A kind of method that forms Schottky diode
Technical field
The present invention relates to a kind of semiconductor device, relate in particular to a kind of method that forms Schottky diode.
Background technology
Schottky diode claims again Schottky barrier diode, and it belongs to a kind of low-power consumption, ultra-speed semiconductor device.Outstanding feature is reverse recovery time extremely short (may diminish to several nanoseconds), and forward conduction voltage drop is the 0.4V left and right only.The maximum characteristics of Schottky (Schottky) diode are that forward voltage drop VF is smaller.In the situation that same electric current, it is little many that its forward voltage drop is wanted.Its recovery time is short in addition.Its multiplex high frequency, low pressure, large current commutates diode (such as Switching Power Supply time utmost point rectifier diode) done; fly-wheel diode, protection diode; also be used in and make rectifier diode in the circuit such as microwave communication, the small-signal detector diode uses, and is more common in communication power supply, frequency converter etc.
Fig. 1-1 is to form the method for Schottky diode in prior art 1 to 1-8, comprises the following steps;
Step 1 comprises N+ substrate 1 and the N-epitaxial loayer 2 that is formed on substrate 1 in growth the first oxide layer 5, the first semiconductor layers on the first semiconductor layer, as shown in Fig. 1-1;
Step 2, growth the first photoresist 13 on the first oxide layer silicon dioxide 5, and remove selectively the first oxide layer 5 and the photoresist 13 of active area periphery, as shown in Fig. 1-2;
Step 3 take the first oxide layer 5 and photoresist 13 as mask, is injected the p-type ion in the first semiconductor layer and is formed guard ring 3 after through diffusion, removes the first photoresist 13, as Figure 1-3;
Step 4, form the second mask layer 10 on the first semiconductor layer and guard ring, the first oxide layer 5 and the second mask layer 10 that remove on the interior active area of guard ring 3 at the interval form a plurality of windows, utilize plasma method to etch a plurality of spaces groove 4 in the first semiconductor layer, as shown in Fig. 1-4 and 1-5;
Step 5 is injected the p-type ion in a plurality of grooves 4, form buried regions 6 after diffusion, and the direction during injection and vertical direction be certain angle once, and the longitudinal section width of the buried regions 6 of formation is greater than the longitudinal section width of groove, as shown in Fig. 1-6;
Step 6, remove on guard ring and the first oxide layer 5 on the first semiconductor layer between guard ring and the second mask layer 10, then guard ring and guard ring around active area on deposit barrier metal layer 7, barrier metal layer and the first semiconductor layer form Schottky contacts, barrier metal layer and buried regions and guard ring form ohmic contact, as shown in Fig. 1-7;
Step 7 is drawn the i.e. positive pole of Schottky the first electrode by metal 8, and drawing Schottky the second electrode by metal 9 is negative pole, as shown in Fig. 1-8.The method of prior art 1 Schottky diode that forms forms buried regions again due to after forming at groove, and therefore when forming buried regions, trenched side-wall can be subject to the pollution of P type ion.
Fig. 2-1 and 2-3 are the block diagram that prior art 2 forms buried regions, be to fill barrier layer 12 after groove forms in groove with the difference of prior art 1, then remove the barrier layer of channel bottom, p-type ion formation buried regions is being injected in the barrier layer that keeps trenched side-wall then in the first semiconductor layer.
Summary of the invention
The problems such as to form the Schottky diode conduction voltage drop large in order to solve in prior art, and the cost that forms diode is high, and difficulty is large.
The present invention proposes a kind of method that forms Schottky diode, comprise the following steps:
A) provide first conduction type the first semiconductor layer;
B) form the second conduction type guard ring in the first semiconductor layer, and a plurality of space and be positioned at guard ring the second conduction type buried regions;
C) form the groove of a plurality of spaces in first conduction type the first semiconductor layer, described groove is positioned on described buried regions, and the longitudinal section width of single groove is equal to or greater than the longitudinal section width of single buried regions;
D) form metal level on first conduction type the first semiconductor layer He in groove;
E) on metal level and the back side of first conduction type the first semiconductor layer form metal electrode.
Further, b described in the method for formation Schottky diode of the present invention) step comprises the following steps:
Form the first mask layer on first conduction type the first semiconductor layer;
The first mask layer is removed in the compartment of terrain, injects the second conductive type ion in the first semiconductor layer to form guard ring, and a plurality of space and be positioned at the second conduction type buried regions of guard ring.
Further, c described in the method for formation Schottky diode of the present invention) step is specially:
Part the first mask layer on the first semiconductor layer between the removal guard ring; form a plurality of spaces groove in first conduction type the first semiconductor layer; described groove is positioned on described buried regions, and the longitudinal section width of single groove is greater than the longitudinal section width of single buried regions.
Further, c described in the method for formation Schottky diode of the present invention) step is specially:
Form a plurality of spaces groove in first conduction type the first semiconductor layer, described groove is positioned on described buried regions, and the longitudinal section width of single groove equals the longitudinal section width of single buried regions.
Further, in the method for formation Schottky diode of the present invention, the longitudinal section of groove is inverted trapezoidal or square.
Further, the first semiconductor layer of the present invention comprises substrate and the epitaxial loayer that is positioned on substrate.
Further, in the method for formation Schottky diode of the present invention, the first conduction type is N-type, and described the second conduction type is the P type, and the second conductive type ion is B or BF
2
Further, in the method for formation Schottky diode of the present invention, the second conductive type ion implantation dosage is 10
11-10
15/ cm
2
Beneficial effect of the present invention: the present invention forms Schottky diode and comprises the following steps: first conduction type the first semiconductor layer a) is provided; B) form the second conduction type guard ring in the first semiconductor layer, and a plurality of space and be positioned at guard ring the second conduction type buried regions; C) form the groove of a plurality of spaces in first conduction type the first semiconductor layer, described groove is positioned on described buried regions, and the longitudinal section width of single groove is equal to or greater than single buried regions longitudinal section width; D) form metal level on first conduction type the first semiconductor layer He in groove; E) on metal level and the back side of first conduction type the first semiconductor layer form metal electrode; The present invention forms that in the method for Schottky diode, buried regions forms prior to groove, the sidewall of groove can not be subject to the second conductive type ion pollution when forming buried regions so, therefore metal level and trenched side-wall form Schottky contacts, increase the Schottky contacts area, reduced the break-over of device pressure drop; And buried regions forms prior to groove, need to not form packed layer in groove, reduces like this process costs and difficulty.
Description of drawings
Fig. 1-1 forms the structural representation of Schottky diode to 1-8 prior art 1.
Fig. 2-1 forms the structural representation of buried regions to 2-3 prior art 2.
Fig. 3-1 forms the structural representation of Schottky diode to the 3-7 embodiment of the present invention.
Fig. 4 another embodiment of the present invention Schottky diode.
Embodiment
Below in conjunction with accompanying drawing, the specific embodiment of the present invention is elaborated.Should be understood that, embodiment described herein only is used for description and interpretation the present invention, is not limited to the present invention.
For clearer description the present invention, following several words are defined, vertically refer to the above-below direction of accompanying drawing; The back side refers to and one side opposite above accompanying drawing, and the longitudinal section width refers to vertically width of intercepting diode of certain zone.
, comprise the following steps to the formation method that 3-7 describes an embodiment of the present invention Schottky diode below by Fig. 3-1:
Provide first conduction type the first semiconductor layer 15, as shown in Fig. 3-1;
Form the second conduction type guard ring 3 in the first semiconductor layer, and a plurality of space and be positioned at guard ring the second conduction type buried regions 6, as shown in Figure 3-4;
Form the groove 4 of a plurality of spaces in first conduction type the first semiconductor layer, described groove is positioned on described buried regions, and the longitudinal section width of single groove is equal to or greater than single buried regions longitudinal section width, as shown in Fig. 3-5;
Form metal level 7 on first conduction type the first semiconductor layer and in groove, as shown in Fig. 3-6;
The back side that forms the second metal electrode 8 and first conduction type the first semiconductor layer on metal level forms metal electrode 9, as shown in Fig. 3-7.
Can find out from such scheme: form the method for Schottky diode in the present invention, buried regions forms prior to groove, the sidewall of groove can not be subject to the pollution of the second conductive type ion when forming buried regions so, therefore metal level and trenched side-wall also form Schottky contacts, increase the Schottky contacts area, reduced the break-over of device pressure drop; And buried regions forms prior to groove, need to not form packed layer in groove, reduces like this process costs and difficulty.
Further, in another embodiment, the formation method of described Schottky diode comprises the following steps:
The first semiconductor layer is provided, the first semiconductor layer comprises N+ substrate 1 and the N-epitaxial loayer 2 that is positioned on substrate, the size of epilayer resistance rate and thickness are determined by the puncture voltage of its device, the first semiconductor layer can by buy separately after the N+ substrate on grown epitaxial layer 2 form, also can directly enough buy the first semiconductor layer that suits the requirements, certain the first semiconductor layer also can be for the semiconductor layer of one deck back side doping N+ ion and positive doping N-ion, as shown in Fig. 3-1;
Growth the first mask layer on the first semiconductor layer, mask layer comprises that the first oxide layer 5 and photoresist layer 11, the first oxide layers that are positioned on oxide layer are generally silicon dioxide or silicon nitride, can be also combination both, the thickness of the first oxide layer is 200nm-500nm, as shown in Fig. 3-2;
The first mask layer on the first semiconductor layer is removed in the compartment of terrain, forms a plurality of windows 13, injects p-type ion B or BF for blocking by window 13 with the mask layer of not removing in the first semiconductor layer
2, implantation dosage is 10
11-10
15/ cm
2, after injection, through diffuseing to form p-type guard ring 3, and a plurality of space and be positioned at the buried regions 6 of guard ring 3 is as shown in Fig. 3-3 and 3-4;
Remove part the first mask layer, utilize plasma etching or reactive ion etching to carve part buried regions and part the first semiconductor layer, form a groove 4 on each buried regions 6, remove photoresist 11, the longitudinal section width of single groove 4 is greater than the longitudinal section width of single buried regions, single groove on vertical since the vertical degree of depth of the downward degree of depth of the first semiconductor layer upper surface less than buried regions, as shown in Fig. 3-5;
Remove on guard ring and the oxide layer on the first semiconductor layer 5 between guard ring, in on groove 4 and the first semiconductor layer on deposit barrier metal layer 7, barrier metal layer 7 and the first semiconductor layer form Schottky contacts, barrier metal layer 7 forms ohmic contact with guard ring 3 and buried regions 6, as shown in Fig. 3-6;
Deposited metal 8 is as the forward extraction electrode of Schottky on barrier metal layer 7, in the back side of the first semiconductor layer deposited metal 9 as Schottky negative sense extraction electrode, as shown in Fig. 3-7.
Fig. 4 is the another kind of Schottky diode of the embodiment of the present invention, this embodiment and above-mentioned enforcement difference are that the longitudinal section width of buried regions equals the longitudinal section width of groove, the formation method of the present embodiment Schottky diode can get by the formation method of the first embodiment Schottky diode, and is no longer burdensome here.
prior art 1 is when injecting P type ion formation buried regions in groove, injection direction and vertical direction are at an angle, such injection can make trenched side-wall be subject to the p-type ionic soil, result causes the sidewall of barrier metal and groove to form ohmic contact rather than Schottky contacts, reduce like this Schottky contacts area, increase the device conduction voltage drop, and embodiment of the present invention buried regions forms prior to groove, therefore trenched side-wall can not be subject to the pollution of P type ion, prior art 1 increases the contact area of Schottky relatively, reduce conduction voltage drop, reduce the power consumption of Schottky diode in application.
Prior art 2 first formed barrier layer 12 in groove before forming buried regions, the formation on barrier layer 12 has increased process costs, increase simultaneously technology difficulty, and from the step of above-mentioned formation embodiment of the present invention Schottky diode get do not need to increase reduce like this process costs and technology difficulty in the barrier layer.
Below describe by reference to the accompanying drawings the preferred embodiment of the present invention in detail; but; the present invention is not limited to the detail in above-mentioned execution mode; in technical conceive scope of the present invention; can carry out multiple simple variant to technical scheme of the present invention, these simple variant all belong to protection scope of the present invention.