that a semiconductor substrate is cooled on a cooling plate. It is a figure which shows the modification of the front-end | tip part of a lift pin. It is a figure which shows the modification of the front-end | tip part of a lift pin.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Alloy heat processing apparatus, 12 ... Heat processing furnace, 20 ... Heating chamber, 22 ... Cooling chamber, 24 ... Hot plate, 26 ... Cooling plate, 30, 34 ... Lift pin, 36 ... Transfer arm, 40 ... Support part, 80 ... Support Piece, W ... Semiconductor substrate.

Claims (6)

A method for manufacturing a semiconductor device, wherein a substrate made of a semiconductor material is carried into a heating furnace including a heating unit, and alloying between the metal formed on the substrate and the semiconductor material is performed.
The temperature of the heating unit is maintained at a temperature that enables alloying of the metal and the semiconductor material, the substrate is loaded into the heating furnace and held on the heating unit for a predetermined time, and then the heating is performed. The substrate is brought into contact with the part to alloy the metal and the semiconductor material,
The substrate is separated from the heating unit, and after holding the substrate on the heating unit for a predetermined time, the substrate is unloaded from the heating furnace and cooled .
Loading and unloading of the substrate with respect to the heating furnace is performed by a transfer arm, and contact and separation of the substrate with respect to the heating unit are performed by lift pins provided in the heating unit so as to be movable up and down,
A method of manufacturing a semiconductor device , wherein a tip end portion of the lift pin opens in a radial direction of the lift pin when the substrate is supported . 2. The method of manufacturing a semiconductor device according to claim 1, wherein the inside of the heating furnace is maintained at a temperature higher than room temperature so that alloying of the metal and the semiconductor material does not proceed. The method of manufacturing a semiconductor device according to claim 1 , wherein a tip portion of the lift pin that contacts the substrate is flat. The tip of the lift pin has a plurality of support pieces extending along the axial direction of the lift pin,
The method of manufacturing a semiconductor device according to claim 1 , wherein the plurality of support pieces are deployed in a radial direction of the lift pins when the substrate is supported. The method for manufacturing a semiconductor device according to claim 1 , wherein at least a portion of the transfer arm that is in contact with the substrate is made of quartz. Claim 1, wherein said transfer arm prior to contacting with said substrate, heating and held only by introducing transfer arm into the heating furnace in a predetermined time in order to unloading the substrate from said heating furnace The manufacturing method of the semiconductor device in any one of -5 .

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